Re: Light Clock Nonsense

From: Paul B. Andersen (paul.b.andersen_at_deletethishia.no)
Date: 12/09/04 

Date: Thu, 09 Dec 2004 11:52:55 +0100

>Paul B. Anderersen wrote
>>The Special Theory of Relativity according to Lorentz, what's that?

Harry wrote:
> You can read his post-1905 papers and books in which he taught relativity
> incl. SRT (calling GRT "Einstein's theory"), or study what Tom Roberts calls
> "LET".
> A theory of modern physics makes predictions about observables. In the end
> Lorentz and Einstein promoted relativity theorie together.
> That their different interpretations caused some confusion can easily be
> seen by reading some papers of that time, such as that of Kennedy-Thorndyke
> in which they mixed up the two interpretations. After Lorentz' death his
> interpretation was slowly forgotten.
>
>>Of course I know that Einstein's and Lorentz' theories are
>>equivalent in that they always predict the same.
>>But they are still different theories.
>>The Special Theory of Relativity is Einstein's own name
>>for his theory.
>
> I agree: if we include metaphysics, then as scientific theory they are
> fundamentally different and indeed cause of much debate; however as theory
> of physics they can't be distinguished. And indeed Einstein gave the label
> SRT to the theory ...
> Now do you think that if you give a name to something then it is
> automatically yours? Or is according to you "SRT" not really physics but
> Einstein's interpretation of relativity?

I think that for a century "The Special Theory of Relativity"
by the vast majority has been considered to be Einstein's theory,
with his interpretation, which is the same as the modern interpretation.
No ether. No physical changes of an object's intrinsic properties
due to its speed relative to something else.

But this is a word game. For all practical purposes,
the theories are the same.

But we seem to differ when it comes to what Einstein's
interpretation was, though.

Let's review our coversation:

| Paul B. Andersen:
|> You [jahn] didn't actually believe that SR say that
|> the moving observer can make the light clock
|> run physically slow, did you?
|> I think you did.

Harry:
| I think Einstein did. See below.

| Paul B. Andersen:
|> Why else should you point out what is blatantly
|> obvious - that the observer's motion cannot
|> affect the light clock in any way.
|>
|> The observers state of motion can however affect
|> the observer's observation of the light clock.
|> And THAT is what it is all about.

Harry:
| Paul, I fully agree with your explanation..
| Note that this is according to Lorentz' interpretation of SRT - Einstein's
| opinion about this was less transparent, and IMO even contrary - according
| to him, for the "travelling" Twin the clock of the "stay-at-home" speeds up
| as a result of his turn-around and for Einstein that was also correct. ;-)

The only way I can interpret this, is that you claim that
Einstein's interpretation was that the observed object
was physically affected - that is its intrinsic properties
are changed - by the actions of the observer.

I think this is an impossible interpretation of the theory
which is based on the two postulates Einstein defined.

To back up your claim, you write:

Harry wrote:
> Sorry, it was 1918: Die Naturwissenschaften of 29 Nov.1918 p.697-712.
> I translate from German, from the viewpoint of the "travelling twin" who is
> by Einstein viewed as remaining stationary in a gravitation well:
>
> "For following GRT, a clock goes faster the higher the gravitation potential
> is at the position that it is located [...]. Calculation shows, that this
> faster running yields exactly twice as much, as the retardation during [the
> stationary phases]."
>
> and:
>
> "But is this gravitation field not simply fictive? [...] For K' "exists" the
> gravitation field in the same sense as whatever other physical thing, that
> simply relative to a coordinate system can be defined, although it isn't
> there concerning system K."
>
> In other words, that point of view was according to him also "real", so that
> it was in his opinion also correct to state that the stay-at home clock ran
> slow, then sped up due to the induced gravitational field, and then ran slow
> again.

I think you with "your other words" said it yourself.
Einstein did NOT think that any of the clocks was affected
physically in any way.
 From the home twin's point of view, the travelling twin's
clock has been running slow.
 From the travelling twin's point of view, the home twin's
clock has been running fast.
Both views are equally valid.
That would obviously NOT have been the case if the difference
in the proper times had been caused by a physical change
in one of the clocks intrinsic properties.

I simply cannot understand why you think
Einstein's words above support you claim.

You must understand that when we in the context
of SR/GR say "the other clock runs fast/slow",
we do not mean that its intrinsic rate is changed,
but that the _measured_ dt'/dt in our frame of reference
and from our vantage point is different from 1.

Paul

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