Have you ever seen the Milky Way? Maybe, but have you ever seen it while standing in the Great White Way—or any Great White Way: Times Square, Piccadilly Circus, or Akihabara? A citizen science research project known as the GLOBE at Night suggests that much of urban humanity—which now constitutes more than half the 7 billion people on the planet—cannot observe the opalescent band of stars, our galactic home, in the vast void of the universe. Instead, we confront a yellowish haze that constitutes modern night, pricked by the occasional extra-bright star or planet.
The problem, of course, is artificial illumination that makes night into day.
In a bid to better understand the extent of light pollution, an international consortium of researchers has used satellite data to map artificial light around the world by capturing cross-sectional slices of atmosphere. The most light-polluted areas are major cities, of course, whether the megalopolis that stretches from Boston to Washington, D.C., or the glittering lights of Shanghai's Bund. The map might serve to better locate ground-based telescopes and other instruments for observing the nocturnal firmament, among other dark sky concerns such as animal behavior.
There are still refuges of darkness. The International Dark Sky Association dubbed Death Valley National Park in California the world's largest dark sky park in February, thanks to its distance from the largest cities of the U.S. Southwest.
"Death Valley is a place to gaze in awe at the expanse of the Milky Way, follow a lunar eclipse, track a meteor shower, or simply reflect on your place in the universe," said U.S. National Park Service Director Jonathan Jarvis in announcing the designation.
Other escapes range from Namibia to New Mexico, but they are dwindling, according to the new maps. While light pollution is a sign of progress—access to light at night afforded by electricity—it is also a record of waste: artificial lights point up rather than solely illuminating what lies beneath. The solution is simple—better lighting design—and has the extra benefit of saving energy. "The light is going in the wrong direction," observed Steven Chu, former U.S. Secretary of Energy, in Copenhagen for the climate conference there in 2009 while standing in front of a projection of the nighttime spread of cities across the globe. "It should be going down, not up."