Eratosthenes knew that in Aswan the sun was directly overhead at noon on the summer solstice.
At the same time, he measured the angle of the sun to a vertical line in Alexandria. He found this
angle to be one(1/50) fiftieth
of a circle
a. What was Eratosthenes's measurement in degrees? (Hint: There are 360cin a complete
circle.)
b. What can you conclude about the angle formed between the two cities and the centre of the
Earth?
c. Suppose Eratosthenes estimated the distance from Aswan and Alexandria to be 900 km.
What circumference would he have found for the Earth?
1 answer