Shortly after seven o’clock on the morning of 4 July 2012, Rolf-Dieter Heuer, the director general of CERN, arrived at work and prepared to tell the world about a new kind of particle — one that helped give everything in the universe its mass. The place was swarming with staff and students, and Heuer wanted to be sure the day ran smoothly.

At the entrance to the facility—the world’s largest particle physics lab— journalists and camera crews chatted in the sun as they waited for shuttle buses to the lab’s main building. There, burly security guards who wore black heavy boots and occasional smiles kept order as the gathering swelled into a crowd.

Minutes after nine o’clock, Heuer, a walking greyscale of charcoal suit, black shirt and silver hair, took hold of a microphone from a Cern technician and turned to the audience in the auditorium. At the back of the room, weary students who had camped overnight raised their heads and rubbed their eyes. The spectacle was about to begin.

Near the front, physicists who had spent their careers hunting the Higgs Boson waited on every word. Heuer welcomed them. Then, with both hands cradling the microphone, he began.

“Today,” he said, “is a special day.”

Fabrice Coffini/AFP/Getty Images

The night before, Peter Higgs — the physicist who had first postulated in 1964 that there must be another kind of particle in the universe, one that had yet to be discovered — had enjoyed a quiet celebration. John Ellis, a professor at Kings College in London, had invited his 83-year-old friend and some other colleagues to his house in Tannay, a small village a short drive north of Cern’s base in Geneva. The house sat in an old apple orchard and was shrouded in an out-of-control wisteria.

As John’s Colombian wife served up pan de yuca and got to work on the filet mignon and a soufflé, made with apple and mint from the garden, the physicists went out into the warm summer evening and cracked open a bottle of champagne.

That July morning, Heuer introduced a succession of speakers to the stage. There was a lot to say. After 20 years of research, billions of dollars, and the effort of thousands of people, the hunt for the Higgs Boson was compressed down to about 100 slides. One by one, the audience was taken through them.

The results built up slowly. CERN had built up evidence from its huge atom-smashing particle accelerator, built specifically to hunt for this mysterious piece of the universe. Now everyone was waiting to hear exactly how certain the researchers were.

The evidence threshold for new particles in physics is known as “5 sigma” — the equivalent of a one in 3.5 million chance of being wrong. Joe Incandela, from the University of California, Santa Barbara, said the cleanest data gave a solid 5 sigma signal. When the slide went up that stated as much, the auditorium broke into cheers and applause.

Fabiola Gianotti, an Italian physicist, followed on by pulling together two different analyses. Individually, both results were strong — but when she clicked on the slide that showed a combination of both results, the room erupted. The trigger was highlighted in a little red box. It said ‘5.0 sigma’.

The ovation was rapturous.

Fabiola tried to calm them down. “I’m not done yet, there’s more to come, be patient,” she told the crowd, but they had heard all they needed to hear.

As she wrapped up, the audience broke into thunderous applause once more. They stood and cheered and stamped and whistled. This was the pay-off for more than 20 years’ work at Cern, from understanding how the boson might rear its head in colliders, to building the LHC and hunting the particle down.

The crowd’s reaction was too much for Peter Higgs. He pulled a crumpled white handkerchief from his pocket, removed his glasses and wiped tears from his eyes. He clapped, slower than the rest, and seemed a man in shock. He looked up and around, as if at a loss of what to make of it all.

At the front of the room, Heuer grabbed a microphone and turned to the audience. “As a layman, I would now say I think we have it. You agree?” The answer came as a roar.

“We have a discovery. We should state it. We have a discovery.”

The microphone went next to the four attending theorists who started it all 50 years ago. Higgs, with jacket collar sticking up but composure regained, congratulated the Cern staff on their achievement. “For me it’s really an incredible thing that it’s happened in my lifetime,” he said. Francois Englert, the theoretical physicist whose work on the mechanism was as pivotal as that of Higgs himself, came down the stairs to stand next to him.

The two men, remarkably, had never met before this day.

Earlier that morning, the burly men in black heavy boots looked out of place among this crowd. But less so now. At the press conference after the talks, Higgs was mobbed by journalists and camera crews. The security staff kept them at bay as best they could, shielding an 83-year-old man, who for that day, at least, was a rockstar. After a handful of interviews, Peter made off for the airport, where he had seats on a cheap flight back to his home in Edinburgh. On the plane, Alan Walker, one of Higgs’ colleagues, asked if Peter cared to celebrate with a bottle of prosecco. Peter declined, and ordered a can of London Pride beer instead.

Two weeks later I met him in Edinburgh, where he is sat at a desk with a laptop, watching the closing minutes of that morning’s seminars again. The video paused at an unfair moment, when Higgs has shed a tear or two and looks almost distraught, a curious manifestation of human joy, made all the more conspicuous by the sea of gleeful faces around him.

How did he feel at that precise moment? “I was about to burst into tears. I was knocked over by the wave of the reaction of the audience. Up until then I was holding back emotionally, but when the audience reacted I couldn’t hold back any more. That’s the only way I can explain it,” he said.

The idea Higgs scribbled down nearly half a century ago became much more than a few pencilled equations in a notebook. The theory itself gained weight, as physicists in the twentieth century found it had real purpose, verified it mathematically, and uncovered indirect evidence that it described nature accurately. At first an obscure note in a journal, the theory acquired an importance that justified a decades-long search, with multibillion-dollar machines, that became the careers, dreams, and lives of thousands of scientists and engineers, and eventually won a Nobel Prize.

This was their success. The tears Higgs cried were not for what he contributed, but for what that contribution had become to others.

The intensity of the scientific process can be all-consuming. Follow the work long enough and it can seem an end in itself: to make exquisitely complex machines, to operate them well, and to pull from its noisy data some obscure but meaningful signal.

All these things are extraordinarily valuable. They develop skills and push technology. But to focus on them is to lose sight of the original goal of the enterprise. These experiments dig out the workings of nature at a fundamental level. What do we know now that we didn’t know before?

Forget the particle for a moment. That was only ever a means to an end, the smoking gun that confirmed something far more fascinating. We know now that the universe is filled with a field that makes massless particles massive.

We understand a little more about how this all came to be.

This story is taken from MASSIVE by Ian Sample, published in the US by Basic Books, and in the UK by Random House.

Buy it now on Amazon US or Amazon UK.