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Thomson, William, 1st Baron Kelvin (of Largs)

heat theory ideas physics

(1824–1907) British physicist and electrical engineer: a pioneer of thermodynamics and electromagnetic theory; he directed the first successful project for a transatlantic cable telegraph.

Thomson’s father had been a farm labourer who became professor of mathematics at Belfast and from 1832 at Glasgow. Two of his children became distinguished physicists and another did well in medicine. Young William studied science in Glasgow from the age of 10, and later was sent to Cambridge. He graduated when he was 21 and went to Paris to work on heat with , returning the next year to become professor of natural philosophy (ie physics) at Glasgow. He held the job for 53 years.

While still an undergraduate he gave a mathematical demonstration of the analogy between the transmission of electrostatic force and heat flow in a uniform solid ( later brought this into his full theory of electromagnetism). Thomson reorganized the theory of magnetism, developing ideas, and introduced the ideas of magnetic susceptibility and permeability, and of the total energy of a magnetic system. Thomson was not only a theoretician but put his knowledge to practical effect, showing that low voltages were better than high ones for the transmission of signals along submarine cables and inventing the mirror galvanometer for the detection of the resulting small currents. He directed work on the first successful transatlantic cable (there had been two previous attempts), which became operational in 1866, bringing him considerable personal wealth. In 1892 he was made a baron, and chose his title from a small river, the Kelvin, passing through the university. He was a major figure in the creation of the Institute of Electrical Engineers. He liked sailing and bought ‘a schooner of 126 × 10 6 g’ (ie 126 t), which prompted him to develop navigational instruments; and his large Glasgow house was among the first to be lit by electricity (in 1881).

As a young man Thomson discovered work, then hardly known, and publicized it; he found that Green’s and his own theorems gave valuable mathematical methods for attacking problems in electricity and in heat.

Thomson did much to develop heat theory. He heard of work when he was in Paris, but it was three years before he secured his paper; he then made its ideas widely known, and used and developed them further. Thomson proposed in 1848 an ‘absolute’ scale of temperature now known as the Kelvin or thermodynamic scale; it is independent of particular substances, but corresponds practically to the scale with 273.16 K as the triple point of water, 0°C. The SI unit of temperature is the kelvin (K). Independently of he formulated the second law of thermodynamics, which states that heat cannot flow spontaneously from a colder to a hotter body. He worked with on the relation of heat and work (the first law of thermodynamics), and also with him found the Joule–Thomson effect. This is the drop in temperature shown by most gases when they emerge from a fine nozzle, as a result of the work done to pull the mutually attracting gas molecules apart, and it is the basis of modern methods for cooling gases for liquefaction. Thomson worked on the theory of the cooling of a hot solid sphere and applied his theory to calculate ages for the Earth and the Sun. He recognized that his method assumed that no continuing heat supply was present: his results were about 10 times lower than present values, which now take into account heat due to radioactivity, which was not discovered until many years after Thomson’s early work.
Thomson was an unusual scientist; his energy, enthusiasm and talent made him dominate British physics in the later 19th-c and he did much to move the focus of physics from Europe to Britain. He was always generous with ideas and in giving credit to others. His productivity was vast; 661 papers, many books and patents, covering the whole of physics (no-one since has ranged so widely) with sundry excursions into other sciences. He had some oddities, of course. He detested vector methods and gave himself much mathematical toil in avoiding them. He did not normally work on one problem for more than a month, and his results were worked out in green pocket books from which he tore sheets for publication. After his first wife died in 1870 he continued to have a great flow of ideas in physics, but he lost the ability to select good ideas from bad, and he pursued some strange notions (like the theory of the ether; and his opposition to the admission of women to Cambridge). He was probably the first scientist to become wealthy through science.

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