Re: FTL and causality violation

In article <1178384400@xxxxxxxxx>, throopw@xxxxxxxxx says...
: Gerry Quinn <gerryq@xxxxxxxxx>
: So long as we assume that the universe has a preferred reference frame
: (i.e. that velocity relative to the vacuum is a meaningful concept)
: there's no reason why FTL should bring about causality violations.
:
: There's no physics that really prevents this - we just drop special
: relativity in favour of a Lorentz-Poincare style aether.

The only problem with that being that the lack of a prefered frame has had
an enormously successful track record ever since Galileo, so the smart money
by now is all lined up against the notion of an ether.

As soon as you demonstrate your FTL drive, the smart money will swing
right around.

: The real problem is answering why, if FTL is possible, particles don't
: seem to be doing it.

Or put another way, if you are trying to figure out what is the most
likely physical model given what we know right now, it'd be that there's
no such thing as absolute simultaneity, and FTL, relativity, causality,
pick only two. (That's a simplification, of course, but IMO a useful one.)

Yes, but since you can't reasonably drop causality, the demonstrated
existence of FTL would leave you with no sensible option but to drop
relativity. Of course, 'no FTL' is more probable from today's
perspective.

If you are trying to find an excuse to get both FTL and causality in
a story, the obvious thing to do is suppose some feller eventually
*does* observe some particles doing it, and these particles prefer one
frame over others.

I wouldn't go that way. I'd say you'd have to manipulate the vacuum in
some sophisticated fashion to unlock the possibility of FTL travel. It
would be a process too complicated to have any probability of occurring
in normal events.

Maybe you would fire a beam of some kind into the vacuum to modify its
properties, or maybe you would expand a naturally existing microscopic
wormhole.

If you wanted to get into the tech, it might be that the aether frame
had significant importance, for example planets or stations that
happened to be almost stationary with respect to it might become
important hubs of interstellar commerce. For example, the ends of the
microscopic wormholes permeating space might be stationary with respect
to it. But really, it would depend on where you wanted to go with the
story, and you might not bother with it at all.

It's not all that simple to set up a hard time paradox even with
relativity and FTL.

- Gerry Quinn



.

Relevant Pages

  • General Frame Covariance in Achronal Quantum General Relativity (was: No new Einstein)
    ... and general relativity, and see how its focal issue is resolved: ... first you have to understand that the term "frame" has little to ... The one associated with the Rindler vacuum (and the ordinary inertial ... boundary imposed by the causal horizon. ...
    (sci.physics.research)
  • Re: FTL and causality violation
    ... So long as we assume that the universe has a preferred reference frame ... there's no reason why FTL should bring about causality violations. ... relativity in favour of a Lorentz-Poincare style aether. ... The only problem with that being that the lack of a prefered frame has had ...
    (rec.arts.sf.written)
  • Re: What is the most plausible FTL/Hyper/Warp Drive that you come accross?
    ... >> that permits FTL travel but prohibits returning back, ... > relativity principle -- that all inertial frames are indistinguishable ... Not if there is no a priori frame that is important. ...
    (rec.arts.sf.science)
  • Re: Alternate history and time travel
    ... there is an absolute frame of reference. ... Special relativity is almost certainly correct. ... You said that FTL ... that FTL implied time travel, but that it did so by definition. ...
    (rec.arts.sf.fandom)
  • Re: FTL and causality violation
    ... extra wiggle room compared to relativity, if FTL were to be discovered. ... Frames are not preferred by particles; a preferred frame is a property ... Gerry Quinn ...
    (rec.arts.sf.written)