Jonathan Reeves <JonathanR@mail.iclshelpdesks.com> writes:
> Correct me if I'm wrong (I'm sure someone will), but all the 'time
> travel' phenomena that I've heard about are to do with
> things(information) apparently moving faster than the speed of light.
> The interpretation that they are moving backwards in time is solely due
> to a refusal to believe that something can travel at FTL speeds, as this
> suggests the currently accepted view of relativity may not be entirely
> correct.
If something can move FTL, then relativity is obviously not correct in the first place. The reason FTL is dismissed in relativity (besides the impossibility of accelerating beyond c) is that it would completely mess up causality, which generally is/was regarded as a bad thing. If you buy Novikov's principle of self-consistency or something similar, then this might not be a serious problem after all - causality gets weird and loopy, but not inconsistent.
However, "time travel" in various forms can be done without FTL. One example would be wormholes, which are allowable solutions to general relativity (even if their physical possibility remains unknown). With wormholes you can move to a distant time and/or space without going FTL in your local frame. The same problems with causality might emerge, but again quantum effects such as the Visser build up of virtual particle or Novikov's principle might keep physics sane.
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