Biologist Nicky Creux rises at 3:30 a.m. some mornings to study the growth and development of sunflowers.

Noah Berger

Midnight karaoke, snake hallucinations, paranoia, and exhaustion: Meet the scientists who work the night shift

All Rodrigo Medellín wanted was a nap. A biologist at the National Autonomous University of Mexico in Mexico City, he had been trapping bats for several nights in a row in the Lacandon rainforest near Guatemala, and was exhausted. “So I lay on the ground,” he says, and blithely fell asleep. Forty winks later, he awoke uneasily. One of the deadliest snakes in Mexico, a tawny fer-de-lance, was slithering by his head, 30 centimeters away. “I did not move and let her pass,” he recalls.

Even after the coast cleared and he set about his bat hunt again, fear wouldn’t loosen its grip on his sleep-deprived mind. That entire night, “I kept hallucinating more snakes,” he says. Every twitching shadow concealed another serpent, every rustling leaf had fangs. Although a veteran of the night shift, Medellín greeted that dawn frazzled.

Working nights is unavoidable, or at least commonplace, in certain scientific fields. If you want to study bat behavior or stellar nebulae or sleep physiology, you may have to become half-nocturnal yourself, and scientists who sign up for the night shift encounter problems that just don’t arise during the day. They tumble down embankments in the pitch black, nod off midexperiment, and grow paranoid in the witching hours. It’s a tough gig, and for these and other reasons psychologists and sleep experts take a dim view of night work, which can disrupt sleep, throw hormones out of whack, and make you measurably dumber. “Human beings are meant to be regulated by light,” says Candice Alfano, a psychologist at the University of Houston in Texas who’s leading a study for NASA that includes a focus on circadian rhythm disruptions. “We still have that biology, even though our social culture has changed dramatically.”

And yet, few of the nocturnal researchers Science talked to would give up their work. Amid the misery and exhaustion, science after hours can still produce moments of serenity, even euphoria. “Either you’re getting to know more about the natural world, or you’re getting to know more about yourself,” Medellín says. “It’s always a source of happiness to me.”

The IceCube Neutrino Observatory at the South Pole attracts a special breed of scientists who can withstand the months-long days or nights.

Stephan Richter, IceCube/NSF

The challenges faced by researchers on the night shift vary significantly by discipline. Biologists, for instance, sometimes upend their whole lives to match the nondiurnal schedules of certain plants and animals.

Nicky Creux, a postdoc at the University of California (UC), Davis, studies sunflowers, whose buds open up just before dawn. That means getting up at 3:30 a.m. for weeklong stretches to set up cameras and dissecting equipment, in order to track the minute-by-minute emergence and growth of anthers and styles, plant reproductive organs. Although she’s naturally a morning lark, “Cycling out to the fields in the dark is pretty miserable,” she laughs. At the end of one recent 6-day stretch, her fine motor skills basically broke down from exhaustion: She kept dropping the tiny flower parts and losing them in the grass. She’s hoping the lost data won’t submarine the whole week.

Creux’s social life suffered as well, because she essentially lived those weeks in a different time zone from everyone around her. “Friends want to go to dinner and I can’t,” she says. “I have to be in bed by 8 p.m.” She also found it hard to abandon the lab to rest while others nearby were still hard at work. “As a scientist, you’re used to working 12-hour shifts, and staying until 7 p.m. I had to get my head around the fact that it’s okay to go home at 3.” Alfano says that like traditional night workers, such as hospital staff, janitors, and truckers, scientists can feel tempted to “cheat” and attend daytime events with friends and family. That can compromise an already spotty sleep schedule. “At some point, you’re really pushing the limit of what your sleep-wake system can do,” she says.

Beyond the strange hours, nocturnal biologists often work in environments that can prove dangerous to human beings, who lack the dim light vision and sharp senses of smell or hearing that most night-adapted species rely on. Hong Young Yan, a fish and frog biologist at the Taiwan National Academy of Science in Taipei, was tramping along a dark trail at night once when a colleague went tumbling down a 30-meter embankment. “Suddenly, he just disappeared,” Yan says. The colleague lived, but sprained an ankle and cried with pain as he limped back to camp. Another time, Yan walked smack into a beehive in the dark, and the colony erupted. “We had to run and jump into a stream” to dodge the swarm, he says.

To help his students overcome their fear of the dark, Medellín performs a little hazing ritual, which involves creeping up behind them in a jaguar mask. He gets a lot of screams. “Some might call it a bit of abuse,” Medellín says, but he argues that maintaining a calm demeanor is essential when you dwell among the bats or other nocturnal animals: “The dark is much more comfortable, if you accept it.”

Bat biologist Rodrigo Medelin says, "The dark is much more comfortable if you accept it."

Amy Cooper

Unlike biologists, astronomers usually moonlight indoors, in relative comfort. But being sedentary has its own downside: drowsiness.

Brent Miszalski, an astronomer in Cape Town who observes at the South African Astronomical Observatory in Sutherland, recalled one night during a multiweek telescope run when he helped clean up after a pipe burst. “I didn’t do anything particularly strenuous,” he says, “but the physical work, combined with the exhaustion, meant that when I had to start observing again, I fell asleep in the chair.” He’s far from alone.

Drowsiness hits regulars on the night shift for two reasons. First, night work violates our body’s expectations about when to sleep and when to remain alert. Second, compensatory daytime sleep usually stinks. Exposure to sunlight prevents the brain from producing melatonin and other natural soporifics. As a result, people sleep fewer hours, and less deeply, during the day. Alfano likens the overall feeling to chronic jet lag.

The poor sleep experienced by night workers also has knock-on effects. It can raise blood pressure and alter levels of hormones, such as ghrelin and leptin, that affect appetite and satiety. As a result, “People tend to snack through night shifts instead of sitting down to eat meals, and those snacks are often quite unhealthy,” says Philip Tucker, a psychologist at Swansea University in the United Kingdom who studies shift workers. Not surprisingly, longtime night shift workers suffer from obesity and other conditions such as cardiovascular disease at rates up to double that of daytime workers.

No studies specifically examine whether scientists on the night shift suffer those problems. And most researchers don’t work at night for months or years at a stretch. Indeed, there’s a trend nowadays toward less night work. Computer technology has automated many tasks, and many observatories and particle accelerators have dedicated technicians to run the complex instruments. Astronomers, for example, can observe the sky remotely by requesting a series of observations and simply waiting for the results, without having to travel and turn their daily routine upside down.

Still, night shifts remain a tradition and even a badge of honor in many fields, and the on/off schedules at such facilities—at Miszalski’s observatory, most astronomers work a “night week” each month—can be physically grueling. “It’s the worst of both worlds,” Tucker says. “A week [at night] definitely disrupts the body clock. But by the time you get to the end, and are approaching adjustment, you go back” to daytime hours, wiping you out all over again. In order to minimize such disruptions, Miszalski prefers working 2-week-long observation shifts every few months.

Repeated night shifts tend to amplify the effect of whatever happens. If things are really cool and interesting, there’s a more euphoric approach to discovery. When things fall apart, the sadness is amplified, too. Working nights will always remain in my mind.

Sergio Speziale, mineral physicist, German Research Centre for Geosciences

The toll on the body can impair the mind as well. Night work may slow down mental processing, shorten attention span, and leave people feeling unmotivated. NASA scientist-astronaut Tracy Caldwell Dyson, who studied gas chemistry in orbit, had to endure several “slam-shifts” during her two tours on the International Space Station. These consisted of a full day’s work, a “silly 2-hour nap,” she says, and another immediate shift, usually to coordinate with ground crews in Russia. During such shifts, Dyson and other astronauts occasionally took computer tests to measure mental sharpness—matching patterns, or adding up strings of small numbers. The results were clear, she says: “We’re kidding ourselves to think we’re at our best when sleep is compromised.”

Astronomer Vivian U, a postdoc at UC Riverside, once tried writing a paper overnight at the United Kingdom Infrared Telescope on Mauna Kea in Hawaii, where the 4267-meter elevation can exacerbate the mental loopiness caused by an extended stint of night work. Feeling inspired, she crafted a brilliant analogy about the similarities between the formation of galaxies and apples falling from trees. The next morning she realized it was gibberish.

All joking aside, night shift–induced mental fogginess does increase the odds of mishaps. Overnight workers contributed in small but significant ways to the accidents at Three Mile Island in Pennsylvania and Chernobyl in Ukraine as well as the Challenger space shuttle explosion. Several studies have found that medical staff working daylong, or longer, shifts make more errors (e.g., misreading electrocardiogram outputs, giving the wrong medication) when chronically deprived of sleep. Nor does the danger stop at work. Studies of doctors and nurses on night shifts found them twice as likely to get in wrecks or nod off behind the wheel on the drive home.

Some facilities have informal rules to save scientists from somnolent stupidity. “I was told to never send an email from the control room at night,” says Lizette Guzman-Ramirez, an astronomer at Leiden Observatory in the Netherlands. “You get up and read it the next morning, and it doesn’t make any sense.” Similarly, some nocturnal scientists have developed tricks to stay alert at 3 a.m. Miszalski and his co-workers have “nonsense conversations” or even “make animal noises” to perk up. When Guzman-Ramirez worked a few 14-hour nights by herself at a telescope in South Africa, she belted out pop songs at the top of her lungs. “I remember singing a lot of ‘Torn,’ by Natalie Imbruglia,” she says. “It was my go-to karaoke song, and I perfected it.”

If 14-hour overnight shifts sound bad, then pity poor polar scientists. During the polar winter they often endure several months without sunlight—the ultimate night shift. Not surprisingly, polar stations attract night owls. “I’ve always had this loathing for sunrise, because I knew I should be in bed already,” says Mack van Rossem, a physicist at the IceCube Neutrino Observatory at the South Pole. But without a sunrise to cap his all-nighters during the winter, Van Rossem found himself drifting through 32-hour “days,” where he’d sleep for 10 hours at once and work for 22. Now that the sun has risen for the year—it poked its head over the horizon in mid-September and won’t set again for months—he’s had trouble sleeping, logging 6 hours a night at most. “It definitely takes me a few hours to get going now,” he says.

Watch: What happens when we stay up all night?

Polar scientists also struggle with another facet of winter life. Many outdoor polar experiments require absolute darkness, and residents at the bases must cover their windows to prevent light from leaking out. “So you’re in a box all the time,” Van Rossem says. “I really missed being able to look out the window.”

John Parker, a medical doctor at the Australian Antarctic base at Davis, agrees. “When you’re not looking out the window, your perspective of life changes,” he says. “Small things become much larger.” He called it mental “myopia,” and in a detail worthy of Edgar Allan Poe, even found himself growing paranoid in the endless nighttime: “I’d lose something and think, ‘Someone’s taken it!’ A bit of suspicion comes in.” Other scientists who worked overnight shifts elsewhere reported similar, if subtler, mood swings, growing more irritable and snappy with colleagues.

Despite these rough patches, Parker appreciated his months-long night shift in Antarctica, calling it an adventure. Activities like dart nights and costume parties helped defuse tension, and the 16-person team held a barbecue in September to welcome the sun back. “It was cloudy, so we didn’t see anything,” he laughs, “but it was a special event.” He’d definitely overwinter there again—following a suitable break. “Maybe after having some fresh fruit.”

Many scientists who work at night share Parker’s sentiments: It was miserable, and I loved it. Some savored the profound quiet, or a perfect sunrise, or shimmering green aurorae on white snow. Some learned to appreciate different tenors of darkness—the relatively bright desert sky at night versus caves and undercanopies so black that opening or closing your eyes makes no difference. If nothing else, some enjoyed binge-watching movies or catching up on neglected work. This past winter in Antarctica, Parker completed a memoir about several humanitarian medical missions he’s served on. “And I can say I wrote my book in 1 night,” he adds.

As they age, many nocturnal scientists find that their capacity for night work has diminished. Yet they still relish the chance to connect more deeply with some beloved species or natural wonder, and somehow the sacrifice and discomfort of night work makes it all the more special.

Sergio Speziale, a mineral physicist at the German Research Centre for Geosciences in Potsdam, has pulled many a long night at synchrotrons and other particle accelerators around the world, and his time served has left him feeling philosophical.“Repeated night shifts tend to amplify the effect of whatever happens,” he says. “If things are really cool and interesting, there’s a more euphoric approach to discovery. When things fall apart, the sadness is amplified, too. Working nights will always remain in my mind. It’s sometimes good to experience that in life.”

If you're interested in learning more about circadian rhythms then listen to our podcast interview with author Sam Kean and check out related research