Eratosthenes of Cyrene (Greek Ἐρατοσθένης; c. 276 BC – c. 195 BC) was a Greek mathematician, poet, athlete, geographer and astronomer. He made several discoveries and inventions including a system of latitude and longitude. He was the first Greek to calculate the circumference of the Earth (with remarkable accuracy), and the tilt of the earth's axis (also with remarkable accuracy); he may also have accurately calculated the distance… (More on Eratosthenes)