[ExI] Great sf writers: A.A. Attanasio

[Adrian Tymes]

On Thu, Sep 2, 2021 at 11:53 AM BillK via extropy-chat <
extropy-chat at lists.extropy.org> wrote:

> On Thu, 2 Sept 2021 at 18:02, Adrian Tymes via extropy-chat
> <extropy-chat at lists.extropy.org> wrote:
> >
> <snip>
> > But clearly it is not time travel.  It just means it won't be seen at A
> - or its consequences (travelling no faster than light) affect A - for a
> few years.  There may be an effect that might occur at A in a few years,
> and whoever teleported to and from B will have foreknowledge of this.  (In
> this example, they might know to be on the far side of a planet from B when
> the radiation arrives, and when that will be.)
> >
> > "Time travel" would require going into the past of A itself, affecting
> things that were already perceived at A.  (Or going into the future - call
> it A' - and then returning to the present, which would be going into the
> past of A'.)  People can and do change the future without time travel (or
> FTL) all the time.
> > _______________________________________________
>
>
> Causality violation needs to involve moving in different frames of
> reference.
> (The maths is complicated).
> See:
> <
> https://physics.stackexchange.com/questions/52249/how-does-faster-than-light-travel-violate-causality#54242
> >
> This is a popular question. A search provides many confused responses.
> :)
>

The problem with using relativity like that, is that it breaks when you
change velocity - change your acceleration - to turn around and come home.
If you ignore that break, FTL might seem to induce time travel, but that's
like ignoring certain steps to "prove" that a perpetual motion machine
works.
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