Would it really be possible to travel to the past as well as the future ?
Before proceeding further, I would like to ask,given a choice would you like to visit the past or the future ?
I would definitely want to go back to the past and right some wrongs, the way Harry Potter does to save his godfather Sirius Black! But then Harry is a wizard , not constrained by laws that we, the muggles inhabiting the four dimensional universe,are. But then what if Harry had been killed in the past ? Dumbledore in his natural flair merely warns that consequences would be too ghastly to discuss. But Dr.Hawking would most probably call it a paradox;such a situation cannot manifest because it is inconsistent with the Law of Causality.
Theoretically, tiny wormholes (a billion-trillion-trillionths of a centimeter across), existing all around us even in time,may in the future be enlarged to accommodate humans,as some scientists think might allow travel to the past but Hawking says such wormholes cannot exist. He draws analogy to the concept of "feedback" in sound
systems (amplified sound output through speaker enters is again picked up by microphone and the cycle continues until the sound system is destroyed.) In the case of the wormhole it is natural radiation that will loop and destroy the wormhole.
So there is no going back!
However, traveling to the future may not be that difficult if we could travel really really fast! No,he is not talking about Chuck Norris or Rajnikant "racing against time and winning it" :D he is talking about traveling as fast as nearly the speed of light. Of course, a reference has to be made to the great Albert Einstein,anything related to speed of light or just advanced physics has to have his signature. Before proceeding to explain how traveling fast could help in time traveling, Dr.Hawking reminds us of Einstein's theory of relativity of time, or in other words time runs faster in space than on Earth.
The network of satellites, called GPS (Global Positioning System) orbiting our planet prove it beyond doubt.Each clock on these satellite seems to gain a a third of a billionth second everyday despite being very accurate.They run a wee bit faster because they are a wee bit distant from the mass of the Earth. The greater the mass is,the slower time goes. If a spacecraft were to orbit a massive black hole,far away in the space, without being sucked by in it, the time in the spacecraft would slow down considerably, the crew on returning to earth would find that that time on Earth has gone much faster.
However, this wouldn't really be practicable. The only practical way to travel to the future, Dr.Hawking,says would be by traveling at a very fast speed,almost nearing the speed of light.For the sake of explanation,he uses a fictional super-fast train whose tracks go right around the earth. This train is so fast that it almost reaches the speed of light (it cannot reach the exact speed of light). As this trains speed reaches close to that of light, it would be traveling so fast that it would be circling the Earth seven times per second! Inside the train, time slows down relative to everything around. So if the train runs for a 100 years, passengers inside would have lived only a week! (check out Hawking's detailed explanation on this)
So, it is possible to travel to the future if our vehicle could run at nearly the speed of light, but do we now possess the capability to create something that can travel at near-light speed ?
CERN's Large Hadron Collider (which has been in news for different reasons),Dr.Hawking says is actually accelerating particles to 99.99% of the speed of light. This implies that the particles do travel in time! Dr.Hawking then talks on how to build a spaceship which would takes us to the future. This huge ship would have have to travel for six years to accelerate up to a speed of 99% of the speed of light and at this speed, time would have so slowed down that while a year may have passed on Earth, but for the passengers of the ship, only a day would have passed !
A final note and a question- why the heck would people like you (assuming you are not a physicist because if you were why would you be reading an amateurish piece such as this one) and me want to go to the future, say a 100 years from now ? If at all civilization exists then, wouldn't we appear so backward ? ;) :D
Either ways, if you still haven't read this awesome book, order for it now !!!