I always thought Michael Crichton brought up an interesting method in Timeline (decent book, god awful movie). The quantum hole theory of the multiverse is an interesting one that hasn't been refuted, nor has the idea of the infinitely repeating universe. There is just so much we don't know in this realm that it's wondrous. If the universe is tied up in higher spatial dimensions and and space-time is a manifestation of the very fabric of space then I have seen some very intriguing physicists theorize that "time travel" in so much as travelers could harness these wormholes Hawking speaks of to travel between these different universes and if we could locate correctly then we could end up in a universe of any form we like, at any point in time.
I also think that the argument of the past paradox is one the universe may not allow. The idea that we can't know if there has been past manipulation because we have no way of knowing what the original timeline would have been, so as they say, absence of evidence is not evidence of absence. Certainly there is little evidence to conclusively support any method, but I have read too many instances of scientists saying things are impossible when they are achieved only a hundred years later to write-off these ideas!
I also think that the argument of the past paradox is one the universe may not allow. The idea that we can't know if there has been past manipulation because we have no way of knowing what the original timeline would have been, so as they say, absence of evidence is not evidence of absence. Certainly there is little evidence to conclusively support any method, but I have read too many instances of scientists saying things are impossible when they are achieved only a hundred years later to write-off these ideas!
My religion is the understanding of my world. My god is the energy that underlies it all. My worship is my constant endeavor to unravel the mysteries of my religion. 
