@Olivier5,
Let me start with you last assertion first:
Quote:And NO, SR DOES NOT insists that each twin MUST treat himself as immobile... is not a psychological theory..
No, of course it isn't, although it's often treated as such when it's being "taught." It's a mathematical theory, with certain procedures and protocols built into the way the math can be applied within the context of SR. It is those mathematical rules which says the person making SR calculations (not the actual twin) MUST treat each twin as stationary.
Quote:In actual fact, both twins are traveling. Period
As I said, EVERYBODY knows that. EVERYBODY, including Einstein and all modern day physicists. EVERYBODY. Do you think you are "enlightening" anyone when you state the obvious?
But what "everybody" (including physicists) doesn't do, is simply point that out, and then say that explains everything there is to know about the theory, about twins, etc. Only YOU do that, as far as I've ever seen.