Light pollution is excessive light production at night in an open environment, produced by man and leading to, decreased visibility of the surroundings. With regard to animals, light pollution can affect their biological rhythms, their nocturnal activities or their migration. Light pollution may affect people by altering biological rhythms and disturbing sleep. Moreover, it reduces visibility of the night sky, and in economic terms, represents useless spending when the light produced is directed towards the sky.
Public lighting is the main culprit. When a city is seen from a distance, the urbanised zone appears to be topped with an orange coloured gaseous dome (from sodium vapour lamps).
Astronomy and environmental defence organisations have brought this problem to the attention of city and town authorities. Better adapted lighting solutions considerably reduce light pollution and generate savings.
Light from public lighting, when it is poorly designed (here, spherical lamps) sends a large amount of its light towards the sky, which diffuses in all directions, creating a halo. © Martial Figenwald