Eratosthenes (276–194 BC)

Eratosthenes of Cyrene (born in Cyrene 276 BC, died in Alexandria 194 BC) was the first scholar to use the term geography, meaning by that the description of Earth. His studies pertained to geography, astronomy, and mathematics and allowed him to confirm the hypothesis about the round shape of the planet and to measure its size with an extremely good approximation. He was also the first to imagine dividing Earth's surface into portions demarcated by meridians and parallels. With a deep interest in nature, he studied tides and their lunar cycle, and by observing the presence of marine fossils far from the sea, he realized the slow transformation of the coastlines.

The starting point that made Eratosthenes estimate the measurement of Earth's circumference was the observation ...