Light pollution (light smog) - a brightening sky artificial light: lights, floodlights, lighting billboards and so on. N. The modern world produces enough light for their needs, that see the stars in the big cities it is impossible even in the clear night. Think about the last time you saw them?
In 1994, the year after the earthquake in Los Angeles for some time, disappeared electricity. The observatory and the local police received a lot of calls, people reported "strange luminous points in the sky," likely meaning an alien invasion! But this mysterious phenomenon is explained very simply: too urbanized Californians have never left the city limits, and never in my life did not see the stars. And in the end they just forgot about their existence.