Re: Speed of Light

[William Beaty <billb@eskimo.com>]

On Mon, 18 Nov 1996, Donald E. Simanek wrote:

> An interesting interpretation. Does this mean that there's no longer any
> reason to experimentally measure the speed of light, since it's already
> been *defined* in terms of the units of length and of time? This would
> assume that we are certain the speed of light is constant. How do we
> *know* that light speed is a constant over time? To what precision do we
> know that? Maybe it's slowly changing with time, or even has short or long
> term fluctuations in value. Can we really claim to have ruled that out?
> How can we even be sure that the length of a meter (or the things which go
> into the operational definition of a meter) doesn't change.

If there are small changes in the length of the meter, in the flow of
time, and in the speed of light, how are we to judge what is REALLY
changing?  It makes some sense to define one of these variables as fixed.
So, in the future if we discover changes in the measured speed of light,
it implies that spacetime is fluctuating.

There have been flamewars about the above topic on newsgroups.  I've heard
that creationists instigate some of this, because a famous Creationist
paper explains the "seven days of creation" as an exponential decrease in
c.

 

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