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Light Pollution & Dark Skies

Dedicated to the prevention of night time light pollution.

Image of Light Pollution in the US as seen from the DMSP satellite.

Saving The Night

Theft is occurring nightly before our very eyes. Increasingly, our dark nocturnal canopy is falling victim to the predatory glare of excessive and misdirected lighting, known by the popular term “light pollution.” This rape of the sky’s quiet majesty is not just a problem of aesthetics, however. Wasted light costs us money, contributes to air pollution, compromises safety and security, intrudes onto our property, and invades our privacy. And although the solution is really quite simple, it will take a concerted and cooperative effort by all of us to address the situation properly.

The culprit in this luminous larceny is misdirected light, illumination gone astray. Light intentionally directed upward, often seen lighting billboards and public buildings, is the worst offender since much of it simply splashes beyond its intended target. Other instances of misdirected lighting result from poorly shielded fixtures that still allow light to escape upward and horizontally. Such illumination not only destroys the beauty of the starry night but actually hinders the eye’s ability to see by creating both glare and deep, dark shadows. In fact, poorly designed lighting installation along thoroughfares may affect a driver’s vision in much the same way as do oncoming highbeam headlights.

There are other important concerns as well. It has been estimated that 30% of the electricity generated for outdoor illumination is wasted. That comes to over $4 billion annually. In the case of taxpayer-funded public lighting, the issue also becomes one of fiscal accountability. Important, too, are the environmental costs of producing the energy to power wasted light. For example, for every kilowatt hour of electricity used, almost two pounds of carbon dioxide and almost two grams of sulfur dioxide (responsible for acid rain) are emitted into the environment. Thus by simply eliminating wasted light, those amounts can be substantially reduced with no adverse effect on necessary lighting and with decidedly positive environmental benefits for the region.

For individuals and families another significant issue is that of light trespass, the spilling of unwanted light onto private property. This concern is already addressed in some local zoning codes where maximum light levels at property lines are established; but as the problem becomes more common, homeowners may also sense that the intrusion of unwanted light keeps them from using their outside property at night as they wish or may even interfere with indoor activities by shining into the house interior. Indeed, legal proceedings could result from such unwanted intrusion as a violation of property rights. Furthermore, poor quality lighting, whether commercial, municipal, or residential, can lessen the appeal of a neighborhood, lowering property values if the area begins to look too bright and gaudy.

Yet the problem of light pollution is easily remedied. In general, good lighting uses only the amount of light necessary for a specific purpose, and that light is directed properly. Lights allowing no illumination above the horizontal plane of the fixture and mounted at the proper height to do their job while avoiding glare and light trespass are the ideal. Inexpensive shields to retrofit older lights accomplish the same thing. In recent years, too, there has been a conscious effort by many municipalities, businesses, and individuals to better address the ways lighting is used and to promote the installation of sensible lighting whenever possible.

So the next time you are out at night, make a note of the way things are lit and why. Which fixtures are examples of good lighting? Which could be improved by shielding? Which are unnecessary? Remember, regardless of how we achieve the goal of reducing light pollution, the simple fact remains that we all win when sensible lighting is used. Good lighting saves energy and money, it reduces pollution, it improves the appearance of neighborhoods and maintains property values, it enhances the scientific and aesthetic appreciation of the glories of the night sky, and it preserves that beauty and inspiration for us and for our children. So when you find yourself lucky enough to be in a place where it is still dark enough to see the sky shimmering with stars, think how much less beauty there would be in the world without it. And become an advocate for sensible and efficient lighting.

John M. McMahon
Associate Professor of Classics, Le Moyne College

Links For More Dark Skies Information

International Dark-Sky Association
New England Light Pollution Advisory Group
American Astronomical Society Light Pollution Page

First appearance: January 23rd, 2011. Page subject to updates.