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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Summertime in Alaska
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Salmon migration in full swing
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First day of National Park Week
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Happy Halloween!
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Nesting season for the leatherbacks
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Río Negro, Amazon basin, Brazil
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Bay Marker Lookout, Sydney Olympic Park, Australia
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Antarctica Day
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Embracing the cold
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Illuminating Annecy
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Spiegelgracht canal in Amsterdam, Netherlands
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Colle Santa Lucia, Dolomites, Italy
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The Zugspitze: Germany s highest point
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World Migratory Bird Day
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Super sandy Sweet 16
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First Cliff Walk
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What happened to these clouds?
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An island for the birds
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Indigo bunting
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Russell lupines, Lake Tekapo, New Zealand
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Cheers! It’s National Wine Day
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Memorial Day
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Schönbrunn Palace Park, Vienna, Austria
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Sydney Harbour Bridge in Sydney, Australia
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Looking for peace on the precipice
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Spring comes to Glacier National Park
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Looking back on 150 years of rail travel
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Let the games begin
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In the valley of the doll
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Cherry blossoms at East Lake Cherry Blossom Park, Wuhan, China
Bing Wallpaper Gallery

