Infinite Points of Light

October 22, 2001

When The Stars Grow Dim
Consider this. It is never truly dark in this city. On an overcast night, the clouds become a rosy-orange canopy, illuminated by the millions of city lights below. On a clear night, there is no spangling array of stars hanging in the sky; instead, there's an orange haze, through which only a few stars can be seen.

This is not some strange vision of another world or of a time when the stars grow dim. It's a reality in the present day. According to the Royal Astronomical Society (RAS), "about 99% of people in the USA and western Europe never see a truly dark starry sky from where they live." The cause? A relatively recent phenomenon known as "light pollution."

At first, it's difficult to see how light, a form of energy that we depend on, can act as a pollutant. But there is an excess of artificial light in the atmosphere around urban areas — so much that it's blocking our view of the stars. According to the RAS, "humans are enveloping the world in a luminous fog."

The Challenge for Astronomers
It's easy to understand how this is of concern to astronomers, both amateur and professional. Trying to see a fainter star from an urban area is like trying to spot a candle's light amidst a blaze of fireworks.

"Skyglow" is the term astronomers use to describe a night sky illuminated by light pollution. It is obviously very pronounced around urban areas; in huge cities like New York, the sky is super-saturated with light. Interestingly though, skyglow is not always associated with cities. Sometimes it can be found in rural areas where local sources, such as gaudily lit shopping malls, cast light skyward.

Getting a good view
Although skyglow is prevalent, there are still places where you can get a clear view of the night sky. Typically, these are remote areas, and they are often home to the world's biggest telescopes, as in Chile, Hawaii, and the Canary Islands. In fact, plans are on track for constructing the world's largest telescope on a site high in the Andes mountains. The site was chosen because it offers an immaculate view of the universe.

Astronomers use terms such as "pristine" and "dark-sky" to describe sites where the view of the heavens is crystal clear. As urban areas develop, such views are becoming a rarity on Earth, a source of great frustration for stargazers.

One astronomer, John E. Bortle, has developed a scale for evaluating levels of skyglow. He explains his scale in this Sky & Telescope magazine article.

Some astronomers see light pollution as tantamount to an assault on the sky. Astronomer Fred Schaaf writes in Sky & Telescope magazine, "Would we allow billboards on all the walls of the Grand Canyon? The sky is a thing even more awesome, diverse, mysterious, promising of knowledge, and beautiful than a geologic wonder."

The sentiments Schaaf expresses point to the wider issue of how light pollution will affect human culture as a whole. Will losing sight of the universe affect us in deeper ways than we realize?

Light Pollution and Human Culture
Dr. Malcolm Smith, director of the Cerro Tololo Interamerican Observatory in Chile, believes that human culture will be affected: "Bit by bit, without realizing, we are all losing a direct connection with the universe. Not only that, light pollution is one of the most rapidly increasing alterations to the natural environment created by humans. Human culture, from philosophy to religion, from art to literature and science, has always developed in relationship with the night sky and the universe beyond. Are we going to deprive future generations of that unnecessarily?"

It may sound dramatic, but it's difficult to argue with the figures — or the images of Earth's illuminated surface. An RAS study found that night never really comes to areas where half the world's population lives. The International Dark-Sky Association reported that in a small study it conducted, the majority of respondents — all 16- and 17-year-olds — had never looked up at the stars before.

The situation is forecasted to deteriorate rather than improve. The Light Pollution Science and Technology Institute in Italy calculates that light pollution is increasing at a rate of 5-10% per year in the US and Europe.

Is there a solution, or is light pollution inevitable in our increasingly urbanized — and electrified — world?

Turning Out the Lights
Urbanization is a trend that will continue to grow, but even so, light pollution can be reduced. The greatest problem is that so much light is directed at the sky when there's actually no need for it. It's the ground, not the sky, that we need to illuminate. As light pollution activists see it, this is an easy problem to correct; all that's needed is better lighting design.

For light pollution activists, the biggest offenders are often commercial outlets such as car dealership lots, gas stations, and shopping malls. Activists also refer to the decorative exterior lights used on buildings (such as hotels) as "vanity lights" — an excessive and wasteful kind of lighting that should be outlawed.

The International Dark Sky Association campaigns for darker skies. They point out the importance of using properly designed light fixtures that focus light where it's needed, don't consume excessive amounts of energy, and minimize glare. The benefits, they say, will not only include a better view of the sky, but also a more comfortable nighttime environment and increased safety for drivers and pedestrians.

More Links
If you're interested in stargazing, you'll get some good practical advice on avoiding skyglow from this article in Sky & Telescope magazine.

Urbanization is the leading cause of light pollution. Read this NASA article, Bright Lights, Big City, and see how images of Earth at night help scientists monitor urban development.

Visit the Web site of the International Dark Sky Association, which campaigns for darker skies.

Look at the First World Atlas of Artificial Night Sky Brightness which was published this August. Note: It's quite technical!

Another benefit would be vast energy savings. In casting so much light to the sky, where it effectively goes unused, there is considerable waste of electrical energy. The International Dark Sky Association puts the cost to the United States at $1 billion per year. As valuable energy is drained from power plants, this gives rise to further pollution: burning fossil fuels releases polluting gases into the atmosphere.

According to the Royal Astronomical Society, thousands of millions of dollars of energy "are tossed uselessly upwards into the sky each year — instead of down onto the ground which we want to illuminate."

The authors of the First World Atlas of Artificial Night Sky Brightness found that Venice, Italy, produced a modest amount of skyglow relative to its population. This was attributed to the "romantic" kind of lighting prevalent in the city.

So, perhaps restoring our view of the night sky is simply a matter of turning down the lights, much as they do in Venice. And wouldn't that be ironic — turning down the lights in order to see things more clearly?


		Light Observe how optical systems project light and images in the Middle School Gateways module, Light. An investigation of telescopes is included

		Casting Larger Eyes at the Skies Read about the world's largest telescope which will be constructed in the Andes mountains.

		Through Hubble's Eye This Riverdeep article explains how escaping Earth's atmosphere is one way to ensure a splendid view of the sky.