Around 255 BC Eratosthenes, a Greek mathematician, estimated the circumference of the earth. He discovered that on a certain day, in the city of Syene, one could see the sun's reflection at the bottom of a deep well. At the same time of day, 500 miles (measured along the earth's surface) North at Alexandria, the sun's rays formed an angle, Am of 7.5 degrees with the tower. Using this information, he was able to estimate the circumference of the earth. Explain how this could be done and estimate the circumference of the earth. How does this compare to the recent calculations of the circumference as 24,901.55 miles? (He worked as if the sun's rays were parallel.