Of the 1,000 or more stars that someone in a remote area can see at night with the naked eye, only a dozen or two are visible to the city dweller. Remember when you were a teenager, and you d walk out into your back yard at night and look up at the sky and think, Oh, my gosh. Being able to see the universe really helps you find your place in the world. But the aesthetics are only part of the picture. The lack of true darkness, experts say, throws a wrench into the biological mechanics of organisms from plants to animals to humans.
Clinical depression is one proven side-effect.
Researchers are now examining a whole host of others. The good news is that, unlike harmful toxins, light pollution is not permanent. A simple flip of a switch, or twist of a bulb, can have an immediate impact. Thinking rationally about outdoor lighting, Alvarez says, and using available technology to put light only where it s needed, also pays off in huge savings of money and energy. If nothing else, it ll help you start seeing darkness in a whole new light.