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 just told 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!"
-- Stephen Hawking, "A Brief History of Time"
