Strutt, Robert [Robin] John, Fourth Baron Rayleigh

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(b. Terling Place, Witham, Essex, England, 28 August 1875; d. Terling, 13 December 1947), physics.

Rayleigh is best-known for his work on atmospheric optics. The first child of the renowned physicist J. W. Strutt, third Baron Rayleigh, he attended Eton from 1889 and matriculated at Trinity College, Cambridge, in 1894. After studying experimental physics, he began research at the Cavendish Laboratory in 1899 and published his first scientific paper. Strutt was elected a fellow of the Royal Society in 1905; and from 1908 he was professor of physics at Imperial College, London, until becoming Baron Rayleigh in 1919.

Strutt’s early research was on radioactivity. In 1900 he had suggested that alpha radiation might consist of charged particles, a fact verified in 1902 by E. Rutherford. From measurements on the helium content of minerals, Strutt proved that their minimum age was significantly greater than that allowed by Kelvin’s geological timetable. Following up the 1884 observations of Emil Warburg on the afterglow in electric discharge and the assertion in 1900 by E. Percival Lewis that the cause of the airglow was nitric oxide, Strutt in 1911 confirmed that discharge airglow was due to a chemically active modification of nitrogen, which he called“active nitrogen.”His suggestion that the effect was an atomic phenomenon was not accepted until about 1925. The Lewis-Rayleigh afterglow opened up an important line of optical research.

By comparing absorption spectra, Strutt and Alfred Fowler confirmed in 1916 the presence of ozone in the atmosphere. Strutt investigated its optical effects, and from the nonuniform density distribution he estimated the upper boundary of high-altitude ozone. He examined luminous glows in other gases and metallic vapors and investigated the airglow of the night sky. Strutt determined that this effect was not due to (third Baron) Rayleigh Scattered sunlight and that it had a green line spectrum, later shown to be characteristic of a transition of atomic oxygen.

Rayleigh distinguished the atmospheric airglow generally observable, especially at low latitudes, from the high-latitude night glow associated with magnetic disturbances and auroral phenomena. Because of his pioneering quantitative research, the unit of sky brightness is called the rayleigh; the order of magnitude for the airglow is less than 102 rayleighs and that for auroral phenomena lies between 102 and 104 rayleighs.

Until his death Rayleigh was occupied with matters pertaining both to science and to his many public duties, serving as foreign secretary of the Royal Society, president of the Royal Institution, and chairman of the governing board of Imperial College.


Rayleigh published over 300 scientific papers. A complete list, in John N. Howard, ed., Summaries and Abstracts of the Scientific Writings of Robert John Strutt, Fourth Baron Rayleigh, From Notes Written by Him, 1945–1947 (Bedford, Mass., 1969), 63–88, is based on the bibliography included in Alfred C. Egerton,“Lord Rayleigh, 1875–1947,”in Obituary Notices of Fellows of the Royal Society of London, 6 (1949), 503–538. A selected list is in Charles R. Strutt,“The Optics Papers of Robert John Strutt, Fourth Baron Rayleigh,”in Applied Optics, 3 (1964), 1116–1119.

Additional biographical material dealing with his family life and background is in Guy Robert Strutt,“Robert John Strutt, Fourth Baron Rayleigh,”ibid., 1105–1112. An expanded version of this appeared in John N. Howard, ed., The Airglow Rayleigh; Robert John Strutt, Fourth Baron Rayleigh, A Memoir by Guy Robert Strutt (Bedford, Mass., 1969), 1–24. Howard included several contemporary biographical notes relating to Rayleigh that appeared in Nature, 125 (1930), 420, and 140 (1937), 456; The Times (London) (15 Dec. 1947), 6d; Proceedings of the Society for Psychical Research, 48 (1948), 330–331; and Proceedings of the Royal Institution of Great Britain, 34 (1948), 156–158. See also A. C. Egerton’s notice, in Dictionary of National Biography (1959), 850–852.

From personal recollection Sydney Chapman contributed“On the Influence of the Fourth Baron Rayleigh on Air Glow and Auroral Research,”in John N. Howard, ed., The Rayleigh Archives Dedication, Air Force Cambridge Research Laboratories, Special Report no. 63 (Bedford, Mass., 1967), 46–53. Charles R. Strutt wrote“The Optics Research of Robert John Strutt, Fourth Baron Rayleigh,”in Applied Optics, 3 (1964), 1113–1115. The results of Strutt and Lewis are contrasted in E. P. Lewis,“The Origin of the Bands in the Spectrum of Active Nitrogen,”in Philosophical Magazine, 25 (1913), 826–832.

Howard has brought together nearly all the primary and secondary literature pertaining to Strutt in“The Scientific Papers of the Lords Rayleigh,”in Actes du XIe congrés international d’histoire de sciences, 1965, IV (1968), 315–318. A short obituary notice in Isis, 39 (1948), 69, refers to a review by N. R. Campbell, ibid., 8 (1926), 177–181, of Strutt’s model scientific biography of his father. This biography, Life of John William Strutt: Third Baron Rayleigh, O.M., F.R.S. was reedited by John N. Howard (Madison, Wis., 1968) and includes 33 pages of annotations by R. J. Strutt keyed to the text.

The early research of R. J. Strutt was considered by C. T. R. Wilson in Cavendish Laboratory, A History of the Cavendish Laboratory 1871–1910 (London, 1910), 211–215. Part of Strutt’s work in its larger scientific context is considered in A. N. Wright and C. A. Winkler, Active Nitrogen (London, 1968), passim. The technical context is considered in F. E. Roach and J. L. Gordon, The Light of the Night Sky (Dordrecht, 1973). L. Badash deals with Strutt’s helium method of geological dating in“Rutherford, Boltwood and the Age of the Earth: The Origin of Radioactive Dating Techniques,”in Proceedings of the American Philosophy Society, 112 (1968), 157–169. See also S. I. Levy, The Rare Earths (London, 1915), ch. 8. John N. Howard described the 22 notebooks of the fourth Baron Rayleigh including over 4,000 experiments from 1916 to 1944 in“The Rayleigh Notebooks,”in Applied Optics, 3 (1964), 1132–1133.

Several previously unpublished MSS and the text of Strutt’s House of Lords debates and letters to the Times (London) are included in John N. Howard, ed., Robert John Strutt, Fourth Baron Rayleigh, Unpublished Manuscripts and Reviews of His Work (Bedford, Mass., 1971), which also contains contemporary reviews of Strutt’s four books. Additional correspondence of Strutt is in the Lodge collection, Library, University College, London.

Thaddeus J. Trenn

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Strutt, Robert [Robin] John, Fourth Baron Rayleigh

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