For time travel to be possible I think the only way it could happen is not by going into our own pasts, but by going to a parallel universe that is at a different stage of our history. Basically by there being infinate numbers of parallel universes, each representing a different nanosecond or something of our past, present and future. Therefore travelling through time would in reality be travelling between universes rather like how it is in the His Dark Materials trilogy, with the knife, only with each universe being the same world at a different time instead of a different universe altogether.
I am convinced that time travel in the true meaning of the word is impossible, partly due to the fact that time isn't actually a medium, and also down to the fact that if someone were to travel back in time the future of the time he arrived at would be altered considerably and irreversably.
I have far too much thinking time.

As for UFO's, I saw one once over London. I watched it as it got higher and higher intill it eventually went too high to see. It was round, and gold and went straight up in a tumbling motion. If it wasn't for the fact that it didn't actually move laterally (as a result of the wind) I would have thought it a balloon. But then, we'll never know.
