Darker Cities, Brighter Stars

The Grand Canyon is a great place to study rocks. It's a geologist's dream, really. But for many obvious reasons, the Grand Canyon is also a great place for regular people to take in the scenic natural beauty. Thinking of it solely as a scientific observation site would be absurd.

“But somehow we still make that mistake about the sky and stars,” says Chris Luginbuhl. He's a co-founder of the Flagstaff Dark Skies Coalition, a local group that encourages the reduction of light pollution to make it easier to observe the night sky -- both for astronomers and for everyone else.

“Dark skies aren't just valuable to astronomers,” says Luginbuhl, who firmly believes that being able to see stars is an important part of life. That he happens to be an astronomer by trade, hey argues, is beside the point.

He and a growing number of advocates are behind a movement to transform cities and communities into better places to observe the night sky. Streetlights are the main target for unnecessarily emitting light directly up into the sky, which reflects off the atmosphere and prevents people and scientists from seeing clearly. This ambient light tends to be greater in concentrated urban areas, but even small towns can suffer from light pollution.

The village of Homer Glen, Illinois, has joined Flagstaff and Borrego Springs, California, as the third “International Dark Sky Community,” a designation awarded by the International Dark-Sky Association. The village has adopted and implemented a new lighting ordinance that focuses on reducing sky glow. Officials have replaced 184 light polluting street light fixtures with lower wattage lights that have shielding to block light from pointing up into the sky.

“Horizontal light emitted from 80 to 120 degrees is the worst for affecting sky glow and astronomical visibility,” says Rowena Davis at the International Dark-Sky Association. It's also kind of pointless. The whole idea of streetlights is to make it easier for people to see the road at night, not the air space just above it.

Another target is lighting that's too bright. Davis says that some light wavelengths, especially in the blue range, can cause glare that makes driving down streets unsafe. “It almost defeats the purpose of having a light,” she says.

The new lights in Homer Glen are about 70 watts, which is a significant drop from the typical 200-watt streetlight bulb. “They're not very bright, but they're bright enough,” Davis says. They're also using less energy, which helps offset the costs of installing new lights and shades.

Given its location in suburban Illinois, Homer Glen isn't exactly a prime astronomical observation site. “Nobody's ever going to put an observatory in Homer Glen,” Davis says. “It's just too close to Chicago.” The city, located about 30 miles away, can be considered a posterchild for light pollution. In November 2008 it was featured on the cover of National Geographic as part of an article about the vanishing night sky in urban areas.

As both Davis and Luginbuhl note, the issue goes beyond stargazing. Light pollution has been found to cause disruptions in the flights of migratory birds and other wildlife like bats and sea turtles. Reducing the amount of city light wasted in the sky can help reduce the impact on wildlife.

Through new lighting technologies and more cognizant lighting ordinances cities and communities can reduce the amount of light pollution they create. And though the problem probably can't be eradicated in the biggest and most densely populated cities, efforts like these can help make it so that when we look up into the sky, we see the lights of stars and not the lights of our cities bouncing back down at us.

Photo credit: Sukree Sukplang / Reuters