In order to obtain the shadow lengths he did, Eratosthenes had to make his measurements on the:
A)vernal equinox.
B)summer solstice.
C)autumnal equinox.
D)winter solstice.

Question

Quizplus · Accepted Answer

Eratosthenes made his measurements on the summer solstice, the time when the Sun is directly overhead at noon in Syene (modern Aswan, Egypt), allowing him to calculate the Earth's circumference using the difference in shadow lengths between Syene and Alexandria.

In Order to Obtain the Shadow Lengths He Did, Eratosthenes