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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An impactful day
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Tibetan New Year
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An aviation celebration
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Singing praises of the oceans
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We have liftoff!
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Dunluce Castle, County Antrim, Northern Ireland
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Honoring our fallen heroes
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World Jellyfish Day
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Merry Christmas!
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Too awesome to be a planet
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Combating extinction with citizen science
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Mount Sopris, Colorado
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African bush elephants in Namibia
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Lionfish off the coast of Indonesia
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All is silent for Big Ben’s musical milestone
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On this shore, history was made
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Vila Franca Islet, São Miguel Island, Azores, Portugal
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An historic forest
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Freshwater plants in Aquário Natural, Brazil
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Johnston Canyon in Banff National Park, Alberta, Canada
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The lemurs of Madagascar
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Festivus
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International Museum Day
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National Pearl Harbor Remembrance Day
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What the hay?
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What are these creatures?
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The Spirit of Harlem by Louis Delsarte
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New Year s Day
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Cappadocia, Türkiye
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Ubud, Bali, Indonesia
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