This article originally appeared in the August 1989 issue.
This article originally appeared in the August 1989 issue.

New commentary by Edward Bartholomew
Original text has been edited and excerpted from the 1989 original.

Astronomers are connoisseurs of light, collecting and analyzing tiny amounts emitted by stars and other distant objects in the universe. Even as they develop ever more powerful instruments, they face deteriorating conditions in the Earth's atmosphere that obscure the view. One of the biggest problems is light pollution—wasteful upward light from electrical outdoor sources that is scattered in the atmosphere and reflected back to Earth. To try to control it, astronomers have stepped into the political arena.

Although city dwellers might feel a wistful nostalgia for a starry night, light pollution does not actually hurt anyone. But it can be objectively defined and measured, unlike a related problem, light trespass—nuisance light that spills onto adjacent properties where it's not wanted.

When light pollution reduces the light-gathering capacity of telescopes, the effectiveness of multimillion-dollar facilities is compromised. Astronomers at the Mount Palomar observatory outside San Diego, which has the second-largest telescope in the world, began to lobby for a restrictive ordinance about 10 years ago when they realized the light scattered in the sky had increased to double the natural background level. Mount Wilson near Los Angeles, another of the world's premiere observatories, actually shut down for a few years because researchers could not use its telescopes with the sky glowing at five times the natural level.

Urban sky glow may seem an inevitable byproduct of civilization. In fact, mathematical models developed to predict the amount of light pollution at a site basically depend on two factors: the population of nearby cities and the viewer's distance from them. Unfortunately, observatories cannot just move when cities unexpectedly boom and sprawl. Only a few sites in the world have ideal altitude and climate, and the investment at existing facilities is expected to last a lifetime.

Some efforts prove that light pollution can be controlled. A strict ordinance passed in 1972 by Tucson, Ariz., has indefinitely extended the life of the world-class observatory at Kitt Peak, 40 miles from downtown. Measurements of sky brightness in 1988 showed that night viewing at the peak was basically unaffected by light pollution.

Ordinances such as Tucson's are politically viable because control of light pollution seems to make economic sense for the owners and users of exterior lighting. Astronomers are not asking people to turn off outdoor lights, but rather to use them more wisely for their basic purpose: to increase visibility at night, thus making travel safer, play more enjoyable, and business more profitable.

Kitt Peak astronomer David Crawford, member of light pollution committees in the Illuminating Engineering Society and International Astronomical Union, has made capital use of the energy issue. “Our big push is to get quality lighting, and by that I mean lighting that gets used and not wasted,” he says. “If we could get all quality lighting—energy-efficient lighting that doesn't cause clutter and confusion on the ground—we'd solve the problem of safety better, we'd keep the sky dark, and we'd save money.”

Crawford believes that light pollution is more than a specialized consideration for projects in a few parts of the world. “I think all architects and designers should be interested in and supportive of quality lighting, instead of blasting light all over the place, causing glare,” he says. “One wants to increase visibility, not destroy it. If an architect and I went out at night to look at lighting installations and grade them, I think we would agree on almost everything. The better lighting jobs are the ones that require thought and common sense.”

The Sodium Controversy The most controversial element of astronomers' lobbying is a preference for low-pressure sodium (LPS) lighting. In this case, what looks better to astronomers looks worse to a lot of other people. Color is the key to the dispute, although efficiency and other factors have been dragged into the fray. LPS lamps are monochromatic: They emit virtually all their light at a single yellow-orange wavelength. This is a windfall to astronomers who use the technique of spectroscopy, which separates light into component wavelengths that reveal the composition of stars and nebulas. Because the single LPS spectral emission line is of little interest to the vast majority of researchers, light of that wavelength reaching the telescope can be filtered out and ignored.

High-pressure sodium (HPS), probably the most widely used lamp type in contemporary outdoor equipment, produces broad-spectrum emissions over much of the visible range. While this greatly improves color balance for human viewing, it also blocks out starlight at many wavelengths. Therefore, excellent cutoff shielding is crucially important for HPS luminaires located near an observatory.

EDWARD BARTHOLOMEW'S THOUGHTS: This summer I went in search of darkness. The occasion was to view the Perseids meteor shower, which happen every summer in mid-August. Because I live in an urban area—Seattle—where there is a significant amount of light pollution, I had to drive about 40 minutes outside of the city to a state park just so that I could begin to observe this natural phenomenon without any interference from the haze of city light. As I returned home from watching this spectacle, I realized what a luxury actual darkness is.

This 1989 article argues for political and technical solutions to a complex issue: our relationship, as human beings, to darkness. The truth is that as a society we no longer value darkness; instead, we have been conditioned to fear it. Throughout the history of Western civilization, from literature to art to religion, the dark has been demonized. Due to advances in lighting technologies, we can ignore the night, thus expanding our time for leisure and productivity beyond the day–night cycle. Our global economies depend on this. Furthermore, our work as lighting designers has made us complicit in the eradication of darkness from our homes, work, communities, and landscapes.

The article represents the start of a lighting industry conversation regarding dark skies and each lighting designer's responsibility to control excessive light pollution through quality design. The effort to create quality lighting for our cities and landscapes, while still being mindful of lighting's impact on the surrounding natural world, has led to significant work and debate when it comes to the prescriptive guidelines that inform how we illuminate our exterior environment.

The most recent development is the long-awaited Model Lighting Ordinance and the inclusion of a significant sustainable-design LEED site credit that encourages a reduction in unnecessary exterior light spill into the night sky. This attempt to preserve darkness in the night sky was started by astronomers and concerned citizens who argued that a darker nighttime environment was ecologically responsible, more energy efficient, and allowed astronomers an unencumbered view through telescopes of objects in the night sky.

In addition, research on the impact of nighttime light on human health has found that excessive nighttime light, especially in the blue spectrum, has been identified as possibly increasing the risk factor for cancer in second shift workers. On the basis of such studies, in December 2007, the International Agency for Research on Cancer, an arm of the World Health Organization, classified night shift work as a “probable carcinogen” due to the disruptive impact that light at night has on human circadian cycles and sleep patterns, especially the endocrine system through the suppression of the sleep hormone melatonin.

These efforts and justifications to preserve the night sky by reducing excessive lighting have often resulted in a defensive approach to lighting design. The dark-sky movement's objective is to constrict how we use light to express architecture, by holding designers responsible for the percentage of uplight and light trespass, which has never been fully embraced by the lighting community. This defensive approach to design promotes a checklist process that can be stifling to the creative process.

These efforts also play into the scarcity narrative of sustainability and energy efficiency, where lighting is the first building system to be constrained, if it is not strongly defended and justified. But instead of a restrictive way to use light, what if there was a practical and creative way to use dark? What if designers expanded their visual spectrum to include shade, shadow, and darkness as vital elements in the visual environment both at night and during the day?

Learning not to fear, but to value the dark encourages a holistic approach to visual problem solving, an approach that is not based solely on lighting, but the totality of visual experience including darkness. As designers gain an understanding of the utility of darkness, a broader and more balanced visual experience emerges. Instead of adding more light to eliminate darkness, designers can allow natural variability, including darkness, to occur. Through the designed use of darkness in all of its forms, designers are able to satisfy a wider range of human visual experience, including the yearning for depth, mystery, and splendor.

As I drove home early that morning from watching the meteor shower, I began to understand that darkness is not merely an absence of light, but a quality of vision, a quality that the addition of more light can never fully realize.

“Darkness does not distress us; we surrender to it as inevitable. If light is scarce then light is scarce; we will immerse ourselves in the darkness and there discover its own particular beauty,” Jun'ichiro Tanazaki, as said in In Praise of Shadows

Edward Bartholomew is principal of Bartholomew Lighting, and a research assistant professor at the University of Washington. He is currently writing a book about designed darkness and its role in vision and architecture.

Local political battles have become intensely heated as jurisdictions near major observatories in California, Arizona, and Hawaii enact restrictive light pollution codes. Surprisingly, a few surveys have shown that when exposed to different streetlighting sources without a lot of fanfare, most people have no preference. This hardly calms the storm over color rendering, however. On the technical side, several widely circulated reports have been prepared for utility companies and municipalities in the affected areas. Most recommend HPS rather than LPS.

“I think the good outdoor lighting engineer or architect sees a real problem with the use of a light source that is very yellow both in its direct light and in its reflected light, which affects visibility,” says Mike Canavan, outdoor lighting specialist with Southern California Edison, whose customers almost unanimously choose HPS for streetlighting. “It is a fact that LPS is the most efficient light source that we have today. And it is also a fact that we can light roadways to a given level of illumination using HPS with less energy than we can with LPS.” This last statement, while generally supported by most U.S. outdoor lighting engineers, may be open to question.

LPS lamps do convert electrical power to visible light more efficiently than other commercially available light sources: figures run about 200 lumens per watt for LPS and 140 for HPS, versus 20 for incandescent. Comparing total lighting systems, however, is much more complicated, and must take many factors into account.

Ballast losses for LPS lamps are proportionately higher than those for HPS lamps. Over the course of their lives, LPS ballasts also experience a moderate to substantial rise in wattage consumed, with the highest rises for constant-lumen lamps that maintain light output over life. HPS lamps experience lumen depreciation without ballast wattage rise.

Fixture efficiency is an even more important factor. Like a biaxial fluorescent lamp, an LPS lamp has a long, hairpin-shaped luminous arc. Because HPS is more of a point source, it lends itself to superior optical control.

Primarily because of the lamp shape, the light distribution from an LPS fixture is typically widespread and diffuse, while good HPS fixtures have more focused, precise optical control. A well-engineered HPS fixture delivers light more efficiently from the source to the target than an LPS fixture can.

LPS proponents often refer to the lamp's widespread use in Europe, where energy costs are high. Canavan explains why fixture efficiency makes a bigger difference in the United States. “Many parts of Europe use a catenary system, in which linear LPS lights are suspended from cable directly above the roadway. In that configuration, LPS can be continuous, and it does a fairly good job of lighting the road. That's not the way we light roads in the United States, and I don't anticipate we ever will. We light roads from off the roadway, and we are moving poles farther and farther from the right-of-way in the interest of safety. We must direct the light onto the task, and given those circumstances, the ball game changes immensely.”

Although there is no final word on the sodium lighting controversy, a comprehensive independent report was prepared in 1984 by Ian Lewin of Lighting Sciences Inc. for the Arizona Public Service Company. Using manufacturers' reported data, independent photometric testing, and computer modeling with the program Site-Lite, Lewin compared technical and cost factors relating to the two types of sodium lighting. He analyzed a variety of fixtures and roadway configurations, chosen to represent everyday practice. The decision for or against LPS is complex,” Lewin's report concludes. “There is no clear overall [economic] superiority for either HPS or LPS … Decisions upon which to use should involve a study of the various factors.”

Shielding, Good Looks, and the Bottom Line
Besides attempting to influence or regulate the choice of lamp, astronomers focus on three other major ways to reduce light pollution. They favor shielded luminaries, limited times of operation, and zoning that restricts outdoor lighting most stringently near an observatory. Most lighting-pollution codes include most or all of these measures.

Shielding in particular is an idea whose time has come, whether or not telescopes are nearby. “Shoebox” fixtures with highly efficient, glare-free optics are now specified for area lighting wherever quality illumination and power savings are important.

Globe-style streetlights pose a real problem, because many designers and clients consider their traditional appearance highly desirable in the daytime. At night, though, they waste a tremendous amount of light and are often glaring. “If you put enough light in that thing to get some light on the ground,” says David Crawford, “you can't see the ground anyway because you've created so much glare. Add a little drizzle, and you can't see a darn thing.” Fortunately, many manufacturers now make decorative outdoor lights that provide cutoff optics in traditional and contemporary globe designs.

A Darker Future
Even the most successful efforts to keep the skies dark may not save observatories forever. Particulate air pollution, space debris, and radio-frequency interference also threaten to put them out of business. To those who suggest that space-based observatories will be the ultimate solution, David Crawford counters, “It costs many times more to do astronomy in space, say a thousand times as much. All observatories are suffering from chronic lack of funding now, so how can we afford to do it in space? It's not a viable solution.”

“For the indefinite future, some sites will stay very dark for astronomy. I'm very optimistic about that,” Crawford says, “because I think both our push and the push of other people for better lighting will get things under control. However, I could be very pessimistic, too, for the long haul. Insensitivity to the environment, whether it's day or night, will get us into deep problems.

“The view of the universe that people get at night, particularly at dark-sky sites, is one of nature's greatest marvels. If we destroy that view, and in a few generations people can only see the Milky Way and galaxies on a screen in a planetarium, it'd be the same as only seeing nature on TV. That's not what we want, I think, for the Earth.”

Light pollution is likely to generate more controversy for years to come, and both sides are still talking. “I think at some point in time we shall have a meeting of the minds,” says Mike Canavan. “I don't think that's going to happen overnight. I certainly think that communication between the astronomer-supportive group [who favor LPS] and those who look at other sources of light as more appropriate is the only path we can travel.”