Robert Andrews Millikan
1868-1953
American Physicist
Robert Andrews Millikan, in his famous oildrop experiment of 1910, measured the charge of the electron. In another important experiment, he verified Einstein's equation for the photoelectric effect and determined the exact value of Planck's constant. For these accomplishments, Millikan was awarded the Nobel Prize in physics in 1923. He also provided a role model for the American-born scientist in the early twentieth century, at a time when most of the great physicists were European.
Millikan was born in Morrison, Illinois, on March 22, 1868, the second son of the Reverend Silas Millikan and his wife, Mary Jane. Nothing about his childhood, spent in the rural Midwest, particularly hinted at a future career as an eminent scientist. After graduating from high school, he worked briefly as a court reporter. His involvement in science began after his sophomore year at Oberlin College in Ohio, when his Greek professor recruited him to teach an elementary physics course. Millikan objected that he had no real knowledge of the subject, but the professor countered that it could not be any harder than Greek. He received his Ph.D. from Columbia University in 1895 and was the only physics graduate student at the time.
After a brief stint in Germany studying with Max Planck (1858-1947), Albert Michelson (1852-1931) invited him to join the physics faculty at the University of Chicago. He remained there for 25 years, attaining the status of full professor in 1910. Millikan had little patience with lecturing, believing that students learned more effectively through solving problems and performingexperiments. He attempted to put this philosophy into practice by writing better physics textbooks. It was so important to him that he was checking page proofs on the morning of his wedding to Greta Erwin Blanchard in 1902.
Robert Millikan. (Library of Congress. Reproduced with permission.)Millikan began attempting to measure the charge of the electron by measuring how tiny charged water droplets moved in an electric field. The results suggested that the charge on the water droplets was always a multiple of a single elementary value. However, since water evaporates quickly, he had trouble getting sufficiently reliable data. He solved this problem by using oil instead. Spraying oil droplets into his small experimental chamber, he measured how the charge they carried affected their fall.
In the photoelectric effect, light hitting metal causes electrons to be emitted. Millikan showed that their energy varied with the frequency of the incident light. From this data he was able to obtain an experimental value for Planck's constant of proportionality relating frequency to energy. During World War I Millikan played a role in developing anti-submarine devices as Vice-Chairman of the National Research Council.
In 1921 Millikan became head of the California Institute of Technology (Caltech), where he remained until 1945. He was a skilled administrator as well as an experimentalist and was known for regularly putting in 12-hour workdays. Under his leadership, the school became one of the United State's leading institutions for scientific research. He also served as professor and chairman of the Norman Bridge Laboratory of Physics there.
At Caltech, Millikan's research interests involved the radiation that Victor Hess (1883-1964) had detected impinging upon Earth from outer space. Millikan confirmed their extraterrestrial origin, and coined the term cosmic rays. By comparing their intensity at various latitudes on Earth, and at different altitudes, he gathered data that helped in the understanding of Earth's magnetic field and the way in which it deflects the incoming radiation.
Millikan was a prolific author. In addition to publishing more than a half-dozen physics textbooks, he wrote and lectured on the reconciliation of science and religion and the proper relationship of science and society. His autobiography was published in 1950. He was active in the larger scientific community, serving as president of the American Physical Society, Vice-President of the American Association for the Advancement of Science, and member of the Committee on Intellectual Cooperation of the League of Nations. He also enjoyed playing golf and tennis. Millikan died on December 19, 1953, in San Marino, California.
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