Humus
The Milky Way over a mountain lake in Wales, a glow of light above the pass

EssaySky4 min read

Dark Sky

Most people in Europe have never seen the Milky Way. Not because it has gone, but because we have lit it away.

By Ida Wrzos

My grandmother used to say that in August, in her village near Siedlce, you didn’t need a torch. Starlight was enough, and the Milky Way was so bright it cast shadows. For a long time I thought she was exaggerating. Then I went to the Bieszczady mountains for the first time.

A sky that disappears

Light pollution is the only kind of pollution you can switch off with a single button. And yet it is growing faster than most others. Every streetlight shining upwards, every billboard and every lit car park adds to a glow that spreads tens of kilometres above our cities.

over 80%
of the world’s people live under light-polluted skies
60%
of Europeans cannot see the Milky Way from home
1/3
of humanity has never seen it
Source: Falchi et al., Science Advances, 2016

The difference is easiest to see in a single photograph. Move the slider: on the left, the original with the glow of a nearby town; on the right, the same sky with the artificial light taken out.

A starry sky over a lake, pines in front and the orange glow of a town on the horizon
The same photograph without the orange glow over the horizon
Simulation: the right side is the same photograph with the glow removed (our edit).Photo: Martin Mark / Wikimedia Commons, CC BY-SA 4.0 (edited by Humus)

Darkness is not emptiness. Around 60 per cent of invertebrates and 30 per cent of vertebrates are active at night. Moths1 A single streetlight can draw in and kill hundreds of insects in one night. circle streetlights until they are exhausted, migrating birds lose their way over lit-up cities, and street trees keep their leaves longer than they should.

New York skyscrapers at night, lit windows and streets
New York at night. The glow above the largest cities can be seen from more than a hundred kilometres away.Photo: Paulo Barcellos Jr. / Wikimedia Commons, CC BY-SA 2.0

Darkness isn’t an absence of light. It is the condition for seeing something that shines more faintly than we do.

Dark sky parks

There are places in Poland that have decided to protect the night. The Izera Dark Sky Park opened in 2009, the first in the country; four years later the Bieszczady Starry Sky Park followed. Local councils there replace streetlights with ones that shine only downwards, in warm light, and visitors come to see the dark.

Stars rising over the La Silla observatory in Chile. A time-lapse.Video: ESO/B. Tafreshi / Wikimedia Commons, CC BY 4.0

I came back from the Bieszczady with one conclusion. My grandmother wasn’t exaggerating. We were the ones who forgot.