Mathematician Eratosthenes and the circumference of the Earth
The Greek scholar Eratosthenes of Cyrene was the author of many works on mathematics, astronomy, geodesy, cartography, and philosophy. He also calculated the Earth's circumference with near-perfect accuracy.
How did the ancient Greeks know the Earth was round? The mathematician Eratosthenes proved this in a fairly simple way back in the 3rd century BC.
