Hi peoples, love these threads, cavediver and son goku as usual and now also apparently onifre and others, have the math covered better than I could hope to. I just want to throw in something for the sake of the thought experiment, for the people who are wanting to believe that "somehow" traveling faster than light would equal "somehow" traveling backward in time.
Let's just allow for the argument that we "could" travel faster than c (yes, postulate magic.) I don't mean any kind of cheating either, like wormholes or space warps or teleportation, traveling from point a to point b without passing through intervening points. (That's a whole different causality breakdown!) I just mean the thing we want to imagine, traveling say 299,999 kps and then speeding up 2 kps and thereby being ("somehow") at a speed of 300,00
1 kps.
We would
like to believe, that if we could do this, we would then be traveling backward through time, yes? That is, we would continue experiencing time moving forward for us, in our spaceship, but observe the universe outside our ship as experiencing time moving backward, like a movie running in reverse, so that when we arrived at our destination, it would be at a date earlier than we left, or at least earlier than when we jumped the "time barrier". Yes?
But this is just a delusion encouraged by science fiction. It isn't the logical result of what backwards duration would really mean in relation to what the physics are telling us about our own duration at near-light speeds. Let's look at what is actually happening and do the "magic" extrapolation for ourselves instead of trusting Buck Rogers.
As we get near the speed of light, time slows down for us. That is, an objective observer outside our frame of reference would see our clocks (and hearts, and thoughts, and actions) moving slower and slower. Yes? Then as we actually arrive
at the speed of light, if we could, they would see our clocks stop. Yes? So then if we "could" go even faster, our clocks would appear to be moving backwards. It would look like a movie running in reverse, not outside the spaceship, but
inside it!
This may sound like six of one and half a dozen of the other, but it isn't. The spacetime event, our spaceship, is still moving forward in time, in that when it gets another second along, it would have gone 300,00
1 kilometers. But it would be some time period earlier inside the ship than the time when the speed had increased. Herein lies the paradox, if time were running backwards in our ship, and when it was running forwards, we were accelerating, then now what we would be doing, from an objective viewpoint, would be what? anti-accelerating?
decelerating?
Sticking with the movie analogy, as we get to the frame where we are breaking the c barrier, the movie would stop. If we "somehow" got to the frame where we were going faster than light, the movie would move one frame backward -- to the point where we were only going as fast as light -- and again, stop.
This is functionally equivalent to, never going faster than light, at all. Any such speed would rewind itself right out of ever having happened, at all,
at all.
* note intentional inexactness with c to ease analogy, it's actually 299,792,458 meters per second plus or minus maybe 4 billionths in change, subject to further whacking
Edited by Iblis, : corrective note
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