The really cool thing about Time Travel, (well, one of the cool things, I mean - heck it's TIME TRAVEL! lol) is that with the quantum physical theory of the multi-verse, the person who goes back in time and alters history would only technically create a paradox, because they'd alter their past, but it wouldn't literally be their past - as they'd already lived that past. So literally a time traveler could go back and kill their great grandfather, and they would create a reality where they were never born, but they'd still have the reality they were born in as well.
Great show guys. I enjoyed this.
Oh, one more thing: I definitely believe a lot of the UFO Sightings we see at disasters (think: the spheres that covered the Japanese meltdown) may very well be time displaced. Actually, the meltdown is debatable because that radiation that is still being dumped into the ocean may be a global threat on the level to require ET Assistance, so those UFOs that the Japanese showed all over their News at the time may actually be ETs.
Anyway, great show. See ya around the Time/Space Continuum. :)