Comment: The moon is the real star

Monday Book

IT'S A sign of just how recently publishers have embraced popular science that this book is being rushed into the shops barely a month ahead of the total eclipse of the sun this August, even though the date of that eclipse has been known for centuries. This is also, of course, a sign of the desperation with which publishers seek to find a topical peg for their books - a peg that usually only succeeds in ensuring sales are concentrated in the weeks around the event. Authors and readers would be better served by a less frenetic approach to the whole business; but given that Joe McEvoy has clearly been working to a tight deadline to meet the needs of this marketing ploy, his book is a lot better than the cheap cash-in that I had feared.

For the few people in the path of totality, a total eclipse does provide a breathtaking visual experience. The bad news is that the astronomy behind eclipses belongs to possibly the most boring byway in the whole of science: celestial mechanics. McEvoy's big mistake is to spend much of the early part of this book explaining the mechanics of eclipses in tedious detail, discussing the orbital calculations involved and the history of eclipse observations, back to the Babylonians. But he misses a chance to discuss the possible significance for life on Earth of having a moon large enough to cause such total solar eclipses while in orbit around our planet.

The most fascinating thing about the moon is that it may be responsible for our own existence. First, it was formed when an object about the size of Mars struck the Earth, melting its surface and spattering a blob of goo out into space, where it solidified to become the moon. The collision gave the Earth its relatively rapid rotation rate, and its cycle of day and night.

Meanwhile, the presence of the large moon enhanced the tides on the Earth's oceans, which may have encouraged our distant ancestors to crawl out of the sea. Once our slightly less distant ancestors turned their eyes skyward, the moon was there to encourage them to speculate about the nature of the universe, providing inspiration to poets and scientists.

McEvoy touches on some of this in the story of Stonehenge, which may well have been used as an eclipse predictor. But he makes no mention of Fred Hoyle's seminal contribution - that comets "seeded" Earth with life from gas clouds in space. And signs of the haste with which the book has been put together are clear in the garbled account of the interaction between Edmond Halley and Isaac Newton, which led to publication of Newton's great work, the Principia. But there is a lovely discussion of the way that eclipse paths were monitored using chains of observers stationed across the country, and the importance of these observations. A pity that this discussion isn't brought up to date, though, with recent observations of the same kind. They suggest that the Sun may vary in size, breathing in and out by a tiny amount on time-scales of decades and centuries.

Later, in his account of the 1919 eclipse, used to test the general theory of relativity, McEvoy gives a completely fictitious account of Albert Einstein's childhood, imagining him to have been the son of a Swiss businessman. Even worse, for a book about science, there is no mention of the influence of James Clerk Maxwell's work on Einstein's thinking. Happily, the rest of the discussion of the general theory is essentially accurate, although very familiar.

The very best bit of the book, which I enjoyed greatly, deals with spectroscopy and the way in which Victorian scientists used solar eclipses to begin to develop an understanding of what the surface of the sun is made of. But even here McEvoy falls into the trap of thinking Robert Bunsen invented the Bunsen burner. He benefited from his assistant Peter Desdega's sharp practice in marketing Michael Faraday's invention under Bunsen's name.

But, just when I was warming to the book, I came to the most futile feature of this kind of frenetic publishing. The final chapter is devoted to what is going to happen on 11 August. This is rather like publishing a review of the football season a month before the last games have been played. In a sane world, the author could have prepared the rest of his book with a little more care, waited until after the event, added a nice chapter on what happened during the eclipse - and published it comfortably in time for Christmas.

John Gribbin

The reviewer is a visiting fellow in astronomy at Sussex University and the biographer of Newton, Halley, Faraday and Einstein