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We have discovered the oldest meteorite impact crater on Earth, in the very heart of the Pilbara region of Western Australia. The crater formed more than 3.5 billion years ago, making it the oldest known by more than a billion years. Our discovery is published today in Nature Communications.

Curiously enough, the crater was exactly where we had hoped it would be, and its discovery supports a theory about the birth of Earth’s first continents.

The very first rocks

The oldest rocks on Earth formed more than 3 billion years ago, and are found in the cores of most modern continents. However, geologists still cannot agree how or why they formed.

Nonetheless, there is agreement that these early continents were critical for many chemical and biological processes on Earth.

Many geologists think these ancient rocks formed above hot plumes that rose from above Earth’s molten metallic core, rather like wax in a lava lamp. Others maintain they formed by plate tectonic processes similar to modern Earth, where rocks collide and push each other over and under.

Although these two scenarios are very different, both are driven by the loss of heat from within the interior of our planet.

We think rather differently.

A few years ago, we published a paper suggesting that the energy required to make continents in the Pilbara came from outside Earth, in the form of one or more collisions with meteorites many kilometres in diameter.

As the impacts blasted up enormous volumes of material and melted the rocks around them, the mantle below produced thick “blobs” of volcanic material that evolved into continental crust.

Our evidence then lay in the chemical composition of tiny crystals of the mineral zircon, about the size of sand grains. But to persuade other geologists, we needed more convincing evidence, preferably something people could see without needing a microscope.

So, in May 2021, we began the long drive north from Perth for two weeks of fieldwork in the Pilbara, where we would meet up with our partners from the Geological Survey of Western Australia (GSWA) to hunt for the crater. But where to start?

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In 1971, a British doctor was trying to puzzle out a mystery: How can a child with no signs of external trauma or injury present with bleeding between the skull and brain? That doctor, A. Norman Guthkelch, was part of a wave of physicians and researchers newly concerned that an epidemic of severe child abuse had been passing, undetected, beneath doctors’ noses.

As one law-review article recounts, “Prior to the 1960s, medical schools provided little or no training on child abuse, and medical texts were largely silent on the issue.” A turning point was the publication of the 1962 article “The Battered-Child Syndrome,” which urged physicians to consider that severe child abuse may be at play when children came in with injuries such as bone fractures, subdural hematomas, and bruising.

The article goes beyond offering medical advice to prescribing an ethical framework that would take hold: “The bias should be in favor of the child’s safety; everything should be done to prevent repeated trauma, and the physician should not be satisfied to return the child to an environment where even a moderate risk of repetition exists.”

Armed with these new insights, Guthkelch hypothesized that the children showing up to his hospital were being abusively shaken. Although they did not show up with the usual fractures or visible forms of physical trauma, the presence of a subdural hematoma could indicate what would come to be widely known as “shaken baby syndrome.”

Decades later, Guthkelch would publicly worry that his hypothesis had been taken too far. After reviewing the trial record and medical reports from one case in Arizona, NPR reported that he was “troubled” that the conclusion was abusive shaking when there were other potential causes. “I wouldn’t hang a cat on the evidence of shaking, as presented,” Guthkelch quipped.

The narrow claim that shaking a baby abusively can result in certain internal injuries morphed into the claim that if a set of internal injuries were present, then shaking must be the cause. On today’s episode of Good on Paper, I talk with a neuroscientist who found himself personally embroiled in this scientific and legal controversy when a caretaker was accused of shaking his child.

Cyrille Rossant is a researcher and software engineer at the International Brain Laboratory and University College London whose Ph.D. in neuroscience came in handy when he delved into the research behind shaken baby syndrome and published a textbook with Cambridge University Press on the scientific controversy that embroiled his family.

Jerusalem Demsas: Many forms of scientific expertise in criminal-justice proceedings have been debunked or come under scrutiny in recent years. Things like bite-mark analysis and blood-spatter analysis used to be commonly understood as rigorous empirical analysis. But these questionable theories often fall apart on closer inspection. 

This is how science is supposed to work. Experts observe, they hypothesize, they test, and they revise their previous understandings of the world. And in academia and in scientific journals, that’s all well and good—but what happens when evolving science is brought into the courtroom? In a courtroom, no one is well positioned to rigorously evaluate a scientific debate: not judges, not jurors, and not even the people calling expert witnesses.

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Illustration by The Atlantic. Source: Getty.

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Solar flares are bursts of radiation from the sun’s surface, sometimes followed by a bubble of magnetized plasma particles called a coronal mass ejection (CME). If they happen to spray out in Earth’s direction, CMEs can cause geomagnetic storms that damage power systems on the ground or spacecraft in orbit. And solar flare radiation itself can disrupt communication networks and satellite operations.

Unfortunately, solar scientists cannot reliably predict when the sun will belch out a flare. After one is observed, every minute counts in the ensuing scramble to adjust power grids or move satellites before they get damaged.

Now researchers have used data from NASA’s Solar Dynamics Observatory to show that distinctive flickering in the huge loops of roiling plasma that arch up out of the sun’s atmosphere, called the corona, seems to signal that a large flare could soon occur. This link could help researchers brace for the flare and look out for signs that an incoming CME could hit Earth within a couple of days.

Emily Mason, a heliophysicist at San Diego-based research firm Predictive Science, and her colleagues observed coronal loops in magnetically active regions where 50 strong solar flares occurred. They found that the loops’ ultraviolet light output varied erratically a few hours before a flare, the team told a recent meeting of the American Astronomical Society in Maryland. “It gives us one to two hours’ warning, with 60 to 80 percent accuracy, that a flare is coming,” Mason says.

“If we want to be able to predict solar storms earlier, then we have to predict when the flare will happen,” says Mathew Owens, a space physicist at the University of Reading in England. “Small gains there are valuable.”

Crucially, the researchers used a near-real-time data stream with just an hour’s lag rather than working with data that have been processed to improve quality, which can take weeks. Mason and her team observed flares on the sun’s outer edges from our perspective, or limbs, because that is where their light can best be seen from Earth. Flares on the sun’s eastern limb will head away from Earth as the sun rotates, but those on the western limb may hit the planet’s atmosphere, Mason says.

For now, our viewpoint means we can’t easily see loops emanating from elsewhere on the sun. But the European Space Agency is planning to launch a spacecraft called Vigil in 2031 that should give us a side-on perspective. “Being able to see the sun from more different angles is the single most important thing that we can do to improve our predictions,” Mason says. She hopes predicting big flares can help keep astronauts and electrical systems safe.

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When we think of concrete, water is usually a key ingredient that comes to mind. But what if I told you it’s possible to create concrete without a single drop of water? This innovative approach is transforming the construction industry by offering sustainability and efficiency in areas where water is scarce or conservation is a priority.

In this article, I’ll explore the fascinating world of waterless concrete and how it’s changing the way we build. We’ll delve into:

• The science behind waterless concrete: Understanding its composition and how it works.
• Benefits and challenges: What makes it a game-changer and the hurdles it faces.
• Applications and future potential: Where it’s being used today and what the future holds.

Join me as we uncover the potential of this groundbreaking material and its impact on modern construction.

Understanding Concrete Without Water

Concrete without water is a surprising twist on a staple construction material. Instead of liquid, it uses a dry mix activated by alternative binding agents. This innovative approach cuts down on water use, addressing scarcity issues. According to a study by Chen et al., waterless concrete can achieve strength comparable to traditional mixtures when specific polymers are introduced during mixing.

The core of this technique revolves around polymers and other chemical compounds that replace water. They initiate the hardening process, reducing the dependency on water. Research highlights that this method can decrease construction time, as some dry-mix formulas set faster. For instance, tests revealed that a polymer-based dry mix showed a 30% faster setting time compared to typical concrete.

By cutting water dependency, this technology not only offers sustainability but also expands construction possibilities in arid regions where water’s a vital yet scarce resource. It’s an exciting aspect of construction that could reshape how we think about building materials.

The Science Behind Dry Concrete

Dry concrete, or waterless concrete, relies on innovative technology to enable binding without liquid. The transformation from traditional to waterless methods represents a significant shift in construction.

Components and Composition

Dry concrete consists of cement, aggregates like sand or crushed stone, and specialized additives. These additives play a crucial role. Polymers and other chemicals replace water, allowing dry concrete to achieve necessary strength and durability. According to a study in the Journal of Advanced Concrete Technology, using polymers can lead to compressive strengths of up to 60 MPa, comparable to conventional concrete. This advanced composition reduces reliance on water while maintaining structural integrity.

Chemical Reaction Process

The chemical reactions in dry concrete differ from those in regular concrete. In standard mixes, water triggers hydration, bonding the cement particles. Here, polymers and other additives initiate the curing process. A report by Construction and Building Materials indicates that certain dry mixes set up to 30% faster due to this alternative reaction. These rapid reactions offer practical and logistical advantages, particularly in environments with limited water availability.

Benefits of Using Concrete Without Water

Concrete without water offers several benefits, making it an appealing choice in modern construction. By using innovative alternatives, it addresses sustainability and efficiency.

Environmental Advantages

Concrete without water significantly reduces water consumption, leading to greater sustainability. Producing traditional concrete consumes a substantial amount of potable water, sometimes up to 200 liters per cubic meter according to USGS data. In contrast, waterless concrete eliminates this need, conserving precious water resources, especially crucial in arid regions. Additionally, this type of concrete often involves less dust emissions during mixing and handling, decreasing air pollution and contributing to cleaner project sites.

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Behold! As the Ides of March approaches, witness as Earth’s shadow engulfs the moon!

Or, put another way, a total lunar eclipse is set to occur on the night of March 13 and into the early-morning hours of March 14. This is one of my favorite astronomical events; unlike its fast-paced and potentially hazardous solar counterpart, a lunar eclipse is slow and majestic, happens at night and doesn’t require any special equipment or optical aid to see. This makes it easy and fun to watch; you can pop outside every 15 minutes or so to check its progress, and you usually won’t miss anything.

The entire eclipse will be visible across essentially all of North America and most of South America.

The timings of the eclipse’s various stages are given below, but to understand those, you first need to understand how all this unfolds.

The moon orbits Earth once every 27 days or so. The phase we see it in (crescent, half full, and so on) depends on the angle between the sun, the moon and Earth. When the moon is new, between Earth and the sun, we are gazing at its unilluminated half, so it looks black. When it’s opposite the sun in the sky, we see its fully illuminated half, so it appears full. The other phases occur in between these two geometries, so we see various amounts of the moon’s surface lit. Despite a common misconception, Earth’s shadow has nothing to do with the phases.

But it’s why we have eclipses! Earth’s shadow falls in the direction away from the sun, so the moon has to be opposite the sun in our sky during an eclipse. This means a lunar eclipse can only happen at full moon. As the moon orbits Earth, it moves into Earth’s shadow, creating the stages of the eclipse.

The easiest way to understand how the eclipse works is to imagine it first as if you’re on the moon, looking up at Earth and the sun. From this viewpoint—which, incidentally, two lunar landers are set to see for this eclipse—it looks as if our planet is slowly moving in front of the sun. At first, you see Earth just barely blocking our star. The amount of light hitting you drops but not by much. Over time, Earth blocks more and more of the sun, and the illumination drops further. You’re in Earth’s shadow, yet because you can still see some of the sun, you’re not in full shadow. We call this part of the shadow the penumbra, which comes from the Latin for “near shadow.”

After about an hour, you see Earth completely block the sun. You’re in the deepest part of the shadow, called the umbra, and it is dark all around you. Eventually, Earth leaves the sun’s face—you leave the umbra and move back into the penumbra—and the ground around you is partially illuminated once again—until Earth moves completely off and the eclipse is over.

What does this look like from Earth? After all, I’d bet this is where you’ll be watching this event from! When there isn’t a lunar eclipse, if you look into the sky opposite the sun, you can’t see Earth’s shadow because it’s projected onto empty space. But if you could see the shadow, it would look like two concentric circles in the sky. The big one is the penumbra, and the smaller one inside it is the umbra. When the moon begins moving into the penumbra, it does technically get darker, but it’s hard to tell at first. Once the moon is much deeper in, its dimming becomes more obvious.

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Do Mom and Dad really know best? A recent study seems to suggest so.

Newresearch finds that parents tend to show higher brain connectivity later in life, connecting raising kids with long-term cognitive benefits.1

This new report, which studied 19,964 females and 17,607 males from the UK Biobank, found that parents who raised children experienced better protection against functional brain aging later in life—and that parenting a higher number of children was associated with higher levels of neuro-connectivity.

“These results are striking, but not necessarily surprising,” Edwina R. Orchard, the lead researcher on this study, told Parents. “There is a growing literature in humans and animals that is consistent with these results, suggesting benefits to the structure and function of the brain in parents with more children.”

Does this mean parents are the smartest people? Not necessarily.

Dr. Hannah Homafar, a Board-certified Neurologist, says this study does not establish causation—only a correlation between parenthood and brain function later in life. So, it’s not clear if parenthood, in particular, improves brain health, or if the benefit is found in the enriching activities that parenthood encourages.

“Engaging in meaningful relationships, staying socially connected, and continuously challenging the brain—whether through caregiving, mentorship, or other complex activities—are all factors that may contribute to cognitive longevity,” Dr. Homafar says.

Still, this study brings promising news for parents—and anyone interested in bettering their cognitive health.

“Understanding these nuances could provide valuable insights for brain health at large, including strategies for preserving cognitive function in aging populations,” she says.

Why Is Parenthood Associated With Better Brain Function?

In this study, protection against functional brain aging was seen in both females and males, suggesting the common parenting environment, rather than pregnancy alone, affects brain function.

Ryan Glatt, a Medical Exercise Specialist and Brain Health Coach, notes that this study doesn’t set out to prove how the parenting environment may help brain function, just that there is a connection. Still, experts have some hypotheses on how parenting could improve brain health.

Benefits of Parenting Challenges

For one thing, Glatt says the subjects’ higher functioning brain connectivity in old age may be thanks to the many mental challenges that come with parenting. From planning family schedules to helping kids with homework, being a parent is often mentally challenging.

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From an airplane, cars crawling down the highway look like ants. But actual ants—unlike cars—somehow manage to avoid the scourge of stop-and-go traffic. Researchers are now studying these insects’ cooperative tactics to learn how to program self-driving cars that don’t jam up.

The free flow of traffic becomes unstable as the density of cars increases on a highway. At 15 vehicles per mile per lane, one driver tapping their brakes can trigger a persistent wave of congestion. “It’s a kind of phase transition,” like water turning from a liquid to a solid form, says Katsuhiro Nishinari, a mathematical physicist at the University of Tokyo, who studies these jamming transitions

Nishinari’s previous research had shown that foraging ants can maintain their flow even at high densities. So what’s their secret? In a recent study published in Transportation Research Interdisciplinary Perspectives, researchers recorded Ochetellus ants on foraging trails and used traffic-engineering models to analyze their movement. They found that the ants don’t jam because they travel in groups of three to 20 that move at nearly constant rates while keeping good distances between one another—and they don’t speed up to pass others.

Human drivers at rush hour are hardly inclined to follow such rules. “We’re maximizing the interests of individuals, [which] is why, at a given point, you start to have a traffic jam,” says study co-author Nicola Pugno, who studies sustainable engineering at the University of Trento in Italy. But self-driving cars, if they one day become ubiquitous, could have more cooperative programming. In one vision of this future, autonomous vehicles would share information with nearby cars to optimize traffic flow—perhaps, the researchers suggest, by prioritizing constant speeds and headways or by not passing others on the road.

This vehicle network would be analogous to ants on a trail, which use scent to coordinate behavior while interacting with one another. “There is no leader,” but this organization emerges anyway, says Noa Pinter-Wollman, a behavioral scientist currently studying ants at the University of California, Los Angeles. And in both ant and vehicle traffic, this type of distributed system can be “very, very strong” and resilient, Nishinari says. (Neither Nishinari nor Pinter-Wollman was involved in the new research.)

Still, ants can do a lot of things that cars—even self-driving ones—can’t, Pinter-Wollman points out. Ants can forge trails as wide as they like, unlike drivers stuck on highways. The insects do sometimes jam up when confined in tunnels, but to keep things moving, “they’ll find a way to walk on the ceiling,” she says. Plus, unlike cars, ants don’t crash; they can literally walk over one another.

Today’s drivers can learn at least one thing from ants to avoid causing a traffic jam, Nishinari says: don’t tailgate. By leaving room between their car and the one ahead of them, drivers can absorb a wave of braking in dense traffic conditions that would otherwise be amplified into a full-blown “phantom” traffic jam with no obvious cause. “Just keeping away,” he says, can help traffic flow smoothly.

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If you want your parents to remain in your child’s—and your—life, I’d start by knocking off the explaining/defending of your father’s actions. He was wrong. Getting a 3-year-old’s long hair cut off while his parents are away is an act of hostility, even if the child agrees to it when his beloved grandfather suggests it. And yes, even if the 3-year-old says he’s happy now with his buzzcut. The problem is not the hair; it’s the decision-making by a grandparent that undercuts a decision made by a parent. I don’t blame your wife for being furious, and I am 99 percent sure your father knew exactly what he was doing. Your defending him is making matters worse.

If you’d recognized the real reason Stella is so angry and stood up for her instead of minimizing her feelings, I would imagine that, a month later, things would not have escalated to this point. While I don’t believe cutting off contact with Alex’s grandparents is a punishment that fits the hair-cutting crime, I’m not surprised that Stella has reached this conclusion. Your insistence that it was no big deal, your inability or refusal to see this from her point of view, even your enlisting of your child to prove your point—that this is all something “so stupid”—is, I’d wager to say, what angers her more than the inciting incident. Tell your dad he was out of line. Tell Stella you know he was out of line. Apologize profusely to her for being such a jerk about it. And then be patient. This too shall pass.

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Photo illustration by Slate. Photo by buraratn/iStock/Getty Images Plus.

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When my son was three years old, he told me one day after preschool that he didn’t want to play with me because I was Black. He went on; Black people are mean, he said, and he only wanted to play with his dad because my husband was white, like him.

We were shocked and I was hurt—my child thought I was bad because I was Black. And even though my son is biracial, he characterized himself as white.

What my son said that day unfortunately reinforced what research has long shown: children absorb racial biases from their environment. I study racial socialization—the ways children learn about race and racism—and I know how early these biases form. I also know that talking about race and racism can shape how children perceive others. Yet when white parents tell me their children say things like “Black people are not nice” or “I don’t want to play with Black kids,” they also tell me they ignore what their children said or simply tell their children it was mean. Without a real conversation about why their child might think that way or how to counter those ideas, children don’t unlearn bias; they just learn not to say it out loud.

In 2022, even though research on white parents discussing racism was still emerging, my colleagues and I argued that they needed to have these conversations with their children. At the time, we pointed to the subtle ways children can absorb racial biases—the diversity (or lack thereof) of their parents’ social circles, the characters they see on TV, and the differences they notice in social class.

But, in 2025, subtlety is a thing of the past. In attacking diversity, equity and inclusion initiatives, the Trump administration is legitimizing and emboldening racism in ways that children—especially white children—undoubtedly notice. If my son, at three years old, could absorb anti-Black messages when overt racism was more widely condemned, imagine what white children today are internalizing in a climate where political leaders openly promote racism.

White parents who see themselves as egalitarian must recognize that the stakes are now higher than ever. If you want to raise children who reject racism rather than passively absorbing it, right now, today, talk with your child about race and racism.

By preschool, children start associating Black people with negative traits and white people with positive traits. These biases form as children pick up on patterns—who holds power, how groups are portrayed in media and how others interact with them. Even subtle nonverbal cues, like smiling at one group and frowning at another, influence children’s preferences. Not surprisingly, young children favor groups receiving positive signals and mimic those behaviors, reinforcing biases. These small cues accumulate, shaping how children perceive racial groups.

While most parents of color talk to their children early about race to prepare them for potential discrimination, white parents often avoid these discussions. In our research on parents of children in the age ranges of 8–12 and 13–17, less than 40 percent of white parents talked to their children about race, and many who did downplayed racism. This avoidance is concerning, given how racial attitudes develop. Without parental guidance, children interpret racial patterns on their own, often reinforcing societal biases.

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