Re: Symmetric Doppler Effect Between Two Observers in Special Relativity

From: jahn (susysewnshow_at_yahoo.com.au)
Date: 12/13/04 

Date: Mon, 13 Dec 2004 08:57:24 -0500

"Harry" <harald.vanlintel@epfl.ch> wrote in message news:41bd9ab3$1@epflnews.epfl.ch...
>
> "David Park" <djmp@earthlink.net> wrote in message
> news:RK%ud.1134$2J2.873@newsread2.news.atl.earthlink.net...
> > "If two inertial observers exchange light signals they will observe the
> same
> > Doppler effect."
> >
> > I have little doubt that this is substantially if not exactly true. But is
> > there any experimental test that specifically verifies this or that puts
> an
> > upper limit on any deviation. What evidence might one cite for the
> > statement?
> >
> > The reason that I am interested in this question is that, for purposes of
> > instruction, I would like to replace:
> >
> > The Postulates of Special Relativity - Time Honored Physicist's Version
> > 1) The speed of light c (= 1) is the same in all inertial frames.
> > 2) The laws of nature are the same in all inertial frames.
> >
> > (I believe that (2) is also referred to as 'the principle of relativity'.)
> >
> > with
> >
> > The Postulates of Special Relativity - Fussy Physicist's Version
> > 1) The speed of light c (= 1) is the same in all inertial frames.
> > 2) All other things being equal, a physical experiment will produce the
> same
> > result if performed at a different time and/or place.
> > 3) If two inertial observers exchange light signals they will observe the
> > same Doppler effect.
> >
> > The reason that I prefer this version is that the original second
> postulate
> > (which I also do not doubt) is so broad that it is almost vague. When the
> > time comes, which law of physics should the student use? It often comes
> into
> > a derivation like a deus ex machina to smooth over a rough point. It is
> easy
> > for a student to misuse it and produce erroneous results. This is perhaps
> a
> > source of many 'paradoxes' and confusions. (Trust me THIS is a law of
> > physics and THAT isn't!)
> >
> > The alternative postulates are quite definite. They relate to definite
> > experimental measurements and at the same time relate directly to
> geometric
> > constructions in the spacetime plane. It is difficult to misuse them.
> >
> > There are two interesting papers on the geometry of spacetime...
> >
> > 1) Dieter Brill & Ted Jacobson, Spacetime and Euclidean Geometry,
> > arXiv:gr-qc/0407022 v1 6 Jul 2004 http://arxiv.org/abs/gr-qc/0407022
> >
> > 2) N. David Mermin, From Einstein's 1905 Postulates to the Geometry of
> Flat
> > Space-Time, arXiv:gr-qc/0411069 v1 15 Nov 2004
> > http://arxiv.org/abs/gr-qc/0411069
> >
> > In both of these papers, when the authors invoke 'the principle of
> > relativity' they actually use it to cover postulate (3) above. That is why
> I
> > am interested in what experimental evidence one might cite in support of
> > this.
> >
> > David Park
> > djmp@earthlink.net
> > http://home.earthlink.net/~djmp/
>
> The oldest experiment of this type that I know and which directly tested
> received frequency:
> An experimental study of the rate of a moving atomic clock, Ives and
> Stilwell, JOSA 28-7, p.215 (July 1938).
> Note that all experiments that test time dilation confirm "symmetric Doppler
> effect".
>
> Harald

I believe David, by symmetric, is refering to this interpretation:

http://www.bun.kyoto-u.ac.jp/~suchii/Einstein/rods&clocks.jpg

It confirms the transverse doppler effect but suggests no
physical change to the clocks or the rods and offers no
argument for an independent notion of time.

Sue...

>
>

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