Dates

• Existence: 1856 - 1940

Biography

Joseph John Thomson (1856-1940) was born in Manchester and attended Owens College, Manchester, in 1871. Thomson won a scholarship to Trinity College, Cambridge, and in 1876 came to the university to read for the Mathematical Tripos. He was elected a fellow of Trinity, and in 1885 was appointed Cavendish Professor of Experimental Physics. Thomson began his life-long investigation of the passage of electricity through gases before his appointment as Cavendish Professor. His work was given impetus in 1895 by Rontgen's discovery of X-rays which Thomson found caused gases through which they passed to become conductors of electricity. Thomson investigated the nature of this phenomenon with Ernest Rutherford, and from their research they were able to determine the process by which a current is passed through a gas and the role X-rays play in this process. Thomson proceeded to the study of discharge-cathode rays. His work led to him to conclude that the rays were a fundamental constituent of the atom, carrying negative electricity, and that their number and arrangement in the atom determined that atom's position in the periodic table. When Thomson first put forward his theory in 1897 his ideas were greeted with scepticism, but two more years of research by himself and others provided the experimental evidence to confirm his ideas about the electron. Thomson continued to study the structure of the atom and the arrangement of electrons within it, but from 1906 to 1914 he also turned his attention to the study of positive rays. He developed and refined the techniques used to photograph positive rays in the discharge tube. The increased sensitivity of his apparatus allowed him to identify new atomic groupings and isolate for the first time isotopes as unstable elements. Thomson resigned as Cavendish Professor in favour of Rutherford in 1919, but held a special chair until his death. He was active outside the university in urging recognition of the importance of scientific education and research to the country as a whole. During the First World War he served on the Board of Invention and Research (B.I.R.), set up by the Admiralty to encourage and coordinate naval research. He was also a member of the Department of Scientific and Industrial Research and became the first President of the Institute of Physics. Thomson also presided over the Royal Commission report on the position of natural science in the education system of Great Britain. In 1915 he was elected President of the Royal Society, which he headed until 1920. In 1919 he was appointed Master of Trinity College, Cambridge, and devoted the last years of his life to running its affairs. He died on 30 August 1940.

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