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Einstein's Relativity and the Beliefs of the Travelling Twin



 
 
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  #1  
Old April 1st 16, 09:35 AM posted to sci.astro
Pentcho Valev
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Default Einstein's Relativity and the Beliefs of the Travelling Twin

During the very brief moment when the travelling twin turns around, he experiences acceleration ("gravitational field"), an effect which can by no means reach the distant Earth of course. Yet Einsteinians find it important to stress that the travelling twin "WILL BELIEVE THAT THIS GRAVITATIONAL FIELD EXISTS THROUGHOUT ALL OF SPACE, AND THAT THIS GRAVITATIONAL FIELD IS CAUSING THE EARTH AND THE REST OF THE UNIVERSE TO ACCELERATE TOWARDS HIM". And now a second belief: "Therefore, Adam will believe that the gravitational field is causing time on Earth to flow much faster than time on his ship":

https://www.youtube.com/watch?v=bjHLboK2M1g
"For Adam to return back to Earth, he will eventually need to fire his rockets to turn around. When he fires his rockets, Adam will still continue to think that his spaceship is standing still. However, in order to believe that his spaceship is standing still, he needs to also believe that there is now a gravitational field present that is cancelling out the force from his rockets. ADAM WILL BELIEVE THAT THIS GRAVITATIONAL FIELD EXISTS THROUGHOUT ALL OF SPACE, AND THAT THIS GRAVITATIONAL FIELD IS CAUSING THE EARTH AND THE REST OF THE UNIVERSE TO ACCELERATE TOWARDS HIM. (...) Therefore, Adam will believe that the gravitational field is causing time on Earth to flow much faster than time on his ship. It is only during the very brief moment when Adam is firing his rockets to turn around that he believes this external gravitational field is present. For the remainder of his trip after he turns his rockets off, Adam will again view time on Earth as moving slowly. Nevertheless, during the very brief moments when he fires his engines, he sees time on Earth flowing so extremely fast that this far more than compensates for the fact that he sees time on Earth flowing slowly during the rest of his journey. This is why Adam will believe that more time has passed for Sarah than for him when he returns."

Essentially this is Einstein's 1918 interpretation of the twin paradox ("A homogenous gravitational field appears" which can only reach the Earth in the beliefs of the travelling twin):

http://sciliterature.50webs.com/Dialog.htm
Albert Einstein 1918: "A homogenous gravitational field appears, that is directed towards the positive x-axis. Clock U1 is accelerated in the direction of the positive x-axis until it has reached the velocity v, then the gravitational field disappears again. An external force, acting upon U2 in the negative direction of the x-axis prevents U2 from being set in motion by the gravitational field. (...) According to the general theory of relativity, a clock will go faster the higher the gravitational potential of the location where it is located, and during partial process 3 U2 happens to be located at a higher gravitational potential than U1. The calculation shows that this speeding ahead constitutes exactly twice as much as the lagging behind during the partial processes 2 and 4."

Pentcho Valev
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  #2  
Old April 1st 16, 04:31 PM posted to sci.astro
Pentcho Valev
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Posts: 7,521
Default Einstein's Relativity and the Beliefs of the Travelling Twin

http://physics.stackexchange.com/que.../246766#246766
Question in StackExchange: "Presentism: doesn't everything exist at the same moment?"

My answer:

Einstein's 1905 invalid argument:

http://www.fourmilab.ch/etexts/einstein/specrel/www/ ON THE ECTRODYNAMICS OF MOVING BODIES, A. Einstein, 1905: "From this there ensues the following peculiar consequence. If at the points A and B of K there are stationary clocks which, viewed in the stationary system, are synchronous; and if the clock at A is moved with the velocity v along the line AB to B, then on its arrival at B the two clocks no longer synchronize, but the clock moved from A to B lags behind the other which has remained at B by tv^2/2c^2 (up to magnitudes of fourth and higher order), t being the time occupied in the journey from A to B."

Why is the moving clock slow and the stationary one fast? No such asymmetry follows from Einstein's 1905 postulates. What validly follows is that the moving clock is slow as judged from the stationary system, and the stationary clock is slow as judged from the moving system. Einstein's conclusion above (the moving clock "lags behind" the stationary one) is invalid - it does not follow from the postulates. So even if Einstein's 1905 postulates were true (actually the second one is false), Newton's absolute time is not refuted by special relativity.
[end of the answer]

Einsteinians at StackExchange will delete my answer of course but for the moment it is there.

Pentcho Valev
 




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