If you feel like automobile headlights have gotten brighter in the last few years, you’re not imagining it. Many now say the same thing. One need only refer to "those" headlights and most people know what one means. In fact, drivers in the United States and the United Kingdom have complained so often that both governments have started looking into the problem.

Most of the attention so far has been on glare and road safety. And to be clear, safety is important. It is, after all, the purpose of automotive lighting. But there’s another part of the story that many people don’t know about. Very bright headlights are impacting nighttime environment. Although lighted vehicles are only a temporary presence in that environment, they can have outsized effects.

​As the world continues to urbanize and vehicle traffic increases, headlights are becoming a source of light pollution. This month we look at how their light emissions move, spread far, and reach places that used to stay dark.

Every night, millions of cars send strong beams of light across the landscape. Unlike streetlights, headlights move and shine straight ahead, not only down. This means they can reach deep into forests, grasslands, wetlands, and other habitats that normally stay dark.

This kind of light pollution is different from the glow of cities or parking lots. It’s sudden, bright, and unpredictable. And because headlights are everywhere, they affect huge areas of land. That is true even for places far from towns or major roads. In some places, headlights are the brightest source of artificial light at night.
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We can even see some of this light from space. Highways trace out faint lines of light in satellite images. The example below shows such an instance.

Scientists already know that artificial light at night can confuse wildlife, change their behavior, and disrupt natural cycles like feeding and reproduction. But most research has focused on fixed sources like street lights. Headlights, which are both mobile and widespread, have been mostly ignored. For animals that depend on darkness to survive, these quick flashes of light can be a serious problem.

Today’s headlights are not the same as the ones from 20 or even 10 years ago. They changed as the arrival of white light-emitting diode (LED) technology revolutionized lighting. Several features of modern lighting make the problem bigger:

1. They’re extremely bright
Auto manufacturers design headlights to help drivers see far ahead. But this means they can shine much more brightly than natural source of nighttime light. Full moonlight has an intensity of 0.1 to 0.3 in a unit called a "lux". Yet a car headlight can reach around 25 lux — more than 100 times brighter. Even a short burst of light can disturb animals that are active at night.

2. They shine horizontally
Most outdoor lights point downward to reduce glare and limit light pollution. Headlights point straight ahead. This sends light directly into nearby habitats, where it can travel far beyond the road. By design, headlights also direct some of their light above the horizontal direction. The intent is to illuminate overhead road signs at night. Yet some of that light bypasses signs and goes into the night sky.

3. They affect huge areas
In Great Britain, headlight beams illuminate more than 2,000 square kilometers of land next to roadways. That’s a larger land area than all the natural grasslands in the region. Passing cars can thus affect even very remote places that are otherwise dark at night.

4. They give off a lot of blue‑rich light
Many headlights using white LED and xenon lamps produce a cool, blue‑white color. This is thought to promote driver alertness and aid low-light vision. But the blue component of white light is especially disruptive at night. It affects the secretion of melatonin, a hormone that helps regulate sleep and daily rhythms in both humans and animals. Blue light also scatters more in the atmosphere than other colors. For this reason it has an outsized effect on the brightness of the night sky.

5. They create sudden flashes
Headlights obviously don’t stay in one place. Each passing car creates a quick burst of brightness, followed by darkness again. Many insects and other nocturnal animals can’t adjust quickly, leaving them confused or vulnerable long after the car has passed. Near major highways and motorways, this confusion can persist for hours.

6. The problem is growing fast
Experts expect automobile traffic around the world to double by 2050. Millions of new roads will follow, some in places that have never had artificial light before. Headlights will reach deeper into wild areas, including some of the most important habitats on Earth. And this effect piles on top of light pollution from static sources. For example, many of those same roads will bring new and permanent roadway lighting.

The same features that harm wildlife also affect drivers. Very bright, blue‑rich white headlights can cause glare and make it harder to see at night. The aging eyes of older drivers are especially sensitive to this. This means that improving headlights can help both people and the environment. We don’t have to choose one or the other.

Poor outcomes are not the inevitable result of using the latest lighting technology for this application. As with other kinds of lighting, mindful design can mitigate a lot of the problem.

Let's go back to the premise underlying the existence of headlights. We do we use them? Because drivers need to see well at night. But brighter is not always better. There is no evidence to suggest that very intense, modern headlights are somehow safer than their predecessors. The key is making the best possible use of the latest lighting technology.

First, regulators should revisit existing standards for automotive headlights. Many standards assume the older, halogen-type light sources. Standards should be updated to reflect current technology. And governments should fund rigorous scientific research that supports evidence-based automotive lighting standards. This includes setting appropriate headlight brightness limits.

Second, automotive designs should make full use of adaptive lighting technologies. Modern headlights can dynamically adjust light beams to shine light only where drivers need it. This reduces glare and keeps light from spilling into nearby habitats.

Third, we need to dial back the momentum toward ever-bluer sources of light. Warmer‑colored headlights create less glare and are less harmful to wildlife. Again, research can help regulators craft rules that limit blue-rich light, protecting drivers, pedestrians, bicyclists and the environment.

Fourth, modern roadway design should explicitly consider light pollution. Transportation planners should think about how headlights affect the land around roads. New road projects, as well as upgrades to old ones, can include features that block or reduce light spill.

​And lastly, it may be time to reduce speed limits. Many traffic accidents, whether they occur during the day or at night, result from excessive speed. Lower speeds, especially at night, cater to longer driver reaction times. This, coupled with optimal traffic and automotive lighting design, maybe the recipe for safer streets.

Vehicle headlights are a growing source of artificial light at night. Yet they remain one of the least studied and regulated. As traffic grows and lighting technology changes, this issue will only become more important. It is creating new pressure on both cities and rural areas, as well as inhabitants of both.

But the worst outcomes can be avoided with adequate attention to the ideas discussed here. Further development of cutting-edge automotive lighting technology is one half of the equation. New research and thoughtful regulation of this lighting is the other.

​Protecting the night doesn’t mean giving up safety. With thoughtful design and good science, we can have safer roads for people and a healthier nighttime environment for wildlife.

Regular readers of the blog know that light pollution is a growing problem around the world. Each year, nights get brighter as humans deploy ever more outdoor lighting. This makes it harder to see the stars at night. It can also harm wildlife, threaten human health, and diminish the natural nighttime environment.

We know that much of this problem comes from wasted light. Lights are often too bright, shine where they are not needed, or stay on when they are not useful to users of outdoor spaces. Of course, this does not mean all outdoor lighting is bad. Lighting is important for safety, work, and amenity in public spaces. The challenge is using the right amount of light in the right places and at the right times.

Public policies can help reduce light pollution, but only if people support them. Many people want darker skies, but they also want safe streets, active businesses, and control over their own property. Any workable solution must balance these needs.

​One possible solution is the use of Lighting Zones. Lighting Zones guide limits on outdoor lighting based on the type of activity on a property and expectations for the availability of light at night. Different places have different lighting needs, and Lighting Zones try to match lighting levels to those needs. This month, we explore how Lighting Zones came to be, what their benefits and drawbacks are, and what new developments in this area mean for urban planning.

Lighting Zones emerged from ideas long used in city planning. Cities often divide land into zones, such as residential, commercial, or industrial areas. An overlay zone adds extra rules to these areas without changing the original zoning. The intent of land-use planning is to promote desirable development outcomes as well as more efficient uses of resources.

The idea is to match allowable activities on land parcels to their geographic situation. Compatible uses tend to cluster together. Zoning tends to isolate and restrict activities the public finds objectionable. In short, planners believe that zoning influences patterns of human behavior. Furthermore, the resulting changes are beneficial to society.

As applied to outdoor lighting, each Lighting Zone has its own rules for new buildings and outdoor spaces. City planners can then check if a new project follows the rules for its zone. This approach allows cities to focus on lighting without rewriting their planning laws.

But zoning rules can be hard to design and use correctly. Also, many urban planners don't learn about outdoor lighting in their formal education. They often know little about lighting technical information. As a result, outdoor lighting policies like ordinances and bylaws can be ineffective.

​The creation of Lighting Zones intended to make lighting rules easier to understand and apply. The idea originated from international standards promoted by the International Commission on Illumination, known by the French abbreviation "CIE". The Environmental Zones first appeared in a 2003 CIE publication intended to reduce obtrusive light at night. In 2011, these ideas were later expanded in the Model Lighting Ordinance (MLO). The result offered local governments a clear way to regulate outdoor lighting.

Lighting Zones are divided into five levels, from Zone 0 to Zone 4. These cover a wide variety of situations from areas with little or no outdoor lighting to very bright places, such as busy city centers or entertainment areas like the Las Vegas Strip. The table below shows the definitions of the Lighting Zones and how they relate to the CIE Environmental Zones.

Lighting allowances tend to scale up as the Lighting Zone number increases. The goal is simple: allow more light where people expect it, and less light where darkness is important. This system helps planners and decision makers set clear limits. Instead of arguing about every new light proposed, they can use the zone rules to guide their choices.

Lighting Zones have several benefits. They are flexible, easy to explain and match well with existing land-use zones. In some cases, local governments map them to their existing zoning systems. Lighting Zones help communities set clear lighting expectations for different areas. They can mediate dispute resolution as land uses change over time. And they are a tool local governments can use to push back against requests for exceptions or adjustments to development rules.

But there are also some drawbacks. Some places do not fit neatly into one zone. If zones are applied carelessly, areas may be given higher lighting limits than they really need. Over time, this can lead to brighter nights instead of darker ones. Some people also worry that Lighting Zones are too simple and do not capture real-world needs. Others may resist them because they do not want new rules or limits on outdoor lighting.

Many communities do not make use of Lighting Zones in their planning systems. At some level this is because of a lack of awareness that they exist. But even when planners know about Lighting Zones, they may hesitate to embrace them. They may find the distinctions between Lighting Zones unclear. In turn, they find it difficult to know when and where to apply them. Elected officials sometimes turn away from adopting policies they don't completely understand. They may also sense a lack of public support for this kind of zoning. 

The Illuminating Engineering Society, a U.S.-based professional organization of lighting engineers, promotes various lighting recommendations. Among its 'recommended practices' is RP-43 ("Lighting Exterior Applications"). 2026 will see a major update to this document. It's relevant to this discussion because RP-43 maintains the Lighting Zone definitions that first appeared in the MLO.

While the new recommendations are not yet published, they are public by way of the American National Standards Institute (ANSI) review process. We know that they contain a few amendments to the Lighting Zones. One major change is the addition of a Natural Conditions Zone. At last, this recognizes that the goal in some places should be to keep them naturally dark. These are places where the human presence at night is small or nonexistent. As a result, there is no expectation of permanently installed outdoor lighting. Where lighting deemed necessary, it should take the form of flashlights/torches and similar portable lighting.

​This is a turning point for the lighting engineering and design community. Before this update, the zone with the most restrictions was Lighting Zone 0. The definition of that zone calls for "little or no lighting" but does not exclude lighting altogether. Establishing the Natural Conditions Zone acknowledges that some situations call for a total prohibition of permanent outdoor lighting installations. As a result, the new RP-43 brings clarity to the Lighting Zone 0 definition. While Lighting Zone 0 still allows the installation of permanent lighting, its use is minimized by design. These updates help protect places where darkness is especially important, while still allowing bright lighting where it is legitimately needed.

Lighting Zones are a useful tool for managing outdoor lighting. When used carefully, they help protect dark skies while keeping places safe and usable at night. But for Lighting Zones to work well, they must be applied thoughtfully and supported by the public. As lighting technology and community needs change, the zones and their rules will also need to change. Right now, the biggest challenges are that many people do not know about Lighting Zones, and some resist new regulations. Better education and clear communication can help show that smart lighting benefits everyone.

​At the end of October we traveled to Westport, Ireland, for the Ninth International Conference on Artificial Light at Night ("ALAN 2025"). This biennial event brings together scientists, lighting experts, environmentalists, and community leaders to hear the latest in both research and practice relating to outdoor lighting and light pollution. This edition of the meeting series saw attendees from 42 countries on six continents, making it the most internationally diverse ALAN conference yet. The focus of the event was simple but powerful: How does artificial light at night affect our world, and what can we do about it?

A major shift in thinking became very clear this year. Many experts now agree that all artificial light at night counts as a form of environmental pollution. This doesn’t mean that we must cut all nighttime light emissions. Rather, the emerging sense is that we should treat nighttime light with the same consideration we apply to other forms of pollution. We should use it only when needed and then in the most responsible way possible. And although the field hasn’t settled on a single definition of “light pollution,” most people at the conference argued that we already know enough to start taking action. What’s missing isn’t information, but rather political will.

​One of the most exciting moments at ALAN 2025 was the official launch of the European Light Pollution Coalition, a new alliance working to protect natural darkness across Europe. Its creation may signal a shift toward a more globally balanced movement less dependent on its traditional centers. But the conference also revealed gaps. For example, no researchers from China attended, despite the country’s sizable influence on research. So while the movement is growing, there’s still work to do to make it truly international.

How we measure nighttime light is changing

Researchers are getting better at understanding what the night actually looks like. A few standout developments:
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• New computer models are making it possible to simulate how light spreads through the atmosphere with much greater accuracy.
• Elena Maggi (University of Pisa) described development of a fully submersible underwater camera system to be used to characterize the ambient light field at night.
• Understanding the significance of measurements continues to evolve. Maggi also noted that "measuring [in general] is not ‘measuring’" to an ecologist. Researchers must define different measurement regimes depending on the relevant ecological context.
• Experts say the most useful measurements now include both color and direction, not just intensity. That's true even as single-channel/panchromatic devices like the Sky Quality Meter remain the de facto workhorse instrument for measuring night sky brightness.

Satellite remote sensing: Great potential and big limitations

Satellites are essential for tracking how bright Earth has become at night. But some widely used platforms are missing key information. The most common satellite sensor used in studies can’t detect many modern LEDs because it isn’t sensitive to color. Alejandro Sánchez de Miguel (Instituto de Astrofísica de Andalucía, Spain) noted that lighting "trends based on DNB images are wrong", referring to the NOAA Visible Infrared Imaging Radiometer Suite Day-Night Band instrument. Satellite sensors like the DNB that are not color sensitive simply do not detect all light emissions from certain sources.

Better satellites now exist. An example is the Chinese SDGSAT-1 mission used to create a new European map of nighttime lighting that includes color. Conference attendees heard that researchers are pushing for a dedicated European “night lights” satellite. Yet even a successful mission proposal means it won't launch until at least 2036. Some presenters also warned that valuable U.S. satellite data could be at risk if long-term funding and storage aren’t secured.

Wildlife and ecosystems: Light pollution is a bigger deal than we thought

Light pollution is increasingly defined as one among many important human-made influences. Researchers argue that it should be part of a multi-stressor approach. Elena Maggi presented this as a “more-than-the-sum-of-the-parts result.” There’s growing interest in:

• Understanding how ALAN harms “ecosystem services” (the benefits nature provides to humans);
• Calculating the economic cost of losing those services;
• Deciding which species to focus with limited resources for conservation; and
• Finding better ways to measure how light affects animals—not just humans.

On that last point, a new "biological V(λ)" is in development intended to better quantify lighting impacts on non-human biology. This is a representation of the sensitivity of different organisms to light according to its color.

Lighting design should start with darkness

Lighting professionals at the conference shared a clear message: good design begins with darkness, not light. Chiara Carucci (Noctua) related that the idea is to treat light like a tool, not an end it itself. It should involve only what’s absolutely necessary. Designers should choose lighting that’s gentle on wildlife, human sleep, and the night sky.

Several speakers argued that industry has the technology to do this, but not always the understanding of why it matters. Andy Jechow (Brandenburg University of Applied Sciences, Germany) noted that while industry often has the engineering knowledge to make what we want, it sometimes “doesn't understand the ‘how’ and ‘why’.” For example, at times it struggles with the idea of controlling light with optics rather than added external shielding.
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There is strong interest in standardizing a set of metrics and measurement protocols in light pollution research. Jechow advocated for the ‘utilance’ of lighting (what fraction of light emissions reach the intended target). Julieta Cignaccio, an Aalborg University PhD student, suggested that because visual perception originates in luminance, a luminance-based metric would be most appropriate. And Brian Espey (Trinity College Dublin, Ireland) called for a more general metric characterizing light pollution in the broadest sense: "Is light pollution getting better? Worse? Bigger? Smaller?"

Policy: Turning knowledge into action

Policy experts emphasized that we have many untapped opportunities to reduce light pollution. For example, biodiversity laws may can regulate lighting, even when they weren’t written with lighting in mind. Yana Yakushina (University of Ghent, Belgium) suggeted looking beyond traditional policy tools to create “coherent legal frameworks”. This includes leveraging environmental policies that may not seem on the surface to address light pollution.

In some places, like Ireland’s County Mayo, more than a quarter of all nighttime light comes from public streetlights alone. As Laura Dixon (Mayo County Council staff) pointed out, that meaning governments have an outsized influence. But when working with decision makers, nothing beats showing them good and bad lighting in person. Stijn Vanderheiden (Flemish Government) argued from his experience working with decision makers that they need to see good and bad outdoor lighting in context. They can then receive relevant information in a concise and useful way.

New mapping tools are helping communities see both exactly where dark places still exist and how to protect them. Vanderheiden gave as an example the new Belgian Astronomical Darkness Necessity Map. Its purpose is to "identify and map scientific, educational, cultural, recreational locations." The creators plan to make a template version available for others to use.

Several speakers noted that most policymakers aren’t opposed to change; rather, they don’t know how light affects the environment. But, as Vanderheiden pointed out, policy makers must start changes. That is, public pressure alone isn't enough.

Human health: It's not just about blue light at night

You’ve probably heard that blue light at night is bad for sleep. That’s true, but it’s only part of the story. At ALAN 2025, researchers explained that even yellow or orange lights can disrupt our body clocks if they’re bright enough. Rob Lucas (University of Manchester, UK) recounted the development of the newer metric called Melanopic Equivalent Daylight Illuminance (“melanopic EDI”). It does a much better job of describing how lighting affects our circadian rhythms. It's important to “avoid lights that 'look' blue,” Lucas advised attendees. Failing to take into account spectrum can under/overestimate effective ‘doses’ of light. In turn, this may imply false equivalence and fuel inappropriate lighting design.

Culture and community: Rethinking our relationship with the night

Social scientists reminded attendees that while the night is always part of nature, we tend to forget that in our over-lit cities. Nick Dunn (University of Lancaster, UK) argued that darkness has become "provisional" in cities, where we don’t often think of why exactly we use light. Nona Schulte-Römer (Humboldt University, Germany) encouraged communities to think more deeply about why we use light in cities and recognize that different groups of people experience nighttime lighting very differently. She underscored the idea that "There is no one ‘public.’ There may be many." Practitioners and activists should thus avoid approaching engagement as though the public were a monolithic entity.
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Effective change comes from focusing on people first and not just policies. Mike Hawtin (North York Moors National Park, UK) summed it up: “We don’t have 'policies.' This is absolutely about people.” He described "engagement at scale" in his park from the smallest parish councils to largest private landowners.

​The next meeting will take place in Valparaíso, Chile, in July 2027, an important step toward ALAN a truly global conversation. Leading the local organizing committee for the 2027 event, Prof. Sebastian Fingerhuth (Pontifical Catholic University of Valparaíso) welcomed all in attendance to visit his country and and enjoy what promises to be another productive and valuable event.

Light pollution is increasing almost everywhere in the world. [1,2] We know that this has serious consequences for society and the environment. [3] Its rate of increase is faster than that of population growth in many countries. This implies that the rate of consumption of artificial light at night is growing. [1]

Researchers think that this results from the lower cost of operating light-emitting diode (LED) lighting compared to earlier lighting technologies. If this is true, it undercuts the claimed environmental benefits attributed to the high energy efficiency of LED. We don't yet know what this means for differences in energy consumption, if indeed energy savings are offset by the growth of new lighting.

​We also know that harms associated with light pollution are reversible. It does not persist in nature like other forms of pollution. When we deploy proven solutions, we see the reductions in light pollution that we expect. [4] Through concerted efforts, we can imagine a future in which it reduces in intensity according to predictions.

This is not only limited to slowing the further growth of light pollution. Activists are beginning to talk about 'restoring' natural nighttime darkness in some places. But what does this mean, and what would the world look like if it were successful? This month we look at the notion of nature restoration and what lessons the broader conservation movement has for dark-skies advocacy.

When we talk about 'restoring' nature, it's important to agree on what that term means. It is often discussed in the context of another word, 'rewilding'. It refers to reverting to environmental conditions resembling those that existed before human manipulation. One finds the term applied often in situations in cities where removal of development traces encourages natural processes to return. [5]

It is important to distinguish rewilding from another kind of restoration referred to as "Nature-based Solutions". [6] The International Union for the Conservation of Nature defined this term in 2006 as "actions to protect, sustainably manage, and restore natural and modified ecosystems that address societal challenges effectively and adaptively, simultaneously benefiting people and nature." [7]

But it's not always synonymous with ecological restoration. In contrast, one definition of 'ecological restoration' is "assisting in the recovery of ecosystems that have been degraded or destroyed, as well as conserving the ecosystems that are still intact". [8] The authors who suggested the definition argue that the rising use of the term 'Nature-based Solutions' "may partially be a rhetorical response to shifting priorities and terminology by funders of research and practice". Yet they say that Nature-based Solutions "reflect a genuine commitment to achieving societal benefit." While the terms are distinct, they "are similar and can be mutually supportive."

Why does this matter? Some scholars have criticized Nature-based Solutions as a relic of colonialism or even a form of greenwashing. [9] It centers humans, in the sense of achieving social benefits, over any intrinsic value nature may have on its own. It relies on truly sustainable environmental management, which is rarely achieved in practice.

It also implies that humans won't conserve something unless they value it, presumably for selfish reasons. In this sense, it follows the implications of a famous quotation from the Senegalese forest engineer Baba Dioum. In 1968, Dioum 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." [10]

All these ideas proceed from the assumption that there is some value to nature restoration, whether for humans or nature itself. Appeals to human wants and needs may be a means to an end in this regard. Dark-sky advocacy often focuses on the purported human benefits of improved outdoor lighting, such as security, public safety, human health and more.

While advocates also point out the harm that light pollution poses to ecosystems, they tend to frame the argument in a way that caters to human motivations. Examples of this include focusing attention on so-called 'charismatic megafauna' like sea turtles or nocturnal insects that pollinate food crops. In this sense, advocacy efforts seem to align with Nature-based Solutions as a matter of pragmatism.

Efforts to bring dark night skies back to areas affected by light pollution usually take the form of "landscape scale nature restoration". The Scottish Nature Agency defines this term to mean "land managers working together to restore nature on a large scale, across multiple land holdings and resulting in multiple benefits for nature and people." [11] It further suggests that "this approach is more effective at achieving environmental, economic and social benefits than working in isolation, on smaller, single sites."

DarkSky International has pursued this for years through its International Dark Sky Places program. [12] The program can be described as Nature-based Solutions with two main goals. First, it aims to increase public awareness of light pollution and reward participating sites for taking steps to address the issue. The second goal — restoring natural nighttime darkness over typically large geographies — is more outcome-based.

The evidence for success in achieving the restoration goal is mixed. [13,14] In recent years it has put increasing emphasis on cities as a source of both problem and solution. Through new designation categories like its "Urban Night Sky Places", it advances the idea that restoration of darkness in more distant sites depends on changes in the lighting of cities. But this approach is still so new that we don't yet know if it works as advertised.

Would a stronger appeal to Nature-based Solutions still result in meaningful restoration of dark skies? One might look toward Attention Restoration Theory for clues. It holds that a connection exists between access to nature and total human wellbeing. [15] But for one thing, we don't know for certain whether the natural nighttime space is a "restorative environment".

It's also unclear whether experiences in nighttime darkness helps move the needle on nature restoration initiatives. That's particularly true given a broad (and maybe innately human) fear of the dark that stokes hesitation toward some nighttime restoration initiatives. It might be an obstacle to moving people to care about this aspect of nature to the point where they would give up something else they valued to protect it.

​Other social concerns can override the human valuation of natural spaces. A recent example is the U.S. migrant detention center popularly known as "Alligator Alcatraz". In mid-2025, this facility opened at a disused airstrip in Big Cypress National Preserve, a federally protected land in south Florida (and an International Dark Sky Park). Aside from concerns about light pollution due to detention activities at the site[16], activists alleged other environmental harms that were not subject to review or meaningful oversight. One might well ask whether the American public would have accepted this activity in a higher-profile U.S. national park like Yosemite or the Grand Canyon.

​Although public attention to light pollution has risen steadily for decades, it is still climbing the "hill of awareness". We have identified a collection of best conservation practices, and there is some evidence for their efficacy. Yet we're a long way from implementation in many parts of the world because it's just not a priority for most of the public.

This argues for a more top-down approach as compared to countries like the U.S., where outdoor lighting policy is distinctly local in flavor. At the same time conservation is often focused on larger landscapes where few people live. To not only slow the growth of light pollution around the world but also reverse the trend requires different ways of thinking.

What about tying restoration to legal requirements? The recently enacted EU Nature Restoration Law aims to do so, obligating EU member states to develop plans to restore at least 30% of habitats in "poor condition" by 2030, 60% by 2040, and 90% by 2050. It even contains some language about light pollution. [17] For now the law is forward-looking, and we don't know if it will yield good results.

Globally, the successful strategy may well instead be to "bend the curve" of light consumption per capita. That is the amount of light emitted in a territory per head of population. In earlier times, that figure seemed to be stable. The advent of LED, with its extreme energy efficiency, seems to have prompted its increase through what economists call "elastic demand".

But human behavior proves difficult to change through heavy-handed regulation. Instead, the more appropriate goal may be to change the human relationship to ALAN. We recently wrote about a combination of hard and soft law in the form of so-called "lightshed management" as a possible approach. It sets targets for light pollution reduction while engaging in extensive community outreach to nudge people toward different behaviors in terms of how they use outdoor lighting. Here, too, the idea remains a theoretical one only for the moment.

​Without targets — preferably binding ones — it is going to be difficult to achieve true restoration of nighttime darkness. Considering the motives for restoration carefully and asking critically whom they benefit is an important step. The implementation best practices remain mostly to be determined. The stakes remain high if we do nothing, but our confidence in successful results once we apply suitable efforts is equally high.

Light pollution is increasing over much of the world. It is a trend that goes back decades and shows no sign of slowing down. We wrote here about the situation as recently as early 2023. At that time, new research showed that skyglow was then increasing at a worldwide average rate of 10 percent each year. A much newer notion is the idea of 'light pollution' from space. We also wrote about that situation in 2023. The concern was then about the changing appearance of the night sky. 

Fast forward only two years, and a completely new concern is now emerging. What happens when satellites can turn night into day? The result is a novel threat we explore in this month's post.

We live in an era some that some call "New Space". This describes activities in outer space dominated by private commercial actors. It contrasts with previous decades when only national space programs could pay the high cost of launch.

That cost plummeted in the 2010s, enabling private companies to launch payloads into space. At first, the main service private satellites provided was global telecommunications. But as investor money poured into the industry, entrepreneurs began to come up with audacious new ideas.

One of those ideas is to harness solar power in space and send it to the ground. This takes different forms including converting sunlight to radio waves. A simpler concept would deploy large reflective surfaces in orbit around the Earth. These would redirect sunlight to the ground to illuminate solar power stations on the ground. The scheme only works near sunrise and sunset, when the reflectors are in sunlight but the sun has set on solar farms.

Proponents of this technology note that it can provide light for other uses. For instance, they say, it could function in place of street lighting over cities. It would provide an illumination level about four times the brightness of full moonlight. That could aid in disaster recovery when utility power is unavailable.

You would be forgiven for thinking this is the first time anyone has proposed such a thing. But it's not. In the Second World War, a group of German scientists at the German Army Artillery proposed building a Sonnengewehr ("sun gun"). They designed a focused beam of sunlight from an orbital reflector as an offensive weapon. And they expected the devastation to be akin to what the world later saw resulting from the U.S. atomic attack on Japan.
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In October 1992, the Russian Federal Space Agency launched the Znamya 2 satellite. Designed as a 'solar sail' testing a new kind of propulsion, the RFSA repurposed it as a 20-meter-wide solar mirror. It consisted of panels of stretched, highly reflective film that deployed after launch.

During a demonstration of the technology, it successfully directed a beam of sunlight to the ground. It yielded a spot 5 kilometers wide with the intensity of full moonlight. The beam swept across Europe from southern France to western Russia at a ground speed of 8 kilometers per second. Though weather along much of the ground track was cloudy, some observers reported seeing bright flash of light as the beam swept past them.

The RFSA tried another test of this technology in 1999 with a larger spot size and a brighter beam. The test failed when the reflective film panels tore after snagging a piece of the Progress spacecraft used to deploy the object. Although the RFSA planned future satellites with even large collecting surfaces, the 1999 failure was the death knell for the program.

More than 25 years later, the concept is again inching closer to reality. An American company called Reflect Orbital applied for clearance to launch and operate a test satellite in 2026. It consists of a thin-film reflector 18 meters on a side and a system to control its orientation in space. By changing that orientation relative to the direction of the Sun, it can direct a beam of sunlight toward Earth.

Like Znamya 2, its beam has a diameter of 5 kilometers on the ground, enough to illuminate a large solar power installation. The beam shines for about four minutes before the satellite disappears over the local horizon. The company plans to eventually launch a flotilla of thousands of these reflectors. That would enable continuous sunlight for about an hour after dusk and an hour before dawn.

Will it work? We don't yet know. The Russian test from the 1990s suggests that something like this is technically workable. But if it does, a host of concerns are expected to follow.

Some problems have to do with the idea of shining a beam of light with the intensity of sunlight onto specific locations at night. A simple calculation suggests that the reflectors will appear on the sky as sources several times brighter than a full Moon. Far from the beams, they'll still look like bright stars, and dozens of them may appear in the sky at any moment.

Scattering of light in the atmosphere will make the edges of the beams 'fuzzy'. The mirror-like surfaces of the reflectors will deteriorate with time due to exposure to the space environment. The beams of light they produce becoming more diffuse, spreading out and losing intensity. This may direct light well away from the intended targets of the beams. Some of that light may end up in ecologically sensitive areas.

As described above, the mirrors have to change their orientation in space as they pass over a given location. Although the company claims that the reorientation will happen quickly, it involves sweeping the light beam across the Earth at high speed. A 2000 study published in the Journal of the Royal Astronomical Society of Canada found that "space-mirror experiments reflecting sunlight to Earth can produce resolved images having surface-brightness sufficient to damage human eyes looking through telescopes or binoculars". Even if the flash is instantaneous, it could cause real harm to the viewer.

In a similar vein, these light beams could be a problem for aviation safety. Pilots have for years reported intense flashes of light from laser pointers on the ground shining up at their planes. At the altitudes of commercial planes, beams of sunlight from space will be larger in size and brighter than they appear on the ground. This could become a significant hazard for civilian and military pilots alike.

There is great potential for misuse of this technology. Sunlight could be weaponized in a way that conventional solar power cannot be. It may be directed toward people and communities that don’t want it. It could also be used to convey battlefield advantage in military conflicts. This adds another layer of complexity in deciding how the technology should be regulated.

The reflective material could be subject to fraying or other kinds of damage on orbit. They may shed material that becomes space debris. Over time, the satellites will inevitably fall back to Earth, whether from atmospheric drag or deliberate action to de-orbit them. Where, when and how they will come back down is not clear.
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Lastly, despite prognostications to the contrary, there is no “inevitability” about this or any other idea for furthering renewable energy sources through methods such as sunlight as a service. Improvements in battery storage are slowly improving renewable energy supplies at night. We may be better off deploying more solar panels on the ground, even knowing that there is a life-cycle cost for producing/recycling the equipment. 

"Greenwashing" is a label describing efforts made to persuade the public that an organization's products or actions are friendly to the environment. Usually they are not, and the greenwashing effort is deceptive.

That seems to be happening in the case of sunlight as a service. The sales literature is full of starry-eyed claims having to do with a purported social good. But it focuses on the notion of sustainability in a narrow sense: providing sunlight from space for "clean" electricity generation. It doesn't consider the full lifecycle of the project from launch to de-orbit.

It doesn't account for the negative externalities of directing light to spaces where it doesn't naturally exist at night. There is abundant evidence for the harms associated with artificial light at night. That in principle includes sunlight directed to the night side of Earth. It interferes with natural rhythms as much as sources of electric lighting.

At the same time, there is no national or international prohibition on this kind of activity in outer space. The international legal framework governing activities in space takes the view that 'what isn't forbidden is allowed'. Norms often change to discourage a harmful activity only when the harm has already been inflicted.

In that sense it resembles obtrusive space advertising, which we wrote about here recently. Dangerous activities in space can occur with only an ill-defined liability system on the other side.

It's unclear how serious any of this is, and projects like Reflect Orbital may not fly at all. Many such audacious ideas never become reality. Some are meant only to attract the intention of investors looking to make quick money as companies are bought and sold.
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It remains to be seen whether there is any successful business model for selling "sunlight as a service". Yet the lure of new wealth from space may prove irresistible. This is a challenge for defenders of the night everywhere, and one that is worth watching closely.