So you want to travel in time?
First you’ll need to find yourself a spaceship and take it for a high-speed round trip. When you come back to earth, your friends, family and pets will all have aged more than you. You will have “leaped” into the future.
Did you know? You may travel to the future by riding a spaceship travelling near the speed of light.
By how much more will they have aged? That will depend on how long the trip was but also the speed at which you travelled. And that’s the catch: to really see a difference you will have to travel near the speed of light. How fast is the speed of light? About 1,000,000,000 kilometres per hour. At that speed, light can circle the globe seven times in a second. By comparison an airplane would take about 45 hours of non-stop flight to circle it once.
But even if you were able to travel to the future, it would be a one-way ticket unless you could go back in time. But travelling back in time is a very puzzling and tricky business. Just think about it: you could stop your parents from ever meeting and having you. But, then, if you were never born, how could you travel into the past in the first place?
That’s what physicists call a paradox and time travel is filled with them. Stephen Hawking, a very famous physicist, actually thinks that the only way out is for time travel to be impossible. After all, as he says, we don’t see tourists from the future.
Did you know? You may be able to travel back in time but only up to when you built your time machine
Other physicists are of a different opinion. One named Kip Thorn thinks that it is possible to travel back in time but only up to the moment when the first time machine was built. That could explain why we don’t see tourists from the future as no time machine exists yet.
But even if time travel were possible, the technology to build a time machine is well beyond what we have now. So don’t expect a visit from your future self any time soon.
Time Travel, NOVA Online http://www.pbs.org/wgbh/nova/time/
How to Build a Time Machine? Scientific American http://www.scientificamerican.com/article.cfm?id=how-to-build-a-time-machi-2002-09
This answer was written by François-Alex Bourque who works as a scientist for the Canadian Department of National Defense.