A star-filled sky is a magnificent sight. It is also an important part of our lives. By studying the sky, we learn about our place in the universe.
Animals also need the night sky. Some animals use the stars to find their way. Others depend on the dark to feel safe.
This natural wonder, like many others, is in danger from human activity. Light pollution is changing our view of the night. We must change our ways, or we will lose the benefits of the starry sky.
One hundred years ago, everyone had a twinkling view of the night sky. At that time, people could see about 1,500 stars. Today, only one in ten Americans has a beautiful, starry view. People in cities see a glowing orange sky and just a few dozen stars instead.
Astronomers were the first to notice the growing problem of light pollution. They began to realize it in the 1970s. They were shocked when they looked into their telescopes and saw that some of the stars and planets that they had studied were gone. They were still there, of course, but city lights made them impossible to see.
Nights started to get brighter more than a century ago. The first long-lasting lightbulb was invented in 1879. Companies began to install electric power lines across the country. More and more people used electricity for lighting.
At the same time, the population grew. Many people moved to the United States. In 1900, there were 76 million Americans. There are more than 300 million today. More people now live in cities and suburbs, and their lights create light pollution.