Light pollution is out of control

Concern about global light pollution is growing. Astronomers are noticing its growing effect on astronomical observations, just as predicted in previous decades. Our artificial light, much of which is not strictly necessary, is interfering with our science.

But it’s not just scientific progress that’s at stake. Can humanity afford to block the opportunities for wonder, awe and contemplation offered by the night sky?

We’ve all seen satellite images of Earth at night, with twinkling interconnected cities lit up like strands of holiday lights. These images show us how our global civilization has grown, how we have progressed and how advanced we have become. But in reality what we are seeing is also light pollution. And we’re starting to pay a price for that pollution.

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In January 2023, the Globe at Night organization released a paper based on 10 years of night sky data. The data didn’t come from satellites, an important point we’ll get to later, it came from citizen scientists scattered around the world.

Globe at Night has published a research article showing that the night sky gets 10% brighter every year. Each year, more of the sky’s faintest stars are drowned out by the skyglow from streetlights, traffic lights, and other sources. For more and more people around the world, the sky shows fewer and fewer stars, not to mention the great arc of the Milky Way.

Globe at Night collected more than 50,000 individual naked-eye observations of the night sky, where they asked citizen scientists to find the faintest stars. The decrease in faint stars visible in these observations over the decade-long effort indicated a sky that was steadily brightening.

Participation map 2022 GLOBE at Night.  For more information, click on the image.  Image Credit: GLOBE at Night/NOAO
Participation map 2022 GLOBE at Night. For more information, click on the image. Image Credit: GLOBE at Night/NOAO

If the Globe at Night newspaper was a rallying cry, other researchers are responding. A pair of researchers has released their own short paper that serves as a sort of addendum to the Globe at Night paper. They are Fabio Falchi from the Applied Physics Department of the Universidade de Santiago de Compostela in Spain, and Salvador Bara, an independent researcher in Spain. Falchi is also affiliated with the Light Pollution Science and Technology Institute in Italy.

A startling analysis by Globe at Night, a citizen science program run by NSF's NOIRLab, concludes that stars are disappearing from human sight at an astonishing rate.  Not only that, but the Milky Way is invisible in our cities, obscuring humanity's connection to nature.  Image credit: NOIRLab/NSF/AURA, P. Marenfeld
A startling analysis by Globe at Night, a citizen science program run by NSF’s NOIRLab, concludes that stars are disappearing from human sight at an astonishing rate. Not only that, but the Milky Way is invisible in our cities, obscuring humanity’s connection to nature and the cosmos. Image credit: NOIRLab/NSF/AURA, P. Marenfeld

Satellite data paints a less worrisome picture, but satellites have a different perspective. They can only measure the light that reaches them, and only by the wavelengths their instruments are tuned to. But the light that reaches them is not necessarily the light that drowns the sky from the point of view of people on the earth’s surface. That’s why the Globe at Night effort eschewed satellite data in favor of citizen scientists scattered around the world.

Forecasts based on satellite data predicted that light pollution will increase by 2% each year, but the Globe at Night effort showed the actual number to be 10%. This is a huge discrepancy and means that light pollution will double in less than 8 years. That number should catch everyone’s attention, but why the discrepancy? Why can’t high-tech satellites get it right?

“Part of this discrepancy could be explained by the inability of these satellites to detect blue light,
emitted in large quantities by LED light that began to be used outdoors about 10 years ago,” write the two researchers. ‘These satellites are also unable to see light that is mainly horizontally emitted, such as that from the growing number of ultra-bright LED billboards and illuminated building facades, well.’

Falchi and Bara urge the construction of new generation satellites capable of overcoming this weakness. Multi-band sensitivity is needed, as is “…multi-angle tracking capability,” according to the pair.

They are not the only ones. In 2020, a group of researchers addressed this issue in a paper titled “Remote Sensing of Night Lights: A Review and Future Outlook.” One of the authors was Christopher Kyba, who also co-authored the Globe at Night article.

Standing next to the Milky Way.  Drowning the night sky isolates us from nature, and that's not good for humans.  Credit: P.Horlek/ESO
Standing next to the Milky Way. Drowning the night sky isolates us from nature, and that’s not good for humans. Credit: P.Horlek/ESO

In that paper, the authors agree with Falchi and Bara that we need satellites that can sense the rapidly spreading LED lights. They also point out that we need a better understanding of the angular patterns of light emission. They don’t stop there. “Perhaps most importantly,” they write, “we argue that higher spatial resolution and multispectral sensors covering the blue to NIR range are needed to more effectively identify lighting technologies, map city functions and monitor consumption. of energy”.

Is fantastic. Detailed and robust data is part of any genuine effort. But we already know that light pollution is on the rise. “People, the media and politicians are used to associating the thaumaturgical properties of artificial light with road safety and personal safety that they don’t seem to deserve”, underline the two researchers. “So, year after year, more and more light is installed to light up the night.”

What can we do about it?

Something in the human psyche wants to eliminate the darkness. We want comfort, security, convenience, and an overall sense of well-being and prosperity. There’s nothing wrong with creating safety if well-lit areas can fight crime, but is more light always the answer? Is there a point of diminishing returns? Not just for us but for the natural world?

“Life on Earth evolved with sunlight during the day and starlight and moonlight, when present, during the night,” write Falchi and Bara. “If we introduce artificial light into ecosystems at levels that exceed, even thousands of times or more, the level experienced under natural conditions, animal behavior will change accordingly.” Increased nighttime illumination could disrupt predator-prey relationships, change mating behavior and even contribute to the extinction of some populations or species.

It’s not just stargazing and the natural world that pay a price for light pollution. Science is also taking a hit, as observatories near urban centers have tackled the problem of light pollution head-on. Take the case of the 100-inch Hooker Telescope at Mt. Wilson Observatory near Los Angeles.

From its completion in 1917 until 1949, it was the largest aperture telescope in the world. But as light pollution increases, it has become increasingly difficult to make useful astronomical observations. The light was blowing out faint star images, and it kept getting worse. Finally, in 1985, in direct response to the growing problem of artificial light, the Hooker Telescope was taken out of service.

The Hooker Telescope enclosure at Mt. Wilson Observatory.  The telescope was decommissioned in 1985 due to light pollution.  Image Credit: By Craig Baker - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=73093247
The Hooker Telescope enclosure at Mt. Wilson Observatory. The telescope was decommissioned in 1985 due to light pollution. Image Credit: By Craig Baker – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=73093247

It was no small matter. The telescope worked well and had played an important role in establishing extragalactic distances, understanding the nature of spiral galaxies, and establishing the expansion of the Universe, among other scientific endeavors. Other instruments at the Mount Wilson Observatory are still in operation, but the Hooker Telescope’s potential has been knocked out by excessive skyglow.

No caring person would say they want species driven to extinction and powerful telescopes shut down while they are still effective. Thoughtful nobody wants sky-gazing to be curtailed. But one of the major issues in this issue is our prosperity. As lighting gets cheaper and LEDs get cheaper, we’re fitting more and more lights and illuminating streets and pathways that never needed them before. What can be done?

For example, we’re not likely to participate in a mass campaign to have streetlights removed, but people have tried other things. “Attempts to control light pollution have been made in recent decades in various localities, at the local to the national level,” write Falchi and Bara. These attempts have been unsuccessful, even when the lights are aimed so that they shine only below the plane of the horizon. “This approach is not
sufficient, since any new light, even if shielded, will add pollution to the night environment after being
reflected by the surfaces intended to be illuminated”, they explain.

Instead, we need to put limits on lighting just as we do on other forms of pollution. The authors point to the Clean Air Act in the United States as an example, which restricts the use of air contaminants such as carcinogenic solvents and toxic fuel additives.

It is axiomatic that human activities will affect nature. But that doesn’t mean we can put on blinders and accept it. Light pollution may not seem like a big deal in a world enduring the growing catastrophe of the global climate crisis. Can’t we just go on the Internet and see the sky in much more detail, and also from different parts of the globe? Sure, but computer monitors aren’t the same as sitting under the sky, watching, and letting your mind absorb it all. These activities form memories that we reflect on and that stir something within us. Even the wildest and most hallucinogenic technological imaginations of a techno-geek like Zuckerberg can never replace him.

This is an astronomy news site. But astronomy divorced from the natural spirit of mankind is a poor enterprise. Without simple stargazing and the way it can engage our imagination and our sense of wonder and awe, most of us might not even care about the science of astronomy.

Embrace the darkness.

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