Turn Down the Lights

While Physics Today's April 2002 cover photo of Earth at night is impressive, I would urge readers to note that the lights seen in this image represent billions of dollars per year of energy wasted on upward-directed outdoor lighting. That issue of the magazine, devoted to the energy situation, appears to address only the need for increased energy production, with conservation barely mentioned. Ernest Moniz and Melanie Kenderdine do point out that efficiency improvements "represent the most effective opportunity for meeting energy and environmental goals in the near to intermediate term" ( page 45). How effective is it to use light fixtures that waste up to a third of their light by directing it upward?

Physics can help with efforts to increase energy reserves; it can also be applied to conservation. The quality of outdoor lighting techniques and fixtures is generally poor worldwide, the US included. Proper outdoor lighting, with fixtures that direct no light upward and that provide nonglaring illumination at appropriate brightness levels, can provide safe nighttime spaces while conserving energy and preserving the wonders of the starry skies.

Part of California's response to its recent energy crisis (see http://www.energy.ca.gov/outdoor_lighting/index.html) was the creation of an innovative project to examine the nature of existing outdoor lighting. The initial results are not surprising: Most facilities are poorly lighted and often at unnecessarily high levels.¹ Such lighting does little to help with safety or security, or to improve the nighttime ambiance of our communities. It is obtrusive to many and wastes a lot of energy. By reducing glare, we can lower the overall levels of outdoor lighting, increase safety, and save energy.

Readers interested in learning more about outdoor lighting issues are invited to spend some time at http://www.darksky.org, the Web site of the International Dark-Sky Association.

1. Nancy Clanton, lighting specialist, presented initial results at the International Dark-Sky Association's annual meeting in Tucson, Arizona, in March 2002. Final results are expected to be published later this summer at http://newbuildings.org/pier/ (click on "Outdoor Lighting").