The Multiverse - Brian Clegg ****

‘When One Universe Isn’t Enough’, it says on the undeniably eye-catching cover of this book. But why should anyone feel short-changed by the universe we happen to live in? The most obvious answer is if they’re fans or creators of science fiction, who may be distinctly unimpressed by the un-SF-like reality we’re lumbered with. As Brian Clegg points out early in the book, even now  – almost 70 years after the invention of the space rocket – only a tiny fraction of astronauts have ever travelled more than 300 miles from the Earth’s surface. If we’re looking for all those ‘strange new worlds’ that Star Trek promised us, we’re not going to find them that way. What we need is a portal to a parallel universe – or, preferably, a whole collection of them.

Since this is a non-fiction book, I hope I’m not spoiling any surprises by saying that we never actually get to this point, or anywhere near it. Like so many other science-fictional ideas that are claimed to have parallels in modern physics, it turns out the reality is highly abstract and totally lacking in the practical applications of its sci-fi counterpart. Even so, the book is a fascinating and enjoyable read, as Clegg takes us through a whole series of theoretical arguments in favour of a multiverse. Or perhaps that should be ‘multiverses’, plural, since the arguments are largely self-contained – dreamed up by experts in their own particular field – and not always compatible with each other. The one thing that most of them have in common is that they are basically ‘meta-theories’ – i.e. high-level, overarching theories that sit above a much more practical, but often unsatisfyingly arbitrary-looking, theory and give it greater cohesion and sense of completeness. Whether that’s something physicists should be spending any time doing, or whether it should really be left to the philosophers, is a debatable point (and one that Clegg discusses in his final chapter) – but it’s still interesting to sit on the sidelines and watch them at it.

Essentially, each chapter – after a few introductory ideas are out of the way – deals with a different theoretical argument for the multiverse. The first three of these aren’t really physics at all, but pure mathematics, dealing with concepts like dimensions, probability and infinity. Then we move on to real physics, in a sequence of chapters that, to me at least, seemed to get increasingly sophisticated and abstract – almost to the point of merging back into pure mathematics at the end. We start on relatively familiar ground with the Big Bang and quantum theory, before moving forward in time to string theory, black holes and – perhaps surprisingly, in this context – quantum computing and information theory. As a rough estimate, I’d say around half of each chapter is background on the field in question rather than being about the multiverse as such, but that’s not a bad thing. I’m an unabashed supporter of ‘bait-and-switch’ tactics in popular science writing – appearing to talk about some exciting sci-fi-like topic while actually explaining really quite serious and difficult physics. It’s the best way to communicate material like this, and Clegg is a master at it.

If there’s anything negative to say about this book – or about its subject matter, rather – then Brian Clegg says it himself in his final chapter, when he dismisses a lot of the arguments he’s been discussing as ‘pointless debate’. The thing that distinguishes a scientific theory from mere speculation is that there should be something in it that has an observable consequence in the real world – for example, it predicts how a machine or electronic circuit will work, or how an experimental measurement will turn out. Arguably, not one of these multiverse theories falls in this category – which puts us right back where we started, in the realm of science fiction.

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Please note, this title is written by the editor of the Popular Science website. 
Our review is still an honest opinion – and we could hardly omit the book 
– but do want to make the connection clear.