With the passing of Nobel prize-winning physicist, Peter Higgs, we reflect on the importance of ‘the God particle’, the Higgs boson. We asked some of the world’s leading thinkers and physicists for their thoughts on Higgs and the legacy of his work. The story of Peter Higgs and his Higgs boson is one that lays bare the power of theory and wonder of the experiments that are built to test them.

John Ellis: Clerk Maxwell Professor of Theoretical Physics at King's College London, and visiting scientist at CERN.

A modest giant of particle physics has left us.

Peter Higgs got his Bachelor’s degree at King’s College London in 1950, and his PhD for research in molecular physics in 1954. His research interests shifted subsequently to quantum field theory, leading in 1964 to his famous papers describing how elementary particles could acquire masses and predicting the existence of the particle that bears his name. In 1967 his theory of mass was incorporated into a unified theory of fundamental interactions, which is the basis of the Standard Model that describes all the visible matter in the Universe. Confirmation of Peter Higgs’s theory had to wait for the discovery of the Higgs boson, which was made at CERN in 2012 by two international teams of experimental physicists.

Peter Higgs was a profoundly modest man. He wiped tears from his eyes when the discovery was announced and said that he had never expected to see it in his lifetime. He also said that the existence of the Higgs boson was not a ‘big deal’, but it was.

Without his theory, atoms could not exist and radioactivity would be a force as strong as electricity and magnetism. His prediction of the existence of the particle that bears his name was a deep insight, and its discovery was the crowning moment that confirmed his understanding of the way the Universe works.

See John debate the future of particle physics after the God particle explains the search for the Higgs boson, discuss the mystery of reality or delve into his IAI academy courses on Why the World Exists and a brief guide to everything. And read Particle Physics: Where Next?

Tara Shears, Particle physicist and professor of Physics at The University of Liverpool

Our theory of particle physics today completely relies on the Higgs mechanism and on Higgs.

Peter Higgs has had a profound influence on the way we understand physics. He was one of a small number of scientists who independently discovered the Higgs mechanism and the only scientist to predict the Higgs boson associated with it. Our theory of particle physics today completely relies on the Higgs mechanism and on Higgs. The Higgs mechanism shows us how fundamental particles get their mass, and how electromagnetism and the weak force are really ultimately part of the same electroweak force. Without Higgs himself, we would never have been able to confirm the mechanism, as the Higgs boson provided its testable prediction. He made a huge contribution to our subject, and we're going to continue exploring what the Higgs boson can tell for quite some time to come in our experiments.

See Tara Shears debate whether particle physics is unscientific and it’s an immaterial world and whether particles exist at all. And delve into her argument that the nature of reality is not beyond experience.

David Tong, Professor of Theoretical Physics at the University of Cambridge.

Those mathematical squiggles on the page carry a truth like nothing else in our world.

What Peter Higgs did was theoretical physics at its purest. He wasn’t motivated by any particular experiment or desire to explain some observed anomaly. He was just playing.

He asked himself: is it possible for the photon – the particle of light – to have a mass? There are reasons, sewn into the heart of physics, why the photon has to be massless. There seems to be no other option. But Higgs postulated that if the photon interacts with a novel kind of particle then it could get a mass.

Higgs’s idea is spectacularly realised in nature in two different ways, neither of which he anticipated. The first is that his idea is what happens inside a superconductor. These are materials that conduct electricity without any resistance. Inside the superconductor, electrons do something funky and pair up and that bound pair of electrons acts just like Higgs postulated particle.

But at a more fundamental level, our whole universe acts like a kind of superconductor. In the 1980s a pair of particles were discovered called (unimaginatively) the W-boson and the Z-boson. They are like the photon in many ways, except they’re heavy. In fact, they’re really heavy. Each of these particles is almost 100 times heavier than a proton. Now, if you’re a particularly devout kind of theoretical physicist, this discovery was already proof of Higgs’s idea because here are two photon-like particles that are enormously heavy and the only way we know that this can happen is through what we now call the Higgs mechanism.

But something was missing: where was the particle that Higgs postulated that gave the W-boson and Z-boson their mass? That took another 30 years to find before it was discovered in CERN in 2012.

There’s also a remarkable human story here. In 1964, Peter Higgs wrote a brief two-page paper explaining how a particle like a photon could get a mass. Almost half a century later, we built a machine capable of probing the depths of the universe to unprecedented levels. And there is Peter’s particle, with all the properties that he suggested. Those mathematical squiggles on the page carry a truth like nothing else in our world.

Join David Tong as he argues for the most exotic particles and supersymmetry being supported by the Higgs and other discoveries in Uncovering Reality. Watch his IAI academy course on what we still don’t know in physics and the mystery of the Higgs.

Harry Cliff, particle physicist at the University of Cambridge and CERN.

Peter Higgs has left an extraordinary legacy for physics in the particle that bears his name. Not only does the Higgs boson tie together our understanding of the fundamental particles that make up the world, it also presents us with several deep puzzles that will keep me and my colleagues busy for decades to come.

See Harry Cliff discuss the Higgs boson, dark matter and other mysteries in The Secrets of the Universe. Read his article the hints of a new fundamental force, as he discusses the lack of a new breakthrough since the discovery of the ‘God Particle’.

David Deutsch, visiting Professor of physics at the Centre for Quantum Computation, the Clarendon Laboratory, Oxford University.

My work never overlapped with that of Higgs. But one very important thing about the work for which he won the Nobel Prize is that it was truly foundational to quantum field theory. Not merely phenomenological or taxonomic.

Frank Close, Emeritus Professor of Physics at the University of Oxford and author of Elusive: How Peter Higgs solved the mystery of mass.

If the Higgs field were not there nothing that we know would exist.

Peter Higgs and his boson were both elusive, which is why my biography of him - and his boson - is titled: “Elusive: How Peter Higgs solved the mystery of mass”. His highly elusive boson took 48 years to appear and when the Nobel Prize was announced in 2013, he too was elusive, having disappeared to his favourite seafood bar in Leith, in secret.

He disliked the limelight but was comfortable with friends and colleagues. During the pandemic lockdown, I talked with him by phone every Friday or Saturday over several months and it was from these conversations that my biography of him and his boson emerged. On one of these occasions, to my surprise Higgs suddenly remarked that the quest for the boson had “ruined my life”. To know nature through mathematics, to see your theory confirmed, to win the plaudits of your peers and join the exclusive club of Nobel laureates: how could all this equate with ruin? To be sure I had not misunderstood, I asked again the next time we spoke. He explained: “my relatively peaceful existence was ending. I don't enjoy this sort of publicity. My style is to work in isolation, and occasionally have a bright idea.”

His idea in 1964 was at the time hardly noticed. Within 40 years however it had become one of the most singular observations about the physical universe and inspired a worldwide collaboration of scientists to find proof of the boson’s existence, and by implication, the theory. Although he did not perceive it this way back then, today we can understand its implications as follows. If we were able to remove all matter, all electromagnetic forces, and also gravity from the universe, the vacuum would not be empty. There would be something left, a weird essence known as the Higgs field. We are immersed in this field much like a goldfish is immersed in water, but for which it could not survive. Likewise, if the Higgs field were not there nothing that we know would exist. The universe would be unstable.

How do we know this idea, which sounds like science fiction, is indeed the nature of reality? How can we make this weird “field” reveal itself? By analogy, an electromagnetic field can be manifested by applying a small amount of energy: strike a match and its effects will burst into light. In quantum field theory, light consists of a burst of particles called photons. Similarly, if we could focus enough energy into the Higgs field, we could make it manifest its presence in the form of Higgs bosons, the analogue of the photons in the electromagnetic field. This idea was around for 40 years before the technology was able to confirm it. Higgs bosons were everywhere in the first moments after the hot Big Bang but as the universe cooled they slumbered and faded into the background. Not until 2012 was technology able to focus enough energy into a small volume at the Large Hadron Collider at CERN to heat up the vacuum and recreate for a brief moment the conditions of that long last epoch when the Higgs bosons were present. And indeed, Higgs bosons were produced in this mammoth experiment. In effect, like some Jurassic Park, the LHC has resurrected Higgs bosons billions of years after they were ubiquitous and playing a key role key in converting the random heat energy of the Big Bang into the forms and structures that today govern the material universe.

See Frank Close debate particle physics and the final theory of the universe in The Theory of Everything.

And some extra content on Higgs and the particle physics which comes in his wake.

Ben Allanach

Watch the in-depth studio interview with Professor of Theoretical Physics at the University of Cambridge, Ben Allanach, on particle physics in crisis, supersymmetry and beyond.

Tevong You

Watch Tevong You’s talk on Beyond the Standard Model, on whether we caught sight of the first new particle after the Higgs boson and if it ushers in the next era of the universe.

Jim Baggot

Join Jim Baggott author of Search for Scientific Truth, Higgs: The Invention and Discovery of the God Particle for his academy talk on Thinking like a Scientist.

Sabine Hossenfelder

Read Sabine Hossenfelder for a more critical angle on the philosophy of physics and the future of particle physics faced with the lack of new discoveries. Or read the write up of her debate on Particles, Physics and Fairy Tales with Gavin Salam, and Bjørn Ekeberg.