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...
Hi Garth,
I think your suspicions about Gerhard Forst are well justified. Here is a message I sent the moderator of ArXiv:
Dear arXiv-moderation,
This concerns the authorship of http://arxiv.org/abs/0712.3934 , "A critical analysis of the GP-B mission. I: on the impossibility of a...
Jim,
Thanks very much for your insights! That all seems to add up. Would it be possible to confirm with someone there from GP-B that the best of this data would hint at a slightly larger than expected frame-dragging effect? (If it hints at anything.)
Best wishes,
Kris
Hi Paul,
You have a point there, at least as far as this particular graph is concerned. I contacted the web page curator, and I think she'll put up a more readable version of this poster for us tomorrow.Magnetar,
That article says the geodetic effect of general relativity has been measured...
Hi Jim,
Thanks very much for the information! Does the possible small hint Francis mentioned refer to frame dragging specifically? Also, do you have any sense whether this is in the direction of a larger effect, or smaller than expected?
As F H-C mentioned, on the two charts of the...
Hi Paul,
I emailed the same address in 1999, to ask when they expected to launch the probe. It was scheduled for that October, but everyone knew they were running way behind. The response was that they were on schedule, and maybe would move the launch ahead to July. (Nice creative touch.)...
Hi Paul,
It's a good system. Without this redundancy, they would be in a bad situation now. They need be able to compare the outputs of multiple devices to correct errors. Two rotate one way, and two the other, but they all have the same axis of rotation. You can find this kind of...
Hi Paul,
The spin axes of all four gyros were aligned with IM Pegasi. These are its coordinates, posted previously by Garth:
RA (J1991.25) : 22h 53m 02.279"
DEC (J1991.25) : +160 50' 28.540"
Kris
Hi Paul,
When these extraneous influences like the polhode motion are estimated, of course that's done separately from the frame-dragging they are trying to measure. The latter is whatever is left when everything else has been accounted for.
This preliminary result is of the form x ± 100...
Hi Sylas,
To give you an example, the guide star moves east/west about -28 marcsec/yr, and -21 marcsec/yr north/south. The Gravity Probe B folks have described it as moving 35 marcsec/yr. That's the total magnitude -- squaring and summing the two values and taking the square root.
If the...
General relativity predicts 41 marcsec/yr. Suppose the measurement were -75 ± 75 marcsec/yr. That would rule out general relativity, while a zero precession would remain possible. So the central value does have meaning.
A previous GP-B web page said the best current estimate of the gyro...
I agree with F H-C that the central value for this data should have some meaning. (Not only because our theories make the same predictions.) It certainly would be interesting to see the east/west drift rates for the other three gyros.
Also, the "Next Steps" section of the same poster...