In his new book, “Life’s Edge,” Carl Zimmer asks the modest questions: What is life? How did it begin? And by what criteria can we define things as “living”? On this week’s podcast, Zimmer, a science columnist for The Times, talks about just how difficult it can be to find answers.“There are actually philosophers who have argued that maybe we should just try not to define life at all, in fact; that maybe we’re getting ourselves into trouble,” Zimmer says. “If you look for a definition of life from scientists, you will find hundreds of them; hundreds of published definitions that are different from each other. And every year a new one comes out, or maybe two, and they just keep going. there was a paper I read not too long ago that said that there are probably as many definitions of life as people who are trying to define life.”Paulina Bren visits the podcast to discuss her new book, “The Barbizon,” an account of the storied hotel for women that first opened in 1928.“It went through all sorts of incarnations,” Bren says. “This hotel really follows in so many ways not just the history of women in the 20th century, but truly the ups and downs, the history, of New York.”Also on this week’s episode, Elisabeth Egan and John Williams talk about what people are reading. Pamela Paul is the host.Here are the books discussed in this week’s “What We’re Reading”:“Visitors” by Anita Brookner“Firekeeper’s Daughter” by Angeline Boulley“I Am, I Am, I Am” by Maggie O’Farrell