From: nospam@de-ster.demon.nl
[missingin action, presumed lost, repost]
Tom Roberts wrote:
> On 10/7/21 8:52 AM, Nicolaas Vroom wrote:
> > Op woensdag 1 september 2021 om 21:27:09 UTC+2 schreef J. J. Lodder:
> >> The assertion was that you can at least in principle use laboratory
> >> measurements of the speed of light to see if it varies.
[snipped a mess of garbled attributions without further comment.
Some of the > >> stuff is by me, some of it is by others]
> The experiment I described is something we routinely do in our optical
> lab. But we don't have any optical cavity that is nearly stable enough,
> because our research does not require it. Obtaining funding to build an
> exceptionally stable cavity is unlikely; nor are we particularly interested.
As I implied in previous postings,
the revolutionary step in the redefinitions of the meter
was to replace material standard meter
(lines on a metal bar) with an optical standard meter.
(the wavelengty of a krypton line, later a laser)
There is no good a-priory reason to assume that the two must be,
and will forever remain the same thing.
That experiment that 'we are not particularly interested in'
could in principle test the question.
(but there are good reasons to believe
that it could not possibly yield a useful result)
The speed of light in all this is merely a red herring.
All there is to it is that experimentally
one can maintain an optical frequency standard
to much greater precision than a wavelength standard.
(by several orders of magnitude)
If we wouldn't care about best reproducibility
we could in principle go back to a wavelength standard
to make c measurable again, but to no better than
the reproducibility of the wavelength standard.
Jan
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