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Path: utzoo!watmath!clyde!bonnie!akgua!gatech!seismo!cmcl2!philabs!micomvax!musocs!mcgill-vision!mouse
From: mouse@mcgill-vision.UUCP (der Mouse)
Newsgroups: net.space,net.physics
Subject: Re: Time Retardation
Message-ID: <332@mcgill-vision.UUCP>
Date: Thu, 21-Nov-85 21:02:08 EST
Article-I.D.: mcgill-v.332
Posted: Thu Nov 21 21:02:08 1985
Date-Received: Mon, 25-Nov-85 07:13:40 EST
References: <8511111807.AA01976@s1-b.arpa>, <399@sesame.UUCP>
Organization: McGill University, Montreal
Lines: 36
Xref: watmath net.space:4795 net.physics:3634
Followups-to: net.physics

[[  This is  getting off  of  space issues, so  I  am  cross-posting  to
net.physics   and  directing   followups  to  net.physics  only.     For
net.physics people, this started in net.space.  ]]

OK, since nobody else responded (or is news just slow to here?)

>> The difference in the rate at which time passes for two different inertial
>> frames of reference is determined by the Lorentz Transformation:
>> 	     ---------
>> 	    /    v**2		v = Velocity of one frame with respect to
>> 	\  / 1 - ----			the other.
>> 	 \/      c**2		c = Speed of light.
>> 

> What  happens  if two ships leave with opposite vectors, and  they  both
> approach the  speed  of light  relative to  their initial frame.   The v
> above, relative  to  each  other, would approach 2*c, giving  a non-real
> answer.  Where am  I goofing?  (Or is it time to invest in  a FTL ship? 
> :-)

     "v = Velocity of one frame with respect to the other".  That is, as
observed by an observer attached  to the other (frame).  The velocity of
frame X  as observed by (an observer in)  frame Y is  (necessarily) less
than c, so the result doesn't go imaginary.  The 2c velocity is obtained
by  measuring from  a third intertial  frame; if you want to get results
for two frames based on quantities observed in a  third, you have to use
more complicated equations.
-- 
					der Mouse

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