Q. 13 :- Why does the sky appear dark instead of blue to an astronaut?
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.