Re: Langevin and Doppler effects...

Le 11/09/2024 à 22:18, "Paul.B.Andersen" a écrit :

 Example #1:
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Terrence will move away at the speed 0.8c in Stella's frame.
When Stella's clock shows 9- y, Terrence will be at the position
x = 0.8c⋅9h = 7.2 ly in Stella frame. (Stella is at x = 0ly)
Terrence clock will run at the rate 1/γ so it will show 9h/γ = 5.4y
 When Stella's clock shows 9+ y, Stella is on her way back.
Terrence will still be at the position x = 7.2 ly,
but will now move at the speed 0.8c towards Stella.
Terrence's clock will now show 30y-5.4y = 24.6y
 When Stella's clock shows 18y, Stella is back.
Terrence will now be at the position x = 7.2ly - 0.8c⋅9y = 0 ly.
Terrence clock will now show 24.6y + 5.4y = 30 y
 Note this:
When Stella is moving away from Terrence and her clock shows 9y,
Terrence clock will _simultaneously_ in Stella,s frame show 5.4y
When Stella is moving towards Terrence and her clock shows 9y,
Terrence clock will _simultaneously_ in Stella,s frame show 24.6y
 Both clocks run at a steady rate, 1 second per second, but
what the two clocks _simultaneously_ will show in Stella's frame
depend on Stella's velocity relative to Terrence.
When Stella abruptly change her direction, her idea of what time is
simultaneous in Terrence frame changes from  5.4y to 22.8y,
 But nothing happens to Terrence clock, it runs normally.
It is _only_ Stella's idea of what is simultaneous that changes.

Yes, I understood very well.
I have known about SR for forty years, and I have thought about it, I think, much more than a simple man who, having studied a few hours, convinced himself that it was very pretty and that Einstein and Minkowski were probably right.
I have thought about it for thousands of hours, and I have always understood that something would go wrong, and WHY it would go wrong.
I will tell you what is wrong with your demonstration which is mathematically impeccable, but physically useless and false if we scratch much deeper. You are not talking to me here about Stella's frame of reference but about two different frames of reference of type M (i.e. M1 for the outward journey, and M2 for the return journey).
It is NOT Syella's frame of reference but something useless, which is found in Stella's frame 1, then in Stella's frame 2.
This explains the time jump during the U-turn, because we go from what is measured by the watch M1 in the outbound frame of reference, to what is measured by the watch M2 in the return frame of reference. That is to say a carrot and a turnip.
This way of seeing things is not correct. For the sake of great clarity (and it is infinitely clearer when we master Hachel's concepts) we must place ourselves in Stella's frame of reference, and never leave it.
Not only do you go from Stella to a hypothetical and mathematical observer M1, but suddenly, M1 no longer following you at the time of the U-turn, you go to another infinitely different observer M2.
This is not correct, and this is not how we should see things.
Even if what you say about M1 and M2 is true.
R.H.