This is partly due to pollution, but even in the cleanest air the sky is lighter near the horizon due to the effect of earth's atmosphere on sunlight.
When looking at a picture of the sun, how could you tell whether or not it's rising or setting?
How many times have you heard a jet plane going over but not been able to find it even though you were looking toward where the sound was coming from?
Are you familiar with the study done by Wolfgang Miltner at Friedrich Schiller University in Germany?
Why is the moon sometimes orange or red? Why is the sky blue? These questions are closely related!
Did you ever wonder why newborn babies have blue eyes? Or how human beings get the various eye colors we have?
We've all seen how when we splash water on cloth, the places where the water hits appear darker than the rest. Does the cloth change color when wet?
Why doesn't the flame just continue to burn underneath the bell, no matter how flat you crush it? The answer is air.
Those tiny dots are actually blood cells moving in the retina of your eye.