@oralloy,
Quote:In your hypothetical, do the two travelers start out at rest with respect to the rest of the universe, and then accelerate up to light speed when they begin their journey towards each other?
Ora that's really a good q. However Ora since all motion is presumably relative anyway I am wondering whether it matters
Thus we've assumed Earth and A to be "stationary." Assume however that Earth and A are situated in a "visible subuniverse" in motion at nearly c with respect to the rest (headed probably in the direction from which you were headed) so that I had been "stationary" throughout the experiment, and when you supposed you were decelerating to join A by firing your retros you were merely slowing down a bit
Quote:...then accelerate up to light speed...
Which we all know they didn't. In my skewed version three velocities are involved: (1) that of A and our subuniverse relative to the rest of it all, which is presumably "at rest," (2) yours before you fire your retros (higher still); and (3) mine (at "rest" with the "rest") considered by A as speeding away in the opposite direction
You'll have to forgive the pun. But incidentally perhaps you can now grasp how the idea of a fixed reference" keeps poking in its unwanted nose
This doesn't resolve your q's at all; you might be right in your implication that how we achieved that starting speed might be a critical issue but I'm just not smart enough to address it