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Ideas | Tony Rehagen

There’s too much artificial light at night to see stars. That’s a problem

The Milky Way shone in the sky over El Roque beach in the Canary Islands in 2015.Carlos De Saa/EPA/File

TWENTY YEARS AGO, I fell in love with a city girl. We were both students at the University of Missouri. She was from Des Moines, population 200,000. I was from St. Elizabeth, Mo., a rural town of 300. She told me about growing up downtown; I regaled her with tales of driving gravel roads at night, and looking at the stars.

“I’ve seen stars before,” she said.

I replied, “Not like this, you haven’t.”

To illustrate my point, one clear evening I drove her through Columbia’s perpetual dusk of streetlights, light-boxes, and neon signs and out into the countryside about 65 miles south. Two miles outside my hometown, I pulled into an open field. We got out of the car and let our eyes adjust to the darkness. Then I pointed up.


Her wide eyes shimmered with thousands of tiny reflected lights. We had trouble picking out the constellations in a crowded cosmic puzzle that seemed to have more stars than sky. And to the south, we saw a purplish-blue strip of haze cutting through the canopy — the Milky Way, a sight she’d never seen.

Most people haven’t. According to an article published in Science Advances, the journal for the American Academy for the Advancement of Science (AAAS), the nighttime view of our own galaxy is obscured from more than a third of humanity, including 80 percent of North Americans.

The reason: our society’s excessive and inappropriate use of artificial lighting.

In other words, light pollution.

Eighty percent of Americans live in urban areas that are wired for virtual daylight 24 hours a day. The Northeast, with its megapolis of seemingly unending urban and suburban landscape, is a particularly bright blob of luminescence when viewed from space. But that sprawling light doesn’t stop at the city limits. It reflects and refracts and seeps into the surrounding rural areas. The AAAS study estimates that more than 99 percent of the US population lives under light-polluted skies.


It’s an issue for more than just stargazers and romantics. By illuminating true nighttime out of existence, we’ve disrupted our bodies’ natural rhythms and endangered our health. Light pollution is also literally pollution in that it invades other ecosystems, throwing off other animals’ nocturnal rest, foraging, and feeding habits. Not to mention all the non-renewable resources that are used to power all these bulbs. And by trapping ourselves beneath a dome of bouncing light beams, we’ve also virtually shut ourselves off from the cosmos, the stars by which our forbearers navigated the earth, scheduled their lives, came to understand the laws of physics, and divined our place in the universe.

“We should think of our night skies as part of our environment,” says Sara Pritchard, associate professor in the Department of Science & Technology Studies at Cornell University who looks at the human impact of light pollution. “We don’t often think about night and the sky as part of the natural world. We think of animals or watersheds. But half of the day is night. So many of our environmental issues occur not just by day but by night as well.”

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The Northeast, with its megapolis of seemingly unending urban and suburban landscape, is a particularly bright blob of luminescence when viewed from space. NASA Earth Observatory

LESS THAN 100 years ago, darkness still held sway over the night. Even after millennia of humans harnessing light — first through domestication of fire for warmth and protection and then, much later, with the discovery of electricity — when the sun set, our days would essentially end. Workers went home, storefronts and businesses shuttered, and almost anyone anywhere in the world could look up on a clear night and see the same dazzling display.


But in the 20th century, artificial lighting advanced in brightness and availability, especially in the power-gridded cities. People swarmed these bright urban centers, eventually crowding into street-lit suburbs and exurbs that reflected the city lights for miles in every direction. As incandescent bulbs have given way to white fluorescents, which in turn have yielded to even sharper LEDs, our lives have gradually been upended. The better we see at night, the more reason we have to stay up, work, and play long past dusk, virtually locking ourselves into perpetual daylight.

Several weeks ago, President Trump created consternation by rolling back energy-efficiency standards on light bulbs, but the truth is, the issue is complicated: The proliferation of more efficient and cheaper LED bulbs create more, and brighter light.

Light pollution can take many forms — it can be the glare of a light source that is too bright, the skyglow that hovers over most inhabited areas, trespass of light falling where it isn’t needed or intended, or the clutter of too many light sources in the same area. The effect can be exacerbated by cloud cover and snowfall in northern regions such as New England. “Clouds and snow amplify what artificial light is already there,” says Pritchard. “The light is going to bounce back and intensify the experience on the ground.”


As with many human-made environmental issues, some of the first adverse effects of our actions were observed not in people, but in the collateral damage to plants and animals. As early as the 1910s, researchers observed the dead bodies of birds that, disoriented by and attracted to the lights shining at night, had flown smack into smokestacks, lighthouses, tall buildings, and other structures. In the middle part of the century, biologists studying the migration of sea turtles began to notice some mothers who normally nested in the sand at night were shying away from well-lit beaches and that the hatchlings already on the beach seemed to be confused, crawling inland, away from the safety of the sea and toward land-based predators.

Over the ensuing decades, scientists became aware of all sorts of ways that human light affected the ecosystem. Almost all nocturnal animals, including bats and rodents and marsupials, were quickly losing their time to feed and forage without fear of exposure to predators. Artificial light prevents trees from adjusting to the changing seasons, and this affects the wildlife who rely on trees for shelter and habitat. Night lights were even interfering with the visual communication among glow-worms and fireflies.

“When I first got interested in the topic [of light pollution] in the mid-1990s, it wasn’t even really a unified field,” says Travis Longcore, an urban ecologist at UCLA. He says it wasn’t until he and a number of other scientists brought their disparate research together in the early 2000s that people started to see the larger problem of the loss of darkness on par with and integral to other preservation and conservation efforts.


“It’s not just an astronomical issue, it’s an ecological issue,” he says. “You can save stuff during the day, but if you don’t address it at night, you might be missing half the picture and wasting your energy.”

Of course, getting people to care about any issue often requires evidence of an immediate personal impact. That moment may have finally come as research now demonstrates that all this light is having myriad adverse effects on our health. Harvard Medical School reports that exposure to artificial light at night is messing with our internal wiring. In particular, blue light, the wavelength prevalent in fluorescent bulbs, LEDs, and the flat screens of TVs, tablets, and smartphones, disrupts our circadian rhythm and suppresses the body’s secretion of melatonin, which regulates our sleep-wake cycle. Such disruption has been linked to depression, insomnia, cardiovascular disease, and even cancer, according to a report from the journal Environmental Health Perspectives. The same article linked light pollution to sleep disorders such as shift-work sleep disorder, for people who rotate shifts or work at night, and delayed sleep-phase syndrome, for people who can’t get to sleep early at night and therefore have trouble waking up in time for school or work. Simply not getting adequate sleep has been blamed for myriad maladies, including depression, obesity, diabetes, and heart disease.

Beyond the physiological perils, light pollution also presents physical dangers. The glare of lights can blind drivers at night, vision can also be impaired by the exaggerated darkness when a bright light is suddenly removed from sight, and even the motion-activated and security lights we’ve installed to scare off would-be vandals and burglars might actually be helping them see better in order to carry out their crimes.

There’s also a scientific cost. Not being able to monitor and explore the celestial bodies above from the ground below is impeding scientific progress. The spreading nighttime glow is a growing threat to astronomers and their once-remote observatories, narrowing their gaze into our universe and our future.

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Meteors from the Perseid meteor swarm burned up in the atmosphere as our own galaxy, the Milky Way, is seen in the clear night sky over Fehmarn, Germany.Daniel Reinhardt/EPA/File

PEOPLE ARE FINALLY, slowly, taking note and action. From a broad conservation perspective, there are now more than 60 Dark Sky Parks across the United States, as designated by the Dark-Sky Association. These are ultra-dark places where the night sky has been preserved for astronomers and stargazers. And there are now three Dark Sky Sanctuaries, including Devils River State Natural Area in Texas, that are considered some of the last places on earth still virtually untouched by artificial light.

From a civic standpoint, 18 states, the District of Columbia, and Puerto Rico have enacted laws to reduce light pollution. Most of these rules only apply to state-owned buildings and grounds and lights on public roadways, but they typically require installation of shielded light fixtures aimed downward, use of low-glare lighting, and regulating the amount of time the lights can be on. But several cities, such as Tucson, Ariz., and Houston have gone further, creating rules for intelligent timing controls that can automatically turn off lights and cut down on waste and even lighting curfews that will turn off lights on roads at hours when they are typically less travelled.

Advocates for darker nights such as the International Dark-Sky Association are careful to emphasize that they are not necessarily pushing for a return to the dark ages, but rather a more responsible approach to night lighting, such as only using lights as bright as needed, only where they are needed, for as long as needed; and minimal blue light emissions, focused downward. While too many recklessly placed and positioned bulbs can harm our environment and health, light still helps people see, travel, and feel safe at night.

“If we only focus on the negatives, we lose sight of the positives,” says Pritchard. “Many poorer communities would like nothing more than clean, reliable sources of light at night.”

Despite the growing recognition of the harm caused by too much light, I can’t help but lament what is being lost.

More than the cost to human health, the ecological impact, and the blinding of astronomy, is our spiritual connection to the night sky. The earliest humans looked to the stars for natural and supernatural guidance. Even before we conquered our own planet, the boundless universe represented the next frontier for exploration. And if nothing else, staring into the heavens has always been good for our own humility.

“At the end of the day, the one sort of big thing that you can touch people with is the idea of losing our sense of place in nature and the universe,” says Longcore. “We can talk about the real impacts, losing sleep, animals dying, waste of our investment in conservation, a number of practical things, but most people who work on this issue recognize it’s about the fundamental human experience of being able to look up into the night sky and think about how small and fragile we are. If you create this lighted cocoon, you never get to contemplate that.”

Even St. Elizabeth, my hometown, is endangered. The village still doesn’t have a stoplight, but poles crowned with ever-brighter street lights seem to pop up all the time. And the nearest city, Jefferson City, while still far away, is not quite as far as it was 20 years ago as the urban sprawl continues unabated.

In the meantime, I still relish my chances to take that college girlfriend, who is now my wife, and our two daughters out to the country and show them the lightshow and the galaxy that they are missing in the city.

Tony Rehagen is a freelance writer based in St. Louis. Follow him on Twitter @trehagen.