On Dec 30, 5:52*am, Tom Roberts wrote in
sci.physics.relativity:
David wrote:
I've been trying to find experimental verification that c is constant
by looking for experiments where wavelength and frequency are measured
independently of each other and results from moving sources are
compared to the results from stationary sources - like the wavelength
of light with frequency f (as measured in a rest frame) from a moving
star compared to the wavelength of light with the same frequency f
created by a source in the rest frame. But I wasn't able to find any
experiment where wavelength and frequency are measured independently
to confirm that their product is a constant.

Consider the operation of a standard lab He-Ne laser. The 3S-2P
transition of neon is Doppler broadened to about 1.5 GHz [#]. The
wavelength is 632.8 nm, and for mirrors 30 cm apart there are about 1
million wavelengths between the mirrors, with spacing between
longitudinal modes of 400-500 MHz. So typically 3 or 4 longitudinal
modes of the mirrors overlap the Doppler-broadened linewith of the
lasing transition in Ne.

* * * * [#] I don't have a reference for the intrinsic linewidth
* * * * of this transition, but the observed 1.5 GHz Doppler-
* * * * broadened width is consistent with the thermal computation
* * * * given in _Fundamentals_of_Light_Sources_and_Lasers_, by
* * * * Mark Csele. So the intrinsic width is considerably smaller
* * * * than the Doppler broadening, and that is all that matters here.

The frequency and wavelength separations of the different longitudinal
modes are fully consistent with the speed of light being constant. This
implies that for moving Ne atoms, the product of frequency times
wavelength for the lasing transition does indeed equal c. This is
optical spectroscopy, and these values are known quite accurately.

This example also refutes Henri Wilson's "BaTh", which claims that the
wavelength of light emitted from a source is the same in all inertial
frames -- for the Doppler-broadened lasing transition to excite multiple
longitudinal modes in the mirrors its wavelength MUST vary with speed.

Note that without the Doppler broadening of the lasing transition, He-Ne
lasers would be vastly more difficult to set up and get working.

Tom Roberts

Bravo Roberts bravo Tom bravo Albert Einstein of our generation
(Hawking is no longer the Albert Einstein of our generation)! At last
you have found the camouflage you needed so badly! Two years ago, when
we discussed an analogous problem, you still knew nothing of
wavelength measurements; you only knew that "on earth the speed of
light is c":

http://groups.google.ca/group/sci.ph...01800ef02911d?
Tom Roberts, Sep 25, 2005: "None of the above measured wavelength
directly. But we do know that on earth the speed of light is c, and in
the GPS the speed of light is c between satellite and ground."

Roberts Roberts some day even your zombies will ask the fatal
questions:

"Oh Divine Master Roberts, why don't you explain both the Doppler
effect and the gravitational redshift in terms of the textbook
formula:

frequency = (speed of light)/(wavelength)

Since the frequency shifts, oh Divine Master, isn't it reasonable to
assume that the speed of light shifts with the frequency, as Divine
Albert did in 1911? If we assume that the speed of light remains
constant and it is the wavelength that shifts with the frequency, will
that assumption have implications that are too silly, oh Divine Master
Roberts?"

Pentcho Valev