Fizeau–Foucault apparatus unit. At the time, Foucault was working at the Paris Observatory under Urbain le Verrier. It was le Verrier's belief, based on extensive celestial mechanics calculations, that the consensus value for the speed of light was perhaps 4% too high. Technical limitations prevented Foucault from separating mirrors R and M by more than about 20 meters. Despite this limited path length, Foucault was able to measure the displacement of the slit image (less than 1 mm) with considerable accuracy. In addition, unlike the case with Fizeau's experiment (which required gauging the rotation rate of an adjustable-speed toothed wheel), he could
Foucault pendulum vector diagrams at the equator to zero at the pole even though the angular velocities are all the same. formula_1 = formula_2 = formula_3 The ratio of the surface velocity at two given latitudes is equal to the ratio of the cosine for the two given latitudes. formula_4 = formula_5 = formula_6 The time to observe one full rotation of the Earth in relation to the plane of a swinging pendulum is one day at the poles (the minimum time) and cannot be observed (infinitely long, the maximum time) at the equator. One of the great insights by Léon Foucault is to