Some time ago, I watched a Stephen Hawking documentary which said that you could travel to the future if you went at a fraction of the speed of light for some amount of time. The explanation was this: Consider an observer O at rest. Let the time traveller be T. O sees T whiz past him and concludes that T's clock is running slower than O's. So when T stops (assume that he remains in the same geographic time-zone), O knows that his own clock will be ahead of T's and so T will get the impression that he has travelled to the future. But now consider T's frame of reference. He sees O whiz past him and concludes that O's clock is running slower than T's. So when T stops, he thinks that his own clock will be ahead of O's. Who is right?