Why Does the Moon Shine?


Quick Answer

The moon appears to shine because its surface reflects sunlight. Light from the sun travels through space to reach the Earth-moon system just over eight minutes after it is emitted. Some of this light falls on the surface of the moon where, according to Universe Today, 12 percent of it is reflected back into space.

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Full Answer

Lunar soil is not exceptionally reflective, so the sunlight that does fall on the lunar surface tends to be either absorbed or scattered. This leaves relatively little light that can bounce back toward observers on Earth. Despite its poor reflective index, the moon is relatively large and very close to Earth, making it one of only three objects in the sky, along with Venus and the sun, bright enough to cast a shadow, according to Universe Today.

The moon varies greatly in apparent brightness throughout the monthly lunar cycle. According to Wikipedia, the Moon is at its brightest when it's full and viewed at high altitude, which puts the observer above much of the Earth's turbulent atmosphere, preferably from a tropical latitude. Even at its brightest, the moon averages only 0.2 lux, which is approximately 500,000 times less bright than the sun as viewed from the Earth.

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