The Darkness That We Need

August 20, 2017

An eternal electric day is creeping across the globe, but our brains and bodies cannot cope in a world without darkness.

Sound dominated my senses as we left the village of San Pedro de Atacama and walked into the desert night. The crunch of shoes on gravel underlay our voices, which were hushed to avoid waking any households or street dogs. Our small group of astronomy writers was escaping from light and, without any flashlights or streetlamps, we struggled to see, so our other senses were heightened. Land that looked red by day was now monochromatic, the rods in our retinas serving as our only visual input.

After about 15 minutes of hiking, we stopped to take some pictures of the sky. I fumbled with my gear and tried to get my bearings, but everything was alien. I was horribly jet-lagged after 10 hours hunched against the window of a 757, another two-hour flight north from Santiago and a two-hour bus ride, and it wan’t just my oxygen-hungry brain that put me out of sorts. The Atacama Desert looked like Mars as drawn by Dr Seuss; I was surrounded by wrong-coloured cliffs and swirling rock formations.

But I was determined to photograph something even more bizarre: the Large Magellanic Cloud, a dwarf galaxy you can see only from the southern hemisphere. I perched my camera on a rock and aimed at the sky, but the cosmic smudge would not resolve in my viewfinder. I stood, brushed dirt from my jeans, and looked up.

The unfamiliar sky momentarily took away what little breath I had left at 8,000 feet in elevation. Above the horizon was the conspicuous Southern Cross. Orion was there, too, but looked as disoriented as I felt, upside down to the world. And there were so many constellations I’d never seen, with hopeful, Latinate names such as Dorado and Reticulum. Countless stars blazed into view as I stared into the smear of the Milky Way.

To most people who have travelled outside the developed world – whether to camp or to meditate or to hunt – such bright and plentiful stars are a glorious sight. But this beauty instilled in me a creeping sense of guilt. At home, 1,500 miles north, I wouldn’t recognise such spangled heavens. From where I live in the American Midwest, the stars might as well not exist. After journeying millions of years, their light is swallowed by city glare and my porch lantern. Those that make it through will still fail: not even bright Betelgeuse can outshine my iPhone. Yet I am an astronomy writer, a person who thinks about stars and planets all the time. What does my neglect of the night sky say about the rest of humanity?

‘We are all descended from astronomers,’ the astrophysicist Neil deGrasse Tyson intones in the rebooted version of the TV show Cosmos. This is as poetic as it is true. Everyone owns the night sky; it was the one natural realm all our ancestors could see and know intimately. No river, no grand mountain or canyon, not even the oceans can claim that. But since Edison’s light bulbs colonised our cities, the vast majority of humans has ceased to see those skies. More than 60 per cent of the world, and fully 99 per cent of the US and Europe, lives under a yellowy sky polluted with light.

For many of us, the only place to see the milky backbone of our own galaxy is on the ceiling of a planetarium. Although humans are diurnal, factories and Twitter and hospitals and CNN are not, so we must conquer the darkness. As a result, almost everything industrialised people build is lit up at night. Malls, hospitals, car dealerships. Streets, bridges, air and sea ports. Buildings on a skyline. These artificial lights identify our cities all the way from the moon. If aliens ever do drop by, this might be their first sign that someone is home.

But cosmology, the study and interpretation of the universe, has always depended on a star-choked dark sky. Ancient civilisations from the Greeks to the Pawnee looked to the stars and saw not only creation tales, but active participants in their lives. Christians, who invest great meaning in the good of light and the evil of darkness, spread a starry message, too: the star of Bethlehem as a beacon to salvation. A millennium and a half later, Galileo looked up and saw a new version of the cosmos, breaking the dawn of modern science. And Edwin Hubble discovered the expansion of the universe by the candlelight of supernovas. All of this happened under virginal skies and, by any measure, we don’t have those anymore. We look at our glowing rectangles, and we opt out of that shared heritage.

Nowhere is light pollution more apparent, almost achingly so, than in satellite images of the Earth from space. The continental United States seems to split in half: the eastern side is brighter than the west, except for the klieg lights of Las Vegas. Highways innervate America, connecting luminous dots of small towns and big cities. Across the Atlantic, Europe shimmers. Moscow is a radiant nine-pointed star. The Nile Delta glows like a dandelion sprouting from mostly indigo Africa. Farther east, Hong Kong and Shanghai are ablaze, and the demilitarised zone separates dark North Korea from South Korea more cleanly than if the peninsula had been cleft in two. Developed society, it’s clear, is where the light is.

Human-controlled light has pierced the night for thousands of years, long before Edison. Campfires warmed our ancestors’ feet and cooked their meals; the Harvard anthropologist Richard Wrangham argues in his book Catching Fire (2009) that gathering around a flame to eat and to commune with others is, in fact, what made us human. Not just fellowship but safety has long been the primary rationale for pushing back the night. ‘Evil spirits love not the smell of lamps,’ as Plato put it.

Comforting, lambent lamplight led us safely home by tattling on the people and potholes and animals that would otherwise do us harm. By the early 17th century, residents of cities such as Paris and London were admonished to keep lights burning in the windows of all houses that faced the streets, as the historian A Roger Ekirch notes in his book At Day’s Close: Night in Times Past (2005). Taxpayers funded oil lamps and candlelit lanterns for the avenues, while only genteel households could afford fine beeswax or spermaceti candles; most people relied on tallow, made from animal fat.

Despite their utility, these artificial lights were sources of danger in their own right. Huge swathes of cities – notably London and Chicago – were consumed in conflagrations that started as accidents, born of the necessity of using flames to see. By the 1800s, gas lamps reduced fire risks, but cities were by no means safer from crime; gaslit London in the late 1880s, full of foggy halos casting shadows down dark alleys, is as famous for murder as anything else. Even now, artificial light provides an artificial sense of security.

A 1997 report from the US National Institute of Justice found no conclusive correlation between night-time lighting and crime rates. The International Dark Sky Association, a dedicated group of night-time advocates, points out that bright, glaring lamps create sharper contrasts between light and darkness, blinding drivers and homeowners alike.

And even so – what price safety! A young but rapidly growing field of research suggests that night-time light itself is far more dangerous than the dark. In a 2012 report, an American Medical Association committee called electric lighting a ‘man-made self-experiment’ creating potentially harmful health effects. Humans, and everything else that lives on this planet with us, evolved during billions of years along a reliable cycle of day and night, with clear boundaries between them. Staunching the flood of artificial light can help restore this divide. Our well-being, and that of our fellow creatures, might depend on us doing so – or at the very least trying. The loss of night-time darkness neglects our shared past, but it might very well cut short our futures too.

The midnight desert was quiet while I knelt with my camera last spring, but the Atacama was far from asleep. Beetles and red scorpions scuttled across the dirt. Vallenar toads crouched on the lomas. South American grey foxes sniffed the earth, hunting furry viscachas and Darwin’s leaf-eared mice. Great horned owls circled overhead, hunting the rodents and the foxes. Nocturnal animals such as these make up 30 per cent of all vertebrates and 60 per cent of all invertebrates on Earth, according to an estimate by the German biologist Franz Hölker and colleagues. These night-dwellers are the most obvious victims of artificial light. Light pollution interferes with their natural rhythms in myriad ways.

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