Light pollution shown for North America using data from the newly released world atlas of artificial night-sky brightness. Credit: The authors of the manuscript. Prepared by Fabio Falchi
A new, comprehensive atlas of worldwide light pollution reveals that one-third of all people cannot see the Milky Way in the sky, including nearly 80 percent of North Americans.
The atlas, painstakingly produced over the course of more than 10 years from satellite data and verified by more than 30,000 on-the-ground measurements, has been published in the journal Science Advances. The work describes the effect of the rapid increase in artificial light on the night sky throughout the world, documenting this lesser-known form of pollution that can affect local ecosystems, damage human health and incur large, unnecessary energy costs. The project also offers suggestions for how to reduce light pollution's impact.
The atlas was assembled using data from the Suomi National Polar-orbiting Partnership (NPP) satellite, a spacecraft about the size of a minivan, that orbits 512 miles (824 kilometers) above Earth to monitor changes in the planet's climate and help with weather forecasting. Study team members ran that data, and observations from the ground, through light-pollution-propagation software to create a set of maps that determine the light pollution experienced at any given location.
"Of course, there is a connection between the development of a country and the pollution," study lead author Fabio Falchi, of the Light Pollution Science and Technology Institute in Italy (known by its Italian acronym ISTIL), told Space.com.
The atlas also allows researchers to pinpoint which places are particularly far from pristine, dark skies. Cairo was the most distant from any region with a view of the Milky Way, Falchi said. Other areas particularly far were the Belgium/Netherlands/Germany transnational region, the Padana plain in northern Italy and the sequence of cities from Boston to Washington, D.C., in the northeastern United States. In some locations including Singapore, inhabitants never experience full night — in fact, the researchers said in press materials, skies are so bright over most of that population that their eyes never fully adapt to night vision.
Several important astronomy sites are still dark at night, including locations in north Chile, Hawaii's Big Island, La Palma in the Canary Islands, Namibia and the Baja California Peninsula in Mexico, Falchi said. Much of Africa, and deserts around the world where the population is low, also offer good skywatching opportunities, he added. However, in many of those places, you can still spot light pollution on the horizon from neighboring areas.
The researchers have prepared an interactive online map hosted by the University of Colorado, Boulder, and Falchi will soon release a printed book through Amazon and CreateSpace called "The World Atlas of Light Pollution" to further document the new research.
"There's increasing research that shows that exposure to artificial light at night is bad for us physically — [it] confuses our circadian rhythms and contributes to sleep disorders and impedes the production of melatonin," said Paul Bogard, author of the recent book on light pollution "The End of Night: Searching for Natural Darkness in an Age of Artificial Light" (Little, Brown and Company, 2013).
"Environmentally, there haven't been a ton of studies, but what we do know are things like the effect on sea turtles, migrating birds, moths, bats," Bogard, who was not part of the new study, told Space.com. "The statistics I always use are, 60 percent of invertebrates are nocturnal, and 30 percent of vertebrate species are nocturnal, so they're relying on darkness to live."