xxxxxIn 1821, after six years of research, the French physicist Augustin-
xxxxxIt was during Napoleon’s Hundred Days in 1815 that the French physicist Augustin-
xxxxxFresnel was born in Broglie, Normandy, and went to school in Caen. After studying at the École Polytechnique in Paris, he began work as a civil engineer for the government. Once having established the wave theory of light -
xxxxxFresnel was a very private man. During a successful career he was made a member of the French Academy of Sciences and of the Royal Society of London, but the pioneer work he achieved was known only to a small group of scientific colleagues. As a result, he received very little public recognition during his lifetime. One of his closest friends was the French physicist and mathematician André Marie Ampère. He lodged in Ampère’s house during the last five years of his life.
xxxxxIncidentally, a scientist who made a series of discoveries concerning the diffraction and polarization of light was the Scotsman David Brewster (1781-
Fresnel: by the French engraver Ambroise Tardieu (1788-
xxxxxThe French physicist and astronomer François Arago (1786-
xxxxxAs we have seen, the French physicist and astronomer François Arago assisted Augustin-
xxxxxHe was born at Estagel, Roussillon, in southern France, and was educated at nearby Perpigan before studying at the École Polytechnique in Paris. It was here that he met Fresnel. He later returned to the Polytechnique as professor of analytical geometry -
xxxxxArago was interested in a number of branches within science. Apart from optics, he made his greatest contribution in electromagnetism and astronomy. In the first named, he elaborated on the findings of the Danish physicist Hans Christian Oersted, and in 1820 discovered that iron enclosed in a coil of copper wire could be magnetized by the passage of an electric current. Then, four years later, he was the first to observe the phenomenon of the production of magnetism by rotation, using a revolving copper disk to deflect a magnetic needle suspended above it. The disk came to be known as “Arago’s disk” and the experiment itself as “Arago’s wheel” (illustrated here and below).
xxxxxHis research in astronomy included the measurement of the diameters of the planets, and the theory that the twinkling of stars was caused by light interference. He also figured in a dispute over who first discovered the location of Neptune, and it was doubtless because of his involvement in this that one of the planet’s rings was later named after him. Among his other investigations was a study of the properties of gases, the speed of sound, and the different types of lightning.
xxxxxAnd quite apart from his own research, Arago played a significant part in assisting in the work of other scientists other than Fresnel. As we have seen, he collaborated with the French scientist André Ampère in experimenting with the relationship between magnets and electric currents. Their joint research was later to assist in the discovery of electromagnetic induction, made by the English physicist Michael Faraday in 1831, and leading to the first electric generator. And, later, he played a prominent role in funding and promoting the photographic process developed by the French physicist Louis-
xxxxxIn addition to his scientific work, Arago was also active in politics in the latter part of his life. A staunch republican and social reformer, after the revolution of 1848 he was elected a minister in the provisional government, and it was under his administration that slavery was outlawed in all French colonies. He ended his political career as deputy for his home region, the Pyrénées Orientales, holding office until the year before his death.