Eratosthenes of Cyrene
died с 194, Alexandria, EgyptGreek scientific writer, astronomer, and poet.He settled in Alexandria с 255 BC and became director of its great library. He is the first person known to have calculated the Earth's circumference, though the exact length of the units (stadia) he used is uncertain. He also measured the tilt of Earth's axis with great accuracy, compiled a star catalog, worked out a calendar that included leap years, and tried to fix the dates of literary and political events since the siege of Troy.
* * *▪ Greek scientistborn c. 276 BC, Cyrene, Libyadied c. 194, Alexandria, EgyptGreek scientific writer, astronomer, and poet, the first man known to have calculated the Earth's circumference.At Syene (now Aswān), some 800 km (500 miles) southeast of Alexandria in Egypt, the Sun's rays fall vertically at noon at the summer solstice. Eratosthenes noted that at Alexandria, at the same date and time, sunlight fell at an angle of about 7° from the vertical. He correctly assumed the Sun's distance to be very great; its rays therefore are practically parallel when they reach the Earth. Given estimates of the distance between the two cities, he was able to calculate the circumference of the Earth. The exact length of the units (stadia) he used is doubtful, and the accuracy of his result is therefore uncertain; it may have varied by 0.5 to 17 percent from the value accepted by modern astronomers. He also measured the degree of obliquity of the ecliptic (in effect, the tilt of the Earth's axis) with great accuracy and compiled a star catalog. His mathematical work is known principally from the writings of Pappus of Alexandria.After study in Alexandria and Athens, Eratosthenes settled in Alexandria about 255 BC and became director of the great library there. He worked out a calendar that included leap years, and he tried to fix the dates of literary and political events since the siege of Troy. His writings include a poem inspired by astronomy, as well as works on the theatre and on ethics. Eratosthenes was afflicted by blindness in his old age, and he is said to have committed suicide by voluntary starvation.
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ERATOSTHENES OF CYRENE° — (c. 275–194 B.C.E.), polymath, author of Geographica, a first rate geography much used by strabo , who cites his description of Arabia (16:4, 2), commenting upon the occupations of the inhabitants (including the Judeans), soil, flora, water… … Encyclopedia of Judaism
Eratosthenes of Cyrene — (c. 276 bc–194 bc) Greek astronomer Eratosthenes was born in Cyrene, now in Libya, and educated at Athens. He then taught in Alexandria where he became tutor to the son of Ptolemy III and librarian. He was prominent in history, poetry,… … Scientists
Eratosthenes — of Cyrene (Greek polytonic|Ἐρατοσθένης; 276 BC 194 BC) was a Greek mathematician, poet, athlete, geographer and astronomer. He made several discoveries and inventions including a system of latitude and longitude. He was the first person to… … Wikipedia
Eratosthenes — von Kyrene (griechisch Έρατοσθένης ὁ Κυρηναῖος; * zwischen 276 und 273 v. Chr. in Kyrene; † um 194 v. Chr. in Alexandria) war ein außergewöhnlich vielseitiger griechischer Gelehrter in der Blütezeit der hellenistischen… … Deutsch Wikipedia
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Cyrene — • A titular see of Northern Africa Catholic Encyclopedia. Kevin Knight. 2006. Cyrene Cyrene † … Catholic encyclopedia
Eratosthenes — Eratosthenes, geb. 276 zu Cyrene, universeller Gelehrter, vorzüglich um die Geographie, Mathematik, Astronomie u. Chronologie verdient, st. 194 v. Chr. den Hungertod, weil ihm allmälige Erblindung das Leben verleidete. Vollständige Ausgabe des… … Herders Conversations-Lexikon
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Cyrene — /suy ree nee/, n. an ancient Greek city and colony in N Africa, in Cyrenaica. * * * Ancient city, North Africa. Located in modern day Libya, it was founded с 630 BC by a group of emigrants from the Aegean island of Thíra. Their leader, Battus,… … Universalium
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