Peak & Prairie

Rocky Mountain Chapter's
Online Newsletter
June / July 1998


Light Pollution
by Dennis Cochran

Is this a joke? Light pollution? The city of Los Angeles, famous for air pollution, may be the largest of a growing number of municipalities that are doing something about light pollution, so it must be something. But what?

L.A. has recognized three aspects to light pollution: light trespass, unwanted light shining into a window from outside or into your eyes when you're driving at night; loss of the night sky, another part of nature which we moderns can no longer take for granted; and the energy and money wasted by lights.

Our forebears didn't have streetlights. They could tell what part of the year it was from the night sky, whether it was time to plant or to harvest. Nowadays we may know a lot of astronomy but very little about the night sky. The connection has been broken. The group that has noticed the sky disappear are the astronomers - including amateur astronomers. It's hard to stargaze if you can't see the stars for the lights.

Amateur astronomy clubs each have a favorite dark-sky site for observations, far from the city and suburbs. Professional astronomers have to build their telescopes in remote locations to escape light pollution. These places are getting harder to find. Los Angeles has decided to reclaim its sky by changing its outdoor light fixtures to Full Cutoff Fixtures. These reflect light down towards the ground. None of it shines sideways into the squinting eyes of nighttime motorists or into bedroom windows.

More importantly, none of the light goes uselessly into the sky. With these cutoff fixtures, they can light the same amount of ground using one tenth of the electricity that the old bulbs burned, saving the city big bucks. Eventually, people will be able to look up and see the stars, the moon, the occasional comet, the streaking meteorite from backyards and parks.

Of course, the conversion of L.A.'s light fixtures is not complete. It will take many years to finish. Even then there will be private light sources unaffected by the city's change of policy, but a big difference will be made and a precedent set. Other towns have done the same, but none so large as L.A.

From a Sierra Club member, I heard of an aspect of light pollution that had never occurred to me as an amateur astronomer: the effect that constant light has on the plants. Plants need light to grow and live, but constant light is unnatural. Perhaps plants need some hours of darkness just as humans do. I don't know, but I do know that an awareness is growing of what we have lost by overlighting our civilization. For more information on light pollution, you can contact the International Dark Sky Association headquarters at 3545 N. Stewart St., Tucson, AZ 85716 (

They can tell you more about the phenomenon of light pollution and what can be done to change it for the better - and save your town a lot of money. Think about this the next time you step outside at night and look up for the stars.