Thursday, March 12, 2009

March 12: Simon Newcomb

Simon Newcomb
March 12, 1835 – July 11, 1909

Simon Newcomb was a Canadian-American astronomer and mathematician. Though he had little conventional schooling, he made important contributions to timekeeping as well as writing on economics, statistics and authoring a science fiction novel.

Newcomb studied mathematics and physics privately and supported himself with some school-teaching before becoming a human computer (a functionary in charge of calculations) at the Nautical Almanac Office in Cambridge, Massachusetts in 1857. At around the same time, he enrolled at the Lawrence Scientific School of Harvard University, graduating BS in 1858.

In the prelude to the American Civil War, many US Navy staff of Confederate sympathies left the service and, in 1861, Newcomb took advantage of one of the ensuing vacancies to become professor of mathematics and astronomer at the United States Naval Observatory, Washington DC. Newcomb set to work on the measurement of the position of the planets as an aid to navigation, becoming increasingly interested in theories of planetary motion.

By the time Newcomb visited Paris, France in 1870, he was already aware that the table of lunar positions calculated by Peter Andreas Hansen was in error. While in Paris, he realised that, in addition to the data from 1750 to 1838 that Hansen had used, there was further data stretching as far back as 1672. Newcomb was able to use the "new" data to revise Hansen's tables.

He was offered the post of director of the Harvard College Observatory in 1875 but declined, having by now settled that his interests lay in mathematics rather than observation.

In 1877 he became director of the Nautical Almanac Office where, ably assisted by George William Hill, he embarked on a program of recalculation of all the major astronomical constants. Despite fulfilling a further demanding role as professor of mathematics and astronomy at Johns Hopkins University from 1884, he conceived with A. M. W. Downing a plan to resolve much international confusion on the subject. By the time he attended a standardisation conference in Paris, France in May 1896, the international consensus was that all ephemerides should be based on Newcomb's calculations. A further conference as late as 1950 confirmed Newcomb's constants as the international standard.

In 1878, Newcomb had started planning for a new and precise measurement of the speed of light that was needed to account for exact values of many astronomical constants. He had already started developing a refinement of the method of Léon Foucault when he received a letter from the young naval officer and physicist Albert Abraham Michelson who was also planning such a measurement. Thus began a long collaboration and friendship. In 1880, Michelson assisted at Newcomb's initial measurement with instruments located at Fort Myer and the United States Naval Observatory, then situated on the Potomac River. However, Michelson had left to start his own project by the time of the second set of measurements between the observatory and the Washington Monument. Though Michelson published his first measurement in 1880, Newcomb's measurement was substantially different. In 1883, Michelson revised his measurement to a value closer to Newcomb's.

Awards and honours

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