Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site watmath.UUCP 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.