Alternative theories being tested by Gravity probe B [Archive]

Garth

Dec20-05, 08:11 AM

The Gravity Probe B satellite has placed four (over redundant) gyroscopes in low polar Earth orbit to primarily test two predictions of General Relativity.

The first effect being tested is (for the GP-B polar orbit) a N-S geodetic precession, caused by the amount a gyro 'leans' over into the slope of curved space.

The second effect being tested is the E-W frame-dragging, Lense-Thirring, or gravitomagnetic effect, caused by the spinning Earth dragging space-time around with it.

Some researchers, such as Kenneth Nordtvedt, have said that the experiment was worth doing when it was first proposed but that now GR has been verified beyond resonable doubt the result of GP-B is a foregone conclusion.

I have now discovered several theories competing with General Relativity(GR) that are being tested and falsified by this experiment:
my Self Creation Cosmology (http://arxiv.org/abs/gr-qc/0302026)).(SCC),
Moffat's Nonsymmetric Gravitational Theory (http://arxiv.org/abs/gr-qc/0405091) (NGT),
Hai-Long Zhao's mass variance SR theory (http://uk.arxiv.org/abs/gr-qc/0512088) (MVSR),
Stanley Robertson's Newtonian Gravity theory (http://arxiv.org/abs/gr-qc/0502088) (NG), and
Junhao & Xiang's Flat space-time theory (http://arxiv.org/abs/physics/0101017) (FST).

As the results will be published in the not too distant future they could be interesting!!

(Note if anybody knows of any other theories with alternative predictions for GP-B please post them as well for comparison.)

1. GPB Geodetic precession
GR = 6.6144 arcsec/yr
SCC = 4.4096 arcsec/yr
NGT = 6.6144 - a small \sigma correction arcsec/yr
MVSR = 6.6144 arcsec/yr
NG = 1.6536 arcsec/yr
FST = 4.4096 arcsec/yr

2. GPB gravitomagnetic frame dragging precession
GR = 0.0409 arcsec/yr
SCC = 0.0409 arcsec/yr
NGT = 0.0409 arcsec/yr
MVSR = 0.0102 arcsec/yr
NG = 0.0102 arcsec/yr
FST = 0.0000 arcsec/yr

I cannot vouch for these other theories, they may well be considered 'crackpot' by some, however all these theories have the advantage, together with GR, that they are able to be falsified by the GP-B results.

We continue to wait and see! :smile:

Garth

Garth

Jan1-06, 11:25 AM

The wait for the results continues into this and next new year! GP-B MISSION NEWS—NASA REPORT & DATA ANALYSIS PROCEEDING AS PLANNED (http://einstein.stanford.edu/)
It is important to emphasize that at this point in the mission, we are only performing maintenance operations on the spacecraft. Our main focus is analyzing the science data we have collected and finishing our final report to NASA. In this regard, our final report to NASA, which is over 450 pages long, is now in the final stages of completion. Our science data analysis is proceeding according to plan. We are in the process of analyzing approximately 1 terabyte (1,000 gigabytes) of data collected from the spacecraft. Two independent analysis teams here at GP-B are working on the data, frequently comparing their results for both quality control and to ensure the validity of the data analysis algorithms.

The main part of the data analysis is expected to be completed late this summer (July-August 2006). At this point, the Harvard-Smithsonian Center for Astrophysics (CfA) will provide our science team with their ultra-precise measurements of the proper motion of the guide star, IM Pegasi. In the final step of the analysis, our science team will combine the gyroscope results with the CfA proper motion measurements of IM Pegasi to arrive at the final experimental results. These results will then be carefully and critically reviewed by international experts in general relativity and data analysis to ensure that our statement of the effects observed are as accurate as possible. Only after this review is complete--early in 2007--will we make a formal and public announcement about the results of this unprecedented test of General Relativity.
Whatever those results might be!

Garth

Nereid

Jan1-06, 09:11 PM

To what extent will the parameter space that GPB and observations of the double pulsar (will) probe overlap, in terms of testing GR and alternatives?

Chronos

Jan2-06, 12:49 AM

The recent pulsar measurements are probably better predictors than GPB could ever hope to be. My prediction: GR will prevail again.

Garth

Jan2-06, 07:07 AM

The recent pulsar measurements are probably better predictors than GPB could ever hope to be. My prediction: GR will prevail again.

This is in line with the thinking of Kenneth Nordtvedt in which case the $700 million spent on GP-B has been wasted! However, I beg to differ.

GP-B is a controlled experiment, all the parameters that may affect the result are well determined. This cannot be said for a remote observation of a distant pulsar system.

As far as experimental/observational comparisons between SCC and GR, especially concerning the binary pulsar PSR B1913+16 (and now the double pulsar PSR J0737-3039B), there are two degeneracies and a third near degeneracy to realise.

1. SCC is conformally equivalent to canonical GR in vacuo, in a vacuum - the Schwarzschild solution - particles and photons follow the geodesics/null geodesics of GR. As all the standard tests of GR, light deflection, precession of the perihelia, time delay, test the behaviour of particles and photons through a vacuum there is no difference between these two theories in predicting the results of these tests.

(The details of the conformal transformation can be found here: The Principles of Self Creation Cosmology and its Comparison with General Relativity (http://arxiv.org/pdf/gr-qc/0212111 ) Section 2, especially Equation 20.)

and the details of the degeneracy of tests can be found here: Resolving the Degeneracy: Experimental tests of the New Self Creation Cosmology and a heterodox prediction for Gravity Probe B (http://arxiv.org/pdf/gr-qc/0302026))

2. As matter becomes degenerate
p -> \frac 13 \rho c^2
the scalar field becomes minimally connected and again the behaviour, even when not in vacuo reduces to canonical GR; although now the full gravitational 'constant' is felt.
G_m = \frac 43 G_{Newton}

Because of these two degeneracies the behaviour of a binary or double pulsar system in SCC is exactly the same as in GR.

3. The third near degeneracy is in tests of the equivalence principle in Eotvos type experiments the violation of the EEP would be about one part in 10−17 or about three orders of magnitude smaller than the present day sensitivity of the experiment. (See Self Creation Cosmology - An Alternative Gravitational Theory (http://arxiv.org/pdf/gr-qc/0405094) section 7.

These degeneracies will be resolved by GP-B, which is the first experiment/observation that is able to distinguish between these two theories.

Note that degeneracy 1 does not apply to the cosmological solution, except in the empty universe, \rho = 0 case. (When SCC converges on the GR Milne model) That is why the SCC cosmological solution is different to that of GR, it is concordant with cosmological observations but without inflation, exotic DM or unknown DE!

Garth

RandallB

Feb19-06, 03:07 PM

Garth
Can you help me understand the Gravity B tests here? I’m having trouble understanding the expected direction of change in angles expected.

First as I read the polar orbit of GPB it is moving north to south as it is viewing IM-Pegasi the guide star being used. (In close alignment with it the guide star would always be blocked by earth during the south to north trip)

First:
GPB gravitomagnetic frame dragging precession.
The most significant measurement to be made (at least some say and IMO). It is the annual change in the orbital alignment with the guide star.
Do I read the term “E-W precession” correctly as relating the alignment moving in the direction of the rotation of earth (as there is no orbital E-W component to precess)? Thus all the theories named here are predicting the orbit to move its alignment to the east of the guide star. Is this correct?

Actually, I would expect the alignment to move west, so I was looking for a theory that agrees with a westward change. I take it then you are not aware of any theory that does.

Second:
GPB Geodetic precession
Looking at the Satellite on the IM-Pegis side of the orbit at the equator. The angle of deflection relates to the alignment of the gyro axis moving. Given three idea gyros at this point in the orbit and axis aligned; 1) E-W, 2) N-S, 3) Earth Radius, which of the three would have their alignment move and which way?
I assume one will not move at all.
Would direction of gyro rotation have any effect on direction?
And do you know a web site that does a good job of explaining why GR expects this beyond just saying “because of GR space-time curvature”.

Thanks
RB

wolram

Feb19-06, 03:25 PM

Congratulations Garth, i think.

Garth

Feb19-06, 04:04 PM

RandallB The orbit was chosen to be a polar orbit precisely to searate out the two effects: geodetic and frame-dragging.

The frame-dragging, or Lense-Thirring, or gravitomagnetic, effect is as the name suggests caused by space-time, and corresponding frames of reference, being dragged round by the revolving Earth in a West to East direction.

The geodetic effect, caused by the curvature of space-time, represents the angle missing from 3600 in the circle drawn on a curved surface, or the amount the gyro axis precesses after being parallel transported one complete orbital revolution - summed up over a year's worth of orbits. Alternatively you can think of it as the angle the gyro 'leans over into the slope' of curvature and is in the direction of motion. Therefore it is a precession in the N-S direction and clearly distinguished from the much smaller frame-dragging precession.

Note: the orbit was accurate to within 10 to secure this distinction, and that gave the launch vehicle a one second window on each day of possible launch(!)

I hope this helps.

wolfram thank you, but a little premature I think? :wink:

Garth

RandallB

Feb20-06, 10:19 AM

The frame-dragging, - - frames of reference, being dragged round by the revolving Earth in a West to East direction. OK that as I expected, the alignment of the entire orbit towards IM-Pegasi is predicted to move to the East. (Or looking at the orbital axis from the guide star view, the left side would lean towards the star)

The geodetic effect, - - Therefore it is a precession in the N-S direction and clearly distinguished from the much smaller frame-dragging precession. Now this is the one I have the most trouble understanding alignment and direction on. What is “precession in the N-S direction” of a gyro axis?

In terms of the angle the gyro axis “leans over” - which of the three idea gyros I described would actually show a change.
At equator the position I described, (Pegasi side GPB moving north to south) two are perpendicular to a radius from earth thus axis ends are pointing E-W & N-S. Which if any of these ends would lean towards earth?

The third axis would be inline with a radius from earth. So for the end pointed toward earth (only on this side) which way would it move N, S, E, or W if at all?

Thanks
RB

Garth

Feb21-06, 03:39 AM

RB - my 'leaning' over explanation is only a 'hand waving' description to try and convey some understanding to what is going on, a full understanding requires the maths.

The precession of a spin S is given by

\frac{dS}{d\tau} = \Omega \times S

where

\Omega = -\frac 12 v \times a -\frac 12 \nabla \times g + (\gamma + \frac 12)v \times \nabla U
(see MHW equation 40.33 page 1118)

In the RHS of the last expression the first term is the SR Thomas precession caused by accelerating a vector - it 'leans over' in 4D space-time. It is zero in GR but not SCC (http://en.wikipedia.org/wiki/Self_creation_cosmology).

The second term is the Lense-Thirring effect g = g_{0j}e_j is the perturbation of the metric caused by the spinning of the Earth.

The third term is the geodetic effect. v is the along spin axis of the satellite's orbit, normal to its plane.

When you work it out for a polar orbit the geodetic precession is in a
N-S direction.

Garth

RandallB

Feb21-06, 09:41 AM

When you work it out for a polar orbit the geodetic precession is in a N-S direction.This is the part that isn’t clear in anything I’ve been able to find. At the end of the day the GPB will be making a measurement on the gyros that have been running for however long and expect them to have have moved from their normal alignments. What will those physical changes in the direct measurements be?

As in my example of three gyros with their spins around x, y, and z coordinates after running a long time, classical Newtonian expectations would say that there would be absolutely no change at all (as if the earth was not rotating). The axis end pointed toward the earth center (while over the equator, the opposite end of the axis would always point at the guide star) would not tip N, S, E, or W at all. The 4 ends of the other axis point N, S, E, & W and no end should tip towards the earth (thus away from the guide star).

None of the six theories predict such a null result. But all predict various amounts of change in the same direction. What is not clear is what direction of tilt will be physically observed by the measurements to be made on GPB. Someone on the team must have defined in clear measurable terms exactly what direction that is to match a “geodetic precession is in a N-S direction”.

Garth

Feb21-06, 01:46 PM

This is the part that isn’t clear in anything I’ve been able to find. At the end of the day the GPB will be making a measurement on the gyros that have been running for however long and expect them to have have moved from their normal alignments. What will those physical changes in the direct measurements be?Read the information on the GP-B (http://einstein.stanford.edu/) website. The gyros are aligned on a star, the IM Pegasi (radio) star has a proper motion that is being tracked by VLBI, the movement of the gryos relative to the star has been tracked using SQUIDs (see the website for details) by the summer this year the one data set will be compared to the other to see how the gyros have moved, various theories predict different N-S and E-W precessions and of course almost everybody expects the experiment will verify the GR prediction, but the team have kept a very open mind on this, which is what makes the experiment so exciting.
As in my example of three gyros with their spins around x, y, and z coordinates after running a long time, classical Newtonian expectations would say that there would be absolutely no change at all (as if the earth was not rotating). The axis end pointed toward the earth center (while over the equator, the opposite end of the axis would always point at the guide star) would not tip N, S, E, or W at all. The 4 ends of the other axis point N, S, E, & W and no end should tip towards the earth (thus away from the guide star).

None of the six theories predict such a null result. But all predict various amounts of change in the same direction. What is not clear is what direction of tilt will be physically observed by the measurements to be made on GPB. Someone on the team must have defined in clear measurable terms exactly what direction that is to match a “geodetic precession is in a N-S direction”.I'm not sure what your problem is. The gyros may not move at all, or they may move in a direction that can be resolved into a N-S and a E-W component, and then we shall see whether these observed precessions match any of the sets of predictions.

Garth

RandallB

Feb21-06, 04:50 PM

I'm not sure what your problem is. In space how do you define up down left right forward and back with no references.
Same thing here, I don’t see a defined reference.

For the gyro that is pointed at the guide star.
Option 1:
The axis end pointed at the star tips up to the North the back end will of course tip down to the south.
Option 2:
The opposite happens, the end axis pointed at the star tips down to the South the back end will of course tip up to the North.

Which option is the N-S move Option 1 or 2?
We can assume N-S means “from North towards the South” movement.
But without defining which end of the gyro is being measured how does any one know what the other is talking about.

Same kind of problem understanding the other gyro measements in 3D.

Garth

Feb21-06, 05:52 PM

In space how do you define up down left right forward and back with no references.
Same thing here, I don’t see a defined reference. From the plane of the satellite's orbit (N-S) and the orientation of the Earth(E-W).
For the gyro that is pointed at the guide star.
Option 1:
The axis end pointed at the star tips up to the North the back end will of course tip down to the south.
Option 2:
The opposite happens, the end axis pointed at the star tips down to the South the back end will of course tip up to the North.

Which option is the N-S move Option 1 or 2?
We can assume N-S means “from North towards the South” movement.
But without defining which end of the gyro is being measured how does any one know what the other is talking about.

Same kind of problem understanding the other gyro measements in 3D.
The Spin vector of the gyro is defined by the Right Hand Screw convention, so long as that convention (or the opposite one) is applied consistently in the analysis there is no ambiguity.

Garth

RandallB

Feb21-06, 06:27 PM

The Spin vector of the gyro is defined by the Right Hand Screw So the direction of gyro rotation makes a differance.
With that Right hand vector pointed at the guide star does that mean option 2 is matchs with a positive N-S move.
And option 1 if the if the vector is away from the guide star?

Garth

Feb21-06, 07:14 PM

As I said it depends on the convention used.

You have to examine the GP-B papers to find the answers to your questions, or simply ask the question on their website.

Garth

Garth

Mar4-06, 10:01 AM

Latest news of the GP-B (http://einstein.stanford.edu/) data analysis: Phase I complete! We are now entering Phase II of the data analysis, which will last 4-5 months. During this phase, the team will analyze the data on a month-to-month basis, in order to identify, model, and remove systematic errors that span many days or months, including effects resulting from spacecraft anomalies. Phase II will culminate in another meeting of the SAC committee in mid to late August. At that point, the team will begin Phase III of the analysis, during which additional systematic effects will be removed and the results from all four gyros will be combined. This final phase of the data analysis is expected to be completed towards the end of this year.

A preliminary plan was laid out for a much more extended SAC review process in the Dec 2006-Jan 2007 time frame, which would include a careful and critical review of the complete analysis and results. It is expected that other international experts will participate in the review process. There was some discussion in SAC #14 about the optimum and most objective method of incorporating a blind or double-blind test of the final results, including incorporation of the Harvard-Smithsonian Center for Astrophysics/York University measurements of guide star proper motion. Decisions on these and other end-around tests will be developed with NASA and the SAC as the process moves forward.

Throughout phases II and III, members of our team will also be preparing a number of scientific and engineering papers for publication, and we will also be working with NASA in planning a formal public announcement of the results of this unprecedented test of General Relativity. We currently anticipate announcing the results at a special session during the American Physical Society (APS) meeting in April 2007.

Another 13 months! :rolleyes:

Garth

Chronos

Mar5-06, 02:27 AM

Indeed, Garth. Let the data speak for itself. I do not lean either way, and I am certain you feel the same way. It will be difficult to sieve through the data . . . I hope you will be critical of that process.

jgraber

Mar7-06, 04:52 AM

Has anyone done a parameterized post-Newtonian analysis? Can one express the expected results in terms of the usual Eddington alpha, beta gamma and higher order parameters? Any refs?
Best,
Jim

jgraber

Mar7-06, 05:04 AM

Garth

Mar7-06, 08:00 AM

I should have googled first. Apparently it tests gamma and alpha-one ( a non-conservative parameter), according to Will.
No doubt that is why Nordstrom thinks the money has been wasted, as gamma has already been strongly constrained and most people believe in the conservation laws.
Best,
Jim
You'll find quite an exchange on the use of the word(s) "believe" (actually belief) in the dark matter, dark energy & gravity (http://physicsforums.com/showthread.php?t=1128208) thread! :smile:

The fact that other viable alternative gravitational/cosmological theories are also being tested by GP-B, such as SCC (V), makes the enterprise worthwhile.

This is especially so in the light of persistent problems with the standard model, even if we gloss over the fact that the Higgs boson/inflaton, the DM particle and DE have not been identified in the laboratory.

A recent paper examines a link between DM and baryonic matter Cold Dark Matter as Compact Composite Objects (http://arxiv.org/abs/astro-ph/0603064) Some of the observations that may be in conflict with the standard viewpoint are:
• The density profile is too cuspy, [4], [5], [6]. The disagreement of the observations with high resolution simulations is alleviated with time, but some questions still remain [5], [6].
• The number of dwarf galaxies in the Local group is smaller than predicted by CCDM simulations, [4], [5], [6]. This problem is also becoming less dramatic with time [5], [6].
• CCDM simulations produce galaxy disks that are too small and have too little angular momentum, [4], [5], [6];
• There is a close relation between rotation curve shape and light distribution. This implies that there is a close coupling between luminous and dark matter which is difficult to interpret, see e.g. [7];
• There is a correlation in early-type galaxies supporting the hypothesis that there is a connection between the DM content and the evolution of the baryonic component in such systems, see e.g.[8];
• The order parameter (either the central density or the core radius) correlates with the stellar mass in spirals[9]. This suggests the existence of a well-defined scale length in dark matter haloes, linked to the luminous
matter, which is totally unexpected in the framework of CDM theory, but could be a natural consequence of DM and baryon interaction.
• There is a mysterious correlation between visible and DM distributions on log−log scale, which is very difficult to explain within the standard CCDM model [10];
• A recent analysis of the CHANDRA image of the galactic center finds that the intensity of the diffuse X-ray emission significantly exceeds the predictions of a model which includes known Galactic sources [11]. The
spectrum is consistent with hot 8 KeV spatially uniform plasma. The hard X-rays are unlikely to result from undetected point sources, because no known population of stellar objects is numerous enough to account for the observed surface brightness.

It also seems that an Age Problem (http://physicsforums.com/showthread.php?t=94479) is raising its head again as observations of old evolved objects are being made at z > 4.

All the more reason to keep an open mind and continue to confirm our "beliefs" with experimental verification.

We live in interesting times!

Garth

Garth

Mar7-06, 09:26 AM

Has anyone done a parameterized post-Newtonian analysis? Can one express the expected results in terms of the usual Eddington alpha, beta gamma and higher order parameters? Any refs?
Best,
JimTry Will's: The Confrontation between General Relativity and Experiment (http://arxiv.org/abs/gr-qc/0510072) or my: Resolving the Degeneracy: Experimental tests of the New Self Creation Cosmology and a heterodox prediction for Gravity Probe B (http://arxiv.org/pdf/gr-qc/0302026) for an alternative model.

They both use the parameterized post-Newtonian (PPN) analysis.

Garth

Garth

May5-06, 07:05 AM

Halfway through Phase II!

The latest release from the Gravity Probe B (http://einstein.stanford.edu/) website.
GP-B DATA ANALYSIS & RESULTS ANNOUNCEMENT STATUS
During the 50-week science phase of the GP-B mission and the 7-week instrument calibration phase, which lasted from August 2004 - Septermber 2005, we collected over a terabyte of experimental data. Analysis has been progressing through a 3-phase plan, each subsequent phase building on those preceding it.

In Phase I, which lasted from the end of September 2005 through February 2006, the analysis focused on a short term—day-by-day or even orbit-by-orbit—examination of the data. The overall goals of this phase were to optimize the data analysis routines, calibrate out instrumentation effects, and produce initial "gyro spin axis orientation of the day" estimates for each gyro individually. At this stage, the focus was on individual gyro performance; there was no attempt to combine or compare the results of all four gyros, nor was there even an attempt to estimate the gyro drift rates.

We are currently progressing through Phase II of the data analysis process, which began at the beginning of March and is scheduled to run through mid-August 2006. During Phase II, our focus is on understanding and compensating for certain long-term systematic effects in the data that span weeks or months. The primary products of this phase will be monthly spin axis drift estimates for each gyro, as well as refined daily drift estimates. In this phase, the focus remains on individual gyro performance.

In Phase III, which is scheduled to run from late August 2006 through December 2006, data from all four gyros will be integrated over the entire experiment. The results of this phase will be both individual and correlated gyro drift rates covering the entire 50-week experimental period for all four gyros. These results will be relative to the position of our guide star, IM Pegasi, which changed continually throughout the experiment. Thus, the final step in the analysis, currently scheduled to occur in January 2007, will be to combine our gyro drift results with data mapping the proper motion of IM Pegasi relative to the unchanging position of a distant quasar. The proper motion of IM Pegasi has been mapped with unprecedented precision using a technique called Very Long Baseline Interferometry (VLBI) by Irwin Shapiro and his team at the Harvard-Smithsonian Center for Astrophysics (CfA), in collaboration with Norbert Bartel at York University in Toronto and French astronomer Jean-Francois Lestrade.

Playing the role of our own harshest critic, our science team will then perform a careful and thorough final review of the analysis and results, checking and cross-checking each aspect to ensure the soundness of our procedures and the validity of our outcomes. We will then turn the analysis and results over to our GP-B Science Advisory Committee (SAC), that has been closely monitoring our experimental methods, data analysis procedures, and progress for 11 years, to obtain its independent review. In addition, we will seek independent reviews from a number of international experts.

Throughout phases II and III, members of our team will be preparing scientific and engineering papers for publication in late 2006-2007. At the same time, we will be working with NASA to plan a formal public announcement of the results of this unprecedented test of General Relativity. We expect to make this announcement of the results in April 2007.

Less than a year to go and counting!

Garth

CarlB

Jul12-06, 02:09 AM

Thanks for the list of off Broadway gravitation theories. Here's another, alternative theorist with a prediction (0.000):

http://www.mass-metricgravity.net/

By the way, I'm working on a flat space gravitation simulator. My original purpose was to show how standard GR differed from the Cambridge gauge gravity version of GR. The Cambridge guys say that their version works on flat space and test particles therefore cross the event horizon in finite coordinate time. Their website is http://www.mrao.cam.ac.uk/~clifford/ .

For reasons having to do with elementary particles, I find the Cambridge theory convincing, and I thought an animation showing the GR particles getting stuck on the event horizon while the Cambridge particles went on through to the singularity would be convincing.

Now so far I've only got the Newtonian gravity running:
http://www.gaugegravity.com/testapplet/SweetGravity.html
but I should get GR running this weekend, and the Cambridge version (which amounts to allowing a non diagonal metric) soon after.

Where this all gets back to this forum is that I would like to include as many gravity theories as possible, and you've listed quite a few. In order for a theory to be used, I have to be able to write the acceleration in terms of position and velocity.

Carl

rusty

Jul21-06, 11:17 AM

CarlB

Jul22-06, 02:05 AM

Professor Collins,

Please allow me to be the first to welcome you to physics forums. Here are links to your three very fascinating papers on gravitation, in the order I think they should be read:

Changing Mass Corrects Newtonian Gravity
Newton's inverse-square law of universal gravitation assumes constant mass. But mass increases with speed and perhaps with gravity. By SR, mass is increased over the rest mass by gamma. Rest mass is here postulated to increase under gravity, by 1/\alpha =1+GM/rc^2. We examine the consequences of introducing this changing mass into Newton's law in flat spacetime. This variable mass affects the metric, relative to an observer away from the influence of gravity, contracting both lengths and times (as measured) by alpha/gamma. The gravitational force, as in orbital calculations, differs from Newton's law by the factor (\gamma/\alpha)^3, and is not quite inverse square. Without adjustable parameters, this accounts fully for the classical tests of GR. The postulated "fifth force" appears at the 10^-9 g level. Gravitationally-influenced space remains Euclidean, but the mass-metric changes make it seem curved when measured.
http://www.arxiv.org/abs/physics/0012059

SN1a Supernova Red Shifts
http://www.arxiv.org/abs/physics/0101033

The shrinking Hubble constant
http://www.arxiv.org/abs/physics/0601013

By the way, I've just got a first cut of a GR simulating program done. I'm not very sure of it, but it seems like it works okay (but I'm not much of a gravity guy):
http://www.gaugegravity.com/testapplet/SweetGravity.html

I've set the initial conditions to illustrate a fairly extreme case of precession. When I get this program running satisfactorily, I will include your equation of motion. I can hardly wait, but ethanol is keeping me busy right now.

Carl

Garth

Jul24-06, 12:39 PM

Mass-metric relativity is a scalar theory of gravity, and is based on the increase of mass with speed and with gravitational potential. Its predictions for the gpb are: geodetic rate -6.56124 arcsec/yr. Note the sign, indicating that the precession is backward instead of forward as in GR. Lense-Thirring rate -.01924 arcsec/yr. Actually, the Lense-Thirring rate is zero but a geodetic perturbation caused by the yearly orbit of earth about the sun induces a geodetic precession in the opposite direction. Let the experiment decide. A basic paper on mass-metric relativity is the lasl arXiv 0012059 paper, by R.L. Collins.

R.L. Collins
Thank you rusty, the line up is now:

Note:
1. The first effect being tested is (for the GP-B polar orbit) a N-S geodetic precession, caused by the amount a gyro 'leans' over into the slope of curved space.

2. The second effect being tested is the E-W frame-dragging, Lense-Thirring, or gravitomagnetic effect, caused by the spinning Earth dragging space-time around with it.

Einstein's General Relativity(GR)
Barber's Self Creation Cosmology).(SCC),
Moffat's Nonsymmetric Gravitational Theory (NGT),
Hai-Long Zhao's mass variance SR theory (MVSR),
Stanley Robertson's Newtonian Gravity theory (NG), and
Junhao & Xiang's Flat space-time theory (FST).
R. L. Collin's Mass-metric relativity (MMR)

The predictions are:

1. GPB Geodetic precession
GR = 6.6144 arcsec/yr
SCC = 4.4096 arcsec/yr
NGT = 6.6144 - a small \sigma correction arcsec/yr
MVSR = 6.6144 arcsec/yr
NG = 1.6536 arcsec/yr
FST = 4.4096 arcsec/yr
MMR = -6.56124 arcsec/yr

2. GPB gravitomagnetic frame dragging precession
GR = 0.0409 arcsec/yr
SCC = 0.0409 arcsec/yr
NGT = 0.0409 arcsec/yr
MVSR = 0.0102 arcsec/yr
NG = 0.0102 arcsec/yr
FST = 0.0000 arcsec/yr
MMR = -0.01924 arcsec/yr

Garth

Garth

Jul24-06, 12:59 PM

Garth

Sep15-06, 04:57 PM

Now into Phase III of the data analysis of Gravity Probe B (http://einstein.stanford.edu/).We are now beginning Phase III—the final phase-of the data analysis—which will last until January-February, 2007. Whereas in Phases I and II the focus was on individual gyro performance, during Phase III, the data from all four gyros will be integrated over the entire experiment. The results of this phase will be both individual and correlated changes in gyro spin axis orientation covering the entire 50-week experimental period for all four gyros. These results will be relative to the position of our guide star, IM Pegasi, which changed continually throughout the experiment. Thus, the final step in the analysis, currently scheduled to occur early in the spring of 2007, will be to combine our gyro spin axis orientation results with data mapping the proper motion of IM Pegasi relative to the unchanging position of a distant quasar. The proper motion of IM Pegasi has been mapped with unprecedented precision using a technique called Very Long Baseline Interferometry (VLBI) by Irwin Shapiro and his team at the Harvard-Smithsonian Center for Astrophysics (CfA), in collaboration with Norbert Bartel at York University in Toronto and French astronomer Jean-Francois Lestrade.

At the end of Phase III, playing the role of our own harshest critic, our science team will then perform a careful and thorough final review of the analysis and results, checking and cross-checking each aspect to ensure the soundness of our procedures and the validity of our outcomes. We will then turn the analysis and results over to the SAC, which has been closely monitoring our experimental methods, data analysis procedures, and progress for 11 years, to obtain its independent review. Moreover, we will seek independent reviews from a number of international experts.

In addition to analyzing the data, members of our team are now in the process of preparing scientific and engineering papers for publication in late 2006-2007. We have also begun discussions with NASA to plan a formal public announcement of the results of this unprecedented test of General Relativity. We expect to make this announcement of the results in April 2007.

Still April 2007, and counting!

Garth

Garth

Sep20-06, 12:27 PM

While we are waiting you may be interested in Francis Everitt's lecture:Testing Einstein in Space: The Gravity Probe B Mission (http://einstein.stanford.edu/highlights/Everitt_Lecture-051806.pdf) dated 18 May 2006.

Garth

Garth

Dec23-06, 05:06 AM

Gravity Probe B Update -- December 22, 2006
==============
GP-B MISSION NEWS
==============

A recent story about GP-B in Nature
=========================
The December 21-28 2006 issue of Nature (v. 444, p. 978-979) contains a short news article stating that Nature has learned that "two unanticipated effects are clouding the [GP-B] team's frame-dragging results" and also that "results were expected by last summer but the announcement never came."

The two issues referred to in Nature have been regularly reported to NASA and our GP-B Science Advisory Committee (SAC) and publicly via these status updates. They are: 1) The effect of polhode motion of the gyros on readout calibration (see the polhode story in last month's update, http://einstein.stanford.edu/highlights/hl_polhode_story.html) and 2) misalignment torques observed and calibrated during the post-science instrument calibration phase in August-September 2005 (see the four weekly updates of September 2005, http://einstein.stanford.edu/highlights/hlindexmain.html.

In August 2005, a three-phase data analysis plan was devised in order to properly handle these and other issues. As first reported in May 2006, our intent--reached in agreement with NASA--has been to make the first science announcement in April 2007. This is still our plan.

If you want to know more about the Polhode motion see Polhode Behavior in GP-B’s Gyros (http://einstein.stanford.edu/highlights/hl_polhode_story.html)

Roll on April! :smile:

Garth

notknowing

Dec31-06, 03:58 AM

Garth

Dec31-06, 05:35 AM

What is actually the main motivation for inventing alternative theories to GR ?
What are their main "advantages" ?
First to 'push the envelope', the concept of scientific truth is that it is a process, one never should believe that the 'final truth' has been found but that the present best theories are always open to experimental testing and theoretical questioning.

Viable alternative theories are important to test the standard theory against, partly to justify and motivate such difficult experiments as Gravity Probe B.

As I said in your quote "Some researchers, such as Kenneth Nordtvedt, have said that the experiment was worth doing when it was first proposed but that now GR has been verified beyond reasonable doubt the result of GP-B is a foregone conclusion." The existence of these other theories argues for a more positive attitude to the experiment.

There are always questions to be asked of the standard theory that other approaches seek to answer. The main questions about the standard \LambdaCDM model IMHO are its necessity to invoke Inflation, exotic non-baryonic DM and DE, while the Higgs Boson/Inflaton the DM particle(s) and DE have not been discovered in laboratory experiments. The existence of the PA and other anomalies are also intriguing.

Different alternative theories have different advantages, but to be viable contenders they must not only predict accurately the outcomes of all the experiments and observations predicted by the standard theory but also have a greater explanatory power by doing so more simply.

Garth

henryco

Jan8-07, 06:16 AM

Dear all,

Just to mention that there is another alternative theory of gravity (mine: gr-qc/0610079) with predictions different from the ones that you have listed.
This is a DArk Gravity theory:

DG predicts:

1) The same geodetic effect as in GR
2) No frame dragging
3) A small (but hopefully within the GP-B accuracy) angular deviation during the year but with a one year period (related to the the speed of earth about the sun).

regards,

F H-C

Garth

Jan8-07, 11:24 AM

Thank you Frederic henryco and welcome to these Forums! Join the club of those waiting for the GP-B results!

Has your Dark Gravity theory been published in a recognised peer reviewed journal? If so we could discuss it in a separate thread, if not you may want to submit it to the Independent Research (http://www.physicsforums.com/forumdisplay.php?s=&daysprune=&f=146) Forum for discussion, but read the "Rules for submission" first!

We now have a line up of eight theories competing in the Gravity Probe B stakes, which are:

Einstein's General Relativity(GR)
Barber's Self Creation Cosmology (http://arxiv.org/abs/gr-qc/0302026) (SCC),
Moffat's Nonsymmetric Gravitational Theory (http://arxiv.org/abs/gr-qc/0405091) (NGT),
Hai-Long Zhao's Mass Variance SR Theory (http://uk.arxiv.org/abs/gr-qc/0512088) (MVSR),
Stanley Robertson's Newtonian Gravity Theory (http://arxiv.org/abs/gr-qc/0502088) (NG), and
Junhao & Xiang's Flat Space-Time Theory (http://arxiv.org/abs/physics/0101017) (FST).
R. L. Collin's Mass-Metric Relativity (http://www.arxiv.org/abs/physics/0012059) (MMR) and
F. Henry-Couannier's Dark Gravity Theory (http://www.arxiv.org/abs/gr-qc/0610079) (DG).

The predictions are:

1. GPB Geodetic precession (North-South)
GR = 6.6144 arcsec/yr
SCC = 4.4096 arcsec/yr
NGT = 6.6144 - a small \sigma correction arcsec/yr
MVSR = 6.6144 arcsec/yr
NG = 1.6536 arcsec/yr
FST = 4.4096 arcsec/yr
MMR = -6.56124 arcsec/yr
DG = 6.6144 arcsec/yr

2. GPB gravitomagnetic frame dragging precession (East-West)
GR = 0.0409 arcsec/yr
SCC = 0.0409 arcsec/yr
NGT = 0.0409 arcsec/yr
MVSR = 0.0102 arcsec/yr
NG = 0.0102 arcsec/yr
FST = 0.0000 arcsec/yr
MMR = -0.01924 arcsec/yr
DG = 0.0000 arcsec/yr

There is the question of whether these alternative theories pass all the other tests of GR as detailed in Clifford Will's paper The Confrontation between General Relativity and Experiment (http://arxiv.org/abs/gr-qc/0510072).

Three months to go, whatever those results may be!

Garth

Polestar101

Jan31-07, 01:06 AM

Hi Garth – New here to the forum but saw your posts and thought I would mention a potential discovery resulting from the GP-B experiment. Please add it to your list.

No, I do not have an alternative gravity theory but I do question the current model of precession and I believe GP-B (with its perfect gyros far above the wobbling earth) is in an ideal position to determine if the precession of the equinox observable (a change in earth orientation of about 50”p/y) is due to the torque of lunisolar forces acting on the oblate earth (current theory) or the observable of a solar system in motion (binary theory of precession). If I guess right, the spacecraft will mimic the precession observable even though it is floating free high above a wobbling earth. This is because we believe the precession observable is due to the motion of the sun and solar system curving through space.

I met with the GP-B team at Stanford a few months ago and they listened and were open minded about the possibility that our sun may have an unknown companion star (which is the theoretical cause of the solar system curving through space at 50”p/y). We discussed the polhode issue and they implied they were getting more signals than originally anticipated and it was a big task to try and separate all of the signals into identifiable buckets. But they were careful to keep the integrity of the experiment and remind me that they could not release results until the public announcement. Nonetheless, we spent a fair amount of time discussing companion star scenarios, which I found interesting.

Bottomline, I think they will either report that it will take more time than expected to sift and interpret all the signals, and or, that our solar system is curving through space at a rate that exceeds the expected results from the relativity experiment. I have posted a model (of the results I expect them to find) on my website at the Binary Research Institute:

http://www.binaryresearchinstitute.org/findingit/gravprobeb.shtml

Regardless of the results of the initial GP-B report I think NASA and Stanford are providing almost priceless research. The raw data should prove to be fundamentally helpful to scientists for years to come as we probe the motions of the earth and solar system on our journey through space. Bravo to Dr. Everitt and team!

CarlB

Jan31-07, 02:00 AM

Polestar 101, I loved your website. What I would like to see is more detailed explanation of why the usual calculations are incorrect.

Polestar101

Jan31-07, 02:27 AM

Carl - Your point is well taken. While I do not have any good theory as to why the current model fails we do have pretty good observable evidence that the earth hardly wobbles at all relative to local objects within the solar system. In other words, our best calculations are that we see about 4"p/y of precession relative to the Moon, Venus and the Persieds (which we are using as local markers) while at the same time we can observe a full 50"p/y of re-orientation relative to the fixed stars and quasars far outside the SS. This tells me there must be a logical explanation to allow the two simultaneous observables but we have not focused on flaws with the current local dynamics model - as of yet.

One simple guess is the Moon tugs on the earth and this is responsible for the nutation observable (the 18 year Saros cycle signature reflects the known motions of the Moon). But the much longer precessional cycle (which is slowly speeding up) does not reflect any known motion of the Moon. Perhaps the unaccounted for dynamic is the SS motion through space (possibly offsetting the tendency towards local precession). Anyway, there are a lot of issues. We hope to address some of them in a new paper once we have access to the GPB public data.

Until then...you take a crack at it, and if it stands the test of time, I will nominate you for the Galileo Award.

Walter

Garth

Jan31-07, 02:58 AM

Polestar welcome to these Forums and welcome to this thread!

What I do not understand about your theory is the 26,000 year precession has been well known since the Ancient Greeks and caused by the Moon & Sun's attraction on the Earth's equatorial bulge, causing a well understood gyroscopic motion. This is a precession of ~50"/yr.

I cannot believe that the analysis by Newcombe at end of the 19th Century and then Lieske with satellite technology in the 1970's is all totally erroneous.

Are you saying that there is another precession of ~ 50"/yr that has not been modelled? In which case why has it not already been observed by stellar observations?

If the Sun and its retinue were in orbit with a companion star with period 25,800 years the companion star would have been discovered by now. In the 1980's I did some work on 'Nemesis', the possible cause of perturbations of the Oort cloud and a possible ~32Myr periodicity of mass extinctions on Earth. That would have had an orbital period of ~32Myr (SMA ~ 105 AU), and the conclusion was it should have already been seen either optically or in the IRAS data (if a brown dwarf).

I notice on your website that you link to several of your papers, but I do not find any references to them being published in peer reviewed journals. In which case such discussion is not appropriate here. You may wish to submit your ideas to the Independent Research (http://www.physicsforums.com/forumdisplay.php?f=146) Forum after first reading their submission rules.

Garth

Polestar101

Jan31-07, 04:24 PM

Hi Garth – It is not really my theory as others have mentioned it for years. And you’re right the precession of the equinox has been observed for thousands of years, and yes, that is the ~50”p/y observable we are discussing.

It has long been assumed to be the result of strictly local forces acting upon the oblate earth producing a gyroscopic motion. Traditionally, it has been measured (by VLBI and others) relative to very distant reference points (stars or quasars far outside the SS) because distant points obviously move less than local points. However, in recent studies of the motion of the equinox relative to objects within the SS it turns out the earth wobbles very little compared to local points of reference (like the Moon). At BRI we have been working to better understand this seeming paradox: an earth that wobbles ~ 4”p/y relative to objects “inside the SS”, while at the same time showing ~ 50”p/y relative to objects “outside the SS”.

One possibility is that part of the total observable, that we have attributed to local forces, might actually be due to the geometric effect of the SS's angular motion through space. This of course brings up the question of what it could be moving around, and hence several astronomers are examining companion star scenarios. As you aptly noted, one of those is a brown dwarf concept, like Nemesis, but there are other Newtonian scenarios that run from blackholes to unknown planet like masses, as well as non-Newtonian scenarios such as MOND, that would raise the far out possibility that it could even be a nearby visible star. Please understand I am not advocating any particular solution on this board, I am just trying to obtain more data at this time to better understand the precession observable.

Can hardly wait until the GPB data is released - so please keep us posted!

Walter

Garth

Jan31-07, 06:35 PM

Walter, what prediction of the East-West and North-South precessions does this theory make?

I still find it difficult to believe that a substantial object with SMA ~ 877 AU would not have already been discovered.

And yes I agree that Francis Everitt and team are doing a marvellous job and roll on April 14th!

Garth

Polestar101

Feb2-07, 01:04 AM

Garth - No prediction as I do not believe SS motion would affect the GR part of the experiment. It is my understanding that just as the GPB team has to remove the effect of the motion of the spacecraft around the earth (~5"), and remove the effect of the motion of the earth around the sun (~20"), so too would they need to remove any signal from the motion of the solar system curving through local space as all of these affect the abberation of light relative to the guidestar. For a graphic see:

http://www.binaryresearchinstitute.org/findingit/gravprobeb.shtml

Your calculation sounds about right for a brown dwarf scenario. And I agree it is doubtful that we would not have seen that type of object by now. Consequetly, if SS motion is confirmed in the ~ 50"p/y range, as the precession data leads me to believe, and we do not find anything in the 500-1000AU range, we need to condsider more exotic scenarios.

Mid April is probably optomistic. My guess is that due to the sheer volume of data (including possible unexpected signals) and the need to better understand and crunch that data, the GPB team will likely need more time. With an experiment this profound we should probably expect the unexpected.

Walter

Garth

Feb10-07, 02:51 AM

Latest news on the publication of GP-B (http://einstein.stanford.edu/) results:Now that the gyro polhode behavior is well understood, we have been able to shift our focus to identifying and addressing some subtle systematic sources of noise and interference that are buried in the data, along with the relativity signals. Identifying and removing as many of these subtle systematic effects as possible is critically important for reducing the margin of error in our final results—especially the frame-dragging result. While we have been making steady progress in these efforts, it has proven to be a slow and painstaking process, and it is now apparent that several more months of data analysis will be required to achieve the lowest possible margin of error.

At the SAC meeting #15 last September, committee members anticipated this situation and recommended that we ask NASA to create a contingency plan, and budget for an extension of the data analysis phase for several months past our scheduled results announcement at the American Physical Society (APS) meeting on 14-17 April 2007 in Jacksonville, FL. To this end, following a meeting with NASA in mid January, NASA has requested a proposal for extending the GP-B data analysis phase through December 2007, and this is in progress.

Consequently, we are now planning a two-phase announcement of the GP-B results. Our first announcement will be made at the April APS meeting, as planned for some time now. (For more information about our presentations at this meeting, see this month's GP-B Mission News story below.) In conjunction with this announcement, NASA is planning a press/media event at NASA Headquarters in Washington DC just prior to the APS meeting. The experimental results in this first announcement will have been presented to and vetted by our Science Advisory Committee during SAC meeting #16, which is scheduled for 23-24 March 2007. These will be preliminary results, representing the lowest margin of error obtainable by that date.

Concurrent with this preliminary results announcement in April, we will be releasing an initial science data set to the National Space Sciences Data Center (NSSDC) at Goddard Space Flight Center in Greenbelt, MD. The remainder of our science data, along with a complete archive of GP-B documents, images, video, and related program information will be released to the NSSDC by the end of May. All GP-B data and information archived at the NSSDC will be publicly available.

Following the APS meeting, our science team is planning to spend several more months removing further systematic sources of noise and interference, with the goal of reducing the margin of error in the result to the lowest possible level. These results will still be relative to the position of our guide star, IM Pegasi, which changed continually throughout the experiment. This proper motion of the guide star has been measured on our behalf by the Harvard-Smithsonian Center for Astrophysics (CfA). Thus, the final step in the analysis will be to combine our gyro spin axis orientation results with data mapping the proper motion of IM Pegasi relative to the unchanging position of a distant quasar.

In late fall, 2007, playing the role of our own harshest critic, our science team will perform a careful and thorough final review of the analysis and results, checking and cross-checking each aspect to ensure the soundness of our procedures and the validity of our outcomes. We will then convene a final SAC meeting to obtain the committee's independent review of the final results. Moreover, we will seek independent reviews from a number of international experts.

We intend to announce the final experimental results of GP-B through a NASA press/media event towards the end of 2007. At that time it is also our intention to have submitted a number of papers on the GP-B results for publication in peer-reviewed scientific and technical journals.(emphasis mine)
I knew it! :rolleyes:

The April APS meeting:GP-B will have a strong presence at the American Physical Society (APS) meeting in Jacksonville, Florida, on 14-17 April 2007. During this meeting, we will emphasize three main themes:

* Successful completion of most challenging space-based experiment in NASA's history
* First scientific results from this historic mission
* Public release of Level2 science data (via NSSDC)

Four members of the GP-B team have been invited to speak at the APS meeting, beginning on Saturday morning, April 14th, with GP-B Principal Investigator, Francis Everitt, giving the plenary conference talk, entitled First Results from Gravity Probe B.

In addition, on Saturday afternoon, two papers related to GP-B will be delivered in Session C12: Experimental Tests of Gravity.

* C12.00004: " Lessons Learned from Gravity Probe B for STEP, LISA and other experiments" by GP-B team members Paul Worden and Sasha Buchman
* C12.00005: "Proper Motion of the GP-B Guide Star" by the Harvard-Smithsonian Center for Astrophysics Gp-B guide star tracking team: Irwin Shapiro, Daniel Lebach, Michael Ratner, Norbert Bartel, Ryan Ransom, Michael Bietenholz, Jerusha Lederman, and Jean-Francois Lestrade

On Sunday morning, April 15th, three members of the GP-B team have been invited to give special talks on three aspects of the GP-B program:

* H7.00001: "The Gravity Probe B Science Instrument," by GP-B Co-Principal Investigator, John Turneaure
* H7.00002: "The Development Challenges of Gravity Probe-B—an ongoing partnership between Physics and Engineering" by GP-B Co-Prinipal Investigator, Bradford Parkinson
* H7.00003: "Gravity Probe B Data Analysis Challenges, Insights, and Results" by GP-B Co-Investigator and Chief Scientist, George (Mac) Keiser

Finally, on Sunday afternoon, April 15th, a large part of the GP-B team and associated scientists and engineers will present 22 poster sessions on a host of scientific and technology topics, as listed below.

Session L1: Poster Session II L1.00011: GRAVITATION

* L1.00012: "Radio Imaging of the Gravity Probe B Guide Star IM Pegasi" by Michael Bietenholz, Ryan Ransom, Norbert Bartel, Daniel Lebach, Michael Ratner, Irwin Shapiro, Jean-Francois Lestrade
* L1.00013: "The 'Core' of the Quasar 3C454.3 as the Extragalactic Reference for the Proper Motion of the Gravity Probe B Guide Star" by Norbert Bartel, Ryan Ransom, Michael Bietenholz, Jerusha Lederman, Daniel Lebach, Michael Ratner, Irwin Shapiro, Leonid Petrov
* L1.00014: "Performance of the Gravity Probe B Inertial Reference Telescope" by Suwen Wang, John Goebel, John Lipa John Turneaure
* L1.00015: "Gravity Probe B Timing System and Roll Phase Determination" by Jie Li , Jeffery Kolodziejczak
* L1.00016: "The Gravity Probe B SQUID Readout Detector" by Barry Muhlfelder, Bruce Clarke, Gregory Gutt, James Lockhart, Ming Luo
* L1.00017: "SQUID Control, Temperature Regulation, and Signal Processing Electronics for Gravity Probe B" by James Lockhart, Barry Muhlfelder, Jie Li, Bruce Clarke, Terry McGinnis, Peter Boretsky, Gregory Gutt
* L1.00018: "Gravity Probe B Science Instrument Assembly (SIA)" by Saps Buchman, Barry Muhlfelder, John Turneaure
* L1.00019: "Polhode Motion of the Gravity Probe-B Gyroscopes" by Michael Dolphin, Alex Silbergleit, Michael Salomon, Paul Worden, Daniel DeBra
* L1.00020: "Evidence for Patch Effect Forces on the Gravity Probe B Gyroscopes" by Dale Gill, Saps Buchman
* L1.00021: "Gravity Probe B Orbit Determination" by Paul Shestople , Huntington Small
* L1.00022: "Simulator Technology of the Gravity Probe-B Mission" by David Hipkins , Robert Brumley , Yoshimi Ohshima , Thomas Holmes
* L1.00023: "Achievement of the Magnetic Environment Requirements for Gravity Probe B" by John Mester, James Lockhart, Michael Taber
* L1.00024: "The Gravity Probe B Gyroscopes" by Saps Buchman, Bruce Clarke, Mac Keiser, Dale Gill, Frane Marcelja, Robert Brumley
* L1.00025: "Gravity Probe B Gyroscope Electrostatic Suspension System (GSS)" by William Bencze, David Hipkins, Tom Holmes, Saps Buchman, Robert Brumley
* L1.00026: "The Gravity Probe B Relativity Mission (GP-B)" by C.W. Francis Everitt
* L1.00027: "Gravity Probe B Experiment Error" by Barry Muhlfelder, G. Mac Keiser, John Turneaure
* L1.00028: "Gravity Probe B Science Data Analysis: Filtering Strategy" by Michael Heifetz, Thomas Holmes, David Hipkins, Alex Silbergleit, Vladimir Solomonik
* L1.00029: "Performance of the Gravity Probe B Cryogenic Sub-System" by Michael Taber, David Murray
* L1.00030: "The Gravity Probe B Drag-free and Attitude Control System" by Michael Adams, Daniel DeBra
* L1.00031: "Features of the Gravity Probe B Space Vehicle" by William Reeve, Gaylord Green
* L1.00032: "Classical Torques on Gravity Probe B Gyroscopes" by Alex Silbergleit, G. Mac Keiser, Yoshimi Ohshima
* L1.00033: "Trapped Flux Mapping for the Gravity Probe B Gyroscopes" by Michael Salomon, John Conklin, Michael Dolphin, G. Mac Keiser, Alex Silbergleit, Paul Worden

Patiently waiting!

Garth

MeJennifer

Feb10-07, 03:06 AM

Patiently waiting!
Agreed!

And it is to be hoped that we won't find 50 years from now that "the reduction of the margin of error" was done with the same kind of "enthusiasm" as Eddington did in 1919.

Polestar101

Feb10-07, 03:35 AM

Garth

Feb10-07, 08:25 AM

Well that prediction did't take long to come true!Too true!

However I take their statement above: The experimental results in this first announcement will have been presented to and vetted by our Science Advisory Committee during SAC meeting #16, which is scheduled for 23-24 March 2007. These will be preliminary results, representing the lowest margin of error obtainable by that date.to mean that they will be publishing the gross geodetic N-S and gravitomagnetic E-W precessions at the April meeting. It seems that we will have to wait until the end of 2007 for the high precession measurements.Here is another: At least one of their unexpected signals (that they have to seperate out) is magnitudes larger than the GR effects they are looking for.Will not the ~50"/yr proper motion caused by the Earth's 26,000 year period precession show up in the tracking of the guide star, and will be well modelled, rather than in the movement of the satellite borne gyroscopes?

Garth

henryco

Feb12-07, 08:05 AM

Well that prediction did't take long to come true! Here is another: At least one of their unexpected signals (that they have to seperate out) is magnitudes larger than the GR effects they are looking for.

Walter

Dear polestar101,

I have just read your email (i had forgotten to check this extra email box all
these days). Your idea looks very interesting also from the point of view of the
expectations in the framework of my dark gravity theory. Indeed, in this theory
i assumed my preferred frame to be the sun frame and then i got an anomalous
angle deviation related to the motion of earth (and GP-B) around the sun.
But if the preferred frame is defined by a larger group of stars, then the
effect should be much larger and may be, as you say, related to the equinoxe
precession. All this is very exciting. I will try to attend the april meeting
where the first announcement of GP-B results is expected.

Unfortunately i cannot access the URL you give. I'm also convinced that the GP-B
results will be a major breakthrough in our understanding of gravity.
Could you please let me know why i'm not able to access your website...may be
its secured isn't it.

best regards

F Henry-couannier

Garth

Feb15-07, 03:02 PM

I'm also convinced that the GP-B
results will be a major breakthrough in our understanding of gravity.

They certainly seem to be making a meal over producing the results! :wink:

Garth

Polestar101

Feb15-07, 06:45 PM

Too true!

Will not the ~50"/yr proper motion caused by the Earth's 26,000 year period precession show up in the tracking of the guide star, and will be well modelled, rather than in the movement of the satellite borne gyroscopes?

Garth

Hi Garth - Since the spacecraft is floating free above the so called wobbling earth it should NOT mimic the earth's general precession. However, if the cause of this precession observable is actually and mainly due to the solar systems motion through space in a binary frame (as we suspect), then this motion (relative to the guidestar) should be detectable.

Just as GPB will pick up the 5"+ per orbit signal as an aberration of light between the spacecraft and the guidestar, and just as they pick up the 20"+ p/y signal due to the earth's orbit around the sun, so too should they pick up a nearly 50"p/y signal if we are correct the precession observable is mainly the geometric effect of a solar system in motion.

My concern is what that signal looks like in the data. The spacecrafts orbital motion has a waveform in synch with the spacecrafts orbit periodicity, which will show many waves during the experiment period, so this known signal will be easy to spot. The orbit of the earth around the sun should also be clear since it is a known motion and the experiment period allows time for both an ascending and descending phase. However, the binary motion (if it exists) would only reveal about 1/26,000ths of its waveform during the experiment period. Since it is completely unexpected, and no one is looking for it, it might just be attributed to anomalous drift or assumed to be part of the pollhode motion?? I just don'y know. Fortunately, the controls on this experiment are so tight and the people involved so professional I am encouraged they will take all precautions to carefully identify every signal before announcing the final GR results.

Time will tell.

Walter Cruttenden

Garth

Feb16-07, 07:01 PM

Well Walter, as I said, I find it hard to believe that:
1. The Moon does not induce the observed 26,000 yr period precession on the Earth as all the models of the geoid predict and,
2. There is an unobserved ~ stellar mass object, which is a binary companion to the Sun with a SMA of ~ 877AU that is responsible for the said observed precession.

On the other hand the Abstract for Francis Everitt's paper (http://absimage.aps.org/image/MWS_APR07-2007-000261.pdf) to be given at the APS Jacksonville conference in April reads.The NASA Gravity Probe B (GP-B) orbiting gyroscope test of General Relativity, launched from Vandenberg Air Force Base on 20 April, 2004, tests two consequences of Einstein's theory: 1) the predicted 6.6 arc-s/year geodetic effect due to the motion of the gyroscope through the curved space-time around the Earth; 2) the predicted 0.041 arc-s/year frame-dragging e®ect due to the rotating Earth.
The mission has required the development of cryogenic gyroscopes with drift-rates 7 orders of magnitude better than the best inertial navigation gyroscopes. These and other essential technologies, for an instrument which once launched must work perfectly, have come into being as the result of an intensive collaboration between Stanford physicists and engineers, NASA and industry. GP-B entered its science phase on August 27, 2004 and completed data collection on September 29, 2005. Analysis of the data has been in continuing progress during and since the mission. This paper will describe the main features and challenges of the experiment and announce the first results.

Let's hope those first results will be able to resolve the gross different predictions of the competing theories mentioned in this thread:

Einstein's General Relativity(GR)
Barber's Self Creation Cosmology (http://arxiv.org/abs/gr-qc/0302026) (SCC),
Moffat's Nonsymmetric Gravitational Theory (http://arxiv.org/abs/gr-qc/0405091) (NGT),
Hai-Long Zhao's Mass Variance SR Theory (http://uk.arxiv.org/abs/gr-qc/0512088) (MVSR),
Stanley Robertson's Newtonian Gravity Theory (http://arxiv.org/abs/gr-qc/0502088) (NG),
Junhao & Xiang's Flat Space-Time Theory (http://arxiv.org/abs/physics/0101017) (FST).
R. L. Collin's Mass-Metric Relativity (http://www.arxiv.org/abs/physics/0012059) (MMR) and
F. Henry-Couannier's Dark Gravity Theory (http://www.arxiv.org/abs/gr-qc/0610079) (DG).

The predictions are:

1. GPB Geodetic precession (North-South)
GR = 6.6144 arcsec/yr
SCC = 4.4096 arcsec/yr
NGT = 6.6144 - a small \sigma correction arcsec/yr
MVSR = 6.6144 arcsec/yr
NG = 1.6536 arcsec/yr
FST = 4.4096 arcsec/yr
MMR = -6.56124 arcsec/yr
DG = 6.6144 arcsec/yr

2. GPB gravitomagnetic frame dragging precession (East-West)
GR = 0.0409 arcsec/yr
SCC = 0.0409 arcsec/yr
NGT = 0.0409 arcsec/yr
MVSR = 0.0102 arcsec/yr
NG = 0.0102 arcsec/yr
FST = 0.0000 arcsec/yr
MMR = -0.01924 arcsec/yr
DG = 0.0000 arcsec/yr

But first, as I said, these alternative theories have to also pass all the other tests of GR as detailed in Clifford Will's paper The Confrontation between General Relativity and Experiment (http://arxiv.org/abs/gr-qc/0510072).

Garth

henryco

Feb21-07, 11:19 PM

Well Walter, as I said, I find it hard to believe that:
1. The Moon does not induce the observed 26,000 yr period precession on the Earth as all the models of the geoid predict and,
2. There is an unobserved ~ stellar mass object, which is a binary companion to the Sun with a SMA of ~ 877AU that is responsible for the said observed precession.

On the other hand the Abstract for Francis Everitt's paper (http://absimage.aps.org/image/MWS_APR07-2007-000261.pdf) to be given at the APS Jacksonville conference in April reads.

Let's hope those first results will be able to resolve the gross different predictions of the competing theories mentioned in this thread:

Einstein's General Relativity(GR)
Barber's Self Creation Cosmology (http://arxiv.org/abs/gr-qc/0302026) (SCC),
Moffat's Nonsymmetric Gravitational Theory (http://arxiv.org/abs/gr-qc/0405091) (NGT),
Hai-Long Zhao's Mass Variance SR Theory (http://uk.arxiv.org/abs/gr-qc/0512088) (MVSR),
Stanley Robertson's Newtonian Gravity Theory (http://arxiv.org/abs/gr-qc/0502088) (NG),
Junhao & Xiang's Flat Space-Time Theory (http://arxiv.org/abs/physics/0101017) (FST).
R. L. Collin's Mass-Metric Relativity (http://www.arxiv.org/abs/physics/0012059) (MMR) and
F. Henry-Couannier's Dark Gravity Theory (http://www.arxiv.org/abs/gr-qc/0610079) (DG).

The predictions are:

1. GPB Geodetic precession (North-South)
GR = 6.6144 arcsec/yr
SCC = 4.4096 arcsec/yr
NGT = 6.6144 - a small \sigma correction arcsec/yr
MVSR = 6.6144 arcsec/yr
NG = 1.6536 arcsec/yr
FST = 4.4096 arcsec/yr
MMR = -6.56124 arcsec/yr
DG = 6.6144 arcsec/yr

2. GPB gravitomagnetic frame dragging precession (East-West)
GR = 0.0409 arcsec/yr
SCC = 0.0409 arcsec/yr
NGT = 0.0409 arcsec/yr
MVSR = 0.0102 arcsec/yr
NG = 0.0102 arcsec/yr
FST = 0.0000 arcsec/yr
MMR = -0.01924 arcsec/yr
DG = 0.0000 arcsec/yr

But first, as I said, these alternative theories have to also pass all the other tests of GR as detailed in Clifford Will's paper The Confrontation between General Relativity and Experiment (http://arxiv.org/abs/gr-qc/0510072).

Garth

Hello,

Please also notice that DG predicts a small preferred frame effect to be seen by GP-B. It's a one year periodicity angular deviation with amplitude 0.005 arcsec...at the limit of GP-B sensitivity but i hope still detectable...and i thinck this is the "subtle effect " they need 10 more months to understand.

PLease have a look at gr-qc/0702028 the latest paper by Turyshev, Nordtvedt and co regarding gravitomagnetism and Lunar Laser Ranging.
It says something incredible! :surprised It says that the frame-dragging is seen in the frame of the observer (earth frame) where there should be nothing at all since in this frame the speed of the earth vanishes...but they keep using there (badly incorrect) the gravitomagnetic field formula of the sun rest frame. Crazy isn't it? PLease check this and tell me if i'm wrong!

Best regards

Fred

Garth

Feb22-07, 02:29 AM

Hello,

Please also notice that DG predicts a small preferred frame effect to be seen by GP-B. It's a one year periodicity angular deviation with amplitude 0.005 arcsec...at the limit of GP-B sensitivity but i hope still detectable...and i thinck this is the "subtle effect " they need 10 more months to understand.

PLease have a look at gr-qc/0702028 the latest paper by Turyshev, Nordtvedt and co regarding gravitomagnetism and Lunar Laser Ranging.
It says something incredible! :surprised It says that the frame-dragging is seen in the frame of the observer (earth frame) where there should be nothing at all since in this frame the speed of the earth vanishes...but they keep using there (badly incorrect) the gravitomagnetic field formula of the sun rest frame. Crazy isn't it? PLease check this and tell me if i'm wrong!

Best regards

Fred
Hi Fred,

Obviously the DG prediction of zero frame-dragging precession should be a much more obvious anomaly than its predicted subtle 0.005" effect.

As far as gr-qc/0702028 is concerned, is not the frame-dragging effect on the Moon's orbit caused by the spinning Earth, not the moving Earth? Therefore should it not be effective in the inertial Earth's frame of reference?

(There is a much more subtle effect of the Earth's rotation about the Sun in the Sun's rest frame.)

Actually analysis of the Moon's orbit is very theory dependent, needing a theory of tides etc., therefore I wouldn't place too much reliance on its conclusions.

Garth

henryco

Feb22-07, 05:14 AM

Hi Fred,

Obviously the DG prediction of zero frame-dragging precession should be a much more obvious anomaly than its predicted subtle 0.005" effect.

Sure! but the small effect would be an additional signature allowing to locate the preferred frame .

As far as gr-qc/0702028 is concerned, is not the frame-dragging effect on the Moon's orbit caused by the spinning Earth, not the moving Earth? Therefore should it not be effective in the inertial Earth's frame of reference?

Not at all the spinning earth, but the moving earth!
Actually, it is true that the first part of the paper deals with the effect of the spinning earth on a rotating body...and this is applied to GP-B just to show us that the formula applied there is the same that will be applied later on the moon orbit analysis. (They never claimed having seen the frame dragging due to the rotation of the earth on the moon orbit, only the geodetic effect, which actually should not be considered a gravitomagnetic effect, and is not the subject of this paper.)

But look at equation 17 : V is the earth speed about the sun: The second part of this
paper using the same GR formula deals with the effect of the earth rotation about the sun
on the moon orbit...an effect which should vanish in the earth reference frame where V=0 of course...and they see it: it's crazy but if this is confirmed it's eaxctly the "subtle effect expected in DG!

Actually analysis of the Moon's orbit is very theory dependent, needing a theory of tides etc., therefore I wouldn't place too much reliance on its conclusions.

Garth
I was also told that the analysis is extremely complicated, but look at formula 27 and the errors they give in the last page of the article! the two effects which are the signatures of the frame dragging (in the earth rest frame!!!???) have 6.6 and 6.1 meters amplitude and the errors are 4mm!!

Please anybody have a look at this ! It's completely crazy. If you agree there is a huge anomaly in this treatment please tell this and ask around you ...then keep me informed if you have news. I could not find the emails of the authors!

regards

F H-C

Garth

Feb24-07, 04:35 PM

Returning to the OP of marshalling as many alternative predictions of the outcome of the Gravity Probe B experiment so they can be compared with the results, which are to be published this year.

It seems from their latest press release that the first results will be published at the APS Jacksonville conference in April and only towards the end of the year will the proper motion of the guide star IM Pegasi be combined with the satellite data to find the most accurate absolute precession relative to a distant quasar.

This is to preserve as much as a 'double blind' element to the experiment to retain the objectivity of the results.

So here again are the predictions as assembled by me and the already known details of the guide star so a rough result will be obtainable in April.

Einstein's General Relativity(GR)
Barber's Self Creation Cosmology (http://arxiv.org/abs/gr-qc/0302026) (SCC),
Moffat's Nonsymmetric Gravitational Theory (http://arxiv.org/abs/gr-qc/0405091) (NGT),
Hai-Long Zhao's Mass Variance SR Theory (http://uk.arxiv.org/abs/gr-qc/0512088) (MVSR),
Stanley Robertson's Newtonian Gravity Theory (http://arxiv.org/abs/gr-qc/0502088) (NG),
Junhao & Xiang's Flat Space-Time Theory (http://arxiv.org/abs/physics/0101017) (FST).
R. L. Collin's Mass-Metric Relativity (http://www.arxiv.org/abs/physics/0012059) (MMR) and
F. Henry-Couannier's Dark Gravity Theory (http://www.arxiv.org/abs/gr-qc/0610079) (DG).

The predictions are:

1. GPB Geodetic precession (North-South)
GR = 6.6144 arcsec/yr
SCC = 4.4096 arcsec/yr
NGT = 6.6144 - a small \sigma correction arcsec/yr
MVSR = 6.6144 arcsec/yr
NG = 1.6536 arcsec/yr
FST = 4.4096 arcsec/yr
MMR = -6.56124 arcsec/yr
DG = 6.6144 arcsec/yr

2. GPB gravitomagnetic frame dragging precession (East-West)
GR = 0.0409 arcsec/yr
SCC = 0.0409 arcsec/yr
NGT = 0.0409 arcsec/yr
MVSR = 0.0102 arcsec/yr
NG = 0.0102 arcsec/yr
FST = 0.0000 arcsec/yr
MMR = -0.01924 arcsec/yr
DG = 0.0000 arcsec/yr

But first, as I said, these alternative theories have to also pass all the other tests of GR as detailed in Clifford Will's paper The Confrontation between General Relativity and Experiment (http://arxiv.org/abs/gr-qc/0510072).

And from The stars of Pegasus (http://www.alcyone.de/SIT/bsc/) from the Bright Star Catalogue, 5th Revised Ed. (Preliminary Version) (Hoffleit+, 1991, Yale University Observatory) as distributed by the Astronomical Data Center at NASA Goddard Space Flight Center.

IM Pegasi

RA J2000 : 22h 53m 2.3s
DEC J2000 : +16° 50' 28"
Proper motion in RA : -0.018 arcsec/y
Proper motion in DEC : -0.024 arcsec/y
mag : 5.64
MK spectral class : K1-2II-III

The Proper motion in RA will affect the E-W precession and the
Proper motion in DEC will affect the N-S precession.

Happy hunting!

Garth

Polestar101

Feb25-07, 07:04 PM

Hello,

Please also notice that DG predicts a small preferred frame effect to be seen by GP-B. It's a one year periodicity angular deviation with amplitude 0.005 arc sec...at the limit of GP-B sensitivity but i hope still detectable...and i think this is the "subtle effect " they need 10 more months to understand.

Fred

Hi Fred - Your work looks very interesting. FYI, in conversations with NASA VLBI they told me there is a .0005"p/y "geometric effect" included in the overall precession observable. While it is generally too small to be noticed they attribute this to the geometric effect of the motion of the solar system around the galactic center. In other words, if the SS revolves 360 degrees around the GC in about 240 million years that rate equals about .0005"p/y as seen from earth. However, since this motion is a galactic motion relative to quasars far outside the galaxy it should not show up in measurements relative to the (much closer) guidestar within the galaxy. This is because the guidestar would be moving in the same galactic frame (assuming there are no other intermediate frames such as a binary frame). Thought this might interest you since the amplitude is the same as the amount you have suggested.

Personally, I think the GPB team has to deal with much larger unexpected effects and it is a combination of all of the effects that makes it difficult to separate the unwanted signals, resulting in the predicted delay.

Walter

Garth

Feb26-07, 02:47 AM

Please anybody have a look at this ! It's completely crazy. If you agree there is a huge anomaly in this treatment please tell this and ask around you ...then keep me informed if you have news. I could not find the emails of the authors!

regards

F H-CSomebody who apparently agrees that something is wrong with their analysis in today's ArXiv. Comment on ”The gravitomagnetic influence on gyroscopes and on the lunar orbit” (http://arxiv.org/PS_cache/gr-qc/pdf/0702/0702120.pdf) Analysis of the gauge residual freedom in the relativistic theory of lunar motion demonstratesthat lunar laser ranging (LLR) is not currently capable to detect gravitomagnetic effects.

Garth

Glen Deen

Feb26-07, 07:28 PM

COBE and WMAP observations of the CMB dipole apex vary slightly. Assume first that the nominal celestial position values are correct, and compute the drift in ecliptic position from the mean COBE epoch to the mean WMAP epoch.

The mean epoch for the COBE mission is taken to be 1991.882 = Nov. 19, 1991. This is the launch date plus 2 years.

The mean epoch for the WMAP mission is taken to be 2002.085 = Feb. 1, 2002. This is the launch date plus 7 months. The published data are for the first year of the mission.

Arc time = 10.203 years

The data are from Bennett et. al., ApJ, 148, 1 (2003)

COBE CMB dipole apex Galactic longitude = 264.26 ±0.33 degrees
COBE CMB dipole apex Galactic latitude = 48.22 ±0.13 degrees

WMAP CMB dipole apex Galactic longitude = 263.85 ±0.10 degrees
WMAP CMB dipole apex Galactic latitude = 48.25 ±0.04 degrees

Convert galactic coordinates to RA, Dec for equator and equinox J2000
COBE RA, Dec = 168.0558, -7.0610
WMAP RA, Dec = 167.8545, -6.8825

Convert equatorial coordinates to ecliptic coordinates
COBE long, lat = 171.8213, -11.2144
WMAP long, lat = 171.5537, -11.1334
differences = -0.2676, +0.0810 degrees
differences = -963.3, +291.7 arc seconds
drift rate = -94.4, +28.3 arc sec per year
precession rate = -50.3, 0.0 arc sec per year

This nominal drift rate is in the ball park of the precession rate, but the error can be eliminated by adjusting or tuning the input data, constraining the offsets to be inside the error boxes.

COBE galactic longitude offset = -45.864% * 0.33 = -0.1513252 degrees
COBE galactic latitude offset = +74.231% * 0.13 = +0.0965003 degrees

WMAP galactic longitude offset = +52.162% * 0.01 = +0.052162 degrees
WMAP galactic latitude offset = +99.963% * 0.04 = +0.039985 degrees

When these offsets are applied to the input data, the results are:
drift rate = -50.3, 0.0 arc sec per year
precession rate = -50.3, 0.0 arc sec per year

Thus, the standard precession rate can be matched by adjusting the input data towards one error bar limit or the other.

This is the drift rate of the equinox relative to the fixed stars, so it is negative. The precession of the stars relative to the equinox is +50.3 arc sec per year.

-Glen

Garth

Feb27-07, 03:08 AM

Hi Glen and welcome to these Forums!

That is an interesting drift rate, but what exactly are you saying?

I notice that the COBE and WMAP dipole apexes are also consistent with each other when the error bars are taken into account.

What is the WMAP apex Galactic lat. and long. for years II and III, i.e. does the drift rate continue?

If so, is this an artifact of the galactic coordinates, i.e. that they are not corrected for equinox precession, or are you saying the CMB dipole is locked to the Earth based RA and dec?

How do you see this CMB precession, if it exists, affecting the GP-B results?

Garth

Glen Deen

Feb27-07, 06:19 AM

Hi Glen and welcome to these Forums!

That is an interesting drift rate, but what exactly are you saying?

I'm saying that the Sun is in an orbit about the barycenter of a binary or ternary star system as evidenced by the lunisolar precession of the equinox. The CMB dipole apex is the direction of the Sun's absolute motion in space. If the Sun is in an orbit, then its direction changes in time with respect to the barycenter. The barycenter's large absolute space velocity vector is constant over thousands of years, so the barycenter can be considered to be an inertial frame. The Sun's absolute motion is the vector sum of the large barycenter velocity and the Sun's orbital velocity. But since the barycenter is an inertial frame, we expect the dipole apex direction to match that of the Sun's orbital velocity vector.

I notice that the COBE and WMAP dipole apexes are also consistent with each other when the error bars are taken into account.

They will point that out if you ask them. Their official position must be that the CMB dipole direction is constant because officially the Sun is not in an orbit.

What is the WMAP apex Galactic lat. and long. for years II and III, i.e. does the drift rate continue?

I have not done a literature search, but I suspect that the WMAP people have not written about the dipole beyond this first-year paper. The data I cited was found in Section 7.1; the dipole was not mentioned in the abstract. I note that the WMAP people have subtracted the COBE dipole from the WMAP data. Why not subtract the "more accurate" WMAP dipole?

If so, is this an artifact of the galactic coordinates, i.e. that they are not corrected for equinox precession, or are you saying the CMB dipole is locked to the Earth based RA and dec?

You could say that galactic coordinates are appropriate since the CMB is cosmic. As you say, it does relieve them from specifying an equinox date. I don't know what you mean by "artifact". The galactic coordinates are tied to the standard equinox of B1950.0. Using the formulas given by Meeus, I convert galactic coordinates to equatorial coordinates referred to the standard equinox of B1950.0. Then I precess those equatorial coordinates to J2000.0 using Meeus's precession formulas. The CMB dipole apex is locked to the Sun, not the Earth.

How do you see this CMB precession, if it exists, affecting the GP-B results?

Garth

I expect GP-B people will observe IM Pegasi precessing with respect to their gyroscopic inertial frame in the same way all stars precess in the Earth's equatorial frame because precession is caused by the Sun's orbit, not the Earth's polar axis 26,000-year wobble they compute from the computed torque induced by lunar and solar gravitational forces on the spinning oblate and tilted Earth as originally specified by Newton. The CMB precession is another way to measure changes in direction of the Sun's velocity vector with respect to the binary or ternary barycenter. The CMB precession does not affect the GP-B results because it is not a cause. Both observations are caused by the Sun's orbital motion.

I imagine that the WMAP PI is aware of this dipole drift. I think he is waiting for independent confirmation before announcing it because it would break so many cherished paradigms. GP-B people could provide this confirmation. He should break his analysis into smaller time segments to see if indeed this dipole drift is secular. The COBE people should break their mission into smaller time segments as well. If the dipole drift is secular, then we can apply a least-squares fit to an over-constrained problem and determine the Keplerian elements of the Sun's orbit.

-Glen

Garth

Feb27-07, 07:33 AM

I'm saying that the Sun is in an orbit about the barycenter of a binary or ternary star system as evidenced by the lunisolar precession of the equinox. The CMB dipole apex is the direction of the Sun's absolute motion in space. If the Sun is in an orbit, then its direction changes in time with respect to the barycenter. The barycenter's large absolute space velocity vector is constant over thousands of years, so the barycenter can be considered to be an inertial frame. The Sun's absolute motion is the vector sum of the large barycenter velocity and the Sun's orbital velocity. But since the barycenter is an inertial frame, we expect the dipole apex direction to match that of the Sun's orbital velocity vector. But the velocity of the Earth realtive to the CMB Surface of Last Scattering is OOM 10-3c, the orbital velocity of the Solar System around a binary companion with SMA ~ 103 AU would be OOM ~ 3 x 10-6c. So the scenario you suggest cannot explain the CMB dipole. The velocity of the sun around its companion would be ~ three hundred times too small.

I note that the WMAP people have subtracted the COBE dipole from the WMAP data. Why not subtract the "more accurate" WMAP dipole? Good point, would it make any difference though? Anybody?

Garth

Glen Deen

Feb27-07, 06:22 PM

But the velocity of the Earth realtive to the CMB Surface of Last Scattering is OOM 10-3c, the orbital velocity of the Solar System around a binary companion with SMA ~ 103 AU would be OOM ~ 3 x 10-6c. So the scenario you suggest cannot explain the CMB dipole. The velocity of the sun around its companion would be ~ three hundred times too small.

Garth

No. My scenario does not explain the CMB dipole. The CMB dipole drift, if it does exist, explains my scenario.

You say the velocity of the Earth, but I'm pretty sure COBE and WMAP give the absolute velocity of the Sun to eliminate the small annual variations. I assume from published information that this is 371 km/s. I claim that we can assign this constant velocity to the binary system barycenter, which becomes an inertial frame. The velocity of the Sun relative to the barycenter is on the order of 1 km/s as you say. So we have a little velocity vector rotating about the arrowhead of a big velocity vector. What matters is in which direction the little vector is pointing as a function of time.

Since the barycenter defines an inertial frame, it doesn't matter whether that frame has absolute motion or not, as long as it is a constant velocity. Right? When we are interested in rotation, we can ignore any constant translation in a fixed direction. It is the rotation that makes the stars appear to precess.

Let's look at a numeric example.

Epoch___ Vsun kms Longitude Latitude
1991.882 371.0000 171.73882 -11.1008
2002.085 371.0000 171.59626 -11.1008
Vec diff 0.905797 81.667532 +0.00000

The vector difference is the Sun's velocity relative to the binary barycenter. As you see it is on the order of 1 km/s. But to get the absolute rotation rate of the Sun I take the difference in longitude dLong = 171.59626 - 171.73882 = -0.14255 degrees, multiply it by 3600 to get arc seconds, and divide it by the time interval = 10.203 years.

Drift rate in longitude = -0.14255*3600/10.203 = -50.30 arc sec/year

Does that make sense now?

-Glen

Garth

Feb27-07, 07:21 PM

No. My scenario does not explain the CMB dipole. The CMB dipole drift, if it does exist, explains my scenario.
Okay, but your statement confused me:But since the barycenter is an inertial frame, we expect the dipole apex direction to match that of the Sun's orbital velocity vector.

The dipole blue apex is the direction of the Sun/Earth motion relative to the Surface of Last Scattering at a velocity ~ 10-3c and can be rendered through vector addition as a motion of the Galaxy COM relative to the SLS.

Garth

Glen Deen

Feb28-07, 07:19 AM

The dipole blue apex is the direction of the Sun/Earth motion relative to the Surface of Last Scattering at a velocity ~ 10-3c and can be rendered through vector addition as a motion of the Galaxy COM relative to the SLS.

Garth
So what? Did you understand my numerical example?
-Glen

Garth

Feb28-07, 05:38 PM

So what? Did you understand my numerical example?
-Glen

I understand your scenario would produce a drift rate as described. However, do you understand the origin of the CMB dipole due to the Sun's motion of ~10-3c relative to the Surface of Last Scattering?

This thread is not the place for a discussion on novel theories, only those published GP-B predictions of alternative theories that can be compared with those of GR.

Please continue your discussion in the IR (http://www.physicsforums.com/forumdisplay.php?f=146) Forum

Garth

cesiumfrog

Feb28-07, 06:43 PM

The predictions are:

1. GPB Geodetic precession (North-South)
GR = 6.6144 arcsec/yr
SCC = 4.4096 arcsec/yr
NGT = 6.6144 - a small \sigma correction arcsec/yr
MVSR = 6.6144 arcsec/yr
NG = 1.6536 arcsec/yr
FST = 4.4096 arcsec/yr
MMR = -6.56124 arcsec/yr
DG = 6.6144 arcsec/yr

2. GPB gravitomagnetic frame dragging precession (East-West)
GR = 0.0409 arcsec/yr
SCC = 0.0409 arcsec/yr
NGT = 0.0409 arcsec/yr
MVSR = 0.0102 arcsec/yr
NG = 0.0102 arcsec/yr
FST = 0.0000 arcsec/yr
MMR = -0.01924 arcsec/yr
DG = 0.0000 arcsec/yr

Could we get error bars on all of these predictions?

This is a great idea for a thread, but obviously (at least, I presume it is obvious to everyone here, yes?) the whole exercise is pointless without the uncertainty limits. This goes double for NGT (which I think should be removed completely until its difference from GR is quantified).

Garth

Mar1-07, 02:28 AM

Could we get error bars on all of these predictions?

This is a great idea for a thread, but obviously (at least, I presume it is obvious to everyone here, yes?) the whole exercise is pointless without the uncertainty limits. This goes double for NGT (which I think should be removed completely until its difference from GR is quantified).
Thank you cesiumfrog that is a good point. In fact most of these predictions are precise predictions using physical constants such as G,MEarth, c, and the satellite's orbital elements. The major source of error are the orbital elements, which have been determined so the predictions are accurate to 0.1 milliarcseconds each.

What is not so accurate are the systematic drifts caused by other effects such as the polhode motion due to the gyroscope spheres not being exactly spherical. It is the determination of these other effects to that accuracy that is going to take until the end of 2007 to determine. There will be a poster "Gravity Probe B Experiment Error" by Barry Muhlfelder, G. Mac Keiser, John Turneaure at the April APS meeting. We will know more then.

As far as NGT is concerned GP-B will not be a falsifiable test, but at least it provides "wriggle room" if the geodetic precession is only a little different from the GR expectation.

Garth

Glen Deen

Mar1-07, 01:38 PM

I understand your scenario would produce a drift rate as described. However, do you understand the origin of the CMB dipole due to the Sun's motion of ~10-3c relative to the Surface of Last Scattering?

This thread is not the place for a discussion on novel theories, only those published GP-B predictions of alternative theories that can be compared with those of GR.

Please continue your discussion in the IR (http://www.physicsforums.com/forumdisplay.php?f=146) Forum

Garth

On February 16 you said:
Well Walter, as I said, I find it hard to believe that:
1. The Moon does not induce the observed 26,000 yr period precession on the Earth as all the models of the geoid predict and,
2. There is an unobserved ~ stellar mass object, which is a binary companion to the Sun with a SMA of ~ 877AU that is responsible for the said observed precession.
Number 2 is a novel theory, and it is the one I am referring to.

I'm saying that if number 2 is true, then the Sun's change in direction in its absolute velocity vector over time due to its orbit about the binary barycenter should be seen as a change in the direction of the apex of the CMB dipole. What I showed was that such a change can be made equal to the 50.3 arcsec/year general longitude precession rate by adjusting the galactic coordinates of the COBE and the WMAP dipole apexes, keeping them within the stated error bars. Thus it is possible to decide on the truth of number 2 using COBE and WMAP as well as GP-B.

-Glen

Garth

Mar1-07, 02:35 PM

On February 16 you said:

Number 2 is a novel theory, and it is the one I am referring to.

I'm saying that if number 2 is true, then the Sun's change in direction in its absolute velocity vector over time due to its orbit about the binary barycenter should be seen as a change in the direction of the apex of the CMB dipole. What I showed was that such a change can be made equal to the 50.3 arcsec/year general longitude precession rate by adjusting the galactic coordinates of the COBE and the WMAP dipole apexes, keeping them within the stated error bars. Thus it is possible to decide on the truth of number 2 using COBE and WMAP as well as GP-B.

-Glen

And if true the 50.3 arcsec/yr precession will also show up in all other space telescopes. Does it?

Garth

Garth

Mar2-07, 03:16 AM

I understand your scenario would produce a drift rate as described.....

Garth

Actually, Glen Deen, and Walter, on further reflection, I do not understand how your scenario would produce such a drift rate in the precession of the equinoxes.

The Earth's polar axis would point in a constant direction relative to the distant stars if there were no lunar gravitational attraction to the Earth's equatorial bulge, no matter if the solar system were in orbit about a solar companion.

The gravitational perturbation on the Earth's orbit would produce a slight precession on the ecliptic, but nowhere near the value otherwise attributed to the lunar action on the geoid.

Your scenario does not make sense. Please keep it out of this serious discussion of the outcome of the GP-B experiment.

Garth

Glen Deen

Mar2-07, 06:13 AM

And if true the 50.3 arcsec/yr precession will also show up in all other space telescopes. Does it?

Garth
That's a very good question! Space telescopes do not have setting circles as Earth telescopes do. All space astrometry is relative to known star positions. Precession is a absolute drift in the ecliptic longitude of all stars, and it can't be detected by any space telescope unless they use precision gyroscopes as absolute references as GP-B does, and they concentrate on the position of a single star over long periods of time. Most space telescopes do not do that.

-Glen

Glen Deen

Mar2-07, 06:29 AM

Actually, Glen Deen, and Walter, on further reflection, I do not understand how your scenario would produce such a drift rate in the precession of the equinoxes.
It doesn't. According to our binary orbit scenario, the equinoxes are fixed in inertial space thanks to the law of conservation of angular momentum. The Sun's orbit makes the stars precess relative to the fixed equinoxes. In 26,000 years the stars return to their original position. This is analogous to the stars appearing to make a complete circuit over one year because of Earth's orbit.
The Earth's polar axis would point in a constant direction relative to the distant stars if there were no lunar gravitational attraction to the Earth's equatorial bulge, no matter if the solar system were in orbit about a solar companion.
I agree.
The gravitational perturbation on the Earth's orbit would produce a slight precession on the ecliptic, but nowhere near the value otherwise attributed to the lunar action on the geoid.
I agree.
Your scenario does not make sense. Please keep it out of this serious discussion of the outcome of the GP-B experiment.

Garth
I can accept that you don't agree with it. I refuse to accept that it doesn't make any sense. Can we take a poll of the others on this list to see if it makes sense to them?

-Glen

Garth

Mar2-07, 06:45 AM

That's a very good question! Space telescopes do not have setting circles as Earth telescopes do. All space astrometry is relative to known star positions. Precession is a absolute drift in the ecliptic longitude of all stars, and it can't be detected by any space telescope unless they use precision gyroscopes as absolute references as GP-B does, and they concentrate on the position of a single star over long periods of time. Most space telescopes do not do that.

-Glen

This is nonsense: - "All space astrometry is relative to known star positions" - so is the alignment of the GP-B gyroscopes 'relative to known star positions'.

GP-B does not measure the ecliptic longitude.

The gyroscopes' axial directions are measured relative to the guide star. The guide star is being tracked by the VLBI and that tracking will detect the precession of the equinoxes if it measures the constantly updated RA and dec. of the star on the Earth based celestial sphere. But in fact they are tracking the proper motion of the IM Pegasi relative to a distant quasar, so they will not detect this precession at all.

The precession of the equinoxes is well known and attributed to the lunar and solar differential gravitational forces on the Earth's oblate spheroid.

There are nutations caused by the Sun's and Moon's changing relative positions.

In addition to this lunisolar precession, the other planets, mainly Jupiter, cause the whole ecliptic to rotate, this planetary precession shift is only 0.47 seconds of arc per year (more than a hundred times smaller than lunisolar precession). All this is well modelled, a binary solar companion would cause an further precession, which would be less than even this. Such a precession has not been observed, although that was what I had first thought you must been alluding to.

The gravitational action of a hypothetical binary solar companion would not affect the GP-B gyroscopes any more than they would the alignment of other space telescopes. It will not affect their axial direction relative to the distant quasar, which is the ultimate reference point. Therefore the question of such a hypothetical binary solar companion has no place in this thread.

Garth

Garth

Mar2-07, 06:48 AM

I can accept that you don't agree with it. I refuse to accept that it doesn't make any sense. Can we take a poll of the others on this list to see if it makes sense to them?

-GlenIf you wish to discuss this unorthodox and unpublished theory you have to do so on the Independent Research (http://www.physicsforums.com/forumdisplay.php?f=146) Forum. Conduct your poll there, after fulfilling that Forum's guidelines.

Garth

Glen Deen

Mar2-07, 01:30 PM

This is nonsense: - "All space astrometry is relative to known star positions"
I could be wrong about that. Can you give me a counter example?
- so is the alignment of the GP-B gyroscopes 'relative to known star positions'.
I never said that.
GP-B does not measure the ecliptic longitude of the ecliptic.
I never said it does.
The gyroscopes are measured relative to the guide star. The guide star is being tracked by the VLBI and that tracking will detect the precession of the equinoxes if it measures the constantly updated RA and dec. of the star on the Earth based celestial sphere.
No. Precession is not observed by the VLBI. Precession is always computed using standard formulas.

The VLBI would measure the apparent place RA, Dec of IM Pegasi at each time of observation. To reduce an apparent place to a mean place at a standard epoch and equinox, I believe they must make the following corrections in order.

1. The effect of annual parallax.
2. The effect of annual aberration.
3. The effect of nutation.
4. The effect of precession.
5. The proper motion of the star.

The idea is that the mean place of any star at a standard epoch and equinox should be constant over time. The first four corrections are computed, not observed, and they are functions of time and place. The time argument is the difference between the observation time and the standard epoch time. The observed proper motion would be whatever it took to move the place after the fourth correction to the known mean place at the standard epoch and equinox.

In fact they are tracking the proper motion of the IM Pegasi relative to a distant quasar, so they will not detect this precession at all.
As I said, precession is not observed; it is computed. Quasars, like all stars, precess relative to the equinox.

Quasars have no parallax or proper motion, so steps 1 and 5 can be eliminated in the place reduction. So quasars provide a powerful check on the successive corrections for annual aberration, nutation, and precession. Now if you believe you know the effects of annual aberration and nutation to a very high precision, then you can use VLBI observations of quasars to "observe" general precession, and you can compare it to the results you got from the standard formula.

The precession of the equinoxes is well known and attributed to the lunar and solar differential gravitational forces on the Earth's oblate spheroid.
Yes, and that is a problem for the binary Sun theory. "Lunisolar" precession may consist of two components: the Newtonian-d'Alembert gravitational torques on the spinning tilted oblate Earth from gravitational forces from the Sun and the Moon plus the Sun's binary orbit motion. In the worst case, I think the Newtonian torques could be eliminated if the oblate Earth were hollow with a uniform shell thickness. If GP-B is observing a too-large "proper motion", I'm suggesting that it is due to the Sun's motion in a binary orbit.

There are nutations caused by the Sun's and Moon's changing relative positions.
Yes.
In addition to this lunisolar precession, the other planets, mainly Jupiter, cause the whole ecliptic to rotate, this planetary precession shift is only 0.47 seconds of arc per year (more than a hundred times smaller than lunisolar precession).
Yes.
All this is well modelled,
But is lunisolar precession modeled from first principles taking into consideration Earth's radial density profile, or is it modeled to match quasar observations? If the latter, then it can be questioned.
a binary solar companion would cause an further precession, which would be less than even this.
Smaller than 0.47 arcsec/year? Not hardly. If you assume the Sun is in a circular orbit a rate of 0.47 arcsec/year would correspond to an orbit period of 2.8 million years. We usually imagine much shorter periods and corresponding greater precession rates. But we don't need to speculate. GP-B can tell us how much it is. In fact, GP-B can refute the binary Sun hypothesis simply by not finding any excess "proper motion".

Such a precession has not been observed, although that was what I had thought you must been alluding to.
We are speculating that GP-B has observed it. If that turns out to be true, then I imagine other space telescopes can also observe it using their less precise gyroscopes.
The gravitational action of a hypothetical binary solar companion would not affect the GP-B gyroscopes any more than they would the alignment of other space telescopes. It will not affect their axial direction relative to the distant quasar, which is the ultimate reference point. Therefore the question of such a hypothetical binary solar companion has no place in this thread.

Garth
We are not talking about gravitational forces of the companion on the Earth inducing something akin to planetary precession. We are talking about the Sun following a curved path in space in its binary orbit. Such a curved path would produce apparent precession of the stars relative to the equinox. Imagine you are sitting on a merry-go-round across from the companion. If the merry-go-round rotated counter-clockwise, the objects on the horizon (analogous to stars) appear to the observer on the merry-go-round to rotate clockwise. Its just like what the stars do over the course of a year as a result of the Earth's orbit around the Sun.

-Glen

henryco

Mar3-07, 04:50 AM

This is the drift rate of the equinox relative to the fixed stars, so it is negative. The precession of the stars relative to the equinox is +50.3 arc sec per year.

-Glen

I thinck this analysis is very interesting. Probably this precession is also responsible for the anomalous WMAP quadrupole correlation with ecliptic and equinoxes directions (see http://www.citebase.org/abstract?id=oai%3AarXiv.org%3Aastro-ph%2F0608318) , so i'm quite surprised that you did not
mention it.

The predictions of a Dark Gravity theory i'm working on are in the Garth's list.
Though the theory keeps opened the possibility that there could be an additional small and anomalous preferred frame effect, a recent and closer reinspection convinced me that this is quite unlikely within this framework.

On the other hand, if i understand well, you and polestar are calling upon an unsubtracted extra proper motion effect of the sun about a neighbour star to explain both the equinoxe precession and the CMB precession and you expect this to be seen by GP-B.

I thinck it's intersting trying to find out a common explanation and i also would not be surprised to see such large effect arrising in GP-B data but within the DG theory i'm working on i would tend to propose another mechanism for it (i already proposed it sometime ago to explain the quadrupole anomalies).

In DG, i have a discontinuity of the gravitational field (by the way responsible for the Pioneer anomaly) and this phenomenon takes ~26000 years to achieve its periodic path scanning the solar system.
These 26000 years show up as the result of dividing the sun potential surface by the present value of the Hubble parameter. So the agreement is at the 15% level (due to the present error on H0 direct estimation).

How could this be related to the equinoxe precession? I have no definitive answer but ....
actually, this discontinuity acts as an unexpected foreground able to deviate or reflect light from any background object (CMB, star) since it is like a border between two areas with different indices.
Because the discontinuity is moving, all background objects should apparently move with it along a 26000 years periodic path...
But i dont see for the time being how i could get your 50''/year:confused:

F Henry-Couannier

Garth

Mar3-07, 07:14 AM

Glen Deen

Mar3-07, 06:13 PM

How could this be related to the equinoxe precession? I have no definitive answer but ....
actually, this discontinuity acts as an unexpected foreground able to deviate or reflect light from any background object (CMB, star) since it is like a border between two areas with different indices.
Because the discontinuity is moving, all background objects should apparently move with it along a 26000 years periodic path...
But i dont see for the time being how i could get your 50''/year:confused:
Henryco, I bring your last paragraph up to the top because I wish to discuss it first. I know nothing about your Dark Gravity theory (maybe I should learn), but I think I recognize your discontinuity. You mean different indexes of refraction, right? I call such a structure a cosmic lens because the speed of light is slower inside than outside. I imagine that every gravitating body is at the center of its own spherical lens. The effect of Earth's lens is called atmospheric refraction. The effect of the Sun's lens is called annual parallax. Since light rays to distant stars are not straight but are refracted at the lens surface, all stars may be much closer than we calculate from geometric parallax. I'm sure the Earth's atmosphere does refract starlight to some extent, but the speculation is that Earth's cosmic lens may contribute some part of the refraction. Every galaxy, every globular cluster and every open cluster ought to have its own cosmic lens as well.

Let's say for the sake of argument that the Sun's hypothetical companion is a white dwarf star. We easily observe Sirius B, so we should much more easily observe this companion. We don't because it would need to have a proper motion that is the negative of the lunisolar precession rate, and such a large proper motion could not have escaped notice. But if this companion were outside the Sun's cosmic lens and inside its focal length, I claim that its rays cannot produce an image in any Earth camera focused at infinity.

I thinck this analysis is very interesting. Probably this precession is also responsible for the anomalous WMAP quadrupole correlation with ecliptic and equinoxes directions (see http://www.citebase.org/abstract?id=oai%3AarXiv.org%3Aastro-ph%2F0608318) , so i'm quite surprised that you did not mention it.
In retrospect I should have. Thanks for mentioning it for me.

The predictions of a Dark Gravity theory i'm working on are in the Garth's list.
Please tell me how to get there.

Though the theory keeps opened the possibility that there could be an additional small and anomalous preferred frame effect, a recent and closer reinspection convinced me that this is quite unlikely within this framework.

On the other hand, if i understand well, you and polestar are calling upon an unsubtracted extra proper motion effect of the sun about a neighbour star to explain both the equinoxe precession and the CMB precession and you expect this to be seen by GP-B.

I don't know what Walter's (polestar's) position is on my speculations regarding a predicted hypothetical secular drift in the CMB dipole apex direction. But we both do expect GP-B to observe a substantial anomalous proper motion in IM Pegasi that should be some fraction up to 100% of the vector that is the exact negative of the lunisolar precession for that place in the sky. In the worst case (100%) the Sun's binary orbit accounts for all of the lunisolar precession, leaving nothing for the Newtonian gravity forces from the Moon and the Sun on the spinning inclined oblate Earth. That extreme may be ruled out since it would seem to require a hollow Earth with a uniform shell thickness.

I thinck it's intersting trying to find out a common explanation and i also would not be surprised to see such large effect arrising in GP-B data but within the DG theory i'm working on i would tend to propose another mechanism for it (i already proposed it sometime ago to explain the quadrupole anomalies).

In DG, i have a discontinuity of the gravitational field (by the way responsible for the Pioneer anomaly) and this phenomenon takes ~26000 years to achieve its periodic path scanning the solar system.
These 26000 years show up as the result of dividing the sun potential surface by the present value of the Hubble parameter. So the agreement is at the 15% level (due to the present error on H0 direct estimation).

F Henry-Couannier
This is interesting. I would like to know more about it.

-Glen

Glen Deen

Mar3-07, 10:20 PM

Even if the Sun were in a 26,000 year orbit with a companion binary the GP-B gyroscopes would still point in a fixed direction relative to the fixed stars.
That is true according to Newtonian mechanics. I have concluded that if the predicted effect occurs, it will be the result of GRT frame dragging. This probably cannot occur to the necessary degree unless the perihelion of the companion is quite near to the Sun, perhaps even inside the solar system. But if it is true, the GP-B gyroscopes would align themselves with the local inertial frame, which my theory supposes rotates with respect to the fixed stars because of frame dragging.

The orbit of the satellite around the Earth, the Earth around the Sun, the Sun around the COM of its supposed binary system, and that COM around the galaxy would not directly affect the pointing of the gyroscopes. They are in free-fall.
Yes, but maybe it's free-fall in a rotating "inertial" frame.

The gyroscopes' axial directions are compared to IM Pegasi. IM Pegasi, a radio binary star, has been being tracked by the VLBI relative to distant quasar 3C454.3. and sometimes two others. When the VLBI data is convoluted with the satellite data the motion of the gyroscopes will be measured relative to the 'fixed stars'.
I agree. If you are right, there won't be any such motion. If frame dragging is occurring, then I think they will see the gyroscopes move relative to the fixed stars.

There will be subtle effects of such a supposed binary companion of the Sun, such as a tiny precession of the ecliptic on top of that caused by the other planets as I described above, but nowhere near the 50.3"/yr precession of the equinoxes, but even so this will not affect the GP-B data, only the astrometric data of a telescope fixed to the wobbling Earth.
The period is too long to see any tiny planetary-like precession from the companion. I think they will see either a substantial fraction of the 50.3"/yr precession or nothing.

In any case, do you think that the gravitational action of the Moon and the Sun on the Earth's oblate spheroid would not produce this 50.3"/yr precession?

Garth
I suggest that it may not produce all of that precession rate. It really depends on what the GP-B people observe. If they see proper motion in IM Pegasi relative to their gyroscopes (due to frame dragging) that is a substantial fraction of 50.3"/yr, then the Moon and Sun must be causing only the remainder.

Since quasars have no annual parallax or proper motion, they can be used to observe general precession because the annual aberration and the nutation can be computed from first principles with no need for observations. If the general precession formulas have been adjusted to minimize the least squared error in the observed precession of a large number of quasars, that is an empirical data fit that can be challenged.

I doubt that the precession formulas were derived from first principles. What I see in Danby's Chapter 13 (Fundamentals of Celestial Mechanics) is that they use the moments of inertia of the spheroidal Earth about its principal axes. How do they know these moments of inertia? I read in Fowler's The Solid Earth -- An Introduction to Global Geophysics on page 110:
Although such a self-compression density model for the earth satisfies the seismic velocity data from which it was derived, it does not satisfy data on the rotation of the earth. In particular, the earth's moment of inertia, which is sensitive to the distribution of mass in the earth, is significantly greater than the moment of inertia for the self-compression model. There must be more mass in the mantle than the self-compression model allows.
So, how do they know the Earth's moment of inertia from its rotation? I wonder if people observe the precession from quasars and calculate what the moment of inertia must be from the equations established by Newton and d'Alembert. The geophysicists are saying that moment of inertia is too high according to their radial density profile calculations. That could mean that the lunisolar precession is too high.

-Glen

Garth

Mar4-07, 01:59 AM

Returning the thread back on track, so far we have the following alternative theories that have been published in refereed journals, or on the Physics ArXiv, that make specific and falsifiable alternative predictions of the outcome of the Gravity Probe B experiment.

Einstein's General Relativity(GR)
Barber's Self Creation Cosmology (http://arxiv.org/abs/gr-qc/0302026) (SCC),
Moffat's Nonsymmetric Gravitational Theory (http://arxiv.org/abs/gr-qc/0405091) (NGT),
Hai-Long Zhao's Mass Variance SR Theory (http://uk.arxiv.org/abs/gr-qc/0512088) (MVSR),
Stanley Robertson's Newtonian Gravity Theory (http://arxiv.org/abs/gr-qc/0502088) (NG),
Junhao & Xiang's Flat Space-Time Theory (http://arxiv.org/abs/physics/0101017) (FST).
R. L. Collin's Mass-Metric Relativity (http://www.arxiv.org/abs/physics/0012059) (MMR) and
F. Henry-Couannier's Dark Gravity Theory (http://www.arxiv.org/abs/gr-qc/0610079) (DG).

The predictions are:

1. GPB Geodetic precession (North-South)
GR = 6.6144 arcsec/yr
SCC = 4.4096 arcsec/yr
NGT = 6.6144 - a small \sigma correction arcsec/yr
MVSR = 6.6144 arcsec/yr
NG = 1.6536 arcsec/yr
FST = 4.4096 arcsec/yr
MMR = -6.56124 arcsec/yr
DG = 6.6144 arcsec/yr

2. GPB gravitomagnetic frame dragging precession (East-West)
GR = 0.0409 arcsec/yr
SCC = 0.0409 arcsec/yr
NGT = 0.0409 arcsec/yr
MVSR = 0.0102 arcsec/yr
NG = 0.0102 arcsec/yr
FST = 0.0000 arcsec/yr
MMR = -0.01924 arcsec/yr
DG = 0.0000 arcsec/yr

And from The stars of Pegasus (http://www.alcyone.de/SIT/bsc/) from the Bright Star Catalogue, 5th Revised Ed. (Preliminary Version) (Hoffleit+, 1991, Yale University Observatory) as distributed by the Astronomical Data Center at NASA Goddard Space Flight Center.

IM Pegasi

RA J2000 : 22h 53m 2.3s
DEC J2000 : +16° 50' 28"
Proper motion in RA : -0.018 arcsec/y
Proper motion in DEC : -0.024 arcsec/y
mag : 5.64
MK spectral class : K1-2II-III

Of course, these alternative theories have to pass all the other tests of GR as detailed in Clifford Will's paper The Confrontation between General Relativity and Experiment (http://arxiv.org/abs/gr-qc/0510072). Some of them might already have failed those tests.

Garth

henryco

Mar4-07, 04:46 AM

Polestar101

Mar4-07, 09:04 PM

Even if the Sun were in a 26,000 year orbit with a companion binary the GP-B gyroscopes would still point in a fixed direction relative to the fixed stars.

The orbit of the satellite around the Earth, the Earth around the Sun, the Sun around the COM of its supposed binary system, and that COM around the galaxy would not directly affect the pointing of the gyroscopes. They are in free-fall.

The gyroscopes' axial directions are compared to IM Pegasi. IM Pegasi, a radio binary star, has been being tracked by the VLBI relative to distant quasar 3C454.3. and sometimes two others. When the VLBI data is convoluted with the satellite data the motion of the gyroscopes will be measured relative to the 'fixed stars'.

There will be subtle effects of such a supposed binary companion of the Sun, such as a tiny precession of the ecliptic on top of that caused by the other planets as I described above, but nowhere near the 50.3"/yr precession of the equinoxes, but even so this will not affect the GP-B data, only the astrometric data of a telescope fixed to the wobbling Earth.

In any case, do you think that the gravitational action of the Moon and the Sun on the Earth's oblate spheroid would not produce this 50.3"/yr precession?

Garth

Garth –If there were only a few arc seconds of precession caused by local forces (most now believe local forces are responsible for ALL of the observed 50”p/y), then the earth’s axis would have to obey the local forces, even if it were occurring within a larger moving frame (a solar system in motion). Thus the precession observable we would see from earth (relative to IM Pegasi) would be equal to the local earth wobble plus the binary motion. In effect, the local wobble helps translate the binary orbital motion into a larger observable. So it is possible much of the observable we call “precession” may in fact be due to the geometric effect of a solar system in motion.

This geometric effect is a little used phrase but I got it from VLBI. In correspondence with VLBI, I was told that the effect of the solar system moving around the galactic core (at the estimated rate of once every 240 million years) would result in a geometric effect of ~.005”p/y within the precession observable as seen from earth. Consequently, if the sun were part of a binary or ternary (as Glen prefers) system that took ~26,000 years to complete one orbit the “geometric effect” would be about 50” p/y. If this were the case then most (but not all) of what we call precession is actually the geometric effect of the binary motion.

The reason this should probably stay in this GP-B thread is because if GP-B discovers that that they have a signal of this magnitude that needs to be separated out it would be a more fundamental discovery than confirming or honing the amount of the GR effects. Or is there another string that looks at unexpected results from GP-B?

Walter

Garth

Mar5-07, 03:24 AM

The reason this should probably stay in this GP-B thread is because if GP-B discovers that that they have a signal of this magnitude that needs to be separated out it would be a more fundamental discovery than confirming or honing the amount of the GR effects. Or is there another string that looks at unexpected results from GP-B?

WalterWalter, as I said in my post #39 above
I notice on your website that you link to several of your papers, but I do not find any references to them being published in peer reviewed journals. In which case such discussion is not appropriate here. You may wish to submit your ideas to the Independent Research (http://www.physicsforums.com/forumdisplay.php?f=146) Forum after first reading their submission rules.
Rather than have a lengthy discussion about all sorts of unpublished speculative theories, which may mislead others reading the Forum and swamp the thread, what I am doing here is collating a number of predictions of the GP-B experiment that have either been published in a peer reviewed journal, or that have been endorsed and accepted on the physics ArXiv e-print archive (http://arxiv.org/). This I hope is in line with the Physics Forums Global Guidelines (http://www.physicsforums.com/showthread.php?t=5374) on Overly Speculative Posts:
One of the main goals of PF is to help students learn the current status of physics as practiced by the scientific community; accordingly, Physicsforums.com strives to maintain high standards of academic integrity. There are many open questions in physics, and we welcome discussion on those subjects provided the discussion remains intellectually sound. It is against our Posting Guidelines to discuss, in most of the PF forums, new or non-mainstream theories or ideas that have not been published in professional peer-reviewed journals or are not part of current professional scientific discussion. Posts deleted under this rule will be accompanied by a private message from a Staff member, with an invitation to resubmit the post in accordance with our Independent Research Guidelines. Poorly formulated personal theories, unfounded challenges of mainstream science, and overt crackpottery will not be tolerated anywhere on the site.

Furthermore I find your theory confused for reasons I will post below.

Garth

Garth

Mar5-07, 04:41 AM

Garth –If there were only a few arc seconds of precession caused by local forces (most now believe local forces are responsible for ALL of the observed 50”p/y), then the earth’s axis would have to obey the local forces, even if it were occurring within a larger moving frame (a solar system in motion). Thus the precession observable we would see from earth (relative to IM Pegasi) would be equal to the local earth wobble plus the binary motion. In effect, the local wobble helps translate the binary orbital motion into a larger observable. So it is possible much of the observable we call “precession” may in fact be due to the geometric effect of a solar system in motion.

There are three issues here that you are confusing, these issues may be expressed as three questions:

1. What is observed on the Earth's surface of the movement of the plane of the Earth's rotation (celestial equator) relative to the plane of the Earth's orbit around the Sun (ecliptic)?

Both the direction of the Earth's rotation axis (because it is an oblate spheroid) and the elements of the Earth's orbit around the Sun may change due to perturbations from other gravitating masses.

2. What is observed by the GP-B satellite of the direction of spin of its four gyroscopes relative to IM Pegasi, a binary radio star that orbits, as the Sun orbits, around the galactic centre?

3. What is the motion of IM Pegasi relative to the distant quasar 3C454.3?

The gyros are in free fall, and great care has gone into making sure all non-gravitational forces (remnant air resistance etc.) on the satellite have been corrected for by using micro-thrusters.

The experiment is testing how a vector is parallel transported through space-time, that is how the gyros' spin access is precessing relative to the distant quasar 3C454.3.

In classical physics the gyros would not precess relative to quasar 3C454.3 at all, but this is not classical physics; in GR and certain other alternative theories, the parallel transportation of the gyros' axial direction vector is expected to precess N-S and E-W by various specific amounts.

The plane of the ecliptic is defined relative to the celestial sphere by the 'Earth as a gyro' spinning at an angle relative to its orbit around the Sun. As I explained in my post #72 above this is affected by the gravitational action on the Earth's oblate spheroid of the Moon, then Sun, then Jupiter and then the other planets and then maybe by a possible solar binary companion. These effects are well modelled, the effect of a binary companion would be small < 0.5"/yr and certainly not the 50.3"/yr precession of the equinoxes.

The gravitational action of the Moon and Sun acting on the Earth's oblate spheroid is cross checked in two independent measurements:

1. The extra nutation of the Earth's axial direction caused by the Sun and Moon varying in relative direction to each other.

2. The accurate determination of the Earth's geoid by the measurements of close Earth satellite orbits.

This geometric effect is a little used phrase but I got it from VLBI. In correspondence with VLBI, I was told that the effect of the solar system moving around the galactic core (at the estimated rate of once every 240 million years) would result in a geometric effect of ~.005”p/y within the precession observable as seen from earth. Consequently, if the sun were part of a binary or ternary (as Glen prefers) system that took ~26,000 years to complete one orbit the “geometric effect” would be about 50” p/y. If this were the case then most (but not all) of what we call precession is actually the geometric effect of the binary motion.

The 'VLBI' geometric effect is a precession of the galactic coordinate system as the Sun orbits the galactic centre, measured relative to the direction of the centre of the galaxy. It does not affect the line of nodes (defined by the intersection of the planes of the ecliptic and that of the celestial equator) relative to distant extra-galactic quasars such as 3C454.3.

Garth

Polestar101

Mar5-07, 02:11 PM

henryco

Mar5-07, 03:24 PM

So give me your best guess: Now that we know there is noise beyond the polhode issue, what do you think is the source of that “…noise and interference…”?

Walter

Polestar101, i thought you were only guessing that the GP-B team has big unexpected effects. Now you say that you know for sure that they see those effects. Are you still in contact with them and did you follow the recent evolution of their analysis? Is polestar your real name? :smile:

In a theory where space is divided into many areas by discontinuities may be can we imagine that freely falling frames determine the inertial frames only up to a rotating motion. In GR, there is no such distinction between what i would call global and local inerty. Gravity and gravity alone is supposed to completely determine the inertial frames. A local inertial frame is in free fall so that locally, gravitational effects are suppressed as required by the equivalent principle. A global inertial frame might be something else: a frame not rotating in such a way that in it, global inertial forces vanish every where.
not rotating with respect to what?
Newton answered with respect to absolute space
Mach answered with respect to the fixed stars
Einstein answered with respect to the total gravitational field (local sources+global background).

Why not a new kind of answer:
A global inertial frame is one which is not rotating with respect to the local superbubble we are living in...but certainly rotating with respect to the fixed stars. Once the global inertial frame is determined, an extra free fall accélération remains to be applied in order to cancel gravity.
Would all this make sense to you?

best regards

F H-C

Garth

Mar5-07, 06:13 PM

Garth – Thank you for your thoughts. Unfortunately, they do not address the recently reported concerns of the GP-B team “…sources of noise and interference that are buried in the data, along with the relativity signals” (Feb 9th release). As you know, these need to be separated out to find the GR effects. So while I applaud your efforts to keep this thread focused on the GR effects, let us be aware that the other data picked up by GP-B needs to be understood as it may well be of fundamental importance to this topic. This is the reason that Glen and I and others have “speculated” about possible other motions or contributing factors.Indeed the other sources of noise and interference have to be understood, but these are affecting the smallest margins of error at the less than 1 milliarcsec/yr level. That is why the proper motion of IM Pegasi, relative to the distant quasar, had to re-assessed at that same level.
It is clear we disagree about the solidity of current precession theory. You may be right that it is well modeled but not from first principles. Consequently, I do not share your confidence that the effect of a hypothetical companion would be limited to .5”p/y. If much of what we call the precession observable turns out to be primarily the geometric effect of a solar system in motion then it would skew this number radically. Nonetheless, I recognize your traditional viewpoint and agree this must be given first consideration until such sources of “…noise and interference…” can be properly understood. But let us keep in mind that those unexpected signals may be hinting at something we don’t know.As I have said, I don't understand your reasoning. If the solar system is orbiting a solar binary companion, which has to be far enough away not to drastically perturb planetary orbits, it would not show up in the precession of the equinoxes, except at that small (< 1 milliarcsec/yr) level. The line of nodes of the intersection of the ecliptic and celestial equator would point to the same distant quasars, and measured against ordinary local stars would show a small precession of galactic coordinates (due to the Sun orbiting the galactic centre) and those local stars' differential galactic rotation described by the Oort constants. If the hypothetical binary companion was actually observable then it would be seen to move at the system's orbital rate relative to the fixed stars. Garth, you have been very supportive of GP-B and party line physics and I sincerely respect your opinions. So give me your best guess: Now that we know there is noise beyond the polhode issue, what do you think is the source of that “…noise and interference…”? The interference, I surmise without yet seeing the GP-B's team analysis, might come from the interaction of the SQUIDs measuring the London effect on the cryogenic gyroscopes' surfaces, from non-inertial forces acting on the spacecraft, drag and thruster leakage, radiation pressures from both external and internal sources and the like.

What is really important is for these 'noises' to be understood correctly and corrected for to reveal the pure relativistic signal, which will yield the answer to the question: "Exactly how is a vector (the gyroscopes' spin axis) parallel transported through the space-time around a rotating Earth in polar orbit around the Sun?"

At a higher level of accuracy (smaller error) the rotation of the Sun about a hypothetical companion could also influence this answer as well as the whole system's rotation around the galaxy.

Periodicities would be important in separating out these various sources of space-time curvature.

The final result is anybody's guess at the moment, so the present question is: "Are the GP-B results consistent with the GR predictions, or with one of the alternatives, or with something completely different (as in F H-C's 'rotating inertial compasses' scenario)?"

As I have said there have been other ways of making the geodetic and frame dragging measurements, such as the dynamics of the double pulsar, but these have theoretical degeneracies in them, so the question is still open.

Not long now to find out!

Garth

Polestar101

Mar13-07, 12:30 AM

Indeed the other sources of noise and interference have to be understood, but these are affecting the smallest margins of error at the less than 1 milliarcsec/yr level.

Do you know for a fact that the unknown signals are less than 1 milliarcsec? That would be good news for GPB. I understand that is the hope and expectation but was there an actual press release that said that? Did I miss something?

Walter

Garth

Mar13-07, 03:25 AM

Do you know for a fact that the unknown signals are less than 1 milliarcsec? That would be good news for GPB. I understand that is the hope and expectation but was there an actual press release that said that? Did I miss something?

WalterWalter from the most recent GP-B website Status update as of 9 February 2007 (http://einstein.stanford.edu/).
Now that the gyro polhode behavior is well understood, we have been able to shift our focus to identifying and addressing some subtle systematic sources of noise and interference that are buried in the data, along with the relativity signals. Identifying and removing as many of these subtle systematic effects as possible is critically important for reducing the margin of error in our final results—especially the frame-dragging result. While we have been making steady progress in these efforts, it has proven to be a slow and painstaking process, and it is now apparent that several more months of data analysis will be required to achieve the lowest possible margin of error.
From which I understand that these subtle systematic effects give errors at the highest level of accuracy they are trying to achieve at the 0.1 milliarcsec level.

The precession of IM Pegasi is already known at the 1 milliarcsec accuracy level, they are evaluating the precession of the gyros at an OOM greater than that.

Of course what they do not say is what are the relativity signals buried in the data and whether they are consistent with the predictions of GR or otherwise.

To refresh this thread, the competing theories and predictions are, with the caveat that some or most of these alternatives may already be inconsistent with present tests of GR as detailed in Clifford Will's paper The Confrontation between General Relativity and Experiment (http://arxiv.org/abs/gr-qc/0510072):

Einstein's General Relativity(GR)
Barber's Self Creation Cosmology (http://arxiv.org/abs/gr-qc/0302026) (SCC),
Moffat's Nonsymmetric Gravitational Theory (http://arxiv.org/abs/gr-qc/0405091) (NGT),
Hai-Long Zhao's Mass Variance SR Theory (http://uk.arxiv.org/abs/gr-qc/0512088) (MVSR),
Stanley Robertson's Newtonian Gravity Theory (http://arxiv.org/abs/gr-qc/0502088) (NG),
Junhao & Xiang's Flat Space-Time Theory (http://arxiv.org/abs/physics/0101017) (FST).
R. L. Collin's Mass-Metric Relativity (http://www.arxiv.org/abs/physics/0012059) (MMR) and
F. Henry-Couannier's Dark Gravity Theory (http://www.arxiv.org/abs/gr-qc/0610079) (DG).

The predictions are:

1. GPB Geodetic precession (North-South)
GR = 6.6144 arcsec/yr
SCC = 4.4096 arcsec/yr
NGT = 6.6144 - a small \sigma correction arcsec/yr
MVSR = 6.6144 arcsec/yr
NG = 1.6536 arcsec/yr
FST = 4.4096 arcsec/yr
MMR = -6.56124 arcsec/yr
DG = 6.6144 arcsec/yr

2. GPB gravitomagnetic frame dragging precession (East-West)
GR = 0.0409 arcsec/yr
SCC = 0.0409 arcsec/yr
NGT = 0.0409 arcsec/yr
MVSR = 0.0102 arcsec/yr
NG = 0.0102 arcsec/yr
FST = 0.0000 arcsec/yr
MMR = -0.01924 arcsec/yr
DG = 0.0000 arcsec/yr

And from The stars of Pegasus (http://www.alcyone.de/SIT/bsc/) from the Bright Star Catalogue, 5th Revised Ed. (Preliminary Version) (Hoffleit+, 1991, Yale University Observatory) as distributed by the Astronomical Data Center at NASA Goddard Space Flight Center.

IM Pegasi

RA J2000 : 22h 53m 2.3s
DEC J2000 : +16° 50' 28"
Proper motion in RA : -0.018 arcsec/y
Proper motion in DEC : -0.024 arcsec/y
mag : 5.64
MK spectral class : K1-2II-III

The Proper motion in RA will affect the E-W precession and the
Proper motion in DEC will affect the N-S precession.

Garth

sylas

Mar14-07, 05:36 AM

Hi Garth. There is another "theory" you might like to add to this list.

Ronald Hatch, famous for work with the GPS system, has proposed a theory which addresses defects as he sees them in relativity. The theory is called "Modified Lorentz Ether Theory" (MLET). It is a part of what Hatch calls "Ether Gauge Physics". The home page for this theory is http://www.egtphysics.net/Index.htm

In a paper at that site, Hatch says:

Another Prediction

Incidentally, I have already predicted [23] that Gravity Probe B will detect a different amount of geodetic precession than that predicted by the general theory. I used a rather long argument to conclude that the predicted spin-orbit component (2.3 arc seconds per year) was only half the size it should be. The rest of the geodetic precession was due to space curvature and contributed 4.6 arc seconds per year. A simple method of arriving at my new prediction is to note that, if one measures time with a clock external to the gravitational field (local clock rate is immaterial), the "space curvature" (gradient of ether density) is twice what the general theory predicts. This leads directly to my prediction that the total geodetic precession measured by GPB will be 9.2 arc seconds per year rather than the general theory prediction of 6.9 arc seconds per year.
—source (http://www.egtphysics.net/GPS/relGPS.pdf )

I don't know the date on this; I think it might be around 2000. The figures may need a bit of fixing. If someone knows what are curvature and spin-orbit components, then it looks like you can just double the spin-obit portion to get Hatch's prediction.

The paper mentions frame dragging, but does not appear to give any alternative prediction that I can see.

I don't know if this is serious enough to merit including in your list, but there you go. You can add to the list:

Ronald Hatch's Modified Lorentz Ether Theory (http://www.egtphysics.net/GPS/relGPS.pdf) (MLET)
1. GPB Geodetic precession (North-South)
MLET = ~9 arcsec/yr

Cheers -- Sylas

Garth

Mar14-07, 05:55 PM

henryco

Mar16-07, 06:12 AM

As I have said there have been other ways of making the geodetic and frame dragging measurements, such as the dynamics of the double pulsar, but these have theoretical degeneracies in them, so the question is still open.
Garth

Hello Garth,

Do you have a reference on this or can you tell us about this degenerescence or on how the frame dragging was measured with the double pulsar: is it the effect of the spin of the compagnion star that is measured on the pulsar trajectory or spin period or something else?

thanks
F H-C

Garth

Mar16-07, 07:17 AM

All these tests to date have only measured the trajectories of planets, stars and photons through a vacuum and compared them with the geodesics of GR.

Einstein's Field Equation

R_{\mu \nu} - 1/2g_{\mu \nu}R = 8\pi GT{\mu \nu}

has only actually been tested in the vacuum case

R_{\mu \nu} = 8\pi GT{\mu \nu}.

Any theory with an action that reduces to that of GR in vacuo will also predict the same geodesics.

One example of such a theory can be found here (http://springerlink.metapress.com/content/r6k036p7380275qu/?p=7e4bd7b15f884e0694865c27e99a6f86&pi=7) and can be downloaded for free here (http://arxiv.org/pdf/gr-qc/0302026).

Discussion about the actions of these two theories can be found here (http://www.springerlink.com/content/q244733l8168812q/) and also free in Section 2 in the eprint here (http://arxiv.org/pdf/gr-qc/0212111 ). References to further papers are also to be found in those papers.

Tests of the Equivalence Principle and the gravitational red shift of light fall into another category, but again there is a degeneracy between these two theories that will first be resolved by GP-B.

Not long now! :rolleyes:

Garth

sylas

Mar28-07, 07:16 AM

Hi Garth,

In the lead up to the release of initial results, I've looked over the links you gave to various predictions.

My comments/questions are as follows.

Zhao's MVSR theory, according to your cited link, predicts zero geodetic effect. You have it recorded as 6.6144. Can you check the paper and either fix the prediction, or explain what I've missed?

I read Robertson as predicting an identical geodetic effect, and a 1/4 gravetomagnetic effect. You see to have given them both as 1/4 the GR prediction.

We agree on Junhao and Xiang. I don't see any mention in their paper of the gravetomagnetic effect; but the style of their theory seems to suggest rotation of the mass will have no effect. Is this right?

I can't see any mention of Gravity Probe B in Collins' paper. How did you obtain the values in that case? Were you able to apply the theory and calculate?

Henry-Couannier seems pretty clear. No frame-dragging.

Cheers -- Sylas

Garth

Mar28-07, 12:53 PM

I'll check, yes you are correct on Zhao and Robertson! Whoops!

The Collins' prediction came from Collins himself on this thread in post #25 ('rusty').

Garth

Garth

Mar28-07, 01:03 PM

The corrected :blushing: (And thank you Sylas!) predictions of the following alternative theories are as follows:

They have been published in refereed journals, or on the Physics ArXiv, and make specific and falsifiable alternative predictions of the outcome of the Gravity Probe B experiment.

Einstein's General Relativity(GR)
Barber's Self Creation Cosmology (http://arxiv.org/abs/gr-qc/0302026) (SCC),
Moffat's Nonsymmetric Gravitational Theory (http://arxiv.org/abs/gr-qc/0405091) (NGT),
Hai-Long Zhao's Mass Variance SR Theory (http://uk.arxiv.org/abs/gr-qc/0512088) (MVSR),
Stanley Robertson's Newtonian Gravity Theory (http://arxiv.org/abs/gr-qc/0502088) (NG),
Junhao & Xiang's Flat Space-Time Theory (http://arxiv.org/abs/physics/0101017) (FST).
R. L. Collin's Mass-Metric Relativity (http://www.arxiv.org/abs/physics/0012059) (MMR) and
F. Henry-Couannier's Dark Gravity Theory (http://www.arxiv.org/abs/gr-qc/0610079) (DG).

The predictions are:

1. GPB Geodetic precession (North-South)
GR = 6.6144 arcsec/yr
SCC = 4.4096 arcsec/yr
NGT = 6.6144 - a small \sigma correction arcsec/yr
MVSR = 0.0 arcsec/yr
NG = 6.6144 arcsec/yr
FST = 4.4096 arcsec/yr
MMR = -6.56124 arcsec/yr
DG = 6.6144 arcsec/yr

2. GPB gravitomagnetic frame dragging precession (East-West)
GR = 0.0409 arcsec/yr
SCC = 0.0409 arcsec/yr
NGT = 0.0409 arcsec/yr
MVSR = 0.0102 arcsec/yr
NG = 0.0102 arcsec/yr
FST = 0.0000 arcsec/yr
MMR = -0.01924 arcsec/yr
DG = 0.0000 arcsec/yr

And from The stars of Pegasus (http://www.alcyone.de/SIT/bsc/) from the Bright Star Catalogue, 5th Revised Ed. (Preliminary Version) (Hoffleit+, 1991, Yale University Observatory) as distributed by the Astronomical Data Center at NASA Goddard Space Flight Center.

IM Pegasi

RA J2000 : 22h 53m 2.3s
DEC J2000 : +16° 50' 28"
Proper motion in RA : -0.018 arcsec/y
Proper motion in DEC : -0.024 arcsec/y
mag : 5.64
MK spectral class : K1-2II-III

Of course, these alternative theories have to pass all the other tests of GR as detailed in Clifford Will's paper The Confrontation between General Relativity and Experiment (http://arxiv.org/abs/gr-qc/0510072). Some of them might already have failed those tests.

Garth

sylas

Mar28-07, 07:49 PM

I'll check, yes you are correct on Zhao and Robertson! Whoops!

The Collins' prediction came from Collins himself on this thread in post #25 ('rusty').

Garth

Found it! Thanks. And I am glad we are on the same page in the other predictions. I've posted a kind of parallel thread to this one in another forum where I am active -- TheologyWeb. (Gravity Probe B -- results due April 14 (http://www.theologyweb.com/campus/showthread.php?t=94632)). It's not a physics forum, but the matter came up in other discussions and there are a number of folks who really enjoy this kind of story, so I made the thread for it.

In my table I omitted Moffatt's theory because I was not able to quantify the expected shift. He gives bounds, but they refer to the stress-energy tensor and I was not able to carry through any calculation to even get a bound on the difference. I added Ron Hatch's "Modified Lorentz Ether Theory", because it is of special interest to some of the folks at TheologyWeb. We have an enthusiastic geocentrist there (yes, really) and he cites Hatch (indirectly) for arguments based on GPS, Aether and so on. Hatch is not a geocentrist, of course.

Rusty has posted twice at this forum, and the two posts seem inconsistent with each other. In his first post, he gave the numbers you have quoted (and which I also have used in the other forum). But about two weeks later Rusty posted msg #11 (http://www.physicsforums.com/showthread.php?p=1055292#post1055292) of "The gpb test of GR" in which he seems to say he gets the same result for geodetic effect. I've posted to that thread to ask him... but I guess he is not active here.

Cheers -- Sylas

Garth

Mar29-07, 02:28 AM

Yes I had missed that, well caught, but in that Rusty's post he doesn't say anything about his geodetic effect, does he?.
Nothing like keeping your options open!

I included Moffat because NGT is published on the ArXiv and in Phys. Rev. D41, 3111 (1990). and J. Math. Phys. 36, 3722 (1995) and like the Brans Dicke theory allows a small variation in the frame-dragging result, which may be detected. Another such theory is Chern-Simons gravity whose frame dragging result has just been published.

I do not include Hatch because it is only a private publication.

Garth

Garth

Mar29-07, 03:08 AM

A new prediction, published today for Chern-Simons (CS) gravity, which arises as a model independent extension of 4-dimensional compactifications of string theory. Here I have also included for completeness the Brans-Dicke theory.

These have all been published in refereed journals, or on the Physics ArXiv, and make specific and falsifiable alternative predictions of the outcome of the Gravity Probe B experiment.

Einstein's General Relativity(GR)
Brans-Dicke theory (BD)
Barber's Self Creation Cosmology (http://arxiv.org/abs/gr-qc/0302026) (SCC),
Moffat's Nonsymmetric Gravitational Theory (http://arxiv.org/abs/gr-qc/0405091) (NGT),
Hai-Long Zhao's Mass Variance SR Theory (http://uk.arxiv.org/abs/gr-qc/0512088) (MVSR),
Stanley Robertson's Newtonian Gravity Theory (http://arxiv.org/abs/gr-qc/0502088) (NG),
Junhao & Xiang's Flat Space-Time Theory (http://arxiv.org/abs/physics/0101017) (FST).
R. L. Collin's Mass-Metric Relativity (http://www.arxiv.org/abs/physics/0012059) (MMR) and
F. Henry-Couannier's Dark Gravity Theory (http://www.arxiv.org/abs/gr-qc/0610079) (DG).
Alexander and Yunes' prediction for the Chern-Simons (http://kr.arxiv.org/abs/hep-th/0703265v1) gravity theory (CS).

The predictions are:

1. GPB Geodetic precession (North-South)
GR = 6.6144 arcsec/yr
BD = (3\omega + 4)/(3\omega + 6) 6.6144 arcsec/yr
SCC = 4.4096 arcsec/yr
NGT = 6.6144 - a small \sigma correction arcsec/yr
MVSR = 0.0 arcsec/yr
NG = 6.6144 arcsec/yr
FST = 4.4096 arcsec/yr
MMR = -6.56124 arcsec/yr
DG = 6.6144 arcsec/yr
CS = 6.6144 arcsec/yr

2. GPB gravitomagnetic frame dragging precession (East-West)
GR = 0.0409 arcsec/yr
BD = (2\omega + 3)/(2\omega + 4) 0.0409 arcsec/yr
SCC = 0.0409 arcsec/yr
NGT = 0.0409 arcsec/yr
MVSR = 0.0102 arcsec/yr
NG = 0.0102 arcsec/yr
FST = 0.0000 arcsec/yr
MMR = -0.01924 arcsec/yr
DG = 0.0000 arcsec/yr
CS = 0.0409 arcsec/yr + CS correction

And from The stars of Pegasus (http://www.alcyone.de/SIT/bsc/) from the Bright Star Catalogue, 5th Revised Ed. (Preliminary Version) (Hoffleit+, 1991, Yale University Observatory) as distributed by the Astronomical Data Center at NASA Goddard Space Flight Center.

IM Pegasi

RA J2000 : 22h 53m 2.3s
DEC J2000 : +16° 50' 28"
Proper motion in RA : -0.018 arcsec/y
Proper motion in DEC : -0.024 arcsec/y
mag : 5.64
MK spectral class : K1-2II-III

Of course, these alternative theories have to pass all the other tests of GR as detailed in Clifford Will's paper The Confrontation between General Relativity and Experiment (http://arxiv.org/abs/gr-qc/0510072). Some of them might already have failed one or more of those tests.

Garth

Kris Krogh

Mar30-07, 07:31 PM

Hi Garth,

The data you have for IM Pegasi have been superseded by more accurate measurements from the HIPPARCOS satellite, which you can find here:

http://archive.ast.cam.ac.uk/hipp/hipparcos.html

The HIPPARCOS catalog gives the proper motion as:

PM(ra) (mas/yr): -20.97
PM(dec) (mas/yr): -27.59
Err(PMra) (mas/yr) 0.61
Err(PMdec) (mas/yr): 0.57

Also, here are some papers describing a quantum-mechanical theory of gravity making a different prediction for Gravity Probe B:

http://lanl.arxiv.org/abs/astro-ph/9910325
http://lanl.arxiv.org/abs/astro-ph/0409615
http://lanl.arxiv.org/abs/astro-ph/0508290
http://lanl.arxiv.org/abs/astro-ph/0606489

This is based on the optics of de Broglie waves rather than space-time curvature. The geodetic precession is the same as in GR, but the frame-dragging effect is zero -- the same thing you've listed for DG. (You could call this WG, for wave gravity.)

Best wishes,

Kris Krogh

Garth

Mar31-07, 03:54 AM

Thank you Kris, and and very warm welcome to these Forums!

Excellent, that is just what I wanted, I will update the list of predictions. Your 'Wave-Gravity' theory looks very interesting, I will study it closely.

I am interested that 'WG' also predicts the observed blue-shift of the Pioneer spacecraft signals, SCC is also able to explain them, but does so as a clock-drift between ephemeris and atomic clocks.

The HIPPARCOS catalogue is very useful, thank you. Though it seems to make the work of the VLBI team rather redundant and does it not bring into question the 'blind' element of the GP-B's team analysis?

However, the VLBI data is necessary as it keeps track of the day by day changes to IM Pegasi relative to the distant quasar to compare with the daily and orbit-by-orbit changes in the direction of the gyroscopes' spin axes relative to IM Pegasi.

As this radio star is a binary its own track across the sky is complicated and on top of that there are other perturbations such as the gyroscopes' polhode motion and the geodetic effect from the Sun to eliminate.

Kris, have you seen we discussed your paper astro-ph/0701653 refuting 'Iorio's "high-precision measurement" of frame-dragging with the Mars Global Surveyor' on the thread Gravity Probe B (http://www.physicsforums.com/showthread.php?t=152825)?

Garth

Garth

Mar31-07, 04:21 AM

Another theory (WG) is here added to the list of predictions.

These theories and their predictions of the Gravity Probe B experiment have all been published in refereed journals, or on the Physics ArXiv. Most of them make specific and falsifiable alternative predictions of the outcomes.

Einstein's General Relativity(GR)
Brans-Dicke theory (BD)
Barber's Self Creation Cosmology (http://arxiv.org/abs/gr-qc/0302026) (SCC),
Moffat's Nonsymmetric Gravitational Theory (http://arxiv.org/abs/gr-qc/0405091) (NGT),
Hai-Long Zhao's Mass Variance SR Theory (http://uk.arxiv.org/abs/gr-qc/0512088) (MVSR),
Stanley Robertson's Newtonian Gravity Theory (http://arxiv.org/abs/gr-qc/0502088) (NG),
Junhao & Xiang's Flat Space-Time Theory (http://arxiv.org/abs/physics/0101017) (FST).
R. L. Collin's Mass-Metric Relativity (http://www.arxiv.org/abs/physics/0012059) (MMR) and
F. Henry-Couannier's Dark Gravity Theory (http://www.arxiv.org/abs/gr-qc/0610079) (DG).
Alexander and Yunes' prediction for the Chern-Simons (http://kr.arxiv.org/abs/hep-th/0703265v1) gravity theory (CS).
Kris Krogh's Wave Gravity Theory (http://lanl.arxiv.org/abs/astro-ph/9910325) (WG)
The predictions are:

A. GPB Geodetic precession (North-South)

GR = 6.6144 arcsec/yr
BD = (3\omega + 4)/(3\omega + 6) 6.6144 arcsec/yr
SCC = 4.4096 arcsec/yr
NGT = 6.6144 - a small \sigma correction arcsec/yr
MVSR = 0.0 arcsec/yr
NG = 6.6144 arcsec/yr
FST = 4.4096 arcsec/yr
MMR = -6.56124 arcsec/yr
DG = 6.6144 arcsec/yr
CS = 6.6144 arcsec/yr
WG = 6.6144 arcsec/yr

B. GPB gravitomagnetic frame dragging precession (East-West)

GR = 0.0409 arcsec/yr
BD = (2\omega + 3)/(2\omega + 4) 0.0409 arcsec/yr
SCC = 0.0409 arcsec/yr
NGT = 0.0409 arcsec/yr
MVSR = 0.0102 arcsec/yr
NG = 0.0102 arcsec/yr
FST = 0.0000 arcsec/yr
MMR = -0.01924 arcsec/yr
DG = 0.0000 arcsec/yr
CS = 0.0409 arcsec/yr + CS correction
WG = 0.0000 arcsec/yr

So there is a degeneracy between the Dark Gravity (DG) and Wave Gravity (WG) theories. It will be interesting to see whether this may be resolved in another test, or whether the theories have fundamentally the same basis that is approached from two different directions.

We also have the tracking of the guide star IM Pegasi from the HIPPARCOS catalogue (http://archive.ast.cam.ac.uk/hipp/hipparcos.html); just key in
'IM Pegassi' into the Target name of that Query Form. (Thank you Kris):

RA (J1991.25) : 22h 53m 02.279"
DEC (J1991.25) : +160 50' 28.540"
Proper motion in RA : -0.02097 \pm 0.00063 arcsec/yr.
Proper motion in DEC : -0.02759 \pm 0.00043 arcsec/yr.
mag : 6.033 (HIPP)
MK spectral class : K1III SB (HIPP)

Of course, these alternative theories have to pass all the other tests of GR as detailed in Clifford Will's paper The Confrontation between General Relativity and Experiment (http://arxiv.org/abs/gr-qc/0510072).

Some of them might already have failed one or more of those tests.

Garth

henryco

Apr1-07, 05:31 AM

Another theory (WG) is here added to the list of predictions.

So there is a degeneracy between the Dark Gravity (DG) and Wave Gravity (WG) theories. It will be interesting to see whether this may be resolved in another test, or whether the theories have fundamentally the same basis that is approached from two different directions.

We also have the tracking of the guide star IM Pegasi from the HIPPARCOS catalogue (http://archive.ast.cam.ac.uk/hipp/hipparcos.html); just key in
'IM Pegassi' into the Target name of that Query Form. (Thank you Kris):

RA (J1991.25) : 22h 53m 02.279"
DEC (J1991.25) : +160 50' 28.540"
Proper motion in RA : -0.02097 \pm 0.00063 arcsec/yr.
Proper motion in DEC : -0.02759 \pm 0.00043 arcsec/yr.
mag : 6.033 (HIPP)
MK spectral class : K1III SB (HIPP)
Garth

:bugeye: this is an april fish, isn't it ?

fred henry-couannier

Garth

Apr1-07, 08:28 AM

:bugeye: this is an april fish, isn't it ?

fred henry-couannier:confused:
Hi Fred,
Please elucidate, my post #101 wasn't meant to be an April Fool joke, although I am always prone to make mistakes......(and how! :rolleyes:)

Fred, did you read Kris' post #99?

[Edit- I have just noticed I have copied out the incorrect errors on the PM in RA and Dec, I followed the wrong line across; they should be as Kris originally said: \pm 0.00061 arcsec/yr and +/- 0.00057 arcsec/yr. respectively. ]

Garth

Garth

Garth

Apr1-07, 08:50 AM

I have here repeated the list of predictions and the Proper Motion of IM Pegasi again with the errors in the PM(RA) and PM(Dec) corrected.

These theories and their predictions of the Gravity Probe B experiment have all been published in refereed journals, or on the Physics ArXiv. Most of them make specific and falsifiable alternative predictions of the outcomes.

Einstein's General Relativity(GR)
Brans-Dicke theory (BD)
Barber's Self Creation Cosmology (http://arxiv.org/abs/gr-qc/0302026) (SCC),
Moffat's Nonsymmetric Gravitational Theory (http://arxiv.org/abs/gr-qc/0405091) (NGT),
Hai-Long Zhao's Mass Variance SR Theory (http://uk.arxiv.org/abs/gr-qc/0512088) (MVSR),
Stanley Robertson's Newtonian Gravity Theory (http://arxiv.org/abs/gr-qc/0502088) (NG),
Junhao & Xiang's Flat Space-Time Theory (http://arxiv.org/abs/physics/0101017) (FST).
R. L. Collin's Mass-Metric Relativity (http://www.arxiv.org/abs/physics/0012059) (MMR) and
F. Henry-Couannier's Dark Gravity Theory (http://www.arxiv.org/abs/gr-qc/0610079) (DG).
Alexander and Yunes' prediction for the Chern-Simons (http://kr.arxiv.org/abs/hep-th/0703265v1) gravity theory (CS).
Kris Krogh's Wave Gravity Theory (http://lanl.arxiv.org/abs/astro-ph/9910325) (WG)
The predictions are:

A. GPB Geodetic precession (North-South)

GR = 6.6144 arcsec/yr
BD = (3\omega + 4)/(3\omega + 6) 6.6144 arcsec/yr
SCC = 4.4096 arcsec/yr
NGT = 6.6144 - a small \sigma correction arcsec/yr
MVSR = 0.0 arcsec/yr
NG = 6.6144 arcsec/yr
FST = 4.4096 arcsec/yr
MMR = -6.56124 arcsec/yr
DG = 6.6144 arcsec/yr
CS = 6.6144 arcsec/yr
WG = 6.6144 arcsec/yr

B. GPB gravitomagnetic frame dragging precession (East-West)

GR = 0.0409 arcsec/yr
BD = (2\omega + 3)/(2\omega + 4) 0.0409 arcsec/yr
SCC = 0.0409 arcsec/yr
NGT = 0.0409 arcsec/yr
MVSR = 0.0102 arcsec/yr
NG = 0.0102 arcsec/yr
FST = 0.0000 arcsec/yr
MMR = -0.01924 arcsec/yr
DG = 0.0000 arcsec/yr
CS = 0.0409 arcsec/yr + CS correction
WG = 0.0000 arcsec/yr

We also have the tracking of the guide star IM Pegasi from the HIPPARCOS catalogue (http://archive.ast.cam.ac.uk/hipp/hipparcos.html):

RA (J1991.25) : 22h 53m 02.279"
DEC (J1991.25) : +160 50' 28.540"
Proper motion in RA : -0.02097 \pm 0.00061 arcsec/yr.
Proper motion in DEC : -0.02759 \pm 0.00057 arcsec/yr.
mag : 6.033 (HIPP)
MK spectral class : K1III SB (HIPP)

Of course, these alternative theories have to pass all the other tests of GR as detailed in Clifford Will's paper The Confrontation between General Relativity and Experiment (http://arxiv.org/abs/gr-qc/0510072).

Some of them might already have failed one or more of those tests.

Garth

henryco

Apr1-07, 01:51 PM

:confused:
Hi Fred,
Please elucidate, my post #101 wasn't meant to be an April Fool joke, although I am always prone to make mistakes......(and how! :rolleyes:)

Fred, did you read Kris' post #99?
Garth

One essential point is the derivability of Kris exponential solution from basic principles. Did i miss something or did Kriss applied a multiplicative superposition principle in his annex while its potential Phi is still additive!?...which of course is equivalent to postulate the exponential factor from the begining...and is therefore not coherent with f/f_0=1+Phi for the single shell!

Kris Krogh

Apr1-07, 05:29 PM

Hi Garth,

Thanks for mentioning my paper on Iorio's claimed frame dragging measurement.

The HIPPARCOS observations of IM Pegasi were published in 1997. You're right that the VLBI measurements are still important. Without them, it wouldn't be possible to get the intended accuracy for Gravity Probe B, 1% of general relativity's frame dragging effect.

From the abstracts of papers to be given by GP-B people at this month's American Physical Society meeting, it looks like they do expect to achieve that by the end of the year. See this one:

http://meetings.aps.org/Meeting/APR07/Event/65193

Hopefully the preliminary results announced this month will be enough to distinguish between the theories on your list. (Except that DG and WG make the same prediction.)

Hi Fred,

In wave gravity, gravitational potentials are additive, not multiplicative. So they do obey the superposition principle. What are not additive are the effects of those potentials. The same could be said of general relativity, which also has nonlinear effects.

In terms of combining massive bodies, things are different, because their masses are transformed by gravitational potentials. For example, if you have two identical, massive, compact bodies and bring them together, the resulting body won't have twice the potential of one. But whatever gravitational potentials are due to each body after they are combined -- those do add linearly.

The predicted transformation of gravitational mass is shown to agree with ranging observations of the lunar orbit, and with the gravitational energy radiated by accelerating bodies.

Kris Krogh

henryco

Apr2-07, 06:11 AM

Hi Garth,

Proper motion in RA : -0.02097 \pm 0.00063 arcsec/yr.
Proper motion in DEC : -0.02759 \pm 0.00043 arcsec/yr.[/b]
Garth

These numbers from Hypparcos are quite in disagreement with those you gave
earlier
Proper motion in RA :-0.018
Proper motion in DEC :-0.024

Did you mean that the motion of the double star system would explain such evolution ?
Didnt these values from VLBI put already into question the blind analysis of the GP-B team?

Hi Kris,

If you had a look at the DG paper, you must have noticed that we have
almost the same predictions, not only for GP-B but also regarding longitudinal Gravitational waves, and the exponential metric solution in my case. much in common !
So i understand well what you do. My concern is that you cannot at the same time say that for one shell your factor f=1+phi and apply a multiplicative
superposition method: f1.f2.f...fn which is only coherent with f=exp(phi) from the begining (a single shell) and not f=1+phi:
I suppose your phi is as usual 2Gm/rc^2. so suppose you divide your single starting shell into two contributions m=m/2+m/2, the incoherency is that
you dont have f=(1+phi/2)(1+phi/2) though you might have f=exp(phi/2)exp(phi/2) if you had defined from the begining your f as an exponential. but then you would not derive it anymore from basic principles.

The main reason for me to suspect an april Joke is that as y do, you danse salsa, play the guitar, run and have almost the same predictions in you theory
as in mine...:wink:

In my case the exponential is derived from a "kind of bi-metric" field theory equations. I think the degenaracy between our two approaches is broken by discontinuities wich are quite specific to my approach and in my case are responsible for the Pioneer anomaly. I have just a little post here: http://www.arxiv.org/abs/physics/0703018 to explain
the Pioneer anomaly following the discontinuity approach.

I'm also interested by the 50''/year of classical torque induced angular deviation in the GP-B abstract you mentionned. This compares very well with
equinoxe precession per year!! did some people have this in mind earlier in this thread ?

Regards,

F H-C

Garth

Apr2-07, 06:57 AM

These numbers from Hypparcos are quite in disagreement with those you gave
earlier
Proper motion in RA :-0.018
Proper motion in DEC :-0.024

Did you mean that the motion of the double star system would explain such evolution ?
Didnt these values from VLBI put already into question the blind analysis of the GP-B team?
No, simply the Hipparchos catalogue was more accurate and measured from a different time base, we wait for the VLBI confirmation of their results!

Kris Krogh

Apr2-07, 10:19 PM

Hi F H-C,

Thanks for raising this question about my paper. For other readers, I should explain you're referring to Appendix A of this: http://arxiv.org/abs/astro-ph/9910325 It outlines a Gedanken experiement from which exponential expressions for velocities of light and de Broglie waves in gravitational potentials are derived. (For a flat, isotropic space-time.)

It starts with a clock or meter stick, around which increasingly distant shells of matter are added. Each new shell has whatever amount of mass is needed to create equal steps in the gravitational potential between shells. It's assumed the potentials due to each shell add linearly. Given the further assumption that the relativity principle applies where gravitational potentials are uniform, it's shown their cumulative effects are described by (nonlinear) exponentials.

To use a classical analogy, you could compare this situation to a stack of rubber bricks, each compressed by those above. The weight of the pile is a linear function of the number of bricks, but the height isn't. These gravitational potentials add linearly, but their effects don't. (And shouldn't.)

The GP-B abstract doesn't describe a 50''/year effect. That's 50'' over the life of the science experiment, which I think was about 18 months. They say the torque was caused by charged patches on the rotor surfaces, when the spin axis of the spacecraft became misaligned.

If GP-B confirms one of the predictions on Garth's list precisely, we'll know that wasn't from "cherry picking" the data. So in that limited sense it's still a double-blind experiment.

Best wishes,

Kris Krogh

henryco

Apr3-07, 02:57 PM

Hi Kris,

The GP-B abstract doesn't describe a 50''/year effect. That's 50'' over the life of the science experiment, which I think was about 18 months. They say the torque was caused by charged patches on the rotor surfaces, when the spin axis of the spacecraft became misaligned.

Yes but this 50"/year should also be converted into some angle that could directly be compared with an equinox precession.
The conversion should involve the cosine of the angle between the gyroscopes spin axis and the ecliptic plane...does somebody know this for GP-B ?

best regards,

F H-C

Garth

Apr3-07, 07:12 PM

Are you saying this 50"/yr precession has been observed by the GP-B, or are you just speculating? They haven't said anything yet about their findings.

Garth

Kris Krogh

Apr3-07, 11:03 PM

Garth

Apr4-07, 02:47 AM

Hi F H-C,

The GP-B spacecraft was designed to keep its roll axis pointed toward IM Pegasi. The gyro rotors spun on the same axis. This 50'' problem occurred when the orientation of the spacecraft (and gyro housing) changed. It doesn't represent any kind of steady precession. Apparently they've found a way to deal with it.Thank you Kris.

From the April APS Programme (http://www.aps.org/meetings/april/index.cfm):L1.00020 Evidence for Patch Effect Forces on the Gravity Probe B Gyroscopes,
DALE GILL, SAPS BUCHMAN, Stanford University
During the course of the GP-B on-orbit experiment the effect of anomalous forces were observed in the motion of the gyroscope rotors. A likely explanation for the origin of these forces is the existence of patch effect charges on the surface of the rotor. The effects observed were:
a) increased misalignment torques; 1 arcsec/deg/day, b) forces along the direction of the spin axis; 10−7 m/s2, c) spin-down rates in excess of residual gas induced spin-down; 0.4-1.5 μHz/hr, d) charge measurement effects, e) modulation of control effort and position in excess of the ones caused by rotor geometry. While varying from gyroscope to gyroscope all effects are consistent with patches of 20-100mV with extent up to dipole configuration. This poster will present data from analysis of on-orbit performance and ground based experimentation to show that the effects arise from variations in the work function of the rotor’s niobium coating. This poster will include details of the process for application of the coating onto the rotor. The results of a ground based experiment to map variation in the work function of flight spare rotors will also be presented. Finally some possibilities to mitigate these effects on future instruments will be presented.
Also:L1.00027 Gravity Probe B Experiment Error,
BARRY MUHLFELDER, G. MAC KEISER, JOHN TURNEAURE, Stanford University
The GP-B experiment error results from both statistical and systematic sources. Excluding all systematic effects, the on-orbit gyroscope readout noise provides an experiment error noise floor limit of 0.2 marcsec/yr. We have also evaluated the effects of more than 200 systematic sources including: thermal sensitivities of the readout system, non-linearities in the telescope readout, roll phase uncertainty, and spacecraft anomalies. The impact of these and other systematic effects has been mitigated by the development of a variety of techniques. Study of the flight data revealed two unanticipated gyroscope behaviors. These two behaviors, a slowly varying readout scale factor and a specific type of Newtonian torque, are now well understood, and have been incorporated into the data analysis model. Residual errors associated with these and other gyroscope behaviors are included as part of the overall systematic error. The consistency of the results for the four independent gyroscopes provides a crosscheck of gyroscope specific error. Proper summing of all errors for the four gyroscopes gives the experiment error. We will present the most current numerical assessment of all GP-B error sources and will give the associated experiment error.

Garth

henryco

Apr4-07, 08:48 AM

Garth

Apr5-07, 11:16 AM

I have found a GP-B geodetic prediction, with an undetermined parameter b, for the five-dimensional extension of GR theory known as Kaluza-Klein gravity (KK), which I have added to the list.

These theories and their predictions of the Gravity Probe B experiment have all been published in refereed journals, or on the Physics ArXiv. Most of them make specific and falsifiable alternative predictions of the outcomes.

Einstein's General Relativity(GR)
Brans-Dicke theory (BD)
Barber's Self Creation Cosmology (http://arxiv.org/abs/gr-qc/0302026) (SCC),
Moffat's Nonsymmetric Gravitational Theory (http://arxiv.org/abs/gr-qc/0405091) (NGT),
Hai-Long Zhao's Mass Variance SR Theory (http://uk.arxiv.org/abs/gr-qc/0512088) (MVSR),
Stanley Robertson's Newtonian Gravity Theory (http://arxiv.org/abs/gr-qc/0502088) (NG),
Junhao & Xiang's Flat Space-Time Theory (http://arxiv.org/abs/physics/0101017) (FST).
R. L. Collin's Mass-Metric Relativity (http://www.arxiv.org/abs/physics/0012059) (MMR) and
F. Henry-Couannier's Dark Gravity Theory (http://www.arxiv.org/abs/gr-qc/0610079) (DG).
Alexander and Yunes' prediction for the Chern-Simons (http://kr.arxiv.org/abs/hep-th/0703265v1) gravity theory (CS).
Kris Krogh's Wave Gravity Theory (http://lanl.arxiv.org/abs/astro-ph/9910325) (WG)
Hongya Liu & J. M. Overduin prediction of the Kaluza-Klein ( http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v538n1/50681/50681.text.html?erFrom=5252751197746712308Guest#sc 8) gravity theory (KK).

The predictions are:

A. GPB Geodetic precession (North-South)

GR = 6.6144 arcsec/yr.
BD = (3\omega + 4)/(3\omega + 6) 6.6144 arcsec/yr. where \omega >6.
SCC = 4.4096 arcsec/yr.
NGT = 6.6144 - a small \sigma correction arcsec/yr.
MVSR = 0.0 arcsec/yr.
NG = 6.6144 arcsec/yr.
FST = 4.4096 arcsec/yr.
MMR = -6.56124 arcsec/yr.
DG = 6.6144 arcsec/yr.
CS = 6.6144 arcsec/yr.
WG = 6.6144 arcsec/yr.
KK = (1 + b/6 - 3b2 + ...) 6.6144 arcsec/yr. where 0 < b < 0.07.

B. GPB gravitomagnetic frame dragging precession (East-West)

GR = 0.0409 arcsec/yr.
BD = (2\omega + 3)/(2\omega + 4) 0.0409 arcsec/yr.
SCC = 0.0409 arcsec/yr.
NGT = 0.0409 arcsec/yr.
MVSR = 0.0102 arcsec/yr.
NG = 0.0102 arcsec/yr.
FST = 0.0000 arcsec/yr.
MMR = -0.01924 arcsec/yr.
DG = 0.0000 arcsec/yr.
CS = 0.0409 arcsec/yr. + CS correction
WG = 0.0000 arcsec/yr.
KK = 0.0409 arcsec/yr.

We also have the tracking of the guide star IM Pegasi from the HIPPARCOS catalogue (http://archive.ast.cam.ac.uk/hipp/hipparcos.html):

RA (J1991.25) : 22h 53m 02.279"
DEC (J1991.25) : +160 50' 28.540"
Proper motion in RA : -0.02097 \pm 0.00061 arcsec/yr.
Proper motion in DEC : -0.02759 \pm 0.00057 arcsec/yr.
mag : 6.033 (HIPP)
MK spectral class : K1III SB (HIPP)

Of course, these alternative theories have to pass all the other tests of GR as detailed in Clifford Will's paper The Confrontation between General Relativity and Experiment (http://arxiv.org/abs/gr-qc/0510072).

Again I emphasise that some of them may well have already failed one or more of those tests.

Garth

Garth

Apr6-07, 03:11 AM

I have been in discussion with Jonathan Kerr about his paper that makes another prediction for GP-B.

Although it has not yet been published, it is at present going through the peer reviewing process.

As time is short and the first results are due to be announced in eleven days time I here include it as an 'also ran', we shall know shortly, hopefully!

The theory is called "Planck scale gravity," (PSG), and makes the following prediction:

A. GPB Geodetic precession (North-South)

GR = 6.6144 arcsec/yr.
PSG = 0.0000 arcsec/yr.

B. GPB gravitomagnetic frame dragging precession (East-West)

GR = 0.0409 arcsec/yr.
PSG = 0.0409 arcsec/yr.

As the prediction pair is unique in my list above the result should be decisive.
Of course, PSG has to pass all the other tests of GR as detailed in Clifford Will's paper The Confrontation between General Relativity and Experiment (http://arxiv.org/abs/gr-qc/0510072). As with the other alternative theories it may have already failed one or more of those tests.

Garth

sylas

Apr7-07, 09:01 PM

Hey Garth... another minor correction.

12. Hongya Liu & J. M. Overduin prediction of the Kaluza-Klein ( http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v538n1/50681/50681.text.html?erFrom=5252751197746712308Guest#sc 8) gravity theory (KK).

...

12. KK = (1 + b/6 - 3b2 + ...) 6.6144 arcsec/yr. where 0 < b < 0.07.

I think that should be |b| < 0.07, and thus -0.07 < b < 0.07; if I read the paper right. I could not make your link work; but the reference is also in the arxiv archive, at gr-qc/0003034 (http://arxiv.org/abs/gr-qc/0003034).

Overduin appears to be one of the researchers directly involved in the GP-B project.

I've found this thread dealing with different predictions has captured the imagination of a number of amateur readers. Even if someone is not a physicist, this adds a bit of drama to the whole proceeding and gets people interested in the idea of science at work. Thanks!

Cheers -- Sylas

Garth

Apr8-07, 01:49 AM

Hey Garth... another minor correction.

I think that should be |b| < 0.07, and thus -0.07 < b < 0.07; if I read the paper right. I could not make your link work; but the reference is also in the arxiv archive, at gr-qc/0003034 (http://arxiv.org/abs/gr-qc/0003034).
You are quite correct! Thank you.
Overduin appears to be one of the researchers directly involved in the GP-B project.
That's interesting, he was in 2005: The nearly flat universe (http://www.springerlink.com/content/m4ql421t1x338h4v/) Authors: R. J. Adler and J. M. Overduin
(1) Gravity Probe B, Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA, 94305-4085, U.S.A.
I've found this thread dealing with different predictions has captured the imagination of a number of amateur readers. Even if someone is not a physicist, this adds a bit of drama to the whole proceeding and gets people interested in the idea of science at work. Thanks!

Cheers -- SylasIt has certainly captured my imagination!

You are welcome.

Garth

sylas

Apr8-07, 02:00 AM

I've been double checking all these numbers for myself from the cited papers, and I have another proposed correction…

2. Brans-Dicke theory (BD)

...

2. BD = (3\omega + 4)/(3\omega + 6) 6.6144 arcsec/yr. where \omega >6.

....

2. BD = (2\omega + 3)/(2\omega + 4) 0.0409 arcsec/yr.

There's no reference given for this prediction. Let me propose including Brans-Dicke corrections to the gravitational Sagnac effect (http://arxiv.org/abs/gr-qc/0006090) (arxiv gr-qc/0006090) by K.K. Nandi, P.M. Alsing, J.C. Evans, T.B. Nayak, also accepted for Phys.Rev. D63 (2001) 084027

In that paper, the Gravity probe corrections appear right at the end. They give multiplying factors for the geodetic effect as 2/3(3/2 - 2ξ/η), and for the Lense-Thirring effect as 1 - σ/η

Now let me try out these tex tags… Looking back in the paper to eqn 98 on page 22, we have:
\begin{equation*}\begin{split}\sigma&= \frac{1}{\sqrt{(2\varpi+3)(2\varpi+4)}}\\
\eta&= \sqrt{\frac{2\varpi+4}{2\varpi+3}}\\
\xi&= 1 - \eta + 2\sigma\end{split}\end{equation*}

Using these, we can calculate the geodetic effect as follows. The end of the paper gives multiplying factors (to first order) from the GR predictions. Here is the solution for the geodetic factor

\begin{equation*}\begin{split}
\frac{2}{3}(\frac{3}{2}-\frac{2\xi}{\eta})&= 1-\frac{4\xi}{3\eta}\\
&=1-\frac{4-4\eta+8\sigma}{3\eta}\\
&=1-\frac{4}{3}\sqrt{\frac{2\varpi+3}{2\varpi+4}}+\fra c{4}{3}-\frac{8}{3}\sqrt{\frac{(2\varpi+3)}{(2\varpi+4)^2( 2\varpi+3)}}\\
&\approx 1-\frac{4}{3}(1-\frac{1}{2(2\varpi+4)})+\frac{4}{3}-\frac{8}{3(2\varpi+4)}\\
&= 1+\frac{1}{3(\varpi+2)}-\frac{4}{3(\varpi+2)}\\
&= 1-\frac{1}{\varpi+2}\end{split}\end{equation*}

The Lense-Thirring effect multiplying factor is given by
\begin{equation*}\begin{split}
1-\frac{\sigma}{\eta}&= 1 - \sqrt{\frac{2\varpi+3}{(2\varpi+4)^2(2\varpi+3)}}\ \
&=1 - \frac{1}{2\varpi+4}\\
&=\frac{2\varpi+3}{2\varpi+4}
\end{split}\end{equation*}

So I get the same factor for the Lense-Thirring effect, but I think the geodetic effect should be ammended to read:

2. BD = (\varpi + 1)/(\varpi + 2) 6.6144 arcsec/yr. where \varpi >6.

Or equivalently

2. BD = (1 - 1/(\varpi + 2)) 6.6144 arcsec/yr. where \varpi > 6

Cheers -- Sylas

Garth

Apr8-07, 08:41 AM

I've been double checking all these numbers for myself from the cited papers, and I have another proposed correction…
.....................
There's no reference given for this prediction. The references are: Weinberg "Gravitation and Cosmology" 1972:

The Lense-Thirring, "frame dragging" effect,
page 248 equation 9.928 and the line following:
Thus the effects of the rotation of a spherical mass on the precession of spins and perihelia are smaller in the Brans Dicke theory than in general relativity, by a factor of (2\omega + 3)(2\omega + 4).

And for the geodetic effect,
page 238 equation 9.6.24 and the next line which gives:
Thus the effect of a modification of Einstein's field equations on the geodetic precession is simply to multiply it with a factor

\frac{(1 + 2\gamma)}{3}

Now in BD (Weinberg equation 9.9.27):
\gamma = \frac{\omega + 1}{\omega + 2}

so the geodetic effect is to multiply the GR result by a factor:

\frac{3\omega + 4}{3\omega + 6}

So your calculation was not too far out.

Garth

sylas

Apr8-07, 11:09 AM

The references are: Weinberg "Gravitation and Cosmology" 1972:

The Lense-Thirring, "frame dragging" effect,
page 248 equation 9.928 and the line following:

And for the geodetic effect,
page 238 equation 9.6.24 and the next line which gives:

Now in BD (Weinberg equation 9.9.27):
\gamma = \frac{\omega + 1}{\omega + 2}

so the geodetic effect is to multiply the GR result by a factor:

\frac{3\omega + 4}{3\omega + 6}

So your calculation was not too far out.

Garth

Come off it Garth. The issue is not my calculation. It that we now have two difference references, using different formulae for the geodetic effect.

Thanks for your reference; I'll see if I can find it, and add it to the list I'm keeping of different predictions.

In the meantime, if you are interested, you may like to look over the reference I used, by Nandi et al. You are probably much more familiar with Brans-Dicke than I am, and I'd certainly appreciate it. The paper at Brans-Dicke corrections to the gravitational Sagnac effect (http://arxiv.org/abs/gr-qc/0006090) (gr-pq/0006090) is proposing a fix to geodetic that is as I described previously. It's not that my calculation is "not too far out". It is that I'm calculating correctly the formulae as given in a different paper.

There is a factor 2/3 floating around. If you do get a chance to look at this paper by Nandi et al, then look at equation 110, which gives the geodetic effect; and the equation 98, which gives parameters in terms of ϖ, and the final paragraph, which summarizes the prediction.

Now perhaps this is yet another different prediction. I don't know. They claim to be using Brans-Dicke, and it is a fairly recent paper that explicitly mentions Gravity Probe B and the expected result. The paper also appeared in Phys Rev D.

Anyone else who can identify the discrepancy please feel free to help out also.

Cheers -- Sylas. 6 days and counting

Garth

Apr8-07, 03:31 PM

Sylas I have read that paper in some depth and have a question about its method.

The basic equation they use for the Sagnac effect, equation1, is a SR effect well tested on ring laser interferometers.

However, they seem to be explaining a curvature effect by a SR flat space-time one.

In BD the correction is due to the perturbation of the curvature of space-time caused by the presence of the scalar field.

As the Sagnac effect is a time delay, is that not already taken care of in the time component of the GR formulae (i.e. the component not dependent on \gamma)? i.e. If applicable in the GR case it is only an alternative description of the same effect and should predict the same geodetic precession. (As it does for frame-dragging)

But note that your calculation of their geodetic effect, (\omega + 1)/(\omega + 2), is simply \gamma. Now \gamma measures the amount of space curvature per unit M (actually, per unit GM) so their interpretation of the geodetic effect is a purely a space curvature one, the time dilation component has dropped out! I don't think this can be correct as the essence of GR and similar metric theories of gravity is that gravitation is a space-time and not just a space curvature effect.

Any difference between the formulae might then simply be due to an inappropriate application of the Sagnac effect.

Note with the BD \omega ~ 500 their BD correction to the GR prediction is ~ (1 +/- 2.10-3), whereas the Weinberg BD correction is ~ (1 - 10-3)

I too am counting!
Cheers,
Garth

LeBourdais

Apr8-07, 11:23 PM

Hello everybody,

First of all, I apologize for my way of writing in English. I hope it won't be too hard for you to understand what I say.

I am a french physicist from Montreal (B.Sc. Physics, 1974, University of Montreal, M.Sc. Physics partly completed, 1976, University of Montreal)

This thread is much interesting. I myself work on a theory of mine since a couple of years. My theory is not primarily concerned with gravitation: it is a theory that is based on a deterministic model of the physical world with nonlocal hidden variables identified explicitly. But in the end, this theory leads to a new model of gravitation. Regarding GP-B, my theory makes the same predictions as GR about geodetic effect and frame-dragging effect. But it predicts things that are different from GR and that could maybe be confirmed by that experiment, mainly:

1- flatness of 3-D geometry
2- universal "cosmological redshift" of momentum (including the momentum of gravitationally bound objects)
3- a phenomenon that leads to "shifts" in signal frequency (like the one observed in the Pioneer Anomaly)

My theory has never been published in a peer reviewed journal nor on arXiv, and I could not even publish it right now in your Independant Research Forum. So I don't expect it to be listed in your list. I just wanted to give my own predictions before the public announcement of the GP-B results, rather than giving it after :wink:

Friendly

Paul Le Bourdais

Garth

Apr9-07, 04:02 AM

Hi Paul and bienvenue to these Forums!

You might try to put your theory onto the Theory Development Forum, the discipline may help you progress with it.

But as you say it hasn't been published and that its GP-B predictions are the same as GR we will leave it off this thread.

Garth

LeBourdais

Apr9-07, 04:44 AM

Hi Paul and bienvenue to these Forums!
Thanks to you Garth.

You might try to put your theory onto the Theory Development Forum, the discipline may help you progress with it.

But as you say it hasn't been published and that its GP-B predictions are the same as GR we will leave it off this thread.
It's okay for me, I understand very well.

Paul

Garth

Apr10-07, 12:38 PM

As there are only 4 days to go I here re-post all the accepted predictions for comparison with the first results due to be announced on Saturday 14th April at the April APS meeting.

These theories and their predictions of the Gravity Probe B experiment have all been published in refereed journals, or on the Physics ArXiv. Most of them make specific and falsifiable alternative predictions of the outcomes.

Einstein's General Relativity(GR)
Brans-Dicke theory (BD)
Barber's Self Creation Cosmology (http://arxiv.org/abs/gr-qc/0302026) (SCC),
Moffat's Nonsymmetric Gravitational Theory (http://arxiv.org/abs/gr-qc/0405091) (NGT),
Hai-Long Zhao's Mass Variance SR Theory (http://uk.arxiv.org/abs/gr-qc/0512088) (MVSR),
Stanley Robertson's Newtonian Gravity Theory (http://arxiv.org/abs/gr-qc/0502088) (NG),
Junhao & Xiang's Flat Space-Time Theory (http://arxiv.org/abs/physics/0101017) (FST).
R. L. Collin's Mass-Metric Relativity (http://www.arxiv.org/abs/physics/0012059) (MMR) and
F. Henry-Couannier's Dark Gravity Theory (http://www.arxiv.org/abs/gr-qc/0610079) (DG).
Alexander and Yunes' prediction for the Chern-Simons (http://kr.arxiv.org/abs/hep-th/0703265v1) gravity theory (CS).
Kris Krogh's Wave Gravity Theory (http://lanl.arxiv.org/abs/astro-ph/9910325) (WG)
Hongya Liu & J. M. Overduin prediction of the Kaluza-Klein ( http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v538n1/50681/50681.text.html?erFrom=5252751197746712308Guest#sc 8) gravity theory (KK).
Kerr's Planck Scale Gravity: now accepted for publication Predictions of Experimental Results from a Gravity Theory (http://redshift.vif.com/JournalFiles/V14NO2PDF/V14N2KER.pdf) (PSG)

The predictions are:

A. GPB Geodetic precession (North-South)

GR = 6.6144 arcsec/yr.
BD = (3\omega + 4)/(3\omega + 6) 6.6144 arcsec/yr. where \omega >6.
SCC = 4.4096 arcsec/yr.
NGT = 6.6144 - a small \sigma correction arcsec/yr.
MVSR = 0.0 arcsec/yr.
NG = 6.6144 arcsec/yr.
FST = 4.4096 arcsec/yr.
MMR = -6.56124 arcsec/yr.
DG = 6.6144 arcsec/yr.
CS = 6.6144 arcsec/yr.
WG = 6.6144 arcsec/yr.
KK = (1 + b/6 - 3b2 + ...) 6.6144 arcsec/yr. where 0 < b < 0.07.
PSG = 0.0000 arcsec/yr.

B. GPB gravitomagnetic frame dragging precession (East-West)

GR = 0.0409 arcsec/yr.
BD = (2\omega + 3)/(2\omega + 4) 0.0409 arcsec/yr.
SCC = 0.0409 arcsec/yr.
NGT = 0.0409 arcsec/yr.
MVSR = 0.0102 arcsec/yr.
NG = 0.0102 arcsec/yr.
FST = 0.0000 arcsec/yr.
MMR = -0.01924 arcsec/yr.
DG = 0.0000 arcsec/yr.
CS = 0.0409 arcsec/yr. + CS correction
WG = 0.0000 arcsec/yr.
KK = 0.0409 arcsec/yr.
PSG = 0.0409 arcsec/yr.

The guide star IM Pegasi has a proper motion given by the HIPPARCOS catalogue (http://archive.ast.cam.ac.uk/hipp/hipparcos.html):

RA (J1991.25) : 22h 53m 02.279"
DEC (J1991.25) : +160 50' 28.540"
Proper motion in RA : -0.02097 \pm 0.00061 arcsec/yr.
Proper motion in DEC : -0.02759 \pm 0.00057 arcsec/yr.
mag : 6.033 (HIPP)
MK spectral class : K1III SB (HIPP)

Of course, these alternative theories have to pass all the other tests of GR as detailed in Clifford Will's paper The Confrontation between General Relativity and Experiment (http://arxiv.org/abs/gr-qc/0510072).

Again I emphasise that some of them may well have already failed one or more of those tests.

Signing off for now...

Garth

LeBourdais

Apr13-07, 09:02 AM

24 Hours to go !

Good luck everyone :smile:

Paul

henryco

Apr14-07, 02:16 PM

24 Hours to go !

Good luck everyone :smile:

Paul

Hi everybody,

You correct me if i'm wrong but GP-B annouced

- Having measured the geodetic effect at the percent level of accuracy
- Have not been able to extract the frame dragging signal yet (they give a 200% error and want to work until december to deliver the final results)

Concerning the frame dragging effect i would have appreciated if they had given at least a preliminary central value...however if i take (too much?)serious the GP-B experimental error poster, the west-east drift rate is reported for gyro2. Though i can see peaks (resonances) oscillating in between the -0.3 and +0.4 arcsec/year , the red plot where the resonances are mitigated seems to indicate that the frame dragging is compatible with zero!(for sure it is incompatible with the GR prediction! )...if some GP-B expert is around, please correct my feeling if i'm wrong.

Best regards

F H-C

sylas

Apr14-07, 02:32 PM

Concerning the frame dragging effect i would have appreciated if they had given at least a preliminary central value...however if i take (too much?)serious the GP-B experimental error poster, the west-east drift rate is reported for gyro2. Though i can see peaks (resonances) oscillating in between the -0.3 and +0.4 arcsec/year , the red plot where the resonances are mitigated seems to indicate that the frame dragging is compatible with zero!(for sure it is incompatible with the GR prediction! )...if some GP-B expert is around, please correct my feeling if i'm wrong.

Best regards

F H-C

There's no point giving a central value. The errors are reported as being around 100 mas/y, which is two and a half times the GR prediction. In other words, if it is compatible with 0 then it is also compatible with GR. Expertise in GR is not required and indeed completely irrelevant. Expertise in GR can only tell you what the GR predition is; what you need now is expertise in tracking the experimental errors and removing systematic effects. You're wrong in saying anything "for sure" about confirming or refuting the GR prediction of framedragging.

Cheers -- Sylas

Kris Krogh

Apr14-07, 02:50 PM

Can someone give me a link or links to where the GP-B results are reported?

Many thanks,

Kris Krogh

MeJennifer

Apr14-07, 03:30 PM

Expertise in GR is not required and indeed completely irrelevant.
Indeed but that is not what Frederic referred to, he referred to GP-B experts.

Actually, I would prefer not to have GR experts "explain" the errors, I like to have a completely theory independent view on these errors.

I don't think anyone is interested in another "Eddington" determining which errors are relevant and which not.

sylas

Apr14-07, 03:51 PM

Indeed but that is not what Frederic referred to, he referred to GP-B experts.

Oops! My apologies. I echo his request, then! I'd love to hear from a GP-B expert also.

What I want to know is why there is a difference between the prediction in the launch press kit (http://einstein.stanford.edu/content/press_kit/hi_res.pdf) (6614.4 NS, 40.9 EW) and in the April 14 2007 press release (http://einstein.stanford.edu/content/press_releases/SU/pr-aps-041807.pdf) (6606 NS, 39 EW).

All numbers in milliarcseconds/year.

I'm guessing orbit parameters; since about an extra 3.5 km in altitude would give that kind of difference, I think. But I need a GP-B expert to confirm for me.

Cheers -- Sylas

henryco

Apr14-07, 04:02 PM

There's no point giving a central value. The errors are reported as being around 100 mas/y, which is two and a half times the GR prediction. In other words, if it is compatible with 0 then it is also compatible with GR. Expertise in GR is not required and indeed completely irrelevant. Expertise in GR can only tell you what the GR predition is; what you need now is expertise in tracking the experimental errors and removing systematic effects. You're wrong in saying anything "for sure" about confirming or refuting the GR prediction of framedragging.

Cheers -- Sylas

Sorry sylas but i have nothing to say "for sure" ! ...since i'm not a prophet...though i must admit i'm very confident in my approach
since on many other (theoretical and experimental) grounds i find it really more satisfying than GR and this i'm ready to discuss in details with anybody (by the way i already had many such discussions in french forums and private communications but very few in english since i dont feel really at ease with my english)... Do you or other people you know find my work or behaviour suspicious in any way ? ...i'm ready to answer any question!

I was just noticing here that generally, whatever the error, it is meaningfull to give a central value and most of the time it is given in any measurement..so i was just wondering what the absence of this central value means here (unfortunately i could not attend the APS meeting). I thought that may be the answer was in the plot of the L1 session i was asking clarification about. Please let me reformulate the question.

At least, is it true that the left/down plot in the L1 poster session :

L1.00027: "Gravity Probe B Experiment Error" by Barry Muhlfelder, G. Mac Keiser, John Turneaure
( Garth, you will find this poster online at http://einstein.stanford.edu/ )

shows the final east-west drift rate for gyro 2 after subtraction of some well understood dominant systematical effects (it remains these resonance peaks which magnitudes are used as the main error estimators) or is it something else ? What do the plots for other gyros look like?

best regards,

F H-C

cosmopot

Apr14-07, 04:19 PM

Kris Krogh

Apr14-07, 04:57 PM

I agree with F H-C that the central value for this data should have some meaning. (Not only because our theories make the same predictions.) It certainly would be interesting to see the east/west drift rates for the other three gyros.

Also, the "Next Steps" section of the same poster describes the current error as 50-100 marcsec/yr. Previously, the GP-B people have used a single number like this to describe combined errors for both the east/west and north/south directions. If that's the case here, the east/west component might be still lower.

At least from a naive inspection, this chart does appear to show the east/west (frame-dragging) effect is close to zero, rather than the 41 marcsec/yr predicted by general relativity.

Kris Krogh

Apr14-07, 05:50 PM

The NASA press release also puts the current estimated GP-B error at 50-100 marcsec/yr, as opposed to a specific 100.

LeBourdais

Apr14-07, 06:05 PM

The NASA press release also puts the current estimated GP-B error at 50-100 marcsec/yr, as opposed to a specific 100.
The very fact that the GP-B estimated error has itself a great margin of error (75 ± 25 marcsec/yr) excludes the possibility of giving any meaning to a central value. Am I wrong ?

Kris Krogh

Apr14-07, 07:15 PM

The very fact that the GP-B estimated error has itself a great margin of error (75 ± 25 marcsec/yr) excludes the possibility of giving any meaning to a central value. Am I wrong ?

General relativity predicts 41 marcsec/yr. Suppose the measurement were -75 ± 75 marcsec/yr. That would rule out general relativity, while a zero precession would remain possible. So the central value does have meaning.

A previous GP-B web page said the best current estimate of the gyro motion relative to the guide star would be presented. The chart in the "GP-B Experiment Error" poster shows an east/west drift rate averaging about zero. I'm hoping that's relative to the guide star's motion, as previously measured -- but maybe it's not. With the guide star moving, certainly the drift is not zero in absolute terms.

Maybe that chart is the result after subtraction of any cumulative drift. But I hope they will follow through and tell us the central value for the drift, and not only the error.

sylas

Apr14-07, 07:33 PM

The link that henryco has given for the poster on errors is goes to the GP-B site, from which you must navigate to the poster. The direct link for the poster is GB-P Experiment Error: A Work in Progress (http://einstein.stanford.edu/content/aps_posters/ExperimentError.pdf) (L1.00027).

Also, the "Next Steps" section of the same poster describes the current error as 50-100 marcsec/yr. Previously, the GP-B people have used a single number like this to describe combined errors for both the east/west and north/south directions. If that's the case here, the east/west component might be still lower.

I gather that the error is an absolute error of comparable magnitude both North-South and East-West; this would mean that the East-West signal is swamped by the errors, and the North-South is obtained to about 1% or thereabouts.

At least from a naive inspection, this chart does appear to show the east/west (frame-dragging) effect is close to zero, rather than the 41 marcsec/yr predicted by general relativity.

Hm. Yes, I see what you guys are getting at. Here's a grab of the chart.
9771

What is this measuring? If it is simply the East/West drift, then indeed the red line is well below the GR prediction of 0.039 (or 0.041, depending on what predictions you read!).

But directly below the grap is that sentence "Impact on experiment error 100 marcsec/yr". This value of 100 is 0.1 on the left hand axis, which is way off the whole scale. I'm not getting this.

Cheers -- Sylas

Kris Krogh

Apr14-07, 08:02 PM

Hi Sylas,

To give you an example, the guide star moves east/west about -28 marcsec/yr, and -21 marcsec/yr north/south. The Gravity Probe B folks have described it as moving 35 marcsec/yr. That's the total magnitude -- squaring and summing the two values and taking the square root.

If the total current error were 50 marcsec/year in magnitude, it's conceivable the east/west component is significantly less. Maybe were're getting down in the range of 41 marcsec/yr predicted by general relativity.

Cheers,

Kris

LeBourdais

Apr14-07, 08:24 PM

General relativity predicts 41 marcsec/yr. Suppose the measurement were -75 ± 75 marcsec/yr. That would rule out general relativity, while a zero precession would remain possible. So the central value does have meaning.
Hi Kris,

The central value here has a meaning only for the combination of three effects (frame-dragging, “polhode” motion and "patches" torques) and the contribution from each of these effects is obviously not still known.

As they say on the "Gravity Probe B" site :

The GP-B instrument has ample resolution to measure the frame-dragging effect precisely, but the team has discovered small torque and sensor effects that must be accurately modeled and removed from the result.

Paul

Kris Krogh

Apr15-07, 04:33 AM

Hi Paul,

When these extraneous influences like the polhode motion are estimated, of course that's done separately from the frame-dragging they are trying to measure. The latter is whatever is left when everything else has been accounted for.

This preliminary result is of the form x ± 100 marcsec/yr or x ± 50 marcsec/yr, where x has to be some specific number. (It can't be anything from -1000 to +1000, or you'd have an uncertainty of ± 1000.) Question is, what is x?

Best wishes,

Kris

LeBourdais

Apr15-07, 04:53 AM

This preliminary result is of the form x ± 100 marcsec/yr or x ± 50 marcsec/yr, where x has to be some specific number. (It can't be anything from -1000 to +1000, or you'd have an uncertainty of ± 1000.) Question is, what is x?
Hi Kris,

You surely have read in my thoughts :biggrin: About one hour ago, I sent an e-mail at the contact address provided on the GP-B official site and I asked the question:

The margin of error for GP-B is told to be 50-100 marcsec/yr. The question I would like to ask is the following: is there any best value for the frame-dragging effect ? That is, can we say the result for the frame-dragging effect is X more or less 50-100 marcsec/yr, X being the best value. If so, is that value of X available ?

I hope I will get an answer :wink:

Best wishes,

Paul

Kris Krogh

Apr15-07, 05:02 AM

Thank you Paul!

LeBourdais

Apr15-07, 05:22 AM

Does anyone know the spin axis orientation for each of the four gyroscopes ?

henryco

Apr15-07, 05:36 AM

Hi Kris,

You surely have read in my thoughts :biggrin: About one hour ago, I sent an e-mail at the contact address provided on the GP-B official site and I asked the question:

I hope I will get an answer :wink:

Best wishes,

Paul

Hi everybody

I also sent an email but received no answer so far.
This plot is very intriguing since it is clearly there to show us and explain to us what is the main source of uncertainty: the 100 marcsec/year.
This is why i believe that the resonance peeks we can see regularly spaced on the plot actually give us the order of magnitude of this error and indeed the higher peeks reach the 40 marcsec level (what else in this plot could justify the 100 marcsec given just below it?). If they dont understand at all what is the origin of these peeks, they can give the most pessimistic error: approximately 2.5 times 40 marcsec. ANother question is: is the reported
drift rate integrated from the origin to the bin time ? Presumably not (it would be indicated) so that the integrated drift rate at the end time must be very close to zero!
But what is even stranger here is that whatever the magnitude of the peeks, the very low dispersion of most points about the mean value and the ability to identify the peaks, subtract them and provide us with a mitigated red fit is a clear indication that whatever value was subtracted before, the error on the mean residual is extremely better than 100marcsec!! and since other sources of errors are negligible compared to this one (the other errors are on the same poster) , my feeling is that they
were able to give a much better error but they decided not to give it and not to give also a central value. If the central value is at zero at the milliarcsec precision level, this might indicate a huge overestimation of the error already enough to produce a kind of earthquake in the community...so may be they want to work 8 more monthes to be sure since this would be a revolutionary
result! Is there some GP-B expert around?

regards

Fred

LeBourdais

Apr15-07, 05:55 AM

Hi everybody

I also sent an email but received no answer so far.

Salut Fred :biggrin:

I think it's a good thing that more than one people ask them for the same question.

Best wishes

Paul

CarlB

Apr15-07, 06:10 AM

Even though the results are preliminary, some theories appear to have been eliminated. Anyone care to write up a synopsis?

sylas

Apr15-07, 08:52 AM

Even though the results are preliminary, some theories appear to have been eliminated. Anyone care to write up a synopsis?

Anything that did not give about 6.6 for the geodetic precession is falsified. We can ignore the frame-dragging predictions as so far not able to be tested.

Here is Garth's list.

Einstein's General Relativity(GR)
Brans-Dicke theory (BD)
Barber's Self Creation Cosmology (http://arxiv.org/abs/gr-qc/0302026) (SCC),
Moffat's Nonsymmetric Gravitational Theory (http://arxiv.org/abs/gr-qc/0405091) (NGT),
Hai-Long Zhao's Mass Variance SR Theory (http://uk.arxiv.org/abs/gr-qc/0512088) (MVSR),
Stanley Robertson's Newtonian Gravity Theory (http://arxiv.org/abs/gr-qc/0502088) (NG),
Junhao & Xiang's Flat Space-Time Theory (http://arxiv.org/abs/physics/0101017) (FST).
R. L. Collin's Mass-Metric Relativity (http://www.arxiv.org/abs/physics/0012059) (MMR) and
F. Henry-Couannier's Dark Gravity Theory (http://www.arxiv.org/abs/gr-qc/0610079) (DG).
Alexander and Yunes' prediction for the Chern-Simons (http://kr.arxiv.org/abs/hep-th/0703265v1) gravity theory (CS).
Kris Krogh's Wave Gravity Theory (http://lanl.arxiv.org/abs/astro-ph/9910325) (WG)
Hongya Liu & J. M. Overduin prediction of the Kaluza-Klein ( http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v538n1/50681/50681.text.html?erFrom=5252751197746712308Guest#sc 8) gravity theory (KK).

The predictions are:

A. GPB Geodetic precession (North-South)

GR = 6.6144 arcsec/yr.
BD = (3\omega + 4)/(3\omega + 6) 6.6144 arcsec/yr. where \omega >6.
SCC = 4.4096 arcsec/yr.
NGT = 6.6144 - a small \sigma correction arcsec/yr.
MVSR = 0.0 arcsec/yr.
NG = 6.6144 arcsec/yr.
FST = 4.4096 arcsec/yr.
MMR = -6.56124 arcsec/yr.
DG = 6.6144 arcsec/yr.
CS = 6.6144 arcsec/yr.
WG = 6.6144 arcsec/yr.
KK = (1 + b/6 - 3b2 + ...) 6.6144 arcsec/yr. where 0 < b < 0.07.

Based on this we have models 3, 5, 7 and 8 as falsified.
The paramaterized models 2, 4 and 12 simply have a new constraint on the free parameter.

The remaining models are:

GR (1)
Parameterized models, which are the same as GR in the limit. 2,4,10,12: BD, NGT, CS, KK.
Models with frame dragging at 25% of what GR expects. 6: NG
Models with no frame-dragging. 9,11: DG, WG.

Cheers -- Sylas

Kris Krogh

Apr15-07, 01:41 PM

Hi Paul,

The spin axes of all four gyros were aligned with IM Pegasi. These are its coordinates, posted previously by Garth:

RA (J1991.25) : 22h 53m 02.279"
DEC (J1991.25) : +160 50' 28.540"

Kris

LeBourdais

Apr15-07, 06:43 PM

The spin axes of all four gyros were aligned with IM Pegasi. These are its coordinates, posted previously by Garth:

RA (J1991.25) : 22h 53m 02.279"
DEC (J1991.25) : +160 50' 28.540"
Hi Kris,

Do you mean to say that the spin of the four gyroscopes have been initially aligned in the same direction ?

That sounds strange :confused:

Paul

Kris Krogh

Apr15-07, 07:07 PM

Hi Paul,

It's a good system. Without this redundancy, they would be in a bad situation now. They need be able to compare the outputs of multiple devices to correct errors. Two rotate one way, and two the other, but they all have the same axis of rotation. You can find this kind of information on the GP-B web site.

Kris

cosmopot

Apr15-07, 07:10 PM

I wrote lots of papers and chatted on many forums but no one challenge my points:
1. GR is nothing but curved spacetime;
2. On curved spacetime, coordinates are not the accurate values of spatial distance or temporal interval or spatial angle.
3. To have those accurate values we need to perform integration with metric form being integrand. However, I did not see any one do so to achieve distance, or angle, or time interval on curved spacetime. Instead, people simply write r, t, \phi and assume they are distance, time, angle respectively.

I am driven crazy by this fact with which many great figures (Einstein, Hilbert, John Baez, Steve Carlip, Francis Everitt being associated.

You can not say spacetime is curved because you have the terminology with some quantities: metric, cutvature, covariance. For example, quantum mechanics uses distance, radius which do not mean we can have definite orbits of micro-particles!!!!!!

Is there any one answering my question??
You know flat space is nothing but:
ds^2=dx^2+dy^2

flat Minkowski spacetime is nothing but:
ds^2=-c^2dt^2+dx^2+dy^2+dz^2
where
ds=dx if dt=dy=dz=0
and
dT=cdt =c time if dx=dy=dz=0 where dT^2=-ds^2

curved spacetime is nothing but:
ds^2=-Ac^2dt^2+Bdx^2+Cdy^2+Ddz^2
where
ds=sqrt(B)dx if dt=dy=dz=0
and
dT=sqrt(A)dt = c time if dx=dy=dz=0 where dT^2=-ds^2
Therefore, t is not time because A varies with position on curved spacetime manifold.

LeBourdais

Apr15-07, 07:21 PM

It's a good system. Without this redundancy, they would be in a bad situation now. They need be able to compare the outputs of multiple devices to correct errors. Two rotate one way, and two the other, but they all have the same axis of rotation. You can find this kind of information on the GP-B web site.
Thanks a lot Kris ! That's really interesting. I will check on the GP-B web site.

By the way, I have received the answer to my question from GP-B Web Site Curator: for the moment now, they got no "best value" for the frame-dragging effect.

Paul

Kris Krogh

Apr15-07, 08:52 PM

Hi Paul,

I emailed the same address in 1999, to ask when they expected to launch the probe. It was scheduled for that October, but everyone knew they were running way behind. The response was that they were on schedule, and maybe would move the launch ahead to July. (Nice creative touch.) They ended up launching in 2004.

If you believe they have no idea how this measurement compares to the expected frame dragging, you're as gullible as I've been about their scheduling of the launch, release of data and analysis. (These delays have hurt me badly.) You can't blame the GP-B people entirely, because politics and diplomacy are necessary to carry out a project like this.

Kris

LeBourdais

Apr15-07, 09:28 PM

henryco

Apr16-07, 01:52 AM

Hi Kris,

Of course they probably know more than they say, but something sure, they won't give a "best value" for frame-dragging before they are ready to do so. Until they do, we can only speculate.

Paul

If it is in conflict with GR, they will never dare give the central value for the frame dragging....which is dramatic since, if all experimentalists behave this way as soon as they get an anomaly...progress is hopeless!
However they can at least answer my simple questions to let us make up our proper mind, and take our own responsability of what we have to say about the result:
How did they obtain the East-West plot?, what was subtracted before?
What does the graph look like for other Gyros?

i didnt got any answer, but i was trying to reach Everitt himself. May be i should better try the email of the guy that has answered your question.
What is it?

cheers,

F H-C

LeBourdais

Apr16-07, 04:09 AM

If it is in conflict with GR, they will never dare give the central value for the frame dragging....which is dramatic since, if all experimentalists behave this way as soon as they get an anomaly...progress is hopeless!
Salut Fred,

Do you mean to say that they would have spent 800 millions dollars to send GP-B in space with the intent of not giving the results if these were contradictory with GR ? :confused:

i didnt got any answer, but i was trying to reach Everitt himself. May be i should better try the email of the guy that has answered your question.
What is it?

There is no secret about it, it's the e-mail address provided on GP-B Web site: www@relgyro.stanford.edu
The person that answered to me is the Web Site Curator.

Take it easy Fred :wink:

Friendly,

Paul

jgraber

Apr16-07, 08:05 AM

henryco

Apr16-07, 08:58 AM

I am posting from the APS meeting in Jacksonville.
You can see the preliminary result that was presented here,
with lots and lots of caveats,
by going to the GPb Homepage,
http://einstein.stanford.edu/index.html
and clicking on poster L1.00028,
Gravity Probe B Science Data Analysis: Filtering Strategy.
The result is called
"Glimpses of Frame Dragging"
and is in the bottom right quadrant of the poster.
One "glimpse" differs from GR by about two sigma,
but everything is still preliminary,
including the size of the sigma,
which is of order 10 mas/y
i.e. milliarcseconds per year.
I believe this particular "glimpse" is based on about 40 days data from one of the gyros.
Also, they have not yet unblinded themselves from the improved drift of the guidestar.
However, they still hope/expect to reduce their sigma to 1 or 2 mas/y by December.
Francis said there may be a small hint of a difference with GR,
but it is still much too early to talk about this seriously.
Jim Graber

Thank you very much for these informations...the problem is that i was not able to understand these plots mainly because of the bad resolution in the scanned axis...i still dont see what the axis in the ellipses plots represent:
the y axis seems to be frame dragging , but the x axis not sure: a north/south effect?
Does the expression "glimpses so far" mean that for the time being it was not possible to extract a continuous frame dragging behind those glimpses?
Are those glimpses the same resonance peeks shown in the east-west plot of the GP-B error poster?
Since you are in Jacksonville may be you have this information.

Thank you again

Best regards,

F H-C

henryco

Apr16-07, 09:06 AM

Salut Fred,

Do you mean to say that they would have spent 800 millions dollars to send GP-B in space with the intent of not giving the results if these were contradictory with GR ? :confused:

Salut Paul,

Of course not... and i apologize. But it's too frustrating for me not
to attend the APS conference and i have difficulties to correctly interpret
the information given on the posters...

Take it easy Fred :wink:

Friendly,

Paul

You are right Paul

amiclt,

Fred

makc

Apr16-07, 09:20 AM

people simply write r, t, \phi and assume they are distance, time, angle respectivelybut noone assumes that they are same distance, time, angle as in flat Minkowski spacetime, or do they?

jgraber

Apr16-07, 01:24 PM

henryco,
the other axis is the geodetic effect.
The center of the largest ellipse is close to the expected GR value.
Jim Graber

henryco

Apr16-07, 03:11 PM

henryco,
the other axis is the geodetic effect.
The center of the largest ellipse is close to the expected GR value.
Jim Graber

OK but as far as i know frame dragging must be continuous, not only happen from time to time as isolated glimpses (or did i miss something? somebody can confirm or invalidate this?)...otherwise this has nothing to do with GR frame dragging. What on earth does this glimpse mean? Once we admit that this measurement is very preliminary and that no one should draw conclusion about it, there should be no problem for the experimentalist to answer this simple question: what does glimpse mean here? does it mean that from time to time there appears to be a short time burst of frame dragging (june 2006...) and that nothing is detected in between two such manifestations so far?
or is this glimpse simply due to the observer selection of a short period of time?
The first is the interpretation i must take the more serious since otherwise i would not be able to understand the question "why glimpses so far?". Moreover i understand in this case why their dominant error comes from the resonance peeks shown in the back/left plot in the error poster since such peeks can really mimic a momentaneous burst of frame dragging but obviously not a constant drift rate. If you are still in Jacksonville may be can you ask some member of the GP-B team these questions...my emails are never answered! what on earth is going on? am i a plague-stricken?

Best regards and thank you for your help if you can get this information/confirmation.

F H-C

jgraber

Apr16-07, 03:30 PM

The fractional data is due to two things: 1 They are not yet done analyzing it.
2. The spacecraft shut down briefly nine times during the eleven months of science data taking.
they are working on "stitching it together."
Best.
Jim Graber

Kris Krogh

Apr16-07, 03:50 PM

Francis said there may be a small hint of a difference with GR,
but it is still much too early to talk about this seriously.
Jim Graber

Hi Jim,

Thanks very much for the information! Does the possible small hint Francis mentioned refer to frame dragging specifically? Also, do you have any sense whether this is in the direction of a larger effect, or smaller than expected?

As F H-C mentioned, on the two charts of the modeled Gyro 3 torque, we can't read any of the labels or numbers on the axes, or the other fine print. Can you fill us in? Also, do the ellipses indicate bounds on possible values?

Best wishes,

Kris Krogh

LeBourdais

Apr16-07, 11:46 PM

As F H-C mentioned, on the two charts of the modeled Gyro 3 torque, we can't read any of the labels or numbers on the axes, or the other fine print.
Hi Kris,

If we look at the upper chart ("Torque Modeling Example : Motion of Gyroscope 3"), the dashed line is referred to as the "estimated relativistic motion" and it is clearly not flat. Therefore, whatever the numbers on the axes, I guess we can conclude that their "best value" for frame-dragging is not zero. Am I missing something ?

Paul

magnetar

Apr17-07, 01:42 AM

Gravity probe-b backs general relativity!:smile:

http://physicsweb.org/articles/news/11/4/11/1

henryco

Apr17-07, 03:07 AM

Hi Kris,

If we look at the upper chart ("Torque Modeling Example : Motion of Gyroscope 3"), the dashed line is referred to as the "estimated relativistic motion" and it is clearly not flat. Therefore, whatever the numbers on the axes, I guess we can conclude that their "best value" for frame-dragging is not zero. Am I missing something ?

Paul
hi paul

I would say:
1) it depends if the y axis actually shows a pure east-west deviation, doest it (i cant decode the y-scale)?
2) even an actual east-west effect can have another origin than frame dragging (for example if we are in the vicinity of resonance peeks as shown in the error poster)...
3) The latter remark is reinforced if the (even preliminary) fitted drift rate is at several sigmas from GR prediction! If i now decode well the scales on the "glimpses plot" there are four glimpses at respectivily and approximately 2,3,8,8 standard deviations from the GR prediction !

Cheers,

Fred

Kris Krogh

Apr17-07, 03:08 AM

Hi Paul,

You have a point there, at least as far as this particular graph is concerned. I contacted the web page curator, and I think she'll put up a more readable version of this poster for us tomorrow.

Magnetar,

That article says the geodetic effect of general relativity has been measured. But that's already been measured more accurately in other ways. The important one for me is frame dragging. They say Gravity Probe B hasn't measured that yet.

jgraber

Apr17-07, 08:12 AM

Hi everyone,
Sorry I can only post on coffee breaks when I am near the APS temporary hotspot. As I understand the "glimpses" each ellipse is a one sigma radius, and GR is very near the center of the earliest, crudest glimpse, and about two radii (i.e. approx two sigma) from the smallest, latest "glimpse", which is still based on a very limited amount of not yet fully processed data. As I understand it, the data in that plot are total motions, including nonrelativistic effects as well as the two GR effects. The speakers mentione three or four of order 40-80 mas/y total that add to the Geodetic Effect and at least one of order 40mas/y that adds to the Frame Dragging Effect. Because of these additions, the GR prediction is offset from the values usually quoted. The values on the "glimpse" chart have minus signs and increase in absolute value downward and to the left. They increase (or decrease) by 20 per grid line and the central values are 80 for the vertical (Frame Dragging) axis and 6580 for the horizontal (Geodetic) axis. The latest "Glimpse" is slightly offset in the direction of larger values, so IF you take it at face value, which is wildly over optimistic in my opinion, it would indicate that both effects are slightly larger than the GR prediction by about 10 mas/y compared to 6600 and 40. However, there will be new, much more reliable numbers in December or so, and the only sensible course in my opinion is to wait until then. remember, there are systematic as well as statistical errors, and the experiment is quoting their current overall sigma as 90-100 mas/y. This is small compared to the Geodetic effect, but totally swamps the Frame Dragging effect. They say the Geodetic effect is totally obvious from the rawish data, but the Frame Dragging Effect must be dug out of the noise. Remember, they found two major unexpected noise sources, and for several months were afraid that they would not be able to report any frame dragging result. It is only because of the large amount of redundancy in the data and the fact that the two GR effects and the two unexpected noise sources have four different mathematical characteristics that they expect to be able to recover something close to the originally expected accuracy.
Best, Jim

LeBourdais

Apr17-07, 08:24 AM

Thank you very much Jim !!! It gives me a better picture of what's going on.

Paul

Kris Krogh

Apr17-07, 03:57 PM

Jim,

Thanks very much for your insights! That all seems to add up. Would it be possible to confirm with someone there from GP-B that the best of this data would hint at a slightly larger than expected frame-dragging effect? (If it hints at anything.)

Best wishes,

Kris

Garth

Apr19-07, 08:05 AM

I have just returned from the APS Meeting at Jacksonville and a holiday in Florida.

As has been well discussed the first results have verified the GR geodetic prediction to 1% but there is no handle on the frame-dragging prediction, basically because unexpected signals so far swamp it, except for 'glimpses'.

By the end of the year the correct removal of these effects will give a robust reading to both precessions.

The running now stands:

Einstein's General Relativity(GR)
Brans-Dicke theory (BD)
Barber's Self Creation Cosmology (http://arxiv.org/abs/gr-qc/0302026) (SCC),
Moffat's Nonsymmetric Gravitational Theory (http://arxiv.org/abs/gr-qc/0405091) (NGT),
Hai-Long Zhao's Mass Variance SR Theory (http://uk.arxiv.org/abs/gr-qc/0512088) (MVSR),
Stanley Robertson's Newtonian Gravity Theory (http://arxiv.org/abs/gr-qc/0502088) (NG),
Junhao & Xiang's Flat Space-Time Theory (http://arxiv.org/abs/physics/0101017) (FST).
R. L. Collin's Mass-Metric Relativity (http://www.arxiv.org/abs/physics/0012059) (MMR) and
F. Henry-Couannier's Dark Gravity Theory (http://www.arxiv.org/abs/gr-qc/0610079) (DG).
Alexander and Yunes' prediction for the Chern-Simons (http://kr.arxiv.org/abs/hep-th/0703265v1) gravity theory (CS).
Kris Krogh's Wave Gravity Theory (http://lanl.arxiv.org/abs/astro-ph/9910325) (WG)
Hongya Liu & J. M. Overduin prediction of the Kaluza-Klein ( http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v538n1/50681/50681.text.html?erFrom=5252751197746712308Guest#sc 8) gravity theory (KK).
Kerr's Planck Scale Gravity: now accepted for publication Predictions of Experimental Results from a Gravity Theory (http://redshift.vif.com/JournalFiles/V14NO2PDF/V14N2KER.pdf) (PSG)

The following are still in the running:

GPB Geodetic precession (North-South)
1. GR = 6.6144 arcsec/yr.
2. BD = (3\omega + 4)/(3\omega + 6) 6.6144 arcsec/yr. where now \omega >60.
4. NGT = 6.6144 - a small \sigma correction arcsec/yr.
6. NG = 6.6144 arcsec/yr.
9. DG = 6.6144 arcsec/yr.
10. CS = 6.6144 arcsec/yr.
11. WG = 6.6144 arcsec/yr.
12. KK = (1 + b/6 - 3b2 + ...) 6.6144 arcsec/yr. where 0 < b < 0.07.

We await the GPB gravitomagnetic frame dragging precession (East-West) result.

1. GR = 0.0409 arcsec/yr.
2. BD = (2\omega + 3)/(2\omega + 4) 0.0409 arcsec/yr.
4. NGT = 0.0409 arcsec/yr.
6. NG = 0.0102 arcsec/yr.
9. DG = 0.0000 arcsec/yr.
10. CS = 0.0409 arcsec/yr. + CS correction
11. WG = 0.0000 arcsec/yr.
12. KK = 0.0409 arcsec/yr.

Those that have fallen by the wayside:

3. SCC = 4.4096 arcsec/yr.
5. MVSR = 0.0 arcsec/yr.
7. FST = 4.4096 arcsec/yr.
8. MMR = -6.56124 arcsec/yr.
13. PSG = 0.0000 arcsec/yr.

Garth

LeBourdais

Apr19-07, 10:04 AM

As has been well discussed the first results have verified the GR geodetic prediction to 1% but there is no handle on the frame-dragging prediction, basically because unexpected signals so far swamp it, except for 'glimpses'.

By the end of the year the correct removal of these effects will give a robust reading to both precessions.
Hi Garth,

Thank you for this status.

Sorry for your theory.

Best wishes
Paul

Garth

Apr19-07, 11:56 AM

Hi Garth,

Thank you for this status.

Sorry for your theory.

Best wishes
Paul

Thank you for your commiserations!

Garth

magnetar

Apr20-07, 05:02 AM

I do not understand why so many "Alternative theories" about gravity???
why so many controversial ??:confused:

sylas

Apr21-07, 05:15 AM

I have just returned from the APS Meeting at Jacksonville and a holiday in Florida.

Hi Garth,

Can you explain the difference between the 6614.4 and 40.9 being quoted in numerous sources before the APS meeting(including many still available in the GP-B site) and the 6606 and 39 numbers now being used? (numbers being GR expectations for geodetic and framedragging effects in milliarcsec/yr)

I'm guessing it could be a difference in the altitude of the final orbit, but I don't know.

Cheers -- Sylas

Garth

Apr21-07, 05:50 AM

That is a good question that wasn't addressed at the meeting, I have only recently become aware of that anomaly myself.

The posters clearly show the latter (6606 and 39 mas/yr) set of values while all their previous literature showed the former (6614.4 and 40.9 mas/yr) set.

The orbit decreased in SMA by about 350 metres during the lifetime of the experiment, but that should have increased the expected precessions by about one part in 10-4 in my estimation.

The present measured value of the geodetic precession is 6638 +/- 97 mas/yr. (Francis Everitt APS Plenary Session 14th April 07)

Note however on the Gravity Probe B Science Data Analysis: Filtering Strategy (http://einstein.stanford.edu/) poster (Click on the title), it says of the geodetic measurement:Current Estimates (“Glimpses”)
-6595 ± 10 milliarcsec/year
-6604 ± 7 milliarcsec/year

GP-B website (http://einstein.stanford.edu/):The experiment’s final result is expected on completion of the data analysis in December of this year. Asked for his final comment, Francis Everitt said: "Always be suspicious of the news you want to hear."

Garth

sylas

Apr21-07, 12:23 PM

That is a good question that wasn't addressed at the meeting, I have only recently become aware of that anomaly myself.

OK... I have gone back to first principles, and I think I have sorted this one out.

The information at the GP-B seems pretty sloppy. I have checked out the Fact Sheet (http://einstein.stanford.edu/content/fact_sheet/GPB_FactSheet-0405.pdf), dated February 2005. The information therein is inconsistent.

Here are the orbit characteristics...

Orbit

Characteristics Polar orbit at 642 kilometers (400 miles), passing over one of the poles every 48.75 min.
Semi-major axis 7,027.4 km (4,366.6 miles)
Eccentricity 0.0014
Apogee altitude 659.1 km (409.5 miles)
Perigee altitude 639.5 km (397.4 miles)

The semi-latus rectum (wiki ref (http://en.wikipedia.org/wiki/Ellipse#Semi-latus_rectum_and_polar_coordinates)) is given as:
a*(1-e^2) = 7.0274*10^6*(1-0.0014^2) = 7.027386226*10^6
which is the same a, up to five figure accuracy.

The formula for geodetic precession is 1.5(GM)^{1.5}c^{-2}R^{-2.5}, where R is the semi-latus rectum (ref: Gravitation and cosmology, S. Weinberg (1972) [pp237-8]).

Plug in

G = 6.6742*10^{-11},
M = 5.976*10^24,
c = 299792458

and we get 1.0155*10^{-12} rad/sec, or 6.60559 arcsec/yr.

However, the same press release, with these same orbit parameters, gives 6.6144

I'm guessing they had already calculated 6.6144 from a projected orbit; and then recalculated for the actual orbit, but did not properly update all the recorded predictions.

The value 6.6144 implies an orbit about 3.7 km smaller in radius.

Now… what formulae do I need to use for the Lense-Thirring effect?

Cheers -- Sylas

Garth

Apr21-07, 03:33 PM

OK... I have gone back to first principles, and I think I have sorted this one out.

The information at the GP-B seems pretty sloppy. I have checked out the Fact Sheet (http://einstein.stanford.edu/content/fact_sheet/GPB_FactSheet-0405.pdf), dated February 2005. The information therein is inconsistent.

Here are the orbit characteristics...

The semi-latus rectum (wiki ref (http://en.wikipedia.org/wiki/Ellipse#Semi-latus_rectum_and_polar_coordinates)) is given as:
a*(1-e^2) = 7.0274*10^6*(1-0.0014^2) = 7.027386226*10^6
which is the same a, up to five figure accuracy.

The formula for geodetic precession is 1.5(GM)^{1.5}c^{-2}R^{-2.5}, where R is the semi-latus rectum (ref: Gravitation and cosmology, S. Weinberg (1972) [pp237-8]).

Plug in

G = 6.6742*10^{-11},
M = 5.976*10^24,
c = 299792458

and we get 1.0155*10^{-12} rad/sec, or 6.60559 arcsec/yr.

However, the same press release, with these same orbit parameters, gives 6.6144

I'm guessing they had already calculated 6.6144 from a projected orbit; and then recalculated for the actual orbit, but did not properly update all the recorded predictions.

The value 6.6144 implies an orbit about 3.7 km smaller in radius.Concur; does that mean their first set of values was simply a mistake?
Now… what formulae do I need to use for the Lense-Thirring effect?

Cheers -- SylasHere it is:

\Omega_{f-d} = \frac{GI}{c^2R^3}[\frac{3\underline{R}}{R^2}(\omega.\underline{R}) - \omega]

Garth

sylas

Apr21-07, 07:30 PM

Concur; does that mean their first set of values was simply a mistake?Here it is:

\Omega_{f-d} = \frac{GI}{c^2R^3}[\frac{3\underline{R}}{R^2}(\omega.\underline{R}) - \omega]

Garth

Thanks Garth... yes, I know that formula. It is a vector equation, and it varies over the whole orbit. So we have some work to try and get a magnitude from it. I was hoping for a straight formula for the magnitude.

I also need a value for I, which is the moment of inertia for the Earth. I can calculate assuming a solid sphere; but distributions of mass are not uniform, so this is only an approximation.

The vectors are \omega, which is in a fixed direction along the Earth's axis, and R, which is the location of the probe. This part has a maximum value over the poles, the dot product is just a product of magnitudes. The direction is the opposite of \omega by the sign differences, so at the poles but in brackets has magnitude 2\omega. But over the equatot, the dot product drops to zero and the magnitude is \omega in the opposite direction.

The suggests a mean magnitude of \omega/2. I think.

Using I = 0.4MR_e^2 as a solid sphere, I get

0.2*GMR_e^2R^{-3}c^{-2}\omega

as a magnitude. My spreadsheet gets very roughly in the ball park with this, at 0.049

But I'm still out by much too much.

Any GP-B experts can help me out?

Thanks -- Sylas

sylas

Apr22-07, 05:35 AM

Followup to my previous post! I have now found a figure for the moment of inertia of the Earth, and am able to get close to the OLD value for the framedragging effect. But I'll go through it all from the beginning with new numbers.

To get accurate values, I have tried to use data to five or six figures of accuracy, or whatever is available. I use SI units, unless explicitly given otherwise.

I've checked out the following sources.

A NASA Planetary fact sheet (http://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html) for the Earth.
The paper A General Treatment of Orbiting Gyroscope Precession ( http://arxiv.org/abs/gr-qc/9909054), by Ronald J.Adler and Alexander S. Silbergleit (arXiv:gr-qc/9909054)
The International Earth Rotation and Reference Systems Service: Useful constants (http://hpiers.obspm.fr/eop-pc/models/constants.html).

Geodetic effect

The geodetic effect is 1.5*(GM)1.5c-2r-2.5, where r is the semilatus-rectum of the probe orbit. This is the semimajor axis times (1-e2), as indicated in a previous post.

The radius of the orbit of GP-B is measured as 7027.4 km (semi-major axis). The eccentricity is e = 0.0014, so the semilatus rectum is 7027.386 km. Adler and Silbergeit use 7028 km with a circular orbit; this was calculated before launch.

The value of GM (gravitational constant times earth mass) is known with great precision; much more than either G or M individually. The value of G*M is 3.986004418*1014 m3s-2 in IERS.

NIST currently gives G as 6.67428*10-11, which would give M as 5.9721864*1024. The NASA page gives Earth mass as 5.9736*1024; this corresponds to G = 6.6727*10-11.

To convert from radians per second to milliarcseconds per year, the factor is 6.50908*1015. That uses a tropical year of 365.24219 days (IERS). The speed of light is 299792458

The only meaningful source of error here is in r, the radius of the orbit. The largest value for the geodetic precession requires r to be small, and the conversion factor to be large. The conversion factor for milliarcseconds/year uses the length of a tropical year, being 365.24219 days; there's no basis for using anything greater.

The calculation is

1.5 * (3.986004418 * 10^{14})^{1.5} * 299792458^{-2} * (7.027386 * 10^6)^{-2.5} * 365.24219 * 86400 * 360 * 3600 * 1000 / 2 / \pi

This gives the geodetic precession as 6603.77 milliarcseconds/year. I can't see any possible way to make this any bigger.

To make matters worse, Adler and Silbergeit also give a correction factor to take account of the Earth's oblate shape. This factor is given as:
1-\frac{9}{8}*J_2*(R/r)^2)

Here R is the radius of the earth and J2 is the quadrupole moment.

For the radius of the Earth, Adler and Silbergeit use 6378 km, NASA gives 6378.1 km, and the IERS gives 6378.1366 km.

For J2, Adler and Silbergeit use 1.083*10-3, and the IERS gives 1.0826359*10-3. The accuracy here will not matter much.

This factor reduces the geodetic prediction, by (1-1.00*10-3), to give a final prediction of 6597.14 milliarcsec/year

How anybody ever got 6614.4 I don't know.

There is an additional precession due to the Sun; but this is in a different plane, and is going to have more effect on framedragging. It is discussed in Adler and Silberguit as well, with a magnitude of 19 milliarcsec/yec, but mostly perpendicular to geodetic precession.

Frame dragging

As derived above (and Adler and Silbergeit confirm) the magnitude of the effect works out to be GJr^{-3}c^{-2}\omega / 2

The moment of inertia for a solid body is J = kMR^2, where k is a "moment of inertia ratio". This ratio is 0.4 for a uniform sphere, but it will be more if the mass density is greater near the surface, and less if the mass density is greater near the center.

Adler and Silbergeit use k = 1/3.024 = 0.3307. The NASA fact sheet gives k = 0.3308.

Using the value of GM from IERS, GJ would be kGMR2, which is about 5.3640*1027, using the NASA value for the radius R of the Earth.

The IERS gives a value for J directly, which is 8.0365*1037; and with their value of G as 6.6742*10-11, this gives GJ = 5.3638*1027.

The length of a sidereal day 23.9345 hours (NASA sheet) so the rotation velocity ω is 7.2921 * 10-5 rad/sec. In IERS it is 7.292115*10-5.

The framedragging effect is
GJr^{-3}c^{-2}\omega/2

This works out to
5.3638*10^{27} * (7.0274 * 10^6)^{-3} * 299792458^{-2} * 7.292115*10^{-5} * 365.24219 * 86400 * 360 * 3600 * 1000 / 2 / \pi / 2

which gives 40.81 milliarcsec/year,

As before, there is a correction factor; this time equal to
1+\frac{9}{8}*J_2*(R/r)^2(1-\frac{3}{7}*MR^2/J))

This works out to 1-2.97*10^{-4}, which brings the prediction back down to 40.80 milliarcseconds/year.

This close to the 40.9; but now I don't know how they are obtaining 39.

Cheers -- Sylas

Garth

Apr22-07, 09:21 AM

henryco

Apr22-07, 03:51 PM

That's a very impressive piece of work, thank you Sylas. :approve:

Why don't you e-mail Alex Silbergleit at: gleit@relgyro.stanford.edu with these questions? And then let us know the answer of course.

Garth

Hi everybody,

Thank you for your efforts to help clarify several points. I still cant decode the axis informations from the plot named Torque modeling example: motion of gyro 3 in the L10028 poster. Can someone who attended the APS conf or GP-B expert help us ?

regards,

F H-C

Garth

Apr23-07, 09:09 AM

henryco

Apr23-07, 01:30 PM

The unexpected torques on the rotors were from:
1) A time dependent polhode (http://en.wikipedia.org/wiki/Polhode) precession due to the gyros not being exactly spherical. The time dependency is modelled by a dissipation of kinetic energy over time.
2) A misalignment torque due to a variation of electric potential over the surface, which can arise due to the polycrystalline structure.
It can be affected by presence of contaminants and is modelled as dipole layer. The patch fields are present on rotor and housing walls and cause forces and torques between these surfaces.

On the Torque modeling example: motion of gyro 3 in the L10028 poster the legend is very unclear, but the x-axis is E-W orientation milliarcsec/yr and the y-axis I believe is Polhode phase angle error.

Garth

Thank you garth. I have asked other questions to the GP-B website curator
and were told that an upgrade will soon be available on their site with clearer
plots... For the time being i dont see how i could read the amount of relativistic motion from this plot where the dashed line represents the estimated relativistic motion.
I also asked how the error plot was obtained on the error poster ...
They also told me that the audio file of their presentations will soon be available online

Best regards,

F H-C

Regards,

F H-C

henryco

Apr23-07, 01:48 PM

The unexpected torques on the rotors were from:
1) A time dependent polhode (http://en.wikipedia.org/wiki/Polhode) precession due to the gyros not being exactly spherical. The time dependency is modelled by a dissipation of kinetic energy over time.
2) A misalignment torque due to a variation of electric potential over the surface, which can arise due to the polycrystalline structure.
It can be affected by presence of contaminants and is modelled as dipole layer. The patch fields are present on rotor and housing walls and cause forces and torques between these surfaces.

On the Torque modeling example: motion of gyro 3 in the L10028 poster the legend is very unclear, but the x-axis is E-W orientation milliarcsec/yr and the y-axis I believe is Polhode phase angle error.

Garth
There are also some other details i would like to know about these effects

1) The dissipative polhod motions must after some time determine the actual rotation axis of the four gyroscopes. its direction should be a priori different
and arbitrary for each one: has this information been given at the conference: the raw "initial" axis direction for each Gyro i.e. after stabilisation (when the polhode dissipative effects become small)

2) If it is true that there is a force proportional to a misalignment...
eventually this force should impose an alignment therefore a preferred direction relative to the stator and if the latter is fixed with respect to distant stars (is it?) this should prevent any relativistic motion at some level...

Sorry for these probably naive questions but since i couldnt attend the conference...

Regards

F H-C

Garth

Apr23-07, 04:09 PM

Yes,

The unexpected signals have complicated the matter somewhat for the GP-B and that explains why it is taking so long to produce the results.

Whereas they were expecting some polhode motion, the new thing was for this to be time dependent. Therefore it has taken some time for them to model this effect correctly. However, the polhode motion is only a minor effect which is only significant when the most accurate readings are required especially for the frame-dragging effect.

However what has nearly spoiled the experiment was the misalignments experienced because of electrostatic patch effects. With the spacecraft rolling about its axis pointing towards the guide star every 77.5 seconds they found a misalignment of up to 1 arcsec/deg/day, potentially larger than the relativity precessions they were looking for.

In their words:... wide variety of unexpected scientific, technical and programmatic difficulties from minor discrepancies to design flaws and outright failures. GP-B provides several excellent examples of the process of recovery from these events...

The first thing they have to do is to model is patch effect correctly using the geometry and rate of change data to isolate the 'noise' from the signal without using the expected relativity answer in the process.

As to the detailed answers to your questions they haven't given much away, because I think they are not sure at present of that answer. They say that it is very much "a work in progress". We will have to wait until the end of the year when all will be revealed, I trust, in the promised published papers.

However I must add that I find Francis Everitt's final comment "Always be suspicious of the news you want to hear." intriguing. It is almost as if he does not want to believe in their results....

Garth

fasterthanjoao

Apr24-07, 11:46 AM

Tripathy

Apr25-07, 01:51 AM

Garth

Apr27-07, 02:29 PM

The Stanford website mentions on the first phase GP-B results dated 14th April 2007:
“….. the data from the GP-B gyroscopes clearly confirm Einstein's predicted geodetic effect to a precision of better than 1 percent. However, the frame-dragging effect is 170 times smaller than the geodetic effect, and Stanford scientists are still extracting its signature from the spacecraft data. The GP-B instrument has ample resolution to measure the frame-dragging effect precisely, but the team has discovered small torque and sensor effects that must be accurately modeled and removed from the result.”

Can anyone answer whether the result of the frame-dragging effect, derived after removal of the much larger torque and sensor effects, can still be considered to be a result obtained from a “controlled” experiment?

That is a good question, which may be asked of both precession measurements even though the Geodetic precession is some 170 times larger.

The GP-B team are working very hard to model and determine the unexpected time dependent polhode and patch effect torques on the gyro rotors to within 0.1 mas so they can be subtracted from the raw data.

They claim they are doing so without using the expected results in the process, thus keeping GP-B a controlled and objective experiment.

However I have two questions:
1. How do you know that you have allowed for all other effects that might be affecting the result? In other words the tendency in any experiment is to keep subtracting sources of 'noise' until the remaining signal is what you expect, and then stop. If the result is not what is expected then you might discover another unknown source of error.

2. Might there be a degeneracy in the modelling of these torques? i.e. Having fitted the time dependent data well to one solution and use that to obtain the final result, might there be another solution that also fits the noise data well that produces a different result?

Garth

Garth

Apr27-07, 02:51 PM

Garth,

Whilst I've read (and unfortunately only understood part) of this thread, it's always been with interest. I've refrained from posting since most of the questions I have about the data you've been posting (thanks, by the way) Garth is that the questions tend to be answered anyway.

Your recent post on the gravity probe B results (sorry your theory didn't work out), and subsequent discussions, are particularly an interesting read from a beginners point of view as it's easy to pick up knowing what's left.

It may be a tall ask, but if you've time, could you offer a brief, simplified post (even a PM?) on the basic large scale changes/implications these theories may have? any other outrageous features you're proficient in are always worth noting! thanks.
I don't claim to be an expert of these other theories, other than SCC and the Brans-Dicke theory, but I have given links to their papers, which you can read up for yourself.

In the BD theory a minimally connected scalar field is added to the GR field equation that has the effect of perturbing the GR space-time and therefore freely-falling particle and photon geodesics, but does not otherwise interact with them. As these perturbations have not been discovered the scalar field must be very weakly connected to matter. The presence of the scalar field affects the cosmological solution and cosmic evolution.

In SCC that scalar field is now non-minimally connected and interacts with particles inducing a scalar field force on particles but not photons. The scalar field force exactly compensates for the perturbation of space-time in vacuo, and SCC freely-falling particle and photon geodesics are the same as those of GR. The coupling constant \lambda was equal to unity. The theory passed all the tests GR does, up to but not including the GP-B geodetic precession prediction. It had interesting cosmological consequences as well as predicting the Pioneer anomaly discussed elsewhere on the Cosmology Forum.

I can see my way clear to a general self creation theory in which \lambda is left as an unknown variable.

The geodetic prediction becomes

\Omega = [(1 - \lambda/3)6.6 + 0.25] arcsec/yr.

(I have found an extra 0.25 arc/sec/yr precession due to cosmological time dilation (clock drift) that makes my original prediction 4.65 arcsec/yr not 4.4 arcsec/yr.)

Unfortunately the theory then predicts the total mass density parameter for the universe to be

\Omega_T = \frac{1}{3\lambda},

so if \lambda is small a lot of DM and DE is required and an attractive feature of the original theory is lost.

I will post more when I have published.

Garth

Garth

Apr28-07, 08:48 AM

I have now (modestly!) included my modified General Theory of Self Creation Cosmology (GSCC) which leaves the \lambda parameter undetermined.

Note that the results published at the April APS meeting in Jacksonville include a modified GR prediction with one decimal place less accuracy. The reason for this modification is not clear, however the modified GR predictions are included in this post.

The running now stands:

Einstein's General Relativity(GR)
Brans-Dicke theory (BD)
Barber's General Theory of Self Creation Cosmology (http://www.physicsforums.com/showthread.php?t=82628&page=9) (GSCC), to be published
Moffat's Nonsymmetric Gravitational Theory (http://arxiv.org/abs/gr-qc/0405091) (NGT)
Stanley Robertson's Newtonian Gravity Theory (http://arxiv.org/abs/gr-qc/0502088) (NG),
F. Henry-Couannier's Dark Gravity Theory (http://www.arxiv.org/abs/gr-qc/0610079) (DG).
Alexander and Yunes' prediction for the Chern-Simons (http://kr.arxiv.org/abs/hep-th/0703265v1) gravity theory (CS).
Kris Krogh's Wave Gravity Theory (http://lanl.arxiv.org/abs/astro-ph/9910325) (WG)
Hongya Liu & J. M. Overduin prediction of the Kaluza-Klein ( http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v538n1/50681/50681.text.html?erFrom=5252751197746712308Guest#sc 8) gravity theory (KK).

The predictions are now:

GPB Geodetic precession (North-South)

GR = 6.606 arcsec/yr.
BD = (3\omega + 4)/(3\omega + 6) 6.606 arcsec/yr. where now \omega >60.
GSCC = [(1 - \lambda/3)6.606 + 0.250]arcsec/yr. where at present \lambda < 0.14.
NGT = 6.606 - a small \sigma correction arcsec/yr.
NG = 6.606 arcsec/yr.
DG = 6.606 arcsec/yr.
CS = 6.606 arcsec/yr.
WG = 6.606 arcsec/yr.
KK = (1 + b/6 - 3b2 + ...) 6.606 arcsec/yr. where 0 < b < 0.07.

We await the GPB gravitomagnetic frame dragging precession (East-West) result.

GR = 0.039 arcsec/yr.
BD = (2\omega + 3)/(2\omega + 4) 0.039 arcsec/yr.
GSCC = 0.039 arcsec/yr.
NGT = 0.039 arcsec/yr.
NG = 0.039 arcsec/yr.
DG = 0.0000 arcsec/yr.
CS = 0.039 arcsec/yr. + CS correction
WG = 0.0000 arcsec/yr.
KK = 0.039 arcsec/yr.

Garth

MeJennifer

Apr28-07, 01:40 PM

Garth, all the respect for your theory, but didn't your theory predict 4.4096 arcsec/yr? How come it now shows a number much closer to the experimental outcome?

Garth

Apr28-07, 02:18 PM

Garth, all the respect for you theory, but didn't you predict 4.4096 arcsec/yr? How come it now shows a number much closer to the experimental outcome?

I have written more on the Self Creation Cosmology (http://www.physicsforums.com/showthread.php?p=1316400#post1316400) thread.

The original theory was highly determined with \lambda = 1. It had many interesting features, which I have been discussing on that thread and it made a particular prediction for GP-B, which appears not to be verified.

Therefore the day after that announcement was made on the 14th April I sat down and looked again at the theory. I realised that there was a cosmological clock drift time dilation to take into account that adds another 0.25 arcsec/yr, but which wasn't enough to save the theory.

I therefore generalised the theory by leaving \lambda undetermined. This meant losing some of the attractive features of the model but still preserving several others. The result is the prediction posted above and I am now writing up the new General Theory of Self Creation Cosmology for publication.

If the final results for GP-B are exactly those predicted by GR then I will finally say goodbye to SCC!

Garth

LeBourdais

Apr29-07, 11:20 AM

I can see my way clear to a general self creation theory in which \lambda is left as an unknown variable.

The geodetic prediction becomes

\Omega = [(1 - \lambda/3)6.6 + 0.25] arcsec/yr.

(I have found an extra 0.25 arc/sec/yr precession due to cosmological time dilation (clock drift) that makes my original prediction 4.65 arcsec/yr not 4.4 arcsec/yr.)

Unfortunately the theory then predicts the total mass density parameter for the universe to be

\Omega_T = \frac{1}{3\lambda},

so if \lambda is small a lot of DM and DE is required and an attractive feature of the original theory is lost.
Hi Garth,

The smaller the value of \lambda, the higher the value of \Omega_T will be. Can you tell us which is the highest value of \Omega_T you would consider acceptable ? This would provide a minimum acceptable value of \lambda and a maximum acceptable value for the geodetic precession.

Paul

Garth

Apr29-07, 04:15 PM

Hi Garth,

The smaller the value of \lambda, the higher the value of \Omega_T will be. Can you tell us which is the highest value of \Omega_T you would consider acceptable ? This would provide a minimum acceptable value of \lambda and a maximum acceptable value for the geodetic precession.

Paul

Hi Paul!

In GSCC if \lambda \neq 1 then ideally \lambda ~ 1/3, which would give \Omega_T ~ 1, concordant with the standard model, however that would be too high a value of \lambda for the present geodetic precession.

I say "present" because I think we ought to wait for the final analysis before being sure what that reading actually is. They have to accurately model the polhode and patch effect torques accurately and unambiguously first.

The present error bars on the geodetic measurement allow for \lambda < 0.14 which gives \Omega_T > 2.33.

It then depends on whether that could be concordant with the WMAP data and exactly how much DE and DM would be required and plausible.

Garth

Garth

May13-07, 06:24 PM

Hi everybody,

Thank you for your efforts to help clarify several points. I still cant decode the axis informations from the plot named Torque modeling example: motion of gyro 3 in the L10028 poster. Can someone who attended the APS conf or GP-B expert help us ?

regards,

F H-C

The Gravity Probe B (http://einstein.stanford.edu/) site now includes slides of Francis Everitt's April 14th talk (http://einstein.stanford.edu/content/aps_posters/APS_talk_Everitt.pdf) which includes a slide in high definition of that diagram; see page 21.

The 'X-axis' is the N-S result, the 'Y-axis' is the W-E result, both in mas.yr-1 . The ellipses are the one sigma error envelopes around the readings at succeeding stages or 'floors' of error reduction.

This is as described by Jim in #171 (http://www.physicsforums.com/showpost.php?p=1305313&postcount=171).

These readings include the Earth geodetic (EG) result, the Earth frame-dragging (EFD) result, the solar geodetic (SG) result and the proper motion (PM) of the guide star.

In the E-W direction the expected values (yr-1) are:
GR EFD = -39, SG = -16, PM = -20 (mas) making a total net expected value of -75 mas.

In the N-S direction the expected values (yr-1) are:
GR EG = -6606, SG = +7, PM = +28 (mas) making a total net expected value of -6571 mas.

These net expected values are marked with the two large green arrows.

However, you can see from that diagram that the latest, March 2007, ellipses are not centred on those values, the frame-dragging result is around -95 mas yr-1 and the geodetic result around -6595 mas yr-1, which makes it very interesting!!

Caveat: Note that the size of the error on the March 2007 'glimpses' are only about 20 mas yr-1 whereas Francis Everitt quoted 6638 \pm97 mas yr-1 for the present evaluation of the geodetic precession. The size of the \pm97 mas error is due to "Residual gyro-to-gyro inconsistencies due to incomplete modeling ~ 100 mas yr-1" (See slide 20 in that lecture presentation)

We wait for December for those errors to be reduced further!

Garth

henryco

May19-07, 04:40 AM

The Gravity Probe B (http://einstein.stanford.edu/) site now includes slides of Francis Everitt's April 14th talk (http://einstein.stanford.edu/content/aps_posters/APS_talk_Everitt.pdf) which includes a slide in high definition of that diagram; see page 21.

The 'X-axis' is the N-S result, the 'Y-axis' is the W-E result, both in mas.yr-1 . The ellipses are the one sigma error envelopes around the readings at succeeding stages or 'floors' of error reduction.

This is as described by Jim in #171 (http://www.physicsforums.com/showpost.php?p=1305313&postcount=171).

These readings include the Earth geodetic (EG) result, the Earth frame-dragging (EFD) result, the solar geodetic (SG) result and the proper motion (PM) of the guide star.

In the E-W direction the expected values (yr-1) are:
GR EFD = -39, SG = -16, PM = -20 (mas) making a total net expected value of -75 mas.

In the N-S direction the expected values (yr-1) are:
GR EG = -6606, SG = +7, PM = +28 (mas) making a total net expected value of -6571 mas.

These net expected values are marked with the two large green arrows.

However, you can see from that diagram that the latest, March 2007, ellipses are not centred on those values, the frame-dragging result is around -95 mas yr-1 and the geodetic result around -6595 mas yr-1, which makes it very interesting!!

Caveat: Note that the size of the error on the March 2007 'glimpses' are only about 20 mas yr-1 whereas Francis Everitt quoted 6638 \pm97 mas yr-1 for the present evaluation of the geodetic precession. The size of the \pm97 mas error is due to "Residual gyro-to-gyro inconsistencies due to incomplete modeling ~ 100 mas yr-1" (See slide 20 in that lecture presentation)

We wait for December for those errors to be reduced further!

Garth

Very interesting indeed...but, i dont see where your 20 mas yr-1 in the MArch glimpse comes from! looking at the March ellipses i rather see something like -98 +- 7 which is more than 3 sigmas away from -75 for the two ellipses!

Anyway if there are 100mas yr-1 gyro to gyro inconsistencies...
i would say that these center values and small errors mean nothing for the time being and i understand that they need more time to clarify the situation.

Here is my favoured scanario: the frame dragging is zero but there are some resonance peaks from time to time as shown in their error poster for gyro 2
If the resonance peaks are much larger in time as may be the case for other gyros , then they are much more difficult to separate from the zero baseline and this is why in the error poster they estimate a 100 mas y-1 for this main source error assuming much larger peaks in the other Gyros than those seen for Gyro 2.

The question is : Does Gyro 2 plot in the error poster only shows an error or an absolute measurement after removing all other sources of errors, sun geodetic an proper star motion effect ? If not something very accurate (very indeed since the final error will come mostly from the resonance peaks as they say there) was subtracted by hand to put the mean to zero...what is it?
The quite ambiguous answer i got from Everitt is:

" You are observant in noticing that the
results for gyro #2 obtained by the geometric
analysis method could be interpreted as giving a
smaller than Einstein east-west drift "
:wink:
"but until
we have completed the full analysis, taking into
account the small but significant misalignment
torques, we should not attach too much importance
to that. There were certain anomalous features
in that gyroscope's performance. We believe we
understand them but remain watchful."

yes but i would say that the mean effect shown by the geometric approach here is so small compare to GR prediction that this should hardly be fortuitous... (unless strange fine tuning between systematical effects and physical effects occured!) :rolleyes:

F Henry-Couannier

Garth

May19-07, 05:28 AM

Very interesting indeed...but, i dont see where your 20 mas yr-1 in the MArch glimpse comes from! looking at the March ellipses i rather see something like -98 +- 7 which is more than 3 sigmas away from -75 for the two ellipses! ~20mas is the crude size across both March error ellipses. I am not willing to accept any smaller value for the error at this stage!Anyway if there are 100mas yr-1 gyro to gyro inconsistencies...
i would say that these center values and small errors mean nothing for the time being and i understand that they need more time to clarify the situation.
quite ...my point exactly.
Here is my favoured scanario: the frame dragging is zero but there are some resonance peaks from time to time as shown in their error poster for gyro 2
If the resonance peaks are much larger in time as may be the case for other gyros , then they are much more difficult to separate from the zero baseline and this is why in the error poster they estimate a 100 mas y-1 for this main source error assuming much larger peaks in the other Gyros than those seen for Gyro 2.An interesting point, but we are not grasping at straws by any chance are we?The question is : Does Gyro 2 plot in the error poster only shows an error or an absolute measurement after removing all other sources of errors, sun geodetic an proper star motion effect ? If not something very accurate (very indeed since the final error will come mostly from the resonance peaks as they say there) was subtracted by hand to put the mean to zero...what is it?
The quite ambiguous answer i got from Everitt is:

" You are observant in noticing that the
results for gyro #2 obtained by the geometric
analysis method could be interpreted as giving a
smaller than Einstein east-west drift "
:wink:
"but until
we have completed the full analysis, taking into
account the small but significant misalignment
torques, we should not attach too much importance
to that. There were certain anomalous features
in that gyroscope's performance. We believe we
understand them but remain watchful."Thank you for that quote from Francis.

yes but i would say that the mean effect shown by the geometric approach here is so small compare to GR prediction that this should hardly be fortuitous... (unless strange fine tuning between systematical effects and physical effects occured!) :rolleyes:

F Henry-CouannierWe wait and see!

Garth

JonathanK

May20-07, 11:09 AM

Hi Garth, I’m new to the forum, enjoying the discussion. Have an update about Planck scale gravity (PSG), which has been mentioned.

Like you I looked at my theory afresh after the preliminary results, did a calculation that shows clearly it was the prediction for the geodetic effect, rather than PSG itself, that was flawed. It sets out the correct prescription from the theory, by deriving the effect numerically from the original conceptual basis.

I don’t know if the geodetic effect has been derived in this way from a flat space theory before (some think it almost synonymous with space curvature). But the component thought in GR to be due to curvature, 2/3 of the total effect, came straight out of a very simple calculation for one of the gyros on GP-B. PSG creates an analogue effect, with the same numerical value. As per the first paper, the main issue was only this curvature component (the other 1/3 had various related questions that weren’t gone into). The new paper is under peer review, but is in preprint at

http://www.podtime.net/sciprint/fm/uploads/files/1178319909Geodetic%20calculation.pdf

Unless the calculation or its conception is wrong, this puts PSG back on track like SCC, rather than having fallen by the wayside.

Thanks, Jonathan

henryco

May20-07, 02:01 PM

~20mas is the crude size across both March error ellipses. I am not willing to accept any smaller value for the error at this stage!
Garth

Sorry but i'm just numerically translating the ellipse information that anybody can see in this plot. In a one sigma horizontal ellipse like this one, the error is half the size of the ellipse, as far as i know. So the error given in this plot by GP-B collaboration is in between 6 and 8 mas y-1...whatever the other issues such as extra 100 mas y-1 error sources that remain to be understood...

cheers,

Fred

SpaceTiger

May20-07, 02:05 PM

:rolleyes:

And when the next prediction fails, will we see another modification/generalization? Come on people, don't you think your time would be better spent working on something new?

marcus

May20-07, 02:32 PM

:rolleyes:

And when the next prediction fails, will we see another modification/generalization? Come on people, don't you think your time would be better spent working on something new?

Nick SpaceTiger, good to see you back!
Pervect said you were busy with PhD thesis and he was urged to step in and fill the gap. Does this mean that the thesis is done now?
or pending approval? In any case congratulations on forthcoming PhD

SpaceTiger

May20-07, 02:52 PM

Nick SpaceTiger, good to see you back!
Pervect said you were busy with PhD thesis and he was urged to step in and fill the gap. Does this mean that the thesis is done now?
or pending approval? In any case congratulations on forthcoming PhD

Hi marcus! I'm afraid my thesis is still a work in progress and mentor duties will be primarily carried out by pervect and Janus, but I'll still be stopping by from time to time. Thanks.

JonathanK

May20-07, 03:22 PM

To SpaceTiger: Hi, what makes the calculation so strong is that it is neither a modification nor a generalisation, as you seem to be saying. The theory hasn't been changed - instead the calculation works straight from the already published conceptual picture, and proves in an unambiguous way what the prediction should have been. The theory is still under development, but not in this area - the numerical value of the curvature component doesn't go into the calculation, it comes out of it. Jonathan

SpaceTiger

May20-07, 03:55 PM

To SpaceTiger: Hi, what makes the calculation so strong is that it is neither a modification nor a generalisation, as you seem to be saying. The theory hasn't been changed - instead the calculation works straight from the already published conceptual picture, and proves in an unambiguous way what the prediction should have been.

So what makes the calculation so strong is the fact that you messed up in the first one?

JonathanK

May20-07, 05:21 PM

Hi, I messed up in the first one for the following reasons!

In the first paper I pointed out a number of ways in which PSG mimics GR, but unfortunately missed one way. Having missed it, I wrote "There is no space curvature in PSG, so it should not mimic GR to the extent of causing a straight line parallel transported through a gravitational field to change its orientation. This removes the curvature component, which is two thirds of the predicted geodetic effect from GR.."

At that point I thought what some think - that only curvature will produce the geodetic effect. After the effect was measured I did a calculation using two points on the spin axis of one of the gyros on GP-B - the centre, and one end, at the surface of the sphere. Worked out their positions after half an orbit, with very slightly different speeds (due to different heights in a Planck scale refractive medium that affects matter). It's a thing that I'd tried last year but never completed - out came the curvature component of the geodetic effect, it gave 4.4 arcsecs/yr. Sad I'd missed it, but happy that it vindicates the theory, as I think it does. But I await the views of others, and would appreciate any thoughts you might have.

JonathanK

May24-07, 06:44 AM

Hello,

Well it seems that if there was a problem with the calculation it would have been pointed out - Garth and probably SpaceTiger have read the paper, hopefully others. It's a very simple idea - matter is slowed in its motion through the field by the same factor as light is slowed (and for that matter as time is slowed), which is sqrt [1 - (2GM/rc^2)]. When one applies that to local matter within an orbiting object, one finds the object turns - the calculation shows this is exactly as in the geodetic effect, both numerically and in terms of direction. I'm all for GSCC, glad it's back on the list - experiment can help shape theories. For PSG it has helped shape the interpretation rather than the theory, and I'll take the lack of criticism as positive. The wider question this has bearing on is what possible interpretations for the geodetic effect do we have, now that it has been measured directly. Is curvature the only one? Thanks, best wishes Jonathan

Garth

Jun14-07, 03:31 AM

Latest June Mission Update (http://einstein.stanford.edu/) from the GP-B team.

Nothing new to report on the results.

This GP-B update is essentially a revised and expanded version of the GP-B press release that we posted in April that tells a more readable and complete story about the goals of GP-B, what we've accomplished to date, the surprises we've encountered and how we're addressing them, and the steps we are taking towards a final results announcement at the end of the year.

1. GP-B SUCCEEDED IN COLLECTING THE DATA TO TEST EINSTEIN'S PREDICTIONS ABOUT GRAVITY

2. THE EFFECTS OF GENERAL RELATIVITY ARE CLEARLY VISIBLE

3. FIRST PEEK AT RESULTS PRESENTED AT APRIL APS MEETING; FINAL RESULTS IN DECEMBER
(geodetic precession = GR to 1% - however present estimate ("hint") of result ~30 mas too high but error is still ~100 mas)

4. THE TWO SURPRISES & THEIR IMPACT ON THE EXPERIMENT
i. Shortly after the gyros were spun up in August 2004, we discovered that the polhode motion of the gyro rotors, which was expected to exhibit a constant pattern throughout the experimental period, was changing over time, significantly complicating the calibration of the gyroscope readout angles.
ii. During the post-experiment instrument calibration testing in August-September 2005, the spin axes of the gyroscopes were found to be affected by certain class of small classical torques, known as "misalignment torques," whose effects must be rigorously separated from the relativity measurements. (Due to electrostatic patches on the rotors and their housing.) (Italics my text)

5. NEXT STEPS-MOVING TOWARDS A FINAL RESULT
i. Fine calibration of the gyroscope/telescope scale factor
ii. Refining the analysis of the misalignment torques
iii. Extremely precise VLBI measurement data will be substituted for the current 1997 Hipparcos [star] Catalogue values for the proper motion of IM Pegasi.

We continue to wait and see! :smile:
Garth

Chronos

Jun15-07, 02:15 AM

But these minor corrections are just that, Garth, minor. I fail to see how they can affect the conclusions. The results are GR concordant and will remain very much so, IMO.

Garth

Jun15-07, 02:32 AM

I was just reporting what the GP-B team said at the conference, in the mist of the errors presently being reduced they saw just the hint of a non-GR signal. See APS talk by Francis Everitt (http://einstein.stanford.edu/content/aps_posters/APS_talk_Everitt.pdf) page 21, you will see the successive error ellipses honing down on a value about 30 mas away from the GR prediction.

Perhaps it was wishful thinking on their part - we shall wait and see!

Garth

wolram

Jun15-07, 02:57 AM

Does every one consider this test (clean) it seems to me like trying to make some sense out of white noise, i mean it is not like a some number registers on a dial, if the test was repeated with the same results it would be more
convincing.

Or is this the one test that has been done with so much care that no other conclusions are probable.

Garth

Jun15-07, 03:15 AM

They have a problem, which they freely admit. The presence of this noise almost ruined the experiment, however it is not white noise and the spurious signal can be extracted objectively.

The two unexpected effects are linked. First the electrostatic patches have put an extra torque on the gyro rotors that perturbs them, secondly the energy used up in this perturbation gradually reduces the polhode motion (wobble) making that more difficult to model.

However once they have accurately modelled the geometry of the patch effects, which are different for each of the four gyro rotors, they can subtract that from the precession signals and accurately model the polhode motion. It is this that they are completing at present.

You can read all about it by following the links on their website (http://einstein.stanford.edu/). :smile:

Garth

Garth

Jun16-07, 07:13 AM

Just to make clear what the present situation is:

(mas = milliarcsec)
The geodetic N-S precession is predicted by GR to be - 6606 mas/yr, however there is a solar geodetic precession N-S component of + 7 mas/yr and the proper motion of IM Pegasi +28 mas/yr to take into account, resulting in a net expected N-S precession of -6571 \pm1 mas/yr.

The frame-dragging E-W precession is predicted by GR to be -39 mas/yr, the solar geodetic precession E-W component of -16 mas/yr and the proper motion of IM Pegasi -20 mas/yr to include, resulting in a net expected N-S precession of -75 \pm1 mas/yr.

From pages 20 and 21 of Francis Everitt's April APS talk, we find: A series of error ellipses on the N-S v E-W precession plot with centres respectively at (-6584 \pm60, -83 \pm22 mas/yr) June 2006, (-6597 \pm17, -92 \pm15 mas/yr) December 2006, (-6595 \pm12, -98 \pm7 mas/yr) March 2007 and (-6603 \pm8, -98 \pm7 mas/yr) March 2007.

It was this last reading for the geodetic precession that Francis Everitt reported at his April APS talk. If we also include that 'glimpse' of the E-W precession as well we have net values of:
(-6603 \pm8, -98 \pm7 mas/yr)
whereas GR predicts:
(-6571 \pm1, -75 \pm1 mas/yr).

In other words the actual readings are larger than GR predicts by 32 mas/yr in geodetic precession and 23 mas/yr in frame-dragging precession.

However, they reported an overall error, which is still being reduced, caused by residual gyro-to-gyro inconsistencies due to incomplete modeling of ~ \pm100 mas/yr.

This renders the present geodetic 'glimpse' as being consistent with GR to within about 1\frac{1}{2}%, whereas the frame-dragging precession is at present swamped by noise.

The running now stands:

Einstein's General Relativity(GR)
Brans-Dicke theory (BD)
Moffat's Nonsymmetric Gravitational Theory (http://arxiv.org/abs/gr-qc/0405091) (NGT)
Stanley Robertson's Newtonian Gravity Theory (http://arxiv.org/abs/gr-qc/0502088) (NG),
F. Henry-Couannier's Dark Gravity Theory (http://www.arxiv.org/abs/gr-qc/0610079) (DG).
Alexander and Yunes' prediction for the Chern-Simons (http://kr.arxiv.org/abs/hep-th/0703265v1) gravity theory (CS).
Kris Krogh's Wave Gravity Theory (http://lanl.arxiv.org/abs/astro-ph/9910325) (WG)
Hongya Liu & J. M. Overduin prediction of the Kaluza-Klein ( http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v538n1/50681/50681.text.html?erFrom=5252751197746712308Guest#sc 8) gravity theory (KK).

The predictions are now:

GPB Geodetic gross precession (North-South)

GR = -6606 mas/yr.
BD = -(3\omega + 4)/(3\omega + 6) 6.606 arcsec/yr. where now \omega >60.
NGT = -6606 - a small \sigma correction mas/yr.
NG = -6606 mas/yr.
DG = -6606 mas/yr.
CS = -6606 mas/yr.
WG = -6606 mas/yr.
KK = -(1 + b/6 - 3b2 + ...) 6606 mas/yr. where 0 < b < 0.07.

We await the GPB gravitomagnetic frame dragging gross precession (East-West) result.

GR = -39 mas/yr.
BD = -(2\omega + 3)/(2\omega + 4) 39 mas/yr.
GSCC = -39 mas/yr.
NGT = -39 mas/yr.
NG = -39 mas/yr.
DG = 0 mas/yr.
CS = -39 mas/yr. + CS correction
WG = 0 mas/yr.
KK = -39 mas/yr.

Note: in the above list only the Kaluza-Klein gravity theory (KK) is able to produce a geodetic precession larger (negatively) than GR if 0 < b < \frac{1}{18}, (by a maximum of 11.5 mas when b = \frac{1}{72}), but it cannot produce a frame-dragging precession larger than GR.

Garth

JonathanK

Jun17-07, 05:00 PM

Garth

Jun18-07, 03:03 AM

About the apparent extra 32 mas/yr - there's a '96 paper by Kenneth Nordtvedt, which shows that the analysis of the lunar laser ranging data done in the '80s also gave a precession slightly greater than the geodetic precession. Nordtvedt's explanation probably wouldn't cover both anomalies, but if he's wrong… I haven't got time to look into it, but Garth, you might want to see if in relation to context the two are equivalent. It would then be a new anomaly.

The paper is "On the 'geodetic precession' of the lunar orbit", Class. Quantum Grav. 13 (1996) 1317-1321.

J.
Relevant papers are:
Kenneth Nordtvedt, Classical and Quantum Gravity, Volume 13, Issue 6, pp. 1317-1321 (1996)
On the `geodetic' precession of the lunar orbit (http://adsabs.harvard.edu/abs/1996CQGra..13.1317N)The Moon's dynamics in the geodetically rotating inertial frame is intrinsically different from its dynamics in a globally fixed frame, possessing different ratios of lunar motion to solar motion, and of tidal strength to squared solar motion. The correct prescription is that the Moon's orbit in globally fixed coordinates equals a dynamically different lunar orbit determined in the geodetically rotating inertial frame plus additional precession of that orbit as it accompanies the local frame.and

Kenneth Nordtvedt, Icarus Volume 114, Issue 1, March 1995, Pages 51-62 The Relativistic Orbit Observables in Lunar Laser Ranging (http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WGF-45NJJ8B-31&_user=10&_coverDate=03%2F31%2F1995&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=be67b5191e845a480f8ca9ad31b08b62) Relativistic corrections to the perigee precession rate are found which include not only 4% enhancement of the well-discussed de Sitter "geodetic precession" term, but also a direct contribution from the solar tidal acceleration which is 10% as large.

Nordtvedt's explanation for the excess precession is solar tidal action on the Moon in orbit around the Earth, which does not apply to the GP-B gyros.

I make two further comments:

1. The analysis of the Moon's orbit is very complicated having to take into account tidal reactions as well as planetary perturbations and other effects. When trying to test for something like the geodetic precession how sure are we that all other effects have been correctly accounted for?

2. All measurements of orbits, geodesics, through empty space cannot reduce a degeneracy between GR and a conformal gravity theory in which the action reduces to that of canonical GR in vacuo.

There is therefore the possibility that the geodetic precession may be equal to GR in such observations as these above yet different from GR for the GP-B gyros. It is this point that has not been taken into account by Kenneth Nordtvedt when he said the experiment was worth doing when it was first proposed in the 1950's and begun in the 1960's, but now it is a foregone conclusion.

If the final results of the two precessions are exactly equal to GR then we can rule out such conformally equivalent gravitational theories.

However if the final GP-B results are different from the GR predictions, while other tests of the geodetic and frame-dragging precessions measuring the orbits of planetary bodies, binary pulsars, or satellites, are equal to the GR predictions, then that would indicate a conformally equivalent non-minimally connected scalar field is at work.

We wait to see. :smile:

Garth

JonathanK

Jun18-07, 05:30 AM

I meant look at the numbers at a shortcut (this can help!). Then only look further if the two discrepancies come out roughly the same, when allowing for orbit differences. But it might be worth waiting for all possible sources of error to be removed from the GP-B data first.

Garth

Jun29-07, 02:37 AM

This paper on today's physics arXiv claims to correct the GR prediction for the frame-dragging precession: Correction of the Frame Dragging Formula due to the Precession of the Coordinate Axes near a Rotating Body (http://au.arxiv.org/PS_cache/arxiv/pdf/0706/0706.4284v1.pdf).The total precession gives the value with respect to chosen coordinate axes, while the precession of the coordinate axes with respect to the distant stars is usually disregarded. We address this problem in two different ways. Firstly, we consider the participation of each particle in the total precession observed from the corresponding particle. Secondly, we find the precession of the coordinate axes and its subtraction from the total precession. Both methods yield the well known value for the geodetic precession and 75% of the well known value for frame dragging effect.So we obtained the same value for the geodetic precession as predicted by the General Relativity and 75% of the general-relativistic value for the frame dragging effect. In the case of the Gravity Probe B experiment this yields 0.030 milli arc-seconds per year.

Personally I don't believe it; the spin axes of the gyroscopes are Fermi-Walker transported along their geodesics but the basis vectors of the comoving frame are not. They are tied by a pure boost to the PPN coordinate grid, which in turn is expected to be tied to an inertial frame fixed relative to the distant quasars.

Furthermore, the present 'glimpses' of the GP-B frame-dragging result, if anything, are greater than the GR prediction!

Garth

wolram

Jun29-07, 03:19 AM

Will there ever be closure to this test? i do not mean the scientific impossibility of proof beyond doubt, just doubts have been quashed
to a CL that is acceptable.

Garth

Jun29-07, 04:29 AM

They originally talked of obtaining an accuracy of 0.1 mas, now I see the quote only to within 1 mas. However, even with that level of accuracy, I think they will falsify many theories, or render their perturbations away from GR too small for those theories, such as BD, to be left any significance.

However of course, as things stand at the present, they could still falsify GR, and then things really would get interesting!

We will have to wait until the end of the year to find out.

Garth

JinHe

Jul7-07, 03:09 PM

I wrote a paper on the explanbation to GP-B data anormaly as suggested by the figure, www.lighttale.com/opin/fdtif.tif, which is taken from Dr Everitt's speech at APS meeting in Florida, 2007.

Flat Spacetime Gravity and Prediction on GP-B Data
Abstract: This paper follows the gravitational principles I proposed before: (1) Space and time are perceived and measured only by means of physical processes which are static to reference frames; (2) Freely falling mass in real surroundings always presents gravity and always has the background flat spacetime which were perceived and measured by the mass frame itself if it had approximately zero mass; (3) Spacetime is not curved and the metric form of general relativity (GR) is called refraction metric on flat spacetime which like refraction medium is effective to curve light rays. Similarly we have effective curvature, effective parallel displacement, etc. (4) The refraction metric (gravitational field) of a mass is generally obtained by holonomic or nonholonomic coordinate transformations. These principles are conceptually different from the ones of GR whose formulas of gyroscope precession in weak gravity are heuristically derived by applying a series of coordinate transformations. This paper shows that the application of rotational coordinate transformation is needed. First public peek at Gravity Probe B results (GP- shows that both geodetic and frame-dragging effects are larger than GR predictions by the amount of about 20 mas/yr. It is suggested that the gap can be fixed by applying rotational coordinate transformation. We wait for the final release of GP-B data analysis in the coming December and see if my calculation is confirmed.

Note: I am kindly asking for someone who is willing to endorse my paper on Arxiv publication. Although I gained the right for my Arxiv free-publication I gained a crackpot title in the meantime and the right is deprived of.

Garth

Jul7-07, 06:30 PM

Although I gained the right for my Arxiv free-publication I gained a crackpot title in the meantime and the right is deprived of.

You actually earned that title when you said in you paper The Faulty Assumptions of the Expanding-Universe Model vs. the Simple and Consistent Principles of a Flat-Universe Model, -- with Additional Prediction on Gravity Probe B Data (http://arxiv.org/abs/astro-ph/0605213): Freely falling particles locally have accelerations of any magnitude and any direction, which also indicates that the gravity can not be locally cancelled too.Freely falling test particles do not "locally have accelerations of any magnitude and any direction"; their accelerations are precisely determined by the Einstein tensor derived from the Riemannian and are equal in the Post Newtonian Approximation to the value in magnitude and direction given by the Newtonian gravitational acceleration at that event in space and time.

In a flat space-time model the geodetic precession is zero but the Newtonian acceleration, which would then be necessary to substitute for the effect of curvature, yields a Thomas precession exactly one half of the GR geodetic precession in the opposite direction. The GP-B result is equal to the GR prediction to within 1\frac{1}{2}%, which is within the present error of measurement, it has therefore falsified your theory (that in any case has not been published in a peer reviewed journal) to many orders of sigma. Any further discussion of your theory must be carried out in the Independent Research (http://www.physicsforums.com/forumdisplay.php?f=146) Forum, having first observed its Rules for submission (http://www.physicsforums.com/showthread.php?t=82301).

Garth

JinHe

Jul7-07, 09:21 PM

You actually earned that title when you said in you paper The Faulty Assumptions of the Expanding-Universe Model vs. the Simple and Consistent Principles of a Flat-Universe Model, -- with Additional Prediction on Gravity Probe B Data (http://arxiv.org/abs/astro-ph/0605213): Freely falling test particles do not "locally have accelerations of any magnitude and any direction"; their accelerations are precisely determined by the Einstein tensor derived from the Riemannian and are equal in the Post Newtonian Approximation to the value in magnitude and direction given by the Newtonian gravitational acceleration at that event in space and time.

In a flat space-time model the geodetic precession is zero but the Newtonian acceleration, which would then be necessary to substitute for the effect of curvature, yields a Thomas precession exactly one half of the GR geodetic precession in the opposite direction. The GP-B result is equal to the GR prediction to within 1\frac{1}{2}%, which is within the present error of measurement, it has therefore falsified your theory (that in any case has not been published in a peer reviewed journal) to many orders of sigma. Any further discussion of your theory must be carried out in the Independent Research (http://www.physicsforums.com/forumdisplay.php?f=146) Forum, having first observed its Rules for submission (http://www.physicsforums.com/showthread.php?t=82301).

Garth

Dear Garth,

Thanks for your suggestion.
"locally have accelerations of any magnitude and any direction", e.g. Earth, between the magnitudes of -g=-9.8m/ss and +2g=19.8m/ss, which is the correct text as written in Appendix in my astro-ph/0605213. You short-circuited my result.

As for flat spacetime gravity, there are many kinds while your suggestion is that THERE IS ONLY ONE KIND IN THE NATURE!!!

JinHe

Jul7-07, 10:35 PM

Dear Garth,
As you suggested we do not talk about my papers.
Let us talk about you suggested problem of Galileo and Einstein universal acceleration in any neighborhood.

Galileo never tested if two masses of different initial speeds share the same universal acceleration locally

Now return to curved spacetime assumption. If there were one set of coordinate system, t, x, y, z, (rectangular coordinates) on curved spacetime then the geodesic motion in terms of the coordinates is
d^2x^i/ds^2 = -\Gamma ^i_jk dx^j/ds dx^k/ds
which is simply:
accelaration = connection times velocity times velocity
which says that local accelerations depends on test particle velocities.
Even though relativists can find their own definitions of velocities and accelerations on CURVED SPACETIME, the above geodesic motion must still hold and two masses of different initial speeds must not share the same universal acceleration locally.

Therefore, Galileo and Einstein universal acceleration imagination is contradictory to the assumption of curved spacetime!!!!

Garth

Jul8-07, 02:42 AM

This thread is to discuss published theories that are being tested by the Gravity Probe B experiment.
As you suggested we do not talk about my papers.
Let us talk about you suggested problem of Galileo and Einstein universal acceleration in any neighborhood.NO! PF is not the place to discuss your misunderstanding of GR or to 'push' "Einstein was wrong" ideas.

Garth

JonathanK

Jul8-07, 10:18 PM

I agree with JinHe over one thing. Sweeping statements about what flat space theories will contain are unhelpful, because they overlook possible individual features. Because GR is a very accurate description, a good flat space (or flat space-time) theory will mimic it closely in one way or another with additional devices, mathematical or conceptual. These make any theory what it is, and you can't assume you know what they'll do - they might even mimic the geodetic effect.

You may not endorse JinHe's paper Garth, but having kindly endorsed mine before it got through peer review, perhaps you'll respond to the point I've made here, which has bearing on this. A precession of the same value as the geodetic precession will arise from flat space if one simply says that the matter in an orbiting object is slowed locally by the same factor as that by which time is slowed in GR. This turns an object (such as a gyro) rather as a stream turns a millwheel, because locally its matter moves at different speeds, at different heights in the field. (But the orbital speed everywhere in the object is the same as at the centre, as in standard gravity.)

Even if you don't check the calculation in the paper "A numerical derivation of the geodetic effect without space curvature", which is at

http://www.podtime.net/sciprint/fm/uploads/files/1178319909Geodetic%20calculation.pdf

please comment on this statement, as what you’ve said relates to it:

A precession of the same value as the geodetic precession will arise from flat space if one simply says that the matter in an orbiting object is slowed locally by the same factor as that by which time is slowed in GR.

Thanks! J

Garth

Jul9-07, 02:58 AM

Hi Jonathan!

There are three points here, and I also want to publish a correction to my statement in my post #224 above:In a flat space-time model the geodetic precession is zero but the Newtonian acceleration, which would then be necessary to substitute for the effect of curvature, yields a Thomas precession exactly one half of the GR geodetic precession in the opposite direction. I posted that too quickly. In fact the Thomas precession of one half of the GR geodetic precession is in the same direction as the GR geodetic precession.

The first point is about JinHe's posts. There are many alternatives to GR out there on the web, the vast majority are 'crackpot' and not only is an enormous amount of time wasted ploughing through them but to do so on PF would be confusing to others who come here to learn what physics is actually all about. That is why there are strict guidelines here. Physics is also all about testing viable alternatives, which is why I started this thread, however the problem is sifting out the wheat, possible viable alternatives to the standard theory, from the crackpot chaff. One clear hurdle is only to consider theories that have passed peer review, which again is in accordance with PF guidelines. On this thread, as there is a clear test, the GP-B experiment, whose results are being published at this time , albeit slowly, I have extended the guidelines to also include papers that have been endorsed for publication on the physics arXiv, this seems to have been accepted by the Moderators, who do a fine job I might add.

Secondly this thread is not about a detailed discussion of these alternatives but rather a compilation of their clear predictions of the outcome of this experiment. But of course there has to be some discussion as here. In a theory without space-time curvature the normal Newtonian gravitational acceleration has to be explained by some Newtonian type gravitational force. This force would accelerate the gyros away (downwards!) from their inertial frame of reference and that acceleration would impart a Thomas precession equal to half the GR geodetic. For such flat space-time theories to equal the GR geodetic precession they would require an extra mechanism to make up this short-fall.

Thirdly about your comment above, it is not true that "time is slowed in GR"; time always passes at the tautological rate of one second per second.....

Relativistic time dilation is the result of the path length through space-time, the proper interval, being less along one path between two events than along the geodesic path between them.

Garth

JonathanK

Jul9-07, 07:07 AM

Sorry the statement I asked you to comment on was rather loosely put - I was trying to keep it short.

Yes, I know about the way time is defined, but mentioned time partly just as a shorthand way of referring to the expression sqrt (1 - [2GM/rc^2]), which in GR is the factor difference between the "timerate" at a given point in the field and at infinity. It's also relevant to the point I'm making that a fundamental expression from GR, if applied in an unexpected way, yields the geodetic effect out of flat space. So there was also an element of showing how little is needed to produce it.

But like you, I posted too quickly - I should have said the curvature component (2/3 of the total effect), rather than the geodetic precession. If one assumes that matter is slowed in flat space by sqrt (1 - [2GM/rc^2]), in addition to any other forces affecting it, then one has explained 2/3 of the geodetic effect. (The other 1/3 has already been explained in other ways, which apply whether space is curved or flat.)

As for the Newtonian force you assume must be needed in a flat space theory, that opens questions about whether the conceptual basis of a theory can mimic GR to the extent of having no acceleration in freefall. It's a rather sweeping statement to say that no theory can possibly do this! I could show you a possible way, but it would be too involved (and might need another pub lunch). But equation 4 in my first paper describes freefall in a new way, and can be checked in about 20 minutes. It gives the speeds all along the trajectory directly, from knowing the speed at a given point.

So anway, the corrected statement I’m hoping you’ll comment on is:

A precession of the same value as the curvature component of the geodetic effect will arise from flat space if one simply says that the matter in an orbiting object is slowed locally by sqrt (1 - [2GM/rc^2]).

Thanks, J

Garth

Jul9-07, 08:05 AM

I am now going away on conference for a few days, so I cannot give a full response. However, if you can fully emulate the time dilation effect in a fully consistent way then you would get the same component, the question is how could you distinguish experimentally between the two theories? If there is no difference between the two then the GP-B will not be testing your theory against GR.

Garth

JonathanK

Jul9-07, 10:03 AM

An interferometer with one arm vertical in the field. This test goes right to the heart of PSG. If light on the radial arm travels further from the centre of the field, it has a faster average speed than light on the horizontal arm. As in the Shapiro experiment with a signal grazing the sun, this has a space component and a time component, and they're equal. In PSG their effects add together, giving a different result from GR.

But there are other differences - the slowing of light and matter I mentioned mimics GR very closely in the radial direction, and makes the post-Newtonian corrections. But in the orbital direction GR doesn't have these corrections, and Newton's circular orbit speed equation stays largely unchanged. But PSG has the slowing of light and matter the same in all directions, which leads to very slight differences to solar system orbits, mass values, and measured distances. The differences to orbit speeds aren't noticed for circular orbits, as the central mass is slightly larger than thought. But the more radial motion there is in the orbit, the more noticeable this becomes - as in the hyperbolic orbits of the Pioneer and flyby anomalies (see first paper).

Also the freefall equation I mentioned should be more accurate than anything else - this is potentially testable. It agrees with numbers from Newtonian gravity arrived at via energy considerations to 12 decimal places. (I challenge anyone to guess how it was derived!)

So these provide testable differences between PSG and GR. As far as the GP-B test is concerned, I’m in a similar position to yours with GSCC, but a more accurate calculation than the one I've done for the geodetic effect, perhaps including the slight differences to solar system parameters, might yield a new prediction before the final results come through (in the meantime, perhaps you could put PSG back on the list). Any suggestions for calculations relating to this would be welcome.

Have a good conference, J

JonathanK

Jul16-07, 02:03 PM

In a theory without space-time curvature the normal Newtonian gravitational acceleration has to be explained by some Newtonian type gravitational force. This force would accelerate the gyros away (downwards!) from their inertial frame of reference and that acceleration would impart a Thomas precession equal to half the GR geodetic. For such flat space-time theories to equal the GR geodetic precession they would require an extra mechanism to make up this short-fall.
Garth

On this PF page from last April

http://www.physicsforums.com/showthread.php?t=167699&page=2

Chris Hillman takes you up on a closely related point. He says only non-gravitational forces produce a Thomas precession, and that "the Thomas term vanishes whenever no non-gravitational forces act on the orbiting object". Let me know if I've missed something, but this seems to remove the problem for flat space theories you've set out.

Garth

Jul16-07, 06:02 PM

The question is: "What does freely falling mean?"

Chris was expanding on what I said; we were both talking from a perspective based on the Equivalence Principle. Thomas precession is an effect which arises when a small object moves in a circular orbit by virtue of some non-gravitational force. (Think of a stone whirled around by some schoolchild at the end of a string.)

Gravitational effects may be caused either by an actual force as in Newtonian gravitation theory, or their observed accelerations are the effect of the curvature of space-time as in GR. (In SCC it was a bit of both)

If they are caused by the effects of the curvature of space-time, as in pure GR, then there is no Thomas Precession, if however they are caused by some force, such as Chris' illustration of a stone whirled around on the end of a string, then there is a Thomas Precession.

Thomas Precession is an effect acting on a gyroscope that is being accelerated relative to the local inertial frame of reference.

In a flat space-time theory such as yours, where there is no curvature effect, then gravitational accelerations, which are the effect of actual forces, must cause Thomas Precession.

I hope this helps,
Garth

JonathanK

Jul16-07, 09:35 PM

It doesn't have space-time, PSG is the gravity part of a theory of time. As I said, the (lateral) conceptual basis doesn't need an object in freefall to be accelerating - and it's the same conceptual basis that led directly to the freefall equation, which gives the right numbers.

Chris Hillman seemed to be discounting all gravitational forces from causing a Thomas precession, including the Newtonian kind you mention, but perhaps he's assuming GR when he says that. J

JinHe

Aug6-07, 01:59 PM

Corrected version:
http://arxiv.org/abs/astro-ph/0604084

I expect it is the correct theory of gravity and the correct prediction for Gravity Probe B. If the theory is falsified I will change my career. Anyway there is small typo problem:
Formula (8): must be: M/2rc^2
Formula (10): must be: M(v/c)^2/2r^2

Garth

Aug6-07, 05:39 PM

Okay Jin, as you have published a eprint on the physics ArXiv in which you quote a definite prediction, I shall include it in the list for falsification, or otherwise, when the final results are published at the end of the year. From your paper I conclude you call your theory "Absolute Relativity", which I shall use as its name here in this thread.

I must admit I am suspicious of your paper, going as it does from a flat-spacetime model of gravitation to derive a 'Bohr atom'-type model of the solar system, complete with a prediction of planetary SMAs similar to Titus-Bode's law, however we will let that pass for the moment...

The main objection is that I do not see a full calculation of the GP-B results, except the mention at equation (15), in particular I see no mention of Thomas precession, which must be there in a flat-spacetime theory if Special Relativistic effects are being accepted. However, from the introduction we have:First public peek at GP-B results shows that both geodetic and frame-dragging effects are larger than GR predictions by the amount of about 25 mas/yr (see Figure 1 which is taken from Everitt (2007)). It is suggested that the gap can be covered by applying the above coordinate transformation, i. e., adding the motional gravity. We wait for the final release of GP-B data analysis in the coming December and see if my calculation is confirmed.

indeed...
So we will take the AR prediction as 'GR + 25 mas' in both the geodetic and frame-dragging measurements.

Note: mas = milliarcsec.

So we now have;
The geodetic N-S precession is predicted by GR to be - 6606 mas/yr, however there is a solar geodetic precession N-S component of + 7 mas/yr and the proper motion of IM Pegasi +28 mas/yr to take into account, resulting in a net expected N-S precession of -6571 \pm1 mas/yr.

The frame-dragging E-W precession is predicted by GR to be -39 mas/yr, the solar geodetic precession E-W component of -16 mas/yr and the proper motion of IM Pegasi -20 mas/yr to include, resulting in a net expected N-S precession of -75 \pm1 mas/yr.

From pages 20 and 21 of Francis Everitt's April APS talk, we find: A series of error ellipses on the N-S v E-W precession plot with centres respectively at (-6584 \pm60, -83 \pm22 mas/yr) June 2006, (-6597 \pm17, -92 \pm15 mas/yr) December 2006, (-6595 \pm12, -98 \pm7 mas/yr) March 2007 and (-6603 \pm8, -98 \pm7 mas/yr) March 2007.

It was this last reading for the geodetic precession that Francis Everitt reported at his April APS talk. If we also include that 'glimpse' of the E-W precession as well we have net values of:
(-6603 \pm8, -98 \pm7 mas/yr)
whereas GR predicts:
(-6571 \pm1, -75 \pm1 mas/yr).

In other words the actual readings are larger than GR predicts by 32 mas/yr in geodetic precession and 23 mas/yr in frame-dragging precession.

However, they reported an overall error, which is still being reduced, caused by residual gyro-to-gyro inconsistencies due to incomplete modeling of ~ \pm100 mas/yr.

This renders the present geodetic 'glimpse' as being consistent with GR to within about 1\frac{1}{2}%, whereas the frame-dragging precession is at present swamped by noise.

The running now stands:

Einstein's General Relativity(GR)
Brans-Dicke theory (BD)
Moffat's Nonsymmetric Gravitational Theory (http://arxiv.org/abs/gr-qc/0405091) (NGT)
Stanley Robertson's Newtonian Gravity Theory (http://arxiv.org/abs/gr-qc/0502088) (NG),
F. Henry-Couannier's Dark Gravity Theory (http://www.arxiv.org/abs/gr-qc/0610079) (DG).
Alexander and Yunes' prediction for the Chern-Simons (http://kr.arxiv.org/abs/hep-th/0703265v1) gravity theory (CS).
Kris Krogh's Wave Gravity Theory (http://lanl.arxiv.org/abs/astro-ph/9910325) (WG)
Hongya Liu & J. M. Overduin prediction of the Kaluza-Klein ( http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v538n1/50681/50681.text.html?erFrom=5252751197746712308Guest#sc 8) gravity theory (KK).
Jin He's Absolute Relativity (http://arxiv.org/PS_cache/astro-ph/pdf/0604/0604084v5.pdf) theory (AR).

The predictions are now:

GPB Geodetic gross precession (North-South)

GR = -6606 mas/yr.
BD = -(3\omega + 4)/(3\omega + 6) 6.606 arcsec/yr. where now \omega >60.
NGT = -6606 - a small \sigma correction mas/yr.
NG = -6606 mas/yr.
DG = -6606 mas/yr.
CS = -6606 mas/yr.
WG = -6606 mas/yr.
KK = -(1 + b/6 - 3b2 + ...) 6606 mas/yr. where 0 < b < 0.07.
AR = -6631 mas/yr.

We await the GPB gravitomagnetic frame dragging gross precession (East-West) result.

GR = -39 mas/yr.
BD = -(2\omega + 3)/(2\omega + 4) 39 mas/yr.
GSCC = -39 mas/yr.
NGT = -39 mas/yr.
NG = -39 mas/yr.
DG = 0 mas/yr.
CS = -39 mas/yr. + CS correction
WG = 0 mas/yr.
KK = -39 mas/yr.
AR = -64 mas/yr.

We wait for the end of the year!

Garth

JinHe

Sep26-07, 09:56 AM

I am earnest to let you know but I have not read the detail.

Garth

Sep27-07, 02:46 AM

No new results to report yet, MISSION UPDATE — SEPTEMBER 2007 (http://einstein.stanford.edu/) In the last three and one half months, we have made significant progress in understanding and addressing both surprises, as well as combining the insights generated by both the geometric and algebraic methodologies towards a final result.

For example, the trapped flux mapping has now been completed for all four gyroscopes and results processed for each throughout the year. One very remarkable result is that we have succeeded in improving by a factor of ~500 the determination of the polhode phase and angle for each gyroscope throughout the duration of the experiment. In particular, the polhode motion for each gyro is now “phase-locked” and known to 0.1 radian (6 degrees) over the course of the experimental year.

As a result, a previous discrepancy between the scale factor calibration computed by the geometric and algebraic methods has been completely eliminated, and these two scale factor determinations are now in full agreement, within the current limits of measurement.

Furthermore, the improved knowledge of the polhode phase has laid the foundation for greatly improved determinations of the patch-effect torques. One of the intriguing puzzles at an earlier stage of the analysis was that the clocking of the gyroscope housings with respect to the rolling spacecraft frame appeared to vary with time, and from gyro to gyro, in a manifestly unphysical way. In other words, the rolling spacecraft is like a flywheel, and the gyro readout planes are very stably locked to it, so there cannot be any physical variation…yet, such variation appeared to be present in the data. Fortunately, the improved polhode phase determinations have effectively eliminated this apparent variation. Moreover, this modeling and estimation of the misalignment torque coefficient, which constitutes the main disturbance of gyro motion, has now been improved by a factor of five.

We are now proceeding with a detailed incorporation of the new results and a corresponding derivation of improved relativity results for review with our Science Advisory Committee (SAC) and with NASA in preparation for our 17th SAC meeting, which is scheduled here at Stanford on the 2nd of November.

Progress continues - but slowly!! :rolleyes:

Garth

yuiop

Oct7-07, 11:21 PM

Hi,
I have a perhaps niaeve question about time dilation with respect to the GP-B experiment.
As I understand it, a clock on the probe would gain time due to reduced gravitational potential at high altitude and lose time due to the motion of the North/South orbit with respect to a clock in a ground station at one of the poles. I am curious if there any time dilation effect due the frame dragging of the earth's gravitational field as the probe passes over the equator. On first inspection of Hafele/ Keating type experiments a clock does not appear to affected by the relative motion of a gravitational field. In the H/K experiments a clock on the ground that is stationary with respect to the gravitational field is slower than a Westbound clock and faster than a Eastbound clock. In other words the clocks only seem to gain or lose time due to rotational motion relative to a distant "fixed" star and are indifferent to the Earth's gravitational rotation. So does frame dragging affect time dilation or does it only affect gyroscopic precession?

Garth

Oct10-07, 02:30 AM

Hi kev!

Time dilation does not affect the E-W frame-dragging precession. It does not even depend on the orbital velocity, only on the properties of space-time (the theory) and the angular momentum of the Earth.

Garth

yuiop

Oct10-07, 11:13 PM

Hi Garth. The angular momentum effect you mention is new to me. Are you refering to angular momentum of the Earth about its own axis, or of the Earth about the Sun, or both?

What difference would you expect to see in elapsed time per orbit (as measured by a clock aboard the sattelite) with:

A) No sidereal rotation of the earth.
B) Earth rotating normally.

How would the elapsed times compare to a clock at the same altitude on an imaginary huge tower at the North pole? (The tower clock is mounted on a counter-rotating platform that cancels out the East-West rotation of the Earth.)

Garth

Oct11-07, 07:27 AM

In GR it is the Earth's angular momentum that quantifies the dragging of space-time around the spinning Earth, which causes the E-W effect called the frame-dragging (http://en.wikipedia.org/wiki/Frame-dragging) precession or Lense-Thirring effect.

Differences between different theories in the elapsed time on-board the satellite do not affect their frame-dragging precession predictions, as I said, but they do affect the predicted geodetic precession; this is one effect being tested by that N-S precession.

As such your second and third questions do not have anything to do with this thread and should be asked on the S&GR forum, however a brief comment would be that a spinning Earth affects the diagonal component g0j of the metric and should slightly reduce the on-board proper time elapsed over one orbit.

g_{0j} = -2\epsilon _{jkl} S^kx^l/r^3

In the case of the Earth's spin I would guess that this effect would be too small to be detectable.

Garth

Garth

Oct25-07, 03:26 AM

We now have an amendment to F. Henry-Couannier's Dark Gravity Theory (http://www.arxiv.org/abs/gr-qc/0610079) (DG).
THE DARK GRAVITY MODEL PREDICTIONS FOR GRAVITY PROBE B (http://www.arxiv.org/abs/astro-ph/0509090).

We found that the dark gravity model predictions crucially depend on the number of privileged coordinate systems leading to two different kinds of scenario. In any case however the geodetic effect is the same as the one in General Relativity. In case we have one single preferred frame (the CMB restframe), no frame dragging is expected. Instead a preferred frame effect arises as a periodic angular precession with a one year period, with amplitude:
\delta\theta_{PF} \leq 0.04′′
well reachable with the experimental accuracy (5.10−4′′/year) of the Gravity Probe B experiment. In case the privileged frame is a local one, centered on the solar system, the privileged frame effect will be an order of magnitude below but still reachable with GPB. On the other hand, we find that in case there is a multiplicity of comoving privileged coordinate systems, one for each space-time elementary volume, we have the same Post Newtonian predictions as in GR for the gravitomagnetic effect.

Frederic is obviously hedging his bets!!

I am also removing the Absolute Relativity theory as there has been no published calculation of the previously included prediction.

So the running now stands:

Note: mas = milliarcsec.

The geodetic N-S precession is predicted by GR to be - 6606 mas/yr, however there is a solar geodetic precession N-S component of + 7 mas/yr and the proper motion of IM Pegasi +28 mas/yr to take into account, resulting in a net expected N-S precession of -6571 \pm1 mas/yr.

The frame-dragging E-W precession is predicted by GR to be -39 mas/yr, the solar geodetic precession E-W component of -16 mas/yr and the proper motion of IM Pegasi -20 mas/yr to include, resulting in a net expected E-W precession of -75 \pm1 mas/yr.

From pages 20 and 21 of Francis Everitt's April APS talk, we find: A series of error ellipses on the N-S v E-W precession plot with centres respectively at (-6584 \pm60, -83 \pm22 mas/yr) June 2006, (-6597 \pm17, -92 \pm15 mas/yr) December 2006, (-6595 \pm12, -98 \pm7 mas/yr) March 2007 and (-6603 \pm8, -98 \pm7 mas/yr) March 2007.

It was this last reading for the geodetic precession that Francis Everitt reported at his April APS talk. If we also include that 'glimpse' of the E-W precession as well we have net values of:
(-6603 \pm8, -98 \pm7 mas/yr)
whereas GR predicts:
(-6571 \pm1, -75 \pm1 mas/yr).

In other words the actual readings are larger than GR predicts by 32 mas/yr in geodetic precession and 23 mas/yr in frame-dragging precession.

However, they reported an overall error, which is still being reduced, caused by residual gyro-to-gyro inconsistencies due to incomplete modelling of ~ \pm100 mas/yr.

This renders the present geodetic 'glimpse' as being consistent with GR to within about 1\frac{1}{2}%, whereas the frame-dragging precession is at present swamped by noise.

The running now stands:

Einstein's General Relativity(GR)
Brans-Dicke theory (BD)
Moffat's Nonsymmetric Gravitational Theory (http://arxiv.org/abs/gr-qc/0405091) (NGT)
Stanley Robertson's Newtonian Gravity Theory (http://arxiv.org/abs/gr-qc/0502088) (NG),
F. Henry-Couannier's Dark Gravity Theory (http://www.arxiv.org/abs/gr-qc/0610079) (DG).
Alexander and Yunes' prediction for the Chern-Simons (http://kr.arxiv.org/abs/hep-th/0703265v1) gravity theory (CS).
Kris Krogh's Wave Gravity Theory (http://lanl.arxiv.org/abs/astro-ph/9910325) (WG)
Hongya Liu & J. M. Overduin prediction of the Kaluza-Klein ( http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v538n1/50681/50681.text.html?erFrom=5252751197746712308Guest#sc 8) gravity theory (KK).

The predictions are now:

GPB Geodetic gross precession (North-South)

GR = -6606 mas/yr.
BD = -(3\omega + 4)/(3\omega + 6) 6.606 arcsec/yr. where now \omega >60.
NGT = -6606 - a small \sigma correction mas/yr.
NG = -6606 mas/yr.
DG = -6606 mas/yr.
CS = -6606 mas/yr.
WG = -6606 mas/yr.
KK = -(1 + b/6 - 3b2 + ...) 6606 mas/yr. where 0 < b < 0.07.

We await the GPB gravitomagnetic frame dragging gross precession (East-West) result.

GR = -39 mas/yr.
BD = -(2\omega + 3)/(2\omega + 4) 39 mas/yr.
NGT = -39 mas/yr.
NG = -39 mas/yr.
DG = -40 mas/yr., or -4 mas/yr., or -39 mas/yr.
CS = -39 mas/yr. + CS correction
WG = 0 mas/yr.
KK = -39 mas/yr.

We continue to wait for Christmas!

Garth

LeBourdais

Oct25-07, 06:18 AM

Hello Garth,

I just want to say that you deserve my deepest respect. You have accepted the experimental verdict and I know that it is not easy. I wish that someday you make a big discovery, you really deserve it.

Paul

Garth

Oct25-07, 06:32 AM

Garth

Oct26-07, 03:39 AM

As there is now a calculation on the physics ArXiv of the GP-B predictions of Absolute Relativity I will re-instate it. My previous comment about Thomas Precession in that theory still holds, but the eprint published predictions stand to be falsified, or otherwise, by the final results expected at the end of this year. The geodetic N-S prediction is 30 mas more negative than GR and the frame-dragging E-W prediction is 20 mas more negative than GR.

Note: mas = milliarcsec.

So we now have;
The geodetic N-S precession is predicted by GR to be - 6606 mas/yr, however there is a solar geodetic precession N-S component of + 7 mas/yr and the proper motion of IM Pegasi +28 mas/yr to take into account, resulting in a net expected N-S precession of -6571 \pm1 mas/yr.

The frame-dragging E-W precession is predicted by GR to be -39 mas/yr, the solar geodetic precession E-W component of -16 mas/yr and the proper motion of IM Pegasi -20 mas/yr to include, resulting in a net expected E-W precession of -75 \pm1 mas/yr.

From pages 20 and 21 of Francis Everitt's April APS talk, we find: A series of error ellipses on the N-S v E-W precession plot with centres respectively at (-6584 \pm60, -83 \pm22 mas/yr) June 2006, (-6597 \pm17, -92 \pm15 mas/yr) December 2006, (-6595 \pm12, -98 \pm7 mas/yr) March 2007 and (-6603 \pm8, -98 \pm7 mas/yr) March 2007.

It was this last reading for the geodetic precession that Francis Everitt reported at his April APS talk. If we also include that 'glimpse' of the E-W precession as well we have net values of:
(-6603 \pm8, -98 \pm7 mas/yr)
whereas GR predicts:
(-6571 \pm1, -75 \pm1 mas/yr).

In other words the actual readings are larger than GR predicts by 32 mas/yr in geodetic precession and 23 mas/yr in frame-dragging precession.

However, they reported an overall error, which is still being reduced, caused by residual gyro-to-gyro inconsistencies (due to incomplete modelling) of ~ \pm100 mas/yr.

This renders the present geodetic 'glimpse' as being consistent with GR to within about 1\frac{1}{2}%, whereas the frame-dragging precession is at present swamped by noise.

The running now stands:

Einstein's General Relativity(GR)
Brans-Dicke theory (BD)
Moffat's Nonsymmetric Gravitational Theory (http://arxiv.org/abs/gr-qc/0405091) (NGT)
Stanley Robertson's Newtonian Gravity Theory (http://arxiv.org/abs/gr-qc/0502088) (NG),
F. Henry-Couannier's Dark Gravity Theory (http://www.arxiv.org/abs/gr-qc/0610079) (DG).
Alexander and Yunes' prediction for the Chern-Simons (http://kr.arxiv.org/abs/hep-th/0703265v1) gravity theory (CS).
Kris Krogh's Wave Gravity Theory (http://lanl.arxiv.org/abs/astro-ph/9910325) (WG)
Hongya Liu & J. M. Overduin prediction of the Kaluza-Klein ( http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v538n1/50681/50681.text.html?erFrom=5252751197746712308Guest#sc 8) gravity theory (KK).
Jin He's Absolute Relativity (http://arxiv.org/PS_cache/astro-ph/pdf/0604/0604084v5.pdf) theory (AR).

The predictions are now:

GPB Geodetic gross precession (North-South)

GR = -6606 mas/yr.
BD = -(3\omega + 4)/(3\omega + 6) 6.606 arcsec/yr. where now \omega >60.
NGT = -6606 - a small \sigma correction mas/yr.
NG = -6606 mas/yr.
DG = -6606 mas/yr.
CS = -6606 mas/yr.
WG = -6606 mas/yr.
KK = -(1 + b/6 - 3b2 + ...) 6606 mas/yr. where 0 < b < 0.07.
AR = -6636 mas/yr.

We await the GPB gravitomagnetic frame dragging gross precession (East-West) result.

GR = -39 mas/yr.
BD = -(2\omega + 3)/(2\omega + 4) 39 mas/yr.
NGT = -39 mas/yr.
NG = -39 mas/yr.
DG = 0 mas/yr.
CS = -39 mas/yr. + CS correction
WG = 0 mas/yr.
KK = -39 mas/yr.
AR = -59 mas/yr.

Garth

henryco

Oct30-07, 01:50 PM

We now have an amendment to F. Henry-Couannier's Dark Gravity Theory (http://www.arxiv.org/abs/gr-qc/0610079) (DG).
THE DARK GRAVITY MODEL PREDICTIONS FOR GRAVITY PROBE B (http://www.arxiv.org/abs/astro-ph/0509090).

Frederic is obviously hedging his bets!!
The running now stands:

Einstein's General Relativity(GR)
Brans-Dicke theory (BD)
Moffat's Nonsymmetric Gravitational Theory (http://arxiv.org/abs/gr-qc/0405091) (NGT)
Stanley Robertson's Newtonian Gravity Theory (http://arxiv.org/abs/gr-qc/0502088) (NG),
F. Henry-Couannier's Dark Gravity Theory (http://www.arxiv.org/abs/gr-qc/0610079) (DG).
Alexander and Yunes' prediction for the Chern-Simons (http://kr.arxiv.org/abs/hep-th/0703265v1) gravity theory (CS).
Kris Krogh's Wave Gravity Theory (http://lanl.arxiv.org/abs/astro-ph/9910325) (WG)
Hongya Liu & J. M. Overduin prediction of the Kaluza-Klein ( http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v538n1/50681/50681.text.html?erFrom=5252751197746712308Guest#sc 8) gravity theory (KK).

The predictions are now:

GPB Geodetic gross precession (North-South)

GR = -6606 mas/yr.
BD = -(3\omega + 4)/(3\omega + 6) 6.606 arcsec/yr. where now \omega >60.
NGT = -6606 - a small \sigma correction mas/yr.
NG = -6606 mas/yr.
DG = -6606 mas/yr.
CS = -6606 mas/yr.
WG = -6606 mas/yr.
KK = -(1 + b/6 - 3b2 + ...) 6606 mas/yr. where 0 < b < 0.07.

We await the GPB gravitomagnetic frame dragging gross precession (East-West) result.

GR = -39 mas/yr.
BD = -(2\omega + 3)/(2\omega + 4) 39 mas/yr.
NGT = -39 mas/yr.
NG = -39 mas/yr.
DG = -40 mas/yr., or -4 mas/yr., or -39 mas/yr.
CS = -39 mas/yr. + CS correction
WG = 0 mas/yr.
KK = -39 mas/yr.

We continue to wait for Christmas!

Garth

Hi Garth

I dont understand why you have (temporarily as it appears since you again indicate my correct zero frame dragging prediction in the most recent post), modified my predictions here? Wasn't it clear that the amendment was only to avoid people take serious the old (2005) erroneous prediction that was still in astro-ph/0509090 ?
Regards

Fred

Garth

Oct30-07, 02:29 PM

Hi Garth

I dont understand why you have (temporarily as it appears since you again indicate my correct zero frame dragging prediction in the most recent post), modified my predictions here? Wasn't it clear that the amendment was only to avoid people take serious the old (2005) erroneous prediction that was still in astro-ph/0509090 ?
Regards

Fred

Sorry Fred, I've been cutting and pasting to try and collect everybody's predictions together, and I copied an out-of-date version of your prediction.

Garth

henryco

Oct31-07, 07:19 AM

The present predictions are:

Note: mas = milliarcsec.

The geodetic N-S precession is predicted by GR to be - 6606 mas/yr, however there is a solar geodetic precession N-S component of + 7 mas/yr and the proper motion of IM Pegasi +28 mas/yr to take into account, resulting in a net expected N-S precession of -6571 \pm1 mas/yr.

The frame-dragging E-W precession is predicted by GR to be -39 mas/yr, the solar geodetic precession E-W component of -16 mas/yr and the proper motion of IM Pegasi -20 mas/yr to include, resulting in a net expected E-W precession of -75 \pm1 mas/yr.

From pages 20 and 21 of Francis Everitt's April APS talk, we find: A series of error ellipses on the N-S v E-W precession plot with centres respectively at (-6584 \pm60, -83 \pm22 mas/yr) June 2006, (-6597 \pm17, -92 \pm15 mas/yr) December 2006, (-6595 \pm12, -98 \pm7 mas/yr) March 2007 and (-6603 \pm8, -98 \pm7 mas/yr) March 2007.

It was this last reading for the geodetic precession that Francis Everitt reported at his April APS talk. If we also include that 'glimpse' of the E-W precession as well we have net values of:
(-6603 \pm8, -98 \pm7 mas/yr)
whereas GR predicts:
(-6571 \pm1, -75 \pm1 mas/yr).

In other words the actual readings are larger than GR predicts by 32 mas/yr in geodetic precession and 23 mas/yr in frame-dragging precession.

However, they reported an overall error, which is still being reduced, caused by residual gyro-to-gyro inconsistencies due to incomplete modelling of ~ \pm100 mas/yr.

This renders the present geodetic 'glimpse' as being consistent with GR to within about 1\frac{1}{2}%, whereas the frame-dragging precession is at present swamped by noise.

The running now stands:

Einstein's General Relativity(GR)
Brans-Dicke theory (BD)
Moffat's Nonsymmetric Gravitational Theory (http://arxiv.org/abs/gr-qc/0405091) (NGT)
Stanley Robertson's Newtonian Gravity Theory (http://arxiv.org/abs/gr-qc/0502088) (NG),
F. Henry-Couannier's Dark Gravity Theory (http://www.arxiv.org/abs/gr-qc/0610079) (DG).
Alexander and Yunes' prediction for the Chern-Simons (http://kr.arxiv.org/abs/hep-th/0703265v1) gravity theory (CS).
Kris Krogh's Wave Gravity Theory (http://lanl.arxiv.org/abs/astro-ph/9910325) (WG)
Hongya Liu & J. M. Overduin prediction of the Kaluza-Klein ( http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v538n1/50681/50681.text.html?erFrom=5252751197746712308Guest#sc 8) gravity theory (KK).
Jin He's Absolute Relativity (http://arxiv.org/PS_cache/astro-ph/pdf/0604/0604084v5.pdf) theory (AR).

The predictions are now:

GPB Geodetic gross precession (North-South)

GR = -6606 mas/yr.
BD = -(3\omega + 4)/(3\omega + 6) 6.606 arcsec/yr. where now \omega >60.
NGT = -6606 - a small \sigma correction mas/yr.
NG = -6606 mas/yr.
DG = -6606 mas/yr.
CS = -6606 mas/yr.
WG = -6606 mas/yr.
KK = -(1 + b/6 - 3b2 + ...) 6606 mas/yr. where 0 < b < 0.07.
AR = -6636 mas/yr.

We await the GPB gravitomagnetic frame dragging gross precession (East-West) result.

GR = -39 mas/yr.
BD = -(2\omega + 3)/(2\omega + 4) 39 mas/yr.
NGT = -39 mas/yr.
NG = -39 mas/yr.
DG = -40 mas/yr., or -4 mas/yr., or -39 mas/yr.
CS = -39 mas/yr. + CS correction
WG = 0 mas/yr.
KK = -39 mas/yr.
AR = -59 mas/yr.

We continue to wait for Christmas!

Garth

Hi GArth,

You again put this wrong prediction.
It's a long time since i have corrected this which was just a calculus mistake (but by the way i could notice that many experts do the same kind of mistakes and this made me realise my own mistake !).

My predition is still:
zero frame dragging and the same geodetic effect as in GR! no effect due to the motion of the earth around the sun or relative to the CMB

Also an extension of the theory could give other kinds of effects (not frame dragging) and even give the same prediction as GR but this is no more the minimal DG theory!

Best regards

F H-C

Garth

Oct31-07, 07:40 AM

Sorry Fred, one last time to try and get it right!

The present predictions are:

Note: mas = milliarcsec.

The geodetic N-S precession is predicted by GR to be - 6606 mas/yr, however there is a solar geodetic precession N-S component of + 7 mas/yr and the proper motion of IM Pegasi +28 mas/yr to take into account, resulting in a net expected N-S precession of -6571 LaTeX graphic is being generated. Reload this page in a moment.1 mas/yr.

The frame-dragging E-W precession is predicted by GR to be -39 mas/yr, the solar geodetic precession E-W component of -16 mas/yr and the proper motion of IM Pegasi -20 mas/yr to include, resulting in a net expected E-W precession of -75 LaTeX graphic is being generated. Reload this page in a moment.1 mas/yr.

From pages 20 and 21 of Francis Everitt's April APS talk, we find: A series of error ellipses on the N-S v E-W precession plot with centres respectively at (-6584 LaTeX graphic is being generated. Reload this page in a moment.60, -83 LaTeX graphic is being generated. Reload this page in a moment.22 mas/yr) June 2006, (-6597 LaTeX graphic is being generated. Reload this page in a moment.17, -92 LaTeX graphic is being generated. Reload this page in a moment.15 mas/yr) December 2006, (-6595 LaTeX graphic is being generated. Reload this page in a moment.12, -98 LaTeX graphic is being generated. Reload this page in a moment.7 mas/yr) March 2007 and (-6603 LaTeX graphic is being generated. Reload this page in a moment.8, -98 LaTeX graphic is being generated. Reload this page in a moment.7 mas/yr) March 2007.

It was this last reading for the geodetic precession that Francis Everitt reported at his April APS talk. If we also include that 'glimpse' of the E-W precession as well we have net values of:
(-6603 LaTeX graphic is being generated. Reload this page in a moment.8, -98 LaTeX graphic is being generated. Reload this page in a moment.7 mas/yr)
whereas GR predicts:
(-6571 LaTeX graphic is being generated. Reload this page in a moment.1, -75 LaTeX graphic is being generated. Reload this page in a moment.1 mas/yr).

In other words the actual readings are larger than GR predicts by 32 mas/yr in geodetic precession and 23 mas/yr in frame-dragging precession.

However, they reported an overall error, which is still being reduced, caused by residual gyro-to-gyro inconsistencies due to incomplete modelling of ~ LaTeX graphic is being generated. Reload this page in a moment.100 mas/yr.

This renders the present geodetic 'glimpse' as being consistent with GR to within about 1LaTeX graphic is being generated. Reload this page in a moment.%, whereas the frame-dragging precession is at present swamped by noise.

The running now stands:

1. Einstein's General Relativity(GR)
2. Brans-Dicke theory (BD)
3. Moffat's Nonsymmetric Gravitational Theory (NGT)
4. Stanley Robertson's Newtonian Gravity Theory (NG),
5. F. Henry-Couannier's Dark Gravity Theory (DG).
6. Alexander and Yunes' prediction for the Chern-Simons gravity theory (CS).
7. Kris Krogh's Wave Gravity Theory (WG)
8. Hongya Liu & J. M. Overduin prediction of the Kaluza-Klein gravity theory (KK).
9. Jin He's Absolute Relativity theory (AR).

The predictions are now:

GPB Geodetic gross precession (North-South)

1. GR = -6606 mas/yr.
2. BD = -LaTeX graphic is being generated. Reload this page in a moment. 6.606 arcsec/yr. where now LaTeX graphic is being generated. Reload this page in a moment. >60.
3. NGT = -6606 - a small LaTeX graphic is being generated. Reload this page in a moment. correction mas/yr.
4. NG = -6606 mas/yr.
5. DG = -6606 mas/yr.
6. CS = -6606 mas/yr.
7. WG = -6606 mas/yr.
8. KK = -(1 + b/6 - 3b2 + ...) 6606 mas/yr. where 0 < b < 0.07.
9. AR = -6636 mas/yr.

We await the GPB gravitomagnetic frame dragging gross precession (East-West) result.

1. GR = -39 mas/yr.
2. BD = -LaTeX graphic is being generated. Reload this page in a moment. 39 mas/yr.
3. NGT = -39 mas/yr.
4. NG = -39 mas/yr.
5. DG = 0 mas/yr.
6. CS = -39 mas/yr. + CS correction
7. WG = 0 mas/yr.
8. KK = -39 mas/yr.
9. AR = -59 mas/yr.

We continue to wait for Christmas!

Garth

henryco

Nov1-07, 09:17 AM

yogi

Nov18-07, 02:58 AM

Garth

Nov18-07, 05:22 PM

Garth - this question was posed by Jonathan in post 210:

"The wider question this has bearing on is what possible interpretations for the geodetic effect do we have, now that it has been measured directly. Is curvature the only one?

Maybe I missed your answer -

Along the same line - assuming the measurements are a confirmation of curvature - don't we still have an unanswered question of whether the curvature is the result of static mass acting upon static space ?
If space-time does suffer curvature as in GR then free falling gyros will exhibit geodesic precession.

You make a cone by cutting a thin slice out of a disk and glueing the cut edges together.

Geodesic precession is caused by the missing slice, there not being quite 3600 in the circle.

If there is no space-time curvature then the gyros in orbit will have to be suffering some type of Newtonian gravitational force perturbing them from their otherwise straight line trajectories.

They will be accelerating from their inertial frames of reference towards the centre of the Earth.

In a space-time continuum an accelerating parallel transported vector will 'lean over' in 4D as its velocity increases.

An accelerating gyro will precess due to this effect, the effect is called Thomas Precession (http://en.wikipedia.org/wiki/Thomas_precession).

However if there is no space-time curvature and all the orbital dynamics is caused by a Newtonian attractive gravitational force then the amount of Thomas precession is precisely half the GR prediction of geodetic precession. Already the first results of GP-B have confirmed the GR geodetic prediction to within 1\frac{1}{2}%.

Other theories have postulated different causes of N-S precession for the GP-B, you will have to read the individual papers as so far I have been unconvinced.

Garth

JonathanK

Nov21-07, 07:15 AM

Hello Garth and all,

Yogi has mentioned what I said about interpretations for the geodetic effect. I've found a way to generalise the calculation I did about this, and put it into an equation. It's easy to check, and shows clearly that curvature is not the only interpretation for the measured effect.

If matter near a mass is slowed (in flat space) by (1 - [2GM/rc^2])^1/2, then different parts of an orbiting spherical object (such as a GP-B gyro) travel at different speeds, resulting in a slight turning of the object in the plane of the orbit, which mimics the geodetic effect. In PSG minor corrections are made to an orbital speed that's the same across the whole object.

The angle of precession θ in degrees for one (circular) orbit arising from this local slowing of matter can be arrived at with

θ = 2 arctan

2[pi]r ( ([1 – (2GM/rc^2)]^1/2) – ([1 – (2GM/r'c^2])^1/2) )
----------------------------------------------------------
r' – r

(or if preferred, tan (θ / 2) = …etc), where r is the distance from the centre of the Earth to the centre of the object, and r' is the distance to a point on its upper edge, equal to r plus the radius of the object.

This gives the curvature component of the geodetic effect (in the case of GP-B 4.4 arcsecs/yr). It gets there in a very different way from GR, and uses only basic gravity parameters.

Sorry about how the above equation is set out, couldn't do sqrt boxes etc. Garth, I'd appreciate it if you'd set it out better, thank you.

The component of the geodetic effect generally thought to be due to curvature is 2/3 of the total effect. The other 1/3 has been explained in ways that apply whether space is curved or flat (for example Shapiro et al, '88).

So this provides an alternative flat space interpretation, which means the measurement of what is known as the geodetic effect doesn't prove the curved space interpretation, it simply proves that the effect exists.

I also now have a better way of explaining why like in GR, PSG has no acceleration in freefall, in reply to your point about the Thomas precession. As in GR, the very nature of space and matter provides an explanation so fundamental that no later 'adjustments' to the description are needed. It can't be gone into here, but the freefall equation (published as equation 4 in the first paper) gives the right speeds to 12 decimal places, all along the trajectory. This came directly from this conceptual basis, so the point I'm making works in more ways than one.

Thanks, good wishes, Jonathan Kerr

Garth

Nov22-07, 10:39 AM

Jonathan I think you had better learn LaTex, at least the tex and itex version used in these Forums!

Your calculation uses the same equations as GR but interprets them differently therefore it comes up with the same prediction, but it will be impossible to test the one theory against the other using this experiment. If all the equations are the same in every prediction then I would say you are simply restating the standard GR theory in unfamiliar and perhaps unhelpful and confusing terminology.

I should have made clear in my 'missing slice' explanation of geodetic precession in post #254 that that argument only explains the spatial part of space-time curvature, which in the GR calculation accounts for \frac{2}{3} of the total.

The other component is the time part of space-time curvature, time dilation, which accounts for the remaining \frac{1}{3} of the total.

There is no need for this to be "explained in ways that apply whether space is curved or flat", it is already accounted for in the curvature of space-time.

Note in GR gravitation is described by the curvature of the space-time manifold, not just by the curvature of space.

Garth

JonathanK

Nov22-07, 12:58 PM

Sorry that I don't know the Latex system you use.

Your calculation uses the same equations as GR but interprets them differently therefore it comes up with the same prediction, but it will be impossible to test the one theory against the other using this experiment.
Garth

You seem to agree with my main point, which is that there is more than one possible interpretation. As I'm sure you realise, I arrived at that equation purely from the concept of matter in flat space being slowed by a certain factor. I could easily show the simple steps that led there, but they're not what matters. They show a general principle, and one that can be verified in other parallel ways. 2/3 of the geodetic effect can definitely be interpreted in this surprisingly simple way, without curvature.

So all that remains is the question of the other 1/3. There are different interpretations within GR for that (I sent you two papers about it early this year, the Shapiro et al one from '88, and a NASA funded study that puts forward more than one interpretation - to both of our surprise, including SR as one of them!)

The Shapiro et al paper described 1/3 of the geodetic effect as being due to "a gravitational analogue of spin orbit coupling". That's what I meant by an explanation that applies whether space is curved or flat.

You can look at exactly how GR interprets the effect, and I acknowledge that as you say this involves the curvature of spacetime, not just of space. But for this flat space interpretation, 2/3 is as I've interpreted it above, and the other 1/3 can be various things, such as (for example) a flat space effect like that described by Shapiro et al.

It's worth pointing out that PSG seems to mimic GR over the motion of both light and matter well in other areas. If it didn't there'd be less point in looking at the geodetic. If anyone would like to help with a more accurate calculation, let me know. (Might even explain the 32 mas/yr, though the error margins may make that impossible.) And any comments would be welcome.

Thanks again for your help Garth. It'd be great if you'd acknowledge that this alternative interpretation works, in this small corner of GR at least. Outside that there's a long way to go of course. J

Garth

Nov22-07, 05:10 PM

Sorry that I don't know the Latex system you use.Try How To LaTex (http://www.physicsforums.com/misc/howtolatex.pdf).You seem to agree with my main point, which is that there is more than one possible interpretation. As I'm sure you realise, I arrived at that equation purely from the concept of matter in flat space being slowed by a certain factor. I could easily show the simple steps that led there, but they're not what matters. They show a general principle, and one that can be verified in other parallel ways. 2/3 of the geodetic effect can definitely be interpreted in this surprisingly simple way, without curvature.Yes, but my point is your expression for motion being "slowed down by a certain factor" is exactly the same as in GR. The question is therefore: "can you physically justify using that equation, or are you just copying it?" As you are using it you were bound to get the same result as GR for the spatial component.So all that remains is the question of the other 1/3. There are different interpretations within GR for that (I sent you two papers about it early this year, the Shapiro et al one from '88, and a NASA funded study that puts forward more than one interpretation - to both of our surprise, including SR as one of them!)I disagree, there is only one interpretation within GR, it is the time component of the effect of space-time curvature.The Shapiro et al paper described 1/3 of the geodetic effect as being due to "a gravitational analogue of spin orbit coupling". That's what I meant by an explanation that applies whether space is curved or flat. They are either misinterpreting the time component of curvature OR they are giving an alternative flat space-time explanation. In the latter case I want to know what happens to the Thomas Precession, which must be taken into account if space-time is flat and the orbiting gyros are not in an inertial frame of reference. Each separate effect must be taken into consideration and correctly accounted for to get a valid prediction.
Thanks again for your help Garth. It'd be great if you'd acknowledge that this alternative interpretation works, in this small corner of GR at least. Outside that there's a long way to go of course. JYou're welcome.

If you want your Planck Scale Gravity (PSG) theory to be included on this thread you will have to give a refereed or Physics ArXiv link to a paper on it that makes a distinct prediction that can be falsified by the GP-B experiment.

If you have a link to a PSG paper published in a refereed journal you can discuss it on these Forums otherwise you can submit it to the Independent Research (http://www.physicsforums.com/forumdisplay.php?f=146) Forum having first observed their submission rules.

Garth

JonathanK

Nov23-07, 04:48 AM

Well, it doesn't matter, and no need to put PSG back on the list, unless you want to. In fact the paper you kindly endorsed, which was published in a refereed journal (linked to in post #126), has a frame dragging prediction, the same as GR. So it does fill the criteria, but I'll let you get on with other things, and thanks again.

The original geodetic prediction was null, but the above equation (post #255), which you've acknowleged as giving the right result, vindicates the theory. It shows that the prediction, not the theory, was wrong, as the measured geodetic effect is in fact mimicked by the original theory, without any changes. I only found this out later, but luckily was able to show it to be true. Vindicating the theory has been my main aim here.

The equation I found is not a GR equation (as far as I know), but as you say, the factor sqrt (1 - [2GM/rc^2]) is of course an expression from GR. PSG is the gravity part of a theory of time, and in it not only is time 'slowed' by this factor, the motion of light and matter are as well. Yes, I can physically justify this - the conceptual basis does just that. According to it GR is largely right, but incomplete in its interpretation - and something in effect very similar to curved space happens in flat space. (And in it GR is of course right about that expression giving the local time rate. I believe I'm allowed to use it in that context…!)

Interestingly, the spatial calculation gave 2.2 arcsec/yr. I then allowed for time rate differences to the two points on the gyro in question, which doubled the difference to their speeds, so they ended up twice as far apart. The trigonometry then gave 4.4 arcsecs/yr, and there's a factor of 2 in the equation, reflecting this doubling. So I assumed I was uncovering an alternative interpretation from a GR one in which space is 1/3 and time is 1/3. But I’m sure you know the GR interpretation.

I disagree, there is only one interpretation within GR, it is the time component of the effect of space-time curvature. They are either misinterpreting the time component of curvature OR they are giving an alternative flat space-time explanation. In the latter case I want to know what happens to the Thomas Precession, which must be taken into account if space-time is flat and the orbiting gyros are not in an inertial frame of reference.
Garth

You’re right, I misused the word "within", when I said "for the other 1/3 there are different interpretations within GR". I'm sure that "surrounding GR" is more accurate. But Shapiro is a well-known GR supporter as far as I know. You'd have to ask him about the Thomas precession - I have no idea what he'd say. My aim has really been to interpret only the first 2/3, and say that the other 1/3 has enough controversy surrounding it for this flat space interpretation to be a possibility. It seems very reasonable to me - thank you for acknowledging that the mathematics for that 2/3 works. It seems not impossible that matter actually is slowed by that factor. Anyway, good wishes, and good luck all for December! Jonathan

hejin

Dec6-07, 02:46 PM

GPB final result, 6 more months, no kidding!

Garth

Dec6-07, 03:43 PM

Unfortunately you are not kidding! :cry:
From the GP-B update (http://einstein.stanford.edu/)

MISSION UPDATE - DECEMBER 2007

PROGRAM STATUS

Over the past three months, GP-B has continued to make outstanding progress.

In our September 25, 2007 status update, we reported that the trapped flux mapping technique had resulted in a dramatic improvement in the determinations of the polhode phase and angle for each gyroscope throughout the entire 353-day experiment period. Applying these results to a central 85-day stretch of data, from December 12, 2004 through March 4, 2005, we obtained a robust and stable measurement of the frame-dragging effect with a reasonable (~30%) error level. We are in process of progressively extending the analysis to increasingly long time intervals in order to reach the full experiment accuracy, potentially to an error margin of less than 5%. Also important is the completion of the study of -- and if necessary elimination of -- any remaining systematic effects that may bias the results of the experiment.

Our progress and results were intensively reviewed by the GP-B Science Advisory Committee (SAC) at its 17th meeting on November 2, 2007. In its subsequent report, the SAC commented on "the truly extraordinary progress that has been made in data analysis since SAC-16 [March 23-24, 2007]" and unanimously concluded "that GP-B is on an accelerating path toward reaching good science results."

It is anticipated that approximately another six months until May 2008 will be needed to complete this full coverage and arrive at a definitive final result. We believe the results will be truly significant and will withstand scrutiny at the deepest scientific level. We agree with the SAC that: "This phase must include an adequate opportunity for the SAC to review the final result in some detail before publications are prepared and public announcements are made."
To this end, we are planning on this review for the May 2008 time frame.

hejin

Dec6-07, 04:40 PM

On the right collumn of the December update there is a graph showing

Einstein expectation: -6571 +- 1*
4-gyro result (1 sigma) for 85 days
(12 Dec 04 -- 4 Mar 05) -6632 +- 43

Garth

Dec6-07, 05:17 PM

On the right collumn of the December update there is a graph showing

Einstein expectation: -6571 +- 1*
4-gyro result (1 sigma) for 85 days
(12 Dec 04 -- 4 Mar 05) -6632 +- 43
That diagram (http://einstein.stanford.edu/cgi-bin/highlights/showpic.cgi?name=GR-85-day_result.jpg) is showing that to a 1 sigma error confidence level the results for the geodetic precession are inconsistent with GR.

This is at about a 68% confidence level, we wait for the 3\sigma 4-gyro results next year, but so far it does look interesting!

It will be especially interesting to see what happens to the frame-dragging result, which is at present swamped by noise.

Garth

fasterthanjoao

Dec6-07, 05:18 PM

Despite having kept up-to-date with this thread since the beginning, I have no productive input except that the recommendation that this thread and the work of the contributors should be entered into a PF cosmological hall of fame. Very good.

Garth

Dec8-07, 04:18 PM

That diagram (http://einstein.stanford.edu/cgi-bin/highlights/showpic.cgi?name=GR-85-day_result.jpg) is showing that to a 1 sigma error confidence level the results for the geodetic precession are inconsistent with GR.

This is at about a 68% confidence level, we wait for the 3\sigma 4-gyro results next year, but so far it does look interesting!
As I posted in the We are in a Schwarzschild black hole--T or F? (http://www.physicsforums.com/showthread.php?p=1533666#post1533666) thread:

Now that is interesting, the GP-B website has withdrawn that diagram and replaced it with one that makes no such claims!

Garth

Garth

Dec25-07, 06:17 PM

If you want to see for yourselves you can still find the original intriguing diagram in a series of slides of a lecture given by Francis Everitt at Cornell University on the 12th November 2007. Gravity Probe B + a Hint of STEP (http://colloquia.physics.cornell.edu/11-12-2007/cornellpres_files/v3_document.htm).

The pertinent slides are slide 3: Seeing General Relativity Directly (http://colloquia.physics.cornell.edu/11-12-2007/cornellpres_files/v3_slide0341.htm) and the slide: RNS vs RWE Algebraic 4-Gyro Joint Estimates (http://colloquia.physics.cornell.edu/11-12-2007/cornellpres_files/v3_slide0426.htm)

That last one clearly shows the inconsistency with the GR prediction to the 1 \sigma confidence level.

Again we wait for the 3 \sigma confidence level results with interest!

Garth

Garth

Dec28-07, 09:02 AM

A critical analysis of the GP-B mission. I: on the impossibility of a reliable measurement of the gravitomagnetic precession of the GP-B gyroscopes (http://es.arxiv.org/abs/0712.3934) by a Gerhard Forst.
In this paper we discuss the impossibility for the Gravity Probe B (GP-B) experiment to provide a clean and undisputable test of the gravitomagnetic precession of its four gyroscopes and of the Lense-Thirring effect. Lense-Thirring effect and geodetic precession have already been measured by Lunar Laser Ranging (LLR), laser ranged satellites, binary pulsars and accretion disks of black holes and neutron stars. In this paper we show that in the GP-B experiment there are critical problems for measuring Lense-Thirring effect and geodetic precession by the GP-B data analysis. The GP-B data analysis is extremely model dependent and relies on the assumptions about the unknown quadrupole moment induced by the gyroscopes rotation, both: (I) its size and (II) its direction with respect to the quadrupole moment due to fabrication and (III) its unknown rate of change due to variations of the gyroscopes rotation rate. The huge systematic biases in the GP-B data amount to about 1000 milliarcsec/year, but the GP-B team has claimed to be able to model 90 % of this signal, thus leaving the systematic biases at the level of about 100 milliarcsec per year, that is $\sim 300 %$ of the Lense-Thirring effect effect of the GP-B gyroscopes; any further modelling will result in a rough test of Lense-Thirring effect that will be highly model dependent and extremely affected by other huge unknown systematic biases. In this paper we show that such claims are necessarily highly model dependent and then are very much affected by huge unknown systematic biases. We give an important example of these systematic biases of which there is no mention in the discussions of the GP-B team.

Has GP-B all been a waste of time and money?

Firstly, it must be said that the team have recognised that there were two unexpected sources of error that almost render the results too inaccurate to test the two precessions, especially the much smaller frame-dragging or gravitomagnetic precession effect.

However, the team are also confident that they can, and are, modelling these errors accurately by using two cross checking independent methods.

I specifically asked the question at the April Conference about whether these methods were genuinely independent in a 'double-blind' way or whether they used the expected GR results in their derivation.

Francis Everitt was quite adamant that that was what one mustn't do and their error reduction modelling was quite independent of the expected results.

Gerhard Forst is disputing this independence, which is a serious charge to make. However I note that his email is a private not an academic address (but then so is mine...), that he isn't an endorser on the ArXiv, which is suspicious, this is his only eprint and he has no papers published in referred journals, which does not say much about his academic credibility.

Given the immense amount of experience and expertise on the GP-B team, at this stage I would rather trust them, although of course when the results are finally published so also is all the data for others to check and dispute.

I can see an undisputed result being a long way off......

Garth

Kris Krogh

Dec30-07, 07:18 PM

Hi Garth,

I think your suspicions about Gerhard Forst are well justified. Here is a message I sent the moderator of ArXiv:

Dear arXiv-moderation,

This concerns the authorship of http://arxiv.org/abs/0712.3934 , "A critical analysis of the GP-B mission. I: on the impossibility of a reliable measurement of the gravitomagnetic precession of the GP-B gyroscopes." This paper may represent an anonymous attack.

The author's name is given as "Gerhard Forst," with the email address g.forst@yahoo.com . He has no prior ArXiv papers, and seems to have no peer-reviewed publications. His affiliation and address are given as:

G. Forst
FGP
Behrenstr. 1
10117 Berlin

Whatever FGP stands for, there is no mention on the web of such an organization at the given address. Was this paper endorsed? If so, can the endorser show "Gerhard Forst" is the author's real name?

There is an interesting similarity to papers by another author, who has a history of tit-for-tat disputes on ArXiv:

"On the impossibility of measuring a galvano-gravitomagnetic effect with current carrying semiconductors in a space-based experiment," http://arxiv.org/abs/gr-qc/0308053

"On the impossibility of using the longitude of the ascending node of GP-B for measuring the Lense-Thirring effect," http://arxiv.org/abs/gr-qc/0404107

"On the impossibility of using certain existing spacecraft for the measurement of the Lense-Thirring effect in the terrestrial gravitational field," http://arxiv.org/abs/gr-qc/0508012

"On the impossibility of measuring the general relativistic part of the terrestrial acceleration of gravity with superconducting gravimeters, http://arxiv.org/abs/gr-qc/0602005

"On some critical issues of the LAGEOS/LAGEOS II Lense-Thirring experiment," http://arxiv.org/abs/0710.1022

In addition to the titles, there are many other similarities. Comparing the most recent of these to the paper in question, there are these sequences:

"...no other tests performed by independent teams, without connections with Ciufolini and coworkers...have been so far reported in literature."

"...no independent team, without connections with the GP-B team, will be able to repeat the GP-B data analysis..."

In the former there are 4 sentences beginning with the word "Indeed." Such a sentence is also found in the latter. I could list further examples.

That author has himself claimed increasingly accurate measurements of the Lense-Thirring effect, which I've discussed here:

http://arxiv.org/abs/astro-ph/0701653

Both those claimed measurements and his reputation would be seriously threatened by a contrary result from Gravity Probe B. I hope the reasons are clear from my paper.

Best regards,

Kris Krogh

Garth

Dec31-07, 04:17 AM

Kris,

Thank you, that is very interesting!

Actually I have read Lorenzo Iorio's papers with interest, I shall be even more critical from now on!

Happy New Year
Garth

henryco

Jan2-08, 08:58 AM

That last one clearly shows the inconsistency with the GR prediction to the 1 \sigma confidence level.

Again we wait for the 3 \sigma confidence level results with interest!

Garth

Hi Garth

Your comments on these results make me consider more seriously another possible prediction in my framework which i had eliminated because it is already ruled out by the 1% precision test of the geodetic effect by LusarLaserRanging. However the DG theory make it possible for a rare event, the appearance or disappearance of a discontinuity of gravity in the neighbourhood of our earth, to occur. If this happened after the LLR tests and before the GP-B data taking, the physics of gravitomagnetism might have changed so that the geodetic test by LLR is no more relevant now!
If so, my prediction would still be:
- no frame dragging (no influence of the earth rotation!) on GP-B gyros
- the same geodetic effect as in GR where enters the speed of GP-B relative to the earth

but now i can consider a prefered frame effect which i did not take serious before.
The formula is the same as the geodetic effect one except that it involves the speed of the earth relative to a preferred frame which is not attached to the earth as i assumed up to now. Whever this preferred frame is attached to the CMB, the galaxy or more locally to our sun does not matter since in all cases the dominant effect comes from that part of the speed which is the speed of the earth relative to our sun.

Thus the additional effect for GP-B is a periodic angular precession with roughly 40 mArcsec amplitude and one year period which should give a contribution on projection to both N-S and E-W GP-B signals.
May be the 85 days represent a favorable period to see these contributions (may be the reason why GP-B has announced a E-W effect on this period and at the sametime there is as you say a strange one sigma inconsistency with GR on th NS effect ) but then
i expect it to disapear on a one year integration.

Best regards,

So may be could you add a second possible prediction for DG :
If preferred frame is not the earth (sun or galaxy or CMB)

Frame dragging 0
Geodetic as in RG
Preferred frame effect: 40marcsec-amplitude one_year-periodic angular precession

Regards

Fred

Garth

Jan2-08, 09:36 AM

Garth

Jan3-08, 06:39 AM

I have also recently found that Jin He's "Absolute Relativity" has been removed from the physics ArXiv, I shall therefore remove it from the list of viable theories being tested by GP-B.

To remind ourselves, that list now stands:

Einstein's General Relativity(GR)
Brans-Dicke theory (BD)
Moffat's Nonsymmetric Gravitational Theory (http://arxiv.org/abs/gr-qc/0405091) (NGT)
Stanley Robertson's Newtonian Gravity Theory (http://arxiv.org/abs/gr-qc/0502088) (NG),
F. Henry-Couannier's Dark Gravity Theory (http://www.arxiv.org/abs/gr-qc/0610079) (DG).
Alexander and Yunes' prediction for the Chern-Simons (http://kr.arxiv.org/abs/hep-th/0703265v1) gravity theory (CS).
Kris Krogh's Wave Gravity Theory (http://lanl.arxiv.org/abs/astro-ph/9910325) (WG)
Hongya Liu & J. M. Overduin prediction of the Kaluza-Klein ( http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v538n1/50681/50681.text.html?erFrom=5252751197746712308Guest#sc 8) gravity theory (KK).

The predictions are now:

GP-B Geodetic gross precession (North-South).

GR = -6606 mas/yr.
BD = -(3\omega + 4)/(3\omega + 6) 6.606 arcsec/yr. where now \omega >60.
NGT = -(6606 - a small \sigma correction) mas/yr.
NG = -6606 mas/yr.
DG = -6606 mas/yr.
CS = -6606 mas/yr.
WG = -6606 mas/yr.
KK = -(1 + b/6 - 3b2 + ...) 6606 mas/yr. where 0 < b < 0.07.

GPB gravitomagnetic frame dragging gross precession (East-West).

GR = -39 mas/yr.
BD = -(2\omega + 3)/(2\omega + 4) 39 mas/yr.
NGT = -39 mas/yr.
NG = -39 mas/yr.
DG = 0 mas/yr.
CS = -39 mas/yr. + CS correction
WG = 0 mas/yr.
KK = -39 mas/yr.

You can see for yourselves the present state of the results in a series of slides of a lecture given by Francis Everitt at Cornell University on the 12th November 2007. Gravity Probe B + a Hint of STEP (http://colloquia.physics.cornell.edu/11-12-2007/cornellpres_files/v3_document.htm).

The pertinent slides are slide 3: Seeing General Relativity Directly (http://colloquia.physics.cornell.edu/11-12-2007/cornellpres_files/v3_slide0341.htm)
and the slide: RNS vs RWE Algebraic 4-Gyro Joint Estimates (http://colloquia.physics.cornell.edu/11-12-2007/cornellpres_files/v3_slide0426.htm)

These last two slides clearly show an inconsistency with the GR prediction at the 1 \sigma confidence level.

Einstein expectation:
-6571 \pm 1* mas
4-gyro result (1 \sigma) for 85 days (12 Dec 04 -- 4 Mar 05)
-6632 \pm 43 mas

(* -6606 mas + 7 mas (solar geodetic) + 28 \pm1 mas (guide star proper motion))

We note that this November 1 \sigma confidence level result is inconsistent with all the above geodetic predictions except KK!

We continue to wait for the 3 \sigma confidence level results in the "final" review now scheduled for May 2008!

Happy New 2008 Year :smile:
Garth

hejin

Jan3-08, 11:12 AM

JonathanK

Jan3-08, 08:03 PM

I have a correction to the equation in post #255, it's 'arctan' rather than '2 arctan', and the positions of the second r and the r' are reversed above the line. I'd only just found it at the time - there's also a slightly more accurate version of the equation, but both give the same numbers for GP-B, which are almost identical to those from GR.

And having thought about it, I would appreciate it if you'd put PSG back on the list Garth - which it seems you'll be posting again anyway. I'm sure you agree the theory hasn't been falsified, and there's a prediction for frame dragging in a peer reviewed journal, of - 39 mas/yr. Like NG, PSG gives the same as GR for both effects - as you pointed out (so acknowledging the basic mathematics), the experiment can't distinguish between the two interpretations for the geodetic. But unlike GR, PSG hasn't been fully worked through yet, and other smaller effects may later be taken into account. At present, PSG has recovered better than other theories, where changes and extra adjustments have been made - the geodetic equation arises simply from applying the main postulate of the original theory, exactly as it was.

Thank you, Jonathan

henryco

Jan4-08, 05:29 PM

Fred, we could all add in extra adjustments in an ad hoc way to make our predictions fit any set of results. On this thread I have limited the discussion to predictions made in published papers or at least to those in eprints on the physics ArXiv.

I find it highly contrived to require your idea of using a "the appearance or disappearance of a discontinuity of gravity in the neighbourhood of the Earth" to fit both the LLR results and the latest GP-B glimpse.

That notwithstanding, if you publish on the ArXiv with a definite falsifiable set of predictions for GP-B then I shall be happy to include them in the 'list'.

Garth

Hi Garth,

It appears that my preferred frame effect is actually not ruled out by LLR data (it is not Lorentz violating)! So i cannot exclude this possible prediction. The theory has a preferred fram effect and th predictions crucially depend on it: The prediction for DG that i gave here (0 frame dragging + same geodetic as in GR) is valid in case my preferred frame is attached to the earth.
If it is attached to the CMB or sun or the galaxy the prediction is the same for frame-dragging and geodetic effect but i have an additional preferred frame effect that you did
mention on this site sometime ago: This effect has no free parameter and gives a clear signature: it would appear as an extraoscillation with1 year period and 40 mArcsec amplitude giving a contribution in both direction (N-S and E-W).

Since you gave here the KK prediction which has a free parameter, it would not be chocking to add this extra preferred frame contribution multiplied by a parameter equal to
zero or one (corresponding to the two possible preferred frames) which makes my theory already much more predictive than KK!
I put this in my latest arXiv version. (gr-qc/0610079)

best regards

Fred

henryco

Jan4-08, 06:11 PM

Since you gave here the KK prediction which has a free parameter, it would not be chocking to add this extra preferred frame contribution multiplied by a parameter equal to
zero or one (corresponding to the two possible preferred frames) which makes my theory already much more predictive than KK!

Fred

Hi Garth,

Rethincking about it, i realise that since you give the prediction for the integrated drift on one year on this forum, my one year oscillation integrated preferred frame effect will anyway not contribute.
So the better is to keep the predictions as they are and just mention that the drifts may not be steady ones and this may provide another discriminating info.

Is that possible?
regards

Fred

Garth

Jan6-08, 07:09 PM

Hi Garth,

Rethincking about it, i realise that since you give the prediction for the integrated drift on one year on this forum, my one year oscillation integrated preferred frame effect will anyway not contribute.
So the better is to keep the predictions as they are and just mention that the drifts may not be steady ones and this may provide another discriminating info.

Is that possible?
regards

Fred

Fred, you have already done so!

Theories are only considered here if they make a falsifiable prediction, or pair of predictions to be tested against the published results.

Predictions have to take into account all factors that influence the result and not just tailored to match results as they come in.

Garth

henryco

Jan7-08, 05:53 AM

Fred, you have already done so!

Theories are only considered here if they make a falsifiable prediction, or pair of predictions to be tested against the published results.

Predictions have to take into account all factors that influence the result and not just tailored to match results as they come in.

Garth

I have already done what ?

Fred

Garth

Jan7-08, 06:48 AM

I have already done what ?henryco: "to keep the predictions as they are and just mention that the drifts may not be steady ones and this may provide another discriminating info."

Remember others will need convincing that your theory's predictions are being verified or falsified by the results of the experiment. So a clear set of predictions would be good.

Garth

notknowing

Jan8-08, 07:50 AM

Hi, Garth,
You made a second mistake!
Instead of removal, my paper stands there sound on Arxiv.

I studied the origin of your mistake. If not true, please forgive me.
You posted my paper directed to 5th version as
http://arxiv.org/PS_cache/astro-ph/pdf/0604/0604084v5.pdf
Such kind of link fails if the original paper is updated. This is because Arxiv let you directly link to PDF ONLY IF the required PDF version is current version!!

My updated version is
http://arxiv.org/abs/astro-ph/0604084
or
http://arxiv.org/abs/astro-ph/0604084v8

If you want to post my fifth version, that is OK if you choose:
http://arxiv.org/abs/astro-ph/0604084v5
but you choice of PDF post failed as I explained above!!

It is interesting to observe that you can reference an arxiv paper which is not published in a refereed journal. Recently, I also referenced my arxiv paper :
http://arxiv.org/abs/0712.1110 (on the same subject) and I was banned for this because I "tried to distribute a personal theory". The paper mentioned above is in addition an extension of a previous paper which was published in a refereed journal. I'm curious whether I will be banned again. Furthermore, I have noticed many posts which contain references to un-refereed Arxiv papers without these persons being banned.

Rudi Van Nieuwenhove

Garth

Jan8-08, 09:19 AM

Hi Rudi!

On this thread I (not being a Moderator) have allowed to be included brief references to papers on the ArXiv that have not been published in refereed journals, yet that do make some sense, and which make a definite falsifiable prediction.

This seems to have been allowed by the Moderators as the predictions will soon be able to be falsified, or just possibly otherwise.

As you can read some rough edges have been left................

Roll on May (??)! :wink:

Garth

Kris Krogh

Jan14-08, 04:09 AM

Hi Garth,

I see today ArXiv has taken down the paper "A critical analysis of the GP-B mission. I: on the impossibility of a reliable measurement of the gravitomagnetic precession of the GP-B gyroscopes," by Gerhard Forst:

http://arxiv.org/abs/0712.3934

The comment field says: "This submission has been withdrawn by the arXiv administrators because 'G.Forst' is a pseudonym of a physicist based in Italy who is unwilling to submit articles under his own name, in violation of arXiv policies"

It's gone now, but I didn't see anything of substance in the paper. The references it cited did not show what was attributed to them.

Best regards, Kris

wolram

Jan14-08, 09:27 AM

Problems getting to KK paper, known compatibility problem, it may be a fault this end.

lucien86

Jan31-08, 01:19 PM

Hi Gath you asked for theories that can be tested via Gravity probe B.

I have half of one that is not yet fully published or finished but I would like to mention it as it is an alternative or rather a modification to GR.
My work is based primarily on looking at what might exist beyond the light velocity barrier so it obviously involves particles with imaginary mass. My real problem is that I don't yet have the precision to make many exact predictions. What is clear though is that the model doesn't easily allow curved space times. At the moment I have gravity mapped as 'accelerating inertial frames' - the frame itself never sees the acceleration.
As far as I'm aware the model should give pretty much identical results to standard GR with one big exception - there should be tachyonic 'shadows'.
Another thing my model predicts is that gravity may be purely classical and have no lower quantum limit - in other words it can never exhibit interference patterns.

Obviously Gravity Probe B isn't going to answer many questions for my theory, but it wasn't designed to - my answers only really deviate from GR above the speed of light. (My theory forbids the folding of space)

I am working on designing a verifiable experiment that can detect tachyonic behavior but I am only an amateur with a tiny budget and other priorities so it is years away.

Garth

Jan31-08, 02:19 PM

lucien86 we have strict guidelines here about not discussing personal theories except on the Independent Research (http://www.physicsforums.com/forumdisplay.php?f=146) Forum, unless they have already been published in a peer reviewed journal.

In this thread I am including theories already published on the physics ArXiv (http://arxiv.org/) as well if they make falsifiable predictions for the GP-B experiment.

I suggest you submit your theory to the IR Forum having first followed their guidelines for submission.

Garth

lucien86

Feb1-08, 02:30 AM

Sure - my whole point is that my theory is not ready to publish there. Half finished means exactly that. As for the IR forum the rules there are so strict that it is actually easier to get published in a big magazine like Nature. I am nowhere near getting published anywhere at the moment - sorry to bother you. - Lucien

Garth

Mar25-08, 04:14 AM

The GP-B website (http://einstein.stanford.edu/index.html) has had a revamp - although there are no new results to report. GP-B Program Extended Through September 2008, and Possibly March 2010

On November 2, 2007, we convened the 17th meeting of our external Science Advisory Committee (SAC) to review our progress in the refinement of the GP-B experimental results. The subsequent SAC report noted "the truly extraordinary progress that had been made in data analysis since SAC-16 [March 23-24, 2007]" and unanimously concluded "that GP-B is on an accelerating path toward reaching good science results."

Following a peer-reviewed bridging proposal to NASA's Science Mission Directorate (SMD) and actions by Stanford and a private donor, the GP-B program has been extended at least through September 2008. Furthermore, SMD opened the opportunity for GP-B to submit a proposal this month to its Senior Review process. This is a bi-annual event in which ongoing NASA science programs undergo a peer-review to determine which of those programs NASA should continue and/or extend in order to achieve the greatest scientific gain. Assuming a successful Senior Review, GP-B will be extended one final time, from October 2008 through March 2010.
There are two unexpected experimental errors that are being reduced.
1. A time variation in the polhode motion of the gyroscopes, which creates complications in the gyro scale factor calibrations (conversion of electrical signals to angles).
2. Much larger than expected classical misalignment torques on the gyroscopes, attributable to “patch effect” (contact potential difference) interactions between the gyro rotors and their housings.

Although these anomalies reduced the best precision obtainable from the 1% goal they still hope to achieve about 2% for the frame-dragging effect and 0.02% for the geodetic effect.

During 2006-early 2007, we made good progress understanding the cause of these complications (and developing sound methodologies for working through them, culminating in an announcement of first results at the annual meeting of the American Physical Society in April 2007. Since that time, the team has continued to improve the results in a number of ways. As experimentalists, we make no assumptions about Einstein’s theory being right or wrong; rather, we collected data, and we are doing everything humanly possible to maximize the precision and accuracy of the final results—whether or not they agree with Einstein’s predictions.

For newbies to this thread a basic explanation of the experiment is given in a slide show (http://einstein.stanford.edu/Media/GP-B_nutshell_slideshow.pdf) on their website.

We note the Seeing General relativity Directly (http://einstein.stanford.edu/highlights/status1.html) slide remains the replaced one, which does not give the game away. Remember the original slide (http://colloquia.physics.cornell.edu/11-12-2007/cornellpres_files/v3_slide0341.htm) gave some interesting results inconsistent with GR at the one \sigma (68%) confidence level!

Garth

JonathanK

Mar27-08, 10:05 PM

Hello Garth and everyone,

well, it seems GP-B may be a long road. My paper on the geodetic effect got through peer review, it's at

http://journalgp.awardspace.com/journal/0202/020203.pdf

PSG gives the same predictions as GR and NG, hope to see it on the list with them, presumably along with Jin He's absolute relativity. Does anyone have a guess as to when the 3 sigma results will be announced? J

Garth

Mar28-08, 04:30 AM

Well first of all Jonathan congratulations on having your paper published!

I do have a problem in including it in the list because in that paper you say:PSG has the same values as GR for both effects being measured by Gravity Probe
B (for frame dragging it is - 39 mas/yr, using more recently released orbit figures). But
unlike GR, PSG has not been fully worked through, and it may be able to explain this
∼ 61 mas/yr anomaly when various smaller effects have been taken into account.

So what hard and fast prediction are you making for the results of this experiment? It seems that you are hedging your bets. The sign of a good scientific theory is that it can be falsified! As indeed my 2002 SCC proved to be! (darn!)

Although this isn't the place to discuss the detail of your theory, and you might like to start a new thread on PSG, as a published alternative theory, to do just that, my initial reaction is to be suspicious of your "time slowing" concept. Time on any particular world-line passes at the tautological rate of "one second per second". Time dilation between two clocks on different world-lines reveals a warping of the space-time continuum otherwise known as curvature and we are back to GR again.

Secondly I have a query about your actual calculation. If there is no curvature then orbital mechanics have to be explained by some type of Newtonian gravitational force accelerating the orbiting masses off their geodesic straight line trajectories. Such an acceleration would produce a Thomas Precession (http://en.wikipedia.org/wiki/Thomas_precession), that is unless you are denying SR as well, which acts to reduce the geodetic effect. I see no mention of that in your paper.

If you like, as it is published, I will include PSG giving a prediction equal to GR.

And I fully expect we will have to wait until 2010 to get the 3 \sigma results! :rolleyes:

Garth

JonathanK

Mar28-08, 12:12 PM

Thanks Garth,

I have the same predictions as GR, but if the anomaly found in the early geodetic results remains (and the delaying of the May announcement perhaps makes it slightly more likely that it is still there) I don't think that everyone will say "Ah well, GR was falsified, too bad". In that instance things would be on hold until some very good clear explanation for the 61 +/- 43 mas/yr turns up. By then the value of the anomaly would be known more accurately, so something might eventually explain it, either from analysing the experimental setup or from theory.

About the slowing of time - I put the word "slowing" in inverted commas in the paper to make it clear that it's not literal, either in GR or PSG. But as I'm making the point there that in PSG it happens by the same factor as the slowing of the motion of light and matter in the field, the word "slowing" is justified.

Though you say it doesn't, the paper actually does mention the question of a Newtonian type force. The conceptual basis removes the need for one, just as curvature does - an orbiting object is in freefall. If one conceptual basis can make an orbiting object be in freefall, then another can, as you'll see when it's published in full (or we can argue about it then! but I think you'll agree). But meanwhile it would be odd to rule out all possible conceptual pictures other than curvature as capable of that.

Anyway, best wishes,

Jonathan

JonathanK

Mar28-08, 07:50 PM

PS. To clarify the first point above, the anomaly is too small to falsify everything at the GR value instantly, making KK theory the new standard view. Both GR and PSG could potentially survive that, but both could be falsified if the final results contained figures further from the GR values.

In the paper I've speculated briefly about the anomaly, but it's too small to be major issue, and doesn't detract from the prediction pair I've given, with mathematical backing for the geodetic prediction. After the equation, the paper says

"This means that PSG is so far consistent with experiment, as a geodetic effect of similar value to that in GR and PSG has been measured."

The final results may change that preliminary measurement, but "of similar value" relates to the same thing. J

Garth

Mar29-08, 05:00 AM

Though you say it doesn't, the paper actually does mention the question of a Newtonian type force. The conceptual basis removes the need for one, just as curvature does - an orbiting object is in freefall.

The question is not whether the gyro is in free-fall, a satellite in Newtonian theory is falling freely, but whether the free-fall state is one where the gyro is accelerating away from its geodesic path, i.e. is it on a 'straight' geodesic trajectory, or not?

If it is on a 'straight' geodesic trajectory, as in GR, then the shape of the orbit is explained by the curvature of space-time and there is no intrinsic acceleration or Thomas precession; if it is not, as in Newtonian gravity, then there is an accelerating force, the Newtonian gravitational force, with the consequence that the gyro suffers a Thomas precession, which in Newtonian gravity (+ SR flat space-time) produces a precession equal to one third of the GR geodetic precession.

As an aside, because of this the initial geodetic result of GP-B has falsified Newton to a high confidence level! For the same reason I am also sure that it has falsified PSG, if that theory does not include space-time curvature.

So my question Jonathan is, "Does PSG include curvature? And if not, how does it produce an elliptical orbit without accelerating the gyro away from its 'straight' geodesic trajectory?"

Garth

JonathanK

Mar29-08, 11:40 AM

There's no acceleration, for the same reasons as there's none in GR. The conceptual picture is one that is surprisingly like curvature, and yet it comes from flat space - it involves a small cluster of lateral jumps. An orbiting object thinks it is travelling in a straight line, and follows a curve only because the nature of space has been changed in a fundamental way.

I have a book on the theory of time, of which PSG is the gravity part ("Motion through time"), also hope to publish a longer paper with the whole conceptual basis - have wondered whether it can be a series of papers, but the concepts are so interdependent that it's difficult to find a dividing line. At present I have published some of the predictions, but not all of the theory.

In the book the concepts explain very much from very few starting assumptions, but the "smoking gun" evidence provided is an explanation of exactly how equation 4 of the first published paper was derived. It directly gives all the speeds on the path of a falling object from infinity, from knowing the speed at a given point. It agrees with numbers from Newton's theory to 12 decimal places, and goes to zero at the Schwartzchild radius of a black hole. I've hoped to show you the theory for some time, look forward to hearing your opinion. Thanks, J

JonathanK

Mar29-08, 02:09 PM

PS perhaps I can give some indication of the kind of thing I mean, using an analogy. When light is refracted around a curve, for example when travelling through an index gradient refractive medium on Earth, does the light undergo an acceleration? No, instead it thinks it is travelling in a straight line, but what it is travelling through has been changed in a fundamental way (without curvature into an extra dimension), and this makes it follow a curve. PSG has something analogous to a refractive medium, which matter responds to at the Planck scale as light does.

Jonathan

Garth

May27-08, 11:57 AM

The latest GP-B website (http://einstein.stanford.edu/) Update:
================================
GP-B STATUS UPDATE -- MAY 23, 2008
================================

NASA's 2008 SENIOR REVIEW OF GP-B

In March 2008 at NASA's invitation, we submitted a proposal to the Science Mission Directorate, Astrophysics Division Senior Review of Operating Missions (Sr. Review), requesting a final 18-month (October 2008 through March 2010), $3.8M extension of GP-B to complete the data analysis and publish the results. In April, as part of the Sr. Review process, GP-B Principal Investigator, Francis Everitt, and Program Manager, William Bencze, made a presentation to the Sr. Review Committee at NASA Headquarters, where it appeared to have been favorably received.

Thus, we were greatly surprised last week to discover that the Sr. Review had recommended that NASA not grant our final funding extension, particularly since another NASA committee--the GP-B Science Advisory Committee (SAC -- http://einstein.stanford.edu/MISSION/mission2.html#sac), chaired by relativistic physicist Clifford Will--stated in its report following the November 2007 meeting: "The SAC was impressed with the truly extraordinary progress that has been made in data analysis since SAC-16 [Mar 2007] Š and we now agree that GP-B is on an accelerating path toward reaching good science results."

The Sr. Review evaluation is an unexpected setback, but we are determined to push ahead and drive to the very best possible result within the resources available.

THE PLIGHT OF FUNDAMENTAL PHYSICS RESEARCH AT NASA

While the Sr. Review outcome has ramifications for GP-B, in broader terms, it points to the challenge of finding support for fundamental physics experiments within the NASA culture of observational missions. This has been an ongoing issue within NASA for decades. In the 1990s, fundamental physics research experiments were scattered over several divisions of NASA, which led in 1999, to the blue-ribbon NASA Advisory Council (NAC) recommending to the NASA Administrator that the agency create a "single home room" for physics missions in space so that these missions would be given the support and visibility they deserved.

The 1999 NAC committee's advice was never heeded. Furthermore, during the 2004 restructuring and consolidation of NASA divisions, the already small budget for fundamental physics research was cut to zero in the NASA Exploration Directorate, entirely eliminating fundamental physics research from that division. This left the Science Mission Directorate (SMD) as the only home for fundamental physics experiments like GP-B. However, in the SMD, physics experiments had to compete directly with the NASA Great Observatories and other astrophysics missions for pieces of an already-decimated research budget. It is no criticism of the SMD Sr. Review to say that of the ten missions under review, GP-B as a physics experiment rather than an observatory was quite unlike the rest and almost impossible to fit within a common intellectual framework. Regrettably, since NASA has failed to establish a fundamental physics research division, several missions besides GP-B have suffered. If such a division existed, we believe the agency's support for the proper completion of GP-B would continue to be strong.

THE CONTINUED RELEVANCE & IMPORTANCE OF GP-B

One of the Sr. Review Committee's main arguments supporting its recommendation that NASA not fund the final extension requested by GP-B, was that the goals of GP-B have already been fulfilled by other measurements, and that GP-B is therefore no longer relevant. This view is in stark contrast with the recommendations of the SAC (2007), NASA's Turner panel review of GP-B (2003), and NASA's Fitch-Taylor NRC review of GP-B (1995). All of these reviews concluded that the GP-B experiment is scientifically justified and should be completed.

Now, in 2008, the scientific justification for completing the GP-B experiment is even more valid. During the past five years, there has been little progress on other relativity experiments, but GP-B was launched, operated, and collected all of the necessary data. After two years of intense work, the GP-B science team is very close to completing the data analysis. GP-B has made, in the view of the SAC, "extraordinary progress" in addressing two unexpected and difficult complications in analysis caused by unanticipated electrostatic patch effect fields within the gyroscope. (These have been reported previously in our Summer 2007, September 2007 and December 2007 status updates, which you can view in the STATUS tab on our Website: http://einstein.stanford.edu/highlights/hlindexmain.html)

GP-B directly studies gravity, one of the most fundamental laws of nature. Inherently, the goals of GP-B differ significantly from those of typical astrophysics missions, where natural laws--inferred theoretically and tested on the ground--are used to interpret observations of astrophysical phenomena. Furthermore, GP-B objectives and methods are qualitatively different from those underlying most astrophysical work. For this reason, the GP-B experiment begs to be evaluated with respect to criteria based on its direct experimental methodology. Direct tests of nature's laws are the foundation of physical science; such tests are the only rational basis for the belief that these laws are, in part, "understood." GP-B seeks to deepen our understanding of gravity in this way.

In addition to its scientific significance, GP-B's technological heritage and operational experience is critically important for future gravity space missions, including tests of the equivalence principle (STEP) and the search for gravitational waves (LISA). NASA stands to loose much of the expertise developed on the GP-B mission if the program is not brought to a proper conclusion.

THE ROAD AHEAD

Our GP-B team has been making steady progress in analyzing the data and working through the unexpected complications discovered within the data. We are now in the home stretch. We have identified the issues that still need to be addressed, and we have prepared a sound plan for completion of the analysis. This plan, which was spelled out in detail in our proposal to the NASA Sr. Review, requires an additional 18-month investment of $3.8M from September 2008 through March 2010. If no further funds are forthcoming from NASA, the analysis efforts will likely cease by October 2008, unless other funding sources can be identified. Since February 2008, GP-B has been funded by contributions from NASA, Stanford University, and a private donor, in approximately equal shares.

We have now clearly confirmed the geodetic effect to a precision of less than 1.5% (97 milli-arcseconds/year). However, because the frame-dragging effect is ~170 times smaller, removing the sources of error from that measurement--especially the non-relativistic torques due to patch effect interactions between the gyro rotors and their housings--is a detailed, painstakingly slow process. We have yet to reach a point of diminishing returns. Until we do, it is our intention to push onward and obtain the best result possible to properly complete this landmark experiment.

We wait to see how accurate they can get their results before the plug is pulled.

However, if it just a matter of $3.8M to complete the analysis up to March 2010 it seems a waste to stop in September this year after spending $800M. :frown:
Anybody got $3.8M to spare?

Garth

Garth

May27-08, 12:30 PM

The reason GP-B is a unique experiment that has not been done before is because all other tests of the geodetic precession and gravito-magnetic effect rely on measuring the trajectories of test particles through space-time. They are not directly measuring the precessions of a physical (solid) gyroscope.

A non-metric theory that is conformally equivalent to GR in vacuo (i.e. its Action reduces to GR in vacuo) will generate the same geodesic trajectories for test particles although the Robertson parameters may be different.

This is significant because in terms of the Robertson PPN parameters all other tests of GR have effectively measured \gamma in the expression:

GM(\frac{1+\gamma}{2}),

whereas the geodetic precession is given by the expression:

GM(\frac{1+2\gamma}{3}).

The \gamma is coupled to G differently, so the measurement of the geodetic precession of an actual gyroscope, rather than just the precession of an orbit, is a unique measurement that has only been carried out by GP-B. It would be a crying shame not to complete the processing of the data obtained.

Garth

Chronos

May28-08, 12:38 AM

Exactly the point of rigorously crunching GP-B data, Garth!

Wallace

May28-08, 12:42 AM

Garth

May28-08, 03:27 AM

I guess the funding panels just didn't believe the data was salvageable and whatever result GP-B would end up claiming would always have a big question mark next to it due to the extra noise. If the funding panel didn't believe the noise could be removed with certainty what would the research community think about the results? I guess they decided not to throw good money after bad.

I have no idea myself about how salvageable the data is, but clearly that was the view of the panel, who I'm sure aren't dodo's. It's a crying shame, but maybe humpty dumpty just can't be put back together again, no matter how much glue we buy.

The Update actually claims that the drying up of the money is due to a funding crisis and the lack of a fundamental physics research division within NASA:
It is no criticism of the SMD Sr. Review to say that of the ten missions under review, GP-B as a physics experiment rather than an observatory was quite unlike the rest and almost impossible to fit within a common intellectual framework. Regrettably, since NASA has failed to establish a fundamental physics research division, several missions besides GP-B have suffered. If such a division existed, we believe the agency's support for the proper completion of GP-B would continue to be strong.

In my post above (http://www.physicsforums.com/showpost.php?p=1745407&postcount=296) I have explained the counter argument to the Sr. Review Committee's main criticism: the goals of GP-B have already been fulfilled by other measurements, and that GP-B is therefore no longer relevant. The GP-B team claim that 'Humpty Dumpty' has been almost put back together and a full repair is at hand. Now, in 2008, the scientific justification for completing the GP-B experiment is even more valid. During the past five years, there has been little progress on other relativity experiments, but GP-B was launched, operated, and collected all of the necessary data. After two years of intense work, the GP-B science team is very close to completing the data analysis. GP-B has made, in the view of the SAC, "extraordinary progress" in addressing two unexpected and difficult complications in analysis caused by unanticipated electrostatic patch effect fields within the gyroscope.

Garth

Wallace

May28-08, 03:39 AM

The Update actually claims that the drying up of the money is due to a funding crisis and the lack of a fundamental physics research division within NASA:

I know what the press release said (from both sides), I'm just trying to read between the lines I guess. If the honchos in NASA thought GP-B still had great things to say, they would have found the money somewhere, regardless of structural barriers.

The GP-B team claim that 'Humpty Dumpty' has been almost put back together and a full repair is at hand.

Again, that's what they are saying. But how long have they been saying that to the funding bodies? At some point patience will wear out. I've been telling my supervisor that the paper I'm working on is 'almost done' for a few months now, does that mean it will be ready tomorrow? Probably not. I don't think I've ever seen a grant application say 'we have a lot of work to do and it might not work out after all of that effort anyway', even though that is very often the truth.

Again, I know very little about GP-B, so this could all be irrelevant, my point in as much as I have one is that you can't really learn anything about this from the words in a press release.

Garth

May28-08, 04:01 AM

my point in as much as I have one is that you can't really learn anything about this from the words in a press release.

Yes, of course, but frustrating all the same!

To make my point though of the uniqueness of the experiment, today's physics arXiv has this paper A Search for New Physics with the BEACON Mission (http://arxiv.org/abs/0805.4033), which makes the following points: However, there are important reasons to question the validity of Einstein’s theory of gravity. Despite the beauty and simplicity of general relativity, our present understanding of the fundamental laws of physics has several shortcomings. The continued inability to merge gravity with quantum mechanics,8 and recent cosmological observations that lead to the unexpected discovery of the accelerated expansion of the universe (i.e., “dark energy”) indicate that the pure tensor gravity field of general relativity needs modification. It is now believed that new physics is needed to resolve these issues.8
Which I agree with, and: The Eddington parameter \gamma whose value in general relativity is unity, is perhaps the most fundamental PPN parameter, 2 in that \frac{1}{2}(\gamma−1) is a measure, for example, of the fractional strength of the scalar gravity interaction in scalar-tensor theories of gravity.1 Currently, the most precise value for this parameter, \gamma−1 = (2.1±2.3)×10-5, was obtained using radio-metric tracking data received from the Cassini spacecraft7 during a solar conjunction experiment. This accuracy approaches the region where multiple tensor-scalar gravity models, consistent with the recent cosmological observations, predict a lower bound for the present value of this parameter at the level of \gamma−1 ~ 10-6−10-7 (see discussion in Ref. 1,8 and references therein). Therefore, improving the measurement of this parameter would provide crucial information to separate modern scalar-tensor theories of gravity from general relativity, probe possible ways for gravity quantization, and test modern theories of cosmological evolution. Which I pointed out in #296 above.

However: The BEACON mission architecture is based on a formation of four small spacecraft placed in circular Earth orbit at a radius of 80,000 km (Fig. 1). Each spacecraft is equipped with three laser transceivers in order to measure the distances to the other spacecraft in the formation.

The experiment is simply a refined measurement of the geodesic orbits of test particles (the spacecraft) in Earth orbit and will therefore fail to discriminate between GR and any conformally equivalent scalar field theory in which the conformal transformation of the Action into the Einstein frame is simply canonical GR, as I explained in #296.

GP-B could resolve such a degeneracy.

Garth

CarlB

May28-08, 11:54 AM

It probably doesn't help that they can't reproduce Einstein's GR. I hope that they publish their raw data so that other people can comb through it.

Garth

May28-08, 12:48 PM

It probably doesn't help that they can't reproduce Einstein's GR. You might be onto something there.....

Just to show you what I mean:
Seeing General Relativity Directly (http://colloquia.physics.cornell.edu/11-12-2007/cornellpres_files/v3_slide0341.htm), from Francis Everitt's lecture slides Gravity Probe B + a Hint of STEP (http://colloquia.physics.cornell.edu/11-12-2007/cornellpres_files/v3_document.htm) presented at Cornell University 12 Nov 2007. Only to 1 \sigma confidence level (so far) though. I hope that they publish their raw data so that other people can comb through it. From GP-B Mission Status Update Summer 2007 (http://einstein.stanford.edu/highlights/hl_061107.html)GP-B DATA ARCHIVE TO BE AVAILABLE THROUGH NSSDC IN JULY

During the past few weeks, while our science team continues to analyze the data, our GP-B data processing team has also been quite busy, compiling an archive of the GP-B raw data—both science data and spacecraft/payload status data, as well as an archive of associated documents, drawings, photos and other information about the GP-B mission. We are currently in the process of transferring this entire archive to the National Space Science Data Center (NSSDC), located at the NASA Goddard Space Flight Center in Greenbelt, Maryland. Transfer of this archive will be completed in late June, and the GP-B archive will then become publicly available sometime thereafter.

Garth

Garth

Jun27-08, 05:27 PM

The latest update from the GP-B team:
All,

Since May 23, 2008, when I sent out our most recent GP-B email status
update and posted the same information on our webiste
(http://einstein.stanford.edu), I've received too many email
responses to reply to each one individually.

Thus, on behalf of the GP-B team, I wish to thank all of you,
collectively, who expressed support for GP-B, and assure you that, in
the words of Mark Twain, "...Rumors of the demise of GP-B are greatly
exaggerated."

Our science team is continuing to make excellent progress in the data
analysis. Members of the team, including several Stanford graduate
students, have produced detailed maps of the trapped magnetic flux in
all four gyro rotors in order to predict the time-varying signal in
the data. This mapping has resulted in a 500-fold improvement in the
determination of the polhode motion throughout the duration of the
experiment, essentially solving the time-varying polhode motion
problem in the data.

This work, in turn, has enabled the team to implement two
complementary methods of removing the disturbing effects of the
classical torques. With the classical torques properly handled,
rather convincing estimates of frame-dragging are now available, but
our team is still investigating all possible systematic disturbing
effects.

Another meeting of the GP-B Science Advisory Committee is being
planned in late August to review our progress in the data analysis
since last November. Also, GP-B will be a central contributor in an
international workshop on "The Nature of Gravity: Confronting Theory
and Experiment in Space" to be held in Bern, Switzerland, 6-10
October 2008, with the following team members as individual invited
speakers: William Bencze, Francis Everitt, Misha Heifetz, George
Keiser, Barry Muhlfelder & Alex Silbergleit.

Meanwhile, we are vigorously exploring funding sources outside NASA,
both through other agencies and private donors, to enable GP-B to
complete the data analysis, publish the final results and bring GP-B
to a conclusion by early 2010.

We very much appreciate the continued interest and support we have
received world-wide, and we will keep you apprised of our status
going forward.

Sincerely,

Bob Kahn
GP-B Public Affairs

Any millionaires out there??

Garth

Garth

Sep27-08, 04:19 AM

GP-B STATUS UPDATE -- September 26, 2008 (http://einstein.stanford.edu/highlights/status1.html).
PROGRAM STATUS

Since our May 23rd status update, GP-B has continued to make significant progress--fiscal and scientific. NASA funding and sponsorship of the program ends on September 30, 2008, but GP-B has secured alternative funding that will enable our science team to continue working at least through December 2009 in order to complete the data analysis and bring GP-B to a proper close.

The GP-B science team is continuing to make large strides in the data analysis. On Friday, August 29, 2008, the 18th meeting of our external GP-B Science Advisory Committee was held at Stanford to report our progress since the previous SAC meeting in November 2007. Their ensuing report to NASA states:

“The progress reported at SAC-18 was truly extraordinary and we commend the GPB team for this achievement. This has been a heroic effort, and has brought the experiment from what seemed like a state of potential failure, to a position where the SAC now believes that they will obtain a credible test of relativity, even if the accuracy does not meet the original goal. In the opinion of the SAC Chair, this rescue warrants comparison with the mission to correct the flawed optics of the Hubble Space Telescope, only here at a miniscule fraction of the cost.” —SAC #18 Report to NASA

On October 6-10, six GP-B team members have been invited to present these dramatically improved, interim results at an International Space Science Institute (ISSI) workshop on "The Nature of Gravity: Confronting Theory and Experiment in Space" to be held in Bern, Switzerland. Following the Bern workshop, these improved interim results will undergo a thorough peer-review and vetting; then towards the end of this year, we plan to announce them publicly.

We very much appreciate your continued interest in GP-B, and we will keep you posted on our progress in future status updates.

December 2009 - we continue to wait and see!

Garth

JonathanK

Oct1-08, 03:43 AM

Hello Garth and all.

As well as working on until at least the end of next year, looks like they might announce some interim results towards the end of this year.. though you never know. Garth, are you going to redo the list? There were several updates to be made a while ago.

best wishes, Jonathan

Garth

Oct2-08, 06:08 AM

Garth, are you going to redo the list? There were several updates to be made a while ago.
I have included PSG as it is accepted for publication, and I have taken your statement that its predictions are the same as those of GR, but note therefore that GP-B will not actually test it against GR. Note also my personal reservations previously expressed!

Einstein's General Relativity(GR)
Brans-Dicke theory (BD)
Moffat's Nonsymmetric Gravitational Theory (http://arxiv.org/abs/gr-qc/0405091) (NGT)
Stanley Robertson's Newtonian Gravity Theory (http://arxiv.org/abs/gr-qc/0502088) (NG),
F. Henry-Couannier's Dark Gravity Theory (http://www.arxiv.org/abs/gr-qc/0610079) (DG).
Alexander and Yunes' prediction for the Chern-Simons (http://kr.arxiv.org/abs/hep-th/0703265v1) gravity theory (CS).
Kris Krogh's Wave Gravity Theory (http://lanl.arxiv.org/abs/astro-ph/9910325) (WG)
Hongya Liu & J. M. Overduin prediction of the Kaluza-Klein ( http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v538n1/50681/50681.text.html?erFrom=5252751197746712308Guest#sc 8) gravity theory (KK).
Kerr's Planck Scale Gravity: Predictions of Experimental Results from a Gravity Theory (http://redshift.vif.com/JournalFiles/V14NO2PDF/V14N2KER.pdf) (PSG)

The predictions are now:

GP-B Geodetic gross precession (North-South).

GR = -6606 mas/yr.
BD = -(3\omega + 4)/(3\omega + 6) 6.606 arcsec/yr. where now \omega >60.
NGT = -(6606 - a small \sigma correction) mas/yr.
NG = -6606 mas/yr.
DG = -6606 mas/yr.
CS = -6606 mas/yr.
WG = -6606 mas/yr.
KK = -(1 + b/6 - 3b2 + ...) 6606 mas/yr. where 0 < b < 0.07.
PSG = -6606 mas/yr.

GPB gravitomagnetic frame dragging gross precession (East-West).

GR = -39 mas/yr.
BD = -(2\omega + 3)/(2\omega + 4) 39 mas/yr.
NGT = -39 mas/yr.
NG = -39 mas/yr.
DG = 0 mas/yr.
CS = -39 mas/yr. + CS correction
WG = 0 mas/yr.
KK = -39 mas/yr.
PSG = -39 mas/yr.

You can see for yourselves the present state of the results in a series of slides of a lecture given by Francis Everitt at Cornell University on the 12th November 2007. Gravity Probe B + a Hint of STEP (http://colloquia.physics.cornell.edu/11-12-2007/cornellpres_files/v3_document.htm).

The pertinent slides are slide 3: Seeing General Relativity Directly (http://colloquia.physics.cornell.edu/11-12-2007/cornellpres_files/v3_slide0341.htm)
and the slide: RNS vs RWE Algebraic 4-Gyro Joint Estimates (http://colloquia.physics.cornell.edu/11-12-2007/cornellpres_files/v3_slide0426.htm)

These last two slides clearly show an inconsistency with the GR prediction at the 1 \sigma confidence level.

Einstein expectation:
-6571 \pm 1* mas
4-gyro result (1 \sigma) for 85 days (12 Dec 04 -- 4 Mar 05)
-6632 \pm 43 mas

(* -6606 mas + 7 mas (solar geodetic) + 28 \pm1 mas (guide star proper motion))

We note that this 07 November 1\sigma confidence level result is inconsistent with all the above geodetic predictions except KK, but nobody takes any notice until at least 3\sigma!

Garth

JonathanK

Oct2-08, 09:39 AM

Thanks Garth,

I appreciate being back on the list. The relevant link is to the second paper published, not the first, as it has the equation that directly produces the geodetic effect curvature component, so vindicating PSG and leading to the prediction you quote above. (And showing that matter could be being affected by a kind of refractive medium at the Planck scale, as light is affected). It's at

http://journalgp.awardspace.com/journal/0202/020203.pdf

If I'm not mistaken, wasn't Jin He's Absolute relativity due to go back on as well? Anyway, it'll be interesting to see what the GP-B team have to say.

best wishes, Jonathan

brightmatter

Feb19-09, 10:14 AM

Gravity Probe B 2009 interim results are arived!!

Garth

Feb23-09, 02:41 AM

Current Mission Status (http://einstein.stanford.edu/highlights/status1.html)
MISSION UPDATE — February 16, 2009
PROGRAM STATUS
Observation of Frame-Dragging

Geodetic Effect Graph--All Gyros Processed data showing geodetic effect in all four gyroscopes.

Frame-Dragging Effect Graph--All Gyros
Processed data indicating frame-dragging effect in all four gyroscopes

The latest GP-B results, detailed in the papers and NASA report described below, show substantial improvement over the preliminary results announced at the April 2007 meeting of the American Physical Society (APS). At that time the geodetic effect was measured with a total uncertainty of 1%, but evidence of the frame-dragging effect as inconclusive.

The latest data analysis that includes a model for the "roll-polhode resonance torque" yields a 15% statistical uncertainty for the Frame-Dragging effect. This 15% uncertainty does not include all systematic effects. Click on the thumbnails at right to view these extraordinary results.

The data analysis leading up to this important result proved more subtle than expected. ‘Patch-effect’ anomalies on the gyro rotor and housing have complicated the gyro behavior in two ways:

1. A changing polhode path affecting the determination of the gyro scale factor.
2. Two larger than expected Newtonian torques.

Put simply, while mechanically both rotor and housing are exceedingly spherical, electrically they are not. Steadily advancing progress, reported to NASA directly and via successive meetings of the SAC, has brought a rather complete understanding of these effects. A turning point came last August with the incorporation of an elegant approach or computing the detailed history of the “roll-polhode resonance” torques discovered a year earlier by Jeff Kolodziejczak of NASA MSFC. The result was a large reduction in previously unexplained discrepancies between the four gyroscopes.

Much further work remains to bring the analysis to completion. To date, limits in computational power have bounded the processing to essentially one point per 97-minute GP-B satellite orbit. The driving period of the roll-polhode resonance torques is at the difference between the 77.5 sec roll period of the spacecraft and a harmonic of the gyroscope polhode period. High-speed computing techniques now in development will lead to more detailed analyses, and allow GP-B to approach the intrinsic limit of the gyro readout.

ISSI Presentations/Publications & Final NASA Science Report

GP-B Science Results--Final NASA Report

Early last October, five members of our GP-B team presented papers on various aspects of the GP-B data analysis at the International Space Science Institute (ISSI) workshop in Bern, Switzerland on “The Nature of Gravity: Confronting Theory and Experiment in Space.”

The five papers summarize the interim results of the GP-B experiment, as also reported to our GP-B external Science Advisory Committee (SAC) at their 18th meeting on August 29, 2008. Following the ISSI meeting, the papers were submitted for publication in the international, refereed journal, Space Science Reviews. They will be reprinted in a hardcover book in the Space Sciences Series of the ISSI, both to be published by Springer later this year.

The papers, along with an introductory preface, comprise the contents of a document entitled “Gravity Probe B Science Results—NASA Final Report,” now posted on our website. Click on the text link or thumbnail at right to view/download it.
GP-B Funding

Richard Fairbank
Richard Fairbank

We are profoundly honored that in January, 2008 Richard Fairbank (founder, Chairman and CEO of Capital One Financial Services Company and one of the three sons of GP-B co-founder, William Fairbank) made a private donation of $512K to Stanford, specifically to support GP-B’s continuing data analysis work. Fairbank’s generous offer was subsequently matched by both Stanford and NASA. This support carried the program until 30 September 2008. All of us here at GP-B are most grateful to Mr. Fairbank for his generous support.

Photo of signing of Stanford-KACST Agreement in October 2008
Signing of the Stanford-KACSTAgreement
in Ocober 2008

Discussions begun last summer with Dr. Turki al Saud, Vice President for Research Institutes at the King Abdulaziz City for Science and Technology (KACST) in Saudi Arabia, have led to the creation of an important Stanford-KACST collaboration, with Professor Charbel Farhat of the Stanford Aero-Astro Department as Co-PI for GP-B data analysis. (The photo at right shows the Stanford-KACST collaboration signing last October.)

As part of this agreement, a team of research scientists from KACST will join the Stanford team to help with the data analysis as well as participate in future projects being developed. Additionally, KACST provided funding for GP-B from October 2008 through December 2009. To maximize the benefit to the scientific and engineering community, we plan to make the capstone of the GP-B program a conference on Fundamental Physics and Innovative Engineering in Space, in honor of William Fairbank.

We thank NASA for forty-four years of continued support since issuing the first research Grant NSG-582 to the program in March 1964. The March 2007 "GP-B Post-Flight Analysis—Final Report" contained an extensive history of GP-B and the NASA personnel who guided it. It is appropriate here to express further special thanks to three individuals, the MSFC Manager Mr. Anthony T. Lyons, the HQ Program Scientist for Physics of the Cosmos Dr. Michael H. Salamon, and the HQ Program Executive Dr. Alan P. Smale. Lastly, we are most grateful to the GP-B Science Advisory Committee (SAC) for their continuing advice and support.

Note the results shown in Figure 13 from Page 21 of the GPB Final NASA Report (http://einstein.stanford.edu/content/final_report/GPB_Final_NASA_Report-020509-web.pdf) (Dec 2008).

Garth

Garth

Nov26-09, 09:33 AM

Okay - now closing in on the GR prediction;
Closing in on Einstein: Frame-Dragging Clearly Visible

The accuracy of the GP-B experimental results has improved seventeen-fold since our preliminary results announcement at the American Physical Society annual meeting in April 2007. At that time, only the larger, geodetic effect was clearly visible in the data. Over the past two and one half years, we have made extraordinary progress in understanding, modeling and removing three Newtonian sources of error—all due to patch potentials on the gyroscope rotor and housing surfaces. The latest results, based upon treatment of 1) damped polhode motion, 2) misalignment torques and 3) roll-polhode resonance torques, now clearly show both frame-dragging and geodetic precession in all four gyroscopes (see figure at top right).

The figure at lower right displays the science estimates as of September 2009, with the gyroscopes analyzed individually and combined. The estimates are indicated with colored "X"s, and the statistical uncertainty associated with each estimate is plotted with a corresponding colored ellipse.

The combined four-gyro result in the figure gives a statistical uncertainty of 14% (~5 marcsec/yr) for the frame-dragging (EW). The gyroscope-to-gyroscope variation gives a measure of the current systematic uncertainty. The standard deviation of this variation for all four gyroscopes is 10% (~4 marcsec/yr) of the frame-dragging effect, suggesting that the systematic uncertainty is similar in size (or smaller) than the statistical uncertainty.

EDIT - This was deleted somehow from my original post - thank you sylas below.
MISSION UPDATE — November 12, 2009 (http://einstein.stanford.edu/highlights/status1.html)

Click on the diagrams to see the present measurements, especially the 'Individual and 4-gyro combined estimates.' and note only 50% error ellipses are plotted.

They have certainly made heavy weather of it.....

Garth

Ich

Nov26-09, 10:57 AM

Well, closing in after modeling away ~95% of the initial uncertainty. I'd say, they needed a result, now they have one.
Better wait for some independent data.

sylas

Nov26-09, 11:42 AM

They have certainly made heavy weather of it.....

Oh yeah... thanks for the heads up. The link is as before, but with new content: MISSION UPDATE — November 12, 2009; Closing in on Einstein: Frame-Dragging Clearly Visible (http://einstein.stanford.edu/highlights/status1.html).

The GR prediction lies just outside the 50% error ellipse of the 4 combined gyros.

At this point, I wonder if they learned more about Newton and gyroscopes than about GR! The confirmation is nice even if not to the accuracy they had originally hoped.

Cheers -- sylas

Polestar101

Nov26-09, 06:55 PM

The GP-B folks have made so many adjustments and re-adjustments of the data I have no confidence they can really tell the difference between polhode noise, aberration of light from a moving solar system or other unquantifiable effects. NASA was right to pull the plug on this one. Bad science.

Garth

Nov27-09, 03:35 AM

Two unexpected errors have crept into the data, misalignment torques and a varying polhode motion.

A constant polhode motion (wobbling) was to be expected, as each sphere was not perfectly symmetrical, however these motions were found to be damped out and that meant removing the effect from the data proved more difficult.

However, adding the variation in spin-down rates to the analysis, the GP-B team currently believes that the underlying reason for both these errors is a single effect caused by "patch effect charges" on the gyro rotors and on the inside surfaces of their housings.

The team are confident that they are modelling these sources of noise in the data accurately because they are using two independent methods, algebraic and geometrical, and the results of each method are being compared for consistency.

The aberration of starlight is clearly observed as predicted and provides the natural system calibration, over both orbital (the satelite's) and annual (the Earth's) orbits.

However the problem is that, given the noise has to be modelled and extracted from the data to find the relativistic signal, should the final signal deviate from GR then few would find the result convincing. Others would be say that they had just modelled the noise incorrectly.

Having come this far it would be madness not to complete the data reduction, which is being done through private funding, and the published raw data could provide a mine for others to dig into for years to come - that is if anybody else will be bothered to do so!

Garth

Polestar101

Nov27-09, 03:49 PM

The aberration of starlight is clearly observed as predicted and provides the natural system calibration, over both orbital (the satelite's) and annual (the Earth's) orbits.

Garth – It is true that the steady signal from the ~5” aberration of light from the spacecraft’s 91 minute orbit around the earth served as a useful calibration tool. The less frequent ~20” aberration (due to the earth’s orbit around the sun) was hardly helpful at all because the periodicity during the allotted time for the experiment was less than 2x and because the incoming GP-B data was broken up so many times (with stops and starts and recalibrations along the way).

But perhaps the biggest blunder of the experiment was failure to account for the moving frame of the solar system. The aberration of light from this effect is large (larger than the diurnal or annual figures and larger than the relativity effects) but looks like drift and is still unquantified because there is still large uncertainty about the exact speed and exact motions of the SS (it may have several). I do not blame the current program scientists for this problem as it was unforeseen by the original designers of the experiment (note the complete absence of any mention of this effect in the literature).

Having come this far it would be madness not to complete the data reduction, which is being done through private funding, and the published raw data could provide a mine for others to dig into for years to come - that is if anybody else will be bothered to do so!

I agree it would be great to thoughtfully take apart and quantify every single signal recorded by GP-B. However, the current team is so focused on finding the relativity effects I believe they are missing the discovery of some very important science about the motion of the solar system. Unintentional bias is hard to get away from in an experiment of this type.

Polhode motion is an extremely tricky thing to quantify and predict (no paper supports its prediction with this many variables). In their attempts to cancel it out the GP-B team is probably throwing out vital information about the moving solar system (all in an effort to find the relativity effects). Personally, I doubt if there was any meaningful polhode motion (think about it - those gyros were pretty darn perfect – and polhode is exactly the sort of thing they were designed to avoid!). Most of the “noise” is likely motion of the frame of the SS, and possibly, motion of our local star group relative to the guide star.

GP-B is a unique experiment. No doubt some day someone will look at the data with a completely virgin mind and reveal key information about the moving solar system. Until then I hope the data is well preserved for future generations.

Walter

sylas

Nov27-09, 04:44 PM

But perhaps the biggest blunder of the experiment was failure to account for the moving frame of the solar system.

I don't think that can be right. The motion of the solar system and of the guide star IM Pegasi was considered and taken into account in the analysis. Not only that, the accuracy of motions was carefully measured and determined to have only a small effect on the uncertainty of the final result.

See: Bartel et. al. (2007) VLBI astrometry for the NASA/Stanford gyroscope relativity mission Gravity Probe B (http://journals.cambridge.org/action/displayAbstract?aid=1929956), in Proceedings of the International Astronomical Union, 3, pp 190-191; doi:10.1017/S1743921308019005.

Cheers -- sylas

Ich

Nov27-09, 04:53 PM

However the problem is that, given the noise has to be modelled and extracted from the data to find the relativistic signal, should the final signal deviate from GR then few would find the result convincing.
Garth, no matter what the outcome is: it is not convincing.
I understand that the published result does not support scc (correct me if I'm wrong), but I wouldn't see it as confirmation or rejection of anything. It is not reproducible, nobody will go down that road again in the foreseeable future, and nobody can follow their corrections without doubt.
It's sad, but I'd say: the experiment failed in this aspect. That's ok, it is bound to happen every now and then.

Garth

Nov27-09, 04:59 PM

Polestar101

Nov28-09, 01:40 AM

Walter, would not motion of the Solar System frame be subsumed into the guide star IM Pegasus' proper motion? This was measured independently by the astrometry team at the VLBI and a report found here: Proper Motion of the GP-B Guide Star (http://einstein.stanford.edu/Media/APS_talk_Shapiro.pdf).

It is certainly useful to exactly define the proper motion of the guide star but remember the reference point has nothing to do with the motion of the instrument that is doing the measuring. The spacecraft that is doing the measuring moves in its regular orbit, and it moves with the earth in its orbit around the sun, and it moves with the earth and solar system as the solar system moves through space – thereby changing orientation relative to the guide star independent of any proper motion of that reference point.

The annual aberration of light effect is described here:The Annual Aberration Signal (http://einstein.stanford.edu/MISSION/mission5.html). It seemed to confirm the orbital aberration effect.

The GP-B team properly describes the orbital aberration and the annual aberration but notice there is no mention of the little known aberration that results from the motion of the solar system. I doubt that it was considered when the experiment was conceived. Even today neither the speed nor exact motion of the SS is known for certain. The Voyager 1 and 2 data suggest the SS is moving at a high rate of speed in a general southwesterly direction. But we need more than two data points before we can match it to the GP-B data.

I actually have a vested interest in the GP-B team getting it wrong (see SCC earlier in this thread, which is falsified by the results), so I am playing Devil's Advocate in supporting their results, and I find no reason at present to think otherwise, but if you have a serious alternative solution to their data analysis I shall be very interested!

Hopefully the GP-B data when juxtaposed against the data from other experiments will be useful to several generations to come – even if not to test Einstein. I will be presenting a poster at the upcoming AGU meeting in SF that looks at how much the SS might be moving and why it may be artificially constrained by current lunisolar precession theory. This could have a bearing on the interpretation of the GP-B data but I freely admit I cannot make full sense of the GP-B data at this point.

sylas

Nov28-09, 03:31 AM

The GP-B team properly describes the orbital aberration and the annual aberration but notice there is no mention of the little known aberration that results from the motion of the solar system. I doubt that it was considered when the experiment was conceived.

It is known and it is tiny. No offense, but at this point it is clear that you have no empirical basis for your interesting personal suppositions, and claims about what the team is ignoring are pure speculation; and not actually based on any understanding of the analysis.

The Sun is not part of a binary star system. Analysis of GP-B does not give you the data you would like to support this hypothesis (of a stellar companion to the Sun). Speculations based on pure supposition that they've somehow failed to notice this are not really acceptable by forum guidelines.

Cheers -- sylas

Polestar101

Nov28-09, 03:06 PM

If it is known - please tell me how it is known.

The fact is the motion of the solar system is not known - it is assumed. The major assumption is that its only motion is around the galactic center in a period of about 240 million years resulting in a change in orientation of about .005" p/y (within the precession observable), but no one really knows if this is correct. In fact, this assumption itself lies on the assumption that all changes in earth orientation are local in nature and there is no accounting for the motion of the frame of the solar system relative to the VLBI reference points. This has nothing to do with a possible stellar companion. Good science simply requires that we not make too many unfounded assumptions. Unfounded assumptions is what got GP-B into its current mess.

Garth

Nov28-09, 06:20 PM

The experiment measured the angular displacement of the four gyros against a distant quasar, the core of 3C 454.3. Which, being at z=0.859 was seen to be a 'fixed direction in space'.

The satellite itself measured the angles between the gyros and the guide star IM Pegasi, a VLBI team independently measured the Proper Motion of the guide star, relative to the quasar. Both IM Pegasi and the quasar are radio objects.

The actual data being measured were the angles between an gryos' axes and the distant quasar. The earth is orbiting the Sun, the Sun is orbiting the Milky Way and the Milky Way is moving through intergalactic space. The total velocity of these motions is approximately 10 -3c.

Using ball-park OOM estimates z = 0.859 converts into a distance of about 1010 light yrs and the galaxy moved about 10 -3 lgt yrs in the ~year data were collected, similarly with the quasar, so the proper motion of the quasar would be OOM 10 -13 rad i.e. ~ 10 -5 milliarcsecs. They hope to measure the displacement angles to an accuracy of about 1 milliarcsec, they have achieved an accuracy of about 10 milliarcsecs so far, so as the proper motion of the quasar relative to the Earth is 5 or 6 OOM smaller than this it can be disregarded.

Garth

sylas

Nov28-09, 06:38 PM

Using ball-park OOM estimates z = 0.859 converts into a distance of about 1010 light yrs and the galaxy moved about 10 -3 lgt yrs in the ~year data were collected, similarly with the quasar, so the proper motion of the quasar would be OOM 10 -13 rad i.e. ~ 10 -5 milliarcsecs. They hope to measure the displacement angles to an accuracy of about 1 milliarcsec, they have achieved an accuracy of about 10 milliarcsecs so far, so as the proper motion of the quasar relative to the Earth is 5 or 6 OOM smaller than this it can be disregarded.

Garth

Or put it another way: 1 milli arc second is about 5 * 10-9 radians. To let actual lateral movement of the solar system distort directions by this amount would require movement of the order of 50 light years over the year or so that data was collected.

Cheers -- sylas

Polestar101

Nov29-09, 05:33 PM

If the solar system changes "orientation" we are not just talking parallax.

VLBI does not account for changes in the solar system’s orientation to reference points outside the moving frame. Quote from NASA VLBI website:

“Changes in the Earth’s orientation in inertial space have two causes: the gravitational forces of the Sun and Moon and the redistribution of the total angular momentum among the solid Earth, ocean and atmosphere. VLBI makes a direct measurement of the Earth’s orientation in space from which geoscientists then model such phenomena as atmospheric angular momentum, ocean tides and currents, and the elastic response of the solid Earth.”

Please note the present methodology is only concerned with local changes - within the frame of the solar system – thereby effectively employing a static solar system model. Yet measurements are made to points far outside the moving frame – without accounting for any motion of the frame relative to the reference points. If the solar system curves through space we would never know it under current methodology because all changes in earth orientation are attributed to local causes.

If the total precession observable includes some component of solar system motion then even though GP-B is be far above the precessing earth it would still pick up some component of precession (due to SS motion) but think it was noise.

A careful reading of the press releases suggests this is exactly the type of “noise” that GP-B has been bothered with since inception.

http://www.space.com/businesstechnology/technology/gravity_probe_b_031231.html

Garth

Nov29-09, 05:43 PM

Polestar, as the measurement is that of the change of angle between the axis of a gyro and the distant quasar, are you claiming the changes in the solar system orientation also changes to orientation of the gyro?

The changes in the Earth's orientation you mention, its change of axis, would not affect the satellite.

The early Space.com site you linked to does accurately predict Several members of the review at the time voiced a minority skepticism about the large extrapolations required from ground testing to GP-B's performance in space. Furthermore, this same minority thought it likely that some "as yet unknown disturbance" may prevent the spacecraft from performing as required.

Why does the build up of electrostatic patches not seem to you to be "exactly the type of “noise” that GP-B has been bothered with since inception."?

Garth

Polestar101

Dec4-09, 03:52 AM

As the SS curves through space the spacecraft, in orbit around the earth, must move with it. Just as GP-B will detect a change in orientation due to the spacecrafts orbit around the earth (seen as a 97 minute wave), and due to the earth’s orbit around the sun (a longer waveform), so too will it detect a change due to the solar system’s change in angular velocity relative to the guide star. I don’t see how it could be any other way. Of course, the later signal probably looks like noise (thought to be polhode or something else) because the short period of the experiment relative to the long wave makes that form difficult to see. All I’m saying is don’t throw out the baby with the bathwater until we know what is hiding in that bathwater.

Re: electrostatic patches. I don't know enough about this to offer an opinion. But I would start with the assumption that those $800 million gyros have done their job and probably picked up real signals far more subtle than we can imagine. EOP is still a science in progress.

Garth

Dec4-09, 08:10 AM

As the SS curves through space the spacecraft, in orbit around the earth, must move with it. Just as GP-B will detect a change in orientation due to the spacecrafts orbit around the earth (seen as a 97 minute wave), and due to the earth’s orbit around the sun (a longer waveform), so too will it detect a change due to the solar system’s change in angular velocity relative to the guide star.

The "solar system’s change in angular velocity relative to the guide star" will be caused by its motion around the galaxy, I have dealt with the motion of the galaxy itself above (it is negligible).

Orbiting the galaxy would cause a geodetic precession of

(\frac{M_G}{M_E})^\frac{3}{2}(\frac{R_E}{R_G})^\fr ac{5}{2} \times 8 \text{arcsecs/yr }

(See MTW 'Gravitation' page 1119 eq 40.35)

i.e. about 10-8 arcsecs per year.

I think this can also be safely ignored!

Garth

Garth

Mar4-10, 06:10 AM

The is a general point here that is being overwhelmed by the discussion of a hypothetical solar companion star.

To save further confusion and time wasting I will re-iterate it.

It is this. If other effects such as poholde and perturbing forces are eliminated then gyros 'point in a constant direction' in space. The curvature of the space-time around the Earth cause two effects on that 'constant direction' that was measured by GP-B, the geodetic and frame-dragging precessions.

The direction of the GP-B gyros axes was referenced to a distant quasar.

All motions of the Earth around the Sun, the Sun around a possible companion, the Sun around the galaxy and the galaxy through space would add up to around 10-3c, as that guide quasar is approximately 1010 light years away then all motions create a parallax of no more than OOM 10-13 rad i.e. ~ 10 -5 milliarcsecs, far smaller than those caused by the curvature of the Earth and Sun's gravitational field that were measured by the experiment.

They can be safely ignored as negligible.

Garth

maurol2

Mar4-10, 06:26 PM

It is this. If other effects such as poholde and perturbing forces are eliminated then gyros 'point in a constant direction' in space. The curvature of the space-time around the Earth cause two effects on that 'constant direction' that was measured by GP-B, the geodetic and frame-dragging precessions.

So, the direction at which the gyroscopes point is not constant, but subjected to, at least, two effects: geodetic and frame-dragging precessions.

Now, imagine for a moment that the movement of the solar system towards the solar apex has an actually unknown characteristic that causes precession in the same way as either geodetic or frame-dragging. I'm not saying that these are geodetic/frame-dragging effects, just that they behave similarly, affecting the orientation of the gyroscopes, that of the earth, and that of the rest of the solar system.
Suppose that this precession is a small component of what we consider to be the known axial precession due to lunisolar causes, as Polestar101 suggested.
Now, when you send a probe to the space to measure small precession effects predicted by GR, your gyroscopes start behaving in an unexpected way.
That's what Polestar101 is saying, if I understood correctly. And I think that that's a possibility that clearly deserves a closer scrutiny.

All motions of the Earth around the Sun, the Sun around a possible companion, the Sun around the galaxy and the galaxy through space would add up to around 10-3c, as that guide quasar is approximately 1010 light years away then all motions create a parallax of no more than OOM 10-13 rad i.e. ~ 10 -5 milliarcsecs, far smaller than those caused by the curvature of the Earth and Sun's gravitational field that were measured by the experiment.

Those are the known, small effects, predicted by GR. Imagine for a moment that there actually are unknown effects, whose causes are being mistaken in the GP-B experiment.

Mauro

sylas

Mar4-10, 11:55 PM

You can't simply eliminate polhode and other perturbing forces to save the experiment without first being able to exactly quantify these effects. And to try and measure them by eliminating anything that does not get to the GR goal is circular reasoning and bad science.

This doesn't make any sense at all. They DO quantify the podhole effect. It was quantified and understood and taken into account from the start. There is an additional effect which was stronger than anticipated; from a tiny residual change on the gyroscopes, which gives an additional effect on the motions. There is no doubt at all that this effect exists. Most of the work of the extended data analysis phase HAS been to quantify this effect -- and not by assumption. When quantified, it can be extracted to reveal any underlying signal.

This is an extra factor influencing the gyroscopes which was larger than anticipated, and has been at the root of the limited accuracy to which results could be given.

The description by Polestar101 is very misleading. It's not bad science at all -- it is precisely what science should do to test GR as well as they can without making assumptions. They quantify all influences and obtain the residual signal, which stands then as a test of the predictions from the frame-dragging effect. There is no assumption of GR involved in that process. Without the proper quantification of the electromagnetic forces, the accuracy of the test is very weak. With proper quantification, the test will improve, though it is unlikely to get to the level of 1% which had originally been hoped.

There's a nice summary of the issues in The Gravity Probe B Bailout (http://spectrum.ieee.org/aerospace/space-flight/the-gravity-probe-b-bailout), IEEE Spectrum, Oct 2008. This report is describing how the team was able to secure additional funding; and their own project page gives more on the existing funding. (Gravity Probe B -- current status -- updated November 12, 2009 (http://einstein.stanford.edu/highlights/status1.html). The work is ongoing, and primarily this is focused upon quantifying the effects of the electromagnetic influences, so that they can be properly take into account -- without just making assumption -- and so improving the accuracy of the true independent test of GR.

Garth

Mar5-10, 02:26 AM

cristo

Mar6-10, 05:52 PM

Offtopic posts have been removed, mostly to here. Please keep this thread on the topic of comparing published theories that have made proper predictions for the Gravity Probe B experiment.

maurol2

Mar6-10, 07:14 PM

Offtopic posts have been removed, mostly to here. Please keep this thread on the topic of comparing published theories that have made proper predictions for the Gravity Probe B experiment.

I've noticed that you've deleted my last reply to Garth, in the name of "topicness". Do as you please. I couldn't care less, except to mention that I don't see why you didn't removed Garth's last comment too. He was the one which initiated that avenue towards "offtopicness", so to speak, presuming about the geometrical migth of GR.

JonathanK

Mar20-10, 09:26 AM

Hello Garth and all,

I just want to point out that strictly because of the very nature of this thread Garth you're not in a position to say "It is this curvature of space-time that cause the geodetic precession and frame-dragging effects that GP-B measured."

There may be other theories apart from mine, on the list of theories that are still viable in the light of the results, that give conceptual interpretations other than curvature for the measured effects.

But whether or not others do it, PSG certainly does. Equation 3 of the second paper on PSG published in a peer reviewed journal, here
http://journalgp.awardspace.com/journal/0202/020203.pdf

generates the curvature component of the geodetic effect from flat space, simply from assuming that an effect like a refractive medium slows matter in the same way as it slows light. That's 2/3 of the effect potentially explained, and because the other 1/3 doesn't require curvature, the equation works as a proof that curvature doesn't necessarily have to be the cause. (Wikipedia, nevertheless, still defines the geodetic effect as a direct result of curvature.)

You checked the equation, found it gives the right numbers, and then put PSG back on the list of viable theories, after more than a year off it. The reason it deserved to go back on the list was that the only premiss that went into the equation was the original starting premiss of PSG, ie that light and matter are slowed by sqrt(1 - [2GM/rc^2]) in a gravity field. (So the equation vindicated the theory, and showed that in the earlier prediction I was wrong, but PSG wasn't.)

Sorry to restate this, but it seems directly relevant to what you've said about the interpretation of the results. (BTW, have been hoping to get back in touch anyway.)

Best wishes, Jonathan Kerr

maurol2

Mar21-10, 08:49 AM

But whether or not others do it, PSG certainly does. Equation 3 of the second paper on PSG published in a peer reviewed journal, here
http://journalgp.awardspace.com/journal/0202/020203.pdf

generates the curvature component of the geodetic effect from flat space, simply from assuming that an effect like a refractive medium slows matter in the same way as it slows light. That's 2/3 of the effect potentially explained, and because the other 1/3 doesn't require curvature, the equation works as a proof that curvature doesn't necessarily have to be the cause. (Wikipedia, nevertheless, still defines the geodetic effect as a direct result of curvature.)

Very interesting. Are you suggesting that this is related also to the origin of the rotation of the planets, or I misunderstood/read too much?

Talking about the likely effect of refractive mediums, you might be interested in this 2003 paper by Consoli & Constanzo:
The motion of the Solar System and the Michelson-Morley experiment (http://arxiv.org/abs/astro-ph/0311576)

They re-analize the Michelson-Morley, Miller and other interferometry experiments, and show that in all cases a fringe shift is in fact detected, only its value is less than expected. They provide an excellent explanation for the differences, based on previous work by Kitto and Cahill, which goes back to Fresnel and the Fresnel drag coefficient.

I mention all this in this context due to a number of reasons:
- Consoli & Constanzo show that ether drag is dependant on the refractive index of the medium, and that this is the explanantion for the diverging results of the various interferometry experiments.
- They talk about a small similar effect caused by gravity, which resembles Fresnel drag, that will be equivalent to what you're proposing in your paper for 2/3 of the geodetic effect.

You might be interested also in this http://en.wikipedia.org/wiki/Aether_drag_hypothesis
and the linked references and papers. In particular those by D. Gezari.

Regards,
Mauro

JonathanK

Mar21-10, 12:34 PM

Hello,

Thanks for the references, if we discuss it in detail it should be elsewhere (or we'll find ourselves there anyway!). But to make something clear - I don't believe in an ether, that was disproved. The original ether was thought to behave rather like matter behaves - unconventional 'ethers' have carried on, but they're so different they shouldn't be called that. The electromagnetic field is an example.

PSG is a gravity theory that comes out of a theory of time, and has a conceptual basis that's different from others I've seen. The visual picture that led to both is in a book 'Motion through time: the missing piece of the puzzle'. Initially it looks at the question of whether the future is decided or undecided, and points out that relativity and quantum theory tell us opposite things on that. My solution does overlap with some other theories, including refractive medium theories, which according to mine are incomplete. Incidentally, my view has special relativity entirely right, except in the interpretation, which is incomplete anyway.

To answer your question about the axial rotation of the planets - although most of them rotate in the right direction, I doubt if either version of the geodetic effect could slowly spin up the planets. But if mine could then it's likely the GR version could as well, so the question lands comfortably within standard physics, and the best thing is probably to ask Garth..

Jonathan

maurol2

Mar21-10, 08:17 PM

Hello,

Thanks for the references, if we discuss it in detail it should be elsewhere (or we'll find ourselves there anyway!). But to make something clear - I don't believe in an ether, that was disproved. The original ether was thought to behave rather like matter behaves - unconventional 'ethers' have carried on, but they're so different they shouldn't be called that. The electromagnetic field is an example.

Oh, I don't believe either in a mechanical and material ether.
But in fact, I certainly do believe that reality is composed by more than matter. Particularly, I believe that there are fields and "forces" that have no material cause, but that interact with and affect matter.
Moreover: matter is just a manifestation of these fields and forces(a kind of condensation), under the right circumstances.
We may not know and observe these fields and forces today in a direct way, but we can start to know them by their effects. And the day will come when we'll be able to observe them directly again, in all their magnificence and harmony.
I also firmly believe that Science, in the great name and tradition that represents, must (and certainly will) study and incorporate these fields and forces into its subjects of study. And when I say Science I mean all the sciencies, from Physics to Biology, from the study of the mineral to the study of the living. Also the social sciences; and the most important study of all: the clear and real understanding of the human being and its true nature.

Garth

Mar22-10, 04:35 AM

Just a point: the geodetic effect is tiny unless you are dealing with an intense gravitational field, when the frame dragging effects would overwhelm it in the case of a rotating black hole, for example.

It is not responsible for the spinning up of the planets; that is due to the simply the conservation of angular momentum.

Unless a theory makes a specific prediction that is being tested by the GP-B experiment please post elsewhere.

Garth

maurol2

Aug15-10, 08:31 AM

Just a point: the geodetic effect is tiny unless you are dealing with an intense gravitational field, when the frame dragging effects would overwhelm it in the case of a rotating black hole, for example.

It is not responsible for the spinning up of the planets; that is due to the simply the conservation of angular momentum.

That can't be so simple, or it is incomplete, considering by example that Venus is slowly spinning in the opposite direction.
Electromagnetic effects will have to be taken into account, sooner or later, to explain this solar system anomaly, and also others.

Chronos

Aug16-10, 03:50 AM

maurol2

Aug16-10, 10:13 AM

Not at all, Venus could easily have been 'flipped' as the result of a past collision. The rotational axis of Uranus is similarly goofy, it points almost directly at the sun [re: http://www.windows2universe.org/our_solar_system/planets_table.html] and also has a slightly retrograde rotation. The former planet Pluto also suffers from this condition. Their current axial orientation is unrelated to how the planets acquired spin.

"Simply". "Easily". I'm dismayed by your fondness for "easy" explanations. "Easy" meaning, of course, that you can explain things (independently of how improbable these explanations really are) using standard physics and models.

Venus has a super-rotating atmosphere. That atmosphere circles the planet in around 4 (earth) days in a westward (Earth's west) direction. That is, most likely, the cause of the planet anomalous spin. The westward(Earth) spinning atmosphere gradually slowed down, and eventually reversed, the spin of the underlying solid planet, due to friction based momentum transfer.

Now, (and this independently if it is the cause of Venus's actual spin or not), we have to explain the reason for the atmosphere's super rotation. And to explain that it will be unavoidable to reckon with and take into account electromagnetic effects.

References:
http://en.wikipedia.org/wiki/Atmosphere_of_Venus
http://www.esa.int/SPECIALS/Venus_Express/SEMYGQEFWOE_0.html
http://www.physorg.com/news194504586.html

Polestar101

Aug17-10, 06:33 PM

You can always blame it on polhode motion : )

Chronos

Aug18-10, 12:44 AM

'Simple' explanations are usually more reliable than 'amazing' explanations, maurol2. Avoiding the issue I raised by injecting unrelated 'facts' does not rescue your 'amazing' model.

maurol2

Aug18-10, 08:32 AM

'Simple' explanations are usually more reliable than 'amazing' explanations, maurol2. Avoiding the issue I raised by injecting unrelated 'facts' does not rescue your 'amazing' model.

What issue do you raised? The fact that the standard model of solar system formation has a potential explanation for the anomalous rotation of some planets, involving one or multiple collisions, does not mean that other cause can be the one responsible.

Uranus, by example, could be a former extrasolar planet, acquired with that particular spin angle.
Or it could have been inclined by the combined tidal effects of Saturn and Jupiter, when they crossed their 1:2 resonance, like this paper suggests:
http://www.planetary.org/blog/article/00000553/
http://www.nature.com/nature/journal/v440/n7088/abs/nature04577.html
That would explain the migration of its satellites, by the way.

With regard to Venus, what I find amazing (without the quotes) is that Venus atmosphere is super rotating with westwards winds of around 200 m/s. Excuse me, but what's the "standard" explanation for that?

And with those continous and extremely strong winds I find plausible(if not obvious), they can be the real cause for Venus's actual spin.

The right thing to do would be to do the calculations, assuming an initial spin in accordance with Venus's position in its orbit, and testing for various atmospheric densities, velocity gradients, Venus's estimated age, etc. etc.

I don't have the time to do that, but maybe some other guy can do it. The hypothesis deserves some serious consideration and research. By the way, I don't think it is an amazing explanation, but a simple, elegant, and pretty obvious(if you think outside the standard box) one.

Finally: As far as I know, Venus's atmospheric super-rotation should be caused by the interaction between Venus's atmosphere and the solar wind. Here are some additional papers, which show a correlation between Earth's atmospheric Angular Momentum (AAM) and Solar Activity (SA). Interestingly, Earth's AAM is also retrograde in its general tendency, and of course, variations on Earth's AAM affect Length of Day (Length of Day) due to conservation of Angular Momentum:
http://adsabs.harvard.edu/abs/2004cosp...35.4731A
http://www.cgd.ucar.edu/cas/adai/papers/Abarca_delRio_etal_JGeodyn03.pdf

Best regards,
Mauro Lacy

maurol2

Aug18-10, 12:33 PM

What issue do you raised? The fact that the standard model of solar system formation has a potential explanation for the anomalous rotation of some planets, involving one or multiple collisions, does not mean that other cause can be the one responsible.

I meant: can't.

The right thing to do would be to do the calculations, assuming an initial spin in accordance with Venus's position in its orbit, and testing for various atmospheric densities, velocity gradients, Venus's estimated age, etc. etc.

I meant: Venus's position in the solar system (distance to the Sun)

Incidentally, a similar process can probably explain Mercury comparatively slow rotation rate.

Garth

Sep30-10, 06:52 AM

It is nearly a year since the last update of Mission Status on the GP-B website ( http://einstein.stanford.edu/highlights/status1.html) and while waiting for a final statement we note the existing published results are homing in on the GR prediction.

The gross GR prediction, including Solar GR effects and guide star motion is:
Geodetic (N-S) –6571 +/- 1 mas/yr and
Frame dragging (E-W) -75 +/1 1 mas /yr.

The average results over the 4 gyros is Geodetic = –6565 mas /yr i.e. within 0.1%,
and Frame dragging = -81 mas /yr i.e. within 8 % of the GR predictions.
These are consistent with GR to within the present experimental error bars.

Several of the alternative theories on the list I have compiled predict the same results as GR, therefore they fall into a different category to those that can be tested against GR by this experiment.

My news is that I have reviewed my theory (self-creation cosmology (http://arxiv.org/abs/1009.5862)) and republished. The field equation can be cast in three forms, as explained in my paper, the Einstein conformal frame, the effective Jordan conformal frame and the true Jordan frame. The standard Brans Dicke theory is cast in the effective Jordan frame as was my 2002 version with its heterodox prediction for GP-B. Cast in the true Jordan frame (JF) it makes the same GP-B prediction as GR and therefore has not been falsified by the experiment. [Note of explanation: In SCC as I now understand it the true JF is to be used for the behaviour of massive particles, i.e. the gyros of GP-B and the effective JF for massless particles, i.e. the behaviour of light.]

Einstein's General Relativity(GR)
Brans-Dicke theory (BD)
Moffat's Nonsymmetric Gravitational theory (http://arxiv.org/abs/gr-qc/0405091) (NGT)
Stanley Robertson's Newtonian Gravity theory (http://arxiv.org/abs/gr-qc/0502088) (NG),
F. Henry-Couannier's Dark Gravity theory (http://www.arxiv.org/abs/gr-qc/0610079) (DG).
Alexander and Yunes' prediction for the Chern-Simons (http://kr.arxiv.org/abs/hep-th/0703265v1) gravity theory (CS).
Kris Krogh's Wave Gravity theory (http://lanl.arxiv.org/abs/astro-ph/9910325) (WG)
Hongya Liu & J. M. Overduin prediction of the Kaluza-Klein ( http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v538n1/50681/50681.text.html?erFrom=5252751197746712308Guest#sc 8) gravity theory (KK).
Kerr's Planck Scale Gravity: Predictions of Experimental Results from a Gravity Theory (http://redshift.vif.com/JournalFiles/V14NO2PDF/V14N2KER.pdf) (PSG)
My Self Creation Cosmology (http://arxiv.org/abs/1009.5862) (SCC),

The predictions are now:

GP-B Geodetic gross precession (North-South).

GR = -6606 mas/yr.
BD = -(3\omega + 4)/(3\omega + 6) 6.606 arcsec/yr. where now \omega >60.
NGT = -(6606 - a small \sigma correction) mas/yr.
SCC = -6606 mas/yr.
NG = -6606 mas/yr.
DG = -6606 mas/yr.
CS = -6606 mas/yr.
WG = -6606 mas/yr.
KK = -(1 + b/6 - 3b2 + ...) 6606 mas/yr. where 0 < b < 0.07.
PSG = -6606 mas/yr.

GPB gravitomagnetic frame dragging gross precession (East-West).

GR = -39 mas/yr.
BD = -(2\omega + 3)/(2\omega + 4) 39 mas/yr.
SCC = -39 mas/yr.
NGT = -39 mas/yr.
NG = -39 mas/yr.
DG = 0 mas/yr.
CS = -39 mas/yr. + CS correction
WG = 0 mas/yr.
KK = -39 mas/yr.
PSG = -39 mas/yr.

Those theories being tested against GR by this experiment are:
BD – Brans Dicke theory; with \omega > 660.
KK - Kaluza-Klein gravity theory; with b < 1.5 x 10-4.
NGT – Nonsymmetric Gravitational theory; it depends on how ‘small’ the \sigma correction is!

The ones falsified by the present results are:
DG - Dark Gravity theory.
WG - Wave Gravity theory.

And the ones not tested against GR by this experiment, and are still consistent with GP-B are:
SCC - Self Creation Cosmology theory.
NG - Newtonian Gravity theory.
CS - Chern-Simons gravity theory.
PSG - Planck Scale Gravity theory.

Garth

JonathanK

Oct1-10, 10:56 AM

Thanks Garth,

Just to point out that the link you posted with PSG theory was the wrong one, it should be
http://journalgp.awardspace.com/journal/0202/020203.pdf

That's the paper (in a peer reviewed journal), "A derivation of the geodetic effect without space curvature", with the equation that shows a 'geodetic' effect with the same value as that of the GR curvature component - but being generated from flat space and using only the simple starting premiss of PSG theory. So that's the relevant link, as it shows why PSG theory is on the 'still consistent with GP-B' list, and gives the same result as GR.

Incidentally, the paper may be a first, in that it may be the first time an alternative interpretation for the geodetic effect (to the GR one) has been put forward on a mathematical basis. The generalised equation is for a single orbit around any mass.

thanks, Jonathan

Polestar101

Oct2-10, 01:03 AM

Garth

Oct2-10, 04:00 AM

Wish I shared your faith in the GP-B results. With so much unexpected noise (all of which needed to be properly accounted for and canceled out to have any chance of getting meaningful results) GP-B became more of an engineering project than a science experiment. Fortunately an objective panel of 15 scientists at NASA recognized the difference, pulled the funding and stated the truth; GP-B “failed to reach its goals”.

While subsequent attempts to engineer a solution were and are commendable they are highly suspect. Any methodology that relies on canceling out unanticipated “noise” by categorizing such unwanted effects as impossible to predict polhode motion (or anything else that is inherently unpredictable) negates the validity of the original science experiment. Good science relies on making and meeting predictions. Getting close to those predictions by “engineering” a preferred result is hardly science.

The only alternative theories that should be taken seriously are those that predicted the unwanted results without need to rely on cancellation of unpredictable signals.

Although I share your reservations and asked a question along similar lines to Francis Everitt about the error reduction at the April 2007 APS meeting, I have no doubt the signal did trace the GR prediction as can be seen here (http://einstein.stanford.edu/highlights/status1.html).

Francis Everitt's reply was that the one thing they mustn't do was perform the analysis with the answer (GR) in mind but try and make it as 'double blind' as possible. The procedure was to carry out the analysis in two teams using two different methods, an algebraic one and a geometric one, with both teams not knowing the proper motion of the guide star until they both came up with their answers. These were then compared for consistency and the proper motion then allowed for to get the result. Also the four gyros are analysed independently to help remove experimental errors by averaging.

Obviously then they have had to refine the process several times over the years to get to the latest published results so the further refinements would not have been 'double blind'.

They intended to complete all possible error reduction by this year and get a +/- 1 mas/yr accuracy ( an order of magnitude larger than originally hoped for), and unlesss they have succeeded in their aims and publish finally before the end of the year it may be that the present state of play is all they have been able to achieve, i.e. a ~ +/- 10 mas/yr (from the diagram of 50% error ellipses).

The level 2 data after preliminary processing is available here (http://nssdc.gsfc.nasa.gov/nmc/datasetDisplay.do?id=ASGR-00002) but does not mean much until "considerable further processing to calibrate the instrument, remove the effects of vehicle dynamics, aberration, guide star proper motion, small classical torques, and other systematic effects before any results about gyro orientation history can be determined".

"This refined processing of the data, which will result in a Level 3 data archive, is precisely what the GP-B team has been working on since October 2005" and they say will also be publicly available. I don't think I'll have the energy to sort through it to check it though! You might!!

Garth

maurol2

Feb12-11, 07:55 AM

[QUOTE=Garth;2911611]Although I share your reservations and asked a question along similar lines to Francis Everitt about the error reduction at the April 2007 APS meeting, I have no doubt the signal did trace the GR prediction as can be seen here (http://einstein.stanford.edu/highlights/status1.html).

Let's accept you (and the GP-B) team are right. Let's assume that after removing all the noise, the remaining effects agree with GR predictions. OK with that: GR accurately predicts the small effects of frame dragging and geodetic precession.

Now, wouldn't be interesting to analyze and try to understand how and from where all that unexpected noise came from? After more than five years, has nobody done that?
I for one, find the noise (and the reason it was completely unexpected) more interesting than the data, don't you think?

Do you have any info related to this? Specifically, to theories or studies done on the noise, not with the objective to remove or cancel it, but to understand it, along with its origin?

Regards,
Mauro

maurol2

Feb12-11, 08:08 AM

Do you have any info related to this? Specifically, to theories or studies done on the noise, not with the objective to remove or cancel it, but to understand it, along with its origin?

Of course, to be able to remove or cancel something, you must be able to understand it (to a certain degree, at least). Don't get me wrong. What I'm saying is: if these effects were standard and known, why were they so unexpected? And also: What's their cause? not in the sense of how they work and affect the results, but in the sense of from where they came from? What's their origin? Why these effects were not expected?

Thanks,
Mauro

Polestar101

Feb13-11, 03:01 PM

Mauro – That is exactly the right question: what motion produced the noise signals?

In order to isolate the geodetic effect and the very small GR effect, the GPB team needs to separate out a number of unwanted signals. The known ones are easy whereas the unknown ones are difficult to spot unless they have a short periodicity. The most obvious one, the well-known aberration of light due to the motion of the spacecraft’s regular orbit around the Earth (slightly changing the telescopes orientation to the guide star with each orbit), amounts to +-5” per orbit, and effectively acts as a calibration tool due to its short predictable periodicity. Another, the aberration of light due to the Earth’s annual orbit around the sun (carrying the spacecraft with it), may be less obvious because the Earth only went around the sun once during the GPB data collection period, and even this period was troubled with interrupted signals due to a number of stop and start issues. But it is a well-known effect, and quite large (+- 20.148”p/y), and therefore should also be readily identifiable.

If the Earth also has another motion, moving with the sun, curving through space due to solar system motion, producing the observable of the stars moving across the sky at about 50” p/y, then a very sensitive spacecraft orbiting the earth should pick up this motion. However, if the earth’s changing orientation to VLBI sources is simply due to a wobbling earth (as posited by current precession nutation theory which constrains ALL solar system motion to zero) then the GPB spacecraft, high above the so called wobbling earth, should not pick up any such signal. But the IAU has found that current precession theory is “inconsistent with dynamical theory” (IAU PO3), suggesting there is something very wrong with the current static sun precession theory. If some portion of the 50”p/y observable is indeed due to the motion of the solar system (as BRI data suggests) then the gyros should pick up this signal, unexpected under current theory. However, because the periodicity of this motion is so long (taking roughly 25,700 years to complete one cycle at the present rate) in relation to the data gathering period of the gyros, it would only reveal a tiny fraction of the waveform peak to trough during the life of the GPB experiment, and therefore it would show up as background drift rather than any obvious cycle. Nonetheless this effect will be fairly large, on the order of up to 50”p/y, if BRI is correct, thus making it immediately obvious that there is a lot of “noise” in the overall signal. This is what I think GPB found, but will we ever know it?

A methodology that is so intent on proving GR, that it effectively endorses a static solar system model, and eliminates noise without specifically identifying the source of all such unwanted noise, is not very objective in my opinion. Like you I have no problem with the existence of GR. It is the integrity of the process, one that may have thrown the baby out with the bathwater (proving solar system motion), and lost the support of NASA and many objective scientists along the way, that is so troublesome.

Garth

May19-11, 03:07 AM

Final Results Published - after 5 years of analysis!

Summary of Final GP-B Experimental Results (http://einstein.stanford.edu/highlights/status1.html)
GP-B STATUS UPDATE — May 4, 2011
After 31 years of research and development, 10 years of flight preparation, a 1.5 year flight mission and 5 years of data analysis, our GP-B team has arrived at the final experimental results for this landmark test of Einstein’s 1916 general theory of relativity. Here is the abstract from our PRL paper (see next section) summarizing the experimental results.

Gravity Probe B, launched 20 April 2004, is a space experiment testing two fundamental predictions of Einstein's theory of General Relativity (GR), the geodetic and frame-dragging effects, by means of cryogenic gyroscopes in Earth orbit. Data collection started 28 August 2004 and ended 14 August 2005. Analysis of the data from all four gyroscopes results in a geodetic drift rate of -6,601.8±18.3 mas/yr and a frame-dragging drift rate of -37:2±7.2 mas/yr, to be compared with the GR predictions of -6,606.1 mas/yr and -39.2 mas/yr, respectively ('mas' is milliarc-second; 1 mas= 4.848 X10-9 radians or
2.778 X10-7 degrees).

The table and diagram below show the individual gyroscope results, the weighted average results for all four gyroscopes combined, and the theoretical predictions for both effects from Einstein's general theory of relativity, as calculated by Stanford physicist, Leonard Schiff.

Note: The individual and combined statistical uncertainties are corrected for the "over" and "under" dispersion using the Χ2 of the individual estimates in the N-S and W-E directions. Please see our PRL paper (next section below) for more detailed information about these results and their derivation.

Gravity Probe B — Final Experimental Results

rN-S (Geodetic Measurement) rW-E (Frame-Dragging Measurement)

Gyroscope #1 -6,588.6±31.7 mas/yr -41.3±24.6 mas/yr
Gyroscope #2 -6,707.0±64.1 mas/ yr -16.1±29.7 mas/yr
Gyroscope #3 -6,610.5±43.2 mas/yr -25.0±12.1 mas/yr
Gyroscope #4 -6,588.7±33.2 mas/yr -49.3±11.4 mas/yr

Weighted-Average Results for All Four Gyroscopes
All Gyroscopes -6,601.8±18.3 mas/yr -37.2±7.2 mas/yr

Schiff-Einstein Predicted Theoretical Values
Theoretical Gyroscope -6,606.1 mas/yr -39.2 mas/yr

The results are consistent with GR and also those theories that are not tested against GR by this experiment because they make the same Geodetic and frame-dragging predictions.

The list that I had compiled now looks like this (no change from the last summary):

Einstein's General Relativity(GR)
Brans-Dicke theory (BD)
Moffat's Nonsymmetric Gravitational theory (http://arxiv.org/abs/gr-qc/0405091) (NGT)
Stanley Robertson's Newtonian Gravity theory (http://arxiv.org/abs/gr-qc/0502088) (NG),
F. Henry-Couannier's Dark Gravity theory (http://www.arxiv.org/abs/gr-qc/0610079) (DG).
Alexander and Yunes' prediction for the Chern-Simons (http://kr.arxiv.org/abs/hep-th/0703265v1) gravity theory (CS).
Kris Krogh's Wave Gravity theory (http://lanl.arxiv.org/abs/astro-ph/9910325) (WG)
Hongya Liu & J. M. Overduin prediction of the Kaluza-Klein ( http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v538n1/50681/50681.text.html?erFrom=5252751197746712308Guest#sc 8) gravity theory (KK).
Kerr's Planck Scale Gravity: Predictions of Experimental Results from a Gravity Theory (http://redshift.vif.com/JournalFiles/V14NO2PDF/V14N2KER.pdf) (PSG)
My Self Creation Cosmology (http://arxiv.org/abs/1009.5862) (SCC),

The predictions are now:

GP-B Geodetic gross precession (North-South).

GR = -6606 mas/yr.
BD = -(3\omega + 4)/(3\omega + 6) 6.606 arcsec/yr. where now \omega >60.
NGT = -(6606 - a small \sigma correction) mas/yr.
SCC = -6606 mas/yr.
NG = -6606 mas/yr.
DG = -6606 mas/yr.
CS = -6606 mas/yr.
WG = -6606 mas/yr.
KK = -(1 + b/6 - 3b2 + ...) 6606 mas/yr. where 0 < b < 0.07.
PSG = -6606 mas/yr.

GPB gravitomagnetic frame dragging gross precession (East-West).

GR = -39 mas/yr.
BD = -(2\omega + 3)/(2\omega + 4) 39 mas/yr.
SCC = -39 mas/yr.
NGT = -39 mas/yr.
NG = -39 mas/yr.
DG = 0 mas/yr.
CS = -39 mas/yr. + CS correction
WG = 0 mas/yr.
KK = -39 mas/yr.
PSG = -39 mas/yr.

Those theories being tested against GR by this experiment are:
BD – Brans Dicke theory; with \omega > 660.
KK - Kaluza-Klein gravity theory; with b < 1.5 x 10-4.
NGT – Nonsymmetric Gravitational theory; it depends on how ‘small’ the \sigma correction is!

And the ones not tested against GR by this experiment, and are still consistent with GP-B are:
SCC - Self Creation Cosmology theory.
NG - Newtonian Gravity theory.
CS - Chern-Simons gravity theory.
PSG - Planck Scale Gravity theory.

Despite the disparaging remarks made the reason the NASA funding was withheld in the final stage was because the funds had run dry, with the cut backs etc. not because they thought the result was untrustworthy. The extra error reduced the final accuracy to that originally hoped for but it had been modeled by two independent methods and the methodology was not intent on proving GR but making an unbiased and independent set of measurements.

The problems with the experiment have been openly discussed, the only problem being IMHO is that should the results have been different from GR then the rest of the GR world would have had found it difficult to accept them.

Garth

TrickyDicky

May19-11, 06:08 AM

Final Results Published - after 5 years of analysis!

Summary of Final GP-B Experimental Results/url]

The results are consistent with GR and also those theories that are not tested against GR by this experiment because they make the same Geodetic and frame-dragging predictions.

The list that I had compiled now looks like this (no change from the last summary):

Einstein's General Relativity(GR)
Brans-Dicke theory (BD)
Moffat's [url=http://arxiv.org/abs/gr-qc/0405091]Nonsymmetric Gravitational theory (http://einstein.stanford.edu/highlights/status1.html) (NGT)
Stanley Robertson's Newtonian Gravity theory (http://arxiv.org/abs/gr-qc/0502088) (NG),
F. Henry-Couannier's Dark Gravity theory (http://www.arxiv.org/abs/gr-qc/0610079) (DG).
Alexander and Yunes' prediction for the Chern-Simons (http://kr.arxiv.org/abs/hep-th/0703265v1) gravity theory (CS).
Kris Krogh's Wave Gravity theory (http://lanl.arxiv.org/abs/astro-ph/9910325) (WG)
Hongya Liu & J. M. Overduin prediction of the Kaluza-Klein ( http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v538n1/50681/50681.text.html?erFrom=5252751197746712308Guest#sc 8) gravity theory (KK).
Kerr's Planck Scale Gravity: Predictions of Experimental Results from a Gravity Theory (http://redshift.vif.com/JournalFiles/V14NO2PDF/V14N2KER.pdf) (PSG)
My Self Creation Cosmology (http://arxiv.org/abs/1009.5862) (SCC),

The predictions are now:

GP-B Geodetic gross precession (North-South).

GR = -6606 mas/yr.
BD = -(3\omega + 4)/(3\omega + 6) 6.606 arcsec/yr. where now \omega >60.
NGT = -(6606 - a small \sigma correction) mas/yr.
SCC = -6606 mas/yr.
NG = -6606 mas/yr.
DG = -6606 mas/yr.
CS = -6606 mas/yr.
WG = -6606 mas/yr.
KK = -(1 + b/6 - 3b2 + ...) 6606 mas/yr. where 0 < b < 0.07.
PSG = -6606 mas/yr.

GPB gravitomagnetic frame dragging gross precession (East-West).

GR = -39 mas/yr.
BD = -(2\omega + 3)/(2\omega + 4) 39 mas/yr.
SCC = -39 mas/yr.
NGT = -39 mas/yr.
NG = -39 mas/yr.
DG = 0 mas/yr.
CS = -39 mas/yr. + CS correction
WG = 0 mas/yr.
KK = -39 mas/yr.
PSG = -39 mas/yr.

Those theories being tested against GR by this experiment are:
BD – Brans Dicke theory; with \omega > 660.
KK - Kaluza-Klein gravity theory; with b < 1.5 x 10-4.
NGT – Nonsymmetric Gravitational theory; it depends on how ‘small’ the \sigma correction is!

And the ones not tested against GR by this experiment, and are still consistent with GP-B are:
SCC - Self Creation Cosmology theory.
NG - Newtonian Gravity theory.
CS - Chern-Simons gravity theory.
PSG - Planck Scale Gravity theory.

Despite the disparaging remarks made the reason the NASA funding was withheld in the final stage was because the funds had run dry, with the cut backs etc. not because they thought the result was untrustworthy. The extra error reduced the final accuracy to that originally hoped for but it had been modeled by two independent methods and the methodology was not intent on proving GR but making an unbiased and independent set of measurements.

The problems with the experiment have been openly discussed, the only problem being IMHO is that should the results have been different from GR then the rest of the GR world would have had found it difficult to accept them.

Garth

But that last remark should also work then the other way, at least for frame-dragging effect, given the large errors of the 4 gyroscopes, from a non-biased POV results compatible with the frame-dragging prediction should also then be difficult to accept.

Of the 4 gyroscopes (centering on the frame-dragging effect) 3 of them (#1,#2, and #3) show errors that admit values compatible with predictions closer to 0 mas/yr than to the -39 mas/yr prediction. One of them (#2) is compatible with a null result. Gyroscope #4 is compatible with -60.6 mas/yr . And these are the numbers achieved after more than 5 years of fitting the raw results to something tolerable.
IMHO, GPB experiment, in the case of the geodetic effect confirms it with little room to doubt of its existence (this had been pretty much been settled by other experiments, but in the case of the Lense-Thirring effect this results are of course compatible with GR but also compatible with very different predictions, including a null effect, and given the error margins wrt the smallness of the effect and the disparity among the 4 gyroscopes, the experiment can't be used either to confirm or reject the effect.
The experiment of course wasn't designed to prove GR, no experiment can do that. It could only falsify or confirm predictions of GR, it confirmed the geodetic effect, and it neither confirmed nor falsify the Lense-Thirring effect due to the lack of accuracy obtained by the gyroscopes.
Apparently all theories but DG and WG are compatible with GBP results, even those two are compatible with the results of one of the 4 gyroscopes.

Polestar101

May20-11, 12:48 AM

Is there a detailed analysis available that explains how they canceled out each of the 50 plus unwanted signals? I am particularly interested to learn how they canceled out the "unpredictable" polhode noise and other "unidentified" signals. Presumably there will be some follow-up report that provides this data?

JonathanK

May26-11, 10:40 AM

Thanks Garth, and perhaps I should say thanks from all of us for what you've done on this over the last few years.

NB. The predictions you posted for my theory PSG are correct, but not the link to them, which is here http://journalgp.awardspace.com/journal/0202/020203.pdf
'A derivation of the geodetic effect without space curvature'.

I agree with the point made above that the geodetic effect result from GP-B is on much more solid ground than that for frame dragging. Best wishes to all.

Garth

Jun2-11, 06:41 AM

Thank you Jonathan, the Final results have today been published in Physical Review Letters, which you may access through the GP-B website: Gravity Probe B: Final Results of a Space Experiment to Test General Relativity (http://einstein.stanford.edu/content/sci_papers/papers/PhysRevLett.106.221101.pdf) and a Viewpoint article by Professor Will: Finally, results from Gravity Probe B (http://einstein.stanford.edu/content/press-media/results_news_2011/C_Will-Physics.4.43-Viewpoint.pdf).

In reply to Polestar101 I quote from Professor Will's article for a summary: However, three important, but unexpected, phenomena were discovered during the experiment that affected the accuracy of the results.

First, because each rotor is not exactly spherical, its principal axis rotates around its spin axis with a period of several hours, with a fixed angle between the two axes. This is the familiar “polhode” period of a spinning top and, in fact, the team used it as part of their analysis to calibrate the SQUID output. But the polhode period and angle of each rotor actually decreased monotonically with time, implying the presence of some damping mechanism, and this significantly complicated the calibration analysis. In addition, over the course of a day, each rotor was found to make occasional, seemingly random “jumps” in its orientation—some as large as 100 milliarcseconds. Some rotors displayed more frequent jumps than others. Without being able to continuously monitor the rotors’ orientation, Everitt and his team couldn’t fully exploit the calibrating effect of the stellar aberration in their analysis. Finally, during a planned 40-day, endof-mission calibration phase, the team discovered that when the spacecraft was deliberately pointed away from the guide star by a large angle, the misalignment induced much larger torques on the rotors than expected. From this, they inferred that even the very small misalignments that occurred during the science phase of the mission induced torques that were probably several hundred times larger than the designers had estimated.

What ensued during the data analysis phase was worthy of a detective novel. The critical clue came from the calibration tests. Here, they took advantage of residual trapped magnetic flux on the gyroscope. (The designers used superconducting lead shielding to suppress stray fields before they cooled the niobium coated gyroscopes, but no shielding is ever perfect.) This flux adds a periodic modulation to the SQUID output, which the team used to figure out the phase and polhode angle of each rotor throughout the mission. This helped them to figure out that interactions between random patches of electrostatic potential fixed to the surface of each rotor, and similar patches on the inner surface of its spherical housing, were causing the extraneous torques. In principle, the rolling spacecraft should have suppressed these effects, but they were larger than expected. The patch interactions also accounted for the “jumps”: they occurred whenever a gyro’s slowly decreasing polhode period crossed an integer multiple of the spacecraft roll period. What looked like a jump of the spin direction was actually a spiraling path—known to navigators as a loxodrome. The team was able to account for all these effects in a parameterized model.

The original goal of GP-B was to measure the frame-dragging precession with an accuracy of 1%, but the problems discovered over the course of the mission dashed the initial optimism that this was possible. Although Everitt and his team were able to model the effects of the patches, they had to pay the price of the increase in error that comes from using a model with so many parameters. The experiment uncertainty quoted in the final result—roughly 20% for frame dragging—is almost totally dominated by those errors. Nevertheless, after the model was applied to each rotor, all four gyros showed consistent relativistic precessions (Fig. 1, bottom). Gyro 2 was particularly “unlucky”—it had the largest uncertainties because it suffered the most resonant jumps.

A full description of the analysis may be found here Post Flight Analysis — Final Report (http://einstein.stanford.edu/content/final_report/GPB_FinalPFAR-091907-prnt.pdf)

Garth

Polestar101

Jun2-11, 05:04 PM

Thanks for the excerpt from Professor Wills (head of review board) who has looked at many of the efforts the team has gone through in trying to identify and separate the various unexpected sources of noise. His own work depends on Einstein’s GR, so it is not surprising that he would support the conclusions, nonetheless he was very clear that a lot of assumptions were made in arriving at the final conclusions.

It is impossible to know if all the assumptions in the parameterized model are ideal for properly categorizing and canceling each noise without knowing for certain the source of each unwanted signal, but the GPB team seems to have done the best they could based on the circumstances.

The inability to continuously monitor the rotors’ orientation meant the stellar aberrations could not be utilized as calibrating tools (as planned) hints at the amount of noise in the overall experiment. But even attempting to use the diurnal and annual aberrations as the main calibration tools shows the experimenters did not plan on accounting for any solar system motion relative to the guide star – meaning they essentially used a static solar system model.

The issue I would still like to understand is if any of the “noise” might be evidence of solar system motion. If for example we discovered the solar system is just slightly accelerating, then it might explain the anomalous acceleration of Pioneer 10 and 11 and possibly shed light on the unexplained force (http://www.space.com/5037-nasa-baffled-unexplained-force-acting-space-probes.html) acting on our spacecraft flybys (Galileo, NEAR, Rosetta, Cassini, etc.), that could theoretically be explained by an accelerating solar system.

Maybe what Everitt calls “strange anomalous torques” are not all “criminals”, as he put it? The point is it probably makes sense to very carefully examine all the assumptions behind the unwanted cancelled-out noise to make sure we didn’t eliminate something even more fundamental than GR, that is, solar system motion.