[ExI] Time Travel and FTL flight

[Adrian Tymes]

On Mon, Sep 6, 2021 at 12:57 PM Ben Zaiboc via extropy-chat <
extropy-chat at lists.extropy.org> wrote:

> I don't understand that. Either you travel faster than light or you don't.
>
It is the method of faster than light travel that matters.

> Either FTL travel can result in time-travel or it can't.
>
You are confused because you look at all FTL travel as the same thing.  It
isn't.

> If it can't, then surely any method that can transport things faster than
> light will work, and if it can, then surely no method should work?
>
No.  Not all methods are the same here.

> Saying it's *how* you get to FTL that matters for whether time-travel is
> (theoretically, but not in fact) possible doesn't make any sense to me,
> when it's the fact that you *are* travelling faster than light that
> determines if you could time-travel or not.
>
Dead wrong.  It is not just the fact that you are travelling faster than
light that matters.  It really is how you get to FTL that matters.

You appear to have a core assumption or belief that it is the fact of FTL
travel that matters.  This assumption or belief is wrong.  If you care to
explain why you believe this, maybe the confusion can be unraveled.  But
you're speaking of it as an a priori fact, so all I can say is that this
"fact" is incorrect.

To give a few examples that have been brought up so far:
1) Accelerating past light speed, if it were possible, might result in time
travel.  (However, it isn't possible for anything with mass.)
2a) Teleporting from point to point, such as by wormholes, gives the effect
of FTL without actually travelling FTL, and does not appear to result in
time travel.
2b) Certain methods of bending spacetime, such as the Alcubierre Drive,
give the effect of FTL without actually travelling FTL, and do not appear
to result in time travel.

One might notice a certain similarity between the latter two examples, that
gives rise to the question of whether this is a general rule.
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