Scientists tell the story that when a 1994 earthquake rocked Los Angeles and knocked out the power, people started calling 911 because something was up with the sky.
They say callers said there was a "giant, silvery cloud" up there. It was the Milky Way. Our home galaxy.
Tall tale? Maybe. But the phenomenon of city lights blowing out the natural light of the stars is real — and it's getting worse.
Researchers say more than 80 percent of the planet — and more than 99 percent of the U.S. and Europe — now lives under skies polluted enough to hinder astronomical observation. That's compared with about 66 percent of the planet in 2000.
Now, they say, "We've got whole generations of people in the United States who have never seen the Milky Way."
In some places, such as Singapore, pollution is so severe that residents might never see true night — and their eyes no longer adapt to full night vision.
Artificial light isn't as well-tracked as some other pollution. This new map is the first update in more than a decade. It was built from a combination of ground measurements and satellite data.
But there are still areas where you can get a proper dark sky — like Australia, Canada and much of the Western U.S.
And reducing light pollution is relatively easy — cover lights so they don't leak into the sky, use less light if you can — or just turn them off when you don't need them.
This video includes clips from The New World Atlas of Artificial Sky Brightness, the European Southern Observatory, lightweavr / CC BY 3.0, Marshall Astor / CC BY 3.0, NASA, Ardash Muradian / CC BY 3.0, Paul Yip / CC BY 3.0, Chris Savage / CC BY 3.0 and Binayak Dasgupta / CC BY 3.0 and images from John Fowler / CC BY 2.0 and the European Southern Observatory.