Have you lost it? Your view of the nighttime sky that is. If you live in a large city, you may have lost most of your view of the night sky.
Light pollution is caused by our expanding cities as people build and install lots of outdoor lighting in their communities. Safety at night is important, however, this "urban sky glow" is light that is being wasted, above and beyond safety and security. It prevents us from seeing the Milky Way and in some places people are now limited to seeing only Polaris, the north star, and a few other select bright stars. Luckily, comet Hale-Bopp was bright enough to see from our homes, but you may miss other spectacular celestial events like meteor showers. Most amateur urban stargazers must travel far from the big city to see constellations or planets.
Excess lighting is a wasteful use of energy and money. You can help prevent light pollution by getting involved in your community's efforts to use more efficient lighting. There's a lot that can be done without cutting down on safety and security. Here are a few examples:
Turn off lights when they are not needed.
Use light timers when you are away from home.
Use motion detection lights when possible instead of leaving lights on all night.
Keep light directed towards the ground or exactly where it is needed. Light fixtures that control light placement and brightness, minimize glare, and save on energy use are the best kind (low pressure sodium lights minimize "sky glow" best and are energy efficient as well for street lighting, parking lots, and security lighting).
Learn all you can about light pollution and/or get involved with an astronomy club or a group that works with their local community to keep skies dark enough for everyone to enjoy.
Adapted from "Astronomy's Problem with Light Pollution," June 1990, International Dark Sky Association.