I don't not believe in time travel because you need two fixed points in space which can transport something safely from one point of time to the other point of time.
When you hop in your delorean and travel back to the past, what is the device that calculates earth's rotation around the sun and it's own rotation? You can't just leave from one point of the earth and expect to land in the exact same point. Furthermore, if you were to travel back in time and “change” history, how would you return to the point you departed from? Changing one thing has far more variations then we can imagine. Last, when you travel tot he past, whats to stop the molecules of not only you but the time machine from disappearing? They haven’t existed so why shouldn’t they now? Remember they were made in the future and not the point of the past to which an individual has returned.
However, if I was given the chance to go back in time and observe history, I'd go and see the rise and fall of the Third Reich.