It was not always this way.  When I was growing up on the south side of Chicago not that long ago, my bedroom was an enclosed porch.  The room may have been a bit cold and drafty in the winter, but I loved the fact that I could lie in bed and watch from my window as the constellations paraded slowly across the sky during the night and throughout the year.  On a typical night, thousands of stars were visible in that urban sky, and the interest in astronomy they kindled in me was a major factor in shaping my interest in a career in science and technology. 

The photo at the top of this page shows the earth at night, as seen from space.  It is a composite of hundreds of pictures taken by NASA satellites. (A higher resolution version is available here.)  Although it is certainly beautiful, it is also disturbing, because it shows how much artificial light is being directed up at the sky.  This light (and the energy it takes to produce it) is not only being wasted--since in most cases it is a byproduct of street and building lighting intended to shine downward--it is also the source of light pollution, because it is scattered by particles in the atmosphere and inadvertently brightens the night sky.

Technology exists to address this problem:  street lights with reflective shields that direct their illumination downward, building lights that are activated by motion sensors instead of remaining on all night, and security lights and cameras that operate in the invisible infrared range, rather than in the visible spectrum.  The International Dark Sky Association and its affiliates and kindred organizations are working through education and activism to raise awareness of light pollution and encourage the adoption of environmentally-friendly lighting.  Their cause is a win-win proposition which, in the long-run, will save energy and money while preserving the beauty of the night sky for future generations.

Links:
= highly recommended

The Flagstaff (Arizona) Dark Skies Coalition. Situated at an altitude of 7,000 ft. (2,150m) and home to several observatories, including the venerable Lowell Observatory (established in 1894), the City of Flagstaff is proud of its dark skies and serious about keeping them dark.  On Wednesday, October 24, David Crawford, executive director of IDA, will present the City of Flagstaff with the organization's designation as the world's first "International Dark-Sky City."

The British Astronomical Association's Campaign for Dark Skies.  British affiliate of the IDA.

Skykeepers.org--California Chapter of the IDA.

"The Bortle Dark Sky Scale," by John E. Bortle, from Sky and Telescope magazine.  A system you can use to rate the darkness of the sky in your area.

Dark Sky Amateurs--a couple of serious amateur astronomers from smoggy Orange County, California, put together this page to tell would-be amateur astronomers how to find dark skies and what to do when they get there.

Dark Sky Observing Site Directory--a list of places to find dark skies in 28 states of the U.S. and 3 Canadian provinces, assembled by Phil Harrington.

The Albuquerque Astronomical Society's Dark Sky Efforts--a nonprofit organization that wants to make New Mexico "the Dark Sky State."

McDonald Park.  This park features dark sky, not burgers and fries.  It's an officially-designated "dark sky preserve" in Abbotsford, British Columbia (Canada).  The site explains what was done and how it was accomplished.

Ketchum, Idaho's Dark Sky Ordinance, passed by the City Council, June 21, 1999.

eLights.com--an Internet-based "lighting superstore" that offers dark sky lighting equipment.  Included on its site are a page with pictures showing how much "sky glow" light pollution in the U.S. has grown just during the past decade, as well as an excellent links page.

The Glarebuster--an innovative outdoor lamp that reduces light pollution and saves energy.  According to Sky and Telescope, "The Glarebuster is an extremely effective full cutoff fixture that accepts a variety of bulbs from standard incandescents to energy-efficient compact fluorescents."
 

"Dossier Lichtverschmutzung"--that's German for "light pollution" and this is the site of Dark Sky Switzerland (in German).