Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/18/84; site lanl.ARPA
Path: utzoo!linus!decvax!genrad!mit-eddie!godot!harvard!seismo!cmcl2!lanl!jlg
From: jlg@lanl.ARPA
Newsgroups: net.physics
Subject: Re: Could someone explain why FTL is illegal?  In small words?
Message-ID: <15639@lanl.ARPA>
Date: Tue, 6-Nov-84 18:16:35 EST
Article-I.D.: lanl.15639
Posted: Tue Nov  6 18:16:35 1984
Date-Received: Thu, 8-Nov-84 19:26:13 EST
References: <327@mhuxt.UUCP> <8130@watarts.UUCP>
Sender: newsreader@lanl.ARPA
Organization: Los Alamos National Laboratory
Lines: 30

> 
>   to put it short:   Einstein assumed that nothing could move faster than
> the speed of light.  From there he deduced his theories.  He redefined
> simultanuity to the measurable simultanuity, meaning that two events happen
> at the same time for an observer if he receives the information at the same
> time at the speed of light.
>   Thus, if something moved faster than the speed of light, it would
> effectly move backward in time according to Einstein's universe, since 
> the observer could now know something before the event occured in his
> reference frame.  (I'm not going to go into the mathematics of his
> hyperbolical space-time, but that is the jist of it).
>   Since Einstein's equation seem to be supported by experimental evidence,
> we assume them to apply in which case FTL would lead to logical contradictions.
> (moving backwards in time is not very logical).
> 
> 				Ue-li Pen
> 				Math Undergrad @ University of Waterloo

He didn't ASSUME that nothing could move faster than light.  He assumed
that the speed of light was the same in all reference frames.  (That is,
if you move toward a light source, the light still seems to be arriving
at the same speed.)  From there he derived special relativity (the form
of which had been around for years - but not rigorously developed from
first principles).  In turn, special relativity implied that something
with rest mass (that is, something traveling slower than light) would
require infinite energy just to accelerate to c.  To go faster than c
would require more than infinite energy!  

If something is found which travels faster than light, it will have 
imaginary rest mass - whatever THAT means.