Why does the sky appear dark instead of blue to an astronaut?

(a) Give reasons for the following: (i) The sky appears to be blue during day time to a person on earth. (ii) The sky near the horizon appears to have a reddish hue at the time of sunset and sunrise. (iii) The sky appears dark instead of blue to an astronaut. (iv) The stars appear to twinkle. (v) The planets do not twinkle.

Why does the sky appear blue?

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

The sky would appear red instead of blue if

Why does clear sky appear blue ?

Why does the sky appear blue on a clear day ?