In Search of the Multiverse – John Gribbin ****

There’s an old saying along the lines of ‘there’s speculation, then there’s more speculation, and then there’s cosmology.’ When it comes down to the likes of thebig bang, while there are alternative theories, it’s arguable that there’s a lot of evidence to make it likely. But what old statesman of science writing John Gribbin does here is launch off with a swallow dive into the deep end of the cosmology speculation pool.

To be fair, this isn’t how Gribbin seems to see it. He argues that some aspects of the multiverse – the idea that there isn’t a single universe but multiple versions of it, whether in a quantum ‘many worlds’ form or through multiple bubbles of inflation happening in a wider multiverse of which our entire universe is just one bubble – are almost inevitably true. This isn’t, in fairness, a view held by all physicists, but he makes a good stab at persuading us that this is the right line to follow.

What is beyond doubt is that Gribbin tells a fascinating story and beguiles us with the many possibilities for multiverses. Sometimes he raises an idea just to dash it. He doesn’t like the ‘bouncing branes’ idea, because he wants more richness than just a single repeating collision. And he finds the idea of virtual ‘Matrix style’ universe running on a higher intelligence’s computers too unlikely. But throughout Gribbin presents us with an entertaining and mind-stretching collection of ideas.

I’m not totally comfortable with everything in the book. Gribbin is too loose with his approach to infinity, employing the concept in a way that is mathematically dubious. He is also prone to make giant leaps of logic that may have an underlying detail we don’t see – but without that detail they are baffling. So, for instance, he says when referring to the first, small examples of a quantum computer in action he says ‘This proved that quantum computing works, proved that Shor’s algorithm works, and makes it very difficult to doubt the existence of the Multiverse.’ That last part is a huge leap that really isn’t obvious to the reader.

I was also a little concerned by Gribbin’s explanation of entropy. He describes a block of ice melting and says there is then less order – which means less information and less complexity. Yet without more explanation, the ‘less information’ bit doesn’t make a lot of sense. You need a lot less information to describe a regular block of ice, which you can describe at a molecular level using some simple formulae, than you do a fluid, where you would have to describe the position and state of every single molecule. It’s not that he’s wrong, but the example is confusing.

So we could have done with a little more clarity in places -and that’s why the book gets four stars rather than five – yet this remains an engaging voyage around the manifold possibilities for the multiverse that many will enjoy.

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Review by Brian Clegg