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 velocity that is imparted to the pendulum bob in comparison to the angular velocity of the Earth. The statements above are thus equivalent to the inverse sine law for the observed time for a full rotation of the pendulum in relation to the rotation of the Earth. There is only one point of connection to the Earth for the swinging pendulum and that point of connection doesn't move in relation to the Earth. To approach the Pendulum Sine Law in basic steps: If it is proposed that; Then it follows that, For the 45° North pendulum with longitudinal swing (Figure