Pioneer Anomaly: Unravelling Physics' Mysteries

[henryco]

Keep in mind the lunar laser ranging project has been collecting data for nearly 40 years. It should be interesting to compare GPB results with those of that study.

Sure! as far as i know, nothing anomalous was found (and the last article by Turyshev confirms this) in LLR data, but i was also told that this analysis is extremely complicated...

Anyway, exporting their data in the sun reference frame it appears that they can even see with great precision a frame-dragging effect due to the Earth motion about the sun in this frame. But the LLR data were taken in the Earth rest-frame so, their frame dragging signal is nothing but the effect they themselves injected in their data by lorentz transporting them in the sun rest-frame (see this month article by Turyshev)!

If, and this is what you can read in red in the latest version of my article gr-qc/0610079, if the transformation group is the Gallile one instead of the Lorentz one, you are still OK with all test of PPN alpha parameters which only test boost invariance and not Lorentz invariance as is always claimed.
But under such transformation, g_munu behaves differently. So LLR data analysers may be should not perform a Lorentz transformation.
In GP-B because you test frame-dragging in a frame where the Earth is rotating, you can really test what is the correct transformation group under boosts.

F H-C

 

[henryco]

Keep in mind the lunar laser ranging project has been collecting data for nearly 40 years. It should be interesting to compare GPB results with those of that study.

Hi,

PLease have a look at gr-qc/0702028 the latest paper by Turyshev, Nordtvedt and co regarding gravitomagnetism.
It says something incredible! It says that the frame-dragging is seen in the frame of the observer (earth frame) where there should be nothing at all since in this frame the speed of the Earth vanishes...but they keep using there (badly incorrect) the gravitomagnetic field formula of the sun rest frame. Crazy isn't it?

Best regards

Fred

 

[Chronos]

Same paper I had in mind, Fred. I didn't notice any problems with their approach, but will read again. Interesting stuff for sure.
http://arxiv.org/abs/gr-qc/0702028
The Gravitomagnetic Influence on Gyroscopes and on the Lunar Orbit
Authors: T. W. Murphy Jr., K. Nordtvedt, S. G. Turyshev

 

[henryco]

In a previous post i said:

...they keep using there (badly incorrect) the gravitomagnetic field formula of the sun rest frame. Crazy isn't it?

Fred

At least, if they are actually working in the sun rest frame, should they study small acceleration perturbations making the trajectory deviating not from a circle as they did , but from a Lorentz transformed circle (moon trajectory should look like a rugby ball after Lorentz transport from a comoving frame). May be they applied this correction elsewhere but it should be mentionned in the paper formula for these to be correct, not elsewhere, i believe...tell me if I'm wrong.

best regards

Fred H-C

 

[Garth]

Garth: I think you mean H₀, don't you? If so, then the MOND figure would be either a coincidence, or easily testable (what value best fits the rotation curves of very distant spirals?).

A paper by Bekenstein & Sagi in today's physics ArXiv asks the same question as in this old post of Nereid's: Do Newton's G and Milgrom's a₀ vary with cosmological epoch ?.

In the scalar tensor gravitational theories Newton's constant G_N evolves in the expanding universe. Likewise, it has been speculated that the acceleration scale a₀ in Milgrom's modified Newtonian dynamics (MOND) is tied to the scale of the cosmos, and must thus evolve. With the advent of relativistic implementations of the modified dynamics, one can address the issue of variability of the two gravitational ''constants'' with some confidence. Using TeVeS, the Tensor-Vector-Scalar gravitational theory, as an implementation of MOND, we calculate the dependence of G_N and a₀ on the TeVeS parameters and the coeval cosmological value of its scalar field, \phi_c. We find that G_N, when expressed in atomic units, is strictly nonevolving, a result fully consistent with recent empirical limits on the variation of G_N. By contrast, we find that a₀ depends on \phi_c and may thus vary with cosmological epoch. However, for the brand of TeVeS which seems most promising, a₀ variation occurs on a timescale much longer than Hubble's, and should be imperceptible back to redshift unity or even beyond it. This is consistent with emergent data on the rotation curves of disk galaxies at significants redshifts.

Garth

 

[HenriPoincare]

http://www.space.com/scienceastronomy/080229- spacecraft -anomaly.html