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Re: electromagnetic literacy



Kopeikin's more recent paper (2/03) is also available on Spires. Checking
citations, I found only 2:

On the Speed of Gravity and the v/c Corrections to the Shapiro Time Delay
Stuart Samuel (LBL)
Phys. Rev. Lett. 90, 231101 (2003)
and

From: Joshua A. Faber <jaf184@lulu.it.northwestern.edu>
Date: Fri, 14 Mar 2003 22:50:26 GMT (8kb)
The speed of gravity has not been measured from time delays
Authors: Joshua A. Faber


Samuel says that the v/c correction is too small to be measured,
where v is the planet speed, so he seems to be in agreement with Faber.

Regards,
Jack

On Sat, 13 Sep 2003, Stephen Speicher wrote:

On Sat, 13 Sep 2003, Marc Kossover wrote:

I was directed to this site
<http://www.metaresearch.org/cosmology/speed_of_gravity.asp>
by an online magazine.

The author makes several assertions about the speed of gravity, arguing
primarily that it's effects are instantly transmitted. He claims certain
astronomical observations of pulsars as evidence.


For more than a dozen years the author of that site has been
making claims about gravity propagating near-instantaneously, and
all through those years he remains impervious to the refutations
provided by experts in the field. Most knowledgeable people no
longer debate the issue with him.

Also, keep in mind that the author of that site also claims to
have scientific evidence that the "Face on Mars" is artificial
and that there are artifacts in the Cydonia region, "artificial,
alphabet-like symbols on Mars."

I was under the impression that the effects of gravity propagate at c,
although no experiments had yet shown this. In particular, I believe that
the work at LIGO and other large interferometers was trying to test this
hypothesis.

Am I confused? What is the state of our knowledge?


There are two different phenomena associated with the loose
notion of the "speed of gravity." LIGO is looking for
gravitational waves -- pertubations in the curvature of spacetime
-- as opposed to finite changes in the propagation of the
gravitational field. It is unequivocally true that according to
general relativity both gravitational waves and finite changes in
the propagation of the gravitational field travel at c.

LIGO has not yet detected gravitational waves -- the project is
not expected to reasonably do so until the next phase -- but
finite changes in the gravitational field _have_ been measured
experimentally, and the result, within experimental error, was c.
See "The post-Newtonian treatment of the VLBI experiment on
September 8, 2002," S.M. Kopeikin, _Physics Letters A_, 312
(3-4): pp. 147-157 Jun 9 2003. The paper is also available from
the physics archive at <http://arxiv.org/abs/gr-qc/0212121>.

(Note that all experts agree as to the technological marvel of
this experiment, but there is some controversy in regard to
whether or not the "speed of gravity" was actually measured.
Personally, I have reviewed all of the relevant technical papers
involved, and I believe that history will judge Kopeikin's
experiment to be a landmark in experimental relativity.)

--
Stephen
speicher@caltech.edu

Ignorance is just a placeholder for knowledge.

Printed using 100% recycled electrons.
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--
"Don't push the river, it flows by itself"
Frederick Perls