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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Bearded reedlings in Flevoland
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Bear Hole Brook, Catskill Mountains, New York
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A misty morning in Brazil
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Sunbeams across Tartu County, Estonia
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First day of autumn
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Celebrating the UN’s International Day of Families
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Ring-tailed lemur
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Daintree Rainforest and Noah Beach, Queensland, Australia
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The Guggenheim turns 60
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International Womens Day
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Penguin Awareness Day
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Shhh, the movie is about to start
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A view from the top
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Summer solstice
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Happy Thanksgiving
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Feeling crabby?
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20 years later
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Walton Lighthouse, Santa Cruz, California
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National Take a Hike Day
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Groundhog Day
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Mildred B. Cooper Memorial Chapel in Arkansas
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Málaga, Spain
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Clouds over the River of Grass
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Patriot Day
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Winter Olympics in Beijing
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Patriot Day
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Fiordland National Park, New Zealand
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Belgium celebrates its independence
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Bridge to infinity
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Happy Mothers Day!
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