This is the coolest thread, Amigo!
Dan - and the Answer:
Eratosthenes was born in 276 BC in a region of northern Africa that is now part of Libya. He studied in Athens, and was the third head librarian of the great library of Alexandria. In addition to calculating the Earth's circumference, Eratosthenes is remembered for his method of finding prime numbers (the Sieve of Eratosthenes), measuring the distance from the Earth to the Sun and the Moon, and numerous, detailed maps of the world as it was known at the time.