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Expansion Is Accelerating

Pangratios Papacosta

The Runaway Universe: The Race to Find the Future of the Cosmos. Donald Goldsmith. x + 232 pp. Perseus Books, 2000. $25.

In 1998 two groups of astronomers discovered independently that the universe may be expanding at an accelerated pace, as if being pushed by a mysterious force. To many, this was clear evidence that the cosmological constant (proposed and later rejected by Einstein as his "greatest blunder") is alive and well. In The Runaway Universe Donald Goldsmith traces the development of 20th-century cosmology from Einstein and Hubble to this 1998 discovery, with special emphasis on the role that the cosmological constant plays in predicting the ultimate fate of the universe.

This is an excellent book on cosmology for the general public, offering readers the latest in the best story ever told—the story of the universe. Goldsmith writes clearly, with touches of wit and metaphysical contemplation. He takes the reader step-by-step through the major discoveries of 20th-century cosmology (sometimes in more detail than necessary), covering such topics as the discovery of the galaxies, Hubble's discovery of an expanding universe, the inflationary period of the Big Bang model, the mysteries of dark matter and why stars explode. Along the way he gives the reader an education in the basic science needed to understand cosmology, explaining (for example) the Doppler effect, gravitational lensing and nucleosynthesis. A glossary of cosmological terms would have been a useful addition.

A few of the chapters deal with the 1998 discovery and events leading up to it. A crucial chapter describes how Type Ia supernovae can be used as standard candles to estimate long distances by a technique similar to the one in which Cepheid variable stars were used to calculate shorter distances. Careful analysis of these stellar objects reveals their speed and their distance from us. Such data could improve the Hubble diagram and suggest the ultimate fate of our universe. Another important chapter describes the significance of the cosmic background radiation of 2.7278 kelvins and the valuable information derived from its anisotropy.

The author skillfully describes the future of the universe as the outcome of a contest between two cosmic parameters—the average density of matter in the universe (?M) and the effect of the cosmological constant on the expanding universe (?L). He describes future projects that will provide more information on the likely outcome of this contest. These include the Sloan Digital Sky Survey, gravity wave detectors and two new satellites that will provide improved data on cosmic background radiation.

Goldsmith spices up the story of cosmology with descriptions of the scientists' personalities and accounts of their antagonisms and rivalries. But he overdoes this when he describes the rivalry of two groups of astronomers in chapter 9, providing more detail than many readers will want to know. This section of the book had a soap opera quality that left me impatient to get back to the main themes of the book.

The wonder of science, and of cosmology in particular, comes not only from what we know but also from the new questions that fresh discoveries can ignite. This book ponders elemental cosmic questions ("If space is something, what is it?") and contemplates the possible existence of exotic particles (for example, gray dust, axions, neutralinos) that may one day play an important role in future cosmological theories.—Pangratios Papacosta, Physics, Columbia College, Chicago

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