Eratosthenes of Cyrene (276195 BC) was a Greek scholar who lived and worked in Cyrene and Alexandria.

Question:

Eratosthenes of Cyrene (276–195 BC) was a Greek scholar who lived and worked in Cyrene and Alexandria. One day while visiting in Syene he noticed that the Sun’s rays shone directly down a well. On this date 1 year later, in Alexandria, which is 500 miles due north of Syene he measured the angle of the Sun to be about 7.2 degrees. See the figure. Use this information to approximate the radius and circumference of Earth.

7.2° Alexandria 500 miles Syene