...and he finally sorted me out on asymmetry, framing, and the lack of uniform motion which dropped the scenario into General Relativity instead of Special Relativity as the explanation for the so-called "Twins Paradox".
Never mentioned this brief correspondence before as I thought all proof of it was long gone, but look what turned up in cleaning out an old file system...
Strange old thing, life...
The asymmetry described does not make sense to me. Both observers should appear the same to the other. Evidently I've forgotten enough so as to keep the paradox a paradox.
ReplyDeleteAnyway that's very cool to have a signed Asimov letter.
Well, I had about the same question and in subsequent notes (long since gone, I suspect), he explained that the asymmetry involved was in the motion -- the twins paradox WOULD be a real problem in circumstances covered by SPECIAL relativity, which only deals with objects in UNIFORM motion in relation to one another -- e.g., same velocity, same acceleration, whatever. That does not occur here because one (or the other, or both, as you will) break the UNIFORMITY by decelerating and turning back around and accelerating home, which is non-uniform motion. In that case, it falls under GENERAL relativity, which is a whole 'nother complex can of worms. But, as he repeated, he didn't know enough about it beyond that to continue an intelligent conversation, which is the nicest "Go away and stop bothering me" note I ever got. Classy guy.
ReplyDeleteGlad I still have the note that survives.