Eratosthenes

Eratosthenes of Cyrene (Greek ; 276 BC - 194 BC) was a Greek mathematician, poet, athlete, geographer and astronomer. His contemporaries nicknamed him "beta" (Greek for "number two") because he supposedly proved himself to be the second in the ancient Mediterranean region in many fields. He is noted for devising a system of latitude and longitude, and for being the first known to have calculated the circumference of the Earth. He also created a map of the world based on the available geographical knowledge of the era.
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Noun
1. Greek mathematician and astronomer who estimated the circumference of the earth and the distances to the moon and sun (276-194 BC)
(hypernym) astronomer, uranologist, stargazer