Have you ever noticed that your shadow is longest in the early morning and in the late afternoon? To tell the time ancients used the position of sun in the sky At noon, when the sun is overhead there is little or no shadow at all. Long time ago people observed that, and used this principle in making of world’s earliest clock, a sun dial.
Look at the illustration to the right and notice the direction of the shadow is away from the source. During midday it would be the shortest, and in afternoon it would be on the opposite side.
I follow you around in the light, I say good bye to you in the night? Who am I? Shadow!