Re: FTL, ether and wind

On 17 veebr, 22:25, thro...@[EMAIL PROTECTED]
 (Wayne Throop) wrote:
> : Crown-Horned Snorkack <chornedsnork...@[EMAIL PROTECTED]
>
> : If you have multiple frames where FTL could occur, how do you avoid
> : time travel?
>
> Is that the goal now?  Well, OK, but note that your originnal question
> was
>     If the roundtrip time between A and B by FTL is exactly zero, and
>     signals sent A to B at FTL and back B to A arrive after a finite
>     time, how do you avoid a preferred frame?
>
> which doesn't involve avoiding time travel.  But if that's the goal,
> then the usual way is some mechanism embodying the so-called
> chronological protection conjecture.

Ah, I see.

 Often illustrated by wormholes;
> you can connect any two spacelike separated events with wormholes,
> so there are "multiple frames where FTL could occur", but if you try
> to move your wormhole ends to have a timelike separation (or indeed
> establish any network of wormholes with a closed timelike curve), you
> must first have a closed lightlike curve, and that would collapse your
> wormhole network.  There are reasons to suppose this would indeed occur.
>
> So.  You "avoid timetravel" because if you try it, your FTL widdget
> implodes before you accomplish it.  (Note that this is not the same
issue
> Niven raised in "theory and practice of time travel", and turned into
> a short story, but it has much the same effect).

So... you have a pair of wormholes whose ends have spacelike
separation, like one end (A) at Earth and the other (B) 3 years in
past on Alpha Centauri - getting through wormhole and back to Earth at
lightspeed takes 1,3 years.

Now, you have another pair of wormholes whose ends also have spacelike
separation - like C near Earth and D 3 years in future 4,3 light years
from Earth, but in a direction different from Alpha Centauri, such
that B is more than 6 light years away from B.

Now you move D. Does it mean that when D reaches 6 light years from B,
A, B, C and D all collapse? Or just C and D?

And that the otherwise unexplained collapse of A and B proves that the
otherwise unknown wormholes C and D must have existed and been moved?

Chronological protection conjecture does, in any case, look more
complex that the existence of an unique preferred frame for all FTL
travel, which would easily assure chronological protection.