William Duncan MacMillan


William Duncan MacMillan was an American mathematician and astronomer.
He was born in La Crosse, Wisconsin to D. D. MacMillan, who was in the lumber business, and Mary Jane MacCrea. He had a sister and two brothers; the last would later becoming managers of Cargill Elevator company of Minneapolis.
William graduated from La Crosse High School in 1888. In 1889 he attended Lake Forest College, then entered the University of Virginia. Later in 1898 he earned an A.B. degree from Fort Worth University. He performed his graduate work at the University of Chicago, earning a M.A. in 1906 and a Ph.D. in 1908.
In 1907, prior to completing his Ph.D., he joined the staff of the University of Chicago as a research assistant in geology. In 1908 he became an associate in mathematics, then in 1909 he began instruction in astronomy at the same institution. His career as a professor began in 1912 when he became an assistant professor. In 1917 the U.S. declared war on Germany, and Dr. MacMillan served as a major in the U.S. army's ordnance department during World War I. Following the war he became associate professor in 1919, then full professor in 1924.
He made noted contributions in 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.
In an Associated Press report Dr. MacMillan speculated on the nature of interstellar civilizations, believing that they would be vastly more advanced than our own. "Out in the heavens, perhaps, are civilizations as far above ours as we are above the single cell, since they are so much older than ours."
The crater MacMillan on the Moon is named in his honor.