In her classroom, Barbee adjusts the lighting via a wall-mounted digital panel a few times during a typical school day. Four different presets range in intensity and in correlated color temperature—an approximation of the wavelength of the light, measured in kelvins, from 2,700 to 6,500. Lower color temperatures appear as warmer hues, like the coruscating colors of a campfire, while higher color temperatures look more like a midday blue sky—cooler and brighter. Barbee generally starts each morning with the “Alert” setting, the coolest and brightest, to help wake up the kids (and herself). She might switch to dimmer lights in orange-ish tones later in the afternoon or whenever the class could use some calming down.
Right now, under these bright, blue lights, Barbee has her students’ attention, and many of them struggle to stay seated, inching forward for a closer look at the water tank. Aydriane, Khloe, Princess, and their classmates spend the next several minutes testing hypotheses for what makes a wooden block sink. Maybe wrapping it in a rubber band? How about taping it to another wooden block? Alas, the wood won’t drop. “This is what scientists do,” Barbee assures her class.
“A lot of times they try something and it doesn’t work, but then they try again,” she adds. “That’s how we get smarter.”
Late last December, I met with Bret Coffman, a business process architect, at the headquarters of Vulcan, the investment and philanthropic firm headed by the Microsoft co-founder Paul Allen. Out the north-facing window of a 10th-floor common room, Coffman and I could see the Space Needle standing tall amid the buildings and cranes of this fast-growing city. To the left, the waters of the Puget Sound glistened under partly cloudy skies. To the right, about a block away, we could see a century-old local business that’s long helped illuminate this skyline: Seattle Lighting.
Coffman landed in the Emerald City 18 years ago from Colorado, one of the nation’s sunniest states. “When I first moved here, I was really unhappy,” he recalled. Two years into his job as the business process architect at Vulcan, Coffman was still struggling with sleep and focus. He needed frequent doses of caffeine to get through the work day. “Thank God there was a Starbucks downstairs,” he said.
His outlook brightened in 2014, when he was asked by company executives for assistance in investigating the potential benefits of circadian lighting. A tunable LED not unlike the ones used in Barbee’s classroom soon appeared above Coffman’s desk, and in words that would become familiar to me over the course of many months and many discussions, he repeated the circadian-lighting refrain: “I immediately started to feel better.”
Just why Coffman and so many others feel this way is something that scientists are only recently beginning to understand—and not everyone agrees on the particulars. For most of the 20th century, it was believed that rods and cones were the eye’s only photoreceptors. That all changed in the early 2000s with the discovery of a third photoreceptor. A few years earlier, researchers had shown that the circadian rhythms of mutant mice lacking rods and cones responded to light, suggesting that what meets the eye results in more than just images formed in the brain. Somewhere, a mysterious photoreceptor was responsible for the circadian system “seeing the light,” says David Berson, a neuroscientist at Brown University who helped identify the new photoreceptors and their preference for blue-spectrum light.