Physics

CERN gears up to ship antimatter across Europe

antimatter, CERN, Physics, Science / Kelly Newman / May 19, 2025

There’s a lot of matter around, which ensures that any antimatter produced experiences a very short lifespan. Studying antimatter, therefore, has been extremely difficult. But that’s changed a bit in recent years, as CERN has set up a facility that produces and traps antimatter, allowing for extensive studies of its properties, including entire anti-atoms.

Unfortunately, the hardware used to capture antiprotons also produces interference that limits the precision with which measurements can be made. So CERN decided that it might be good to determine how to move the antimatter away from where it’s produced. Since it was tackling that problem anyway, CERN decided to make a shipping container for antimatter, allowing it to be put on a truck and potentially taken to labs throughout Europe.

A shipping container for antimatter

The problem facing CERN comes from its own hardware. The antimatter it captures is produced by smashing a particle beam into a stationary target. As a result, all the anti-particles that come out of the debris carry a lot of energy. If you want to hold on to any of them, you have to slow them down, which is done using electromagnetic fields that can act on the charged antimatter particles. Unfortunately, as the team behind the new work notes, many of the measurements we’d like to do with the antimatter are “extremely sensitive to external magnetic field noise.”

In short, the hardware that slows the antimatter down limits the precision of the measurements you can take.

The obvious solution is to move the antimatter away from where it’s produced. But that gets tricky very fast. The antimatter containment device has to be maintained as an extreme vacuum and needs superconducting materials to produce the electromagnetic fields that keep the antimatter from bumping into the walls of the container. All of that means a significant power supply, along with a cache of liquid helium to keep the superconductors working. A standard shipping container just won’t do.

So the team at CERN built a two-meter-long portable containment device. On one end is a junction that allows it to be plugged into the beam of particles produced by the existing facility. That junction leads to the containment area, which is blanketed by a superconducting magnet. Elsewhere on the device are batteries to ensure an uninterrupted power supply, along with the electronics to run it all. The whole setup is encased in a metal frame that includes lifting points that can be used to attach it to a crane for moving around.

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Physics of the perfect cacio e pepe sauce

fluid dynamics, Food science, phase separation, Physics, rheology, Science / Kelly Newman / April 29, 2025

The trick: Add corn starch separately to make the sauce rather than using pasta water.

Cacio e pepe is an iconic pasta dish that can be frustratingly difficult to make Credit: Simone Frau

Nobody does pasta quite like the Italians, as anyone who has tasted an authentic “pasta alla cacio e pepe” can attest. It’s a simple dish: just tonnarelli pasta, pecorino cheese, and pepper. But its simplicity is deceptive. Cacio e pepe (“cheese and pepper”) is notoriously challenging to make because it’s so easy for the sauce to form unappetizing clumps with a texture more akin to stringy mozzarella rather than being smooth and creamy.

A team of Italian physicists has come to the rescue with a foolproof recipe based on their many scientific experiments, according to a new paper published in the journal Physics of Fluids. The trick: using corn starch for the cheese and pepper sauce instead of relying on however much starch leaches into the boiling water as the pasta is cooked.

“A true Italian grandmother or a skilled home chef from Rome would never need a scientific recipe for cacio e pepe, relying instead on instinct and years of experience,” the authors wrote. “For everyone else, this guide offers a practical way to master the dish. Preparing cacio e pepe successfully depends on getting the balance just right, particularly the ratio of starch to cheese. The concentration of starch plays a crucial role in keeping the sauce creamy and smooth, without clumps or separation.”

There has been a surprising amount of pasta-related physics research in recent years, particularly around spaghetti—the mechanics of slurping the pasta into one’s mouth, for instance, or spitting it out (aka, the “reverse spaghetti problem”). The most well-known is the question of how to get dry spaghetti strands to break neatly in two rather than three or more scattered pieces. French physicists successfully explained the dynamics in an Ig Nobel Prize-winning 2006 paper. They found that, counterintuitively, a dry spaghetti strand produces a “kick back” traveling wave as it breaks. This wave temporarily increases the curvature in other sections, leading to many more breaks.

In 2020, physicists provided an explanation for why a strand of spaghetti in a pot of boiling water will start to sag as it softens before sinking to the bottom of the pot and curling back on itself in a U shape. Physicists have also discovered a way to determine if one’s spaghetti is perfectly done by using a simple ruler (although one can always use the tried-and-true method of flinging a test strand against the wall). In 2021, inspired by flat-packed furniture, scientists came up with an ingenious solution to packaging differently shaped pastas: ship them in a flat 2D form that takes on the final 3D shape when cooked, thanks to carefully etched patterns in the pasta.

And earlier this year, physicists investigated how adding salt to a pasta pot to make it boil faster can leave a white ring on the bottom of the pot to identify factors leading to the perfect salt ring. They found that particles released from a smaller height fall faster and form a pattern with a clean central region. Those released from a greater height take longer to fall to the bottom, and the cloud of particles expands radially until the particles are far enough apart not to be influenced by the wakes of neighboring particles, such that they no longer form a cloud. In the latter case, you end up with a homogeneous salt ring deposit.

Going through a phase (separation)

ompare the effect of: water alone; pasta water that retains some starch (obtained by cooking 100 g of pasta in 1 liter of water); and pasta water “risottata” — Comparing the effect of water alone, pasta water that retains some starch, and pasta water “risottata.” Credit: G. Bartolucci et al., 2025

So it shouldn’t be the least bit surprising that physicists have now turned their attention to the problem of the perfect cacio e pepe sauce. The authors are well aware that they are treading on sacred ground for Italian traditionalists. “I hope that eight Italian authors is enough [to quell skepticism],” co-author Ivan Di Terlizzi of the Max Planck Institute for the Physics of Complex Systems told The New York Times back in January. (An earlier version of the paper was posted to the physics preprint arXiv in January, prompting that earlier coverage.)

Terlizzi and his fellow author are all living abroad and frequently meet for dinner. Cacio e pepe is among their favorite traditional dishes to make, and as physicists, they couldn’t help but want to learn more about the unique physics of the process, not to mention “the more practical aim to avoid wasting good pecorino,” said Terlizzi. They focused on the separation that often occurs when cheese and water are mixed, building on earlier culinary experiments.

As the pasta cooks in boiling water, the noodles release starch. Traditionally, the chef will extract part of the water and starch solution—which is cooled to a suitable temperature to avoid clumping as the cheese proteins “denaturate”—and mix it with the cheese to make the sauce, adding the pepper last, right before serving. But the authors note that temperature is not the only factor that can lead to this dreaded “mozzarella phase.”

According to the authors, if one tries to mix cheese and water without any starch, the clumping is more pronounced. There is less clumping with water containing a little starch, like water in which pasta has been cooked. And when one mixes the cheese with pasta water “risottata”—i.e., collected and heated in a pan so enough water evaporates that there is a higher concentration of starch—there is almost no clumping.

Effect of trisodium citrate on the stability of Cacio e pepe sauce. — Effect of trisodium citrate on the stability of cacio e pepe sauce. Credit: G. Bartolucci et al., 2025

So starch plays a crucial role in the process of making cacio e pepe. The authors devised a set of experiments to scientifically investigate the phase behavior of water, starch, and cheese mixed together in various concentrations and at different temperatures. They primarily used standard kitchen tools to make sure home cooks could recreate their results (although not every kitchen has a sous vide machine). This enabled them to devise a phase diagram of what happens to the sauce as the conditions change.

The authors found that the correct starch ratio is between 2 to 3 percent of the cheese weight. Below that, you get the clumping phase separation; above that, and the sauce “becomes stiff and unappetizing as it cools,” they wrote. Pasta water alone contains too little starch. Using pasta water “risottata” may concentrate the starch, but the chef has less control over the precise amount of starch. So the authors recommend simply dissolving 4 grams of powdered potato or corn starch in 40 grams of water, heating it gently until it thickens—a transition known as starch gelatinization—and combining that gel with the cheese. They also recommend toasting the black pepper briefly before adding it to the mixture to enhance its flavors and aromas.

They ran the same set of experiments using trisodium citrate as an alternative stabilizer, which is widely used in the food industry as an emulsifier—including in the production of processed cheese, since it enhances smoothness and prevents unwanted clumping, exactly the properties one desires for a perfect cacio e pepe sauce. The trisodium citrate at concentrations above 2 percent worked just as well at avoiding the mozzarella phase, “though at a cost of deviating from strict culinary tradition,” the authors concluded. “However, while the sauce stabilization is more efficient, we found the taste of the cheese to be slightly blunted, likely due to the basic properties of the salt.”

The team’s next research goal is to conduct similar experiments with making pasta alla gricia—basically the same as cacio e pepe, with the addition of guanciale (cured pork cheek). “This recipe seems to be easier to perform, and we don’t know exactly why,” said co-author Daniel Maria Busiello, Terlizzi’s colleague at the Dresden Max Planck Institute. “This is one idea we might explore in the future.”

DOI: Physics of Fluids, 2025. 10.1063/5.0255841 (About DOIs).

Jennifer is a senior writer at Ars Technica with a particular focus on where science meets culture, covering everything from physics and related interdisciplinary topics to her favorite films and TV series. Jennifer lives in Baltimore with her spouse, physicist Sean M. Carroll, and their two cats, Ariel and Caliban.

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The physics of bowling strike after strike

bowling, Physics, Science, sports science / Mike M. / April 16, 2025

More than 45 million people in the US are fans of bowling, with national competitions awarding millions of dollars. Bowlers usually rely on instinct and experience, earned through lots and lots of practice, to boost their strike percentage. A team of physicists has come up with a mathematical model to better predict ball trajectories, outlined in a new paper published in the journal AIP Advances. The resulting equations take into account such factors as the composition and resulting pattern of the oil used on bowling lanes, as well as the inevitable asymmetries of bowling balls and player variability.

The authors already had a strong interest in bowling. Three are regular bowlers and quite skilled at the sport; a fourth, Curtis Hooper of Longborough University in the UK, is a coach for Team England at the European Youth Championships. Hooper has been studying the physics of bowling for several years, including an analysis of the 2017 Weber Cup, as well as papers devising mathematical models for the application of lane conditioners and oil patterns in bowling.

The calculations involved in such research are very complicated because there are so many variables that can affect a ball’s trajectory after being thrown. Case in point: the thin layer of oil that is applied to bowling lanes, which Hooper found can vary widely in volume and shape among different venues, plus the lack of uniformity in applying the layer, which creates an uneven friction surface.

Per the authors, most research to date has relied on statistically analyzing empirical data, such as a 2018 report by the US Bowling Congress that looked at data generated by 37 bowlers. (Hooper relied on ball-tracking data for his 2017 Weber Cup analysis.) A 2009 analysis showed that the optimal location for the ball to strike the headpin is about 6 centimeters off-center, while the optimal entry angle for the ball to hit is about 6 degrees. However, such an approach struggles to account for the inevitable player variability. No bowler hits their target 100 percent of the time, and per Hooper et al., while the best professionals can come within 0.1 degrees from the optimal launch angle, this slight variation can nonetheless result in a difference of several centimeters down-lane.

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Quantum hardware may be a good match for AI

AI, Computer science, image classification, Physics, quantum computing, quantum mechanics, Science / Kelly Newman / April 11, 2025

Quantum computers don’t have that sort of separation. While they could include some quantum memory, the data is generally housed directly in the qubits, while computation involves performing operations, called gates, directly on the qubits themselves. In fact, there has been a demonstration that, for supervised machine learning, where a system can learn to classify items after training on pre-classified data, a quantum system can outperform classical ones, even when the data being processed is housed on classical hardware.

This form of machine learning relies on what are called variational quantum circuits. This is a two-qubit gate operation that takes an additional factor that can be held on the classical side of the hardware and imparted to the qubits via the control signals that trigger the gate operation. You can think of this as analogous to the communications involved in a neural network, with the two-qubit gate operation equivalent to the passing of information between two artificial neurons and the factor analogous to the weight given to the signal.

That’s exactly the system that a team from the Honda Research Institute worked on in collaboration with a quantum software company called Blue Qubit.

Pixels to qubits

The focus of the new work was mostly on how to get data from the classical world into the quantum system for characterization. But the researchers ended up testing the results on two different quantum processors.

The problem they were testing is one of image classification. The raw material was from the Honda Scenes dataset, which has images taken from roughly 80 hours of driving in Northern California; the images are tagged with information about what’s in the scene. And the question the researchers wanted the machine learning to handle was a simple one: Is it snowing in the scene?

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Fewer beans = great coffee if you get the pour height right

coffee brewing, fluid dynamics, Food science, granular media, Physics, Science / Kelly Newman / April 9, 2025

Based on their findings, the authors recommend pouring hot water over your coffee grounds slowly to give the beans more time immersed in the water. But pour the water too slowly and the resulting jet will stick to the spout (the “teapot effect”) and there won’t be sufficient mixing of the grounds; they’ll just settle to the bottom instead, decreasing extraction yield. “If you have a thin jet, then it tends to break up into droplets,” said co-author Margot Young. “That’s what you want to avoid in these pour-overs, because that means the jet cannot mix the coffee grounds effectively.”

Smaller jet diameter impact on dynamics. Credit: E. Park et al., 2025

That’s where increasing the height from which you pour comes in. This imparts more energy from gravity, per the authors, increasing the mixing of the granular coffee grounds. But again, there’s such a thing as pouring from too great a height, causing the water jet to break apart. The ideal height is no more than 50 centimeters (about 20 inches) above the filter. The classic goosenecked tea kettle turns out to be ideal for achieving that optimal height. Future research might explore the effects of varying the grain size of the coffee grounds.

Increasing extraction yields and, by extension, reducing how much coffee grounds one uses matters because it is becoming increasingly difficult to cultivate the most common species of coffee because of ongoing climate change. “Coffee is getting harder to grow, and so, because of that, prices for coffee will likely increase in coming years,” co-author Arnold Mathijssen told New Scientist. “The idea for this research was really to see if we could help do something by reducing the amount of coffee beans that are needed while still keeping the same amount of extraction, so that you get the same strength of coffee.”

But the potential applications aren’t limited to brewing coffee. The authors note that this same liquid jet/submerged granular bed interplay is also involved in soil erosion from waterfalls, for example, as well as wastewater treatment—using liquid jets to aerate wastewater to enhance biodegradation of organic matter—and dam scouring, where the solid ground behind a dam is slowly worn away by water jets. “Although dams operate on a much larger scale, they may undergo similar dynamics, and finding ways to decrease the jet height in dams may decrease erosion and elongate dam health,” they wrote.

Physics of Fluids, 2025. DOI: 10.1063/5.0257924 (About DOIs).

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First tokamak component installed in a commercial fusion plant

fusion, Physics, plasma, Science, stellarator, tokamak / Shannon Garcia / April 2, 2025

A tokamak moves forward as two companies advance plans for stellarators.

There are a remarkable number of commercial fusion power startups, considering that it’s a technology that’s built a reputation for being perpetually beyond the horizon. Many of them focus on radically new technologies for heating and compressing plasmas, or fusing unusual combinations of isotopes. These technologies are often difficult to evaluate—they can clearly generate hot plasmas, but it’s tough to determine whether they can get hot enough, often enough to produce usable amounts of power.

On the other end of the spectrum are a handful of companies that are trying to commercialize designs that have been extensively studied in the academic world. And there have been some interesting signs of progress here. Recently, Commonwealth Fusion, which is building a demonstration tokamak in Massachussets, started construction of the cooling system that will keep its magnets superconducting. And two companies that are hoping to build a stellarator did some important validation of their concepts.

Doing donuts

A tokamak is a donut-shaped fusion chamber that relies on intense magnetic fields to compress and control the plasma within it. A number of tokamaks have been built over the years, but the big one that is expected to produce more energy than required to run it, ITER, has faced many delays and now isn’t expected to achieve its potential until the 2040s. Back in 2015, however, some physicists calculated that high-temperature superconductors would allow ITER-style performance in a far smaller and easier-to-build package. That idea was commercialized as Commonwealth Fusion.

The company is currently trying to build an ITER equivalent: a tokamak that can achieve fusion but isn’t large enough and lacks some critical hardware needed to generate electricity from that reaction. The planned facility, SPARC, is already in progress, with most of the supporting facility in place and superconducting magnets being constructed. But in late March, the company took a major step by installing the first component of the tokamak itself, the cryostat base, which will support the hardware that keeps its magnets cool.

Alex Creely, Commonwealth Fusion’s tokamak operations director and SPARC’s chief engineer, told Ars that the cryostat’s materials have to be chosen to be capable of handling temperatures in the area of 20 Kelvin, and be able to tolerate neutron exposure. Fortunately, stainless steel is still up to the task. It will also be part of a structure that has to handle an extreme temperature gradient. Creely said that it only takes about 30 centimeters to go from the hundreds of millions of degrees C of the plasma down to about 1,000° C, after which it becomes relatively simple to reach cryostat temperatures.

He said that construction is expected to wrap up about a year from now, after which there will be about a year of commissioning the hardware, with fusion experiments planned for 2027. And, while ITER may be facing ongoing delays, Creely said that it was critical for keeping Commonwealth on a tight schedule. Not only is most of the physics of SPARC the same as that of ITER, but some of the hardware will be as well. “We’ve learned a lot from their supply chain development,” Creely said. “So some of the same vendors that are supplying components for the ITER tokamak, we are also working with those same vendors, which has been great.”

Great in the sense that Commonwealth is now on track to see plasma well in advance of ITER. “Seeing all of this go from a bunch of sketches or boxes on slides—clip art effectively—to real metal and concrete that’s all coming together,” Creely said. “You’re transitioning from building the facility, building the plant around the tokamak to actually starting to build the tokamak itself. That is an awesome milestone.”

Seeing stars?

The plasma inside a tokamak is dynamic, meaning that it requires a lot of magnetic intervention to keep it stable, and fusion comes in pulses. There’s an alternative approach called a stellarator, which produces an extremely complex magnetic field that can support a simpler, stable plasma and steady fusion. As implemented by the Wendelstein 7-X stellarator in Germany, this meant a series of complex-shaped magnets manufactured with extremely low tolerance for deviation. But a couple of companies have decided they’re up for the challenge.

One of those, Type One Energy, has basically reached the stage that launched Commonwealth Fusion: It has made a detailed case for the physics underlying its stellarator design. In this instance, the case may even be considerably more detailed: six peer-reviewed articles in the Journal of Plasma Physics. The papers detail the structural design, the behavior of the plasma within it, handling of the helium produced by fusion, generation of tritium from the neutrons produced, and obtaining heat from the whole thing.

The company is partnering with Oak Ridge National Lab and the Tennessee Valley Authority to build a demonstration reactor on the site of a former fossil fuel power plant. (It’s also cooperating with Commonwealth on magnet development.) As with the SPARC tokamak, this will be a mix of technology demonstration and learning experience, rather than a functioning power plant.

Another company that’s pursuing a stellarator design is called Thea Energy. Brian Berzin, its CEO, told Ars that the company’s focus is on simplifying the geometry of the magnets needed for a stellarator and is using software to get them to produce an equivalent magnetic field. “The complexity of this device has always been really, really limiting,” he said, referring to the stellarator. “That’s what we’re really focused on: How can you make simpler hardware? Our way of allowing for simpler hardware is using really, really complicated software, which is something that has taken over the world.”

He said that the simplicity of the hardware will be helpful for an operational power plant, since it allows them to build multiple identical segments as spares, so things can be swapped out and replaced when maintenance is needed.

Like Commonwealth Fusion, Thea Energy is using high-temperature superconductors to build its magnets, with a flat array of smaller magnets substituting for the three-dimensional magnets used at Wendelstein. “We are able to really precisely recreate those magnetic fields required for accelerator, but without any wiggly, complicated, precise, expensive, costly, time-consuming hardware,” Berzin said. And the company recently released a preprint of some testing with the magnet array.

Thea is also planning on building a test stellarator. In its case, however, it’s going to be using deuterium-deuterium fusion, which is much less efficient than deuterium-tritium that will be needed for a power plant. But Berzin said that the design will incorporate a layer of lithium that will form tritium when bombarded by neutrons from the stellarator. If things go according to plan, the reactor will validate Thea’s design and be a fuel source for the rest of the industry.

Of course, nobody will operate a fusion power plant until sometime in the next decade—probably about at the same time that we might expect some of the first small modular fission plants to be built. Given the vast expansion in renewable production that is in progress, it’s difficult to predict what the energy market will look like at that point. So, these test reactors will be built in a very uncertain environment. But that uncertainty hasn’t stopped these companies from pursuing fusion.

John is Ars Technica’s science editor. He has a Bachelor of Arts in Biochemistry from Columbia University, and a Ph.D. in Molecular and Cell Biology from the University of California, Berkeley. When physically separated from his keyboard, he tends to seek out a bicycle, or a scenic location for communing with his hiking boots.

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Hints grow stronger that dark energy changes over time

cosmology, dark energy, Dark Energy Spectroscopic Instrument, Lambda CDM, Physics, Science, the standard model / DJ Henderson / March 20, 2025

In its earliest days, the Universe was a hot, dense soup of subatomic particles, including hydrogen and helium nuclei, aka baryons. Tiny fluctuations created a rippling pattern through that early ionized plasma, which froze into a three-dimensional place as the Universe expanded and cooled. Those ripples, or bubbles, are known as baryon acoustic oscillations (BAO). It’s possible to use BAOs as a kind of cosmic ruler to investigate the effects of dark energy over the history of the Universe.

DESI is a state-of-the-art instrument and can capture light from up to 5,000 celestial objects simultaneously. — DESI is a state-of-the-art instrument that can capture light from up to 5,000 celestial objects simultaneously.

That’s what DESI was designed to do: take precise measurements of the apparent size of these bubbles (both near and far) by determining the distances to galaxies and quasars over 11 billion years. That data can then be sliced into chunks to determine how fast the Universe was expanding at each point of time in the past, the better to model how dark energy was affecting that expansion.

An upward trend

Last year’s results were based on analysis of a full year’s worth of data taken from seven different slices of cosmic time and include 450,000 quasars, the largest ever collected, with a record-setting precision of the most distant epoch (between 8 to 11 billion years back) of 0.82 percent. While there was basic agreement with the Lamba CDM model, when those first-year results were combined with data from other studies (involving the cosmic microwave background radiation and Type Ia supernovae), some subtle differences cropped up.

Essentially, those differences suggested that the dark energy might be getting weaker. In terms of confidence, the results amounted to a 2.6-sigma level for the DESI’s data combined with CMB datasets. When adding the supernovae data, those numbers grew to 2.5-sigma, 3.5-sigma, or 3.9-sigma levels, depending on which particular supernova dataset was used.

It’s important to combine the DESI data with other independent measurements because “we want consistency,” said DESI co-spokesperson Will Percival of the University of Waterloo. “All of the different experiments should give us the same answer to how much matter there is in the Universe at present day, how fast the Universe is expanding. It’s no good if all the experiments agree with the Lambda-CDM model, but then give you different parameters. That just doesn’t work. Just saying it’s consistent to the Lambda-CDM, that’s not enough in itself. It has to be consistent with Lambda-CDM and give you the same parameters for the basic properties of that model.”

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Small charges in water spray can trigger the formation of key biochemicals

biochemistry, Biology, chemistry, origin of life, Physics, Science / Beth Washington / March 16, 2025

Once his team nailed how droplets become electrically charged and how the micro-lightning phenomenon works, they recreated the Miller-Urey experiment. Only without the spark plugs.

Ingredients of life

After micro-lightnings started jumping between droplets in a mixture of gases similar to that used by Miller and Urey, the team examined their chemical composition with a mass spectrometer. They confirmed glycine, uracil, urea, cyanoethylene, and lots of other chemical compounds were made. “Micro-lightnings made all organic molecules observed previously in the Miller-Urey experiment without any external voltage applied,” Zare claims.

But does it really bring us any closer to explaining the beginnings of life? After all, Miller and Urey already demonstrated those molecules could be produced by electrical discharges in a primordial Earth’s atmosphere—does it matter all that much where those discharges came from? Zare argues that it does.

“Lightning is intermittent, so it would be hard for these molecules to concentrate. But if you look at waves crashing into rocks, you can think the spray would easily go into the crevices in these rocks,” Zare suggests. He suggests that the water in these crevices would evaporate, new spray would enter and evaporate again and again. The cyclic drying would allow the chemical precursors to build into more complex molecules. “When you go through such a dry cycle, it causes polymerization, which is how you make DNA,” Zare argues. Since sources of spray were likely common on the early Earth, Zare thinks this process could produce far more organic chemicals than potential alternatives like lightning strikes, hydrothermal vents, or impacting comets.

But even if micro-lightning really produced the basic building blocks of life on Earth, we’re still not sure how those combined into living organisms. “We did not make life. We just demonstrated a possible mechanism that gives us some chemical compounds you find in life,” Zare says. “It’s very important to have a lot of humility with this stuff.”

Science Advances, 2025. DOI: 10.1126/sciadv.adt8979

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These hot oil droplets can bounce off any surface

bouncing droplets, inverse leidenfrost effect, Leidenfrost effect, Physics, Science / Mike M. / March 4, 2025

The Hong Kong physicists were interested in hot droplets striking cold surfaces. Prior research showed there was less of a bouncing effect in such cases involving heated water droplets, with the droplets sticking to the surface instead thanks to various factors such as reduced droplet surface tension. The Hong Kong team discovered they could achieve enhanced bouncing by using hot droplets of less volatile liquids—namely, n-hexadecane, soybean oil, and silicon oil, which have lower saturation pressures compared to water.

Follow the bouncing droplet

The researchers tested these hot droplets (as well as burning and normal temperature droplets) on various solid, cold surfaces, including scratched glass, smooth glass, acrylic surfaces, surfaces with liquid-repellant coatings from candle soot, and surfaces coated with nanoparticles with varying “wettability” (i.e., how well particles stick to the surface). They captured the droplet behavior with both high-speed and thermal cameras, augmented with computer modeling.

The room-temperature droplets stuck to all the surfaces as expected, but the hot and burning droplets bounced. The team found that the bottom of a hot droplet cools faster than the top as it approaches a room-temperature surface, which causes hotter liquid within the droplet to flow from the edges toward the bottom. The air that is dragged to the bottom with it forms a thin cushion there and prevents the droplet from making contact with the surface, bouncing off instead. They dubbed the behavior “self-lubricated bouncing.”

“It is now clear that droplet-bouncing strategies are not isolated to engineering the substrate and that the thermophysical properties of droplets themselves are critical,” Jonathan B. Boreyko of Virginia Tech, who was not involved in the research, wrote in an accompanying commentary.

Future applications include improving the combustion efficiency of fuels or developing better fire-retardant coatings. “If burning droplets can’t stick to surfaces, they won’t be able to ignite new materials and allow fires to propagate,” co-author Pingan Zhu said. “Our study could help protect flammable materials like textiles from burning droplets. Confining fires to a smaller area and slowing their spread could give firefighters more time to put them out.”

DOI: Newton, 2025. 10.1016/j.newton.2025.100014 (About DOIs).

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Research roundup: 7 cool science stories from February

ancient egypt, fluid dynamics, Herculaneum scrolls, Physics, research roundup, Science / Shannon Garcia / March 1, 2025

Dancing sea turtles, the discovery of an Egyptian pharaoh’s tomb, perfectly boiled eggs, and more.

X-ray image of the PHerc.172 scroll Credit: Vesuvius Challenge

It’s a regrettable reality that there is never time to cover all the interesting scientific stories we come across each month. In the past, we’ve featured year-end roundups of cool science stories we (almost) missed. This year, we’re experimenting with a monthly collection. February’s list includes dancing sea turtles, the secret to a perfectly boiled egg, the latest breakthrough in deciphering the Herculaneum scrolls, the discovery of an Egyptian pharaoh’s tomb, and more.

Dancing sea turtles

There is growing evidence that certain migratory animal species (turtles, birds, some species of fish) are able to exploit the Earth’s magnetic field for navigation, using it both as a compass to determine direction and as a kind of “map” to track their geographical position while migrating. A paper published in the journal Nature offers evidence of a possible mechanism for this unusual ability, at least in loggerhead sea turtles, who perform an energetic “dance” when they follow magnetic fields to a tasty snack.

Sea turtles make impressive 8,000-mile migrations across oceans and tend to return to the same feeding and nesting sites. The authors believe they achieve this through their ability to remember the magnetic signature of those areas and store them in a mental map. To test that hypothesis, the scientists placed juvenile sea turtles into two large tanks of water outfitted with large coils to create magnetic signatures at specific locations within the tanks. One tank features such a location that had food; the other had a similar location without food.

They found that the sea turtles in the first tank performed distinctive “dancing” moves when they arrived at the area associated with food: tilting their bodies, dog-paddling, spinning in place, or raising their head near or above the surface of the water. When they ran a second experiment using different radio frequencies, they found that the change interfered with the turtles’ internal compass, and they could not orient themselves while swimming. The authors concluded that this is compelling evidence that the sea turtles can distinguish between magnetic fields, possibly relying on complex chemical reactions, i.e., “magnetoreception.” The map sense, however, likely relies on a different mechanism.

Nature, 2025. DOI: 10.1038/s41586-024-08554-y (About DOIs).

Long-lost tomb of Thutmose II

Archaeologists found a simple tomb near Luxor and identified it as the 3,500-year-old burial site of King Thutmose II. Credit: Egypt’s Ministry of Tourism and Antiquities

Thutmose II was the fourth pharaoh of the Tutankhamun (18th) dynasty. He reigned only about 13 years and married his half-sister Hatshepsut (who went on to become the sixth pharaoh in the dynasty). Archaeologists have now confirmed that a tomb built underneath a waterfall in the mountains in Luxor and discovered in 2022 is the final resting place of Thutmose II. It’s the last of the 18th dynasty royal tombs to be found, more than a century after Tutankhamun’s tomb was found in 1922.

When it was first found, archaeologists thought the tomb might be that of a king’s wife, given its close proximity to Hatshepsut’s tomb and those of the wives of Thutmose III. But they found fragments of alabaster vases inscribed with Thutmose II’s name, along with scraps of religious burial texts and plaster fragments on the partially intact ceiling with traces of blue paint and yellow stars—typically only found in kings’ tombs. Something crucial was missing, however: the actual mummy and grave goods of Thutmose II.

It’s long been assumed that the king’s mummy was discovered in the 19th century at another site called Deir el-Bahari. But archaeologist Piers Litherland, who headed the British team that discovered the tomb, thinks that identification was in error. An inscription stated that Hatshepsut had the tomb’s contents relocated due to flooding. Litherland believes the pharaoh’s actual mummy is buried in a second tomb. Confirmation (or not) of his hypothesis won’t come until after archaeologists finish excavating what he thinks is the site of that second tomb, which is currently buried under multiple layers of rock and plaster.

Hidden images in Pollock paintings

“Troubled Queen” reveals a “hidden” figure, possibly a soldier. Credit: D.A. Morrissette et al., CNS Spectrums 2025

Physicists have long been fascinated by the drip paintings of “splatter master” Jackson Pollock, pondering the presence of fractal patterns (or lack thereof), as well as the presence of curls and coils in his work and whether the artist deliberately exploited a well-known fluid dynamics effect to achieve them—or deliberately avoided them. Now psychiatrists are getting into the game, arguing in a paper published in CNS Spectrums that Pollock—known to incorporate images into his early pre-drip paintings—also used many of the same images repeatedly in his later abstract drip paintings.

People have long claimed to see images in those drip paintings, but the phenomenon is usually dismissed by art critics as a trick of human perception, much like the fractal edges of Rorschach ink blots can fool the eye and mind. The authors of this latest paper analyzed Pollock’s early painting “Troubled Queen” and found multiple images incorporated into the painting, which they believe establishes a basis for their argument that Pollock also incorporated such images into his later drip painting, albeit possibly subconsciously.

“Seeing an image once in a drip painting could be random,” said co-author Stephen M. Stahl of the University of California, San Diego. “Seeing the same image twice in different paintings could be a coincidence. Seeing it three or more times—as is the case for booze bottles, monkeys and gorillas, elephants, and many other subjects and objects in Pollock’s paintings—makes those images very unlikely to be randomly provoked perceptions without any basis in reality.”

CNS Spectrums, 2025. DOI: 10.1017/S1092852924001470

Solving a fluid dynamics mystery

Soap opera in the maze: Geometry matters in Marangoni flows.

Every fall, the American Physical Society exhibits a Gallery of Fluid Motion, which recognizes the innate artistry of images and videos derived from fluid dynamics research. Several years ago, physicists at the University of California, Santa Barbara (UCSB) submitted an entry featuring a pool of red dye, propelled by a few drops of soap acting as a surfactant, that seemed to “know” how to solve a maze whose corridors were filled with milk. This is unusual since one would expect the dye to diffuse more uniformly. The team has now solved that puzzle, according to a paper published in Physical Review Letters.

The key factor is surface tension, specifically a phenomenon known as the Marangoni effect, which also drives the “coffee ring effect” and the “tears of wine” phenomenon. If you spread a thin film of water on your kitchen counter and place a single drop of alcohol in the center, you’ll see the water flow outward, away from the alcohol. The difference in their alcohol concentrations creates a surface tension gradient, driving the flow.

In the case of the UCSB experiment, the soap reduces local surface tension around the red dye to set the dye in motion. There are also already surfactants in the milk that work in combination with the soapy surfactant to “solve” the maze. The milk surfactants create varying points of resistance as the dye makes its way through the maze. A dead end or a small space will have more resistance, redirecting the dye toward routes with less resistance—and ultimately to the maze’s exit. “That means the added surfactant instantly knows the layout of the maze,” said co-author Paolo Luzzatto-Fegiz.

Physical Review Letters, 2025. DOI: 10.1073/pnas.1802831115

How to cook a perfectly boiled egg

There’s more than one way to boil an egg, whether one likes it hard-boiled, soft-boiled, or somewhere in between. The challenge is that eggs have what physicists call a “two-phase” structure: The yolk cooks at 65° Celsius, while the white (albumen) cooks at 85° Celsius. This often results in overcooked yolks or undercooked whites when conventional methods are used. Physicists at the Italian National Research Council think they’ve cracked the case: The perfectly cooked egg is best achieved via a painstaking process called “periodic cooking,” according to a paper in the journal Communications Engineering.

They started with a few fluid dynamics simulations to develop a method and then tested that method in the laboratory. The process involves transferring a cooking egg every two minutes—for 32 minutes—between a pot of boiling water (100° Celsius) and a bowl of cold water (30° Celsius). They compared their periodically cooked eggs with traditionally prepared hard-boiled and soft-boiled eggs, as well as eggs prepared using sous vide. The periodically cooked eggs ended up with soft yolks (typical of sous vide eggs) and a solidified egg white with a consistency between sous vide and soft-boiled eggs. Chemical analysis showed the periodically cooked eggs also contained more healthy polyphenols. “Periodic cooking clearly stood out as the most advantageous cooking method in terms of egg nutritional content,” the authors concluded.

Communications Engineering, 2025. DOI: 10.1038/s44172-024-00334-w

More progress on deciphering Herculaneum scrolls

X-ray scans and AI reveal the inside of ancient scroll — X-ray scans and AI reveal the inside of an ancient scroll. Credit: Vesuvius Challenge

The Vesuvius Challenge is an ongoing project that employs “digital unwrapping” and crowd-sourced machine learning to decipher the first letters from previously unreadable ancient scrolls found in an ancient Roman villa at Herculaneum. The 660-plus scrolls stayed buried under volcanic mud until they were excavated in the 1700s from a single room that archaeologists believe held the personal working library of an Epicurean philosopher named Philodemus. The badly singed, rolled-up scrolls were so fragile that it was long believed they would never be readable, as even touching them could cause them to crumble.

In 2023, the Vesuvius Challenge made its first award for deciphering the first letters, and last year, the project awarded the grand prize of $700,000 for producing the first readable text. The latest breakthrough is the successful generation of the first X-ray image of the inside of a scroll (PHerc. 172) housed in Oxford University’s Bodleian Libraries—a collaboration with the Vesuvius Challenge. The scroll’s ink has a unique chemical composition, possibly containing lead, which means it shows up more clearly in X-ray scans than other Herculaneum scrolls that have been scanned.

The machine learning aspect of this latest breakthrough focused primarily on detecting the presence of ink, not deciphering the characters or text. Oxford scholars are currently working to interpret the text. The first word to be translated was the Greek word for “disgust,” which appears twice in nearby columns of text. Meanwhile, the Vesuvius Challenge collaborators continue to work to further refine the image to make the characters even more legible and hope to digitally “unroll” the scroll all the way to the end, where the text likely indicates the title of the work.

What ancient Egyptian mummies smell like

mummified bodies in the exhibition area of the Egyptian museum in Cairo. — Mummified bodies in the exhibition area of the Egyptian Museum in Cairo. Credit: Emma Paolin

Much of what we know about ancient Egyptian embalming methods for mummification comes from ancient texts, but there are very few details about the specific spices, oils, resins, and other ingredients used. Science can help tease out the secret ingredients. For instance, a 2018 study analyzed organic residues from a mummy’s wrappings with gas chromatography-mass spectrometry and found that the wrappings were saturated with a mixture of plant oil, an aromatic plant extract, a gum or sugar, and heated conifer resin. Researchers at University College London have now identified the distinctive smells associated with Egyptian mummies—predominantly”woody,” “spicy,” and “sweet,” according to a paper published in the Journal of the American Chemical Society.

The team coupled gas chromatography with mass spectrometry to measure chemical molecules emitted by nine mummified bodies on display at the Egyptian Museum in Cairo and then asked a panel of trained human “sniffers” to describe the samples smells, rating them by quality, intensity, and pleasantness. This enabled them to identify whether a given odor molecule came from the mummy itself, conservation products, pesticides, or the body’s natural deterioration. The work offers additional clues into the materials used in mummification, as well as making it possible for the museum to create interactive “smellscapes” in future displays so visitors can experience the scents as well as the sights of ancient Egyptian mummies.

Journal of the American Chemical Society, 2025. DOI: 10.1021/jacs.4c15769

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Scientists unlock vital clue to strange quirk of static electricity

electromagnetism, Physics, Science, static electricity, triboelectric effect / 9u50fv / February 20, 2025

Scientists can now explain the prevailing unpredictability of contact electrification, unveiling order from what has long been considered chaos.

Static electricity—specifically the triboelectric effect, aka contact electrification—is ubiquitous in our daily lives, found in such things as a balloon rubbed against one’s hair or styrofoam packing peanuts sticking to a cat’s fur (as well as human skin, glass tabletops, and just about anywhere you don’t want packing peanuts to be). The most basic physics is well understood, but long-standing mysteries remain, most notably how different materials exchange positive and negative charges—sometimes ordering themselves into a predictable series, but sometimes appearing completely random.

Now scientists at the Institute of Science and Technology Austria (ISTA) have identified a critical factor explaining that inherent unpredictability: It’s the contact history of given materials that controls how they exchange charges in contact electrification. They described their findings in a new paper published in the journal Nature.

Johan Carl Wilcke published the first so-called “triboelectric series” in 1757 to describe the tendency of different materials to self-order based on how they develop a positive or negative charge. A material toward the bottom of the list, like hair, will acquire a more negative charge when it comes into contact with a material near the top of the list, like a rubber balloon.

The issue with all these lists is that they are inconsistent and unpredictable—sometimes the same scientists don’t get the same ordering results twice when repeating experiments—largely because there are so many confounding factors that can come into play. “Understanding how insulating materials exchanged charge seemed like a total mess for a very long time,” said co-author Scott Waitukaitis of ISTA. “The experiments are wildly unpredictable and can sometimes seem completely random.”

A cellulose material’s charge sign, for instance, can depend on whether its curvature is concave or convex. Two materials can exchange charge from positive (A) to negative (B), but that exchange can reverse over time, with B being positive and A being negative. And then there are “triangles”: Sometimes one material (A) gains a positive charge when rubbed up against another material (B), but B will gain a positive charge when rubbed against a third material (C), and C, in turn, will gain positive charge when in contact with A. Even identical materials can sometimes exchange charge upon contact.

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Microsoft demonstrates working qubits based on exotic physics

Apple, Computer science, Majorana, Physics, quantum computing, quantum mechanics, quasiparticles, Science / Mike M. / February 20, 2025

Microsoft’s first entry into quantum hardware comes in the form of Majorana 1, a processor with eight of these qubits.

Given that some of its competitors have hardware that supports over 1,000 qubits, why does the company feel it can still be competitive? Nayak described three key features of the hardware that he feels will eventually give Microsoft an advantage.

The first has to do with the fundamental physics that governs the energy needed to break apart one of the Cooper pairs in the topological superconductor, which could destroy the information held in the qubit. There are a number of ways to potentially increase this energy, from lowering the temperature to making the indium arsenide wire longer. As things currently stand, Nayak said that small changes in any of these can lead to a large boost in the energy gap, making it relatively easy to boost the system’s stability.

Another key feature, he argued, is that the hardware is relatively small. He estimated that it should be possible to place a million qubits on a single chip. “Even if you put in margin for control structures and wiring and fan out, it’s still a few centimeters by a few centimeters,” Nayak said. “That was one of the guiding principles of our qubits.” So unlike some other technologies, the topological qubits won’t require anyone to figure out how to link separate processors into a single quantum system.

Finally, all the measurements that control the system run through the quantum dot, and controlling that is relatively simple. “Our qubits are voltage-controlled,” Nayak told Ars. “What we’re doing is just turning on and off coupling of quantum dots to qubits to topological nano wires. That’s a digital signal that we’re sending, and we can generate those digital signals with a cryogenic controller. So we actually put classical control down in the cold.”

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