Question

When Eratosthenes observed the angle at which the Sun's rays produced a shadow from a column in Alexandria, he was

A. Measuring the circumference of the Earth.
B. Demonstrating the great distance to the Sun
C. Measuring the distance between Alexandria and Syene.
D. Demonstrating the flatness of the Earth.
E. Measuring the latitude of Alexandria

Answer 1

Eratosthenes was measuring the circumference of the Earth by using the difference in the angle of the Sun's rays in two different cities.

Step-by-step explanation:

When Eratosthenes observed the angle at which the Sun's rays produced a shadow from a column in Alexandria, he was measuring the circumference of the Earth. He used the shadow to determine that the Sun's rays at Syene and Alexandria created different angles due to the curvature of the Earth. Knowing that at noon on the summer solstice, the Sun was directly overhead at Syene and created an angle of about 7 degrees in Alexandria, he was able to calculate that Alexandria was approximately 1/50 of Earth's circumference away from Syene. Multiplying the distance between Alexandria and Syene (5000 stadia) by 50 gave him the total circumference of the Earth, which he estimated to be 250,000 stadia.