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Alternative theories being tested by Gravity probe B 
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#19
Mar706, 03:52 AM

P: 59

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


#20
Mar706, 04:04 AM

P: 59

I should have googled first. Apparently it tests gamma and alphaone ( a nonconservative 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 


#21
Mar706, 07:00 AM

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PF Gold
P: 3,273

The fact that other viable alternative gravitational/cosmological theories are also being tested by GPB, 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 All the more reason to keep an open mind and continue to confirm our "beliefs" with experimental verification. We live in interesting times! Garth 


#22
Mar706, 08:26 AM

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PF Gold
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They both use the parameterized postNewtonian (PPN) analysis. Garth 


#23
May506, 06:05 AM

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PF Gold
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Halfway through Phase II!
The latest release from the Gravity Probe B website. Garth 


#24
Jul1206, 01:09 AM

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


#25
Jul2106, 10:17 AM

P: 2

R.L. Collins 


#26
Jul2206, 01:05 AM

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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 inversesquare 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 [tex]1/\alpha =1+GM/rc^2[/tex]. 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 [tex](\gamma/\alpha)^3[/tex], 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 [tex]10^9[/tex] g level. Gravitationallyinfluenced space remains Euclidean, but the massmetric 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 


#27
Jul2406, 11:39 AM

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PF Gold
P: 3,273

Note: 1. The first effect being tested is (for the GPB polar orbit) a NS geodetic precession, caused by the amount a gyro 'leans' over into the slope of curved space. 2. The second effect being tested is the EW framedragging, LenseThirring, or gravitomagnetic effect, caused by the spinning Earth dragging spacetime around with it. Einstein's General Relativity(GR) Barber's Self Creation Cosmology).(SCC), Moffat's Nonsymmetric Gravitational Theory (NGT), HaiLong Zhao's mass variance SR theory (MVSR), Stanley Robertson's Newtonian Gravity theory (NG), and Junhao & Xiang's Flat spacetime theory (FST). R. L. Collin's Massmetric relativity (MMR) The predictions are: 1. GPB Geodetic precession GR = 6.6144 arcsec/yr SCC = 4.4096 arcsec/yr NGT = 6.6144  a small [itex]\sigma[/itex] 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 


#28
Jul2406, 11:59 AM

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


#29
Sep1506, 03:57 PM

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#30
Sep2006, 11:27 AM

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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 


#31
Dec2306, 04:06 AM

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Gravity Probe B Update  December 22, 2006
Roll on April! Garth 


#32
Dec3106, 02:58 AM

P: 185

What is actually the main motivation for inventing alternative theories to GR ? What are their main "advantages" ? 


#33
Dec3106, 04:35 AM

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PF Gold
P: 3,273

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 GPB 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 [itex]\Lambda[/itex]CDM model IMHO are its necessity to invoke Inflation, exotic nonbaryonic 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 


#34
Jan807, 05:16 AM

P: 38

Dear all,
Just to mention that there is another alternative theory of gravity (mine: grqc/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 GPB accuracy) angular deviation during the year but with a one year period (related to the the speed of earth about the sun). regards, F HC 


#35
Jan807, 10:24 AM

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PF Gold
P: 3,273

Thank you Frederic henryco and welcome to these Forums! Join the club of those waiting for the GPB 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), HaiLong Zhao's Mass Variance SR Theory (MVSR), Stanley Robertson's Newtonian Gravity Theory (NG), and Junhao & Xiang's Flat SpaceTime Theory (FST). R. L. Collin's MassMetric Relativity (MMR) and F. HenryCouannier's Dark Gravity Theory (DG). The predictions are: 1. GPB Geodetic precession (NorthSouth) GR = 6.6144 arcsec/yr SCC = 4.4096 arcsec/yr NGT = 6.6144  a small [itex]\sigma[/itex] 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 (EastWest) 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 


#36
Jan3107, 12:06 AM

P: 27

Hi Garth – New here to the forum but saw your posts and thought I would mention a potential discovery resulting from the GPB experiment. Please add it to your list.
No, I do not have an alternative gravity theory but I do question the current model of precession and I believe GPB (with its perfect gyros far above the wobbling earth) is in an ideal position to determine if the precession of the equinox observable (a change in earth orientation of about 50”p/y) is due to the torque of lunisolar forces acting on the oblate earth (current theory) or the observable of a solar system in motion (binary theory of precession). If I guess right, the spacecraft will mimic the precession observable even though it is floating free high above a wobbling earth. This is because we believe the precession observable is due to the motion of the sun and solar system curving through space. I met with the GPB team at Stanford a few months ago and they listened and were open minded about the possibility that our sun may have an unknown companion star (which is the theoretical cause of the solar system curving through space at 50”p/y). We discussed the polhode issue and they implied they were getting more signals than originally anticipated and it was a big task to try and separate all of the signals into identifiable buckets. But they were careful to keep the integrity of the experiment and remind me that they could not release results until the public announcement. Nonetheless, we spent a fair amount of time discussing companion star scenarios, which I found interesting. Bottomline, I think they will either report that it will take more time than expected to sift and interpret all the signals, and or, that our solar system is curving through space at a rate that exceeds the expected results from the relativity experiment. I have posted a model (of the results I expect them to find) on my website at the Binary Research Institute: http://www.binaryresearchinstitute.o...avprobeb.shtml Regardless of the results of the initial GPB report I think NASA and Stanford are providing almost priceless research. The raw data should prove to be fundamentally helpful to scientists for years to come as we probe the motions of the earth and solar system on our journey through space. Bravo to Dr. Everitt and team! 


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