Earth's rotation Foucault in 1851, which consisted of a lead-filled brass sphere suspended from the top of the Panthéon in Paris. Because of the Earth's rotation under the swinging pendulum, the pendulum's plane of oscillation appears to rotate at a rate depending on latitude. At the latitude of Paris the predicted and observed shift was about clockwise per hour. Foucault pendulums now swing in museums around the world. Earth's rotation period relative to the Sun (solar noon to solar noon) is its "true solar day" or "apparent solar day". It depends on the Earth's orbital motion and is thus affected by changes
Foucault pendulum vector diagrams determines when the Earth's rotation will be observable and only if the "z"-component is not balanced in the same direction on each side. The magnitude of the opposing component is proportional to how long it takes for one full turn of the Earth to be observed in relation to the plane of the pendulum. The length of time is a minimum of one day at the poles, increases from the pole to the equator, and is not visible at the equator (infinitely long). For any two points in the pendulum swing that are equidistant from the center of the swing