Arthur Holly Compton, 1892-1962
Arthur Holly Compton died on March 15 , in Berkeley California, as a result of a cerebral hemorrhage suffered two weeks earlier. He was sixty-nine.
He had retired last year as distinguished service professor of natural philosophy in Washington University (St. Louis) where he had served as chancellor from 1945 until 1953. he was planning to be active in retirement as professor-at-large between Washington University, the University of California (Berkeley) and the College of Wooster (Ohio), and had gone to Berkeley to deliver a lecture series on "Man, Science and Society".
Compton received his B.Sc. from the College of Wooster, where his father, Elias Compton, was professor of philosophy, and received his Ph.D. in 1916 at Princeton University. The next year he was an instructor at the University of Minnesota, and then was for two years a research engineer at Westinghouse Lamp company in Pittsburgh. the year 1919-20 was spent at Cambridge (England) as a National Research Fellow, after which he was appointed Wayman Crow professor and head of the Department of Physics at Washington University, where he remained until 1923. During 1923-45 he served as professor of physics and dean of physical sciences at the University of Chicago, until he returned to Washington University as chancellor in 1945. He was president of the American Physical Society in 1934, of the American Association of Scientific Workers in 1939-40, and of the American Association for the Advancement of Science in 1942. in 1927 he shared the Nobel Prize in physics with C.T.R. Wilson.
His career was marked by an extraordinary range of great accomplishments in physics, in higher education, in war-time scientific research, and in efforts to improve human and international relations.
While a student at Princeton he devised a beautiful demonstration of the Earth's rotation, which ought to be known to all teachers of physics. A toroidal glass tube is filled with water, and mounted so that it can be "flipped" through 180 degrees about a diameter as axis. Before flipping, the water is at rest relative to the tube, which is turning, relative to the fixed stars, in its own plan with the component of the Earth's rotational angular velocity normal to that plane. After flipping, the water drifts relative to the tube, at a rate proportional to that angular velocity component. By measuring the drifts produced by three successive flips about each of three mutually perpendicular axes, one finds the Earth's angular velocity as a vector; that is, one can infer which local direction is north, what is the observer's latitude, and what is the absolute value of the length of the day.
His first major discovery was the detailed measurement and interpretation of the wave-length change occurring when X-rays are scattered, especially by materials of low atomic number. The is now generally known as the Compton Effect. He showed that the loosely bound electrons in the material scatter the X-rays in accordance with the principles of conservation of momentum and energy, as if they consist of a stream of photons, each having momentum of hv/c, as well as energy, hv. The energy aspect goes back to Planck and Einstein; but the Compton effect afforded the first clear demonstration that the X-ray photons also carry quantized amounts of momentum.
the next few years were marked by the development of coincidence methods by Compton and A.W. Simon in Chicago, and independently by W. Bothe and H. Geiger in Germany. These experiments showed that individual scattered X-ray photons and recoil electrons appear at the same instant in time, contrary to some views that were then being developed by Bohr, Kramers, and Slater in an attempt to reconcile quantum views with the continuous waves of electromagnetic theory.
Compton also discovered the phenomenon of total reflexion of X-rays, and their complete polarization (with C.F. Hagenow), and first obtained (with (R.L. Doan) X-ray spectra from ruled gratings. This latter work had an important consequence in leading to a distinct improvement in our knowledge of the electronic charge. By measuring an X-ray wave-length with a ruled grating of known grating space, and then using a crystal to diffract the same rays, one can determine the absolute value of the grating space of the crystal. Combining this with the measured crystal density, it is possible to obtain the Avogadro number, and combining this with the Faraday, the electronic charge is obtained. The outcome was that the Millikan oil drop value had to be revised, it being finally recognized that systematic errors had been made in measuring the viscosity of air, a quantity which enters into the oil drop method.
From about 1930, Compton directed his attention mainly to the study of cosmic rays. In the next ten years he was in charge of a major programme involving a world-wide study of the geographic variations of their intensity. This resulted in full confirmation of some observations made in 1927 by J. Clay, indicating a latitude effect on the intensity. The world survey, in the service of which Compton made many long voyages, showed correlation of the intensity of cosmic rays with geomagnetic, rather than geographic, latitude. This opened the way for extensive subsequent studies of the interaction of the Earth's magnetic field with the incoming isotropic stream of primary charged particles.
In 1941 he was appointment chairman of the National Academy of Sciences Committee to Evaluate Use of Atomic Energy in War. In the autumn of 1941, the Committee worked with those responsible for studying this problem in Great Britain, and also with the S-1 committee headed by Dr. L.J. Biggs, then director of the National Bureau of Standards. This led to recommendations to the United States Government for the setting up of a major effort starting in January 1942. Compton assumed the active direction of the group, which was known by the 'cover name' of Metallurgical Laboratory of the University of Chicago, which concentrated on development of controlled uranium fission reactors for the production of plutonium. Within the first the first controlled uranium fission reactor was operating at Chicago, this specific project being largely due to the efforts of E. Fermi, L. Szilard, E.P. Wigner, and a host of co-workers. More experimental reactors were designed and built at Oak Ridge, Tennessee and at the newly established Argonne Laboratory in the suburbs of Chicago. Here was carried out the work which led to the large plutonium-producing reactors built at Hanford, Washington, which produced the plutonium for the atom bomb that destroyed Nagasaki in August 1945.
Throughout the War, Compton also played an important part in the general planning of the atom bomb project, include the setting up of the laboratory at Los Alamos, New Mexico, and in reaching the military-political decisions about the use of the bombs in Japan. He has given a personal account of these matters in his book, Atomic Quest (Oxford University Press 1956).
Compton became chancellor of Washington University in 1945, bringing with him a close associate from the days of his work on cosmic rays, Joyce Stearns, as dean of faculties. He turned with great vigour to the task of re-making a University which had greatly suffered through the depression years and the War years. in eight years filled with hard work he set it along a path toward greatness along which it continues to move. Then in 1953 he asked to be relieved from administrative duties, so that he could return to teaching, and devote himself entirely to problems of the social impact of science and technology, and to ways of promoting world brotherhood and the relieving of international tensions. He was planning to continue active work on such problems into the retirement which ended soon after it began.
Edward U. Condon