Caltech 101: Age of the earth and the perils of lead

How old is the earth? No one knew for sure until 1953, when Caltech geochemist Clair Patterson said “4.55 billion years”—something he learned from analyzing the decay rate of lead isotopes in meteorites and in the earth’s oldest rocks. He later studied lead pollution in the oceans and atmosphere; using careful lab and sampling techniques, he proved that environmental lead was increasing, and that modern humans’ bodies contain 1,000 times as much lead as did prehistoric humans’.

Due largely to his research and advocacy, pollution controls were eventually established in the U.S. auto industry, and leaded gasoline and paint were phased out. In recognition of this work, Patterson received the Tyler World Prize for Environmental Achievement in 1995, just months before he died. His determined, often lonely crusade against lead pollution inspired the character Sam Beech in Saul Bellow’s novel The Dean’s December.

Adapted from “Caltech 101,” a series that ran in the Pasadena Star-News. For more tidbits on Caltech’s history, culture, current research, and more, visit http://today.caltech.edu and click on Caltech 101 at the lower right.

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