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Sir Joseph Larmor (1857 - 1942):
Theoretical physicist


Joseph Larmor was born at Magheragall, County Antrim on 11 July 1857. He was educated at the Royal Academical Institution and gained his BA and MA from Queen's College, Belfast. He entered Cambridge University in 1876, gaining a fellowship in 1880. He was Senior Wrangler in that year. He was appointed Professor of Natural Philosophy at Queen's College, Galway, in 1880, but returned to St John's five years later as a lecturer in Mathematics and in 1903 became Lucasian Professor of Mathematics.

Larmor was elected Fellow of the Royal Society in 1892 and became its Secretary, having earlier received the Society's Royal Medal and the Copley Medal. In 1909 he was knighted and was Unionist Member of Parliament for the University of Cambridge from 1911 to 1922. He was given the freedom of the city of Belfast and many honorary degrees.

On retirement in 1932 he moved to Holywood, County Down where he died on 19 May 1942. A lunar crater, on the far side of the moon, has been named after him. His portrait by Frank McKelvey is on display in the Great Hall of Queen's University, Belfast.

Larmor was a great mathematical physicist after the manner of MacCullagh, Hamilton and FitzGerald, the "three Irish giants" in whose steps he walked. His main preoccupation was with electrodynamics, stimulated by the work of James Clerk Maxwell. Over a life that spanned the 19th and 20th centuries, Larmor stood at the threshold of the new physics of relativity and quantum theory but it was a threshold that he never truly crossed. As with others of his era, FitzGerald and Kelvin, J.J.Thomson and Lorentz (of Leiden), the concept of the aether was central to Larmor's thinking. Indeed the word appears in the title of his book Aether and Matter, published in 1900. In reality there was no unique aether but several, Larmor's being one in which the interaction between matter and aether was possible only through electric charges, electrons , seated in the aether.

Aether and Matter is a reiteration of work originally published between 1894/7. In his 1897 paper, Larmor wrote down a set of equations that connect the way in which observers in relative motion see physical events. These equations were later re-stated by Lorentz and tumbled out of Einstein's iconoclastic formulation of relativity in 1905. Tellingly, the equations are known today, not by the name of Larmor, but of Lorentz. Larmor is perpetuated by a theorem, a formula, a frequency and a characteristic length, the Larmor radius, cited day and daily in laboratories round the world, in a branch of physics that has become established only in the years since Larmor's death, on 19 May 1942.



Born: 11 July 1857
Died: 19 May 1942
Patrick Devlin