OUT COLD

You spend a third of your life unconscious, paralyzed, and hallucinating. Nobody knows why.

We call it sleep, and after 5,000 years of trying to understand it, the honest scientific answer to "what is sleep for?" is still "we're working on it." In the meantime, we've built a $700 billion global industry around the inability to do something that jellyfish manage without a brain.

Out Cold is the story of humanity's long, frequently wrong, and occasionally fatal relationship with sleep. It begins in ancient temples where priests charged admission to watch you nap and told you the gods were speaking. It moves through Aristotle (who thought dinner vapors put you to sleep), a 32-day cave experiment involving rectal thermometers, and a 17-year-old in San Diego who stayed awake for eleven days and then lost the science fair. It covers the man who invented the light bulb and hated sleep so much he lied about how little of it he got. The military's 80-year quest to build a soldier who doesn't need to sleep (they can't). The hormone your body makes for free that a $3.3 billion supplement industry sells back to you in gummy form, possibly. The sleep tracker that watches you all night, grades your performance, and may be making the whole problem worse.

From the author of Close Enough: The Absurd History of Measuring Everything comes a book about the gap between what we know about sleep and what we pretend to know, the industries that profit from that gap, and the very human tendency to build elaborate systems on top of our own ignorance and then charge money for them.

You will learn why your teenager can't wake up (biology, not laziness), why your night-shift coworker is getting sicker (the WHO has opinions), and why the best sleep interventions are free, boring, and require no purchases, which is why nobody is selling them to you.

You will not learn how to sleep better. You will learn why that's a harder question than it sounds.