[maxerickson]

We don't have the physics to arbitrarily travel backward through time (high speed wormholes work in theory, as a practical matter we don't have wormholes or a way to maintain relativistic speeds), so it anyway doesn't really make a whole lot of sense to speculate about how what we don't know might work. Say someone invents a new formulation of physics and time travel just trivially falls out of it, with tidy solutions for distance and momentum and everything else.

[dexwiz]

I totally agree. Speculation on time travel is like writing science fiction. Its based on reality, but definitely isn't real today, and probably won't be real tomorrow.

All I'm saying is that time travel likely won't be taking an absolute point in space time (x, y, z, t), and only making a single, discontinuous change to t.