Born Mar. 22, 1868, in Morrison, 111.; died Dec. 19, 1953, in San Marino, Calif. American physicist.

Millikan graduated from Oberlin College in Ohio in 1891 and received his doctorate from Columbia University in 1895. In 1895–96 he worked at the Universities of Berlin and Gottingen; in 1896 he began working at the University of Chicago. During World War I (1914–18) he was vice-chairman of the National Research Council and developed meteorological instruments and devices for detecting submarines. From 1921 to 1945 he was the director of the Norman Bridge Laboratory at the California Institute of Technology. He made a precise measurement of the charge on an electron using a method that he had developed. He experimentally verified Einstein’s equation for the photoelectric effect and was the first directly to determine the numerical value of Planck’s constant (1912–15). He developed the method of atomic spectroscopy in the far ultraviolet region. He studied cosmic rays by means of an ionization chamber. He received the Nobel Prize in 1923.