William Duncan MacMillan

Background

MacMillan was born on July 24, 1871, in La Crosse, Wisconsin, the son of Duncan D. Macmillan and Mary Jean MacCrea.

Education

MacMillan graduated from La Crosse High School in 1888. The next year he attended Lake Forest College, then entered the University of Virginia, and finally Fort Worth University (now Oklahoma City University), from which he received the Bachelor of Arts in 1898. He then went to the University of Chicago, where he spent most of his working life. He took the Master of Arts there in 1906 and the Ph.D. in 1908.

Career

A pupil of F. R. Moulton, MacMillan became a research assistant, first in geology from 1907 until 1908 and then in mathematics and astronomy from 1908 until 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 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 and H. W. M. Olbers, 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. 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. 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.

Achievements

• MacMillan is noted for his contributions to mathematics and astronomy. He was an early proponent of a theory in the context of solving Olbers's paradox that would later be called the "tired-light hypothesis" of cosmology.

Works

More photos

• book

  • Statics and the Dynamics of a Particle 1927
  • Periodic Orbits about an Oblate Spheroid 1909
  • Dynamics of rigid bodies 1936

Membership

• American Association for the Advancement of Science , United States

• Royal Astronomical Society , United Kingdom

• American Mathematics Society , United States

Connections

Nothing is known of MacMillan's family.

Father:

Duncan D. Macmillan

Mother:

Mary Jane MacCrea

References

• Dictionary of Scientific Biography Volume 7
  1973