Federal toxicology researchers on Monday finally published a long-controversial analysis that claims to find a link between high levels of fluoride exposure and slightly lower IQs in children living in areas outside the US, mostly in China and India. As expected, it immediately drew yet more controversy.

The study, published in JAMA Pediatrics, is a meta-analysis, a type of study that combines data from many different studies—in this case, mostly low-quality studies—to come up with new results. None of the data included in the analysis is from the US, and the fluoride levels examined are at least double the level recommended for municipal water in the US. In some places in the world, fluoride is naturally present in water, such as parts of China, and can reach concentrations several-fold higher than fluoridated water in the US.

The authors of the analysis are researchers at the National Toxicology Program at the National Institute of Environmental Health Sciences. For context, this is the same federal research program that published a dubious analysis in 2016 suggesting that cell phones cause cancer in rats. The study underwent a suspicious peer-review process and contained questionable methods and statistics.

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It's difficult to comprehend what 1,000 cubic kilometers of rock would look like. It's even more difficult to imagine it being violently flung into the air. Yet the Yellowstone volcanic system blasted more than twice that amount of rock into the sky about 2 million years ago, and it has generated a number of massive (if somewhat smaller) eruptions since, and there have been even larger eruptions deeper in the past.

All of which might be enough to keep someone nervously watching the seismometers scattered throughout the area. But a new study suggests that there's nothing to worry about in the near future: There's not enough molten material pooled in one place to trigger the sort of violent eruptions that have caused massive disruptions in the past. The study also suggests that the primary focus of activity may be shifting outside of the caldera formed by past eruptions.

Understanding Yellowstone

Yellowstone is fueled by what's known as a hotspot, where molten material from the Earth's mantle percolates up through the crust. The rock that comes up through the crust is typically basaltic (a definition based on the ratio of elements in its composition) and can erupt directly. This tends to produce relatively gentle eruptions where lava flows across a broad area, generally like you see in Hawaii and Iceland. But this hot material can also melt rock within the crust, producing a material called rhyolite. This is a much more viscous material that does not flow very readily and, instead, can cause explosive eruptions.

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Some version of the Hula-Hoop has been around for millennia, but the popular plastic version was introduced by Wham-O in the 1950s and quickly became a fad. Now, researchers have taken a closer look at the underlying physics of the toy, revealing that certain body types are better at keeping the spinning hoops elevated than others, according to a new paper published in the Proceedings of the National Academy of Sciences.

“We were surprised that an activity as popular, fun, and healthy as hula hooping wasn’t understood even at a basic physics level,” said co-author Leif Ristroph of New York University. “As we made progress on the research, we realized that the math and physics involved are very subtle, and the knowledge gained could be useful in inspiring engineering innovations, harvesting energy from vibrations, and improving in robotic positioners and movers used in industrial processing and manufacturing.”

Ristroph's lab frequently addresses these kinds of colorful real-world puzzles. For instance, in 2018, Ristroph and colleagues fine-tuned the recipe for the perfect bubble based on experiments with soapy thin films. In 2021, the Ristroph lab looked into the formation processes underlying so-called "stone forests" common in certain regions of China and Madagascar.

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When fast radio bursts (FRBs) were first detected in 2007, they were a complete enigma. As their name implies, these events involve a very brief eruption of radio emissions and then typically silence, though a few objects appear to be capable of sending out multiple bursts. By obtaining enough data from lots of individual bursts, researchers gradually put the focus on magnetars, versions of neutron stars that have intense magnetic fields.

But we still don't know whether a magnetar is a requirement for an FRB or if the events can be triggered by less magnetized neutron stars as well. And we have little hint of the mechanism that produces the burst itself. Bursts could potentially be produced by an event in the star's magnetic field itself, or the star could be launching some energetic material that subsequently produces an FRB at some distance from the star.

But now, a rare burst has provided indications that FRBs likely originate near the star and that they share a feature with the emissions of pulsars, another subtype of neutron star.

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Silicon chip manufacturers like Intel and TSMC are constantly outdoing themselves to make ever smaller features, but they are getting closer to the physical limits of silicon.

“We already have very, very high density in silicon-based architectures where silicon performance degrades sharply,” said Ki Seok Kim, a scientist working at the Massachusetts Institute of Technology’s Research Laboratory of Electronics.

One way around this problem is to replace silicon with graphene-like 2D materials that maintain their semiconducting properties even at a single-atom scale. Another way is building 3D chips, which squeeze more transistors into the same area without making transistors smaller. Kim’s team did both, building a 3D chip out of vertically stacked 2D semiconductors.

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Back in 2019, we told you about an intriguing experiment to test a famous anthropological legend about an elderly Inuit man in the 1950s who fashioned a knife out of his own frozen feces. He used it to kill and skin a dog, using its rib cage as a makeshift sled to venture off into the Arctic. Metin Eren, an archaeologist at Kent State University, fashioned rudimentary blades out of his own frozen feces to test whether they could cut through pig hide, muscle, and tendon.

Sadly for the legend, the blades failed every test, but the study was colorful enough to snag Eren an Ig Nobel Prize the following year. And it's just one of the many fascinating projects routinely undertaken in his Experimental Archaeology Laboratory, where he and his team try to reverse-engineer all manner of ancient technologies, whether they involve stone tools, ceramics, metal, butchery, textiles, and so forth.

Eren's lab is quite prolific, publishing 15 to 20 papers a year. “The only thing we’re limited by is time,” he said. Many have colorful or quirky elements and hence tend to garner media attention, but Eren emphasizes that what he does is very much serious science, not entertainment. “I think sometimes people look at experimental archaeology and think it’s no different from LARPing,” Eren told Ars. “I have nothing against LARPers, but it’s very different. It’s not playtime. It’s hardcore science. Me making a stone tool is no different than a chemist pouring chemicals into a beaker. But that act alone is not the experiment. It might be the flashiest bit, but that's not the experimental process.”

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Manta rays are elegantly shaped. They swim by flapping their fins like enormous wings, and their gills filter for plankton with the utmost precision. These creatures have now inspired human innovations that take soft robots and water filters to the next level.

With fins that borrow their shape and motion from mantas, a soft robot created by a team of researchers at North Carolina State University and the University of Virginia improves on a previous model by reaching speeds of 6.8 body lengths per second, nearly double what its predecessor was capable of. This makes it the fastest soft robot so far. It is also more energy-efficient than its previous iteration and can swim not just on the surface, but upward and downward, just like an actual manta ray.

Another research team at MIT used the gills of these creatures, which filter for plankton, to improve commercial water filtration systems. Their gill openings are also the perfect size to help them breathe while they feed, absorbing oxygen from water on its way out. The rays’ balance of feeding and breathing helped the researchers figure out a filter structure that more precisely controls inflow and outflow.

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Over the holiday weekend, all but one member of the editorial board of Elsevier's Journal of Human Evolution (JHE) resigned "with heartfelt sadness and great regret," according to Retraction Watch, which helpfully provided an online PDF of the editors' full statement. It's the 20th mass resignation from a science journal since 2023 over various points of contention, per Retraction Watch, many in response to controversial changes in the business models used by the scientific publishing industry.

"This has been an exceptionally painful decision for each of us," the board members wrote in their statement. "The editors who have stewarded the journal over the past 38 years have invested immense time and energy in making JHE the leading journal in paleoanthropological research and have remained loyal and committed to the journal and our authors long after their terms ended. The [associate editors] have been equally loyal and committed. We all care deeply about the journal, our discipline, and our academic community; however, we find we can no longer work with Elsevier in good conscience."

The editorial board cited several changes made over the last ten years that it believes are counter to the journal's longstanding editorial principles. These included eliminating support for a copy editor and a special issues editor, leaving it to the editorial board to handle those duties. When the board expressed the need for a copy editor, Elsevier's response, they said, was "to maintain that the editors should not be paying attention to language, grammar, readability, consistency, or accuracy of proper nomenclature or formatting."

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Behold the frogfish. This bizarre creature really is a fish, despite its bullfrog face, pectoral fins that look like webbed feet, and a froglike mouth that snaps up unsuspecting prey.

But the way it lures its prey is even weirder. Frogfish belong to the anglerfish family known as Antennariidae. Like their anglerfish cousins who lurk in the ocean’s depths, these ambush predators attract their next meal via an appendage on their heads that they use like a fishing lure. This appendage is known as the illicium and thought to have once been a dorsal fin. It has a specialized skin flap, the esca at the end. It tantalizes small fish and crustaceans into thinking it’s a worm until they come too close.

How frogfish controlled the illicium was previously unknown. Led by biologist Naoyuki Yamamoto of Nagoya University, a team of researchers have now discovered that a specialized population of motor neurons have evolved to allow it to shake the illicium around like a wriggling worm. Yamamoto thinks they were originally dorsal fin motor neurons that became more specialized.

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There is rarely time to write about every cool science paper that comes our way; many worthy candidates sadly fall through the cracks over the course of the year. But as 2024 comes to a close, we've gathered ten of our favorite such papers at the intersection of science and culture as a special treat, covering a broad range of topics: from reenacting Bronze Age spear combat and applying network theory to the music of Johann Sebastian Bach, to Spider-Man inspired web-slinging tech and a mathematical connection between a turbulent phase transition and your morning cup of coffee. Enjoy!

Reenacting Bronze Age spear combat

An experiment with experienced fighters who spar freely using different styles. Credit: Valerio Gentile/CC BY

The European Bronze Age saw the rise of institutionalized warfare, evidenced by the many spearheads and similar weaponry archaeologists have unearthed. But how might these artifacts be used in actual combat? Dutch researchers decided to find out by constructing replicas of Bronze Age shields and spears and using them in realistic combat scenarios. They described their findings in an October paper published in the Journal of Archaeological Science.

There have been a couple of prior experimental studies on bronze spears, but per Valerio Gentile (now at the University of Gottingen) and coauthors, practical research to date has been quite narrow in scope, focusing on throwing weapons against static shields. Coauthors C.J. van Dijk of the National Military Museum in the Netherlands and independent researcher O. Ter Mors each had more than a decade of experience teaching traditional martial arts, specializing in medieval polearms and one-handed weapons. So they were ideal candidates for testing the replica spears and shields.

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We’d been chatting for the better part of two hours when Chris Kraft’s eyes suddenly brightened. “Hey,” he said, “Here’s a story I’ll bet you never heard.” Kraft, the man who had written flight rules for NASA at the dawn of US spaceflight and supervised the Apollo program, had invited me to his home south of Houston for one of our periodic talks about space policy and space history. As we sat in recliners upstairs, in a den overlooking the Bay Oaks Country Club, Kraft told me about a time the space shuttle almost got canceled.

It was the late 1970s, when Kraft directed the Johnson Space Center, the home of the space shuttle program. At the time, the winged vehicle had progressed deep into a development phase that started in 1971. Because the program had not received enough money to cover development costs, some aspects of the vehicle (such as its thermal protective tiles) were delayed into future budget cycles. In another budget trick, NASA committed $158 million in fiscal year 1979 funds for work done during the previous fiscal year.

This could not go on, and according to Kraft the situation boiled over during a 1978 meeting in a large conference floor on the 9th floor of Building 1, the Houston center’s headquarters. All the program managers and other center directors gathered there along with NASA’s top leadership. That meeting included Administrator Robert Frosch, a physicist President Carter had appointed a year earlier.

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Whether it’s braving the long line at a trendy new restaurant or hanging on just a few minutes longer to see if there’s a post-credits scene after a movie, the decision to persevere or ditch it depends on specific regions of our brains.

Waiting is not always about self-control. Deciding to wait (or not to wait) also involves gauging the value of the potential reward. In an experiment that investigated wait times among people with lesions in the frontal cortex of the brain, University of Pennsylvania psychologist Joe Kable and his research team found that subjects with damage to certain regions of the prefrontal cortex were less likely to wait things out.

“[Our] findings suggest that regions of the frontal cortex make computationally distinct contributions to adaptive persistence,” he and his team said in a study recently published in the Journal of Neuroscience.

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The art of space mission patches is now more than six decades old, dating to the Vostok 6 mission in 1963 that carried Soviet cosmonaut Valentina Tereshkova into low-Earth orbit for nearly three days. The patch for the first female human spaceflight showcased a dove flying above the letters designating the Soviet Union, CCCP.

That patch was not publicly revealed at the time, and the use of specially designed patches was employed only infrequently by subsequent Soviet missions. NASA's first mission patch would not follow for two years, but the practice would prove more sticky for missions in the United States and become a time-honored tradition.

The first NASA flight to produce a mission-specific patch worn by crew members was Gemini 5. It flew in August 1965, carrying astronauts Gordon Cooper and Pete Conrad on an eight-day mission inside a small Gemini spacecraft. At the time, it was the longest spaceflight conducted by anyone.

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'Tis the season for many holiday traditions, including the Ugly Christmas Sweater—you know, those 1950s-style heavy knits featuring some kind of cartoonish seasonal decoration, like snowflakes, Santa Claus, or—in the case of Mark Darcy from Bridget Jones' Diary (2001)—Rudolph the Red-Nosed Reindeer. "It’s obnoxious and tacky, but also fuzzy and kind of wholesome—the fashion equivalent of a Hallmark Christmas movie (with a healthy dose of tongue-in-cheek)," as CNN's Marianna Cerini recently observed.

Fashion (or lack thereof) aside, sweaters and other knitted fabric are also fascinating to physicists and mathematicians. Case in point: a recent paper published in the journal Physical Review Letters examining the complex mechanics behind the many resting shapes a good Jersey knit can form while at rest.

Knitted fabrics are part of a class of intertwined materials—which also includes birds' nests, surgical knots, knotted shoelaces, and even the degradation of paper fibers in ancient manuscripts. Knitted fabrics are technically a type of metamaterial: an engineered material that gets its properties not from the base materials but from their designed structures. The elasticity (aka, stretchiness) of knitted fabrics is an emergent property: the whole is more than the sum of its parts. How those components (strands of yarn) are arranged at an intermediate scale (the structure) determines the macro scale properties of the resulting fabric.

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There are thousands of YouTube videos in which DIY science enthusiasts cut grapes in half—leaving just a thin bit of skin connecting them—and put the grapes in the microwave, just to marvel at the sparks and plume of ionized gas (plasma) that the grapes produce. This quirky property of grapes might help make more efficient quantum sensors, according to a new paper published in the journal Physical Review Applied.

The plasma-inducing grape effect was first observed in 1994, per the authors. As previously reported, the usual explanation for the generation of plasmas is that grapes are so small that the irradiating microwaves become highly concentrated in the grape tissue, ripping some the molecules apart to generate charged ions (adding to the electrolytes already present in the grapes). The electromagnetic field that forms causes ions to flow from one grape half to the other via the connecting skin—at least at first. That's when you get the initial sparks. Eventually, the ions start passing through the surrounding air as well, ionizing it to produce that hot plume of plasma.

But in 2019, Trent University scientists showed that explanation isn't quite right. The skin bridge isn't necessary for the effect to occur. Rather, the plasma is generated by an electromagnetic "hot spot." The grapes have the right refractive index and size to "trap" microwaves, so putting two of them close together leads to the generation of a hot spot between them. The trick also works with gooseberries, large blackberries, and quail eggs, as well as hydrogel beads—plastic beads soaked in water. ("Many microwaves were in fact harmed during the experiments," co-author Hamza Khattak admitted at the time.)

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When you want to move an object from one place to another, you usually grab it with your hands or a robotic arm. But what if you want to move something you cannot touch without damaging or disrupting it, like a droplet of liquid? A solution proposed by a team of scientists at the North Carolina State University is a metamaterial that can change shape in response to magnetic fields.

This material had to be easily deformable to change shape, yet at the same time stiff enough to bear loads. “That seemed contradictory—how do you make something that is stiff and deformable at once?” says Jie Yin, a mechanical metamaterials researcher at NC State. His team did it with ferromagnetic elastomers, kirigami cuts, balloons, and magnets.

Refreshable Braille display

“There is not much research on using magnets to manipulate non-magnetic objects. It is very, very hard,” says Yinding Chi, another NC State researcher and lead author of the study. The idea Chi and his colleagues came up with could be compared to a refreshable Braille display. They imagined a surface dotted with domes that could rise, turn, or depress on demand, allowing it to dynamically form relief-like images or move in a pattern similar to waves in the ocean. Objects would then move on these surfaces like they were carried by waves. “This way, you can move various objects without using grippers,” Yin says.

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There is now a genetic excuse not to bother cutting carbs. Humans have genetically adapted to eating starchy foods, and our ancestors may have been carb-ivores even before modern Homo sapiens emerged.

The salivary amylase gene, known as AMY1, is already known to have helped us adapt to eating carbs. It encodes amylase, an enzyme that breaks starches found in pasta and bread down to glucose—and may have given us a taste preference for them. Humans have multiple copies of the gene, which may help us produce high levels of the enzyme.

Researchers from the University of Buffalo and the Jackson Laboratory have now found that, while most copies of this gene arose with the advent of farming, modern humans and our closest relatives had accumulated extra copies long before agriculture.

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Flu season is ramping up across the US, but Louisiana—the state that has reportedly barred its health department from promoting flu shots, as well as COVID-19 and mpox vaccines—is leading the country with an early and strong surge.

Louisiana's flu activity has reached the "Very High" category set by the Centers for Disease Control and Prevention, according to the latest data. The 13-category scale is based on the percentage of doctor's visits that were for influenza-like illnesses (ILIs) in the previous week. Louisiana is at the first of three "Very High" levels. Oregon is the only other state to have reached this level. The rest of the country spans the scale, with 13 jurisdictions at "High," including New York City and Washington, DC. There are 11 at "Moderate," 10 at "Low," and 19 at "Minimal."

Map of ILI activity by state Credit: CDC

Last week, NPR, KFF Health News, and New Orleans Public Radio WWNO reported that the state had forbidden the health department and its workers from promoting annual flu shots, as well as vaccines for COVID-19 and mpox. The policy was explicitly kept quiet and officials have avoided putting it in writing.

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Charlotte, a green sea turtle, was hit by a boat back in 2008. This left it with an affliction colloquially referred to as the “bubble butt,” a kind of floating syndrome that makes it impossible for a turtle to dive. Most sea turtles suffering from issues like this simply die at sea, since the condition leaves them stranded at the surface where they can’t forage, sleep, and avoid predators like sharks. But fate had other plans for Charlotte.

Charlotte didn’t end up as a shark’s lunch and didn’t starve to death floating helplessly in the ocean. Instead, it got rescued shortly after the boat accident and eventually found a home at Mystic Aquarium in Stonington, Connecticut, where it received professional care. That was the first time Charlotte got lucky. The second time came when a collaboration formed: Adia, a company specializing in 3D-printing solutions; Formlabs, one of the world’s leading manufacturers of 3D printers; and New Balance Athletic, a sportswear giant based in Boston. This team chose Charlotte as a technology showcase, which basically turned the turtle into an Oscar Pistorius of the sea—just without the criminal conviction.

Weights and diet

Sea turtles are marine reptiles, which means they don’t have gills like fish—they need air to breathe. The lungs also play a key role in their buoyancy regulation system, which allows them to rest for extended periods of time at the sea floor or float at a precisely chosen depth. A sea turtle can precisely choose the depth at which it achieves neutral buoyancy by inhaling the exactly right volume of air.

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