Consummate Greek scholar whose status as second best in each field earned him the nickname "Beta." He served as librarian at the great library in Alexandria, and wrote works of mathematics, geography, philosophy, and astronomy. He also wrote a poem called Hermes which described the fundamentals of astronomy in verse! Although most of Eratosthenes' writings are lost, many are preserved through the writings of commentators.

Among Eratosthenes' accomplishments was the accurate measurement the diameter of the Earth by observing that, on the day of the summer solstice, the Sun was directly overhead in Syene while it was 7° from the zenith in Alexandria, which he assumed was due north of Syene (Dunham 1990). Unfortunately, since the original work On the Measurement of the Earth was lost, the details of Eratosthenes' procedure are not known. Eratosthenes also determined the obliquity of the ecliptic, prepared a star map containing 675 stars, suggested that a leap day be added every fourth year, tried to construct an accurately-dated history, and developed the "sieve of Eratosthenes " method of finding prime numbers. At the age of 80, blind and weary, he died of voluntary starvation.

Additional biographies: MacTutor (St. Andrews), Bonn, Greek and Roman Science and Technology