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Wilson, Charles Thomson Rees

cloud chamber cambridge expansion

(1869–1959) British physicist: the inventor of the Wilson cloud chamber.

Wilson left a Scottish sheep farm as a child of 4, and was educated in Manchester, eventually as a biology student there. Then he went to Cambridge, did well in physics and became a teacher in Bradford for 4 years before returning to Cambridge in 1896 and staying there for a long career.

In 1894 he had been attracted by the brilliant cloud effects he observed from the summit of Ben Nevis, and in Cambridge he examined methods of producing artificial clouds in the laboratory by the sudden expansion of moist air. The expansion drops the temperature of the gas and the water vapour partly condenses as droplets on the walls and on any available nuclei. Wilson showed that if filterable dust is absent, then charged ions (produced eg by X-rays) will serve as nuclei. By 1911 he had devised his cloud chamber, in which the path of an ion is made visible as a track of water droplets. It was soon used to detect and examine the alpha-and beta-particles from radioelements, and it quickly became a favourite device for particle physicists, especially in the 1920s and 1930s. It was also the ancestor of the bubble chamber devised by in the 1950s.

Another of Wilson’s researches also began on Ben Nevis, as a result of his own electrification (his hair stood on end) during a storm in 1895. He studied electrical effects in dry and moist air and he noted that a sensitive, well-insulated electrometer shows slow leakage, by day or night, even underground; he concluded that radiation from sources outside the atmosphere might be the cause. In 1911 studied this further, and the discovery of cosmic rays proved that Wilson was right. His interest in atmospheric electricity remained; in his long retirement in Scotland, he flew at age 86 over the Outer Isles to observe thunderstorms, and presented his last paper on this subject, aged 87. He shared the Nobel Prize in 1927 for his cloud chamber.

Wilson, Edward Osborne [next] [back] Wilson, Charles Kemmons - Overview, Personal Life, Career Details, Chronology: Charles Kemmons Wilson, Social and Economic Impact

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