HOLLY
COMPTON
At an early point Karl introduced Arthur to the study of X-rays, which was to be the younger brother's main line of work for many years. In 1913 he followed Karl to Princeton, and for his Ph.D. thesis studied the angular distribution of X-rays reflected from crystals. On graduation in 1916 he married a classmate from Wooster College, Betty McCloskey, who became an intelligent and enthusiastic partner in his later activities. Compton was named instructor in physics at the University of Minnesota, one of a number of state-supported schools that were working hard to teach science and to introduce the spirit of pure research. The experiments begun here eventually led Compton to state that magnetization of a material depends not on the orbits of the electrons in it, but on the electron's own elementary characteristics; he was the first to suggest the existence of quantized electron spin.
Meanwhile he found a job in industry. Engineering had always attracted him, and in 1917 he took a well-paid position as research engineer for Westinghouse. In this work (and in later work helping General Electric develop fluorescent lighting) Compton was starting on a path that many American physicists followed. Industrial laboratories were growing even more rapidly than academic ones; before World War I industry employed less than 10 percent of the members of The American Physical Society, and not long after, 25 percent.
In 1919 Compton was awarded one of the first National Research Council fellowships. These gave many American physicists of the 1920's and 1930's a chance to study as they chose, and for Compton this meant X-rays. He took his fellowship to the Cavendish Laboratory in England. But the X-ray apparatus there turned out to be inadequate, so he worked on allied problems with gamma rays. He conclusively verified earlier studies by others that showed puzzling variations of wavelength with scattering angle. Back in the United States as head of the physics department in Washington University, St. Louis, Compton pursued this problem, now working again with X-rays. Since his childhood he had possessed great self-confidence, manual skill, ingenuity and patience. All these combined to help him perfect his apparatus and measure the shift of wavelength with scattering angle that is now known as the Compton effect. Studying this result, he carefully considered and eliminated various attempts at classical explanation. In late 1922 he hit upon the stunningly simple answer, which required special relativity and quantum mechanics, both used in ways that were scarcely understood at the time. When he reported his experimental and theoretical results at meetings of The American Physical Society, Compton stimulated strong interest and strong opposition. But his work quickly triumphed and had a powerful effect on the development of quantum theory. Compton's work, along with the work of others of his generation, marks the emergence of American theoretical physics as the equal of any in the world.
In 1923 Compton took up the professorship at the University of Chicago just vacated by Millikan. Like his predecessor he proved to be a remarkable teacher, attracting and stimulating many students. With their help he continued to produce important papers, first on X-rays and later on cosmic rays. Following the family tradition of Christian service to education, just after the Second World War he reluctantly left physics research to become a highly successful chancellor of Washington University.
During the war Compton was in charge of the "Metallurgical Laboratory" in Chicago where Enrico Fermi and others worked on the fission chain reaction. Leading the Met Lab was a nerve-wracking job, for the scientists there were under intense pressure. They were never sure that German scientists would not be the first to set off a nuclear bomb. Compton and many others had always felt that physics was important to the future of the nation, but this was the first time American physicists had seen that their very lives and freedom might depend on the progress of their research. When the world's first nuclear reactor went critical at the Met Lab on December 2, 1942, physicists became central figures in a new geopolitics.
Momentous though the development of the chain reaction may be, the development of atomic physics and quantum mechanics may turn out in the long run to be still more important. Compton's crucial contribution to this is laid out in the following paper, reproduced from the Physical Review (vol. 21, 1923, p. 483-502).
