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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Spotted owlet, Bangkok, Thailand
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Let s get lost
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Happy Bee Day to you
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Books for children of all ages
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Keep shining
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International Day of Mangrove Conservation
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International Surfing Day
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Sailing across the ice
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Badlands National Park turns 44
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Let the Highland games begin
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Winter solstice
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Illuminations on the Gulf of Poets
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Christmas Bird Count turns 125
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It’s Opening Day for Major League Baseball
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Flying high on National Bird Day
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Daylight saving time
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The Kelpies statues in Falkirk, Scotland
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Borrego Badlands
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The largest living organism on Earth
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National Park Week: Everglades National Park
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The Vestibule at Diocletian s Palace, Split, Croatia
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A gentle wind fills this sail
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The Bahamas as seen from the ISS
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One giant leap for penguins
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Kochia, Hitachi, Ibaraki prefecture, Japan
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Bear Hole Brook, Catskill Mountains, New York
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Mexican giant cardon cactus
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Tassili n’Ajjer, Sahara, Algeria
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Kirkilai lakes, Biržai Regional Park, Lithuania
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Desert rose of Qatar
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