actually, technically time travel is possible. a russian space ship was orbiting earth at a pretty high speed for like a couple months, and they recorded the time on earth, and the time on the space shuttle and the shuttle was like 1/10th of a second behind, so time slowed down for him and he is 1/10th of a second younger. its not much at all but its still pretty cool, i watched a show on tv about it, and actually every time you run, or walk or whatever, you could be slowing time down in an unmeasurable amount. though they said they didnt know if there is a specific speed you need to excede for it to actually slow time down.
and they said that if you were going the speed of light time would just stop, and you would probably have to excede the speed of light to go back in time.