according to the theory of relitivity you could not go BACK in time but, you could theoreticly go foreward. You would need to be traveling close to the speed of light for there to be a major effect (lets say 99.999999999 percent the speed of light) so you go say to pluto and come back. Well because you were travelling near the speed of light it may take you a few minutes. But back on earth it would be years and years (maybes hundreds?) so when you did comeback your body would only have ages a few minutes but everyone else would be long gone.