Re: The Speed of Light


"Gary Edstrom" <gedstrom@xxxxxxxxxxx> wrote in message
news:mn2fj2l5kcoofpeth5u71lk9bb4rdciuba@xxxxxxxxxx
Ok, I have a limited physics background. I have just enough knowledge
of relativity to be dangerous! A couple of questions from a simpleton
concerning the speed of light:

1. Why is the speed of light 300E6 m/s? Why isn't it a tenth that
speed? Why isn't it ten times that speed?

You have had some excellent responses from some knowledgeable people so I
will only give you my perspective. First the actual speed of light is
irrelevant because it can be made any value we like by simply choosing a
different set of units. What is relevant is that it is invariant ie does
not depend on the speed of its source. That this is the case is actually
quite deep and without going into the details is really equivalent to
electric charge conservation. An outline (and it is only an outline) can be
found here
http://www.upscale.utoronto.ca/GeneralInterest/DBailey/SubAtomic/Lectures/LectF13/Lect13.htm

In fact relativity really has nothing to do with light - the speed c that
appears in relativity depends purely on the principle of relativity -
nothing to do with light at all. See
http://arxiv.org/abs/physics/0110076,
and an ancient, but I still think excellent, post by Tom Roberts
http://groups.google.com/groups?hl=en&lr=&c2coff=1&selm=54jfst%24glp%40ssbunews.ih.lucent.com


2. Since the speed of light is finite, what is there in a vacuum that
limits its speed?


What is it in space that makes the angles of triangles add up to 180%? And
why 180 - what is so special about that mystical number? Surely something
must cause it? How can something so pervasive not have a cause? Answer -
it has no cause in the sense of some physical agency - it is simply a
property of Euclidian geometry. The same with what in a vacuum limits it
speed - it is simply of property on space-time geometry.

If a vacuum is truly empty as we classically think
of 'empty', shouldn't the speed of light in a vacuum be infinite?


That does not logically follow.

What holds it back?

That same thing that holds back the angles in triangles from being different
from 180% - geometry.

Thanks
Bill


Gary


.

Relevant Pages

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