Clair Patterson

Born on 2 June 1922 in Mitchellville, Iowa, Clair Patterson was a Caltech geochemist who determined the age of Earth and advocated for reducing global lead pollution. After earning his AB from Grinnell College in 1943 and his MA from the University of Iowa in 1944, Patterson joined the Manhattan Project. Working first at the University of Chicago, then at Oak Ridge, Tennessee, he helped develop the high-precision mass spectrometers needed to separate uranium-235 from other isotopes. After the end of World War II, Patterson returned to the University of Chicago, earning his PhD in 1951. The following year, Patterson accepted a research fellowship at Caltech, where he would remain for the rest of his career. He continued his work with mass spectrometry, developing a radiometric dating technique based on the decay rate of uranium isotopes to lead. In 1953 Patterson used the technique to determine the age of Earth, which he found to be 4.5 billion years, much older than previously believed. In 1956 he further refined that age to 4.55 billion years. It was his work with lead that led to his other great achievement. In trying to sterilize his lab against lead contamination, he discovered that lead was everywhere—in the environment and in the food chain—and the levels were significantly higher than in pre-industrial times. He lobbied to remove lead from consumer products such as gasoline and paint, despite fierce opposition from oil companies, government agencies, and even other scientists. His efforts helped influence passage of the Clean Air Act of 1970 and the development of unleaded gas. Among the many awards he received was the 1973 J. Lawrence Smith Medal of the National Academy of Sciences, the 1980 V. M. Goldschmidt Award of the Geochemical Society, and the 1995 Tyler Prize for Environmental Achievement. Patterson died in 1995 at age 73. (Photo credit: Archives, California Institute of Technology)

Date in History: 2 June 1922