The starry nighttime sky is disappearing from view for most of the planet’s population.
Rampant artificial light in many parts of the world has become another urban pollutant, erasing our view of the night sky, blinding ground-based telescopes and threatening the health of humans and the planetary ecosystem.
The vanishing night sky is the subject of “The City Dark,” a documentary written and directed by Ian Cheney.
“The film begins with a very simple question,” Cheney says. “What do we lose when we lose the night and the darkness and the night sky?”
That’s both a personal and a global question for Cheney, who spent his childhood stargazing on his family’s farm in the rural northeastern state of Maine, and came to miss the night sky after moving to New York as a young man.
“Most kids in the world are now growing up without being able to see the Milky Way galaxy, this band of light that represents the hundreds of millions, the billions, of stars in our home galaxy that our sun is one of,” Cheney says. “And we will see, as our people evolve, what that means, whether that means we have fewer scientists, or fewer poets or fewer philosophers. But I certainly think there is no end to the inspiration you can gain from a beautiful view of the night sky.”
Along with inspiration, there is scientific knowledge to be gleaned, as astronomers look to space for clues about the origins of the universe.
But direct observation has become nearly impossible in big cities as their light bounces off the dust in the atmosphere and creates a diffuse pinkish glow that can drown out all but a dozen or so of the brightest stars.
“We’re limited to how far deep in space we can go,” College of Staten Island astronomy professor Irving Robbins says in the documentary. “When you look at the sky, it’s like I have a beautiful painting, very nice. But now I come along and erase all of it. I just leave a few spots. That’s what light pollution does.”
Cheney believes shielding outdoor lights so they illuminate only the street below is less intrusive and more efficient.
And while city lights help humans see where they are going at night, they actually cause many animal species to lose their way.
For example, migrating birds seem to have a star map encoded in their brains that helps them navigate as they fly north in the spring and south in the fall. When birds fly over cities, they often confuse the artificial lights below with the stars aboveand run into glass. A zoologist estimates that perhaps a billion birds a year die that way.
Too much light also interferes with human circadian rhythms, which depend on 24-hour cycles of darkness and light.
Epidemiologist Richard Stevens at the University of Connecticut Health Center says there is evidence linking rising rates of breast cancer in the industrializing world with the growing number of women working night shifts under artificial light.
Lighting manufacturers are responding to growing demand for bulbs that mimic natural light, and efforts are under way around the world to establish “dark sky preserves,” where light pollution is at a minimum.
“The City Dark” filmmaker Cheney is hopeful the night sky can be saved.
“There is something comforting and esthetically pleasing about our city lights,” he says, “we just have to find a way to have them and our stars, too.”