Simon Newcomb

Canadian-born American astronomer. Developer of the astronomical ephemeris. He moved to the United States in 1853, where he worked as a mathematics teacher and a calculator for the Nautical Ephemeris Bureau. In 1858, he entered the Faculty of Science at Harvard University, and upon graduation, he became a member of the U.S. Naval Observatory and a mathematics professor at the Naval Academy. In 1877, he transferred to the Nautical Ephemeris Bureau, where he was its chief editor until 1897. In 1884, he was appointed professor at Johns Hopkins University, where he lectured on mathematics and astronomy.

Before entering university, he studied Laplace's famous work "Celestial Mechanics" on his own, and while working at the Naval Observatory, he engaged in research into determining the positions of celestial bodies using a 26-inch (65 cm) mirror. During his time as Director of the Nautical Almanac, he planned and carried out detailed calculations of the motions of the moon and planets, which he had long intended to do. To this end, he deepened his understanding of the theory of celestial mechanics and improved the accuracy of astronomical navigation. At the International Astronomical Congress held in Paris in 1896, he proposed using astronomical constants that were the same all over the world for calculating nautical almanacs, and it was resolved to adopt the values ​​published in a paper by Newcomb the previous year as these constants. He also worked hard to edit the Journal of the American Mathematical Society and to establish the American Astronomical Society. His main achievements were the systematic determination of fundamental astronomical constants and the creation of ephemeris tables for the planets. In particular, he analyzed the difference between the Hansen table of the moon and the apparent motion into periodic and accidental terms, and elucidated that the cause was fluctuations in the Earth's rotation, providing the basis for the establishment of ephemeris tables. He was an honorary professor at seven universities in the United States and ten universities in Europe, an honorary member of 45 foreign academic societies, and received the gold medal from the Royal Astronomical Society of the United Kingdom. He also trained many outstanding celestial dynamicists, including George William Hill (1838-1914) and Brown.

[Shimamura Fukutaro]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

カナダ生まれのアメリカの天文学者。天体暦の開発者。1853年アメリカに移り、数学教師や航海暦局計算係を務め、1858年ハーバード大学理学部に入学、卒業とともにアメリカ海軍天文台員および海軍兵学校の数学教授。1877年航海暦局に転入し1897年まで編暦局長、1884年ジョンズ・ホプキンズ大学教授を兼任し、数学・天文学を講義。

　大学入学以前に独学でラプラスの名著『天体力学』を勉強し、海軍天文台員時代に26インチ（65センチメートル）鏡を用いて天体位置決定の研究に従事。航海暦局長時代にかねて意図していた月および惑星の運動の綿密な計算を企画実施した。このため天体力学の理論を深め、天文航法の精度を高めた。1896年パリで開催の国際天文学会において、航海暦計算に万国同一の天文定数を用いることを提唱し、その定数として前年ニューカムが論文発表した値を採用することが決議された。またアメリカ数学会誌の編集、アメリカ天文学会の創設に尽力した。主業績は天文基礎定数を体系的に決定し、諸惑星の位置推算表を作成したことである。とくに月のハンセン運行表と視運動との差を周期項と偶発項に分析し、その原因は地球自転の変動にあることを解明し、暦表時制定の基礎を与えた。アメリカの7大学、ヨーロッパの10大学の名誉教授、45の外国学会の名誉会員に推され、イギリス王立天文協会から金賞を受けた。またヒルGeorge William Hill（1838―1914）やブラウンら、優れた天体力学者を育成した。

［島村福太郎］

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