@layman,
Quote:Of course it's impossible, as every respectable physicist will readily acksnowledge. Nonetheless, I have asked this question many time in this thread:
Assume that A and B are both moving inertially and are also moving with respect to each other, which they both acknowledge. Now then If:
1. A claims that B's clock is moving slower than his, AND
2. B claims that A's clock is moving slower than his, THEN
3. Is it possible for BOTH of them to be right?
That's a much better question than the twins paradox. But maybe the twins paradox was Langevin's way to explain this question to the masses. In any case, in SR there is no solution that I know of, other than: "the question does not apply, since they will never be able to experimentally verify what the answer is."
This suggests that SR is 'locally' valid only: at that monent, at this point of the trajectory, if one object is close enough to the speed of light compared to another object, then X, Y and Z are observed (eg time dilatation, length reduction, mass increase). However, the values of X, Y and Z cannot be 'summed' or integrated over long distances and long periods. They don't necessarily 'add up'. This is what 'local' means in this context.
I BELIEVE that general relativity attempts to solve these sorts of problems by looking at the macro picture and integrating gravity. The problem is that its equations are far more complex, and very hard to solve... So there is progress on this front but it is very slow: we lack the mathematics to crack the case.
I suppose another way to look at it is to say that time dilatation and other odd SR-predicted phenomena are mere illusions or perception issues due to high relative speed, like the dopler effect. But since time dilatation has been observed experimentally, i think that doesn't work. Time is not absolute in GR either.