What is a Foucault pendulum?

A Foucault pendulum is a simple pendulum suspended from a long wire, allowing its plane of oscillation to rotate freely. First demonstrated by Léon Foucault in 1851 at the Panthéon in Paris, it provides visible proof of Earth's rotation. The pendulum's swing appears to rotate clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere.

How does the Foucault pendulum prove Earth's rotation?

The pendulum swings in a fixed plane relative to the stars due to inertia. However, because Earth rotates beneath it, the pendulum appears to rotate when viewed from the ground. The rate of rotation depends on latitude: at the North or South Pole, the plane completes one rotation every 24 hours. At the equator, there is no apparent rotation.

What is the Coriolis effect?

The Coriolis effect is an apparent deflection of moving objects when viewed from a rotating reference frame like Earth. It affects weather systems, ocean currents, and long-range projectiles. For a Foucault pendulum, the Coriolis force causes the oscillation plane to rotate relative to the ground at a rate proportional to sin(latitude).

Why does latitude affect the rotation rate?

The rotation rate is proportional to the sine of the latitude. At the poles (90°), sin(90°)=1, giving maximum rotation — one full rotation per day. At the equator (0°), sin(0°)=0, so there is no rotation. At 45° latitude, the period is about 34 hours. This geometric relationship reflects how Earth's rotation affects objects at different latitudes.

Home▸Physics & Mechanics▸Foucault Pendulum Simulator - Earth Rotation, Coriolis Effect and Precession

🧪 Foucault Pendulum Simulator - Earth Rotation, Coriolis Effect and Precession

Simulate Leon Foucault's classic pendulum demonstrating Earth's rotation. Observe the Coriolis effect and sidereal day precession at different latitudes - a beautiful demonstration of non-inertial reference frames.

Physics & Mechanics2DModerate60 FPS

⚙ Under the hood

This simulation demonstrates the Foucault pendulum's behavior, illustrating the effects of Earth rotation, the Coriolis effect, and precession. It provides a visual representation of these complex phenomena.

Foucault PendulumCoriolis EffectPrecession

2D · HTML5 Canvas 2D · 60 FPS target · runs fully client-side, no install