Can physics help answer questions about who we are, why we are here, and what the meaning of life is? In the UK in the 1920s and 1930s, many writers expounded the new physics of the time-relativity and quantum mechanics-in popular books with philosophical leanings. Some of those books were popular in both senses of the term: They explained physics to laypeople, and they sold extraordinarily well. That booming market turned some popularizers into celebrities. Of those authors and their books, none were as successful as James Jeans and The Mysterious Universe, published in 1930.