Sunday, June 19, 2005

Latest News On Time Travel!

I have been fascinated by time travel since I was a little kid but I just started to understand time travel a little bit more when I was learning Relativity and Quantum Physics. Einstein discovered that time travel is possible in his Theory of Relativity many decades ago. I would like to talk about the latest findings done by the physicists today in this post. I just got to know three latest findings, two are for wormholes and another one explained the paradox of time travel.

For a long time, wormholes are the theoretical tunnels which seemed the best way for us to do time traveling. Using wormholes to do time traveling can be seen in this way. Mark 2 holes at the opposite ends of a paper to represent 2 points in space-time. Then the paper can be bent so that 2 points are on placed top of each other. In this way, a person can theoretically go through a wormhole and appear at another space-time. The region that a time traveler will pass through called the throat, exotic matter is used to fill the throat to keep the wormhole open.

Calculations by Stephen Hsu and Roman Buniy of the University of Oregon show that a wormhole combining exotic matter with semi-classical space-time would be fundamentally unstable.

“We aren’t saying you can’t build a wormhole. But the ones you would like to build – the predictable ones where you can say Mr Spock will land in New York at 2pm on this day – those look like they will fall apart.” Dr. Hsu said.

A different approach to the question of wormholes was done by Chris Fewter of the University of York and Thomas Roman of Central Connecticut State University. Their calculations show that, even it is possible to build a wormhole, the throat would be too small for time travel.

“It might - in theory - be possible to carefully fine-tune the geometry of the wormhole so that the wormhole throat became big enough for a person to fit through. But building a wormhole with a throat radius big enough to just fit a proton would require fine-tuning to within one part in 10 to the power of 30. A human-sized wormhole would require fine-tuning to within one part in 10 to the power of 60. Frankly no engineer is going to be able to do that” Says Fewter.

According to Einstein, space-time can curve back and allowing us to travel to the past. Time travel to the past is thought to be possible by physicists and nevertheless it gives some uncomfortable contradictions. The obvious one would be that theoretically, we can travel back in time and do something which will change the present. This is something I always wanted to do when I was a kid although I didn’t think about the consequences of it. If you think more, it will eventually mess up the whole theory of time travel.

Today, a team of physicists from US and Austria says that it is possible if only there are physical constraints acting to prevent the present from changes in the past. This new model uses the laws of quantum mechanics to get rid of the paradox. The physical constraints exist because of the laws of quantum mechanics although they don’t account for backwards movement of time before. This model is easy to understand as quantum behaviour is governed by probabilities. There are a numbers of possibilities regarding its state before something is observed. But the possibilities will shrink to 1 when the state is measured, which means the uncertainty is eliminated.

"Quantum mechanics distinguishes between something that might happen and something that did happen," Professor Dan Greenberger, of the City University of New York, US.



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