What do we see when we see up?

On a clear day or a clear night, when we see up in the sky, we see clouds, stars and moons and sometimes planets and artificial satellites, So what are we actually looking at , the sky or the space?


What’s the difference?

What you “see” is light; either from our sun, reflected by things in our atmosphere; or from stars so far away that it takes years to reach us.

The blue of a blue sky during the daytime is sunlight, scattered in all directions by the atmosphere; this is why you can see it even when you aren’t looking directly at the sun.

The stars are still shining in the daytime just as brightly as they were at night, but you can’t see them because the blue of the blue sky is so much brighter than the stars. Imagine a guy speaking to you from twenty feet away; you can hear him just fine. Now surround him with a sea of people who are all yelling. He’s still speaking as loudly as before, but you can’t hear him what with all the yelling. Same idea.