Light Pollution

Light pollution often appears in cities as a hazy band of orange and yellow that floats above sleeping towns at night, the consequence of bright, wasteful night lighting. In recent years, the problem has quickly become an extremely serious one and is disturbing astronomers, amateur and professional alike. Yet with most urban areas continuing to grow rapidly, there is no sure solution in sight.

Later, you can share your experiences and offer your opinions and solutions.

Light pollution is affecting all types of astronomers in many different ways, and all share concern for the problem:

Observatories with their gigantic telescopes -- many larger but less clear than the Hubble Space Telescope -- sit atop high hills, even mountains. Mostly run by either the government or by universities, these observatories escaped the more mild light pollution of years past. But recently, some observatories have had to relocate, overrun by growing cities.

Serious amateur astronomers are motivated by their intense interests -- not only by light pollution -- to venture away from the city. The primary consequence for these enthusiasts has been that they must move farther and farther away to escape the lights of the city.

Star-gazers are being affected as well. They may be curious about the night sky and may regularly attend their local planetarium shows, fascinated by the wonders above on the dome. Yet the prospect of spending a late night crouching in pitch-black, mosquito-infested fields far away from the city does not yet have extensive appeal. Thus, light pollution is perhaps most seriously destroying a once plentiful group of so-called "backyard astronomers."

In fairness to the many cities burdened with growing populations and with concerns about the night sky, it must be understood that some light pollution in the city at night is unavoidable: for everyone's safety, parking lots and streets must be lit and stores must keep security lights on to deter crime.

What is of real concern, then, is the wasteful, unnecessary lighting -- true light pollution. The central causes of the excess light pollution in many cities today are the wasteful designs of street and security lights and billboards:

• Street lights with exposed lamps waste a good portion of their light because it radiates out in every direction, much of it lost in the night sky. More expensive to power and to maintain than more efficient versions, they are far cheaper to build and continue to be used by cities pressed to build new road networks for their suburbs.

• Billboards are often lit from the bottom, so much of the light from the exposed lamps escapes, again obscuring our view of the sky. Not only is the design wasteful, but many would argue that it is unnecessary in many cases to even have the signs burning away long after the streets have been abandoned for the night.

Considering the extent of the problem and the difficulty of changing the design of street lights and billboards everywhere, tackling the problem will certainly be quite difficult.

Many communities and individuals have recognized the problem of light pollution and are beginning to develop solutions, like replacing wasteful street lights. Lighting companies, too, have begun to manufacture more effective, efficient lighting fixtures. Despite these efforts, much remains to be done to restore the dark splendor of the night sky.

In 1988, the International Dark-Sky Association (IDA) was formed as a non-profit organization intended to create an awareness of the problem. Its initiatives are largely educational, as the group tries to expose what it calls the "value and effectiveness of quality nighttime lighting."

Improving the design of lighting fixtures is the most important goal for all concerned with light pollution. The IDA even publishes a list of Good Lighting Fixtures and Where to Get Them.

Logo. Courtesy the International Dark Sky Association.

Street lights should be shielded -- covered on the top and on the sides so that the light shines only on the street. Certainly, this does not eliminate the excess light entirely, but it limits the amount of light pollution thrown off by exposed lamps. In addition, many of these lighting techniques can be more efficient and cheaper to power and maintain.
Illustration. With its sides shielded, this street lamp would throw off far less light into the night sky by directing its light towards the street.



• Billboards should be lit from the top with covered lamps. Though there will still be light in the "dark" sky, the damage to our views will be minimized.
  Illustration. By shining from the top down, this billboard would send less excess light into the sky.

How Light Pollution Affects You

If you have ever tried to observe the night sky and have had trouble with light pollution, then please tell us about your experiences, give tips to help others avoid light pollution and share your ideas about minimizing the problem.

Check out the Astronomy Gallery as we begin to accumulate advice.