Re: Speed of Light

["Donald E. Simanek" <dsimanek@eagle.lhup.edu>]

On Mon, 18 Nov 1996, Rauber, Joel              Phys wrote:

> Of course the speed of light is now know to infinite precision, as the meter 
> is now defined as a certain fraction of the distance that light travels in a 
> second.  Namely
> 10^ (-299792458) of a second. This was adopted in 1983.  "I interpret this 
> as basically pushing all the uncertainty in c, into the uncertainty that 
>  there already is iin a meter"
>
> Joel

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.

	-- Donald

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Dr. Donald E. Simanek                            Office: 717-893-2079
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