[net.physics] timeout on time dilation?

trc (09/16/82)

In one arguement for time dilation, a thought experiment is done that
has a moving observer bounce a beam of light off a mirror, in a
direction perpendicular to his direction of motion.  A stationary
observer sees the light moving on a diagonal, and so concludes
that time is slowed in the moving frame, since the speed of light
is constant, and he saw the beam travel farther than the moving
observer.

Suppose frame b moves right with respect
to frame a, and projects a beam at an angle backwards such that
the beam's wavefront appears to move perpendicularly in frame a.
Then the beam travels less distance in the non-moving frame, and so
takes less time than in the moving frame.  Thus, time appears
expanded, according to this experiment. This  is
the exact opposite of what is suggested by the other experiment.

Should we conclude from this that there is a fundamental problem?
EG, that maybe the light wouldnt appear to go at a constant velocity
in different directions for the moving frame.   Or should we
conclude that time dilation is dependent upon the direction of
motion, perhaps. Or is something wrong with this experiment?


				Tom Craver
				houti!trc