Question

Which ancient Egyptian scientist calculated the circumference of the earth to within 200 km of its true value? describe briefly how he did it:

Answer 1

Eratosthenes was the founder of scientific chronology; he endeavored 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 reference), 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 Pentathlosafter 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]






Eratosthenes of Cyrene (/ɛrəˈtɒsθəniːz/; Greek: Ἐρατοσθένης ὁ Κυρηναῖος, IPA: [eratostʰénɛːs]; c. 276 BC[1] – c. 195/194 BC[2]) was a Greek mathematician, geographer, poet, astronomer, and music theorist. He was a man of learning, becoming the chief librarian at the Library of Alexandria. He invented the discipline of geography, including the terminology used today.[3]