Is time travel possible?
Name: Brian Lintz
Date: Around 1993
Is time travel possible?
I assume that you mean time travel at a different rate than the
rate that we are all now traveling forward in time. All of us and all the
matter around us is currently traveling forward in time at the same rate ( at
least locally) and there does not seem to be a way in which we can alter that.
Relativistically time is dilated when we observe it in quickly moving
reference frames and a twin that has been traveling and returns will be
slightly younger than the twin that stayed behind in a stationary reference
system. This experimental fact indicates that to move into frames where time
is dilated effects all the manifestations of elapsed time for objects or
beings. I think that this means the time traveler would be effected by the
time travel as well. The mystery in the time travel stories is how the
travelers have escaped being effected by the change in frames. There is no
known way that someone can travel ahead or back in time. It would appear that
there are several contradictions that would occur if it were possible. One of
these would be the effect on what are called world lines and their restriction
to be in what is called the forward light cone.
Actually, some physicists a few years back did work out a way in
which time travel would be possible. One of the instigators was Kip Thorne,
and I actually saw him give a talk on this. It seems that if civilization
could advance sufficiently far to handle black holes with ease, so we could
put black holes in a box of some sort, for example, then they found a way in
which one could start with two black holes close together, and then pull them
apart, and instantaneous travel would be possible between the two black holes.
Because of the theory of relativity, instantaneous travel and travel backwards
(or forwards) in time are essentially equivalent (you actually have to take
two instantaneous trips to get back to the same point in space at an earlier,
or later, time). However, even with this scheme it was impossible to travel
back to a time before the "time machine" was created. Which is good, since we
really do not want people going around killing their grandmothers before their
mothers were born. I think I may have read that there was something wrong
with this scheme. So, in the end, it could be nobody really knows how to
travel backwards in time. It is fun to speculate though!
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Update: June 2012