Lord Rayleigh, scientifique britannique

Lord Rayleigh, en entier John William Strutt, 3e baron Rayleigh de Terling Place, (né le 12 novembre 1842, Langford Grove, Maldon, Essex, Angleterre — décédé le 30 juin 1919, Terling Place, Witham, Essex), physicien anglais qui fait des découvertes fondamentales dans les domaines de l'acoustique et de l'optique qui sont à la base de la théorie de la propagation des ondes dans les fluides. Il a reçu le prix Nobel de physique en 1904 pour son isolation réussie de l'argon, un gaz atmosphérique inerte.

Quiz

Hommes de distinction anglais: réalité ou fiction?

En Grande-Bretagne, un chevalier a le titre de «Monsieur».

Strutt a souffert d'une mauvaise santé tout au long de son enfance et de sa jeunesse, et il a dû être retiré d'Eton et de Harrow. En 1857, il entame quatre années d'études privées sous la direction d'un tuteur. En 1861, Strutt entra au Trinity College de Cambridge, où il obtint un baccalauréat en 1865. Il développa très tôt un intérêt passionnant pour les aspects expérimental et mathématique des sciences physiques et, en 1868, il acheta une tenue d'appareil scientifique pour la recherche indépendante. Dans son premier article, publié en 1869, il a donné une exposition lucide de certains aspects de la théorie électromagnétique de James Clerk Maxwell, le physicien écossais, en termes d'analogies que l'homme moyen comprendrait.

Une attaque de fièvre rhumatismale peu de temps après son mariage en 1871 a menacé sa vie pendant un certain temps. Un voyage de récupération en Égypte a été suggéré, et Strutt a emmené son épouse, Evelyn Balfour, la sœur d'Arthur James Balfour, sur une péniche sur le Nil pour des vacances d'hiver prolongées. Au cours de cette excursion, il a commencé à travailler sur son grand livre, The Theory of Sound, dans lequel il a examiné les questions des vibrations et de la résonance des solides et des gaz élastiques. Le premier volume parut en 1877, suivi d'un second en 1878, axé sur la propagation acoustique dans les milieux matériels. Après quelques révisions au cours de sa vie et des réimpressions successives après sa mort, l'œuvre est restée le premier monument de la littérature acoustique.

Shortly after returning to England he succeeded to the title of Baron Rayleigh in 1873, on the death of his father. Rayleigh then took up residence at Terling Place, where he built a laboratory adjacent to the manor house. His early papers deal with such subjects as electromagnetism, colour, acoustics, and diffraction gratings. Perhaps his most significant early work was his theory explaining the blue colour of the sky as the result of scattering of sunlight by small particles in the atmosphere. The Rayleigh scattering law, which evolved from this theory, has since become classic in the study of all kinds of wave propagation.

Rayleigh’s one excursion into academic life came in the period 1879–84, when he agreed to serve as the second Cavendish Professor of Experimental Physics at Cambridge, in succession to James Clerk Maxwell. There Rayleigh carried out a vigorous research program on the precision determination of electrical standards. A classical series of papers, published by the Royal Society, resulted from this ambitious work. After a tenure of five years he returned to his laboratory at Terling Place, where he carried out practically all his scientific investigations.

A few months after resigning from Cambridge, Rayleigh became secretary of the Royal Society, an administrative post that, during the next 11 years, allowed considerable freedom for research.

Rayleigh’s greatest single contribution to science is generally considered to have been his discovery and isolation of argon, one of the rare gases of the atmosphere. Precision measurements of the density of gases conducted by him in the 1880s led to the interesting discovery that the density of nitrogen obtained from the atmosphere is greater by a small though definite amount than is the density of nitrogen obtained from one of its chemical compounds, such as ammonia. Excited by this anomaly and stimulated by some earlier observations of the ingenious but eccentric 18th-century scientist Henry Cavendish on the oxidation of atmospheric nitrogen, Rayleigh decided to explore the possibility that the discrepancy he had discovered resulted from the presence in the atmosphere of a hitherto undetected constituent. After a long and arduous experimental program, he finally succeeded in 1895 in isolating the gas, which was appropriately named argon, from the Greek word meaning “inactive.” Rayleigh shared the priority of the discovery with the chemist William Ramsay, who also isolated the new gas, though he began his work after Rayleigh’s publication of the original density discrepancy.Shortly before winning the Nobel Prize, Rayleigh wrote the entry on argon for the 10th edition (1902) of the Encyclopædia. In 1904 Rayleigh was awarded the Nobel Prize for Physics; Ramsay received the award in chemistry for his work on argon and other inert elements. The next year Rayleigh was elected president of the Royal Society.

In his later years, when he was the foremost leader in British physics, Rayleigh served in influential advisory capacities in education and government. In 1908 he accepted the post of chancellor of the University of Cambridge, retaining this position until his death. He was also associated with the National Physical Laboratory and government committees on aviation and the treasury. Retaining his mental powers until the end, he worked on scientific papers until five days before his death, on June 30, 1919.