Lord Kelvin was a Scottish physicist, engineer, mathematician, and inventor. His name is associated with a number of laws and effects, and most famously the Kelvin or absolute temperature scale. He worked in many fields and was passionate about the unity of science and the importance of a mathematical treatment of it.

Born William Thomson in Belfast on 26 June 1824, where his father James Thomson was a professor of engineering, he moved to Scotland at the age of eight when his father was appointed professor of mathematics at the University of Glasgow. William began attending this for school classes at the age of ten. He studied mathematics, physics, chemistry, and astronomy. He went to Cambridge from 1841, the year of publication of his first paper, which was on Fourier series. He graduated as second wrangler and was elected a fellow of Peterhouse in 1845. He was the first winner of the Smith's Prize.

Then he moved to Paris to work with the influential French scientists working on heat, magnetism, and fluid flow, whose scientific and mathematical approach he had long found congenial to his own thinking. In 1846 Thomson returned to Glasgow to be appointed professor of natural philosophy, with his father's help in getting the post. He held this post until 1899.

In 1848 he proposed his absolute scale of temperature, now named after him, as is the unit it's measured in, the kelvin. In these years he built on Sadi Carnot and Joule's new theory of thermodynamics, and was himself improved upon by Clausius.

It was Joule who persuaded Thomson that heat was dynamic, that is an effect of motion of matter, rather than perhaps a fluid called caloric, an earlier theory. In 1856 he published a paper on the relationship between magnetism and polarized light, as part of an intended unification of all phenomena as motions in a fluid occupying space: not only electricity and magnetism, as Maxwell successfully achieved based on Thomson's work, but also gravitational and chemical effects.

Despite becoming an elder statesman of physics and highly influential, he was not as marvellously correct as Faraday, Maxwell, or Darwin. He is infamous for his dismissal of Darwin's theory because the Earth could not have been anything like old enough for so much evolution to have occurred; this criticism also applied to then-new ideas on geology. Without knowing about radioactivity, he thought of the Earth as a hot body cooling down. When radioactivity did come onto the scene he disagreed with Rutherford's theory of it. Also (thanks, spiregrain) he thought x-rays would turn out to be an elaborate hoax.

Among the devices he invented was one called the mirror galvanometer, and this was instrumental to the success of the trans-Atlantic cable, a project he was one of the main advisers for. It was in this capacity that he was knighted in 1866. He was created Baron Kelvin of Largs in 1892. He was elected a Fellow of the Royal Society of London in 1851, and served three times as president of the Royal Society of Edinburgh: 1873-1878, 1886-1890, and from 1895 until his death, in Netherhall near Largs in Ayrshire on 17 December 1907.


The heading of the BBC site incorrectly spells his name Thompson: I have e-mailed them a correction.

William Thomson, who was not to become Lord Kelvin until 1892, began investigating the age of the earth in the 1840s, but only published articles on the subject after Charles Darwin published The Origin of Species in 1859. Thomson rejected Darwin’s uniformitarianism, believing that his own work on thermodynamics showed that the earth must cool and thus change over time. He also rejected natural selection, which he believed entailed a rejection of design in nature.

Thomson marshaled a number of compelling arguments for a relatively young earth, including one based on the age of the sun and another involving the effect of tides on the earth’s rotation. His most famous, however, involved a direct calculation of the age of the earth’s crust based on the assumption that the earth was once molten and had cooled to its present temperature. Based on the available physical and geological data, Thomson concluded in the 1860s that the earth was probably about 100,000,000 years old, a number that most geologists and biologists found plausible and unproblematic. By 1897, after several intermediate estimates, Kelvin had determined that the earth’s crust was about 24,000,000 years old. His research was cited both by non-Darwinian evolutionists such as Lamarckians and by creationists as evidence that the slow process of natural selection was insufficient to account for the diversity of life.

In part because of his preeminence as a physicist, Kelvin’s geochronological work was highly regarded by other scientists. After the discovery that radioactive elements emit heat, however, scientists began to discuss the possibility that the earth and sun are heated by radioactivity, rather than only by initial heat. Kelvin himself admitted that the discovery of radium should affect calculations concerning the age of the earth, although he did not revise his earlier work.

The introduction of radioactivity to geochronology is illustrative of the degree to which the physics of the early twentieth century constituted a scientific revolution. The idea that matter could continuously emit heat violated the principle of conservation of energy, but in 1905 Albert Einstein’s special theory of relativity claimed that matter could be converted into energy. Kelvin, very much a nineteenth century physicist, publicly rejected relativity.

This is based on a little piece of my too-long-for-E2 college honors thesis, George Frederick Wright and the Harmony of Science and Revelation.

Work Cited

  • Joe D. Burchfield, Lord Kelvin and the Age of the Earth (Chicago: University of Chicago Press, 1990).
  • Stephen Jay Gould, The Structure of Evolutionary Theory (Cambridge, Mass.: Belknap, 2002).
  • A. Hallam, Great Geological Controversies, 2nd edition (Oxford: Oxford University Press, 1989).
  • Sandra Herbert, Charles Darwin, Geologist (Ithaca, N.Y.: Cornell University Press, 2005).

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