Eratosthenes' measurements of Earth's size involved
A)a deep well in Syene.
B)a pillar's shadow in Alexandria.
C)surveying the distance between Alexandria and Syene.
D)all of the above

Question

Quizplus · Accepted Answer

Eratosthenes used all three methods mentioned in options A, B, and C to measure the size of the Earth. He calculated the Earth's circumference by measuring the angle of the sun's rays at two different locations at the same time. He used the deep well in Syene to observe that the sun was directly overhead at noon on the summer solstice. He then measured the angle of the shadow of a pillar in Alexandria, which was not directly under the sun at the same time. Using the distance between Alexandria and Syene, which was known from previous surveys, he could calculate the Earth's circumference. Therefore, the correct answer is D, all of the above.

Eratosthenes' Measurements of Earth's Size Involved