A Brief History of Time
Two of twentieth century physics’ greatest achievements are the general theory of relativity and the theory of quantum mechanics. The former, conceived by Albert Einstein, explains the force of gravity in terms of the curvature of four-dimensional space-time and deals with the large-scale structure of the universe. The latter is based on the concept of energy as bundles or quanta and Werner Heisenberg’s uncertainty principle and is concerned with phenomena on the subatomic level. Both theories have been enormously successful in explaining phenomena at their respective scales. Physicists have also developed grand unified theories which have unified three of the four forces in the universe: the electromagnetic, which holds atoms together; the strong, which binds the components of the nucleus of the atom; and the weak, which is involved in radioactive decay. They have failed, however, to reconcile general relativity with quantum mechanics or to unify the force of gravity with the other three fundamental forces. There is no place in general relativity for the uncertainty principle. Physicists are seeking a new theory which will successfully integrate general relativity and quantum mechanics into a quantum theory of gravitation.
The search for that unified theory of relativity and quantum mechanics is the primary theme of A Brief History of Time: From the Big Bang to Black Holes. This is a challenging, qualitative examination of historical and contemporary views on the nature of time and the universe (as opposed to a literal history of time) by one of the major figures in theoretical physics in the 1970’s and 1980’s. Stephen W. Hawking, Lucasian Professor of Mathematics at Cambridge University, the chair once held by Sir Isaac Newton, is a victim of amyotrophic lateral sclerosis (Lou Gehrig’s disease); he has been slowly losing control over his physical faculties, but his mental abilities have remained unimpaired. In this, his first effort at writing for a nontechnical audience, Hawking provides brief excursions into a number of areas of modern physics, but his real concern is cosmology. Using but one equation, he traces the changing concepts of the size, structure, history, and nature of the universe from the work of ancient Greeks, through that of Galileo, Newton, and Einstein, to his own work. He presents clear but sophisticated and demanding descriptions of such phenomena as black holes and the arrow of time.
Hawking has organized the book into thematic chapters, with the discussion within each chapter arranged chronologically. He begins with a review of the many cosmologies that have appeared in Western civilization. The second chapter examines the changing views of space and time, culminating in Einstein’s theory of general relativity. Then comes a discussion of the concept of an expanding universe. The next two chapters, on the uncertainty principle and the fundamental particles and forces, complete the background discussion. Two chapters on black holes are followed by one presenting Hawking’s views on the origin and future of the universe. The penultimate chapter discusses arrows of time, devices which distinguish the past from the future, providing a direction for the passage of time. In the final chapter, Hawking considers what a unified theory might look like. Included in the book are biographical sketches of Einstein, Galileo, and Newton, as well as a glossary of scientific terms.
There are three decisions that every author of a nontechnical work on cosmology or other aspects of modern physics must make. The first is one of presentation. The language of theoretical physics is mathematics. How will the popularizer replace the equations...
(The entire section is 1505 words.)