Eratosthenes of Cyrene (;, ; The Suda states that he was born in the 126th Olympiad, (276–272 BC). Strabo (Geography, i.2.2), though, states that he was a „pupil” of Zeno of Citium (who died 262 BC), which would imply an earlier year-of-birth () since he is unlikely to have studied under him at the young age of 14. However, γνωριμος can also mean „acquaintance”, and the year of Zeno’s death is by no means definite. Cf. Eratosthenes entry in the Dictionary of Scientific Biography was a Greek mathematician, geographer, poet, astronomer, and music theorist. He was a man of learning, becoming the chief librarian at the Library of Alexandria. He invented the discipline of geography, including the terminology used today. He is best known for being the first person to calculate the circumference of the Earth, which he did by applying a measuring system using stadia, which was a standard unit of measure during that time period. His calculation was remarkably accurate. He was also the first to calculate the tilt of the Earth’s axis (again with remarkable accuracy). Additionally, he may have accurately calculated the distance from the Earth to the Sun and invented the leap day. He created the first map of the world incorporating parallels and meridians, based on the available geographical knowledge of the era. 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. In number theory, he introduced the sieve of Eratosthenes, an efficient method of identifying prime numbers. He was a figure of influence who declined to specialize in only one field. According to an entry in the Suda (a 10th-century reference), his critics scorned him, calling him Beta, from 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.

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