This is my Amazon.co.uk review of Max Tegmark's "Our Mathematical Universe", published by Allen Lane, an imprint of Penguin Books. [Permalink to review]
If Max Tegmark is correct (and I have to say I think he *is*), we inhabit a universe that is just one of several hierarchies of multiverse that exist by virtue of the fact that they are mathematical structures. Not simply "describable" by mathematics, but that they fundamentally *are* maths. It's a conclusion that a lot of people have reacted against, and some of the implications are mind-boggling, but Max outlines his reasoning with wit and clarity in this very enjoyable romp between the physics of the Very Big to the Very Small and back to us humans. What is the meaning of Life? What gives meaning to the Universe? The ultimate answer is us, self-aware substructures within a larger mathematical entity, apparently evolving as the Schroedinger wavefunction through infinite-dimensioned Hilbert space, seeding clones at every quantum decoherence point, generating vast (infinite) numbers of parallel universes that are themselves part of this grander mathematical multiverse.
Max writes in an accessible and engaging style - it is clear that he is enjoying himself in coming up with his ideas (they seem to usually strike him when he's riding a bike (unlike a huge truck in Stockholm when he was a kid, fortunately for the Max in this universe) or walking in a park with one of his colleagues - in some ways these little biographical details add to the charm, and allow parallels to be drawn to the incredible writing of Richard Feynman.
That said, you can tell that Max knows this is an uphill struggle - many of his ideas strike deeply at some of the core notions we have as humans. Could there really be an infinite number of "yous" within this contiguous spacetime, not to mention within an infinite number of parallel spinoffs of this universe, each with the same subjective feeling that they are unique? These are not concepts that Max tosses out to deal with tricky problems - they are a fundamental prediction of certain formulations of physics. I have to say that I have not read a better description of cosmic inflation than Max presents here - I thought I had run the gamut of popular science descriptions, but this book makes several aspects much clearer, and provokes the reader to think on a wider level about the implications, and how we might test them.
The final chapter is a gem - what are the major existential threats facing humanity, and what should we be doing about them? As far as we can tell, we are alone in the Universe. He's a bit pessimistic here, in thinking that other civilisations are unlikely, and I very much hope that he is wrong (or do I?), but even so, there are multiple hazards that we will need to avoid if we are going to fulfil the role that we seem compelled to adopt - WE are what gives the universe meaning, so WE need to protect ourselves, our planet, our science. Whether it's dodging asteroids, or avoiding hostile artificial intelligence take-over, we would do well to plan ahead. Increasing scientific literacy is critical - this will drive both research and the intelligent use of new information as it arises. In the end, this is the only way we can hope to avoid a possible Great Cosmic Filter - if it lies ahead of our current technological state, it could well be the reason why we have not found other alien civilisations yet.
Is this an easy introduction to a complex subject? Is it a sales pitch for a radical reformulation of what we think of as "reality"? Is it Max's musings through the worlds of physics and ethics? It's all of the above and more. In at least some universes it is destined to become a classic, and those are the universes that are most likely to retain intelligent life. Probably.