Re: Bell's Spaceship paradox

On 22 f=E9v, 02:09, Ilja Schmelzer <ilja.schmel...@xxxxxxxxxxxxxx>
wrote:
On 15 Feb., 21:47, jacques <jacques.f...@xxxxxxx> wrote:



The position that Lorentz contraction is not physical is simply wrong.
Time dilation is also physical, it gives a real time difference in the
case of the twin "paradox".

Ilja

Length and time (x,t) or (x',t') are coordinates (respectively in lab
frame, and rocket co-moving frame) in the paradox.
They are measured according to the rules of SR, based on the SR
simultaneity concept which is not absolute, making he measure quite
"conventionnal".
In the round trip, at the end of the loop, they recover their initial
values.
But elapsed proper time is not a coordinate it measures the
"length" (affine parameter, with right parametrization) of the world
line by a clock associated to this line.
In my understanding, that makes a conceptual difference which may
explain why at the end of the round trip the elapsed proper time of
traveler and lab observer (integrated on their respective worldline)
are different but not their size.
Jacques

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