"Beyond Weird" - Philip Ball

Amazon link

I mentioned Peter Woit's generally favourable review of this book in a previous post.

"Beyond Weird", despite its cheesy title, makes a good impression from the very start. Ball is an engaging writer who knows his stuff and doesn't patronise the reader. It's like he's talking to a curious colleague who uses quantum theory (a chemist or applied physicist, for example) but doesn't research it. The tone would work well for a recent physics graduate or someone in the final stages of their QM course.

The problem with quantum mechanics is that the mathematics makes plenty of sense in itself (Schrödinger's equation and its many solutions in concrete circumstances such as the structure and behaviour of the hydrogen atom, for example)  but the many constructs of the theoretical apparatus don't align with any compelling concept of 'reality'. To properly engage with the 'interpretation problem' you have to understand the maths, which means taking a course first.

Before I studied quantum mechanics (with the Open University - SM358) I thought I had a grasp - as an educated person with a technical background - of quantum theory, at least at a conceptual level. I knew, or thought I knew, about the uncertainty principle, the wave function and its collapse, the double slit experiment and its paradoxical interpretation and so on.

I spent the first third of my QM course learning a lot of details about Schrödinger's equation in its time dependent and stationary forms, about spin spaces, kets, operators, expansions in terms of eigenfunctions, Hilbert spaces and so on. I was internalising this complex apparatus and making it work and I couldn't anchor any of it into the real world. I was confused, baffled, a sufferer from extreme cognitive dissonance. It was not pleasant.

Eventually I managed to organise all this stuff into something which kind of made internal sense, and kept reminding myself that in the end its only function was to produce a number between zero and one as regards observable outcomes. I had become acculturated, but I still didn't know what any of it really told me about reality.

And I think that only after this 'preparation' is a reader really able to engage profitably with Philip Ball's book.

Ball is good on superpositions and what it would mean if they were observable. He's as good as you could expect on decoherence and einselection, although it would have been useful to have had a more explanatory appendix given its centrality in accounting for 'collapse' (but perhaps that's more a signifier for my own lack of clarity). He is also good at debunking some of the more ontological-realist views of the wavefunction. There are also clear accounts of Bell's theorem and quantum computing.

And then it starts to unravel. Ball clearly has a thing about the many-worlds interpretation (which has a stronghold at his alma mater, Oxford). His customary cool deserts him for visceral distaste. His debunking is anticlimactic, however, depending on philosophical sophistry about identity-continuity before and after 'splitting' of worlds. The MWI does not hang on such arguments.

In the final chapters things get worse. Ball's enthusiasm for 'it from bit', an information-centric approach to the interpretation problem, gets the better of him. Unfortunately the ideas swirling around in this currently active area of investigation are even more formless and confusing than the more conventional ideas he's been debunking all along. We finish the book shaking our heads and asking, 'What was that about?'.

If you read one book on the interpretation of quantum mechanics, and you have studied QM as an undergraduate, this may well be the book for you. It will confirm that you were right to be concerned that the Copenhagen stuff you were taught does not put an end to the discussion, and it will straighten out and firm up many of your questions and half-formed, tentative conclusions.

Just don't think it will give you any final answers: there are none.

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See also Roy Simpson's review: "A second review of "Beyond Weird" by Philip Ball".