Question

Why an astronaut in space finds sky to be dark

Answer 1

Before knowing that first of all u shud know why the sky looks blue from earth. This is due to difrraction of light by the atmosphere. The blue light is having less wavelength than any other color of visible spectrum, so it diffracts very much in the atmosphere making it to appear blue. In space there is no atmosphere, so there is no diffraction and so the sky is black.