It's Turtles All The Way Down

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In A Brief History of Time (Bantam Books, 1988), Stephen Hawking tells the story of an elderly woman who confronted Bertrand Russell at the end of a lecture on orbital mechanics, claiming she had a theory superior to his. "We don't live on a ball revolving around the Sun," she said, "we live on a crust of earth on the back of a giant turtle." Wishing to humor the woman Russell asked, "And what does this turtle stand on?" "On the back of a second, still larger turtle," was her confident answer. "But what holds up the second turtle?" he persisted, now in a slightly exasperated tone. "It's no use, young man," the old woman replied, "it's turtles all the way down."