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Libby, Willard Frank


(b. Grand Valley, Colorado, 17 December 1908; d. Los Angeles, California, 8 September 1980),

chemistry, nuclear science, radiochemistry, radiochemical dating, paleoarchaeology, paleoanthropology.

Libby is best known as the developer of the radiocarbon dating technique for determining the age of artifacts based on the radioactive isotope carbon-14 (ordinary carbon is primarily carbon-12), for which he was awarded the Nobel Prize in Chemistry in 1960. He also developed a radioactive dating technique for substances using tritium (hydrogen-3). He served as Atomic Energy commissioner and advocated the use of fallout shelters and other measures to counter the perceived nuclear threat from the Soviet Union. His political stance as a “cold warrior” was controversial.

Early Life and Education . Libby was the son of a farmer, Ora Edward Libby, and his wife, Eva May Libby (née Rivers). In 1913 the family, including Willard and his two brothers and two sisters, moved to an apple ranch north of San Francisco. A tall youth who would eventually grow to six feet, three inches, Willard developed his legendary strength by working on the farm. He attended elementary and high school in Sebastopol, California. In high school he played tackle and was called Wild Bill, a nickname that followed him all his life.

In 1926 Libby graduated from high school, and the following year he entered the University of California at Berkeley. (While there he earned money by building apple boxes, which sometimes brought in as much as one hundred dollars per week.) Libby was interested in English history and literature, but he decided on a more practical career and enrolled as a mining engineer at Berkeley. Because his boardinghouse roommates were chemistry graduate students, he became interested in chemistry in his junior year and enrolled in chemistry, physics, and mathematics courses. After receiving his BS degree in 1931, he continued his university work at Berkeley, studying under physical chemists Gilbert Newton Lewis, dean and chairman of the College of Chemistry, and Wendell M. Latimer.

As a graduate student, Libby built his first Geiger-Müller tube and improved it to detect minute amounts of radioactivity, including elements not theretofore believed to be radioactive, such as the lanthanide element, samarium. Throughout his life he constructed Geiger counters, which he claimed to be more sensitive than those available commercially.

Academic Positions . In 1933 Libby received his PhD degree and joined the Berkeley faculty, becoming first an instructor (1933–1938), then an assistant professor (1938–1945), and subsequently in 1945, an associate professor. In October 1945 he moved to Chicago. On 9 August 1940 he married Leonor Lucinda Hickey. Their twin daughters, Janet Eva and Susan Charlotte, were born in 1945. On 8 December 1941, the day after the Japanese attacked Pearl Harbor, Libby’s sabbatical Guggenheim Fellowship at Princeton University was interrupted, and in 1942 he joined the Metallurgical Laboratory at the University of Chicago to work on the top secret Manhattan Project to develop a nuclear bomb, remaining there until 1945. Simultaneously, he also worked under Harold C. Urey, the 1934 Nobel chemistry laureate, at Columbia University to develop methods for separating uranium isotopes by gaseous diffusion for production of the bomb. This led to Libby’s interest in nuclear science. In 1946 he showed that cosmic radiation in the upper atmosphere produces traces of tritium, the heaviest isotope of hydrogen (hydrogen-3), which can be used as a tracer for atmospheric water. By measuring tritium concentrations, he developed a method for dating well water and wine as well as for measuring circulation patterns of water and the mixing of ocean waters.

In October 1945 Libby became professor of chemistry in the Department of Chemistry and the Institute for Nuclear Studies (now the Enrico Fermi Institute for Nuclear Studies) at the University of Chicago (1945– 1959). At age thirty-six he became the youngest full professor at Chicago, where he carried out the work resulting in his winning the 1960 Nobel Prize in Chemistry “for his method to use carbon-14 for age determination in archaeology, geology, geophysics, and other branches of science.”

Atomic Energy Commission . On 1 October 1954 Libby was appointed to the U.S. Atomic Energy Commission (AEC). He continued to mentor graduate students at Chicago but reduced his research activities and concentrated on his AEC duties. Because he was already a member of the AEC General Advisory Committee, which developed the commission’s policy, he was familiar with its modus operandi.

Libby soon became deeply involved in the problem of nuclear fallout. In 1953, on the recommendation of the Rand Corporation of Santa Monica, California, he established and directed Project Sunshine to study the worldwide effect of nuclear weapons. He was the first person to measure nuclear fallout in dust, soil, rain, human bone, and other sources, and he wrote articles and testified before the U.S. Congress on this problem. He stated that all human beings are exposed to some fallout of natural radiation from sources such as drinking water and claimed that the combination of the body’s natural radioactivity, cosmic radiation, and natural radiation of the earth’s surface was more hazardous than the fallout resulting from nuclear testing. Along with most scientists at the time, he believed that the effect of nuclear fallout on human genetics was minimal. It later became known that testing of nuclear weapons resulted in a large global increase in the carbon-14 levels in the atmosphere, which decreased exponentially after the cessation of atmospheric testing in 1963.

As a result of his post on the AEC, Libby became a well-known and controversial figure, and his portrait appeared on the cover of the 15 August 1955 issue of Time magazine. Many scientists considered him to be a mere “yes man” for the Eisenhower administration. Libby, however, defended his position and responded to what he considered misguided thinking. For example, he wrote to Albert Schweitzer, who had stated that future generations would probably suffer from fallout, that Schweitzer was unaware of the most recent data and that continued nuclear testing was needed for the defense of the United States and the survival of the free world. On 30 June 1959 he resigned from the AEC to resume scientific research but continued to assert the need for nuclear testing. He suggested that industries use isotopes in factories and farms. He was a member of the international Atoms for Peace project, which supported nuclear energy for nonmilitary purposes. Libby thought that more scientists should assume positions of political power rather than serve as mere advisors, and he was pleased when 1951 Nobel chemistry laureate Glenn T. Seaborg was appointed chairman of the AEC in 1961.

Libby resigned from the AEC largely because his wife wanted to return to California, and in 1959 he became professor of chemistry at the University of California at Los Angeles (UCLA), a position that he retained until his death. Ideologically committed to the Cold War, he joined nuclear physicist Edward Teller in opposing two-time Nobel laureate Linus Pauling’s petition that nuclear testing be banned.

To prove that nuclear war was survivable Libby built a fallout shelter at his new home, using sandbags and railroad ties. He assumed that a shelter would provide safety in case of a nuclear attack. In a series of articles for the Associated Press News Service, he argued that every home should have a shelter. After a fire burned Libby’s shelter, nuclear physicist and nuclear testing critic Leo Szilard joked, “This proves not only that there is a God but that he has a sense of humor” (Seymour and Fisher, 1988,

p. 288).

Nobel Prize . On 10 December 1960, Libby received the Nobel Prize in Chemistry “for his method to use carbon-14 for age determination in archaeology, geology, geophysics, and other branches of science.” According to Professor Arne Westgren, chairman of the Nobel Committee for Chemistry of the Royal Swedish Academy of Sciences,

The idea you had 13 years ago of trying to determine the age of biological materials by measuring their C-14 activity was a brilliant impulse. Thanks to your great experimental skill, acquired during many years devoted to the study of weakly radioactive substances, you have succeeded in developing a method that is indispensible [sic] for research work in many fields and in many institutes throughout the world. Archaeologists, geologists, geophysicists, and other scientists are greatly indebted to you for the valuable support you have given them in their work. (Westgren, 1964, p. 592)

Carbon-14 . Libby’s radiocarbon dating method is based on carbon-14, the radioisotope discovered by Martin D. Kamen and Samuel Ruben. In 1936 Kamen was working at the Radiation Laboratory of future Nobel physics laureate Ernest O. Lawrence as one of the chemists working among a larger number of physicists. (The Ernest Orlando Lawrence Berkeley National Laboratory [LBNL], formerly the Berkeley Radiation Laboratory and usually shortened to Berkeley Lab or LBL, is a U.S. Department of Energy [DOE] national laboratory conducting unclassified scientific research. Managed and operated by the University of California, the Berkeley Lab holds the distinction of being the oldest of the U.S. Department of Energy’s National Laboratories. The word Radiation was removed from the title because of the public’s fear of radiation.) Kamen performed numerous photosynthetic studies with Ruben, using the short-lived carbon-11, with a half-life of only twenty-one minutes.

Because very few persons could then run a mass spectrometer, which was much more difficult to use than a Geiger counter, Lawrence campaigned to find a long-lived radioisotope of carbon. In the fall of 1939 he assigned Kamen and Ruben the task of finding carbon-14 or any long-lived activity in that part of the periodic table. Harold C. Urey, the 1934 Nobel chemistry laureate, and his group at Columbia University were competing with Lawrence’s group in a race to use isotopes as biological tracers.

To help Kamen and Ruben, Lawrence offered both his 37-inch and 60-inch cyclotrons; all the time that they needed; and help from Emilio Segrè, Glenn T. Seaborg, and anyone else at the Radiation Laboratory. In September 1939 Kamen planned a detailed program dealing with every conceivable method for preparing long-lived isotopes of carbon, nitrogen, and oxygen. He was especially interested in reactions that would produce isotopes chemically separable from the target material bombarded in the cyclotron, such as carbon-14 from nitrogen-14 in ammonium nitrate—to prevent dilution of the radioactive isotope by its stable isotope.

During January 1940 Kamen began continuously exposing a graphite probe target to collect stray deuterons in the internal beam of the 37-inch cyclotron as the most likely nuclear reaction to yield carbon-14:

By 27 February 1940 Kamen and Ruben had removed the last uncertainty—that the activity of the sample might have resulted from the long-lived sulfur-35 produced by the reaction of deuterons on the sulfur as a possible contaminant of the graphite target. They estimated the half-life of carbon-14 as at least one thousand years and wrote a preliminary account for publication as a short letter, “Radioactive Carbon of Long Half-Life” (1940). Because of Ruben’s concern with departmental politics and with obtaining tenure, Kamen allowed him to list his name first on the letter, and thus Kamen’s contribution to one of the major discoveries in nuclear science was slighted.

Although this discovery was certainly of Nobel caliber, Ruben’s death in 1943 from an accident involving phosgene precluded a joint award to him and Kamen, because Nobel Prizes are not awarded posthumously. In 1960 neither Westgren’s presentation speech nor Libby’s acceptance lecture for his Nobel Prize mentioned Kamen and Ruben’s work—a gross miscarriage of justice in the opinion of some.

Radiocarbon Dating . Libby claimed that he first thought that the “notion of radiocarbon dating” was “beyond reasonable credence,” and at the start he decided that he should pursue the project in secret. His second wife, Leona Marshall Libby, noted that he “did not tell anyone of his final goal of proving [that] radiocarbon dating would be able to reveal the history of civilization because he felt that if he talked about such a crazy idea he would be labeled a crackpot and would not be able to get money to fund his research nor [sic] students to help him” (Taylor, 2000–2001, p. 38). When asked what the most difficult and critical part of the work was, Libby stated: “Being smart enough to keep it secret until it was in hand.… I don’t care who you are. You couldn’t get anyone to support it. It’s obviously too crazy” (Taylor, 2000–2001, p.38). Apparently, at first Urey was the only one who knew the goal of the work.

In 1939 cosmic-ray physicist Serge Alexander Korff, whom Libby acknowledged in his Nobel lecture, discovered that cosmic rays create showers of neutrons when they strike atoms in the atmosphere. Because nitrogen, which constitutes about 78 percent of the atmosphere, easily absorbs neutrons and then decays into the radioactive isotope carbon-14,

Libby believed that traces of carbon-14 should always occur in atmospheric carbon dioxide (CO2) and that because carbon dioxide is continuously being incorporated into plant tissues during photosynthesis, plants should also contain traces of carbon-14. Because animal life depends on plant life, animals should also contain traces of carbon-14. After an organism died, no additional carbon-14 would be incorporated into its tissues, and that which was already present would begin to decay at a constant rate. Kamen had found its half-life to be 5,730 years—a short time compared to the age of Earth but long enough for an equilibrium to be established between the production and decay of carbon-14. According to West-gren, “it should be possible, by measuring the remaining activity, to determine the time elapsed since death, if this occurred during the period between approximately 500 and 30,000 years ago” (Westgren, 1964, p. 590).

Libby collaborated with Aristide von Grosse of Temple University, who was then working at the Houdry Process Corporation and who had constructed there an apparatus that could concentrate the heavier isotopes of carbon, with Libby’s first graduate student at Chicago, Ernest C. Anderson, and with postdoctoral fellow James R. Arnold in successfully separating radiocarbon in nature—in methane (CH4) produced by the decomposition of organic matter. Because a diffusion column such as von Grosse’s was expensive to operate, Libby and Anderson used an inexpensive Geiger counter to construct a device that was very sensitive to the radiation of a given sample. They were able to eliminate 99 percent of the background radiation occurring naturally in the environment with 8-inch-thick iron walls to shield the counter and to use a chemical process to burn the sample into pure lampblack (an electrical conductor), which they then placed on the inner walls of a Geiger counter’s sensing tube.

To check the accuracy of his radiocarbon dating technique, Libby applied it to samples of redwood and fir trees whose exact ages had been determined by counting the annual rings and to historical artifacts whose ages were known, such as a piece of timber from Twelfth Dynasty Egyptian pharaoh Sesostris III’s funerary boat. (It was actually 3,750 years old and was estimated by Libby’s method to be 3,261 years old.) In his University of Chicago doctoral dissertation, Anderson established the fact that there was little variation with latitude by determining the radioactivity of animal and plant material obtained worldwide from the North Pole to the South Pole. By 1947 Libby had perfected his radiocarbon dating technique.

Among the archaeological objects that Libby accurately dated were prehistoric sloth dung from Chile, linen

wrappings from the Dead Sea Scrolls, bread from a house in Pompeii buried by volcanic ashes in the eruption of Vesuvius in 79 CE, charcoal from a campsite at Stonehenge, and corncobs from a cave in New Mexico. By using wood samples from forests once buried by glaciers, he showed that the last Ice Age in North America ended from ten thousand to eleven thousand years ago, not the twenty-five thousand years previously estimated by geologists. By dating human-made artifacts from North America and Europe, such as a primitive sandal from Oregon and charcoal specimens from various campsites, he repudiated the idea of an Old World and a New World and showed that the oldest dated human settlements around the world began at about the same era. Radiochemical dating was rapidly recognized as a basic technique for determining dates within the last seventy thousand years. Perhaps its most publicized use has been in dating the shroud of Turin.

Radiocarbon dating has been applied to a broad variety of problems. For example, because the generation of cells in the human body has been difficult to study, understanding of cell turnover has been limited. On 15 July 2005 Swedish researchers demonstrated that the level of carbon-14 in genomic DNA closely parallels its levels in the atmosphere and can be used to determine the time point when the DNA was synthesized and cells were born. They used Libby’s technique to establish the age of cells in the cortex of the adult human brain and showed that while non-neuronal cells are exchanged, occipital neurons are as old as the individual. This supports the view that postnatal neurogenesis does not occur in this region. Retrospective birth dating has become a generally applicable strategy that can be used to measure cell turnover in humans under physiological and pathological conditions.

Libby concluded his Nobel lecture with this description of his radiocarbon dating technique:

In general, the samples may have to be inspected with some care under a relatively high-powered glass and then treated with properly chosen chemicals. But all of these things can be done and with techniques that are no more difficult than those used by the average hospital technician, and a sample can be obtained which should give authentic radiocarbon dates. The dating technique is one which requires care, but which can be carried out by adequately trained personnel who are sufficiently serious-minded about it. It is something like the discipline of surgery—cleanliness, care, seriousness, and practice. With these things it is possible to obtain radiocarbon dates which are consistent and which may indeed help roll back the pages of history and reveal to mankind something more about his ancestors, and in this way perhaps about his future. (Libby, 1964, p. 610)

In his presentation speech, Westgren said that Libby’s method “is so simple—which is probably not always the case with chemical research distinguished with the Nobel Prize—that everyone should be able to understand the conditions and principles for its execution” (Westgren, 1964, p. 589). A scientist who had nominated Libby for the prize characterized his work as follows: “Seldom has a single discovery in chemistry had such an impact on the thinking in so many fields of human endeavour. Seldom has a single discovery generated such wide public interest” (Westgren, 1964, pp. 591–592).

Honors and Professional Activities . In addition to the Nobel Prize, Libby received a number of other awards. They included the Research Corporation Award for the radiocarbon dating technique (1951), Columbia University’s Chandler Medal for outstanding achievement in the field of chemistry (1954), the American Chemical Society Maryland Section’s Remsen Memorial Lecture Award (1955), City College of New York’s Bicentennial Lecture Award (1956), the American Chemical Society’s Glenn T. Seaborg Award for Nuclear Chemistry (1956), the Franklin Institute’s Elliott Cresson Medal (1957), the American Chemical Society Chicago Section’s Willard Gibbs Medal (1958), Dickinson College’s Priestley Award (1959), the Albert Einstein Society’s Albert Einstein Medal (1959), the Geological Society of America’s Day Medal (1961), the California Alumnus of the Year Award (1963), and the American Institute of Chemists’ Gold Medal (1970).

Libby received honorary degrees from Wesleyan University (1955), Syracuse University (1957), the University of Dublin’s Trinity College (1957), Carnegie Institute of Technology (1959), Georgetown University (1962), Manhattan College (1963), University of Newcastle-upon-Tyne (1965), Gustavus Adolphus College (1970), the University of South Florida (1975), and the University of Colorado (1977). He was a scientific and technology consultant for industrial firms, the U.S. Department of Defense, scientific organizations, and universities. The author of numerous articles and several books, he belonged to the editorial boards of several scientific journals and magazines and was a member of numerous learned societies in the United States and abroad.

Last Days . In 1962 Libby became director of the Institute of Geophysics and Planetary Physics at UCLA, a post that he retained for the rest of his life. He considered the new scientific frontier to be outer space and argued that the United States should support a large space exploration program to prevent the Soviet Union from controlling outer space, an outcome which, he believed, would mean domination of the world by the USSR.

In 1966 Libby and his wife Leonor divorced, and in December 1966 he married physicist Leona Marshall (née Woods), a professor of environmental engineering at UCLA and a staff member of the Rand Corporation. Libby retired in 1976 and died at age seventy-one from the complications of pneumonia. He was cremated.


The Willard F. Libby Papers, c. 1954–1976, collection number 1276, comprising 278 boxes (139 linear ft.), four cartons (four linear ft.), and nine oversize boxes, are preserved at the University of California, Los Angeles Library, Department of Special Collections, Los Angeles, CA 90095-1575. They consist of correspondence, notebooks, research materials, publications, lectures, and memorabilia related to Libby’s career as a chemist, and items related to his involvement in the U.S. Atomic Energy Commission, tritium experiments, radiocarbon dating, the Institute of Geophysics and Planetary Physics, and UCLA. Further information is available from


With Ernest C. Anderson, Sidney Weinhouse, et al. “Radiocarbon from Cosmic Radiation.” Science 105 (1947): 576–577.

With Ernest C. Anderson and James R. Arnold. “Age Determinations by Radiocarbon Content: World-Wide Assay of Natural Radiocarbon.” Science 109 (1949): 227–228.

Sensitive Radiation Detection Techniques for Tritium, Natural Radioactivities, and Gamma Radiation. Dayton, OH: U.S. Air Force, Air Material Command, 1951.

Radiocarbon Dating. 2nd ed. Chicago: University of Chicago Press, 1955.

Technical Report on “Chemical Effects of Radiation.” AFOSR No. TN-60-1269. Washington, DC: U.S. Department of Commerce, Office of Technical Services, 1961.

“Radiocarbon Dating.” In Nobel Lectures Including Presentation Speeches and Laureates’ Biographies: Chemistry 1942–1962. Amsterdam and New York: Elsevier, 1964. Also available from

Marlowe, Greg. Oral History Interview with Willard Frank Libby, April 12 and 16, 1979. OH 290. College Park, MD: Center for History of Physics, American Institute of Physics, 1979.

Collected Papers/Willard F. Libby. Edited by Rainer Berger and Leona Marshall Libby. 7 vols.: Vol. 1, Tritium and radiocarbon; Vol. 2, Radiochemistry, Hot Atoms & Physical Chemistry; Vols. 3–4, Radioactivity and Particle Physics and Radioactive Fallout and Technology; Vol. 5, Solar System Physics and Chemistry; Vol. 6, Papers for the Public; Vol. 7, Talking to People. Santa Monica, CA: Geo Science Analytical, 1981.


Asimov, Isaac. Asimov’s Biographical Encyclopedia of Science and Technology. New rev. ed. Garden City, NY: Doubleday, 1972.

Farber, Eduard. Nobel Prize Winners in Chemistry, 1901–1961. Rev. ed. New York: Abelard-Schuman, 1963.

Kauffman, George B. “Willard Frank Libby (1908–1980).” In The History of Science in the United States: An Encyclopedia, edited by Marc Rothenberg. New York and London: Garland Publishing, 2000.

Millar, David, Ian Millar, John Millar, et al. Chambers Concise Dictionary of Science. Cambridge, U.K.: Cambridge University Press, 1989.

Porter, Roy, ed. The Biographical Dictionary of Scientists. 2nd ed. New York: Oxford University Press, 1994.

Ruben, Samuel, and Michael D. Kamen. “Radioactive Carbon of Long Half-Life.” Physical Review 57 (1940): 549.

Seymour, Raymond B., and Charles H. Fisher. Profiles of Eminent American Chemists. Sydney, Australia: Litarvan Enterprises, 1988.

Taylor, Royal Ervin. “Fifty Years of Radiocarbon Dating.”

American Scientist 88 (2000): 60–67.

———. “Origins of a Nobel Idea: The Conception of Radiocarbon Dating.” Chemical Heritage 18, no. 4 (2000–2001): 8–9, 36–40.

Wasson, Tyler, ed. Nobel Prize Winners. New York: W.H. Wilson, 1987.

Westgren, Arne. “Chemistry 1960.” In Nobel Lectures Including Presentation Speeches and Laureates’ Biographies: Chemistry 1942–1962. Amsterdam and New York: Elsevier, 1964. Also available from

“Willard Frank Libby—Biography.” In Nobel Lectures Including Presentation Speeches and Laureates’ Biographies: Chemistry 1942–1962. Amsterdam and New York: Elsevier, 1964. Also available from

Wollaston, George F. “Willard Libby 1908–1980.” In Nobel Laureates in Chemistry, 1901–1992, edited by Laylin K. James. Washington, DC: American Chemical Society, 1993.

Young, Robyn V., ed. World of Chemistry. Farmington Hills, MI:

Gale Group, 2000.

George B. Kauffman

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Libby, Willard F. (1908-1980)

Libby, Willard F. (1908-1980)

American chemist

Chemist Willard F. Libby developed the radiocarbon dating technique used to determine the age of organic materials. With applications in numerous branches of science, including archaeology, geology , and geophysics, radiocarbon dating has been used to ascertain the ages of both ancient artifacts and geological events, such as the end of the Ice Age. In 1960, Libby received the Nobel Prize for his radiocarbon dating work. During World War II, Libby worked on the Manhattan Project to develop an atomic bomb and was a member of the Atomic Energy Commission for several years in the 1950s. An outspoken scientist during the Cold War between the United States and the former Soviet Union, Libby advocated that every home have a fallout shelter in case of nuclear war. Libby, however, was a strong proponent of the progress of science, which he believed resulted in more benefits than detriments for the human race.

Willard Frank Libby was born to Ora Edward and Eva May Libby on a farm in Grand Valley, Colorado. In 1913, the family, which included Libby and his two brothers and two sisters, moved to an apple ranch north of San Francisco, California, near Sebastopol, where Libby received his grammar school education. A large boy who would eventually grow to be 6 feet 3 inches tall, Libby developed his legendary stamina while working on the farm. He played tackle for his high school football team and was called "Wild Bill," a nickname used by some throughout Libby's life. After graduating from high school in 1926, Libby enrolled at the University of California, Berkeley. He made money for college by building apple boxes, earning one cent for each box and sometimes $100 in a week. "I was the fastest box maker in Sonoma County," he told Theodore Berland, who interviewed Libby for his book The Scientific Life.

Although Libby was interested in English literature and history, he felt obligated to seek a more lucrative career and entered college to become a mining engineer. By his junior year, however, Libby became interested in chemistry , spurred on by the discussions of his boarding house roommates, who were graduate students in chemistry. Libby took on a heavy course load, focusing on mathematics, physics , and chemistry. After receiving his B.S. in chemistry in 1931, he entered graduate school at Berkeley and studied under the American physical chemist Gilbert Newton Lewis and Wendell Latimer, who were pioneering the physical chemistry field.

Libby received his Ph.D. in 1933 and was appointed an instructor in chemistry at Berkeley. After the Japanese bombed Pearl Harbor in 1941, Libby, who was on a year sabbatical as a Guggenheim Fellow at Princeton University, joined a group of scientists in Chicago, Illinois, to work on the Manhattan Project, a government-sponsored effort to develop an atomic bomb. During this time, he worked with American chemist and physicist Harold Urey at Columbia University on gaseous diffusion techniques for the separation of uranium isotopes (isotopes are different forms of the same element having the same atomic number but different atomic weights). After the war, he accepted an appointment as a professor of chemistry at the University of Chicago and began to conduct research at the Institute of Nuclear Studies.

In 1939, scientists at New York University had sent radiation counters attached to balloons into the earth's upper atmosphere and discovered that neutron showers were created by cosmic rays hitting atoms. Further evidence indicated that these neutrons were absorbed by nitrogen, which then decayed into radioactive carbon14. In addition, two of Libby's former students, Samuel Ruben and Martin Kamen, made radioactive carbon14 in the laboratory for the first time. They used a cyclotron (a circular device that accelerates charged particles by means of an alternating electric field in a constant magnetic field ) to bombard normal carbon12 with neutrons, causing it to decay into carbon14.

Intrigued by these discoveries, Libby hypothesized that radioactive carbon14 in the atmosphere was oxidized to carbon dioxide . He further theorized that, since plants absorb carbon dioxide through photosynthesis, all plants should contain minute, measurable amounts of carbon14. Finally, since all living organisms digest plant life (either directly or indirectly), all animals should also contain measurable amounts of carbon14. In effect, all plants, animals, or carbon-containing products of life should be slightly radioactive.

Working with Aristide von Grosse, who had built a complicated device that separated different carbons by weight, and graduate student Ernest C. Anderson, Libby was successful in isolating radiocarbon in nature, specifically in methane produced by the decomposition of organic matter. Working on the assumption that carbon14 was created at a constant rate and remained in a molecule until an organism's death, Libby thought that he should be able to determine how much time had elapsed since the organism's death by measuring the half-life of the remaining radiocarbon isotopes. (Half-life is a measurement of how long it takes a substance to lose half its radioactivity.) In the case of radiocarbon, Libby's former student Kamen had determined that carbon14's half-life was 5,370 years. So, in approximately 5,000 years, half of the radiocarbon is gone; in another 5,000 years, half of the remaining radiocarbon decays, and so on. Using this mathematical calculation, Libby proposed that he could determine the age of organisms that had died as many as 30,000 years ago.

Because a diffusion column such as von Grosse's was extremely expensive to operate, Libby and Anderson decided to use a relatively inexpensive Geiger counter to build a device that was extremely sensitive to the radiation of a chosen sample. First, they eliminated 99% of the background radiation that occurs naturally in the environment with 8-inch-thick (20 cm) iron walls to shield the counter. They then used a unique chemical process to burn the sample they were studying into pure carbon lampblack, which was then placed on the inner walls of a Geiger counter's sensing tube.

Libby first tested his device on tree samples, since their ages could be determined by counting their rings. Next, Libby gathered tree and plant specimens from around the world and discovered no significant differences in normal age-related radiocarbon distribution. When Libby first attempted to date historical artifacts, however, he found his device was several hundred years off. He soon realized that he needed to use at least several ounces of a material for accurate dating. From the Chicago Museum of Natural History, Libby and Anderson obtained a sample of a wooden funerary boat recovered from the tomb of the Egyptian King Sesostris III. The boat's age was 3,750 years; Libby's counter estimated it to be 3,261 years, only a 3.5% difference. Libby spent the next several years refining his technique and testing it on historically significant, and sometimes unusual objects, such as prehistoric sloth dung from Chile, the parchment wrappings of the Dead Sea Scrolls, and charcoal from a campsite fire at Stonehenge, England. Libby saw his new dating technique as a way of combining the physical and historical sciences. For example, using wood samples from forests once buried by glaciers , Libby determined that the Ice Age had ended 10,000 to 11,000 years ago, 15,000 years later than geologists had previously believed. Moving on to man-made artifacts from North America and Europe (such as a primitive sandal from Oregon and charcoal specimens from various campsites), Libby dispelled the notion of an Old and New World, proving that the oldest dated human settlements around the world began in approximately the same era. For many years after Libby's discovery of radiocarbon dating, the journal Science published the results of dating studies by Libby and other scientists from around the world. In 1960, Libby was awarded the Nobel Prize in chemistry for his work in developing radiocarbon dating. In his acceptance speech, as quoted in Nobel Prize Winners, Libby noted that radiocarbon dating "may indeed help roll back the pages of history and reveal to mankind something more about his ancestors, and in this way, perhaps about his future." Further progress in radiocarbon dating techniques extended its range to approximately 70,000 years.

In related work, Libby had shown in 1946 that cosmic rays produced tritium, or hydrogen3, which is also weakly radioactive and has a half-life of 12 years. This radioactive form of hydrogen combines with oxygen to produce radioactive water . As a result, when the United States tested the Castle hydrogen bomb in 1954, Libby used the doubled amount of tritium in the atmosphere to date various sources of water, deduce the water-circulation patterns in the United States, and determine the mixing of oceanic waters. He also used the method to date the ages of wine, since grapes absorb rain water.

In 1954, U.S. President Dwight D. Eisenhower appointed Libby to the Atomic Energy Commission (AEC). Although he continued to teach graduate students at Chicago, Libby drastically reduced his research efforts and plunged vigorously into his new duties. Previously a member of the commission's General Advisory Committee, which developed commission policy, Libby was already acquainted with the inner workings of the commission. He soon found himself embroiled in the nuclear fallout problem. Upon a recommendation by the Rand Corporation in 1953, Libby formed and directed Project Sunshine and became the first person to measure nuclear fallout in everything from dust, soil , and rain to human bone.

As a member of the AEC, Libby testified before the U.S. Congress and wrote articles about nuclear fallout. He noted that all humans are exposed to a certain amount of natural radiation in sources such as drinking water. He went on to point out that the combination of the body's natural radioactivity , cosmic radiation, and the natural radioactivity of the earth's surface was more hazardous than fallout resulting from nuclear testing. Libby assumed, and most scientists of the day concurred, that the effects of nuclear fallout from careful testing on human genetics were minimal.

See also Chemical bonds and physical properties; Chemical elements; Cosmic microwave background radiation; Dating methods; Nuclear winter

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Willard Frank Libby

Willard Frank Libby

The American chemist Willard Frank Libby (1908-1980) pioneered in radiocarbon dating, for which he received the Nobel Prize.

Willard Libby, a farmer's son, was born on December 17, 1908, at Grand Valley, Colorado. After schooling near Sebastopol, California, he entered the University of California at Berkeley, graduating in 1931, earning his doctorate in 1933, and teaching physical chemistry there until World War II.

Libby's most notable achievement, the method of radiocarbon dating, stemmed from the 1939 discovery that cosmic rays at about 10 miles' altitude interacted with air to give a relatively high density of neutrons. This implied rapid formation of radiocarbon by neutron capture by the abundant nitrogen isotope. Radiocarbon has a long halflife (about 5,730 years), decaying into nitrogen. It may be assumed that after many thousands of years its rate of formation equals its rate of disintegration. If it is rapidly oxidized to carbon dioxide and this enters the biosphere, all living things will have the same specific radiocarbon content, that is, the same proportion of this isotope to the others. But at death carbon absorption stops and thereafter the specific radiocarbon content of the organic remains will steadily diminish with time. Accurate measurements should therefore establish the time that has elapsed since death; a new method of geological dating is thus provided.

During the war Libby worked on isotope separation by the gaseous-diffusion method, and his ideas on radiocarbon dating remained embryonic. In 1945 he moved to the Enrico Fermi Institute of Nuclear Studies, Chicago, and began an extensive study of radiocarbon. The halflife was accurately measured on the artificially produced isotope. The natural isotope was discovered by comparing the radioactivity of methane from sewage and petroleum. The former, only recently out of the biosphere, had a measurably higher activity.

These measurements were made on borrowed equipment by an expensive technique known as isotope enrichment, so Libby decided to devise a simpler method using more sensitive apparatus. Unfortunately, more sensitive counters picked up "background" radiation, much of it due to penetrating cosmic rays. Attempts by Libby to shield the apparatus in various ways met with limited success. The problem was solved by surrounding the counting equipment containing the sample with counters which switched off the central counter whenever an interfering particle (muon) arrived. With this refined apparatus Libby, with E.C. Anderson, made radiocarbon dating a practical possibility. For this work Libby received the Nobel Prize for chemistry in 1960. His method has now become an important routine tool in archeology.

From 1954 until 1959 Libby was research associate in the Geophysical Laboratory of the Carnegie Institute and simultaneously served on the U.S. Atomic Energy Commission. In 1959 he was appointed professor of chemistry at the University of California. In addition to his work on radiocarbon he applied similar considerations to tritium; thus he showed that water remains about nine days in the atmosphere between evaporation and precipitation. Libby was long interested in the behavior of "hot atoms," that is, those whose high energies derive from recoil in nuclear transformations, and used isotopes to study exchange reactions, especially in solution.

In 1966, Libby divorced his wife Leonor and later married Leona Woods Marshall, a professor of environmental engineering at UCLA. Libby remained at the University of California as the Director of the Institute of Geophysics until his retirement in 1976. He died in Los Angeles on September 8, 1980, from complications ensuing from a bout with pneumonia.

Further Reading

A sketch of Libby's life is in Eduard Farber, Nobel Prize Winners in Chemistry, 1901-1961 (rev. ed. 1963). A similar sketch can be found in the H.W. Wilson Company's Nobel Prize Winners (1987). For background see Theodore Berland, The Scientific Life (1962), and Lynn and Gray Poole, Men Who Dig Up History (1968). A more recent biographical sketch is included in the H.W. Wilson Company's Nobel Prize Winners (1987). □

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Libby, Willard Frank

Willard Frank Libby, 1908–80, American chemist, b. Grand Valley, Colo., grad. Univ. of California (B.S., 1931; Ph.D., 1933). He taught (1933–45) at the Univ. of California and was a chemist (1941–45) in the war research division at Columbia. From 1945 to 1954 he was with the Univ. of Chicago and was a member of the committee of reviewers for the Atomic Energy Commission (AEC); he was then (1954–59) an AEC commissioner. In 1959 he joined the faculty of the Univ. of California at Los Angeles. Libby was awarded the 1960 Nobel Prize in Chemistry for his development (c.1946) of radioactive carbon-14 dating. He was the recipient of several other prizes, including the 1959 Albert Einstein award. Libby wrote Radiocarbon Dating (1955).

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"Libby, Willard Frank." The Columbia Encyclopedia, 6th ed.. . 27 Apr. 2017 <>.

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Libby, Willard Frank

Libby, Willard Frank (1908–80) Professor of chemistry at the University of California and director of the Institute of Geophysics, Libby developed a method for dating sediments and artefacts using carbon-14. The method is described in his book Radiocarbon Dating, first published in 1952.

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"Libby, Willard Frank." A Dictionary of Earth Sciences. . 27 Apr. 2017 <>.

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Libby, Willard Frank

Libby, Willard Frank (1908–80) US chemist. From 1941 to 1945, he worked on the separation of isotopes for the atomic bomb. In 1960, Libby received the 1960 Nobel Prize in chemistry for his development of carbon dating.

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