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Home » Page 55

Radioactive BEC could form a ‘superradiant neutrino laser’

Radioactive atoms in a Bose–Einstein condensate (BEC) could form a “superradiant neutrino laser” in which the atomic nuclei undergo accelerated beta decay. The hypothetical laser has been proposed by two researchers US who say that it could be built and tested. While such a neutrino laser has no obvious immediate applications, further developments could potentially assist in the search for background neutrinos from the Big Bang – an important goal of neutrino physicists.

Neutrinos – the ghostly particles produced in beta decay – are notoriously difficult to detect or manipulate because of the weakness of their interaction with matter. They cannot be used to produce a conventional laser because they would pass straight through mirrors unimpeded. More fundamentally, neutrinos are fermions rather than bosons such as photons. This prevents neutrinos forming a two-level system with a population inversion as only one neutrino can occupy each quantum state in a system.

However, another quantum phenomenon called superradiance can also increase the intensity and coherence of the radiation from photons. This occurs when the emitters are sufficiently close together to become indistinguishable. The emission then comes not from any single entity but from the collective ensemble. As it does not require the emitted particles to be quantum degenerate, this is not theoretically forbidden for fermions. “There are devices that use superradiance to make light sources, and people call them superradiant lasers – although that’s actually a misnomer” explains neutrino physicist Benjamin Jones of the University of Texas at Arlington and a visiting professor at the University of Manchester. “There’s no stimulated emission.”

In their new work, Jones and colleague Joseph Formaggio of Massachusetts Institute of Technology propose that, in a BEC of radioactive atoms, superradiance could enhance the neutrino emission rate and therefore speed up beta decay, with an initial burst before the expected exponential decay commences. “That has not been seen for nuclear systems so far – only for electronic ones,” says Formaggio. Rubidium was used to produce the first ever condensate in 1995 by Carl Wiemann and Eric Cornell of University of Colorado Boulder, and conveniently, one of its isotopes decays by beta emission with a half-life of 86 days.

Radioactive vapour

The presence of additional hyperfine states would make direct laser cooling of rubidium-83 more challenging than the rubidium-87 isotope used by Wiemann and Cornell, but not significantly more so than the condensation of rubidium-85, which has also been achieved. Alternatively, the researchers propose that a dual condensate could be created in which rubidium-83 is cooled by sympathetic cooling with rubidium-87. The bigger challenge, says Jones, is the Bose–Einstein condensation of a radioactive atom, which has yet to be achieved: “It’s difficult to handle in a vacuum system,” he explains, “You have to be careful to make sure you don’t contaminate your laboratory with radioactive vapour.”

If such a condensate were produced, the researchers predict that superradiance would increase with the size of the BEC. In a BEC of 106 atoms, for example, more than half the atoms would decay within three minutes. The researchers now hope to test this prediction. “This is one of those experiments that does not require a billion dollars to fund,” says Formaggio. “It is done in university laboratories. It’s a hard experiment but it’s not out of reach, and I’d love to see it done and be proven right or wrong.”

If the prediction were proved correct, the researchers suggest it could eventually lead towards a benchtop neutrino source. As the same physics applies to neutrino capture, this could theoretically assist the detection of neutrinos that decoupled from the hot plasma of the universe just seconds after the Big Bang – hundreds of thousands of years before photons in the cosmic microwave background. The researchers emphasize, however, that this would not currently be feasible.

Sound proposal

Neutrino physicist Patrick Huber of Virginia Tech is impressed by the work. “I think for a first, theoretical study of the problem this is very good,” he says. “The quantum mechanics seems to be sound, so the question is if you try to build an experiment what kind of real-world obstacles are you going to encounter?” He predicts that, if the experiment works, other researchers would quite likely find hitherto unforeseen applications.

Atomic, molecular and optical physicist James Thompson of University of Colorado Boulder is sceptical, however. He says several important aspects are either glossed over or simply ignored. Most notably, he calculates that the de Broglie wavelength of the neutrinos would be below the Bohr radius – which would prevent a BEC from feasibly satisfying the superradiance criterion that the atoms be indistinguishable.

“I think it’s a really cool, creative idea to think about,” he concludes, “but I think there are things we’ve learned in atomic physics that haven’t really crept into [the neutrino physics] community yet. We learned them the hard way by building experiments, having them not work and then figuring out what it takes to make them work.”

The proposal is described in Physical Review Letters.

Bayes’ rule goes quantum

How would Bayes’ rule – a technique to calculate probabilities – work in the quantum world? Physicists at the National University of Singapore, Japan’s University of Nagoya, and the Hong Kong University of Science and Technology in Guangzhou have now put forward a possible explanation. Their work could help improve quantum machine learning and quantum error correction in quantum computing.

Bayes’ rule is named after Thomas Bayes who first defined it for conditional probabilities in “An Essay Towards Solving a Problem in the Doctrine of Chances” in 1763.  It describes the probability of an event based on prior knowledge of conditions that might be related to the event. One area in which it is routinely used is to update beliefs based on new evidence (data). In classical statistics, the rule can be derived from the principle of minimum change, meaning that the updated beliefs must be consistent with the new data while only minimally deviating from the previous belief.

In mathematical terms, the principle of minimum change minimizes the distance between the joint probability distributions of the initial and updated belief. Simply put, this is the idea that for any new piece of information, beliefs are updated in the smallest possible way that is compatible with the new facts. For example, when a person tests positive for Covid-19, they may have suspected that they were ill, but the new information confirms this. Bayes’ rule is a therefore way to calculate the probability of having contracted Covid-19 based not only on the test result, and the chance of the test yielding a false negative, but also on the patient’s initial suspicions.

Quantum analogue

Quantum versions of Bayes’ rule have been around for decades, but the approach through the minimum change principle had not been tried before. In the new work, a team led by Ge Bai, Francesco Buscemi and Valerio Scarani set out to do just that.

“We found which quantum Bayes’ rule is singled out when one maximizes the fidelity (which is equivalent to minimizing the change) between two processes,” explains Bai. “In many cases, the solution is the ‘Petz recovery map’, proposed by Dénes Petz in the 1980s and which was already considered as being one of the best candidates for the quantum Bayes’ rule. It is based on the rules of information processing, crucial not only for human reasoning, but also for machine learning models that update their parameters with new data.”

Quantum theory is counter-intuitive, and the mathematics is hard, says Bai. “Our work provides a mathematically sound way to update knowledge about a quantum system, rigorously derived from simple principles of reasoning, he tells Physics World. “It demonstrates that the mathematical description of a quantum system—the density matrix—is not just a predictive tool, but is genuinely useful for representing our understanding of an underlying system. “It effectively extends the concept of gaining knowledge, which mathematically corresponds to a change in probabilities, into the quantum realm.”

A conservative stance

The “simple principles of reasoning” encompass the minimum change principle, adds Buscemi. “The idea is that while new data should lead us to update our opinion or belief about something, the change should be as small as possible, given the data received.

“It’s a conservative stance of sorts: I’m willing to change my mind, but only by the amount necessary to accept the hard facts presented to me, no more.”

“This is the simple (yet powerful) principle that Ge mentioned,” he says, “and it guides scientific inference by preventing unwanted biases from entering the reasoning process.”

An axiomatic approach to the Petz recovery map

While several quantum versions of the Bayes’ rule have been put forward before now, these were mostly based on the fact of having analogous properties to their classical counterpart, adds Scarani. “Recently, Francesco and one co-author proposed an axiomatic approach to the most frequently-used quantum Bayes rule, the one using the Petz recovery map. Our work is the first to derive a quantum Bayes rule from an optimization principle, which works very generally for classical information, but which has been used here for the first time in quantum information.

The result is very intriguing, he says: “we recover the Petz map in many cases, but not all. If we take that our new approach is the correct way to define a quantum Bayes rule, then previous constructions based on analogies were correct very often, but not quite always; and one or more of the axioms are not to be enforced after all. Our work is therefore is a major advance, but it is not the end of the road – and this is nice.”

Indeed, the researchers say they are now busy further refining their quantum Bayes’ rule. They are also looking into applications for it. “Beyond machine learning, this rule could be powerful for inference—not just for predicting the future but also retrodicting the past,” says Bai. “This is directly applicable to problems in quantum communication, where one must recover encoded messages, and in quantum tomography, where the goal is to infer a system’s internal state from observations.

“We will be using our results to develop new, hopefully more efficient, and mathematically well-founded methods for these tasks,” he concludes.

The present study is detailed in Physical Review Letters.

The top five physics Nobel prizes of the 21st century revealed

With the 2025 Nobel Prize for Physics due to be unveiled on Tuesday 7 October, Physics World has been getting in the mood by speculating who might win. It’s a prediction game we have fun with every year – and you can check out our infographic to make your own call.

Quantum physics is our hot favourite this time round – it’s the International Year of Quantum Science and Technology and the Nobel Committee for Physics aren’t immune to wider events. But whoever wins, you know that the prize will have been very carefully considered by committee members.

Over the 125 years since the prize was first awarded, almost every seminal finding in physics has been honoured – from the discovery of the electron, neutrino and positron to the development of quantum mechanics and the observation of high-temperature superconductivity.

But what have been the most significant physics prizes of the 21st century? I’m including 2000 as part of this century (ignoring pedants who say it didn’t start till 1 January 2001). During that time, the Nobel Prize for Physics has been awarded 25 times and gone to 68 different people, averaging out at about 2.7 people per prize.

Now, my choice is entirely subjective, but I reckon the most signficant prizes are those that:

  • are simple to understand;
  • were an experimental or theoretical tour-de-force;
  • have long-term implications for science and open new paths;
  • expose deeper questions at their heart;
  • were on people’s bucket lists and/or have long, historical links;
  • were won by people we’d heard of at the time;
  • are of wider interest to non-physicists or those with only a passing interest in the subject.

So with that in mind, here’s my pick of the five top physics Nobel prizes of the 21st century. You’ll probably disagree violently with my choice so e-mail us with your thoughts.

5. Neutrino oscillation – 2015 prize

Tiny success The SuperKamiokande detector in Japan, where neutrino oscillations were first spotted, led to the 2015 Nobel Prize for Physics to Takaaki Kajita and Art McDonald. (Courtesy: Kamioka Observatory, Institute for Cosmic Ray Research, University of Tokyo)

Coming in at number five in our list of top physics Nobels of the 21st century is the discovery of neutrino oscillation, which went to Takaaki Kajita and Art McDonald in 2015. The neutrino was first hypothesized by Wolfgang Pauli back in 1930 as “a desperate remedy” to the fact that energy didn’t seem to be conserved when a nucleus emits an electron via beta decay. Fred Reines and Clyde Cowan had won a Nobel prize in 1995 for the original discovery of neutrinos themselves, which are chargeless particles that interact with matter via the weak force and are fiendishly hard to detect.

But what Kajita (at the Super-Kamikande experiment in Japan) and McDonald (at the Sudbury Neutrino Observatory in Canada) had done is to see them switch, or “oscillate”, from one type to another. Their work proved that these particles, which physicists had assumed to be massless, do have mass after all. This was at odds with the Standard Model of particle physics – and isn’t it fun when physics upends conventional wisdom?

What’s more, the discovery of neutrino oscillation explained why Ray Davies and John Bahcall had seen only a third of the solar neutrinos predicted by theory in their famous experiment of 1964. This discrepancy arose because solar neutrinos are oscillating between flavours as they travel to the Earth – and their experiment had detected only a third as it was sensitive mainly to electron neutrinos, not the other types.

4. Bose–Einstein condensation – 2001 prize

A Bose–Einstein condensate emerges from a cloud of cold rubidium atoms
Cool finding The first Bose–Einstein condensate (BEC) was created in 1995 from a cloud of cold rubidium atoms by Eric Cornell and Carl Wieman, with the “spike” in the density of atoms indicating many atoms occupying the same quantum state – the signature of a BEC. Cornell and Wieman won the 2001 Nobel Prize for Physics along with Wolfgang Ketterle, who made a BEC a few months later (Courtesy: NIST/JILA/CU-Boulder)

At number four in our list of the best physics Nobel prizes of the 21st century is the 2001 award, which went to Eric Cornell, Wolfgang Ketterle and Carl Wieman for creating the first Bose–Einstein condensates (BECs). I love the idea that Cornell and Wieman created a new state of matter – in which particles are locked together in their lowest quantum state – at exactly 10.54 a.m. on Monday 5 June 1995 at the JILA laboratory in Boulder, Colorado.

First envisaged by Satyendra Nath Bose and Albert Einstein in 1924, Cornell and Wieman created the first BEC by cooling 2000 rubidium-87 atoms to 170nK using the then new techniques of laser and evaporative cooling. Within a few months, Wolfgang Ketterle over at the Massachusetts Institute of Technology also made a BEC from 500,000 sodium-23 atoms at 2 μK.

Since then hundreds of groups around the world have created BECs, which have been used for everything from slowing light to making “atom lasers” and even modelling the behaviour of black holes. Moreover, the interactions between the atoms can be finely controlled, meaning BECs can be used to simulate properties of condensed-matter systems that are extremely difficult – or impossible – to probe in real materials.

3. Higgs boson – 2013 prize

Francois Englert and Peter Higgs.
Particle pioneers Peter Higgs (right) in the CERN auditorium with François Englert on 4 July 2012 when the discovery of the Higgs boson was announced, for which the pair won the 2013 Nobel Prize for Physics. (Courtesy: CERN/Maximilien Brice)

Coming in at number three is the 2013 prize, which went to François Englert and the late Peter Higgs for discovering the mechanism by which subatomic particles get mass. Their work was confirmed in 2012 by the discovery of the so-called Higgs boson at the ATLAS and CMS experiments at CERN’s Large Hadron Collider.

Higgs and Englert didn’t, of course, win for detecting the Higgs boson, although the Nobel citation credits the ATLAS and CMS teams in its citation. What they were being credited for was work done back in the early 1960s when they published papers independently of each other that provided a mechanism by which particles can have the masses we observe.

Higgs had been studying spontaneous symmetry breaking, which led to the notion of massless, force-carrying particles, known as Goldstone bosons. But what Higgs realized was that Goldstone bosons don’t necessarily occur when a symmetry is spontaneously broken – they could be reinterpreted as an additional quantum (polarization) state of a force-carrying particle.

The leftover terms in the equations represented a massive particle – the Higgs boson – avoiding the need for a massless unobserved particle. Writing in his now-famous 1964 paper (Phys. Rev. Lett. 13 508), Higgs highlighted the possibility of a massive spin-zero boson, which is what was discovered at CERN in 2012.

That work probably got more media attention than all Nobel prizes this century, because who doesn’t love a huge international collaboration tracking down a particle on the biggest physics experiment of all time? Especially as the Standard Model doesn’t predict what its mass should be so it’s hard to know where to look. But it doesn’t take top slot in my book because it “only” confirmed what we had expected and we’re still on the look-out for “new physics” beyond the Standard Model.

2. Dark energy – 2011 prize

Cooper-fig1
Cosmic discovery The universe has been expanding since the dawn of time, but instead of slowing down, in the last five or six billion years the expansion has sped up, bagging the 2011 Nobel prize for Saul Perlmutter, Adam Riess and Brian Schmidt. (Courtesy: NASA/WMAP Science Team)

Taking second place in our list is the discovery that the expansion of the universe is not slowing down – but accelerating – thanks to studies of exploding stars called supernovae. As with so many Nobel prizes these days, the 2011 award went to three people: Brian Schmidt, who led the High-Z Supernovae Search Team, and his colleague Adam Riess, and to Saul Perlmutter who led the rival Supernova Cosmology Project.

Theirs was a pretty sensational finding that implied that about three-quarters of the mass–energy content of the universe must consist of some weird, gravitationally repulsive substance, dubbed “dark energy”, about which even now we still know virtually nothing. It had previously been assumed that the universe would – depending on how much matter it contains – either collapse eventually in a big crunch or go on expanding forever, albeit at an ever more gentle pace.

The teams had been studying type 1a supernovae, which always blow up in the same way when they reach the same mass, which means that they can be used as “standard candles” to accurately measure distance in the universe. Such supernovae are very rare and the two groups had to carry out painstaking surveys using ground-based telescopes and the Hubble Space Telescope to find enough of them.

The teams thought they’d find that the expansion of the universe is decelerating, but as more and more data piled up, the results only appeared to make sense if the universe has a force pushing matter apart. The Royal Swedish Academy of Sciences said the discovery was “as significant” as the 2006 prize, which had gone to John Mather and the late George Smoot for their discovery in 1992 of the minute temperature variations in the cosmic microwave background – the fossil remnants of the large-scale structures in today’s universe.

But to me, the accelerating expansion has the edge as the implications are even more profound, pointing as they do to the composition and fate of the cosmos.

1. Gravitational waves – 2017 prize

Artist's impression of gravitational waves from a black-hole binary
Space–time collision Artist’s impression of a black-hole binary system generating gravitational waves, the discovery of which led to the 2017 Nobel Prize for Physics for Barry Barish, Kip Thorne and Rainer Weiss, which is (so far) the top physics prize of the 21st century. (Courtesy: LIGO/T Pyle)

And finally, the winner of the greatest Nobel Prize for Physics of the 21st century is the 2017 award, which went to Barry Barish, Kip Thorne and the late Rainer Weiss for the discovery of gravitational waves. Not only is it the most recent prize on my list, it’s also memorable for being a genuine first – discovering the “ripples in space–time” originally predicted by Einstein. The two LIGO detectors in Livingston, Louisiana, and Hanford, Washington, are also astonishing feats of engineering, capable of detecting changes in distance tinier than the radius of the proton.

The story of how gravitational waves were first observed is now well known. It was in the early hours of the morning Monday 14 September 2015, just after staff who had been calibrating the LIGO detector in Livingston had gone to bed, when gravitational waves created from the collision of two black holes 1.3 billion light-years away hit the LIGO detectors in the US. The historic measurement dubbed GW150914 hit the headlines around the world.

More than 200 gravitational-wave events have so far been detected – and observing these ripples, which had long been on many physicists’ bucket lists, has over the last decade become almost routine. Most gravitational-wave detections have been binary black-hole mergers, though there have also been a few neutron-star/black-hole collisions and some binary neutron-star mergers too. Gravitational-wave astronomy is now a well-established field not just thanks to LIGO but also Virgo in Italy and KAGRA in Japan. There are also plans for an even more advanced Einstein Telescope, which could detect in a day what it took LIGO a decade to spot.

Gravitational waves also opened the whole new field of “multimessenger astronomy” – the idea that you observe a cosmic event with gravitational waves and then do follow-up studies using other instruments, measuring it with cosmic rays, neutrinos and photons. Each of these cosmic messengers is produced by distinct processes and so carries information about different mechanisms within its source.

The messengers also differ widely in how they carry this information to the astronomer: for example, gravitational waves and neutrinos can pass through matter and intergalactic magnetic fields, providing an unobstructed view of the universe at all wavelengths. Combining observations of different messengers will therefore let us see more and look further.

  • Think we’re right or spectacularly wrong with our pick of the top five Nobel physics prizes of the 21st century? Get in touch by e-mailing us with your thoughts.

ASTRO 2025: expanding the rules of radiation therapy

“ASTRO 2025 has opened with a palpable sense of momentum. The turnout has been really strong and the energy is unmistakable,” said Catheryn Yashar, president-elect of the American Society for Radiation Oncology (ASTRO). “There’s a buzz in the exhibit hall, lots of talking in the lobby. And the sessions have generated excitement – it’s data that’s challenging our long held standards and testing the expanding rules of radiation therapy.”

Yashar was speaking at a news briefing arranged to highlight a select few high-impact abstracts. And in accord with the ASTRO 2025 meeting’s theme of “rediscovering radiation medicine and exploring new indications”, the chosen presentations included examples of innovative techniques and less common indications, including radiotherapy treatments of non-malignant disease and a novel combination of external-beam radiation with radioligand therapy.

Keeping heart rhythm under control

Ventricular tachycardia (VT) is a life-threatening heart rhythm disorder that’s usually treated with medication, implantation of a cardiac device and then catheter ablation, an invasive procedure in which a long catheter is inserted via a leg vein into the heart to destroy abnormal cardiac tissue. A research team at Washington University School of Medicine has now shown that stereotactic arrhythmia radiation therapy (STAR) could provide an equally effective and potentially safer treatment alternative.

Shannon Jiang at ASTRO 2025
STAR researcher Shannon Jiang from Washington University School of Medicine. (Courtesy: ©ASTRO/Nick Agro 2025)

STAR works by delivering precision beams of radiation to the scarred tissue that drives the abnormal heart rhythm, without requiring invasive catheters or anaesthesia.

“Over the past several years, STAR has emerged as a novel non-invasive treatment for patients with refractory VT,” said Shannon Jiang, who presented the team’s findings at ASTRO. “So far, there have been several single-arm studies showing promising results for STAR, but there are currently no data that directly compare STAR to catheter ablation, and that’s the goal for our study.”

Jiang and colleagues retrospectively analysed data from 43 patients with recurrent refractory VT (which no longer responds to treatment). Patients were treated with either STAR or repeat catheter ablation at a single institution. The team found that both treatments were similarly effective at controlling arrhythmia, but patients receiving radiation had far fewer serious side effects.

Within one year of the procedure, eight patients (38%) in the ablation group experienced treatment-related serious adverse events, compared with just two (9%) in the STAR group. These complications occurred sooner after ablation (median six days) than after radiation (10 months). In four cases, patients receiving ablation died within a month of treatment, soon after experiencing an adverse event, and one patient did not survive the procedure. In contrast, in the STAR group, there were no deaths attributed to treatment-related side effects. One year after treatment, overall survival was 73% following radiation and 58% after ablation; at three years (the median follow-up time), it was 45% in both groups.

“Despite the fact that this is a retrospective, non-randomized analysis, our study provides some important preliminary data that support the use of STAR as a potentially safer and equally effective treatment option for patients with high-risk refractory VT,” Jiang concluded.

Commenting on the study, Kenneth Rosenzweig from Icahn School of Medicine at Mount Sinai emphasizes that the vast majority of patients with VT will be well cared for by standard cardiac ablation, but that radiation can help in certain situations. “This study shows that for patients where the ablation just isn’t working anymore, there’s another option. Some patients will really need the help of radiation medicine to get them through, and work like this will help us figure out who those patients are and what we can do to improve their quality-of-life.”

A radiation combination

A clinical trial headed up at the University of California, Los Angeles, has shown that adding radioligand therapy to metastasis-directed radiation therapy more than doubles progression-free survival in men with oligometastatic prostate cancer, without increasing toxicity.

“When we pair external-beam radiation directed to tumours we can see with a radiopharmaceutical to reach microscopic disease we can’t see, patients can experience a notably longer interval before progression,” explained principal investigator Amar Kishan.

Patients with oligometastatic prostate cancer (up to five metastases outside the prostate after initial therapy) are increasingly treated with metastasis-directed stereotactic body radiation therapy (SBRT). While this treatment can delay progression and the need for hormone therapy, in most patients the cancer recurs, likely due to the presence of undetectable microscopic disease.

Amar Kishan at ASTRO 2025
Delaying cancer progression Amar Kishan from the University of California, Los Angeles. (Courtesy: ©ASTRO/Scott Morgan 2025)

Radioligand therapy uses a radiopharmaceutical drug to deliver precise radiation doses directly to tumours. For prostate cancer, the drug combines radioactive isotope lutetium-177 with a ligand that targets the prostate-specific membrane antigen (PSMA) found on cancer cells. Following its promising use in men with advanced prostate cancer, the team examined whether adding radioligand therapy to SBRT could also improve progression-free survival in men with early metastatic disease.

The phase II LUNAR trial included 92 men with oligometastatic prostate cancer and one to five distant lesions as seen on a PSMA PET/CT scan. The patients were randomized to receive either SBRT alone (control arm) or two cycles of the investigational PSMA-targeting drug 177Lu-PNT2002, eight weeks apart, followed by SBRT.

At a median follow-up of 22 months, adding radioligand therapy improved median progression-free survival from 7.4 to 17.3 months. Hormone therapy was also delayed, from 14.1 months in the control group to 24.3 months. Of 65 progression events observed, 64 were due to new lesions rather than regrowth at previously treated sites. Both treatments were well tolerated, with no difference in severe side effects between the two groups.

“We conclude that adding two cycles of 177Lu-PNT2002 to SBRT significantly improves progression-free survival in men with oligorecurrent prostate cancer, presumably by action on occult metastatic disease, without an increase in toxicity,” said Kishan. “Ultimately, while this intervention worked well, 64% of patients even on the investigational arm still had some progression, so we could further optimize the dose and cycle and other variables for these patients.”

Pain relief for knee osteoarthritis

Osteoarthritis is a painful joint disease that arises when the cartilage cushioning the ends of bones wears down. Treatments include pain medication, which can cause significant side effects with long-term use, or invasive joint replacement surgery. Byoung Hyuck Kim from Seoul National University College of Medicine described how low-dose radiotherapy (LDRT) could help bridge this treatment gap.

Byoung Hyuck Kim at ASTRO 2025
Easing arthritis pain Byoung Hyuck Kim from Seoul National University College of Medicine. (Courtesy: ©ASTRO/Scott Morgan 2025)

LDRT could provide a non-invasive alternative treatment for knee osteoarthritis, a leading cause of disability, Kim explained. But while it is commonly employed in Europe to treat joint pain, its use in other countries is limited by low awareness and a lack of high-quality randomized evidence. To address this shortfall, Kim and colleagues performed a randomized, placebo-controlled trial designed to provide sufficient evidence to incorporate LDRT into clinical standard-of-care.

“There’s a clinical need for moderate interventions between weak pain medications and aggressive surgery, and we think radiation may be a suitable option for those patients, especially when drugs and injections are poorly tolerated,” said Kim.

The multicentre trial included 114 patients with mild to moderate knee osteoarthritis. Participants were randomized to receive one of three treatments: 0.3 Gy radiotherapy in six fractions; 3 Gy in six fractions; or sham irradiation where the treatment system did not deliver radiation – an approach that had not been tested in previous studies.

The use of pain medication was limited, to avoid masking effects from the radiation itself. Response was considered positive if the patients (who did not know which treatment they had received) exhibited improvements in pain levels, physical function and overall condition.

“Interestingly, at one month [after treatment], the response rates were very similar across all groups, which reflects a strong placebo effect from the sham group,” said Kim. “At four months, after the placebo effect had diminished, the 3 Gy group demonstrated significantly higher response rate compared to the sham control group; however, the 0.3 Gy group did not.”

The response rates at four months were 70.3%, 58.3% and 41.7%, for the 3 Gy, 0.3 Gy and sham groups, respectively. As expected, with radiation doses less than 5% of those typically used for cancer treatments, no radiation-related side effects were observed.

“Our study shows that a single course of low-dose radiotherapy improves knee osteoarthritis symptoms and function at four months, with no treatment-related toxicity observed,” Kim concluded. “So our trial could provide objective evidence and suggest that LDRT is a non-pharmacologic scalable option that merits further trials.”

“While small, [the study] was really well executed in terms of being placebo controlled. It clearly showed that the 3 Gy arm was superior to the placebo control arm and there was a 30% benefit,” commented Kristina Mirabeau-Beale from GenesisCare. “So I think we can say definitively that the benefit is from radiation more than just the placebo effect of interacting with our healthcare system.”

Quantum information or metamaterials: our predictions for this year’s Nobel Prize for Physics

Infographic showing Nobel physics prizes in terms of field of research
Courtesy: Alison Tovey/IOP Publishing

On Tuesday 7 October the winner(s) of the 2025 Nobel Prize for Physics will be announced. The process of choosing the winners is highly secretive, so looking for hints about who will be this year’s laureates is futile. Indeed, in the immediate run-up to announcement, only members of the Nobel Committee for Physics and the Class for Physics at the Royal Swedish Academy of Sciences know who will be minted as the latest Nobel laureates. What is more, recent prizes provide little guidance because the deliberations and nominations are kept secret for 50 years. So we really are in the dark when it comes to predicting who will be named next week.

If you would like to learn more about how the Nobel Prize for Physics is awarded, check out this profile of Lars Brink, who served on the Nobel Committee for Physics on eight occasions.

But this level of secrecy doesn’t stop people like me from speculating about this year’s winners. Before I explain the rather lovely infographic that illustrates this article – and how it could be used to predict future Nobel winners – I am going to share my first prediction for next week.

Inspired by last year’s physics Nobel prize, which went to two computer scientists for their work on artificial intelligence, I am predicting that the 2025 laureates will be honoured for their work on quantum information and algorithms. Much of the pioneering work in this field was done several decades ago, and has come to fruition in functioning quantum computers and cryptography systems. So the time seems right for an award and I have four people in mind. They are Peter Shor, Gilles Brassard, Charles Bennett and David Deutsch. However, only three can share the prize.

Moving on to our infographic, which gives a bit of pseudoscientific credibility to my next predictions! It charts the history of the physics Nobel prize in terms of field of endeavour. One thing that is apparent from the infographic is that since about 1990 there have been clear gaps between awards in certain fields. If you look at “atomic, molecular and optical physics”, for example, there are gaps between awards of about 5–10 years. One might conclude, therefore, that the Nobel committee considers the field of an award and tries to avoid bunching together awards in the same field.

Looking at the infographic, it looks like we are long overdue a prize in nuclear and particle physics – the last being 10 years ago. However, we haven’t had many big breakthroughs in this field lately. Two aspects of particle physics that have been very fruitful in the 21st century have been the study of the quark–gluon plasma formed when heavy nuclei collide; and the precise study of antimatter – observing how it behaves under gravity, for example. But I think it might be a bit too early for Nobels in these fields.

One possibility for a particle-physics Nobel is the development of the theory of cosmic inflation, which seeks to explain the observed nature of the current universe by invoking an exponential expansion of the universe in its very early history. If an award were given for inflation, it would most certainly go to Alan Guth and Andrei Linde. A natural for the third slot would have been Alexei Starobinsky, who sadly died in 2023 – and Nobels are not awarded posthumously. If there was a third winner for inflation, it would probably be Paul Steinhardt.

Invisibility cloaks

2016 was the last year when we had a Nobel prize in condensed-matter physics, so what work in that field would be worthy of an award this year? There has been a lot of very interesting research done in the field of metamaterials – materials that are engineered to have specific properties, particularly in terms of how they interact with light or sound.

A Nobel prize for metamaterials would surely go to the theorist John Pendry, who pioneered the concept of transformation optics. This simplifies our understanding of how light interacts with metamaterials and helps with the design of objects and devices with amazing properties. These include invisibility cloaks –the first of which was built in 2006 by the experimentalist David Smith, who I think is also a contender for this year’s Nobel prize. Smith’s cloak works at microwave frequencies, but my nomination for the third slot has done an amazing amount of work on developing metamaterials for practical applications in optics. If you follow this field, you know that I am thinking of the applied physicist Federico Capasso – who is also known for the invention of the quantum cascade laser.

US scientific societies blast Trump administration’s plan to politicize grants

Almost 60 US scientific societies have signed a letter calling on the US government to “safeguard the integrity” of the peer-review process when distributing grants. The move is in to response to an executive order issued by the Trump administration in August that places accountability for reviewing and awarding new government grants in the hands of agency heads.

The executive order – Improving Oversight of Federal Grantmaking – calls on each agency head to “designate a senior appointee” to review new funding announcements and to “review discretionary grants to ensure that they are consistent with agency priorities and the national interest.”

The order outlines several previous grants that it says have not aligned with the Trump administration’s current policies, claiming that in 2024 more than a quarter of new National Science Foundation (NSF) grants went to diversity, equity, and inclusion and what it calls “other far-left initiatives”.

“These NSF grants included those to educators that promoted Marxism, class warfare propaganda, and other anti-American ideologies in the classroom, masked as rigorous and thoughtful investigation,” the order states. “There is a strong need to strengthen oversight and coordination of, and to streamline, agency grantmaking to address these problems, prevent them from recurring, and ensure greater accountability for use of public funds more broadly.”

Increasing burdens

In response, the 58 agencies – including the American Physical Society, the American Astronomical Society, the Biophysical Society, the American Geophysical Union and SPIE – have written to the majority and minority leaders of the US Senate and House of Representatives, to voice their concerns that the order “raises the possibility of politicization” in federally funded research.

“Our nation’s federal grantmaking ecosystem serves as the gold standard for supporting cutting-edge research and driving technological innovation worldwide,” the letters states. “Without the oversight traditionally applied by appropriators and committees of jurisdiction, this [order] will significantly increase administrative burdens on both researchers and agencies, slowing, and sometimes stopping altogether, vital scientific research that our country needs.”

The letter says more review and oversight is required by the US Congress before the order should go into effect, adding that the scientific community “is eager” to work with congress and the Trump administration “to strengthen our scientific enterprise”.

The curious history of Nobel prizes: from lighthouses to gravitational waves

Next week, the winners of the 2025 Nobel Prize for Physics will be revealed. In the run-up to the announcement I’m joined in this podcast by my colleague Matin Durrani, who has surveyed the last quarter century of Nobel prizes and picked his top five physics prizes of the 21st century – so far.

We also look back to two early Nobel prizes, which were given for very puzzling reasons. One was awarded in 1908 to Gabriel Lippmann for an impractical colour-photography technique that was quickly forgotten; and the other in 1912 to Gustaf Dalén for the development of several technologies used in lighthouses.

Our predictions

It’s a mug’s game, we know, but we couldn’t resist including a few predictions of who could win this year’s physics Nobel. Perhaps a prize for quantum algorithms could be announced on Tuesday, so stay tuned.

And finally, we round off this episode with a fun Nobel quiz. Do you know how old Lawrence Bragg was when he became the youngest person to win the physics prize?

Articles mentioned in this podcast:

“Nobel prizes you’ve never heard of: how a Swedish inventor was honoured for a technology that nearly killed him”

“Nobel prizes you’ve never heard of: how an obscure version of colour photography beat quantum theory to the most prestigious prize in physics”

“Inside the Nobels: Lars Brink reveals how the world’s top physics prize is awarded”

Courtesy: American ElementsThis podcast is supported by American Elements, the world’s leading manufacturer of engineered and advanced materials. The company’s ability to scale laboratory breakthroughs to industrial production has contributed to many of the most significant technological advancements since 1990 – including LED lighting, smartphones, and electric vehicles.

Nobel prizes you’ve never heard of: how a Swedish inventor was honoured for a technology that nearly killed him

Black-and-white photograph of Nils Gustaf Dalén. He's wearing an old-fashioned high-collared shirt and has a large, bushy moustache.
Nils Gustaf Dalén. (Courtesy: Nobel Foundation archive)

The winner of the 1912 Nobel Prize for Physics was, by some margin, the unlikeliest physics Nobel laureate in history. He wasn’t a physicist, for starters. He wasn’t even a chemist. He was an inventor by the name of Nils Gustaf Dalén, and the invention that won him the prize was closely connected – in more ways than one – to the industrial accident that almost cost him his life.

To understand why members of the Royal Swedish Academy of Sciences plumped for Dalén in 1912 over his more famous contemporaries (including such luminaries as Max Planck and Albert Einstein) it helps to know a bit about the man himself. Like Alfred Nobel, Dalén was Swedish, born in 1869 in the small farming community of Stenstorp. Located around 140 km north-east of Gothenburg, Stenstorp is now home to a museum in Dalén’s honour, but as a young man, he did not seem like museum material. On the contrary, he was incredibly lazy – so lazy, in fact, that he invented a machine to make coffee and turn the light on for him in the mornings.

This ingenious device brought Dalén some local notoriety, but his big break came when Sweden’s most famous inventor at the time, Gustaf de Laval, saw him demonstrate a device for measuring milk fat content. Encouraged by de Laval to attend university, Dalén sold his family’s farm and enrolled at what is now the Chalmers University of Technology. After spending an additional year at ETH Zürich in Switzerland, he returned to Sweden to set up his first engineering firm.

A light in the darkness

The engineering challenge that set Dalén on the path to the Nobel was hugely important in a country like Sweden with a long, complex coastline. Years before the advent of GPS, or even reliable radio communications, lighthouses were the main way of warning ships away from danger. However, they were extremely expensive and hard to maintain. As well as needing 24-hour attention from skilled and hardy humans, they required huge amounts of propane fuel, necessitating frequent (and frequently dangerous) resupply trips.

The obvious way of reducing these costs was to make lighthouses burn something else. Acetylene was attractive because it could be manufactured in industrial quantities, and it produced a bright light when burned. Unfortunately, it was also highly explosive, meaning it couldn’t be safely bottled or shipped.

To tame the acetylene dragon, Dalén developed three separate inventions. The first was a combination of asbestos and diatomaceous earth that Dalén called “agamassan” after his company (Aktiebolaget Gasaccumulator) and the Swedish word for compound, massan. By filling a container with agamassan, wetting it with acetone and then forcing acetylene into the container under pressure, Dalén showed that the acetylene would dissolve in the acetone and become trapped within the agamassan like water in a sponge. Under these conditions, it could be shipped, stored and even dropped without exploding.

Having made acetylene safe to use, Dalén turned his hand to making it economical. His second invention was a device that automatically turned the acetylene supply on and off. This saved fuel and enabled the light to flash (distinguishing it from other light sources on the shore) without the need for cumbersome rotation mechanisms.

Photo of a lighthouse on a small rock in a bay with the coastline clearly visible close behind
Let there be light The first light designed to use Gustaf Dalén’s technology is located near Djurgården in Stockholm, Sweden. It has since been converted to run on electricity. (Courtesy: Holger Ellgard, CC BY-SA 3.0)

Dalén’s third invention enabled even greater automation. Rather than relying on human lighthouse-keepers to switch acetylene burners on at night and off in the morning, Dalén developed a valve that could do it automatically. This valve worked by means of a set of metal rods, one of which was blackened while the others were polished. When the blackened rod absorbed enough heat from the Sun, it would expand and close the valve. At dusk, or in foggy conditions, the blackened rod would return to the temperature of the others, contract, and open the valve.

Choosing a laureate

While Dalén was perfecting the use of acetylene gas for lighthouses, the Nobel Committee for Physics was getting on with its usual business of recommending candidates for the prize. In 1909 the committee suggested the radio pioneer Guglielmo Marconi and his academic counterpart Karl Ferdinand Braun. The wider Academy accepted this choice. In 1910 the committee recommended the father of modern molecular science, Johannes Diderik van der Waals, and he also won the Academy’s approval. In 1911 the quantum theorist Wilhelm Wien, whose joint nomination with Max Planck in 1908 provoked such bitter disputes that neither of them got the prize, finally got the nod from both the committee and the Academy (Planck would have to wait for his prize until 1918).

By the early autumn of 1912, there was every indication that the Academy would again accept the committee’s recommendation, which was Heike Kammerlingh Onnes, who had liquefied helium for the first time in 1908 and subsequently used it to discover superconductivity. Although Dalén had also been nominated, Mats Larsson, a physicist at Stockholm University who served on the committee between 2016 and 2023, says he wasn’t a serious contender.

“It’s clear from the report from the Nobel committee to the Academy that they recognize there is an importance to Dalén’s inventions, but it doesn’t reach the standard for a Nobel prize,” says Larsson. With only a single nomination from a member of the Academy’s technical section, Larsson adds, “Dalén is not even on the shortlist.”

An industrial accident

Then, before the Academy could vote, tragedy struck. On 27 September 1912, during an experiment so risky it was performed in a quarry rather than in Aktiebolaget Gasaccumulator’s Stockholm factory, an explosion left Dalén seriously injured. The next day, Sweden’s national paper of record, Dagens Nyheter, put the accident on its front page, describing Dalén’s face as “unrecognizable” and his right side as “horribly massacred and burned”. Though conscious and talking when taken to hospital, he was not expected to survive.

Gustaf Dalén and his wife Elma arm in arm
A devoted couple Gustaf Dalén and his wife Elma outside their home in 1937. (Courtesy: Wikimedia Commons)

Nobel prizes cannot be awarded posthumously. If Dalén had died of his injuries, it is unlikely that his colleagues would have voted to honour him. But though Dalén’s doctors could not save his eyesight, they did save his life. By the time the Academy convened to vote on the 1912 Nobel prizes, he was recovering in the care of his family and very much on the minds of his sympathetic colleagues.

We don’t know exactly what happened next. “The material [in the Nobel archives] is very meagre,” Larsson explains. “It just says there was a vote and Dalén won the prize.”

Still, it’s easy to imagine that someone in the Academy must have pled Dalén’s cause. “This is our national hero who fought the war against ignorance and against darkness,” agrees Karl Grandin, who directs the Academy’s Center for History of Science. “And he loses his sight in the purpose of bringing light to the world. It was a symbolic thing.”

Dalén’s most enduring invention

Dalén was too unwell to attend the usual Nobel prize celebrations in Stockholm. Instead, he sent his brother, a physician, to accept the prize on his behalf. Eventually, though, he recovered well enough to resume his duties at Aktiebolaget Gasaccumulator. In time, he even returned to inventing. And herein lies the final twist in his story.

During his convalescence, the blind Dalén noticed something that had apparently escaped his attention when he could still see. His wife, Elma, worked very hard around the house, and cooking for him and their four children was especially tiresome. It would be much easier, Dalén decided, if she had a device that could cook several dishes at once, at different temperatures.

In 1922, ten years after losing his sight and winning the Nobel prize, Dalén unveiled the invention that would become his most enduring. Named, like agamassan, after the initials of his company, the AGA cooker is still sold today, bringing warmth to kitchens just as its inventor brought safe, effective and economical illumination to lighthouses. Gustaf Dalén may be the least likely physics Nobel laureate in history, but it would be facile to dismiss him as undeserving. After all, how many other physics laureates can boast of saving hundreds of thousands of lives at sea, while also relieving the drudgery of hundreds of thousands back home?

  • This article was amended on 4 November 2025 to correct the Swedish spellings of Dalén’s hometown and company.

Kirigami-inspired parachute falls on target

A Kirigami-inspired parachute
On target A Kirigami-inspired parachute deploying to slow down the delivery of a water bottle from a drone. (Courtesy: Frédérick Gosselin)

Inspired by the Japanese art of kirigami, researchers in Canada and France have designed a parachute that can safely and accurately deliver its payloads when dropped directly above its target. Tested in realistic outdoor conditions, the parachute’s deformable design stabilizes the airflow around its porous structure, removing the need to drift as it falls. With its simple and affordable design, the parachute could have especially promising uses in areas including drone delivery and humanitarian aid.

When a conventional parachute is deployed, it cannot simply fall vertically towards its target. To protect itself from turbulence, which can cause its canopy to collapse, it glides at an angle that breaks the symmetry of the airflow around it, stabilizing the parachute against small perturbations.

But this necessity comes at a cost. When dropping a payload from a drone or aircraft, this gliding angle means parachutes will often drift far from their intended targets. This can be especially frustrating and potentially dangerous for operations such as humanitarian aid delivery, where precisely targeted airdrops are often vital to success.

To address this challenge, researchers led by David Mélançon at Polytechnique Montréal looked to kirigami, whereby paper is cut and folded to create elaborate 3D designs. “Previously, kirigami has been used to morph flat sheets into 3D shapes with programmed curvatures,” Mélançon explains. “We proposed to leverage kirigami’s shape morphing capability under fluid flow to design new kinds of ballistic parachutes.”

Wind-dispersed seeds

As well as kirigami, the team drew inspiration from nature. Instead of relying on a gliding angle, many wind-dispersed seeds are equipped with structures that stabilize the airflow around them: including the feathery bristles of dandelion seeds, which create a stabilized vortex in their wake; and the wings of sycamore and maple seeds, which cause them to rapidly spin as they fall. In each case, these mechanisms provide plants with passive control over where their seeds land and germinate.

For their design, Mélançon’s team created a parachute that can deform into a shape pre-programmed by a pattern of kirigami cuts, etched into a flexible disc using a laser cutter. “Our parachutes are simple flat discs, with circumferential slits inspired by a kirigami motif called a closed loop,” Mélançon describes. “Instead of attaching the payload with strings at the outer edge of the disk, we directly mount it its centre.”

When dropped, a combination of air resistance and the weight of the free-falling payload deformed the parachute into an inverted, porous bell shape. “The slits in the kirigami pattern are stretched, forcing air through its multitude of small openings,” Mélançon continues. “This ensures that the air flows in an orderly manner without any major chaotic turbulence, resulting in a predictable trajectory.”

The researchers tested their parachute extensively using numerical simulations combined with wind tunnel experiments and outdoor tests, where they used the parachute to drop a water bottle from a hovering drone. In this case, the parachute delivered its payload safely to the ground from a height of 60 m directly above its target.

Easy to make

Mélançon’s team tested their design with a variety of parachute sizes and kirigami patterns, demonstrating that designs with lower load-to-area ratios and more deformable patterns can reach comparable terminal velocity to conventional parachutes – with far greater certainty over where they will land. Compared with conventional parachutes, which are often both complex and costly to manufacture, kirigami-based designs will be far easier to fabricate.

“Little hand labour is necessary,” Mélançon says. “We have made parachutes out of sheets of plastic, paper or cardboard. We need a sheet of material with a certain rigidity, that’s all.”

By building on their design, the researchers hope that future studies will pave the way for new improvements in package home delivery. It could even advance efforts to deliver urgently needed aid during conflicts and natural disasters to those who need it most.

The parachute is described in Nature.

Nobel prizes you’ve never heard of: how an obscure version of colour photography beat quantum theory to the most prestigious prize in physics

Black-and-white photo of Gabriel Lippmann. He's dressed formally, in a suit with a bow tie tucked beneath the collar, and he's wearing round spectacles. He has a large moustache with pointy, waxed ends.
Gabriel Lippmann. (Courtesy: Nobel Foundation archive)

By the time Gabriel Lippmann won the Nobel Prize for Physics, his crowning scientific achievement was already obsolete – and he probably knew it. Four days after receiving the 1908 prize “for his method of reproducing colours photographically based on the phenomenon of interference”, Lippmann, a Frenchman with a waxed moustache that would shame a silent film villain, ended his Nobel lecture with the verbal equivalent of a Gallic shrug.

After nearly 20 years of work, he admitted, the minimum exposure time for his method – one minute in full sunlight – was still “too long for the portrait”. Though further improvements were possible, he concluded, “Life is short and progress is slow.”

Why did Lippmann win a Nobel prize for a method that not even he seemed to believe in? It certainly wasn’t for a lack of alternatives. The early 1900s were a heady time for physics discoveries and inventions, and other Nobels of the era reflect this. In 1906 the Royal Swedish Academy of Sciences awarded the physics prize to J J Thomson for discovering the electron. In 1907 its members voted for Albert Michelson of the aether-defying Michelson–Morley experiment. So what made the Academy choose, in 1908, a version of colour photography that wouldn’t even let you take a selfie?

An elegant solution

Let’s start with the method itself. Unlike other imaging processes, Lippmann photography directly records the entire colour spectrum of an object. It does this by using standing waves of light to produce interference fringes in a light-sensitive emulsion backed by a mirrored surface. The longer the wavelength of light given off by the object, the larger the separation between the fringes. It’s an elegant application of classical wave theory. It’s easy to see why Edwardian-era physicists loved it.

A photo of bright red flowers in a vase. The colours are very vivid
Capturing colour A still life taken by Lippmann using his method between 1890 and 1910. By the latter part of this period, the method had fallen out of favour, superseded by the simpler Autochrome process. (Photo in public domain)

Lippmann’s method also has an important practical advantage. Because his photographs don’t require pigments, they retain their colour over time. Consequently, the images Lippmann showed off in his Nobel lecture look as brilliant today as they did in 1908.

The method’s disadvantages, though, are numerous. As well as needing long exposure times, the colours in Lippmann photographs are hard to see. Because they are virtual, like a hologram, they are only accurate when viewed face-on, in perpendicular light. Lippmann’s original method also required highly toxic liquid mercury to make the mirrored back surface of each photographic plate. Though modern versions have eliminated this, it’s not surprising that Lippmann’s method is now largely the domain of hobbyists and artists.

A French connection

If technical merit can’t explain Lippmann’s Nobel, could it perhaps have been due to politics? The easiest way to answer this question is to look in the Nobel archives. Although the names of Nobel prize nominees and the people who nominated them are initially secret, this secrecy is lifted after 50 years. The nomination records for Lippmann’s era are therefore very much available, and they show that he was a popular candidate. Between 1901 and 1908, he received 23 nominations from 12 different people – including previous laureates, foreign members of the Academy, and scientists from prestigious universities invited to make nominations in specific years.

Funnily enough, though, all of them were French.

Faced with this apparent conspiracy to stamp the French tricolour on the Nobel medal, Karl Grandin, who directs the Academy’s Center for History of Science, concedes that such nationalistic campaigns were “quite common in the first years”. However, this doesn’t mean they were successful: “Sometimes when all the members of the French Academy have signed a nomination, it might be impressive at one point, but it might also be working in the opposite way,” he says.

A clash of personalities

Because Nobel Foundation statutes stipulate that discussions and vote numbers from the prize-awarding meeting of the Academy are not recorded, Grandin can’t say exactly how Lippmann came out on top in 1908. He does, however, have access to an illuminating article written in 1981 by a theoretical physicist, Bengt Nagel.

Drawing on the private letters and diaries of Academy members as well as the Nobel archives, Nagel showed that personal biases played a significant role in the awarding of the 1908 prize. It’s a complicated story, but the most important strand of it centres on Svante Arrhenius, the Swedish physical chemist who’d won the Nobel Prize for Chemistry five years earlier.

Today, Arrhenius is best known for predicting that putting carbon dioxide in the Earth’s atmosphere will affect the climate. In his own lifetime, though, Grandin says that Arrhenius was also known for having a long-running personality conflict with a wealthy Swedish mathematician called Gustaf Mittag-Leffler.

“Stockholm at the time was a small place,” Grandin explains. “Everyone knew each other, and it wasn’t big enough to host both Arrhenius and Mittag-Leffler.”

Arrhenius and Mittag-Leffler
Double trouble The feuding between Svante Arrhenius (left) and Gustaf Mittag-Leffler played a major role in Gabriel Lippmann winning the Nobel Prize for Physics. (Images in public domain)

Arrhenius wasn’t the chair of the Nobel physics committee in 1908. That honour fell to Knut Angstrom, son of the Angstrom the unit is named after. Still, Arrhenius’ prestige and outsized personality gave him considerable influence. After much debate, the committee agreed to recommend his preferred choice for the prize, Max Planck, to the full Academy.

This choice, however, was not problem-free. Planck’s theory of the quantization of matter was still relatively new in 1908, and his work was not demonstrably guiding experiments. If anything, it was the other way around. In principle, the committee could have dealt with this by recommending that Planck share the prize with a quantum experimentalist. Unfortunately, no such person had been nominated.

That was awkward, and it gave Mittag-Leffler the ammunition he needed. When the matter went to the Academy for a vote, he used members’ doubts about quantum theory to argue against Arrhenius’ choice. It worked. In Mittag-Leffler’s telling, Planck got only 13 votes. Lippmann, the committee’s second choice, got 46.

A consensus winner

Afterwards, Mittag-Leffler boasted about his victory. “Arrhenius wanted to give it to Planck…but his report, which he had nevertheless managed to have unanimously accepted by the committee, was so stupid that I could easily have crushed it,” he wrote to a French colleague. “Two members even declared that after hearing me, they changed their opinion and voted for Lippmann. I would have had nothing against sharing the prize between [quantum theorist Wilhelm] Wien and Planck,” Mittag-Leffler added, “but to give it to Planck alone would have been to reward ideas that are still very obscure and require verification by mathematics and experimentation.”

A photo of the Matterhorn rising above an Alpine landscape. The colours are a little washed out, but do not appear artificially tinted
True colours A photo of the Matterhorn taken by Gabriel Lippmann between 1891 and 1899, using his then-newly-developed method of colour photography. The colours appear as they did in the original image, and were not added afterwards. (Image in public domain)

Lippmann’s work posed no such difficulties, and that seems to have swung it for him. In a letter to a colleague after the dust had settled, Angstrom called Lippmann “obviously a prizeworthy candidate who did not give rise to any objections”. However, Angstrom added, he “could not deny that the radiation laws constitute a more important advance in physical science than Lippmann’s colour photography”.

Much has been written about excellent scientists getting overlooked for prizes because of biases against them. The flip side of this – that merely good scientists sometimes win prizes because of biases in their favour – is usually left unacknowledged. Nevertheless, it happens, and in 1908 it happened to Gabriel Lippmann – a good scientist who won a Nobel prize not because he did the most important work, but because his friends clubbed together to support him; because Academy members were wary of his quantum rivals; and above all because a grudge-holding mathematician and an egotistical chemist had a massive beef with each other.

And then, four years later, it happened again, to someone else.

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