Hawking attempts to explain a range of subjects in cosmology, including the big bang, black holes and light cones, to the nonspecialist reader. His main goal is to give an overview of the subject, but he also attempts to explain some complex mathematics. In the 1996 edition of the book and subsequent editions, Hawking discusses the possibility of time travel and wormholes and explores the possibility of having a universe without a quantum singularity at the beginning of time.Early in 1983, Hawking first approached Simon Mitton, the editor in charge of astronomy books at Cambridge University Press, with his ideas for a popular book on cosmology. Mitton was doubtful about all the equations in the draft manuscript, which he felt would put off the buyers in airport bookshops that Hawking wished to reach. With some difficulty, he persuaded Hawking to drop all but one equation.[4] The author himself notes in the book's acknowledgements that he was warned that for every equation in the book, the readership would be halved, hence it includes only a single equation: E = mc2. The book does employ a number of complex models, diagrams, and other illustrations to detail some of the concepts it explores.