The Black Hole War

Modern physics abounds in concepts that capture the imagination. Perhaps no concept has had greater impact on the popular imagination than that of the black hole, a concentration of mass so great that even light cannot escape its gravitational attraction. Black holes can be understood in terms of Albert Einstein’s general theory of relativity. The quantum theory of black holes is generally attributed to Stephen Hawking, a British physicist who realized that a black hole could actually evaporate, becoming smaller and emitting elementary particles created from the vacuum as it does so. The Black Hole War of the title is a dispute among physicists over the content of black holes, that is, whether the identity of the particles that made up a black hole becomes forever lost to science.

Susskind’s book provides a description of the dispute, character sketches of the disputants, an introduction to the more esoteric concepts, and anecdotes from scientific conferences and academic culture generally, interspersed in a way that keeps the reader entertained. There is Susskind himself, who despite his august academic accomplishmentshe holds an endowed chair at Stanfordfinds a great deal of humor in physics and its development. There is Hawking, who as Lucasian Professor of Mathematics holds the chair once occupied by Isaac Newton and has been battling Lou Gehrig’s disease since graduate school. Hawking now lectures from a wheelchair using a voice synthesizer; in earlier times he used human translators. Despite his physical limitations, Hawking is regarded as a great showman who can hold an audience’s rapt attention. There is Gerard ’t Hooft, who early in his career was able to solve some of the key problems of the so-called standard model of elementary particle physics and who is regarded by Susskind as one of the cleverest people in physics. Going back in time there is Albert Einstein, whose equations of general relativity provide the theoretical framework for the big bang cosmology and who rejected the quantum theory as incomplete, and Neils Bohr, mentor to a generation of quantum physicists, who defended it successfully against many of Einstein’s counter examples.

Susskind provides qualitative explanations for many modern physics concepts, some of which are part of the average physicist’s intellectual toolkit and some of which are familiar only to researchers in the esoteric realm of black holes and strange particles. As he describes it, the human brain, which has evolved to understand the physics of everyday lifefor example, how to hit a target with a rockhas to undergo a certain amount of rewiring to deal with events outside routine experience. The need for rewiring became apparent when it was realized that light traveled at great but finite speed. Further rewiring is needed to deal with very large and very small numbers, distances, and time intervals and spaces of different dimensions. Physical theories are nowadays most naturally formulated mathematically, and to communicate them to the layman writers such as Susskind make extensive use of mental pictures and analogies. The analogies will be more helpful to some readers than others.

Many readers will be familiar with the Heisenberg Uncertainty Principle, which states that the position and momentum (mass times velocity) of a particle cannot be simultaneously known with perfect precision. An important consequence of this is the realization that at an atomic level all matter is in constant motion. Heisenberg and Bohr considered position and momentum to be complementary observables. One could measure the position of a particle in one type of experiment at the cost of giving up information about its momentum, or measure its momentum in another, giving up information about its position. Bohr elevated the notion of complementarity to a general principle, noting that properties often come in...

(The entire section is 1589 words.)