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## Alternative theories being tested by Gravity probe B

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.
 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
 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

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 Quote by jgraber 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 thread!

The fact that other viable alternative gravitational/cosmological theories are also being tested by GP-B, such as SCC, 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
 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 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

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 Quote by jgraber 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
Try Will's: The Confrontation between General Relativity and Experiment or my: Resolving the Degeneracy: Experimental tests of the New Self Creation Cosmology and a heterodox prediction for Gravity Probe B for an alternative model.

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

Garth

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Halfway through Phase II!

The latest release from the Gravity Probe B 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
 Recognitions: Homework Help Science Advisor 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/testappl...etGravity.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

 Quote by Garth 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).(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). 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! Garth
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
 Recognitions: Homework Help Science Advisor 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/testappl...etGravity.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

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 Quote by rusty 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

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 Quote by rusty 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
rusty has MMR been published in a peer reviewed journal?

If not you can publish it here in the Independent Research Forum and we can discuss it.

Garth

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Now into Phase III of the data analysis of Gravity Probe B.
 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
 Recognitions: Gold Member Science Advisor While we are waiting you may be interested in Francis Everitt's lecture:Testing Einstein in Space: The Gravity Probe B Mission dated 18 May 2006. Garth

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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/highlig...ode_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/highlig...indexmain.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

Roll on April!

Garth

 Quote by Garth 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).(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). 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! Garth
Thanks Garth for this interesting overview. I printed out your table and will look at it again when the Gravity Probe B results are available .
What is actually the main motivation for inventing alternative theories to GR ?
What are their main "advantages" ?

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 Quote by notknowing 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 $\Lambda$CDM 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
 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