City skyline
Photo: © 2008 Jupiterimages Corporation
In the dark depths of winter, it's hard to fathom that we suffer from too much light. Yet "light pollution," a term astronomers coined for light that obscures the stars at night, is now recognized as a health and environmental hazard. The cause is brightly lit buildings, parking lots, stadiums, bridges...even that fixture by your front door.

Light pollution does more than block the Big Dipper. The International Dark-Sky Association (IDA) estimates that wasted light squanders the equivalent of 32 million barrels of oil or 9 million tons of coal each year in the United States. Birds that rely on moonlight and stars to guide migration become confused around cities and veer off course; so do amphibians that hunt and mate at night. Light pollution can also disturb the body's production of melatonin, which may leave us more vulnerable to certain cancers.

Fortunately, Americans are seeing the light. At least 15 states have ordinances putting limits on use of outdoor lights. The IDA's website,, lists the manufacturers that have earned its "fixture seal of approval." sells affordable outdoor fixtures that are "night sky"–friendly: well shielded and directed downward. Now, about that porch light...

Got the Milky Way in Sight? mySky

Then try this: The Celestron SkyScout ($199) and Meade mySky (right, $159) use GPS to help locate, identify, and provide history on tens of thousands of planets, stars, and constellations.