Astronauts on the Moon look back at Earth, whose diameter is about 12,800 km. Because the Earth-Moon distance is about 400,000 km and the Moon's diameter is about 3500 km, how much bigger or smaller will Earth appear in their sky than the Moon does in the sky?
A) the same, obviously
B) 114 times
C) 3.7 times
D) 0.27 times

Question

Quizplus · Accepted Answer

The apparent size of an object in the sky is determined by its angular diameter, which depends on the object's actual size and its distance from the observer. Since the Earth's diameter is about 12,800 km and the Moon's diameter is about 3,500 km, the Earth is approximately 3.7 times larger in diameter than the Moon. Given the distances involved, this ratio roughly translates to how much larger the Earth would appear to an observer on the Moon compared to how the Moon appears from Earth, despite the difference in distances.

Astronauts on the Moon Look Back at Earth, Whose Diameter