Also, personally I think it is entirely possible that we have been visited by aliens. Why is it so difficult to believe, you think we are the only life in the universe? Of course the idea is mixed up in a whole lot of mythology, it's a magnet for crackpots. But underneath all that, the central position that we may have been visited by aliens and we may have observed them, is not really crazy, when you think about it coolly and logically. I haven't seen any evidence in my life that can convince me either way and I am comfortable with that ambiguity.