Arago, Dominique François

Dominique François Arago (26.02.1786 - 2.X 1853) was a French scientist and politician and a member of the Paris Academy of Sciences (1809), from 1830 its permanent secretary. He was born in Estagel. He studied at the École Polytechnique (Paris), where he was professor in 1809—30, and in 1813—46 also at the Paris Observatory. In 1830—48 he was a member of the Chamber of Deputies. His work was in the field of astronomy, physics, mathematics and meteorology. He was the author of many discoveries in optics and electromagnetism. In 1811 he discovered the chromatic polarisation of light (independently of J. Biot and D. Brewster) and was the first to observe the rotation of the plane of polarisation of light in quartz. He detected the partial polarisation of light on reflection and refraction. He defended the wave theory of light. In 1820 he found that iron filings become magnetised near a conductor carrying an electric current, and in 1824 the action of a rotating metal plate on a magnetic needle (the so-called magnetism of rotation). He established the connection between the polar aurorae and magnetic storms. Together with Biot he measured the refractive index of various gases (1806), and with P. Dulong the pressure of vapour (1830). He was the author of many popular-science works, which were translated into other languages more than once, in particular into Russian. He had a considerable influence on French science. It was on his instructions that the French physicists A. Fizeau and J. Foucault measured the speed of light experimentally, and that the French astronomer U. Le Verrier discovered the planet Neptune theoretically. Foreign member of the St Petersburg Academy of Sciences (1829). The Copley Medal (1825).