What Is Light Pollution? (And How Can We Clean It Up?)

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The night sky over Mt. Doom may be the most beautiful sight the heavens afford. The mountains of Tongariro National Park on the North Island of New Zealand served as the home of Sauron and foundry of the One Ring in Peter Jackson’s Lord of the Rings films, and there is little human development there. On the night I crossed through in 2011, a brief flurry had passed, there were no street lights in any direction, and the main road was but a tiny ribbon of black dividing two banks of snow. Enveloped in darkness, it really felt like the "Land of Mordor where the Shadows lie."

Where I looked up, what I saw was the universe—a vision of space depicted only in film and imaged by Hubble. The sky was dark, but not dark. There were many colors; vivid patches of teal and navy so brazenly colorful that it took a moment to process exactly what I was seeing. The celestial continents of color were stars—billions of them—so far and so faint that they ceased being pixels on a black display and formed instead a mosaic of the cosmos. There is so much up there.


All night skies are not created equal, and the reason for this is called "light pollution." It is the cumulative effect of every excessive spot of artificial lighting in an area. These photons zip from every direction and toward the sky, and, as a result, we live beneath solid domes of luminescent haze. This has consequences: It smothers starlight, harms scientific discovery, and disrupts natural habitats and ecosystems.

Astronomers lament light pollution for the simple fact that we can't study what we can't see. Until every astronomer has his or her own personal Hubble, they are limited to their earthbound telescopes. Moreover, nonscientists are denied the chance to experience the cosmos in which we live. (For more on how light pollution affects astronomers, check out this PBS documentary.)

Environmentalists note that where there is light, there is electricity being used. That needless lighting wastes natural resources and thus harms the environment is self-evident. There's a good chance you turn off the lights when you leave a room. This same logic applies on a macro scale. Why keep a fast food sign lit at midnight when it won't be open until 6 a.m.?

Biologists and ecologists, meanwhile, assert that light pollution also harms the ecosystem. The International Dark Sky Association, a non-profit organization which advocates for sensible reform, describes how tens of thousands of sea turtle hatchlings die annually due to artificial light. The turtles are born on the beach and know only how to find the sea by using the natural glow of the horizon. Now surrounded by artificial lighting, the infant animals lose their way and die soon thereafter. Migratory birds, meanwhile, use the moon and stars for navigation and hunting. Artificial lighting is like holding a magnet to their natural compass. Birds find themselves in well-lighted cities, and things don't end well.


Nobody wants the world to fall into total darkness. We want light and need light. But it can be improved. Just as smog isn’t produced by any single car, but by thousands, the easiest change one can make involves inspecting one's own exterior lighting. What does it illuminate, and is it necessary? Specifically, in which direction is the light shining? Once you notice this, you’ll never be able to un-notice it: An alarming number of lamp posts and outdoor home lighting fixtures shine outward and upward, needlessly lighting surrounding trees and chimney tops rather than the sidewalks and yards where those lumens are actually needed. These lamps should be shielded or redirected or both.

Do you have home security lighting? Some dispute that it's actually helping you. What is inarguable, however, is that said lighting need not shine every minute of the night. Motion sensors save not only electricity, but also light for when there's actually something to see.

Lastly, consider educating your local government on the the problem of light pollution. This might sound like too much work already, but we're not talking about getting the Secretary of the Interior on the phone. Your local councilperson was voted into office to hear what constituents have to say. Bring up the issue! The Astronomical League's official magazine, Reflector, has published a how-to guide for getting a local lighting ordinance passed, and the International Dark Skies Association in conjunction with the Illuminating Engineering Society of North America has a model lighting ordinance for city planners and officials to use when rethinking lighting policies. Forward that material along. One need not even sell your local elected official on the wonders of starlight: Too much lighting means more glare, which can be a dangerous hazard for drivers and pedestrians alike.

After all, you shouldn’t have to walk into Mordor to appreciate the visceral wonder of the night sky.