Foreword

THE TITLE OF THIS BOOK DIFFERS by only two letters from that of a book first published in 1988. A Brief History of Time was on the London Sunday Times best-seller list for 237 weeks and has sold about one copy for every 750 men, women, and children on earth. It was a remarkable success for a book that addressed some of the most difficult issues in modern physics. Yet those difficult issues are also the most exciting, for they address big, basic questions: What do we really know about the universe? How do we know it? Where did the universe come from, and where is it going? Those questions were the essence of A Brief History of Time , and they are also the focus of this book.

In the years since A Brief History of Time was published, feedback has come in from readers of all ages, of all professions, and from all over the world. One repeated request has been for a new version, one that maintains the essence of A Brief History yet explains the most important concepts in a clearer, more leisurely manner. Although one might expect that such a book would be entitled A Less Brief History of Time , it was also clear from the feedback that few readers are seeking a lengthy dissertation befitting a college-level course in cosmology. Thus, the present approach. In writing A Briefer History of Time we have maintained and expanded the essential content of the original book, yet taken care to maintain its length and readability. This is a briefer history indeed, for some of the more technical content has been left out, but we feel we have more than compensated for that by the more probing treatment of the material that is really the heart of the book.

We have also taken the opportunity to update the book and include new theoretical and observational results. A Briefer History of Time describes recent progress that has been made in finding a complete unified theory of all the forces of physics. In particular, it describes the progress made in string theory, and the “dualities” or correspondences between apparently different theories of physics that are an indication that there is a unified theory of physics. On the observational side, the book includes important new observations such as those made by the Cosmic Background Explorer satellite (COBE) and by the Hubble Space Telescope.

Some forty years ago Richard Feynman said, “We are lucky to live in an age in which we are still making discoveries. It is like the discovery of America—you only discover it once. The age in which we live is the age in which we are discovering the fundamental laws of nature.” Today, we are closer than ever before to understanding the nature of the universe. Our goal in writing this book is to share some of the excitement of these discoveries, and the new picture of reality that is emerging as a result.