Unpacking the History of Quantum Mechanics
Senior Lecturer in History & Philosophy of Science Dr Kristian Camilleri is currently completing work on a book which challenges the standard understanding of the history of quantum mechanics. The book manuscript is provisionally titled Quantum Mechanics and Its Discontents: The Making of An Orthodoxy. In this interview, Kristian sat down with current HPS PhD candidate Samara Greenwood to discuss his ongoing work.
First, can you tell us what your book is about?
My book is about the debate (or perhaps better to say, the lack of debate!) over one of the most controversial and paradoxical theories in twentieth century physics – quantum mechanics.
Quantum mechanics is a theory which explains the behaviour of atoms and sub-atomic particles but does so in a way that challenges many of our basic assumptions about the nature of reality. According to the standard narrative, the ‘orthodox view’, commonly known as the ‘Copenhagen interpretation’, emerged in the late 1920s. This view, so the story goes, remained the dominant view within physics for much of the century. But, in the 1980s, new views began to emerge and today there are many competing interpretations of quantum mechanics.
In my book, I go back and look at how and why prominent early critics of the orthodoxy, such as [Albert] Einstein, [Erwin] Schrödinger, and [Louis] de Broglie (who were also key architects of the theory) failed to mobilise support for alternative views or programs of research. Why did heterodox views only really begin to gain support in the 1970s? Why did the orthodoxy prevail for several decades? Why wasn’t there greater opposition to the almost complete abandonment of a conception of reality that had previously underpinned our understanding of physics? These are tricky questions!
My book tracks the story over about five decades from the mid-1920s, when quantum mechanics took shape, to the 1970s, when the tide began to turn. Importantly, I show there wasn’t actually an orthodox view per se. Everyone had a different take on the theory. The book has therefore forced me to engage in a revision of what we even mean by ‘the orthodoxy’, let alone how we explain it.
What is original about your take on these events, compared to other work in this area?
The orthodox view of quantum mechanics is typically referred to as the Copenhagen Interpretation. The term was only coined in the 1950s, but it’s used retrospectively.
I try to tell a history of the orthodoxy without recourse to this notion of the Copenhagen Interpretation, which I – following some other scholars – expose as a myth. The term obscures the complexity of the picture, both in regards the divisions between people who professed allegiance to the orthodoxy and vacillations in their own view over time. In some cases, adherents to the so-called Copenhagen Interpretation have such different views that they are almost indistinguishable from views we would call heterodox.
What my research suggests is that a lot of physicists, perhaps many more than we previously thought, did entertain doubts about quantum mechanics as a ‘complete theory’ of the subatomic world, but didn’t feel compelled to do anything about it. They weren’t sufficiently roused to action and, in fact, continued to work on orthodox quantum mechanics. We might then get the illusion that they supported the views of leading physicists, like Niels Bohr or Werner Heisenberg, when, in fact, you’ll find they didn’t. They either kept their views private or, if they did make them public, didn’t act on them.
I then have to explain why people held these doubts but didn’t bother to mount a serious case for the opposition. I focus on how leading dissidents, such as Einstein, Schrodinger and de Broglie, failed to mobilise support around them. As one historian, Joan Bromberg, put it, orthodoxies need followers. It wasn’t because of lack of reputation – they’re all Nobel prize winners. Rather, I look at the way their particular intellectual temperaments and their failure to generate a culture of research contributed to this loss. It is only when you get social organisation happening between dissenting physicists that you begin to see real progress. This mobilisation of action began in the 1960s and 1970s, and both the rebellious spirit of counterculture and strong leadership played a part in this. I take all that into account in my explanation.
Could you tell us a little bit more about your research on intellectual temperament and the development of research cultures?
Many of the professors who worked on quantum mechanics and practiced the orthodoxy, such as Bohr and [Max] Born, were marvellous teacher-researchers. They were inspiring, encouraging and emboldening. As you would expect, young, gifted, aspiring physicists then gravitated to those centres which embodied what I call the teaching-research nexus. Indeed, this is something we try to enshrine at the University of Melbourne, that teaching should inform research and research should inform teaching.
This is in striking contrast to people like Einstein, Schrödinger and De Broglie, who had very little interest in training students. While Schrödinger and de Broglie did teach, they kept it strictly separate from what they were researching. They didn’t like having postdocs or graduate students.
The practitioners of the orthodoxy were also masterful at sourcing funding from philanthropic organisations in the United States such as the Rockefeller Foundation and using the system to help draw in talented researchers. The dissenters weren’t. They were undoubtedly great physicists but they weren’t leaders. They didn’t know how to create the institutional conditions under which programs of research would flourish. They also had no interest in doing so by intellectual temperament. It was not their game.
Later, new spaces were created where dissent could safely occur. This happened in the 1960s and 1970s, through subcultures creating their own underground networks and research journals such as the Epistemological Letters of the Ferdinand Gonseth Foundation. They staged conferences where they ensured all views were heard. It was a very permissive environment, unlike what you found in most of the traditional institutes. You also had leaders like John Bell, who gave young researchers the inspiration and encouragement they needed.
By looking at this later period, you can see what was missing for the dissenters in the earlier periods.
What do you hope readers will take away from your book?
Beyond people who take an interest in the history of physics, I hope the book will shed some light on the formation of scientific orthodoxies.
As part of my research, I looked at writing on the history of religious orthodoxy but found noticeable differences. In the science there is an absence of an authority figure who dictates a doctrine or manifesto. How scientific orthodoxies are established is therefore a lot more elusive.
My own thought is that it operates at a much more informal level, where scientific orthodoxies are maintained by constant chatter and communication and face-to-face gathering. That aspect of intellectual life, the power to move people through the spoken word and through conversation, is also a major part of the book. I hope that may inform other studies of how orthodoxies are formed.
What is the backstory to the book? What led you to write this book and not a different one?
I have been writing and researching the history of quantum mechanics for some time. I’d written an earlier book on Heisenberg and his philosophy of quantum mechanics. I kept coming back to the problem that the views of an individual figure couldn’t explain the larger issues we were interested in.
There were two books which prompted my questions. One was James Cushing’s Quantum Mechanics: Historical Contingency and the Copenhagen Interpretation, which I still go back to frequently. The other was Mara Beller’s Quantum Dialogue: The Making of a Revolution, which had quite an impact. In my view, she came closest to understanding many of the issues and I certainly build on her work.
Both works were published in the 1990s, but what happened over the course of many, many years is I gathered a bigger and broader picture of what was going on. At one point I remember thinking, now is the time to commit. I feel I have something original to say on these questions and feel it’s important enough to devote all that time and energy to putting it into a book. So that’s what I have been involved in for the last two years, a lot of it in lockdown!
Your book sounds fantastic, and I look forward to it being published. I understand you are also involved in an international project on the anniversary of Quantum Mechanics. Can you tell us about that?
In 2025 it will be 100 years since the first paper on quantum mechanics, the ‘birth certificate’ if you will, was published by Werner Heisenberg. I am involved in a working group on the history of quantum physics where we are planning for what we are calling the Quantum Century.
We are organising a series of public facing events around the history of quantum physics. These won’t be confined to its early development but will also examine things that have happened over the century since.
One of the projects I’m involved in is locating the physicists as they moved around the various institutes. We are creating a map with a timeline dimension to it, to show these frequent moves. The working group is headed up by Alex Blum and Michel Janssen and includes some very eminent historians, such as David Kaiser. I’m enjoying being part of such a great project.
Dr Kristian Camilleri is Senior Lecturer in the History and Philosophy of Science (HPS) program. After studying both physics and HPS at Melbourne University, he went on to complete his PhD in HPS. Dr Camilleri has published in the history and philosophy of modern physics and has collaborated with other scholars from around the world on the History and Foundations of Quantum Physics project. He teaches a range of subjects across HPS, including the first-year subject From Plato to Einstein (HSPC10001); the second-year subject Thinking about Science: Past and Present (HPSC30037); and the HPS capstone subject The Dynamics of Scientific Change (HSPC30035).