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It's past midnight and you should be asleep

. But eyes open, you sit at your computer as the soft glow of the screen casts a bluish light across your face. You're just not tired yet.

You might be thinking: I'm just naturally a night owl. According to sleep scientist Kenneth Wright, however, that sleep rhythm might not be so natural after all. "People are now living in an environment with reduced exposure to sunlight and increased exposure to electrical light at night," Wright says. "The consequence is that there's a delay in our internal clocks."

In the last few decades, scientists have discovered that the bright lights from your computer, alongside other electric lights in your life, are sending subtle cues to your brain that it's still daytime out, even when you know it's night. Today Wrightpublished his study of how 21st-century people adjust to sleep when there are no artificial lights around at all. He discovered that his test subjects—even the staunch night owls—could reset their internal clocks within a week. They just had to go camping.

In his study, published in the science journal Current Biology, Wright sent eight healthy adults out for a midsummer trip into the Colorado Rockies. With the exception of a data-monitoring bracelet–which tracked the sleep and activity levels of the subjects, and the brightness of the daylight–Wright's campers ventured into nature old-school. They had no personal electronics and nothing to illuminate their surroundings but the sun, moon, and the flickering glow of an evening campfire.

After a week of camping, snoozing at times of their own choosing, Wright brought his subjects back into the lab. He measured the daily change in their levels of melatonin (a hormone our bodies secrete when our biological clock says it's time for bed), and compared it and the bracelet information with the same measurements he took a week before the trip. He found that everyone's sleep schedule—especially that of the night owls—moved significantly toward the natural rise and fall of the sun.

"Lights have a powerful effect beyond vision," Wright says. "When we go abating that internal biological time, there are consequences."

Keeping Time

The 24-hour day is wired into our biology. "Within our brain we all have a master clock," Wright says. Called the suprachiasmatic nucleus, he says, the "clock" is actually a chunk of the brain that keeps time by sharing electrical signals and chemicals through groups of cells at a constant and punctual rhythm. This is called the circadian rhythm. "Those cells will continue to show that 24-hour rhythm, even when they're cut out and put into a petri dish," Wright says.

The body's clock prompts physical responses such as the production of melatonin to "help to coordinate when we wake up and when we sleep," he says. But like other age-old timekeeping devices, ours it isn't always accurate. Some people's clocks run slow, but "most people have a clock that's slightly longer than 24 hours," Wright says. So to keep in synch with the natural day, your brain takes cues from your surroundings to make slight corrections in timekeeping. Darkness in the evening adjusts when you body begins to produce melatonin, and bright light in the morning tunes the melatonin shutoff valve.

"We're relatively unconscious of light that's regulating our circadian rhythms," says George Brainard, a neuroscientist at Thomas Jefferson University who was not involved in the study. Near your eye's photoreceptive cells—which turn light waves into the colored film-reel of your vision—are nerves cells containing melanopsin, a recently discovered pigment that signals your internal clock without effecting sight.

Oddly enough, your internal clock doesn't treat all light the same. For reasons not entirely understood, "light in the blue part of the spectrum is especially potent," Brainard says. This is one reason that the glowing embers of a campfire didn't stop Wright's campers from readjusting their clocks. "Firelight is relatively dim and shifted toward the red end of the spectrum. It's much less dramatic in its ability to promote biological responses," he says.

Unfortunately for all of us living in the modern world, bluish light is the kind of electric light we see most often. TVs, computer screens, fluorescent lights, and LED displays all produce light shifted toward the blue end of the light spectrum (it's for this reason that a computer or TV in a dark room will make the walls look blue). This, Wright says, is helping to turn a lot of us into night owls.

Living With Artificial Light

Can the rest of us readjust our internal clocks without ditching our laptops and running for the wilderness? Michael Herf, a programmer and coinventor of the free computer lighting software F.lux, thinks so.

F.lux is a free-to-use computer program that synchs the color of your computer display with your sunrise and sunset. In the evening your computer display dims a warm red, and in the morning it boots back up to blue-white. I've been using F.lux a bit over a year, and though the color change usually takes me by surprise, the warmer lighting at night is certainly soothing. "Computers are hard on our eyes at night," Herf says. "We're really trying to give you a way to reduce the amount of blue light you see."

Herf had no idea about the effect of blue light on our circadian rhythm when he created the program. "The initial goal was just to match the room lighting and make reading a computer like reading a book," he says. "But it turns out computers and tablets are in the [brightness] range where the amount of blue light has a huge effect on the body and circadian rhythm."

As of yet, no studies have been done on F.lux. "But I think it's a great idea," says Wright. However, he advises that if people want to obtain an earlier bedtime and realign their internal clock for good, there are more effective measures.

"The first is to maintain a consistent sleep schedule. This means you're also maintaining a consistent light–darkness schedule," Wright says, so you won't be sending your brain mixed signals. "Step number two is to increase your exposure to sunlight in the morning." Wright's study subjects received four times as much natural light, and Wright argues that light in the morning plays just as big a role in setting your internal clock as darkness in the evening. Lastly, "in the evening hours you should reduce your exposure to electronic devices like TVs and computers." While programs like F.lux might help reduce blue light, any color light with enough brightness will still alter your circadian rhythm.

Brainard thinks we can live (and sleep) in harmony with electric lighting, but only if we create and use lights designed for our biology. That means less blue and fluorescent lighting before bedtime. Even NASA is taking note. Under his guidance the International Space Station will be changing the lightbulbs in 2016 to a less disruptive and less fluorescent blue light. "Electrical lighting is fundamentally a good thing," Brainard says. "It's a hallmark of human civilization. But there are unseen consequences."

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