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Eratosthenes

This article is about the Greek scholar of the third century BC. For the crater named after him, see Eratosthenes (crater). For the ancient Athenian statesman of the fifth century BC, see Eratosthenes (statesman).
Eratosthenes of Cyrene (/ɛrəˈtɒsθəniːz/; Greek: Ἐρατοσθένης ὁ Κυρηναῖος, romanized: Eratosthénēs ho Kurēnaĩos, IPA: [eratostʰénɛːs]; c. 276 BC[note 1] – c. 195/194 BC)[note 2] was a Greek polymath: a mathematician, geographer, poet, astronomer, and music theorist. He was a man of learning, becoming the chief librarian at the Library of Alexandria. His work is comparable to what is now known as the study of geography, and he introduced some of the terminology still used today.[1]

Eratosthenes
Born
276 BC[note 1]
Cyrene
Died
194 BC (around 82)[note 2]
Alexandria
Occupation
Scholar
Librarian
Poet
Inventor
Known for
Sieve of Eratosthenes
Founder of Geography
He is best known for being the first person to calculate the circumference of the Earth, which he did by comparing angles of the mid-day Sun at two places, a known North-South distance apart.[2] His calculation was remarkably accurate. He was also the first to calculate the tilt of the Earth's axis, again with remarkable accuracy.[3] Additionally, he may have accurately calculated the distance from the Earth to the Sun and invented the leap day.[4] He created the first global projection of the world, incorporating parallels and meridians based on the available geographic knowledge of his era.

Eratosthenes was the founder of scientific chronology; he endeavoured to revise the dates of the chief literary and political events from the conquest of Troy. Eratosthenes dated The Sack of Troy to 1183 BC. In number theory, he introduced the sieve of Eratosthenes, an efficient method of identifying prime numbers.

He was a figure of influence in many fields. According to an entry[5] in the Suda (a 10th-century encyclopedia), his critics scorned him, calling him Beta (the second letter of the Greek alphabet) because he always came in second in all his endeavors.[6] 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.[7]

I don't understand how this man knew this,
How could he?
We are more advanced,
And know the earth is indeed flat,
How could someone how lived 2200 years ago know the earth round?
More lies.