George Francis FitzGerald(1851–1901)

George Francis FitzGerald was born at Kill-o'-the-Grange in Monkstown, on the south side of Dublin Bay, on the third of August 1851, the eldest son of the Reverend William FitzGerald, who at the time was a tutor at Trinity College, Dublin and later Bishop of Killaloe and then of Cork. The boy was educated at home by his mother and her sister, and entered Trinity at sixteen in 1867. He took the gold medal in mathematics and in experimental science in his BA examinations of 1871, was elected a Fellow of Trinity in 1877 after a celebrated fellowship examination, and in 1881 succeeded John Robert Leslie as Erasmus Smith's Professor of Natural and Experimental Philosophy at Trinity, the chair he held until his death twenty years later.

The intellectual horizon of his Dublin generation in physics was the work of his predecessor and friend James Clerk Maxwell, whose Treatise on Electricity and Magnetism had appeared in 1873. FitzGerald set himself to extend Maxwell's electromagnetic theory into the experimental questions that the Treatise had left open. His paper of 1883, On a Method of Producing Electromagnetic Disturbances of Comparatively Short Wave-Lengths, set out the principle that an oscillating electric circuit, of the kind that could be built in a laboratory, must radiate electromagnetic waves into the surrounding space at the frequency of its oscillation. It was the theoretical anticipation, four years before the fact, of the experiment by which Heinrich Hertz of Karlsruhe in 1887 first generated and detected radio waves; FitzGerald's later remark that Hertz had been the man whose hand had reached up and plucked the apple from the Maxwellian tree is the standard description of the relation between the two works.

His second great paper, a letter of barely two columns published in the New York journal Science on the seventeenth of May 1889, addressed the embarrassing null result of the Michelson and Morley interferometer experiment of 1887, which had failed to detect the motion of the Earth through the supposed luminiferous ether. FitzGerald proposed that the failure was real, not experimental, and that material bodies in motion through the ether must contract along the direction of motion by a small amount, precisely sufficient to cancel the expected interference shift. Hendrik Lorentz of Leiden arrived independently at the same conclusion in 1892 and again in 1895, with a fuller mathematical apparatus, and the result is known as the Lorentz-FitzGerald contraction.

Einstein, in the foundational paper of June 1905 on the electrodynamics of moving bodies, would re-derive the same contraction as a consequence of his two postulates of special relativity, and would replace the ether-mechanical interpretation FitzGerald had reached for with the kinematic interpretation in which the contraction is a consequence of the relativity of simultaneity. The contraction itself, in the form FitzGerald and Lorentz had given it, stood. It is the first of the famous consequences of special relativity to have been written down.

FitzGerald taught at Trinity through the 1880s and 1890s as the central figure of Irish physics, and corresponded extensively with Heaviside, Lodge, Larmor and the wider Maxwellian circle. He was elected a Fellow of the Royal Society in 1883 and received the Society's Royal Medal in 1899. He died at his house in Dublin on the twenty-second of February 1901, in his fiftieth year, after a long stomach illness, and is buried at Mount Jerome cemetery. The FitzGerald name in modern physics carries the weight of the two-column letter to Science of May 1889 from which the first written intuition of relativistic length contraction descends.