Macmillan, William Duncan

(b. La Crosse, Wisconsin, 24 July 1871; d. Si Paul, Minnesota, 14 November 1948)

astronomy, mathematics.

William Macmillan was the son of Duncan D. Macmillan and Mary Jean MacCrea, He attended Lake Forest College, the University of Virginia, and Fort Worth University, from which he received the B.A. in 1898. He then went to the University of Chicago, where he spent most of his working life. He took the M.A. there in 1906 and the Ph.D. in 1908. A pupil of F. R. Moulton, he became a research assistant, first in geology (1907–1908) and then in mathematics and astronomy (1908–1909). He held a succession of posts in astronomy at the university, becoming professor emeritus in 1936,

Macmillan’s interests centered around cosmogony and related topics in applied mathematics. Probably his most widely known works were his textbooks of theoretical mechanics. He made a number of original contributions to potential theory, the theory of differential equations with periodic coefficients, and the theory of automorphic functions. He took an active part in the then-controversial discussions of the theory of relativity, contributing to A Debate on the Theory of Relativity (New York, 1927) with R. D. Carmichael, H. T. Davis, and others.

One of Macmillan’s most influential pieces of work was an attempt to remove the supposed paradox of P. L. de Cheseaux (1744) and H. W. M. Olbers (1823), whereby, with the hypothesis of an infinite and uniform distribution of stars throughout space, the night sky would shine with a brightness corresponding to their average surface brightness. In 1918 and 1925 Macmillan proposed a form of continual material creation (Astrophysical Journal, 48 (1918), 35, and Science, 62 (1925), 63–72, 96–99, 121–127). His main concern was with the formation of the planets and stars. Among his so-called postulates he included two according to which the universe maintains a steady state, and another according to which the energy of a large region of the universe, supposedly unbounded, is conserved. He acknowledged that matter is converted to energy in stellar interiors, and explained away the De Cheseaux-Olbers paradox as a disappearance or dissipation of the radiation traversing empty space. (This radiation was to reappear in the form of hydrogen atoms.) Subsequently, R. A. Millikan, one of Macmillan’s colleagues at Chicago, used his theory to account for the origin of cosmic rays, but by 1935 A. H. Compton proved that it could not account for the high energies of much cosmic radiation. The theory was then abandoned. It should be noted that, unlike more recent steady-state theories, Macmillan’s identified a source from which the mass or energy of the created particle was drawn. He did not suggest creation ex nihito.

BIBLIOGRAPHY

Macmillan collaborated with F. R. Moulton, C. S. Sliehter, et al., in Contributions to Cosmogony and the Fundamental Problems of Geology. The Tidal and Other Problems (Washington, D.C, 1909), and with Moulton, F, R. Longley, et al., in Periodic Orbits, Carnegie Institution of Washington publ, no. 161 (Washington, D.C., 1920). His best-known work was Theoretical Mechanics, 3 vols. (New York, 1927–1936). On the background to Macmitlan’s writings on cosmogony, see J. D. North, The Measure of the Universe (Oxford, 1965), esp. 18, 198–199, and 260–261.

J. D. North