Review On Time Machine Plans
October 1, 2009 4 Comments
Super-Science, NOT Fantasy!
Science Fact: Scientists say building a time machine may be extremely difficult. But time travel is not against the laws of physics!
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 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.
Ever since Einstein, scientists have considered three-dimensional space and time not as two different things, but as different aspects of four-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, 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, timelike curves” – 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, timelike 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.
Since the 1930’s, physicists have speculated about the existence of “wormholes” in the fabric of space. Wormholes are essentially gateways 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. The difficulty lies 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 by the U.S. physicist Kip Thorne, suggests 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!
As a variation on the rotating cylinder, some scientists have suggested 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 two-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!
Civilizations with the technology to harness black holes might be better advised to leave wormholes alone 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 time the mass of the Sun, 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 factory. Then spin the cylinder up to 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, timelike curve.” It would emerge thousands, 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 timeship. 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!