It is Peer Review Week and celebrations are well under way at IOP Publishing (IOPP), which brings you the Physics World Weekly podcast.
Reviewer feedback to authors plays a crucial role in the peer-review process, boosting the quality of published papers to the benefit of authors and the wider scientific community. But sometimes authors receive very unhelpful or outright rude feedback about their work. These inappropriate comments can shake the confidence of early career researchers, and even dissuade them from pursuing careers in science.
Our guest in this episode is Laura Feetham-Walker, who is reviewer engagement manager at IOPP. She explains how the publisher is raising awareness of the importance of constructive and respectful peer review feedback and how innovations can help to create a positive peer review culture.
As part of the campaign, IOPP asked some leading physicists to recount the worst reviewer comments that they have received – and Feetham-Walker shares some real shockers in the podcast.
The publisher also offers a Peer Review Excellence training and certification programme, which equips early-career researchers in the physical sciences with the skills to provide constructive feedback.
This episode of the Physics World Weekly podcast features two medical physicists working at the heart of the UK’s National Health Service (NHS). They are Mark Knight, who is chief healthcare scientist at the NHS Kent and Medway Integrated Care Board, and Fiammetta Fedele, who is head of non-ionizing radiation at Guy’s and St Thomas NHS Foundation Trust in London.
They explain how medical physicists keep people safe during healthcare procedures – while innovating new technologies and treatments. They also discuss the role that artificial intelligence could play in medical physics and take a look forward to the future of healthcare.
This episode was created in collaboration with IPEM, the Institute of Physics and Engineering in Medicine. IPEM owns the journal Physics in Medicine & Biology.
In this episode of the Physics World Weekly podcast we explore two related areas of physics, statistical physics and thermodynamics.
First up we have two leading lights in statistical physics who explain how researchers in the field are studying phenomena as diverse as active matter and artificial intelligence.
Cugliandolo is also chief scientific director of Journal of Statistical Mechanics, Theory, and Experiment (JSTAT) and Mézard has just stepped down from that role. They both talk about how the journal and statistical physics have evolved over the past two decades and what the future could bring.
The second segment of this episode explores how intense storms can affect your cup of tea. Our guests are the meteorologists Caleb Miller and Giles Harrison, who measured the boiling point of water as storm Ciarán passed through the University of Reading in 2023. They explain the thermodynamics of what they found, and how the storm could have affected the quality of the millions of cups of tea brewed that day.
The Journal of Statistical Mechanics, Theory, and Experiment is a multi-disciplinary, peer-reviewed international journal created by the International School for Advanced Studies (SISSA) and IOP Publishing, which also brings you Physics World.
Though she isn’t a physicist or an engineer, Margot Taylor has spent much of her career studying electrical circuits. As the director of functional neuroimaging at the Hospital for Sick Children in Toronto, Canada, Taylor has dedicated her research to the most complex electrochemical device on the planet – the human brain.
Taylor uses various brain imaging techniques including MRI to understand cognitive development in children. One of her current projects uses a novel quantum sensing technology to map electrical brain activity. Magnetoencephalography with optically pumped magnetometry (OPM-MEG) is a wearable technology that uses quantum spins to localize electrical impulses coming from different regions of the brain.
Physics World’s Hamish Johnston caught up with Taylor to discover why OPM-MEG could be a breakthrough for studying children, and how she’s using it to understand the differences between autistic and non-autistic people.
The OPM-MEG helmets Taylor uses in this research were developed by Cerca Magnetics, a company founded in 2020 as a spin-out from the University of Nottingham‘s Sir Peter Mansfield Imaging Centre in the UK. Johnston also spoke to Cerca’s chief executive David Woolger, who explained how the technology works and what other applications they are developing.
Margot Taylor: understanding the brain
What is magnetoencephalography, and how is it used in medicine?
Magnetoencephalography (MEG) is the most sensitive non-invasive means we have of assessing brain function. Specifically, the technique gives us information about electrical activity in the brain. It doesn’t give us any information about the structure of the brain, but the disorders that I’m interested in are disorders of brain function, rather than disorders of brain structure. There are some other techniques, but MEG gives us amazing temporal and spatial resolution, which makes it very valuable.
So you’re measuring electrical signals. Does that mean that the brain is essentially an electrical device?
Indeed, they are hugely complex, electrical devices. Technically it’s electrochemical, but we are measuring the electrical signals that are the product of the electrochemical reactions in the brain.
When you perform MEG, how do you know where that signal’s coming from?
We usually get a structural MRI as well, and then we have very good source localization approaches so that we can tell exactly where in the brain different signals are coming from. We can also get information about how the signals are connecting with each other, the interactions among different brain regions, and the timing of those interactions.
Good fit Margot Taylor and her team are working with quantum MEG helmets in various sizes, from large adult (purple) down to one-year-old (green). (Courtesy: Hospital for Sick Children)
Why does quantum MEG make it easier to do brain scans on children?
The quantum technology is called optically pumped magnetometry (OPM) and it’s a wearable system, where the sensors are placed in a helmet. This means there is allowed movement because the helmet moves with the child. We’re able to record brain signals in very young children because they can move or sit on their parents’ laps, they don’t have to be lying perfectly still.
Conventional MEG uses cryogenic technology and is typically one size fits all. It’s designed for an adult male head and if you put in a small child, their head is a long way from the sensors. With OPM, however, the helmet can be adapted for different sized heads. We have little tiny helmets up to bigger helmets. This is a game changer in terms of recording signals in little children.
Can you tell us more about the study you’re leading at the Hospital for Sick Children in Toronto using a quantum MEG system from the UK’s Cerca Magnetics?
We are looking at early brain function in autistic and non-autistic children. Autism is usually diagnosed by about three years of age, although sometimes it’s not diagnosed until they’re older. But if a child could be diagnosed with autism earlier, then interventions could start earlier. And so we’re looking at autistic and non-autistic children as well as children that have a high likelihood of being autistic to see if we can get brain signals that will predict whether they will go on to get a diagnosis or not.
How do the responses you measure using quantum MEG differ between autistic and non-autistic people, or those with a high likelihood of developing autism?
We don’t have that data yet because we’re looking at the children who have a high likelihood of being autistic, so we have to wait until they grow up and for another year or so to see if they get a diagnosis. For the children who do have a diagnosis of autism already, it seems like the responses are atypical, but we haven’t fully analysed that data. We think that there is a signal there that we’ll be able to report in the foreseeable future, but we have only tested 32 autistic children so far, and we’d like to get more data before we publish.
Testing times Margot Taylor (right) and her postdoctoral fellow Julie Sato (left) place a quantum MEG helmet on a research participant (postdoc Kristina Safar). (Courtesy: Hospital for Sick Children)
Do you have any preliminary results or published papers based on this data yet?
We’re still analysing data. We’re seeing beautiful, age-related changes in our cohort of non-autistic children. Because nobody has been able to do these studies before, we have to establish the foundational datasets with non-autistic children before we can compare it to autistic children or children who have a high likelihood of being autistic. And those will be published very shortly.
Are you using the quantum MEG system for anything else at the moment?
With the OPM system, we’re also setting up studies looking at children with epilepsy. We want to compare the OPM technology with the cryogenic MEG and other imaging technologies and we’re working with our colleagues to do that. We’re also looking at children who have a known genetic disorder to see if they have brain signals that predict whether they will also go on to experience a neurodevelopmental disorder. We’re also looking at children who are born to mothers with HIV to see if we can get an indication of what is happening in their brains that may affect their later development.
David Woolger: expanding applications
Can you give us a brief description of Cerca Magnetics’ technology and how it works?
When a neuron fires, you get an electrical current and a corresponding magnetic field. Our technology uses optically pumped magnetometers (OPMs), which are very sensitive to magnetic fields. Effectively, we’re sensing magnetic fields 500 million times lower than the Earth’s magnetic field.
To enable us to do that, as well as the quantum sensors, we need to shield against the Earth’s magnetic field, so we do this in a shielded environment with both active and passive shielding. We are then able to measure the magnetic fields from the brain, which we can use to understand functionally what’s going on in that area.
Are there any other applications for this technology beyond your work with Margot Taylor?
There’s a vast number of applications within the field of brain health. For example, we’re working with a team in Oxford at the moment, looking at dementia. So that’s at the other end of the life cycle, studying ways to identify the disease much earlier. If you can do that you can potentially start treatment with drugs or other interventions earlier.
Outside brain health, there are a number of groups who are using this quantum technology in other areas of medical science. One group in Arkansas is looking at foetal imaging during pregnancy, using it to see much more clearly than has previously been possible.
There’s another group in London looking at spinal imaging using OPM. Concussion is another potential application of these sensors, for sports or military injuries. There’s a vast range of medical-imaging applications that can be done with these sensors.
Have you looked at non-medical applications?
Cerca is very much a medical-imaging company, but I am aware of other applications of the technology. For example, applications with car batteries have potential to be a big market. When they make car batteries, there’s a lot of electrochemistry that goes into the cells. If you can image those processes during production, you can effectively optimize that production cycle, and therefore reduce the costs of the batteries. This has a real potential benefit for use in electric cars.
What’s next for Cerca Magnetics’ technology?
We are in a good position in that we’ve been able to deliver our initial systems to the research market and actually earn revenue. We have made a profit every year since we started trading. We have then reinvested that profit back into further development. For example, we are looking at scanning two people at once, looking at other techniques that will continue to develop the product, and most importantly, working on medical device approval. At the moment, our system is only sold to research institutes, but we believe that if the product were available in every hospital and every doctor’s surgery, it could have an incredible societal impact across the human lifespan.
Magnetoencephalography with optically pumped magnetometers
Seeing the light A schematic showing the working principle behind optically pumped magnetometry (OPM). (CC BY 4.0 Trends in Neurosciences45 621)
Like any electrical current, signals transmitted by neurons in the brain generate magnetic fields. Magnetoencephalography (MEG) is an imaging technique that detects these signals and locates them in the brain. MEG has been used to plan brain surgery to treat epilepsy. It is also being developed as a diagnostic tool for disorders including schizophrenia and Alzheimer’s disease.
MEG traditionally uses superconducting quantum interference devices (SQUIDs), which are sensitive to very small magnetic fields. However, SQUIDs must be cryogenically cooled, which makes the technology bulky and immobile. Magnetoencephalography with optically pumped magnetometers (OPM-MEG) is an alternative technology that operates at room temperature. Optically pumped magnetometers (OPMs) are small quantum devices that can be integrated into a helmet, which is an advantage for imaging children’s brains.
The key components of an OPM device are a cloud of alkali atoms (generally rubidium), a laser and a photodetector. Initially, the spins of the atoms point in random directions (top row in figure), but applying a polarized laser of the correct frequency aligns the spins along the direction of the light (middle row in figure). When the atoms are in this state, they are transparent to the laser so the signal reaching the photodetector is at a maximum.
However, in the presence of a magnetic field, such as that from a brain wave, the spins of the atoms are perturbed and they are no longer aligned with the laser (bottom row in figure). The atoms can now absorb some of the laser light, which reduces the signal reaching the photodetector.
In OPM-MEG, these devices are placed around the patient’s head and integrated into a helmet. By measuring the signal from the devices and combining this with structural images and computer modelling, it’s possible to work out where in the brain the signal came from. This can be used to understand how electrical activity in different brain regions is linked to development, brain disorders and neurodivergence.
This episode of the Physics World Weekly podcast looks at quantum computing from two different perspectives.
Our first guest is Elena Blokhina, who is chief scientific officer at Equal1 – an award-winning company that is developing hybrid quantum–classical computing chips. She explains why Equal1 is using quantum dots as qubits in its silicon-based quantum processor unit.
Next up is Brandon Grinkemeyer, who is a PhD student at Harvard University working in several cutting-edge areas of quantum research. He is a member of Misha Lukin’s research group, which is active in the fields of quantum optics and atomic physics and is at the forefront of developing quantum processors that use arrays of trapped atoms as qubits.
What does Shrinivas Kulkarni finds fascinating? When I asked him that question I expected an answer related to his long and distinguished career in astronomy. Instead, he talked about how the skin of sharks has a rough texture, which seems to reduce drag – allowing the fish to swim faster. He points out that you might not win a Nobel prize for explaining the hydrodynamics of shark skin, but it is exactly the type of scientific problem that captivates Kulkarni’s inquiring mind.
But don’t think that Kulkarni – who is George Ellery Hale Professor of Astronomy and Planetary Sciences at the California Institute of Technology (Caltech) – is whimsical when it comes to his research interests. He says that he is an opportunist, especially when it comes to technology, which he says makes some research questions more answerable than others. Indeed, the scientific questions he asks are usually guided by his ability to build technology that can provide the answers.
Kulkarni won the 2024 Shaw Prize in Astronomy for his work on variable and transient astronomical objects. He says that the rapid development of new and powerful technologies has meant that the last few decades been a great time to study such objects. “Thirty years ago, the technology was just not there,” he recalls, “optical sensors were too expensive and the necessary computing power was not available.
Transient and variable objects
Kulkarni told me that there are three basic categories of transient and variable objects. One category covers objects that change position in the sky – with examples including planets and asteroids. A second category includes objects that oscillate in terms of their brightness.
“About 10% of stars in the sky do not shine steadily like the Sun,” he explains. “We are lucky that the Sun is an extremely steady star. If its output varied by just 1% it would have a huge impact on Earth – much larger than the current global warming. But many stars do vary at the 1% level for a variety of reasons.” These can be rotating stars with large sunspots or stars eclipsing in binary systems, he explains.
It might surprise you that every second, somewhere in the universe, there is a supernova
The third and most spectacular category involve stars that undergo rapid and violent changes such as stars that explode as supernovae. “It might surprise you that every second, somewhere in the universe, there is a supernova. Some are very faint, so we don’t see all of them, but with the Zwicky Transient Facility (ZTF) we see about 20,000 supernovae per year.” Kulkarni is principal investigator for the ZTF, and his leadership at that facility is mentioned in his Shaw Prize citation.
Kulkarni explains that astronomers are interested in transient and variable objects for many different reasons. Closer to home, scientists monitor the skies for asteroids that may be on collision courses with Earth.
“In 1908 there was a massive blast in Siberia called the Tunguska event,” he says. This is believed to be the result of the air explosion of a rocky meteor that was about 55 m in diameter. Because it happened in a remote part of the world, only three people are known to have been killed. Kulkarni points out that if such a meteor struck a populated area like Southern California, it would be catastrophic. By studying and cataloguing asteroids that could potentially strike Earth, Kulkarni believes that we could someday launch space missions that nudge away objects on collision courses with Earth.
Scanning the skies The Zwicky Transient Facility uses a camera attached to the Samuel Oschin Telescope at the Palomar Observatory. (Courtesy: Caltech Optical Observatories)
At the other end of the mass and energy range, Kulkarni says that studying spectacular events such as supernovae provides important insights into origins of many of the elements that make up the Earth and indeed ourselves. He says that over the past 70 years astronomers have made “amazing progress” in understanding how different elements are created in these explosions.
Kulkarni was born in1956 in Kurundwad, which is in the Indian state of Maharashtra. In 1978, he graduated with an MS degree in physics from the Indian Institute of Technology in New Delhi. His next stop was the University of California, Berkeley, where he completed a PhD in astronomy in 1983. He joined Caltech in 1985 and has been there ever since.
You could say that I live on adrenaline and I want to produce something very fast, making significant progress in in a short time
A remarkable aspect of Kulkarni’s career is his ability to switch fields every 5–10 years, something that he puts down to his curious nature. “After I understand something to a reasonable level, I lose interest because the curiosity is gone,” he says. Kulkarni adds that his choice of a new project is guided by his sense of whether rapid progress can be made in the field. “You could say that I live on adrenaline and I want to produce something very fast, making significant progress in in a short time”.
He gives the example of his work on gamma-ray bursts, which are some of the most powerful explosions in the universe. He says that this was a very fruitful field when astronomers were discovering about one burst per month. But then the Neil Gehrels Swift Observatory was launched in 2004 and it was able to detect 100 or so gamma-ray bursts per year.
Looking for new projects
At this point, Kulkarni says that studying bursts became a “little industry” and that’s why he left the field. “All the low-hanging fruit had been picked – and when the fruit is higher on the tree, that is when I start looking for new projects”.
It is this restlessness that first got him involved in the planning and operation of two important instruments, the Palomar Transient Factory (PTF) and its successor the Zwicky Transient Facility (ZTF). These are wide-field sky astronomical surveys that look for rapid changes in the brightness or position of astronomical objects. The PTF began observing in 2009 and the ZTF took over in 2018.
Kulkarni says that he is fascinated by the engineering aspects of astronomy and points out that technological advances in sensors, electronics, computing and automation continue to transform how observational astronomy is done. He explains that all of these technological factors came together in the design and operation of the PTF and the ZTF.
His involvement with PTF and ZTF allowed Kulkarni to make many exciting discoveries during his career. However, his favourite variable object is one that he discovered in 1982 while doing a PhD under Donald Backer. Called PSR B1937+21, it is the first millisecond pulsar ever to be to observed. It is a neutron star that rotates more than 600 times per second while broadcasting a beam of radio waves much like a lighthouse.
“I was there [at the Arecibo Observatory] all alone… it was very thrilling,” he says. The discovery provided insights into the density of neutron stars and revitalized the study of pulsars, leading to large-scale surveys that target pulsars.
When you find a new class of objects, there’s a certain thrill knowing that you and your students are the only people in the world to have seen something
Another important moment for Kulkarni occurred in 1994, when he and his graduate students were the first to observe a cool brown dwarf. These are objects that weigh in between gas-giant planets (like Jupiter) and small main-sequence stars. “When you find a new class of objects, there’s a certain thrill knowing that you and your students are the only people in the world to have seen something. That was kind of fun.”
Kulkarni is proud of his early achievements, but don’t think that he dwells on the past. “This is a fantastic time to do astronomy. The instruments that we’re building today have an enormous capacity for information delivery.”
Pioneering observations The image on the left shows the brown dwarf GL229B (small central object) as seen by Kulkarni and colleagues in 1994. On the right shows a similar image taken by the Hubble Space Telescope in 1995, confirming the discovery. The large object on the left of both images is a red dwarf star. (Courtesy: T Nakajima (Caltech)/S Durrance (JHU)/S Kulkarni (Caltech)/D Golimowski (JHU)/NASA)
He mentions images released by the European Space Agency’s Euclid space telescope, which launched last year. He describes them as “gorgeous pictures” but points out that the real wonder is that he could zoom in on the images by a factor of 10 before the pixels became apparent. “It was just so rich, a single image is maybe a square degree of the sky. The resolution is just amazing.”
And when it comes to technology, Kulkarni is adamant that it’s not only bigger and more expensive telescopes that are pushing the frontiers of astronomy. “There is more room sideways,” he says, meaning that much progress can be made by repurposing existing facilities.
Indeed, ZTF and PTF both use (used) the Samuel Oschin telescope at the Palomar Observatory in California. This is a 48-inch (1.3 metre) facility that saw first light 75 years ago. With new instruments, old telescopes can be used to study the sky “ferociously” he says.
Kulkarni told me that even he was surprised at the number of papers that ZTF data have spawned since the facility came online in 2018. One important reason, says Kulkarni, is that ZTF immediately shares its data freely with astronomers around the world. Indeed, it is the explosion in data from facilities like the ZTF along with rapid improvements in data processing that Kulkarni believes has put us in a golden age of astronomy.
Beyond the technology, Kulkarni says that the very nature of the cosmos means that there will always be opportunities for astronomers. He muses that the universe has been around for nearly 14 billion years and has had “many opportunities to do some very strange things – and a very long time to cook up those things – so there’s no shortage of phenomena to explore”.
Great time to be an astronomer
So it is a great time to consider a career in astronomy and Kulkarni’s advice to aspiring astronomers is to be pragmatic about how they approach the field. “Figure out who you are and not you want to be,” he says. “If you want to be an astronomer. There are roughly three categories open to you. You can be a theorist who puts a lot of time understand the physics, and especially the mathematics, that are used to make sense of astronomical observations.”
At the other end of the spectrum are the astronomers who build the “gizmos” that are used to scan the heavens – generating the data that the community rely on. The third category, says Kulkarni, falls somewhere between these two extremes and includes the modellers. These are the people who take the equations developed by the theorists and create computer models that help us understand observational data.
“Astronomy is a fantastic field and things are really happening in a very big way.” He asks new astronomers to, “Bring a fresh perspective, bring energy, and work hard”. He also says that success comes to those who are willing to reflect on their strengths and weaknesses. “Life is a process of continual improvement, continual education, and continual curiosity.”
This article has been updated to correct a misinterpretation of this null result.
Things can go a bit off-topic at Physics World and recent news about dark matter got us talking about the beauty of the Black Hills of South Dakota. This region of forest and rugged topography is smack dab in the middle of the Great Plains of North America and is most famous for the giant sculpture of four US presidents at Mount Rushmore.
A colleague from Kansas fondly recalled a family holiday in the Black Hills – and as an avid skier, I was pleased to learn that the region is home to the highest ski lift between the Alps and the Rockies.
The Black Hills also have a special place in the hearts of physicists – especially those who are interested in dark matter and neutrinos. The region is home to the Sanford Underground Research Facility, which is located 1300 m below the hills in a former gold mine. It was there that Ray Davis and colleagues first detected neutrinos from the Sun, for which Davis shared the 2002 Nobel Prize for Physics.
Today, the huge facility is home to nearly 30 experiments that benefit from the mine’s low background radiation. One of the biggest experiments is LUX–ZEPLIN, which is searching for dark-matter particles.
Hypothetical substance
Dark matter is a hypothetical substance that is invoked to explain the dynamics of galaxies, the large-scale structure of the cosmos, and more. While dark matter is believed to account for 85% of mass in the universe, physicists have little understanding of what it is – or indeed if it actually exists.
So far, the best that experiments like LUX–ZEPLIN have done is to tell physicists what dark matter isn’t. Now, the latest result from LUX–ZEPLIN places the best-ever limits on the nature of dark-matter particles called WIMPs.
The measurement involved watching several tonnes of liquid xenon for 280 days, looking for flashes of light that would be created when a WIMP collides with a xenon nuclei. However no evidence was seen for collisions with WIMPs heavier than 9 GeV/c2 – which is about 10 times the mass of the proton.
The team says that the result is “nearly five times better” than previous WIMP searches. “These are new world-leading constraints by a sizable margin on dark matter and WIMPs,” explains Chamkaur Ghag, who speaks for the LUX–ZEPLIN team and is based at University College London.
Digging for treasure
“If you think of the search for dark matter like looking for buried treasure, we’ve dug almost five times deeper than anyone else has in the past,” says Scott Kravitz of the University of Texas at Austin who is the deputy physics coordinator for the experiment.
This will not be the last that we hear from LUX–ZEPLIN, which will collect a total of 1000 days of data before it switches off in 2028. And it’s not only dark matter that the experiment is looking for. Because it is in a low background environment, LUX–ZEPLIN is also being used to search for other rare or hypothetical events such as the radioactive decay of xenon, neutrinoless double beta decay and neutrinos from the beta decay of boron nuclei in the Sun.
LUX–ZEPLIN is not the only experiment at Sanford that is looking for neutrinos. The Deep Underground Neutrino Experiment (DUNE) is currently under construction at the lab and is expected to be completed in 2028. DUNE will detect neutrinos in four huge tanks that will each be filled with 17,000 tonnes of liquid argon. Some neutrinos will be beamed from 1300 km away at Fermilab near Chicago and together the facilities will comprise the Long-Baseline Neutrino Facility.
One aim of the facility is to study the flavour oscillation of neutrinos as they travel over long distances. This could help explain why there is much more matter than antimatter in the universe. By detecting neutrinos from exploding stars, DUNE could also shed light on the nuclear processes that occur during supernovae. And, it might even detect the radioactive decay of the proton, a hypothetical process that could point to physics beyond the Standard Model.
On 15 August 1977 the Big Ear radio telescope in the US was scanning the skies in a search for signs of intelligent extraterrestrial life. Suddenly, it detected a strong, narrow bandwidth signal that lasted a little longer than one minute – as expected if Big Ear’s field of vision swept across a steady source of radio waves. That source, however, had vanished 24 hours later when the Ohio-based telescope looked at the same patch of sky.
This was the sort of technosignature that searches for extraterrestrial intelligence (SETI) were seeking. Indeed, one scientist wrote the word “Wow!” next to the signal on a paper print-out of the Big Ear data.
Ever since, the origins of the Wow! signal have been debated – and now, a trio of scientists have an astrophysical explanation that does not involve intelligent extraterrestrials. One of them, Abel Méndez, is our guest in this episode of the Physics World Weekly podcast.
Méndez is an astrobiologist at the University of Puerto Rico at Arecibo and he explains how observations made at the Arecibo Telescope have contributed to the trio’s research.
Abel Méndez, Kevin Ortiz Ceballos and Jorge I Zuluaga describe their research in a preprint on arXiv.
This episode of the Physics World Weekly podcast explores how physics can be used as a force for good – helping society address important challenges such as climate change, sustainable development, and improving health.
Our guest is the Swiss physicist Christophe Rossel, who is a former president of the European Physical Society (EPS) and an emeritus scientist at IBM Research in Zurich.
Rossel is a co-editor and co-author of the book EPS Grand Challenges, which looks at how science and physics can help drive positive change in society and raise standards of living worldwide as we approach the middle of the century. The huge tome weighs in at 829 pages, was written by 115 physicists and honed by 13 co-editors.
Rossel talks to Physics World’s Matin Durrani about the intersection of science and society and what physicists can do to make the world a better place.
Margot Taylor – director of functional neuroimaging at Toronto’s Hospital for Sick Children – is our first guest in this podcast. She explains how she uses optically-pumped magnetometers (OPMs) to do magnetoencephalography (MEG) studies of brain development in children.
An OPM uses quantum spins within an atomic gas to detect the tiny magnetic fields produced by the brain. Unlike other sensors used for MEG, which must be kept at cryogenic temperatures, OPMs can be deployed at room temperature in a simple helmet that puts the sensors very close to the scalp.
The OPM-MEG helmets are made by Cerca Magnetics and the UK-based company’s managing director joins the conversation to explain how the technology works. David Woolger also talks about the success the company has enjoyed since its inception in 2020.
Our final guest in this podcast is Stuart Nicol, who is chief investment officer at Quantum Exponential – a UK-based company that invests in quantum start-ups. He gives his perspective on the medical sector, talks about a company called Siloton that is making a crucial eye-imaging technology more accessible.
Atomic clocks on the Moon. It might sound like a futuristic concept, but atomic clocks already abound in space. They can be found on Earth-orbiting satellites that provide precision timing for many modern technologies.
The clocks’ primary function is to generate the time signals that are broadcast by satellite navigation systems such as GPS. These signals are also used to time-stamp financial transactions, enable mobile-phone communications and coordinate electricity grids.
But why stop at orbits a mere 20,000 km from Earth’s surface? Should we establish a network of atomic clocks on the Moon? This is the subject of a new paper by two physicists at NIST in Boulder, Colorado – Neil Ashby and Bijunath Patla.
They say that their study was inspired by NASA’s ambitious Artemis programme, which aims to land people on the Moon as early as 2026. The duo points out that navigation and communications on and near the Moon would benefit from a precision time standard. One option is to use a time signal that is broadcast from Earth to the Moon. Another option is to create a lunar time standard using one or more atomic clocks on the Moon, or in lunar orbit.
Faster pace
The problem with using a signal from Earth is that a clock on the Moon runs at a faster pace than a clock on Earth. This time dilation is caused by the difference in gravitational potential at the two locations and is described nicely by Einstein’s general theory of relativity.
Using that theory, the NIST duo calculate that a clock on the Moon will gain about 56 µs per day when compared to a clock on Earth. What’s more, this rate is not constant because of the eccentricity of the Moon’s orbit and the changing tidal effects of solar-system bodies other than the Earth, which would also cause fluctuations in the difference between earthbound and Moon-bound clocks.
Because of these variations, the duo argue that it would be better to create a network of atomic clocks on the surface of the Moon – and in lunar orbit. This would provide a distributed system of lunar time, much like the distributed system that currently exists on Earth.
“It’s like having the entire Moon synchronized to one ‘time zone’ adjusted for the Moon’s gravity, rather than having clocks gradually drift out of sync with Earth’s time,” explains Patla. This could form the basis of a high-precision lunar positioning system. “The goal is to ensure that spacecraft can land within a few metres of their intended destination,” Patla says.
They also calculated the difference in clock rates on Earth and at the four Lagrange points in the Earth–Moon system. These are places where satellites can sit fixed relative to the Earth and Moon. There, clocks would gain a little more than 58 µs per day compared to clocks on Earth.
They conclude that atomic clocks placed on satellites at these Lagrange points could be used as time transfer links between the Earth and Moon.
If you have been watching skateboarding at the Olympics, you may be wondering how the skaters manage to keep going up and down ramps long after friction should have consumed their initial gravitational potential energy.
That process is called pumping, and most skaters will learn how to do it by going back and forth on a half-pipe. If you are not familiar with the lingo, a half-pipe comprises two ramps that are connected by a lower (sometimes flat) middle section. A good skateboarder can skate up the side of a ramp, turn around and do the same on the other side – and continue to oscillate back and forth in the half-pipe.
What’s obvious about the physics of this scenario is that the gravitational potential energy of the skater while at the top of the half-pipe will be quickly lost to friction. So how does a skater keep going? How do they pump kinetic energy into the system?
Variable pendulum
It turns out that the process is similar to an obscure way that you can keep a playground swing going – by standing on the seat and shifting your centre of mass by squatting down in the centre of a swing and rising up at both ends of a swing (see video below). This can be understood in terms of a pendulum with a length that varies in a regular way – and that is how Florian Kogelbauer at ETH Zurich and colleagues in Japan have modelled pumping in a skateboard half-pipe.
Their model considers how a skilled skater modulates their centre of mass relative to the surface of the half-pipe. Essentially this involves crouching down as the skateboard travels across the flat bit of the halfpipe, then pushing up from the board during the curved ascent of the ramp. Pushing up reduces the moment of inertia of the system, and conservation of angular momentum dictates that the skater must speed up.
The team compared their model to video data of experienced and inexperienced skaters pumping a half-pipe. They found that experienced skaters did indeed adhere to their model of pumping. They now plan to extend their model to include other movements done by skaters during pumping. They also say that their model could be used to better understand the physics of other sports such as ski jumping.
This podcast explores the extraordinary life of the Pakistani physicist Abdus Salam, who is celebrated for his ground-breaking theoretical work and for his championing of physics and physicists in developing countries.
In 1964, he founded the Abdus Salam International Centre for Theoretical Physics (ICTP) in Trieste, Italy – which supports research excellence worldwide with a focus on physicists in the developing world. In 1979 Salam shared the Nobel Prize for Physics for his work on the unification of the weak and electromagnetic interactions.
Salam spent most of his career at Imperial College London and the university is gearing up to celebrate the centenary of his birth in January 2026. In this episode of the Physics World Weekly podcast, Imperial physicists Claudia de Rham and Ian Walmsley look back on the extraordinary life of Salam – who died in 1996. They also talk about the celebrations at Imperial College.
It is no coincidence that “going viral” is used to describe how ideas spread on social media. Researchers have long used models of infectious disease to understand how information – and indeed misinformation – is rapidly disseminated.
But, according to the physicist Wenrong Zheng, these models can struggle to accurately describe how rumours spread.
“Infectious disease models mostly view the spread of rumours as a passive process of receiving infection, thus ignoring the behavioural and psychological changes of people in the real world, as well as the impact of external events on the spread of rumours,” explains Zheng, who is based at China’s Shandong Normal University.
To address this shortcoming, Zheng teamed up with Fengming Liu and Yingping Sun to create a model of how rumours spread that is inspired by the chain reaction of nuclear fission (atom splitting). This process begins with a uranium nuclei spontaneously splitting into two smaller nuclei and several neutrons. If these neutrons are absorbed by other uranium nuclei, it is more likely that those nuclei will split – thus setting off a chain reaction of fission.
The two most common isotopes of uranium are uranium-238 and uranium-235. The former must absorb multiple neutrons before it will split, whereas the latter will split after just one absorption.
Multiple reception
In the trio’s model, a neutron travelling through a piece of uranium is the rumour. A uranium-235 nucleus is a person who immediately disseminates the rumour upon receiving it. A uranium-238 nucleus is a person who must receive the rumour several times before disseminating it.
“When individuals encounter rumours, they are influenced by their personal interests and decide whether to spread or whether repeated exposure is needed before spreading,” explains Zheng. “Based on different considerations of uranium fission thresholds, individuals are divided into groups based on the influence of their own interest thresholds, fully considering individual behaviour and differences, which is more in line with the reality.”
The researchers conclude that their model is better than some infectious disease models at mimicking the real-life spreading of rumours. They also suggest that rumours often spread slowly at first, which could mean that the spread of misinformation could be countered.
This episode of the Physics World Weekly podcast features an interview with Margaret Arakawa. She is chief marketing officer at IonQ – which makes trapped ion quantum computers. An economist by training, Arakawa spent 25 years in the (classical) computing industry before joining IonQ. We chat about why she made the move to the quantum sector and about the wide range of opportunities for non-physicists in the quantum-technology industry.
Arakawa also talks about the challenges of marketing quantum technology to customers who might not understand the underlying physics and explains why the quantum industry must avoid hype.
Our second guest is Nat Mendelsohn, who represents the English Midlands on the Institute of Physics’ Student Community Panel. He talks to Physics World’s Katherine Skipper about the student experience – what is good and what can be improved. He also explains how the COVID-19 pandemic continues to have a profound impact on higher education.
Finally, I chat with Skipper about her trip to Prague for the 42nd International Conference on High Energy Physics. High on the agenda was what collider of the future will be the successor of the Large Hadron Collider.
Our first guest in this episode of the Physics World Weekly podcast is Derek Sutherland, who is head of FuZE-Q physics at the US-based company Zap Energy. He explains how the US-based firm is designing a fusion system that does not rely on magnets, cryogenics or high-powered lasers to generate energy. We also chat about the small-scale fusion industry in general, and about career opportunities for physicists in the sector.
This episode also features an interview with theoretical physicist and author Claudia de Rham. She talks to Physics World’s Matin Durrani about her new popular-science book The Beauty of Falling. They also chat about her research, which addresses a range of fundamental problems associated with gravity – from quantum to cosmological scales.
This episode is supported by Pfeiffer Vacuum. The company provides all types of vacuum equipment, including hybrid and magnetically-levitated turbopumps, leak detectors and analysis equipment, as well as vacuum chambers and systems. You can explore all of its products on the Pfeiffer Vacuum website.
New and exciting technologies feature in this episode of the Physics World Weekly podcast.
Our first guest is the neuroscientist and physicist Jelena Lazovic Zinnanti, who recalls how she discovered (by accident) that nanometre-sized diamond particles shine brightly in magnetic resonance imaging (MRI) experiments. Based at Max Planck Institute for Intelligent Systems, she explains how this diamond dust could someday replace gadolinium as a contrast agent in MRI medical scans.
This episode also features an interview with Mahdi Bodaghi of Nottingham Trent University, who is an expert in 4D and 3D printing. He talks about the engineering principles that guide 4D printing and how the technique can be used in a wide range of applications including the treatment of coronary heart disease and the design of flatpack furniture. Bodaghi also explains how 3D printing can be used to create self-healing asphalt.
Mahdi Bodaghi is on the editorial board of the journal Smart Materials and Structures. It is published by IOP Publishing, which also brings you Physics World.
Back in April of this year we reported that researchers in Germany and Austria were the first to use a laser to excite a low-lying metastable nuclear state of thorium-229. Now an independent team in the US has repeated the feat. Their work is seen as important progress in the development of a solid-state nuclear clock.
Such a device could rival today’s best atomic clocks in terms of accuracy. But unlike atomic clocks, a thorium-based nuclear clock could be a completely solid state device (the best atomic clocks use trapped atoms or ions cooled to cryogenic temperatures).
As a result, nuclear clocks could be much easier to operate outside of metrology labs, where they could find a wide range of applications including precision measurements of Earth’s gravitational field. What is more, because the frequency of such a clock is defined by nuclear forces it could be used to identify physics beyond the Standard Model of particle physics.
The idea of a thorium-229 nuclear clock was first proposed in 2003, but it proved very difficult to make accurate measurements of the frequency of the light involved in the clock transition – something that is key to the development of a clock.
This year, the research has accelerated and now Ricky Elwell of the University of California, Los Angeles and colleagues are the second group to use a laser to excite the clock transition in thorium-229 nuclei embedded in a crystal lattice. What is more, the precision of their measurement of the transition frequency is about an order of magnitude better than that of the German and Austrian team.
Ewell and colleagues report their measurements in Physical Review Letters and the science writer Rachel Berkowitz has written an accompanying piece in Physics. She points out that the team has found that the crystal appears to affect the transition – which could be important for the development of nuclear clocks.
Connexion
