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 Earth increased by the inverse of the sine of the latitude. In the examples, the pendulums are of great size to aid in the visualization of the pendulum swing in relation to the Earth (shown as blue circles). The pendulum is drawn so that 90 degrees of pendulum arc sweeps out 90 degrees of arc on the surface of the Earth. Views from the side, the front, and above (right, center, left) are provided to aid in the interpretation of the diagrams and arrows are provided to show the direction of the Earth's rotation. The schematic at the bottom of