i firmly believe the day science figures out teleportation, we'll also have time travel.
back on-topic, what Pete said about the intensity of time travel in the Terminator universe sounds really good, as does the circumstances surrounding the initial attempt on Sarah Conner's life. the humans had won, and this was Skynet's last act of defiance. and that is why it seems that T1 is block universe (time is a loop) and the sequels are all... not block universe (the times, they are a-changin').
i've been thinking about time travel for a while now, sparked by the odd juxtaposition of The 4400 and the Ancient Astronaut theory in a conversation i had with someone i work with. and that made me think about the mutability of time and events, and what was said about a historian watching someone making a decision and coming to give them information that would change it.
it would be fucking spectacular if this was happening all the time, like some agency decided on a Timeline Prime that should not be deviated from and seeds agent through the continuum to make sure the right decisions get made. how hellish would that job be? like the Doctor, finding out Pompeii was all him. and what would the messengers be taken as? in olden times, angels, obviously. HAH.