I'm not sure where this belongs, but since I have a specific question, I'm putting it here. I saw this article about time travel in my Yahoo news feed. It seems to be an accurate article (except perhaps for the quote below) unlike many of the science articles that I've seen floating around in cyberspace. My one question comes from near the end of the article.
.A couple of other domains offer hope for would-be time travelers. Moving faster than light — the universal reference point — would do the trick
I don't understand how superluminal speed results in moving back in time. As you approach c relative to an outsider, the observer sees your clock slowing down. However, if you were superluminal, then according to the Lorentz transforms, the clock does not run backward but instead time takes on a complex value. I have no idea how to interpret a two dimensional time value except to say that is why superluminal speed impossible.