Lyman, Theodore

(b. Boston, Massachusetts, 23 November J874; d. Brookline, Massachusetts, 11 October 1954)

experimental physics.

Lyman came from an old and wealthy Massachusetts family. His great-grandfather was a very successful Boston merchant. His father, also Theodore, was a marine biologist who served one term in Congress. His mother, the former Elizabeth Russell, was the granddaughter of a U.S. minister to Sweden. Theodore Lyman never married and spent his life in his grandfather’s mansion on a large estate in Brookline.

He received the B.A. degree in 1897 and the Ph.D. in 1900 from Harvard. After a year at the Cavendish Laboratory in Cambridge and a summer at Göttingen he returned to Harvard as an instructor in physics. His entire career was spent at Harvard, where he was director of the Jefferson Physical Laboratory from 1910 to 1947 and held the Hollis professorship (the oldest endowed scientific chair in the United States) from 1921 until he retired.

Lyman’s doctoral dissertation was devoted to the problem of applying the concave grating to the measurement of spectral lines in the extreme ultraviolet, a region where the rays cannot pass through air. The technical problems were great and consumed six years. In the work Lyman found false lines in the spectrum which he was able to explain as due to periodic errors in the grating ruling. The clarification of these “Lyman ghosts” in 1900 constituted his doctoral thesis. His first published measurement of wavelengths in the “Lyman region”(1906) gave the first accurate measurements below 2,000 Å. and extended the known extreme ultraviolet region significantly. Viktor Schumann in Germany had used a fluorite prism to disperse the light that did not permit wavelength determination.

Lyman’s later scientific work was devoted to measuring various spectra and the optical properties of various materials in the region and to extending the ultraviolet spectrum to the final limit of 500Å., which he attained in 1917. In 1914 he announced the discovery of the fundamental series of hydrogen, which was an essential part of the foundation on which Bohr developed the quantum theory of the atom.

Never in robust health, Lyman retired from his professorship in 1925 but continued as director of the Jefferson Physical Laboratory until 1947. His last paper was published in 1935, although he continued to direct doctoral dissertations until 1942.

He was a member of the National Academy of Sciences, the American Philosophical Society, the American Academy of Arts and Sciences (president, 1924–1927), the American Physical Society (president, 1921–1922); an honorary member of the Optical Society of America and the Royal Institution of Great Britain; and a fellow of the Royal Geographical Society.

He received the Rum ford Medal of the American Academy of Arts and Sciences, the Cresson Medal of the American Philosophical Society, and the Ives Medal of the Optical Society of America.

BIBLIOGRAPHY

I. Original Works. Lyman published about forty scientific papers. Hismost important work was The Spectroscopy of the Extreme Ultra-Violet (New York, 1914; rev. ed., 1928). Important papers include: “An Explanation of False Spectra From Diffraction Gratings,” in Physical Review, 16 (1903), 257–266; and “The Spectrum of Helium in the Extreme Ultra-Violet,” in Astrophysical Journal, 60 (1924), 1–14.

II. Secondary Literature. See the discussion of Lyman and his work by P. W. Bridgman, in Biographical Memoirs. National Academy of Sciences, 30 (1957), 237–250, which includes a complete bibliography.

Ralph A. Sawyer