June 19, 240 B.C.: The Earth Is Round, and It’s This Big

Greek astronomer, geographer, mathematician and librarian Eratosthenes calculates the Earth's circumference. His data was rough, but he wasn't far off.

Source: http://www.wired.com/thisdayintech/2012/06/june-19-240-b-c-the-earth-is-round-and-its-this-big/

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