William Thomson, Baron Kelvin, was born on 26 June 1824 in Belfast, Northern Ireland, the fourth of six children. His father, James Thomson, a textbook writer, taught mathematics, first in Belfast and later as a professor at the University of Glasgow; he taught his sons the most recent mathematics. At the age of 10, William matriculated at the University of Glasgow, where he was introduced to the work of Jean-Baptiste-Joseph Fourier, who was much maligned by British scientists at the time. Thomson was the first to promote the idea that Fourier’s mathematics, although applied solely to the flow of heat, could be used in the study of other forms of energy—whether fluids in motion or electricity flowing through a wire.

William entered Cambridge in 1841 and took a B.A. degree four years later with high honours. After finishing at Cambridge, Thomson went to Paris, where he worked in the laboratory of the physicist and chemist Henri-Victor Regnault to gain practical experimental competence to supplement his theoretical education. The chair of natural philosophy (later called physics) at the University of Glasgow fell vacant in 1846 and following a campaign by his father, William was unanimously elected to it at the age of 22.

Thomson’s scientific work was guided by the conviction that the various theories dealing with matter and energy were converging toward one great, unified theory. He also undertook significant work on electricity and magnetism. Not only did he advance the ideas of others including Faraday, Fourier and Joule, but his own contributions to science helped lay the foundations of modern physics. These included a major role in the development of the second law of thermodynamics; the absolute temperature scale (measured in kelvins); the dynamical theory of heat; the mathematical analysis of electricity and magnetism, including the basic ideas for the electromagnetic theory of light; the geophysical determination of the age of the Earth; and fundamental work in hydrodynamics. His theoretical work on submarine telegraphy and his inventions for use on submarine cables aided Britain in capturing a preeminent place in world communication during the 19th century.

Thomson was said to be entitled to more letters after his name than any other man in the Commonwealth. He received honorary degrees from universities throughout the world and was lauded by engineering societies and scientific organizations. He published more than 600 papers and was granted dozens of patents. He was elected a fellow of the Royal Society in 1851 and served as its president from 1890 to 1895 and was knighted in 1866. He was also the first scientist to be elevated to the peerage when he was created Baron Kelvin of Largs in 1892. He died at his estate in Ayshire, Scotland on 17 December 1907 and was buried in Westminster Abbey, London.