Stephen Hawking in A Brief History of Time: From the Big Bang to Black Holes recounts the following exchange:

A well-known scientist (some say it was Bertrand Russell) once gave a public lecture on astronomy. He described how the earth orbits around the sun and how the sun, in turn, orbits around the center of a vast collection of stars called our galaxy. At the end of the lecture, a little old lady at the back of the room got up and said: “What you have told us is rubbish. The world is really a flat plate supported on the back of a giant tortoise.” The scientist gave a superior smile before replying, “What is the tortoise standing on?” “You’re very clever, young man, very clever,” said the old lady. “But it’s turtles all the way down!”

So, “turtles all the way down” refers to a belief about how the universe is constructed–our world rests on the back of a turtle, which rests on the back of a second turtle, which rests on the back of a third, etc.—and more generally refers to an infinite regression type of situation or problem or argument.

The turtle stacking nexus must be somewhere in Virginia, because so far this summer I’ve had to relocate seven turtles, going the wrong way on busy streets or otherwise getting themselves into trouble.

First, there was this turtle, then that turtle, then the following quick succession of honorable turtles:

Here’s Turtle Three:

turtle3_web.jpg

Turtles Four and Five:

turtle_four_five.jpg

Turtle Six:

turtle_six.jpg

Turtle Seven:

turtle_seven.jpg

So how many turtles support the world on their backs?

Well, at least seven.