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Re: Why did Einstein bring up the concept of simultaneity when he formulate SRT?

From	Thomas Heger <ttt_heg@web.de>
Newsgroups	sci.physics.relativity
Subject	Re: Why did Einstein bring up the concept of simultaneity when he formulate SRT?
Date	2018-07-16 17:57 +0200
Message-ID	<fr3tj1F4jh5U1@mid.individual.net> (permalink)
References	(8 earlier) <b322c0b9-0a82-0540-f9a4-1885338522dc@PointedEars.de> <fqtn6vFtv1eU1@mid.individual.net> <12dd9b6f-dd01-1241-049d-2f28c9a5889f@PointedEars.de> <fr1adaFk6n9U1@mid.individual.net> <6e3069af-0efa-0142-f028-a434a8c5f3f8@PointedEars.de>

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Am 15.07.2018 um 21:05 schrieb Thomas 'PointedEars' Lahn:
> Thomas Heger wrote:
>> Am 14.07.2018 um 15:28 schrieb Thomas 'PointedEars' Lahn:
>>> Thomas Heger wrote:
>>>> Am 12.07.2018 um 18:53 schrieb Thomas 'PointedEars' Lahn:
>>>>> Thomas Heger wrote:
>>>>>> Am 11.07.2018 um 23:26 schrieb Volney:
>>>>>>> No, Ken, you are showing your lack of knowledge of relativistic motion.
>>>>>>> If the moving observer uses a clock showing his proper time (a local,
>>>>>>> co-moving clock, for example his wristwatch), he should cook a 5 minute
>>>>>>> egg for 5 minutes on his clock. Only if he is trying to use the
>>>>>>> stationary observer's clock should he invoke the gamma factor.
>>>>>> There are no 'stationary observers'.
>>>>> Yes, there are.
>>>> The postulate of relativity was, that you cannot distinguish an internal
>>>> frame of reference with some velocity from one at rest.
>>> By experiment, regarding *absolute* motion.
>>
>> Now you try to reconcile relativity and absolute motion?
> 
> No, I don’t.  You describe the principle (not: postulate) or relativity
> almost correctly (_inertial_, not "internal"), but you neglect to mention
> that from it follows that there is no *absolute* motion.  Obviously, the
> principle of *relativity* does NOT deny *relative* motion; if it did,
> *that* would be a contradiction in terms.
> 
>>>> So how could you distinguish one at rest from one with a certain velocity???
>>> In relative motion of two frames of reference, you pick one frame
>>> as the rest frame or “(coordinate( system at rest” (Einstein, “On the
>>> Electrodynamics of  Moving Bodies” [OE(d)oMB]).  Then the other frame
>>> is the “moving frame” (ibid.).
>>
>> Einstein wrote something really strange in his book.
> 
> Einstein’s *books* (he was usually only a *co-author* of them) are
> *summaries* of his work for the interested layman.  They are NOT his
> scientific theories; those have been published, as it is done, in
> scientific papers and his doctoral thesis:
> 
> <https://einsteinpapers.press.princeton.edu/>
> 
>> The concept is imho nonsense:
> 
> But you have no clue, so your no-so-humble opinion does not matter.

The quote was not from Einstein's book, but from 'Annalen der Physik' 1905.

That was his original -peer reviewed- paper in a scientific magazine.

It was in German, but google provides a (rough) translation, which I 
provide here:

***********quote**************************

We also think of the two bar ends (A and B) attached clocks, which are 
synchronous with the clocks of the system at rest, that means: their 
measurement correspond respectively to the "time of the system at rest" 
at the place where they are located; So these clocks are "synchronous in 
the system at rest".

We further imagine that each clock has an observer moving with it, and 
that these observers apply to the two clocks the criterion for the 
synchronous movement of two clocks set forth in §1. At the time *) t_g, 
let a ray of light emanate from A, be reflected in B at time t_B, and 
return to A at time t_A. Taking into account the principle of the 
constancy of the speed of light, we find:

           t_B -t_A = r_AB /V-v

wherein r_AB is the length of the moving rod - measured in the 
stationary system. Observers moving with the moving rod would thus find 
the two clocks out of sync, while observers in the system at rest would 
declare the clocks in sync. Thus, we see that we must not attach 
absolute importance to the concept of equality, but that two events 
which, viewed from one coordinate system, are simultaneous, viewed from 
a system moving relative to that system, are no longer to be understood 
as simultaneous events ,

*) "Time" here means "time of the stationary system" and at the same 
time "pointing of the moving clock, which is in the place in question".

************end quote**********************************************
(translation by google, a little adjusted by me)

What Einstein does is this:

he declared the runtime of the signal would be caused by the different 
times at the moving clocks at the ends of the rod.

But that is nonsense, since the runtime of a signal is caused by the 
signal in motion, not by the time of the starting point.

To make this a little more obvious we could replace light by sound and 
use 330 m/s instead of 300,000 km/s.

Then we would have a much 'shorter' rod (in Einstein's 'logic'), if the 
speed would reach c (speed of sound).

But that is not a very good idea, since the signal and its finite 
velocity does not alter the moving rod, but the measurement by the 
moving observers. Also times would then be different at both ends, since 
time is assumed as readings of clocks (in SRT logic).

So his concept of simultaneity (what is meant with '§1') is not a good 
idea neither.

Instead the finite velocity of light should be taken into account and 
the run-time of the signals should be compensated.

What Einstein does instead is declaring the distorted measurements as real.

TH

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