It might be hard to believe, but there was a time when time wasn’t as exact as it is now. When people would come over on “Tuesday” rather than “Tuesday at exactly 2:30.” Ainissa Ramirez is a scientist and author of The Alchemy of Us How Humans and Matter Transformed One Another, and she tells the story of how Materials Science made time so important. Strangely enough, it involves a woman who sold time, using a watch named Arnold.