Eratosthenes (ca 275 B.C.), a scholar and librarian at theUniversity at Alexandr

Question

Eratosthenes (ca 275 B.C.), a scholar and librarian at theUniversity at Alexandria, is credited with calculating thecircumference of the earth using the following method: Eratostenesobserved that on the summer solstice the sin was directly overheadat noon in Syene (the present site of Aswan), while at the sametime in Alexandria, which was due north, the rays of the sun wereinclined 7o12' north of Syene along the earth's surface.Using the known distance between the two cities of 5000 stades(approximately 530 miles), he was able to approximate thecircumference of the earth.

Make a diagram that depicts this method and calculate thecircumference in stades and in miles. How does this result compareto present-day estimates?

Explanation / Answer

Use the followingwebsite to help you with this solution. Remember to calculate milesand stades, also 7o12' is equal to 7.2obecause 12' is minutes (12/60=1/5=.2). In the end, Eratosthenesestimation will only be ~2000 off to current estimations.

http://www.phys-astro.sonoma.edu/observatory/eratosthenes/

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