| • Science | • People | • Locations | • Timeline |
Foucault's Pendulum in the Panthéon, Paris
A Foucault pendulum, or Foucault's pendulum, named after the French physicist Jean Foucault, was conceived as an experiment to demonstrate the rotation of the Earth and the Coriolis force. It is a tall pendulum free to oscillate in any vertical plane and capable of running for many hours, and was first exhibited in 1851 from the ceiling of the Panthéon in Paris.
At almost any location on Earth -- except the equator -- it can be observed that the plane within which the pendulum swings slowly rotates. At either the North Pole or South Pole, the plane of oscillation of a pendulum rotates once per sidereal day (in essence, the pendulum remains in the same plane while the Earth rotates underneath it, as predicted by Newton's first law of motionNewton's laws of motion are the three scientific laws which Isaac Newton discovered concerning the behaviour of moving bodies. These laws are fundamental to classical mechanics. Newton first published these laws in Philosophiae Naturalis Principia Mathema). At other latitudes, the plane of oscillation of a pendulum rotates with an angular speed proportional to the sine of its latitudeLatitude denoted φ, gives the location of a place on Earth north or south of the Equator. Latitude is an angular measurement ranging from 0° at the Equator to 90° at the poles. Usually, the difference in latitude largely affects the climate and/or wea; thus one at 45° rotates once every 1.4 days and one at 30° every 2 days.