Unidentified flying object (commonly abbreviated as UFO or U.F.O.) is the popular term for any aerial phenomenon whose cause cannot be easily or immediately identified. Both military and civilian research show that a significant majority of UFO sightings have been identified after further investigation, either explicitly or indirectly through the presence of clear and simple explanatory factors.
- Some years ago I had a conversation with a layman about flying saucers — because I am scientific I know all about flying saucers! I said "I don't think there are flying saucers'. So my antagonist said, "Is it impossible that there are flying saucers? Can you prove that it's impossible?" "No", I said, "I can't prove it's impossible. It's just very unlikely". At that he said, "You are very unscientific. If you can't prove it impossible then how can you say that it's unlikely?" But that is the way that is scientific. It is scientific only to say what is more likely and what less likely, and not to be proving all the time the possible and impossible. To define what I mean, I might have said to him, "Listen, I mean that from my knowledge of the world that I see around me, I think that it is much more likely that the reports of flying saucers are the results of the known irrational characteristics of terrestrial intelligence than of the unknown rational efforts of extra-terrestrial intelligence." It is just more likely. That is all.
- Richard Feynman in The Character of Physical Law (1964)
- Anyway, I have to argue about flying saucers on the beach with people, you know. And I was interested in this: they keep arguing that it is possible. And that's true. It is possible. They do not appreciate that the problem is not to demonstrate whether it's possible or not but whether it's going on or not.
- Richard Feynman in The Meaning of It All : Thoughts of a Citizen Scientist (1998)