Light and shadow are friends. They usually go together. Light can't shine through you. Your body stops (阻止,阻碍) it from passing. There is only a dark spot (点) on the ground next to you. The light can't reach the dark spot. This is your shadow.
At noon the sun shines over your head. Your body stops very little light from reaching the
ground. So your shadow is quite short. But in early morning or late afternoon, the sun is low in the sky. Your body stops a lot of light from reaching the ground. Then your shadow is quite long.
We love sunlight, because neither animals nor plants can live without it. Sunlight can make people healthy. We love shadow, too. Most of us like to stand in the shade of a tree or have a walk in the shadow of trees in summer. Light and shadow usually go together.