Antoniseb. Actually it's essentially a test for the constancy of Big "G". The Bureau of Standards and all scientists being confined to our environs....sensitive experiments to determine G have been done classically with Eotvos-type apparatus. In more recent decades, Mossbauer effect tests for small variations in local g fields have evolved with sensitivity being inversely proportional to bandwith, and bandwidth approaching monochromaticity...hence a graser. As this stuff is very sensitive and highly classified, you're going to need a "Q" level clearance to talk about it sensibly with the people in charge. It's why I proposed the Mossbauer test near a refueling nuke plant in 1982. A minute acceleration will produce a resonance detuning of the apparatus, but so will a gravitational gradient. Both of those are accompanied by a commensurate shift in the neutrino sea gradient which is omnipresent. Jerry's thinking of a Cavendish-type apparatus is OK and could carry out the result if launched in a satellite that journey's out to Pluto and back....but due to the torsion balance nuances, with great sensitivity to mechanical vibrations, a Mossbauer test is far more robust. Solid State. Zirconium steel tubes. No delicate springs to withstand a shuttle or rocket launch. The solar neutrino flux is likely anisotropic due to parity effects, and zodiacal gas and dust in the solar plane should cause a varying value of "G" depending on R, theta, and phi....and a bit of MOND. Had this discussion with Ken G in a few e-mails two years ago. Didn't open it up in the forum, or in my physics talks at the AAPT because it was predicting flat rotation curves at large R, which Vera Rubin discussed at MIT years ago, and I had no data to work on, or access to be a principal scientist in an investigation...so I routinely left it out.
The other thing that should show up is a persistent change of solid state "shot noise" vs R, theta, and phi from the sun. The guillotine once again, a first rate theory predicts...I'll bet a bottle of Rob's Root Beer. pete.

__________________
A third rate theory forbids
A second rate theory explains after the fact
A first rate theory predicts...A. Lomonosov

While I have no reason to believe that the density of neutrinos has any impact on 'G', let's assume that it is something you'd like to test. There was a proposed mission to launch a pair of dense spheres which would be loosely contained in a sphere of nearly uniform density including an ion engine to keep the outer sphere moving in an ideal ballistic path (measured by the motion of the inner spheres). This keeps dust, solar wind, and other factors from affecting the experiment. The experiment will test how the two inner spheres orbit each other.

Given your idea, there's no reason other than price that such an experiment couldn't be put on a New Horizons type trajectory. Would this give the kind of precision you are looking for?

__________________
Forming opinions as we speak

GP-B Program Extended Through September 2008, and Possibly March 2010

http://einstein.stanford.edu/highlights/status1.html

...and possibly through 2010? Without releasing any concrete information as to whether the current data set is consistent with General Relativity or not? This program is already more than forty years old - we could all die before anything concrete is published!

__________________
jwj

It's ok not to know. We should try harder to find out.

I can understand your logic, Jerry, but...
doing that would obviate the whole reason for using a zero g environment in the first place....at least for gyroscopes.

Do you think the exact polhode precession could be duplicated precisely.?
Even if the spheres could be duplicated exactly, duplicating the space environment on earth would not be possible, neither would it be possible to duplicate the precise patch effect....and its response in a zero g environ.

Most are unaware that the original conception was to do earth-based gyros, but it was easily shown that the suspension and unbalanced mass torques on earth-based gyros were far more problematic than that of their (greatly improved) performance in zero g.

Furthermore, working out the equations for constrained motion for gyroscopes (earth-based) is far more complex, and even though they were eventually obtained for the geodetic precession (only ~0.4 arcsec/yr. on earth), I am not sure the frame dragging portion of the precession was ever obtained precisely for constrained gyro motion, especially since there were some ambiguous assumptions in doing so.

So 'modeling' the polhode from the orbital data is appropriate.

. Here's a video simulation of the modeled Polhode effect over time....from the orbital data:
http://einstein.stanford.edu/Media/P...animation.html

Now, having said all that...I want you to realize there actually was pre-launch testing of possible Polhode effects; its just that, in part, because of the above mentioned complications in constrained moton, that modeling did not match the orbital data....at least that's the assumption.

Do I think the polhode theory provides the definitive answer for the anomalous precession? Not necessarily; and I think that other 'causes' should be suspected and modeled....especially since the introduction of Tajmar/ deMatos's unusual experimetal results ...which indicate much larger Gravitomagnetic response of superconductors than would otherwise be expected by GR. (More on that in the bold print below).

G^2

Excellent ; Jerry; you are thinking outside the box now....the GR box.

We should follow GR as far as it can take us; but it is important to realize it does have its limits and when we get to its limitations, it is appropriate to take the next step by considering possibilities beyond its scope.

I believe it was Hehl who admitted that Gen Rel. was not at all adept in handling correlated spins. If I remember his comment was along the lines that GR has an axiom that all motion can be transformed away by an appropriate choice of reference frame, but with correlated spins that is not possible. Thus he, like others, have recognized the limitations of GR.
Your recognition of that point is noted.

........

**The other modeling I would like to see (in GP-B) is that which would take into account the Tajmar / deMatos effect. As I mentioned to Publius some time back, the greatly enhanced gravitomagnetic field of the gyros should not influence the frame dragging precession portion of the experiment.....BUT that was ONLY considering its interaction (or lack of interaction) of a SINGLE gyroscope with the earth's gravitomagnetic field.

The problem developes when we realize there are FOUR gyros in GB-P, two spinning one direction and 2 spinning the other direction....(which was done for redundancy to cross check and make for greater accuracy in the data).

If we consider the multiple effects of 4 greatly increased GM fields of the 4 SC gyroscopes, then we have to deal with their INTERACTION WITH EACH OTHER. Surely if the gravitomagnetic field of a superconducting Gyro is enhanced as great as Tajmar experiments suggest, then the interaction of the dipole GM field of each gyro with the others must be taken into account.

Even though each gyro is magnetically isolated, it is impossible to gravitomagnetically isolate them....Gravitomagnetism is an angular momentum transferring field, the interaction between gyros of which can very possibly mimic unbalanced torque (or at least confound any modeling) of polhode / electrostatic coupling of the gyro to the frame.

Hope that all made sense.
All comments welcome.
.
G^2

When can I pop the bubbly?

2010? *sigh*

SNIPPET That's not the only thing it's impossible to isolate from either. pete

__________________
A third rate theory forbids
A second rate theory explains after the fact
A first rate theory predicts...A. Lomonosov

Yes, very good, thank you.

In a later release, the Gprobe website stated all of the variance could possibly be accounted for in patch effects; rather than a combination. If you followed the experiment from the start, you know they placed much emphasis on the fact that all of the data reduction techniques were in place before the probe was launched, including the anticipated corrections necessary due to in-flight calibration checks.

In trying to back-out the data due to unanticipated results, there must be assumptions. Splines on top of splines - Every additional month of data massaging reduces the credibility of the product.

__________________
jwj

It's ok not to know. We should try harder to find out.

True, Pete. Don't know what you're getting at, but there are several other relativistic effects that are known to alter the precesssion of the gyroscopes which must be subtracted from the data.

1.There is a correction to the geodetic precession due to earth's oblateness....which amounts to about 7 milliarc sec/yr.

2. There is a SOLAR geodetic precession sometimes called the DeSitter-Fokker effect which is identical to the terrestrial geodetic effect, but is due to the mass of the sun.....and which amounts to....(let me check....you don't think I remember all these figures do you? ).....OK, about 19 milliarc sec/yr.

3. And there is starlight deflection from the guide star (due to the solar gravitational field) which varies through the year due to guidestar's changing position with respect to the sun as viewed from earth. I'm not sure of its value but probably varies between 0 and 15 or 20 milliarc sec. or so during the year.

None of these can be 'shielded' against....and they are simply calculated and subtracted from the data stream.

These above are the only three relativistic effects (besides the ones GP-B is designed to measure - earth's geodetic and frame dragging) that I know about which have been accounted for .

The other effect which I know has not been included is the spin-spin gravitomagnetic interaction between the gyroscopes that I have been pointing out in my previous post.

G^2

BTW,
(There are other completely distinguishable non-relativistic signals superimposed on the above,.... some variable...like aberration of starlight, etc. that also must be accounted for;.. but I only wanted to mention the relativistic ones).

-----------------
--"What's another name for thessaurus?" --

Gravity Probe B scores 'F' in NASA review

__________________
Everything I need to know I learned through Googling.

__________________
Everything I need to know I learned through Googling.

2 things:

ToSeek: Does merging 10 threads make things problematic, in terms of following conversations?

Generally: So, does this mean that Gravity Prob B = teh suck or just that there is no need to keep it operating? Was it considered a success, or is that TBD?

CJSF

__________________
Two years ago moved from my town
I was looking up past the city lights
But the city lights got in my way

See the constellation ride across the sky
No cigar, no lady on his arm
Just a guy made of dots and lines

-from "See The Constellation"
by They Might Be Giants

You tell me. Most of the threads seemed to be temporally independent, so I don't think merging them should be much of a problem.

EDIT: I just went through the thread, and I think the only confusing things are the references to other threads that are no longer separate threads, but some of those didn't work even before I did the big merge.

__________________
Everything I need to know I learned through Googling.

Fair enough. In this case merging the 10 seems to be a good idea.

CJSF

__________________
Two years ago moved from my town
I was looking up past the city lights
But the city lights got in my way

See the constellation ride across the sky
No cigar, no lady on his arm
Just a guy made of dots and lines

-from "See The Constellation"
by They Might Be Giants

Well, I have to admit that part of the appeal is having the 245th thread on this forum still be an active one.

__________________
Everything I need to know I learned through Googling.

Funding runs out in September.

I have mixed feelings about this. I hate to see any science team disassembled; and I believe gravity is not understood at the most fundamental level - we need this type of science team, and more experiments of this type.

What is disappointing, is that they have not really released anything useful years after the end of the mission.

As far as the data, either there is an unexpected 'patch effect' that the team has focused their attention on, or the physics behind their observations is not understood, or both. I said several pages up I would rather see another mission, or a construction of new spheres to see if the type of patch effects they speculated entangled their data are the root cause of the failure to observe frame dragging effects.

In any case, I hope the final report includes some salvagable data, and clues for where we should keep looking.

Perhaps it is time to look elsewhere.

__________________
jwj

It's ok not to know. We should try harder to find out.

There is something called a Final Report here:

http://einstein.stanford.edu/

See right side page and click on Final Report. It's a 12 meg pdf file.

http://einstein.stanford.edu/content...91907-scrn.pdf

So what's the result of all this testing so far?

The biennial senior reviews are generally tasked to rank extended (post-primary-mission) support for a number of missions (and sometimes archive services) under the purview of NASA astrophysics, with regard to the likely science impact specifically of the proposed extended funding period. This year, they had to rank Swift, Chandra, GALEX, the warm extension for Spitzer, NASA funding for US investigators with XMM-Newton and INTEGRAL, operation of RXTE, two additional years of operation for WMAP, and extended analysis funds for GP-B (which ceased actual operations some time back). As I read the snippets of the review that have shown up around the web, the feeling (which I would have shared) was that it appeared unlikely that they could get a result from the additional 2 years or so which would be definitive (i.e. believed by anyone not on the team, to put things crudely). The