Call it millennial, generation Y or fin de siècle, high-energy physics during the last two decades of the 20th century had a special flavour. The principal pieces of the Standard Model of particle physics had come together remarkably tightly – so tightly, in fact, that physicists had to rethink what instruments to build, what experiments to plan, and what theories to develop to move forward. But it was also an era when the hub of particle physics moved from the US to Europe.

The momentous events of the 1980s and 1990s will be the focus of the 4th International Symposium on the History of Particle Physics, which is being held on 10–13 November at CERN. The meeting will take place more than four decades after the first symposium in the series was held at Fermilab near Chicago in 1980. Entitled The Birth of Particle Physics, that initial meeting covered the years 1930 to 1950.

Speakers back then included trailblazers such as Paul Dirac, Julian Schwinger and Victor Weisskopf. They reviewed discoveries such as the neutron and the positron and the development of relativistic quantum field theory. Those two decades before 1950 were a time when particle physicists “constructed the room”, so to speak, in which the discipline would be based.

The second symposium – Pions to Quarks – was also held at Fermilab and covered the 1950s. Accelerators could now create particles seen in cosmic-ray collisions, populating what Robert Oppenheimer called the “particle zoo”. Certain discoveries of this era, such as parity violation in the weak interaction, were so shocking that C N Yang likened it to having a blackout and not knowing if the room would look the same when the lights came back on. Speakers at that 1985 event included Luis Alvarez, Val Fitch, Abdus Salam, Robert Wilson and Yang himself.

The third symposium, The Rise of the Standard Model, was held in Stanford, California, in 1992 and covered the 1960s and 1970s. It was a time not of blackouts but of disruptions that dimmed the lights. Charge-parity violation and the existence of two types of neutrino were found in the 1960s, followed in the 1970s by deep inelastic electron scattering and quarks, neutral currents, a fourth quark and gluon jets.

These discoveries decimated alternative approaches to quantum field theory, which was duly established for good as the skeleton of high-energy physics. The era culminated with Sheldon Glashow, Abdus Salam and Steven Weinberg winning the 1979 Nobel Prize for Physics for their part in establishing the Standard Model. Speakers at that third symposium included Murray Gell-Mann, Leon Lederman and Weinberg himself.

Changing times

The upcoming CERN event, on whose programme committee I serve, will start exactly where the previous symposium ended. “1980 is a natural historical break,” says conference co-organizer Michael Riordan, who won the 2025 Abraham Pais Prize for History of Physics. “It begins a period of the consolidation of the Standard Model. Colliders became the main instruments, and were built with specific standard-model targets in mind. And the centre of gravity of the discipline moved across the Atlantic to Europe.”

The conference will address physics that took place at CERN’s Super Proton Synchrotron (SPS), where the W and Z particles were discovered in 1983. It will also examines the SPS’s successor – the Large Electron-Positron (LEP) collider. Opened in 1989, it was used to make precise measurements of these and other implications of the Standard Model until being controversially shut down in 2000 to make way for the Large Hadron Collider (LHC).

There will be coverage as well of failed accelerator projects, which – perhaps perversely – can be equally interesting and revealing as successful facilities

Speakers at the meeting will also discuss Fermilab’s Tevatron, where the top quark – another Standard Model component – was found in 1995. Work at the Stanford Linear Accelerator Center, DESY in Germany, and Tsukuba, Japan, will be tackled too. There will be coverage as well of failed accelerator projects, which – perhaps perversely – can be equally interesting and revealing as successful facilities.

In particular, I will speak about ISABELLE, a planned and partially built proton–proton collider at Brookhaven National Laboratory, which was terminated in 1983 to make way for the far more ambitious Superconducting Super Collider (SSC). ISABELLE was then transformed into the Relativistic Heavy Ion Collider (RHIC), which was completed in 1999 and took nuclear physics into the high-energy regime.

Riordan will talk about the fate of the SSC, which was supposed to discover the Higgs boson or whatever else plays its mass-generating role. But in 1993 the US Congress terminated that project, a traumatic episode for US physics, about which Riordan co-authored the book Tunnel Visions. Its cancellation signalled the end of the glory years for US particle physics and the realization of the need for international collaborations in ever-costlier accelerator projects.

The CERN meeting will also explore more positive developments such as the growing convergence of particle physics and cosmology during the 1980s and 1990s. During that time, researchers stepped up their studies of dark matter, neutrino oscillations and supernovas. It was a period that saw the construction of underground detectors at Gran Sasso in Italy and Kamiokande in Japan.

Other themes to be explored include the development of the Web – which transformed the world – and the impact of globalization, the end of the Cold War, and the rise of high-energy physics in China, and physics in Russia, former Soviet Union republics, and former Eastern Bloc countries. While particle physics became more global, it also grew more dependent on, and vulnerable to, changing political ambitions, economic realities and international collaborations. The growing importance of diversity, communication and knowledge transfer will be looked at too.

The critical point

The years between 1980 and 2000 were a distinct period in the history of particle physics. It took place in the afterglow of the triumph of the Standard Model. The lights in high energy physics did not go out or even dim, to use Yang’s metaphor. Instead, the Standard Model shed so much light on high-energy physics that the effort and excitement focused around consolidating the model.

Particle physics, during those years, was all about finding the deeply hidden outstanding pieces, developing the theory, and connecting with other areas of physics. The triumph was so complete that physicists began to wonder what bigger and more comprehensive structure the Standard Model’s “room” might be embedded in – what was “beyond the Standard Model”. A quarter of a century on, our attempt to make out that structure is still an ongoing task.

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Richard Muller, a physicist at the University of California, Berkeley, was in his office when someone called Liz showed up who’d once taken one of his classes. She said her family had invited a physicist over for dinner, who touted controlled nuclear fusion as a future energy source. When Liz suggested solar power was a better option, the guest grew patronizing. “If you wanted to power California,” he told her, “you’d have to plaster the entire state with solar cells.”

Fortunately, Liz remembered what she’d learned on Muller’s course, entitled “Physics for Future Presidents”, and explained why the dinner guest was wrong. “There’s a kilowatt in a square metre of sunlight,” she told him, “which means a gigawatt in a square kilometre – only about the space of a nuclear power plant.” Stunned, the physicist grew silent. “Your numbers don’t sound wrong,” he finally said. “Of course, today’s solar cells are only 15% efficient. But I’ll take a look again.”

It’s a wonderful story that Muller told me when I visited him a few months ago to ask about his 2008 book Physics for Future Presidents: the Science Behind the Headlines. Based on the course that Liz took, the book tries to explain physics concepts underpinning key issues including energy and climate change. “She hadn’t just memorized facts,” Muller said. “She knew enough to shut up an expert who hadn’t done his homework. That’s what presidents should be able to do.” A president, Muller believes, should know enough science to have a sense for the value of expert advice.

Dissenting minds

Muller’s book was published shortly before Barack Obama’s two terms as US president. Obama was highly pro-science, appointing the Nobel-prize-winning physicist Steven Chu as his science adviser. With Donald Trump in the White House, I had come to ask Muller what advice – if any – he would change in the book. But it wasn’t easy for me to keep Muller on topic, as he derails easily with anecdotes of fascinating situations and extraordinary people that he’s encountered in his remarkable life.

Born in New York City, Muller, 81, attended Bronx High School of Science and Columbia University, joining the University of California, Berkeley as a graduate student in the autumn of 1964. A few weeks after entering, he joined the Free Speech Movement to protest against the university’s ban on campus political activities. During a sit-in, Muller was arrested and dragged down the steps of Sproul Hall, Berkeley’s administration building.

As a graduate student, Muller worked with Berkeley physicist Luis Alvarez – who would later win the 1968 Nobel Prize for Physics – to send a balloon with a payload of cosmic-ray detectors over the Pacific. Known as the High Altitude Particle Physics Experiment (HAPPE), the apparatus crashed in the ocean. Or so Muller thought.

As Muller explained in a 2023 article in the Wall Street Journal, US intelligence recovered a Chinese surveillance device, shot down over Georgia by the US military, with a name that translated as “HAPI”. Muller found enough other similarities to conclude that the Chinese had recovered the device and copied it as a model for their balloons. But by then Muller had switched to studying negative kaon particles using bubble chambers. After his PhD, he stayed at Berkeley as a postdoc, eventually becoming a professor in 1980.

Muller is a prominent contrarian, publishing an article advancing the controversial – though some now argue that it’s plausible – view that the COVID-19 virus originated in a Chinese lab. For a long time he was a global-warming sceptic, but in 2012, after three years of careful analysis, he publicly changed his mind via an article in the New York Times. Former US President Bill Clinton cited Muller as “one of my heroes because he changed his mind on global warming”. Muller loved that remark, but told me: “I’m not a hero. I’m just a scientist.”

Muller was once shadowed by a sociology student for a week for a course project. “She was like [the anthropologist] Diane Fosse and I was a gorilla,” Muller recalls. She was astonished. “I thought physicists spent all their time thinking and experimenting,” the student told him. “You spend most of your time talking.” Muller wasn’t surprised. “You don’t want to spend your time rediscovering something somebody already knows,” he said. “So physicists talk a lot.”

Recommended recommendations

I tried again to steer Muller back to the book. He said it was based on a physics course at Berkeley known originally as “Qualitative physics” and informally as physics for poets or dummies. One of the first people to teach it had been the theorist and “father of the fusion bomb” Edward Teller. “Teller was exceedingly popular,” Muller told me, “possibly because he gave everyone in class an A and no exams.”

After Teller, fewer and fewer students attended the course until enrolment dropped to 20. So when Muller took over in 1999 he retitled it “Physics for future presidents”, he refocused it on contemporary issues, and rebuilt the enrolment until it typically filled a large auditorium with about 500 students. He retired in 2010 after a decade of teaching the course.

Making a final effort, I handed Muller a copy of his book, turned to the last page where he listed a dozen or so specific recommendations for future presidents, and asked him to say whether he had changed his mind in the intervening 17 years.

Fund strong programmes in energy efficiency and conservation? “Yup!”

Raise the miles-per-gallon of autos substantially? “Yup.”

Support efforts at sequestering carbon dioxide? “I’m not much in favour anymore because the developing world can’t afford it.”

Encourage the development of nuclear power? “Yeah. Particularly fission; fusion’s too far in the future. Also, I’d tell the president to make clear that nuclear waste storage is a solved problem, and make sure that Yucca mountain is quickly approved.”

See that China and India are given substantial carbon credits for building coal-fired power stations and nuclear plants? “Nuclear power plants yes, carbon credits no. Over a million and a half people in China die from coal pollution each year.”

Encourage solar and wind technologies? “Yes.” Cancel subsidies on corn ethanol? “Yes”. Encourage developments in efficient lighting? “Yes.” Insulation is better than heating? “Yes.” Cool roofs save more energy than air conditioners and often better than solar cells? “Yes.”

The critical point

Muller’s final piece of advice to the future president was that the “emphasis must be on technologies that the developing world can afford”. He was adamant. “If what you are doing is buying expensive electric automobiles that will never sell in the developing world, it’s just virtue signalling in luxury.”

I kept trying to find some new physics Muller would tell the president, but it wasn’t much. “Physics mostly stays the same,” Muller concluded, “so the advice mainly does, too.” But not everything remains unvarying. “What changes the most”, he conceded, “is how the president listens”. Or even whether the president is listening at all.

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