(March 19, 2012 at 2:53 pm)Stimbo Wrote: Re: time travel paradoxes. I heard a particularly elegant hypothesis some years ago on this sort of thing (sorry I can't attribute it). The scenario is that a future version of you travels back to our present and shoots the current you, setting up the classic paradox - since you get shot in the present, you can't exist in the future to travel back to shoot yourself; so you don't get shot and can thus travel back etc etc. One way this could be prevented is for events to be arranged in such a way as to cause your future self's arm to jerk at the critical moment, inflicting nothing more serious than a shoulder wound. This wound, in turn, is what causes your future self's arm to jerk and save your life. The bottom line is that history relative to the time traveller will always find a way to protect itself. Similarly, if you travelled back to assassinate Hitler, either you would be captured before the attempt, or your gun or bomb or whatever would mysteriously jam, or instead of killing him you just end up pissing him off even more. Of course it's all speculation and guesswork based on zero evidence, but it really is a beautiful notion. Plus it makes great sci-fi.
This is similar to the paradox Stephen Hawking used to explain why logically, time travel to the past is impossible. If something is impossible ( i.e becoming your own grandfather, shooting your past self) then you cannot ( by definition, essentially) make it happen, by going back in time, or any other means. Wormholes to the past also defy logic and physics - it would create a feedback loop and destroy itself, and you would need a negative energy density to traverse one.
Time travel to the future is what we are doing now.
