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Path: utzoo!watmath!jagardner
From: jagardner@watmath.UUCP (Jim Gardner)
Newsgroups: net.sf-lovers
Subject: Re: FTL Travel
Message-ID: <15754@watmath.UUCP>
Date: Mon, 15-Jul-85 15:43:59 EDT
Article-I.D.: watmath.15754
Posted: Mon Jul 15 15:43:59 1985
Date-Received: Wed, 17-Jul-85 03:12:06 EDT
References: <2702@topaz.ARPA>
Reply-To: jagardner@watmath.UUCP (Jim Gardner)
Organization: U of Waterloo, Ontario
Lines: 48

[...]

A little relativity theory: we begin with the basic law of
physics F=ma.  What this says is that Force is proportional
to acceleration (provided the mass of the accelerating body
remains constant).  Now one way of interpreting special relativity
says that F=ma is ONLY true for velocities that are small in
comparison to the speed of light.  When you get really fast,
the law breaks down.  You need a lot more force to get the
same amount of acceleration once you get going fast enough.
The faster you're going, the more force you need to get even
a little increase in speed.  Finally, it takes an infinite amount
of force to push something past the speed of light.

All this means is that you can't just put a big rocket engine
on your space-ship and propel it to faster-than-light speeds.
Somehow or other, you have to "get out of the game"; warp drives,
for example, bop out of normal space into a different sort of
environment and bop back into normal space somewhere else,
by-passing the normal space in between.  Another approach is
to diminish the mass of your ship in some currently unknown
way, to compensate for the diminishing return you're getting
from the force you apply.

Tachyons get around the problem by _starting_out_ going faster
than the speed of light.  Since they're already past the boundary,
you don't run into the infinite force problem, so they can happily
do whatever they want.

				Jim Gardner
				University of Waterloo

P.S. Physicists are greatly disquieted by the suggestion that F=ma
could ever be untrue.  Therefore they usually keep the equation and
redefine the "m" (mass) so that the equation still works at high
speeds.  They say that a moving particle has a higher mass than a
particle at rest; as a particle moves faster and faster, its mass
increases, until at the speed of light, its mass is infinite, which
is it would take infinite force to increase the particle's speed.
Of course, then the physicists have to explain why motion adds to
a particle's mass.  Their explanation is that the kinetic energy
of the particle is as good as mass, and indeed, energy is the same
as mass for the purposes of relativity.  Put in equation form,
this is E=m.  And if you use archaic units of measurement, it turns
out that you need a conversion factor in this equation, so you get
E=mc**2.