An estimated 83 per cent of the world’s population now lives under light-polluted skies, and roughly a third of humanity can no longer see the Milky Way from where they stand. Those figures come from the world atlas of artificial night sky brightness, published in 2016, and the picture has worsened since. Citizen science measurements published in Science in 2023 found the night sky brightening by nearly ten per cent a year. At that rate, a child born in a place where 250 stars are visible will see only about 100 of them by their eighteenth birthday.
The loss is quiet. Nobody notices the stars going out, because they go out one at a time, and because the light doing it is the light we asked for.
How light pollution affects sleep and health
The body reads light as instruction. Artificial light at night suppresses melatonin and unsettles the circadian rhythm that most of our physiology runs on, and the research links that disruption to poorer sleep, low mood and a longer list of physical conditions than is comfortable to read. For most of evolutionary history, darkness arrived on schedule every night. The body still expects it, and increasingly does not get it.
What the night loses besides stars
Wildlife has no blackout curtains. Sea turtle hatchlings follow the brightest horizon, which for millions of years was the sea and is now often the car park behind the beach. Migrating birds navigate by stars and collide with lit buildings by the hundreds of millions each year. Nocturnal insects, already in decline, spiral around streetlights instead of pollinating and feeding the food chain that depends on them.
There is also the plain arithmetic. A large share of outdoor lighting shines sideways or upward, illuminating the underside of clouds at considerable expense. Whatever else darkness is, it is cheaper.
Where darkness remains
There are still places the atlas colours black. The Cederberg is one of them, a corridor of genuinely dark sky three hours north of Cape Town, and the people who lived here longest read that sky closely. In |Xam accounts recorded in the nineteenth century, a girl of the Early Race threw wood ash into the sky so that people could see their way home at night, and the ash became the Milky Way.
That darkness is the reason Bliss & Stars points a 20-inch telescope at it, and the reason Orion’s Odyssey is built around four nights of it. No equipment is needed for most of it. On the darkest moonless nights, the Milky Way is bright enough to cast a faint shadow.
Unlike most environmental damage, this kind reverses instantly. The dark is still there, behind the light. It comes back the moment the lights go off.
