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From: mwe@astrovax.UUCP
Newsgroups: net.physics
Subject: Re: Query - re. Speed of Light
Message-ID: <52@astrovax.UUCP>
Date: Thu, 13-Oct-83 11:14:05 EDT
Article-I.D.: astrovax.52
Posted: Thu Oct 13 11:14:05 1983
Date-Received: Fri, 14-Oct-83 06:35:25 EDT
References: <256@flairvax.UUCP>
Organization: Princeton Univ. Astrophysics
Lines: 20

First, about experimental evidence:

We know to high accuracy (about 1 part in 10 to the 34th power I think)
that the photon has no rest mass. Special Relativity then indicates that
it travels at the speed of light. Of course, we have no independent measure
of the speed of light, having only "photon beams" to play with. (yes,
I know about gravitational waves, and as soon as we find one, we can
worry about its speed: also if your hard core then a neutrino is also
massless, but they're so sneaky its hard to get velocities anywhere near
as accurately as for light) If you believe SR, which is considered well
grounded in experiment, then you are forced to the conclusion that 
proper time does not pass in a frame moving with speed c. It therefore
seems to be a particularly uninteresting frame to be in (unless of course
you're massless, in which case you can't exist in any other frame). I'm
not sure if field of view has any meaning in a frame where time does not
pass, but you have the right limiting case: the direct forward direction 
fills your field of view. As you are traveling at c however, nothing comes
at you. This field of view is discovered as you run into things in your path.
I also don't think that the infinite blueshift ahead of infinite redshift
behind has any meaning. Speed c really is a limiting special case.