One might have hoped that the 2022 Nobel Prize in Physics, which was awarded to Alain Aspect, John Clauser, and Anton Zeilinger for enormous contributions to the foundations of quantum mechanics, would finally put to rest the long-standing controversies over that theory’s interpretations. If anything, though, the prizewinning work only emphasized the aggravating features that have driven those debates over the last century.
Werner Heisenberg (left) and Niels Bohr (right) in heated conversation during a meal at a 1936 conference at the Institute for Theoretical Physics (now the Niels Bohr Institute) at the University of Copenhagen.
Werner Heisenberg (left) and Niels Bohr (right) in heated conversation during a meal at a 1936 conference at the Institute for Theoretical Physics (now the Niels Bohr Institute) at the University of Copenhagen.
The editorial team behind the new Oxford Handbook of the History of Quantum Interpretations justifies the need for its monumental volume by foregrounding that paradox. As noted in the introduction, quantum mechanics is a fantastically successful theory that remains radically ambiguous in its foundations and meaning. It demands interpretation but remains strangely recalcitrant. There are many competing interpretations, all of which are unsatisfactory in some way, and it seems there will be no resolution anytime soon.
The editors, who are led by the historian of science Olival Freire, argue that a handbook is the best way to tackle such a controversial subject because any single-authored volume would inevitably be biased. Instead we have a wonderfully diverse group of authors, disciplinary perspectives, writing styles, and levels of technicality. The downside of the format is its sheer scale: 51 full-length articles plus an introduction, which span over 1200 pages. The diversity is certainly an asset but can sometimes be confusing. For example, there are easily a dozen different presentations of Niels Bohr’s philosophy of physics, which are all intellectually stimulating but perhaps overwhelming for someone new to the material.
But anyone with a grounding in quantum physics or its history and philosophy will find the handbook an extremely valuable volume. Although it can function as an encyclopedia (What are the differences between de Broglie–Bohm theory and modal interpretations, again?), it strikes me more as something of a quantum superposition of a few books. It could be a history of quantum physics. But depending on how you read it, it could also be a book on the historiography of quantum physics, or one on the measurement problem, or one on the sociocultural influences on modern physics, or one on what it means to interpret a theory at all.
The connections between the articles make for fascinating reading. One can learn about the famed debates over quantum theory that occurred at the early Solvay Conferences on Physics through José Perillán’s chapter on rhetorical strategies used to support various interpretations, or through Richard Staley’s look at how concepts formed. Or one could examine the role of experiments in quantum interpretations through Climério Paulo da Silva Neto’s chapter on tabletop instruments, or through David Kaiser’s contribution on probing cosmological entanglements. I imagine the best audience for this book is someone like myself, who is familiar with one aspect of quantum scholarship and wants to get up to speed on another. Anyone thinking of starting a research project touching on quantum interpretations should start here.
One of the many interesting themes that emerge across the volume is how it prompts the reader not only to question the orthodox understanding of quantum mechanics—namely, the Copenhagen interpretation—but to question the very idea that there ever was such a quantum orthodoxy. In other words, the assumption that there was or is a default approach to quantum mechanics comes under a great deal of scrutiny.
Don Howard’s chapter leads the charge in dismantling the Copenhagen myth, but many of the other authors also contribute to complicating its traditional position in the historiography. They show, for example, that the interpretation was not stable over time (it differed before and after World War II), over place (opinions on what the interpretation was diverged in Denmark and Germany), or even within the Copenhagen social circle itself (Bohr and Werner Heisenberg never really agreed on anything).
That creates a sense of a genuinely open field: All the modern interpretations are on something of an equal footing. There is not really a reigning champion that needs to be dethroned. Instead, the approaches can demonstrate their strengths and weaknesses on their own terms. Bohr’s ideas are not necessarily the point of departure.
That said, having so many plausible contenders in one place, each presented so forcefully, can be somewhat dizzying. But it surely reinforces the initial premise of the volume: that the interpretation of quantum mechanics is a live field, one with rich opportunities for innovation and creative thinking. It also emphasizes the strange nature of quantum theory, which is remarkably productive despite seeming unstable and fractured. Its mysteries are clearly not going to be resolved in the near future, which makes this handbook a launching point for future work rather than a summary of past efforts.
Matthew Stanley teaches the history and philosophy of physics at New York University’s Gallatin School of Individualized Study. He is the author of Einstein’s War: How Relativity Triumphed amid the Vicious Nationalism of World War I (2019).
