As cities grow, our once pristine view of the stars is increasingly being whitewashed by the glow of lights beaming upward. Astronomers, whose view of the heavens is being dimmed, are taking the lead in sounding the alarm. Their efforts have helped make the Czech Republic the first country to enact a national law against light pollution. Other countries are also taking a stand.
The International Astronomical Union has warned that we will lose sight of the stars unless we aim our lights downward only. British astronomer John Mason of the U.K. Campaign for Dark Skies says city lights are making stars an endangered species.
"Wouldn't it be a tragedy if in 25 to 30 years time, the only way you could get a view of a really dark sky was either to go on holiday to the Andes or some remote part of Africa or Asia, or go to a planetarium in your local town? There are very large parts of the developed world where it's impossible to get a view of a really dark sky," Mr. Mason said.
U.S. and Italian scientists using satellite images have created an atlas of metropolitan light emissions worldwide. The chairman of the International Astronomical Union's working group on light pollution, Malcolm Smith, says the images suggest billions of dollars worth of lost energy is flowing upward. But Mr. Smith sees light pollution as a cultural issue as well as economic. "Culturally, mankind's association with the universe has stimulated his development of his cultures. There is a long history involving navigation, art, poetry - all kinds of things involving our connection with the universe we live in. That is being lost bit by bit," he said.
A major step against ever-brightening urban glow is taking place in the Czech Republic. An anti-air pollution law going into effect in June contains a section to fight light pollution. A key provision requires shielded fixtures that block upward beams. Astronomer Jenik Hollan of the Nicholas Copernicus Observatory in Brno says putting it in a law protecting the air is logical.
"You can see light pollution. People often think that air above cities is dirty because they see light over the town as they are approaching it. But it is not so dirty. People just think it is dirty because it is lit by bad streetlights," Mr. Hollan said.
The International Dark Sky Association in Tucson, Arizona, a group that claims 3,600 members in 70 countries, calls the Czech law a great leap forward in combating light pollution around the world.
"We certainly hope that this will get the attention of other countries, who might see the obvious advantage for a national law," said David Crawford, the organization's executive director. "The advantage, of course, is it improves nighttime visibility, and hence safety and security. In principle, it can save a lot of energy, and it preserves the dark skies. So it's one of the very few issues where everyone actually does win."
Efforts to curb excess illumination are also underway from the Australian Outback to Britain's Sherwood Forest. The Czech law resembles one enacted in Italy's Lombardy region after 25,000 citizens petitioned against obtrusive outdoor lighting.
Many U.S. states also restrict outdoor lighting, as have cities and counties in Arizona, the site of several observatories.
Laws are also in force in areas of Chile, thanks to persuasive astronomers who staff the three big observatories there. Malcolm Smith, who directs one of them, says Chilean authorities understand the economic implications, including the attraction of dark skies for tourists.
But while the problem can be held in check, he is under no illusion the clock can be turned back.
"It is possible to bring this thing under control. I think it's very difficult to reverse it given the natural wish of populations to continue their natural development," Malcolm Smith said.