FitzGerald, GF

FitzGerald, George Francis

ACHIEVEMENT(S): FitzGerald-Lorentz contraction

NICKNAME/ALIAS: None

DATE/PLACE OF BIRTH: 3 August 1851, at Dublin, Ireland

DATE/PLACE/AGE AT DEATH: 22 February 1901, at Dublin, Ireland. Aged 49

DISCIPLINE: Physicist

FIELD: Physics

LANGUAGE: English

PARENTS: William FitzGerald and Anne Frances Stoney

SIBLINGS: One elder and one younger brother (Maurice)

SPOUSE: Harriette Mary Jellett

CHILDREN: Three sons and five daughters

EDUCATION: Private tutors; Trinity College, Dublin, 1867-71

MAJOR WORK: "The Ether and the Earth's Atmosphere", 1889

LIFE AND TIMES: FitzGerald was awarded a fellowship at Trinity College, Dublin, in

1877, and became a tutor in mathematical physics. In 1881 he became professor of natural and experimental philosophy, a post he held until his death in 1901. FitzGerald established the first physics laboratory at Trinity College.

From his studies of radiation, in 1882 FitzGerald predicted that a rapidly oscillating (i.e. alternating) electric current from a Leyden jar should generate electromagnetic waves, a prediction proved correct in 1887 by the German physicist Hertz's* early experiments with "electric waves."

For his work on electromagnetic radiation, FitzGerald was elected a member of the Royal Society* in 1883.

In 1887, FitzGerald read about the American physicists Michelson & Morley and their attempt to detect the motion of the Earth relative to the ‘ether’ - the hypothetical medium permeating all space within which most physicists thought that electromagnetic radiation traveled. Michelson & Morley measured the velocity of light simultaneously in two directions at right-angles to each other, but found no difference in values, so the velocity was unaffected by the Earth's motion through the ether, and the speed of light was the same for all observers, regardless of their relative motion.

This result was disturbing to physicists as it thus challenged one of the central beliefs of classical physics.

In 1889, FitzGerald wrote a letter to the journal 'Science' entitled "The Ether and the Earth's Atmosphere", in which he proposed that the Michelson-Morley result could be accounted for (while preserving the classical concepts of physics) by assuming that all bodies moving through the ether were shortened (along the direction of its motion) relative to an observer. So although light traveling forwards against the ether from a moving body would, in fact, go slower (as expected by classical physics), only an observer outside the system could know this, because the measuring rods would also

contract (making the forward journey of the light shorter) in such a way that the light would appear not to be slower.

FitzGerald discussed his contraction hypothesis with, amongst others, Lodge*, who presented it in a paper to the Physical Society in May 1892. In 1895 the Dutch physicist Lorentz* independently arrived at and considerably developed the same hypothesis, and it became known as the

‘FitzGerald-Lorentz contraction.’

Four years after FitzGerald's death, the contraction hypothesis was incorporated and given a different interpretation in Einstein's* general theory of relativity. (However, Einstein reversed the classical view by proposing that the speed of light is a universal constant, and showing how the FitzGerald-Lorentz contraction then becomes a logical consequence of the relative motion of different observers. Significant at speeds approaching that of light, the contraction is therefore a consequence of the

properties of space and time and does not depend on compression, cooling, or

any similar physical disturbance).

ASSESSMENT: His contraction attempted to resolve the problem of the ether.

EXTRA CONNECTIONS: None

ONELINER: George FitzGerald, of the ‘FitzGerald-Lorentz contraction’

BIBLIOGRAPHY:

DSB, EB, DNB

Biog Dict Phys