Two men were sitting in adjacent seats on a plane, when one of the men said, Let's talk. I've heard that flights will go quicker if you strike up a conversation with your fellow passenger.

The other man, who had just opened his book, closed it slowly, and said to the first, What would you like to discuss?
Oh, I don't know, said the first man. How about nuclear power?
OK, said man number 2. That could be an interesting topic. But let me ask you a question first. A horse, a cow, and a deer all eat grass. The same stuff. Yet a deer excretes little pellets, while a cow turns out a big patty, and a horse produces clumps of dried grass. Why do you suppose that is?
Jeez, said the first man. I have no idea.
Well, then, said the second man, How is it that you feel qualified to discuss nuclear power when you don't know shit?