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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Northern coast of Colombia
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Are you older than this lake?
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Once upon a midafternoon dreary…
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Lavender fields on the Valensole Plateau in Provence, France
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Gazing down on planet Earth
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Dog days of summer
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National Aviation Day
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Who created the Easter Bunny?
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A learning garden
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A timeless view of the night sky
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All is silent for Big Ben’s musical milestone
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We have liftoff!
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Jasper National Park, Alberta, Canada
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Aït Benhaddou, Morocco
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Coming home to roost
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National Park Week: Olympic National Park, Washington
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Dance of the egret
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Celebrating National Park Week, April 21-29
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Museum Mile Festival
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Caribou on the move
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A throng of ice and spires
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National Bison Day
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Patriot Day
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Bournemouth beach huts
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It s Independence Day in Mexico
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A national icon
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Jane’s Carousel delights
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D-Day remembered
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Mountains fit for a queen
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The ruins of Italica, Andalusia, Spain
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