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From: Thomas Heger <ttt_heg@web.de>
Newsgroups: sci.physics.relativity
Subject: Re: [SR and synchronization] Cognitive Dissonances and Mental
 Blockage
Date: Thu, 29 Aug 2024 08:10:54 +0200
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Am Dienstag000027, 27.08.2024 um 12:25 schrieb Richard Hachel:
> Le 27/08/2024 à 07:31, Thomas Heger a écrit :
> 
>> The very word 'relativity' requires mutually symmetric perspectives.
> 
> Absolutely.
> 
>> Since both perspectives are of equal rights, we need to accept both 
>> views as valid, hence need mutually symmetric perspectives.
> 
> Magnifico! Wunderschön !!!
> 
Thanks.

But this is obvious and certainly not disputed.

But Einstein, however, had not written about a symmetric system of clock 
synchronization.

Instead he used something, one could call 'external time' (kind of 'true 
time').

But there exists no such thing as true time and time is only local.

This would mean, that a clock at point A would shows the local 'A-time' 
and clocks at point B show B-time.

This would not necessarily allow to synchronize clocks at all, if A-time 
does not run at the same tick rate as B-time.

But supposed you have a clock from A, bring that to B and synchronize 
this by technical means with A-time-clocks at A.

Now: what would you need to do, to synchronize these clocks?

It needs to be a way, which could also be applyed at B and would give 
the same result.

Since we need some sort of operators at both sides, we need to assume, 
that at both locations are some kind of itelligent beings and these able 
to read messages and operate a clock.

These 'observers' get also names and we could them 'A' and 'B' for 
simplicity.

The operator A would send out a signal, which gets sent back by B, once 
it arrives at B.

'A' would measure the delay for the round trip, cuts that value in half 
and send the value to the far side B, together with a coded time message.

The observer B would decode the message and adjusts the clock in 
question aappropriately.

Now B could do the same and would gain the same result.

This is therefore a valid method to synchronize clocks.

The method used by Einstein is not valid, because actually ONLY 'A-time' 
was used and no operator at the far side was mentionend.

Another method, which is often used in textbooks about relativity 
requires a 'man in the middle' (called 'M', for instance).

This is a possible way to synchronize clocks, too.

But this method had the disadvantage, that synchronization would depend 
on the position and state of motion of the observer 'M'.

This method would also only allow to synchronize two clocks, while 
synchronization should be valid throughout an entire frame of reference.

TH