From: utzoo!decvax!duke!harpo!ihps3!houxi!deimos!ariel!houti!trc
Newsgroups: net.physics
Title: paradoxical twins
Article-I.D.: houti.154
Posted: Wed Sep 15 19:28:39 1982
Received: Thu Sep 16 02:57:10 1982


Now that simultaneity has been settled (I hope) how about the good old
twins paradox?

My question here is, if both frames of reference are equally good,
then why should one twin age differently than the other?  In fact,
it would seem to me to be reasonable to argue that, there is in fact
a prefered (stationary) frame of reference, but that the only way to
detect the difference is to check the relative time dilation effects
between two frames.


I have heard it argued that the difference is that one undergoes
acceleration and the other doesnt, and that this somehow explains
the effect.  However, the difference in ages doesnt occur during
the acceleration, for the most part, but rather during the long
period of free fall.

Suppose one ship starts out, and stops at some distance away.
Then it, and another ship from earth take off and meet at the center.
The later ship stops, and accelerates back to earth.  (It has gone a
bit past center, so that it can accelerate to match the other ship's
velocity at exactly the center.) Now both ships have undergone the
exact same accelerations, but the first to leave will be carrying a
much younger twin.

Another interesting effect, not necessarily related, is that a spaceship
that travels away from one and near SOL velocities (NSOLV)
and then turns and comes back, will appear to have taken longer
to go away than to get back - that is, the information it radios
back will be compressed relative to the information it sent on
the way out.  Thus, events will appear slowed on the way out,
and actually faster on the way back.    (Time dilation would still
apply, but it would be modified by this effect.)

Couldnt it be argued that this is in fact a real effect, and that
time dilation is dependent upon direction of velocitiy?

				Tom Craver
				houti!trc