Foucault Pendulum

A freely swinging pendulum whose plane slowly rotates, the first direct laboratory proof that Earth spins.

Core Principles & Analysis

• Léon Foucault hung a 28-kg bob on a 67-metre wire in the Paris Panthéon in 1851.
• The swing plane precesses at a rate proportional to the sine of the latitude — a full turn per day at the poles, none at the equator.
• It demonstrated Earth’s rotation without a single astronomical observation.

Specifications & Metrics

• YEAR: 1851