Eratosthenes o Cyrene (//; Greek: Ἐρατοσθένης, IPA: [eratostʰénɛːs]; c. 276 BC – c. 195/194 BC) wis a Greek mathematician, geografer, poet, astronomer, an muisic theorist. He wis a man o learin, acomin the chief leebrarian at the Leebrar o Alexandria. He inventit the discipline o geografie, includin the terminology uised the day.
He is best kent for bein the first person tae calculate the circumference o the Yird, that he did bi comparin angles o the mid-day Sun at twa places a kent North-Sooth distance apairt. His calculation wis remerkably accurat. He wis an aw the first tae calculate the tilt o the Yird's axis, again wi remerkable accuracy. Additionally, he mey hae accuratly calculatit the distance frae the Yird tae the Sun an inventit the leap day. He creatit the first map o the warld, incorporatin parallels an meridians based on the available geografic knawledge o his era.
Eratosthenes wis the foonder o scienteefic chronology; he endeavoured tae revise the dates o the chief leeterar an poleetical events frae the conquest o Troy. Eratosthenes datit The Sack o Troy tae 1183 BC. In nummer theory, he introduced the sieve o Eratosthenes, an efficient method o identifeein prime nummers.
He wis a feegur o influence in mony fields. Accordin tae an entry in the Suda (a 10t-century reference), his creetics scorned him, cryin him Beta (the seicont letter o the Greek alphabet) acause he ayeweys cam in seicont in aw his endeavors. Nanetheless, his devotees nicknamed him Pentathlos efter the Olympians that war weel roondit competitors, for he haed pruiven himsel tae be knawledgeable in ivery aurie o learin. Eratosthenes yearned tae unnerstaund the complexities o the entire warld.
- The Suda states that he wis born in the 126t Olympiad, (276–272 BC). Strabo (Geography, i.2.2), tho, states that he wis a "pupil" (γνωριμος) o Zeno o Citium (who died 262 BC), that wad implee an earlier year-o-birth (c. 285 BC) syne he is unlikely tae hae studied unner him at the young age o 14. However, γνωριμος can an aa mean "acquaintance", an the year o Zeno's daith is bi no means definite. Cf. Eratosthenes entry in the Dictionary of Scientific Biography (1971)
- The Suda states he died at the age o 80, Censorinus (De die natali, 15) at the age o 81, an Pseudo-Lucian (Makrobioi, 27) at the age o 82.
- Roller, Duane W. Eratosthenes' Geography. New Jersey: Princeton University Press, 2010.
- Ridpath, Ian (2001). The Illustrated Encyclopedia of the Universe. New York, NY: Watson-Guptill. p. 31. ISBN 0-8230-2512-8.
- "Eratosthenes (276 - 195 B.C.)". Cornell University. Accessed 28 Julie 2019.
- Alfred, Randy (19 Juin 2008). "June 19, 240 B.C.: The Earth Is Round, and It's This Big". Wired. Retrieved 22 Juin 2013.
- Entry ε 2898
- See also Asimov, Isaac. Asimov's Biographical Encyclopedia of Science and Technology, new revised edition. 1975. Entry #42, "Eratosthenes", Page 29. Pan Books Ltd, London. ISBN 0-330-24323-3. This was also asserted by Carl Sagan 31 minutes into his Cosmos episode The Shores of the Cosmic Ocean
- Chambers, James T. "Eratosthenes of Cyrene." Dictionary Of World Biography: The Ancient World (January 1998): 1–3.