Famously sneaky particles have been caught behaving in a new way.

For the first time, scientists have detected neutrinos scattering off the nucleus of an atom. The process, predicted more than four decades ago, provides a new way to test fundamental physics. It will also help scientists to better characterize the neutrino, a misfit particle that has a tiny mass and interacts so feebly with matter that it can easily sail through the entire Earth.
The detection, reported online August 3 in Science, “has really big implications,” says physicist Janet Conrad of MIT, who was not involved with the research. It fills in a missing piece of the standard model, the theory that explains how particles behave: The model predicts that neutrinos interact with nuclei. And, says Conrad, the discovery “opens up a whole new area of measurements” to further test the standard model’s predictions.

Scientists typically spot neutrinos when they interact with a single proton or neutron. But the new study measures “coherent” scattering, in which a low-energy neutrino interacts with an entire atomic nucleus at once, ricocheting away and causing the nucleus to recoil slightly in response.

“It’s exciting to measure it for the first time,” says physicist Kate Scholberg of Duke University, spokesperson for the collaboration — named COHERENT — that made the new finding.

In the past, neutrino hunters have built enormous detectors to boost their chances of catching a glimpse of the particles — a necessity because the aloof particles interact so rarely. While still rare, coherent neutrino scattering occurs more often than previously detected types of neutrino interactions. That means detectors can be smaller and still catch enough interactions to detect the process. COHERENT’s detector, a crystal of cesium and iodine, weighs only about 15 kilograms. “It’s the first handheld neutrino detector; you can just carry it around,” says physicist Juan Collar of the University of Chicago.

Collar, Scholberg and colleagues installed their detector at the Spallation Neutron Source at Oak Ridge National Laboratory in Tennessee. The facility generates bursts of neutrons and, as a by-product, produces neutrinos at energies that COHERENT’s detector can spot. When a nucleus in the crystal recoils due to a scattering neutrino, a flash of light appears and is captured by a light sensor. The signal of the recoiling nucleus is incredibly subtle — like detecting the motion of a bowling ball when hit by a ping-pong ball — which is why the effect remained undetected until now.
The amount of scattering the researchers saw agreed with the standard model. But such tests are still in their early stages, says physicist Leo Stodolsky of the Max Planck Institute for Physics in Munich, who was not involved with the research. “We’re looking forward to more detailed studies to see if it really is accurately in agreement with the expectations.” Physicists hope to find a place where the standard model breaks down, which could reveal new secrets of the universe. More precise tests may reveal discrepancies, he says. “That would be extremely interesting.”

Measuring coherent neutrino scattering could help scientists understand the processes that occur within exploding stars, or supernovas, which emit huge numbers of neutrinos (SN: 02/18/17, p. 24). The process could be used to detect supernovas as well — if a supernova explodes nearby, scientists could spot its neutrinos scattering off nuclei in their detectors.

Similar scattering might also help scientists detect dark matter, an invisible source of mass that pervades the universe. Dark matter particles could scatter off atomic nuclei just as neutrinos do, causing a recoil. The study indicates that such recoils are detectable — good news since several dark matter experiments are currently attempting to measure recoils of nuclei (SN: 11/12/16, p. 14). But it also suggests a looming problem: As dark matter detectors become more sensitive, neutrinos bouncing off the nuclei will swamp any signs of dark matter.

Coherent neutrino scattering detectors could lead to practical applications as well: Small-scale neutrino detectors could eventually detect neutrinos produced in nuclear reactors to monitor for attempts to develop nuclear weapons, for example.

Physicist Daniel Freedman of MIT, who predicted in 1974 that neutrinos would scatter off nuclei, is pleased that his prediction has finally been confirmed. “It’s a thrill.”

I heard it for the first time a few days ago: “She’s copying me!” my 4-year-old wailed in a righteous complaint about her little sister. And she most certainly was copying, repeating the same nonsense word over and over. While it was distressing to my older kid, I thought it was funny that it took her so long to realize her sister copies almost everything she does.

This egregious violation occurred just after I had read about an experiment that pitted young kids against bonobos in a test to see who might copy other individuals more. I’ll get right to the punch line: Kids won, by a long shot. The results, published online July 24 in Child Development, show that despite imitation annoying older siblings everywhere, it’s actually really important.

“Imitation is one of the most essential skills for being human,” says study coauthor Zanna Clay, a comparative psychologist at the University of Birmingham and Durham University, both in England. Learning how to talk, operating the latest iPhone and figuring out how to buy bulk goods at the local co-op — these skills all rely on imitation. Not only that, but imitation is also important for cementing social relationships. My daughter notwithstanding, “Humans like to be imitated, and we like those who imitate us,” Clay says.
Clay and her colleague Claudio Tennie tested just how strong the urge to imitate is in 77 children ages 3 to 5 and a group of 46 bonobos ages 3 to 29. In one-on-one trials, the researchers sat next to the kids and bonobos with a small wooden box about the size of a hand. Inside was a treat: a sticker for the kids and a bit of apple for the bonobos.

Before opening the box, the researcher performed nonsensical actions over it, either rubbing the box with the back of the hand and doing a wrist twist in the air or tracing a cross into the top of the box and then tracing the edges.

These hand motions were totally irrelevant to the actual opening of the box. Nonetheless, after seeing the gestures, the vast majority of the kids made the same motions before trying to open their own box. Not a single bonobo, though, copied the irrelevant actions.
What the bonobos did — not copying the meaningless gestures — “is the rational thing to do,” says Clay. “Yet the irrational thing that the kids did is part of the reason why human cultures have evolved so rapidly and so diversely.”

Such excessive imitation, called overimitation, is a special form of copying in which people perform actions that clearly serve no purpose. It may be behind rituals, social norms and language that keep our societies running smoothly.

And it may be unique to humans: Other studies have failed to spot overimitation among chimpanzees and orangutans. These findings hint that our powerful urge to imitate even nonsensical gestures may be one of the things that separate humans from other apes.

Speed has its limits — on the open road and the Serengeti. Midsize animals tend to be the speedsters, even though, in theory, the biggest animals should be the fastest. A new analysis that relates speed and body size in 474 species shows that the pattern holds for animals whether they run, fly or swim (see graphs below) and suggests how size becomes a liability.

This relationship between speed and size has long stumped scientists. Big animals have longer legs or flippers to get from point A to point B. And bigger bodies have higher metabolic rates and more fast-twitch muscle cells, needed to convert chemical energy into mechanical energy and rapidly accelerate. So, why aren’t wildebeests faster than cheetahs?
The make-or-break factor is the time it takes an animal to accelerate to its top theoretical speed, an upper limit based on mass and metabolic rate, researchers report July 17 in Nature Ecology & Evolution. Fast-twitch muscle cells provide the power for acceleration but tire quickly. When an animal gets too big, it takes too long to accelerate, and these cells use up their energy before hitting top speeds. More modestly built critters need less time to accelerate to those speeds.

The researchers gathered speed and size data from past lab and field studies. The animals (some shown as icons in the slideshow below) ranged in mass from 30-microgram Spanish mites to a blue whale weighing 108 metric tons.

Maybe it’s more than reptile fashion. The high percentage of citified sea snakes wearing black might be a sign that pollution is an evolutionary force.

Off the coasts of Australia and New Caledonia, some turtle-headed sea snakes (Emydocephalus annulatus) sport pale bands on their dark skins. Others go all black. In 15 places surveyed, the all-black form was more likely to predominate in waters near cities, military sites or industrial zones than along reefs near less built-up coastlines, says evolutionary ecologist Rick Shine of the University of Sydney.
That trend plus some analysis of trace elements in snakes’ skin suggests that the abundant dark forms could turn out to be an example of industrial melanism, Shine and his colleagues propose August 10 in Current Biology.

The most famous example of this evolutionary phenomenon comes from a dark form of peppered moth that overtook pale populations in 19th century England (SN: 6/25/16, p. 6). Dark wings created better camouflage from hungry birds in the grimy industrializing landscape.
Shine doesn’t think the sea snakes are going for camouflage, though. Instead, the snakes could be more like the dark-feathered pigeons of Paris. The melanin that gives that city’s feral birds their urban chic also does a great job of binding traces of toxic metals such as zinc, explains evolutionary ecologist Marion Chatelain of the University of Warsaw. When birds molt, getting rid of darker feathers lets them unload more of the unhealthful urban pollutants, she and colleagues have reported.
This could explain why marine biologist and study coauthor Claire Goiran has so many dark turtle-headed sea snakes in a lagoon not far from her campus, the University of New Caledonia in Nouméa. Earlier studies had found only downsides to dark coloration: Seaweed spores preferentially settle on dark snakes and sprout fuzz that can cut swimming speed by 20 percent and cause a snake to shed its skin more often than normal.
To test a scenario of industrial melanism, or darkening due to pollution, the researchers collected data on skin colors for a total of about 1,450 snakes, both live and museum specimens, from 15 sites in New Caledonia and Australia. Higher percentages of all-dark snakes wriggled around the nine polluted sites surveyed. At one, a remote Australian reef that the military had long used as a bombing range, all 13 specimens were dark.

To test shed skins for trace metals, Goiran and Shine enlisted Paco Bustamante of the University of La Rochelle in France, who studies trace metal contamination in marine life.

Researchers managed to collect sloughed skins from 17 turtle-headed snakes, which inconveniently shed their skin underwater. To compare light and dark patches, the scientists turned to two local species of sea kraits, which have banded skin and visit land to shed it.
Overall, skins held concentrations of trace elements higher than those that can cause health problems in birds and mammals, the researchers report. In the krait skins, dark zones had slightly more of some contaminants, such as zinc and arsenic, than the pale bluish-white bands did.

The idea that polluted water favors melanized sea snakes “is a reasonable hypothesis based on what we know,” Chatelain says. Definitive tests will require more data and different approaches. Genetic testing, for example, would clarify whether dark populations arose instead from small groups of pioneers that happened to have a lot of black snakes.

That testing could be a long way off. Sea snakes are evolutionary cousins of cobras and mambas, and some of the species swimming around Australia and New Caledonia are “bowel-looseningly large,” Shine says. At least the little turtle-headed ones, which eat eggs of small reef fishes, have venom glands that have atrophied and “probably couldn’t fit a human finger in their mouths.” But until someone figures out how to keep them alive in captivity for more than a few days, Shine isn’t expecting definitive genetics.

China’s first emperor broke the mold when he had himself buried with a terra-cotta army. Now insight into the careful crafting of those soldiers is coming from the clays used to build them. Custom clay pastes were mixed at a clay-making center and then distributed to specialized workshops that cranked out thousands of the life-size figures, new research suggests.

Roughly 700,000 craftsmen and laborers built Emperor Qin Shihuang’s palatial mausoleum in east-central China between 247 B.C. and 210 B.C. A portion of those workers gathered clay from nearby deposits and prepared it in at least three forms, researchers propose in the August Antiquity. On-site or nearby workshops used different signature clay recipes for terra-cotta warriors, parts of mostly bronze waterfowl figures and paving bricks for pits in which the soldiers originally stood.
Around 7,000 ceramic foot soldiers, generals and horses — equipped with a variety of bronze weapons — make up the army, which was accidentally discovered in 1974 by farmers digging a well. The emperor would have regarded the ceramic statues as a magic army that would protect him as he ruled in the afterlife, many researchers suspect.

Building and assembling the multitude was an enormous task. Workers poured clay mixtures into casts of torsos, limbs and other body parts, and then assembled the bodies, taking care to create different facial features for each soldier. Finished statues, now mostly gray, were covered in colored lacquers and likely fired in kilns. Most figures were placed inside one giant pit. Earthen walls formed 11 parallel corridors where statues stood in battle-ready rows.

Still, no workshops or debris firmly linked to the statue-making process have been found. As a result, the number, size, location and organization of workshops involved in producing the emperor’s ceramic troops remain uncertain.

Archaeologist Patrick Quinn of University College London and three Chinese colleagues studied the composition of clay samples from the site. The pieces were taken from 12 terra-cotta warriors, two acrobat statues found in a second pit, five clay bricks from the floor of the largest pit, clay fragments from inside three bronze waterfowl statues found in a third pit and part of an earthen wall in the acrobat pit.

Microscopic analysis of the samples revealed that the clay came from deposits near the tomb’s location, the scientists say. But the recipes for different parts varied. Paving bricks contained only a mixture of dark and light clays, while the clay used for warriors and acrobats had sand worked in. Sand and plant fragments were folded into a clay mixture that formed the core of the bronze waterfowl.
Sand may have made the clay more malleable for shaping into ornate figures and increased statues’ durability, the researchers speculate. Plant pieces may have helped reduce the weight of birds’ clay cores. A clay-processing site at or just outside the emperor’s mausoleum must have doled out the appropriate clay pastes to an array of workshops where potters made statues, bricks or other objects, the scientists propose.

What’s more, many statue and waterfowl samples show signs of having been slowly heated in kilns at maximum temperatures of no more than 750˚ Celsius. That’s lower by 150˚ C or more than some previous estimates, the investigators say. Fires set in an attack on the tomb after the emperor’s death may have refired some of the clay, accounting for the temperature discrepancy, the researchers say.

“I’m not at all surprised by the new findings,” says East Asian art historian Robin D.S. Yates of McGill University in Montreal. Legal and administrative documents previously found at two other Qin Empire sites describe workshops that specialized in various types of craft production, Yates says.

In some cases, artisans’ stamps and inscriptions on terra-cotta warriors match those on excavated roof tiles from Emperor Qin’s mausoleum. The markings suggest that some workshops made several types of ceramic objects, says East Asian art historian Lothar Ledderose of Heidelberg University in Germany. Inscriptions on statues also indicate that artisans working at off-site factories during the Qin Empire collaborated with potters at local workshops to produce the terra-cotta army, Ledderose says.

Early in Inferior, science writer Angela Saini recalls a man cornering her after a signing for her book Geek Nation, on science in India. “Where are all the women scientists?” he asked, then answered his own question. “Women just aren’t as good at science as men are. They’ve been shown to be less intelligent.”

Saini fought back with a few statistics on girls’ math abilities, but soon decided that nothing she could say would convince him. It’s a situation that may feel familiar to many women. “What I wish I had was a set of scientific arguments in my armory,” she writes.
So she decided to learn the truth about what science really does tell us about differences between the sexes. “For everyone who has faced the same situation,” she writes, “the same desperate attempt to not lose control but have at hand some real facts and a history to explain them, here they are.”

In Inferior, Saini marshals plenty of facts and statistics contradicting sexist notions about women’s bodies and minds. She cites study after study showing little or no difference in male and female capabilities.

But it’s the book’s historical perspective that makes it most compelling. Only by understanding the cultural context of the men whose studies and ideas first pointed to gender imbalances can we see how deeply biases run, Saini argues.

Charles Darwin’s influential ideas reflected his times, for instance. In The Descent of Man, he wrote that “man has ultimately become superior to woman” via evolution. To a woman active in her local women’s movement, Darwin wrote, “there seems to me to be a great difficulty from the laws of inheritance … in [women] becoming the intellectual equals of man.”

If that idea sounds absurd now, don’t fool yourself into thinking it has vanished. Saini’s book is full of examples right up to today of scientists who have started from this and other flawed premises, which have led to generations of flawed studies and results that reinforce stereotypes. But the tide has been turning, as more women have entered science and more scientists of both sexes seek to remove bias from their work.
Saini does an excellent job of dissecting research on evolution, neuroscience and even the long-standing notion that women’s sexual behavior is driven by their interest in stable, monogamous relationships. By the end, it’s clear that science doesn’t divide men and women; we’ve done that to ourselves. And as scientists become more rigorous, we get closer to seeing ourselves as we really are.

A tiny, shimmying cantilever wiggles a bit more than expected in a new experiment. The excess jiggling of the miniature, diving board–like structure might hint at why the strange rules of quantum mechanics don’t apply in the familiar, “classical” world. But that potential hint is still a long shot: Other sources of vibration are yet to be fully ruled out, so more experiments are needed.

Quantum particles can occupy more than one place at the same time, a condition known as a superposition (SN: 11/20/10, p. 15). Only once a particle’s position is measured does its location become definite. In quantum terminology, the particle’s wave function, which characterizes the spreading of the particle, collapses to a single location (SN Online: 5/26/14).
In contrast, larger objects are always found in one place. “We never see a table or chair in a quantum superposition,” says theoretical physicist Angelo Bassi of the University of Trieste in Italy, a coauthor of the study, to appear in Physical Review Letters. But standard quantum mechanics doesn’t fully explain why large objects don’t exist in superpositions, or how and why wave functions collapse.

Extensions to standard quantum theory can alleviate these conundrums by assuming that wave functions collapse spontaneously, at random intervals. For larger objects, that collapse happens more quickly, meaning that on human scales objects don’t show up in two places at once.

Now, scientists have tested one such theory by looking for one of its predictions: a minuscule jitter, or “noise,” imparted by the random nature of wave function collapse. The scientists looked for this jitter in a miniature cantilever, half a millimeter long. After cooling the cantilever and isolating it to reduce external sources of vibration, the researchers found that an unexplained trembling still remained.

In 2007, physicist Stephen Adler of the Institute for Advanced Study in Princeton, N.J., predicted that the level of jitter from wave function collapse would be large enough to spot in experiments like this one. The new measurement is consistent with Adler’s prediction. “That’s the interesting fact, that the noise matches these predictions,” says study coauthor Andrea Vinante, formerly of the Institute for Photonics and Nanotechnologies in Trento, Italy. But, he says, he wouldn’t bet on the source being wave function collapse. “It is much more likely that it’s some not very well understood effect in the experiment.” In future experiments, the scientists plan to change the design of the cantilever to attempt to isolate the vibration’s source.

The result follows similar tests performed with the LISA Pathfinder spacecraft, which was built as a test-bed for gravitational wave detection techniques. Two different studies found no excess jiggling of free-falling weights within the spacecraft. But the new cantilever experiment tests for wave function collapse occurring at different rate and length scales than those previous studies.
Theories that include spontaneous wave function collapse are not yet accepted by most physicists. But interest in them has recently become more widespread, says physicist David Vitali of the University of Camerino in Italy, “sparked by the fact that technological advances now make fundamental tests of quantum mechanics much easier to conceive.” Focusing on a simple system like the cantilever is the right approach, says Vitali, who was not involved with the research. Still, “a lot of things can go wrong or can be not fully controlled.”

To conclude that wave function collapse is the cause of the excess vibrations, every other possible source will have to be ruled out. So, Adler says, “it’s going to take a lot of confirmation to check that this is a real effect.”

Air pollution is a drag for renewable energy. Dust and other sky-darkening air pollutants slash solar energy production by 17 to 25 percent across parts of India, China and the Arabian Peninsula, a new study estimates. The haze can block sunlight from reaching solar panels. And if the particles land on a panel’s flat surface, they cut down on the area exposed to the sun. Dust can come from natural sources, but the other pollutants have human-made origins, including cars, factories and coal-fired power plants.

Scientists collected and analyzed dust and pollution particles from solar panels in India, then extrapolated to quantify the impact on solar energy output in all three locations. China, which generates more solar energy than any other country, is losing up to 11 gigawatts of power capacity due to air pollution, the researchers report in the Aug. 8 Environmental Science & Technology Letters. That’s a loss of about $10 billion per year in U.S. energy costs, says study coauthor Mike Bergin of Duke University. Regular cleaning of solar panels can help. Cleaning the air, however, is harder.

Sea stars and their relatives eat, breathe and scuttle around the seafloor with tiny tube feet. Now researchers have gotten their first-ever look at similar tentacle-like structures in an extinct group of these echinoderms.

It was suspected that the ancient marine invertebrates, called edrioasteroids, had tube feet. But a set of unusually well-preserved fossils from around 430 million years ago, described September 13 in Proceedings of the Royal Society B, provides proof.

Usually, when an echinoderm dies, “the tube feet are the first things that go,” says Colin Sumrall, a paleobiologist at the University of Tennessee, Knoxville who wasn’t part of the study. “The thing that’s so stunning is that they didn’t rot away.”
An abundance of soft-bodied creatures from the Silurian Period, which lasted from 444 million to 419 million years ago, are preserved in a fossil bed in Herefordshire, England. The edrioasteroids found in this bed were probably buried alive by volcanic ash, entrapped before their soft tissues could break down, says study coauthor Derek Briggs, a paleontologist at Yale University. Decaying tissue then left a void that was filled in by minerals, which preserved the shape of the appendages.
Briggs and his collaborators slowly ground three fossils down, taking pictures layer-by-layer to build up a three-dimensional view. The specimens are a new genus and species, the analysis revealed. Unlike relatively flat sea stars and sand dollars, the species — dubbed Heropyrgus disterminus — had a conical body about 3 centimeters long. Its narrower end anchored in the seabed. The other end sported a set of five plates partially covering dozens of tube feet arranged in a pentagonal ring.
Today’s echinoderms use hydraulic pressure in a water vascular system to extend and retract their tube feet, which serve a variety of roles. The feet can help animals pull in tiny particles of food, filter water or gases, and even inch along the seafloor. Based on the placement of H. disterminus’s tube feet (and the fact that it’s stuck in one place), the animal probably used the appendages mostly for feeding and gas exchange, Briggs suggests. The fossils didn’t preserve the internal tubing that hooks up to the tube feet, but Briggs’ team thinks that it’s a series of canals arranged like spokes connected to a wheel hub.

Sumrall isn’t surprised that this edrioasteroid had tube feet. “It’s exactly what we would have expected,” he says. But all other preserved tube feet to date come from classes of echinoderms that still have living relatives today. Edrioasteroids are less closely related to modern echinoderms, so this find broadens the range of species that scientists know sported the structures.

H. disterminus does have a few surprises, though: Its tube feet are found in two sets, in an arrangement not seen in any other echinoderms. And while it has five-point symmetry in its fleshy top part (like most other echinoderms), that transitions to eight-point symmetry in its long, columnar body.

For certain HIV antibodies, having a buddy or two makes a big difference in the fight against the virus.

Combining the antibodies, called broadly neutralizing antibodies, may stop more strains of HIV than any single one can do alone, two new studies suggest. A “triple-threat” antibody molecule can bind to three different spots on the virus, researchers report online September 20 in Science. In Science Translational Medicine, a second team describes a cocktail of two single antibodies that each target a different region of the virus. Both methods prevented infection from multiple strains of an HIV-like virus in monkeys.
“We have known for many years that broadly neutralizing antibodies are extremely powerful antibodies,” says molecular biologist Nancy Haigwood of the Oregon Health & Science University in Portland, who was not involved in either study. Using more than one of these antibodies “is the most promising approach” to block HIV infection in humans because it offers more coverage, she says.

This extra coverage is needed because HIV is a master of mutation. “It’s really adopted every bit of what I would call molecular trickery to outwit our immune system, and it’s a constant battle,” says Gary Nabel, coauthor of the study in Science and chief scientific officer of Sanofi in Cambridge, Mass. The immune system keeps trying to recognize parts of the virus, but mutations in the virus can alter those sites. “You really want to have this broadside attack against the virus that hits multiple targets,” he says.

Broadly neutralizing antibodies are powerful because they can bind to multiple strains of HIV (SN: 8/19/17, p.7). The antibodies stop HIV from getting into cells to infect them. Still, “there is no single antibody” that can block all strains, says virologist Dan Barouch of Beth Israel Deaconess Medical Center in Boston.

Barouch and colleagues tackled the issue by mixing two of the antibodies together. The researchers divided 20 rhesus monkeys into four groups, giving one group the cocktail, two groups the individual antibodies and one group a saline solution with no antibodies. A day later, all of the monkeys were exposed to a mix of two simian-human immunodeficiency virus, or SHIV, strains. The outer protein that surrounds HIV, where antibodies bind, is the same in SHIV. None of the five animals that received the antibody cocktail became infected, while all of the other animals did, the researchers report in Science Translational Medicine.

Nabel and colleagues took a different tack: They developed a molecule that combines the binding talents of three antibodies into one. The researchers tested their “tri-specific” antibody in rhesus monkeys, giving eight animals the trio antibody while two other groups each received just one of the broadly neutralizing antibodies that inspired the molecule. The animals were exposed to a mix of SHIV strains five days later. Of the 16 monkeys in the solo antibody groups, 11 developed infections. None of the eight animals dosed with the trio antibody did.
Both teams’ antibody approaches “show impressive protection against a combination of viruses, suggesting that they would be effective” against diverse HIV strains in humans, Haigwood says.

Virologist David Margolis of the University of North Carolina School of Medicine in Chapel Hill notes that the approaches are most likely to have preventative potential, but they also may be therapeutic. The antibody combinations might “replace oral antiretroviral therapy, or stand in for oral therapy in medical situations where pills cannot be taken,” he says.

The next step for both methods is to test the combination antibodies in people, the authors say. Whether the strategy is most effective as a preventative measure, treatment or both, the papers suggest that “to achieve optimal protection in humans,” multiple antibodies or antibody targets are going to be needed, Barouch says.