sci.physics.particle

On 16 Mar, 20:30, BradGuth wrote:
> On Mar 16, 9:14 am, Tom Roberts wrote:
>
>
>
>
>
> > The Speaking Clock wrote:
> > > On 15 Mar, 08:57, Pentcho Valev wrote:
> > >> [... his usual nonsense]
>
> > > Would the speed of light be a non wiggly constant at the very edge of
> > > the universe - bending around it?
>
> > The speed of light is a constant, c, for any LOCAL measurement anywhere
> > in the universe. I guess that includes "non wiggly". It also includes
> > essentially all measurements of light speed here on earth. At least that=

> > is what GR predicts, and there are no observations that contradict it.
>
> > =A0 =A0 =A0 =A0 [Ignore Valev when he brings up Pound-Rebka and similar
> > =A0 =A0 =A0 =A0 =A0experiments -- they do not measure speed.]
>
> > But if you want to see light "bending around the universe" then that
> > would certainly require a non-local path, and there's no solid
> > prediction of the result (given the uncertainties in the physical
> > situation you have in mind).
>
> > It is rather difficult to perform a non-local measurement of the speed
> > of light, but it has been done by sending radar waves across the solar
> > system to reflect back from mars and venus. By measuring the round-trip
> > delay repeatedly over several years, and fitting to the planetary
> > orbits, one can deduce the round-trip speed of light for these paths.
> > That speed varies, depending on how close to the sun the path passes;
> > look up "Shapiro time delay". The results are in excellent agreement
> > with the predictions of GR.
>
> > =A0 =A0 =A0 =A0 Some people claim this is due to the solar atmosphere.
> > =A0 =A0 =A0 =A0 They are wrong: by doing this for multiple wavelengths t=
he
> > =A0 =A0 =A0 =A0 effect of the solar atmosphere can be identified, and is=

> > =A0 =A0 =A0 =A0 found to be negligible. Of course it would be highly
> > =A0 =A0 =A0 =A0 unlikely that such a different effect could mimic the GR=

> > =A0 =A0 =A0 =A0 dependence on path. Indeed, measurements using pulsars
> > =A0 =A0 =A0 =A0 agree with the GR predictions for paths that never go
> > =A0 =A0 =A0 =A0 inside earth's orbit, and we know what the solar
> > =A0 =A0 =A0 =A0 atmosphere is out here.
>
> > Tom Roberts
>
> But photons clearly represent mass, thus the solar atmosphere of
> photons does offer mass for other passing photons to interact with.
> . - Brad Guth- Hide quoted text -
>
> - Show quoted text -

Photons are just light packets of energy with no mass. Mass and
energy are interconnected, but if there is something for photons to
interact with in a solar atmosphere then it is not mass. I'm a whelk
and so I'd say that the universe is even stranger than the dreams of
the most rabid string theorists, but mass is an outdated concept
anyways. I mean - what the hell is mass?