Portions of this entry contributed by Michel Barran

American physical chemist, geophysicist and cosmochemist who was a student at the University of Montana (1914-1917), then at University of California at Berkeley (where he received his Ph.D. in physical chemistry 1923) and Copenhagen from 1923-1924, where he studied atomic physics with Niels Bohr. He begin his teaching career at Johns Hopkins University as an instructor in the chemistry department (1924-1929), and became a pioneer in the application of quantum mechanics to chemistry. In 1929, he moved to Colombia University and was appointed associate professor (1929-1934), then full professor (1934-1945). From 1933 to 1940, he was editor of the Journal of Chemical Physics. In 1931, with F. Brickwedde and G. Murphy, Urey evaporated four liters of hydrogen down to one millimeter and then measured the spectrum of the remainder. The result was a set of lines displaced slightly from the hydrogen lines, amounting to the discovery of deuterium, or heavy hydrogen, for which Urey was awarded in 1934 Nobel Prize in chemistry and had a significant influence on chemistry, physics and medicine. During the 1930s, Urey's group separated isotopes of oxygen, carbon, nitrogen and sulphur, and worked on medical and biological applications of isotopes.

During World War II, in spite of his profound pacifism, he directed isotope separation studies of the Manhattan Project. After the war, he became a professor at the Institute for Nuclear Studies, University of Chicago (1945-1958) at the same time as Fermi. He was subsequently a professor-at-large at the University of California, San Diego (1958-1972). Urey was also an advocate of nuclear arms control, working actively with other scientists to promote global cooperation and to prevent nuclear proliferation and conflict.

In his postwar career, Urey turned almost fully to geochemistry and cosmochemistry. His work with the heavy isotope oxygen-18 led him to devise methods for estimating the temperature of the ocean during times as far back as 180 million years ago. This led him into the study of the relative abundance of the elements on Earth and the development of a theory of the origin of the elements and of their abundances in the Sun and other stars. He also investigated properties of the Earth's early atmosphere. In this context, he studied the composition of meteorites. His interests in biology, elemental abundances, and the origin of the solar system led him to propose his student Stanley Miller to perform the so-called "Miller-Urey's Electric Discharge Experiment" and to take seriously the experimental results (1953).

After 1958, Urey became a scientific counselor and adviser to the space program, campaigning and arguing for the most economical and scientifically sound method of conducting space research. Several hundred papers by Urey are listed in Poggendorff volumes VI and VIIb.

Miller