Libby Develops Radiocarbon Dating

Willard F. Libby, a physical chemist, is best known for leading a team at the University of Chicago that developed a technology in the late 1940s—radiocarbon dating—that revolutionized how we understand the history of the earth and its living species. It has successfully determined the age of artifacts up to 50,000 years ago.

Libby was the son of a California farmer and attended college and graduate school at the University of California at Berkeley. In the 1930s, he was a chemistry instructor at Berkeley and a researcher with an ambitious group of radiochemists at the university’s Lawrence Radiation Laboratory. “Berkeley was really some place. And the discoveries made during that time are still the main bulwark and substance of chemical nuclear chemistry,” Libby later recalled. “The seminar ran the whole nine years, and we began to be major contributors to the whole field.”

One of the most important outcomes of its research was the discovery of carbon-14 on February 27, 1940, by two chemists, Martin Kamen and Samuel Rubin. They determined that the basic element of carbon had a radioactive isotope, carbon-14, which contained two additional neutrons and could be dated back thousands of years.

Libby left Berkeley for Princeton University in 1941 on a Guggenheim Fellowship, and, when World War II broke out, he went to work at Columbia University, where he participated on the Manhattan Project to develop an atomic weapon.

After the war ended, Libby returned to his research in nuclear chemistry at the department of chemistry and Institute for Nuclear Studies at the University of Chicago. In 1947, picking up where Kamen and Rubin had left off, Libby first proposed the theory of radiocarbon dating, and demonstrated its effectiveness soon afterward.

Libby’s theory was rooted in the principal that all living things are composed of carbon. He determined the date of an artifact by comparing its quantity of carbon 14 with the levels present in the current atmosphere. The amount of carbon 14 deteriorates at a consistent and known rate in an organism once it dies. Libby and his team developed a formula to determine the age of the sample based on the amount of carbon 14 left in the specimen. He tested the radioactive half-lives of numerous historic artifacts, from the bones of ancient people to the wood of a sunken ship. In June 1952, Time Magazine popularized Libby’s discovery, running an article describing how radiocarbon dating was used to measure the age of a charred piece of oak from England’s mysterious Stonehenge monument “at 3,800 years old—give or take about 275 years.”

Libby was awarded the Nobel Prize in Chemistry 1960 "for his method to use carbon-14 for age determination in archaeology, geology, geophysics, and other branches of science."

Further Reading

Willard F. Libby,Oral History (1979)

Willard F. Libby Papers, University of California-Los Angeles

Time Magazine article on Radiocarbon dating