Being a novice on this abstract subject, I had just read that one theory says if one could exceed the speed of light, one would go back in time. (This is probably old hat to those well versed on these concepts.) On one hand, I can kinda understand it from the few times I have read about this (before getting a headache), however…
Upon finding this Wiki image, I have rethought this to ask: Why would one go backward along the “time” axis (traveling from the future light cone to the past light cone along the “time” axis) instead of traveling beyond the bounds of the future light cone*??? And, if one could leave the light cone…where would one be in the “absolute elsewhere”? …Or, is it just unknown (and cannot be known until we can break the v=c barrier) what lies beyond? :dubious:
*in a previous SD post, I was informed one would be moving at v=c to exist on the surface of the light cone, and v<c to be inside the light cone. So, v>c would put me outside the future light cone, correct?
Pretty much, yep. At v=c, you’re on the light cone; at v < c, you’re inside it, and if any object could move > c, it could cross outside of light cones.
This leads to viewpoints, from people moving < c, but very, very fast, where the FTL guy appears to move backward in time. That means he could be used to send a message backward in time, and that leads to time-travel paradoxes.
(My old physics prof spoke of the “magical typewriter” that printed out, on paper, what you would type in on the keyboard…before you typed it in. Everyone immediately asked, doesn’t that deny human free will? And, yeah, it kinda does.)
That image shows the situation in one reference frame. If you can go the same amount faster than light in all reference frames, then you can travel FTL in one frame, accelerate to another frame, travel FTL back to where you started and end up in the past.
It’s not true that traveling FTL in a single reference frame lets you travel back in time.