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Gravity Probe B

  1. Jan 24, 2007 #1

    Chronos

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    Here is the latest on GPB:
    http://einstein.stanford.edu/

    A couple of interesting quotes:

    . . . In addition to analyzing the data, members of our team are now in the process of preparing scientific and engineering papers for publication in 2007, including the reporting of the first results of this historic experiment at the American Physical Society (APS) Meeting in Jacksonville, FL on 14-17 April 2007. We have also begun discussions with NASA to plan a formal public announcement just prior to the APS meeting.

    . . . The December 21-28 2006 issue of Nature (v. 444, p. 978-979) contains a short news article stating that Nature has learned that “two unanticipated effects are clouding the [GP-B] team's frame-dragging results” and also that “results were expected by last summer but the announcement never came.”
     
    Last edited: Jan 24, 2007
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  3. Jan 24, 2007 #2

    Garth

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    Continuing the quote from the GP-B website:

    They have spent some time calibrating the four gyroscopes' individual Polhode "wobble" (due to them not being exactly spherically symmetric) and are on track for an April announcement.

    Note: the recent claims by Iorio that he has measured the frame-dragging precession from the Mars Polar Orbital Surveyor High-precision measurement of frame-dragging with the Mars Global Surveyor spacecraft in the gravitational field of Mars and found it to be (0.9937 ± 0.0053) times the GR prediction has been refuted by Kris Krogh in today's eprint: Iorio’s “high-precision measurement” of frame-dragging with the Mars Global Surveyor.

    Iorio had claimed too high a precision on an orbit that was not that well determined - 'angular momentum wheel desaturation' thrusters had been regularly used for one thing and also there would have been unmodelled atmospheric braking for another.


    Garth
     
    Last edited: Jan 24, 2007
  4. Jan 29, 2007 #3

    Garth

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    Just to ratify that point: On the Systematic Errors in the Detection of the Lense-Thirring Effect with a Mars Orbiter.
    Garth
     
  5. Feb 6, 2007 #4

    Garth

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    In today's ArXiv Murphy, Nordtvedt and Turyshev, The Gravitomagnetic Influence on Gyroscopes and on the Lunar Orbit are pre-emptying the GP-B result (due in April) by showing that
    This is re-iterating Kenneth Nordtvedt's oft quoted assertion that the GP-B experiment was worth doing when it was first suggested in the 1960's but now the result is a foregone conclusion the experiment has been a waste of time and money.

    However note the result I am interested in is the geodetic precession, which will resolve a degeneracy in the predictions of GR and SCC, a non-metric modification of GR.

    Nordtvedt, et al., have not acknowledged that such a degeneracy can exist.

    Garth
     
    Last edited: Feb 6, 2007
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