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12 Jun 2018
Taken from the June 2018 issue of Physics World

Philip Moriarty reviews Quantum Sense and Nonsense by Jean Bricmont

To say that I eagerly anticipated the arrival of my review copy of Jean Bricmont’s latest book would be an understatement approaching “we physicists have maybe got one or two loose ends to tie up when it comes to interpreting quantum mechanics” proportions. Bricmont – theoretical physicist, philosopher and emeritus professor at the Université catholique de Louvain – became, along with his co-author Alan Sokal, the scourge of postmodernists far and wide following the publication of Fashionable Nonsense: Postmodern Intellectuals’ Abuse of Science back in the 1990s. I thoroughly enjoyed Fashionable Nonsense, and with Bricmont’s latest book – titled Quantum Sense and Nonsense – was looking forward to a characteristically clear-headed analysis of the myriad interpretations of quantum mechanics that are now used and abused by physicists and non-physicists alike.

As a veteran of the so-called “science wars” that formed the backdrop to Fashionable Nonsense, where scientific realists were pitted against those who dismissed science’s claims to objective “truth” (however that might be defined), Bricmont is better equipped than most to expose the signature excesses of the worst of the “woo” surrounding quantum physics out there. And for those of you not aware of just how bad it can get, here’s Deepak Chopra – author, public speaker, widely lauded New Age guru (3.34 million Twitter followers and counting) and proponent of, um, quantum healing – on what quantum physics can do for you: “Viewing your body from the perspective of quantum physics opens up new modes of understanding and experiencing the body and its ageing. The practical essence of this new understanding is that human beings can reverse their ageing.” Or how about this gem? “Quantum healing involves a shift in the fields of energy information, so as to bring about a correction in an idea that has gone wrong.”

As I like to put it during the Skeptics in the Pub and Café Scientifique talks where I “critique” Chopra’s clueless take on the subject, his writings remind me of that classic 1970s Morecambe and Wise sketch with André Previn – “All the right words, just not necessarily in the right order.” To be fair to Chopra, at least he hasn’t quite plumbed the depths of claiming that lobsters hold the secret to life, the universe and everything. We can instead thank the latest kid on the self-help guru block, University of Toronto psychologist and author of 12 Rules For Life, Jordan B Peterson, for this insight into our crustacean kin. Peterson has also had very Chopra-esque things to say about quantum mechanics, but that’s a whole other story. As is the expanding “quantum life coaching” industry. Yes, you read that right.

If, like me, you were expecting Quantum Sense and Nonsense to be a take on quantum woo that echoes the style and approach of Fashionable Nonsense, then you may be slightly disappointed with Bricmont’s new book. That’s not to say that it isn’t an important, informative and at times engaging read. But it’s a book that falls between two camps. Indeed, one might even suggest that it exists in a superposition of states. It opens by stating, laudably, that “although this book belongs to the ‘popular physics’ category, its main purpose is cultural rather than scientific. We shall try to explain to the lay reader the basic principles of quantum theory”. But Bricmont also simultaneously wants to do justice to the many complexities and intricacies of the subject with the type of diligence we’d expect of a theoretical physicist of his standing. This leads to a rather disjointed and difficult read at times – a lot is asked of a reader who’s familiar with the subject matter, let alone a lay audience.

I agree with Bricmont that we physicists must shoulder a portion of the blame for fuelling the rise of woo

Moreover, while I agree entirely with Bricmont that we physicists must shoulder a fair portion of the blame for fuelling the rise of woo by making excitable and ill-advised pronouncements over the years about the nature of quantum mechanics (particularly with regard to the role of consciousness, the observer and that confounded cat), I would have preferred a slightly more up-front rebuttal of the more egregious pop-sci claims out there. As it is, chapter 11, titled “The cultural impact of quantum mechanics”, feels somewhat tacked on, piecemeal, and not as integrated as one might expect given the opening statements regarding the rationale for the book.

In this context, it was also rather surprising that the exceptionally important topic of decoherence – the suppression of the interference effects that are the very essence of quantum “weirdness” – is relegated to a throwaway footnote buried in the middle of the book. The scrambling of phase coherence due to interactions with the environment is now seen by most physicists as key to explaining how the big, bad classical world (and all its attendant myths, mysticism and misinformed gurus) emerges from the quantum. Decoherence thus plays a central role in disentangling quantum sense from nonsense, and Bricmont’s book would have benefitted from a brief review of the topic at the very least.

On the spectre of quantum weirdness, I should admit that I read this book and Philip Ball’s most recent, Beyond Weird: Why Everything You Knew About Quantum Physics is Different, in short succession. Brian Clegg’s review of the latter in April’s Physics World is spot on: Ball is an exceptionally talented writer who manages to combine accessibility and thoroughness in razor-sharp prose. This sets a very high bar for Bricmont’s book, and I came away from it with the distinct sense of a certain lack of coherence by comparison.

But when Bricmont is good, he’s very, very good. His insights into thorny (meta)physical and philosophical issues such as determinism, non-locality, hidden variables and Bell’s inequalities, and the ontological-versus-epistemological nature of the wavefunction are sharp and deserve to be widely read. I also especially enjoyed his sure-to-be-contentious critique of the Many Worlds Interpretation. (But then, as a dyed-in-the-wool experimentalist for whom empiricism is everything, I would say that. I’ll remain agnostic about all interpretations of quantum physics until experimental evidence gives one or other the edge. That, after all, is how science works.)

Similarly, Bricmont’s revised history of quantum mechanics is a fascinating read, in which the development of the field is considered against the socio-political backdrop of the time. David Bohm’s career, and the associated (lack of) influence of the “de Broglie–Bohm pilot-wave theory”, were particularly affected by those political underpinnings. But whether this theory deserves its centrepiece status in the book is questionable. The reader does get a heads up very early on that Bricmont is a proponent of de Broglie–Bohm (and that it’s hardly a universally accepted theory). But while it’s true that the pilot-wave idea perhaps deserves rather more attention than it has garnered (if only as an ingredient worth keeping in the conceptual mix), it’s certainly not a silver-bullet solution to the interpretational difficulties of quantum mechanics.

I think it’s unlikely that Quantum Sense and Nonsense would ever top my list of recommended quantum-physics books for the non-physicist. There are more readable “lay” introductions out there; in particular, Beyond Weird. Where Bricmont’s book comes into its own, however, is in providing a thorough overview and analysis for a Physics World audience – a readership that is already likely to have an appreciation of the foundational principles and the deep interpretational issues that continue to plague quantum physics. Undergraduate and postgraduate students, and their lecturers and tutors alike, will all benefit from Bricmont’s far-from-traditional take, including his well-placed closing plea for rather less hubris when it comes to waxing lyrical about what quantum mechanics tells us about our place in the universe (or multiverse, if you’re so inclined). After all, if there’s one field of physics in which we should admit to uncertainty about our interpretations, it’s quantum mechanics.

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