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Author Topic: Has Gravity Probably Been been a Big Flop?  (Read 2111 times)

Offline Yomi

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Has Gravity Probably Been been a Big Flop?
« on: 05/04/2009 12:29:29 »
Gravity Probe B (GPB) is a huge project of NASA and Standford university, in which a satellite carrying four ultra-sensitive gyroscopes were put into orbit around Earth. The idea was to test two of Einstein's General Theory of Relativity (GR) effects: the geodetic effect and inertial frame dragging.

The geodetic effect represents the effect that the curvature of spacetime have on a spinning, moving body, as predicted by GR. The geodetic effect is relatively large and should not have posed any problems for GPB to detect.

Inertial frame dragging is a GR prediction that the rotation of an object would alter space and time, dragging a nearby object out of position compared to the predictions of Newtonian physics. The predicted effect is incredibly small about one part in a few trillion, according to Wikipedia.

Although the Wikipedia article on the geodetic effect states that it has been confirmed to the 1% level, there is evidence that the best value that they obtained are not in agreement with Einstein's GR! This NASA/Stanford slide: http://colloquia.physics.cornell.edu/11-12-2007/cornellpres_files/v3_sli...
is showing that to a 1 sigma error confidence level the results for the geodetic precession are inconsistent with GR.

There were two unexpected sources of error affecting the gyros that almost ruined the whole effort, but the project scientists are confident that they can filter out the errors and reveal the true data. They are still struggling with the geodetic effect, never mind the very much smaller frame dragging effect.

So what if this whole effort turns out one big waste of money, with no clear result?


 

Offline Vern

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Has Gravity Probably Been been a Big Flop?
« Reply #1 on: 05/04/2009 13:22:55 »
Quote
So what if this whole effort turns out one big waste of money, with no clear result?
I suspect that if the original question was worth an answer, the experiment will  not be a waste of money. Whether the result is positive or negative, it will provide evidence for a better understanding.
 

Offline syhprum

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Has Gravity Probably Been been a Big Flop?
« Reply #2 on: 05/04/2009 21:47:59 »
If you wish to view this slide show you must first go to Cornell university and then sneak up on it the URL will not take you directly there.
I think this was a heroic effort if every experiment gave the predicted result straight away there would be no need to do science.
 

Offline Soul Surfer

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Has Gravity Probably Been been a Big Flop?
« Reply #3 on: 08/04/2009 20:22:15 »
The proper understanding and results of this effect are probably vital for the way matter behaves in extreme conditions notably the collapse inside black holes and the very earliest stages of the big bang
 

Offline yor_on

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Has Gravity Probably Been been a Big Flop?
« Reply #4 on: 09/04/2009 02:15:17 »
I'm amazed that it even is possible to send such delicate machinery up in space. But it's worth it, those questions we have in physics are very like the 'meaning of life' to me.
 

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Has Gravity Probably Been been a Big Flop?
« Reply #4 on: 09/04/2009 02:15:17 »

 

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