by David K. Randall
In 1994, an earthquake knocked out electricity in Los Angeles, delivering previously unknown darkness to many residents. Some were alarmed by a silvery light in the black sky. Until then, apparently, the only Milky Way they had ever seen was a candy bar. But perhaps they got some good shut-eye that night.
It wasn’t always this way, Randall writes. People evolved to sleep long hours in a world that got very dark and stayed that way, every night. But modern conditions and lifestyles have left many people short on sleep. Ambient light — which sabotages release of sleep-inducing melatonin — is just one of the many risk factors that Randall investigates in making the case for getting more sleep.
“Without deep sleep, our brain morphs from being our greatest evolutionary asset to our greatest weakness,” Randall writes. In the