Science: The Philosophers' Stone

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Pressure never bothered Willard Libby.

The University of California was an exciting place in the '30s, with new atomic theory and discoveries tumbling off the line as fast as fruit boxes. After his switch from mining engineering to chemistry, Libby quickly got his B.A., his M.A., his Ph.D., and stayed on as an instructor. But his interest was always research, not teaching. In his laboratory experiments in radioactive chemistry, he became one of the first to realize that atomic techniques had abolished the traditional distinction between chemistry and physics. Because of his daring, energetic research methods, he acquired, and still wears, the sobriquet "Wild Bill."

Clean Shirts. In 1940 Libby married Leonor Hickey, a young teacher of physical education who first heard about Libby from a friend's maid ("He's not terribly exciting," said the maid, "but he always wears clean shirts"), and still regards him as a goodhearted country boy who wears unsophisticated clothes. "He thinks he's a wonderful bridge player," confides Mrs. Libby, "but he's really lousy." Libby got a Guggenheim Fellowship and moved to Princeton, but a few months later the Japanese bombed Pearl Harbor and he offered his services to Nobel Prizewinner Harold Urey. Urey arranged for Libby's transfer to Columbia University, and he plunged into the historic Manhattan (atom bomb) Project, working through the war with great effect on the key problem of separating the isotopes of uranium. Not until news of the Hiroshima bomb came out did Libby mention his work at home. On that day he came home with a tall stack of newspapers and said triumphantly: "This is what I've been doing." Libby did not stay with the atom bomb after the war—not because he was opposed to working on weapons, but because, like many other scientists, he wanted to get back to independent research. He was taken on by the newly formed Institute of Nuclear Studies at the University of Chicago, where he became fascinated by the faint natural radioactivity that pervades the atmosphere. A significant part of this activity comes from carbon 14, an unstable carbon isotope formed when cosmic rays hit nitrogen high in the atmosphere.

It was hard to detect with the instruments that existed then, but Libby charged at the problem with his peculiar combination of creative abandon and meticulous care, and soon plucked a great prize. Since carbon 14 is mixed in the atmosphere, it is taken up by living plants, supplying a small part of the carbon in all living organisms. Its half-life is about 5,000 years, i.e., half its atoms disintegrate in that time. So when a plant or animal dies and ceases to take up fresh carbon 14, the radioactivity of its substance should decline with the passage of time. If the decline can be measured accurately, it will tell the age of the carbon-bearing object, whether it is an Egyptian mummy or an Ice-Age peat bed.

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