# Question: 2 one assumption that eratosthenes made was that the earth...

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2. One assumption that Eratosthenes made was that the earth was a perfect sphere. What are 5 other assumptions critical to this calculation?

Eratosthenes was a Greek mathematician who lived 276-194 BC. At summer solstice he waited until noon, when the sun was directly overhead in Aswan. He placed a gnomon (basically a stick) at the bottom of the well at 90° to the ground, and noticed that it cast no shadow. Then at the same time he had others place a gnomon in Alexandria. He found that the tip of the gnomon made an angle of 7° to the edge of the shadow, where the gnomon was again at 90° with the ground. Based on records at the Library of Alexandria, he knew that the distance from Aswan to Alexandria was 5,000 stadia.