What If: Serious Scientific Answers to Absurd Hypothetical Questions

What If?: Serious Scientific Answers to Absurd Hypothetical Questions is a 2014 non-fiction book by Randall Munroe in which the author answers hypothetical science questions sent to him by readers of his webcomic, xkcd. The book contains a selection of questions and answers originally published on his blog What If?, along with several new ones. The book is divided into several dozen chapters, most of which are devoted to answering a unique question. What If? was released on September 2, 2014 and was received positively by critics. A sequel to the book, titled What If? 2, was released on September 13, 2022.