Re: starship-design: Re: Still doing stardrives?

[Steve VanDevender <stevev@efn.org>]

Ben Franchuk (Woodelf) writes:
 > I think the best we can 
 > get for speed is .7 C in the speed of matter moving.
 > see:  http://www.autodynamics.org/welcome.html

I wouldn't trust that autodynamics.org web site for accurate
scientific information.  I will diplomatically say that I do not
find their viewpoint representative of mainstream physics
thinking.

 > Note even with a perfect engine as time slows down when you 
 > reach the speed of light, the output of the engine will drop
 > off too since it slows down.

Sigh.  It seems there is a bottomless well of relativistic
misconception I will never be able to drain.

Time does not slow down _for the engine_.  A non-accelerating
observer will see time slow down on the ship as it accelerates
away, but the ship itself does not experience any physical change 
other than acceleration.  The laws of physics are the same no
matter what speed you go; that's one of the fundamental
principles of relativity.  If you feed the same amount of fuel to 
the engine it will produce the same thrust, no matter when you do 
it or how fast you're traveling relative to anything else.

It's been a while since I exhorted anyone to find and read Taylor 
and Wheeler's _Spacetime Physics_, and apparently it's time for a 
reminder.