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Subject: Re: Sync two clocks
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Date: Mon, 19 Aug 24 23:15:28 +0000
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From:  Richard Hachel   <r.hachel@jesauspu.fr>
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Le 19/08/2024 à 22:32, "Paul.B.Andersen" a écrit :
> Below I show how two real clocks in the real world can be
> synchronised, strictly according to Einstein's method.
> 
> We have to equal clocks C_A and C_B. They are not synced in any way,
> but they are using the same time unit, let's call it second.
> The clocks run at the same rate.
> 
> In our very big, inertial lab, we have two points A and B which are
> separated by some distance. Let's call the transit time for light
> to go from A to B is x seconds. We will _define_ that the transit time
> is the same from B to A. (This follows from Einstein's definition
> of simultaneity).
> 
> At point A we have:
> Clock C_A, a light-detector, a flash-light and a computer.
> The computer can register the time shown by C_A when
> the flash-light is flashing, and when the light-detector
> registers a light-flash.
> 
> At point B we have:
> Clock C_B, a light-detector, a mirror and a computer.
> The computer can register the time shown by C_B when
> the light-detector registers a light-flash.
> 
> In the following we will synchronise clock C_B to clock C_A.
> That is, we will adjust clock C_B so it become synchronous
> with clock C_A.
> 
> Now we let the flash-light at point A flash.
> At this instant, C_A is showing tA = n seconds.
> tA is measured by C_A at A.
> 
> When the flash hits the light-detector at B,
> Clock C_B shows tB = m seconds.
> tB is measured by C_B at B.
> 
> A short time later the light detector at A registers
> the light reflected by the mirror at B.
> At this instant Clock C_A shows t'A = n + 2x seconds.
> t'A is measured by C_A at A.
> 
> Einstein:
>   "The two clocks synchronise if  tB − tA = t'A − tB."
> 
> Or: tB = (tA + t'A)/2 = (n+n+2x)/2 = (n + x)
> 
> That is, to be synchronous clock C_B must show a time midway
> between tA and t'A when the light is reflected by the mirror.
> So  tB should show (n + x) seconds when the light is reflected
> by the mirror.
> But at that instant tB is showing m seconds, so to make the two
> clocks synchronous, we must adjust clock C_B by:
>   δ = (n-m) + x seconds.
> 
> 
> After this correction, we have:
> 
>   tB  − tA = (m - n) seconds +  δ     = x seconds
>   t'A − tB = (n + 2x - m) seconds - δ = x seconds
> 
> The clocks are now synchronised.
> 
> Please explain what in the above you find impossible
> to do in your lab.

I have explained these things a hundred times.
It is impossible to synchronize two watches A and B located in different 
places.
It is not a technical problem, it is not a problem of intelligence, it is 
simply that it is as impossible as finding a round square, or a natural 
number between 5 and 6.
Because nature is not made like that.
Anyone who wants to synchronize watches with each other does not realize 
that he is looking for rabbit horns.
The only thing we can do is to find a kind of abstract, imaginary 
synchronization procedure, called the Einstein procedure where tAB is 
supposed to be equal to tBA not only for the point M which is the only 
real origin of the synchronization, but for everyone.
We then have a useful procedure, but false.
There is no global synchronization, but a synchronization of type M, as I 
have explained.
A and B, as I explained, will never "live" in the same global, real, and 
reciprocal present moment.
IT IS A POWERFUL NOTION THAT SQUATS IN THE MIND OF MAN, but it is an A B S 
T R A T NOTION, it is not physically real.

R.H.