sci.physics.particle

Tom wrote:
> The speed of light varies depending on the strength of the
> gravitational field. Einstein said that.

He said that in 1911, early on the then-unfinished journey to General
Relativity. GR itself does not really have this property -- the _LOCAL_
speed of light is everywhere c. When measured over non-local paths the
speed of light can vary, but there is no definite dependence on
"strength of the gravitational field", it's rather that one must compute
an integral over the path to obtain the theoretical value for such a
speed measurement.

Yes, as one prolific idiot around here is fixated on,
in the APPROXIMATION of weak fields and restriction to
paths at fixed gravitational potential, for Newtonian
coordinates one can express the non-local COORDINATE
speed of light in terms of the gravitational potential.
In 1911 Einstein did not understand all the caveats
mentioned here, but certainly did by 1915; this idiot
still does not understand them.


> You might want to check out:
> arXiv:gr-qc/0704.3485
> and the references therein.

Arxiv.org gives "bad identifier".


Tom Roberts