Alternative theories being tested by Gravity probe B

[sylas]

You can't simply eliminate polhode and other perturbing forces to save the experiment without first being able to exactly quantify these effects. And to try and measure them by eliminating anything that does not get to the GR goal is circular reasoning and bad science.

This doesn't make any sense at all. They DO quantify the podhole effect. It was quantified and understood and taken into account from the start. There is an additional effect which was stronger than anticipated; from a tiny residual change on the gyroscopes, which gives an additional effect on the motions. There is no doubt at all that this effect exists. Most of the work of the extended data analysis phase HAS been to quantify this effect -- and not by assumption. When quantified, it can be extracted to reveal any underlying signal.

This is an extra factor influencing the gyroscopes which was larger than anticipated, and has been at the root of the limited accuracy to which results could be given.

The description by Polestar101 is very misleading. It's not bad science at all -- it is precisely what science should do to test GR as well as they can without making assumptions. They quantify all influences and obtain the residual signal, which stands then as a test of the predictions from the frame-dragging effect. There is no assumption of GR involved in that process. Without the proper quantification of the electromagnetic forces, the accuracy of the test is very weak. With proper quantification, the test will improve, though it is unlikely to get to the level of 1% which had originally been hoped.

There's a nice summary of the issues in The Gravity Probe B Bailout, IEEE Spectrum, Oct 2008. This report is describing how the team was able to secure additional funding; and their own project page gives more on the existing funding. (Gravity Probe B -- current status -- updated November 12, 2009. The work is ongoing, and primarily this is focused upon quantifying the effects of the electromagnetic influences, so that they can be properly take into account -- without just making assumption -- and so improving the accuracy of the true independent test of GR.

 

[Garth]

It is this. If other effects such as poholde and perturbing forces are eliminated then gyros 'point in a constant direction' in space. The curvature of the space-time around the Earth cause two effects on that 'constant direction' that was measured by GP-B, the geodetic and frame-dragging precessions.

So, the direction at which the gyroscopes point is not constant, but subjected to, at least, two effects: geodetic and frame-dragging precessions.

You have not understood the experiment. If other effects are eliminated then the gyro's do 'point in a constant direction' in space. It is space itself that is curved by the presence of the Earth's, and to a lesser degree, the Sun's gravitational fields. There is a further effect caused by the dilation (or 'curvature') of time.

It is this curvature of space-time that cause the geodetic precession and frame-dragging effects that GP-B measured.

Please start another thread about whether the Sun has a companion or not, it is irrelevant to this experiment.

Garth

 

[cristo]

Offtopic posts have been removed, mostly to [thread=383916]here[/thread]. Please keep this thread on the topic of comparing published theories that have made proper predictions for the Gravity Probe B experiment.

 

[maurol2]

Offtopic posts have been removed, mostly to [thread=383916]here[/thread]. Please keep this thread on the topic of comparing published theories that have made proper predictions for the Gravity Probe B experiment.

I've noticed that you've deleted my last reply to Garth, in the name of "topicness". Do as you please. I couldn't care less, except to mention that I don't see why you didn't removed Garth's last comment too. He was the one which initiated that avenue towards "offtopicness", so to speak, presuming about the geometrical migth of GR.

 

[JonathanK]

Hello Garth and all,

I just want to point out that strictly because of the very nature of this thread Garth you're not in a position to say "It is this curvature of space-time that cause the geodetic precession and frame-dragging effects that GP-B measured."

There may be other theories apart from mine, on the list of theories that are still viable in the light of the results, that give conceptual interpretations other than curvature for the measured effects.

But whether or not others do it, PSG certainly does. Equation 3 of the second paper on PSG published in a peer reviewed journal, here
http://journalgp.awardspace.com/journal/0202/020203.pdf

generates the curvature component of the geodetic effect from flat space, simply from assuming that an effect like a refractive medium slows matter in the same way as it slows light. That's 2/3 of the effect potentially explained, and because the other 1/3 doesn't require curvature, the equation works as a proof that curvature doesn't necessarily have to be the cause. (Wikipedia, nevertheless, still defines the geodetic effect as a direct result of curvature.)

You checked the equation, found it gives the right numbers, and then put PSG back on the list of viable theories, after more than a year off it. The reason it deserved to go back on the list was that the only premiss that went into the equation was the original starting premiss of PSG, ie that light and matter are slowed by sqrt(1 - [2GM/rc^2]) in a gravity field. (So the equation vindicated the theory, and showed that in the earlier prediction I was wrong, but PSG wasn't.)

Sorry to restate this, but it seems directly relevant to what you've said about the interpretation of the results. (BTW, have been hoping to get back in touch anyway.)

Best wishes, Jonathan Kerr

 

[maurol2]

But whether or not others do it, PSG certainly does. Equation 3 of the second paper on PSG published in a peer reviewed journal, here
http://journalgp.awardspace.com/journal/0202/020203.pdf

generates the curvature component of the geodetic effect from flat space, simply from assuming that an effect like a refractive medium slows matter in the same way as it slows light. That's 2/3 of the effect potentially explained, and because the other 1/3 doesn't require curvature, the equation works as a proof that curvature doesn't necessarily have to be the cause. (Wikipedia, nevertheless, still defines the geodetic effect as a direct result of curvature.)

Very interesting. Are you suggesting that this is related also to the origin of the rotation of the planets, or I misunderstood/read too much?

Talking about the likely effect of refractive mediums, you might be interested in this 2003 paper by Consoli & Constanzo:
http://arxiv.org/abs/astro-ph/0311576"

They re-analize the Michelson-Morley, Miller and other interferometry experiments, and show that in all cases a fringe shift is in fact detected, only its value is less than expected. They provide an excellent explanation for the differences, based on previous work by Kitto and Cahill, which goes back to Fresnel and the Fresnel drag coefficient.

I mention all this in this context due to a number of reasons:
- Consoli & Constanzo show that ether drag is dependant on the refractive index of the medium, and that this is the explanantion for the diverging results of the various interferometry experiments.
- They talk about a small similar effect caused by gravity, which resembles Fresnel drag, that will be equivalent to what you're proposing in your paper for 2/3 of the geodetic effect.

You might be interested also in this http://en.wikipedia.org/wiki/Aether_drag_hypothesis"
and the linked references and papers. In particular those by D. Gezari.

Regards,
Mauro

 

[JonathanK]

Hello,

Thanks for the references, if we discuss it in detail it should be elsewhere (or we'll find ourselves there anyway!). But to make something clear - I don't believe in an ether, that was disproved. The original ether was thought to behave rather like matter behaves - unconventional 'ethers' have carried on, but they're so different they shouldn't be called that. The electromagnetic field is an example.

PSG is a gravity theory that comes out of a theory of time, and has a conceptual basis that's different from others I've seen. The visual picture that led to both is in a book 'Motion through time: the missing piece of the puzzle'. Initially it looks at the question of whether the future is decided or undecided, and points out that relativity and quantum theory tell us opposite things on that. My solution does overlap with some other theories, including refractive medium theories, which according to mine are incomplete. Incidentally, my view has special relativity entirely right, except in the interpretation, which is incomplete anyway.

To answer your question about the axial rotation of the planets - although most of them rotate in the right direction, I doubt if either version of the geodetic effect could slowly spin up the planets. But if mine could then it's likely the GR version could as well, so the question lands comfortably within standard physics, and the best thing is probably to ask Garth..

Jonathan

 

[maurol2]

Hello,

Thanks for the references, if we discuss it in detail it should be elsewhere (or we'll find ourselves there anyway!). But to make something clear - I don't believe in an ether, that was disproved. The original ether was thought to behave rather like matter behaves - unconventional 'ethers' have carried on, but they're so different they shouldn't be called that. The electromagnetic field is an example.

Oh, I don't believe either in a mechanical and material ether.
But in fact, I certainly do believe that reality is composed by more than matter. Particularly, I believe that there are fields and "forces" that have no material cause, but that interact with and affect matter.
Moreover: matter is just a manifestation of these fields and forces(a kind of condensation), under the right circumstances.
We may not know and observe these fields and forces today in a direct way, but we can start to know them by their effects. And the day will come when we'll be able to observe them directly again, in all their magnificence and harmony.
I also firmly believe that Science, in the great name and tradition that represents, must (and certainly will) study and incorporate these fields and forces into its subjects of study. And when I say Science I mean all the sciencies, from Physics to Biology, from the study of the mineral to the study of the living. Also the social sciences; and the most important study of all: the clear and real understanding of the human being and its true nature.

 

[Garth]

Just a point: the geodetic effect is tiny unless you are dealing with an intense gravitational field, when the frame dragging effects would overwhelm it in the case of a rotating black hole, for example.

It is not responsible for the spinning up of the planets; that is due to the simply the conservation of angular momentum.

Unless a theory makes a specific prediction that is being tested by the GP-B experiment please post elsewhere.

Garth

 

[maurol2]

Just a point: the geodetic effect is tiny unless you are dealing with an intense gravitational field, when the frame dragging effects would overwhelm it in the case of a rotating black hole, for example.

It is not responsible for the spinning up of the planets; that is due to the simply the conservation of angular momentum.

That can't be so simple, or it is incomplete, considering by example that Venus is slowly spinning in the opposite direction.
Electromagnetic effects will have to be taken into account, sooner or later, to explain this solar system anomaly, and also others.

 

[Chronos]

Not at all, Venus could easily have been 'flipped' as the result of a past collision. The rotational axis of Uranus is similarly goofy, it points almost directly at the sun [re: http://www.windows2universe.org/our_solar_system/planets_table.html] and also has a slightly retrograde rotation. The former planet Pluto also suffers from this condition. Their current axial orientation is unrelated to how the planets acquired spin.

 

[maurol2]

Not at all, Venus could easily have been 'flipped' as the result of a past collision. The rotational axis of Uranus is similarly goofy, it points almost directly at the sun [re: http://www.windows2universe.org/our_solar_system/planets_table.html] and also has a slightly retrograde rotation. The former planet Pluto also suffers from this condition. Their current axial orientation is unrelated to how the planets acquired spin.

"Simply". "Easily". I'm dismayed by your fondness for "easy" explanations. "Easy" meaning, of course, that you can explain things (independently of how improbable these explanations really are) using standard physics and models.

Venus has a super-rotating atmosphere. That atmosphere circles the planet in around 4 (earth) days in a westward (Earth's west) direction. That is, most likely, the cause of the planet anomalous spin. The westward(Earth) spinning atmosphere gradually slowed down, and eventually reversed, the spin of the underlying solid planet, due to friction based momentum transfer.

Now, (and this independently if it is the cause of Venus's actual spin or not), we have to explain the reason for the atmosphere's super rotation. And to explain that it will be unavoidable to reckon with and take into account electromagnetic effects.

References:
http://en.wikipedia.org/wiki/Atmosphere_of_Venus
http://www.esa.int/SPECIALS/Venus_Express/SEMYGQEFWOE_0.html
http://www.physorg.com/news194504586.html

 

[Polestar101]

You can always blame it on polhode motion : )

 

[Chronos]

'Simple' explanations are usually more reliable than 'amazing' explanations, maurol2. Avoiding the issue I raised by injecting unrelated 'facts' does not rescue your 'amazing' model.

 

[maurol2]

'Simple' explanations are usually more reliable than 'amazing' explanations, maurol2. Avoiding the issue I raised by injecting unrelated 'facts' does not rescue your 'amazing' model.

What issue do you raised? The fact that the standard model of solar system formation has a potential explanation for the anomalous rotation of some planets, involving one or multiple collisions, does not mean that other cause can be the one responsible.

Uranus, by example, could be a former extrasolar planet, acquired with that particular spin angle.
Or it could have been inclined by the combined tidal effects of Saturn and Jupiter, when they crossed their 1:2 resonance, like this paper suggests:
http://www.planetary.org/blog/article/00000553/[/URL]
[url]http://www.nature.com/nature/journal/v440/n7088/abs/nature04577.html[/url]
That would explain the migration of its satellites, by the way.

With regard to Venus, what I find amazing (without the quotes) is that Venus atmosphere is super rotating with westwards winds of around 200 m/s. Excuse me, but what's the "standard" explanation for that?

And with those continuous and extremely strong winds I find plausible(if not obvious), they can be the real cause for Venus's actual spin.

The right thing to do would be to do the calculations, assuming an initial spin in accordance with Venus's position in its orbit, and testing for various atmospheric densities, velocity gradients, Venus's estimated age, etc. etc.

I don't have the time to do that, but maybe some other guy can do it. The hypothesis deserves some serious consideration and research. By the way, I don't think it is an amazing explanation, but a simple, elegant, and pretty obvious(if you think outside the standard box) one.

Finally: As far as I know, Venus's atmospheric super-rotation should be caused by the interaction between Venus's atmosphere and the solar wind. Here are some additional papers, which show a correlation between Earth's atmospheric Angular Momentum (AAM) and Solar Activity (SA). Interestingly, Earth's AAM is also retrograde in its general tendency, and of course, variations on Earth's AAM affect Length of Day (Length of Day) due to conservation of Angular Momentum:
[url]http://adsabs.harvard.edu/abs/2004cosp...35.4731A[/url]
[url]http://www.cgd.ucar.edu/cas/adai/papers/Abarca_delRio_etal_JGeodyn03.pdf[/url]


Mauro Lacy

 

[maurol2]

What issue do you raised? The fact that the standard model of solar system formation has a potential explanation for the anomalous rotation of some planets, involving one or multiple collisions, does not mean that other cause can be the one responsible.

I meant: can't.

The right thing to do would be to do the calculations, assuming an initial spin in accordance with Venus's position in its orbit, and testing for various atmospheric densities, velocity gradients, Venus's estimated age, etc. etc.

I meant: Venus's position in the solar system (distance to the Sun)

Incidentally, a similar process can probably explain Mercury comparatively slow rotation rate.

 

[Garth]

It is nearly a year since the last update of Mission Status on the GP-B website and while waiting for a final statement we note the existing published results are homing in on the GR prediction.

The gross GR prediction, including Solar GR effects and guide star motion is:
Geodetic (N-S) –6571 +/- 1 mas/yr and
Frame dragging (E-W) -75 +/1 1 mas /yr.

The average results over the 4 gyros is Geodetic = –6565 mas /yr i.e. within 0.1%,
and Frame dragging = -81 mas /yr i.e. within 8 % of the GR predictions.
These are consistent with GR to within the present experimental error bars.

Several of the alternative theories on the list I have compiled predict the same results as GR, therefore they fall into a different category to those that can be tested against GR by this experiment.

My news is that I have reviewed my theory (self-creation cosmology) and republished. The field equation can be cast in three forms, as explained in my paper, the Einstein conformal frame, the effective Jordan conformal frame and the true Jordan frame. The standard Brans Dicke theory is cast in the effective Jordan frame as was my 2002 version with its heterodox prediction for GP-B. Cast in the true Jordan frame (JF) it makes the same GP-B prediction as GR and therefore has not been falsified by the experiment. [Note of explanation: In SCC as I now understand it the true JF is to be used for the behaviour of massive particles, i.e. the gyros of GP-B and the effective JF for massless particles, i.e. the behaviour of light.]

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)
10. My Self Creation Cosmology (SCC),

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. SCC = -6606 mas/yr.
5. NG = -6606 mas/yr.
6. DG = -6606 mas/yr.
7. CS = -6606 mas/yr.
8. WG = -6606 mas/yr.
9. KK = -(1 + b/6 - 3b² + ...) 6606 mas/yr. where 0 < b < 0.07.
10. 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. SCC = -39 mas/yr.
4. NGT = -39 mas/yr.
5. NG = -39 mas/yr.
6. DG = 0 mas/yr.
7. CS = -39 mas/yr. + CS correction
8. WG = 0 mas/yr.
9. KK = -39 mas/yr.
10. PSG = -39 mas/yr.

Those theories being tested against GR by this experiment are:
BD – Brans Dicke theory; with \omega > 660.
KK - Kaluza-Klein gravity theory; with b < 1.5 x 10^-4.
NGT – Nonsymmetric Gravitational theory; it depends on how ‘small’ the \sigma correction is!

The ones falsified by the present results are:
DG - Dark Gravity theory.
WG - Wave Gravity theory.

And the ones not tested against GR by this experiment, and are still consistent with GP-B are:
SCC - Self Creation Cosmology theory.
NG - Newtonian Gravity theory.
CS - Chern-Simons gravity theory.
PSG - Planck Scale Gravity theory.

Garth

 

[JonathanK]

Thanks Garth,

Just to point out that the link you posted with PSG theory was the wrong one, it should be
http://journalgp.awardspace.com/journal/0202/020203.pdf

That's the paper (in a peer reviewed journal), "A derivation of the geodetic effect without space curvature", with the equation that shows a 'geodetic' effect with the same value as that of the GR curvature component - but being generated from flat space and using only the simple starting premiss of PSG theory. So that's the relevant link, as it shows why PSG theory is on the 'still consistent with GP-B' list, and gives the same result as GR.

Incidentally, the paper may be a first, in that it may be the first time an alternative interpretation for the geodetic effect (to the GR one) has been put forward on a mathematical basis. The generalised equation is for a single orbit around any mass.

thanks, Jonathan

 

[Polestar101]

Wish I shared your faith in the GP-B results. With so much unexpected noise (all of which needed to be properly accounted for and canceled out to have any chance of getting meaningful results) GP-B became more of an engineering project than a science experiment. Fortunately an objective panel of 15 scientists at NASA recognized the difference, pulled the funding and stated the truth; GP-B “failed to reach its goals”.

While subsequent attempts to engineer a solution were and are commendable they are highly suspect. Any methodology that relies on canceling out unanticipated “noise” by categorizing such unwanted effects as impossible to predict polhode motion (or anything else that is inherently unpredictable) negates the validity of the original science experiment. Good science relies on making and meeting predictions. Getting close to those predictions by “engineering” a preferred result is hardly science.

The only alternative theories that should be taken seriously are those that predicted the unwanted results without need to rely on cancellation of unpredictable signals.

 

[Garth]

Wish I shared your faith in the GP-B results. With so much unexpected noise (all of which needed to be properly accounted for and canceled out to have any chance of getting meaningful results) GP-B became more of an engineering project than a science experiment. Fortunately an objective panel of 15 scientists at NASA recognized the difference, pulled the funding and stated the truth; GP-B “failed to reach its goals”.

While subsequent attempts to engineer a solution were and are commendable they are highly suspect. Any methodology that relies on canceling out unanticipated “noise” by categorizing such unwanted effects as impossible to predict polhode motion (or anything else that is inherently unpredictable) negates the validity of the original science experiment. Good science relies on making and meeting predictions. Getting close to those predictions by “engineering” a preferred result is hardly science.

The only alternative theories that should be taken seriously are those that predicted the unwanted results without need to rely on cancellation of unpredictable signals.

Although I share your reservations and asked a question along similar lines to Francis Everitt about the error reduction at the April 2007 APS meeting, I have no doubt the signal did trace the GR prediction as can be seen here.

Francis Everitt's reply was that the one thing they mustn't do was perform the analysis with the answer (GR) in mind but try and make it as 'double blind' as possible. The procedure was to carry out the analysis in two teams using two different methods, an algebraic one and a geometric one, with both teams not knowing the proper motion of the guide star until they both came up with their answers. These were then compared for consistency and the proper motion then allowed for to get the result. Also the four gyros are analysed independently to help remove experimental errors by averaging.

Obviously then they have had to refine the process several times over the years to get to the latest published results so the further refinements would not have been 'double blind'.

They intended to complete all possible error reduction by this year and get a +/- 1 mas/yr accuracy ( an order of magnitude larger than originally hoped for), and unlesss they have succeeded in their aims and publish finally before the end of the year it may be that the present state of play is all they have been able to achieve, i.e. a ~ +/- 10 mas/yr (from the diagram of 50% error ellipses).

The level 2 data after preliminary processing is available here but does not mean much until "considerable further processing to calibrate the instrument, remove the effects of vehicle dynamics, aberration, guide star proper motion, small classical torques, and other systematic effects before any results about gyro orientation history can be determined".

"This refined processing of the data, which will result in a Level 3 data archive, is precisely what the GP-B team has been working on since October 2005" and they say will also be publicly available. I don't think I'll have the energy to sort through it to check it though! You might!

Garth

 

[maurol2]

Although I share your reservations and asked a question along similar lines to Francis Everitt about the error reduction at the April 2007 APS meeting, I have no doubt the signal did trace the GR prediction as can be seen here.

Let's accept you (and the GP-B) team are right. Let's assume that after removing all the noise, the remaining effects agree with GR predictions. OK with that: GR accurately predicts the small effects of frame dragging and geodetic precession.

Now, wouldn't be interesting to analyze and try to understand how and from where all that unexpected noise came from? After more than five years, has nobody done that?
I for one, find the noise (and the reason it was completely unexpected) more interesting than the data, don't you think?

Do you have any info related to this? Specifically, to theories or studies done on the noise, not with the objective to remove or cancel it, but to understand it, along with its origin?

Regards,
Mauro

 

[maurol2]

Do you have any info related to this? Specifically, to theories or studies done on the noise, not with the objective to remove or cancel it, but to understand it, along with its origin?

Of course, to be able to remove or cancel something, you must be able to understand it (to a certain degree, at least). Don't get me wrong. What I'm saying is: if these effects were standard and known, why were they so unexpected? And also: What's their cause? not in the sense of how they work and affect the results, but in the sense of from where they came from? What's their origin? Why these effects were not expected?

Thanks,
Mauro

 

[Polestar101]

Mauro – That is exactly the right question: what motion produced the noise signals?

In order to isolate the geodetic effect and the very small GR effect, the GPB team needs to separate out a number of unwanted signals. The known ones are easy whereas the unknown ones are difficult to spot unless they have a short periodicity. The most obvious one, the well-known aberration of light due to the motion of the spacecraft ’s regular orbit around the Earth (slightly changing the telescopes orientation to the guide star with each orbit), amounts to +-5” per orbit, and effectively acts as a calibration tool due to its short predictable periodicity. Another, the aberration of light due to the Earth’s annual orbit around the sun (carrying the spacecraft with it), may be less obvious because the Earth only went around the sun once during the GPB data collection period, and even this period was troubled with interrupted signals due to a number of stop and start issues. But it is a well-known effect, and quite large (+- 20.148”p/y), and therefore should also be readily identifiable.

If the Earth also has another motion, moving with the sun, curving through space due to solar system motion, producing the observable of the stars moving across the sky at about 50” p/y, then a very sensitive spacecraft orbiting the Earth should pick up this motion. However, if the earth’s changing orientation to VLBI sources is simply due to a wobbling Earth (as posited by current precession nutation theory which constrains ALL solar system motion to zero) then the GPB spacecraft , high above the so called wobbling earth, should not pick up any such signal. But the IAU has found that current precession theory is “inconsistent with dynamical theory” (IAU PO3), suggesting there is something very wrong with the current static sun precession theory. If some portion of the 50”p/y observable is indeed due to the motion of the solar system (as BRI data suggests) then the gyros should pick up this signal, unexpected under current theory. However, because the periodicity of this motion is so long (taking roughly 25,700 years to complete one cycle at the present rate) in relation to the data gathering period of the gyros, it would only reveal a tiny fraction of the waveform peak to trough during the life of the GPB experiment, and therefore it would show up as background drift rather than any obvious cycle. Nonetheless this effect will be fairly large, on the order of up to 50”p/y, if BRI is correct, thus making it immediately obvious that there is a lot of “noise” in the overall signal. This is what I think GPB found, but will we ever know it?

A methodology that is so intent on proving GR, that it effectively endorses a static solar system model, and eliminates noise without specifically identifying the source of all such unwanted noise, is not very objective in my opinion. Like you I have no problem with the existence of GR. It is the integrity of the process, one that may have thrown the baby out with the bathwater (proving solar system motion), and lost the support of NASA and many objective scientists along the way, that is so troublesome.

 

[Garth]

Final Results Published - after 5 years of analysis!

Summary of Final GP-B Experimental Results

GP-B STATUS UPDATE — May 4, 2011
After 31 years of research and development, 10 years of flight preparation, a 1.5 year flight mission and 5 years of data analysis, our GP-B team has arrived at the final experimental results for this landmark test of Einstein’s 1916 general theory of relativity. Here is the abstract from our PRL paper (see next section) summarizing the experimental results.

Gravity Probe B, launched 20 April 2004, is a space experiment testing two fundamental predictions of Einstein's theory of General Relativity (GR), the geodetic and frame-dragging effects, by means of cryogenic gyroscopes in Earth orbit. Data collection started 28 August 2004 and ended 14 August 2005. Analysis of the data from all four gyroscopes results in a geodetic drift rate of -6,601.8±18.3 mas/yr and a frame-dragging drift rate of -37:2±7.2 mas/yr, to be compared with the GR predictions of -6,606.1 mas/yr and -39.2 mas/yr, respectively ('mas' is milliarc-second; 1 mas= 4.848 X10-9 radians or
2.778 X10-7 degrees).

The table and diagram below show the individual gyroscope results, the weighted average results for all four gyroscopes combined, and the theoretical predictions for both effects from Einstein's general theory of relativity, as calculated by Stanford physicist, Leonard Schiff.

Note: The individual and combined statistical uncertainties are corrected for the "over" and "under" dispersion using the Χ2 of the individual estimates in the N-S and W-E directions. Please see our PRL paper (next section below) for more detailed information about these results and their derivation.

Gravity Probe B — Final Experimental Results

rN-S (Geodetic Measurement) rW-E (Frame-Dragging Measurement)

Gyroscope #1 -6,588.6±31.7 mas/yr -41.3±24.6 mas/yr
Gyroscope #2 -6,707.0±64.1 mas/ yr -16.1±29.7 mas/yr
Gyroscope #3 -6,610.5±43.2 mas/yr -25.0±12.1 mas/yr
Gyroscope #4 -6,588.7±33.2 mas/yr -49.3±11.4 mas/yr

Weighted-Average Results for All Four Gyroscopes
All Gyroscopes -6,601.8±18.3 mas/yr -37.2±7.2 mas/yr

Schiff-Einstein Predicted Theoretical Values
Theoretical Gyroscope -6,606.1 mas/yr -39.2 mas/yr

The results are consistent with GR and also those theories that are not tested against GR by this experiment because they make the same Geodetic and frame-dragging predictions.

The list that I had compiled now looks like this (no change from the last summary):

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)
10. My Self Creation Cosmology (SCC),

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. SCC = -6606 mas/yr.
5. NG = -6606 mas/yr.
6. DG = -6606 mas/yr.
7. CS = -6606 mas/yr.
8. WG = -6606 mas/yr.
9. KK = -(1 + b/6 - 3b² + ...) 6606 mas/yr. where 0 < b < 0.07.
10. 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. SCC = -39 mas/yr.
4. NGT = -39 mas/yr.
5. NG = -39 mas/yr.
6. DG = 0 mas/yr.
7. CS = -39 mas/yr. + CS correction
8. WG = 0 mas/yr.
9. KK = -39 mas/yr.
10. PSG = -39 mas/yr.

Those theories being tested against GR by this experiment are:
BD – Brans Dicke theory; with \omega > 660.
KK - Kaluza-Klein gravity theory; with b < 1.5 x 10^-4.
NGT – Nonsymmetric Gravitational theory; it depends on how ‘small’ the \sigma correction is!And the ones not tested against GR by this experiment, and are still consistent with GP-B are:
SCC - Self Creation Cosmology theory.
NG - Newtonian Gravity theory.
CS - Chern-Simons gravity theory.
PSG - Planck Scale Gravity theory.

Despite the disparaging remarks made the reason the NASA funding was withheld in the final stage was because the funds had run dry, with the cut backs etc. not because they thought the result was untrustworthy. The extra error reduced the final accuracy to that originally hoped for but it had been modeled by two independent methods and the methodology was not intent on proving GR but making an unbiased and independent set of measurements.

The problems with the experiment have been openly discussed, the only problem being IMHO is that should the results have been different from GR then the rest of the GR world would have had found it difficult to accept them.

Garth

 

[TrickyDicky]

Final Results Published - after 5 years of analysis!

of Final GP-B Experimental Results/url]The results are consistent with GR and also those theories that are not tested against GR by this experiment because they make the same Geodetic and frame-dragging predictions.

The list that I had compiled now looks like this (no change from the last summary):

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)
10. My Self Creation Cosmology (SCC),

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. SCC = -6606 mas/yr.
5. NG = -6606 mas/yr.
6. DG = -6606 mas/yr.
7. CS = -6606 mas/yr.
8. WG = -6606 mas/yr.
9. KK = -(1 + b/6 - 3b² + ...) 6606 mas/yr. where 0 < b < 0.07.
10. 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. SCC = -39 mas/yr.
4. NGT = -39 mas/yr.
5. NG = -39 mas/yr.
6. DG = 0 mas/yr.
7. CS = -39 mas/yr. + CS correction
8. WG = 0 mas/yr.
9. KK = -39 mas/yr.
10. PSG = -39 mas/yr.

Those theories being tested against GR by this experiment are:
BD – Brans Dicke theory; with \omega > 660.
KK - Kaluza-Klein gravity theory; with b < 1.5 x 10^-4.
NGT – Nonsymmetric Gravitational theory; it depends on how ‘small’ the \sigma correction is!And the ones not tested against GR by this experiment, and are still consistent with GP-B are:
SCC - Self Creation Cosmology theory.
NG - Newtonian Gravity theory.
CS - Chern-Simons gravity theory.
PSG - Planck Scale Gravity theory.

Despite the disparaging remarks made the reason the NASA funding was withheld in the final stage was because the funds had run dry, with the cut backs etc. not because they thought the result was untrustworthy. The extra error reduced the final accuracy to that originally hoped for but it had been modeled by two independent methods and the methodology was not intent on proving GR but making an unbiased and independent set of measurements.

The problems with the experiment have been openly discussed, the only problem being IMHO is that should the results have been different from GR then the rest of the GR world would have had found it difficult to accept them.

Garth

But that last remark should also work then the other way, at least for frame-dragging effect, given the large errors of the 4 gyroscopes, from a non-biased POV results compatible with the frame-dragging prediction should also then be difficult to accept.

Of the 4 gyroscopes (centering on the frame-dragging effect) 3 of them (#1,#2, and #3) show errors that admit values compatible with predictions closer to 0 mas/yr than to the -39 mas/yr prediction. One of them (#2) is compatible with a null result. Gyroscope #4 is compatible with -60.6 mas/yr . And these are the numbers achieved after more than 5 years of fitting the raw results to something tolerable.
IMHO, GPB experiment, in the case of the geodetic effect confirms it with little room to doubt of its existence (this had been pretty much been settled by other experiments, but in the case of the Lense-Thirring effect this results are of course compatible with GR but also compatible with very different predictions, including a null effect, and given the error margins wrt the smallness of the effect and the disparity among the 4 gyroscopes, the experiment can't be used either to confirm or reject the effect.
The experiment of course wasn't designed to prove GR, no experiment can do that. It could only falsify or confirm predictions of GR, it confirmed the geodetic effect, and it neither confirmed nor falsify the Lense-Thirring effect due to the lack of accuracy obtained by the gyroscopes.
Apparently all theories but DG and WG are compatible with GBP results, even those two are compatible with the results of one of the 4 gyroscopes.

 

[Polestar101]

Is there a detailed analysis available that explains how they canceled out each of the 50 plus unwanted signals? I am particularly interested to learn how they canceled out the "unpredictable" polhode noise and other "unidentified" signals. Presumably there will be some follow-up report that provides this data?

 

[JonathanK]

Thanks Garth, and perhaps I should say thanks from all of us for what you've done on this over the last few years.

NB. The predictions you posted for my theory PSG are correct, but not the link to them, which is here http://journalgp.awardspace.com/journal/0202/020203.pdf
'A derivation of the geodetic effect without space curvature'.

I agree with the point made above that the geodetic effect result from GP-B is on much more solid ground than that for frame dragging. Best wishes to all.

 

[Garth]

Thank you Jonathan, the Final results have today been published in Physical Review Letters, which you may access through the GP-B website: Gravity Probe B: Final Results of a Space Experiment to Test General Relativity and a Viewpoint article by Professor Will: Finally, results from Gravity Probe B.

In reply to Polestar101 I quote from Professor Will's article for a summary:

However, three important, but unexpected, phenomena were discovered during the experiment that affected the accuracy of the results.

First, because each rotor is not exactly spherical, its principal axis rotates around its spin axis with a period of several hours, with a fixed angle between the two axes. This is the familiar “polhode” period of a spinning top and, in fact, the team used it as part of their analysis to calibrate the SQUID output. But the polhode period and angle of each rotor actually decreased monotonically with time, implying the presence of some damping mechanism, and this significantly complicated the calibration analysis. In addition, over the course of a day, each rotor was found to make occasional, seemingly random “jumps” in its orientation—some as large as 100 milliarcseconds. Some rotors displayed more frequent jumps than others. Without being able to continuously monitor the rotors’ orientation, Everitt and his team couldn’t fully exploit the calibrating effect of the stellar aberration in their analysis. Finally, during a planned 40-day, endof-mission calibration phase, the team discovered that when the spacecraft was deliberately pointed away from the guide star by a large angle, the misalignment induced much larger torques on the rotors than expected. From this, they inferred that even the very small misalignments that occurred during the science phase of the mission induced torques that were probably several hundred times larger than the designers had estimated.

What ensued during the data analysis phase was worthy of a detective novel. The critical clue came from the calibration tests. Here, they took advantage of residual trapped magnetic flux on the gyroscope. (The designers used superconducting lead shielding to suppress stray fields before they cooled the niobium coated gyroscopes, but no shielding is ever perfect.) This flux adds a periodic modulation to the SQUID output, which the team used to figure out the phase and polhode angle of each rotor throughout the mission. This helped them to figure out that interactions between random patches of electrostatic potential fixed to the surface of each rotor, and similar patches on the inner surface of its spherical housing, were causing the extraneous torques. In principle, the rolling spacecraft should have suppressed these effects, but they were larger than expected. The patch interactions also accounted for the “jumps”: they occurred whenever a gyro’s slowly decreasing polhode period crossed an integer multiple of the spacecraft roll period. What looked like a jump of the spin direction was actually a spiraling path—known to navigators as a loxodrome. The team was able to account for all these effects in a parameterized model.

The original goal of GP-B was to measure the frame-dragging precession with an accuracy of 1%, but the problems discovered over the course of the mission dashed the initial optimism that this was possible. Although Everitt and his team were able to model the effects of the patches, they had to pay the price of the increase in error that comes from using a model with so many parameters. The experiment uncertainty quoted in the final result—roughly 20% for frame dragging—is almost totally dominated by those errors. Nevertheless, after the model was applied to each rotor, all four gyros showed consistent relativistic precessions (Fig. 1, bottom). Gyro 2 was particularly “unlucky”—it had the largest uncertainties because it suffered the most resonant jumps.

A full description of the analysis may be found here Post Flight Analysis — Final Report

Garth

 

[Polestar101]

Thanks for the excerpt from Professor Wills (head of review board) who has looked at many of the efforts the team has gone through in trying to identify and separate the various unexpected sources of noise. His own work depends on Einstein’s GR, so it is not surprising that he would support the conclusions, nonetheless he was very clear that a lot of assumptions were made in arriving at the final conclusions.

It is impossible to know if all the assumptions in the parameterized model are ideal for properly categorizing and canceling each noise without knowing for certain the source of each unwanted signal, but the GPB team seems to have done the best they could based on the circumstances.

The inability to continuously monitor the rotors’ orientation meant the stellar aberrations could not be utilized as calibrating tools (as planned) hints at the amount of noise in the overall experiment. But even attempting to use the diurnal and annual aberrations as the main calibration tools shows the experimenters did not plan on accounting for any solar system motion relative to the guide star – meaning they essentially used a static solar system model.

The issue I would still like to understand is if any of the “noise” might be evidence of solar system motion. If for example we discovered the solar system is just slightly accelerating, then it might explain the anomalous acceleration of Pioneer 10 and 11 and possibly shed light on the http://www.space.com/5037-nasa-baffled-unexplained-force-acting-space-probes.html" acting on our spacecraft flybys (Galileo, NEAR, Rosetta, Cassini, etc.), that could theoretically be explained by an accelerating solar system.

Maybe what Everitt calls “strange anomalous torques” are not all “criminals”, as he put it? The point is it probably makes sense to very carefully examine all the assumptions behind the unwanted cancelled-out noise to make sure we didn’t eliminate something even more fundamental than GR, that is, solar system motion.

 

[jumpjack]

Is it possible to explain in a simple way how to calculate the intensity of gravity effect detected by probe-b?
I mean, I know the formula F=GMm/r^2 for "standard" gravity, but how can I calculate the force generated by a rotating body?
I guess I need to know the distance of the test-body from the main-body, and the length of test-body (to calculate the force which makes it "rotate"), but which is the formula?

And can the Moon generate a similar force by rotating around the Earth? It's another kind of "mass current", I think.