Our world is getting brighter, as we turn more and more lights on across the planet. But all that light shining from the ground makes it harder to see the lights shining from the sky. It's now gotten so bad that the Milky Way is almost impossible to see in most of the United States - but Australia's view remains pretty good. Milky Way seen over the ALMA observatory (Image: ESO/Y. Beletsky)
A team of international researchers has created the most complete global atlas of light pollution ever created to show just what you can — and, increasingly, can't — see in your own patch of night sky. They detailed their results yesterday in a paper in Science Advances. In addition to tracking global light pollution, their new atlas also focuses on the slow global fade of the world's most iconic dark sky object: The Milky Way.
In the US, 80 per cent of people on the ground cannot see the Milky Way anymore because of light pollution. Worldwide, the number is less extreme, with 30 per cent of the population unable to see the Milky Way, but the percentages veer wildly up and down when you look at individual countries, with some having almost no night sky visibility. Australia is the least polluted amongst the G20 countries, though by no means the least polluted worldwide.
Global map of light pollution (Image: Science Advances)
Singapore was found to be the most light-polluted of all countries, with skies so bright over the whole country that no spot of the country was dark enough at night for human eyes to adapt to night vision. Though the atlas shows how bad the problem has gotten today, it's actually been a long time coming.
"My sense is the the growth in artificial sky brightness began to accelerate after WWII, tracking fossil fuel consumption," co-author of the study Chris Elvidge of NOAA told Gizmodo. "Fossil fuels provide the electricity for the lights and the mobility to facilitate urban sprawl."
Elvidge recommended a number of counter measures to counteract the problem. Those included switching to motion-detector lights at night, turning off lighted-signs at night and replacing street lamp fixtures with lights that shine only down, not up. Especially important, however, could be changing from traditional lightbulbs to amber-coloured bulbs.
"The colour which is most highly scattered is blue. This is the blue sky effect you see during the day," Elvidge explained. "By cutting down on emissions in the blue, light pollution can be reduced. There is already a large stock of amber lights installed worldwide — high pressure sodium lamps."
Another possibility for people in light-polluted areas who are still hoping to catch a glimpse of the Milky Way is to use this interactive map that the researchers have released to find the remaining dark sky patches closest to them.
Interactive night sky atlas over America (Image: CIRES capture courtesy of NOAA)
Be forewarned, though: Those dark patches are not likely to be above you. Particularly in the US, dark skies can increasingly be found only on public lands or exceptionally remote areas. "Some of our national parks are just about the last refuge of darkness — places like Yellowstone and the desert southwest," co-author of the paper Dan Duriscoe of the National Park Service service noted in a statement.
Still, don't feel too bad for America. When you look at their skies in contrast with some of the areas even more hard hit by light pollution — like Berlin, which you can see inside of a "light dome" in this night photo of the city below — these islands of remaining darkness amidst the swelling light almost seem lucky. For now at least, some Americans can still see the Milky Way. It's just a bit of a trek to get there first.
Berlin's "light dome" (Image: A. Jechow/IGB)