Question

Why does an astronaut see sky colour as black instead of blue?

Answer 1

Because no scatter of light taken place in space

Answer 2

This is because of scattering of light particles.

IN EARTH :-

There is a presence of atmosphere which has various smaller particles which scatter the light travel down the atmosphere.

Now,

When the light of sun (white in colour) enters the atmosphere of earth it is scattered by the light particles present in the atmosphere...

As we know that :-

Blue colour has the shortest wavelength and red colour has the longest wavelength, the light particles scatter the blue light very easily and quickly.

The blue light then scatters everywhere imparting blue colour to sky.

Now,

IN SPACE :-

In space there is no atmosphere.

There is no particles which can scatter light particles. There is complete vacuum

Thus, no scattering occurs in space and astronauts see sky colour as black instead of usual blue colour as seen on earth.