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An example of a "full-cutoff" light fixture, which directs light downward, not outward, and emits no light above the horizontal. Photograph courtesy the International Dark Sky Association
Light pollution has been growing for years, but now it's accelerating, says Green, a cofounder of the New England Light Pollution Advisory Group (NELPAG). Ironically, part of the problem stems from increased lighting efficiency. Electric-power companies are replacing the incandescent and mercury-vapor street lamps that have been around for decades with sodium- and metal-halide lamps. The new lights are two to three times more efficient: while a 100-watt mercury lamp will deliver about 4,500 lumens (a lumen is a unit of light strength), a low-pressure sodium lamp can do the same job with only a 35-watt fixture. But instead of reducing wattage and gaining efficiency, many utility companies are replacing old lamps with new lamps of similar wattage that give out more light, much of which beams upward--where it blocks the more ancient light of stars.
"It's sad, especially for kids," says Green. "I'd like my 12-year-old son to see the Milky Way the way I could, and he can't see it anywhere within 100 miles of Boston with any decency."
Hindered stargazing isn't the only issue. In this country, "About $2 billion per year is wasted in light that goes straight up and out," Green says, citing a statistic from the International Dark Sky Association (IDSA) of Tucson, Arizona. Much of the squandered money is tax dollars. Green offers his own town of Lexington, Massachusetts, as an example. With a population of 28,000 and more than 3,000 street lights, Lexington spends $200,000 to $300,000 annually on outdoor lighting. The town estimated a $180,000 budget shortfall for its next fiscal year; rather than cutting back the fire department or high-school programs, says Green, voters opted to turn off half the street lights.
Besides obliterating stars and wasting funds, excess lighting is unhealthy and may even be unsafe. Too much light at night upsets human diurnal cycles, producing mental fatigue, a fact that torturers have exploited for years. Light
Harvard's exterior lighting gets both raves and hisses from dark-sky advocates. The Law School's Austin Hall (top) glares brightly, while Radcliffe Quad near Hilles Library uses lights with full-cutoff fixtures.
The good news is that the recommended solution is easy: just turn off the lights. Acknowledging that most communities aren't ready for total darkness, Green suggests they avoid overly bright bulbs and shield and position lights to shine only where needed. He urges towns to reduce street-light wattage and to use "full-cutoff" street lamps, which emit no light above the horizontal. Businesses can point building and billboard lights downward rather than up; individuals can use fixtures with hoods and reflectors that throw beams downward.
IDSA supports local legislation requiring full-cutoff streetlights. In Maine, Connecticut, Arizona, and New Mexico, state and municipal governments have acted to control light pollution, and similar legislation is under consideration in Massachusetts, Texas, Wisconsin, and Iowa. To help novices write ordinances for their towns, NELPAG has put together a 70-page circular complete with statistics, information on different lighting options, sample bylaws, and real examples. "We're getting hundreds of requests," Green reports.
But major obstacles remain. Electric-power companies often fight local legislation, perhaps, Green suggests, because they don't want municipal electric bills to drop. More important is a lack of awareness and education. Even Harvard has a spotty lighting record, Green says: while walkway lights are well adjusted, many spotlights point up at domes atop residential buildings. Ironically, some of the worst glare is around the Harvard Observatory. "We have several telescopes on the observatory grounds for teaching and public use, and one on the Science Center," Green says, "but the lighting has grown so bad over the last 10 years that it's difficult to see anything."
He is convinced that when more people begin thinking in terms of light pollution, efforts to fix the problem will snowball. "People subconsciously care--they just don't know it," Green says. "It's like smoking was 20 or 30 years ago--most people didn't smoke, but you assumed that you couldn't do anything about it. It was just a fact of life. Of course, now we see that it can be changed."