Foucault Pendulum

One fairly common sight in university science buildings is a Foucault Pendulum. Here is a short explanation of what this is and does.

The Foucault pendulum (English: /fuːˈkoʊ/ foo-KOH; French pronunciation: ​[fuˈko]) or Foucault's pendulum is a simple device named after French physicist Léon Foucault and conceived as an experiment to demonstrate the Earth's rotation. The pendulum was introduced in 1851 and was the first experiment to give simple, direct evidence of the earth's rotation. Today, Foucault pendulums are popular displays in science museums and universities.

At either the North Pole or South Pole, the plane of oscillation of a pendulum remains fixed relative to the distant masses of the universe while Earth rotates underneath it, taking one sidereal day to complete a rotation. So, relative to Earth, the plane of oscillation of a pendulum at the North Pole – viewed from above – undergoes a full clockwise rotation during one day; a pendulum at the South Pole rotates counterclockwise. 

When a Foucault pendulum is suspended at the equator, the plane of oscillation remains fixed relative to Earth. At other latitudes, the plane of oscillation precesses relative to Earth, but more slowly than at the pole.

See Wikipedia: Foucault pendulum. 

You can see the white pieces that are knocked over as the earth turns.