Foucault, Léon

(1819-1868)

   physicist

   Born in Paris, Léon Foucault, with hippolyte fizeau, sought to use photography in astronomic studies (1845), and did research in photometrics and spectroscopy, putting in place a method for measuring the speed of light with the help of turning mirrors, applied in both air and water, confirming in turn augustin fresnel's theory of undulation (1850). Foucault proved the existence of electric currents in conductors placed in variable magnetic fields, a direct consequence of the laws of induction (Foucault's currents). In 1851, in the Panthéon in Paris, he carried out a famous experiment that would prove the rotation of the earth. with a pendulum (Foucault's pendulum) weighing 20 kilograms and suspended from a steel wire 67 meters in length, he demonstrated that its oscillation remained in a fixed plan in relation to a set point. Then, the following year, he invented the gyroscope, an instrument that produced the same result. In 1857, he conceived the idea of replacing the spherical mirror in telescopes with a parabolic one made of silvered glass, eliminating the aberration caused by specificity. Foucault was named to the Academy of Sciences in 1865.