Is it that ridicolous to believe in UFO's? If you consider how big the universe is, and how many planets there are out there that may well be harbouring life... then if there are many different life forms out there, surely the chances that we are the most developed would be fairly small? We don't know how far technology can go, so who knows, it doesn't seem that unlikely that some alien species may have got its own 'UFO'.

Although, I don't believe in all that for other reasons.