The language of light: standardizing light pollution measurements

Image credit: U.S. National Park Service / Dan Duriscoe
1676 words / 7-minute read

For as much as we know about light pollution, there is still much we don't. Scientists all over the world struggle to understand the details. Although we frame our work as an effort to preserve "dark skies", there is much more to it than that. On the surface it seems like a matter of whether we can see the stars at night. Below that surface, it's about managing a massive public resource that affects everyone.

Every other year, researchers gather to discuss the latest results and find ways forward. These include the social and public policy dimensions of our work. The recent Light Pollution: Theory, Modelling and Measurement (LPTMM) conference attracted astronomers, lighting designers, ecologists, public officials and others. This year's edition of LPTMM focused on standardizing how we measure light pollution. It's clear that lacking a common vocabulary is holding back scientific discovery.

​This month we look at the case for standardization in light pollution research and why it matters. It's much more than a dry, pedantic matter of academic bookkeeping. Rather, it's a vivid and logical problem with many practical effects. And it may be the missing key to making our neighborhoods safer and lowering our taxes in the process.

Validating (fear of) the dark

As a form of environmental science, light pollution research has immediate applications. Artificial light at night (ALAN) harms our world in many ways. It is a known hazard to almost all living things including humans. It brightens the night sky, hampering our views of the cosmos. It has some kind of interaction with crime and public safety. Most importantly, it represents a waste of energy and of money.

We didn't start out with that in mind. Early lighting technologies were very inefficient. As our understanding of human vision improved, so did our lighting. But the last quarter-century has seen a revolution in how we light the world at night. Light-emitting diodes (LEDs) have made outdoor lighting cheap to own and operate. As a consequence, there is now much more outdoor lighting than ever before. That has sent light pollution skyrocketing worldwide.

​Many people are afraid of the dark. Various influences conditioned them to believe that a brighter space is always a safer space. The availability of cheap and highly energy-efficient outdoor lighting caters to that perception. But it also validates a fear that people feel viscerally even if it isn't always rational. Any attempt to change the trajectory of light pollution must confront this reality. 

Bad lighting is the public's loss

Bright lighting creates harsh shadows where threats can hide. Its glare can be blinding to motorists, pedestrians, bicyclists and others. While intended to make the night more like the day, it can also leave people feeling exposed in outdoor spaces. But smart, well-designed lighting often yields a different response. It can help people feel secure and reassured when outdoors at night — even empowered. And it can achieve that by simply reducing or eliminating waste.

Outdoor light at night is a kind of shared public resource like roads or water. Poor-quality outdoor lighting is a colossal waste of energy and money. It is light paid for by taxpayers that often shines into bedroom windows or escapes into outer space. The goal of understanding light pollution is to design better lighting installations.

​Done well, this protects the fiscal bottom lines of towns and cities. It's also of interest to the world of private enterprise. There are reasons to believe that light pollution influences climate change. As "sustainability" is top of mind for many people nowadays, this matters more than ever. Demonstrating the true sustainability of good lighting design can be a powerful motive for change.

The language barrier: a bug's-eye view

When researchers across disciplines can't understand each other's work, we lose real opportunities. The light-pollution research community experiences this now in an immediate way. To illustrate this, consider for whom we characterize the nighttime environment.

Light pollution research began decades ago in the astronomy community. As the most impacted "early adopters", astronomers considered skyglow a real threat to their profession. Long before there were space telescopes, astronomers built observatories far from cities. Clear, dry air on mountaintop sites was already good for their observations. Moving further from cities isolated their telescopes from interfering city lights.

The human perception of the night sky became centered in astronomers' measurement systems. They used tools tuned to the physiology of the human eye. Their goal was to characterize the night according to how people see it. That was a natural consequence in a science that began with the human eye as its only detector of light.

Of course, that happened long before we began to understand how ALAN affects other organisms. Our human experience of light at night can be very different than that of other animals. A migrating bird, a sea turtle, or a nocturnal insect doesn't care about human vision metrics. They can sense specific colors of light, like blue or ultraviolet, that humans may not register at all.

Lighting scientists and engineers largely adopted the astronomers' human-centric approach. They devised measurement quantities and units tied to the human visual response. Again, this makes sense if the point is to light the world to cater to human needs. But we're not the only ones who inhabit outdoor spaces at night. Biologists studying light pollution found themselves awash in the wrong measurement tools. To this day, they tell other researchers to stop measuring light like (and for) humans.

Astronomers publish their skyglow data using "human-eye units". Biologists can't use that data to figure out if, say, a local ecosystem is in danger due to ALAN. Meanwhile, skyglow researchers don't understand the metrics ecologists throw back at them. This breakdown stalls scientific progress. Biologists can't explain a species' needs to lighting engineers in accessible language. Engineers can't design better street lights that keep neighborhoods safe while protecting wildlife. Everyone becomes stuck in a never-ending loop of guessing. 

Stepping into standards

In everyday speech, "standard" means "basic" or "normal". But in science and technology, a standard is a kind of superpower. It is an official, universal prescription that everyone agrees to follow. And they don't happen by accident or simple acclamation. Instead, bodies like the International Organization for Standardization (ISO) bring together global experts to write the rules. Then, the public gets a chance to review them before they become official.

Standardizing measurements has a particular goal in mind: creating accountability. If a city or a scientist says "we are following the ISO standard," everyone on Earth knows exactly what that means.
As a kind of a rulebook, technical standards are only useful if people actually use them. Standards that don't get enough buy-in from end users risk being disregarded or even ignored. At the same time, no standard is agreeable to everyone. By design they are re-evaluated every few years. If users see a need for change, a process follows to revise the standard. In each case, the first version is just a jumping-off point.

To do this, technical standards rely on the International System of Units (SI), a kind of modern metric system. The SI is the ultimate global dictionary for measurement. It uses 7 base units and 22 derived units to measure everything in the universe. There's no need to invent strange new units to fix the light pollution language barrier. We need only take care to root our light measurements in a system the global scientific community already trusts.

In turn, standardizing measurements can improve public confidence in scientists and their work. High-profile disagreements among scientists can lead to belief the scientific method is failing. Yet disagreement isn't a sign of weakness. It’s how we test, break, and improve our ideas. In fact, it's science's greatest strength.

​But there's a big difference between arguing over theories and arguing because your rulers are different. Current confusion in light pollution science happens because researchers use different measurement tools. Standardizing our methods and reporting units helps clear up these unnecessary misunderstandings. When scientists speak the same language, it eliminates false disagreements. It also gives the public well-deserved confidence in the safety and resource advice scientists provide.

Society wins when we come together

Standardizing measurements isn’t only neat bookkeeping for scientists in lab coats. It has practical, real-world effects that everyone should care about. If scientists standardize their language, they can give unassailable data to city planners. Decision-makers can in turn write better outdoor lighting policies. Those policies, if implemented well, can save money, reduce pollution, and improve public safety. It's much harder to reach these goals if scientists keep talking past each other.

How do we actually fix this scientific Tower of Babel? We can't expect everyone to wake up tomorrow and agree on a single language. So we need a plan.

An idea that emerges is a simple, two-part strategy. First, we propose forming specialized expert working groups across different sciences. For roughly a year, these teams will draft the basic ground rules for measuring light in their specific fields. Next, everyone will gather at an international pre-standardization congress. Think of this as a global peace summit for science. There, researchers can debate these ideas and hammer out a shared compromise. The result would be ready for submission to international bodies like the ISO to become an official, global standard. It’s a transparent, human process designed to get everyone speaking the same language.

​Ensuring an inclusive process, one that is both flexible and scalable, is crucial. If a durable standard results, the real work begins. We must then lobby for acceptance of the outcome in the research community. We must also socialize the results to encourage uptake and practical use of the standard. We'll know if we're successful by every scientific paper and government report showing adherence.
Achieving this result will take years, and it starts with admitting we need to try something different. The road to a standard for light pollution measurements leads toward a direction in which nights are better, safer, and maybe just a little darker.