Pavlov’s Dog And Schrödinger’s Cat

A man walks into a library and approaches the librarian. He asks, “Excuse me, do you have any books on Pavlov’s dog and Schrödinger’s cat?”

The librarian thinks for a moment and replies, “It rings a bell, but I’m not sure if it’s here or not.”

The man looks at the librarian, puzzled, and asks, “What do you mean?”

The librarian responds, “Well, according to Schrödinger’s theory, the cat could either be alive or dead until we observe it. So, until we check, the book could both be here and not be here at the same time.”

The man, impressed with the librarian’s explanation, says, “Wow, that’s pretty deep. I guess I’ll just have to take a chance and look for it myself.”

As he’s walking away, the librarian yells out to him, “But don’t forget, if you hear a meow, it’s probably not a book!”