Thomson, Joseph John

Born Dec. 18,1856, at Cheetham Hill, near Manchester; died Aug. 30,1940, in Cambridge. British physicist. Fellow of the Royal Society of London (1884); the society’s president from 1915 to 1920.

Thomson graduated from Owens College in Manchester in 1876 and from Trinity College of Cambridge University in 1880. He was a lecturer at Trinity College from 1882 to 1884 and became master of the college in 1918. Thomson was a professor at Cambridge University and the director of the Cavendish Laboratory from 1894 to 1919. From 1905 to 1918 he was also a professor at the Royal Institution in London.

Thomson’s early works dealt with the calculation of the electromagnetic field of a moving charged sphere, vortex theory, and the precise measurement of the ratio of absolute electrostatic units to electromagnetic units. While studying gas discharges, he and his coworkers carried out a series of historic investigations that led to his discovery of the electron. In 1897 he became the first to measure the ratio of the charge of the electron to its mass. In 1906 he received a Nobel Prize for his research on the electrical conductivity of gases. Thomson provided an explanation of the continuous spectrum of X rays, established the nature of positive ions, and proposed the first model of the structure of the atom (seeATOMIC PHYSICS). In 1911 he developed the method of parabolas for measuring the ratio of the charge of a particle to its mass; this method played a great role in the study of isotopes.

Thomson’s activities in organizing scientific research were of great importance. Under his leadership, the Cavendish Laboratory became a leading center for research in physics. Such great British physicists as E. Rutherford, C. Wilson, F. W. Aston, and O. Richardson worked at the laboratory under his direction. A staunch supporter of classical physics, Thomson adhered to the ether hypothesis.