Why can't you see the starry sky now?

After nightfall, advertising lights and neon lights in shopping malls and hotels are dazzling. Some intense light beams even go straight into the sky, making night like day, which is called artificial day. In such a "city that never sleeps", the invasion of light causes too strong light sources to affect the daily rest of others, making it difficult to fall asleep at night, disturbing the normal biological clock of the human body and leading to low work efficiency during the day. The sky is too bright to see the stars, which affects astronomical observation and aviation, and many observatories are forced to stop working.

According to astronomical statistics, when the sky is not polluted by light at night, about 7000 stars can be seen, while in big cities where street lights, background lights and landscape lights are scattered randomly, only about 20~60 stars can be seen.

The problem of light pollution was first put forward by the international astronomical community in the 1930s. They believe that light pollution is the negative influence of bright sky caused by urban outdoor lighting on astronomical observation. Later, Britain and the United States and other countries called it "interference light", while Japan called it "light damage".