Foucault pendulum facts for kids
The Foucault pendulum is a special science experiment. It was created by a French scientist named Léon Foucault. He invented it to show us something amazing: that the Earth is always spinning!
Imagine a very long string with a heavy ball at the end, swinging back and forth. The Foucault pendulum uses this idea to prove that our planet is constantly rotating.
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How Does a Foucault Pendulum Work?
A Foucault pendulum is usually a very long wire with a heavy weight, called a bob, at the end. It swings freely from a high ceiling.
The Basic Idea
When a pendulum swings, it usually keeps swinging in the same direction. Think of it like a swing set: it goes forward and backward in the same line. The Foucault pendulum is special because its swing plane (the direction it swings) stays fixed in space.
Why It Shows Earth's Spin
The clever part is that while the pendulum's swing plane stays fixed, the Earth underneath it is constantly rotating. So, from our point of view on Earth, it looks like the pendulum's swing is slowly turning. This turning is actually the Earth moving beneath the pendulum!
- At the North Pole or South Pole, the pendulum's swing plane would make a full circle in about 24 hours. This is because the Earth spins completely under it.
- At the equator, a Foucault pendulum would not appear to turn at all. This is because the Earth's rotation at the equator is parallel to the pendulum's swing.
- In places between the poles and the equator, the pendulum's swing plane turns more slowly. The speed of the turn depends on how far north or south you are.
This simple but powerful experiment was one of the first direct proofs that the Earth spins on its axis.
Where Can You See a Foucault Pendulum?
Many science museums and universities around the world have Foucault pendulums. They are popular exhibits because they clearly show the Earth's rotation.
- One famous Foucault pendulum is in the Panthéon in Paris, France. This is where Léon Foucault first showed his experiment to the public in 1851.
- You can also find them in places like the California Academy of Sciences in the United States and the Musée des Arts et Métiers in Paris.
These pendulums are often very large, with long wires and heavy bobs. This helps them swing for a long time and makes the Earth's rotation easier to see.
Who Was Léon Foucault?
Léon Foucault (1819–1868) was a French physicist. He was known for his work in optics and for inventing the Foucault pendulum. His experiment helped people truly understand that the Earth is always spinning, not standing still.
Images for kids
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A Print of the Foucault Pendulum, 1895
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Animation of a Foucault pendulum on the northern hemisphere. The green trace shows the path of the pendulum bob over the ground.
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A Foucault pendulum at the North Pole: The pendulum swings in the same plane as the Earth rotates beneath it.
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An excerpt from the magazine Le Petit Parisien dated November 2, 1902, on the 50th anniversary of the experiment.
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The animation describes the motion of a Foucault pendulum at a latitude of 30°N.
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The device described by Wheatstone.
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Foucault pendulum at the Musée des Arts et Métiers
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Foucault pendulum at the Ranchi Science Centre
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Foucault pendulum at the California Academy of Sciences
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Foucault pendulum at the Devonshire Dome, University of Derby
See also
In Spanish: Péndulo de Foucault para niños
