The coffee-cup universe

Colin Ronan, one of the leading writers on astronomy of his day, who died this summer aged 74, hands the reader the universe on a plate in this sumptuous book. It is a beautifully orchestrated tour of astronomy and cosmology, of such completeness that it is hard to think of any representation of our ideas of the cosmos left uncovered.

The book tackles difficult, inaccessible ideas: wormholes in space, curved space and the inability of astronomers to account for more than 1 per cent of the mass of the universe predicted by the Big Bang theory. It offers layer upon layer of explanation in a format that makes compelling reading, at least initially. Double-page spreads under broad headings such as "Observatory earth", "Nebulae and galaxies", "The sun and stars", open to reveal stunning detail on how the universe works. The pages on the singularity - a massively heavy, infinitely dense dimensionless object - which is the centre of a black hole, are particularly beguiling.

The book's introduction says "it is relatively straightforward merely to describe the wonders of the universe, but much more rewarding to understand why the universe behaves as it does." The aim is to provide "explanations of a kind not otherwise easily attainable, using straightforward language and analogies with familiar times and events". So it is that visible spiral galaxies supported in an invisible halo of dark matter become the cream swirling on a cup of coffee. The swirling cream certainly has a similar shape to the spiral galaxies, NGC 4321, in the adjacent photograph taken by the Hubble Space Telescope. But does the familiar photo really help us to understand the unfamiliar photo?

One of the tenets of cognitive psychology, which explores how we understand, is that the student should make the subject matter his or her own. Understanding comes from the interaction between the student's prior knowledge and the new information, mediated by creative human imagination.

Yet in the comprehensiveness of its descriptions and explanations, The Universe Explained holds the hand of our imagination at every turn. Much of our sense of wonder at the "mysteries of space" is removed. Here, in glorious computer-generated Technicolor, the mysteries are explained neatly away, like so many butterflies pinned down in a lepidopterist's collection. With its inter-related icons and arresting graphic design, this is a book of the computer and television age where attention spans are measured in seconds. But to study every page in detail requires days of commitment. This commitment might have paid greater dividends in understanding if the reader's curiosity was more engaged. For all its visual delights, whether the book succeeds in its aim of helping the reader to understand (in the deepest sense of that word) why the universe behaves as it does, is debatable.

Lynton McLain is tutor in science journalism on the postgraduate course in science communication at Imperial College, University of London.