CAD:moore (02/02/83)
#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