Did Neolithic humans build this structure to celebrate Pi Day? Not likely. Pi Day is a relatively recent phenomenon—invented by a physicist in 1988 and designated by Congress a national holiday in 2009. But it"s already almost certainly the most popular holiday celebrating a mathematical constant. While Pi Day is a young tradition, the number π (pi) itself has been a fascination since antiquity, when it was first calculated as the ratio of a circle"s circumference to its diameter.
Pi Day
Today in History
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Frost on autumn leaves
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Amelia Earhart
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Plitvice Lakes National Park in Croatia
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Lighting it up for Vivid Sydney
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Chapel of St. Michel on Lake Serre-Ponçon, Hautes-Alpes, France
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It s a good day to be green
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Longer days mean warmer sand
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Happy International Day of Forests!
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Great Smoky Mountains National Park, Tennessee
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Yungang Grottoes, Shanxi, China
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The Christmas Bird Count begins
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SantaPark, Lapland, Finland
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A splash by the sea
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Mosque-Cathedral of Córdoba, Andalusia, Spain
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Celebrating freedom
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Big sky at Big Bend
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World Migratory Bird Day
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All eyes on sustainability
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World Lion Day
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Arrr! Can you talk like a pirate?
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Diving into World Oceans Day
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Let s get lost
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Listening to the sea
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Sundance Film Festival
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Daylight saving time begins
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Hohenzollern Castle near Stuttgart, Germany
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Manatee Appreciation Day
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Long-eared owl in the Czech Republic
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Constitution Day and Citizenship Day
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Who doesn’t love a ‘Puppy’?
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