Final answer:
Eratosthenes was an ancient Greek scholar who significantly advanced geographic knowledge by creating a system of longitude and latitude, and calculating the Earth's circumference with remarkable accuracy using observations of the Sun. His contributions also included heading the Library of Alexandria.
Step-by-step explanation:
Eratosthenes of Cyrene was a prominent Greek scholar who made significant contributions to geography during the Hellenistic period. Living between 276 and 194 B.C.E., he is credited with devising one of the first known systems of longitude and latitude. Moreover, he calculated the Earth's circumference using geometric methods based on observations of the Sun. Although there is some uncertainty regarding the exact length of the stadium, a unit of measurement used by Greeks, Eratosthenes' calculation was remarkably close to the actual size, either within 1% or 20% of the correct value of 40,000 kilometers, depending on which stadium length was applied.
His method involved using the differences in the angle of the Sun's shadow at two different locations, Alexandria and Syene (modern-day Aswan). Through this method, he was able to estimate the Earth's circumference at about 250,000 stadia by observing that the Sun's angle was 1/50th of a circle, or 7.2 degrees, different between these two points. Eratosthenes also served as the head of the famous Library of Alexandria, which housed the cumulative knowledge of the ancient world and laid important foundations for future learning.