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Happy Birthday Mr. Thomson!

Young J.J. Thomson

Joseph John Thomson was born in Cheetham Hill, Manchester, England on 18 December 1856. His father, Joseph James Thomson, was an antique bookseller and publisher and his mother, Emma Thomson, came from a family who owned a cotton spinning company. At the age of 14, J.J., as he came to be known, enrolled at Owens College in Manchester (which later became the University of Manchester). At Owens, J.J. studied engineering, mathematics, physics and chemistry. During his second year, when he was 16 years old, J.J.ís father died.

In 1876, Thomson was awarded an entrance scholarship to Trinity College in Cambridge, England and in 1880 he completed his degree, finishing second in his class. After graduation, Thomson stayed in Cambridge and was made a Fellow of Trinity. During this time, J.J. concentrated on studies in physics, and began experimental work at the Cavendish Laboratory under Lord Rayleigh. Thomson entered physics at an important point in its history. Following the great discoveries of the 19th century in electricity, magnetism, and thermodynamics, many physicists believed that their science was complete and would yield no new great discoveries. A year later, Thomson published his first major paper in the Philosophical Magazine showing that an electrified sphere, by acting as a current when it moves, would have an extra mass as a result of its charge. This work was the first hint of a connection between mass and energy.

Thomson's achievements were recognized by his peers early on, an in 1884 he was elected a fellow of the Royal Society of London and appointed to the chair of physics at the Cavendish Laboratory. On January 22, 1890 J.J. Thomson married Rose Paget. Rose was a researcher at the Cavendish lab and among the first generation of women permitted into advanced studies at the University. J.J. and Rose had two children: George Paget Thomson became a prominent physicist himself and was later awarded the Nobel Prize (1937) for proving that the electron was in fact a wave, and Joan Paget Thomson often accompanied her father in his travels.

Joseph John Thomson

Thomson's most important line of work helped to smash Daltonís theory that atoms resembled tiny billiard balls. Thomson conducted experiments with a newly discovered scientific oddity, the cathode ray tube (now familiar to most people because of cathode ray TV and computer screens). Thomson observed that cathode rays, a strange stream of particles that appeared to fly across a vacuum tube when an electric current was introduced across it, would bend in the presence of a magnetic field. Thomson realized that these strange particles, which he called corpuscles, had a negative electrical charge and were much less massive than the atoms from which they came. This discovery showed that atoms were not solid billiard balls, but were made up of equally charged positive and negative components. The discovery of J.J.ís corpuscles, now called electrons, caused a sensation in scientific circles in 1897 and eventually resulted in his being awarded a Nobel Prize (1906). Thomsonís discovery would also lead one of his students, Ernest Rutherford, to redefine the atomic model.

In 1918, Thomson became Master of Trinity College, Cambridge, where he remained until his death. J.J. Thomson died on August 30, 1940 and is buried in Westminster Abbey, close to Isaac Newton.

For more information on the work of J.J. Thomson, visit our module titled Atomic Theory I: The Early Days.

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