These tough little buggers, also known as tardigrades, could keep calm and carry on until the sun boils Earth’s oceans away billions of years from now, according to a new study that examined water bears’ resistance to various astronomical disasters. This finding, published July 14 in Scientific Reports, suggests that complex life can be extremely difficult to destroy, which bodes well for anyone hoping Earthlings have cosmic company. Most previous studies of apocalyptic astronomical events — like asteroid impacts, neighboring stars going supernova or insanely energetic explosions called gamma-ray bursts — focused on their threat to humankind. But researchers wanted to know what it would take to annihilate one of the world’s most resilient creatures, so they turned to tardigrades.
The tardigrade is basically the poster child for extremophiles. These hardy, microscopic critters are up for anything. Decades without food or water? No problem. Temperatures plummeting to –272° Celsius or skyrocketing to 150°? Bring it on. Even the crushing pressure of deep seas, the vacuum of outer space and exposure to extreme radiation don’t bother water bears.
Water bears are so sturdy that they probably won’t succumb to nuclear war, global warming or any astronomical events that wreak havoc on Earth’s atmosphere — all of which could doom humans, says Harvard University astrophysicist Avi Loeb. To exterminate tardigrades, something would have to boil the oceans away (no more water means no more water bears). So Loeb and colleagues calculated just how big an asteroid, how strong a supernova, or how powerful a gamma-ray burst would have to be to inject that much energy into Earth’s oceans.
“They actually ran the numbers on everyone’s favorite natural doomsday weapons,” marvels Seth Shostak, an astronomer at the SETI Institute in Mountain View, Calif.
Loeb’s team found that there are only 19 asteroids in the solar system sufficiently massive enough to eradicate water bears, and none are on a collision course with Earth. A supernova — the explosion of a massive star after it burns through its fuel — would have to happen within 0.13 light-years of Earth, and the closest star big enough to go supernova is nearly 147 light-years away. And gamma-ray bursts — thought to result from especially powerful supernovas or stellar collisions — are so rare that the researchers calculated that, over a billion years, there’s only about a 1 in 3 billion chance of one killing off tardigrades. “Makes me wish I were an extremophile like a tardigrade,” says Edward Guinan, an astrophysicist at Villanova University in Pennsylvania who was not involved in the work.
But even tardigrades can’t cheat death forever. In the next seven billion years, the sun will swell into a red giant star, potentially engulfing Earth and surely sizzling away its water. But the fact that tardigrades are so resistant to other potential apocalypses in the interim implies that “life is tough, once it gets going,” Shostak says.
Scientists pour a lot of brainpower into understanding how their experimental equipment works.
You don’t want to be fooled into thinking you’ve made a great discovery because of some quirk in the apparatus you didn’t know about. Just the other day, a new paper published online suggested that the instruments used to detect gravitational waves exhibited such a quirk, tricking scientists into claiming the detection of waves that maybe weren’t really there.
It appears that gravity wave fans can relax, though. A response to the challenge pretty much establishes that the new criticism doesn’t undermine the wave discoveries. Of course, you never know — supposedly well-established results sometimes do fade away. Often that’s because scientists have neglected to understand the most important part of the entire experimental apparatus — their own brains.
It’s the brain, after all, that devises experiments and interprets their results. How the brain perceives, how it makes decisions and judgments, and how those judgments can go awry are at least as important to science as knowing the intricacies of nonbiotic experimental machinery. And as any brain scientist will tell you, there’s still a long way to go before understanding the brain will get crossed off science’s to-do list. But there has been progress. A recent special issue of the journal Neuron offers a convenient set of “perspective” papers exploring the current state of understanding of the brain’s inner workings. Those papers show that a lot is known. But at the same time they emphasize that there’s a lot we don’t know.
Glancing at the table of contents reveals the first lesson about understanding the brain: It’s a complex problem that needs to be approached from multiple perspectives.
On one level, there’s the dynamics of electrical currents that constitute the main signaling method of the brain’s nerve cells. Then on a higher level there’s the need to figure out the rules by which nerve cells make connections (synapses) and create the neural circuitry for processing sensory input, learning and behaving. Another challenge is understanding how nerve cell networks represent memories and how you recall what you’ve learned. And it’s essential to understand how neurobiological processing conducted by molecules and cells and electrical signaling gets translated into behaviors, from simple bodily movements to complex social interactions.
Nerve cells in the brain, or neurons, are known to communicate among themselves by transmitting electrical signals, aided by chemical signaling at the synapses connecting the neurons. But there are gaps in understanding how that process takes the brain from perceptions to thoughts to actions. Each of Neuron’s perspective papers both describes what’s already known about how the brain works and offers speculations where scientists lack full knowledge about how the brain does it jobs.
Much of the effort to explain the brain involves mapping the electrical signaling throughout the entire network of nerve cell connections. Per Roland of the University of Copenhagen, for instance, discusses how those signals vary in space and time. He emphasizes the important balance between signaling that incites neurons to send signals and the messaging that inhibits signaling, keeping some neurons quiet. Sophie Denève and colleagues of the Ecole Normale Supérieure in Paris also emphasize the balance between excitation and inhibition in neural circuitry. That balance is important, they say, for understanding how the whole brain can learn to do things based on changes in the connections between individual neurons. Somehow the rules governing synaptic connections between cells enable such “local” activity to modify the “global” neural circuitry that carries out the brain’s many functions. Excitation-inhibition balance, plus feedback from the global network influencing synapse strength, “can ensure that global functions can be learned with local learning rules,” Denève and colleagues write.
Almost all these approaches to figuring out the brain involve how it manipulates information. In a sense, the ultimate key question is how the brain conducts the mysterious process by which it absorbs information in the form of lights and colors, sounds, smells and tactile inputs and transforms them into physical actions — ideally behaviors that are appropriate responses to the inputs. Just (OK, not “just,” but sort of) as in a computer, the brain transforms input into output; information about the external world is manipulated to produce information about how to react to it.
But because sensory input has its limits, and some of it is ambiguous, the informational variables of the external world cannot be gauged with certainty, Xaq Pitkow and Dora Angelaki of Baylor College of Medicine and Rice University in Houston point out in their perspective. So the brain’s behavioral choices must be based on some method of computing probabilities to infer the likely state of the world — and then choosing the wisest (probably) actions in response.
“It is widely accepted that the brain somehow approximates probabilistic inference,” Pitkow and Angelaki write. But nobody really knows how the brain does it. Pitkow and Angelaki propose that multiple populations of the brain’s neurons perform various computations to make appropriate behavioral decisions.
Patterns of electrical signaling by these neurons must represent the original sensory stimuli — that is, the patterns in the stimuli are encoded in the patterns of electrical signaling among the neurons. Those neural signaling patterns, in Pitkow and Angelaki’s description, are then recoded into another set of patterns; that process sorts out the important variables in the environment from those that don’t matter. Those patterns are then decoded in the process of generating behavioral actions.
In sum, the brain appears to implement algorithms for collecting and assessing information about the environment and encoding that information in messages that tell the body what to do. Somehow those algorithms allow the brain to conduct statistical computations that combine beliefs about the environment with the expected outcome of different behaviors.
Pitkow and Angelaki present sophisticated speculation about the possible ways the brain could accomplish this task. It’s clearly an unimaginably complicated process, and figuring out how the brain does it will require more sophisticated experiments than neuroscientists have so far imagined. Much research on brain function in animals, for instance, offers the animal a choice of two options, given various external conditions. But tasks of that nature are vastly simpler than the jobs that evolution optimized brains for.
“The real benefit of complex inferences like weighing uncertainty may not be apparent unless the uncertainty has complex structure,” Pitkow and Angelaki argue. “Overly simple tasks” are “ill-suited to expose the inferential computations that make the brain special.”
And so truly understanding the brain, it seems, will require better experiments — using apparatus that is more fully understood than the brain now is — of sufficient complexity to be worthy of probing the brain’s abilities.
Some deep-sea tube worms get long in the tooth … er, tube. Living several decades longer than its shallow-water relatives, Escarpia laminata has the longest known life span for a tube worm, aging beyond 300 years, researchers report in the August Science of Nature.
E. laminata lives 1,000 to 3,300 meters deep in the Gulf of Mexico, near seafloor vents that seep energy-rich compounds that feed bacteria that feed the tube worms. In 2006, biologists marked 356 E. laminata in their natural habitat and measured how much the creatures had grown a year later. To estimate the ages of tube worms of different sizes, the researchers plugged E. laminata’s average yearly growth rate — along with estimates of birthrates and death rates, based on observations of another 1,046 tube worms — into a simulation. The species’s typical life span is 100 to 200 years, the researchers calculate, but some larger tube worms may be more than 300 years old.
With few large predators, deep-sea tube worms have got it good, says study coauthor Alanna Durkin, a biologist at Temple University in Philadelphia. “Once they find a seat at the buffet, they’re pretty set for hundreds of years.” The researchers’ methodology appears robust, says ocean scientist David Reynolds of Cardiff University in Wales, who was not involved in the work. Although variable environmental conditions could affect growth rate over time, he says.
Everybody poops, but the poop of bloblike filter feeders called giant larvaceans could be laced with microplastics.
Every day, these gelatinous creatures (Bathochordaeus stygius) build giant disposable mucus mansions to round up zooplankton into their stomachs — sometimes sifting through around 80 liters of seawater per hour. Kakani Katija and her colleagues at the Monterey Bay Aquarium Research Institute now suggest that tiny plastic particles also make their way in — and out — of giant larvaceans’ guts.
Microplastics pervade the ocean. Their combined mass could reach 250 million metric tons by 2025. Scientists don’t know a lot about where microplastics stick around in open water ecosystems.
To see if plastics could end up on the larvacean menu, Katija and colleagues tried feeding the animals brightly colored microplastics. An underwater robot equipped with camera gear helped the researchers monitor plastic intake from above. Some animals did end up scarfing down the particles, and some of those particles ended up in the organism’s waste, which showers down on the seafloor, Katija and colleagues report August 16 in Science Advances.
“Plastics are sometimes seen as a sea surface issue, and more and more we’re seeing that’s not necessarily true,” Katija says.
Just how much plastic ends up passing through giant larvaceans in the wild remains unclear. But the researchers suspect that the creatures’ poop, as well as their mucus houses, could transfer microplastics from the water’s surface to the depths of the sea (along with nutrients such as carbon that cycle through the environment). And that pollution transfer may impact the ecosystems at either end.
The story of how Charles Darwin’s trip around the world on the HMS Beagle inspired his ideas about evolution is well-known. Less familiar, however, may be the decades of detailed research that he conducted after that 1830s voyage. As biologist James Costa chronicles in Darwin’s Backyard, many of those studies took place at Down House, Darwin’s country home southeast of London.
The estate’s relative isolation enabled Darwin to conduct in-depth anatomical analyses of everything from barnacles to birds. Darwin supplemented that work with hands-on experiments. He bred and raised 16 varieties of pigeons, trying to show that the fancy types preferred by breeders had developed from only a few ancestral wild types. In his gardens, Darwin laid out intricate plots where he studied the diversity and growth of grasses and weeds, as well as how earthworms churn the soil. On nearby hillsides, he investigated orchid pollination and reproduction. (Not all of his experiments were successful: One year, cows ate and trampled his orchids.) Some experiments were considered quirky by 19th century standards, but the work provided data supporting Darwin’s notions about trait variability in a population and how natural selection drives changes in populations over time.
Stories of Darwin’s rich — and in some cases, tragic — family life are woven throughout Costa’s account. Without appreciating this aspect of his life, Costa claims, neither Darwin nor his accomplishments can be fully understood. For example, he enlisted his wife, cousins and nieces — and even his butler and governess — in assisting with his homespun field studies.
One outstanding aspect of the book: Each chapter ends with a description of some of Darwin’s experiments that nonscientists can perform on their own. Readers will enjoy the tales Costa tells and the experience of re-creating some of the famous naturalist’s most enlightening work.
People hunted giant sloths in the center of South America around 23,120 years ago, researchers say — a find that adds to evidence that humans reached South America well before Clovis hunters roamed North America 13,000 years ago.
Evidence of people’s presence at Santa Elina rock-shelter, in central-west Brazil, so long ago raises questions about how people first entered South America. Early settlers may have floated down the Pacific Coast in canoes before heading 2,000 kilometers east to the remote rock-shelter, or they might have taken an inland route from North America, Denis Vialou of the National Museum of Natural History in Paris and colleagues report in the August Antiquity. Other proposed Stone Age South American sites lie much closer to the coast than Santa Elina does.
Excavations revealed remains of hearths, stone artifacts and bones of giant sloths. Sloth remains included small, bony plates from the skin that humans apparently made into ornaments of some kind by adding notches and holes.
Three different dating methods indicate that people reached Santa Elina over 20,000 years ago.
BOSTON — A decades-long debate over who once occupied a settlement located near the caves where the Dead Sea Scrolls were found has taken a chaste turn.
Analyses of 33 newly excavated skeletons of people buried at the West Bank site, Qumran, supports a view that the community consisted of a religious sect of celibate men. Anthropologist Yossi Nagar of the Israel Antiquities Authority in Jerusalem presented the findings November 16 at the annual meeting of the American Schools of Oriental Research. Preliminary radiocarbon dating of one of the Qumran bones indicates that the interred bodies are around 2,200 years old — close to the same age as the ancient texts, which are estimated to have been written between around 150 B.C. and A.D. 70. Plus, reexamination of 53 previously unearthed human skeletons from Qumran’s cemetery, now housed in France, found that six of seven individuals formerly tagged as women were actually men, Nagar said. A small number of children have also been excavated at Qumran.
Israel Antiquities Authority anthropologists Hanania Hizmi and Yevgeny Aharonovich directed the latest excavations at Qumran in 2016. The researchers called in Nagar to study the skeletons. He identified 30 of the newly excavated individuals as definitely or probably males, based on factors that include pelvic shape and body sizes. (There was not enough evidence to assign a sex to the remaining three.) At the time of their deaths, the men ranged in age from around 20 to 50 or more, Nagar estimated. “I don’t know if these were the people who produced the Qumran region’s Dead Sea Scrolls,” Nagar said. “But the high concentration of adult males of various ages buried at Qumran is similar to what has been found at cemeteries connected to Byzantine monasteries.” The Byzantine Empire, founded in A.D. 330, was an extension of the Roman Empire in the eastern Mediterranean. Earlier investigations of Qumran suggested it was founded more than 2,700 years ago. Warfare led to its abandonment before it was settled again for about 200 years, up to around the year A.D. 68. Discovery of the Dead Sea Scrolls, which include parts of the Hebrew Bible, in 11 nearby caves between 1947 and 1956 stimulated intense interest in who had occupied Qumran. In February of 2017, researchers revealed they had found another cave in the same area that possibly held scrolls or pieces of papyrus and leather intended to be written on.
An influential early theory held that members of an ancient, celibate Jewish sect, the Essenes, lived at Qumran and either wrote the Dead Sea Scrolls or were caretakers of these religious, legal and philosophical documents. But over the past 30 years, other possible inhabitants of Qumran have been proposed, including Bedouin herders, craftsmen and Roman soldiers.
Qumran individuals show no signs of war-related injuries and are not predominantly young adult men, as would be expected of a cemetery for soldiers, Nagar said. The Qumran skeletons can’t be confirmed as Essenes, but their identity as part of a community of celibate men appears probable, he added.
Extraction and analysis of DNA from the Qumran skeletons would help confirm that they are all, or almost all, men, said Jonathan Rosenbaum, a professor of Jewish Studies at Gratz College in Melrose Park, Pa.
Researchers removed small samples of bone from some of the newly excavated Qumran skeletons before reburying the finds in their original resting places. Nagar wasn’t sure if any attempts to retrieve DNA from bone samples would be launched.
With each new year, science offers a fresh list of historical occasions ideally suited for a Top 10 list.
Science’s rich history guarantees a never-ending supply of noteworthy anniversaries. Centennials of births, deaths or discoveries by prominent scientists (or popular centennial fractions or multiples) offer reminders of past achievements and context for appreciating science of the present day. To keep the holiday spirit pleasant, we’ll omit the plagues and natural disasters (so no mention of the centennial of the Spanish flu pandemic or the tricentennial of the Gansu earthquake in the Qing Empire). But that leaves plenty of math, medicine, astronomy and quantum stuff. Such as:
Quantum teleportation (25th anniversary) At a physics meeting in Seattle in March 1993, Charles Bennett of IBM thrilled science fiction fans everywhere by revealing the theory of quantum teleportation. (A few days later, a paper by Bennett and his teleportation collaborators appeared in Physical Review Letters.) Bennett described how quantum experimentalists Alice and Bob could use quantum entanglement to erase the identity of a quantum particle at one location and restore it at a remote location — just like Captain Kirk disappearing in the Enterprise transporter and reappearing on some dangerous alien planet. It’s not magic, though. Alice and Bob must each possess one of a pair of entangled quantum particles. If Alice wants to teleport a quantum particle to Bob, she must let it interact with her entangled particle and send the result to Bob by e-mail (or text, or phone call, or snail mail). That interaction destroys Alice’s copy of the particle to be teleported, but Bob can reconstruct it using his entangled particle after Alice e-mails him. In 1993, it was just an idea, but a few years later it was successfully demonstrated in the lab.
Arnold Sommerfeld (150th birthday) Born in Königsberg, Prussia, (now part of Russia) on December 5, 1868, Arnold Sommerfeld played a major role in advancing early quantum theory in the years after Niels Bohr introduced the quantum version of the hydrogen atom. Sommerfeld showed how to extend quantum ideas from circular to elliptical electron orbits, making him kind of like a Kepler to Bohr’s Copernicus. Earlier Sommerfeld had been one of the first strong supporters of Einstein’s special theory of relativity. Sommerfeld also mentored an all-star cast of 20th century physicists, his students including Wolfgang Pauli, Werner Heisenberg and Hans Bethe.
Jean Fourier (250th birthday) Jean Baptiste Joseph Fourier, born March 21, 1768, survived multiple arrests during the French Revolution and ended up working for Napoleon, who made him a baron. With Napoleon’s demise, Fourier struggled to regain political favor and acceptance in the academic world, and eventually succeeded, but his political and diplomatic embroilments consumed much of his time when he should have been doing math. Nevertheless he did important work on the mathematics of heat diffusion and developed useful techniques for solving equations. His most famous achievement, Fourier’s theorem, allows complex periodic processes to be broken down into a series of simpler wave motions. It has wide application in many realms of physics and engineering.
James Joule (200th birthday) James Joule was born into a family of brewers on December 24, 1818. The brewery provided a laboratory where he developed exceptional experimental skills. Despite no formal scientific training and no academic job, he still became one of England’s leading scientists. His experimental skill led him to precisely establish the amount of work needed to produce a quantity of heat and the relationship between heat and electricity.
Most famously, he demonstrated the law of conservation of energy. Whether mechanical, electrical or chemical, energy’s quantitative relationship to heat remained the same, regardless of the substances used in conducting the measurements, Joule showed. In other words, energy is conserved — a truth now known as the First Law of Thermodynamics. There were no Nobel Prizes in those days, so Joule’s main reward was the designation of the standard unit of energy as the joule.
Henrietta Swan Leavitt (150th birthday) Born in Massachusetts on July 4, 1868, Henrietta Swan Leavitt attended Oberlin College in Ohio and then Radcliffe College, where she studied astronomy. Her excellent academic record impressed Edward Pickering, the director of the Harvard Observatory, where she volunteered to be a research assistant and soon earned a permanent job. She worked on mapping stars with the latest photographic and spectroscopic methods, eventually measuring the brightnesses of thousands of stars. Some of those stars varied in brightness over time (one of them, Delta Cephei, gave such stars the name Cepheid variables). Leavitt analyzed these Cepheids more thoroughly than her predecessors and noticed that the stars’ brightness varied on a regular schedule that depended on their intrinsic brightness. Leavitt worked out the “period-luminosity relationship” in 1908, giving astronomers a powerful tool for measuring the distance to stars and other astronomical objects.
Distance to a Cepheid nearby could be determined by parallax, enabling the determination of its intrinsic brightness based on its brightening-dimming schedule. Then, using nearby Cepheids’ intrinsic brightness, the bright-dim period for a more distant Cepheid could be used to infer its intrinsic brightness. That made it possible to calculate the star’s distance. Leavitt’s work made much of the 20th century’s dramatic revision of humankind’s conception of the cosmos possible. “Her discovery of the period-luminosity relationship in Cepheid variable stars is absolutely fundamental in transforming people’s ideas about first, our own galactic system and second, providing the means to demonstrate that galaxies do in fact exist,” historian Robert Smith said in a talk last January.
Spontaneous Generation, Not (350th anniversary) Casual observations of nature had led the ancients to believe that life sometimes spontaneously generated itself from decaying organic matter — think maggots appearing in rotten meat. Francesco Redi, an expert on the effects of snake venom, thought otherwise. Born in Italy, educated at the University of Pisa and then medical school in Florence, Redi conducted various experiments on the effects of snakebites, realizing that the danger stemmed from venom entering the bloodstream. In his masterwork Experiments on the Generation of Insects, published in 1668, he described clever experiments that showed maggots could appear only if flies had access to the meat to lay their eggs. He didn’t close the case on all claims of spontaneous generation, but his work was a major first step toward eliminating received dogma in biology and replacing it with experiment and reason.
Discovery of helium (150th anniversary) On August 18, 1868, French astronomer Jules Janssen witnessed a total eclipse of the sun in Guntur, India, and recorded the colors in the spectrum of solar prominences. He realized that he could record the colors even without an eclipse, and in the following days he observed a curious bright yellow line. He wrote a paper and sent it off to the French Academy of Sciences. Later that year, English astronomer Joseph Lockyer observed the same spectral line, wrote a paper and also sent it to the French Academy of Sciences. Legend (apparently true) has it that the papers arrived within minutes of each other, so Janssen and Lockyer shared in the discovery of the yellow line, whatever it was.
Lockyer soon argued that it was the signature of a new chemical element, unknown on Earth. He called it helium, for Helios, the Greek god of the sun. Some experts doubted that the line signified a new element or insisted that such an element must exist only on the sun and would never have any usefulness on Earth. But their balloon burst in 1895 when William Ramsay in London found helium gas within a uranium-containing mineral. (Others working in Sweden found the gas at about the same time.) Uranium emits alpha particles, the nuclei of helium atoms, so all those alpha particles need to do is find some stray electrons buzzing around to become helium atoms. But nobody understood that at the time because radioactivity hadn’t been discovered yet.
Ignaz Semmelweis (200th birthday) Born on July 1, 1818, in Hungary, Ignaz Semmelweis almost single-handedly (or maybe dual-handedly) showed how to bring public health out of the dark ages and into modernity by identifying the importance of washing your hands. After attending medical school in Vienna, he practiced midwifery for a while and then studied surgery and statistics. He then joined the staff at a teaching hospital, where he noticed a large (statistically suspicious) difference between two clinics in deaths of mothers or their babies from puerperal fever. He eventually realized that in one of the clinics doctors conducted autopsies and apparently carried cadaver contamination to the birthing room. Semmelweis concocted a solution for cleansing hands after autopsies; the puerperal fever death rate then dropped dramatically. But his insight was widely resisted by the medical establishment. It was only much later, after Louis Pasteur established the importance of germs in transmitting disease, that Semmelweis’ method could be successfully explained and then adopted.
Richard Feynman (100th birthday) One of the most nonconformist of theoretical physicists, Richard Feynman (born May 11, 1918) gained public notoriety late in life as a member of the Presidential Commission investigating the space shuttle Challenger explosion. He was also skilled at playing bongo drums. Among physicists, he was most highly regarded for his original approach to quantum mechanics and formulation of quantum field theory (work earning a share of the 1965 Nobel Prize in physics). Later he was an early leading advocate of research into quantum computing. Hans Bethe, another physics Nobel laureate, considered Feynman to be a most unusual kind of genius. “He was a magician,” Bethe once said. “Feynman certainly was the most original physicist I have seen in my life.”
Noether’s theorem (centennial) On any list of history’s great mathematicians who were ignored or underappreciated simply because they were women, you’ll find the name of Emmy Noether. Despite the barricades erected by 19th century antediluvian attitudes, she managed to establish herself as one of Germany’s premier mathematicians. She made significant contributions to various math specialties, including advanced forms of algebra. And in 1918, she published a theorem that provided the foundation for 20th century physicists’ understanding of reality. She showed that symmetries in nature implied the conservation laws that physicists had discovered without really understanding.
Joule’s conservation of energy, it turns out, is a requirement of time symmetry — the fact that no point in time differs from any other. Similarly, conservation of momentum is required if space is symmetric, that is, moving to a different point in space changes nothing about anything else. And if all directions in space are similarly equivalent — rotational symmetry — then the law of conservation of angular momentum is assured and figure skating remains a legitimate Olympic sport. Decades after she died in 1935, physicists are still attempting to exploit Noether’s insight to gain a deeper understanding of the symmetries underlying the laws of the cosmos. On any decent list of history’s great mathematicians, regardless of sex or anything else, you’ll find the name of Emmy Noether.
As mice plumped up on a high-fat diet, some of their taste buds vanished. This disappearing act could explain why some people with obesity seem to have a weakened sense of taste, which may compel them to eat more.
Compared with siblings that were fed normal mouse chow, mice given high-fat meals lost about 25 percent of their taste buds over eight weeks. Buds went missing because mature taste bud cells died off more quickly, and fewer new cells developed to take their place. Chronic, low-level inflammation associated with obesity appears to be behind the loss, researchers report March 20 in PLOS Biology. Taste buds, each a collection of 50 to 100 cells, sense whether a food is sweet, sour, bitter, salty or umami (savory). These cells help identify safe and nourishing food, and stimulate reward centers in the brain. The tongue’s taste bud population is renewed regularly; each bud lasts about 10 days. Special cells called progenitor cells give rise to new taste bud cells that replace old ones.
Some studies have suggested that taste becomes duller in people with obesity, although why that is has remained unclear. But if taste becomes less intense, “then maybe you don’t get the positive feeling that you should,” which could give way to more overeating, says study coauthor Robin Dando, who studies the biology of taste at Cornell University. Nearly 40 percent of U.S. adults have obesity, determined by a person’s body mass index, a ratio of weight to height. The condition is linked to a number of health problems, including heart disease, diabetes and cancer.
The study’s finding that obesity-induced inflammation impacts the presence of taste buds “provides a possible link between obesity and taste,” says Kathryn Medler, a taste physiologist at the University at Buffalo in New York, who was not involved with the research.
Obesity triggers low-level, ongoing inflammation in the body, which can harm cells. The taste tissues of the obese mice had a higher amount of a type of protein called a cytokine, which regulates inflammation, than their normal-weight kin, the researchers found. This particular cytokine, called tumor necrosis factor alpha, seems to be damaging to taste buds, the researchers found. In a test with mice that couldn’t make the cytokine, the obese mice didn’t have missing taste buds. Another experiment showed that mice engineered not to gain excess weight on the high-fat diet — and that therefore didn’t have obesity-related inflammation — also had the regular amount of taste buds.
Along with learning more about how taste buds are damaged by inflammation, Dando is interested in working toward new treatments for obesity, perhaps by countering the dulled sense of taste. “These mice lose taste buds,” he says. “Can we bring them back?”
A strand of spaghetti snaps easily, but an exotic substance known as nuclear pasta is an entirely different story.
Predicted to exist in ultradense dead stars called neutron stars, nuclear pasta may be the strongest material in the universe. Breaking the stuff requires 10 billion times the force needed to crack steel, for example, researchers report in a study accepted in Physical Review Letters.
“This is a crazy-big figure, but the material is also very, very dense, so that helps make it stronger,” says study coauthor and physicist Charles Horowitz of Indiana University Bloomington. Neutron stars form when a dying star explodes, leaving behind a neutron-rich remnant that is squished to extreme pressures by powerful gravitational forces, resulting in materials with bizarre properties (SN: 12/23/17, p. 7).
About a kilometer below the surface of a neutron star, atomic nuclei are squeezed together so close that they merge into clumps of nuclear matter, a dense mixture of neutrons and protons. These as-yet theoretical clumps are thought to be shaped like blobs, tubes or sheets, and are named after their noodle look-alikes, including gnocchi, spaghetti and lasagna. Even deeper in the neutron star, the nuclear matter fully takes over. The burnt-out star’s entire core is nuclear matter, like one giant atomic nucleus.
Nuclear pasta is incredibly dense, about 100 trillion times the density of water. It’s impossible to study such an extreme material in the laboratory, says physicist Constança Providência of the University of Coimbra in Portugal who was not involved with the research. Instead, the researchers used computer simulations to stretch nuclear lasagna sheets and explore how the material responded. Immense pressures were required to deform the material, and the pressure required to snap the pasta was greater than for any other known material.
Earlier simulations had revealed that the outer crust of a neutron star was likewise vastly stronger than steel. But the inner crust, where nuclear pasta lurks, was unexplored territory. “Now, what [the researchers] see is that the inner crust is even stronger,” Providência says.
Physicists are still aiming to find real-world evidence of nuclear pasta. The new results may provide a glimmer of hope. Neutron stars tend to spin very rapidly, and, as a result, might emit ripples in spacetime called gravitational waves, which scientists could detect at facilities like the Advanced Laser Interferometer Gravitational-wave Observatory, or LIGO. But the spacetime ripples will occur only if a neutron star’s crust is lumpy — meaning that it has “mountains,” or mounds of dense material either on the surface or within the crust.
“The tricky part is, you need a big mountain,” says physicist Edward Brown of Michigan State University in East Lansing. A stiffer, stronger crust would support larger mountains, which could produce more powerful gravitational waves. But “large” is a relative term. Due to the intense gravity of neutron stars, their mountains would be a far cry from Mount Everest, rising centimeters tall, not kilometers. Previously, scientists didn’t know how large a mountain nuclear pasta could support.
“That’s where these simulations come in,” Brown says. The results suggest that nuclear pasta could support mountains tens of centimeters tall — big enough that LIGO could spot neutron stars’ gravitational waves. If LIGO caught such signals, scientists could estimate the mountains’ size, and confirm that neutron stars have superstrong materials in their crusts.
