In the years since the publication of Hawking's A Brief History of Time, readers have repeatedly told Hawking of their great difficulty in understanding some of the book's most important concepts. This is the reason for A Briefer History: his wish to make its content more accessible to readers--as well as to bring it up-to-date with the latest scientific observations and findings. Purely technical concepts, such as the mathematics of chaotic boundary conditions, are gone. Conversely, subjects of wide interest that have now been given entire chapters of their own, including relativity, curved space, and quantum theory. This reorganization has allowed the authors to expand areas of recent progress, from string theory to exciting developments in the search for a unified theory of all the forces of physics.--From publisher description.