Definitions for "Foucault"
Foucault is a small lunar impact crater that lies along the southern edge of Mare Frigoris, to the southeast of Harpalus crater. In the rugged terrain to the south of Foucault is Sharp crater. The outer perimeter of Foucault forms a somewhat irregular circle, with slight outward bulges to the south and northeast.
French physicist who determined the speed of light and showed that it travels slower in water than in air; invented the Foucault pendulum and the gyroscope (1819-1868)