@layman,
I said:
Quote:I'm familiar with the "light clock" illustrations, FBM. Let me ask you a couple questions about them, though.
I then went on to ask you two questions. My intent was, after getting your answers, to then ask you what ASSUMPTIONS you were basing your answers on. Then ask you where those assumptions came from, and then ask you whether, if your assumptions had been different, your answers would have been any different.
Instead, I will try to shortcut that drawn-out process (although this will not be nearly as instructive as if YOU had given me your answers (after thinking them through and then articulating them---not as easy as it sounds).
Previously you took information about light clocks from this site:
http://galileoandeinstein.physics.virginia.edu/lectures/srelwhat.html
So lets look there. Notice that, before any real discussion starts, he tells you that "]The one thing he’s
sure of is that it ["it" being the light in Jill's frame] must be moving at c = 186,300 miles per second, relative to him—
that’s what Einstein tells him."
Think about that for a minute. He is
presupposing the absolute truth of Al's "light postulate." Could you (or he) have started with a different assumption? Sure. You could have with an AST assumption which would have been just the opposite, i.e., that "the light in Jill's frame is NOT moving at c relative to him."
Nothing the guy says after this could possibly serve to in any way support or prove Al's light postulate. It's already been assumed. So it would just be begging the question to say that what you deduce from what you assume proves what you assumed to begin with.
But let's go on. What else is assumed here? Well, skipping the details for now, he concludes that "Jill is aging more slowly
because she’s moving!" So it is necessarily assumed that Jill IS MOVING to reach this conclusion.
Let's go on. Then he says:
Quote:But this isn’t the whole story—we must now turn everything around and look at it from Jill’s point of view. Her inertial frame of reference is just as good as Jack’s. She sees his light clock to be moving at speed v (backwards) so from her point of view his light blip takes the longer zigzag path, which means his clock runs slower than hers. That is to say, each of them will see the other to have slower clocks, and be aging more slow
So here we have the opposite assumption, i.e., that Jack (NOT JILL) is moving. This is not the statement of a "fact" anymore than was Jack's assumption stated as a "fact." It is MERELY an assumption, i.e., how one will "see" the other.
Is either assumption warranted? Are both warranted? Can both assumptions be "fact" as opposed to mere assumptions? Can each clock ACTUALLY run slower than the other?
What would Jill "see" if Jill assumed (as Jack did) that she is moving? Would she reach the same conclusion?
It will not help to say "both are correct." They can't both be correct in any meaningful way. At least one of them must be mistaken.
Tautologies are empty. Saying "A is A" (i.e, because A assumes he is motionless then he will "see" himself is motionless) says nothing of substance. Neither does saying "B is B"
Keep in mind that the whole premise is that there REALLY IS relative motion between the two. Therefore the whole premise NECESSARILY implies that they cannot BOTH be at rest.
