Dominique François Arago

French physicist (1786–1853)

Born in Estagel, France, Arago was educated at the Ecole Polytechnique in Paris and then spent some years in Spain, where he accompanied Jean Baptiste Biot on a measurement of an arc of meridian. On his return to Paris in 1809 he was elected to the Académie des Sciences and received the chair of analytical geometry at the Ecole Polytechnique. In 1830 he succeeded J. B. J. Fourier as the permanent secretary of the Ecole Polytechnique. Arago worked in a number of branches of physics.

His first investigations concerned the polarization of light and in 1811 he discovered chromatic polarization. He was a vigorous defender of A. J. Fresnel's wave theory of light against the criticisms of Laplace and Biot, who both supported the corpuscular theory. In 1838 he described an experiment to decide the issue by comparing the speed of light in air with that in a denser medium. Shortly before Arago's death, Léon Foucault and Armand Fizeau proved that the experiment supported the wave theory.

Arago also worked on electromagnetism, showing that a coil of wire carrying a current could act as a magnet. He also found that a rotating copper disk could deflect a magnetic needle suspended above it. (This arrangement, known as Arago's disk, depends on magnetic induction.)

In astronomy, Arago discovered the Sun's chromosphere. He also played a part in the discovery of Neptune by Urbain Leverrier.

Arago was a fierce republican and, from 1830 onward, he was involved in political life as deputy for the Pyrenées Orientales. In 1848 he became a government minister and, among other measures, abolished slavery in the French colonies.

Arago, François (1786-1853), leading French physicist and republican deputy, and a key figure in the public launch of the daguerreotype. Having met Daguerre in 1838, it was he who first introduced the discovery at the Academy of Sciences on 7 January 1839 and, in accordance with his political convictions, skilfully arranged that the French government should acquire the process and make it available to the world. In the 1840s he continued to promote the technique at the Academy.

— Quentin Bajac

Bibliography

• McCauley, A., “‘François Arago and the Politics of the French Invention of Photography’”, in D. P. Younger (ed.), Multiple Views: Logan Grant Essays on Photography (1991)

Arago, François (1786-1853). French scientist, professor, and republican politician. Best known as an astronomer, Arago was elected in 1809 to the Académie des Sciences, for which he composed éloges. He became a member of parliament during the July Monarchy. After the Revolution of February 1848 he entered the government as minister for the Navy. His political career ended when he was defeated in the 1852 elections.

[Ceri Crossley]

Arago, Dominique François (dômēnēk' fräNswä' ärägō') , 1786–1853, French physicist and astronomer. He is noted for his discoveries in magnetism and optics as well as for his astronomical observations. Arago was an ardent supporter of the wave theory of light. In 1811 he invented the polariscope and later developed a polarimeter. His collected works (1854–62) include his well-known Astronomie populaire (4 vol.).