THE PLANETS

By Dava Sobel

Viking. 270 pp. $24.95

Dava Sobel's previous works -- the best known is probably Longitude -- established her as an author who excels at making readers care about seemingly dull issues involving science and technology. She has an unerring eye for the telling detail, the incredible coincidence, the human foible that turns every story into a compelling narrative. In Longitude, for example, readers found themselves caught up in the minutiae of designing a reliable clock that could be carried on a ship to the distant corners of the globe. I can testify that the book made my visit to the Greenwich Observatory immensely richer and more rewarding than it otherwise would have been.

The Planets is a somewhat different kind of book. Instead of homing in on a single issue like the determination of longitude, she takes readers on a kind of lyrical tour of the solar system. The book is organized as a series of more or less unconnected essays, each dealing with one of the planets. Starting with Mercury, the planet closest to the sun, she works her way outward to Pluto and the newly discovered bodies beyond, closing with a description of a party at the Jet Propulsion Lab celebrating the arrival of the Cassini space probe at Saturn.

Having taught the basics of the solar system for years, I thought I was in for just another recital of the rich variety of environments found on our planetary neighbors. Nothing could have been farther from the truth. With one glaring exception, each of these essays is a little gem, telling an interesting story without overwhelming the reader with facts. And each essay is full of what I think of as the "Sobel touch," mingling odd historical coincidences with up-to-the-minute NASA readout of data.

For example, she tells the story of the 19th-century discovery of the planets Uranus and Neptune in the form of a fictionalized letter between the only two women astronomers who had discovered comets -- the American astronomer Maria Mitchell and Caroline Herschel, sister of the discoverer of Uranus and a major astronomer in her own right. These were the first two discoveries of planets not visible to the naked eye, and they forever changed our view of our home solar system. The fascinating details -- how discrepancies in the orbit of Uranus began to accumulate, the gyrations astronomers went through to preserve the Newtonian universe (arguing that Uranus must have been hit by a giant comet just before it was discovered, for example), the obstinacy of senior astronomers in refusing to listen to two young men who argued that the discrepancies were caused by a planet still farther out -- are all related in the chatty style you would expect in this sort of letter. You end by thinking that if Caroline Herschel didn't write such a letter, she should have.

The intriguing and memorable facts keep coming. Did you know that the "year" of the planet Venus, named for the goddess of love, is about the same as the duration of a human pregnancy? Or that William Herschel lived just long enough for Uranus to make one circuit around the sun? Or that 19th-century scientists theorized that the planet Vulcan, now firmly enshrined as the home of Star Trek's Mr. Spock, actually existed? (It was supposed to be closer to the sun than Mercury, and was dreamt up to explain some discrepancies in that planet's orbit -- discrepancies that we now understand have to do with Einstein's theory of relativity.)

Sobel writes about the discovery of the last planet, Pluto, in a straightforward style, and is mercifully brief in her discussion of the schoolmarmish efforts of some astronomers to expunge it from the list of planets. This tempest in a teapot, as Sobel explains, has to do with the fact that Pluto is actually the first of many objects orbiting the sun far out in the reaches of space -- think of them as a kind of cosmic junk pile -- rather than the last of the inner planets.

All of which brings me to an aspect of this book that I found profoundly disturbing. The chapter on Jupiter begins by describing Galileo (who first saw that planet's moons) as "a Pisces with Leo rising." I assumed that this was just another of Sobel's literary flourishes and thought nothing of it. But as I progressed through the chapter, and the astrological references began to accumulate, it began to dawn on me -- "My God, she actually believes this stuff!" And if she doesn't, I'm troubled by the possibility that a sympathetic reader could be fooled into believing that she does.

To have an author of Sobel's standing casually juxtapose statements about the discoveries made by space probes and statements about astrology only adds fuel to the bonfires of pseudoscience and irrationality.

The public deserves better. *

James Trefil is Clarence J. Robinson Professor pf Physics at George Mason University. His latest book is "Human Nature: A Blueprint for Managing the Earth -- By People, For People."