Talk:Gravity Probe B

FAX checksum problem
I only heard of this as an unsubstantiated rumor, so I removed it. Please give source, if you want to put it back in. Here is the official text Highlight April 19 why the launch was scrubbed. Awolf002 22:33, 20 Sep 2004 (UTC)

Science results?
Great mission review; are there any science results to report? Even an arxiv report? linas 00:25, 30 October 2005 (UTC)


 * Someone really should add write-up if there are any results, it is already end of 2005 and there is big silence. Maybe did they did not find the effect that was predicted? 195.70.48.242 14:28, 13 December 2005 (UTC)

We're all waiting for the results. I'm sure as soon as they are public, someone is going to add it all, here. Awolf002 14:35, 13 December 2005 (UTC)


 * Aww, come on, its been a year and a half, there's gotta be a preprint discussing at least preliminary results. linas 15:11, 13 December 2005 (UTC)

Well, they finished taking the calibration data set just three months ago. Also, they seem to have a good mechanism to keep "the lid" on all preliminary results. Patience, friends! Awolf002 18:21, 13 December 2005 (UTC)


 * Speaking as a former student intern on the project, who just visited there over Winter Break, I can say that the timeline for finishing data analysis is around the end of summer (2006). After that, it will be peer-reviewed, and hopefully released around the end of 2006.  Grodin Tierce 19:27, 20 January 2006 (UTC)


 * Patience - The phase 2 they are working on at the moment (June 2006) is to get the monthly estimate of each gyro individually pointing with respect to the guide star. Phase 3 will correlate the gyro readings into a single estimate for the satellite. The *final* stage (predicted April 2007) is to reference the gyro motion to the stella background instead of the guide star coordinates they have been working in so far, by adding in the measured motion of the guide star. This motion measurement has been done by a completely different team, and was started years before the launch to improve the reliability of the measurement. This separation of the detailed gyro motion analysis and the guide star motion could be seen as quite an effective way of not only "blinding" the gyro analysis team to the "right answer", but demonstrating that they are so blinded. NeilUK 07:14, 11 June 2006 (UTC)


 * Let's just wait until the official announcment in April until we try to judge their results, which no one in the public has been informed of.--Planetary 16:56, 19 July 2006 (UTC)


 * keep on with the patience. April announcement will be interim results, more analysis through the rest of 2007 will improve the expected error marginNeilUK 09:14, 12 February 2007 (UTC)


 * More patience -- the final results are now expected in May 2008. I've updated the date on the page. BentSm (talk) 23:59, 16 December 2007 (UTC)


 * Even more patience the results are now not expected until September 2008, and possibly March 2010! Garthbarber (talk) 10:39, 25 March 2008 (UTC)

PROOF!!!
I seriously doubt that: "When the mission is successfully completed, GP-B will be the most precise attempt at verification of any effect predicted by general relativity." This would have to exceed the accuracy of timing which has been the most precicely defined SI unit there is for years. GR predicts the speed of light in a certain media and i think this number will stay unprecedented for quite a while.

So in light of these circumstances, could anyone verify the given sentence?Slicky 17:23, 28 March 2006 (UTC)


 * First: You should distinguish special relativity and general relativity. Second: The value of light speed in vacuum is not predicted by any theory, it's a convention given by SI definition of meter. Previously it was a measured value. Third: The special relativity theory says that the speed of light in vacuum is constant, but this is a postulate not a prediction. --Egg &#9993; 22:22, 28 March 2006 (UTC)

GPS Satellites Beating GPB to the punch?
I read an article within the last few years suggesting that data from GPS satellites had already been used to verify directly the same that GBP is testing.

I can't find the article now. Anyone care to comment?

If technological change accelerates enouugh, we should expect to see this kind of thing a lot. We might stop planning any experiment that takes more than 3 years to perform, assuming things will be so different in 3 years, it's not worth the risk.

I also read that article. I remembered from it that GPS had to account for frame dragging in order for it to work, thus it indirectly proved that frame dragging exists. There was some controversy that the test was not necessary because of this. I think this subject deserves a "Controversy" section in the main article.

The article I think you're talking about is a Nature paper - I. Ciufolini and E. C. Pavlis, A confirmation of the general relativistic prediction of the Lense-Thirring effect, Nature 431, 958 (2004). However, its results seem to be far from accepted; see for example http://arxiv.org/abs/gr-qc/0410110. Going into the detail without overwhelming the entry with technical stuff would be tricky; a reference on the page for frame-dragging might be appropriate, though. Chrislintott 09:47, 8 February 2007 (UTC)

dates
Is there some reason to state the mission runs from 2004 to 2005 and not say 2007? It's understandable that people are confused about the lack of results.Potatoswatter 04:57, 19 November 2006 (UTC)

The mission itself ran from 2004 to 2005. It's the data analysis which is still underway

Chrislintott

Never tested before
This mission is testing some relativistic phenomena that no one has tested before. They might exist or not. If not, General Relativity will be wrong, as someone is already predicting, if so many many people will come to consult this article next April.


 * I think the point is that we didn't have sensitive enough equipment to test them. I hardly think people are going to dump existing results like time dilation and its effect on GPS or neutrino oscillations, or the precession in Mercury's orbit, and the host of other things already confirmed.  Ever.  BTW your link doesn't work.

4.249.63.240 (talk) 21:22, 6 May 2011 (UTC)

Text referencing arXiv publication
I feel, the new text (quoting a 0.5% accuracy of an MGS analysis) referencing an non-peer reviewed (yet) article on the arXiv server is premature. We cannot use this type of attribution in my reading of WP:RS. The claims related to this should be removed. Awolf002 02:56, 19 January 2007 (UTC)

The text says that a claim has been made, which is true. It's usual in astronomy to cite arXiv preprints pending the (often slow) peer review process. I suggest the text is left unless the paper is withdrawn. Chrislintott 10:26, 19 January 2007 (UTC)

Aim of the Gravity Probe B experiment
The aim of the Gravity Probe B mission, which the article had stated in the first paragraph until recently as

"to measure the stress-energy tensor (the distribution, and especially the motion, of matter) in and near Earth, and thus to test related models in application of Einstein's general theory of relativity"

was recast, per (Revision as of 09:59, 28 March 2007, "copyedit" by User:Potatoswatter as

"to measure the stress-energy tensor (the distribution, and especially the motion, of matter) in and near Earth, thus testing Einstein's general theory of relativity and our precise models of space."

(The former statement had been in place since Revision as of 19:34, 9 May 2004.)

There's a profound difference between these two statements: The former claims that certain models are being tested, concerning the distribution of stress-energ, or IOW: the distribution and motion of matter, in and near earth (i.e. notions for which definition and method of measurement is provided by the general theory of relativity). The latter claims not only that certain models of space (or: spacetime) are being tested, concerning presumably for instance "curvature" of the region containing earth (i.e. notions for which definition and method of measurement is provided by the general theory of relativity), but it claims also a test of the general theory of relativity itself.

It is straightforward (to me) to point out the view on the aim of the Gravity Probe B mission as "test of certain models (in application of the general theory of relativity)", especially by considering the negative or contrary expectation-sentences

"The model, that the interior bulk mass of earth rotated approx. at the same angular velocity as earth's surface, is wrong if ... (certain finds had been made by the Gravity Probe B mission)", or

"The model, that the region including earth has a particular frame-dragging curvature, is wrong if ... (certain finds had been made by the Gravity Probe B mission)".

(In application of the general theory of relativity, the latter of course represents the definition and method of measurement for the former. Btw.: the experimental determination, that the latter model, and consequently also the former model, are not wrong after all, is IMHO an awesome accomplishment and insight. Had it not been for the Gravity Probe B experiment -- how would we've ever known anything about mass or motion of earths interior?)

On the other hand, I'm unable (at present, by myself) to point out the view, that a test of the general theory of relativity itself were involved; considering in particular the negative or contrary expectation-sentence

"The general theory of relativity itself is wrong if ...".

I'm unable to complete this sentence by referring to particular models, or to certain finds by the the Gravity Probe B mission, which are available (or which are even just about to become available) in application of the general theory of relativity; which in turn cannot be both be applied and presumed wrong in attempting to express a consistent expectation-sentence.

Consequently I'll restore the aim of the Gravity Probe B mission as stated since 2004, incorporating the test of models concerning space (or spacetime curvature) pointed out recently.Frank W ~@) R 07:34, 18 April 2007 (UTC)

Moving Mission progress to a timeline article?
Would there be consensus to rename the section "Mission progress" to "Gravity Probe B mission timeline" and move it to a separate article? It seems to me that the current section was useful during the data taking campaign, but has now become an "obstacle," when reading this article. Awolf002 11:54, 18 April 2007 (UTC)


 * I agree. The timeline was quite exciting during the mission (did you, like me, follow the IOC phase day by day, nail-biting stuff!), but the article has to move with the experiment status, which is now practically finished. NeilUK 07:31, 19 April 2007 (UTC)

Okay, I will change that shortly, if nobody else objects. (Yes, it was a nail-biting time when I helped writing that section :) Awolf002 11:16, 19 April 2007 (UTC)

Added results to the top of the article
Many comments in the discussion ask for results, so I've put them up where they can be seen, without having to wade to the links in the article to the off-site pubs. If you want to edit these a little, that's fine, but please leave at least a mention that the results so far are as expected, right at the top. NeilUK 07:31, 19 April 2007 (UTC) OOps, sorry, didn't intend to create a sock, 193.195.77.146 is me, having an idle wwilf and forgot to log in before editting NeilUK 07:33, 20 April 2007 (UTC)

There is no known general relativistic prediction of gravitomagnetic effect
There is no known general relativistic prediction of gravitomagnetic effect other than dipole gravity proposed by Jeong. His paper was published in 1999. But no one noticed its implication. Now it seems that the Stanford team needs his theory more than ever because it is the only theory that derives Lense-Thirring force directly from the linearized theory of general relativity. The conventionally known gravitomagentism obtained from the modified Maxwell's equation is not of general relativity. So they should be careful when deciding what theory they have to use to compare the GPB data with. —Preceding unsigned comment added by 70.128.226.243 (talk) 10:59, 31 March 2008 (UTC)

Updated "Perfect Sphere" section
Recent news confirms that the quartz spheres are no longer the most perfect spheres. —Preceding unsigned comment added by Djtachyon (talk • contribs) 14:39, 1 July 2008 (UTC)

Unless you have a reference to a reliable source to back up the above claim, ypou shouldn't have edited the article. I searched for a good reference (doing a Wikipedia search on "Avogadro Project" is a good starting place) but could not find any reference. 75.84.238.18 (talk) 11:52, 1 March 2010 (UTC)

need references
The Future section needs references. RJFJR (talk) 17:33, 4 December 2008 (UTC)

References added on the tests with the LAGEOS satellites, with the MGS probe and the Sun
I added some references to papers published in refereed journals concerning the tests with the LAGEOS satellites. I also added something on the Sun's Lense-Thirring effect. To the moderator(s): please note that some acts of vandalisms may be done because such references are about papers by a researcher whose papers were systematically removed in the past in the voice frame-dragging by Italian IPs. GraviMat (talk) 18:38, 14 May 2009 (UTC)

Additional sources




-- John Broughton (♫♫) 22:26, 8 October 2009 (UTC)

Another one, from today: Mike Peel (talk) 21:17, 4 May 2011 (UTC)


 * I have added the latest announcement (diff). Please feel free to add more references and details. - Subh83 (talk &#124; contribs) 05:12, 6 May 2011 (UTC)

just me?
Does this phrasing confuse anybody else or is it appropriate to relativity? "A gyroscope's axis when parallel transported around..." parallel to what? should there be a comma before transported? 4.249.63.240 (talk) 21:16, 6 May 2011 (UTC)
 * I recommend you follow the link; it'll take you to an explanation of parallel transports. --Tesseraktik (talk) 23:13, 6 May 2011 (UTC)

Language
Hi, just wondering about the wording etiquette on the main page in the news section. It says that it is 'confirmed' but under scientific parlance shouldnt it say that it is 'supported'? Mwheatley1990 (talk) 14:49, 7 May 2011 (UTC)

Whoever changed it, thanks Mwheatley1990 (talk) 21:16, 8 May 2011 (UTC)

Changes made
I removed a paragraph reporting unpublished (and biased against GP-B) comments and other blogs-based stuff. I replaced it with a peer-review journal article commenting on the situation after GP-B. Danguard00 (talk) 13:52, 27 June 2012 (UTC)

Not the first time in history
The statement: "Gravity Probe B marks the first time in history that a university has been in control of the development and operations of a space satellite funded by NASA." is incorrect. See for example: http://en.wikipedia.org/wiki/Explorer_52

Final Outcome?
I'm a layperson (no science background) and after reading this article I just had to ask -- can someone explain the final result in plain English? It sounds to me like the result is basically that the experiment was a failure -- due to problems with the data they collected, they couldn't actually determine if anything they measured was accurate or not? Is that correct, or am I misunderstanding something? DS Cable (talk) 16:14, 3 November 2014 (UTC)

Answering your question: No one dares to refute Einstein unless you are a Neo Nazi. No, the experiment was not a failure. That is not to say that $750 million spent on this non usable space mission were well spent, but was nice private schooling/paramilitary subsidy. The experiment showed that within the parameters placed, after all that good engineering, no prediction was detectable. If the Einstein trademark was not involved, that would have been grounds for questioning Steven Hawking's Black Holes and the Dark Matter reasoning. But that is the politics of science and money. Such is not a matter for Wikipedia to resolve. 64.237.234.82 (talk) 19:12, 23 June 2016 (UTC)

External links modified
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External links modified (January 2018)
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No reference for a seemingly improbable quote
Hello,

Please forgive any breach of etiquette as this is my first contribution to a wiki entry.

No reference for quote:

"The progress reported at SAC-18 ... 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 minuscule fraction of the cost."

I bring this up because I could not find the original report and to my mind the fix for Hubble has no similarity to the GPB data analysis effort. I cannot see a single point of similarity except they were both NASA missions. So I think that this quote requires a reference if it is to be included in the article. So I'm looking for someone to point out errors in my thinking before adding a note to the effect that it needs a reference. 134.79.32.22 (talk) 19:52, 1 July 2022 (UTC)

After a year without any response to the critique above I have added a "Needs citation" note to the passage in question. — Preceding unsigned comment added by 67.161.8.42 (talk) 22:32, 6 August 2023 (UTC)

After nearly four (4) months no one has suggested a reference for the quote, therefore I will remove it from the article. — Preceding unsigned comment added by 67.161.8.42 (talk) 20:55, 30 November 2023 (UTC)

A Commons file used on this page or its Wikidata item has been nominated for speedy deletion
The following Wikimedia Commons file used on this page or its Wikidata item has been nominated for speedy deletion: You can see the reason for deletion at the file description page linked above. —Community Tech bot (talk) 15:38, 30 April 2023 (UTC)
 * Gravity Probe B.jpg