Quantum physics requires imaginary numbers to explain reality

Imaginary numbers might seem like unicorns and goblins — interesting but irrelevant to reality.

But for describing matter at its roots, imaginary numbers turn out to be essential. They seem to be woven into the fabric of quantum mechanics, the math describing the realm of molecules, atoms and subatomic particles. A theory obeying the rules of quantum physics needs imaginary numbers to describe the real world, two new experiments suggest.

Imaginary numbers result from taking the square root of a negative number. They often pop up in equations as a mathematical tool to make calculations easier. But everything we can actually measure about the world is described by real numbers, the normal, nonimaginary figures we’re used to (SN: 5/8/18). That’s true in quantum physics too. Although imaginary numbers appear in the inner workings of the theory, all possible measurements generate real numbers.

Quantum theory’s prominent use of complex numbers — sums of imaginary and real numbers — was disconcerting to its founders, including physicist Erwin Schrödinger. “From the early days of quantum theory, complex numbers were treated more as a mathematical convenience than a fundamental building block,” says physicist Jingyun Fan of the Southern University of Science and Technology in Shenzhen, China.
Some physicists have attempted to build quantum theory using real numbers only, avoiding the imaginary realm with versions called “real quantum mechanics.” But without an experimental test of such theories, the question remained whether imaginary numbers were truly necessary in quantum physics, or just a useful computational tool.

A type of experiment known as a Bell test resolved a different quantum quandary, proving that quantum mechanics really requires strange quantum linkages between particles called entanglement (SN: 8/28/15). “We started thinking about whether an experiment of this sort could also refute real quantum mechanics,” says theoretical physicist Miguel Navascués of the Institute for Quantum Optics and Quantum Information Vienna. He and colleagues laid out a plan for an experiment in a paper posted online at arXiv.org in January 2021 and published December 15 in Nature.

In this plan, researchers would send pairs of entangled particles from two different sources to three different people, named according to conventional physics lingo as Alice, Bob and Charlie. Alice receives one particle, and can measure it using various settings that she chooses. Charlie does the same. Bob receives two particles and performs a special type of measurement to entangle the particles that Alice and Charlie receive. A real quantum theory, with no imaginary numbers, would predict different results than standard quantum physics, allowing the experiment to distinguish which one is correct.

Fan and colleagues performed such an experiment using photons, or particles of light, they report in a paper to be published in Physical Review Letters. By studying how Alice, Charlie and Bob’s results compare across many measurements, Fan, Navascués and colleagues show that the data could be described only by a quantum theory with complex numbers.

Another team of physicists conducted an experiment based on the same concept using a quantum computer made with superconductors, materials which conduct electricity without resistance. Those researchers, too, found that quantum physics requires complex numbers, they report in another paper to be published in Physical Review Letters. “We are curious about why complex numbers are necessary and play a fundamental role in quantum mechanics,” says quantum physicist Chao-Yang Lu of the University of Science and Technology of China in Hefei, a coauthor of the study.

But the results don’t rule out all theories that eschew imaginary numbers, notes theoretical physicist Jerry Finkelstein of Lawrence Berkeley National Laboratory in California, who was not involved with the new studies. The study eliminated certain theories based on real numbers, namely those that still follow the conventions of quantum mechanics. It’s still possible to explain the results without imaginary numbers by using a theory that breaks standard quantum rules. But those theories run into other conceptual issues, making them “ugly,” he says. But “if you’re willing to put up with the ugliness, then you can have a real quantum theory.”

Despite the caveat, other physicists agree that the quandaries raised by the new findings are compelling. “I find it intriguing when you ask questions about why is quantum mechanics the way it is,” says physicist Krister Shalm of the National Institute of Standards and Technology in Boulder, Colo. Asking whether quantum theory could be simpler or if it contains anything unnecessary, “these are very interesting and thought-provoking questions.”

Neandertals were the first hominids to turn forest into grassland 125,000 years ago

Neandertals took Stone Age landscaping to a previously unrecognized level.

Around 125,000 years ago, these close human relatives transformed a largely forested area bordering two central European lakes into a relatively open landscape, say archaeologist Wil Roebroeks of Leiden University in the Netherlands, and his colleagues. Analyses of pollen, charcoal, animal fossils and other material previously unearthed at two ancient lake basins in Germany provide the oldest known evidence of hominids reshaping their environments, the scientists report December 15 in Science Advances.

The excavated areas are located within a site called Neumark-Nord. Neandertals’ daily activities there, apparently ongoing throughout the year, had a big environmental impact, the researchers suspect. Those pursuits, which occurred over a span of about 2,000 years, included setting campfires, butchering game, collecting wood, making tools and constructing shelters, they say.

“We might be dealing with larger and less mobile groups of [Neandertals] than commonly acknowledged,” Roebroeks says, thanks in part to warming temperatures after around 150,000 years ago that cleared ice sheets from resource-rich locations such as Neumark-Nord.
His team can’t say whether Neandertals set fires to clear large tracts of land at Neumark-Nord, a practice that has been observed among some modern hunter-gatherers. The geological remnants of many small campfires may look much like those of a small number of large fires, Roebroeks says.

Finds at Neumark-Nord play into an ongoing debate about when humans began to have a dominating influence on the natural world. Some scientists regard this period as a new geological epoch, the Anthropocene (SN: 4/1/13). It’s unclear when the Anthropocene began and whether its roots extend back to the Stone Age.

Regular fire use by members of the Homo genus began around 400,000 years ago (SN: 4/2/12). Evidence of human occupations associated with increased fire setting and shifts to open habitats date to around 40,000 years ago in Australia; 45,000 years ago in highland New Guinea; and 50,000 years ago in Borneo.

Analyses of lake cores and stone-tool sites in southern-central Africa indicate that fires set by increasing numbers of humans kept the landscape open even as rainy conditions conducive to forest growth developed around 85,000 years ago. Open environments still predominate in this part of Africa, Yale University paleoanthropologist Jessica Thompson and her colleagues reported May 5 in Science Advances. “Humans and close human relatives like Neandertals have likely been [modifying] their ecosystems for a very long time,” Thompson says.

A large coal mining operation revealed ancient Neumark-Nord sediments in 1985. German scientists then excavated a large lakeside site, wrapping up that project in the mid-1990s. The same team excavated a smaller site at a lake basin located about 100 meters from the first site between 2004 and 2008.

Pollen from these sites indicates that grasses and herbs, hallmarks of an open landscape, appeared in a brief window of time around 125,000 years ago, Roebroeks and his colleagues say. Large numbers of stone artifacts — some showing signs of having been heated, possibly to make finished edges sharper — and animal bones displaying butchery marks date to the same time at Neumark-Nord, when Neandertals but not Homo sapiens inhabited Europe.
Stone tools and bone fragments displaying signs of heating, burned wood, charred seeds and dense patches of charcoal particles suggested that Neandertals had frequently set fires near the Neumark-Nord lakes.

Pollen from two other sites in the same mountainous part of Germany, where researchers previously found small numbers of stone tools suggesting a limited Neandertal presence, show that forests dominated there when Neandertals inhabited Neumark-Nord’s grasslands. That strengthens the view that Neandertals altered the Neumark-Nord landscape rather than settling there after forests had shrunk, Roebroeks says.

Archaeologist Manuel Will of Eberhard Karls University of Tübingen in Germany agrees. “Neandertal evidence from Neumark-Nord should be a wake-up call for the international scientific community to include archaeologists [studying] the Paleolithic record as part of any team trying to define and identify the beginning of the Anthropocene,” says Will, who did not participate in the new study.

The Parker Solar Probe is the first spacecraft to visit the sun’s atmosphere

For the first time, a spacecraft has made contact with the sun. During a recent flyby, NASA’s Parker Solar Probe entered the sun’s atmosphere.

“We have finally arrived,” Nicola Fox, director of NASA’s Heliophysics Science Division in Washington, D.C., said December 14 in a news briefing at the fall meeting of the American Geophysical Union. “Humanity has touched the sun.”

Parker left interplanetary space and crossed into solar territory on April 28, 2021, during one of its close encounters with the sun. While there, the probe took the first measurements of exactly where this boundary, called the Alfvén critical surface, lies. It was about 13 million kilometers above the sun’s surface, physicists reported at the meeting, held online and in New Orleans, and in Physical Review Letters on December 14.

“We knew the Alfvén critical surface had to exist,” solar physicist Justin Kasper of the University of Michigan in Ann Arbor said at the news briefing. “We just didn’t know where it was.”
Finding this crucial layer was one of Parker’s main goals when it launched in 2018 (SN: 7/5/18). The Alfvén critical surface is important because it marks where packets of plasma can separate from the sun and become part of the solar wind, the speedy stream of charged particles that constantly emanates from the sun (SN: 8/18/17). The solar wind and other, more dramatic forms of space weather can wreak havoc on Earth’s satellites and even on life (SN: 2/26/21). Scientists want to pinpoint exactly how the wind gets started to better understand how it can impact Earth.

The Alfvén critical surface also may hold the key to one of the biggest solar mysteries: why the sun’s corona, its wispy outer atmosphere, is so much hotter than the sun’s surface (SN: 8/20/17). With most heat sources, temperatures drop as you move farther away. But the sun’s corona sizzles at more than a million degrees Celsius, while the surface is only a few thousand degrees.

In 1942, physicist Hannes Alfvén proposed a solution to the mystery: A type of magnetic wave might carry energy from the solar surface and heat up the corona. It took until 2009 to directly observe such waves, in the lower corona, but they didn’t carry enough energy there to explain all the heat (SN: 3/19/09). Solar physicists have suspected that what happens as those waves climb higher and meet the Alfvén critical surface might play a role in heating the corona. But until now, scientists didn’t know where this frontier began.

With the boundary identified, “we’ll now be able to witness directly how coronal heating happens,” Kasper said.

As Parker crossed the invisible boundary, its instruments recorded a marked increase in the strength of the local magnetic field and a drop in the density of charged material. Out in the solar wind, waves of charged particles gush away from the sun. But below the Alfvén critical surface, some of those waves bend back toward the surface of the sun.
Surprisingly, Parker’s measurements showed that the Alfvén critical surface is wrinkly. “That was one of the big outstanding questions,” says solar physicist Craig DeForest of the Southwest Research Institute in Boulder, Colo., who is a member of the Parker probe team but was not part of this measurement.

“There was some debate in the community about whether the Alfvén surface would exist as a surface at all,” he says. Decades ago, scientists imagined the boundary as a smooth sphere surrounding the sun like a snow globe. More recently, some thought it would be so ragged that it wouldn’t be apparent when the spacecraft crossed it.

Neither of those images turned out to be correct. The surface is smooth enough that the moment of crossing was noticeable, Kasper said. But during the spacecraft’s close approach to the sun in April, it crossed in and out of the boundary three times. The first dip lasted about five hours, the last only half an hour.

“The surface clearly has some structure and warp to it,” Kasper said.

That structure could influence everything from the way solar eruptions leave the sun to the way the solar wind interacts with itself farther out from the sun, DeForest says. “That has consequences that we don’t know yet, but are likely to be profound,” he says. “This is very exciting. It’s terra incognita.”

Parker is still orbiting the sun and planning to make several more close approaches over the next few years, eventually getting within 6 million kilometers of the solar surface. That should bring Parker into the solar corona again and again, solar physicist Nour Raouafi of the Johns Hopkins Applied Physics Laboratory in Laurel, Md., said in the news briefing. The spacecraft may have made another journey past the Alfvén critical surface in August and will have another opportunity in January.

“The expectation is that as we fly closer and closer to the sun, we’ll keep crossing this boundary,” Raouafi said. But the boundary might not be in the same place every time. As the sun’s activity changes, the level of the Alfvén critical surface is expected to rise and fall as if the corona is breathing in and out, he said.

That’s another thing that scientists hope to observe for the first time.

Nostalgia may have bona fide benefits in hard times, like the pandemic

Over 300 years ago, Swiss physician Johannes Hofer observed disturbing behaviors among Swiss mercenaries fighting in far-flung lands. The soldiers were prone to anorexia, despondency and bouts of weeping. Many attempted suicide. Hofer determined that the mercenaries suffered from what he called “nostalgia,” which he concluded was “a cerebral disease of essentially demonic cause.”

Nowadays, nostalgia’s reputation is much improved. Social psychologists define the emotion — which Hofer saw as synonymous with “homesickness” — as a sentimental longing for meaningful events from one’s past. And research suggests that nostalgia can help people cope with dementia, grief and even the disorientation experienced by immigrants and refugees (SN: 3/1/21).

Nostalgia may even help people cope with the COVID-19 pandemic. In a study published September 8 in Social, Psychological and Personality Science, researchers found when some lonely, unhappy people reminisced about better, pre-pandemic moments, they felt happier. The results suggest that nostalgia can serve as an antidote to loneliness during the pandemic, the researchers conclude.

“A good analogy is the immune system,” says social psychologist Tim Wildschut of the University of Southampton in England. “A viral infection may make you ill, but it also activates your immune system and your immune system makes you better. Loneliness reduces happiness but also triggers nostalgia, and nostalgia increases happiness.”

In the new study, Wildschut and colleagues first surveyed over 3,700 participants in the United States, United Kingdom and China to assess people’s levels of loneliness, nostalgia and happiness during the early days of the pandemic. Surveys varied slightly by country, but for most questions or statements, participants responded on a scale from 1 to 7, with 1 for “not at all” and 7 for “very much.” For instance, participants in the United States rated how isolated they felt from the rest of the world in the week prior to the survey, how happy they felt compared with their peers and their overall feelings of nostalgia.

The researchers found that across the three countries, people who scored relatively high in loneliness also, not surprisingly, scored lower in happiness. But when the team drilled down on the role nostalgia plays, they found people who didn’t indulge in those memories were the least happy.

“Loneliness [triggers] unhappiness and nostalgia. Then unhappiness and nostalgia fight with each other,” says coauthor Constantine Sedikides, a social psychologist also at the University of Southampton.

Meanwhile, in three experiments with new sets of U.S. participants, the researchers manipulated people’s nostalgia levels, using the spring 2020 lockdown as a proxy for heightened loneliness. For example, in one experiment conducted in April 2020, the researchers recruited just over 200 online participants. The team induced nostalgia in half the participants by having them write four words describing a specific nostalgic event from their past. Participants were then prompted to write freely for three minutes about how that past experience made them feel. People in the control group completed the same tasks but about ordinary past experiences.

Those experiments revealed that, compared with the control group, participants in the nostalgia group reported slight but statistically significant higher happiness levels, as measured by the same 1-7 scale used in the earlier surveys. For instance, in the experiment with the 200-plus participants, the researchers found that happiness scores in the nostalgia group averaged 5.64 compared with 5.3 in the control group. Statistical analysis suggests that nostalgia can explain about 2 percent of the variation in happiness, the researchers say.

Those results may sound trivial, but even small variations can yield large results when viewed across large populations or across time, says personality psychologist Friedrich Götz of the University of British Columbia in Vancouver.

“Let’s say you are a happy person every day of your life. Chances are you will have a more fulfilled life than if you are a less happy person,” Götz says. “So 2 percent can make a difference because our happiness influences how we act, feel and think every day of our lives.”
The hope that nostalgia-induced happiness could build up over time underpins some researchers’ long-term goal of harnessing and deploying techniques to trigger nostalgic memories as a form of therapy. Nostalgia can connect people to their past, present and even desired future selves, these researchers say. And since many nostalgic memories often involve other people, they can also help people feel linked to a wider community.

In one study, for example, existential psychologist Clay Routledge and colleagues tapped nostalgia’s social side. Participants first completed an established “nostalgia inventory,” where they rated on a scale from 1 to 5 how nostalgic they felt about 20 aspects of their past lives, such as family and vacations. The researchers then asked people about the types of studies that they might want to participate in later on. Two of those potential studies involved meeting other participants while two others did not.

Participants reporting high levels of nostalgia, especially those nostalgic for social experiences, were more likely than other participants to select the studies that involved meeting new people, the researchers reported in the December 2015 Journal of Personality and Social Psychology. That suggests that proneness to remembering meaningful past social experiences engenders future social experiences, the team says.

“Nostalgia isn’t just people remembering time with loved ones,” says Routledge, of North Dakota State University in Fargo. “It’s orienting them toward building new social experiences.”

A key question, though, is if nostalgia’s benefits can persist beyond that fleeting moment of remembrance. Wildschut’s team found that nostalgia’s benefits, in terms of happiness, faded after just a day or two. But nostalgia-induced happiness persisted for a couple days when the researchers reminded people to think about that special memory.

Crucially, nostalgia therapy may not be for everyone. Researchers reported in October 2019 in Personality and Individual Differences that invoking nostalgia in individuals who viewed relationships as a source of comfort and security increased those people’s intention to engage with others. The reverse, however, held true for individuals who saw relationships as a source of pain.

“For these types of avoidant people … nostalgia pushed them in the opposite direction. They were even less likely to want to connect with others on a deeper level,” says existential and social psychologist Andrew Abeyta of Rutgers University–Camden in New Jersey.
Wildschut and colleagues found a similar result when investigating whether invoking nostalgia among Syrian refugees living in Saudi Arabia could increase self-esteem, sense of meaning in life, feelings of social belonging and optimism.

In that study, refugees in an experimental group wrote about meaningful events from their past, while refugees in a control group wrote about ordinary events. The experiment showed that triggering nostalgia in refugees high in resilience — a trait defined by a capacity to withstand and recover from adversity — resulted in more positive emotions than those reported by resilient refugees in a control group, the team concluded in the December 2019 European Journal of Social Psychology. But while inducing nostalgia in refugees low in resilience did help them feel a greater sense of continuity in life and more socially connected compared with a low-resilience control group, nostalgic memories also made them feel less optimistic about the future.

“When you push the test of nostalgia to those extremes, it’s a very, very tough test,” Wildschut says.

Caveats aside, Wildschut remains optimistic about developing some form of nostalgia therapy. He recalls a conversation with his young daughter many years ago. When he asked her how long nostalgia lasts, she replied “forever,” Wildschut says. “What she meant is that the memory is there, and you can recall it any time.” Ultimately, he and other nostalgia researchers hope to one day identify suitable candidates for nostalgia therapy and then train those people to recall special memories whenever they feel blue.

A Jupiter-like planet orbiting a white dwarf hints at our solar system’s future

A glimpse of our solar system’s future has appeared thousands of light-years away in the constellation Sagittarius. There a giant planet like Jupiter orbits a white dwarf, a dim, dense star that once resembled the sun.

In 2010, that star passed in front of a much more distant star. Like a magnifying glass, the white dwarf’s gravity bent the more distant star’s light rays so that they converged on Earth and made the distant star look hundreds of times brighter. A giant planet orbiting the white dwarf star also “microlensed” the distant star’s light, revealing the planet’s presence.

In 2015, 2016 and again in 2018 astrophysicist Joshua Blackman of the University of Tasmania in Hobart, Australia and colleagues pointed the Keck II telescope in Hawaii at the far-off system, which lies some 5,000 to 8,000 light-years from Earth. The team was in search of the giant planet’s star, but saw, well, nothing.

“We expected that we’d see a star similar to the sun,” Blackman says. “And so we spent quite a few years trying to figure out why on Earth we didn’t see the star which we expected to see.”
After failing to detect any light from the spot where the planet’s star should be, Blackman’s team concluded that the object can’t be a typical star like the sun — also known as a main sequence star, which generates energy by converting hydrogen into helium at its center. Instead, the star must be something much fainter. The microlensing data indicate that the star is roughly half as massive as the sun, so the object isn’t massive enough to be a neutron star or black hole. But a white dwarf star fits the bill perfectly, the researchers report online October 13 in Nature.

“They’ve carefully ruled out the other possible lens stars — neutron stars and black holes and main sequence stars and whatnot,” says Ben Zuckerman, an astronomer at UCLA, who was not involved with the work. He notes that only a handful of planets have ever been found orbiting white dwarfs.

The new planet is the first ever discovered that is orbiting a white dwarf and resembles Jupiter in both its mass and its distance from its star. Blackman’s team estimates that the planet is one to two times as massive as Jupiter and probably lies 2.5 to six times farther from the white dwarf star than Earth does from the sun. For comparison, Jupiter is 5.2 times farther out from the sun than Earth is. The white dwarf is somewhat larger than Earth, which means the planet is much bigger than its host star.

The white dwarf formed after a sunlike star expanded and became a red giant star. Then the red giant ejected its outer layers, exposing its hot core. That former core is the white dwarf star.

Our sun will turn into a white dwarf about 7.8 billion years from now, so the new discovery is “a snapshot into the future of our solar system,” Blackman says. As the sun becomes a red giant, it will engulf and destroy its innermost planet, Mercury, and perhaps Venus too. But Mars, Jupiter and more distant planets should survive.

And Earth? No one yet knows what will happen to it.

Huge numbers of fish-eating jaguars prowl Brazil’s wetlands

In a tract of central Brazilian wetlands, jaguars spend their days wading through chest-deep waters searching for fish. When not hunting, the big cats playfully grapple with each other back on land. Their life is unlike any other known jaguar population’s existence in the world.

New findings reveal a degree of flexibility in diet and lifestyle previously unseen among jaguars. The discovery may provide key context on the cats’ role in food webs, helping scientists better understand the effect of environmental changes on the species, researchers report October 6 in Ecology.

Jaguars (Panthera onca), which are usually territorial loners that hunt on land, live in a wide array of habitats, ranging from North American deserts to grasslands and tropical rainforests in Central and South America. The cats are also found in the Pantanal, an immense tropical wetland — the largest of its kind in the world — that sprawls over parts of Brazil, Bolivia and Paraguay.

Ecologists Manoel dos Santos-Filho of the Universidade do Estado de Mato Grosso in Cáceres, Brazil, and Carlos Peres of the University of East Anglia in Norwich, England, knew of rumors of large numbers of jaguars sighted near Brazil’s Taiamã Ecological Station. That large ecological reserve is located in the remote, northern reaches of the Pantanal.
After relaying these anecdotes to Taal Levi, a wildlife ecologist at Oregon State University in Corvallis, the researchers started a project to better understand the jaguars’ biology and population status in the protected area.

Taiamã is seasonally flooded, with no roads or trails, so the team had to access the reserve by boat, setting up motion-activated cameras along waterways to gather data on jaguar numbers. The area’s abundance of jaguars, however, was obvious immediately.

“You set your foot out of the boat, and there’s a jaguar footprint there already,” says Charlotte Eriksson, a wildlife scientist also at Oregon State University. “There are scratches on trees. There are jaguar scats. There’s just an unbelievable presence of this apex predator wherever you go, which is something I’ve never experienced anywhere before.”

The team deployed 59 cameras, which operated from 2014 to 2018, and collected more than 1,500 videos of jaguars. The researchers also captured 13 jaguars and fitted them with GPS or radio-tracking collars to gain insight into the animals’ population density, movements and social interactions.

Based on their data, Eriksson and colleagues estimate that the Taiamã Ecological Station hosts the highest density of jaguars ever recorded: 12.4 animals per 100 square kilometers, nearly triple some of the next highest estimates elsewhere. Jaguars were also the most common mammal spotted on the cameras.

Video footage showed jaguars carrying off large fish. When the team analyzed 138 scat samples, the researchers found 46 percent had fish remains in them and 55 percent contained aquatic reptiles, such as caiman or turtles. Just 11 percent contained mammal remains.
Jaguars are well-documented in taking on challenging prey, including underwater fare (SN: 7/15/16). Eriksson and her team think that the Taiamã felines have not only the most fish-dependent diet among jaguars, but also among all big cats. There are tigers in Bangladesh that live in flooded mangrove forests and sometimes eat fish, but those cats still primarily eat land-based food, the researchers say.

The cameras and tracking collars also showed that the Taiamã jaguars were spending a lot of time near each other, sometimes traveling, fishing and playing together. This is all exceptionally odd behavior for jaguars, at least based on what scientists know about the cats elsewhere in the world.

In terms of social behavior, “what we knew of jaguars from before this study is basically that they are solitary, and they meet up to mate. And that’s about it,” Eriksson says, noting anecdotes of the cats sharing prey carcasses as rare counterexamples.
The profusion of aquatic prey in the flooded preserve — protected from human encroachment — may be responsible for the jaguars’ superlative density and their rich social lives. It’s possible there’s so much food available, Eriksson says, that there is “no real need to fight over it.”

Another idea is that aquatic prey concentrated along the river margins are accessible in only certain areas, Levi says. This may encourage jaguar territories to dissolve, since obtaining access to multiple fishing spots requires getting along with other jaguars. Other animals behave in similar ways. Brown bears, for example, congregate in great numbers to feed at salmon spawning grounds, despite the bears’ typically solitary nature, Levi says.

The abundance of jaguars and their social behavior is not surprising, given the available food resources, says Todd Fuller, a conservation biologist at the University of Massachusetts Amherst. Still, he finds the new information exciting.

Fuller, who was not involved with the research, says the study helps bring researchers’ understanding of jaguars’ ecology and conservation closer to what’s known about most other large cat species, and “that is a very good thing.”

Jaguars in the Pantanal face many threats and are declining within Brazil, Eriksson says, suffering from drought, fire and agricultural expansion. Evaluating how jaguars might respond to such changes is paramount. In 2020, half of the study area burned, so Eriksson is currently assessing the impact of the fires on the jaguars and their periodically submerged home.

She also wants to investigate how the Taiamã jaguars’ taste for fish is affecting how often the animals eat land-living prey and what strategies the cats use to catch fish.

“We think we know a lot about these charismatic, large predators,” she says, “but there are still things to learn.”

No, COVID-19 vaccines won’t make you infertile

The World Health Organization has warned that the globe is dealing with two pandemics. One is the spread of the coronavirus, but the other, equally dangerous, is the spread of misinformation and disinformation. False or misleading information has sprung up about the virus, treatments, vaccines, masks and just about every other aspect of the pandemic (SN: 5/6/21).

Some of these lies or half-truths are purposefully used by a few people to help sell vitamin supplements, books, and DVDs, or to boost their own influence. But the vast majority of people may have heard misinformation from a friend or relative, seen it on social media or heard it repeated by celebrities or politicians. In a survey of adults in the United States conducted by the Kaiser Family Foundation, nearly 8 in 10 people believe or aren’t sure about the truthfulness of at least one common falsehood about the pandemic. About 46 percent of people believe or are unsure about one to three falsehoods related to the pandemic, and 32 percent believe or are uncertain whether four or more erroneous statements are true or false. Only 22 percent of adults in the survey didn’t believe any of the false statements.
One particularly pernicious rumor is that coronavirus vaccines cause infertility. In the survey, 8 percent of people said they believe that false statement. Another 23 percent of people surveyed weren’t sure whether studies had shown a link between the vaccines and infertility. And it doesn’t help people tell truth from fiction when celebrities spread incorrect information. Recently, the Green Bay Packers’ quarterback Aaron Rodgers said he lied about being vaccinated because of concerns that the COVID-19 vaccine may cause infertility, as People magazine reports. That follows rapper Nicki Minaj’s tweeting that her cousin’s friend in Trinidad had suffered swollen testicles after getting the vaccine. That claim was disputed by the health minister of Trinidad and Tobago, according to CNN.

It’s not just athletes and celebrities spreading false rumors about COVID-19 vaccines and infertility, however. That misinformation is everywhere. In Kibera, an informal settlement in Kenya’s capital of Nairobi, community health volunteers hear two main concerns about getting the vaccine: “Can I have children after this?” and “Can I have the vaccine if I have diabetes or cancer [or other health problems]?” There’s a split between who is asking those questions, says Eddah Ogogo, the primary healthcare program coordinator for the international nonprofit organization CFK Africa that is helping coordinate vaccine distribution. “The younger population [is] scared about infertility. The older population is scared about comorbidities,” she says.

The easier conversation to have is reassuring people that the vaccine won’t interfere with their medications and may help those with health problems avoid the most serious complications of COVID-19. But, says Ogogo, “when it comes to fertility, there are those who get convinced. They say, ‘Wow! That’s good to know’,” and they get their shot. And then, “there are those who say, ‘I’ll keep asking around and when I get the information I want I will come [get vaccinated].’” Just under 7 percent of adults in Kenya are fully vaccinated, mostly due to lack of access to vaccines, but misinformation plays a role too, Ogogo says (SN: 2/26/21).
Local and global news outlets alike often make the disclaimer that there is no evidence that the COVID-19 vaccines cause infertility. But that lackluster response leaves the door open for misinterpretation or rumors of a cover-up. In fact, there is evidence that the vaccines do not cause infertility. One study found that there was no difference in pregnancy rates after embryo transfers in women who had antibodies against the coronavirus from vaccination or infection compared with women who had no antibodies, researchers reported in Fertility and Sterility Reports in September. In clinical trials testing the vaccines, accidental pregnancies happened in both the vaccine group and the unvaccinated control group at similar rates, data posted in the April Nature Reviews Immunology show. Miscarriage rates were also similar, researchers reported in a Lancet study published October 21 look at pregnancies in the AstraZeneca vaccine trial.

Real-world data from Israel of more than 15,000 pregnant women also shows the benefits of the vaccine. About half of the pregnant people were vaccinated with the vaccine from Pfizer and its German partner BioNTech. Only about 2 percent got infected with the coronavirus — mostly between their first and second shots. But among unvaccinated women, the infection rate continued to climb, reaching about 4 percent by the end of the study, suggesting that vaccination can prevent infection during pregnancy, researchers reported in July in JAMA.

That’s good news because pregnant women who get COVID-19 are more likely to deliver their babies prematurely and may be admitted to the intensive care unit or die at a higher rate than uninfected women, a study of studies published last year in the British Medical Journal found. And men who get COVID-19 may have lower levels of testosterone and low sperm counts after infection, and may be more likely to have erectile dysfunction, three studies show. It’s not clear whether any of those problems continue long-term.

But those are consequences of COVID-19, not the vaccines. The Pfizer mRNA vaccine did not harm sperm production, researchers reported in June in JAMA, adding to the mounting evidence that vaccines are safe. That fact may eventually percolate down to people who are scared that getting the vaccine will damage their fertility.

In its latest report on managing “the infodemic” — the deluge of information about COVID-19, both true and false, that people encounter every day — the WHO laid out both short- and long-term strategies for making people less vulnerable to misinformation. One thing is clear though, the report states. “Both innocent circulation of misinformation and malicious disinformation campaigns have triggered actions across the globe that put [people] at a higher risk of spreading the coronavirus and making them more liable to harming their health.”

The U.S. Surgeon General’s office put together a handy checklist to help people vet the information they’re seeing or hearing. The checklist is part of a toolkit for teaching people how to combat misinformation in their own communities, including talking — preferably in-person rather than online — to friends and family members who may have bought into conspiracy theories. “We need people in communities all across our country to have these conversations,” Surgeon General Vivek Murthy told ABC news. If the Kaiser survey is any indication, there’s no shortage of folks who could benefit from such discussions.

How missing data makes it harder to measure racial bias in policing

From 2012 to 2015, a team of researchers collected 2.9 million police officer patrol records in Chicago. The team’s analysis of that data, from nearly 7,000 officers, showed that Black police officers were less likely to arrest civilians than white police officers patrolling the same neighborhood (SN: 2/11/21). Officers arrested on average eight people per shift, with Black officers making 24 percent fewer arrests than white officers. But an alternate analysis, one that excluded shifts where no arrests occurred, flipped the results. That made it appear as if Black officers issued 12 percent more arrests than white officers.

Failing to account for events that don’t happen — police allowing a jaywalker to pass, opting not to make an arrest (usually for minor issues like possessing a small amount of drugs) or never firing a drawn gun — is problematic, says policing expert Dean Knox of the University of Pennsylvania. “Instead of drawing the conclusion that minority officers are engaging in less enforcement,” he says of his Chicago study, “you could mistakenly conclude that they are engaging in more enforcement.” The flip occurred because, compared with white officers, Black officers more often went out on patrols without issuing any arrests.

Nonevents of this nature are commonly excluded in policing data. Though a large body of evidence suggests that police in the United States discriminate against Black people, Knox says, many police departments only collect data on a smattering of the interactions between their officers and civilians. Cell phone videos, like those of Eric Garner in a chokehold and George Floyd struggling to breathe, tend to emerge only when encounters have spiraled out of control. That makes it difficult to measure racial bias in policing or come up with targeted solutions to reduce that bias.

How, though, can researchers studying policing account for nonevents? The laborious Chicago data collection by Knox and his team is not always feasible. And even that rigorous study, reported in Science earlier this year, still had gaps: The team had data on when police stopped, arrested or used force on civilians, but not on minor interactions that didn’t meet the department’s recording requirements.

When research teams accept these problematic datasets at face value, writes Knox in a November 4 essay in Science, they often arrive at contradictory conclusions. Disagreements in the literature allow public officials and the media to cherry-pick studies that support their viewpoint, whether arguing for or against implicit bias training to overcome unconscious stereotypes or prioritizing the recruitment of minority officers.
A long chain of events
Knox wrote the essay following the publication of a controversial, and now retracted, study that appeared in 2019 in the Proceedings of the National Academy of Sciences. “White officers are not more likely to shoot minority civilians than non-White officers,” the authors of that study wrote. They concluded that policies aimed at increasing police diversity would do little to stem racial disparities in police killings.

The study gained enormous traction, especially among conservative media outlets and politicians, Knox says. “This was one of the go-to pieces that people use to deny the existence of bias in policing.”

But the authors’ findings were mathematically baseless, says Knox, who along with Jonathan Mummolo, a policing expert at Princeton University, wrote an article debunking the study in Medium. Some 800 academics and researchers signed the piece. The team failed to consider total police encounters and then measure what fraction of those encounters resulted in deadly violence, Knox says.
But that narrow focus on fatal police shootings, a rare occurrence that typically happens at the culmination of a long chain of events, ignores all potential biases earlier in the chain, Knox says. The first potential bias in a chain of events starts with an officer’s decision to approach a civilian or let them pass. Knox acknowledges that a separate layer of research is needed to account for societal level disparities, such as the presence of more officers in Black, often impoverished, neighborhoods and longstanding discriminatory practices that reduce the quality of education and other services in such neighborhoods.

“Even if you can’t see all the things that happened before, just acknowledging they exist is imperative,” Knox says.

Consider this real-life example. On July 10, 2015, Texas state trooper Brian Encinia pulled over Sandra Bland, a Black woman, for failing to signal a lane change. The exchange grew heated and culminated with Encinia arresting Bland for failing to follow orders. Bland’s subsequent death in a county jail caused public outcry.

Focusing solely on Bland’s arrest, and not all that happened before, would provide little information on how Bland wound up in jail for such a minor offense, or how to prevent such an outcome in the future. But because Encinia’s body camera recorded the entire exchange, policing researchers, in this case interested in tone and language, could identify key steps leading up to her arrest. For instance, the researchers reported in Law and Society Review in 2017, Encinia’s language starts off polite but becomes increasingly agitated as Bland refuses to comply with his orders. His once formal commands, such as “step out of the car” become informal and unprofessional: “I’m going to yank you out of here.”

That word “yank” indicates that Encinia is losing control of the situation, says Belén Lowrey-Kinberg, a criminologist at St. Francis College in New York City. Previous research has shown that when officers pivot from formal to informal language, violence can follow.

While this is a case study of a single event, the study provides “a great example of how situations can escalate,” says criminologist Justin Nix of the University of Nebraska Omaha.

Fixing flawed data
Flawed police data does not need to be thrown out, Knox says. His team has developed an algorithm to account for gaps in the data at all points in a police-civilian interaction. The algorithm weights the various possible degrees of discrimination at each point in a chain of events — perhaps race did not factor into Encinia’s decision to pull Bland over because he could not see her face, for example, or maybe race played a large role because most drivers in that area are white. The range of values resulting from the summation of those events suggests the possible amounts of discrimination in any given scenario, Knox says.

The program operates on a very general principle, Knox says. “What are the data that you see?” and “What are the data that you don’t see?”

Thinking about the whole chain of events also points to how to collect better statistics.

Consider a study of police shootings by Nix and policing expert John Shjarback of Rowan University in Glassboro, N.J., that appeared November 10 in PLOS One. The researchers were interested in racial disparities in officers’ use of force against Black and white civilians. National databases include only shootings that result in a civilian’s death. But whether someone lives or dies after being shot hinges on several factors, such as proximity to a trauma center, location of the gunshot wound and access to first aid. So researchers sought to examine all police shootings, including those that resulted in injury but not death. To do so, they relied on records from four states — California, Colorado, Florida and Texas — that have collected this information for years.
The data revealed that some 45 percent of victims suffer nonfatal injuries. Factoring in the relative populations of Black and white civilians showed that for all four states, racial disparities in injuries were higher than racial disparities in fatalities. For example, from 2009 to 2014 in Florida, Black people were roughly three times more likely than whites to be shot and killed by police, but over five times more likely to be injured. Across all four states, and for reasons that are not entirely clear, Black victims are 7 percent less likely to die of their injuries than white victims.

National databases that only include records of civilians who die at the hands of the police underestimate officers’ use of deadly force against Black civilians, Nix says. Death “is the end of a very long sequence of events. In our paper we backed up one link in the chain.” That is, the researchers looked at all instances where officers used deadly force and not just those that resulted in death.

Knox is now working with two police departments to break down police-civilian encounters in more detail. Those departments require officers to turn on their body cameras when they believe an interaction with a civilian will rise to the level of an official interaction. (Officers have discretion at this point in the process, Knox acknowledges, so as with the Chicago study, that first link in the chain remains elusive.) Knox and his team will analyze scripts from each encounter for language and tone, such as normal voice or shouting — a quantitative version of the approach Lowrey-Kinberg used to unpack the encounter between Encinia and Bland. Computer vision techniques will parse out gestures, such as “weapon drawn.” Knox says he hopes the data will help his team get closer to reconstructing entire interactions, including identifying nonevents in any given chain.

“You don’t want just the side of the story as written by an officer,” Knox says. “You want the whole interaction.”

New high-speed video reveals the physics of a finger snap

It all happens in a snap. New high-speed video exposes the blink-and-you’ll-miss-it physics behind snapping your fingers.

The footage reveals the extreme speed at which the gesture occurs, and shows that friction plus the compressibility of the finger pads are key to humans’ ability to snap properly, researchers report November 17 in Journal of the Royal Society Interface.

Finger snaps last only about seven milliseconds — that’s roughly 20 times as fast as the blink of an eye, says biophysicist Saad Bhamla of Georgia Tech in Atlanta. After slipping off the thumb, the middle finger rotates at a rate up to 7.8 degrees per millisecond, nearly what a professional baseball pitcher’s arm can achieve, the team found. And a snapping finger accelerates almost three times as fast as pitchers’ arms.

When covered with high-friction rubber or low-friction lubricant, fingers made snaps that fell flat, the team found, indicating that bare fingers have a level of friction ideal for a speedy snap (SN: 8/1/19). That friction between thumb and middle finger allows energy to be stored before it’s suddenly unleashed. Too little friction means less pent-up energy and a slower snap. But too much friction impedes the finger’s release, also slowing the snap.

Bhamla and colleagues were inspired by a scene in the 2018 movie Avengers: Infinity War. The supervillain Thanos snaps his fingers while wearing a supernatural metal glove, obliterating half of the universe’s life. The team wondered if it would be possible to snap while wearing a rigid glove. Typically, when the fingers press together in a snap, they compress, increasing the contact area and friction between them. So the researchers tested snapping with fingers covered by hard thimbles. Sure enough, the snaps were sluggish.

So Thanos’ snap would have been a dud. No superheroes needed: Physics saves the day.

Earth will warm 2.7 degrees Celsius based on current pledges to cut emissions

This year was supposed to be a turning point in addressing climate change. But the world’s nations are failing to meet the moment, states a new report by the United Nations Environment Programme.

The Emissions Gap Report 2021: The Heat Is On, released October 26, reveals that current pledges to reduce greenhouse gas emissions and rein in global warming still put the world on track to warm by 2.7 degrees Celsius above preindustrial levels by the end of the century.

Aiming for “net-zero emissions” by midcentury — a goal recently announced by China, the United States and other countries, but without clear plans on how to do so — could reduce that warming to 2.2 degrees C. But that still falls short of the mark, U.N. officials stated at a news event for the report’s release.

At a landmark meeting in Paris in 2015, 195 nations pledged to eventually reduce their emissions enough to hold global warming to well below 2 degrees C by 2100 (SN: 12/12/15). Restricting global warming further, to just 1.5 degrees C, would forestall many more devastating consequences of climate change, as the Intergovernmental Panel on Climate Change, or IPCC, reported in 2018 (SN: 12/17/18). In its latest report, released in August, the IPCC noted that extreme weather events, exacerbated by human-caused climate change, now occur in every part of the planet — and warned that the window to reverse some of these effects is closing (SN: 8/9/21).
Despite these dire warnings, “the parties to the Paris Agreement are utterly failing to keep [its] target in reach,” said U.N. Secretary-General António Guterres. “The era of half measures and hollow promises must end.”

The new U.N. report comes at a crucial time, just days before world leaders meet for the 2021 U.N. Climate Change Conference, or COP26, in Glasgow, Scotland. The COP26 meeting — postponed from 2020 to 2021 due to the COVID-19 pandemic — holds particular significance because it is the first COP meeting since the 2015 agreement in which signatories are expected to significantly ramp up their emissions reductions pledges.

The U.N. Environment Programme has kept annual tabs on the still-yawning gap between existing national pledges to reduce emissions and the Paris Agreement target (SN: 11/26/19). Ahead of the COP26 meeting, 120 countries, responsible for emitting just over half of the world’s greenhouse gas emissions, announced their new commitments to address climate change by 2030.

The 2021 report finds that new commitments bring the world only slightly closer to where emissions need to be by 2030 to reach warming targets. With the new pledges, total annual emissions in 2030 would be 7.5 percent lower (about 55 gigatons of carbon dioxide equivalent) than they would have been with pledges as of last year (about 59 gigatons). But to stay on track for 2 degrees C of warming, emissions would have to be about 30 percent lower than the new pledges, or about 39 gigatons each year. To hold warming to 1.5 degrees C requires a roughly 55 percent drop in emissions compared with the latest pledges, to about 25 gigatons a year.

“I’m hoping that the collision of the science and the statistics in the gap analysis, and the voices of the people will promote a greater sense of urgency,” says Gabriel Filippelli, a geochemist at Indiana University–Purdue University Indianapolis.

On October 26, Filippelli, the editor of the American Geophysical Union journal GeoHealth, and editors in chief of other journals published by the organization coauthored a statement in Geophysical Research Letters. Theyurged world leaders at COP26 to keep the “devastating impacts” of climate change in check by immediately reducing global carbon emissions and shifting to a green economy. “We are scientists, but we also have families and loved ones alongside our fellow citizens on this planet,” the letter states. “The time to bridge the divide between scientist and citizen, head and heart, is now.”

Publishing that plea was a departure for some of the scientists, Filippelli says. “We have been publishing papers for the last 20 to 30 years, documenting the train wreck of climate change,” he says. “As you can imagine, behind the scenes there were some people who were a little uncomfortable because it veered away from the true science. But ultimately, we felt it was more powerful to write a true statement that showed our hearts.”