Time Travel == through wormholes

Worm Holes...

The Wormhole is a type of black hole time machine, based on the theory that hypothetical short cuts across the space time continuum exists which could enable travel back and forward in time. A wormhole can be seen as a black hole in one universe connected to a black hole in another universe, although they appear in the imagination of science fiction writers that in fact. Albert Einstein and Nathan Rosen first realised in 1935 that the theory of general relativity allowed for the "Einstein-Rosen Bridge" (now refured to as wormholes), although initially this bridge was only thought to be possible through space, not time...

Donnie Darko is one of my favourate films about time travel, if you've not seen the film check the website out,
It mentions the philosophy of time travel.