Jonathan Reeves wrote:
> Anders Sandberg replied:
>
> >> 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)
>
> FTL does not depend on _accelerating_ beyond c. A constant
> acceleration of less than c would result in travel at faster than the
> speed of light relative to your start point.
no it would not. You would approach c, but never pass it, even to any outside observers. You can have two objects moving just below c in opposite directions as outside observers see it, but they will still appear to each other as separating at just under c.
> >> 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.
>
> Problems with causality/wormholes are due to the 'space/time
> continuum' - an artifact of relativity theory.