# The number that never stops

Thomas Blaikie

THE JOY OF PI by David Blatner Penguin, £12.99, pp. 124 Even those, like myself, largely befuddled by maths at school will remem- ber that moment of initiation into a higher mystery when the teacher first wrote the symbol for pi on the board and explained that there was a number that never stops. So there is some sense behind the idea of The Joy of Pi, which is one of a number of books being published at the moment which attempt to make quirky and difficult areas of knowledge available to the general reader. Two of these have been very suc- cessful: the huge-selling Longitude by Dava Sobel, where the secret of success seems to have been to leave out the difficult science and concentrate on telling a good story, and Simon Singh's Fermat's Last Theorem, which is more ambitious and does include careful mathematical explanation. All these books, including The Joy of Pi, are published in America by the same small, independent firm, Walker and Company, while Longitude and Fermat originate in England from one of the last of the independent publishers, Fourth Estate.

The Joy of Pi offers itself in a rather uncertain format. It is one of those square books where the main text is interrupted by joky marginalia in boxes or circles. Perhaps this is an attempt to jazz up the basic story- line, although this is told efficiently enough. The problem of finding the ratio between the radius and circumference of a circle has been known about since the ear- liest civilisations. Archimedes discovered the limits of pi by using geometry, but it was not until the 17th century that an arith- metical method was discovered that allowed pi to be calculated to over 100 places. Today there are some Russian brothers living in America who have calculated pi to 8 billion digits using a computer.

David Blatner employs an extreme bread-and-butter style, telling the story of Archimedes and the bath as if it had never been heard before, indulging in loose poet- icisms (Numbers, like people, have quali- ties and characteristics') and generally being irritatingly pally ('We humans aren't very good at remembering large chunks of information'). This is all harmless enough, although the imprecision of it sits oddly in a book about maths and will have real mathematicians in fits. The serious difficul- ty arises, as it often does with this kind of book, when there is a need to explain something complex. This is important in the case of pi because the two great turning points in its history that enabled more dig- its to be calculated depended on the use of very advanced maths. Blather tries to hurry past, leaving a hopeful trail of unexplained symbols and terms that will be unintelligi- ble to anybody with less than A-level maths and not very clear, I am reliably informed by a friend with a maths degree, to a true mathematician.

To be fair, it may be that more sophisti- cated explanations would lose the attention of all but the specialist reader but still you have to ask what you are left with. Knowing more and more digits of pi is of very little practical value. For engineering purposes three or four decimal places are considered sufficient. Blatner is vague about his claim that greater knowledge of pi might deepen our understanding of physics. Despite some similarities in the use of computers, pi does not have the larger significance for human life that the equations controlling irregular shapes have in Tom Stoppard's Arcadia. But perhaps it is the uselessness of pi, its randomness and untamability, combined with its admittedly maddening mystery, that is the source of its fascination and that will provide a small but sturdy following for this book.