Time-Travel is easy. All of us do it every day. But only in one direction. For thousands of years,scientists and philosophers have talked of time as a "river that flows steadily onward year-after-year". But what if there were a way to swim against the flow? Or to run down the bank ahead of the river? Might we might be able to journey back-and-forth in time just as we travel through space. The idea is not as far-fetched as it sounds. And the implications for the future are intriguing.
Super-Science , NOT Fantasy!
Ever since Einstein,
scientists have considered
time and 3-dimensional
space not as
2 different things but as
different aspects of
a 4-dimensional "space-time". Quantum
physicists(who study the world of subatomic particles) often find it easier to
explain events by assuming time runs
backward as well as forward despite however much it defies common sense.
At the other extreme, cosmologists looking at the Universe
on a grand scale have found that space and time can
be warped by
gravity and speed.
Back in the
1940s, German mathematician
Kurt Goedel proved that
if we could
warp and twist
space-time enough creating
what he called
"Closed, Time-like Curves (CTC)" -- then we could bore tunnels through time itself. But no one knew how
to do the twisting.
Until black holes.
The gravitational pull of a black hole is so enormous that
it distorts the very fabric of space-time into what is called a
singularity. When singularities
were found to spin, it was proved that Closed, Time-like Curves not only can
occur -- they MUST occur! The
singularity forms a doughnut shape in space-time while the hole in the middle
is a perilous gateway to somewhere -- or when.
3 Ways to Travel in Time Without Breaking the Rules
 |
| Wormhole-artist depiction |
1. Wormholes
Since the 1930s, physicists have speculated about the
existence of "wormholes" in the fabric of space. Wormholes are
essentially gateway between different parts of the Universe and are made by linking a
pair of black
holes. This effectively
creates a tunnel
through time and
space: a traveler entering at one end would exit the other at a
different time as well as a different place.
 | |
| Kip Thorne |
The difficulty likes in keeping the wormhole open while the traveler makes his journey. If the opening snaps shut, he will never survive to emerge at the other end. For years, scientists believed that the transit was physically impossible. But recent research especially the U.S. physicist Kip Thorne -- suggest that it could be done using exotic materials capable of withstanding the immense forces involved. Even then, the time machine would be of limited use.
For example, you could not return to a time before the wormhole was created. Using wormhole technology would also require a society so technologically advanced that it could master and exploit the energy within black holes. But the trip would NOT be impossible -- just very, very difficult!
2.Rotating cylinder
 | |
| Frank Tipler |
Civilizations with the technology to harness black holes might be better advised to leave wormholes and try the time-warp method suggested by U.S. astronomer Frank Tipler. He has a simple recipe for a time machine.
First, take a piece of material 10 times the mass of the Sun. Then squeeze it together and roll it into a long, thin, super-dense cylinder (a bit like a black hole that has passed through a spaghetti factor). Lastly, spin this cylinder at a few billion revolutions-per-minute and see what happens.
Tipler predicts that a ship following a carefully plotted spiral course around the cylinder would immediately find itself on a "Closed, Time-like Curve". It would emerge thousand -- even billions -- of years from its starting point and possibly several galaxies away.
There are problems, though. For the mathematics to work properly, Tipler's cylinder has to be infinitely long. Also, odd things happen near the ends, and you need to steer well clear of them in your time-ship. However, if you make the device as long as you can and stick to paths close to the middle of the cylinder, you should survive the trip!
There are problems, though. For the mathematics to work properly, Tipler's cylinder has to be infinitely long. Also, odd things happen near the ends, and you need to steer well clear of them in your time-ship. However, if you make the device as long as you can and stick to paths close to the middle of the cylinder, you should survive the trip!
3. Cosmic Strings
 |
| Cosmic strings- An artist view |
As a variation on the rotating cylinder, some scientists have suggest using "cosmic strings" to construct a time machine. At the moment, these are purely theoretical objects that might possibly be left over from the creation of the Universe in the Big Bang.
A black hole contains a one-dimensional singularity -- an infinitely small point in the space-time continuum. A cosmic string, if such a thing existed, would be a 2-dimensional singularity an infinitely thin line that has even stranger effects on the fabric of space and time.
Although no one has actually found a cosmic string, astronomers have suggested that they may explain strange effects seen in distant galaxies. By maneuvering two cosmic strings close together -- or possibly just one string plus a black hole -- it is theoretically possible to create a whole array of "closed timelike curves". Your best bet is to fire two infinitely long cosmic strings past each other at very high speeds, then fly your ship around them in a carefully calculated figure-eight. In theory, you would be able to emerge anywhere, anytime!
What If Tourists From the Future Could Visit Us ?
If time machines are possible, it is likely that someone in the Future will already have constructed
one. After all, in the Future there is time to complete even the largest engineering project! Even if humans are not up to the task, creatures from other planets may try. So why are we not overrun by visitors from the Future?
This is the argument used by the famous English physicist Stephen Hawking in what he called his "Chronology Protection Conjecture". Like many other scientists, Hawking is troubled by the weird paradoxes of time-travel. He argues that the Universe simply couldn't allow time-travel to happen because its evolution since the Big Bang cannot be reversed. If the Universe were to contract instead of expanding, asks Hawking, would human beings "un-evolve" in the same way as they have evolved over millions of years?
A second explanation for the absence of visitors envisaged so far lets the voyager go back before the moment the machine was first constructed. So relax. Since no one has built a time machine yet, out-of-time tourists are not a problem!
If time machines are possible, it is likely that someone in the Future will already have constructed
one. After all, in the Future there is time to complete even the largest engineering project! Even if humans are not up to the task, creatures from other planets may try. So why are we not overrun by visitors from the Future?
This is the argument used by the famous English physicist Stephen Hawking in what he called his "Chronology Protection Conjecture". Like many other scientists, Hawking is troubled by the weird paradoxes of time-travel. He argues that the Universe simply couldn't allow time-travel to happen because its evolution since the Big Bang cannot be reversed. If the Universe were to contract instead of expanding, asks Hawking, would human beings "un-evolve" in the same way as they have evolved over millions of years?
A second explanation for the absence of visitors envisaged so far lets the voyager go back before the moment the machine was first constructed. So relax. Since no one has built a time machine yet, out-of-time tourists are not a problem!
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