​In January, we wrote about new research showing that the world at night is lighting up fast. At the same time, something else is happening that may change the nighttime world as much. The orbital region around the Earth is filling up due to increasing activity in the commercial space sector. Thousands of new satellites, and the debris they create, may change the night sky forever. But how significant is the problem, and what can we do about it?

Satellites have been around for almost seven decades. For years, countries launched them one at a time for specific purposes. Most satellites served to relay communications across continents at the speed of light. In the 1960s, engineers began to experiment with flying small, coordinated groups of satellites. Called "constellations", these groups performed specific tasks like relaying time signals. This is the basis for modern conveniences like the Global Positioning System, or GPS.

By the end of the 2010s there were a few thousand satellites overhead. These ranged in altitude from a few hundred kilometers to about 37,000 kilometers. Those highest satellites, in "geosynchronous" orbits, can dwell indefinitely over any particular place. Their distance, coupled with the speed of light, made for somewhat slow communications. But times were changing. The cost of launching payloads into space was dropping.

​In 2019, the American company SpaceX launched the first group of satellites representing a new use of outer space. Called "Starlink", the project aimed to provide high-speed Internet to almost every place on Earth. The company plans to deploy up to 35,000 Starlink satellites by the end of the 2020s. Others, following suit, have proposed as many as 393,000 more. These so-called "megaconstellations" are unprecedented in the use of outer space by humans.

There are many concerns about how these activities in space will affect our planet. To maintain these large numbers of satellites in orbit, launches will become an almost daily event. Rocket launches produce materials that foul the air and water, and they can damage launch sites. Satellites coming back to Earth will deposit significant amount of metal in the upper atmosphere. And the current best practice in disposing of what returns to Earth is to dump it in the ocean.

Little in the way of international law governs these activities. The current legal framework descends from the Outer Space Treaty (OST). Signed in 1967, much of the treaty speaks to the peaceful exploration of space. It prohibits territorial claims on other worlds and the deployment of nuclear weapons in space. And it makes countries liable for damages caused by spacecraft launched from their territories.

But the OST does not envision uses of space like satellite megaconstellations. The governance system the OST establishes is slow to act. And countries downplay environmental concerns as they rush to cash in on the megaconstellation phenomenon. All the while, the risks of space debris are growing. Congested orbital space increases the chances of collisions between satellites. The space is also filling with debris shed by satellites and discarded items like used rocket bodies. These objects threaten new collisions and make space more dangerous. Some speculate that the generation of space debris could quickly spiral out of control.

​Astronomers grew nervous after the first Starlink launch. Strings of bright objects appeared in the night sky around the world. Reflecting sunlight to the night side of Earth, the satellites began appearing in telescope data. Radio transmissions from satellite to ground interfered with sensitive radio telescopes. The astronomical community organized a series of conferences in 2020-2021 to discuss the problem. They recruited participation from the space industry to find creative solutions to the problem. One result is the establishment of the Centre for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference.

​There is another way in which these large satellite constellations may affect the night sky. The rules of optics dictate the size of the smallest object that an optical system can resolve. Telescopes on the ground can resolve objects that are a little smaller than a meter in size. Smaller objects are not resolved, but their light still makes it into telescopes (and human eyes) at night. The result is a faint, diffuse glow across the night sky. This raises the brightness of the sky background, much like skyglow from light sources on the ground.

In 2021, researchers published a simple model to quantify how much light this contributes to the night sky. They made estimates for conditions before the first Starlink launch in 2019. The results suggested that by that time, satellites and debris ('space objects') raised the sky brightness by 10% above its natural level.

​As the night sky gets brighter, it becomes difficult to see cosmic light from beyond. Raising the background level lowers the contrast  between the sky and objects like stars and galaxies. For casual stargazers, it means seeing fewer stars at night. They may also miss faint phenomena like weak aurorae and dim meteors. Professional astronomers stand to lose some of their data. This means either they do less science or spend more money to build even bigger telescopes. This may have serious consequences in coming decades.

Another group published a study the following year that identified small debris particles as the problem. While they're much smaller objects than satellites, there are very many more of them. Given their small sizes, even the world's largest telescopes can't resolve them. The scientists concluded that if the generation of new debris can be minimized, the effect on the night sky might be minimal.

​The expected effect from space objects is small for now. Compared to skyglow in and near cities, it's almost negligible. The problem will be most noticeable in the least light-polluted places, like astronomical observatory sites. But that depends very much on what the future of space debris production is like. If satellites don't grind each other into dust through collisions, the worst outcomes may be avoided.

A combination of design and operations improvements and public policy changes is likely needed. This may involve changes to our understanding of what the "environment" is by taking a fresh look at our policies. While some space companies are willing participants in these efforts, others have yet to come to the table.

There is still much about this story that causes alarm. The night sky is changing, both from light pollution on the ground and, to a lesser extent, from space. While the problem of ground-based light pollution has demonstrated solutions, we don't yet have the answers for satellites. In both situations, the decisions we make today as a society will most certainly affect the future of our night sky.

Summary: Most efforts to reduce light pollution to date have focused on the public sector. But as night skies continue to brighten around the world, private enterprise can play in protecting dark night skies. Corporate social responsibility (CSR) and environment, social, and governance (ESG) principles may be powerful — and thus far unappreciated — levers on the problem.

CSR and ESG are hot topics in the global corporate world. But what do they really mean? CSR establishes values and sets an agenda, while ESG turns that agenda into goals with measurable impact. In a sense, CSR makes up the "S" ("social") in ESG by operationalizing the vision that CSR establishes.

The actions of early 20th century industrialists like John D. Rockefeller and Andrew Carnegie exemplify CSR. They spent billions of dollars on social causes, the legacy of which remains with us to this day. ESG traces its roots to the South African anti-apartheid movement that began in the late 1950s. It only became well known in 2006 when the United Nations launched the "Principles for Responsible Investment."

CSR is qualitative due to the many nuances of measuring social impact. ESG criteria tend to consist of quantitative metrics. It provides a way for companies, investors and the public to check how well companies stick to the sustainability and corporate responsibility goals they set. The current understanding of ESG considers the environment a stakeholder in all businesses. No particular industry or sector is exempt.

This framework is not immune to criticism. A major disadvantage of CSR and ESG is that small businesses shoulder much of its costs. Some critics contend that they undermine the primary aim of business, which is to create (financial) value for shareholders. They can also draw unwanted scrutiny over ever aspect of a company's business. And in some cases, CSR/ESG initiatives can distract from the need for meaningful, systemic change. ​

​The corporate world now ignores CSR and ESG at its own peril. Corporate boards increasingly seek advice on how to pursue these ideas. Some now see environmental concerns as among the stakeholders that their business affects.

But much of the pressure to do so still comes from the outside. One recent survey found that almost three-fourths institutional investors do not trust companies to achieve their stated sustainability and ESG goals. Investors and regulators alike are applying pressure on companies. And it's becoming hard for them to hide the environmental and social harms associated with their activities.

What about forces operating inside organizations? There is some evidence that companies prioritizing CSR and ESG principles have increased employee productivity and reduced turnover. Other data suggest that consumers, especially younger people, prefer to buy from companies that exhibit a strong sense of social responsibility. Failing to recognize this can even cost companies more in the long run.

Light pollution is an environmental issue at its core. It involves many known and suspected hazards to plants, animals and even people. With each passing year, the weight of the evidence grows bigger. And because the world still produces some 80 percent of its electricity from fossil fuel sources, light pollution is also a climate issue.

Light pollution arguably harms businesses' environmental stakeholders, yet it costs little to nothing to undo the damage. Many businesses will find it even saves them money to reduce their artificial light at night emissions in both their supply chains and at their facilities. Companies that fail to take advantage of these savings may be seen — pardon the pun — in a bad light. It may lead to accusations that they only care about higher-profile environmental issues. In turn, that implies that their assessments of environmental stakeholder needs are inadequate.

Wherever companies operate, they extract profits from those territories and communities. As the social significance of climate change rises, it is a disadvantage when the public perceives a company is doing harm rather than good. Those that do considerable business with governments may find these concerns turn into requirements. Planning ahead to be able to react quickly to a changing business landscape conveys a clear advantage.

There is even a nexus among ESG, land use planning, the public regulatory regime, and dark skies. In countries like Wales and New Zealand, large territories are under management as International Dark Sky Reserves. Both the central governments and local councils in those places are proactive in framing light pollution as an environmental concern. ​

Summary: Chromaticity shift is affecting an increasing number of commercial outdoor lighting products. This may affect public perception of solid-state lighting and could change the nature of skyglow over cities. This post explores what it is, why it's happening, and what can be done about it.

Comparing the two, it's clear that the purple lights emit much more blue light compared to light of all other colors. Bill and Cathie write, "The measurements show that for the purple lamp, the blue peak is about 2.5x stronger than the peak of green- yellow-red wavelengths. In the normal street lamp, the blue peak is about 1/2x the peak of the green-yellow-red."
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There is now a great deal of evidence that blue life is harmful to wildlife. In particular, in many species it disrupts the natural circadian rhythm necessary for wellbeing. We also know that blue light scatters better in the atmosphere than other colors. The strong scattering means that blue light is a main contributor to the phenomenon of skyglow over cities. Bluer light sources mean brighter night skies and fewer stars seen overhead.

The impact of shifting street lights can be reduced if cities replace them promptly. Failed lights are usually covered by manufacturer warranties, and cities are entitled to replacements at no cost. But the saga of chromaticity shift follows reports of other, widespread LED street lighting failures. For example, in 2019 the city of Detroit, Michigan, settled a dispute with the manufacturer of almost 20,000 of its street lights that failed not long after installation. The settlement did not cover the full replacement cost, leaving the city on the hook to the tune of $3 million. Replacing shifting street lights may come with similar costs.

There is a bigger story here than just one of purple street lights. There are of course risks attendant to any emerging technology, some of which might not become apparent for years. Business Insider suggests that the problem for American Electric Lighting was sourcing poor-quality parts from overseas manufacturers: "Those vendors are typically building products at scale, trying to squeeze out every efficiency they can without infringing on the patents on the high-quality, higher-priced versions. Sometimes that makes for a less-good LED."

These are dollars-and-cents decisions for lighting manufacturers. In the last decade, market forces exerted a huge downward pressure on LED lighting prices. Converting the world's existing lighting to LED was a tremendous, once-in-a-lifetime opportunity. Responding to customer demand created supply issues, and companies looked toward what was both cheap and available. The quality of some of the electronic components used in their products simply wasn't high. And some companies are now obligated to provide very expensive replacements under warranty.

These cautionary tales should inform the next generation of advanced lighting product development. It calls into question what other elements of the infrastructure of cities, now so deeply dependent on technology, may be next to fail. In our increasingly interconnected world, purple street lights are a metaphor for the ties that bind — and sometimes fail -- us.

The color qualities of light are only one aspect of the decisions that local governments face when they decide to modernize their street lighting. For many tasked with making decisions, it can be a confusing topic to navigate. Our expertise and experience advising cities choosing new lighting can make the difference in the success of retrofit projects. Contact us today to find out how we can help your city.

When you hear the term "light pollution", what comes to mind? While it's actually a broad term encompassing effects both on the ground and in the night sky, most people think of it as the inability to see the stars at night. That effect in particular, called "skyglow", results from light emitted on the ground up toward the sky. That light scatters in the atmosphere, which redirects it back toward the ground. There it competes with starlight and causes the sky to look grayish and washed out.

Thanks to research described in a new paper in the journal Science, we know that skyglow is increasing around the world at a stunning rate. The study, published in January, found the rate of increase is about ten percent per year when averaged around the world. 

Researchers in Germany analyzed tens of thousands of observations made by citizen-scientists between 2011 and 2022 as part of the "Globe At Night" project. The organizers ask participants to first locate familiar constellations in the night sky. They present maps of those constellations showing differing numbers of stars to show varying degrees of skyglow. The participants decide among the charts which best matches their own local night skies. This provides robust estimates of night sky brightness that scientists can compare against other sources of data about light pollution.

The new work is the first large-scale analysis of the Globe At Night estimates. Until now, Earth-orbiting satellites provided the only global view of light pollution. Earlier studies involving satellite images concluded that light pollution on the ground grew at a much slower pace. A 2017 study concluded that the rate was around two percent per year in the first half of the last decade. 

The new estimate in Science looks up from the ground instead of down from space, which may explain some of the difference. The satellites used to gather the night-lights data don't see blue light at all. They were not designed to make light pollution measurements in particular, so their onboard sensors aren't ideal for the job.

Their insensitivity to blue light is a problem given how the color of light at night continues to change. Since around 2010, many cities across the world converted their stock of public lighting to new, white light-emitting diode (LED) technology. They did this in hopes of realizing major reductions in energy use and financial cost with these energy-efficient light sources.

But white LED emits a lot more blue light than earlier lighting technologies. Satellites thus tend to under-count the amount of light at night they receive in space. That same blue light also scatters more strongly in the atmosphere than other colors. All other factors being equal, that effect explains in part why nights are getting brighter.

Besides to the color issue, satellites also miss some of the light directed upward from the ground because it becomes skyglow. Since they are above the atmosphere, satellites only detect light rays that reach them. Some of those rays never make it because they're redirected back down to the ground. So while ground-based observers saw their night skies brighten in the past decade, satellites recorded a much slower rate of change.

Furthermore, some light sources emit in ways that makes it unlikely their light will be seen directly in space. Sources like lit windows of buildings and illuminated signs emit light toward the horizon. Those sources are among the most important contributors to skyglow, but very little light they emit gets to the satellites. And there is evidence that at certain hours of the night, those sources dominate light escaping from cities.

Visual observers on the ground sense at least some of the "missing" light that satellites don't see. That way of estimating the brightness of the night accounts for both the increase in light emissions and a trend toward bluer sources. Citizen-scientists also extend the reach of light pollution studies. It's often easier to recruit them to count stars where they live than place light sensors in the field. That is especially true in very remote locations around the globe.

But even considering that volunteers provided about 50,000 measurements in the preceding decade, the information is incomplete. Vast swathes of land contained no observers at all. That left scientists to make informed guesses in places like Africa, where satellites suggest night lights are increasing the fastest.

Although the study authors note that known methods of reducing light pollution yield reliable results, current initiatives aren't producing results. This concerns light pollution researchers and activists alike. Skyglow is one symptom of a larger problem involving overuse of artificial light at night. We know it has negative impacts on everything from wildlife to energy use, traffic safety, and more. It's about much more than whether we can see the stars at night.

As more people realize the seriousness of the issue, governments are taking note. Countries like Mexico have recently classified light pollution as a form of environmental pollution. This can bring the mechanisms of existing environmental laws to bear on the problem.

The failure to reduce light pollution has real and lasting effects on communities. Wasted outdoor light at night involves measurable social and financial costs. Yet the new study authors admit that these messages about light pollution might heard by governments if the data were better geographically distributed.

More people participating in Globe at Night would improve the reliability of the results. If the number of participants increased by a factor of 10, we would begin to see trends on scales smaller than whole continents. As lead author Christopher Kyba said, "If we could do that, we would surely find places that are doing better than average, and we could try to figure out what they are doing right."