Why the Sky is Blue
The blue glow of Earth's atmosphere is visible from afar.
The photo on the left, taken from low-earth orbit, shows a full Moon rising above the Earth's horizon. The Moon is silhouetted against the blackness of space. The surface of the Earth is shrouded by clouds and the glow of the atmosphere.
The photo on right, taken from low-lunar orbit, shows a gibbous Earth rising over the Moon's horizon. The Moon has no atmosphere. The black sky extends to its surface. In the far distance, Earth's blue atmosphere, white clouds and brown continents can be seen.
