Solvay

One hundred years ago, classical physics collapsed into complete confusion at the first and most famous Solvay conference to be held in Brussels. We look at the event, its founder and the vast legacy he left

They were all there for the photo op: Albert Einstein, Max Planck, Ernest Rutherford, Marie Curie, Henri Poincaré and a handful of other luminaries of 20th-century physics. As was considered proper at the time, they all posed solemnly and self-assuredly. According to Marc Henneaux, a physicist and the present director of the International Solvay Institutes for Physics and Chemistry, their composure belied an inner bafflement: "The 1911 conference was essentially about confusion. It has acquired a legendary status, because up until then theories propounded by physicists had completely failed to explain newly observed phenomena at an atomic level, like atomic radiation, for instance. Indications of their existence had been detected before. But it wasn’t until 1911 that physicists felt they needed to come up with a radical new theory to explain them,” says Henneaux. “If you read the attendees’ impressions of the conference, you can see that they felt they were on the eve of a revolution.” The conference, says Henneaux, dashed the hopes of those that thought the newly discovered phenomena could be fitted neatly in the old edifice of classical physics. The 1911 Solvay Conference, held in the Hotel Métropole, went on to become famous, not so much for a scientific breakthrough, but rather for a scientific breakdown.

In the 15 years following the conference, the much-anticipated revolution took place: quantum physics was born. Early in 1927, German physicist Werner Heisenberg formulated his Uncertainty Principle [key to the development of quantum theory], and at the 5th Solvay Conference in the autumn of that year, he and Danish physicist Niels Bohr declared to their colleagues that quantum mechanics were now “complete and irrevocable”.

“This closed the chapter begun in 1911,” says Henneaux. “If 1911 was about confusion, 1927 was about an accomplished theoretical construction. Not that quantum physics was finished – research into the field continues today. But the principles of quantum mechanics that were formulated then are still taught today.” Not that everyone agreed with them at the time including, most famously, Einstein. Says Henneaux: “You see, in 1911 Einstein was one of the younger generation. By 1927 he was an authority, who didn't agree with the work of the younger physicists, like Heisenberg, Born or Schrödinger.” It was at the 1927 Solvay Conference that Einstein is alleged to have asserted to Heisenberg: “God doesn't play dice with the universe.” To which Niels Bohr retorted: “Einstein, stop telling God what to do!”

Skimming through the records of Solvay conferences can be a pleasure, says Henneaux, who is in charge of organising the scientific gatherings today. “Another important one was held in 1958, where there was a lengthy discussion between Robert Oppenheimer, father of the atomic bomb, and the American physicist John Wheeler on the possibility of black hole formation. Wheeler argued that a star could not collapse into a black hole, while Oppenheimer argued the opposite. We now know, of course, that it can. And Wheeler changed from being an opponent of the idea to its main champion.”

The era of superstar physicists might be over, says Henneaux, but every few years, the Solvay conference still assembles Nobel prize-winners and other top physicists to discuss ongoing issues. “Discussion has always been a central aspect of the Solvay conferences. They are at least as important as the presentations. A speaker presents the state of the art in a given domain, and then there is a discussion.” This year, the conference is in its 25th edition; the theme is again ‘Quantum physics – where is it today?’

In the official group photo of the 1911 Solvay Conference attendees, one man is doubly out of place. First, because he wasn't a physicist – in fact he had never even been to university. Second, because he wasn't even there. He couldn't make it to the photo-shoot and had someone sit in for him; his face was pasted onto the picture later. Even for those pre-Photoshop days, it was a hatchet job: his face appears much too big for his body. The missing man was Ernest Solvay, a wealthy industrialist and philanthropist, who was also the conference organiser and subsequent founder of the International Solvay Institutes for Physics and Chemistry, which continues to organise the conferences.

Born in 1838 in Rebecq, Walloon Brabant, Solvay suffered from acute pleurisy for most of his adolescence, and subsequently missed out on university. At 22, he became assistant manager of his uncle's chemical factory in Schaerbeek, where he spent most of his free time studying and experimenting. In 1861, he developed the so-called Solvay process for the manufacture of soda ash from brine and limestone. (Soda ash is needed in a variety of industrial products, most notably glass). He founded his own company in 1863, and patented his procedure. Solvay & Cie soon expanded to the UK, Germany and the United States, turning its owner into a man of considerable means.

The International Solvay Institutes for Physics and Chemistry will celebrate its centenary in a series of events that will, organisers say, turn Brussels into the “world capital of physics” for the duration. For a full list, see www.solvayinstitutes.be.  Photo: Edificio Molitor, Archives de l'Université Libre de Bruxelles.

Read full article in The Bulletin, October 21.