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From: Python <python@invalid.org>
Newsgroups: sci.physics.relativity
Subject: Re: [SR and synchronization] Cognitive Dissonances and Mental
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Date: Wed, 21 Aug 2024 09:22:35 +0200
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Le 21/08/2024 à 08:15, Thomas Heger a écrit :
> Am Dienstag000020, 20.08.2024 um 08:16 schrieb Python:
>> Le 20/08/2024 à 08:02, Thomas Heger a écrit :
>>> Am Montag000019, 19.08.2024 um 14:56 schrieb Python:
>>>> Le 19/08/2024 à 08:44, Thomas Heger a écrit :
>>>>> Am Sonntag000018, 18.08.2024 um 12:05 schrieb Python:
>>>>>
>>>>>>>> Two identical clocks, A and B, are stationary relative to each 
>>>>>>>> other at a certain distance. Their identical functioning (within 
>>>>>>>> measurement accuracy) allows us to assume that they "tick at the 
>>>>>>>> same rate." NOTHING more is assumed, especially regarding the 
>>>>>>>> time they display; the purpose is PRECISELY to adjust one of 
>>>>>>>> these clocks by applying a correction after a calculation 
>>>>>>>> involving the values indicated on these clocks during specific 
>>>>>>>> events, events that occur AT THE LOCATION OF EACH CLOCK.
>>>>>>>>
>>>>>>>> Einstein’s procedure is not strictly a synchronization procedure 
>>>>>>>> but a method to VERIFY their synchronization. This is the main 
>>>>>>>> difference from Poincaré’s approach. However, it can be proven 
>>>>>>>> that Poincaré’s method leads to clocks synchronized in 
>>>>>>>> Einstein’s sense. You can also transform Einstein’s verification 
>>>>>>>> method into a synchronization procedure because it allows 
>>>>>>>> calculating the correction to apply to clock A.
>>>>>>>>
>>>>>>>> *Steps of Einstein's Method:*
>>>>>>>>
>>>>>>>> When clock A shows t_A, a light signal is emitted from A towards B.
>>>>>>>>
>>>>>>>> When this signal is received at B, clock B shows t_B, and a 
>>>>>>>> light signal is sent from B back towards A.
>>>>>>>>
>>>>>>>> When the signal is received at A, clock A shows t'_A.
>>>>>>>
>>>>>
>>>>>>> Relativity requires mutally symmetric methods. So if you 
>>>>>>> synchronize clock B with clock A, this must come to the same 
>>>>>>> result, as if you would synchronize clock A with clock B.
>>>>>>
>>>>>> It is.
>>>>>
>>>>> No, it is not!
>>>>
>>>> It is. It is explained in my initial post : What is (AB)/c to you?
>>>
>>> AB was actually meant as:
>>>
>>> distance from A to B,
>>>
>>> even if A and B are in fact position vectors, hence AB would usually 
>>> be the scalar product of A and B (what is absurd).
>>
>> Yes it would be absurd. BTW you are conflating affine spaces with
>> vector spaces here.
>>
>>> Besides of this little formal issue (actually meant was |r_AB| ), 
>>
>> Well, Thomas, this is utterly ridiculous. Any reader understands what
>> AB as it appears in 2AB/(t'_A - t_A) is the distance AB. From high
>> school to Ph. D.
> 
> "the distance AB" is not equal to "AB"!

The distance between A and B can be denoted in a lot of ways. The point
is to ensure that there is no ambiguity given the context. As a matter
of fact Einstein in the ORIGINAL paper used an overbar on top of
AB 
(https://myweb.rz.uni-augsburg.de/~eckern/adp/history/einstein-papers/1905_17_891-921.pdf)

So if there were someone to blame here, it would be the translator.

But there is no one to blame the context is clear enough.

> Actually meant was: 'A' and 'B' denote locations in a certain coordinate 
> system, hence are technically position vectors.

Technically there are points in an affine space. Don't pontificate on
math when you are ignorant of it Thomas.

> Because a product of vectors is possible, 'AB' would be the product of A 
> and B.

You are ridiculous.

> If you want to adress the distance from point 'A' to point 'B' you 
> cannot simply say 'AB'.

You can.

> Whether or not 'any reader understands' is patently irrelevant.

It is not. Every text as an intended audience.

>>> Einstein had not written AB/c (or r_AB/c).
>>
>> It appears after ONE step of elementary algebra from the two first
>> equations on page 3 there :
>>
>> https://users.physics.ox.ac.uk/~rtaylor/teaching/specrel.pdf
>>
>> Do you really think that readers (physicists) in 1905 couldn't
>> immediately recognize this from two so simple equations, Thomas ?
> 
> SRT is certainly a socio-cultural mystery and the question you wrote is 
> also a mystery.

A mystery to YOU because you are stupid.

> I have not dealt with that question, but here with a formal issue.
> 
> My point was, that 'AB' is not a valid symbol for 'distance from point A 
> to point B'.

And you are wrong.

>>> What he had actually written was
>>>
>>> r_AB/(c-v)
>>
>> This is in paragraph 3. We are dealing with paragraph 2 here.
> 
> Sure, but §3 does not contain the equation you quoted.

I didn't pretend otherwise, you did. Moreover §3 is off-topic: we
are talking about clocks synchronization here.

> to remind you, that's what you have written:
> 
>  >"... It is. It is explained in my initial post : What is (AB)/c to 
> you?.."

Yes. And (AB)/c can be derived from equations in part I.2 by elementary
algebra.

>>>>> Einstein's method did not allow mutally symmetric synchronization.
>>>>
>>>> The procedure can be proven symmetric. Face it.
>>>
>>> No, it wouldn't.
>>
>> It can be shown. This is a very simple exercise even for high school
>> students. You cannot seriously pretend to be an engineer Thomas.
>>
>>> I take as example two spaceships in 1 lightseconds distance, which 
>>> are called A and B.
>>>
>>>
>>>
>>> Both have a HUGE clock strapped to that spaceship and use a VERY HUGE 
>>> telescope to read the clock of the other ship.
>>
>> The is NO reading of another clock with a telescope in the procedure
>> described at paragraph 2 (nor elsewhere in the article)
> 
> 
> Sure, there ain't.

So STOP mentioning it!!!

> But it should, because relativity requires mutually symmetric relations.

You say "it should" because you fail to understand the procedure, as
a matter of fact it shouldn't. Values of t_A and t_A' can be
communicated to B, as well as value of t_B to A by any means. Including
carrier pigeons or slugs. It doesn't matter.

Moreover the procedure described in paragraph I.2 IS SYMMETRIC!

It is high school level math. You really want me to show you the proof
or can you try to write it down by yourself?

> This means:
> 
> if one side can apply a certain method, than the other side should be 
> allowed to apply the same method, too.

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