Alternative theories being tested by Gravity probe B

[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

 

[Garth]

The wait for the results continues into this and next new year! GP-B MISSION NEWS—NASA REPORT & DATA ANALYSIS PROCEEDING AS PLANNED

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]

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]

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

 

[Garth]

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 realize.

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 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)

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 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]

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 website that does a good job of explaining why GR expects this beyond just saying “because of GR space-time curvature”.

Thanks
RB

 

[wolram]

Congratulations Garth, i think.

 

[Garth]

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?

Garth

 

[RandallB]

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]

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 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]

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]

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 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]

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 anyone know what the other is talking about.

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

 

[Garth]

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 anyone 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]

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]

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]

Latest news of the GP-B 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!

Garth

 

[Chronos]

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]

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?

Jim

 

[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.

Jim

 

[Garth]

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.

Jim

You'll find quite an exchange on the use of the word(s) "believe" (actually belief) in the https://www.physicsforums.com/showthread.php?t=1128208 thread!

The fact that other viable alternative gravitational/cosmological theories are also being tested by GP-B, such as V[/URL], 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 [url=http://arxiv.org/abs/astro-ph/0603064]Cold Dark Matter as Compact Composite Objects[/url] [quote]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.[/quote]

It also seems that an [url=https://www.physicsforums.com/showthread.php?t=94479]Age Problem[/url] 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]

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?

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

 

[Garth]

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

 

[CarlB]

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]

Another prediction for the gpb, based on mass-metric relativity.

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

 

[CarlB]

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]

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]

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

 

[Garth]

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

 

[Garth]

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

 

[Garth]

Polhode motion?

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

Roll on April!

Garth

 

[notknowing]

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" ?

 

[Garth]

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

 

[henryco]

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]

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 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 (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) and
F. Henry-Couannier's Dark Gravity Theory (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.Three months to go, whatever those results may be!


Garth