Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Eratosthenes of Cyrene was a Greek mathematician, elegiac poet, athlete, geographer, and astronomer. He made several discoveries and inventions including a system of latitude and longitude. He was the first Greek to calculate the circumference of the earth (with remarkable accuracy), and the tilt of the earth's axis (also with remarkable accuracy); he may also have accurately calculated the distance from the earth to the sun and invented the leap day. He also created a map of the world based on the available geographical knowledge of the era. Eratosthenes was also the founder of scientific chronology; he endeavored to fix the dates of the chief literary and political events from the conquest of Troy. According to the entry ¿¿¿¿¿¿¿¿¿¿¿ in the Suda (¿ 2898), his contemporaries nicknamed him ¿¿¿¿ (beta, the second letter of the Greek alphabet) because he supposedly proved himself to be the second best in the world in almost any field.