Light pollution masks night sky for 83% of people

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A stunning view, but one few people get to see regularly: the Milky Way, seen here over Dinosaur National Monument in the US.
Dan Duriscoe

A third of humanity is blind to the brilliant starry streak of the Milky Way in the ink-black night sky, thanks to light pollution from Earth, a new study shows.

An international team led by Fabio Falchi from the Light Pollution Science and Technology Institute in Thiene, Italy imaged light pollution – such as light from cities that impinges on starlight – across the world.

Some 99% of those in Europe and the US, and 83% of the population overall, experience some form of light pollution.

The researchers say their work, published in Science Advances, will help scientists such as astronomers who must factor light pollution levels in their work.

But light pollution isn’t just an annoying hurdle for professional star-gazers – it’s ruining the human experience of looking up and contemplating the universe, they write.

Falchi and his colleagues gathered data from high-resolution satellite Suomi NPP, which scanned the Earth for light emanating from cities.

And since clouds, snow and mist can obscure the night sky, their data was incomplete without observations made from the ground up. An army of citizen and professional scientists used hand-held or vehicle-mounted meters to measure light pollution.

They found the vast majority of the world’s population, when they look up at night, has their view of the cosmos marred by Earthly light.

Astronomical Society Victoria’s Barry Clark says blue light, which is part of the visible spectrum emitted from energy-efficient light bulbs and electronics, is the most damaging to star visibility.

“Light pollution is a consequence of poor lighting practice – over-bright lights and light fittings, advertising billboards. It allows far too much light to go directly up into the sky,” Clark says.

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Asia in the New World Atlas of Artificial Sky Brightness, as seen in Google Earth.
Falchi et al, 2016, Science Advances

The study reports statistics on light pollution in every country in terms of how much of their population lives under artificial light as well as the artificial light’s brightness. The entire population of Singapore lives under a bright night sky.

But the winners for the most pristine night skies are in Africa: Chad, the Central African Republic and Madagascar. More than three-quarters of their population aren’t affected by artificial light.

Clark says the best places to avoid light pollution are in inland Australia or in the middle of the ocean.

“It’s virtually pristine in terms of the view,” he says. “In the cities the sky gets turned into perpetual twilight and you see very little of all the wonderful detail in the sky.”

The paper suggests a few ways to lower light pollution such as installing sensors on street lights controlled by traffic and the weather so they only switch on when needed.

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