The End of Night Look up at the sky at night. What can you see? Before electric lights, people could often see about 2,500 different stars. Now, light fills the skies over our cities. This is called light pollution. Because of it, people in cities can often only see about ten stars! Most of the time, light helps us. We can see because of it. It gives plants energy. But light isn't always good. We need times of dark to rest. One hundred years ago, we had those times of dark. Now the night is like day. Some scientists are worried about how this light affects our health. These scientists are studying the effects of light pollution. Other scientists are finding ways to stop light pollution and make our lives better. For example, many streetlights now have covers. The covers focus the light toward the ground. They stop the light from going up into the sky. They also save energy. The covers are a small change, but they can still have a positive effect.