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 17-mile-long, circular Large Hadron Collider (LHC) at CERN near Geneva, had delivered on its promise by showing signals of a new fundamental piece of nature that matched expectations for the Higgs.
The existence of this tiny object was first suggested by physicist Peter Higgs in 1964. For years, the prophecy had lost meaning to most scientists, including Higgs himself. But gradually it became clear that the Higgs boson was not just an exotic sideshow in the particle circus, but the main event. The particle and its associated Higgs field was found to be responsible for giving mass to all other particles and creating the structure of galaxies, stars and planets that define our universe and make our species possible. Physicists believed this story for decades, but it wasn’t proven until July 4, 2012, when researchers from two experiments at the LHC announced their discovery, confirming the prediction Higgs made all those years ago.
But the finding, scientifically exciting as it may be, pushed a shy Peter Higgs into the public eye. When he shared the Nobel Prize in Physics the following year, Higgs left his home in Edinburgh and camped out in a pub on the other side of town on the day of the announcement, so the prize committee couldn’t 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 the Mass (Basic books, 2022). Scientific American spoke to Close about the particle, the quest to find it, and the man who started it all.
[An edited transcript of the interview follows.]
Your book is called untouchable† The Higgs boson itself was certainly elusive, and it took physicists decades and many billions of dollars to find. But Higgs the man also emerges in your book as an elusive person.
One of the biggest shocks I had when I interviewed him was when he said the boson discovery had been “destroyed” [his] life.” I thought, “How can it ruin your life when you’ve done some nice math, and then it turns out that you’ve mysteriously hit the pulse of nature, and everything you’ve believed in has turned out to be correct, and you Did you win a Nobel Prize? How can these things lead to ruin?” He said, “My relatively peaceful existence came to an end. My style is to work in isolation and have a bright idea every now and then.” He is a very withdrawn person who was put in the spotlight.
That, in my opinion, is why Peter Higgs the person is still elusive to me, even though I’ve known him for 40 years.
You quote Higgs who said that this idea was “the only really original idea I ever had.” Do you think that’s true?
Yes, but how many of us can say we’ve had even one really brilliant idea? There is no doubt that he had a really brilliant idea. In physics, the people who have done really big things tend to do a lot of big things. Higgs is unique in this uniqueness. It’s easy to dismiss it as luck, and it was obvious that luck was part of it. But being in the right place at the right time is something you have to recognize. Higgs had spent two to three years trying to really understand a particular problem. And because he’d done that hard work and was still trying to deepen his understanding of this very deep concept, when a paper appeared on his desk with a related question, Higgs happened to have the answer because of the work he’d done. He sometimes says: “I am mainly 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’ 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 told me that his first reaction was one of relief that it was indeed confirmed. At that moment he knew [the particle existed] finally, and he felt a deep sense of poignancy that that really was the case in nature – then panicked that his life would change.
Why was the Higgs discovery so important?
Higgs’ discovery was that mass is not intrinsic to particles. It is a result of the entire cosmos. This comes about because there are a number of things that do this. And the strange, counter-intuitive aspect of it is that if the vacuum [of space] completely empty, it would be less stable than if you filled it with this mysterious stuff we call the Higgs field. That’s so counterintuitive that I wonder if that’s why it took so long for this idea to come up. And we now know it’s true.
Most people have heard of the electromagnetic field. If you add energy to an electromagnetic field, you can turn it into photons. Likewise, there’s this stuff we call the Higgs field. If we could spend enough energy on that, in principle we could excite it and produce Higgs bosons. The Higgs boson and the Higgs field are analogous to photons and the electromagnetic field.
Striking a match, however, produces millions of photons, but to produce one Higgs boson, we have to concentrate 125 billion electron volts in one spot, which they did at the LHC. That’s why we’ve known about photons for 100 years and recently found the Higgs boson.
It’s been 10 years since the discovery of the Higgs boson, and some people are disapproving the lack of an equally exciting finding since then at the LHC. Are you disappointed that no new high-profile discovery was made after the Higgs?
This discovery was a groundbreaking moment in human culture. It is a discovery that will stand side by side with the discovery of the Rutherford atom and nucleus. It is 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 missing how profound it was.
What are the prospects for the next 10 years at the LHC?
Finding the Higgs boson was like climbing a mountain. When Higgs did his job, we didn’t even know where the mountain range was or how high it might be. The Standard Model of particle physics didn’t even exist. There was a vague realization that there was a Higgs boson somewhere on this peak that would really be proof that this whole structure was there. From the late 1990s, we had an idea of how high the mountain was. And then it wasn’t until 2012 that we finally hit that peak.
Now we go down the other side of the mountain, across the plains, and they extend all the way to Planck’s scale [the minimum limit of the universe]† If we’re right, somewhere on the plains there are other mountain ranges where supersymmetry particles or dark matter particles exist. But we have no clear indication of how far you need to travel across the plains to see these new mountain ranges. That’s the difference between where we are now and where we’ve been over the decades. We have no convincing way of telling how far to go. It’s elusive.