Time
Travel Theories
This page discusses some theories of time travel very briefly.
This is meant to provide an overview of some theories. It does
not provide information about every theory, and the explanations
provided here are, by no means, complete. The theories that it
discusses include an explanation of forward time travel, black holes,
CTCs, and wormholes.
Forward Time Travel
Physicists
agree that forward time travel is, in fact, possible.
Einstein’s Theory of
Relativity provides that
the faster one moves, the slower time goes relative to the earth. The implications of this allow for forward
time travel. If one could move close to
the speed of light, then one might orbit the earth for what would seem
to be
only a few hours. The time in orbit
might actually be several years on earth.
This theory has been tested using atomic clocks, extremely
accurate
clocks. Two clocks were set to the exact
same time, and one was flown around the earth on a jet traveling at
high speeds
(no where near the speed of light mind you).
When the jet landed, the clock that had been stationary was
slightly
ahead of the clock that had been traveling.
The problem seems to be that, as of yet,
scientists do not have the means to make matter travel anywhere near
light
speed. Furthermore, this only works in
one direction; if someone were to use relativity as a means to travel
to the
future, that person would have no way to come back.
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Backward Time Travel
Backward
time travel has become a big topic of discussion. Physicists
disagree about whether or not
backward time travel can actually exist within the laws of physics and
how it
might exist. There are several
different theories as to how time travel to the past might actually
work.
Black Holes
Black
holes represent one theory. Most black
holes come to a point, called a singularity, at which all matter that
enters
them is destroyed beyond recognition.
However, there is a possibility that another type of black hole
exists. This kind, called Kerr holes,
rotate preventing the creation of a singularity. Therefore
there is a chance that these black
holes could pull matter through to the other side pushing it out
through a
white hole (which is essentially a black hole in reverse).
Once through a white hole one could find
himself in a parallel universe or, potentially, in the past. But the theory of black holes being used in
time travel presents two serious problems.
No Kerr holes have been discovered.
Even if Kerr holes do exist, there is a chance that they might
still
destroy all matter that enters them: “Anything attempting to enter and
exit a
black hole will be sucked in and destroyed before it even reaches the
singularity” (How stuff will work).
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CTCs
Another
theory suggests that closed time-like curves (CTC) could aid a person
in
traveling back in time. A CTC is
essentially a time loop, and it could theoretically allow a person to
travel
back and encounter his ancestors. All that person would have to do is
wait get back to the beginning of the time loop. As with most
other methods for backward time
travel, there is wide debate about whether or not the laws of physics
allow for
the creation of CTCs. Stephen Hawking,
one of today’s leading physicists, asserts that physics and nature
“would
either prevent CTCs from forming or destroy any would-be time traveler
who
approached.” Furthermore, CTCs would
only enable a person to travel back as far as it was created. This means that if I were to create a CTC
today, I might be able to travel back to today five years from now, but
I would
not be able to travel back to 1787 to see the Constitutional
Convention.
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Wormholes
The most
promising theory for
backward time travel involves using wormholes.
Wormholes allow matter to move through them faster than the
speed of
light. Time, therefore, changes within a
wormhole: “Time could behave in strange ways inside a wormhole.” Wormholes could allow a person to traverse
long
distances in only a matter of seconds.
They even could allow him to travel into the past.
Kip Thorne points out, "A single
wormhole…could have time hook up towards the future or towards the past
and…you
can actually manipulate the wormhole to change how time hooked up"
(Nova). Wormholes have two mouths
which are, in essence, twins. Scientists
could therefore use the twins
paradox to enable a person to
travel back in time. If they sent one
mouth of the wormhole into space at light speed and kept the other end
on
earth, then, by simply stepping through the wormhole a person could
travel to
yesterday. However, as with most time
travel theories, wormholes only can reach back as far as they were
created. Furthermore, wormholes usually only
last a few seconds.
They would need to be held open using negative energy to allow
for a
person to safely travel through it. Even
if these problems were solved, yet another problem presents itself; in
computer
simulations in which wormholes are used to travel back in time, every
time the
wormhole approaches the point at which it might be used as a time
machine, it
explodes. However, scientists have yet
to develop the theory that might unite Einstein’s theories of
relativity and of
gravity with quantum mechanics—quantum gravity.
Quantum gravity may provide the solution to the problems with
wormholes—on the other hand, it might not.
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Time travel
to the future is clearly possible as it is in accordance with the laws
of
physics. Whether or not backward time
travel is a possibility remains to be seen.
Unfortunately for fans of time travel science fiction, most
theories involving
backward time travel only allow for time travel after the point at
which the
first time machine is created.
Furthermore, the theories have holes in them that may never be
resolved. For the time being, fans of time
travel
science fiction will have to content themselves with novels and with
movies.
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