Q.13. Why does the sky appear dark instead of blue to an astronaut?
The dark color is nothing but the absence of the light.
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 the sky appears black to them.
scattering of light give rise to many usual securing such as the tyndall effect..as there is no atmosphere in space and hence light does not scatter into its constituent colours that is why sky apper dark instead of blue to an astronaut in space.