“The great questions that physics addresses are within each of us, […] that primordial curiosity still burns in everyone’s soul”.

“Genesis. The Great Story of How everything began”, prologue, Guido Tonelli

Nature, the Sky, the Stars. Since the time of the Neanderthals who populated Europe 40,000 years ago, Humanity has always faced an ancestral question: "What is the origin of all this?". A question that withstands time, challenging the most brilliant minds of our century and fuelling the flame of a Research that transcends time, bringing us closer to the most primitive and fundamental roots of our existence.

This is "The Great Story of How everything began," a fascinating journey into the mystery of existence that we undertook during the San Raffaele Scientific Retreat 2025, accompanied by Guido Tonelli, physicist at CERN in Geneva and Professor of General Physics at the University of Pisa.

In this context, we had the privilege of talking with Prof. Tonelli about numerous topics: his life dedicated to Research, the Higgs boson, our roots, the future of our Society.

Photo credit: Gioele Giombato

The Discovery of the Higgs Boson: A New Vision of the Universe and a Rediscovered Fragility

Prof. Tonelli, you led the CMS experiment at CERN in Geneva that led to the discovery of the Higgs boson in 2011 and the awarding of the Nobel Prize in Physics to Peter Higgs and François Englert in 2013. What was the most exciting moment that marked this discovery?

Everyone may remember July 4, 2012, the day of the official announcement, but those of us who lived it firsthand remember with trepidation especially the preceding months, when we were overwhelmed by a rollercoaster of emotions. One day we were sure that the signal of the new particle was really before our eyes, the next day everything seemed to have vanished. It is the most beautiful part of every scientific discovery: on the one hand you would like to take a leap and say "We did it", on the other you are terrified that it might be a false alarm. Such mix of emotions—moments of enthusiasm alternating with periods of fear or depression—is an unforgettable experience.

I have been working on the experiment for over twenty years and I vividly remember the day I was certain that it was indeed the Higgs boson. I recall it well because it was my birthday, November 8, 2011. On that day, two groups of researchers independently reported to me, just a few hours apart, the same excess of events at 125 GeV [Giga electron Volt. The electron Volt (eV) is a unit of measurement of energy widely used in nuclear and particle physics, Editor's note], in the most promising mass range for observing the Higgs boson.

With the caution I mentioned before, I said to those young researchers: "Now you have to do everything you can to kill this signal." At that moment, everyone's eyes sparkled. We all knew that if we had not managed to make that strange signal disappear from the data, we would have had to announce the new discovery to the world, as in fact happened.

Photo credit: Gioele Giombato

Why was the discovery of the Higgs boson so important?

Today, more than ten years later, we have better understood the extraordinary importance of that discovery. It has radically changed our vision of the world. For thousands of years, scientists and ordinary people have considered mass as an intrinsic property of matter. Now we know that mass arises dynamically from an interaction. No particle is born with mass; it becomes massive or remains light depending on its interaction with a field that permeates the entire universe—the Higgs field.

The Higgs field is something intangible and invisible; its presence eluded Galileo, Newton, Einstein—some of history’s greatest scientists. Protons, neutrons, and electrons—the basic building blocks of all material objects from humans to galaxies—combine to form nuclei and atoms thanks to this interaction mechanism between elementary particles and the Higgs field.

The creation of every material structure incorporates an intrinsic fragility: if the Higgs field were to change slightly or vanish altogether, organized matter could not exist—and our entire universe would dissolve. We have discovered how our universe acquired a persistent material form—a mechanism enabling its evolution over nearly 14 billion years. Without the Higgs boson, there would be no hydrogen nuclei, cosmic dust clouds, stars, galaxies—or us.

Everything around us—even ourselves—has an intimate structure born from this powerful yet fragile mechanism.

For millennia, humanity viewed rivers and mountains or celestial bodies like the Moon and Sun as almost eternal elements—our ancestors even deified them. Scientists in this century tell us instead that even a grain of sand is something incredibly rare and precious. Ordinary matter constitutes only 5% of the entire universe; within this already small fraction, organized matter in atoms and molecules accounts for less than 1%. And it is inherently fragile: if the Higgs field changed its properties even slightly, all organized material forms would disintegrate.

Perhaps we should start caring not only for ourselves or living forms sharing our planet but also for all material forms—even those seemingly humble or insignificant.

Reading passages from your book " Genesis. The Great Story of How everything began," faced with the fragility and beauty of the universe, one feels invited to change perspective.

Every time we look at reality differently—as has happened multiple times throughout history—our societies change as well. When we adopt a new perspective on matter or the universe itself, relationships between people change too.

I don’t think this transformation will happen within months—it will likely take many years or decades—but this new vision will shape future generations profoundly.

Collaboration at CERN: The Richness of Exchange

At CERN, thousands of researchers collaborate from over 100 nations, with professional backgrounds ranging from physics to engineering, computer science, and other technical and scientific disciplines. How does this cultural and professional diversity contribute to enriching research approaches and fostering scientific innovation?

For us, collaboration is a necessity. In fundamental research, if you don’t use this approach, you fail. No nation in the world—not even the richest, most powerful, or most advanced—could tackle these challenges alone. Large-scale international collaborations leverage the potential of coherent teamwork: when thousands of people manage to work in a coordinated way, incredible results can be achieved.

In collaborative work, there’s an element of enhancement that arises from interactions and the speed of exchanges. No one can investigate the most elusive and complex natural phenomena alone. That’s why it’s necessary to involve all the best minds on the planet. Fortunately, intelligence is distributed somewhat everywhere in the world; it follows a democratic distribution and doesn’t only flourish in the richest and most advanced countries. The girl or boy destined to revolutionize modern science could be born in Calcutta or Cairo, Beijing or Rio de Janeiro. What we must do is to create conditions so that if this happens, the new Einstein or Marie Curie finds their way to emerge and shine.

Photo credit: Gioele Giombato

The CMS collaboration, which built and now manages the large detector, consists of about 5,500 people (including physicists, engineers, computer scientists), representing 241 scientific institutes across 54 nations. How do you maintain an overall vision for experiments that are so complex and articulated?

Our work involves trying to solve questions for which no one has yet found an answer. To do this, it’s necessary to take new paths—ones not yet explored—to invent new tools and develop new theories. In our work, it’s essential to be somewhat rebellious. At CERN projects follow a hierarchy, but it’s very different from what we’re accustomed to. Scientists form an anarchic community that doesn’t obey commands unless convinced. For this reason, the experiment leader isn’t appointed from above but is chosen by everyone through direct election where the vote of the youngest Ph.D. student carries the same weight as that of the most senior professor. And every leadership position is temporary: you’re elected for two or four years and then pass the baton.

We’re a bit like a large symphony orchestra where musicians elect the conductor and follow them because they recognize their authority—because there’s mutual respect and trust.

Photo credit: Gioele Giombato

Science Communication: Sharing Knowledge with the Community

In addition to being a great scientist, you are also a highly regarded communicator. What motivated you to dedicate yourself to science communication?

I started writing books relatively late—about ten years ago—and somewhat by chance. A journalist friend encouraged me to publish what I shared with audiences during my lectures. When my first book La nascita imperfetta delle cose (The Imperfect Birth of Things), dedicated to the discovery of the Higgs boson, was published, I realized that books create a special relationship with readers.

I began receiving emails or physical letters from readers of all kinds: successful entrepreneurs or cloistered nuns, eleven-year-old children or elderly people over ninety. Many shared their life stories with me; some asked questions about curious topics; all expressed gratitude and affection because through my books they understood things they never imagined they could grasp.

I don’t particularly like the verb to divulge; I prefer to say to share. I want to share with my community the beauty of concepts developed by contemporary science. Scientific knowledge offers a truly fascinating view of the world—for everyone—not just for specialists. Moreover, science profoundly shapes our societies; the more aware we are of what stirs within scientific fields, the better prepared we’ll be to understand how society will transform.

I feel this almost as a civic duty—a form of giving back to society that shaped me—and as a small gift to young readers: something that will allow them to face their future with deeper tools of knowledge.

Photo credit: Gioele Giombato

How can we promote greater trust in science, especially in an era where scientific denialism and fake news are rampant?

We mustn’t build barriers or respond with intolerance—or worse—with aggression. I think the right attitude is listening and patience. We mustn’t tire of explaining or repeating arguments but also strive to understand others’ fears—to reassure and console: "I, as a scientist, listen to you; perhaps I’ll convince you in some cases; in others I might not succeed—but I’m still here by your side."

In your opinion, how do physics and philosophy interact?

I think that there is fertile ground for meeting and exchange between the two disciplines. The questions that contemporary physics asks are very similar to the great philosophical questions, just think of cosmology, the origin of the world.

But science cannot answer equally relevant questions: what is the meaning of our existence? What is right and what is wrong? How do you organize a society that wants to reduce injustice? What laws allow the human community to alleviate the suffering of the most fragile? and so on. To answer these questions, a permanent interaction between scientists and philosophers, theologians and artists, historians and humanists would be necessary. Contemporary science can develop enormous potential, but, left to itself, it could also make us run great risks.

Paradoxically, science could lead us toward either humanity’s worst possible world—or toward a more aware humanity that heals wounds on our planet while consoling humans and reducing their suffering. Only through knowledge—and awareness of all past mistakes humanity has made—with contributions from historians and philosophers, artists and humanists can scientists build true progress together with everyone else.

What advice would you give to a young person today?

My advice is not to be afraid of making mistakes. If you have passion within you, pursue it without hesitation. If you’re unsure which direction to take, accept even paths that don’t fully convince you—knowing they might not be right for you. As soon as you realize something isn’t for you, change direction immediately! You’ll find nothing catastrophic happens—even if time feels lost—if you’re strongly motivated; you can recover. It is important to always remember that life is yours: in ten years you might regret not having pushed the accelerator all the way down when it was time to do so.

Interview by Giulia Moretti