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Time Travel

Ronald Mallet's Theoretical Time machine

Ronald Mallett believes that anything containing energy could warp space-time, and as a result, he has designed a time machine that uses light, rather than mass.

His theoretical time machine consists of a ring of two intense beams of light,
Rollover or click on this image for a closer look at Ronald Mallett's Time Machine.
circling in opposite directions. By slowing down the light in an ultra-cold bath of atoms and increasing the intensity of the beams, space-time inside the ring would become warped. Eventually, space and time would become so distorted by the circling light that time would become a dimension similar to space - a dimension that you could move along! If you entered the ring and walked in the correct direction, you could walk back through time - maybe even passing yourself as you entered the ring!

Travelling into the future...

Einstein's special theory of relativity shows that time travel into the future is possible. The theory demonstrates that the way we perceive time is relative to our motion. Objects travelling at speeds close to the speed of light (about 300 000 kilometres per second) age more slowly than stationary objects.

In 1975, Professor Carrol Alley tested Einstein's theory using two synchronised atomic clocks. Carol loaded one clock onto a plane, which was flown for several hours, while the other clock remained on the ground. At the end of its flight, the clock on the plane was slightly behind the one on the ground. Time had actually slowed down for the clock on the plane. It had travelled forward in time.

Into the past?

But what about time travel into the past? In theory, the laws of physics tell us that backward time travel may be possible. However, there are many problems with putting these ideas into practice. Ronald Mallett, Professor of theoretical physics at Connecticut University, made one of the most promising discoveries to date.

According to Einstein's theory of gravitation, any object with mass will cause a warp in space-time, similar to a bowling ball on a mattress. Because space and time has been stretched, clocks operate slower close to Earth than in the vast areas between galaxies. Previous theoretical designs of time machines have used this concept of mass distorting space-time, however they would require a tremendous amount of energy to work.

However, putting Ronald's theory into practice presents plenty of problems. For example, the temperature of the ring would have to be close to absolute zero (-273°C), so humans would find it difficult to use. It would also be impossible to travel back to a time before the machine was switched on. This explains why people from the future haven't visited us - we are yet to build a time machine for them to exit from.

Ronald hopes that travellers from the future may be able to overcome these difficulties and use the rings of light that we construct today as portals to our time.


So, you want to travel across the universe without wasting years in a space ship? Wormholes might just be the answer.

The universe appears as three dimensions in space (up-down, left-right, and forward-backward) and a fourth dimension known as time. Wormholes are connections between two different places in space and time. Although this is difficult to visualise in four dimensions, it is easier to see in two.

Imagine two points on an enormous sheet of paper, several metres apart. You could travel between the points by following a line on the piece of paper. Alternatively, you could fold the paper over so that the two points touch. By folding the paper, you are making a 'wormhole' in the two-dimensional paper world.

Although there is no experimental evidence for the existence of wormholes, theorists believe that they may exist. Wormholes first appeared possible in Einstein's theory of gravity, in 1913.

However, physicists had almost forgotten about them until the mid-eighties, when Carl Sagan included them in his novel Contact, wherein Ellie Arroway, the main character in the book, travels to the centre of our galaxy through a wormhole. A scientist himself, Carl wanted to describe the wormhole with as much scientific accuracy as possible. He asked Kip Thorne, a physicist at the California Institute of Technology, to examine the general properties necessary for a wormhole to stay open...---see WORMHOLES page---...

Negative energy

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