Alternative theories being tested by Gravity probe B

[Garth]

Hi Rudi!

On this thread I (not being a Moderator) have allowed to be included brief references to papers on the ArXiv that have not been published in refereed journals, yet that do make some sense, and which make a definite falsifiable prediction.

This seems to have been allowed by the Moderators as the predictions will soon be able to be falsified, or just possibly otherwise.

As you can read some rough edges have been left...

Roll on May (??)!

Garth

 

[Kris Krogh]

Hi Garth,

I see today ArXiv has taken down the paper "A critical analysis of the GP-B mission. I: on the impossibility of a reliable measurement of the gravitomagnetic precession of the GP-B gyroscopes," by Gerhard Forst:

http://arxiv.org/abs/0712.3934

The comment field says: "This submission has been withdrawn by the arXiv administrators because 'G.Forst' is a pseudonym of a physicist based in Italy who is unwilling to submit articles under his own name, in violation of arXiv policies"

It's gone now, but I didn't see anything of substance in the paper. The references it cited did not show what was attributed to them.

Kris

 

[wolram]

Problems getting to KK paper, known compatibility problem, it may be a fault this end.

 

[lucien86]

Hi Gath you asked for theories that can be tested via Gravity probe B.


I have half of one that is not yet fully published or finished but I would like to mention it as it is an alternative or rather a modification to GR.
My work is based primarily on looking at what might exist beyond the light velocity barrier so it obviously involves particles with imaginary mass. My real problem is that I don't yet have the precision to make many exact predictions. What is clear though is that the model doesn't easily allow curved space times. At the moment I have gravity mapped as 'accelerating inertial frames' - the frame itself never sees the acceleration.
As far as I'm aware the model should give pretty much identical results to standard GR with one big exception - there should be tachyonic 'shadows'.
Another thing my model predicts is that gravity may be purely classical and have no lower quantum limit - in other words it can never exhibit interference patterns.

Obviously Gravity Probe B isn't going to answer many questions for my theory, but it wasn't designed to - my answers only really deviate from GR above the speed of light. (My theory forbids the folding of space)

I am working on designing a verifiable experiment that can detect tachyonic behavior but I am only an amateur with a tiny budget and other priorities so it is years away.

 

[Garth]

lucien86 we have strict guidelines here about not discussing personal theories except on the Independent Research Forum, unless they have already been published in a peer reviewed journal.

In this thread I am including theories already published on the physics ArXiv as well if they make falsifiable predictions for the GP-B experiment.

I suggest you submit your theory to the IR Forum having first followed their guidelines for submission.

Garth

 

[lucien86]

Sure - my whole point is that my theory is not ready to publish there. Half finished means exactly that. As for the IR forum the rules there are so strict that it is actually easier to get published in a big magazine like Nature. I am nowhere near getting published anywhere at the moment - sorry to bother you. - Lucien

 

[Garth]

Data Analysis Extended Again!

The GP-B website has had a revamp - although there are no new results to report.

GP-B Program Extended Through September 2008, and Possibly March 2010

On November 2, 2007, we convened the 17th meeting of our external Science Advisory Committee (SAC) to review our progress in the refinement of the GP-B experimental results. The subsequent SAC report noted "the truly extraordinary progress that had been made in data analysis since SAC-16 [March 23-24, 2007]" and unanimously concluded "that GP-B is on an accelerating path toward reaching good science results."

Following a peer-reviewed bridging proposal to NASA's Science Mission Directorate (SMD) and actions by Stanford and a private donor, the GP-B program has been extended at least through September 2008. Furthermore, SMD opened the opportunity for GP-B to submit a proposal this month to its Senior Review process. This is a bi-annual event in which ongoing NASA science programs undergo a peer-review to determine which of those programs NASA should continue and/or extend in order to achieve the greatest scientific gain. Assuming a successful Senior Review, GP-B will be extended one final time, from October 2008 through March 2010.

There are two unexpected experimental errors that are being reduced.

1. A time variation in the polhode motion of the gyroscopes, which creates complications in the gyro scale factor calibrations (conversion of electrical signals to angles).
2. Much larger than expected classical misalignment torques on the gyroscopes, attributable to “patch effect” (contact potential difference) interactions between the gyro rotors and their housings.

Although these anomalies reduced the best precision obtainable from the 1% goal they still hope to achieve about 2% for the frame-dragging effect and 0.02% for the geodetic effect.

During 2006-early 2007, we made good progress understanding the cause of these complications (and developing sound methodologies for working through them, culminating in an announcement of first results at the annual meeting of the American Physical Society in April 2007. Since that time, the team has continued to improve the results in a number of ways. As experimentalists, we make no assumptions about Einstein’s theory being right or wrong; rather, we collected data, and we are doing everything humanly possible to maximize the precision and accuracy of the final results—whether or not they agree with Einstein’s predictions.

For newbies to this thread a basic explanation of the experiment is given in a slide show on their website.

We note the Seeing General relativity Directly slide remains the replaced one, which does not give the game away. Remember the http://colloquia.physics.cornell.edu/11-12-2007/cornellpres_files/v3_slide0341.htm gave some interesting results inconsistent with GR at the one $\sigma$ (68%) confidence level!

Garth

 

[JonathanK]

Hello Garth and everyone,

well, it seems GP-B may be a long road. My paper on the geodetic effect got through peer review, it's at

http://journalgp.awardspace.com/journal/0202/020203.pdf

PSG gives the same predictions as GR and NG, hope to see it on the list with them, presumably along with Jin He's absolute relativity. Does anyone have a guess as to when the 3 sigma results will be announced? J

 

[Garth]

Well first of all Jonathan congratulations on having your paper published!

I do have a problem in including it in the list because in that paper you say:

PSG has the same values as GR for both effects being measured by Gravity Probe
B (for frame dragging it is - 39 mas/yr, using more recently released orbit figures). But
unlike GR, PSG has not been fully worked through, and it may be able to explain this
∼ 61 mas/yr anomaly when various smaller effects have been taken into account.

So what hard and fast prediction are you making for the results of this experiment? It seems that you are hedging your bets. The sign of a good scientific theory is that it can be falsified! As indeed my 2002 SCC proved to be! (darn!)

Although this isn't the place to discuss the detail of your theory, and you might like to start a new thread on PSG, as a published alternative theory, to do just that, my initial reaction is to be suspicious of your "time slowing" concept. Time on any particular world-line passes at the tautological rate of "one second per second". Time dilation between two clocks on different world-lines reveals a warping of the space-time continuum otherwise known as curvature and we are back to GR again.

Secondly I have a query about your actual calculation. If there is no curvature then orbital mechanics have to be explained by some type of Newtonian gravitational force accelerating the orbiting masses off their geodesic straight line trajectories. Such an acceleration would produce a Thomas Precession, that is unless you are denying SR as well, which acts to reduce the geodetic effect. I see no mention of that in your paper.

If you like, as it is published, I will include PSG giving a prediction equal to GR.

And I fully expect we will have to wait until 2010 to get the 3 $\sigma$ results!

Garth

 

[JonathanK]

Thanks Garth,

I have the same predictions as GR, but if the anomaly found in the early geodetic results remains (and the delaying of the May announcement perhaps makes it slightly more likely that it is still there) I don't think that everyone will say "Ah well, GR was falsified, too bad". In that instance things would be on hold until some very good clear explanation for the 61 +/- 43 mas/yr turns up. By then the value of the anomaly would be known more accurately, so something might eventually explain it, either from analysing the experimental setup or from theory.

About the slowing of time - I put the word "slowing" in inverted commas in the paper to make it clear that it's not literal, either in GR or PSG. But as I'm making the point there that in PSG it happens by the same factor as the slowing of the motion of light and matter in the field, the word "slowing" is justified.

Though you say it doesn't, the paper actually does mention the question of a Newtonian type force. The conceptual basis removes the need for one, just as curvature does - an orbiting object is in freefall. If one conceptual basis can make an orbiting object be in freefall, then another can, as you'll see when it's published in full (or we can argue about it then! but I think you'll agree). But meanwhile it would be odd to rule out all possible conceptual pictures other than curvature as capable of that.

Anyway, best wishes,

Jonathan

 

[JonathanK]

Ps

PS. To clarify the first point above, the anomaly is too small to falsify everything at the GR value instantly, making KK theory the new standard view. Both GR and PSG could potentially survive that, but both could be falsified if the final results contained figures further from the GR values.

In the paper I've speculated briefly about the anomaly, but it's too small to be major issue, and doesn't detract from the prediction pair I've given, with mathematical backing for the geodetic prediction. After the equation, the paper says

"This means that PSG is so far consistent with experiment, as a geodetic effect of similar value to that in GR and PSG has been measured."

The final results may change that preliminary measurement, but "of similar value" relates to the same thing. J

 

[Garth]

Though you say it doesn't, the paper actually does mention the question of a Newtonian type force. The conceptual basis removes the need for one, just as curvature does - an orbiting object is in freefall.

The question is not whether the gyro is in free-fall, a satellite in Newtonian theory is falling freely, but whether the free-fall state is one where the gyro is accelerating away from its geodesic path, i.e. is it on a 'straight' geodesic trajectory, or not?

If it is on a 'straight' geodesic trajectory, as in GR, then the shape of the orbit is explained by the curvature of space-time and there is no intrinsic acceleration or Thomas precession; if it is not, as in Newtonian gravity, then there is an accelerating force, the Newtonian gravitational force, with the consequence that the gyro suffers a Thomas precession, which in Newtonian gravity (+ SR flat space-time) produces a precession equal to one third of the GR geodetic precession.

As an aside, because of this the initial geodetic result of GP-B has falsified Newton to a high confidence level! For the same reason I am also sure that it has falsified PSG, if that theory does not include space-time curvature.

So my question Jonathan is, "Does PSG include curvature? And if not, how does it produce an elliptical orbit without accelerating the gyro away from its 'straight' geodesic trajectory?"

Garth

 

[JonathanK]

There's no acceleration, for the same reasons as there's none in GR. The conceptual picture is one that is surprisingly like curvature, and yet it comes from flat space - it involves a small cluster of lateral jumps. An orbiting object thinks it is traveling in a straight line, and follows a curve only because the nature of space has been changed in a fundamental way.

I have a book on the theory of time, of which PSG is the gravity part ("Motion through time"), also hope to publish a longer paper with the whole conceptual basis - have wondered whether it can be a series of papers, but the concepts are so interdependent that it's difficult to find a dividing line. At present I have published some of the predictions, but not all of the theory.

In the book the concepts explain very much from very few starting assumptions, but the "smoking gun" evidence provided is an explanation of exactly how equation 4 of the first published paper was derived. It directly gives all the speeds on the path of a falling object from infinity, from knowing the speed at a given point. It agrees with numbers from Newton's theory to 12 decimal places, and goes to zero at the Schwartzchild radius of a black hole. I've hoped to show you the theory for some time, look forward to hearing your opinion. Thanks, J

 

[JonathanK]

Ps

PS perhaps I can give some indication of the kind of thing I mean, using an analogy. When light is refracted around a curve, for example when traveling through an index gradient refractive medium on Earth, does the light undergo an acceleration? No, instead it thinks it is traveling in a straight line, but what it is traveling through has been changed in a fundamental way (without curvature into an extra dimension), and this makes it follow a curve. PSG has something analogous to a refractive medium, which matter responds to at the Planck scale as light does.

Jonathan

 

[Garth]

The latest GP-B website Update:

================================
GP-B STATUS UPDATE -- MAY 23, 2008
================================

NASA's 2008 SENIOR REVIEW OF GP-B

In March 2008 at NASA's invitation, we submitted a proposal to the Science Mission Directorate, Astrophysics Division Senior Review of Operating Missions (Sr. Review), requesting a final 18-month (October 2008 through March 2010), $3.8M extension of GP-B to complete the data analysis and publish the results. In April, as part of the Sr. Review process, GP-B Principal Investigator, Francis Everitt, and Program Manager, William Bencze, made a presentation to the Sr. Review Committee at NASA Headquarters, where it appeared to have been favorably received.

Thus, we were greatly surprised last week to discover that the Sr. Review had recommended that NASA not grant our final funding extension, particularly since another NASA committee--the GP-B Science Advisory Committee (SAC -- http://einstein.stanford.edu/MISSION/mission2.html#sac), chaired by relativistic physicist Clifford Will--stated in its report following the November 2007 meeting: "The SAC was impressed with the truly extraordinary progress that has been made in data analysis since SAC-16 [Mar 2007] Š and we now agree that GP-B is on an accelerating path toward reaching good science results."

The Sr. Review evaluation is an unexpected setback, but we are determined to push ahead and drive to the very best possible result within the resources available.

THE PLIGHT OF FUNDAMENTAL PHYSICS RESEARCH AT NASA

While the Sr. Review outcome has ramifications for GP-B, in broader terms, it points to the challenge of finding support for fundamental physics experiments within the NASA culture of observational missions. This has been an ongoing issue within NASA for decades. In the 1990s, fundamental physics research experiments were scattered over several divisions of NASA, which led in 1999, to the blue-ribbon NASA Advisory Council (NAC) recommending to the NASA Administrator that the agency create a "single home room" for physics missions in space so that these missions would be given the support and visibility they deserved.

The 1999 NAC committee's advice was never heeded. Furthermore, during the 2004 restructuring and consolidation of NASA divisions, the already small budget for fundamental physics research was cut to zero in the NASA Exploration Directorate, entirely eliminating fundamental physics research from that division. This left the Science Mission Directorate (SMD) as the only home for fundamental physics experiments like GP-B. However, in the SMD, physics experiments had to compete directly with the NASA Great Observatories and other astrophysics missions for pieces of an already-decimated research budget. It is no criticism of the SMD Sr. Review to say that of the ten missions under review, GP-B as a physics experiment rather than an observatory was quite unlike the rest and almost impossible to fit within a common intellectual framework. Regrettably, since NASA has failed to establish a fundamental physics research division, several missions besides GP-B have suffered. If such a division existed, we believe the agency's support for the proper completion of GP-B would continue to be strong.

THE CONTINUED RELEVANCE & IMPORTANCE OF GP-B

One of the Sr. Review Committee's main arguments supporting its recommendation that NASA not fund the final extension requested by GP-B, was that the goals of GP-B have already been fulfilled by other measurements, and that GP-B is therefore no longer relevant. This view is in stark contrast with the recommendations of the SAC (2007), NASA's Turner panel review of GP-B (2003), and NASA's Fitch-Taylor NRC review of GP-B (1995). All of these reviews concluded that the GP-B experiment is scientifically justified and should be completed.Now, in 2008, the scientific justification for completing the GP-B experiment is even more valid. During the past five years, there has been little progress on other relativity experiments, but GP-B was launched, operated, and collected all of the necessary data. After two years of intense work, the GP-B science team is very close to completing the data analysis. GP-B has made, in the view of the SAC, "extraordinary progress" in addressing two unexpected and difficult complications in analysis caused by unanticipated electrostatic patch effect fields within the gyroscope. (These have been reported previously in our Summer 2007, September 2007 and December 2007 status updates, which you can view in the STATUS tab on our Website: http://einstein.stanford.edu/highlights/hlindexmain.html)

GP-B directly studies gravity, one of the most fundamental laws of nature. Inherently, the goals of GP-B differ significantly from those of typical astrophysics missions, where natural laws--inferred theoretically and tested on the ground--are used to interpret observations of astrophysical phenomena. Furthermore, GP-B objectives and methods are qualitatively different from those underlying most astrophysical work. For this reason, the GP-B experiment begs to be evaluated with respect to criteria based on its direct experimental methodology. Direct tests of nature's laws are the foundation of physical science; such tests are the only rational basis for the belief that these laws are, in part, "understood." GP-B seeks to deepen our understanding of gravity in this way.In addition to its scientific significance, GP-B's technological heritage and operational experience is critically important for future gravity space missions, including tests of the equivalence principle (STEP) and the search for gravitational waves (LISA). NASA stands to loose much of the expertise developed on the GP-B mission if the program is not brought to a proper conclusion.

THE ROAD AHEAD

Our GP-B team has been making steady progress in analyzing the data and working through the unexpected complications discovered within the data. We are now in the home stretch. We have identified the issues that still need to be addressed, and we have prepared a sound plan for completion of the analysis. This plan, which was spelled out in detail in our proposal to the NASA Sr. Review, requires an additional 18-month investment of $3.8M from September 2008 through March 2010. If no further funds are forthcoming from NASA, the analysis efforts will likely cease by October 2008, unless other funding sources can be identified. Since February 2008, GP-B has been funded by contributions from NASA, Stanford University, and a private donor, in approximately equal shares.

We have now clearly confirmed the geodetic effect to a precision of less than 1.5% (97 milli-arcseconds/year). However, because the frame-dragging effect is ~170 times smaller, removing the sources of error from that measurement--especially the non-relativistic torques due to patch effect interactions between the gyro rotors and their housings--is a detailed, painstakingly slow process. We have yet to reach a point of diminishing returns. Until we do, it is our intention to push onward and obtain the best result possible to properly complete this landmark experiment.

We wait to see how accurate they can get their results before the plug is pulled.

However, if it just a matter of $3.8M to complete the analysis up to March 2010 it seems a waste to stop in September this year after spending $800M.
Anybody got $3.8M to spare?

Garth

 

[Garth]

The reason GP-B is a unique experiment that has not been done before is because all other tests of the geodetic precession and gravito-magnetic effect rely on measuring the trajectories of test particles through space-time. They are not directly measuring the precessions of a physical (solid) gyroscope.

A non-metric theory that is conformally equivalent to GR in vacuo (i.e. its Action reduces to GR in vacuo) will generate the same geodesic trajectories for test particles although the Robertson parameters may be different.

This is significant because in terms of the Robertson PPN parameters all other tests of GR have effectively measured $\gamma$ in the expression:

$$GM(\frac{1+\gamma}{2})$$,

whereas the geodetic precession is given by the expression:

$$GM(\frac{1+2\gamma}{3})$$.

The $\gamma$ is coupled to G differently, so the measurement of the geodetic precession of an actual gyroscope, rather than just the precession of an orbit, is a unique measurement that has only been carried out by GP-B. It would be a crying shame not to complete the processing of the data obtained.

Garth

 

[Chronos]

Exactly the point of rigorously crunching GP-B data, Garth!

 

[Wallace]

I guess the funding panels just didn't believe the data was salvageable and whatever result GP-B would end up claiming would always have a big question mark next to it due to the extra noise. If the funding panel didn't believe the noise could be removed with certainty what would the research community think about the results? I guess they decided not to throw good money after bad.

I have no idea myself about how salvageable the data is, but clearly that was the view of the panel, who I'm sure aren't dodo's. It's a crying shame, but maybe humpty dumpty just can't be put back together again, no matter how much glue we buy.

 

[Garth]

I guess the funding panels just didn't believe the data was salvageable and whatever result GP-B would end up claiming would always have a big question mark next to it due to the extra noise. If the funding panel didn't believe the noise could be removed with certainty what would the research community think about the results? I guess they decided not to throw good money after bad.

I have no idea myself about how salvageable the data is, but clearly that was the view of the panel, who I'm sure aren't dodo's. It's a crying shame, but maybe humpty dumpty just can't be put back together again, no matter how much glue we buy.

The Update actually claims that the drying up of the money is due to a funding crisis and the lack of a fundamental physics research division within NASA:

It is no criticism of the SMD Sr. Review to say that of the ten missions under review, GP-B as a physics experiment rather than an observatory was quite unlike the rest and almost impossible to fit within a common intellectual framework. Regrettably, since NASA has failed to establish a fundamental physics research division, several missions besides GP-B have suffered. If such a division existed, we believe the agency's support for the proper completion of GP-B would continue to be strong.

In my post above I have explained the counter argument to the Sr. Review Committee's main criticism:

the goals of GP-B have already been fulfilled by other measurements, and that GP-B is therefore no longer relevant.

The GP-B team claim that 'Humpty Dumpty' has been almost put back together and a full repair is at hand.

Now, in 2008, the scientific justification for completing the GP-B experiment is even more valid. During the past five years, there has been little progress on other relativity experiments, but GP-B was launched, operated, and collected all of the necessary data. After two years of intense work, the GP-B science team is very close to completing the data analysis. GP-B has made, in the view of the SAC, "extraordinary progress" in addressing two unexpected and difficult complications in analysis caused by unanticipated electrostatic patch effect fields within the gyroscope.

Garth

 

[Wallace]

The Update actually claims that the drying up of the money is due to a funding crisis and the lack of a fundamental physics research division within NASA:

I know what the press release said (from both sides), I'm just trying to read between the lines I guess. If the honchos in NASA thought GP-B still had great things to say, they would have found the money somewhere, regardless of structural barriers.

The GP-B team claim that 'Humpty Dumpty' has been almost put back together and a full repair is at hand.

Again, that's what they are saying. But how long have they been saying that to the funding bodies? At some point patience will wear out. I've been telling my supervisor that the paper I'm working on is 'almost done' for a few months now, does that mean it will be ready tomorrow? Probably not. I don't think I've ever seen a grant application say 'we have a lot of work to do and it might not work out after all of that effort anyway', even though that is very often the truth.

Again, I know very little about GP-B, so this could all be irrelevant, my point in as much as I have one is that you can't really learn anything about this from the words in a press release.

 

[Garth]

my point in as much as I have one is that you can't really learn anything about this from the words in a press release.

Yes, of course, but frustrating all the same!

To make my point though of the uniqueness of the experiment, today's physics arXiv has this paper A Search for New Physics with the BEACON Mission, which makes the following points:

However, there are important reasons to question the validity of Einstein’s theory of gravity. Despite the beauty and simplicity of general relativity, our present understanding of the fundamental laws of physics has several shortcomings. The continued inability to merge gravity with quantum mechanics,⁸ and recent cosmological observations that lead to the unexpected discovery of the accelerated expansion of the universe (i.e., “dark energy”) indicate that the pure tensor gravity field of general relativity needs modification. It is now believed that new physics is needed to resolve these issues.⁸

Which I agree with, and:

The Eddington parameter $\gamma$ whose value in general relativity is unity, is perhaps the most fundamental PPN parameter, ² in that $\frac{1}{2}$($\gamma$−1) is a measure, for example, of the fractional strength of the scalar gravity interaction in scalar-tensor theories of gravity.¹ Currently, the most precise value for this parameter, $\gamma$−1 = (2.1±2.3)×10^-5, was obtained using radio-metric tracking data received from the Cassini spacecraft ⁷ during a solar conjunction experiment. This accuracy approaches the region where multiple tensor-scalar gravity models, consistent with the recent cosmological observations, predict a lower bound for the present value of this parameter at the level of $\gamma$−1 ~ 10^-6−10^-7 (see discussion in Ref. 1,8 and references therein). Therefore, improving the measurement of this parameter would provide crucial information to separate modern scalar-tensor theories of gravity from general relativity, probe possible ways for gravity quantization, and test modern theories of cosmological evolution.

Which I pointed out in #296 above.

However:

The BEACON mission architecture is based on a formation of four small spacecraft placed in circular Earth orbit at a radius of 80,000 km (Fig. 1). Each spacecraft is equipped with three laser transceivers in order to measure the distances to the other spacecraft in the formation.

The experiment is simply a refined measurement of the geodesic orbits of test particles (the spacecraft ) in Earth orbit and will therefore fail to discriminate between GR and any conformally equivalent scalar field theory in which the conformal transformation of the Action into the Einstein frame is simply canonical GR, as I explained in #296.

GP-B could resolve such a degeneracy.

Garth

 

[CarlB]

It probably doesn't help that they can't reproduce Einstein's GR. I hope that they publish their raw data so that other people can comb through it.

 

[Garth]

It probably doesn't help that they can't reproduce Einstein's GR.

You might be onto something there...

Just to show you what I mean:
Seeing General Relativity Directly[/url], from Francis Everitt's lecture slides http://colloquia.physics.cornell.edu/11-12-2007/cornellpres_files/v3_document.htm

GP-B DATA ARCHIVE TO BE AVAILABLE THROUGH NSSDC IN JULY

During the past few weeks, while our science team continues to analyze the data, our GP-B data processing team has also been quite busy, compiling an archive of the GP-B raw data—both science data and spacecraft /payload status data, as well as an archive of associated documents, drawings, photos and other information about the GP-B mission. We are currently in the process of transferring this entire archive to the National Space Science Data Center (NSSDC), located at the NASA Goddard Space Flight Center in Greenbelt, Maryland. Transfer of this archive will be completed in late June, and the GP-B archive will then become publicly available sometime thereafter.

Garth

 

[Garth]

"Rumors of the demise of GP-B are greatly exaggerated."

The latest update from the GP-B team:

All,

Since May 23, 2008, when I sent out our most recent GP-B email status
update and posted the same information on our webiste
(http://einstein.stanford.edu), I've received too many email
responses to reply to each one individually.

Thus, on behalf of the GP-B team, I wish to thank all of you,
collectively, who expressed support for GP-B, and assure you that, in
the words of Mark Twain, "...Rumors of the demise of GP-B are greatly
exaggerated."

Our science team is continuing to make excellent progress in the data
analysis. Members of the team, including several Stanford graduate
students, have produced detailed maps of the trapped magnetic flux in
all four gyro rotors in order to predict the time-varying signal in
the data. This mapping has resulted in a 500-fold improvement in the
determination of the polhode motion throughout the duration of the
experiment, essentially solving the time-varying polhode motion
problem in the data.

This work, in turn, has enabled the team to implement two
complementary methods of removing the disturbing effects of the
classical torques. With the classical torques properly handled,
rather convincing estimates of frame-dragging are now available, but
our team is still investigating all possible systematic disturbing
effects.

Another meeting of the GP-B Science Advisory Committee is being
planned in late August to review our progress in the data analysis
since last November. Also, GP-B will be a central contributor in an
international workshop on "The Nature of Gravity: Confronting Theory
and Experiment in Space" to be held in Bern, Switzerland, 6-10
October 2008, with the following team members as individual invited
speakers: William Bencze, Francis Everitt, Misha Heifetz, George
Keiser, Barry Muhlfelder & Alex Silbergleit.

Meanwhile, we are vigorously exploring funding sources outside NASA,
both through other agencies and private donors, to enable GP-B to
complete the data analysis, publish the final results and bring GP-B
to a conclusion by early 2010.

We very much appreciate the continued interest and support we have
received world-wide, and we will keep you apprised of our status
going forward.
Bob Kahn
GP-B Public Affairs

Any millionaires out there??

Garth

 

[Garth]

GP-B STATUS UPDATE -- September 26, 2008

GP-B STATUS UPDATE -- September 26, 2008.

PROGRAM STATUS

Since our May 23rd status update, GP-B has continued to make significant progress--fiscal and scientific. NASA funding and sponsorship of the program ends on September 30, 2008, but GP-B has secured alternative funding that will enable our science team to continue working at least through December 2009 in order to complete the data analysis and bring GP-B to a proper close.

The GP-B science team is continuing to make large strides in the data analysis. On Friday, August 29, 2008, the 18th meeting of our external GP-B Science Advisory Committee was held at Stanford to report our progress since the previous SAC meeting in November 2007. Their ensuing report to NASA states:

“The progress reported at SAC-18 was truly extraordinary and we commend the GPB team for this achievement. This has been a heroic effort, and has brought the experiment from what seemed like a state of potential failure, to a position where the SAC now believes that they will obtain a credible test of relativity, even if the accuracy does not meet the original goal. In the opinion of the SAC Chair, this rescue warrants comparison with the mission to correct the flawed optics of the Hubble Space Telescope, only here at a miniscule fraction of the cost.” —SAC #18 Report to NASA

On October 6-10, six GP-B team members have been invited to present these dramatically improved, interim results at an International Space Science Institute (ISSI) workshop on "The Nature of Gravity: Confronting Theory and Experiment in Space" to be held in Bern, Switzerland. Following the Bern workshop, these improved interim results will undergo a thorough peer-review and vetting; then towards the end of this year, we plan to announce them publicly.

We very much appreciate your continued interest in GP-B, and we will keep you posted on our progress in future status updates.

December 2009 - we continue to wait and see!

Garth

 

[JonathanK]

Hello Garth and all.

As well as working on until at least the end of next year, looks like they might announce some interim results towards the end of this year.. though you never know. Garth, are you going to redo the list? There were several updates to be made a while ago.

best wishes, Jonathan

 

[Garth]

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!

1. Einstein's General Relativity(GR)
2. Brans-Dicke theory (BD)
3. Moffat's Nonsymmetric Gravitational Theory (NGT)
4. Stanley Robertson's Newtonian Gravity Theory (NG),
5. F. Henry-Couannier's Dark Gravity Theory (DG).
6. Alexander and Yunes' prediction for the Chern-Simons gravity theory (CS).
7. Kris Krogh's Wave Gravity Theory (WG)
8. Hongya Liu & J. M. Overduin prediction of the http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v538n1/50681/50681.text.html?erFrom=5252751197746712308Guest#sc8 gravity theory (KK).
9. 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).

1. GR = -6606 mas/yr.
2. BD = -$(3\omega + 4)/(3\omega + 6)$ 6.606 arcsec/yr. where now $\omega$ >60.
3. NGT = -(6606 - a small $\sigma$ correction) mas/yr.
4. NG = -6606 mas/yr.
5. DG = -6606 mas/yr.
6. CS = -6606 mas/yr.
7. WG = -6606 mas/yr.
8. KK = -(1 + b/6 - 3b² + ...) 6606 mas/yr. where 0 < b < 0.07.
9. PSG = -6606 mas/yr.

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

1. GR = -39 mas/yr.
2. BD = -$(2\omega + 3)/(2\omega + 4)$ 39 mas/yr.
3. NGT = -39 mas/yr.
4. NG = -39 mas/yr.
5. DG = 0 mas/yr.
6. CS = -39 mas/yr. + CS correction
7. WG = 0 mas/yr.
8. KK = -39 mas/yr.
9. 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. http://colloquia.physics.cornell.edu/11-12-2007/cornellpres_files/v3_document.htm .

The pertinent slides are slide 3: http://colloquia.physics.cornell.edu/11-12-2007/cornellpres_files/v3_slide0341.htm
and the slide: http://colloquia.physics.cornell.edu/11-12-2007/cornellpres_files/v3_slide0426.htm

These last two slides clearly show an inconsistency with the GR prediction at the 1 $\sigma$ confidence level.

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

(* -6606 mas + 7 mas (solar geodetic) + 28 $\pm$1 mas (guide star proper motion))

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

Garth

 

[JonathanK]

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]

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 modeled 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 modeled 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