<P> Eratosthenes was the founder of scientific chronology; he endeavored to revise the dates of the chief literary and political events from the conquest of Troy . Eratosthenes dated The Sack of Troy to 1183 BC . In number theory, he introduced the sieve of Eratosthenes, an efficient method of identifying prime numbers . </P> <P> He was a figure of influence in many fields . According to an entry in the Suda (a 10th - century reference), his critics scorned him, calling him Beta (the second letter of the Greek alphabet) because he always came in second in all his endeavors . Nonetheless, his devotees nicknamed him Pentathlos after the Olympians who were well rounded competitors, for he had proven himself to be knowledgeable in every area of learning . Eratosthenes yearned to understand the complexities of the entire world . </P> <P> The son of Aglaos, Eratosthenes was born in 276 BC in Cyrene . Now part of modern - day Libya, Cyrene had been founded by Greeks centuries earlier and became the capital of Pentapolis (North Africa), a country of five cities: Cyrene, Arsinoe, Berenice, Ptolemias, and Apollonia, Cyrenaica . Alexander the Great conquered Cyrene in 332 BC, and following his death in 323 BC, its rule was given to one of his generals, Ptolemy I Soter, the founder of the Ptolemaic Kingdom . Under Ptolemaic rule the economy prospered, based largely on the export of horses and silphium, a plant used for rich seasoning and medicine . Cyrene became a place of cultivation, where knowledge blossomed . Like any young Greek, Eratosthenes would have studied in the local gymnasium, where he would have learned physical skills and social discourse as well as reading, writing, arithmetic, poetry, and music . </P> <P> Eratosthenes went to Athens to further his studies . There he was taught Stoicism by its founder, Zeno of Citium, in philosophical lectures on living a virtuous life . He then studied under Aristo of Chios, who led a more cynical school of philosophy . He also studied under the head of the Platonic Academy, who was Arcesilaus of Pitane . His interest in Plato led him to write his very first work at a scholarly level, Platonikos, inquiring into the mathematical foundation of Plato's philosophies . Eratosthenes was a man of many perspectives and investigated the art of poetry under Callimachus . He was a talented and imaginative poet . He wrote poems: one in hexameters called Hermes, illustrating the god's life history; and another, in elegiacs called Erigone, describing the suicide of the Athenian maiden Erigone (daughter of Icarius). He wrote Chronographies, a text that scientifically depicted dates of importance, beginning with the Trojan War . This work was highly esteemed for its accuracy . George Syncellus was later able to preserve from Chronographies a list of 38 kings of the Egyptian Thebes . Eratosthenes also wrote Olympic Victors, a chronology of the winners of the Olympic Games . It is not known when he wrote his works, but they highlighted his abilities . </P>

When was the circumference of the earth first calculated