Why is the sky dark at night?
The stars are there however - if we look far enough out into deep space! - Astronomers have just been forced to raise their estimate of galaxies in the universe to 125 billion after studying an extremely small area of the southern sky through the Hubble telescope. The area was only the size of a grain of rice held at arms length but contained many galaxies 11 billion light years away.
Actually the night sky is very bright with stars shining all over the place. It is just the way our eyes have evolved that makes it seem dark. We are a daylight animal that needs to see in the daytime. The tremendously powerful light from the sun, being so close to Earth is just too powerful and simply overwhelms the starlight during the day.
If our eyes had evolved so that we could see very well at night - the daylight would be much too bright for us. Our eyes can adjust somewhat for night vision but it is limited. Animals that hunt at night - such as the owl - have evolved eyes that can see well at night but the daytime seems awful bright to them.
If we had evloved on another planet far from the sun, such as pluto, where the sun just looks like a bright star and did not overwhelm the sky during daytime - our eyes would have evolved so that we could see very well just by starlight.
Recently light amplifiers have been invented that enable us to see very well at night using just the starlight. It was one of the main advantages we had during the Gulf War when our soldiers and helicopter pilots used the light amplifiers to see their targets using just starlight.
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