Hawking's time machine
There has always been a great deal of interest about time-travel. It has been the centre of many science fictions. Frankly, who wouldn't want to travel through time and aspire to a part of this surreal experience? But as of now, it seems the idea of time machine is still a dream. But according to eminent astrophysicist Stephen Hawking, the notion of time-travel is in fact, quite realistic and he strongly believes that humans would be able to travel millions of years into the future and repopulate their devastated planet. In an article earlier this month, published in the British tabloid, Daily Mail, the noted cosmologist outlined theoretically his ideas on time travel. It may be mentioned here that, this is his second surprise, after expressing his belief in the existence of extraterrestrials.
To put it simply, time travel means, moving between different points in time. The laws of physics accommodate the idea of time travel through what is known as 'wormhole'. According to Dr. Hawking, a wormhole is a "Tiny tunnels or shortcut through space and time that constantly form, disappear and reform within the quantum world. And it actually links two separate places and points of time". A wormhole, which is also permitted by the Einstein's field equations of general relativity, is unfortunately too small (just a billion-trillion-trillionth of a centimetre) for people to pass through. However, scientists believe that it may be possible to catch one such wormhole and make it big enough for people or spaceships to enter and travel through time! But Prof. Hawking also believes that this applies only to forward movement in time. On the impossibility of backward time travel, the Professor explained that it would violate the law of causality, which says that effect must follow cause. But in the case of travel backwards in time, cause will have to follow the effect! He explains, if you go back in time and destroy the time machine, then how is it that you travelled to the past in the first place? The author of the best seller, "A brief History of Time", also believes that radiation feedback might collapse any wormhole even if scientists manage to expand it to a usable size, making them useless for actual travel. But in that case, what is the other option? In his own words, "Time flows like a river and it seems as if each of us is carried relentlessly along by time's current. But time is like a river in another way. It flows at different speeds in different places and that is the key to travelling into the future". It was Einstein who first proposed the idea that there are places where time slows down and there are others where time speeds up. And it is the black hole, the region of space-time from which nothing, not even light can escape due to its intensely strong gravity, which has a dramatic effect on time, slowing it down. And Dr. Hawking strongly believes that this particular nature of a black hole makes it a natural time machine!
Another key aspect of time-travel is travelling at the speed of light. Hawking explains, "believe it or not, travelling close to the speed of light transports you to the future". Being a firm believer of time-travel, Dr. Hawking maintains that if such a mechanism were invented, a trip to the edge of the galaxy would take just 80 years! Would humans ever be able to travel through time in the future? Only time will tell.