Eight in ten North Americans can no longer see the Milky Way
About 83 percent of humanity sleeps under skies measurably brighter than natural darkness, including 99 percent of people in Europe and the United States. Most North Americans have never seen the Milky Way from home. The culprit is not light itself but light that is wasted, misdirected or simply unnecessary.
Light pollution means artificial light disturbing the natural rhythm of day and night. It comes in several overlapping flavours: trespass, when a neighbour's lamp shines through your bedroom window; over-illumination, using far more light than a task needs; glare; visual clutter; and skyglow, the orange dome over a city that drowns out stars. Sources include building lighting, advertising, car parks, offices, factories, streetlights and floodlit stadiums. The problem is worst in industrial, crowded parts of North America, Europe and Asia and in big cities such as Cairo and Tehran.
It keeps spreading. Skyglow already touches about 23 percent of the world's land. Global light pollution rose at least 49 percent between 1992 and 2017 and another 16 percent from 2014 to 2022, though France cut its own by a third over that later stretch through policy. Habits differ even among rich countries: American cities send three to five times more light into space per person than German ones. United States homes used 81 billion kilowatt hours for lighting in 2020.
Much of the excess comes from habit. Some lighting norms rest on consensus rather than vision science, many people wrongly assume brighter always means safer, and designers often specify more light than needed or pick fittings that throw it in the wrong direction. Fixtures rated full cutoff release no light at angles above 80 degrees from straight down, cutting both trespass and skyglow.
Concern dates back to the late 19th century, but action began only in the 1950s, and a worldwide dark-sky movement took shape in the 1980s with the International Dark-Sky Association, now DarkSky International. Several American cities set outdoor lighting rules against trespass, the Federal Communications Commission handles complaints about overly bright tower strobes, and the LEED green building standard rewards designs that limit stray light. Fixes are often simple, like better-aimed fittings and more suitable bulbs, but wider change depends on public awareness and legislation.
Source: Light pollution
