Why is outer space black?
In the most scientific sense, space is not black, it is filled with radiation, light waves and radio waves and much more. It is the omnipresence of this radiation that gives space its temperature of 2.7 deg kelvin, cold but not zero. Only because the radiation is so sparse and because it has little or nothing to reflect off of, it’s too “dim” for your eye to see, so it appears black to your eye. Unless there is some solid or gaseous matter to reflect the light off of, the way the earth’s air atmosphere reflects sunlight, you won’t see anything, and if you can’t see anything then it seems black to your perception. Matter reflects light, space does not, it mearly transmits it. And it’s the reflected light that hits your eye that accounts for the color and brightness of the matter.
