Was there a pendulum at the Eiffel Tower?
A giant pendulum was once suspended from the Eiffel Tower to prove the Earth rotates.
In 1889, scientists used the Eiffel Tower's massive height to replicate the famous Foucault pendulum experiment. They hung a heavy lead weight from a long wire on the second floor. As it swung, the pendulum appeared to change direction over several hours. In reality, the pendulum moved in a straight line while the Earth turned beneath it, providing a clear visual demonstration of our planet's rotation.
Nerd Mode
In 1851, French physicist Léon Foucault first demonstrated his namesake pendulum at the Panthéon in Paris. By 1889, the newly completed Eiffel Tower offered a superior platform for such experiments due to its record-breaking height of 300 meters. For the 1889 World's Fair, a pendulum was suspended from the tower's second floor, roughly 115 meters above the ground, to fascinate the public and validate scientific theories.The physics relies on the Coriolis effect and the conservation of angular momentum. A pendulum's plane of oscillation remains fixed in space while the planet rotates underneath it. At the poles, a pendulum would appear to complete a full circle every 24 hours. However, at the latitude of Paris (approximately 48.8 degrees North), the rotation takes about 31.8 hours to appear to complete a full 360-degree circuit.The Eiffel Tower experiment was significant because the length of the wire reduced the frequency of the swings. Longer pendulums have a slower period, which minimizes air resistance and mechanical interference, leading to more precise measurements of the Earth's angular velocity. This specific demonstration helped solidify the tower's reputation as a serious scientific laboratory rather than just an aesthetic monument.
Verified Fact
FP-0009397 · Feb 22, 2026