Clockstoppers, Back to the future, Star trek, Kate and Leopold, Minority Report, The Terminator. The idea of travelling forward into the future or back into the past has always fascinated science fiction writers. It certainly had fascinated me when I read the novel "The Time machine" a very long time back. Who wouldnt get fascinated? Wouldnt it be cool to be able to go back to the past and prevent some terrible mistake from happenning and also be able to travel to the future and see whether you really succeed in winning the person you had a crush on (Instead of depending on crystal balls or tarot cards)? Time travelling is still an unsolved problem in physics. But amazingly, some weirdness of the quantum world now suggest that time travel is possible - at least in theory.People have been suggesting ideas for time travel since centuries, but it was Albert Einsten who laid the foundation for the theoretical possibility of time travel with his theory of Special relativity. But first lets define "Time". There is no particular defination for time (you'll probably just look at your watch when someone says 'time') but Time has been designated as the fourth dimension of our universe, the first three being length, breadth and height (space that is). According to Einstein's theory of special relativity, time slows as an object approaches the speed of light. This has been observed in real life too. A high precision watch was sent on a space shuttle and when it came back it was back by fraction of a second. if one were to move away from the Earth at really very high velocities and return, more time would have passed on Earth than for the traveler. In this sense it is accepted that relativity allows "travel into the future". But the problem lies here. It is almost impossible to travel at a speed anywhere even close to the speed of light.
Lets consider you are in a race. During the race you discover a hidden shortcut. You take the shortcut without anyone noticing it. so you reach the finish line earlier than the others but because the others dont know about it, you win. Similarly there has to be a way to fool the universe, some kind of a shortcut to make you look as if you are travelling really fast. Physicist Kip Thorne believes that there could be some type of tunnel-like structure existing in the universe that could be used as a time travel portal. This tunnel-like structure is called a wormhole.
You know what a Black-hole is. Black holes have a huge gravitational pull that nothing can escape from them, not even light. The centre of a black hole is an infinitely dense point, called a singularity, where the laws of Physics no longer apply. Einstein's equations prove that such a singularity doesn't just end in a single point, but creates a tunnel that goes right through and opens out on the other side. Now this other side is somewhere else in spacetime, either in the future or in the past. Such a tunnel is called a wormhole. Unfortunately these things are still a hypothesis and there is absolutely no evidence. But you never know.
No matter what, problems will continue to exist like the very famous 'grandfather paradox'. What if you went back in time and prevented your grandfather from meeting your grandmother so that your mother was never born? Then you would never have been born... and so on. And also the 'Parallel universe' paradox. How can see yourself in the future or past when you are travelling? How can you split yourself? You cannot travel and not travel at the same time. But like I said you never know. Man has been able to invent things which once could be seen only on Dexter's Labroratory. Man has been able to prove my most favourite law of Physics - "Matter can neither be created nor destroyed" wrong (You probably know about Anti-matter). Anyway, Ladies and Gentlemen, fasten your seatbelts, I bet we are not far from days where we would enter into a Time-machine or a Teleportation-machine (Desperately waiting for this one. Eh! how much I hate travelling).
