For much of human history, light and dark have served as shorthands for good and evil. This enduring dichotomy has convinced us, with the help of evolutionary instincts, that nighttime is something to be feared. But night is not so much the opposite of day as part of a continuous and balanced cycle. A river does not stand in opposition to the sun. Each sustains us.
Because we spend so little time in the dark—since the invention of the arc lamp in the mid-1800s, we’ve grown accustomed to ever-present light—its centrality to the web of life tends to elude us. As a result, we treat the night sky like the endless void we mistake it for: Darkness is immaterial. What is there to pollute? In recent decades, however, a growing number of scientists, doctors, astronomers, and conservationists have raised the alarm about the loss of darkness, about the erosion of this once-plentiful and vital resource.
In the evening, for instance, when light levels dip low enough, our brains know to release melatonin, a hormone that helps us sleep and regulates our circadian rhythms and immune systems. Melatonin also has been shown to suppress cancer growth. In a study funded by the National Institute for Environmental Health Sciences, melatonin-rich blood, produced after two hours of complete darkness, actively slowed the growth of a breast cancer tumor. Blood low in melatonin from exposure to artificial light stimulated growth.
Electric light also bleeds into the atmosphere in ways that firelight doesn’t, through a phenomenon known as Rayleigh scattering, in which shorter-wavelength light (such as blue light) is made visible by particulate matter in the atmosphere. It emanates from bedrooms, street lamps, airports, parking lots, military bases, and more, the aggregation of which creates an ashen glow over densely populated areas. Astronomers were some of the first to notice the phenomenon, which blotted out all but the brightest stars and made far-off objects like asteroids and comets hard to see, even with high-powered telescopes. It was as if the lens of the Earth’s atmosphere had been smudged. Today, Honolulu’s skyglow can be seen from the summit of Haleakalā on Maui.
Electric light—particularly that of LEDs, which often are rich in blue light (the same kind that suppresses melatonin production)—has also wreaked ecological havoc in Hawai‘i. Thousands of Hawaiian petrels and Newell’s shearwaters have been victims of what is known as “fallout,” when a blinded bird flies into a building or becomes so disoriented by lights that they crash to the ground. “I’ve actually had them fall at my feet,” says Jay Penniman, project manager of Maui Nui Seabird Recovery Project.
Scientists aren’t sure why lights affect seabirds this way. It may be because some of the ocean creatures they eat are bioluminescent or because their celestial navigation system is short-circuited. Either way, on the ground, the birds are far more likely to eaten by cats or run over by cars. The Hawaiian petrel population has fallen by 78 percent since 1993, according to the Kaua‘i Endangered Seabird Recovery Project. Newell’s shearwaters decreased in number by 94 percent over the same period.
In response to Hawai‘i’s ebbing night, authorities have attempted to rein in excess illumination. In 2012, the state passed a law requiring that all lighting along state roadways or on state property be shielded to avoid shining into the sky and have a correlated color temperature of no more than 3,800 Kelvins. (The lower a light’s color temperature, the “warmer” or more candle-like its hue.) Richard Wainscoat, an astronomer at the University of Hawai‘i at Mānoa’s Institute for Astronomy, wishes the law went further, limiting the color temperature to as low as 2,700 Kelvins and mandating blue-light filters, which render short-wavelength light invisible, creating a more yellow glow.
Hawai‘i County, which Penniman says has one of the most progressive lighting ordinances in the world, has installed blue-light filters on the lights illuminating most of its public roadways. The island also created a special zone around Maunakea where lights must be shielded and dimmed so as not to interfere with the astronomy taking place at the observatories above.
As a result, Hawai‘i Island is a rare sanctuary from the glow of modern life, a place to escape the light and see the night sky as previous generations saw it. For Kalei Nu‘uhiwa, a researcher at the Edith Kanaka‘ole Foundation and an expert on the Hawaiian moon calendar, preserving this refuge is as important as preserving Hawai‘i’s native forests or its coral reefs. To her, erasing the stars means the loss of culture and knowledge. “Sure, I can read about [a constellation] in a book,” she says, “but until I actually stand in a spot and see it, it doesn’t become part of my inner core being.”
For early Hawaiians, and many still today, the night sky contains entire encyclopedias of information. The moon is a celestial planting guide, while the stars act as an exact, never-failing GPS and dictate the seasons. The constellation Makali‘i, for instance, marks Makahiki, the beginning of the Hawaiian new year.
Nu‘uhiwa says the nine stars of Makali‘i are growing fainter, however. Already, except in the darkest skies, two are nearly invisible. As the stars change, so do the stories. Makali‘i is the same star cluster as Pleiades, or the Seven Sisters from Roman mythology; if only seven stars are visible, the Roman story becomes more legible, easier to grasp. What will Hawaiians call Makali‘i when there are only a few stars left?
Penniman says that our fear of the dark dates back millennia. “In the human psyche, there is a fear of the unknown, the dark, and what is hidden there,” he says. “I think it’s our responsibility to try and help others realize that the dark is not a bad thing. It’s a good thing, an essential thing.”