# Idelson, Naum Ilich

# Idelson, Naum Ilich

(*b*. St. Petersburg, Russia, 13 March 1885; *d*. near Riga, Latvian S.S.R., 14 July 1951)

*astronomy, history of astronomy*

Idelson’s father, a mathematician, wished his son to become a lawyer. After graduating from the Gymnasium he entered the law faculty of St. Peterburg University, studying mathematics at the same time in the physical-mathematical faculty. His brilliance enabled him to graduate in 1909 from both faculties. For a while he was assistant to a barrister, but his interest in mathematics led to his teaching that subject in a secondary school. Obviously a born teacher, he devoted all his free time to serious scientific studies—theoretical astronomy and celestial mechanics.

In 1914 Idelson was elected a member of the Russian Astronomical Society and of the society of Amateur Naturalists. The latter society brought together many professional and amateur astronomers. In 1918 Idelson was invited to join the computational bureau of the astronomical section of the P. F. Lesgaft Scientific Institute, headed by the extraordinary scientist and revolutionary N. A. Morozov (named Shlisselburgsky). This bureau computed the astronomical tables known as “The Canon of Solar Eclipses” (similar to Oppolzer’s well-known “Canon of Eclipses”), which are indispensable for the study of the chronology of Russian history.

Although a project for compiling a Russian astronomical yearbook had been proposed in April 1917 at the First All-Russian Astronomical Congress in Petrograd, not until 1919 was a special institution created—the State Computing Institute—to satisfy the new nation’s need for precise astronomical data for both scientific and practical use. Idelson became the head of the group computing the basic tables of the yearbook, for which project he studied in depth the theory and technique of compiling astronomical ephemerides.

In 1923 the Astronomical-Geodesic Institute was merged with the Computing Institute to form the Leningrad Astronomical Institute (from 1943 the Institute of Theoretical Astronomy of the Academy of Sciences of the U.S.S.R.). Idelson became the head of its astrometrical section and, in 1924, assistant to the director, B. V. Numerov. In 1924 Idelson visited the Berlin Computing Institute, the Computing Institute at Frankfurt-am-Main, the Paris Bureau of Longitudes, and a number of French observatories. His familiarity with the activity of foreign astronomical computing institutions aided the progress of corresponding work at the new institute, which besides the basic *Astronomical Yearbook* began publication in 1929 of the *Marine Astronomical Yearbook and, later, the Aviation Yearbook and Ephemerides of 500 Zinger Pairs.*

At the end of 1920 the Pulkovo Observatory invited Idelson to direct the Petrograd section of its computing bureau, where he organized the compilation of tables of Besselian values A, B, C, D, and E for 1920-1960, necessary for processing meridional observations. Idelson also conducted a huge project for deriving corrections of the equinox from the series of Pulkovo observations of the sun’s position in 1904-1915.

In 1926 Idelson, who had taught mathematics, mechanics, and geophysics at various higher educational institutions, was invited to Leningrad University. In 1933 he became professor of astronomy there, giving courses in theoretical astrometry, theory of tides, potential theory, theory of the shape of the earth, theory of mathematical analysis of observations, general mechanics, history of astronomy, and history of mechanics. From 1930 to 1937 he also occupied the chair of theoretical mechanics at the Leningrad Institute of Precision Mechanics and Optics.

In December 1941, Idelson was evacuated from blockaded Leningrad to Kazan, where he lectured on celestial mechanics at Kazan University, occupied the chair of geophysics, and headed the gravimetry laboratory. After his return to Leningrad he renewed his work at the university, at the Institute of Precision Mechanics and Optics, and at the Pulkovo Observatory, where he directed the astrometrical section.

Idelson’s areas of basic scientific interest were fundamental astrometry, celestial mechanics, and the history of astronomy. His works related to the theory of ephemerides, published in the appendixes to the *Astronomichesky ezhegodnik* (“Astronomical Year-book”) in 1941 and 1942, gained wide recognition, as did those in potential theory and the theory of the shape of the earth, the subject of his basic monograph *Teoria potentsiala s prilozheniem k teorii figury Zemli i geofizike* (“Potential Theory With an Application to the Theory of the Shape of the Earth and to Geophysics”).

Idelson left a deep mark on the history of astronomy. Particularly notable are his excellent book *Istoria kalendarya* (“History of the Calendar,” 1925) and his articles on this subject in the *Great Soviet Encyclopedia;* his discerning commentaries and articles on Clairaut, Appell, Lobachevsky, Copernicus, and Galileo; and his sketches of Newton, Laplace, and Le Verrier. It is curious that one of Idelson’s first publications in the history of astronomy, *Istoria i astronomia* (“History and Astronomy,” 1925), was devoted to a criticism of the “horoscopical method” of investigating the facts of world history developed by Morozov. In it he showed a broad knowledge of the scientific literature of antiquity and great feeling for the spirit of the epoch. He established the authenticity of ancient scientists’ astronomical observations and the special importance of Ptolemy’s *Almagest* in the history of science.

Idelson’s most important and original work in the history of astronomy was *Etyudy po istorii planetnykh teory*, in which he masterfully investigated the development from Hipparchus to Kepler of mathematical methods of representing the movement of the planets. The precision of his succinct description of the scientists of the past and the depth of his scientific analysis make Idelson an unsurpassed authority on problems in the history of astronomy. Unfortunately, all his work in this field has been published only in Russian and has not attracted the foreign attention that it deserves.

## BIBLIOGRAPHY

I. Original Works. The complete list of Idelson’s works in Yakhontova’s biography (see below) includes more than 70 titles. The following is a representative list: “Tables auxiliaires pour le calcul des quantités Besseliennes A, B, C, D, E, pour 0^{h} temps sidéral Poulkovo et 12^{h} temps sidéral Greenwich pour les époques 1920-1960,” in *Izvestiya Glavnoi astronomicheskoi observatorii v Pulkove*, no. 91 (1921), pp. 235-274; *Istoria kalendarya* (“History of the Calendar”; Leningrad, 1925); *Uravnitelnye vychislenia po sposobu naimenshikh kvadratov* (“Equalizing Calculations for the Method of Least Squares”; Leningrad, 1926; 2nd ed., rev. and enl., 1932); “Die Stokesche Formel in der Geodäsie als Lösung einer Randwertaufgabe,” in *Beiträge zur Geophysik*, **29** , no. 2 (1931), 156-160, written with N. R. Malkin; *Teoria potentsiala i ee prilozhenia k geofizike* (“The Theory of Potential and Its Application to Geophysics”), 2 pts. (Leningrad-Moscow, 1931-1932), 2nd ed., rev. and enl. (Moscow-Leningrad, 1936); “Über die Bestimmung der Figur der Erde aus Schwerkraftmessungen,” in *Comptes rendus de la 7 séance de la Commission géodésique baltique* (Helsinki, 1935), pp. 9-23; “Reduktsionnye vychislenia v astronomii” (“Calculations of Reductions in Astronomy”), in *Astronomichesky ezhegodnik SSSR na 1941 g*. (“Astronomical Yearbook of the U.S.S.R. for 1941”; Moscow, 1940), pp. 379-432;“Zamechania po povodu teorii Lomonosova o kometnykh khvostakh” (“Remarks on Lomonosov’s Theory of Comet Tails”), in *Lomonosov. Sbornik statey i materialov* (“Lomonosov. Collected Papers and Materials”; Moscow-Leningrad, 1940), pp. 66-116; “Galiley v istorii astronomii”(“Galileo in the History of Astronomy”), in *Galileo Galilei, 1564-1642* (Moscow, 1943), pp. 68-141; “Zakon vsemirnogo tyagotenia i teoria dvizhenia Luny” (“The Universal Law of Gravity and the Theory of the Moon’s Movement”), *in Isaac Newton, 1643-1727 (Moscow, 1943), pp. 161-210; Sposob naimenshikh kvadratov i teoria matematicheskoy obrabotki* nablyudeny (“The Method of Least Squares and the Theory of the Mathematical Treatment of Observations“; Moscow, 1947); “Zhizn i tvorchestvo Kopernika”(“The Life and Work of Copernicus”), in *Nikolay Kopernik* (Moscow, 1947), pp. 5-42; “Etyudy po istorii planetnykh teory” (“Studies in the History of the Theory of Planetary Movement”), *ibid*., pp. 84-179; “Lobachevsky—Astronom,” in *Istoriko-matematicheskie issledovaniya*, no. 2 (1949), pp. 137-167; and “Raboty A. N. Krylova po astronomii” (“The Works of A. N. Krylov in Astronomy”), in *Trudy Instituta istorii estestvoznaniya i tekhniki. Akademiya nauk SSSR*, **15** (1956), 24-31.

II. Secondary Literature. An obituary is in *Astronomichesky tsirkular SSSR*, no. 117 (1951), p. 14. Biographies include N. S. Yakhontova in *Istorikoastronomicheskie issledovaniya*, no. 4 (1958), pp. 387-405, with complete bibliography; and S. N. Korytnikov, *ibid*., pp. 407-431, dealing with Idelson’s work in the history of astronomy. See also *Bolshaya sovetskaya entsiklopedia*, 2nd ed., XVII, 327.

P. G. Kulikovsky

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