约瑟夫·拉莫尔1857—1942

Sir Joseph Larmor (11 July 1857 – 19 May 1942) was an Irish mathematician, theoretical physicist, and British politician who made breakthroughs in the understanding of electricity, dynamics, thermodynamics, and the electron theory of matter. His most influential work was Aether and Matter, a theoretical physics book published in 1900.

Biography

Joseph Larmor was born on 11 July 1857 in Magheragall, County Antrim, the son of Hugh Larmor, a Belfast shopkeeper and his wife, Anna Wright. The family moved back to Belfast, where he was educated at the Royal Belfast Academical Institution, and then studied mathematics and experimental science at Queen's College, Belfast (B.A., 1874; M.A., 1875), where one of his teachers was John Purser. He subsequently studied at St John's College, Cambridge, where in 1880 he was Senior Wrangler (J. J. Thomson was second wrangler that year) and Smith's Prizeman, getting his M.A. in 1883.

After teaching physics for five years at Queen's College, Galway, Larmor accepted a lectureship in mathematics at Cambridge in 1885. In 1903, he was appointed Lucasian Professor of Mathematics, a position he held until his retirement in 1932. He never married. He was knighted by King Edward VII in 1909.

Motivated by his strong opposition to Home Rule for Ireland, in February 1911 Larmor ran for and was elected a Member of Parliament for Cambridge University with the Conservative party. He remained in parliament until the 1922 general election, at which point the Irish question had been settled. Upon his retirement from Cambridge in 1932, Larmor moved back to County Down in Northern Ireland.

Larmor was a plenary speaker in 1920 at the International Congress of Mathematicians (ICM) in Strasbourg. He also was an invited speaker at the ICM in 1924 in Toronto and in 1928 in Bologna.

Larmor died in Holywood, County Down on 19 May 1942 at the age of 84.

Research

Larmor proposed that the aether could be represented as a homogeneous fluid medium which was perfectly incompressible and elastic. Larmor believed the aether was separate from matter. He united Lord Kelvin's model of spinning gyrostats (see Vortex theory of the atom) with this theory. Larmor held that matter consisted of particles moving in the aether. Larmor believed the source of electric charge was a particle (which as early as 1894 he was referring to as the electron). Larmor held that the flow of charged particles constitutes the current of conduction (but was not part of the atom). Larmor calculated the rate of energy (radiation) from an accelerating electron. Larmor explained the splitting of the spectral lines in a magnetic field by the oscillation of electrons.

Larmor also created the first solar system model of the atom in 1897. He also postulated the proton, calling it a "positive electron". He said the destruction of this type of atom making up matter "is an occurrence of infinitely small probability".

In 1919, Larmor proposed sunspots are self-regenerative dynamo action on the Sun's surface.

Quotes from one of Larmor's voluminous work include:

"while atoms of matter are in whole or in part aggregations of electrons in stable orbital motion. In particular, this scheme provides a consistent foundation for the electrodynamic laws, and agrees with the actual relations between radiation and moving matter".

"A formula for optical dispersion was obtained in § 11 of the second part of this memoir, on the simple hypothesis that the electric polarization of the molecules vibrated as a whole in unison with the electric field of the radiation".

“…that of the transmission of radiation across a medium permeated by molecules, each consisting of a system of electrons in steady orbital motion, and each capable of free oscillations about the steady state of motion with definite free periods analogous to those of the planetary inequalities of the Solar System;”

“'A' will be a positive electron in the medium, and 'B' will be the complementary negative one...We shall thus have created two permanent conjugate electrons A and B; each of them can be moved about through the medium, but they will both persist until they are destroyed by an extraneous process the reverse of that by which they are formed".

Discovery of Lorentz transformation

Parallel to the development of Lorentz ether theory, Larmor published an approximation to the Lorentz transformations in the Philosophical Transactions of the Royal Society in 1897,