In 1851, when French physicist Léon Foucault performed his pendulum experiment in Paris, he became the first to prove what many scientists of his day already suspected—that the Earth spins on an axis. He conducted his first experiments 170 years ago, in early January 1851, with a relatively small prototype in the cellar of his home. Just a month later, Foucault performed his most famous pendulum demonstration, using a 62-pound spherical weight attached to a 220-foot wire, which was hung from the dome of the Panthéon, a Parisian monument. As the pendulum swung back and forth in a fixed plane, the pointed end of the weight traced lines in a compass-like circle of sand below it. As time passed, the angle of these lines began to change, demonstrating to onlookers that the Earth itself was rotating underneath the pendulum, and by extension, everyone watching was rotating as well, spinning on the surface of the great blue marble around its axis.
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Today in History
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Kochia, Hitachi, Ibaraki prefecture, Japan
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’Chess on ice’
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Take a break! It s Labor Day!
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National Garden Week
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Mount Fuji Day
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Let s crack the code
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Lace up your hiking boots for Mountain Day
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Does this chameleon look a little insecure?
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World Environment Day
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Row, row, row your gondola
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Lands End, Cornwall, England
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Celebrating women in science
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What, no escalator?
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Remembering the Velvet Revolution
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National Frog Month
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Saint Nicholas Day in Verbier, Switzerland
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Happy World Meteorological Day
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Avalanche Lake Trail at Adirondack High Peaks, New York
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International Lighthouse Weekend
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Lake Tekapo, New Zealand
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Atop the roof of Africa
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Old man s whiskers growing wild
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Anniversary of Pinnacles National Park, California
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National Park Week continues
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Acadia transformed
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Jackie Robinson Day
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Seasonal lights dazzle in Japan
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Make your way up a picturesque passageway of Chefchaouen
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Where the wildflowers grow
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Bidding summer adieu
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