The Science of Discworld is a 1999 book by novelist Terry Pratchett and popular science writers Ian Stewart and Jack Cohen. Three sequels, The Science of Discworld II: The Globe, The Science of Discworld III: Darwin's Watch, and The Science of Discworld IV: Judgement Day, have been written by the same authors.The book alternates between a typically absurd Discworld story and serious scientific exposition after each chapter.The purpose of the book is both to entertain and educate.