Question

why does sky appear dark instead of blue to an astronauts?

Answer 1

There's no such thing as sky. What we see directly is space. You can see that at night. During the day, due to the sun there's scattering of light and blue scatters the most due to earths atmosphere hence the sky.

Blue light has the shortest wavelength and the highest frequency in the visible light spectrum. It is scattered more than red light which has the longest wavelength and the shortest frequency. So, when the Sun is high in the sky, blue light is scattered in all directions as sunlight passes through the atmosphere and we see the sky as blue.

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.