Arago, François

(1786-1853)

   astronomer, physicist, political figure

   Born in Estagel, Pyrénées-Orientales, François Arago, through the influence of pierre-simon laplace, was appointed secretary of the Bureau of Longitudes. In 1806, with jean-baptiste BiOT,he measured the arc of the terrestrial meridian in Spain, which, in turn, led to the discovery of the phenomenon of the production of magnetism by rotation and proof of the relationship between the Aurora and variations in terrestrial magnetism. Professor at the École polytechnique, director of the observatory, then of the Bureau of Longitudes, he served as a leftist deputy from 1830 to 1848. A member of the provisional government after the Revolution of February 1848, as minister of war and the navy, he helped to pass the laws abolishing slavery in the colonies. Elected to the Constituent Assembly, member of the executive commission, and deputy to the Legislative Assembly (May 1849), he left political life after the coup d'état of December 2, 1851. Arago's other scientific work covered various fields. A supporter of the undulatory theory of light, he measured, with Biot, the index of reflection of several gases, discovering the rotary and chromatic polarization of light, especially by observing the Aurora. With André-Marie Ampère, he studied electromagnetic phenomena and measured the terrestrial magnetic field to determine planetary diameters. In 1839, he helped in the invention of photography by presenting the work done by Jacques Daguerre before the Academy of Sciences. François Arago was himself named to the Academy of Sciences in 1809.