Sherlock Holmes and Dr Watson go camping, and pitch their tent under the stars. During the night, Holmes wakes his companion and says: "Watson, look up at the stars, and tell me what you deduce."
Watson says: "I see millions of stars, and even if a few of those have planets, its quite likely there are some planets like Earth, and if there are a few planets like Earth out there, there might also be life."
Holmes replies: "Watson, you idiot. Somebody stole our tent ...
