Eratosthenes was the first person to accurately estimate the size of the Earth.He accomplished this feat by
A) sailing around the world and estimating his average rate of travel.
B) comparing the length of an Earth day with the distance between the Earth and the Sun.
C) measuring the severity of the greatest earthquakes.
D) observing shadows cast simultaneously at two different cities that were separated by a known distance.

Question

Quizplus · Accepted Answer

Eratosthenes observed that on the summer solstice, the sun was directly overhead in the city of Syene, but it cast a shadow in Alexandria, which was located at a known distance to the north. By measuring the angle of the sun's rays hitting a vertical column in Alexandria, he was able to calculate the angle between the sun and the vertical column in Syene. Using this information, he estimated the size of the Earth to be approximately 40,000 kilometers in circumference. Therefore, choice D is the correct answer.

Eratosthenes Was the First Person to Accurately Estimate the Size