Rainer Weiss, who shared the Nobel Prize for Physics in 2017 for the discovery of gravitational waves, died on 25 August at the age of 92. Weiss came up with the idea of detecting gravitational waves by measuring changes in distance as tiny as 10^–18 m via an interferometer several kilometres long. His proposal eventually led to the formation of the twin Laser Interferometer Gravitational-Wave Observatory (LIGO), which first detected such waves in 2015.

Weiss was born in Berlin, Germany, on 29 September 1932 shortly before the Nazis rose to power. With a father who was Jewish and an ardent communist, Weiss and his family were forced to flee the country – first to Czechoslovakia and then to the US in 1939.  Weiss was raised in New York, finishing his school days at the private Columbia Grammar School thanks to a scholarship from a refugee relief organization.

In 1950 Weiss began studying electrical engineering at Massachusetts Institute of Technology (MIT) before switching to physics, eventually earning a PhD in 1962, developing atomic clocks under the supervision of Jerrold Zacharias,. He then worked at Tufts University before moving to Princeton University, where he was a research associate with the astronomer and physicist Robert Dicke.

In 1964 Weiss returned to MIT, where he began developing his idea of using a large interferometer to measure gravitational waves. Teaming up with Kip Thorne at the California Institute of Technology (Caltech), Weiss drew up a feasibility study for a kilometre-scale laser interferometer. In 1979 the National Science Foundation funded Caltech and MIT to develop the proposal to build LIGO.

Construction of two LIGO detectors – one in Hanford, Washington and the other at Livingston, Louisiana, each of which featured arms 4 km long – began in 1990, with the facilities opening in 2002. After almost a decade of operation, however, no waves had been detected so in 2011 the two observatories were upgraded to make them 10 times more sensitive than before.

On 14 September 2015 – during the first observation run of what was known as Advanced LIGO, or aLIGO – the interferometer detected gravitational waves from two merging black holes some  1.3 billion light-years from Earth. The discovery was announced by those working on aLIGO in February 2016.

The following year, Weiss was awarded one half of the 2017 Nobel Prize for Physics “for decisive contributions to the LIGO detector and the observation of gravitational waves”. The other half was shared by Thorne and fellow Caltech physicist Barry Barish, who was LIGO project director.

‘An indelible mark’

As well as pioneering the detection of gravitational waves, Weiss also developed atomic clocks and led efforts to measure the spectrum of the cosmic microwave background via weather balloons. He co-founded NASA’s Cosmic Background Explorer project, measurements from which have helped support the Big Bang theory describing the expansion of the universe.

In addition to the Nobel prize, Weiss was awarded the Gruber Prize in Cosmology in 2006, the Einstein Prize from the American Physical Society in 2007 as well as the Shaw Prize and the Kavli Prize in Astrophysics, both in 2016.

MIT’s dean of science Nergis Mavalvala, who worked with Weiss to build an early prototype of a gravitational-wave detector as part of her PhD in the 1990s, says that every gravitational-wave event that is observed “will be a reminder of his legacy”.

“[Weiss] leaves an indelible mark on science and a gaping hole in our lives,” says Mavalvala. “I am heartbroken, but also so grateful for having him in my life, and for the incredible gifts he has given us – of passion for science and discovery, but most of all to always put people first.”

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William Phillips is a pioneer in the world of quantum physics. After graduating from Juniata College in Pennsylvania in 1970, he did a PhD with Dan Kleppner at the Massachusetts Institute of Technology (MIT), where he measured the magnetic moment of the proton in water. In 1978 Phillips joined the National Bureau of Standards in Gaithersburg, Maryland, now known as the National Institute of Standards and Technology (NIST), where he is still based.

Phillips shared the 1997 Nobel Prize for Physics with Steven Chu and Claude Cohen-Tannoudji for their work on laser cooling. The technique uses light from precisely tuned laser beams to slow atoms down and cool them to just above absolute zero. As well as leading to more accurate atomic clocks, laser cooling proved vital for the creation of Bose–Einstein condensates – a form of matter where all constituent particles are in the same quantum state.

To mark the International Year of Quantum Science and Technology, Physics World online editor Margaret Harris sat down with Phillips in Gaithersburg to talk about his life and career in physics. The following is an edited extract of their conversation, which you can hear in full on the Physics World Weekly podcast.

How did you become interested in quantum physics?

As an undergraduate, I was invited by one of the professors at my college to participate in research he was doing on electron spin resonance. We were using the flipping of unpaired spins in a solid sample to investigate the structure and behaviour of a particular compound. Unlike a spinning top, electrons can spin only in two possible orientations, which is pretty weird and something I found really fascinating. So I was part of the quantum adventure even as an undergraduate.

What did you do after graduating?

I did a semester at Argonne National Laboratory outside Chicago, working on electron spin resonance with two physicists from Argentina. Then I was invited by Dan Kleppner – an amazing physicist – to do a PhD with him at the Massachusetts Institute of Technology. He really taught me how to think like a physicist. It was in his lab that I first encountered tuneable lasers, another wonderful tool for using the quantum properties of matter to explore what’s going on at the atomic level.

Quantum mechanics is often viewed as being weird, counter-intuitive and strange. Is that also how you felt?

I’m the kind of person entranced by everything in the natural world. But even in graduate school, I don’t think I understood just how strange entanglement is. If two particles are entangled in a particular way, and you measure one to be spin “up”, say, then the other particle will necessarily be spin “down” – even though there’s no connection between them. Not even a signal travelling at the speed of light could get from one particle to the other to tell it, “You’d better be ‘down’ because the first one was measured to be ‘up’.” As a graduate student I didn’t understand how deliciously weird nature is because of quantum mechanics.

Is entanglement the most challenging concept in quantum mechanics?

It’s not that hard to understand entanglement in a formal sense. But it’s hard to get your mind wrapped around it because it’s so weird and distinct from the kinds of things that we experience on a day-to-day basis. The thing that it violates – local realism – seems so reasonable. But experiments done first by John Clauser and then Alain Aspect and Anton Zeilinger, who shared the Nobel Prize for Physics in 2022, basically proved that it happens.

What quantum principle has had the biggest impact on your work?

Superposition has enabled the creation of atomic clocks of incredible precision. When I first came to NIST in 1978, when it was still called the National Bureau of Standards, the very best clock in the world was in our labs in Boulder, Colorado. It was good to one part in 10¹³.

Because of Einstein’s general relativity, clocks run slower if they’re deeper in a gravitational potential. The effect isn’t big: Boulder is about 1.5 km above sea level and a clock there would run faster than a sea level clock by about 1.5 parts in 10¹³. So if you had two such clocks – one at sea level and one in Boulder – you’d barely be able to resolve the difference. Now, at least in part because of the laser cooling and trapping ideas that my group and I have worked on, one can resolve a difference of less than 1 mm with the clocks that exist today. I just find that so amazing.

What research are you and your colleagues at NIST currently involved in?

Our laboratory has been a generator of ideas and techniques that could be used by people who make atomic clocks. Jun Ye, for example, is making clocks from atoms trapped in a so-called optical lattice of overlapping laser beams that are better than one part in 10¹⁸ – two orders of magnitude better than the caesium clocks that define the second. These newer types of clocks could help us to redefine the second.

We’re also working on quantum information. Ordinary digital information is stored and processed using bits that represent 0 or 1. But the beauty of qubits is that they can be in a superposition state, which is both 0 and 1. It might sound like a disaster because one of the great strengths of binary information is there’s no uncertainty; it’s one thing or another. But putting quantum bits into superpositions means you can do a problem in a lot fewer operations than using a classical device.

In 1994, for example, Peter Shor devised an algorithm that can factor numbers quantum mechanically much faster, or using far fewer operations, than with an ordinary classical computer. Factoring is a “hard problem”, meaning that the number of operations to solve it grows exponentially with the size of the number. But if you do it quantum mechanically, it doesn’t grow exponentially – it becomes an “easy” problem, which I find absolutely amazing. Changing the hardware on which you do the calculation changes the complexity class of a problem.

How might that change be useful in practical terms?

Shor’s algorithm is important because of public key encryption, which we use whenever we buy something online with a credit card. A company sends your computer a big integer number that they’ve generated by multiplying two smaller numbers together. That number is used to encrypt your credit card number. Somebody trying to intercept the transmission can’t get any useful information because it would take centuries to factor this big number. But if an evildoer had a quantum computer, they could factor the number, figure out your credit card and use it to buy TVs or whatever evildoers buy.

Now, we don’t have quantum computers that can do this yet – they can’t even do simple problems, let alone factor big numbers. But if somebody did do that, they could decrypt messages that do matter, such as diplomatic or military secrets. Fortunately, quantum mechanics comes to the rescue through something called the no-cloning theorem. These quantum forms of encryption prevent an eavesdropper from intercepting a message, duplicating it and using it – it’s not allowed by the laws of physics.

Quantum processors can be made from different qubits – not just cold atoms but trapped ions, superconducting circuits and others, too. Which do you think will turn out best?

My attitude is that it’s too early to settle on one particular platform. It may well be that the final quantum computer is a hybrid device, where computations are done on one platform and storage is done on another. Superconducting quantum computers are fast, but they can’t store information for long, whereas atoms and ions can store information for a really long time – they’re robust and isolated from the environment, but are slow at computing. So you might use the best features of different platforms in different parts of your quantum computer.

But what do I know? We’re a long way from having quantum computers that can do interesting problems faster than classical device. Sure, you might have heard somebody say they’ve used a quantum computer to solve a problem that would take a classical device a septillion years. But they’ve probably chosen a problem that was easy for a quantum computer and hard for a classical computer – and it was probably a problem nobody cares about.

When do you think we’ll see quantum computers solving practical problems?

People are definitely going to make money from factoring numbers and doing quantum chemistry. Learning how molecules behave could make a big difference to our lives. But none of this has happened yet, and we may still be pretty far away from it. In fact, I have proposed a bet with my colleague Carl Williams, who says that by 2045 we will have a quantum computer that can factor numbers that a classical computer of that time cannot. My view is we won’t. I expect to be dead by then. But I hope the bet will encourage people to solve the problems to make this work, like error correction. We’ll also put up money to fund a scholarship or a prize.

What do you think quantum computers will be most useful for in the nearer term?

What I want is a quantum computer that can tackle problems such as magnetism. Let’s say you have a 1D chain of atoms with spins that can point up or down. Quantum magnetism is a hard problem because with n spins there are 2ⁿ possible states and calculating the overall magnetism of a chain of more than a few tens of spins is impossible for a brute-force classical computer. But a quantum computer could do the job.

There are quantum computers that already have lots of qubits but you’re not going to get a reliable answer from them. For that you have to do error correction by assembling physical qubits into what’s known as a logical qubit.  They let you determine whether an error has happened and fix it, which is what people are just starting to do. It’s just so exciting right now.

What development in quantum physics should we most look out for?

The two main challenges are: how many logical qubits we can entangle with each other; and for how long they can maintain their coherence. I often say we need an “immortal” qubit, one that isn’t killed by the environment and lasts long enough to be used to do an interesting calculation. That’ll determine if you really have a competent quantum computer.

Reflecting on your career so far, what are you most proud of?

Back in around 1988, we were just fooling around in the lab trying to see if laser cooling was working the way it was supposed to. First indications were: everything’s great. But then we discovered that the temperature to which you could laser cool atoms was lower than everybody said was possible based on the theory at that time. This is called sub-Doppler laser cooling, and it was an accidental discovery; we weren’t looking for it.

People got excited and our friends in Paris at the École Normale came up with explanations for what was going on. Steve Chu, who was at that point at Stanford University, was also working on understanding the theory behind it, and that really changed things in an important way. In fact, all of today’s laser-cooled caesium atomic clocks use that feature that the temperature is lower than the original theory of laser cooling said it was.

Another thing that has been particularly important is Bose–Einstein condensation, which is an amazing process that happens because of a purely quantum-mechanical feature that makes atoms of the same kind fundamentally indistinguishable. It goes back to the work of Satyendra Nath Bose, who 100 years ago came up with the idea that photons are indistinguishable and therefore that the statistical mechanics of photons would be different from the usual statistical mechanics of Boltzmann or Maxwell.

Bose–Einstein condensates, where almost all the atoms are in the same quantum state, were facilitated by our discovery that the temperature could be so much lower. To get this state, you’ve got to cool the atoms to a very low temperature – and it helps if the atoms are colder to start with.

Did you make any other accidental discoveries?

We also accidentally discovered optical lattices. In 1968 a Russian physicist named Vladilen Letokhov came up with the idea of trapping atoms in a standing wave of light. This was 10 years before laser cooling arrived and made it possible to do such a thing, but it was a great idea because the atoms are trapped over such a small distance that a phenomenon called Dicke narrowing gets rid of the Doppler shift.

Everybody knew this was a possibility, but we weren’t looking for it. We were trying to measure the temperature of the atoms in the laser-cooling configuration, and the idea we came up with was to look at the Doppler shift of the scattered light. Light comes in, and if it bounces off an atom that’s moving, there’ll be a Doppler shift, and we can measure that Doppler shift and see the distribution of velocities.

So we did that, and the velocity distribution just floored us. It was so odd. Instead of being nice and smooth, there was a big sharp peak right in the middle. We didn’t know what it was. We thought briefly that we might have accidentally made a Bose–Einstein condensate, but then we realized, no, we’re trapping the atoms in an optical lattice so the Doppler shift goes away.

It wasn’t nearly as astounding as sub-Doppler laser cooling because it was expected, but it was certainly interesting, and it is now used for a number of applications, including the next generation of atomic clocks.

How important is serendipity in research?

Learning about things accidentally has been a recurring theme in our laboratory. In fact, I think it’s an important thing for people to understand about the way that science is done. Often, science is done not because people are working towards a particular goal but because they’re fooling around and see something unexpected. If all of our science activity is directed toward specific goals, we’ll miss a lot of really important stuff that allows us to get to those goals. Without this kind of curiosity-driven research, we won’t get where we need to go.

In a nutshell, what does quantum meant to you?

Quantum mechanics was the most important discovery of 20th-century physics. Wave–particle duality, which a lot of people would say was the “ordinary” part of quantum mechanics, has led to a technological revolution that has transformed our daily lives. We all walk around with mobile phones that wouldn’t exist were it not for quantum mechanics. So for me, quantum mechanics is this idea that waves are particles and particles are waves.

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This episode features a wide-ranging interview with the astrochemist Ewine van Dishoeck, who is professor emeritus of molecular astrophysics at Leiden Observatory in the Netherlands. In 2018 she was awarded The Kavli Prize in Astrophysics and in this podcast she talks about her passion for astrochemistry and how her research combines astronomy, astrophysics, theoretical chemistry and laboratory experiments.

Van Dishoeck talks about some of the key unanswered questions in astrochemistry, including how complex molecules form on the tiny specks of dust in interstellar space. We chat about the recent growth in our understanding of exoplanets and protoplanetary discs and the prospect of observing signs of life on distant planets or moons.

The Atacama Large Millimetre Array radio telescope and the James Webb Space Telescope are two of the major facilities that Van Dishoeck has been involved with. She talks about the challenges of getting the astronomy community to agree on the parameters of a new observatory and explains the how collaborative nature of these projects ensures that instruments meet the needs of multiple research communities.

Van Dishoeck looks to the future of astrochemistry and what new observatories could bring to the field. The interview ends with a call for the next generation of scientists to pursue careers in astrochemistry.

This podcast is sponsored by The Kavli Prize.

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If David Jess were a professional footballer – and not a professional physicist – he’d probably be a creative midfielder: someone who links defence and attack to set up goal-scoring opportunities for his team mates. Based in the Astrophysics Research Centre at Queen’s University Belfast (QUB), Northern Ireland, Jess orchestrates his scientific activities in much the same way. Combining vision, awareness and decision-making, he heads a cross-disciplinary research team pursuing two very different and seemingly unconnected lines of enquiry.

Jess’s research within the QUB’s solar-physics groups centres on optical studies of the Sun’s lower atmosphere. That involves examining how the Sun’s energy travels through its near environment – in the form of both solar flares and waves. In addition, his group is developing instruments to support international research initiatives in astrophysics, including India’s upcoming National Large Solar Telescope.

But Jess is also a founding member of the Predictive Sports Analytics (PSA) research group within QUB and Ulster University’s AI Collaboration Centre – a £16m R&D facility supporting the adoption of AI and machine-learning technologies in local industry. PSA links researchers from a mix of disciplines – including physics, mathematics, statistics and computer science – with sports scientists in football, rugby, cycling and athletics. Its goal is to advance the fundamental science and application of predictive modelling in sports and health metrics. 

Joined-up thinking

Astronomy and sports science might seem worlds apart, but they have lots in common, not least because both yield vast amounts of data. “We’re lucky,” says Jess. “Studying the closest star in the solar system means we are not photon-starved – there’s no shortage of light – and we are able to make observations of the Sun’s atmosphere at very high frame rates, which means we’re accustomed to managing and manipulating really big data sets.”

Similarly, big data also fuels the sports analytics industry. Many professional athletes wear performance-tracking sports vests with embedded GPS trackers that can generate tens of millions of data points over the course of, say, a 90-minute football match. The trackers capture information such as a player’s speed, their distance travelled, and the number of sprints and high-intensity runs.

“Trouble is,” says Jess, “you’re not really getting the ebb and flow of all that data by just summing it all up into the ‘one big number’.” Researchers in the PSA group are therefore trying to understand how athlete data evolves over time – often in real-time – to see if there’s some nuance or wrinkle that’s been missed in the “big-picture” metrics that emerge at the end of a game or training session.

It’s all in the game for PSA

Set up in 2023, the Predictive Sports Analysis (PSA) research group in Belfast has developed collaborations with professional football teams, rugby squads and other sporting organizations across Northern Ireland and beyond. From elite-level to grassroots sports, real-world applications of PSA’s research aim to give athletes and coaches a competitive edge. Current projects include:

• Player/squad speed distribution analyses to monitor strength and conditioning improvements with time (also handy for identifying growth and performance trajectories in youth sport)
• Longitudinal examination of acceleration intensity as a proxy for explosive strength, which correlates with heart-rate variability (a useful aid to alert coaching staff to potential underlying cardiac conditions)
• 3D force vectorization to uncover physics-based thresholds linked to concussion and musculoskeletal injury in rugby

The group’s work might, for example, make it possible not only to measure how tired a player becomes after a 90-minute game but also to pinpoint the rates and causes of fatigue during the match. “Insights like this have the power to better inform coaching staff so they can create bespoke training regimes to target these specific areas,” adds Jess.

Work at PSA involves a mix of data mining, analysis, interpretation and visualization – teasing out granular insights from raw, unfiltered data streams by adapting and applying tried-and-tested statistical and mathematical methods from QUB’s astrophysics research. Take, for example, observational studies of solar flares – large eruptions of electromagnetic radiation from the Sun’s atmosphere lasting for a few minutes up to several hours.

“We might typically capture a solar-flare event at multiple wavelengths – optical, X-ray and UV, for example – to investigate the core physical processes from multiple vantage points,” says Jess. In other words, they can see how one wavelength component differs from another or how the discrete spectral components correlate and influence each other. “Statistically, that’s not so different from analysing the player data during a football match, with each player offering a unique vantage point in terms of the data points they generate,” he adds.

If that sounds like a stretch, Jess insists that PSA is not an indulgence or sideline. “We are experts in big data at PSA and, just as important, all of us have a passion for sports,” says Jess, who is a big fan of Chelsea FC. “What’s more, knowledge transfer between QUB’s astrophysics and sports analytics programmes works in both directions and delivers high-impact research dividends.”  

The benefits of association

In-house synergies are all well and good, but the biggest operational challenge for PSA since it was set up in 2023 has been external. As a research group in QUB’s School of Mathematics and Physics, Jess and colleagues need to find ways to “get in the door” with prospective clients and clubs in the professional sports community. Bridging that gap isn’t straightforward for a physics lab that isn’t established in the sports-analytics business.

But clear communication as well as creative and accessible data visualization can help successful engagement. “Whenever we meet sports scientists at a professional club, the first thing we tell them is we’re not trying to do their job,” says Jess. “Rather, it’s about making their job easier to do and putting more analytical tools at their disposal.”

PSA’s skill lies in extracting “hidden signals” from big data sets to improve how athlete performance is monitored. Those insights can then be used by coaches, physiotherapists and medical staff to optimize training and recovery schedules as well as to improve the fitness, health and performance of individual athletes and teams.

Validation is everything in the sports analytics business, however, and the barriers to entry are high. That’s one reason why PSA’s R&D collaboration with STATSports could be a game-changer. Founded in 2007 in Newry, Northern Ireland, the company makes wearable devices that record and transmit athlete performance metrics hundreds of times each second.

STATSports is now a global leader in athlete monitoring and GPS performance analysis. Its technology is used by elite football clubs such as Manchester City, Liverpool, Arsenal and Juventus, as well as national football teams (including England, Argentina, USA and Australia) and leading teams in rugby and American football.

The tie-up lets PSA work with an industry “name”, while STATSports gets access to blue-sky research that could translate into technological innovation and commercial opportunities.

“PSA is an academic research team first and foremost, so we don’t want to just rest on our laurels,” explains Jess. “With so much data – whether astrophysics or sports analytics – we want to be at the cutting edge and deliver new advances that loop back to enhance the big data techniques we’re developing.”

Right now, PhD physicist Eamon McGleenan provides the direct line from PSA into STATSports, which is funding his postgraduate work. The joint research project, which also involves sports scientists from Saudi Pro League football club Al Qadsiah, uses detailed data about player sprints during a game. The aim is to use force, velocity and acceleration curves – as well as the power generated by a player’s legs – to evaluate the performance metrics that underpin athlete fatigue.

By reviewing these metrics during the course of a game, McGleenan and colleagues can model how an athlete’s performance drops off in real-time, indicating their level of fatigue. The hope is that the research will lead to in-game modelling systems to help coaches and medical staff at pitch-side to make data-driven decisions about player substitutions (rather than just taking a player off because they “look leggy”).

Six physicists who also succeeded at sport

Quantum physicist Niels Bohr was a keen footballer, who played in goal for Danish side Akademisk Boldklub in the early 1900s. He once let a goal in because he was more focused on solving a maths problem mid-game by scribbling calculations on the goal post. His mathematician brother Harald Bohr also played for the club and won silver at the 1908 London Olympics for the Danish national team.

Jonathan Edwards, who originally studied physics at Durham University, still holds the men’s world record for the triple-jump. Edwards broke the record twice on 7 August 1995 at the World Athletics Championships in Gothenburg, Sweden, first jumping 18.16m and then 18.29m barely 20 minutes later.

David Florence, who studied physics at the University of Nottingham, won silver in the single C1 canoe slalom at the Beijing Olympics in 2008. He also won silver in the doubles C2 slalom at the 2012 Olympics in London and in Rio de Janeiro four years later.

Louise Shanahan is a middle-distance runner who competed for Ireland in the women’s 800m race at the delayed 2020 Summer Olympics while still doing a PhD in physics on the properties of nanodiamonds at the University of Cambridge. She has recently set up a sports website called TrackAthletes.

US professional golfer Bryson DeChambeau is nicknamed “The Scientist” owing to his analytical, science-based approach to the sport – and the fact that he majored in physics at Southern Methodist University in Dallas, US. DeChambeau won the 2020 and 2024 US Open.

In 2023 Harvard University’s Jenny Hoffman, who studies the electronic properties of exotic materials, became the fastest woman to run across the US, completing the 5000 km journey in 47 days, 12 hours and 35 minutes. In doing so, she beat the previous record by more than a week.

Matin Durrani

The transfer market

Jess says that the PSA group has been inundated with applications from physics students since it was set up. That’s not surprising, argues Jess, given that a physics degree provides many transferable skills to suit PSA’s broad scientific remit. Those skills include being able to manage, mine and interpret large data sets; disseminate complex results and actionable insights to a non-specialist audience; and work with industry partners in the sports technology sector.

“We’re looking for multidisciplinarians at PSA,” says Jess, with a nod to his group’s ongoing PhD recruitment opportunities. “The ideal candidates will be keen to move beyond their existing knowledge base in physics and maths to develop skills in other specialist fields.” There have also been discussions with QUB’s research and enterprise department about the potential for a PSA spin-out venture – though Jess, for his part, remains focused on research.

“My priority is to ensure the sustainability of PSA,” he concludes. “That means more grant funding – whether from the research councils or industry partners – while training up the next generation of early-career researchers. Longer term, though, I do think that PSA has the potential to be a ‘disruptor’ in the sports-analytics industry.”

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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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