The Erased Sky

Urban lighting has made the stars disappear. Today, the majority of city dwellers no longer see the Milky Way—an object nevertheless visible to humanity since its origins.

Light pollution is born from artificial light diffused toward the sky, directly or reflected by air particles. This luminous halo of cities drowns weak stars. To quantify it, astronomer John Bortle proposes in 2001 a scale from 1—perfectly black sky—to 9—downtown center. Urban lighting has made the stars disappear.

One episode remains famous. During the 1994 earthquake in Los Angeles, a giant blackout plunges the city into darkness; residents call emergency services and observatories to report a strange "silver cloud" in the sky. It was the Milky Way, which they had never seen. Today, the majority of city dwellers no longer see the Milky Way—an object nevertheless visible to humanity since its origins.

Beyond cultural loss, excess nocturnal light disrupts ecosystems—migratory birds, insects, sea turtles—and human biological rhythm. Dark night has become a rare resource, which dark sky reserves now attempt to protect.