Willard Frank Libby was an American chemist whose technique of carbon-14 (or radiocarbon) dating provided an extremely valuable tool for archaeologists, anthropologists, and earth scientists. For this development, he was honored with the Nobel Prize in Chemistry in 1960. Libby was born in Grand Valley, Colorado, on December 17, 1908, to Ora Edward Libby and his wife Eva May. He attended grammar and high schools near Sebastopol, California, between 1913 and 1926, moving to the University of California, Berkeley, in 1927. He received his B.S. in 1931 and his Ph.D. in 1933. After receiving his Ph.D., Libby spent the 1930s building sensitive Geiger counters to measure weak natural and artificial radioactivity. He worked for 2 years as the personal research assistant to G. N. Lewis on the Berkeley campus. In 1939, he became an instructor in the College of Chemistry at Berkeley, and he later became an assistant professor. In 1941, Libby was awarded a Guggenheim fellowship, for which he spent most of that year at Princeton University. With the start of U.S. involvement in World War II, he moved to New York and joined Columbia University’s Division of War Research to work on the Manhattan Project with Harold Urey (Nobel Prize in Chemistry, 1934) alongside Glenn Seaborg (Nobel Prize in Chemistry, 1951). Libby was responsible for the gaseous diffusion separation and enrichment of uranium-235, which was used in the atomic bomb that was dropped on Hiroshima, Japan. Most separation was accomplished by gaseous diffusion of uranium hexafluoride (UF6), but other techniques were employed as well. The bulk of this separation work was done at Oak Ridge, Tennessee. Libby also showed that tritium is a product of cosmic radiation. In 1945, he became a professor at the University of Chicago in the Department of Chemistry and Institute for Nuclear Studies (now the Enrico Fermi Institute for Nuclear Studies). It was during this chapter in his life that he earned the international renown for which he is regarded today.
Libby had available to him two invaluable facts when he conceived of the carbon-14 dating method. First, he was intimately familiar with the 1932 discovery of the neutron by Sir James Chadwick (Nobel Prize in Physics, 1935), who was involved in the Manhattan Project. Second, he was familiar with the work of Martin Kamen and Samuel Ruben, who in 1940 used the cyclotron of E. O. Lawrence (Nobel Prize in Physics, 1939) at Berkeley to bombard graphite and discover radioactive carbon-14 (an isotope of carbon) and found that it had a half-life of approximately 5,700 years. In addition, other researchers during the 1940s had found that some of the nitrogen in the atmosphere was turned into carbon-14 when hit with cosmic rays. In 1947, Libby, who was then at the Institute for Nuclear Studies, figured that a plant would absorb some of this trace carbon-14 while it absorbed ordinary carbon dioxide in photosynthesis. Once the plant died, it could no longer absorb carbon, and the carbon-14 it contained would decay with a known half-life without being replaced. Therefore, if the concentration of carbon-14 with respect to the stable carbon-12 left in the remains of the plant could be calculated, the amount of time that had passed since the plant had died could be determined because the unstable radioactive carbon-14 isotope decays at a measurable rate on the death of an organism. With postdoctorate James Arnold, graduate student Ernie Anderson, and a $5,000 grant, Libby led a team that developed carbon-14 dating using a highly sensitive Geiger counter, a logical development from his 1930s research. He tested his process on objects of known age, such as timbers from Egyptian tombs. The tests proved to be reliable, and it was assumed that this technique was accurate for organic objects that were tens of thousands of years old. For his work on carbon-14 dating, Libby received the Nobel Prize in Chemistry in 1960, joining fellow Alpha Chi Sigma fraternity members Seaborg and Linus Pauling (Nobel Prize in Chemistry, 1954). In 1954, while at Chicago, Libby became the first chemist ever appointed to the Atomic Energy Commission. In that capacity, he headed President Eisenhower’s international “Atoms for Peace” project and studied the effects of radioactive fallout. In 1959, he became a professor of chemistry at the University of California, Berkeley, a position he held until his retirement in 1976. He taught honors freshman chemistry from 1959 to 1963 (it was a university tradition that senior faculty teach this class). He was also director of the University of California statewide Institute of Geophysics and Planetary Physics (IGPP), which was an exciting post during the time of lunar landings. He served in that capacity until his death. He also started the first environmental engineering program at the University of California, Los Angeles, in 1972. Throughout his long career, Libby wrote many articles and books, including Radiocarbon Dating (1955), which went through several editions. He was the recipient of several other awards, including the 1959 Albert Einstein award. Even brilliant men such as Libby could sometimes get things wrong. For example, Libby once suggested that the Tunguska event might have resulted from a small piece of antimatter from space. The actual cause is now thought to have been a comet. He died in 1980 in Los Angeles.
References:
- Arnold, J. R., & Libby, W. F. (1951). Radiocarbon dates. Science, 113, 111-120.
- Libby, W. F. (1946). Atmos 3He and radiocarbon from cosmic radiation. Physical Review, 69, 671-672.
- Libby, W. F. (1951). Radiocarbon dates (part 2). Science, 114, 291-296.
- Libby, W. F. (1955). Radiocarbon dating. Chicago: University of Chicago Press.
- Libby, W. F. (1972). Radiocarbon dating, memories, and hopes. In Proceedings of the 8th International Conference on Radiocarbon Dating (pp. 27-43). Wellington: Royal Society of New Zealand.
- Libby, W. F., Anderson, E. C., & Arnold, J. R. (1949). Age determination by radiocarbon content: World-wide assay of natural radiocarbon. Science, 109, 227-228.
