1 article for "Eratosthenes"

**Eratosthenes**[Astro*Index]

(BC276-196) Born at Cyrene (Shahat, Libya), died at Alexandria.

An Alexandrian Greek mathematician, astronomer, and geographer. Appointed by Ptolemy III to take charge of the Library of Alexandria, and to serve as tutor for Ptolemy's son. Among the first to use trigonometry, he accurately measured the circumference of the Earth. He devised a method for finding prime numbers that is called the "sieve of Eratosthenes." He suggested inserting an extra day each four years to force the Egyptian solar calendar into alignment with the seasons. He attempted a method of accurate dating, starting with the Trojan war. His map of the known world (from the Caspian Sea to Ethiopia, and from Ceylon to the British Isles) was better than any before his time. He determined the Obliquity of the Ecliptic. His star map contained 675 stars. At 80, he died of voluntary starvation.

See also: ♦ Earth, Size of

Astro*Index Copyright © 1997 Michael Erlewine