In 1977 I wrote a short technical paper entitled ‘Possible ultimate fate of the universe’ which was published in the Quarterly Journal of the Royal Astronomical Society. A number of colleagues found this paper amusing. Just then, Weinberg's excellent book The first three minutes appeared and it occurred to me that it would be interesting to have a book about the end of the universe. Soon I was requested by the astronomical magazine Sky and Telescope to write a popular version of my paper for them. This appeared in January 1979 under the title ‘The ultimate fate of the universe’. The response to this article convinced me that a popular book on the subject would not be inappropriate. The result is this present book.

I have written the book with the person who has no special scientific knowledge in mind. All the technical terms mentioned and all the physical processes described are explained in as simple language as I have been able to use. However, I have avoided oversimplification. This means that some parts of the book will require close attention by the reader who does not have any scientific background, but I hope that everyone who cares to read the book will be able to follow the main ideas without much difficulty.

I have made free use of some of the books and articles mentioned in the bibliography for the more standard parts of this book.