A professor has just finished lecturing at some august university about the origin and structure of the universe, and an old woman in tennis shoes walks up to the lectern. "Excuse me, sir but you've got it all wrong," she says. "The truth is that the universe is sitting on the back of a huge turtle."
The professor decides to humor her "Oh really?" he asks. "Well, tell me, what is the turtle standing on?"
The lady has a ready reply: "Oh, it's standing on another turtle."
The professor asks, "And what is that turtle standing on?"
Without hesitation, she says, "Another turtle."
The professor still game, repeats his question.
A look of impatience comes across the woman's face.
She holds up her hand, stopping him in mid-sentence.
"Save your breath, sonny," she says. "It's turtles all the way down."