stephen@alberta (10/19/83)
A question which has always bothered me:
Person A moves east at 3/4 C
Person B moves west at 3/4 C
As far as the third ("stationary") observer is concerned, they have
a relative speed of 1.5C.
How do A and B view each other? What would A percieve B's speed
as? Could A see B?
Stephen Samuel
(alberta!stephen)alle@ihuxb.UUCP (Allen England) (10/22/83)
Your mistake is in adding the two velocities together to get the relative velocity. Vt = V1 + V2 only holds for velocities much less than the speed of light. That is one of the basic differences between Newtonian Physics and Relativity. Allen England at AT&T Bell Laboratories, Naperville, IL ihnp4!ihuxb!alle
guy@rlgvax.UUCP (Guy Harris) (10/22/83)
Relativistic velocity addition don' work that way. A and B will each see
the other as approaching them at some velocity between 3/4C and C (I
don't have the exact formula at hand).
Guy Harris
{seismo,mcnc,brl-bmd,allegra}!rlgvax!guystudent@nmtvax.UUCP (10/22/83)
The law (or theory) of Relativity states that velocities are not
simply additive as the laws of Newton stated. The actual method
of determining the final relative velocity is
V1 + V2
Vt = ----------
1 + V1*V2
Note: if this formula reminds you of a geometry formula for the
addition of the tangents of two angles congradulations, it's
supposed to.
Note also: I know the sign in the bottom is positive but we not
working in Euclidean space.
--
Sincerely;
Greg Hennessy
..ucbvax!unmvax!nmtvax!studentgwyn%brl-vld@sri-unix.UUCP (11/10/83)
From: Doug Gwyn (VLD/VMB) <gwyn@brl-vld> More precisely, the velocity-addition formula is the law for hyperbolic tangents.