Falling Upwards: How We Took to the Air, by Richard Holmes. Pantheon. 416 pages. $35.

Some years ago, when I lived in California, a colleague — a distinguished silver-haired English historian — got a surprise birthday present from his wife: a sunset hot-air-balloon trip. “It sets the perfect stage for your romantic escapade,” the balloon company’s advertising copy reads, recommending balloons as ideal platforms for marriage proposals as well as weddings, anniversaries, and birthdays. “Your loved ones will thank you for the time of their lives!” Champagne and soft drinks are part of the package: $350 a couple for an…