Eratosthenes was a Greek mathematician, geographer, poet, and astronomer who lived in the third century BCE. He is best known for accurately calculating the circumference of the Earth using a method involving shadows and geometry. Eratosthenes also made significant contributions to astronomy, geography, and mathematics during his lifetime.
Erastosthes was the first person to attempt to figure out the size of the earth, and although he was not exact, he was very close for his time. He lived in the third Century BC