Time Travel

[Kartoffelsalat]

I didn't read every post here, so if somebody already said any of this, well... never mind.

I read that a time machine would not actually travel across time but would instead warp the space-time continuum. It could only start warping time as soon as it was invented. So you could only travel back in time to the instant your time machine was complete. You couldn't kill your grandparents if you invented the machine, but you could do it (I suppose) if you used somebody else's who invented it before you were born.

Also, I read somwhere that it has been proven (I have no idea how) that one could build such a machine. The guy who proved this came up with a parts list, which included an infinitely long spinning cylinder. Nobody that I know of has found one of these yet, but if you've got one laying around, go ahead and post and let me know.