From: utzoo!decvax!ucbvax!CAD:moore
Newsgroups: net.physics
Title: Re: Faster-than-light precognition retra - (nf)
Article-I.D.: ucbcad.440
Posted: Wed Feb  2 13:46:45 1983
Received: Thu Feb  3 06:30:22 1983

#R:sri-arpa:-33000:ucbcad:20300002:000:690
ucbcad!moore    Feb  2 13:46:00 1983

Wait, don't give up so soon! In the book "Problem Book in Relativity
and Gravitation" by Lightman, Press, Price, and Teukolsky, they
work out the problem of observer A sending a tachyon pulse (velocity
u > 1) to an observer B who is moving at velocity v directly away from
A. B then immediately responds with a tachyon pulse back to A. The
roundtrip time as measured by A is then:
	
	t = L*[1/u + (1-u*v)/(u-v)]

    where L is the distance between A and B when B recieves the pulse.
    and all velocities are in multiples of c.

and this gives t < 0 for u > [1+(1-v**2)**.5]/v. Thus you can get
an effect before the cause.

		The universe is stranger than we can suppose,

			Peter Moore