I think that it is IMPOSSIBLE! I think that if somebody in the future would have invented a time machine they would have come back in the past to say that the time machine has been invented...
Wow...now THATS something to think about
My roommate is going to be working on this kind of thing for his final-year project, to get his degree in Mathematical Physics. Apparently warp drive is already theoretically possible...physicists have the equations to prove it LOL...
And the neat thing is YOU don't feel any acceleration...because what's happening is that space-time is moving around you. You're staying stationary, and feel no inertia.
If we can warp space-time, what's to stop us from putting it in reverse?