The Planets by Dava Sobel

A box of heavenly chocolates

I have to confess the style is not one I relish - it smacks too much of eating a whole box of soft chocolates, with no hard centres. So the rings of Saturn become: "a lusty billion-part harmony of bodies swirling in accordance with [Kepler's] laws, humming elliptically around Saturn, the near ones outpacing the far, at speeds determined by distance from that wandering star."

If you do like soft centres, don't be put off by me. I'll get my grumpy old man gripes off my chest first; they mostly concern factual errors. The early universe did not expand exponentially for a billion years (if it had, there would be nothing to see in it today); the sun appears as a disc on the sky, not a circle; the date attributed to William Gilbert's experiments on magnetism is wrong; and Edmond Halley was not Astronomer Royal at the time he was in command of a Royal Navy ship.

Whether such details matter depends on whether you regard the book as scientific history or as entertainment. Sobel makes her own position plain by including a chapter on Uranus and Neptune which largely consists of a fictional imagined letter from one female astronomer, Caroline Herschel, to another, Maria Mitchell. The note explaining the background to this fictionalisation is a lot more interesting than the letter itself, but less entertaining.

Clearly, we are expected to regard this book as an entertainment, and on those terms it succeeds admirably. It also brings a warm glow to find, at a time when many people are getting excited about the discovery of a "tenth planet", that Sobel appreciates that Pluto is no longer regarded as a planet but as one member of a group of icy bodies orbiting beyond Neptune that is now known to include Xena.

Strictly as entertainment, though, there is one glaring omission. The illustrations are almost all historical - ancient maps of the Earth or Mars, Galileo's telescope, and so on. Yet there is a wealth of modern colour imagery of planets and moons available. Why wasn't any of it used?

Sobel's strengths, as you might expect, lie in the realms of biographical and historical anecdote and the re-telling of mythology - although I do think it a little twee to say merely that the God Zeus "beguiled" the princess Europa. Part of the mythology that gets a fuller treatment is astrology, with a whole, rather uncritical, chapter to itself, which sits uneasily alongside the description of the modern understanding of the jovian system gleaned from space probes such as the Galileo mission.

Describing the "natal chart" for the spacecraft as if it were as significant as the discovery of the oceans of Jupiter's moon Europa is going too far, especially when prefaced by the statement that "had astronomy and astrology not parted ways so long ago, some of the Galileo mission's problems might have been foreseen". Had astrology and astronomy not parted ways, there probably would never have been a Galileo mission!

Sobel comes across as a kind of New Age tree-hugger, probably an enthusiastic fan of what she thinks Jim Lovelock means by the Gaia hypothesis, who has had friendly conversations with several astronomers. The lyrics of the song "Aquarius" from Hair tell us that "when the Moon is in the Seventh House, and Jupiter aligns with Mars, then peace will guide the planets, and love will steer the stars." Sobel introduces a description of a solar eclipse by telling us that "When the Moon is a pool of soot hiding the bright solar sphere,/ and the sky deepens to a crepuscular blue,/ the Sun's magnificent corona... flashes into view". And goes on in the same vein. As I said, it's an entertaining book.

John Gribbin new book is 'The Fellowship' (Allen Lane)