To be a great physicist
I never met Robert Brout but on 4th June 2007 I interviewed him over a scratchy Skype line at his home in Brussels about his part in what has become the story of the Higgs boson. He was joined by Francois Englert. Together they wrote the first paper to describe how particle masses might arise from the kind of field Peter Higgs is now famous for.
When I began work on Massive I arranged to visit Brout and Englert in Belgium. The day I arrived, in June 2009, Robert wasn't well enough to make it. I sat in Englert's office at the Free University of Brussels and talked through the pair's history: how they came to know each other, how they worked at Cornell University but returned to live in the same city, to work at the same university, where they first circled and then cracked the problem of particle masses.
I was sorry not to meet Brout. When I interviewed the pair in 2007 I laughed more than I had in a long time. These two men, Brout the mentor of Englert, seemed to me to enjoy a depth of friendship that made the word inadequate. It was less an interview, more an eavesdropping on a conversation between the two. They finished one another's sentences, poked fun at themselves, and described their feelings on events not so much to me, but to each other.
Robert Brout died on 3rd May 2011. Since hearing the news, I wanted to go through my old interview notes and share some of his comments from our conversation. There was one sentence in particular that has lodged in my mind.
You might know that the mechanism for generating particle masses can be traced back to 1960 and work by Yoichiro Nambu, who framed the issue in terms of superconductor theory. I will spare you the details, though the book will not, but the link is that when a photon moves into a superconductor, it becomes massive and as a consequence doesn't travel very far.
Brout and Englert seized on Nambu's idea and developed it. Brout told me that in 1963 he was "completely clear that it was possible to generate mass with some kind of scalar particle", i.e. something like the Higgs boson. "But it took some time to have the complete vision," he said.
The two physicists spent months checking their work for errors and for good reason. They were outsiders when it came to particle physics and the idea they were playing around with was radical. Come the spring of 1964 they had failed to find any mistakes and were confident the work was sound.
Here's what Brout said of that time, though as you will see, he is talking to Englert too.
We were having a beer together on a terrace overlooking a park and we were both very excited. The fact that we could account for the masses of some of the gauge particles, but keep the photon massless, the fact we could realise this excited us terribly. I thought, Francois, that for the first time in my life, I felt what it might be to be a great physicist.
For the first time in my life, I felt what it might be to be a great physicist.
That line has stuck with me. I can remember how he said it. It made me think of the greats and imagine, hopelessly, but as best I might, the heady feeling of knowing for an instant that you have seen deeper into nature than anyone else.
There were six physicists who described in 1964 how particles might get their masses. Brout and Englert were the first. Sadly all six have never met as a group and any chance of that happening is now gone. The closest they came was in 2010, when all six shared the Sakurai prize for theoretical physics. Only Peter Higgs was missing from the award ceremony.