Moulton, Forest Ray

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(b. Osceola County, Michigan, 29 April 1872; d. Wilmette, Illinois, 7 December 1952)

astronomy, mathematics.

Forest Ray Moulton was the eldest of eight children born to Belah and Mary Smith Moulton. He was named Forest Ray because his poetic mother thought him a “perfect ray of light and happiness in that dense forest.” He received his early education in a typical frontier school and at home. At the age of sixteen he taught in this same school, where one of the students was his brother Harold, who was later to become the first head of the Brookings Institute. At the age of eighteen he enrolled in Albion College, where he received his B.A. in 1894. Moulton received his Ph.D. in astronomy, Summa cum laude, from the University of Chicago (1899). He also received honorary degrees from Albion College (1922), Drake University (1939), and the Case School of Applied Science (1940).

Moulton had a variety of careers. His academic life began at the University of Chicago with his appointment, while a graduate student, in 1896 as an assistant in astronomy, and it continued through his appointment as professor in 1912 until retirement in 1926. From 1927 to 1936 he was a director of the Utilities Power and Light Corporation of Chicago. He was also a trustee of the Exposition Committee of Chicago’s Century of Progress from 1920 to 1936, and its director of concessions from 1931 to 1933. From 1936 to 1940 he was executive secretary of the American Association for the Advancement of Science. During his tenure in this position, he edited more than twenty symposium volumes.

In 1898, while still a graduate student at Chicago, Moulton was invited by Thomas Crowder Chamberlin, then chairman of the geology department, to participate in an investigation of the earth’s origin. Chamberlin’s investigations on glacial movements had raised doubts that were relevant to the then existing theories. Kant had originally proposed his nebular hypothesis in 1755. Halfa century later, and with no knowledge of Kant’s theory, Laplace developed a similar theory. He suggested that the earth had originated in a vast mass of blazing gas, which had been thrown off by the sun and had liquefied into a molten sphere. According to this theory the earth was steadily cooling off from its original molten state. After the primordial sun, which was five and a half billion miles in diameter, had cast away the planets, it reached its present diameter and a rotational velocity of 270 miles per second. When Moulton imagined that all planets were returned to the sun, his calculations indicated that the sun would not have enough momentum to hurl off any rings of matter. Chamberlin and his group investigated everything that was written on the origin of the solar system. The most promising prospect was offered by that of nebular “knots,” revealed in photographs of spiral nebulae, which could have served as collecting centers.

On 28 May 1900 there was an eclipse of the sun. Chamberlin and Moulton meticulously studied the photographs that illustrated the sun’s eruptive nature. Their observation of great clouds of gaseous matter flaring out and away from the sun’s surface led to the planetesimal hypothesis proposed in 1904. They proposed that the nebula quickly cooled and solidified, creating small chunks of matter, the planetesimals. Although today neither the Laplace-Kant nor the Moulton-Chamberlin hypothesis stands by itself, both provide a basis for current theories.

During World War I Moulton was assigned to do ballistics research at Fort Sill. Here he is said to have effectively doubled the range of artillery. His work was the forerunner of the efforts in World War II to get improved ballistics tables faster and more accurately, which was one of the links giving impetus to contemporary high speed electronic computing equipment.

In 1920, Moulton, one of the founders of the Society for Visual Education, gave the first radio address broadcast from the University of Chicago. As one of the pioneers of educational broadcasting, Moulton was heard weekly in Chicago from 1934 to 1936, and in Washington from 1938 to 1940.

Moulton was a fellow of the American Academy of Arts and Sciences, the American Physical Society, and the Royal Astronomical Society; President of Sigma Xi, and Honorary Foreign Associate of the British Association for the Advancement of Science. He was also an active member of many other professional societies.

In 1897 Moulton married Estelle Gillete. They had four children and were divorced in 1938. In 1939 he married Alicia Pratt of Winnetka, Illinois. They were divorced in 1951.


I. Original Works. No complete bibliog. of Moulton’s publications has been published. His major bks. include An Introduction to Celestial Mechanics (London–New York, 1902, 1914, 1935); Descriptive Astronomy (Chicago, 1912, 1921, 1923); Periodic Orbits (Washington, 1920); Differential Equations (New York, 1930), written with D. Buchanan, T. Buck, F. Griffin, W. Longley, and W. MacMillan; and New Methods in Exterior Ballistics (Chicago, 1926). The last work is the beginning of a contemporary mathematical approach to the science of ballistics. For interesting and opposing reviews of this work see J. E. Rowe, Bulletin of the American Mathematical Society, 34 (1928), 229–332, and L. S. Dederick, ibid., 667.

The first twenty vols, of the Carnegie Institution of Washington Yearbooks (1902–1921) provide a clear picture of the work of Moulton and Chamberlin on the planetesimal hypothesis. Yearbook, no. 2 (1903), 261–270, contains a report by T. C. Chamberlin, entitled “Fundamental Problems of Geology,” in which he describes the progress of the investigators and collaborators, and their roles and status to date. Yearbook, no. 3 (1904), 255–256, contains a letter from Moulton to Chamberlin describing different hypotheses and their applications, pertinent observational data, and the laws derived from the data. Other vols. of the Yearbook and their relevant p. nos. are no. 1, 25–43; no. 3, 195–258; no. 4, 171–190; no. 5, 166–172; no. 6, 195; no. 7, 204–205; no. 8, 28–52, 224–225; no. 9, 48–222; no. 10, 45, 222–225; no. 11, 13–44, 264–266; no. 12, 52, 292, 297; no. 13, 45–46, 356–357, 376; no. 14, 36–37, 289, 368; no. 15, 358–362; no. 16, 307–319; no. 17, 297; no. 18, 39, 343–345, 349–351; no. 19, 21, 366–382, 386; and no. 20, 412–425. See also “The Development of the Planetesimal Hypothesis,” in Science, n.s. 30 (1909), 642–645, written with T. C. Chamberlin; “An Attempt to Test the Nebular Hypothesis by an Appeal to the Laws of Dynamics,” in Astrophysical Journal, 11 (1900), 103; and “Evolution of the Solar System,” ibid., 22 (1905), 166.

One of Moulton’s more important papers from the standpoint of current research is “The Straight Line Solutions of the Problem of nBodies,” in Annals of Mathematics, 12 (1910–1911), 1–17. In this paper the number of straight line solutions is found for n arbitrary masses. This is the generalization of the problem solved by Lagrange for three bodies. Moulton also attacks what is a sort of converse of this problem by determining, when possible, n masses such that if they are placed at n arbitrarily collinear points, they will, under proper initial projection, always remain in a straight line. This paper was originally presented to the Chicago Section of the American Mathematical Society on 28 December 1900 (see Bulletin of the American Mathematical Society, 7 [1900–1901], 249–250).

II. SECONDARY LITRATURE. The anonymous “The Washington Moultons, Forest Ray, ’94, and Harold Glenn, 1907,” in Io Triumphe (March, 1947) (Albion College Alumni Magazine), is an excellent art. with portraits of both Forest and Harold. This art. also contains a photograph of the seven Moulton brothers and their sister on the occasion of the awarding of an M.A. to Mary Moulton by Wayne University in 1945. Other biographical arts. appear in Current Biography (1946), 421–423; The National Cyclopaedia of American Biography, XLIII (1946), 314315; and A. J. Carlson, “Forest Ray Moulton: 1872–1952,” in Science, 117 (1953), 545–546.

Henry S. Tropp

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