In most situations, light helps us see. But now humans are using too much of it. In fact, it's a kind of pollution.
According to scientific research, about 2,500 stars can be seen by the human's eyes. But because of light pollution, you can only see 200 to 300 stars from today's countryside, and no more than ten stars from a city. In most big cities, people can't see the sky filled with stars like they did in their childhood.
Light pollution influences more than just our view of sky. Research shows that lots of nighttime light can harm wildlife, too. When birds fly to another place over cities, they sometimes get lost by bright light and fly in circles until they drop from tiredness. Sea turtles (海龟) need dark beaches for laying eggs, but they can't find good places because of those bright lights. Too much light at night may even harm human's health, but scientists are not sure of that. They are still learning more.
In order to stop things from going worse, the governments and organizations (组织) are working hard to reduce light pollution. Many cities and towns have taken actions to reduce the use of lights at night. Lights are used only when and where they are truly needed. They also shine lights down at the ground instead of up into the sky and use lower brightness levels.
Hopefully, in the near future, humans can enjoy the clear and beautiful sky again and all the wildlife will live a peaceful life, too.