There's an RPG called Contiuum about time travel that brings up a lot of good points. One of them is time travel and space travel MUST be the same. One, realtivity shows this so. Two, if reverse time travel were possibile, you'd still need to end up where the Earth was back then. Since everything is moving, it's not in the same space.

I mean, even though I haven't moved from my desk since starting this comment I have in fact moved in space. The me of a minute ago was somewhere different than the me of now.

Weird, huh?