to begin with, time travel isnt possible. a fact. there are loads of self contradictions in the concept of time travel itself. even if the human race succeeds in defying the laws of physics then this is the most important time of history of homo sapiens. I hope our future time travelers come back and wake up Bush on his trip to the kindergarten on sep 11. But of course they havent. which means theyr not interested which means they are americans :p there u go
wait a second. time travel (forward & backward) is permitted by physics my friend. Read up!