Low-level sea clouds can make offshore wind farms more efficient, say researchers at the University of Twente in the Netherlands. This increase in efficiency is due to atmospheric mixing effects that shrink the wake of slower air behind nearby turbines, and the team say it could help wind farm designers make the most of ambient conditions.

Scientists have known for decades that multiple wind farms can be significantly less efficient than a single, isolated one. This is because air slows down as it moves through turbine blades, creating a wake that impairs the performance of wind farms downstream. This slow-air wake may extend for tens of kilometres, and in extreme cases it can even stretch beyond 100 km. “How quickly the wake recovers depends on how effectively atmospheric mixing pulls air from the stronger wind above and on the sides,” explains Davide Selvatici, a physicist who co-led the research with his colleague Richard Stevens.

In their latest study, which appears in PRX Energy, Selvatici and Stevens show that the presence of low-level stratocumulus clouds can enhance this mixing via a process called radiative cooling. This occurs when air at the top of a cloud radiates heat into space and becomes cooler, much like the ground does on a clear night. Because cooler air is denser than the surrounding air, it sinks, generating an enhanced downward motion that intensifies atmospheric turbulence. This ongoing mixing helps sustain the cloud by drawing moisture up from the surface below.

Fully three-dimensional simulations

To piece together this picture, Selvatici and Stevens needed to accurately model the turbulence in cloud tops and the way that air flows through a wind farm. They used large-eddy simulations to study how low-lying clouds impact the length of a wind farm’s wake. They also performed high-resolution simulations of stratocumulus-topped boundary layers across a range of atmospheric conditions: clear skies, cloudy skies without radiative cooling; and cloudy skies with radiative cooling.

These simulations are fully three-dimensional, and Selvatici explains that creating them meant solving equations within the model to determine how wind moves in all three directions, while also incorporating changes in temperature, water vapour and liquid water suspended within the cloud. For this, they relied on the Navier-Stokes equations (the standard equations used to describe the movement of fluids such as air) with some modifications. “We use an extended set of equations to include the effects of heat and moisture and to represent the energy and momentum extracted by the wind turbines under local wind conditions,” Selvatici explains.

“Effects can be significant”

The pair’s results indicate that the effects of cloud-top cooling can be significant. When these effects are present, the mean wind speed within a wake returns to approximately 90% of the incoming wind speed about 17 km beyond the end of the wind farm. In simulations without cloud-top cooling, however, the mean wind speed remained below 90% even 32 km beyond the end of the farm.

“Clouds are inherently coupled to the atmosphere, making it difficult to isolate their effects, but by comparing simulations with and without cloud-top cooling, we identified cloud-top cooling as an important process for wind farm wake recovery,” Selvatici explains.

Since wind farm power production increases with the cube of wind speed, even a modest reduction in wind speed can have a considerable effect, he adds. The problem is that most existing wind-farm models either simplify cloud-related processes or exclude them altogether. “Our results demonstrate that these should be taken into account,” says Stevens, “particularly in regions with frequent low-level clouds as over the North Sea, where many wind farms are found and where the annual cloud coverage is higher than 30%.”

Stevens adds that a better understanding of these effects could improve wind farm design and inform how far individual wind farms should be placed from each other. However, Selvatici notes that they’re not yet able to offer definite practical advice. “We cannot conclude whether wind farms should indeed be placed closer together in cloudy regions because our simulations represented idealized conditions,” he says.

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In a finding that could reshape how ophthalmologists think about one of the most delicate complications of corneal surgery, a team of computational engineers has built the first detailed computer model of a human eye in which the Descemet membrane—the paper-thin basement layer at the back of the cornea—has become detached. By simulating the fluid–structure interaction between the aqueous humor sloshing inside the eye’s anterior chamber and the flexible, detached membrane itself, the researchers have produced quantitative predictions about the mechanical stresses such a detachment imposes, and about how different transplanted corneas might alter those stresses during post-operative thermal therapy.

The study, published in the Annals of Biomedical Engineering, addresses a long-standing blind spot in ocular biomechanics. Detachment of the Descemet membrane is a recognized complication of cataract surgery, corneal transplantation and certain corneal dystrophies, and it can cause significant corneal swelling and vision loss if the membrane does not reattach. Yet most previous computational examinations of the anterior chamber have treated the eye’s interior as rigid-walled plumbing, focusing on fluid flow or heat transfer while excluding the complex two-way coupling between the intraocular fluid and the fragile ocular structures suspended within it. The new work changes that by modeling the detached Descemet membrane as a deformable, elastic solid that bends, stretches and deforms under the pressure and shear of the aqueous humor flowing around it.

The researchers, led by Ammar I. Alsabery of the Islamic University in Najaf, Iraq, together with colleagues from the University of Basrah, King Khalid University in Saudi Arabia, Saveetha School of Engineering in India, and Universiti Kebangsaan Malaysia, employed a coupled numerical scheme that solves simultaneously for the buoyancy-driven flow of aqueous humor and for the structural deformation of the membrane. The geometry represents the anterior chamber—the fluid-filled space between the cornea and the iris—with a warm region corresponding to the lens contact zone held at an isothermal hot temperature, mimicking the thermal gradients that arise in ocular warming therapies and in normal physiological conditions.

At the heart of the analysis is the Rayleigh number, a dimensionless parameter that governs the strength of natural convection: warmer, less dense fluid rises while cooler fluid sinks, generating circulating currents within the chamber. The team varied the Rayleigh number across three orders of magnitude, from 10³ to 10⁶, which corresponds to temperature differences spanning from a fraction of a degree to 250 Kelvin. This range deliberately encompasses both the mild thermal gradients present in the living eye and the much more aggressive temperature differences applied during clinical thermal therapy of the cornea, allowing the same model to speak to both resting physiology and active treatment.

Equally central to the study is the elasticity modulus of the detached membrane. The researchers swept this property across nine orders of magnitude, from 10⁸ to 10¹¹, a range designed to represent everything from highly compliant, freshly detached tissue to the much stiffer mechanical character of donor corneal tissue used in transplantation. Because the Descemet membrane’s stiffness varies with age, disease state and surgical history, this parametric approach lets the model answer a question that clinicians genuinely care about: does the type of cornea grafted into a patient change the mechanical load experienced by a detached membrane during recovery? The answer, according to the simulations, is nuanced. The cornea type does affect the stress imparted on the detached Descemet membrane, but it does not affect the thermal characteristics of the anterior chamber or the overall displacement behavior within it. In other words, stiffer transplanted tissue changes the mechanical environment at the membrane itself without appreciably altering the convective heat transfer patterns of the aqueous humor circulating beneath it.

The fluid dynamics of the anterior chamber turned out to be far more sensitive to geometry than to tissue stiffness. One of the most striking results concerns the iris, the pigmented diaphragm whose length in the model determines the extent of the hot, isothermal contact region associated with the lens. When the team simulated a shrinkage of the iris—effectively reducing the length of the contacting part of the lens held at the hot temperature—they found that the convective thermal characteristic of the anterior chamber rose by approximately 78 percent. This dramatic enhancement arises because the reduced iris length reshapes the buoyancy-driven circulation cells, allowing warmer fluid to travel more freely and exchange heat more efficiently with its surroundings. For clinicians, the implication is that the geometry of the anterior chamber, shaped in part by the iris and the lens, is a first-order determinant of how heat is distributed during thermal therapy, potentially more important than the material properties of the graft itself.

The temperature difference applied during thermal therapy also proved to be a powerful lever. Raising the applied thermal gradient from 2.5 Kelvin to 25 Kelvin—a tenfold increase—promoted heat transfer within the anterior chamber by 47.6 percent. While the scaling is sublinear rather than directly proportional to the temperature difference, the result confirms that modest increases in therapeutic temperature can yield meaningful gains in convective heat delivery without requiring a hundredfold jump in applied thermal load. The finding offers a quantitative framework for calibrating thermal treatments of the anterior segment: therapy protocols could, in principle, be tuned to achieve target heat transfer rates while respecting the narrow thermal safety margins of living ocular tissue.

Technically, the simulations belong to a class of problems known as fluid–structure interaction, or FSI, in which the fluid equations and the solid mechanics equations are coupled and solved together rather than in isolation. In this case, the aqueous humor—an essentially water-like fluid—drives natural convection under the influence of gravity, while the detached Descemet membrane responds to the pressure and viscous stresses exerted by that flow. The membrane’s deformation, in turn, modifies the shape of the fluid domain, feeding back into the flow field. This two-way coupling is computationally demanding but essential, because a rigid-wall approximation would entirely miss the bending and displacement of the detached membrane, along with the localized stress concentrations that could determine whether the membrane reattaches, tears further, or remains stable during healing. The methodology builds on the team’s earlier FSI studies of flexible fins, baffles and partitions in convective systems, as well as their prior work applying FSI modeling to blood flow in abdominal aortic aneurysms under thermal treatment, adapting those engineering tools to the peculiar geometry and physiology of the human eye.

The choice to represent the detached Descemet membrane as a flexible structure rather than a fixed boundary is what gives the study its clinical bite. Prior models of aqueous humor flow, including foundational work on fluid flow in the anterior chamber of the human eye published decades ago, captured the buoyancy-driven currents but assumed static, impermeable walls. By letting the membrane move, the new simulations capture the interplay between hemodynamics-like fluid loading and tissue compliance—precisely the interplay that governs how a detached membrane flutters against the aqueous humor, how stresses concentrate at its edges and attachments, and how different graft stiffnesses redistribute those stresses across the corneal structure. The team’s results suggest that surgeons and biomaterials scientists selecting corneal grafts for patients prone to Descemet membrane detachment could use stress predictions of this kind to weigh graft stiffness as part of the decision, even though the overall thermal environment of the chamber will remain largely unchanged.

Beyond transplantation, the model has direct relevance to thermal therapy of the eye, a class of treatments in which controlled warming is applied to manage conditions of the anterior segment. Because the simulations connect an easily controlled clinical variable—the applied temperature difference—to a measurable outcome in convective heat transfer, and because they quantify the role of iris geometry in shaping the thermal flow field, they provide a template for patient-specific treatment planning. A clinician armed with imaging of a patient’s anterior chamber geometry could, in principle, use models of this type to predict how a planned thermal protocol will distribute heat in the presence of a detached membrane, and whether the resulting stresses on the membrane fall within tolerable limits.

The work is not without its simplifications, as the authors themselves frame the study as an evaluation of corneal transplantation processes rather than a complete clinical simulator. The anterior chamber geometry is idealized, the aqueous humor is treated with standard transport properties, and the elasticity modulus range, while broad, samples the problem in parametric steps rather than matching every individual patient’s tissue. Real eyes also feature aqueous production and drainage, blinking, saccadic motion and ocular pulse effects that a steady natural-convection FSI model does not capture. Nonetheless, the paper’s central contribution—demonstrating that corneal stiffness governs membrane stress while iris geometry and thermal gradient govern heat transfer—stands as a clean separation of effects that future, more detailed models will need to reproduce.

The research was supported by the Universiti Kebangsaan Malaysia Research Grant GP-2024-K006388 and by the Deanship of Research and Graduate Studies at King Khalid University through a large Research Group Project. As computational biomechanics continues to migrate from engineering journals into clinical planning, studies like this one mark a shift toward treating the eye not as a static optical instrument but as a living, deformable, fluid-filled machine—one in which a membrane thinner than a human hair can dominate the mechanical conversation, and where the difference between a compliant and a stiff cornea may one day inform the surgeon’s graft choice.

Earthquakes that propagate at higher speeds make the ground move more than it would in slower but otherwise comparable earthquakes, say geophysicists. Using physics-based models, Mohamed Abdelmeguid and colleagues at the California Institute of Technology in the US showed that so-called “supershear” ruptures produce stronger and longer-duration ground motion than equivalent subshear ruptures. Because models of ground motion that underpin infrastructure standards do not account for this effect, these models may need to be updated to accurately describe hazards such as the 2025 Myanmar earthquake, which produced supershear ruptures in both directions.

Geophysicists have identified two categories of earthquake based on how fast their ruptures propagate through the Earth’s crust. Shear waves, or S waves, travel at certain expected velocities (the shear-wave velocity) depending on the stiffness and density of the ground. When a rupture travels faster than the shear-wave velocity of the surrounding ground, it is termed a supershear earthquake. Otherwise, it is subshear.

Although Abdelmeguid notes that supershear ruptures were first predicted theoretically in the 1970s, and have subsequently been observed in both laboratory experiments and the real world, most previous studies focused on their underlying mechanisms and the transition from subshear to supershear. The new study, which appears in the Bulletin of the Seismological Society of America, goes a step further by examining how the ground motion in a supershear quake differs from that of an otherwise comparable subshear one. The question is relevant, Abdelmeguid says, because nearly 36% of strike-slip earthquakes during the past 15 years contained supershear rupture, yet existing models do not factor it in.

Supershear simulations

To address this gap, Abdelmeguid and colleagues developed a dynamic rupture model that generates simulated ground motion data and used it to identify the characteristics of supershear earthquakes. They found that prolonged supershear propagation produces what they term “a distinct spatial pattern of stronger and longer-duration shaking”. However, episodic supershear segments, where rupture speed intermittently changes between supershear and subshear, produce ground motion similar to subshear ruptures.

Simulations like these are important because some supershear rupture scenarios are poorly represented in the observational record. This record is used to develop ground motion models, so simulations can “reveal physical dependencies that may not be apparent from existing observations,” Abdelmeguid says.

Characterizing the 2025 Myanmar earthquake

The 2025 Myanmar earthquake – a supershear quake in which many regions experienced higher than expected ground shaking – is a case in point. It occurred on the 1200-kilometre-long Sagaing Fault, which lies at the boundary of the Burma microplate and the Sunda plate and is not far from Mandalay, the country’s second-largest city. At magnitude 7.7, it was the largest earthquake in Myanmar in over a century, and the long rupture meant that large parts of Myanmar and Thailand were affected, with thousands of deaths and injuries as well as severe damage to infrastructure.

Initial studies were inconclusive about whether this earthquake’s rupture exhibited intermittent or sustained supershear speed. This lack of consensus is partly because recording intermittent supershear rupture is challenging when near-fault sensors are sparse, as is the case in Myanmar (and indeed most countries, with notable exceptions such as Japan, Taiwan, New Zealand and parts of the US).

A new study published in PNAS addresses this question. Using satellite earth observations, teleseismic data and CCTV footage as well as the available near-fault seismic sensor data, researchers led by Lingling Ye at the Southern University of Science and Technology (SUSTech) in China modelled the rupture process of the Myanmar quake. The result, Ye says, is a “well-resolved rupture process” that “reveals previously unrecognized dynamic rupture features”. Notably, the team’s simulations showed that the rupture transitioned between supershear and subshear as it tore through around 460 kilometres of the country.

Influence of geometry and stress distribution

To understand the cause of these variations, the researchers examined the geometry and stress distribution along the fault. Based on an existing fault model, they calculated a parameter called fault misalignment, which acts as an indicator for irregularities in the fault geometry. Higher fault misalignment, for example, indicates higher bends and branches in the fault.

When the researchers overlaid fault misalignment with the observed rupture speed, they noticed that supershear speeds coincided with fault stretches that had lower misalignment. For fault stretches with higher misalignment, subshear speed prevailed, meaning that the rupture decelerates at locations with high fault misalignment, transitioning from supershear to subshear. The researchers also found that the rupture speed, whether supershear or subshear, responded to the varying levels of local stress, with higher stress levels inducing faster rupture speed.

Although not unique in exhibiting supershear behaviour, the 2025 Myanmar earthquake rupture propagated away from the epicentre on both sides, travelling around 80 kilometres to the north and 380 kilometres to the south. Initial studies debated whether the ruptures on both sides were supershear. The researchers found that the northern rupture propagation was not supershear and claim that its shorter rupture length is caused by a combination of the fault’s complex structure and low accumulated stress resulting from the magnitude 6.8 earthquake that struck in 2012.

“Every earthquake has unique behaviour”

In future work, Ye is eager to revisit the 2023 Turkey doublet earthquakes, which she says have many more near-fault strong motion observations than the 2025 Myanmar quake, as well as a now well characterized complex fault system. “Every earthquake has unique behaviour,” she says. “Determining the key features that control their rupture processes is still underway.”

For Abdelmeguid, who recently started his own research group at the University of Houston, US, understanding these complex rupture processes is important because it will ultimately improve our understanding of geophysical processes and the ground motion models that are used for engineering applications. “We are currently extending this work to examine ground motions generated by ruptures on more complex faults, including cases in which fault geometry and heterogeneity influence both ground motion and the dynamic process, as observed during the multiple earthquakes,” he tells Physics World.

• This article was amended on 2 September 2026 to clarify the nature of the rupture propagation in the 2025 Myanmar earthquake. The researchers found that the northern rupture was subshear, not supershear as originally stated.

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Usually, when physicists want to model the merger of two black holes, they use supercomputers. Now, however, physicists in the US have found a possible shortcut. In a study published in Physical Review Letters, they show that, of the final states permitted by energy and angular momentum, the remnant of a non-spinning black hole merger ends up in a state quite close to one that maximizes the system’s entropy – a surprising and puzzling result that reinforces the deep connection between thermodynamics and black holes.

“Our group has long believed that black hole thermodynamics could provide a new perspective on binary black hole mergers,” says team member Monica Rincon-Ramirez, a postdoctoral researcher at Pennsylvania State University. “While black hole thermodynamics is well established for equilibrium systems, much less is understood in the highly dynamical regime of mergers.”

Merging black holes

Black hole mergers occur when two black holes that orbit each other spiral inward with increasing speed, losing both energy and angular momentum by emitting gravitational waves until they eventually converge in a violent clash. After the moment of merger, the remnant oscillates vigorously, “ringing down” into a quiescent, rotating object known as a Kerr black hole that can be described in terms of just two quantities: mass and spin.

Meanwhile, the gravitational waves – ripples in the fabric of spacetime – from this energetic collision propagate through space virtually uninterrupted. These gravitational waves encode information about their source, and when we detect them on Earth (millions of light-years away from their origin), we can use them to predict the remnant’s size and spin. However, doing this requires solving complex equations from Einstein’s general theory of relativity using computationally expensive numerical simulations.

Connecting black holes and thermodynamics

Thermodynamics is the branch of physics concerned with the relationships between energy, heat, work and temperature. For ordinary matter, thermodynamics can describe how energy flows from one system to another in simple terms, even for complex systems with numerous particles and degrees of freedom. For example, rather than meticulously tracking each individual particle, concepts such as entropy – a measure of a system’s disorder – can be used to describe the final state of the entire system.

Physicists have long known that black holes obey laws that closely parallel the laws of thermodynamics, with the event horizon and surface gravity of black holes being analogous to entropy and temperature, respectively. Building on this established connection, Rincon-Ramirez and colleagues at the University of Mississippi, the University of California, Berkeley, and Northwestern University as well as Penn State investigated whether black hole thermodynamics could go beyond describing the properties of isolated, stationary black holes and provide, in addition, a principle for determining the final state of a merger.

The maximum-entropy conjecture

After accounting for the energy and angular momentum carried away by gravitational waves, the researchers tracked the evolving mass and angular momentum of a binary, mapped these values to those of hypothetical Kerr black holes, and calculated the corresponding entropy. They found that the Kerr entropy reaches a maximum at a mass and spin strikingly close to the final mass and spin predicted by numerical relativity simulations. Indeed, the two methods agreed with each other to within a few percent. “The Kerr entropy turned out to be remarkably meaningful for the binary system as a whole,” Rincon-Ramirez says.

Interpreting and presenting these results proved to be a challenge, however. “What we found was completely unexpected,” says Rincon-Ramirez. After deliberating among themselves as to why the final black hole’s parameters should lie so close to those of the maximum-entropy black hole, they ultimately chose to extend the conversation to the scientific community. By presenting their puzzling results and a broad conjecture, which they term the “maximum entropy conjecture for black hole mergers”, they hope to sharpen their findings through rigorous testing and eventually place them on a firm mathematical foundation within general relativity.

In the meantime, the researchers plan to extend their conjecture to more general binary black hole systems. By studying systems such as highly spinning and eccentric binaries, they hope to gain further understanding of the role of thermodynamic quantities in general relativity. “Ultimately, we hope this work will contribute to a more complete thermodynamic framework for highly dynamical spacetimes,” Rincon-Ramirez says.

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“Solar towers” that convert sunlight into heat could play a useful role in the renewable energy transition, but high installation costs and complex requirements limit their attractiveness to commercial operators. A team of researchers from Germany’s Karlsruher Institut für Technologie (KIT) and the German Aerospace Center (DLR) is now taking steps to change that. By creating a freely accessible database of information about how these plants work, they aim to accelerate research on solar thermal energy and drive improvements that could allow the technology to be more widely deployed in the future.

Unlike photovoltaic panels, concentrating solar power (CSP) plants do not convert sunlight directly into electricity. Instead, they generate heat by using an array of movable mirrors called heliostats to funnel sunlight onto a receiver located at the top of a tower. This heat can be used to drive a turbine to produce electricity immediately, but it can also be stored and used to generate electricity at night or on cloudy days. Depending on the plant’s location and setup, the heat could even be used directly for industrial applications and district heating.

The problem, explains study leader Kaleb Phipps, is that operating solar power tower plants safely and efficiently is a complex and expensive task. “CSP technologies have the potential to help the transition to a renewable energy system,” says Phipps, a research fellow at KIT’s Scientific Computing Center. “However, they are still not financially viable and there are operating challenges associated with them.”

Before researchers can develop and reliably test new, improved processes, Phipps explains that they need access to real-world operational CSP data. “We believe that modern data-driven machine learning methods like ours can help solve a lot of these problems,” he says.

849 gigabytes of operational data

To construct their database, which is known as PAINT, researchers collected data from the CSP tower near Jülich, Germany. These data include the exact positions of the tower’s 2014 mirrors, their dimensions, how they are warped and the way they rotate and tilt. The team also obtained fine-grained weather data for the entire 2021-2024 period under study, plus a further 218 000 images to help determine whether the mirrors were efficiently directing sunlight precisely to the top of the tower.

All in all, the PAINT database contains 849 gigabytes of operational data organized using the SpatioTemporal Asset Catalog (STAC) standard. To make these data FAIR (findable, accessible, interoperable and reusable), the researchers developed software to simplify access to the database and then published the data in a way that is freely available to all users.

Their goal, they say, is for other researchers to use this FAIR database to develop “digital twins”, or virtual replicas, of real-world CSP plants. When combined with machine-learning models, such twins can be used to answer questions such as whether the mirrors are aligned for maximal light absorption (one of the most important parameters for efficient operation) in near real time.

Community reaction

“The fact that we are receiving many positive responses regarding the data and that people seem to appreciate it is our biggest success,” Phipps says. Such responses are especially gratifying, he adds, because constructing databases like PAINT can be an arduous task.

“The main difficulties were about collecting the data, cleaning and unifying it into standard formats and parsing and organising all the metadata, which was originally complete chaos,” Phipps recalls. “We therefore put a lot of time and effort into creating standardized and automated workflows so that the process is as transparent as possible and can be reused for future data.”

The team also faced challenges when trying to convince peers that this work counted as “research”, he adds. “The fact that the data itself didn’t directly result in a new algorithm or method meant that lots of people didn’t believe we would be able to publish the results or achieve anything with them,” says Phipps. “Luckily, we were able to prove the doubters wrong.”

While the PAINT database currently contains data from only one CSP, the KIT researchers, who report their work in Nature Energy, are hoping to expand it. “We really need contributions from other CSP power plants around the world to transform the database into a truly international and diverse source for researchers,” Phipps says. “As data from different facilities is added in the future, it will be possible to develop a common standard for open operational data in solar tower research. This would speed up the development and promote a widespread adoption of this technology.”

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Along the vast ocean floor lives a species of glass sponge known as Venus’ flower basket. Though delicate-looking,

Et si les femmes et les hommes ne vivaient pas leurs rapports sexuels de la même manière ? Une nouvelle étude révèle des écarts frappants sur le plaisir, la satisfaction et même la durée perçue des rapports.

The movie "The Matrix" prompts reflection on reality being a simulation. While science can't disprove this idea, it raises philosophical questions. Evidence suggests our understanding of the universe may be limited to an illusion created by a higher power.