Kelvin, Lord [William Thomson] (1824-1907)

Lord Kelvin (William Thomson) was a leading nineteenth century physicist, and one of the few scientists at the time to win great wealth from his work. Born in Belfast, the son of a mathematician, his family moved to Glasgow where he joined the University at the age of 11 to study natural philosophy. When he was seventeen, he moved to Cambridge where he studied problems in electromagnetism, comparing the distribution of electrostatic force in a region with the distribution of heat in a solid, work that paved the way for James Clerk Maxwell's explanation of the electromagnetic field. In 1845 he moved to Paris where he gained valuable experimental experience working in the laboratory of Henri Regnault and was introduced to the work of Sadi Carnot on the motive power of heat. From this, Thomson developed the idea of an absolute temperature scale and, after returning to Glasgow, proposed such a scale (1848) setting absolute zero at In 1851 Thomson declared the compatibility of Carnot's theory that heat was a fluid and Joule's mechanical heat theory, as long as it was accepted that heat cannot pass to a hotter body from a colder body (now the second law of thermodynamics), and was amongst the first to recognize the significance of the conservation of energy. Thomson worked with Joule for several years, culminating in the demonstration and explanation of the Joule-Thomson effect (the temperature change of a gas as it expands into a vacuum).

Thomson was well known by the public for his involvement in laying the first successful Atlantic telegraph cable, for which he developed a method of signalling and a sensitive galvanometer. Many of these inventions were patented, bringing him considerable financial rewards. He also had a keen interest in the age of the Earth, which he grossly underestimated using a method based on the Earth's rate of cooling (at the time, this error caused severe embarrassment to Darwin's theory of evolution by natural selection). Towards the end of his life, in the 1890s, he was honoured as the greatest living physicist, and created Baron Kelvin of Largs in 1892. He is buried next to Isaac Newton in Westminster Abbey, and another enduring memorial is the naming after him of the absolute temperature scale.