Physics

quantum-computing-progress:-higher-temps,-better-error-correction

Quantum computing progress: Higher temps, better error correction

Amazon, Computer science, ibm, Physics, quantum computing, quantum mechanics, Science / /
conceptual graphic of symbols representing quantum states floating above a stylized computer chip.

There’s a strong consensus that tackling most useful problems with a quantum computer will require that the computer be capable of error correction. There is absolutely no consensus, however, about what technology will allow us to get there. A large number of companies, including major players like Microsoft, Intel, Amazon, and IBM, have all committed to different technologies to get there, while a collection of startups are exploring an even wider range of potential solutions.

We probably won’t have a clearer picture of what’s likely to work for a few years. But there’s going to be lots of interesting research and development work between now and then, some of which may ultimately represent key milestones in the development of quantum computing. To give you a sense of that work, we’re going to look at three papers that were published within the last couple of weeks, each of which tackles a different aspect of quantum computing technology.

Hot stuff

Error correction will require connecting multiple hardware qubits to act as a single unit termed a logical qubit. This spreads a single bit of quantum information across multiple hardware qubits, making it more robust. Additional qubits are used to monitor the behavior of the ones holding the data and perform corrections as needed. Some error correction schemes require over a hundred hardware qubits for each logical qubit, meaning we’d need tens of thousands of hardware qubits before we could do anything practical.

A number of companies have looked at that problem and decided we already know how to create hardware on that scale—just look at any silicon chip. So, if we could etch useful qubits through the same processes we use to make current processors, then scaling wouldn’t be an issue. Typically, this has meant fabricating quantum dots on the surface of silicon chips and using these to store single electrons that can hold a qubit in their spin. The rest of the chip holds more traditional circuitry that performs the initiation, control, and readout of the qubit.

This creates a notable problem. Like many other qubit technologies, quantum dots need to be kept below one Kelvin in order to keep the environment from interfering with the qubit. And, as anyone who’s ever owned an x86-based laptop knows, all the other circuitry on the silicon generates heat. So, there’s the very real prospect that trying to control the qubits will raise the temperature to the point that the qubits can’t hold onto their state.

That might not be the problem that we thought, according to some work published in Wednesday’s Nature. A large international team that includes people from the startup Diraq have shown that a silicon quantum dot processor can work well at the relatively toasty temperature of 1 Kelvin, up from the usual milliKelvin that these processors normally operate at.

The work was done on a two-qubit prototype made with materials that were specifically chosen to improve noise tolerance; the experimental procedure was also optimized to limit errors. The team then performed normal operations starting at 0.1 K, and gradually ramped up the temperatures to 1.5 K, checking performance as they did so. They found that a major source of errors, state preparation and measurement (SPAM), didn’t change dramatically in this temperature range: “SPAM around 1 K is comparable to that at millikelvin temperatures and remains workable at least until 1.4 K.”

The error rates they did see depended on the state they were preparing. One particular state (both spin-up) had a fidelity of over 99 percent, while the rest were less constrained, at somewhere above 95 percent. States had a lifetime of over a millisecond, which qualifies as long-lived int he quantum world.

All of which is pretty good, and suggests that the chips can tolerate reasonable operating temperatures, meaning on-chip control circuitry can be used without causing problems. The error rates of the hardware qubits are still well above those that would be needed for error correction to work. However, the researchers suggest that they’ve identified error processes that can potentially be compensated for. They expect that the ability to do industrial-scale manufacturing will ultimately lead to working hardware.

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Event Horizon Telescope captures stunning new image of Milky Way’s black hole

astronomy, astrophysics, black holes, Event Horizon Telescope, Physics, Science / /
A new image from the Event Horizon Telescope has revealed powerful magnetic fields spiraling from the edge of a supermassive black hole at the center of the Milky Way, Sagittarius A*.

Enlarge / A new image from the Event Horizon Telescope has revealed powerful magnetic fields spiraling from the edge of a supermassive black hole at the center of the Milky Way, Sagittarius A*.

EHT Collaboration

Physicists have been confident since the1980s that there is a supermassive black hole at the center of the Milky Way galaxy, similar to those thought to be at the center of most spiral and elliptical galaxies. It’s since been dubbed Sagittarius A* (pronounced A-star), or SgrAfor short. The Event Horizon Telescope (EHT) captured the first image of SgrAtwo years ago. Now the collaboration has revealed a new polarized image (above) showcasing the black hole’s swirling magnetic fields. The technical details appear in two new papers published in The Astrophysical Journal Letters. The new image is strikingly similar to another EHT image of a larger supermassive black hole, M87*, so this might be something that all such black holes share.

The only way to “see” a black hole is to image the shadow created by light as it bends in response to the object’s powerful gravitational field. As Ars Science Editor John Timmer reported in 2019, the EHT isn’t a telescope in the traditional sense. Instead, it’s a collection of telescopes scattered around the globe. The EHT is created by interferometry, which uses light in the microwave regime of the electromagnetic spectrum captured at different locations. These recorded images are combined and processed to build an image with a resolution similar to that of a telescope the size of the most distant locations. Interferometry has been used at facilities like ALMA (the Atacama Large Millimeter/submillimeter Array) in northern Chile, where telescopes can be spread across 16 km of desert.

In theory, there’s no upper limit on the size of the array, but to determine which photons originated simultaneously at the source, you need very precise location and timing information on each of the sites. And you still have to gather sufficient photons to see anything at all. So atomic clocks were installed at many of the locations, and exact GPS measurements were built up over time. For the EHT, the large collecting area of ALMA—combined with choosing a wavelength in which supermassive black holes are very bright—ensured sufficient photons.

In 2019, the EHT announced the first direct image taken of a black hole at the center of an elliptical galaxy, Messier 87, located in the constellation of Virgo some 55 million light-years away. This image would have been impossible a mere generation ago, and it was made possible by technological breakthroughs, innovative new algorithms, and (of course) connecting several of the world’s best radio observatories. The image confirmed that the object at the center of M87is indeed a black hole.

In 2021, the EHT collaboration released a new image of M87showing what the black hole looks like in polarized light—a signature of the magnetic fields at the object’s edge—which yielded fresh insight into how black holes gobble up matter and emit powerful jets from their cores. A few months later, the EHT was back with images of the “dark heart” of a radio galaxy known as Centaurus A, enabling the collaboration to pinpoint the location of the supermassive black hole at the galaxy’s center.

SgrAis much smaller but also much closer than M87*. That made it a bit more challenging to capture an equally sharp image because SgrAchanges on time scales of minutes and hours compared to days and weeks for M87*. Physicist Matt Strassler previously compared the feat to “taking a one-second exposure of a tree on a windy day. Things get blurred out, and it can be difficult to determine the true shape of what was captured in the image.”

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Report: Superconductivity researcher found to have committed misconduct

Nature, Physics, research fraud, research misconduct, Science, superconductivity / /

Definitely not super —

Details of what the University of Rochester investigation found are not available.

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Image of a large lawn, with a domed building flanked by trees and flagpoles at its far end.

Enlarge / Rush Rhees Library at the University of Rochester.

We’ve been following the saga of Ranga Dias since he first burst onto the scene with reports of a high-pressure, room-temperature superconductor, published in Nature in 2020. Even as that paper was being retracted due to concerns about the validity of some of its data, Dias published a second paper claiming a similar breakthrough: a superconductor that works at high temperatures but somewhat lower pressures. Shortly afterward, that got retracted as well.

On Wednesday, the University of Rochester, where Dias is based, announced that it had concluded an investigation into Dias and found that he had committed research misconduct. (The outcome was first reported by The Wall Street Journal.)

The outcome is likely to mean the end of Dias’ career, as well as the company he founded to commercialize the supposed breakthroughs. But it’s unlikely we’ll ever see the full details of the investigation’s conclusions.

Questionable research

Dias’ lab was focused on high-pressure superconductivity. At extreme pressures, the orbitals where electrons hang out get distorted, which can alter the chemistry and electronic properties of materials. This can mean the formation of chemical compounds that don’t exist at normal pressures, along with distinct conductivity. In a number of cases, these changes enabled superconductivity at unusually high temperatures, although still well below the freezing point of water.

Dias, however, supposedly found a combination of chemicals that would boost the transition to superconductivity to near room temperature, although only at extreme pressures. While the results were plausible, the details regarding how some of the data was processed to produce one of the paper’s key graphs were lacking, and Dias didn’t provide a clear explanation. Nature eventually pulled the paper, and the University of Rochester initiated investigations (plural!) of his work.

Those investigations cleared Dias of misconduct, and he quickly was back with a report of another high-temperature superconductor, this one forming at less extreme pressures—somewhat surprisingly, published again by Nature. This time, things fell apart much more rapidly, with potential problems quickly becoming apparent, and many of the paper’s authors, not including Dias, called for its retraction.

The University of Rochester started yet another investigation, which is the one that has now concluded that Dias engaged in research misconduct.

The extent of this misconduct, however, might never be revealed. These internal university investigations are generally not made public, even if it might be in the public’s interest to know. The only recent exception is a case where a researcher accused of misconduct sued her university for defamation over the outcome of the investigation. The university submitted its investigation report as evidence, allowing it to become part of the public record.

Behind the scenes

That said, we have learned a fair bit about what has happened inside Dias’ lab, thanks to Nature News, a sister publication of the scientific journal that published both of Dias’ papers. It conducted a tour-de-force of investigative journalism, talking to Dias’ grad students and obtaining the peer review evaluations of Dias’ two papers.

The investigation showed that, for the first paper, Dias simply told his graduate students that the key data came from before he had set up his own lab, which explains why they weren’t aware of it. The students claimed that the ensuing investigations didn’t contact any of them, suggesting they were extremely similar in scope. By contrast, the students claim to have been more aware that the results presented in the second paper didn’t match up with experiments and, in at least one case, suggested Dias clearly misrepresented his lab’s work. (The paper claimed to have synthesized a chemical that the students say was simply purchased from a supplier.)

They were the ones who organized the effort to retract the paper and said that the final investigation actually sought their input.

Meanwhile, on the peer review side, the reporting does not leave Nature looking especially good. Both papers required several rounds of revision and review before being accepted, and even after all this work, most of the reviewers were ambiguous at best about whether the paper should be published. It was an editorial decision to go ahead despite that.

While things seem to have worked out in the end, the major institutions involved here—Nature and the University of Rochester—aren’t coming out of this unscathed. Neither seems to have taken early indications of misconduct as seriously as it should have. As for Dias, the reporting in the Nature News piece should be career-ending. And it’s worth considering that, in the absence of the reporter’s work, the research community would probably remain unaware of most of the details of Dias’ misconduct.

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This stretchy electronic material hardens upon impact just like “oobleck”

conductive polymers, flexible electronics, kitchen science, materials science, oobleck, Physics, polymers, Science / /

a flexible alternative —

Researchers likened material’s structure to a big bowl of spaghetti and meatballs.

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This flexible and conductive material has “adaptive durability,” meaning it gets stronger when hit.

Enlarge / This flexible and conductive material has “adaptive durability,” meaning it gets stronger when hit.

Yue (Jessica) Wang

Scientists are keen to develop new materials for lightweight, flexible, and affordable wearable electronics so that, one day, dropping our smartphones won’t result in irreparable damage. One team at the University of California, Merced, has made conductive polymer films that actually toughen up in response to impact rather than breaking apart, much like mixing corn starch and water in appropriate amounts produces a slurry that is liquid when stirred slowly but hardens when you punch it (i.e., “oobleck”). They described their work in a talk at this week’s meeting of the American Chemical Society in New Orleans.

“Polymer-based electronics are very promising,” said Di Wu, a postdoc in materials science at UCM. “We want to make the polymer electronics lighter, cheaper, and smarter. [With our] system, [the polymers] can become tougher and stronger when you make a sudden movement, but… flexible when you just do your daily, routine movement. They are not constantly rigid or constantly flexible. They just respond to your body movement.”

As we’ve previously reported, oobleck is simple and easy to make. Mix one part water to two parts corn starch, add a dash of food coloring for fun, and you’ve got oobleck, which behaves as either a liquid or a solid, depending on how much stress is applied. Stir it slowly and steadily and it’s a liquid. Punch it hard and it turns more solid under your fist. It’s a classic example of a non-Newtonian fluid.

In an ideal fluid, the viscosity largely depends on temperature and pressure: Water will continue to flow regardless of other forces acting upon it, such as being stirred or mixed. In a non-Newtonian fluid, the viscosity changes in response to an applied strain or shearing force, thereby straddling the boundary between liquid and solid behavior. Stirring a cup of water produces a shearing force, and the water shears to move out of the way. The viscosity remains unchanged. But for non-Newtonian fluids like oobleck, the viscosity changes when a shearing force is applied.

Ketchup, for instance, is a shear-thickening non-Newtonian fluid, which is one reason smacking the bottom of the bottle doesn’t make the ketchup come out any faster; the application of force increases the viscosity. Yogurt, gravy, mud, and pudding are other examples. And so is oobleck. (The name derives from a 1949 Dr. Seuss children’s book, Bartholomew and the Oobleck.) By contrast, non-drip paint exhibits a “shear-thinning” effect, brushing on easily but becoming more viscous once it’s on the wall. Last year, MIT scientists confirmed that the friction between particles was critical to that liquid-to-solid transition, identifying a tipping point when the friction reached a certain level and the viscosity abruptly increased.

Wu works in the lab of materials scientist Yue (Jessica) Wang, who decided to try to mimic the shear-thickening behavior of oobleck in a polymer material. Flexible polymer electronics are usually made by linking together conjugated conductive polymers, which are long and thin, like spaghetti. But these materials will still break apart in response to particularly large and/or rapid impacts.

So Wu and Wang decided to combine the spaghetti-like polymers with shorter polyaniline molecules and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate, or PEDOT:PSS—four different polymers in all. Two of the four have a positive charge, and two have a negative charge. They used that mixture to make stretchy films and then tested the mechanical properties.

Lo and behold, the films behaved very much like oobleck, deforming and stretching in response to impact rather than breaking apart. Wang likened the structure to a big bowl of spaghetti and meatballs since the positively charged molecules don’t like water and therefore cluster into ball-like microstructures. She and Wu suggest that those microstructures absorb impact energy, flattening without breaking apart. And it doesn’t take much PEDOT:PSS to get this effect: just 10 percent was sufficient.

Further experiments identified an even more effective additive: positively charged 1,3-propanediamine nanoparticles. These particles can weaken the “meatball” polymer interactions just enough so that they can deform even more in response to impacts, while strengthening the interactions between the entangled long spaghetti-like polymers.

The next step is to apply their polymer films to wearable electronics like smartwatch bands and sensors, as well as flexible electronics for monitoring health. Wang’s lab has also experimented with a new version of the material that would be compatible with 3D printing, opening up even more opportunities. “There are a number of potential applications, and we’re excited to see where this new, unconventional property will take us,” said Wang.

This stretchy electronic material hardens upon impact just like “oobleck” Read More »

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A giant meteorite has been lost in the desert since 1916—here’s how we might find it

astrophysics, Chinguetti meteorite, geophysics, meteorites, Physics, Science / /

“This story has everything…” —

A tale of “sand dunes, a guy named Gaston, secret aeromagnetic surveys, and camel drivers.”

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Chinguetti slice at the National Museum of Natural History

Enlarge / Chinguetti slice at the National Museum of Natural History. A larger meteorite reported in 1916 hasn’t been spotted since.

In 1916, a French consular official reported finding a giant “iron hill” deep in the Sahara desert, roughly 45 kilometers (28 miles) from Chinguetti, Mauritania—purportedly a meteorite (technically a mesosiderite) some 40 meters (130 feet) tall and 100 meters (330 feet) long. He brought back a small fragment, but the meteorite hasn’t been found again since, despite the efforts of multiple expeditions, calling its very existence into question.

Three British researchers have conducted their own analysis and proposed a means of determining once and for all whether the Chinguetti meteorite really exists, detailing their findings in a new preprint posted to the physics arXiv. They contend that they have narrowed down the likely locations where the meteorite might be buried under high sand dunes and are currently awaiting access to data from a magnetometer survey of the region in hopes of either finding the mysterious missing meteorite or confirming that it likely never existed.

Captain Gaston Ripert was in charge of the Chinguetti camel corps. One day he overheard a conversation among the chameliers (camel drivers) about an unusual iron hill in the desert. He convinced a local chief to guide him there one night, taking Ripert on a 10-hour camel ride along a “disorienting” route, making a few detours along the way. He may even have been literally blindfolded, depending on how one interprets the French phrase en aveugle, which can mean either “blind” (i.e. without a compass) or “blindfolded.” The 4-kilogram fragment Ripert collected was later analyzed by noted geologist Alfred Lacroix, who considered it a significant discovery. But when others failed to locate the larger Chinguetti meteorite, people started to doubt Ripert’s story.

“I know that the general opinion is that the stone does not exist; that to some, I am purely and simply an imposter who picked up a metallic specimen,” Ripert wrote to French naturalist Theodore Monod in 1934. “That to others, I am a simpleton who mistook a sandstone outcrop for an enormous meteorite. I shall do nothing to disabuse them, I know only what I saw.”

Encouraged by a separate report of local blacksmiths claiming to recover iron from a giant block somewhere east or southeast of Chinguetti, Monod intermittently searched for the meteorite several times over the ensuing decades, to no avail. A pilot named Jacques Gallouédec thought he spotted a dark silhouette in the Saharan dunes in the 1980s. But neither Monod nor a second expedition in the late 1990s—documented by the UK’s Channel 4—could find anything. Monod concluded in 1989 that Ripert had likely mistakenly identified a sedimentary rock “with no trace of metal” as a meteorite.

Still, as Rutgers University physicist Matt Buckley noted on Bluesky, “This story has everything: giant unexplained meteorites, sand dunes, a guy named Gaston, ductile nickel needles, secret aeromagnetic surveys, and camel drivers.” So naturally, it intrigued Stephen Warren of Imperial College London, Oxford University’s Ekaterini Protopapa, and Robert Warren, who began their own search for the mysterious missing meteorite in 2020.

A giant meteorite has been lost in the desert since 1916—here’s how we might find it Read More »

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Alternate qubit design does error correction in hardware

Computer science, photons, Physics, quantum computing, quantum mechanics, Science / /

We can fix that —

Early-stage technology has the potential to cut qubits needed for useful computers.

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Image of a complicated set of wires and cables hooked up to copper colored metal hardware.

Nord Quantique

There’s a general consensus that performing any sort of complex algorithm on quantum hardware will have to wait for the arrival of error-corrected qubits. Individual qubits are too error-prone to be trusted for complex calculations, so quantum information will need to be distributed across multiple qubits, allowing monitoring for errors and intervention when they occur.

But most ways of making these “logical qubits” needed for error correction require anywhere from dozens to over a hundred individual hardware qubits. This means we’ll need anywhere from tens of thousands to millions of hardware qubits to do calculations. Existing hardware has only cleared the 1,000-qubit mark within the last month, so that future appears to be several years off at best.

But on Thursday, a company called Nord Quantique announced that it had demonstrated error correction using a single qubit with a distinct hardware design. While this has the potential to greatly reduce the number of hardware qubits needed for useful error correction, the demonstration involved a single qubit—the company doesn’t even expect to demonstrate operations on pairs of qubits until later this year.

Meet the bosonic qubit

The technology underlying this work is termed a bosonic qubit, and they’re not anything new; an optical instrument company even has a product listing for them that notes their potential for use in error correction. But while the concepts behind using them in this manner were well established, demonstrations were lagging. Nord Quantique has now posted a paper in the arXiv that details a demonstration of them actually lowering error rates.

The devices are structured much like a transmon, the form of qubit favored by tech heavyweights like IBM and Google. There, the quantum information is stored in a loop of superconducting wire and is controlled by what’s called a microwave resonator—a small bit of material where microwave photons will reflect back and forth for a while before being lost.

A bosonic qubit turns that situation on its head. In this hardware, the quantum information is held in the photons, while the superconducting wire and resonator control the system. These are both hooked up to a coaxial cavity (think of a structure that, while microscopic, looks a bit like the end of a cable connector).

Massively simplified, the quantum information is stored in the manner in which the photons in the cavity interact. The state of the photons can be monitored by the linked resonator/superconducting wire. If something appears to be off, the resonator/superconducting wire allows interventions to be made to restore the original state. Additional qubits are not needed. “A very simple and basic idea behind quantum error correction is redundancy,” co-founder and CTO Julien Camirand Lemyre told Ars. “One thing about resonators and oscillators in superconducting circuits is that you can put a lot of photons inside the resonators. And for us, the redundancy comes from there.”

This process doesn’t correct all possible errors, so it doesn’t eliminate the need for logical qubits made from multiple underlying hardware qubits. In theory, though, you can catch the two most common forms of errors that qubits are prone to (bit flips and changes in phase).

In the arXiv preprint, the team at Nord Quantique demonstrated that the system works. Using a single qubit and simply measuring whether it holds onto its original state, the error correction system can reduce problems by 14 percent. Unfortunately, overall fidelity is also low, starting at about 85 percent, which is significantly below what’s seen in other systems that have been through years of development work. Some qubits have been demonstrated with a fidelity of over 99 percent.

Getting competitive

So there’s no question that Nord Quantique is well behind a number of the leaders in quantum computing that can perform (error-prone) calculations with dozens of qubits and have far lower error rates. Again, Nord Quantique’s work was done using a single qubit—and without doing any of the operations needed to perform a calculation.

Lemyre told Ars that while the company is small, it benefits from being a spin-out of the Institut Quantique at Canada’s Sherbrooke University, one of Canada’s leading quantum research centers. In addition to having access to the expertise there, Nord Quantique uses a fabrication facility at Sherbrooke to make its hardware.

Over the next year, the company expects to demonstrate that the error correction scheme can function while pairs of qubits are used to perform gate operations, the fundamental units of calculations. Another high priority is to combine this hardware-based error correction with more traditional logical qubit schemes, which would allow additional types of errors to be caught and corrected. This would involve operations with a dozen or more of these bosonic qubits at a time.

But the real challenge will be in the longer term. The company is counting on its hardware’s ability to handle error correction to reduce the number of qubits needed for useful calculations. But if its competitors can scale up the number of qubits fast enough while maintaining the control and error rates needed, that may not ultimately matter. Put differently, if Nord Quantique is still in the hundreds of qubit range by the time other companies are in the hundreds of thousands, its technology might not succeed even if it has some inherent advantages.

But that’s the fun part about the field as things stand: We don’t really know. A handful of very different technologies are already well into development and show some promise. And there are other sets that are still early in the development process but are thought to have a smoother path to scaling to useful numbers of qubits. All of them will have to scale to a minimum of tens of thousands of qubits while enabling the ability to perform quantum manipulations that were cutting-edge science just a few decades ago.

Looming in the background is the simple fact that we’ve never tried to scale anything like this to the extent that will be needed. Unforeseen technical hurdles might limit progress at some point in the future.

Despite all this, there are people backing each of these technologies who know far more about quantum mechanics than I ever will. It’s a fun time.

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Mathematicians finally solved Feynman’s “reverse sprinkler” problem

fluid dynamics, mathematical modeling, mathematical physics, Physics, reverse sprinkler, Richard Feynman, Science / /

A decades-old conundrum —

We might not need to “unwater” our lawns, but results could help control fluid flows.

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Light-scattering microparticles reveal the flow pattern for the reverse (sucking) mode of a sprinkler, showing vortices and complex flow patterns forming inside the central chamber. Credit: K. Wang et al., 2024

A typical lawn sprinkler features various nozzles arranged at angles on a rotating wheel; when water is pumped in, they release jets that cause the wheel to rotate. But what would happen if the water were sucked into the sprinkler instead? In which direction would the wheel turn then, or would it even turn at all? That’s the essence of the “reverse sprinkler” problem that physicists like Richard Feynman, among others, have grappled with since the 1940s. Now, applied mathematicians at New York University think they’ve cracked the conundrum, per a recent paper published in the journal Physical Review Letters—and the answer challenges conventional wisdom on the matter.

“Our study solves the problem by combining precision lab experiments with mathematical modeling that explains how a reverse sprinkler operates,” said co-author Leif Ristroph of NYU’s Courant Institute. “We found that the reverse sprinkler spins in the ‘reverse’ or opposite direction when taking in water as it does when ejecting it, and the cause is subtle and surprising.”

Ristroph’s lab frequently addresses these kinds of colorful real-world puzzles. For instance, back in 2018, Ristroph and colleagues fine-tuned the recipe for the perfect bubble based on experiments with soapy thin films. (You want a circular wand with a 1.5-inch perimeter, and you should gently blow at a consistent 6.9 cm/s.) In 2021, the Ristroph lab looked into the formation processes underlying so-called “stone forests” common in certain regions of China and Madagascar. These pointed rock formations, like the famed Stone Forest in China’s Yunnan Province, are the result of solids dissolving into liquids in the presence of gravity, which produces natural convective flows.

In 2021, his lab built a working Tesla valve, in accordance with the inventor’s design, and measured the flow of water through the valve in both directions at various pressures. They found the water flowed about two times slower in the nonpreferred direction. And in 2022, Ristroph studied the surpassingly complex aerodynamics of what makes a good paper airplane—specifically what is needed for smooth gliding. They found that paper airplane aerodynamics differ substantially from conventional aircraft, which rely on airfoils to generate lift.

Mechanik (1883).” data-height=”1298″ data-width=”1200″ href=”https://cdn.arstechnica.net/wp-content/uploads/2024/02/feynman7.jpg”>Illustration of a Mechanik (1883).” height=”692″ src=”https://cdn.arstechnica.net/wp-content/uploads/2024/02/feynman7-640×692.jpg” width=”640″>

Enlarge / Illustration of a “reaction wheel” from Ernst Mach’s Mechanik (1883).

Public domain

The reverse sprinkler problem is associated with Feynman because he popularized the concept, but it actually dates back to a chapter in Ernst Mach’s 1883 textbook The Science of Mechanics (Die Mechanik in Ihrer Entwicklung Historisch-Kritisch Dargerstellt). Mach’s thought experiment languished in relative obscurity until a group of Princeton University physicists began debating the issue in the 1940s.

Feynman was a graduate student there at the time and threw himself into the debate with gusto, even devising an experiment in the cyclotron laboratory to test his hypothesis. (In true Feynman fashion, that experiment culminated with the explosion of a glass carboy used in the apparatus because of the high internal pressure.)

One might intuit that a reverse sprinkler would work just like a regular sprinkler, merely played backward, so to speak. But the physics turns out to be more complicated. “The answer is perfectly clear at first sight,” Feynman wrote in Surely You’re Joking, Mr. Feynman (1985). “The trouble was, some guy would think it was perfectly clear [that the rotation would be] one way, and another guy would think it was perfectly clear the other way.”

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astronomers-found-ultra-hot,-earth-sized-exoplanet-with-a-lava-hemisphere

Astronomers found ultra-hot, Earth-sized exoplanet with a lava hemisphere

astronomy, astrophysics, exoplanets, lava worlds, Physics, Science, Transiting Exoplanet Survey Satellite / /
Like Kepler-10 b, illustrated above, the exoplanet HD 63433 d is a small, rocky planet in a tight orbit of its star.

Enlarge / Like Kepler-10 b, illustrated above, newly discovered exoplanet HD 63433 d is a small, rocky planet in a tight orbit of its star.

NASA/Ames/JPL-Caltech/T. Pyle

Astronomers have discovered an unusual Earth-sized exoplanet they believe has a hemisphere of molten lava, with its other hemisphere tidally locked in perpetual darkness. Co-authors and study leaders Benjamin Capistrant (University of Florida) and Melinda Soares-Furtado (University of Wisconsin-Madison) presented the details yesterday at a meeting of the American Astronomical Society in New Orleans. An associated paper has just been published in The Astronomical Journal. Another paper published today in the journal Astronomy and Astrophysics by a different group described the discovery of a rare small, cold exoplanet with a massive outer companion 100 times the mass of Jupiter.

As previously reported, thanks to the massive trove of exoplanets discovered by the Kepler mission, we now have a good idea of what kinds of planets are out there, where they orbit, and how common the different types are. What we lack is a good sense of what that implies in terms of the conditions on the planets themselves. Kepler can tell us how big a planet is, but it doesn’t know what the planet is made of. And planets in the “habitable zone” around stars could be consistent with anything from a blazing hell to a frozen rock.

The Transiting Exoplanet Survey Satellite (TESS) was launched with the intention of helping us figure out what exoplanets are actually like. TESS is designed to identify planets orbiting bright stars relatively close to Earth, conditions that should allow follow-up observations to figure out their compositions and potentially those of their atmospheres.

Both Kepler and TESS identify planets using what’s called the transit method. This works for systems in which the planets orbit in a plane that takes them between their host star and Earth. As this occurs, the planet blocks a small fraction of the starlight that we see from Earth (or nearby orbits). If these dips in light occur with regularity, they’re diagnostic of something orbiting the star.

This tells us something about the planet. The frequency of the dips in the star’s light tells us how long an orbit takes, which tells us how far the planet is from its host star. That, combined with the host star’s brightness, tells us how much incoming light the planet receives, which will influence its temperature. (The range of distances at which temperatures are consistent with liquid water is called the habitable zone.) And we can use that, along with how much light is being blocked, to figure out how big the planet is.

But to really understand other planets and their potential to support life, we have to understand what they’re made of and what their atmosphere looks like. While TESS doesn’t answer those questions, it’s designed to find planets with other instruments that could answer them.

Astronomers found ultra-hot, Earth-sized exoplanet with a lava hemisphere Read More »

astronomers-think-they-finally-know-origin-of-enormous-“cosmic-smoke-rings“

Astronomers think they finally know origin of enormous “cosmic smoke rings“

astronomy, astrophysics, galactic winds, Odd Radio Circles, Physics, Science / /

Space oddity —

Massive stars burn out quickly. When they die, they expel their gas as outflowing winds.

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Odd radio circles, like ORC 1 pictured above, are large enough to contain galaxies in their centers and reach hundreds of thousands of light years across.

Enlarge / Odd radio circles are large enough to contain galaxies in their centers and reach hundreds of thousands of light years across.

Jayanne English / University of Manitoba

The discovery of so-called “odd radio circles” several years ago had astronomers scrambling to find an explanation for these enormous regions of radio waves so far-reaching that they have galaxies at their centers. Scientists at the University of California, San Diego, think they have found the answer: outflowing galactic winds from exploding stars in so-called “starburst” galaxies. They described their findings in a new paper published in the journal Nature.

“These galaxies are really interesting,” said Alison Coil of the University of California, San Diego. “They occur when two big galaxies collide. The merger pushes all the gas into a very small region, which causes an intense burst of star formation. Massive stars burn out quickly, and when they die, they expel their gas as outflowing winds.”

As reported previously, the discovery arose from the Evolutionary Map of the Universe (EMU) project, which aims to take a census of radio sources in the sky. Several years ago, Ray Norris, an astronomer at Western Sydney University and CSIRO in Australia, predicted the EMU project would make unexpected discoveries. He dubbed them “WTFs.” Anna Kapinska, an astronomer at the National Radio Astronomy Observatory (NRAO) was browsing through radio astronomy data collected by CSIRO’s Australian Square Kilometer Array Pathfinder (ASKAP) telescope when she noticed several strange shapes that didn’t seem to resemble any known type of object. Following Norris’ nomenclature, she labeled them as possible WTFs. One of those was a picture of a ghostly circle of radio emission, “hanging out in space like a cosmic smoke ring.”

Other team members soon found two more weird round blobs, which they dubbed “odd radio circles” (ORCs). A fourth ORC was identified in archival data from India’s Giant MetreWave Radio Telescope, and a fifth was discovered in fresh ASKAP data in 2021. There are several more objects that might also be ORCs. Based on this, the team estimates there could be as many as 1,000 ORCs in all.

While Norris et al. initially assumed the blobs were just imaging artifacts, data from other radio telescopes confirmed they were a new class of astronomical object. They don’t show up in standard optical telescopes or in infrared and X-ray telescopes—only in the radio spectrum. Astronomers suspect the radio emissions are due to clouds of electrons. But that wouldn’t explain why ORCs don’t show up in other wavelengths. All of the confirmed ORCs thus far have a galaxy at the center, suggesting this might be a relevant factor in how they form. And they are enormous, measuring about a million light-years across, which is larger than our Milky Way.

As for what caused the explosions that led to the formation of ORCs, new data reported in 2022 was sufficient to rule out all but three possibilities. The first is that ORCs are the result of a shockwave from the center of a galaxy, perhaps arising from the merging of two supermassive black holes. Alternatively, they could be the result of radio jets spewing particles from active galactic nuclei. Finally, ORCs may be shells caused by starburst events (“termination shock”), which would produce a spherical shock wave as hot gas blasted out from a galactic center.

A simulation of starburst-driven winds at three different time periods, starting at 181 million years. The top half of each image shows gas temperature, while the lower half shows the radial velocity.

Enlarge / A simulation of starburst-driven winds at three different time periods, starting at 181 million years. The top half of each image shows gas temperature, while the lower half shows the radial velocity.

Cassandra Lochhaas / Space Telescope Science Institute

Coil et al. were intrigued by the discovery of ORCs. They had been studying starburst galaxies, which are noteworthy for their very high rate of star formation, making them appear bright blue. The team thought the later stages of those starburst galaxies might explain the origin of ORCs, but they needed more than radio data to prove it. So the team used the integral field spectrograph at the W.M. Keck Observatory in Hawaii to take a closer look at ORC 4, the first radio circle observable from the Northern Hemisphere. That revealed a much higher amount of bright, heated, compressed gas than one would see in an average galaxy. Additional optical and infrared imaging data revealed that the stars in the ORC 4 galaxy are about 6 billion years old. New star formation seems to have ended some billion years ago.

The next step was to run computer simulations of the odd radio circle itself spanning the course of 750 million years. Those simulations showed an initial 200-million-year period with powerful outflowing galactic winds, followed by a shock wave that propelled very hot gas out of the galaxy to create a radio ring. Meanwhile, a reverse shock wave sent cooler gas back into the central galaxy.

“To make this work, you need a high-mass outflow rate, meaning it’s ejecting a lot of material very quickly. And the surrounding gas just outside the galaxy has to be low density, otherwise the shock stalls. These are the two key factors,” said Coil. “It turns out the galaxies we’ve been studying have these high-mass outflow rates. They’re rare, but they do exist. I really do think this points to ORCs originating from some kind of outflowing galactic winds.” She also thinks that ORCs could help astronomers understand more about galactic outflowing winds since it enables them to “see” those winds through radio data and spectrometry.

Nature, 2024. DOI: 10.1038/s41586-023-06752-8  (About DOIs).

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Study: The best free-throw shooters share these biomechanical traits

12 days of Christmas, basketball, Biomechanics, Physics, Science, sports science / /

There’s rarely time to write about every cool science-y story that comes our way. So this year, we’re once again running a special Twelve Days of Christmas series of posts, highlighting one science story that fell through the cracks in 2020, each day from December 25 through January 5. Today: Using markerless motion capture technology to determine what makes the best free throw shooters in basketball.

Markerless motion-capture technology shows the biomechanics of free-throw shooters. Credit: Jayhawk Athletic Peformance Laboratory.

Basketball season is in full swing, and in a close game, the team that makes the highest percentage of free throws can often eke out the win. A better understanding of the precise biomechanics of the best free-throw shooters could translate into critical player-performance improvement. Researchers at the University of Kansas in Lawrence used markerless motion-capture technology to do just that, reporting their findings in an August paper published in the journal Frontiers in Sports and Active Living.

“We’re very interested in analyzing basketball shooting mechanics and what performance parameters differentiate proficient from nonproficient shooters,” said co-author Dimitrije Cabarkapa, director of the Jayhawk Athletic Performance Laboratory at the University of Kansas. “High-speed video analysis is one way that we can do that, but innovative technological tools such as markerless motion capture systems can allow us to dig even deeper into that. In my opinion, the future of sports science is founded on using noninvasive and time-efficient testing methodologies.”

Scientists are sports fans like everyone else, so it’s not surprising that a fair amount of prior research has gone into various aspects of basketball. For instance, there has been considerable debate on whether the “hot hand” phenomenon in basketball is a fallacy or not—that is, when players make more shots in a row than statistics suggest they should. A 1985 study proclaimed it a fallacy, but more recent mathematical analysis (including a 2015 study examining the finer points of the law of small numbers) from other researchers has provided some vindication that such streaks might indeed be a real thing, although it might only apply to certain players.

Some 20 years ago, Larry Silverberg and Chia Tran of North Carolina State University developed a method to computationally simulate the trajectories of millions of basketballs on the computer and used it to examine the mathematics of the free throw. Per their work, in a perfect free throw, the basketball has a 3 hertz backspin as it leaves the player’s fingertips, the launch is about 52 degrees, and the launch speed is fairly slow, ensuring the greatest probability of making the basket. Of those variables launch speed is the most difficult for players to control. The aim point also matters: Players should aim at the back of the rim, which is more forgiving than the front.

There was also a 2021 study by Malaysian scientists that analyzed the optimal angle of a basketball free throw, based on data gleaned from 30 NBA players. They concluded that a player’s height is inversely proportional to the initial velocity and optimal throwing angle, and that the latter is directly proportional to the time taken for a ball to reach its maximum height.

Graphic showing the contrast in release angles between proficient and nonproficient shooters.

Enlarge / Graphic showing the contrast in release angles between proficient and nonproficient shooters.

Jayhawk Athletic Performance Laboratory.

Cabarkapa’s lab has been studying basketball players’ performance for several years now, including how eating breakfast (or not) impacts shooting performance, and what happens to muscles when players overtrain. They published a series of studies in 2022 assessing the effectiveness of the most common coaching cues, like “bend your knees,” “tuck your elbow in,” or “release the ball as high as possible.” For one study, Cabarkapa et al. analyzed high-definition video of free-throw shooters for kinematic differences between players who excel at free throws and those who don’t. The results pointed to greater flexion in hip, knee, and angle joints resulting in lower elbow placement when shooting.

Yet they found no kinematic differences in shots that proficient players made and those they missed, so the team conducted a follow-up study employing a 3D motion-capture system. This confirmed that greater knee and elbow flexion and lower elbow placement were critical factors. There was only one significant difference between made and missed free-throw shots: positioning the forearm almost parallel with an imaginary lateral axis.

Study: The best free-throw shooters share these biomechanical traits Read More »

these-scientists-explored-the-good-vibrations-of-the-bundengan-and-didgeridoo

These scientists explored the good vibrations of the bundengan and didgeridoo

12 days of Christmas, acoustics, bundengan, didgeridoo, Musical Instruments, Physics, Science / /

On the fifth day of Christmas —

Their relatively simple construction produces some surprisingly complicated physics.

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Indonesian performers onstage with one playing a bundengan

Enlarge / The bundengan (left) began as a combined shelter/instrument for duck hunters but it is now often played onstage.

There’s rarely time to write about every cool science-y story that comes our way. So this year, we’re once again running a special Twelve Days of Christmas series of posts, highlighting one science story that fell through the cracks in 2020, each day from December 25 through January 5. Today: the surprisingly complex physics of two simply constructed instruments: the Indonesian bundengan and the Australian Aboriginal didgeridoo (or didjeridu).

The bundengan is a rare, endangered instrument from Indonesia that can imitate the sound of metallic gongs and cow-hide drums (kendangs) in a traditional gamelan ensemble. The didgeridoo is an iconic instrument associated with Australian Aboriginal culture that produces a single, low-pitched droning note that can be continuously sustained by skilled players. Both instruments are a topic of scientific interest because their relatively simple construction produces some surprisingly complicated physics. Two recent studies into their acoustical properties were featured at an early December meeting of the Acoustical Society of America, held in Sydney, Australia, in conjunction with the Australian Acoustical Society.

The bundengan originated with Indonesian duck hunters as protection from rain and other adverse conditions while in the field, doubling as a musical instrument to pass the time. It’s a half-dome structure woven out of bamboo splits to form a lattice grid, crisscrossed at the top to form the dome. That dome is then coated with layers of bamboo sheaths held in place with sugar palm fibers. Musicians typically sit cross-legged inside the dome-shaped resonator and pluck the strings and bars to play. The strings produce metallic sounds while the plates inside generate percussive drum-like sounds.

Gea Oswah Fatah Parikesit of Universitas Gadja Mada in Indonesia has been studying the physics and acoustics of the bundengan for several years now. And yes, he can play the instrument. “I needed to learn to do the research,” he said during a conference press briefing. “It’s very difficult because you have two different blocking styles for the right and left hand sides. The right hand is for the melody, for the string, and the left is for the rhythm, to pluck the chords.”

Much of Parikesit’s prior research on the bundengan focused on the unusual metal/percussive sound of the strings, especially the critical role played by the placement of bamboo clips. He used computational simulations of the string vibrations to glean insight on how the specific gong-like sound was produced, and how those vibrations change with the addition of bamboo clips located at different sections of the string. He found that adding the clips produces two vibrations of different frequencies at different locations on the string, with the longer section having a high frequency vibration compared to the lower frequency vibration of the shorter part of the string. This is the key to making the gong-like sound.

This time around, Parikesit was intrigued by the fact many bundengan musicians have noted the instrument sounds better wet. In fact, several years ago, Parikesit attended a bundengan concert in Melbourne during the summer when it was very hot and dry—so much so that the musicians brought their own water spray bottles to ensure the instruments stayed (preferably) fully wet.

A bundengan is a portable shelter woven from bamboo, worn by Indonesian duck herders who often outfit it to double as a musical instrument.

Enlarge / A bundengan is a portable shelter woven from bamboo, worn by Indonesian duck herders who often outfit it to double as a musical instrument.

Gea Oswah Fatah Parikesit

“A key element between the dry and wet versions of the bundengan is the bamboo sheaths—the material used to layer the wall of the instrument,” Parokesit said. “When the bundengan is dry, the bamboo sheaths open and that results in looser connections between neighboring sheaths. When the bundengan is wet, the sheaths tend to form a curling shape, but because they are held by ropes, they form tight connections between the neighboring sheaths.”

The resulting tension allows the sheaths to vibrate together. That has a significant impact on the instrument’s sound, taking on a “twangier” quality when dry and a more of metallic gong sound when it is wet. Parikesit has tried making bundengans with other materials: paper, leaves, even plastics. But none of those produce the same sound quality as the bamboo sheaths. He next plans to investigate other musical instruments made from bamboo sheaths.“As an Indonesian, I have extra motivation because the bundengan is a piece of our cultural heritage,” Parikesit said. “I am trying my best to support the conservation and documentation of the bundengan and other Indonesian endangered instruments.”

Coupling with the human vocal tract

Meanwhile, John Smith of the University of New South Wales is equally intrigued by the physics and acoustics of the didgeridoo. The instrument is constructed from the trunk or large branches of the eucalyptus tree. The trick is to find a live tree with lots of termite activity, such that the trunk has been hollowed out leaving just the living sapwood shell. A suitably hollow trunk is then cut down, cleaned out, the bark removed, the ends trimmed, and the exterior shaped into a long cylinder or cone to produce the final instrument. The longer the instrument, the lower the pitch or key.

Players will vibrate their lips to play the didgeridoo in a manner similar to lip valve instruments like trumpets or trombones, except those use a small mouthpiece attached to the instrument as an interface. (Sometimes a beeswax rim is added to a didgeridoo mouthpiece end.) Players typically use circular breathing to maintain that continuous low-pitched drone for several minutes, basically inhaling through the nose and using air stored in the puffed cheeks to keep producing the sound. It’s the coupling of the instrument with the human vocal tract that makes the physics so complex, per Smith.

Smith was interested in investigating how changes in the configuration of the vocal tract produced timbral changes in the rhythmic pattern of the sounds produced. To do so, “We needed to develop a technique that could measure the acoustic properties of the player’s vocal tract while playing,” Smith said during the same press briefing. “This involved injecting a broadband signal into the corner of the player’s mouth and using a microphone to record the response.” That enabled Smith and his cohorts to record the vocal tract impedance in different configurations in the mouth.

Producing complex sounds with the didjeridu requires creating and manipulating resonances inside the vocal tract.

Enlarge / Producing complex sounds with the didjeridu requires creating and manipulating resonances inside the vocal tract.

Kate Callas

The results: “We showed that strong resonances in the vocal tract can suppress bands of frequencies in the output sound,” said Smith. “The remaining strong bands of frequencies, called formants, are noticed by our hearing because they fall in the same ranges as the formants we use in speech. It’s a bit like a sculptor removing marble, and we observe the bits that are left behind.”

Smith et al. also noted that the variations in timbre arise from the player singing while playing, or imitating animal sounds (such as the dingo or the kookaburra), which produces many new frequencies in the output sound. To measure the contact between vocal folds, they placed electrodes on either side of a player’s throat and zapped them with a small high frequency electric current. They simultaneously measured lip movement with another pair of electrics above and below the lips. Both types of vibrations affect the flow of air to produce the new frequencies.

As for what makes a desirable didgeridoo that appeals to players, acoustic measurements on a set of 38 such instruments—with the quality of each rated by seven experts in seven different subjective categories—produced a rather surprising result. One might think players would prefer instruments with very strong resonances but the opposite turned out to be true. Instruments with stronger resonances were ranked the worst, while those with weaker resonances rated more highly.  Smith, for one, thinks this makes sense. “This means that their own vocal tract resonance can dominate the timbre of the notes,” he said.

These scientists explored the good vibrations of the bundengan and didgeridoo Read More »

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Watch sand defy gravity and flow uphill thanks to “negative friction”

12 days of Christmas, collective motion, engineering, fluid dynamics, granular flow, granular materials, Physics, Science / /

On the second day of Christmas —

Applying magnetic forces to single iron oxide-coated particles spurs strange collective motion.

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There’s rarely time to write about every cool science-y story that comes our way. So this year, we’re once again running a special Twelve Days of Christmas series of posts, highlighting one science story that fell through the cracks in 2023, each day from December 25 through January 5. Today: how applying magnetic forces to individual “micro-roller” particles spurs collective motion, producing some pretty counter-intuitive results.

Engineering researchers at Lehigh University have discovered that sometimes sand can actually flow uphill.

Enlarge / Engineering researchers at Lehigh University have discovered that sometimes sand can actually flow uphill.

Lehigh University

We intuitively understand that the sand pouring through an hourglass, for example, forms a neat roughly pyramid-shaped pile at the bottom, in which the grains near the surface flow over an underlying base of stationary particles. Avalanches and sand dunes exhibit similar dynamics. But scientists at Lehigh University in Pennsylvania have discovered that applying a magnetic torque can actually cause sand-like particles to collectively flow uphill in seeming defiance of gravity, according to a September paper published in the journal Nature Communications.

Sand is pretty fascinating stuff from a physics standpoint. It’s an example of a granular material, since it acts both like a liquid and a solid. Dry sand collected in a bucket pours like a fluid, yet it can support the weight of a rock placed on top of it, like a solid, even though the rock is technically denser than the sand. So sand defies all those tidy equations describing various phases of matter, and the transition from flowing “liquid” to a rigid “solid” happens quite rapidly. It’s as if the grains act as individuals in the fluid form, but are capable of suddenly banding together when solidarity is needed, achieving a weird kind of “strength in numbers” effect.

Nor can physicists precisely predict an avalanche. That’s partly because of the sheer number of grains of sand in even a small pile, each of which will interact with several of its immediate neighboring grains simultaneously—and those neighbors shift from one moment to the next. Not even a supercomputer can track the movements of individual grains over time, so the physics of flow in granular media remains a vital area of research.

But grains of sand that collectively flow uphill? That is simply bizarre behavior. Lehigh University engineer James Gilchrist manages the Laboratory for Particle Mixing and Self-Organization and stumbled upon this odd phenomenon while experimenting with “micro-rollers”: polymer particles coated in iron oxide (a process called micro-encapsulation). He was rotating a magnet under a vial of micro-rollers one day and noticed they started to pile uphill. Naturally he and his colleagues had to investigate further.

For their experiments, Gilchrist et al. attached neodymium magnets to a motorized wheel at 90-degree intervals, alternating the outward facing poles. The apparatus also included a sample holder and a USB microscope in a fixed position. The micro-rollers were prepared by suspending them in a glass vial containing ethanol and using a magnet to separate them from dust or any uncoated particles. Once the micro-rollers were clean, they were dried, suspended in fresh ethanol, and loaded onto the sample holder. A vibrating motor agitated the samples to produce flattened granular beds, and the motorized wheel was set in motion to apply magnetic torque. A gaussmeter measured the magnetic field strength relative to orientation.

Uphill granular flow of microrobotic microrollers. Credit: Lehigh University.

The results: each micro-roller began to rotate in response to the magnetic torque, creating pairs that briefly formed and then split, and increasing the magnetic force increased the particle cohesion. This in turn gave the micro-rollers more traction and enabled them to move more quickly, working in concert to counterintuitively flow uphill. In the absence of that magnetic torque, the miro-rollers flowed downhill normally. The torque-induced action was so unexpected that the researchers coined a new term to describe it: a “negative angle of repose” caused by a negative coefficient of friction.

“Up until now, no one would have used these terms,” said Gilchrist. “They didn’t exist. But to understand how these grains are flowing uphill, we calculated what the stresses are that cause them to move in that direction. If you have a negative angle of repose, then you must have cohesion to give a negative coefficient of friction. These granular flow equations were never derived to consider these things, but after calculating it, what came out is an apparent coefficient of friction that is negative.”

It’s an intriguing proof of principle that could one day lead to new ways to control how substances mix or separate, as well as potential swarming microrobotics applications. The scientists have already started building tiny staircases with laser cutters and videotaping the micro-rollers climbing up and down the other. One micro-roller can’t overcome the height of each step, but many working collectively can do so, per Gilchrist.

DOI: Nature Communications, 2023. 10.1038/s41467-023-41327-1  (About DOIs).

Listing image by Lehigh University

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