Ten years ago scientists announced one of the most momentous discoveries in physics: the Higgs boson. The particle, predicted 48 years earlier, was the missing piece in the Standard Model of particle physics. The machine built in part to find this particle, the 27-kilometer-long, circular Large Hadron Collider (LHC) at CERN near Geneva, had fulfilled its promise by showing signals of a new fundamental bit of nature that matched expectations for the Higgs.
The existence of this tiny object had first been proposed by physicist Peter Higgs in 1964. For years, the significance of the prediction was lost on most scientists, including Higgs himself. But gradually it became clear that the Higgs boson was not just an exotic sidesshow in the particle circus but rather the main event. The particle and its associated Higgs field turned out to be responsible for giving all other particles mass and, in turn, creating the structure of galaxies, stars and planets that define our universe and enable our species. Physicists believed this story for many decades, but it wasn’t proven until July 4, 2012, when researchers from two experiments at the LHC announced their discovery and confirmed the Higgs made all those years ago.
Yet the finding, however scientifically thrilling, pushed a press-shy Peter Higgs into the public eye. When he shared the Nobel Prize in Physics the next year, Higgs left his home in Edinburgh and camped out at a pub across town on the day of the announcement so the prize committee wouldn’t be able to reach him. Physicist Frank Close tells the story of Higgs and the physicist’s big idea in his new book Elusive: How Peter Higgs Solved the Mystery of Mass (Basic Books, 2022). Scientific American spoke to Close about the particle, the quest to find it and the man who began it all.
[An edited transcript of the interview follows.]
Your book is called Elusive. Certainly the Higgs boson itself was elusive and took physicists decades and many billions of dollars to find. But Higgs the man emerges in your book as an elusive person as well.
One of the biggest shocks I had when I was interviewing him was when he said the discovery of the boson “ruined [his] life.” I thought, “How can it ruin your life when you have done some beautiful mathematics, and then it turns out you had mysteriously touched on the pulse of nature, and everything you’ve believed in has been shown to be correct, and you’ ve won a Nobel Prize? How can these things amount to ruin?” He said, “My relatively peaceful existence was ending. My style is to work in isolation and occasionally have a bright idea.” He is a very retiring person who was being thrust into the limelight.
That, to my mind, is why Peter Higgs the person is still elusive to me even though I’ve known him for 40 years.
You quote Higgs as saying that this idea was “the only really original idea I’ve ever had.” Do you think that’s true?
Yes, but how many of us can say we’ve even had one really brilliant idea? There’s no doubt that he had a really brilliant idea. In physics, the people who have done really big things tend to do many big things. Higgs is unique in this being once and once only. It’s easy to dismiss it as luck, and clearly luck was part of it. But being in the right place at the right time, you have to recognize it. Higgs had spent two to three years really trying to understand a particular problem. And because he had done that hard work and was still trying to deepen his understanding of this very profound concept, when a paper turned up on his desk posing a related question, Higgs happened to have the answer because of the work he’d done. He sometimes says, “I’m primarily known for three weeks of my life.” I say, “Yes, Peter, but you spent two years preparing for that moment.”
The discovery of the Higgs boson came nearly 50 years after Higgs’s prediction, and he said he never expected it to be found in his lifetime. What did it mean to him that the particle was finally detected?
He said to me that his first reaction was one of relief that it was indeed confirmed. At that moment he knew [the particle existed] after all, and he felt a profound sense of being moved that was really the way it was in nature—and then panic that his life was going to change.
Why was Higgs’s discovery so important?
Higgs’s discovery was that mass is not something intrinsic to particles. It is a result of the whole cosmos. This comes about because there is some field of stuff out there that does this. And the strange, counterintuitive aspect of it is that if the vacuum [of space] was completely empty, it would be less stable than if you filled it with this mysterious stuff that we call the Higgs field. That’s so counterintuitive that I wonder if that’s why it took so long for this idea to emerge. And we now know it is true.
Most people have heard of the electromagnetic field. If you add energy to an electromagnetic field, you can excite it into photons. Similarly, there is this stuff we call the Higgs field. If we could apply enough energy to that, we could, in principle, excite it and produce Higgs bosons. The Higgs boson and the Higgs field are analogous to photons and the electromagnetic field.
However, striking a match produces millions of photons, but to produce one Higgs boson, we have to concentrate 125 billion electron volts into one spot, which is what they did at the LHC. That’s the reason we’ve known about photons for 100 years and just recently found the Higgs boson.
It’s been 10 years since the discovery of the Higgs boson, and some people have been decrying the lack of a similarly exciting finding at the LHC since then. Are you disappointed that there hasn’t been another high-profile discovery after the Higgs?
This discovery was a seminal moment in human culture. It’s a discovery that will rank alongside the discovery of the Rutherford atom and the nucleus. It’s the discovery that we are immersed in this still mysterious essence, the Higgs field, which ultimately leads to structure in the universe. To expect other discoveries since then to meet this standard is to miss how profound this one was.
What is the outlook for the next 10 years at the LHC?
Finding the Higgs boson was like climbing up a mountain. When Higgs did his work, we didn’t even know where the mountain range was or how tall it might be. The Standard Model of particle physics didn’t even exist. There was a vague awareness that somewhere on this peak, there was a Higgs boson that would really be proof that this whole structure was there. As of the late 1990s, we had a sense of how high the mountain was. And then it wasn’t until 2012 when we finally scaled that peak.
Now we’re going down the other side of the mountain, across the plains, and they extend all the way out to the Planck scale [the minimum limit of the universe]. If we’re correct, somewhere out there on the plains are other mountain ranges where particles of supersymmetry exist or dark matter particles exist. But we have no clear indication of how far across the plains you have to travel to see these new mountain ranges. That is the difference between where we are now and where we have been these past decades. We don’t have any compelling way of telling how far we have to go. It’s elusive.