Saturday, June 1, 2013

Who Said Geography First

JUNE 2013

I’ve always liked Eratosthenes since I first heard about his accomplishments from Carl Sagan while watching Cosmos.  Eratosthenes was Greek scholar born in Cyrene (276 BC) which is located in present day Libya and died in Alexandria (194 BC), the capital of Egypt during this time.  He was educated in Athens and appointed as the third Chief Librarian of the Great Library of Alexandria in 240 BC.  While at the library he wrote a book about the world, called geography, and introduced the climatic concepts of torrid, temperate, and frigid zones.  He is most famous for calculating the circumference of the earth by comparing the angle of the shadow of the sun at summer solstice noon at Alexandria and Syene (directly south), and knowing the distance between the two, he calculated Earth is 250 000 stadia (~25 000 miles or 40 000 km).

(note: the diagram incorrectly lists 35 000 Miles)

Other claims of fame include calculating the tilt of Earth’s axis at 23.4º and possibly the distance to the sun.  He also created the first world map incorporating latitude and longitude.  Finally, he along with his friend, Archimedes, made several contributions to mathematics including the Sieve of Eratosthenes which is a simple algorithm that determines prime numbers.  One of Eratosthenes philosophical beliefs was that there was good and bad in all nations and criticized Aristotle for arguing that Greeks are better and should keep themselves racially pure.

About: Eratosthenes

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