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Where do thunderstorms form?

The amount of moisture in soil – and the way this moisture is distributed – combined with wind patterns in the lowest few kilometres of the atmosphere can influence where thunderstorms begin and how they develop. This new finding, from researchers at the UK Centre for Ecology and Hydrology (UKCEH) could help in the development of new early warning systems for such events, which are increasing worldwide and becoming more intense and dangerous as the climate warms.

Thunderstorms can develop quickly on hot afternoons, sometimes in less than half an hour of clouds building up, but predicting where they originate can be difficult.

A team of researchers led by meteorologist Christopher Taylor has now discovered that patches of dry soil 10–50 km across can combine with the wind field and affect how quickly convective storm clouds (cumulonimbus) form and grow.

“We already knew that differences in wind speed and direction with height (the ‘vertical wind shear’) in the atmosphere are critical ingredients for severe storm development, whilst gradients in land surface heating across the landscape can induce weak winds near the ground,” explains Taylor. “These two elements are usually studied separately, but we put them together and found that convective clouds grow very rapidly when the winds that steer them, some 3–4 km above the ground, oppose local surface-generated winds near the ground.”

This combination, he says, effectively increases the supply of moist, buoyant air into a cloud, accelerating the updraughts responsible for lightning and heavy rain.

“Storm initiations are clearly favoured in specific locations”

The result, he explains, challenges conventional thinking that over flat terrain, where cumulonimbus first develop, is essentially random. “In fact, under the conditions we studied – across sub-Saharan Africa – storm initiations are clearly favoured in specific locations, based on a combination of soil and wind conditions on that day.”

The work, which is detailed in Nature, could help in the development of more localized storm forecasting, he says, particularly in tropical areas where soil moisture gradients and wind shear are strong and can lead to flash flooding, lightning and strong winds.

The UKCEH team obtained its result by studying satellite images of 2.2 million afternoon storms in 2004–2024. They were able to obtain high-resolution data from the images and so observe fine-scale details of the wetness of soils.

The principle they have identified would be applicable to predicting thunderstorm formation in other parts of the world, such as Asia, the Americas, Australia and Europe – and not just the worst-hit tropical regions in Africa.

Ground-based measurement networks are scarce in Africa

Taylor and colleagues say they have been working with meteorological services in Africa for the last few years and contributing to international efforts to provide early warning systems for severe storms. Convective storms can be particularly damaging in built-up urban areas with intense rainfall damaging infrastructures such as roads and sanitation systems. “Unlike in the UK, where ground-based measurement networks are the backbone of weather forecasting, they are scarce in Africa and there are only a handful of meteorological radars here, explains Taylor. “We therefore had to rely on satellite data, which provide good quality information on some aspects of the coupled land-atmosphere system – notably the temperature (and therefore the height) of clouds and estimates of moisture in the top few centimetres of the soil.”

From this information, the researchers inferred how soil moisture affects evapotranspiration and atmospheric heating, how pressure gradients created by these heating patterns affect winds locally and, finally, how these inferred local winds interact with growing convective clouds.

The insights gleaned from this study could help improve the accuracy of short-term weather forecasts by providing a better indication of where storms are likely to appear within a region, Taylor says. “Just how much more skilful a forecast will be is an open question, but we have good reason to believe that in parts of Africa it could provide a big advance. In general, weather forecasting is a rapidly evolving field thanks to AI, and so the translation from research finding to application could be rapid.”

The researchers say they are now starting to look at how weather forecast models depict the processes described in their work. “Early indications suggest that models solving physical equations on a fine enough grid (of around 4 km) can capture the relationships between soil moisture, wind shear and cloud growth, but operational weather forecast models will require more accurate information on spatial variations of soil moisture to produce better forecasts,” says Taylor.

“We are also looking at how predictive models based on deep learning can exploit the new knowledge to provide forecasters with early indications of where storms may appear later in the day,” he reveals.

Researchers from China dominate IOPP outstanding reviewer awards

More than 1600 researchers from 74 different countries have won “outstanding reviewer awards” from IOP Publishing, with researchers from China making up almost a third of awardees. The annual award recognises scientists who have delivered exceptional peer-review reports for IOP Publishing journals over the past year.

Reviewer feedback to authors plays a crucial role in the peer-review process, boosting the quality of published papers for the benefit of authors and the wider scientific community. Awards such as those from IOP Publishing are an attempt by publishers to raise the importance of courteous and constructive peer review.

This year’s recipients were selected from about 35,000 reviewers who submitted peer-review reports to IOP Publishing journals in 2025. Journal editors evaluated nominees based on the volume, timeliness and quality of their reviews.

A total of 1621 individuals have been honoured with a 2025 award. China makes up 30% of awardees followed by 16% from the US and just over 6% from India. Some 10% of this year’s award winners are also based in lower middle-income countries or territories.

“High quality peer review is essential to maintaining trust in science as it safeguards the quality and integrity of academic work,” notes Laura Feetham-Walker, IOP Publishing’s reviewer engagement manager. “I’d like to thank this year’s winners, whose thoughtful and rigorous reviews help advance scientific discovery and strengthen the communities we serve.”

The IOPP’s outstanding reviewer programme has been awarded annually since 2016. The IOPP also recently introduced a peer review excellence certification programme that provides free peer review training and certification. In 2025, more than 1500 reviewers took the initiative.

Quiz of the week: how many antiprotons did CERN transport by truck?

 

Fancy some more? Check out our puzzles page.

Magnetic friction defies centuries-old law

Through new experiments with magnetic materials, physicists in Austria, Hong Kong and Germany have overturned a simple law of friction that has held for over 300 years. Led by Clemens Bechinger at the University of Konstanz, the team’s discovery shows how internal collective dynamics in these materials can cause friction to peak at a certain applied, load before dropping sharply. The effect could prove especially promising in applications where friction needs to be precisely controlled.

In 1699, French physicist Guillaume Amontons published his rediscovery of an effect first observed by Leonardo da Vinci: that the force of friction between two sliding surfaces is proportional to the load pressing them together. He also showed that this relationship is monotonic, meaning friction continues to grow as the load increases, forcing stronger interactions between the surfaces.

Since then, Amontons’ law has held up to close experimental scrutiny. “It is actually quite remarkable that this simple law holds across a wide range of very different materials,” Bechinger says. “At the same time, this classical picture does not account for systems where internal degrees of freedom – such as magnetic order – play an active role.”

Little microscopic insight

For all its success, Amontons’ law offers little insight into the microscopic mechanisms underlying friction. To probe these mechanisms, many studies have turned to atomic force microscopy, which measures the motion of a nanoscale tip as it is scanned across a surface. While powerful, this technique can only capture frictional mechanisms over extremely local regions. As a result, it is less well suited to systems where friction emerges from larger-scale effects.

In particular, magnetic materials host regions of aligned atomic spins that can extend across millimetres. When two magnetic surfaces slide past each other, these spins continuously reorient in response to their changing interactions. However, this reconfiguration isn’t instantaneous.

Famously, magnetic systems can display hysteresis, whereby a material’s response to an external magnetic field depends to the history of its magnetization. For two interacting magnetic surfaces, hysteresis means that spin realignments to lag behind the sliding motion, causing the system to undergo repeated cycles of delayed switching. In the process, the kinetic energy of the sliding motion is partly dissipated, increasing the overall friction experienced by the surfaces.

To explore these effects in more detail, Bechinger’s team developed a new experimental platform that moves beyond the constraints of conventional techniques. Instead of applying a load directly, they varied the interaction strength between two extended magnetic surfaces by precisely controlling their separation distance.

Monitoring magnetization

“Using millimetre-sized rotatable magnets, this allowed us to directly monitor the orientations of their magnetization during sliding, and to correlate these changes quantitatively with the measured friction force,” Bechinger explains.

As the surfaces were brought closer together, the researchers observed that friction initially rose, in line with the expectations of Amontons’ law. However, this trend did not continue indefinitely: at an intermediate separation distance, friction reached a maximum.

“A peak occurs when competing magnetic interactions drive the system into a frustrated state,” Bechinger continues. “This causes repeated, hysteretic switching of magnetic orientations during sliding, which strongly enhances energy dissipation.”

Beyond this point, the effect was weakened by further decreases in separation distance, and friction dropped sharply: a clear departure from the monotonic behaviour predicted by Amonton’s law.

Altogether, the team’s findings show that friction can arise entirely from the internal collective dynamics of the material, rather than from direct mechanical contact alone. As Bechinger explains, the ability to tune these effects could open up new technological possibilities.

“This opens up new possibilities for designing wear-free, contactless frictional systems and suggests that friction itself can serve as a sensitive probe of microscopic ordering,” he says. “Potential applications could range from magnetic sensing to programmable metamaterials.”

The research is described in Nature Materials.

Word wave puzzle no.1

  1. Enter a word guess – in this game the word has six letters.
  2. After submitting your guess, each letter in the guessed word is coloured to provide feedback:
    • Green: The letter is correct and is in the correct position in the target word.
    • Yellow: The letter is correct but is in the wrong position in the target word.
    • Grey: The letter is not in the target word at all.
  3. Using this colour feedback, refine your next guess.
  4. Continue guessing until you correctly identify the hidden word(s) or run out of attempts.

If you need any hints, read our news article here.

Fancy some more? Check out our puzzles page.

How IOP Publishing cut its carbon footprint by 36% since 2020

My guest in this episode of the Physics World Weekly podcast is Liz Martin, who is sustainability lead at IOP Publishing. We chat about how the scholarly publisher has reduced its carbon emissions by 36% when compared to a 2020 baseline – and the challenges and opportunities for achieving further reductions.

Martin talks about the importance of cooperation and partnerships – both internal and external – to achieving environmental goals. This includes engaging with both suppliers and employees on how to reduce carbon emissions.

IOP Publishing is a wholly owned subsidiary of the Institute of Physics, which is the professional body and learned society for physics in the UK and Ireland. It produces over 100 scholarly journals, around half of which are published jointly with or on behalf of partner societies and research organizations. Physics World is also brought to you by IOP Publishing.

  • You can download a PDF of IOP Publishing’s Sustainability Report 2025 here.

Many-body effects at the world’s largest physics conference

Many-body physics is the study of large ensembles of interacting particles and their collective behaviour. These systems are notoriously difficult to simulate, yet they underpin phenomena such as superconductivity and superfluidity. Thus, they are of great interest to understand. As a many-body physicist myself, I arrived at my first American Physical Society (APS) meeting with a different curiosity: understanding what the largest physics conference in the world was all about.

Last week, I joined a crowd of 14,000 scientists convening in Denver, Colorado for the annual Global Physics Summit, hosted by the APS.

On Sunday morning, the day before the conference, I walked alone through the streets of downtown Denver. Silence filled the frigid air. A light flurry of snow covered the empty streets in white. It seemed that the city was still asleep.

But Denver was abruptly awakened on Monday morning, as I found myself well-accompanied by the crowd collectively moving towards the Colorado Convention Center for an 8 a.m. start. Inside, the conference was humming with its own emergent dynamics, with lines forming around coffee stations and people bustling to find their way to wherever they were going.

Throughout the day, I was faced with the repeated indecision of choosing between over 80 simultaneous sessions. Some sessions housed APS’s infamous blitz talks with speakers racing to pack as many graphs and equations into their allotted 10 min. Having barely enough time to write down the takeaways, I tried, often in vain, to fill my memory as quickly as possible.

Other sessions featured longer talks on hot topics in physics. By evening, my mind was swimming with notions of scalable quantum computing and physics funding issues and public engagement opportunities and the infiltration of AI slop into every corner of the scientific process. These sessions offered me a necessary reminder that science is not performed in a vacuum. With that said, the purely technical sessions on ultracold atomic gases served as a necessary reprieve for me that day.

Ultracold atoms, cooled to only a fraction of a degree above absolute zero, provide physicists with a clean and controllable platform for studying quantum many-body physics. At its heart, this physics is governed by interparticle correlations.

Seeing single atoms
Seeing single atoms A fluorescence image taken under a quantum gas microscope. Each dot is one atom (Courtesy: Candice Chua)

During my PhD, we measured two-body correlations and observed bosons spatially bunching together—unlike their antisocial fermionic counterparts. While the stereotypical physicist may be notoriously antisocial, the APS lanyard seemed to overturn that reputation.

Over dinner one evening, I requested a table for one. Only a moment later, I was joined by a physicist I’d never met before, and the evening unfolded behind pleasant chatter of 2D materials and the lack of vegetables in our travel diets.

Two tables down sat a professor whose work I admired. I’ll admit that I embarrassingly (or, more favourably, courageously) walked to the washroom so that I could pass by his table and say hello. I had met him once last year, but he didn’t remember me. So, I kept talking until he agreed that he remembered, and that it was nice to run into each other again. Whether true or not, I accepted it as a win. Without an APS lanyard, I probably would have avoided that conversation.

Single-atom resolution

On Thursday, a session titled “Novel imaging and quantum sensing technologies” caught my eye since I work with a quantum gas microscope. The microscope is a high-magnification imaging system that affords us the resolution of individual atoms. The microscopic information is far richer than what is obtained by a bulk imaging technique such as absorption.

Similarly, at the conference, I found the greatest value in individual conversations. Conversing with employees at the career fair, though exhausting, was far more effective than listening to panels on how to plan for careers that I couldn’t decide if I wanted.

By the end of the week, I started to recognize people I had already met over the few days prior. I saw every reunion or simple “Oh! Hi” as miraculous rather than a given, based on the size of the conference. People shared with me their personal journeys navigating the hardships and uncertainties of today’s world, others about the trade-offs and uncertainties in their experimental results. Some of the most fulfilling and deeply human conversations were the spontaneous ones that arose outside the doors of sessions that we had meant to be in.

When Friday rolled around, the city emptied as quickly as it had filled. For me, I retreated into the sunny Boulder mountains, mulling over the lingering resolution of singular people whose shared words and ideas were now intertwined with my own. Ignoring my fear of getting lost, I followed my instincts deeper into the dry heat of the afternoon, one step at a time.

Pressure quench increases superconducting transition temperature

Could a new pressure quenching technique help researchers move forward on the road to reaching room-temperature superconductivity? Researchers at the University of Houston are pinning their hopes on this approach and say they have already used it to achieve a record-high superconducting transition temperature (Tc) of 151 K at ambient pressure in a metastable phase of HgBa2Ca2Cu3O8+δ (or HBCCO) The phase remains stable for around at least three days when held at 77 K, although its Tc degrades when heated to above 200 K.

Achieving ambient-pressure room-temperature superconductivity remains the holy grail for scientists working in this field. This is because superconductors that work at ambient temperatures and pressures could revolutionize a host of application areas, including increasing the efficiency of electrical generators and transmission lines through lossless electricity transmission. They would also greatly simplify technologies such as magnetic resonance imaging (MRI) that rely on the generation or detection of magnetic fields.

While much progress has been made in the last decades, increasing the Tc often relies on squashing materials at extremely high pressure – usually in a device known as a diamond anvil cell (DAC). Some examples include the sulphide material H3S, which has a Tc of 203 K when compressed to pressures of 150 GPa and the cerium hydrides, CeH9 and CeH10, which boast high-temperature superconductivity at lower pressures of about 80 GPa with a Tc of around 100 K.

HBCCO is a high-temperature superconducting cuprate that has a Tc of 133 K at ambient pressure. This can be pushed to 164 K by applying a pressure of 31 GPa to it.

High-pressure-induced metastable superconducting phase

The high Tc of HBCCO is thought to come from the high electron density of states of a possible “van Hove singularity” associated with the two-dimensional CuO2 planes in it. In the new work, a team led by Ching-Wu Chu and Liangzi Deng of the Department of Physics and Texas Center for Superconductivity at the University of Houston decided to study a high-pressure-induced metastable superconducting phase in the material that they think might be able to form at ambient pressure as a result of this singularity (which leads to strong interactions between electrons) and/or other anomalies in the electronic energy spectrum.

To investigate further, the researchers developed a pressure-quench protocol to stabilize this metastable phase at ambient pressure. Their process involves first identifying the target phase in a DAC under high pressures of between 10–30 GPa. Next, the material is quenched (that is, the pressure is rapidly removed) at 4.2 K.

Chu and Deng confirmed that they had indeed isolated this phase and not another using synchrotron X-ray diffraction (at the 16-ID-B beamline of the Advanced Photon Source) before removing it from the cell. These measurements also show that the pressure-quenched phase at ambient pressure retains its original crystal structure, but possibly contains defects, generated under pressure and during quenching. The researchers think that these defects might help preserve the metastable high- Tc phase.

Thanks to their technique, they say they have achieved a hitherto unreported ambient-pressure Tc of 151 K.

Tiny samples

The experiments were far from easy, however, they say. The samples were extremely small (around just 50–80 microns in size), so handling them in high-pressure experiments is inherently challenging, explains Chu. Another major difficulty was preventing the electrical leads used for the resistivity measurements from breaking during the pressure-quenching process. Recovering the samples after quenching for more detailed analyses at ambient pressures was technically demanding too.

Looking ahead, the researchers say they would now like to better understand where the high Tc in HBCCO comes from – both under pressure before quenching and at ambient pressure after quenching. “We would also like to elucidate the mechanisms that lock in the high Tc phase at ambient pressure after quenching,” says Chu.

The impact of the new work, which is detailed in PNAS, might even extend beyond superconductivity, adds Deng. “Indeed, our approach could allow us stabilize quantum metastable states at ambient pressure that have enhanced or unique properties that only emerge under pressures. Based on our experimental results, using theoretical modelling and AI-driven approaches, we would like to identify different types of quantum materials that are suitable for pressure quenching.”

Researchers at CERN transport antiprotons by truck in world‑first experiment

Researchers at the CERN particle-physics lab have successfully transported antiprotons in a lorry across the lab’s main site. The feat, the first of its kind, follows a similar test with protons in 2024. CERN says the achievement is “a huge leap” towards being able to transport antimatter between labs across Europe.

Antimatter is almost identical to ordinary matter except that the electric charge and magnetic moment are reversed. But if equal amounts of matter and antimatter were created in the Big Bang, as is widely believed, they would have annihilated each other, leaving an empty universe. Physicists therefore suspect there are hidden differences that may explain why matter survived and antimatter all but disappeared.

CERN’s Baryon-Antibaryon Symmetry Experiment (BASE) experiment focuses on measuring the magnetic moment (or charge-to-mass ratio) of protons and antiprotons to search for such differences.

These measurements need to be extremely precise but this is difficult at CERN’s “Antimatter Factory”, which produces the antiprotons, due to inference from nearby equipment. To carry out more precise measurements, the team therefore needs a way of transporting the antiprotons to labs further afield.

To do so, in 2020 the BASE team began developing a device, known as BASE-STEP (for Symmetry Tests in Experiments with Portable Antiprotons), to store and transport antiprotons.

It works by trapping particles in a Penning trap composed of gold-plated cylindrical electrode stacks made from oxygen-free copper that is surrounded by a superconducting magnet bore operated at cryogenic temperatures.

The device, which also contains a carbon-steel vacuum chamber to shield the particles from stray magnetic fields, is then mounted on an aluminium frame. This allows it to be transported using standard forklifts and cranes and withstand the bumps and vibrations of transport.

In 2024, BASE researchers used the device to transport a cloud of about 105 trapped protons across CERN’s Meyrin campus for four hours.

After that feat, the researchers began to adjust BASE-STEP to handle antiprotons and yesterday the team successfully transported a trap containing a cloud of 92 antiprotons around the campus for 30 minutes, travelling up to 42 km/h.

With further improvements and tests, the team now hope to transport the antiprotons further afield. The first destination on the team’s list is the Heinrich Heine University (HHU) in Düsseldorf, Germany, which would take about eight hours.

“This means we’d have to keep the trap’s superconducting magnet at a temperature below 8.2 K for that long,” says BASE-STEP’s leader Christian Smorra. “So, in addition to the liquid helium , we’d need to have a generator to power a cryocooler on the truck. We are currently investigating this possibility.”

If possible to transport to HHU, physicists would then use the particles to search for charge-parity-time violations in protons and antiprotons with a precision at least 100 times higher than currently possible at CERN.

Heavier cousin of the proton discovered at the LHC

Researchers at the Large Hadron Collider (LHC) have discovered a new particle, the Ξcc⁺, (“Xi cc plus”), a heavier cousin of the proton. The particle’s fleeting existence had made it invisible for decades, but the upgraded LHCb detector captured it in just one year of data, opening a new window into the forces that hold quarks together.

Quarks are the fundamental building blocks of protons and neutrons, which in turn combine to form atomic nuclei. Protons themselves are made from two up quarks and one down quark, held together by the strong force. This is described by a sophisticated theory known as quantum chromodynamics (QCD). The Ξcc⁺ is unusual because it replaces the two up quarks with heavier charm quarks, keeping just one down quark.

“Up and down quarks are labels we give to distinguish the different types of quark,” Tim Gershon of the University of Warwick, told Physics World in an email. “In the Ξcc⁺, both up quarks are replaced by the heavier charm quark. Since the charm and up quarks differ only by their mass – in particular having the same charge – this provides an ideal way to test QCD,” explains Gershon who is spokesperson-elect for LHCb.

This quark content change makes the Ξcc⁺ roughly four times heavier than a proton. Its extremely short lifetime, less than a trillionth of a second, is why previous experiments could not detect it, despite the particle being produced frequently in LHC collisions.

Upgrade was crucial

“The key development that made the observation possible was the upgrade of the LHCb detector,” Gershon says. “We could observe the Ξcc⁺ in one year of data-taking, while we had not been able to do so in a decade of data collected with the original LHCb detector.”

The Ξcc⁺ appears briefly in proton–proton collisions before decaying into three lighter particles: a Λc⁺ baryon, a K⁻ meson, and a π⁺ meson. These decay further into five final particles, including a proton, two K⁻ mesons, and two π⁺ mesons. By reconstructing the trajectories of these particles, researchers saw a sharp signal corresponding to the existence of the Ξcc⁺ particle.

This observation also settles a long-standing question. Over twenty years ago, the SELEX experiment at Fermilab in the US reported hints of the particle. However, the signal could not be confirmed. The LHCb measurement provides a clear, unambiguous detection.

“Studies of particles containing two heavy quarks are very interesting for tests of the QCD binding mechanisms, and this observation provides important new data in that direction,” Gershon says.

The discovery relied on upgrades to the LHCb detector. A silicon pixel system called the Vertex Locator tracks particle paths with incredible precision, while a Ring Imaging Cherenkov system identifies particle types based on the light they emit. These improvements allow the detector to collect much larger amounts of data than before, making rare particle discoveries possible.

The discovery of the Ξcc⁺ is just the beginning. Physicists now aim to measure its properties in detail, including its lifetime and additional decay channels. Beyond this, they hope to find even heavier cousins, where one or both charm quarks are replaced by a beauty quark – called Ξbc and Ξbb respectively.

“These may be out of reach with the current LHCb detector – although we will try our best!” Gershon says. “But we do expect to be able to observe them with a future upgrade called LHCb Upgrade II. Unfortunately, the UK funding for this upgrade has recently been put in doubt due to decisions made at the UKRI funding agency. This latest result reiterates the uniqueness of LHCb – no other experiment can make these measurements – and the importance of finding a solution to be able to fund LHCb Upgrade II.”

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