It’s a contraption that makes the lists of “Greatest Inventions Ever”; at the same time, it’s accused of causing global disaster. It has changed everything from architecture to people’s food habits to their voting patterns, to even the way big business washes its windows. It has saved countless lives . . . while causing countless deaths. Most of us are glad it’s there. But we don’t know how, or when, it got there. It’s air conditioning. For thousands of years, humankind attempted to do something about the slow torture of hot weather. Everything was tried: water power, slave power, electric power, ice made from steam engines and cold air made from deadly chemicals, “zephyrifers,” refrigerated beds, ventilation amateurs and professional air-sniffers. It wasn’t until 1902 when an engineer barely out of college developed the “Apparatus for Treating Air”—a machine that could actually cool the indoors—and everyone assumed it would instantly change the world. That wasn’t the case. There was a time when people “ignored” hot weather while reading each day’s list of heat-related deaths, women wore furs in the summertime, heatstroke victims were treated with bloodletting . . . and the notion of a machine to cool the air was considered preposterous, even sinful. The story of air conditioning is actually two stories: the struggle to perfect a cooling device, and the effort to convince people that they actually needed such a thing. With a cast of characters ranging from Leonardo da Vinci and Richard Nixon to Felix the Cat, Cool showcases the myriad reactions to air conditioning— some of them dramatic, many others comical and wonderfully inconsistent—as it was developed and presented to the world. Here is a unique perspective on air conditioning’s fascinating history: how we rely so completely on it today, and how it might change radically tomorrow.