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Credit: Virginia State Parks
923 words / 4 minute read
The natural night sky looms large over humanity's past, present and future. Once a province only of the gods, the night sky is now our portal to understanding the universe. Light pollution, a phenomenon of only the last two centuries, now threatens to separate much of humanity from the starry heavens. Should access to a night sky unspoiled by light pollution be reserved only to those who live, or can travel to, rural places? Or should we aspire to a world that affords such access to all?
Under one sky
There are many reasons why people work toward preserving dark night skies. As our window on the cosmos, the night sky is the source of information that fuels astronomy. "Astrotourists" travel around the world unique experiences under the stars. Closer to home, casual stargazers find recreation opportunities under almost any skies.
We know that actions taken to protect the night sky have myriad benefits on the ground, too. Light pollution has negative effects on most wildlife species. Darker places, on the other hand, offer refuge to plants and animals already stressed by habitat loss and climate change. Better outdoor lighting can also improve public safety while using less energy. Taken altogether, these are powerful reasons for reducing light pollution.
But if we set all that aside, there's an equally strong argument that access to the night sky has a prominent place in what it means to be human. Dark night skies were once accessible to all people in the world, and they inspired great works of art, literature and music. The sky is part of the cultural heritage of all humanity. It's one of the few aspects of the natural world that we all share.
As such, it may be true that all people should have equal access to the stars. If so, then light pollution is more than an environmental threat. It interferes with access to an important cultural resource.
Cheomseongdae, an astronomical observatory in Gyeongju, South Korea. Built in around the 7th century CE, it may be the oldest surviving such structure in the world. Photo by Flickr user ecodallaluna.
An international view
To date there is little recognition in law for these ideas. Many of the assertions about humanity's rights come from the United Nations. A few UN-sponsored activities have either implied a right to access the night sky or called for it outright. For example, Article 1 of the the La Laguna Declaration of 1994 asserts that “persons belonging to future generations have the right to an uncontaminated and undamaged Earth, including pure skies.”
The United Nations Educational, Scientific and Cultural Organization (UNESCO) held a conference on these ideas in 2007. The resulting "Declaration in Defense of the Night Sky and the Right to Starlight" considers "an unpolluted night sky" to be "an inalienable right of humankind". The Declaration elevates the right to starlight to a place alongside "all other environmental, social, and cultural rights".
Another relevant UN statement is the 1972 UNESCO Convention for the Protection of the World Cultural and Natural Heritage. This action established the UNESCO World Heritage Programme. It has applied the label to astronomy sites, both ancient (e.g, the Chankillo Archaeoastronomical Complex, Peru) and modern (e.g., Jodrell Bank Observatory, UK). But so far it has resisted designating the night sky, or nighttime landscapes.
The night sky is both cultural and natural heritage. It transcends national boundaries; there is, for instance, no "American sky" or "Chinese sky" belonging to those cultures alone. And it’s not a problem that the night sky, or space, is an “intangible” thing. UNESCO already recognizes such forms of cultural heritage. Under the existing framework, the night sky could receive the same kind of recognition and protection as any object the UN recognizes.
The uses of outer space are now beginning to affect the quality of night skies on Earth. The space over our heads is increasingly crowded, with the planned launch of hundreds of thousands of new satellites in the 2020s. These satellite "megaconstellations" are gradually transforming the appearance of the night sky. And yet the main international treaty governing the use of space is silent on the subject. When the nations of the world signed the Outer Space Treaty in 1967, these concerns were on no one's radar.
Photo by Warwick University
Stars for all humankind
Threats to human health from the pollution of air, water and soil can dictate measures to reduce those pollutants. There is an emerging consensus among researchers that nighttime darkness is key to our health and wellbeing. Reasons exist suggesting that regular access to nature is good for us. And there's even evidence of disparities in the way light at night affects poor neighborhoods and communities of color.
Does nature itself have some say in all this? Nations have begun to recognize certain "rights of nature" that can lead to rehabilitation of environmental harms. That's true even when no real person has suffered any obvious injury. Touted as a legal means to combat climate change, it's possible the same principles apply to night-sky conservation.
In an era when so much divides us, whether neighbor versus neighbor of culture versus culture, the night sky is something we all share. Over time, we may come to realize that seeing the stars is not only something of value to people who can afford to escape the nighttime glow of the world's cities. Rather, it's an integral part of the human experience that should be available to all. Solving the global problem of light pollution is simple and cost effective. And it just might make all of our nights a little better.
There are many ways to bring back the stars to the places where we live, work and play. Contact us today to find out how we can help.
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Credit: Y. Beletsky (LCO)/ESO
1,215 words / 5-minute read
My friend, Dr. Al Grauer, is an astronomer with the Catalina Sky Survey in Arizona. The project aims to find many of the thousands of small asteroids that may one day collide with our planet. It relies on convenient access to dark night skies to see these faint interlopers.
As part of his work, Al became interested in what factors contribute to the brightness of the night sky. In turn, that determines how sensitive the Survey is. It's therefore important to understand those factors to know how effective the Survey can be at achieving its mission.
In studying this subject, Al made an observation that has stuck with me ever since I first heard him say it: "The natural night sky is alive with its own light." To understand the significance of dark skies and what we stand to lose to light pollution, Al argues, we need to understand the night sky as nature alone influences it.
Here, we review those sources and what we know about them. The results are important in framing what we mean when we talk about "dark skies".
As night falls
A remarkable transformation happens each day on Earth. Day becomes night and night becomes day again with a perfect predictability. This 24-hour, light-dark-light-dark cycle is the basis for one of the most basic of all biological rhythms. It also sets up a convenient way to record the passage of time.
Each day, the main event begins as the sun sets and the transition to night begins. From sunset until the onset of nighttime darkness, the brightness of the night sky decreases by about one million times. Once the Sun is about 18 degrees below the horizon, its direct light misses the top of the atmosphere and the observer is fully immersed in the Earth's shadow. This is "night".
The three phases of twilight from sunset to night. Graphic by T.W. Carlson, licensed under CC BY-SA 3.0.
Until that time, direct or scattered sunlight determines the brightness of the sky in any direction. As that light fades away, the stars begin to appear. After some time the sky gets no darker until several hours later as morning approaches. Then the process repeats, but in reverse order.
Sources of natural light in the night sky
Say you're outside at night in the most remote corner of the world. What would you see in the sky at night?
Absent light pollution, the sky is not black at night from anywhere on Earth. It's not even completely black as seen from space. Instead, natural light sources brighten the night sky in an understandable way. Once we know what those sources are, we can figure out how much light they contribute.
There are two main sources of natural light that we see in the night sky. One kind originates in our own atmosphere. The main component, called "airglow", originates over 100 kilometers overhead. In the upper atmosphere, atoms and molecules interact with each other in ways that causes the emission of light. This light is always present, but it can vary in brightness and distribution over minutes to hours.
Layers of airglow in the Earth's atmosphere seen from low orbit. The colors come from neutral sodium (yellow; 80-100 km) and oxygen (green, 100 km; and red, 200-300 km) atoms. NASA photo ISS042-E-037847, made by European Space Agency astronaut Samantha Cristoforetti. Public domain.
Toward the Earth's poles, near where its magnetic field emerges from inside our planet, a different effect can be seen. This is the "aurora". Energetic particles from the outer atmosphere of the Sun interact with the Earth's magnetic field. The resulting light is often very bright and seen as shimmering curtains of bright green and pink known as the Northern or Southern Lights.
The other source of natural light can be called "astronomical" and refers to light originating above our atmosphere. The most familiar variety is moonlight, which varies in brightness throughout the 29-day cycle of lunar phases. At its brightest, the Moon is still vastly fainter than most artificial light sources.
Some astronomical light comes from within the Solar System. Dust shed by comets and colliding asteroids fills space near the inner planets. The dust scatters sunlight toward us, lighting up the twilight and night sky as a ghostly, cone-shaped glow called the zodiacal light.
Fainter light sources are further away still. Masses of stars in our Milky Way blend together in the familiar glowing clouds seen from dark-sky sites. Dust elsewhere in our galaxy scatters starlight toward us. Even distant galaxies themselves contribute a tiny amount of light to our night skies.
What light pollution adds
Putting together all these sources, one comes up with a number that represents the typical brightness of the natural night sky. That represents a point of comparison for describing a light polluted night sky. Calling that amount of light one "unit" allows us to describe city skies in multiples. Rural areas might be around 2-5 units in brightness. The most light-polluted cities can exceed 1,000 units.
Light pollution isn't very much like those natural sources. Its spectrum often looks very different. When artificial light is directed into the night sky, it scatters in the atmosphere and forms "skyglow". This is the washed-out appearance of the night sky familiar to city dwellers that makes the stars difficult to see. Because bluer colors of light scatter more in the atmosphere, white light in particular makes this problem worse.
It also contributes to light received on the ground, which can be harmful to wildlife. Biology is tuned to natural brightnesses and rhythms like the lunar cycle. Some species, like the dung beetle, use the night sky to navigate. Others need nighttime darkness to avoid predators and find both food and mates.
Setting all that aside, skyglow robs us of our heritage as humans. The night sky is one of the few things that all humans share in common. For thousands of years it inspired great and enduring works of art, music and literature. Still today, seeing the Milky Way at night evokes a sense of awe and wonder. But now, more than ever, many people can no longer see the Milky Way from where they live.
Protecting an important resource
The Senegalese conservationist Baba Dioum once said "In the end we will conserve only what we love; we will love only what we understand; and we will understand only what we are taught." He emphasized the importance of understanding and learning from nature as the keys to protecting it.
The night sky at night is not perfectly devoid of light, like a dark canvas waiting for paint. Rather, as Al Grauer puts it, it's alive with its own light. Besides benefitting the ecology, natural darkness is worth preserving for its own values. Understanding that darkness to be imperfect establishes an important frame of reference.
What is "darkness"? And where does "night" begin and end? These questions still lack definitive answers. It may be that there are only literal shades of gray contributed by both natural and artificial light at night. The absolutes of light and dark we imagine may not be so absolute after all.
Effective conservation the resource of the night benefits from deep understanding and experience. We can contribute both to the pursuit your own dark-sky goals. Contact us today to find out how we can help.