THE BIRTH OF TIME

How old is the universe? The answer (and the story of how the answer was determined) is the subject of this demanding but not overwhelming account of astronomers at work.

The prolific Gribbin (Almost Everyone's Guide to Science, 1999), an astrophysicist turned science popularizer, has a special interest in this question, for a project that he initiated at the University of Sussex contributed to the answer. He traces the search for the age of the universe from the early 17th century (when the Christian establishment pronounced 4004 b.c. to be the date of creation) through the ensuing encroachment of scientists into what had originally been the domain of theologians. He shows the difficulties faced by early geologists and physicists who grappled with the issue (Kelvin calculated the age of the sun at 20 million years, while shortly thereafter Rutherford estimated the age of the earth at not less than 500 million years) and outlines the work of the 20th-century astronomers who created the Hubble Space Telescope. The central character is Edwin Hubble, who built a cosmic distance ladder outward from the Milky Way to the globular clusters, the Magellanic Clouds, the Andromeda Galaxy, and the Virgo cluster of galaxies. The subsequent controversy over the best estimate of the number known as Hubble's Constant (from which can be calculated the date of the Big Bang) is the topic of Gribbin's later chapters. He explains why one side in the debate argued for a value twice as large as the other side, the differences in the various measuring techniques employed to find the correct answer, and the technical advances that made such work possible. The absence of unnerving mathematical formulas and the use of everyday images—the movement of a swarm of bees, for example, or a person walking down an up escalator—to depict unfamiliar cosmic phenomena help smooth the way for the nonscientist reader.

Close attention is required, but the fascinating story Gribbin has to tell is worth the effort.