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From: "Paul.B.Andersen" <relativity@paulba.no>
Newsgroups: sci.physics.relativity
Subject: Re: Langevin's paradox again
Date: Tue, 16 Jul 2024 13:42:20 +0200
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Den 15.07.2024 21:38, skrev Richard Hachel:
> Le 15/07/2024 à 20:14, "Paul.B.Andersen" a écrit :
>> Den 15.07.2024 15:10, skrev Richard Hachel:
>>> Le 15/07/2024 à 14:57, "Paul.B.Andersen" a écrit :
>>>
>>>> The scenario is:
>>>>
>>>> Terrence is inertial.
>>>> Stella passes Terrence with the speed 0.8c relative to Terrence.
>>>> At the instant when Stella is adjacent to Terrence they both set
>>>> their clocks to zero, and Stella starts her rocket engine so that
>>>> she accelerates at the constant acceleration c per year (≈ 0.97g)
>>>> towards Terrence.
>>>> Some time later, Stella will again pass Terrence at the speed 0.8c.
>>>>
>>>> The only question I want answered is:
>>>> What do Stella's clock and Terrence's clock show
>>>> at the instant when Stella passes Terence the second time?
>>>
>>> But it's a very simple question.
>>> Why don't you do it to show me you understand?

>> I can only give you the answer according to SR.
>> You will find all the equations and the method to
>> solve the problem here:
>> https://paulba.no/pdf/TwinsByMetric.pdf
>> 
>> But you have told me that SR doesn't give the right answer
>> when acceleration is involved, so please give the answer according
>> to your corrected equations.
>> 
>> Or are you telling me that the greatest relativistic physicist
>> in the universe (Doctor Richard Hachel) is unable to answer
>> the simple question?

Since this is a post sent 1h 20 m after a very confused post
where you wrote:
"I ask you for a few moments, and I will answer you."
I suppose that the answer is in this post.

> 
> Lots of interesting things, but a lot of things repeated from what 
> relativists say, and which is not a personal thought.
> This is all very interesting but it is difficult to have an honest and 
> coherent discussion on this for several reasons.
> The first being that the position of the relativists is today a matter 
> of dogma, almost in the same way as Christian or Muslim dogmas. I agree 
> on some things (I'm not a crank who denies everything), but I disagree 
> on others.
> It is very difficult today to attack the SR, even partially, even with 
> enormous arguments. SR has apparently become more of a faith than a 
> science, and this is not normal.
> It becomes almost impossible to correct errors that are however clear, 
> even if only in the correct explanation of Langevin. The SR is totally 
> incoherent in the face of Hachel who will protest by saying that the 
> apparent speeds are contradictory if we do not apply the notion of 
> reciprocity of relativistic effects on lengths AND DISTANCES, which will 
> explain why OBSERVABLE speeds instantaneous are incorrect, and why the 
> use of real speeds brings a lot of understanding to the whole, which 
> will also explain that the metric of rotating frames of reference is 
> abstract and completely false.
> But I repeat it clearly, the problem is human, and even in the face of 
> theoretical evidence, humans will still say "it is impossible that I am 
> wrong".
> 
> R.H.

A lot of words, but I didn't see an answer to the question:
What do Stella's clock and Terrence's clock show
at the instant when Stella passes Terence the second time?

Is that because you are unable to answer the question?
No, that cannot be the case. The greatest relativistic physicist
in the universe (Doctor Richard Hachel) can obviously answer
the question he called "a very simple question".

Try again?

The scenario is still:

Terrence is inertial.
Stella passes Terrence with the speed 0.8c relative to Terrence.
At the instant when Stella is adjacent to Terrence they both set
their clocks to zero, and Stella starts her rocket engine so that
she accelerates at the constant acceleration c per year (≈ 0.97g)
towards Terrence.
Some time later, Stella will again pass Terrence at the speed 0.8c.

The only question I want answered is:
What do Stella's clock and Terrence's clock show
at the instant when Stella passes Terence the second time?
It's two invariant proper times, so they are "absolute".

One statement in the mentioned "confused post" of yours was:

'your question is: "As Stella passes Vo=0.8c, it accelerates towards the 
earth (a=1 ly/y²)"'

That made me wonder if you had misunderstood something.

So to be sure:
"she accelerates at the constant acceleration c per year (≈ 0.97g)
  towards Terrence."

means that the direction of the acceleration (a vector) is
always toward Terrence, but since Stella at the first passing is
moving away from  Terrence at the speed 0.8c, her speed will
first be reduced (she's braking) and eventually reach zero,
and thereafter she will move towards Terrence at increasing speed.
It should not be hard to guess what the speed is when she passes 
Terrence the second time.


-- 
Paul

https://paulba.no/