I am reading 1635: The Dreeson Incident. It's an alternative history, part of the 1632 universe created by Eric Flint. I had never learned so much about this period of history until I started reading this series. It's really neat, to me. And I wonder what would life be like now, if I even existed now, if someone went back in time and made massive changes to the world. Besides that we would have been on the moon by 1776, at the latest. And what other eras could someone do affect the future? I think there are times that no matter how advanced the people going back in time were, that they could not change the future much, because of how backwards the time they went was, or that they would all be killed for witches or something.