Question

Why does the sky appear dark (or black) to an astronaut instead of blue?

Answer 1

As an astronaut moves far away from the earth atmosphere and fly at very high altitude in the space, the medium becomes rarer. Due to the absence of air molecules or fine particles, there is hardly any scattering of light. That is why, the sky appears dark to an astronaut flying at very high altitudes, as scattering of light is not prominent at such heights.

Answer 2

Explanation:

The sky appears dark instead of blue to an astronaut because there is no atmosphere in the outer space that can scatter the sunlight. As the sunlight is not scattered, no scattered light reach the eyes of the astronauts and the sky appears black to them.