Of all the wonders of physics, none is more fascinating and mind-bending than quantum theory. But there is one aspect of it that, frankly, I find tedious – and as this book is dedicated to that aspect, I wasn’t hugely looking forward to reading it. The aspect in question is interpretations of quantum theory. Such is my distaste for these speculations that my book on quantum entanglement, The God Effect, only makes passing reference to them.
Quantum theory itself describes how very small particles – both matter and less substantial, like photons of light – behave. It’s a weird world, but a consistent one. The trouble comes when you try to make the bridge between that world and the ‘normal’ world we experience. For example, unless they are observed, quantum particles don’t have a precise location. Instead there is a range of possibilities, each with it’s probability predicted precisely by an equation. But until you check where a particle is, it isn’t in a single place. This is fine and all works well. But the ‘enigma’ of the title is how it works. How a particle (say) goes from being a range of possibilities to an actual location.
We usually loosely ascribe this fixing of the state of a particle to a measurement or an observation – but does that imply it requires conscious attention? (Which is why this book also considers consciousness.) This led Einstein to wryly ask if the moon is still there if no one is looking at it. In practice it seems obvious consciousness is not involved. A detector like a Geiger counter is enough to fix a location. But those who have agonized about this for years think that a totally isolated Geiger counter that had no contact with anything else whatsoever would not make an observation, but would go into an entangled state with the particle.
So apart from the original Copenhagen interpretation, which simply describes the probability wave function collapsing on contact with a macro object and doesn’t fuss too much about the detail, there are now a whole range of interpretations from the many worlds idea to Bohm’s transformation of reality that works on the whole universe all at once.
The trouble I have with all this is that it isn’t really science. It’s more metaphysics than physics. The interpretations all predict the same thing – quantum physics happening the way it does – but don’t really add anything because they remain speculation. If at some point we get a clear indication of an interpretation that can have our support as being distinguished by data as the best one, I’d be happy to think about it, but for the moment I can’t help but feel it’s a waste of time. I’m quite happy to say that quantum physics works the way it does and I don’t really care how it is interpreted. Just enjoy the science!
As it happens, it wasn’t as bad an experience reading the book as I thought. Bruce Rosenblum and Fred Kuttner make the various interpretations and the way this whole business strays into the nature of consciousness quite approachable, and they get the message across without resorting to too much painful philosophy. I would say, though, that they tend to labour the point. There’s a long and rather boring section with a story about someone visiting a world where macro objects behave like quantum particles that is entirely unnecessary, especially as all the same examples are gone through again later using an actual quantum particle. I really can’t see the point of this.
There are also a few not-quite-right moments when the pair stray from science to history of science (they are scientists, not writers, which perhaps explains this). One example that jumped out at me was the comment about philosopher George Berkeley that Berkeley was a bishop, going on to say ‘It was common in those days for English academics to be ordained as Anglican priests, though the celibacy of Newton’s day was no longer required. Berkeley married.’ The big problem here is that Berkeley and Newton were contemporaries. Admittedly Berkeley was younger, but their working lives overlapped in a big way (in fact Berkeley’s most famous contribution to science was his attack on Newton’s ‘method of fluxions). The point they seem to have missed is that Berkeley wasn’t a priest because he was an academic. He was a bishop first, and a philosopher in his spare time. He wasn’t a professional academic at all.
Overall, an interesting contribution to books on quantum theory if you want to know more about interpretations, but because of the topic, not one I can get too excited about.
Hardback: 
Review by Brian Clegg
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