People/Eratosthenes: Difference between revisions
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===Sticks and shadows===
[[File:GNplBjKWsAAVPVU.jpg|thumb|sticks and shadows, but not on a curve]]
Assuming the earth was a globe and assuming the sun was far away, Eratosthenes made a math formula to determine what would be the circumference of the assumed globe Earth. Details were given in his treatise On the measurement of the Earth which is now lost (another one of those "we lost that technology"). However, some details of these calculations appear in works by other authors such as Cleomedes, Theon of Smyrna and Strabo.
Eratosthenes compared the noon shadow at midsummer between Syene (now Aswan on the Nile in Egypt) and Alexandria. He '''assumed that the sun was so far away''' that its rays were essentially parallel (obviously never looked up to see the sun's Crepuscular rays), and then with a knowledge of the distance between Syene and Alexandria, he gave the length of the circumference of the Earth as 250,000 stadia.
Using this same assumption, you can use the following math formula to turn a dining room table into a sphere.▼
▲Using
Distance on the meridian (<math>d</math>) and the difference in latitude (<math>\alpha</math>) to the relation between the perimeter (<math>P</math>) and the angle of the circle (<math>360 ^\circ</math>)
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