The 1911 Solvay Conference on The Theory of Radiation and the Quanta
This famous picture shows the attendees at the first Solvay Conference on physics held at the Hôtel Métropole in Brussels in October 1911. Seated on the right side of the table and talking with each other are Henri Poincaré and Marie Curie. At about the time of this picture, Marie Curie was informed she had won a second Nobel Prize. To her right and in a similar posture is Jean Perrin: he had already done his work on Brownian motion for which he would later win the Nobel Prize. Paul Langevin is standing on the far right and Marcel Brillouin is at the left corner of the table to the left of the head (pasted in, since he wasn’t present for the photo session) of Ernest Solvay. These are the leading figures of the French attendees at the conference. Albert Einstein is standing next to Paul Langevin, and Hendrik Lorentz is sitting at the head of the table to the right of Solvay, the Belgian industrialist and sponsor of the conference. In addition to the people already mentioned, four others had won or would win Nobel Prizes: a total of at least eight laureates (about a third of the attendees).
Much has been written about the conference in the primary literature (e.g. conference proceedings, Einstein’s letters, papers by Poincaré on the theory of quanta published shortly after the conference, reviews of the conference published by attendees) and secondary literature (e.g. reviews of the scientific content of the presentations, history of the founding and early years of the International Solvay Institute).
I have been actively researching and writing a book about the first Solvay Conference and the participants since 2019. (I have published two previous books.) The title of this book is The First Solvay Conference: A Community Faces Quantum Theory. I expect that I will have a book manuscript ready for the publisher in late 2028 or early 2029. (I have signed a publishing contract for this book with SpringerNature.)
The First Solvay Conference was a decisive turning point because it resulted in the acceptance that the issues and challenges in physics that had been emerging over the previous 20 years might be resolved by a theory of quanta and that therefore such a theory did merit further effort. This acceptance and effort set the direction for physics for the following 25 to 50 years.
What happened at the conference that resulted in such impact? In a word, science. The practice of science is deeply tied to community acceptance of new paradigms and to the scientists who are members of that community. My book explores what made that acceptance of quanta and of research on quantum theory possible; beyond the content of the papers, it looks at the discussion, interactions, influences and ideas of the participants before, during and after the conference. This exploration emphasizes the development of the participants’ attitude to the theory of quanta (both those who influenced and who were influenced), and also on the personal and social interactions between colleagues, especially Marie Curie, Paul Langevin, Jean Perrin, Henri Poincaré and Albert Einstein. These interactions involve both their personal dynamics and intrigue, and also their implication and involvement in polarizing social issues of their time: pseudoscience, misogyny, xenophobia, nationalism and the Dreyfus affair.
The subject of the book, the result of these considerations and developments, is thus a story of people and science at the onset of the quantum era. The pieces of the story—drawn together by the first Solvay Conference in Physics in 1911—are the people (the attendees) and physics (the problems discussed in the meeting room). I am writing about how the attendees lived, how they worked, how they were connected in their personal, social and professional lives, and how they connected with prominent social issues of their time. I researched this through personal letters and records in archives, and through newspapers and court records. For the physics, I am writing about the problems and anomalies accumulating before the Conference, which were discussed in the meeting. I researched this through the published work on the issues and how they became long-standing unresolved problems (what Thomas Kuhn, in The Structure of Scientific Revolutions, called anomalies) and through notes kept during the Conference sessions.
Within two years after the Solvay Conference, Niels Bohr, then in England, published his atomic model, which is sometimes referred to as the old quantum mechanics. Perhaps he heard about the Conference directly from James Jeans (or even Ernest Rutherford). They are standing in the same row with Langevin and Einstein. Maurice de Broglie, standing by the easel, was a secretary at the conference; he published the official report with Langevin. He was accompanied by his younger brother, Louis de Broglie, then a teenager. The experience changed Louis de Broglie's career plans: he decided to study physics. Ten years later, Langevin and Perrin encouraged and supervised the doctoral research of Louis de Broglie that introduced wave-particle duality. New quantum mechanics quickly followed.
Einstein at the 1911 Solvay Conference
Einstein did not look forward positively to the Conference. In October 1911, in a letter to his close friend Michele Besso (for the letter see the Einstein papers where it is letter 296) Einstein refers to an upcoming meeting of physicists in Brussels as „wenn auch noch der Hexensabbat in Brüssel vorbei ist“. It appears he was expecting a witch’s brew of participants.
After the conference, Einstein wrote again to Michele Besso (letter 303 from the same source) and recalled, “I returned last night from Brussels, where I spent much time with Perrin, Langevin and Madame Curie, and became quite enchanted with these people. The latter even promised to come visit us with her daughters.” He enjoyed the social life at the conference.
Langevin and Perrin were closely socially connected and Marie Curie had been drawn into this circle. Marguerite Borel was a central connection in this social network. Marguerite’s husband was the mathematician Émile Borel and Marguerite was the daughter of Paul Appel. Appel and Poincaré were lifelong friends.
National Geographic Genius: Einstein at the Solvay Conference
In Episode 5 of the National Geographic TV production Genius: Einstein at the 22:10 mark, we see Einstein engaged in small talk over the title “Solvay Conference, Brussels, 1911.” He and Arnold Sommerfeld (in this picture the man standing directly behind Solvay and Lorentz, who are seated) notice Marie Curie entering the room and establish that she is the only woman at the conference. At 22:31 Sommerfeld tells Einstein, “Haven’t you heard? She’s been cavorting around Paris with a married man.” and 15 seconds later adds, “Poincaré thinks she should be asked to leave the Conference.”
At the 39:17 mark, Marie Curie admits to Einstein that she was having an affair with Paul Langevin, who was also at the conference. The affair—her husband, Paul Curie, had died over 5 years earlier, and Langevin was married with four children—did cause a scandal in the Paris press immediately after the conference. The series seems to use the scene to establish a later conversation between Marie Curie and Mileva Einstein with potential for comparing and contrasting the two couples.
Would anyone at the First Solvay Conference have criticized Marie Curie over it? Yes, privately, Marcel Brillouin was critical and expressed concerns about the effect on their children.
Would H. Poincaré have suggested that Curie should leave the Conference? Certainly not! When the first wave of the story broke in the Paris press (based on a fanciful and unverified interview with Paul Langevin’s mother-in-law) as they were preparing to leave Brussels to return to Paris, H. Poincaré, Jean Perrin and Paul Langevin stepped in to shield her. All three provided interviews to the Brussels press denying the story and defending her. Although Poincaré didn’t get involved personally (as far as we know), his cousin—Raymond Poincaré, the President of France during World War I—was involved in responding to the scandal and successfully intervened with the respectable press. He represented Paul Langevin and his friend Alexandre Millerand—also a future French President—represented Marie Curie in court in divorce proceedings and in a criminal case for adultery and complicity in adultery.