The light pollution that shrouds cities and regions in the night causes an average of 90 percent of the stars to disappear that would otherwise be visible to the naked eye. Of the 3000 to 4000 stars that can be observed in a dark night sky, less than a hundred are visible in a brightly lit city.
Today, 83 percent of the world's population and 99 percent of Europeans live under light-polluted skies. For 60 percent of Europeans, the Milky Way is hidden from view.
Big cities create a sky glow that is visible at a distance of up to 160 km.
Light pollution is now so severe that the darkest areas of Europe are twice as bright as they would be under natural conditions.