georgir
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JohnWisp said:Here is what I said.
5) Both twins think each are time dilated. So, they conduct Einstein's clock synchronization method to compare their clocks.
6) After they compare, they have exact time values from the comparison. So, either t1<t2, t2 >t1 or t1=t2. Since these are actual time values, they are real numbers and must obey the law of trichotomy.Where in these statements do you think I said the clocks end up synchronized? In fact, I don't know how these clocks turn out. Do you?
Both twins think the other's clock is dilated, only during the period between the first's acceleration and the second's acceleration. But they can not use clock synchronization during that time.
After the second's acceleration, both think their clocks are running at the same rate. And they can measure the difference in their readings.
That difference will match the difference that the first twin thinks accumulated between their accelerations, not what the second twin thinks. This is because before and after the acceleration, the second twin will have a different definition of "now" for locations other than his own.
The very act of acceleration will appear to cause a shift in time, a redefinition of "now" at all distant locations. Locations in the direction of the acceleration will seem to shift into the future, the further away they are the bigger the shift. And likewise locations in the other direction will seem to shift into the past.
So in this specific setup the twin accelerating second will think this for the other's clock: it starts to run slow, but when he suddenly launches it jumps forward in time, and not only makes up the difference but reverses it. Then they both agree, the second twin's clock is behind.
EDIT: This describes the setup with instant acceleration. I didn't read other replies in detail and am not sure why references to constant acceleration were made in some of them, or if the OP is interested in discussing such an alternative scenario.