上海花千坊爱上海

Inspired by how ants move through narrow spaces by shortening their legs, scientists have built a robot that draws in its limbs to navigate constricted passages.

The robot was able to hunch down and walk quickly through passages that were narrower and shorter than itself, researchers report January 20 in Advanced Intelligent Systems. It could also climb over steps and move on grass, loose rock, mulch and crushed granite.

Such generality and adaptability are the main challenges of legged robot locomotion, says robotics engineer Feifei Qian, who was not involved in the study. Some robots have specialized limbs to move over a particular terrain, but they cannot squeeze into small spaces (SN: 1/16/19).
“A design that can adapt to a variety of environments with varying scales or stiffness is a lot more challenging, as trade-offs between the different environments need to be considered,” says Qian, of the University of Southern California in Los Angeles.

For inspiration, researchers in the new study turned to ants. “Insects are really a neat inspiration for designing robot systems that have minimal actuation but can perform a multitude of locomotion behaviors,” says Nick Gravish, a roboticist at the University of California, San Diego (SN: 8/16/18). Ants adapt their posture to crawl through tiny spaces. And they aren’t perturbed by uneven terrain or small obstacles. For example, their legs collapse a bit when they hit an object, Gravish says, and the ants continue to move forward quickly.

Gravish and colleagues built a short, stocky robot — about 30 centimeters wide and 20 centimeters long — with four wavy, telescoping limbs. Each limb consists of six nested concentric tubes that can draw into each other. What’s more, the limbs do not need to be actively powered or adjusted to change their overall length. Instead, springs that connect the leg segments automatically allow the legs to contract when the robot navigates a narrow space and stretch back out in an open space. The goal was to build mechanically intelligent structures rather than algorithmically intelligent robots.

“It’s likely faster than active control, [which] requires the robot to first sense the contact with the environment, compute the suitable action and then send the command to its motors,” Qian says, about these legs. Removing the sensing and computing components can also make the robots small, cheap and less power hungry.

The robot could modify its body width and height to achieve a larger range of body sizes than other similar robots. The leg segments contracted into themselves to let the robot wiggle through small tunnels and sprawled out when under low ceilings. This adaptability let the robot squeeze into spaces as small as 72 percent its full width and 68 percent its full height.
Next, the researchers plan to actively control the stiffness of the springs that connect the leg segments to tune the motion to terrain type without consuming too much power. “That way, you can keep your leg long when you are moving on open ground or over tall objects, but then collapse down to the smallest possible shape in confined spaces,” Gravish says.
Such small-scale, minimal robots are easy to produce and can be quickly tweaked to explore complex environments. However, despite being able to walk across different terrains, these robots are, for now, too fragile for search-and-rescue, exploration or biological monitoring, Gravish says.

The new robot takes a step closer to those goals, but getting there will take more than just robotics, Qian says. “To actually achieve these applications would require an integration of design, control, sensing, planning and hardware advancement.”

But that’s not Gravish’s interest. Instead, he wants to connect these experiments back to what was observed in the ants originally and use the robots to ask more questions about the rules of locomotion in nature (SN: 1/16/20).

“I really would like to understand how small insects are able to move so rapidly across certain unpredictable terrain,” he says. “What is special about their limbs that enables them to move so quickly?”

The dwarf planet Quaoar has a ring that is too big for its metaphorical fingers. While all other rings in the solar system lie within or near a mathematically determined distance of their parent bodies, Quaoar’s ring is much farther out.

“For Quaoar, for the ring to be outside this limit is very, very strange,” says astronomer Bruno Morgado of the Federal University of Rio de Janeiro. The finding may force a rethink of the rules governing planetary rings, Morgado and colleagues say in a study published February 8 in Nature.
Quaoar is an icy body about half the size of Pluto that’s located in the Kuiper Belt at the solar system’s edge (SN: 8/23/22). At such a great distance from Earth, it’s hard to get a clear picture of the world.

So Morgado and colleagues watched Quaoar block the light from a distant star, a phenomenon called a stellar occultation. The timing of the star winking in and out of view can reveal details about Quaoar, like its size and whether it has an atmosphere.

The researchers took data from occultations from 2018 to 2020, observed from all over the world, including Namibia, Australia and Grenada, as well as space. There was no sign that Quaoar had an atmosphere. But surprisingly, there was a ring. The finding makes Quaoar just the third dwarf planet or asteroid in the solar system known to have a ring, after the asteroid Chariklo and the dwarf planet Haumea (SN: 3/26/14; SN: 10/11/17).

Even more surprisingly, “the ring is not where we expect,” Morgado says.
Known rings around other objects lie within or near what’s called the Roche limit, an invisible line where the gravitational force of the main body peters out. Inside the limit, that force can rip a moon to shreds, turning it into a ring. Outside, the gravity between smaller particles is stronger than that from the main body, and rings will coalesce into one or several moons.

“We always think of [the Roche limit] as straightforward,” Morgado says. “One side is a moon forming, the other side is a ring stable. And now this limit is not a limit.”

For Quaoar’s far-out ring, there are a few possible explanations, Morgado says. Maybe the observers caught the ring at just the right moment, right before it turns into a moon. But that lucky timing seems unlikely, he notes.

Maybe Quaoar’s known moon, Weywot, or some other unseen moon contributes gravity that holds the ring stable somehow. Or maybe the ring’s particles are colliding in such a way that they avoid sticking together and clumping into moons.

The particles would have to be particularly bouncy for that to work, “like a ring of those bouncy balls from toy stores,” says planetary scientist David Jewitt of UCLA, who was not involved in the new work.

The observation is solid, says Jewitt, who helped discover the first objects in the Kuiper Belt in the 1990s. But there’s no way to know yet which of the explanations is correct, if any, in part because there are no theoretical predictions for such far-out rings to compare with Quaoar’s situation.

That’s par for the course when it comes to the Kuiper Belt. “Everything in the Kuiper Belt, basically, has been discovered, not predicted,” Jewitt says. “It’s the opposite of the classical model of science where people predict things and then confirm or reject them. People discover stuff by surprise, and everyone scrambles to explain it.”

More observations of Quaoar, or more discoveries of seemingly misplaced rings elsewhere in the solar system, could help reveal what’s going on.

“I have no doubt that in the near future a lot of people will start working with Quaoar to try to get this answer,” Morgado says.

For nearly 650 years, the fortress walls in the Chinese city of Xi’an have served as a formidable barrier around the central city. At 12 meters high and up to 18 meters thick, they are impervious to almost everything — except subatomic particles called muons.

Now, thanks to their penetrating abilities, muons may be key to ensuring that the walls that once protected the treasures of the first Ming Dynasty — and are now a national architectural treasure in their own right — stand for centuries more.

A refined detection method has provided the highest-resolution muon scans yet produced of any archaeological structure, researchers report in the Jan. 7 Journal of Applied Physics. The scans revealed interior density fluctuations as small as a meter across inside one section of the Xi’an ramparts. The fluctuations could be signs of dangerous flaws or “hidden structures archaeologically interesting for discovery and investigation,” says nuclear physicist Zhiyi Liu of Lanzhou University in China.
Muons are like electrons, only heavier. They rain down all over the planet, produced when charged particles called cosmic rays hit the atmosphere. Although muons can travel deep into earth and stone, they are scattered or absorbed depending on the material they encounter. Counting the ones that pass through makes them useful for studying volcano interiors, scanning pyramids for hidden chambers and even searching for contraband stashed in containers impervious to X-rays (SN: 4/22/22).

Though muons stream down continuously, their numbers are small enough that the researchers had to deploy six detectors for a week at a time to collect enough data for 3-D scans of the rampart.

It’s now up to conservationists to determine how to address any density fluctuations that might indicate dangerous flaws, or historical surprises, inside the Xi’an walls.

Today’s red jungle fowl — the wild forebears of the domesticated chicken — are becoming more chickenlike. New research suggests that a large proportion of the wild fowl’s DNA has been inherited from chickens, and relatively recently.

Ongoing interbreeding between the two birds may threaten wild jungle fowl populations’ future, and even hobble humans’ ability to breed better chickens, researchers report January 19 in PLOS Genetics.

Red jungle fowl (Gallus gallus) are forest birds native to Southeast Asia and parts of South Asia. Thousands of years ago, humans domesticated the fowl, possibly in the region’s rice fields (SN: 6/6/22).
“Chickens are arguably the most important domestic animal on Earth,” says Frank Rheindt, an evolutionary biologist at the National University of Singapore. He points to their global ubiquity and abundance. Chicken is also one of the cheapest sources of animal protein that humans have.

Domesticated chickens (G. gallus domesticus) were known to be interbreeding with jungle fowl near human settlements in Southeast Asia. Given the unknown impacts on jungle fowl and the importance of chickens to humankind, Rheindt and his team wanted to gather more details. Wild jungle fowl contain a store of genetic diversity that could serve as a crucial resource for breeding chickens resistant to diseases or other threats.

The researchers analyzed and compared the genomes — the full complement of an organism’s DNA — of 63 jungle fowl and 51 chickens from across Southeast Asia. Some of the jungle fowl samples came from museum specimens collected from 1874 through 1939, letting the team see how the genetic makeup of jungle fowl has changed over time.

Over the last century or so, wild jungle fowl’s genomes have become increasingly similar to chickens’. Between about 20 and 50 percent of the genomes of modern jungle fowl originated in chickens, the team found. In contrast, many of the roughly 100-year-old jungle fowl had a chicken-ancestry share in the range of a few percent.

The rapid change probably comes from human communities expanding into the region’s wilderness, Rheindt says. Most modern jungle fowl live in close vicinity to humans’ free-ranging chickens, with which they frequently interbreed.

Such interbreeding has become “almost the norm now” for any globally domesticated species, Rheindt says, such as dogs hybridizing with wolves and house cats crossing with wildcats. Pigs, meanwhile, are mixing with wild boars and ferrets with polecats.
Wild populations that interbreed with their domesticated counterparts could pick up physical or behavioral traits that change how the hybrids function in their ecosystem, says Claudio Quilodrán, a conservation geneticist at the University of Geneva not involved with this research.

The effect is likely to be negative, Quilodrán says, since some of the traits coming into the wild population have been honed for human uses, not for survival in the local environment.

Wild jungle fowl have lost their genetic diversity as they’ve interbred too. The birds’ heterozygosity — a measure of a population’s genetic diversity — is now just a tenth of what it was a century ago.

“This result is initially counterintuitive,” Rheindt says. “If you mix one population with another, you would generally expect a higher genetic diversity.”

But domesticated chickens have such low genetic diversity that certain versions of jungle fowl genes are being swept out of the population by a tsunami of genetic homogeneity. The whittling down of these animals’ genetic toolkit may leave them vulnerable to conservation threats.

“Having lots of genetic diversity within a species increases the chance that certain individuals contain the genetic background to adapt to a varied range of different environmental changes and diseases,” says Graham Etherington, a computational biologist at the Earlham Institute in Norwich, England, who was not involved with this research.

A shallower jungle fowl gene pool could also mean diminished resources for breeding better chickens. The genetics of wild relatives are sometimes used to bolster the disease or pest resistance of domesticated crop plants. Jungle fowl genomes could be similarly valuable for this reason.

“If this trend continues unabated, future human generations may only be able to access the entirety of ancestral genetic diversity of chickens in the form of museum specimens,” Rheindt says, which could hamper chicken breeding efforts using the wild fowl genes.

Some countries such as Singapore, Rheindt says, have started managing jungle fowl populations to reduce interbreeding with chickens.

The worst procrastinators probably won’t be able to read this story. It’ll remind them of what they’re trying to avoid, psychologist Piers Steel says.

Maybe they’re dragging their feet going to the gym. Maybe they haven’t gotten around to their New Year’s resolutions. Maybe they’re waiting just one more day to study for that test.

Procrastination is “putting off to later what you know you should be doing now,” even if you’ll be worse off, says Steel, of the University of Calgary in Canada. But all those tasks pushed to tomorrow seem to wedge themselves into the mind — and it may be harming people’s health.
In a study of thousands of university students, scientists linked procrastination to a panoply of poor outcomes, including depression, anxiety and even disabling arm pain. “I was surprised when I saw that one,” says Fred Johansson, a clinical psychologist at Sophiahemmet University in Stockholm. His team reported the results January 4 in JAMA Network Open.

The study is one of the largest yet to tackle procrastination’s ties to health. Its results echo findings from earlier studies that have gone largely ignored, says Fuschia Sirois, a behavioral scientist at Durham University in England, who was not involved with the new research.

For years, scientists didn’t seem to view procrastination as something serious, she says. The new study could change that. “It’s that kind of big splash that’s … going to get attention,” Sirois says. “I’m hoping that it will raise awareness of the physical health consequences of procrastination.”

Procrastinating may be bad for the mind and body
Whether procrastination harms health can seem like a chicken-and-egg situation.

It can be hard to tell if certain health problems make people more likely to procrastinate — or the other way around, Johansson says. (It may be a bit of both.) And controlled experiments on procrastination aren’t easy to do: You can’t just tell a study participant to become a procrastinator and wait and see if their health changes, he says.
Many previous studies have relied on self-reported surveys taken at a single time point. But a snapshot of someone makes it tricky to untangle cause and effect. Instead, in the new study, about 3,500 students were followed over nine months, so researchers could track whether procrastinating students later developed health issues.

On average, these students tended to fare worse over time than their prompter peers. They were slightly more stressed, anxious, depressed and sleep-deprived, among other issues, Johansson and colleagues found. “People who score higher on procrastination to begin with … are at greater risk of developing both physical and psychological problems later on,” says study coauthor Alexander Rozental, a clinical psychologist at Uppsala University in Sweden. “There is a relationship between procrastination at one time point and having these negative outcomes at the later point.”

The study was observational, so the team can’t say for sure that procrastination causes poor health. But results from other researchers also seem to point in this direction. A 2021 study tied procrastinating at bedtime to depression. And a 2015 study from Sirois’ lab linked procrastinating to poor heart health.

Stress may be to blame for procrastination’s ill effects, data from Sirois’ lab and other studies suggest. She thinks that the effects of chronic procrastinating could build up over time. And though procrastination alone may not cause disease, Sirois says, it could be “one extra factor that can tip the scales.”

No, procrastinators are not lazy
Some 20 percent of adults are estimated to be chronic procrastinators. Everyone might put off a task or two, but chronic procrastinators make it their lifestyle, says Joseph Ferrari, a psychologist at DePaul University in Chicago, who has been studying procrastination for decades. “They do it at home, at school, at work and in their relationships.” These are the people, he says, who “you know are going to RSVP late.”

Though procrastinators may think they perform better under pressure, Ferrari has reported the opposite. They actually worked more slowly and made more errors than non-procrastinators, his experiments have shown. And when deadlines are slippery, procrastinators tend to let their work slide, Steel’s team reported last year in Frontiers in Psychology.

For years, researchers have focused on the personalities of people who procrastinate. Findings vary, but some scientists suggest procrastinators may be impulsive, worriers and have trouble regulating their emotions. One thing procrastinators are not, Ferrari emphasizes, is lazy. They’re actually “very busy doing other things than what they’re supposed to be doing,” he says.

In fact, Rozental adds, most research today suggests procrastination is a behavioral pattern.

And if procrastination is a behavior, he says, that means it’s something you can change, regardless of whether you’re impulsive.

Why procrastinators should be kind to themselves
When people put off a tough task, they feel good — in the moment.
Procrastinating is a way to sidestep the negative emotions linked to the task, Sirois says. “We’re sort of hardwired to avoid anything painful or difficult,” she says. “When you procrastinate, you get immediate relief.” A backdrop of stressful circumstances — say, a worldwide pandemic — can strain people’s ability to cope, making procrastinating even easier. But the relief it provides is only temporary, and many seek out ways to stop dawdling.

Researchers have experimented with procrastination treatments that run the gamut from the logistical to the psychological. What works best is still under investigation. Some scientists have reported success with time-management interventions. But the evidence for that “is all over the map,” Sirois says. That’s because “poor time management is a symptom not a cause of procrastination,” she adds.

For some procrastinators, seemingly obvious tips can work. In his clinical practice, Rozental advises students to simply put down their smartphones. Silencing notifications or studying in the library rather than at home can quash distractions and keep people on task. But that won’t be enough for many people, he says.

Hard-core procrastinators may benefit from cognitive behavioral therapy. In a 2018 review of procrastination treatments, Rozental found that this type of therapy, which involves managing thoughts and emotions and trying to change behavior, seemed to be the most helpful. Still, not many studies have examined treatments, and there’s room for improvement, he says.

Sirois also favors an emotion-centered approach. Procrastinators can fall into a shame spiral where they feel uneasy about a task, put the task off, feel ashamed for putting it off and then feel even worse than when they started. People need to short-circuit that loop, she says. Self-forgiveness may help, scientists suggested in one 2020 study. So could mindfulness training.

In a small trial of university students, eight weekly mindfulness sessions reduced procrastination, Sirois and colleagues reported in the January Learning and Individual Differences. Students practiced focusing on the body, meditating during unpleasant activities and discussed the best way to take care of themselves. A little self-compassion may snap people out of their spiral, Sirois says.

“You made a mistake and procrastinated. It’s not the end of the world,” she says. “What can you do to move forward?”

Supercooled water is two of a kind, a new study shows.

Scientists have long suspected that water at subfreezing temperatures comes in two distinct varieties: a high-density liquid that appears at very high pressures and a low-density liquid at lower pressures. Now, ultrafast measurements have caught water morphing from one type of liquid to the other, confirming that hunch. The discovery, reported in the Nov. 20 Science, could help explain some of water’s quirks.

The experiment “adds more and more evidence to the idea that water really is two components … and that that is the reason that underlies why water is so weird,” says physicist Greg Kimmel of Pacific Northwest National Laboratory in Richland, Wash., who was not involved in the study.

When free from impurities, water can remain liquid below its typical freezing point of zero degrees Celsius, forming what’s called a supercooled liquid. But the dual nature of supercooled water was expected to appear in a temperature realm so difficult to study that it’s been dubbed “no-man’s-land.” Below around –40° C, water remains liquid for mere instants before it crystallizes into ice. Making the task even more daunting, the high-density phase appears only at very high pressures. Still, “people have dreamt about how to do an experiment,” says Anders Nilsson of Stockholm University.
Thanks to speedy experimental maneuvers, Nilsson and colleagues have infiltrated that no-man’s-land by monitoring water’s properties on a scale of nanoseconds. “This is one of the major accomplishments of this paper,” says computational chemist Gül Zerze of Princeton University. “I’m impressed with their work.”

The scientists started by creating a type of high-density ice. Then, a pulse from an infrared laser heated the ice, forming liquid water under high pressure. That water then expanded, and the pressure rapidly dropped. Meanwhile, the researchers used an X-ray laser to investigate how the structure of the water changed, based on how the X-rays scattered. As the pressure decreased, the water transitioned from a high-density to low-density fluid before crystallizing into ice.

Previous studies have used ultrafast techniques to find hints of water’s two-faced demeanor, but those have been done mainly at atmospheric pressure (SN: 9/28/20). In the new work, the water was observed at about 3,000 times atmospheric pressure and –68° C. “It’s the first time we have real experimental data at these pressures and temperatures,” says physicist Loni Kringle of Pacific Northwest National Laboratory, who was not involved with the experiment.

The result could indicate that supercooled water has a “critical point” — a certain pressure and temperature at which two distinct phases merge into one. In the future, Nilsson hopes to pinpoint that spot.

Such a critical point could explain why water is an oddball liquid. For most liquids, cooling makes them become denser and more difficult to compress. Water gets denser as it is cooled to 4° C, but becomes less dense as it is cooled further. Likewise, its compressibility increases as it’s cooled.

If supercooled water has a critical point, that could indicate that the water experienced in daily life is strange because, under typical pressures and temperatures, it is a supercritical liquid — a weird state that occurs beyond a critical point. Such a liquid would not be the high-density or low-density form, but would consist of some regions with a high-density arrangement of water molecules and other pockets of low density. The relative amounts of those two structures, which result from different arrangements of hydrogen bonds between the molecules, would change as the temperature changes, explaining why water behaves strangely as it is cooled.

So despite the fact that the experiment involved extreme pressures and temperatures, Nilsson says, “it influences water in our ordinary life.”

2022 was the year many people decided the coronavirus pandemic had ended.

President Joe Biden said as much in an interview with 60 Minutes in September. “The pandemic is over,” he said while strolling around the Detroit Auto Show. “We still have a problem with COVID. We’re still doing a lot of work on it. But the pandemic is over.”

His evidence? “No one’s wearing masks. Everybody seems to be in pretty good shape.”

But the week Biden’s remarks aired, about 360 people were still dying each day from COVID-19 in the United States. Globally, about 10,000 deaths were recorded every week. That’s “10,000 too many, when most of these deaths could be prevented,” the World Health Organization Director-General Tedros Adhanom Ghebreyesus said in a news briefing at the time. Then, of course, there are the millions who are still dealing with lingering symptoms long after an infection.
Those staggering numbers have stopped alarming people, maybe because those stats came on the heels of two years of mind-boggling death counts (SN Online: 5/18/22). Indifference to the mounting death toll may reflect pandemic fatigue that settled deep within the public psyche, leaving many feeling over and done with safety precautions.

“We didn’t warn people about fatigue,” says Theresa Chapple-McGruder, an epidemiologist in the Chicago area. “We didn’t warn people about the fact that pandemics can last long and that we still need people to be willing to care about yourselves, your neighbors, your community.”

Public health agencies around the world, including in Singapore and the United Kingdom, reinforced the idea that we could “return to normal” by learning to “live with COVID.” The U.S. Centers for Disease Control and Prevention’s guidelines raised the threshold for case counts that would trigger masking (SN Online: 3/3/22). The agency also shortened suggested isolation times for infected people to five days, even though most people still test positive for the virus and are potentially infectious to others for several days longer (SN Online: 8/19/22).

The shifting guidelines bred confusion and put the onus for deciding when to mask, test and stay home on individuals. In essence, the strategy shifted from public health — protecting your community — to individual health — protecting yourself.
Doing your part can be exhausting, says Eric Kennedy, a sociologist specializing in disaster management at York University in Toronto. “Public health is saying, ‘Hey, you have to make the right choices every single moment of your life.’ Of course, people are going to get tired with that.”

Doing the right thing — from getting vaccinated to wearing masks indoors — didn’t always feel like it paid off on a personal level. As good as the vaccines are at keeping people from becoming severely ill or dying of COVID-19, they were not as effective at protecting against infection. This year, many people who tried hard to make safe choices and had avoided COVID-19 got infected by wily omicron variants (SN Online: 4/22/22). People sometimes got reinfected — some more than once (SN: 7/16/22 & 7/30/22, p. 8).
Those infections may have contributed to a sense of futility. “Like, ‘I did my best. And even with all of that work, I still got it. So why should I try?’ ” says Kennedy, head of a Canadian project monitoring the sociological effects of the COVID-19 pandemic.

Getting vaccinated, masking and getting drugs or antibody treatments can reduce the severity of infection and may cut the chances of infecting others. “We should have been talking about this as a community health issue and not a personal health issue,” Chapple-McGruder says. “We also don’t talk about the fact that our uptake [of these tools] is nowhere near what we need” to avoid the hundreds of daily deaths.

A lack of data about how widely the coronavirus is still circulating makes it difficult to say whether the pandemic is ending. In the United States, the influx of home tests was “a blessing and a curse,” says Beth Blauer, data lead for the Johns Hopkins University Coronavirus Resource Center. The tests gave an instant readout that told people whether they were infected and should isolate. But because those results were rarely reported to public health officials, true numbers of cases became difficult to gauge, creating a big data gap (SN Online: 5/27/22).
The flow of COVID-19 data from many state and local agencies also slowed to a trickle. In October, even the CDC began reporting cases and deaths weekly instead of daily. Altogether, undercounting of the coronavirus’s reach became worse than ever.

“We’re being told, ‘it’s up to you now to decide what to do,’ ” Blauer says, “but the data is not in place to be able to inform real-time decision making.”

With COVID-19 fatigue so widespread, businesses, governments and other institutions have to find ways to step up and do their part, Kennedy says. For instance, requiring better ventilation and filtration in public buildings could clean up indoor air and reduce the chance of spreading many respiratory infections, along with COVID-19. That’s a behind-the-scenes intervention that individuals don’t have to waste mental energy worrying about, he says.

The bottom line: People may have stopped worrying about COVID-19, but the virus isn’t done with us yet. “We have spent two-and-a-half years in a long, dark tunnel, and we are just beginning to glimpse the light at the end of that tunnel. But it is still a long way off,” WHO’s Tedros said. “The tunnel is still dark, with many obstacles that could trip us up if we don’t take care.” If the virus makes a resurgence, will we see it coming and will we have the energy to combat it again?

A group at the National Bureau of Standards at B­oulder, Colo., now reports an extremely accurate [speed of light] measurement using the wavelength and frequency of a helium-neon laser.… The result gives the speed of light as 299,792.4562 kilometers per second.

Update
That 1972 experiment measured the two-way speed of light, or the average speed of photons that traveled from their source to a reflective surface and back. The result, which still holds up, helped scientists redefine the standard length of the meter (SN: 10/22/83, p. 263). But they weren’t done putting light through its paces. In the late 1990s and early 2000s, photons set a record for slowest measured speed of light at 17 meters per second and froze in their tracks for one-thousandth of a second (SN: 1/27/01, p. 52). For all that success, one major hurdle remains: directly testing the one-way speed of light. The measurement, which many scientists say is impossible to make, could resolve the long-standing question of whether the speed of light is uniform in all directions.

Some immune defenses of the brain may have their roots in the gut.

A new study in mice finds that immune cells are first trained in the gut to recognize and launch attacks on pathogens, and then migrate to the brain’s surface to protect it, researchers report online November 4 in Nature. These cells were also found in surgically removed parts of human brains.

Every minute, around 750 milliliters of blood flow through the brain, giving bacteria, viruses or other blood-borne pathogens an opportunity to infect the organ. For the most part, the invaders are kept out by three membrane layers, called the meninges, which wrap around the brain and spinal cord and act as a physical barrier. If a pathogen does manage to breach that barrier, the researchers say, the immune cells trained in the gut are ready to attack by producing a battalion of antibodies.

The most common route for a pathogen to end up in the bloodstream is from the gut. “So, it makes perfect sense for these [immune cells] to be educated, trained and selected to recognize things that are present in the gut,” says Menna Clatworthy, an immunologist at the University of Cambridge.

Clatworthy’s team found antibody-producing plasma cells in the leathery meninges, which lie between the brain and skull, in both mice and humans. These immune cells produced a class of antibodies called immunoglobulin A, or IgA.

These cells and antibodies are mainly found in the inner lining of the gut and lungs, so the scientists wondered if the cells on the brain had any link to the gut. It turned out that there was: Germ-free mice, which had no microbes in their guts, didn’t have any plasma cells in their meninges either. However, when bacteria from the poop of other mice and humans were transplanted into the mice’s intestines, their gut microbiomes were restored, and the plasma cells then appeared in the meninges.

“This was a powerful demonstration of how important the gut could be at determining what is found in the meninges,” Clatworthy says.

Researchers captured microscope images of an attack in the meninges of mice that was led by plasma cells that had likely been trained in the guts. When the team implanted a pathogenic fungus, commonly found in the intestine, into the mice’s bloodstream, the fungus attempted to enter the brain through the walls of blood vessels in the meninges. However, plasma cells in the membranes formed a mesh made of IgA antibodies around the pathogen, blocking its entry. The plasma cells are found along the blood vessels, Clatworthy says, where they can quickly launch an attack on pathogens.

“To my knowledge, this is the first time anyone has shown the presence of plasma cells in the meninges. The study has rewritten the paradigm of what we know about these plasma cells and how they play a critical role in keeping our brain healthy,” says Matthew Hepworth, an immunologist at the University of Manchester in England who was not involved with the study. More research is needed to classify how many of the plasma cells in the meninges come from the gut, he says.

The finding adds to growing evidence that gut microbes can play a role in brain diseases. A previous study, for instance, suggested that in mice, boosting a specific gut bacterium could help fight amyotrophic lateral sclerosis, or ALS, a fatal neurological disease that results in paralysis (SN: 7/22/19). And while the new study found the plasma cells in the brains of healthy mice, previous research has found other gut-trained cells in the brains of mice with multiple sclerosis, an autoimmune disease of the brain and the spinal cord.

For now, the researchers want to understand what cues plasma cells follow in the guts to know it is time for them to embark on a journey to the brain.

It’s official: 2020 now has the most named storms ever recorded in the Atlantic in a single year.

On November 9, a tropical disturbance brewing in the northeastern Atlantic Ocean gained enough strength to become a subtropical storm. With that, Theta became the year’s 29th named storm, topping the 28 that formed in 2005.

With maximum sustained winds near 110 kilometers per hour as of November 10, Theta is expected to churn over the open ocean for several days. It’s too early to predict Theta’s ultimate strength and trajectory, but forecasters with the National Oceanic and Atmospheric Administration say they expect the storm to weaken later in the week.

If so, like most of the storms this year, Theta likely won’t become a major hurricane. That track record might be the most surprising thing about this season — there’s been a record-breaking number of storms, but overall they’ve been relatively weak. Only five — Laura, Teddy, Delta, Epsilon and Eta — have become major hurricanes with winds topping 178 kilometers per hour, although only Laura and Eta made landfall near the peak of their strength as Category 4 storms.

Even so, the 2020 hurricane season started fast, with the first nine storms arriving earlier than ever before (SN: 9/7/20). And the season has turned out to be the most active since naming began in 1953, thanks to warmer-than-usual water in the Atlantic and the arrival of La Niña, a regularly-occurring period of cooling in the Pacific, which affects winds in the Atlantic and helps hurricanes form (SN: 9/21/19). If a swirling storm reaches wind speeds of 63 kilometers per hour, it gets a name from a list of 21 predetermined names. When that list runs out, the storm gets a Greek letter.

While the wind patterns and warm Atlantic water temperatures set the stage for the string of storms, it’s unclear if climate change is playing a role in the number of storms. As the climate warms, though, you would expect to see more of the destructive, high-category storms, says Kerry Emanuel, an atmospheric scientist at MIT. “And this year is not a poster child for that.” So far, no storm in 2020 has been stronger than a Category 4. The 2005 season had multiple Category 5 storms, including Hurricane Katrina (SN: 12/20/05).

There’s a lot amount of energy in the ocean and atmosphere this year, including the unusually warm water, says Emanuel. “The fuel supply could make a much stronger storm than we’ve seen,” says Emanuel, “so the question is: What prevents a lot of storms from living up to their potential?”
A major factor is wind shear, a change in the speed or direction of wind at different altitudes. Wind shear “doesn’t seem to have stopped a lot of storms from forming this year,” Emanuel says, “but it inhibits them from getting too intense.” Hurricanes can also create their own wind shear, so when multiple hurricanes form in close proximity, they can weaken each other, Emanuel says. And at times this year, several storms did occupy the Atlantic simultaneously — on September 14, five storms swirled at once.

It’s not clear if seeing hurricane season run into the Greek alphabet is a “new normal,” says Emanuel. The historical record, especially before the 1950s is spotty, he says, so it’s hard to put this year’s record-setting season into context. It’s possible that there were just as many storms before naming began in the ‘50s, but that only the big, destructive ones were recorded or noticed. Now, of course, forecasters have the technology to detect all of them, “so I wouldn’t get too bent out of shape about this season,” Emanuel says.

Some experts are hesitant to even use the term “new normal.”

“People talk about the ‘new normal,’ and I don’t think that is a good phrase,” says James Done, an atmospheric scientist at the National Center for Atmospheric Research in Boulder, Colo. “It implies some new stable state. We’re certainly not in a stable state — things are always changing.”