Alternative theories being tested by Gravity probe B

Garth

Quote by JonathanK

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 (NGT)
Stanley Robertson's Newtonian Gravity Theory (NG),
F. Henry-Couannier's Dark Gravity Theory (DG).
Alexander and Yunes' prediction for the Chern-Simons gravity theory (CS).
Kris Krogh's Wave Gravity Theory (WG)
Hongya Liu & J. M. Overduin prediction of the Kaluza-Klein gravity theory (KK).
Kerr's Planck Scale Gravity: Predictions of Experimental Results from a Gravity Theory (PSG)

The predictions are now:

GP-B Geodetic gross precession (North-South).

GR = -6606 mas/yr.
BD = -[itex](3\omega + 4)/(3\omega + 6)[/itex] 6.606 arcsec/yr. where now [itex]\omega[/itex] >60.
NGT = -(6606 - a small [itex]\sigma[/itex] 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 = -[itex](2\omega + 3)/(2\omega + 4)[/itex] 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.

The pertinent slides are slide 3: Seeing General Relativity Directly
and the slide: RNS vs RWE Algebraic 4-Gyro Joint Estimates

These last two slides clearly show an inconsistency with the GR prediction at the 1 [itex]\sigma[/itex] confidence level.

Einstein expectation:
-6571 [itex]\pm[/itex] 1* mas
4-gyro result (1 [itex]\sigma[/itex]) for 85 days (12 Dec 04 -- 4 Mar 05)
-6632 [itex]\pm[/itex] 43 mas

(* -6606 mas + 7 mas (solar geodetic) + 28 [itex]\pm[/itex]1 mas (guide star proper motion))

We note that this 07 November 1[itex]\sigma[/itex] confidence level result is inconsistent with all the above geodetic predictions except KK, but nobody takes any notice until at least 3[itex]\sigma[/itex]!

Garth

JonathanK

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

Gravity Probe B 2009 interim results are arived!!

Garth

Current Mission Status

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 (Dec 2008).

Garth

Garth

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

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

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

Quote by Garth

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.

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

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

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

Quote by Garth

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).

Quote by Garth

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

Quote by Polestar101

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, in Proceedings of the International Astronomical Union, 3, pp 190-191; doi:10.1017/S1743921308019005.

Cheers -- sylas

Ich

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

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.

I was at the 2007 APS meeting in Jacksonville to hear the first results of the experiment and asked the question of Francis Everitt specifically about the desire to find the GR effects affecting the modelling of the noise and hence not finding new physics. Francis emphatically stated that that was what they were not doing but modelling the errors in an independent (actually two independent) ways.

The annual aberration of light effect is described here:The Annual Aberration Signal. It seemed to confirm the orbital aberration effect.

As far as the difficulty of modelling polhode motion, and no real sphere is ever perfect and free from such effect, they have spent four years now on the problem and so they would probably agree with your statement

Polhode motion is an extremely tricky thing to quantify and predict !

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!

Edit: Crossed post with both sylas and Ich.

Garth

Polestar101

Quote by Garth

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.

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.

Quote by Garth

The annual aberration of light effect is described here:The Annual Aberration Signal. 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.

Quote by Garth

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

Quote by Polestar101

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

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

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

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