Eratosthenes of Cyrene (Greek Ἐρατοσθένης; 276 BCE - 194 BCE) was a Greek mathematician, poet, athlete, geographer an astronomer. His contemporaries nicknamed him "beta" (Greek for "number two") because he supposedly proved himself to be the second in the ancient Mediterranean region in many fields. He is noted for devising a system of latitude and longitude, and for being the first known person to have calculated the circumference of the Earth. 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.