Re: starship-design: (no subject)

[kuo@bit.csc.lsu.edu (Isaac Kuo)]

Kyle R. Mcallister wrote:

>Why would FTL be allowed in a hyperbolic universe better than in a
>convex one?

Because in a hyperbolic universe, space-time is expanding at an
accelerating rate, making it impossible to return to your past
point of origin even if you go FTL (the more hyperbolic, the
faster FTL is allowed).

>Why do we think our universe is convex (or was it hyperbolic?)?

Because we think there is an average positive energy density in
the universe.  The attractive force of gravity from positive
energy (e.g. normal matter) indicates that space-time is "curving
inwards" upon itself.

>Why does general relativity accept FTL better than special relativity?

Because it allows for curved spacetime, which can potentially
allow global behaviors very unlike the local behavior.

As an analogy, imagine the difference between walking on the surface
of a sphere and walking on the surface of an infinite flat plane.
In the former case, you can walk in one direction and eventually
end up where you began.  Can't be done in the latter case.

>Kyle

>P.S.: Tried to find the answers on my own, but couldn't. I'm not
>suggesting that we design an FTL ship.
-- 
    _____     Isaac Kuo kuo@bit.csc.lsu.edu http://www.csc.lsu.edu/~kuo
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