Greetings from iainthepict. This blog of mine is meant to be like a 'Book of Days' or a kind of 'Scottish Year Book' if you will. The idea was to present an event for each day of the year. Somewhere in here, you can find out what happened, affecting Scotland and the Scots, on any given day of the year. Your comments and observations are very welcome.
The photograph is by Sam Perkins (check him out on Facebook at Sam Perkins Photography) and was taken near Oban.

Tuesday, 14 February 2012

Charles Thomson Rees Wilson

Charles Thomson Rees Wilson, physicist and joint Nobel prize winner in 1927, with Arthur Holly Compton, was born on the 14th of February, 1869.

Physicist, Charles Thomson Rees Wilson, known to his friend and colleagues as C. T. R., won the Nobel Prize in Physics, in 1927. Wilson won the Nobel Prize “ for his method of making the paths of electrically charged particles visible by condensation of vapour,” although he shared the 1927 Prize money with Arthur Holly Compton, who had made use of Wilson's discovery to gain his share “for his discovery of the effect named after him.” Wilson wasn't left out in the naming stakes, though as he had the cloud chamber named after him. According to Ernest Rutherford, winner of the 1908 Nobel Prize for Chemistry, the Wilson Cloud Chamber was “the most original and wonderful instrument in scientific history.” Wilson's chamber remained the standard device for almost twenty years and led on to Donald A. Glaser's 1952 development of the 'bubble chamber'. These days, the cloud chamber has been replaced by instruments such as tracking chambers, sampling calorimeters, and scintillators.

The Wilson Cloud Chamber was a wonderful device that made the paths of electrically charged subatomic particles visible for the first time. Wilson's breakthrough allowed scientists to study those particles and so the cloud chamber became an absolutely indispensable aid to research. Wilson made atomic particles photographable, by condensing water droplets on the ions that were produced along the paths described by the particles. Wilson's 1911 series of photographs of electrons and individual particles, the tracks of which he described, according to 'Les Prix Nobel', as “little wisps and threads of clouds,” became famous, long before his Nobel Prize win. Wilson's remarkable visual evidence proved the existence of subatomic particles, and substantiated theories of nuclear phenomena. With the addition of a magnetic field, different particles became distinguishable by the curvature of their tracks.

The Wilson Cloud Chamber, which he had perfected by 1923, became indispensable in the study of nuclear physics and was widely used in the study of radioactivity, X-rays, cosmic rays, and other nuclear or particle phenomena. Many important achievements are credited to its use in scientific experimentation. One of those, which led to Compton's Nobel Prize, was the demonstration of the existence of recoil electrons, thus proving the 'Compton Effect', which occurs in x-ray scattering, where the momentum of the quantum of radiation is taken up by the recoil electron. Wilson's cloud chamber was also used by Anderson, which gained him the 1936 Nobel Prize for his discovery of the positron.

Not satisfied by his early achievements, in 1916, Wilson became involved in the study of thunderstorms and lightning, and he put that to good use when he  devised a method of protecting British wartime barrage balloons from lightning. Later, in 1956, he published a theory of atmospheric electricity. Wilson also created a new form of electroscope, with which he was able to measure the electric field in the atmosphere. That new device of Wilson's had a sensitivity 100 times greater than anything previously available. Apart from his eponymous chamber, he also had the Wilson Condensation Cloud formations, those that occur after a nuclear detonation, named after him.

Charles Thomson Rees Wilson was born in the farmhouse of Crosshouse, by Glencorse, near Edinburgh, on the 14th of February, 1869. His father, a farmer, died when wee Charlie was only four, whereupon the family moved to Manchester. The farmer's boy was then able to go to a private school, before heading off to become a biology undergraduate at Owen's College, now part of  the University of Manchester. He received his bachelor's degree in 1887 and the following year, Wilson went to Cambridge with an entrance scholarship.

At Sidney Sussex College, Wilson realised his vocation wasn't biology and medicine, but physics and chemistry; and the world of science can be thankful for that. Perhaps it can be thankful also to the influence of another Scot, Balfour Stewart, who held the Chair of Physics. Wilson gained his physics degree in 1892 and, after that, he was engaged in research at the Cavendish Laboratory, under the direction of Sir Joseph John Thomson, the British physicist to whom the electron is eternally grateful. Due to the legacy of yet another Scot, James Clerk Maxwell, Wilson was granted the eponymous Student title, which enabled him to devote three further years to research. So it was that during that time, from about 1894, Wilson did a large part of his research into ionizing particles.

The story goes that Wilson developed his hypothesis when he was climbing on Ben Nevis in 1894 and observed coronas produced by sunlight on mist. Now Ben Nevis isn't that high, so there's no overly rarefied atmosphere and we can rule out hallucinations. So it was that, as early as 1896, Wilson's primitive air expansion chamber was assembled. Using Röntgen's newly discovered X-rays to charge the subatomic particles in the air, he found that, when the moist air was then expanded and thus cooled, it became supersaturated and the moisture condensed around the charged ions to produce a vapour cloud of water droplets. A key aspect was dust free air, because every scientist up to then had thought that the water droplets formed around dust, rather than subatomic, particles.

However, his employment effectively deferred his ability to spend a great deal of time on his cloud chamber until 1910. Between 1900 and 1919, Wilson was a University Lecturer at Sidney Sussex, where he was in charge of the advanced teaching of practical physics at the Cavendish Laboratory. During that time, he was also employed for a year by the Meteorological Council to do research. In 1913, Wilson was appointed Observer in Meteorological Physics at the Solar Physics Observatory. In 1918, Wilson was appointed Reader in Electrical Meteorology and, in 1925, he was appointed Jacksonian Professor of Natural Philosophy (i.e., Physics) at Cambridge.

When he retired, in 1934, Wilson went home to Scotland and, when he was eighty, he moved to Carlops, near Edinburgh. But he hadn't really retired as it was there that he completed his theory of atmospheric electricity, submitting the manuscript to the Royal Society in August, 1956, when he was eighty-seven. Charles Thomson Rees Wilson died on the 15th of November, 1959.

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