RE: starship-design: FTL

[Steve VanDevender <stevev@efn.org>]

L. Parker writes:
 > Steve,
 > 
 > > For any FTL-moving object, there is one observer moving at a particular
 > > speed relative to the events in question who will see the object's
 > > motion as infinitely fast and the events as simultaneous.  Consequently
 > > any FTL motion will look like infinite speed to someone.  Does that
 > > help?  :-)
 > 
 > Sorry, I learned logic in sixth grade, I didn't get physics until high school.
 > I just can't quite see it. I guess what I am trying to say is that I don't 
 > believe in violation of causality, period. Therefore, current understanding 
 > of physical laws as they relate to relativity and FTL MUST be flawed.

What I should have said is that "FTL motion _can_ look like infinite
speed to someone moving at the right speed".  Understanding how that
works requires a basic understanding of the Lorentz transformation,
which I will leave to more talented and experienced teachers like Taylor
and Wheeler.

The solution most physicists have settled on is that relativity and FTL
are not compatible, and although there is no proof that FTL must be
impossible, it seems to be a safe assumption, especially if you want to
preserve causality.  Although for simplicity, most of the examples have
been discussed in the context of special relativity, general relativity
is more potentially forgiving of FTL.  However, despite tantalizing
apparent loopholes, it doesn't seem to allow FTL either; every apparent
loophole so far imagined also turns out to be unconstructable, or
requires the universe to have properties that it doesn't actually seem
to possess.