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Challenging a 300-year-old law of friction

Researchers at the University of Konstanz have uncovered a new mechanism of sliding friction: resistance to motion that arises without any mechanical contact, driven purely by collective magnetic dynamics. The study, published in Nature Materials, shows that friction does not necessarily increase steadily with load, as postulated by Amontons’ law—one of the oldest and most fundamental empirical laws of physics—but can instead exhibit a pronounced maximum when internal magnetic ordering becomes frustrated.

For more than three centuries, Amontons’ law has linked friction directly to load, reflecting the everyday experience that heavier objects are harder to move; for example, pushing a heavy piece of furniture requires far more effort than sliding a light chair. This behavior is commonly attributed to tiny deformations of the surfaces in contact under load, which increase the number of microscopic contact points and thereby enhance friction.

In most classical situations, these deformations remain small and do not qualitatively change the internal structure of the materials during sliding. It is therefore not clear whether Amontons’ law will also hold when sliding induces much stronger internal reconfigurations, as can occur in magnetic materials where motion can modify the magnetic order.

Terahertz spin waves can be converted into computer signals, study shows

What will the computers of tomorrow look like? Chances are good that spintronics will play a decisive role in the next generation of computers. In spintronics, the intrinsic angular momentum of an electron (the spin) is used to store, process and transmit data. This technology is already in use today, for example in hard drives. However, the scope of what is possible extends much further: More recent approaches aim at using not just individual spins, but entire spin waves made up of partly hundreds of trillions of spins. Such collective spin excitations are known as magnons. They could enable extremely energy-efficient data transmission—even in the terahertz range.

So far, so good. But how can these spin waves be coupled to today’s technology? “If we develop a concept to perform computer calculations with magnons, it must be compatible with the technology we currently use,” says physicist Davide Bossini from the University of Konstanz. “To reach this goal, you have to convert the spin wave into an electrical charge signal.” This spin-to-charge conversion is one of the major challenges of spintronics.

AI rebuilds molecules from exploding fragments

Researchers at the Department of Energy’s SLAC National Accelerator Laboratory and collaborating institutions recently built a generative AI model that can recreate molecular structures from the movement of the molecule’s ions after they are blasted apart by X-rays, a technique called Coulomb explosion imaging.

The research, published in Nature Communications, is an important step toward being able to take snapshots of molecules during chemical reactions—an advance that could have important impacts in medicine and industry. The machine learning model closely predicted the geometries of a range of different molecules made of less than ten atoms, paving the way for applying the technique to larger molecules.

“We were pretty excited about this,” said Xiang Li, an associate scientist at SLAC’s Linac Coherent Light Source (LCLS) and lead author of the study. “It is the first AI model built for molecular structure reconstruction from Coulomb explosion imaging.”

Clearest evidence yet that giant planets spin faster than their cosmic lookalikes

For decades, astronomers have struggled to differentiate giant planets from brown dwarfs, a class of objects more massive than planets but too small to ignite nuclear fusion like true stars. Through a telescope, these cosmic lookalikes can have overlapping brightness, temperatures, and even atmospheric fingerprints. The striking similarity leaves astronomers unsure if they have observed an oversized planet or an undersized star. Now, a Northwestern University-led team has uncovered a crucial clue that separates the two: how fast they spin.

In a new study, astrophysicists found the clearest evidence yet that giant planets spin significantly faster than their brown dwarf counterparts. The new results suggest rotation measurements may provide a powerful new diagnostic for classifying these indistinguishable populations and suggest that these two objects evolve differently, perhaps even forming through distinct processes.

The study was published in The Astronomical Journal. It marks the largest survey of spin measurements of directly imaged extrasolar planets and brown dwarfs to date.

How two dim stars came together to shine brightly

Brown dwarfs get a bad rap in the stellar world, often labeled as “failed stars” for their inability to sustain nuclear fusion at their cores. The mass of these objects falls between planets and stars, ranging from 13 to 80 times the mass of Jupiter. Because they aren’t massive enough to sustain fusion, they are far fainter and cooler than their stellar comrades.

Now, a new finding led by researchers at Caltech shows how these dim bulbs can join together to shine brightly. Searching through archival observations captured by the Zwicky Transient Facility (ZTF) at Caltech’s Palomar Observatory, researchers have identified a very tight-knit pair of brown dwarfs in which one is actively siphoning material from the other.

Ultimately, the brown dwarfs are expected to merge to form a new star; alternatively, the brown dwarf gaining the extra mass will ignite to become a star. Either way, a pair of failed stars will have created a brilliant new star.

Large-scale look at the exposome shows combined environmental exposures rival genetics in shaping human health outcomes

For decades, scientists have been carefully unraveling the role of genes in disease by examining how small variations in a person’s genetic code can shape lifelong risk of developing common conditions such as cancer, diabetes, or heart disease. But genetics only tell part of the story.

The other part comes from all the external and internal exposures a person experiences during their lifetime, which can range from pollution to infections to diet and lifestyle. Cumulatively, these exposures—and the body’s biological response to them—make up what scientists have termed the exposome.

A team led by scientists at Harvard Medical School has now conducted what may be the largest-scale study to date to quantify the relationships between exposures and health outcomes, testing more than 100,000 associations. The work demonstrates the importance of studying potential environmental disease risks in aggregate rather than one at a time.

NASA’s Hubble unexpectedly catches comet breaking up

In a happy twist of fate, NASA’s Hubble Space Telescope witnessed a comet in the act of breaking apart. The chance of that happening while Hubble watched is extraordinarily minuscule. The findings are published in the journal Icarus.

The comet K1, whose full name is C/2025 K1 (ATLAS)—not to be confused with interstellar comet 3I/ATLAS—was not the original target of the Hubble study.

“Sometimes the best science happens by accident,” said co-investigator John Noonan, a research professor in the Department of Physics at Auburn University in Alabama. “This comet got observed because our original comet was not viewable due to some new technical constraints after we won our proposal. We had to find a new target—and right when we observed it, it happened to break apart, which is the slimmest of slim chances.”

Wearable thermoelectric technology uses thin films to generate electricity from body heat

Seoul National University College of Engineering has announced that a research team led by Prof. Jeonghun Kwak of the Department of Electrical and Computer Engineering, with co-first authors Dr. Juhyung Park and Dr. Sun Hong Kim, has developed a flexible and thin “pseudo-transverse thermoelectric generator” capable of producing electricity from body heat. The research findings appear in Science Advances.

Thermoelectric generators, which convert temperature differences into electricity, are attracting attention as a next-generation energy technology for wearable electronics because they can supply power without batteries. In particular, thin-film thermoelectric generators are lightweight and flexible, allowing them to be comfortably attached to skin or clothing.

However, this thin structure also presents a limitation. Thermoelectric generators require a temperature difference between hot and cold sides to generate electricity. When such a device is attached flat to the skin, body heat passes directly through the thin film and dissipates into the surrounding air—similar to heat passing through a sheet of paper. As a result, little to no temperature difference is formed across the device, making electricity generation difficult.

Most mass spectrometers can process just a few molecules at once: Reengineered prototype does a billion simultaneously

Mass spectrometry is already a powerful tool for determining what kind and how many molecules are present in a given sample. But most instruments still analyze their molecules one or just a few at a time, an approach that is inefficient and costly, and in which rare, but significant molecules can easily fall between the cracks.

A more powerful version of the technology could one day allow scientists to read the full molecular contents of a single cell, track thousands of chemical reactions at once, and ultimately accelerate efforts like drug development.

Now, a new study describes the first big step in that direction by producing a prototype, dubbed MultiQ-IT, that’s capable of handling vast numbers of molecules at once. The findings, published in the journal Science Advances, offer a blueprint for faster, more sensitive instruments that could position mass spectrometry for the kind of transformation that reshaped genomics and computing.

Is glass a solid or a super slow liquid? Physicists create equilibrium glassy phase from rod-shaped particles

Glass appears to be a solid, but in theory it sometimes behaves more like an extremely slow liquid. Physicists in Utrecht now show that glass-like structures can also exist in equilibrium, which is something many theories say should be impossible.

The bottom parts of medieval window panes, such as those in old cathedrals, are often thicker than the top. Has the material slowly flowed downward over the centuries, and does this mean that glass actually flows? This is a persistent myth, and the explanation lies in the way glass was produced in the Middle Ages. Because window panes were made by hand, their structure was often irregular and contained thinner and thicker parts. The panes were usually installed in the frame with the thicker side at the bottom, which made them more stable.

Still, the story touches on a real physics question. What glass actually is, a solid or a very slow liquid, turns out to be more difficult to answer than it seems.

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