We all have some idea of what time is--past, present, and future--but there is nothing we can do about it. We live in the present, we remember the past, we have no idea what the future will be. But suppose we could move ourselves to the past or the future--travel in time! Here are stories ranging from time machines to changing history to alternate time-lines to time-traveling ghosts. And we don't even need a Delorean.