Jokes.

Occasionally, I get a letter from someone who is in 'contact' with extraterrestrials. I am invited to 'ask them anything.' And so over the years I've prepared a little list of questions. The extraterrestrials are very advanced, remember. So I ask things like, 'Please provide a short proof of Fermat's Last Theorem'

- Carl Sagan, Demon-Haunted World: Science as a candle in the dark