The subject is the speed of light. This is what Edward L. Hamilton, PhD Univ of Colorado, post-doctoral fellowship at Northwestern Univ. had to say on this.John of Japan said:Thanks for the correction, Farmer Ed. It's been a long time since I studied the stuff.
This is something I very recently read an article about, and I certainly could have missed the boat. I'll be interested in what your physicist friend says.
There 'tis!At the moment, the speed of light is DEFINED to be constant in a volume.
NIST (the former National Bureau of Standards) has defined the speed of
light as 299,792,458 m/s exactly. Thus, the speed of light in a vacuum is
always exactly that speed. Distances are defined relative to that
standard, and all other speeds are regarded as a fraction of that
standard. The distance that light travels in 1/299,792,458 seconds is used
as the definition for a meter.
In other words, it's not possible for the speed of light to change, ever,
in the SI unit system.
. . .
Roughly speaking, the answer to your question is: The speed of light is
arbitrary, so it can be defined to be constant. Non-arbitrary
dimensionless parameters that contain the speed of light are not assumed
to be constant, but have been found to be constant in all the experiments
we've been able to perform so far. . . (Edward L. Hamilton, PhD, research physicist)
Ed
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