Popular Science

For a woman in her mid-40s to mid-50s, it arrives without warning. She wakes up, overheated, wondering why it’s so hot in the house—until she sees the thermostat is set for 70 degrees, same as always. Or, she’s midway through a work presentation when heat rises from her chest to her face, and she wonders if the flush on her cheeks is visible to everyone in the room. 

It’s a hot flash—a rite of passage for the majority of women in either perimenopause, the years leading up to menopause, or the years beyond it. Menopause itself is diagnosed after 12 consecutive months without a period, but the hot flashes don’t always get the memo.

Here’s everything doctors currently know about hot flashes.

What is a hot flash, and who gets them?

Hot flashes are a sudden heat flare up often paired with flushed skin and sweating. They don’t usually last long, between a minute and five minutes in duration.

Most women experience a hot flash about four and a half to five years after their last period, Dr. Monica Christmas, an OB/GYN at University of Chicago Medicine and director of its menopause program tells Popular Science. She also is the associate medical director of the nonprofit Menopause Society, which provides healthcare professionals with tools and resources to support women through the transition.

Women have grappled with hot flashes—whether simply annoying or genuinely debilitating—for centuries. In 1582, Dr. Jean Liebault of France was among the first to document the phenomenon. But while we know much more about hot flashes and night sweats than Liebault ever did, one question still stumps experts. 

“What we can’t answer is why doesn’t everybody get them,” Christmas says. “Because everybody doesn’t get them. I have patients that will say, ‘I don’t know,’ if I say, ‘Are you having any hot flashes or night sweats?’ And as soon as they say that, I’m like, ‘You’re not having them.’” 

What’s actually happening inside women’s bodies during a hot flash? 

During a hot flash, a woman might feel like she’s spiking a high fever, but physiologically, that’s not what is happening. As women approach menopause and the ovaries begin to make less estrogen, the brain’s internal thermostat—the hypothalamus—becomes hypersensitive to even small shifts in temperature, Christmas says.

The body “thinks” it’s overheating, even when the actual temperature hasn’t changed much. In response, our bodies try to cool us down. Blood vessels dilate, which is supposed to help dissipate some of that heat, but then that triggers a sweating reflex.

“Many people will say, ‘I feel this out of nowhere, this surge of warmth that typically is from the nipple line up,’” she says. “And then as soon as the heat came on, and I felt like I was internally heated up or on fire, I start to sweat.” 

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How do women experience hot flashes differently? 

Exactly how an individual woman experiences hot flashes varies wildly. Some describe very mild symptoms. Others grapple with profuse sweating. Some experience only hot flashes during the day, while some have regular night sweats. About four in five women experience them at some point during the menopause transition, according to the American College of Obstetricians & Gynecologists.

“There’s a lot of variability,” Christmas says. Common triggers include alcohol, caffeine, high-sugar and highly processed foods, along with stress.

Black women also are more likely to experience more severe and longer-lasting symptoms, sometimes up to 11 years, she says. And research also shows that women with more severe, longer-lasting hot flashes and night sweats appear to be at higher risk of cardiovascular disease.

That doesn’t mean treating hot flashes automatically lowers heart risk, Christmas says. But it does reinforce that these women deserve particularly careful attention to blood pressure, cholesterol, and lifestyle. “I want to make sure I’m doing everything possible to minimize that risk,” she says when she treats her patients. 

There’s more to hot flashes than hormonal changes

For decades, the entire process was blamed purely on estrogen loss, Christmas says. But that explanation left some unanswered questions. 

“That doesn’t explain why every menopausal woman doesn’t have night sweats,” she says. “And it also doesn’t quite explain why we can sometimes start to experience them during the perimenopause transition because during perimenopause, people still have some estrogen.” 

Newer research now is telling a more complex story. When the brain recognizes that a woman’s estrogen levels are low, nerve cells in the hypothalamus called KNDy neurons (pronounced “candy”) become overactive, releasing neurotransmitters, which are chemical signals the brain uses to send messages throughout the body. These neurotransmitters include kisspeptin, dynorphin, and neurokinin B. 

“It’s actually those neurotransmitters that seem to have more of an impact on our ability to regulate our internal temperature,” Christmas says. “They’re not hormones.” 

What to do if you get a hot flash

For women in the middle of their hot flash years—along with the 10 percent of menopausal women who continue to experience them—there are treatments. 

Estrogen-based hormone therapy can help, but not every woman, including those with a history of blood clots or breast cancer, can take hormone therapy. 

Hormone therapy can help alleviate hot flashes. Video: Hormone therapy – Four things a Mayo Clinic women’s health specialist wants you to know., Mayo Clinic

Fortunately, researchers’ new understanding about the role of KNDy neurons has allowed for new treatments that block the brain signals that trigger hot flashes in the first place. The FDA approved a new drug called Veozah (it’s chemical name is fezolinetant) in 2023. It targets the neurokinin 3 receptor, which plays a key role in regulating body temperature. 

Lynkuet, another drug (with the chemical name elinzanetant), came along in 2025. It blocks both the neurokinin 1 and neurokinin 3 receptors, interrupting the process that triggers hot flashes at two points instead of one. 

Other medications can also provide relief, though weren’t originally developed for hot flashes, Christmas says. Some SSRIs and SNRIs; gabapentin, a neurologic medication; and oxybutynin, used for overactive bladder, are all used off-label for hot flashes and night sweats. 

Cognitive behavioral therapy and hypnosis also have been shown to reduce hot flashes. “I’m menopausal, too, so I know if I’m under a lot of stress or in a stressful situation, I’m going to probably have more hot flashes than not,” Christmas says. 

“So there’s certainly something about being able to calm our central nervous system down that seems to have an impact, too.”

If you’re struggling with hot flashes, Christmas recommends seeing your healthcare provider for help. Treatments are available. What’s more, in some cases, hot flashes or night sweats could signal other issues, including thyroid disorders, cancer, and infections, among others. 

But bottom line, when it comes to hot flashes, you don’t have to sweat them out.

In Ask Us Anything, Popular Science answers your most outlandish, mind-burning questions, from the everyday things you’ve always wondered to the bizarre things you never thought to ask. Have something you’ve always wanted to know? Ask us.

The post What happens inside your body during a hot flash appeared first on Popular Science.

In March, we reported on a wild bobcat that had been hit and dragged by a car, who also got her head stuck in the car’s grill. As if things could get any worse, the wild feline arrived at Raven Ridge Wildlife Center in Pennsylvania on a Sunday, and the nearby veterinary practice was closed. But thanks to two lucky acquaintances, a mobile x-ray machine was brought in, revealing that the bobcat had broken two legs. 

Thanks in part to the fact that her bone fractures were clean breaks, her team decided to risk a surgery. The next morning, two surgeons operated on the bobcat contemporaneously. After the operation, Tracie Young, director of the Raven Ridge Wildlife Center, told Popular Science that she was doing “fantastic” and “starting to act like a bobcat.” 

The female feline has been healing at Raven Ridge Wildlife Center for two months. Image: Dawn Rise Ekdahl / Raven Ridge Wildlife Center.

In her great misfortune, the cat has been rather lucky—and it seems like the luck is holding. Two striking coincidences have now come together to get her a custom-made cage for her rehabilitation. 

“After two months of recovery, the bobcat now needs to be moved outside for exercise and to begin building muscle tone,” the wildlife center wrote on social media. “We had to devise a safe and creative way to get her outdoors, necessitating the construction of special caging. We determined that a custom dog kennel would be the only viable option.”

However, the problems were twofold: time and money. The dog kennel builders the wildlife center contacted needed at least eight months to build the rehab cage, and the project would cost thousands of dollars. But then Raven Ridge’s photographer Dawn called her neighbor Glen for suggestions, who turned out to be the owner of a kennel-building business and could build the kennel in two weeks. 

The custom-built kennel was made for the bobcat in only two weeks. Image: Dawn Rise Ekdahl / Raven Ridge Wildlife Center.

And if you think that’s enough of a coincidence, it gets even better. The very day construction commenced, Raven Ridge Wildlife Center received a letter with a generous donation. A woman named Raven Minervino has passed away, and her husband wrote that she had consistently supported the wildlife center. After she died, her husband had asked that rather than getting flowers, people make donations in her memory. The letter had a donation in her memory large enough to pay for the custom bobcat cage.

“Thanks to all this support, we successfully moved the bobcat to the new enclosure, where she is now exploring, exercising, and much happier,” reads the social media post. Raven Ridge plans to (or perhaps already has) put a plaque in Minervino’s memory on the cage. 

Both of the bobcat’s broken legs have healed, and since having the custom cage, she has put on ten pounds, bringing her to the much healthier total of 19 pounds. Adult female bobcats weigh approximately 15 to 20 pounds on average

The post Bobcat that survived being hit by a car gets a custom-built kennel appeared first on Popular Science.

To effectively travel on Mars, rovers need to deal with a lot of sand. German engineers have created a new kind of ground rover that uses swimming motions to push through sand that may otherwise cause the  wheels to get stuck. Its inspiration: the African sandfish (Scincus scincus), a lizard known for burrowing into the Sahara Desert and literally swimming through its sand like a fish. It’s one of the animal kingdom’s strangest methods of propulsion, but it may help shape the future of Mars exploration.

A video of the rover, released this week by the University of Würzburg, shows a mini-fridge-sized, silver rover making its way through a sandy, Martian-mimicking test floor. Rather than rolling forward, each of its four wheels cuts through the sand in what looks like a figure-eight motion. The rover pushes on several yards and then cuts a corner and returns to where it started.

“The wheels mimic the animal’s [sandfish’s]characteristic interaction with the ground, generating both longitudinal and lateral forces,” University of Würzburg researcher Amenosis Lopez said in a statement. “The rover leaves sinusoidal tracks in the sand.” 

The sandfish: nature’s cute solution to slippery sand 

Though most people likely associate space rovers with round wheels or tracks reminiscent of those on WALL-E, neither design is ideal for dealing with Mars’s uniquely harsh and sandy environment. Sand is unique because it’s a material with both solid and liquid-like qualities. On top of sand’s mixed texture, rovers roaming on the Red Planet have to deal with steep slopes and uneven terrain, where varying levels of slipperiness can cause imbalance. Patches of softer sand are also a nightmare for wheels, making the prospect of a rover getting stuck never far from mind

But nature figured out a solution to this issue millions of years ago, and it’s called the sandfish. Contrary to its name, the Sahara Desert native is a lizard in the skink family. Above ground, the sandfish uses its tiny legs to scrabble around much the same as any lizard. Things get more interesting when it burrows down into the sand. X-ray imaging shows  the sandfish propelling itself forward under the sand, using a powerful waving motion to generate thrust and overcome drag. The result looks like an animal swimming through the sand, remarkably similarly to how a fish would oscillate its body to move through water

Engineers at Georgia Tech took those observations and used them to create their own sandfish robot in 2011. Testing with their robots showed that the little lizard’s oddly wedged shaped head may also help it generate lift forces and more easily swim through sand. 

Sink or swim: new rover did both 

Researchers working on the sandfish-inspired robot said it outperformed a wheeled version when navigating through a sandy test track. Where the round wheels would wobble and weave, the oscillating wheels stayed relatively stable. That’s not to say the new approach worked right out of the gate. Early models of the design were reportedly so heavy that the  rover literally sank into the sand. The team went back to the drawing board and made a second version, this time increasing each wheel’s width and reducing overall mass

It’s unlikely these oddball new wheels will become the main chassis system for NASA rovers, at least not in the immediate future. More work still needs to be done to increase their overall controllability and account for slippage that can occur in complicated, real-world environments. There are also the added variables of accounting for scientific instruments and other cargo a rover might have to carry. 

More than anything, the wheel design is a testament to the sandfish’s innate ingenuity and evolutionary gifts. Many scientists only recently began to truly appreciate these traits and what other technology they could inspire. 

The post New Mars rover could swim through sand like a desert lizard appeared first on Popular Science.

Cows are not necessarily known for their intelligence, but that less-than-stellar reputation is beginning to change. A 13-year-old pet cow in Austria named Veronika uses brooms to scratch her back, which qualifies as a form of tool use. Tool use is considered a general marker for intelligence in animals. The domestic cow species that live in close contact with humans are also highly social animals, another sign of intelligence. 

New research finds that one domestic species of cow (Bos taurus taurus) can recognize humans and distinguish between them. The cows show a visual preference for new human faces and can match a known handler’s voice to their face. The findings are detailed in a small study published today in the journal PLOS One.

To see whether cows can discriminate between familiar and unfamiliar faces, the team collected data from 32 Prim’Holstein cows. This breed originated in Holland and is the most common dairy cow breed in France. In one single lactation, they can generate about 22,000 pounds of milk. 

The team played videos of familiar and unfamiliar male faces with the sound off for the cows, and measured how long the animals looked at the video. Specifically, the team was looking for cross-modal recognition, or the cognitive ability to recognize objects presented in two different sensory settings. 

They also played videos of both familiar and unfamiliar human faces, while broadcasting audio corresponding to one of the two men. Each man also said the same sentence. The team measured the animals’ heart rates as they watched the videos, to see if the bovines responded to the videos emotionally. 

Experimental setup for visual preference and cross-modal tests. The cow was positioned centrally between two screens. Each screen showed a video of a person’s face: one familiar and one unfamiliar to the cow. During cross-modal tests, a speaker placed between the screens played the voice of one of the two individuals. Cameras recorded the cow’s behavioral responses throughout the test. Image: Amichaud et al., 2026, PLOS One, CC-BY 4.0

The cows were not afraid of the videos without sound and stared at the unfamiliar faces longer. According to the team, the staring shows that the animals can distinguish between an unknown and known face. 

When researchers paired the videos with sound, the cows spent more time staring at the video when the voice matched the face. This shows that the cows can pair a face with the voice that they know. Captive big cats can also do this with their handlers. 

Based on their heart rate, neither the familiar or unfamiliar voices appeared to affect the cows’ emotional response. 

The team notes that a video and sound recording are not a full interaction with a human, but these results indicate that cows can tell the difference between familiar and unfamiliar people, and they can tell humans apart by face and voice. To better understand the animals and their welfare, future studies could examine how cows interact with specific people.

The post Cows can tell humans apart, new study finds appeared first on Popular Science.

NASA’s Psyche spacecraft is currently en route to a small, metal-rich asteroid near Jupiter. However, the barely 3,600-pound probe recently required a little help from Mars to complete its lengthy 2.2-billion-mile mission. Despite its complex gravity assist earlier this month, the groundbreaking spacecraft still found time to snap some travel photos showcasing its Red Planet flyby. NASA released the latest image from Psyche’s trip on May 20, which offers a gorgeous view of Mars just hours before Earth’s neighbor temporarily eclipsed the cosmic traveller.

According to NASA, the image was taken on May 15 at about 8:03 a.m. EDT by the spacecraft’s multispectral imager instrument. The thin crescent view of Mars is due to the spacecraft’s approach at what’s known as a high phase angle. The fingernail slice of Red Planet actually looks brighter and wider than mission specialists anticipated, thanks to a large level of sunlight scattering through the dusty Martian atmosphere. Interestingly, the instrument’s original unfiltered image wouldn’t look very discernible to the human eye. Instead, scientists processed the photo into a natural-color palette using the probe’s red, blue, and green imager filter data.

Launched in October 2023, Psyche is destined for 16 Psyche, a 140-mile-wide rock that astronomers theorize may be the remnant of an ancient planetary core. Once there, the spacecraft will study its iron magnetic properties, as well as use its imagers and spectrometers to analyze the asteroid’s chemical and elemental compositions. 

Thanks to the Martian gravity assist, Psyche is scheduled to reach its destination in 2029. At its closest pass, Psyche swung around the Red Planet barely 2,800 miles above the surface at a speed of around 12,333 miles per hour.

The post Mars shines in ethereal photo from Psyche space probe appeared first on Popular Science.

What’s the weirdest thing you learned this week? Well, whatever it is, we promise you’ll have an even weirder answer if you listen to Popular Science’s hit podcast. The Weirdest Thing I Learned This Week hits Spotify, YouTube, Apple, and everywhere else you listen to podcasts every-other Wednesday morning. It’s your new favorite source for the strangest science-adjacent facts, figures, and Wikipedia spirals the editors of Popular Science can muster. If you like the stories in this post, we guarantee you’ll love the show.

FACT: There’s more than one way to sterilize a hippo, but there’s no easy way to sterilize a hippo

By Rachel Feltman

If you’re a longtime fan of Pablo Escobar’s hippos, you may have heard that their time is running out. After years of trying to deal with these feral hippos conservatively, the Colombian government recently announced that they’ll have to cull some of them to curb their rampant population growth. An Indian billionaire did recently make a last-minute offer to save the hippos at any cost, but transporting a grown hippo—an incredibly deadly animal that weighs literal tons—is no easy feat, so it’s likely that some, if not all, of the planned culling will still take place.

This is not for lack of trying. Like, seriously: The government really, really tried to avoid killing any hippos. But the years-long effort to sterilize these animals has largely failed, and researchers say we’re running out of time to avoid a population too large to deal with. That got me wondering… what makes it so difficult to sterilize a hippo?

As you’ll learn in this week’s episode, sterilizing a hippo surgically is a difficult, dangerous, and expensive endeavor. And while chemical castration (AKA shooting hippos with birth control darts) might sound simpler, it’s… still difficult, dangerous, and expensive. 

For a hippo palate cleanser, I also dive into the herculean effort made to save Fiona the hippo a few years back, which required milking a hippo (a feat never before attempted!) and replicating hippo milk.    

FACT: John Steinbeck took part in a failed deep-sea drilling expedition

Featuring Ben Lillie (the co-founder of Caveat, our favorite venue in NYC!)

This week’s episode features special guest Ben Lillie, otherwise known as the keeper of our favorite place to do Weirdest Thing live shows! He spun a yarn about Project Mohole, a failed deep-sea drilling expedition that took place back in the 1960s. The expedition featured a surprising crew member: John Steinbeck, who covered the endeavor for LIFE Magazine in… very Steinbeck-ian fashion. 

Ben came across this story while working on a live show all about jargon. You can catch that show live and in-person at Caveat on Wednesday, May 27. 

FACT: Joseph Pilates didn’t mean for his workout to get so bougie

By Sara Kiley Watson

Pilates is a super trendy workout modality right now, and it’s gotten a reputation for being pretty elitist. But Joseph Pilates—yes, he was a real guy, and his name was Pilates—didn’t set out to create a workout that looked good on the ‘gram. He didn’t even set out to create a workout that people would spend loads of money on. The former circus performer actually dreamed up the exercises that would become pilates while interned in a prison camp. You can learn more about the reformer’s journey from janky hospital bed to sleek boutique workout equipment in this week’s episode, or by checking out this article I wrote about the history of Pilates. 

The post There’s more than one way to sterilize a cocaine hippo. Unfortunately, both ways suck.  appeared first on Popular Science.

Long before humans smacked “delete” to obliterate typos, we fixed mistakes and revised written language the old-fashioned way: by rubbing errors clean off the page.

The quintessential pink eraser is now a mainstay in household junk drawers, classrooms, and office supply cabinets, but how exactly do these ingenious little pieces of technology work? How do erasers erase?

The history of erasers

Humans have marked stuff with graphite for thousands of years. However, modern pencils—which encase graphite, or a mixture of graphite and clay, in wood—date back to the 17th century. 

Contemporary erasers, meanwhile, came fashionably late. Their precursors include balled-up stale bread and wax. Then, in the 18th century, natural rubber was used as an eraser. Later, in the 19th century, raw rubber erasers were toughened up with heat and sulphur. And, finally plastic erasers debuted in the 20th century. Whether erasers were snackable, heat-treated, or even electrified, the fundamentals of erasing remain. Pencils and erasers work together through the forces of attraction—and friction.

A late 19th century postcard shows people harvesting natural rubber from rubber trees. Early erasers were made using natural rubber. Image: Contributor / Getty Images / Sepia Times

“When you run a pencil over paper, tiny little pieces of carbon flake off and stay on the paper, and that’s what leaves the pencil mark,” Dr. Joseph A. Schwarcz, a chemistry professor who directs the Office for Science and Society at McGill University, tells Popular Science. The pencil’s “lead”—a misnomer, as it’s not actually lead—isn’t just lodged between the fibers in paper; as graphite particles shear off, they also sit atop the page and remain there due to “a very small attraction between molecules,” Schwarcz explains. 

That’s where the eraser comes in, Schwarcz says. “There’s a greater adhesion of those little [graphite] particles to rubber than to the paper, so when you rub the rubber over the paper, it removes them.”

Several thousand years before colonizers commercialized rubber, Mesoamericans developed tools and recreational items with natural latex by tapping and processing the fluid in native rubber trees. While synthetic erasers, composed of substances such as polyvinyl chloride, are now more popular than natural rubber in some parts of the world, all erasers generally work the same way: “The graphite particles are attracted more to the eraser than they are to the paper,” says Schwarcz. 

“There’s also a slight abrasion effect, where you’re dislodging the graphite particles by friction,” Schwarcz adds. This process erodes some of the paper, which helps explain why so many different varieties of erasers exist; softer erasers tend to be gentler on the page, while firmer erasers are generally more durable and precise. 

The science behind the attraction

The chemical attractions Schwarcz describes are called van der Waals forces. “Molecules have tiny little charges distributed over the atoms, and the positive charges will attract the negative charges. So paper will have some molecules with negative charges that are attracted to the positive surfaces of the graphite,” Schwarcz says. Basically, when you write with a pencil, the graphite stays on the page thanks to forces of attraction.

But the attraction between graphite and paper is pretty weak. So when you rub an eraser on a piece of paper, friction basically disrupts the attraction between the graphite and the page, and the graphite that was once on the paper ends up sticking to the eraser.

On a molecular level, graphite is made up of many two-dimensional sheets of carbon, known as graphene, stacked one upon another and held together by van der Waals forces. 

“There’s this cloud of electrons on one layer of graphene, and another cloud of electrons on another layer of graphene,” Dr. Justin Caram, an associate professor of chemistry at the University of California, Los Angeles, tells Popular Science. The electrons on these sheets can “randomly fluctuate” to make one side a little positively charged, and the other a little negatively charged. 

“Because positive and negative charges interact with each other, that binds things together,” Caram says. In other words, we have van der Waals forces to thank for why graphite sticks together on a page.

Although individual sheets of graphene are “completely neutral and have no intrinsic dipole”—or inherently positive and negative side—“they still interact with each other because of these random fluctuations.” Caram adds, “That’s what a van der Waals force is. It’s basically a force between any two things where the electrons can move around and compensate for one another,” keeping things together—if somewhat weakly.

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What about erasable markers and inks?

Whiteboard markers and dry erasers function similarly to pencil erasers but with added complexity, incorporating a slick writing surface to prevent ink absorption and an oily release agent to suspend ink over the board. A quick swipe of a dry eraser easily disrupts the bond between the oily agent and the whiteboard.

However, some erasable inks work differently. Penmakers such as Pilot use thermochromic ink that responds to temperature changes (sort of like a mood ring), becoming clear when exposed to heat. 

So as you rub an eraser against the page, this friction boosts temperatures above 140 degrees Fahrenheit, triggering a regulator in the ink. This temporarily breaks “the bond between the color former and the color developer,” writes Pilot, “effectively erasing your writing.” 

The word “effectively” is doing a whole lot of work in this sentence, because whatever you’ve written is still technically there—absorbed into the paper. Pilot explains: “With enough cooling, (like placing the paper in a freezer), at approximately [negative four degrees Fahrenheit], the components would combine again, and your writing could reappear!”

To err(ase) is human

Ink isn’t usually reactive to temperature like erasable inks, making it tricky or impossible to “erase” errors without marring writing surfaces like paper. “Ink is carried by liquid into the fibers [ of a piece of paper], and when the liquid dries the ink stays behind,” says Caram. Compared to graphite, “it’s much more embedded in the actual molecular network that makes up the paper.”

Mass-produced correction fluids, pens, and tapes (think: Wite-Out, Tipp-Ex, and Liquid Paper) took off in the mid-20th century to conceal inky, typewritten mistakes. Yet, the underlying concept of covering up errors by effectively painting over them is much older. 

Ancient artisans in Egypt used white paint to cover up errors on papyrus, including to narrow the gut of a jackal in an illustration from the Book of the Dead, researchers at Cambridge’s Fitzwilliam Museum said in March.

A secretary uses an eraser to fix a mistake on a page in her Underwood typewriter in a photograph taken around 1945. Image: Stringer / Getty Images / Herbert

Many pencils now feature built-in erasers, an innovation that was first patented in Philadelphia in 1868. Yet, as inseparable as they now seem, modern pencils and erasers didn’t wed right away. 

Japanese pencil and stationery maker Tombow, for example, released its first pencil in 1913; the company tells Popular Science that it developed its first eraser, the Iron Helmet Eraser (“Tetsu-kabuto Jikeshi”), 26 years later. 

Due to “wartime economic blockades,” Tombow said its initial eraser was “manufactured using oils and fats instead of natural rubber.” Material shortages later drove the development of plastic erasers. 

Now, even as screen time defines much of modern life, the modern pencil and eraser live on, as students, artists, and office workers snap them up by the billions each year. 

With pencil and pen sales projected to rise (and autocorrect now ever present in written communication), errors and revisions haven’t really gone anywhere; some tools just make them more (or less) obvious to others. 

Whether you’re a scribe touching up a sacred text or a student erasing doodles in the margins, mistakes are only human. And one way or another, covering them up is, too.

In Ask Us Anything, Popular Science answers your most outlandish, mind-burning questions, from the everyday things you’ve always wondered to the bizarre things you never thought to ask. Have something you’ve always wanted to know? Ask us.

The post How do erasers actually work? It’s surprisingly complicated. appeared first on Popular Science.

Tyrannosaurus rex is iconic for its ferocity and big teeth, as well as those teeny-tiny arms. The Cretaceous Period apex predator wasn’t the only carnivore with underdeveloped forelimbs, however. At least five groups of two-legged, mostly meat-eating theropod dinosaurs experienced a shortening of the upper arms over the course of their evolutionary journey. But why did they have such comically small claws? One team of researchers believes the answer is simple.

“It’s a case of ‘use it or lose it,’” University College London paleontologist Charlie Scherer said in a statement.

Scherer and his colleagues recently examined the data for 82 theropod species, including those in T. rex’s tyrannosaurid family. Their study published today in the Proceedings of the Royal Society B Biological Sciences argues a combination of massive skulls and crushing jaws—coupled with increasingly large prey—had many theropods relying increasingly less on their forearms.

“We sought to understand what was driving this change and found a strong relationship between short arms and large, powerfully built heads,” explained Scherer. “The head took over from the arms as the method of attack.”

The team based their conclusions on a new system of assessing dinosaur skull strength based on attributes like overall dimensions, how tightly bones were joined in the head, and bite force. Unsurprisingly, T. rex came in first place for bite force, followed by the Tyrannotitan. Almost as large as a T. rex, the Tyrannotitan lived in present-day Argentina during the Early Cretaceous over 30 million years before its famous descendent. In each example, the reason for short arms likely coincided with hunting larger and larger dinner targets.

“Trying to pull and grab at a 100–foot–long sauropod with your claws is not ideal. Attacking and holding on with the jaws might have been more effective,” added Scherer.

Overall, the team identified a bigger correlation between skull strength and smaller arms than with either skull or body size. This conclusion is further supported by some theropod dinosaurs with strong heads, tiny forelimbs, and a relatively small stature. For example, Majungasaurus roamed present-day Madagascar 70 million years ago while weighing about 1.75 tons—around a fifth the size of T. rex.

Not every dinosaur’s limbs shrank in the same way, either. Abelisaurids like Majungasaurus exhibited smaller arms past their elbows as well as their hands, while tyrannosaurid arms reduced proportionally. In each case, it seems that the theropods initially had far more success latching onto prey with their powerful jaws, then evolution did the rest of the work.

As to which dinosaur had the teeniest forearms, the answer according to Scherer is clear.

“The Carnotaurus had ridiculously tiny arms, smaller than the T. rex,” he said.

The post Why were T. rex’s arms so tiny? Paleontologists finally find an answer. appeared first on Popular Science.

The happy-face spider (Theridion grallator) is famous for the particularly cheery looking patterns on top of its abdomen. Ecologists in Hawaii first described the tiny, vibrantly green arachnids in 1900, and have long assumed them to be unique to the islands. However, an unexpected encounter thousands of miles away recently surprised researchers combing through the forested slopes of the Himalayan mountains.

According to their study published in the journal Evolutionary Systematics, there is at least one more smiley spider species in the world. Of course, such a discovery deserves an equally appropriate name. Without further ado, it’s time to meet the Himalayan happy-face spider (Theridion himalayana).

Mature male (left) and female (right) of Theridion himalayana sp. nov. Credit: Devi Priyadarshini and Ashirwad Tripathy.

The meetup began in 2023 during an expedition in the northern state of Uttarakhand, a region home to many animals that remain unknown to science. Researchers from India’s Forest Research Institute and the Regional Museum of Natural History intended to catalogue ant biodiversity at the foot of the Himalayan mountains, but they kept getting distracted by the insects’ eight-legged neighbors.

“My co-author [Ashirwad Tripathy] kept sending me spiders from high altitude regions for identification,” Regional Museum of Natural History biologist Devi Priyadarshini said in a statement.

Priyadarshini recalled on “one fine day,” her colleague sent a photo of an arachnid clinging to a Daphniphyllum leaf. That was when she “froze in shock.”

“I had seen the Hawaiian spider during my master’s program…I knew instantly we had a jackpot because of its striking resemblance,” explained Priyadarshini.

Over the next few months, Tripathy continued to document every similar spider he saw during his survey. While each of the 32 examples clearly belonged to the same species, they all showcased an array of smiley dot-and-stripe coloration patterns (known as morphs) on their bodies. Once in the lab, the team conducted a DNA analysis of their specimens and discovered about an 8.5 percent genetic variation from the Hawaiian happy-face spider. This confirmed it evolved completely independent of the almost identical island spiders, thus earning the name Theridion himalayana.

“The name [Theridion] Himalayana was decided as the species name because we both wanted to pay our respects to the mighty Himalaya mountain ranges, which have been standing tall not just guarding our country but also holding a plethora of biodiversity within them,” added Tripathy.

Although the green coloration obviously helps both spiders blend into the surrounding vegetation, the exact reason for their back patterns remains unclear. Priyadarshini said this question is “definitely indicative of a deeper genetic mystery” that deserves further investigation. However, another shared trait is even stranger. Both species have a fondness for ginger plants, even though ginger isn’t native to Hawaii.

“How did the [Hawaiian] spiders choose an invasive species and ginger exactly?” wondered Priyadarshini, who theorized T. himalayan may be an “elder cousin” of T. grallator.“Although this sounds like a tall claim now, it will be our further scope of work to establish any missing links,” she said.

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There’s a SMILE beaming down from high above Earth. On May 19, the European Space Agency (ESA) and the Chinese Academy of Sciences (CAS) launched a Vega-C rocket from Europe’s Spaceport in French Guiana with a payload representing years of international collaboration. Known as the Solar wind Magnetosphere Ionosphere Link Explorer (SMILE), the spacecraft will soon begin studying the sun’s immensely powerful solar winds and their relationship with Earth’s atmospheric safeguards.

You wouldn’t be reading this without our magnetosphere. The protective shield generated from deep inside Earth has protected the planet from the sun’s most destructive solar winds for billions of years. Without this barrier, life could never survive on what would be a barren, irradiated rock. But while it’s clear that the magnetosphere is Earth’s natural defense system against cosmic radiation and geomagnetic storms, astronomers still aren’t sure exactly how it works. 

“We are about to witness something we’ve never seen before—Earth’s invisible armor in action,” ESA director general Josef Aschbacher said in a statement.

Over the next month, SMILE will slowly increase its altitude with 11 engine burns before settling into a large elliptical orbit over the North and South Pole. Actual data collection will start in July using the spacecraft’s four tools, including a pair of X-ray and ultraviolet cameras. 

SMILE is the first mission to examine the magnetosphere with X-rays, and the UV equipment will capture the northern and southern lights for up to 45 hours at a time. By combining the two data sources, astronomers hope to gain a better understanding of how the planet is affected by the sun’s constant bombardment of solar winds and frequent coronal mass ejections. The project is planned to last three years.

“The evidence that Smile collects will help us better understand planet Earth and our Solar System as a whole,” explained ESA Smile project scientist Philippe Escoubet. “And the science it uncovers will improve our models of Earth’s magnetic environment, which could ultimately help keep our astronauts and space technologies safe for decades to come.”

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While every bumble bee colony has a queen, the process for becoming that queen bee may be a bit more democratic than monarchical. The worker bees appear to select which baby will be queen one day, according to a new study published in the journal Insect Biochemistry and Molecular Biology.

The key to this selection process lies in the juvenile hormone. This hormone in insects is responsible for their development, molting, and eventual reproduction. When the team gave the juvenile hormone to worker bees, they passed it along to all of the larvae in the colony through feeding. The more juvenile hormone the larvae received, the more likely they were to become queen. 

According to the team, this is the first study to show that bumble bee caste is determined by the workers and shifts our understanding of bee colony dynamics. Instead of a top-down hierarchy, the colony appears to be a more decentralized system, where the caregivers and workers can alter the future of baby bees. 

Less like Mean Girls?

Understanding the fate of the bee larvae is key to understanding their social behavior. Their whole system relies on a division of reproductive labor—some females will reproduce, while the others help. 

“Since all these females share the same DNA, it’s a striking example of how the same genotype can produce very different forms,” Etya Amsalem, a study co-author and entomologist at Penn State, said in a statement. “It’s also a practical question since bumble bees are important for pollination, so knowing how to produce queens could improve commercial breeding and management.”

In addition to their different social roles, queen bees and worker bees are also very different physically. Bumblebee queens are larger, live longer lives, and will reproduce. Worker bees are smaller in stature and do not reproduce or live as long.

While it was clear that hormones were involved in how workers determine the queen, the exact mechanisms behind it were more vague. 

“A single female egg in bumblebees holds the blueprint for two completely different life paths: the giant, reproductive queen or the small, sterile worker,” added study co-author and postdoctoral researcher Seyed Ali Modarres Hasani. “We wanted to understand what triggers the change in the female life trajectory, when does it happen and who controls the process.”

A matter of hormones

In the study, the team used three worker bees and a cluster of larvae. They applied juvenile hormone at different doses and times, and administered it either to workers or directly to larvae. They then traced the hormone’s movement, measuring  larval mass and recording which individuals became queens or workers.

“Every colony will produce many new queens at the end of the season,” Amsalem said. “These queens will leave the colony, mate and go into winter diapause, and then each queen will start a new colony in the next spring. In that sense, producing as many queens—and males—at the end of the season is the ultimate purpose of the colony.”

When the juvenile hormone was applied directly to the larvae, not only did they not turn into queens, but the worker bees ended up eliminating most of these larvae.

When the workers were treated with the juvenile hormone, they put it into the food that they make for the larvae. These larvae then ingested the hormone, and were heavier and much more likely to become queens.

“We also determined that larvae are only sensitive to this hormone on days seven and eight of their development,” Hasani said. “By tracing the juvenile hormone, we saw that the workers pass the hormone into the food they make from nectar and pollen.”

Queen development and the colony’s future

These results suggest that queen production is linked to how the colony progresses through the summer’s warmer months until it eventually collapses in the fall.

“Bumblebee workers do not reproduce when the colony is young, but they can activate their ovaries and produce males as the colony ages, which causes an increase in juvenile hormone levels,” Amsalem said. “As a result, over time, they feed larvae more of the hormone. When enough workers do this simultaneously, usually towards the end of the season, larvae receive doses that are high enough during the critical window to develop into queens.”

These results could help improve bee colony management at a hormonal level, explain how complex insect societies evolve, and how hormonal signals interact to shape colony structure.

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For decades, many paleoarchaeologists believed Neanderthals went extinct largely because they just weren’t intelligent enough to compete with their Homo sapien relatives. However, mounting historical evidence suggests this was far from the case. The latest discovery to help the Neanderthal’s reputation ion? The ancient hominins knew when and how to safely snack on shellfish potentially thousands of years before their human descendants.

The findings published today in the Proceedings of the National Academy of Sciences focus on Neanderthals who lived at Los Aviones Cave in present-day Cartagena, Spain. Researchers discovered the remains of 115,000-year-old mollusks including gastropods and limpets that were clearly harvested as food. This contradicts past theories about Neanderthals, which suggested they had difficulty adapting to coastal environments and utilizing marine resources. What’s more, the Neanderthals here didn’t eat shellfish in large quantities all the time. Instead, they knew to make the most of them between November and April during the colder seasons.

Los Aviones Cave in Spain is a notable Neanderthal archaeological site. Credit: ICTA-UAB

“They consumed marine resources throughout the year, but with a very clear preference for winter and autumn months,” explained Asier García-Escárzaga, a study co-author and archaeologist at Spain’s Universitat Autònoma de Barcelona Institute of Environmental Science and Technology.

García-Escárzaga says this seasonal pattern often followed by more modern human populations in Europe wasn’t a coincidence. The winter reproduction cycle of many mollusks also results in higher amounts of meat as well as improved flavor and texture. Summer months increase health risks like toxic algae contamination or rapid spoiling.

But how did researchers determine exactly when these shellfish were harvested? It all has to do with the mollusks’ shell carbonate and their oxygen isotopic levels. This level fluctuates depending on seawater temperature and functions like a “prehistoric thermometer,” according to García-Escárzaga.

The findings reveal that Spain’s coastal Neanderthals relied on a diverse diet featuring high-quality oceanic proteins filled with Omega-3 and zinc, both of which aid in reproductive health and brain development. With that in mind, it’s entirely possible that humans’ closest evolutionary ancestors influenced our own love of shellfish.

“What we see at Los Aviones is a fully modern subsistence strategy,” García-Escárzaga and his colleagues wrote in their study.

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The Garden of Fugitives is one of Pompeii’s most haunting sites. Discovered during archaeological excavations in 1961, the former vineyard quickly became a gravesite for over a dozen people who perished amid the eruption of Mount Vesuvius and its choking, burning hot pyroclastic cloud that enveloped the city in 79 CE.

Although the victims’ bodies eventually decomposed underneath the pumice and ash, the unique burial conditions at their time of death presented a remarkable opportunity for future archaeologists. Shortly after their identification, researchers created chilling, highly detailed casts of their final moments by carefully pouring plaster into the hollowed spaces they left behind. These echoes of the ancient Roman catastrophe have taught historians a lot about life at the time of the eruption, even if much of the Pompeiians’ personal information is lost to time.

However, modern diagnostic imaging technology has yielded unexpected evidence that points to one of the Garden of Fugitives’ professions. Based on recent findings highlighted in the E-journal of the Pompeii Excavations, a man who died fleeing the volcanic destruction carried a bag of tools that indicate he was an ancient Roman doctor, or medicus.

Experts peered into a nearly 2,000-year-old encasement using both X-ray and computer tomography techniques. The images revealed that the plaster mold contained a cloth bag filled with bronze and silver coins, as well as a small container made from organic material and metal fittings. Inside this container was a slate tablet and delicate metal tools. Similar tablets were often used by Roman medical professionals to prepare various treatments and cosmetics. Meanwhile, the metal accessories resembled surgical equipment.

Archaeologists acknowledged that while the cumulative evidence isn’t conclusive, it strongly suggests the man was a medicus in the futile process of attempting to outrun Mount Vesuvius’ pyroclastic cloud. While subtle, the details offer poignant, extremely humanizing context for one of Pompeii’s thousands of otherwise anonymous casualties. 

“As far back as two thousand years ago, there were those who did not merely practice medicine—confined to specific office hours—but simply were physicians at every moment,” park director Gabriel Zuchtriegel said in a statement translated from Italian. “This man brought his tools with him to be ready to rebuild his life elsewhere…but perhaps also to help others.”

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It would make more sense if only a few related cultures exhibited it, but the trait is everywhere. No matter where you are in the world, the humans living there are about 90 percent right-handed while the remaining 10 percent are predominantly left-handed. This curious facet isn’t seen in our primate relatives, either.

Evolutionary biologists and neuroscientists have spent decades trying to understand why the vast majority of Homo sapiens prefer using their right limb, but have since come up…well, empty handed. According to researchers at the University of Oxford in the U.K., the answer may finally be within our grasp. After comparing behavioral, neurological, and social characteristics from 41 species of monkeys and apes with humans, they say the answer isn’t found in our hands at all. It’s in our legs.

Their findings are detailed in a study recently published in the journal PLOS Biology. Using a statistical modeling framework focused on interspecies evolutionary relationships, researchers first considered some of the most prominent theories on handedness. These included aspects like diet, habitat, body mass, social structures, tool usage, and locomotion. In every case, we humans remained outliers in patterns that otherwise might explain the attribute in other primates.

They then introduced two hypothetical influences into their comparisons: brain size and the length ratios between legs and arms. That arm-leg ratio may seem arbitrary, but it’s considered a standard reference point for bipedal movement. Once these traits were included, humanity’s handedness exception disappeared entirely. Basically, big brains and long legs correlate directly with dominant hands.

“This is the first study to test several of the major hypotheses for human handedness in a single framework. Our results suggest it is probably tied to some of the key features that make us human, especially walking upright and the evolution of larger brains,” study co-author and University of Oxford evolutionary anthropologist Thomas Püsche said in a statement. “By looking across many primate species, we can begin to understand which aspects of handedness are ancient and shared, and which are uniquely human.”

The new approach meant that Püsche’s team didn’t have to stop there. With the same modeling, researchers estimated handedness preferences across extinct human ancestors. The results align with a slow evolutionary shift towards the right limb. Early hominin species like Ardipithecus and Australopithecus likely only had slight leanings towards right-hand dominance comparable to present-day great apes. However, the arrival of the Homo genus saw increasing right-handedness through Homo ergaster, Homo erectus and Neanderthals. The culmination can now be seen in Homo sapiens.

The study’s authors did note an interesting exception to the rule in Homo floresiensis, the famous “hobbit” ancestors native to Indonesia. At the same time, their physiology likely explains the outlier. H. floresiensis featured a small body and brain that specialized in upright climbing and walking, not full bipedalism.

With these conclusions, researchers now believe two phases took place for humanity’s transition to overwhelming right-handedness. Ancient ape ancestors first started walking upright, which then allowed them to use their upper limbs more frequently for other tasks. As brains continued to develop and grow, rightward focus solidified in today’s H. sapiens.

“Our findings identify bipedalism and neuroanatomical expansion as likely key drivers of uniquely human lateralization, while also revealing broader ecological patterns shaping handedness across primates,” the study’s authors wrote.

From here, researchers hope to study how human cultures further entrenched right-handed dominance, why left-handed alternatives still exist at all, and if similar limb trends are visible in other animals.

“This work provides a framework for disentangling human-specific adaptations from general primate trends in the evolution of behavioral asymmetries,” the team added.

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The remains of an ancient dingo is shining new light on deep relationships between Australia’s First Nations and the wild dogs. Barkindji ancestors deliberately cared for and buried the dingo along the Baaka (Darling River) about 800 miles west of Sydney. 

The dingo is known as garli in Barkindji language and they lived alongside the Barkindji as part of the community. While burying the dog, the Barkindji took great care in building a midden, or a spot to place organic material. The people living there continued to bring river mussel shells to the midden for hundreds of years after the dingo’s death. Archaeologists believe that this marks the first time this type of post-death feeding ritual has been scientifically documented. The findings are detailed in a study published today in the journal Australian Archeology.

The garli skeleton site before excavation, Kinchega National Park. Image: Dr. Amy Way, Australian Museum.

“While Barkindji people have always known about this cultural practice, this discovery is really powerful because it provides new details on the depth of that relationship between Barkindji people and dingoes,” study co-author Dr. Amy Way, an archaeologist at the Australia Museum and university, said in a statement. “If garli were buried with the same care and respect we see for human ancestors, including mothers and elders, it tells us these animals were profoundly valued and loved.”

The burial site was first identified in 2020 by Barkindji Elder Uncle Badger Bates and National Parks and Wildlife Service (NPWS) archaeologist Dan Witter within a road cutting as erosion exposed the skeleton. Barkindji custodian Dave Doyleand and Elder Barb Quayle worked alongside the team during the analysis and excavation requested by the Menindee Aboriginal Elders Council. Elderlders guided the care of the remains throughout the research, including smoking ceremonies at the beginning of the excavation to honor their departed ancestor. 

The male dingo was deliberately buried sometime between 963 and 916 years ago within a midden along the river. It was about four to seven years old, and his heavily worn teeth suggest a long life spent hunting.

Interestingly, the dingo had several healed injuries, including a broken lower leg and broken ribs. Based on the injuries, the dog may have been kicked by a kangaroo while hunting. This shows that the dingo likely survived with prolonged care by the Barkindji people. 

“This confirms these traditions were much more widespread than we once thought,” added study co-author Dr. Loukas Koungoulos, a postdoctoral fellow at the University of Western Australia and research associate at the Australian Museum. “Dingoes like this garli weren’t simply tolerated around camps. They were tamed, lived with people and were embedded in daily life.”

Return to Country of the garli, which can be seen lying on paperbark on the table. Left to Right: Dr Amy Way, Aunty Cheryl Blore, Aunty Patsy Quayle, Uncle Badger Bates, Dr Sam Player, Dr Rebecca Jones, Aunty Evelyn Bates, Dr Loukas Koungoulos, Dave Doyle and Aunty Barb Quayle. CREDIT: Australian Museum.

When the dingo died, he was buried in a midden that appears to have been built right before the burial or at the same time People kept adding to it for hundreds of years after death. Barkindji Elders say that these ongoing additions formed part of a “feeding” ritual that honored the dog as an ancestor and that the site was maintained across multiple generations. After the analysis,  the dingo’s remains were returned to Country. In Indigenous contexts, the word Country is capitalized to include the physical land and deep spiritual, cultural, and social dimensions of the area that are integral to identity and heritage.

“This research reinforces what Barkindji people have always known,” Dr Way said. “These relationships with animals, ancestors and Country were deep, deliberate and ongoing.”

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As if we needed reminding, new research documenting dozens of previously unknown insect species highlights just how little we know about our fellow planet-dwellers. 

For the first time, researchers have comprehensively revisioned the Platydracus genus of beetles in China. Meaning flat dragon, Platydracus is a genus of rove beetles. In this new review, the team recorded over 100 species, a majority of which are new to science. Their work highlights how it’s not just the small and bland species that get overlooked in taxonomic work—sometimes, even large and colorful animals go unnoticed. 

In fact, these beetles are pretty large (frequently several centimeters long) and a lot of them mimic wasps or have bright colors. And yet, many of them have either gone completely unnoticed in the wild or sat for years unidentified in museum collections.

“It is striking that so many new species can remain hidden among large and colourful beetles. It shows how little we actually know about biodiversity and that even highly visible species can still go unnoticed,” Alexey Solodovnikov, senior author of the study recently published in the journal Insect Systematics and Diversity, said in a statement. 

Solodovnikov is a systematic entomologist at the University of Copenhagen who studies rove beetles. His team’s work puts a spotlight on the Linnean shortfall, or the difference between the number of scientifically named and described species and the number of species that exist in reality. 

Comparison of two newly discovered Platydracus species and one previously known species. Image: Natural History Museum Denmark

For example, Platydracus is part of the rove beetle family Staphylinidae. This large family consists of approximately 70,000 known species, though researchers estimate that these are only 20-25 percent of the actual number of rove beetle species. More broadly, there are about 925,000 formally described insect species. This number is shockingly low compared to how many insect species exist, which is estimated at over five million. What’s more, even the species we do know are frequently insufficiently recorded, according to the study. 

The team also rectified some mistakes, which included cases of species having been described based on, per today’s taxonomic standards, too little knowledge. 

“Many species were originally described on a very limited basis. With more collected specimens and modern methods of examination, we can now test and refine earlier species delimitations while adding new species to nature’s mosaic,” Solodovnikov explained. “This gives us a much more accurate picture of biodiversity, which is crucial both for our understanding of nature and for our ability to protect it.” 

The researchers closely studied the beetle’s bodies and used DNA barcoding—a method that uses an organism’s genetic sequence to recognize the species. They found that sometimes species can look very different despite having the same DNA markers. The oppositescenario—having different DNA markers, but appearing very similar—can also happen.

Ultimately, the study stands as a reminder that we still have a long way to go in mapping out all the life that we share the planet with.

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Most sharks have five gill slits on either side. But Hexanchus griseus, a giant and mysterious shark species, has an even six gill slits. These fish, appropriately called the sixgill shark, live in both tropical and temperate waters around the world and can reach up to 14-feet-long. They’ve existed since before the dinosaurs, and yet marine biologists still don’t know very much about them. 

One of the problems—for researchers, anyway—is that sixgills usually live in deep oceanic waters, at depths of up to 9,800 feet. It also doesn’t help that they usually favor extremely low-light environments. Among other reasons, these aspects make sixgills difficult to study.

Sixgill sharks (Hexanchus griseus) are older than dinosaurs and are typically found in the deeper parts of the ocean. Image: Seattle Aquarium.

However, these ancient giants have been spotted in Washington State’s Puget Sound year-round, and in water as shallow as 20 feet. Scientists at Seattle Aquarium believe that female sixgills are giving birth in these waters, and new research by the aquarium demonstrates that they have birthing site fidelity. According to the aquarium, they appear to come back to the Salish Sea to give birth numerous times. 

Once the baby sharks—or pups—come into this world, Puget Sound turns into their nursery for some time, though researchers don’t know for how long. The young sixgills spend the summer and fall in more southern locations of the Salish Sea, and migrate more north in the winter and spring. They usually travel less than two miles a day, and frequently come up to shallow waters at dusk before going down into deeper waters at dawn, probably looking for prey. 

“We think these patterns repeat until they eventually depart for the open ocean. This consistency of movement and behavior reinforces the strength of our opportunity to study sixgill sharks in Puget Sound,” according to a statement from Seattle Aquarium. “Through our research, we hope to answer questions about the life history and ecology of sixgill sharks—including migration, growth rates and prey preferences.” 

The aquarium also aims to study previously unexamined physiological aspects of sixgills, and understand human influence. 

The team created a custom “cradle” to safely hold a shark while they work quickly to examine it. Image: Seattle Aquarium.

From May to September, Seattle Aquarium researchers and veterinarians will try to study the elusive species at three different locations in Puget Sound, going to each one once a month. There, the team will lift sharks to the surface, and either bring them onto the boat or keep them at the side of the vessel and flip them upside down. This position triggers a trance-like state in several shark species. Either way, the team will make sure that the sharks can breathe through all of those gills.

Once the sharks are secured, the team will examine them. They should be able to collect measurements, obtain tissue samples, take photos, and deploy wearable tags in only five to 10 minutes. The tags that will then supply information about movement, habitat use, and feeding ecology. The scientists will then return the sharks to the open water. 

“Our goal is to answer as many questions as possible,” Dani Escontrela, a researcher at the Seattle Aquarium, said in the statement. “We’re collaborating with agencies like the Washington Department of Fish & Wildlife, the Big Fish Lab at Oregon State University, Point Defiance Zoo & Aquarium and other researchers to fill gaps in expertise, all while keeping animal health and well-being our top priority.”

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Your immune system has one job: to protect you. And most of the time, it does that job like a pro. 

But occasionally it gets a bit overzealous, even paranoid. It mistakes harmless, even wonderful things—flowers, peanuts, cats—for threats, and attacks them (and you—mostly you) with a senseless, chaotic vengeance.

For most allergy sufferers, this might mean giving up a few tasty foods, staying inside during high pollen counts, or rehoming the cat—or, more realistically, the person allergic to the cat. But for a tiny number of people, the immune system decides to take aim at one of the most essential substances on earth: water.

Yes, it is possible to be allergic to water. And the condition is even stranger than it sounds.

“Imagine not being able to go into the pool, or the lake, or the ocean,” says dermatologist Dr. Amir Bajoghli, who has treated a patient with this rare condition. “My patient also has to take much faster showers, as you might imagine. It definitely interferes with quality of life.”

Yes, you can be allergic to water

The medical term for an allergy to water is aquagenic urticaria, a form of hives. The condition is so rare that only an estimated 100 to 150 cases have ever been reported. However, researchers believe many more cases go undiagnosed: When a patient comes in complaining of hives, “it could be water” is probably not the first thing that leaps to mind.

People with this rare condition break out in hives like these when exposed to water. Image: Getty Images / Yuliia Kokosha

“Honestly, a lot of general physicians aren’t even aware of it,” says Bajohgli, an adjunct professor at Georgetown University School of Medicine. “It’s rare, and it’s not on their radar.”

Although scientists don’t fully understand exactly how aquagenic urticaria works, they believe water itself isn’t the culprit. Rather, it appears that certain people’s skin responds differently to water contact, setting off a reaction in the skin’s outermost layer. This triggers the body’s mast cells (immune cells that sound the alarm during allergic reactions), which releases histamine, the troublemaking chemical responsible for allergic responses. 

Within minutes of water touching the skin, a person with aquagenic urticaria will develop raised, intensely itchy welts. The reaction typically lasts anywhere from 30 minutes to an hour, and the longer the exposure, the more severe the symptoms.

You can still drink water, but sweating can be a problem

Interestingly, and luckily, aquagenic urticaria does not interfere with the body’s need for life-sustaining hydration. In other words, drinking water is fine. When water is swallowed and processed by the gut rather than absorbed through the skin, it doesn’t trigger the same immune response, Bajoghli says.

“The gut, just like the skin and the lungs, is one of the first forms of defense,” he says, “but in this case, somehow, it’s not eliciting the response in the gut the way it does in the skin.”

Bajoghli notes that some patients with aquagenic urticaria do react to their own sweat, although his patient does not. Sweat, he explains, involves an entirely different biological process than external water making contact with the skin.

Scientists believe an unidentified substance in the skin may be triggering this reaction, although much remains unknown. 

“It’s still, medically, for us, a mystery,” he says.

How to test if you’re allergic to water

For better or worse (mostly better), water is inescapable. Because of its ubiquity, and also because aquagenic urticaria is something of a medical unicorn, it often takes a while for patients or doctors to connect the dots. 

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Once it occurs to the patient and provider that water could be the culprit, diagnostic testing is fairly straightforward. It typically involves applying water-soaked compresses to the skin and waiting. In most positive cases, symptoms appear within five minutes, although the test can take up to 30.

“We wait 30 minutes before we call it negative,” Bajoghli says.

The importance of very quick showers

So, what is life like for a person whose body treats H₂O as a sworn enemy? For Bajoghli’s patient, an active teenager involved in sports, the condition reshapes even the most basic daily routines. Among other things, this means really fast showers. 

“When he showers for about two minutes, the symptoms are more subdued and milder in nature,” Bajoghli says. “If he takes a longer shower, they’re more severe and they persist longer.”

The good news is that aquagenic urticaria is unlikely to cause a major allergic reaction. It is, however, chronic; patients should not expect it to resolve on its own.

Treatment options do exist, however. Bajoghli’s patient takes an antihistamine called cyproheptadine, which reduces symptoms enough to make that two-minute shower manageable. Timing is important: taking the antihistamine about an hour before water exposure helps maximize its effectiveness.

For patients who need more relief, Bajoghli says a newer drug called omalizumab has shown promise.

For now, the mechanisms behind aquagenic urticaria, including the identity of the substance—or antigen—that triggers it, remain poorly understood, and that knowledge gap makes it difficult to develop more targeted treatments.

“We’re really looking forward to finding out what that antigen is,” Bajoghli says, “and hopefully one day solving this.”

In Ask Us Anything, Popular Science answers your most outlandish, mind-burning questions, from the everyday things you’ve always wondered to the bizarre things you never thought to ask. Have something you’ve always wanted to know? Ask us.

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Social media is widely considered to be bad for one’s mental health, at least anecdotally. However, it can have some positive impacts, such as videos of animals chewing food very loudly. What could possibly be better than a closeup of an animal’s snout as it crunches on a carrot? 

This week, zoos around the United States have been using social media to highlight one particularly cute muncher—tree kangaroos. Ahead of World Tree Kangaroo Day on May 21, conservation organization AZA SAFE (Saving Animals From Extinction): Tree Kangaroo of Papua New Guinea is inviting organizations working with tree kangaroos to compete in this year’s International Tree Kangaroo Crunch-a-Thon. 

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In the aptly-named competition, participants posted videos on Instagram and/or Facebook of their tree kangaroo eating something. The competition categories are Most Likes, Most Views, and Judges’ Choice, and winners will be announced on May 17, Australian Eastern Standard Time. 

The organizers even provide crunchy food recommendations: bell peppers, celery, romaine hearts, snap peas, green beans, cucumbers, and zucchini—with the caveat that the last two vegetables might not have the best crunch. 

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“In partnership with the AZA Tree Kangaroo SAFE program, we’re participating in the Tree Roo Crunch-a-Thon to help shine a spotlight on this endangered species,” reads a social media post by Roger Williams Park Zoo & Carousel Village featuring three munching, pink-nosed brown and white tree kangaroo. “Our Zoo is home to three Matschie’s tree kangaroos – a species of tree kangaroo native to the cloud forests of Papua New Guinea.”

Tree kangaroos are 14 species in the Dendrolagus genus, the sole arboreal kangaroo group. They are herbivorous marsupials with bushy tails, and usually have long arms and padded back feet. Tree kangaroos live in parts of Australia, Indonesia, and New Guinea’s rainforests. The Golden-mantled tree kangaroo (Dendrolagus pulcherrimus) is among the world’s most endangered mammals and only lives in a small area of Papua New Guinea. 

In the words of the Crunch-a-Thon organizers, “let the crunching begin!” 

The post Watch adorable animals compete for best chewer in 2026 Crunch-a-Thon appeared first on Popular Science.

There’s nothing quite like the sound of an airplane toilet flushing. But that incredibly loud sucking sound is actually something of an engineering marvel. These toilets flush, with no water, while zooming along at 500 miles per hour. 

In this episode of Ask Us Anything by Popular Science, we get into all the smelly details of how airplane toilets actually work.

Ask Us Anything answers your most outlandish, mind-burning questions—from the everyday things you’ve always wondered to the bizarre things you never thought to ask. So, yes, there’s a reason we can’t remember being babies and no, not all cats hate water. If you have a question for us, send us a note. Nothing is too outlandish or too ordinary.

This episode is based on the Popular Science article “How do airplane toilets work?”

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Full Episode Transcript

Sarah Durn: You’re six years old, wedged into a middle seat on your very first flight.

Your ears are popping. The engine sounds impossibly loud. Somewhere a baby is crying. And after nervously sipping one too many ginger ales, you realize there’s something else you need to do.

So you make the LONG walk down the NARROW aisle to the airplane bathroom. 

You open the weird sliding door, and this lavatory is tiny. And, after doing your business, you hesitantly hit the flush button.

For one horrifying second, you’re convinced the toilet might actually suck you into the sky.

But what exactly is happening here? How do airplane toilets work?

Turns out, the answer involves physics, pressure differentials, and one surprisingly clever engineering trick. 

Welcome to Ask Us Anything from the editors of Popular Science, where we answer your questions about our weird world, from “why do parrots talk like people” to “what’s the coldest temperature humans can survive?” No question is too ordinary or too outlandish.

I’m Sarah Durn, an editor at PopSci. 

Laura Baisas: And hello, I’m news editor Laura Baisis.

SD: Here at Popular Science, we can’t stop thinking about all the world’s strangest questions, and this week, we’re wondering how the heck airplane toilets actually work, something Laura actually edited a story on. 

So Laura, what’s going on here? What happens when we use the bathroom at 35,000 feet?

LB: First of all, you can relax. The toilet is not strong enough to suck you out of the plane. 

SD: Ah, thank God. Childhood fear officially resolved. 

LB: But that terrifying slurp sound, very real. And it turns out that airplane toilets use a surprisingly clever system that takes advantage of something that planes already have at high altitude, the enormous pressure difference between the cabin and the outside of the plane.

SD: So every time we flush on a plane, physics is essentially doing the dirty work? 

LB: Pretty much. We love physics.

SD: Oh, we do.

LB: And once you learn how the system actually works, from vacuum toilets to something called blue ice, I’m pretty sure you’ll never hear that sound the same way again. 

SD: All right. I’m in. Tell me all the airplane bathroom facts.

LB: I’d be happy to. But before we dive into the science of sky-high plumbing, we want to hear from you. What questions are swirling around your brain? Submit your question by clicking the “Ask Us” link at popsci.com/ask. Again, that’s popsci.com/ask, and click the “Ask Us” link.

SD: We’ll be right back with more about airplane toilets after this quick break.

SD: Welcome back! Okay, Laura, before we get into all the smelly details, I think we need to talk about the history of airplane toilets because early flying was kind of a nightmare.

LB: Oh, absolutely. I mean, that glamorous golden age of air travel, a lot less glamorous if you needed to pee.

SD: Right. So in the very earliest days of aviation, planes just, you know, straight up no bathrooms at all.

LB: Which makes sense if you remember early flights were a lot shorter and planes flew so much closer to the ground.

SD: Yeah, exactly. Pilots were basically flying by sight, and it’s said that early pilots actually peed into their shoes and then would just toss it into the air. 

LB: I still can’t believe that’s real.

SD: Me neither. Or they’d make a hole in the cockpit floor…and just go ahead and, you know, pee through that. 

LB: Correct. This is all so, so bad. So bad. 

SD: But it does get better. I mean, kind of. As passenger air travel became more common in the later 1920s, airlines were like, “Okay, we should probably do something about the bathroom sitch.”

So early passenger planes basically had buckets. Just, you know, a bucket in the back of the plane. 

LB: Ah, truly a luxury travel experience. 

SD: Very chic, very elegant. Then in the late 1930s, the first enclosed plane lavatory debuted on the DC-4 passenger plane. But even those were pretty primitive. The toilet had a removable bowl that crews had to take out and dump after landing.

LB: Yeah, not sure I’d want that job. 

SD: Yeah, same. Eventually planes, though, started using chemical toilets, you know, kind of like a fancy porta potty situation. Waste would sit in these tanks full of bright blue disinfectant liquid.

LB: Ah, yes, we come to the origin of one of aviation’s most disgusting phrases: blue ice.

SD: It doesn’t sound disgusting, which is what throws me. 

LB: It’s kind of a misnomer. 

SD: I know. It sounds like something a superhero would use. But anyways, explain it to us. What is blue ice?

LB: So blue ice forms when waste leaks from a plane at a really high altitude. Since it’s so cold outside, the waste instantly freezes onto the aircraft.

SD: Okay, which is already kinda gross. 

LB: Yeah, and then sometimes, I’m gonna emphasize this, very, very rarely it can break off as the plane descends.

SD: Wait, meaning frozen airplane toilet waste can theoretically fall from the sky? That’s what blue ice is? Frozen human waste raining from above?

LB: Again, gross, but very, very rare, but yes, it can.

SD: Okay. Awful. New fear unlocked. Hate that. Really bad. 

LB: But the good news is that modern airplane toilets are much, much more sophisticated. Most commercial planes today use vacuum toilet systems, which are lighter, cleaner, and honestly kind of ingenious. 

SD: Okay, so let’s get into it. What’s actually happening when we flush while up in the sky?

LB: Okay, so the key thing to understand here is pressure. Airplanes fly at very high altitudes, usually between 31,000 and 42,000 feet up. There, the air pressure outside of the plane is way lower than inside of the cabin.

SD: Because the cabin is pressurized so all of us, you know, can breathe.

LB: Exactly. Breathing equals important. Right. 

SD: Right. 

LB: So engineers realized they could use that pressure difference to their advantage. So when you hit the flush button in an airplane bathroom, a valve opens between the toilet bowl and a waste tank. So because the air pressure is lower on the tank side, everything gets sucked downward incredibly fast.

SD: Which explains the very loud sucking sound.

LB: Exactly. And one reason engineers love this system is because it saves a ton of weight. Traditional toilets need a lot of water, but on airplanes water is heavy and heavier planes burn more fuel.

SD: So instead of gallons and gallons of water, plane toilets mostly use air pressure.

LB: Right, which is why the flush is so dramatic and loud and fast.

SD: Okay, and, you know, silly question, but can you actually get sucked into an airplane toilet?

LB: No. Despite what every child, and honestly some adults, might believe, the vacuum is nowhere near powerful enough to suck a human into the plumbing.

SD: Oh, thank goodness.

LB: Although aviation experts do say that you should close the lid before flushing because the suction can splash some gross things around more than you’d maybe like.

SD: Ooh, yikes. Noted forever.

LB: And that’s… Come on, that’s just good general toilet flushing behavior anywhere. You know, flush with that lid down.

SD: Yeah, I’m a strict lid down girl.

LB: Yep, same. Same. 

And, you know, airplane toilet systems are also designed with a lot of safety features. There are pressure valves, sealed tanks, all kinds of redundancies to make sure the cabin stays pressurized and everything works safely. 

SD: Right, ’cause you don’t wanna mess with the air pressure on a plane. 

LB: Absolutely not.

SD: Okay, so when you flush an airplane toilet, where does everything actually go?

LB: So all the waste gets sucked through pipes into holding tanks elsewhere in the aircraft, and contrary to a very persistent myth, planes do not just simply dump sewage while flying. The waste stays on board until the plane lands.

SD: Unless it’s blue ice.

LB: Unless it’s blue ice. But remember, very rare and not that often anymore. Planes are more sophisticated with their waste.

SD: I’m gonna be so aware of anything falling from the sky. 

LB: I know. 

SD: Watch out. We’re really helping, you know, just assuage a lot of childhood fears on this episode.

LB: You know, we aim to please here.

SD: And okay, so then after the plane lands comes the very misleadingly named honey truck.

LB: The honey truck. Uh, yeah, unfortunately the honey truck is a lot grosser than it sounds. After landing, airport ground crews bring over these specialized service trucks that connect to the aircraft and pump all of that waste out of the holding tanks.

SD: The fact that they’re called honey trucks feels like a crime. Like, who is naming things—blue ice, honey trucks—what the heck is going on?

LB: But, at major airports this happens constantly. Honey trucks are always roving around, pumping waste from planes into their holding tanks for disposal.

Kinda cute, sort of like a poop version of WALL-E happening all along the tarmac without us even knowing. 

SD: Is it cute? Do we think that’s cute? 

LB: I kind… You know what? I kind of do. It’s important. It’s important, so I think it’s cute.

SD: Fair. Yeah, I can’t imagine being the person assigned to the airplane poop truck.

LB: And apparently, as I said, those very important crews also deal with people flushing things they absolutely should not flush. 

SD: Oh, no. 

LB: According to one aircraft engineer, mechanics have found diapers, silverware, soda cans. 

SD: Soda cans? 

LB: Soda cans. And airplane toilet pipes are tiny, so clogs are a huge deal, not to mention they can cause major delays.

SD: Yeah, you do not wanna be the person responsible for grounding a plane because you flushed your ginger ale can.

LB: There are already enough reasons you could get delayed. Do not delay a flight because you decided to flush that can, exactly.

SD: People are crazy.

LB: A clog can even take a plane out of service for days while mechanics fix the plumbing.

SD: It’s honestly incredible that these toilets don’t have more issues. I mean, they’re really clever little pieces of technology. 

LB: And the engineering behind all of this is fascinating. These systems have to work safely, reliably, and hygienically while flying hundreds of people through the sky at 500 miles per hour. It’s amazing.

SD: Airplane toilets are one of those weird engineering marvels most of us never think about unless we’re hearing the very loud slurp sound.

LB: And yep, never gonna hear that sound the same way again. 

SD: Yeah, same. 

LB: Or think of blue ice and honey the same way again, if I’m being honest. And with that image in mind, we’ll be right back after this quick break.

SD: Welcome back. Since this episode is all about flying toilets, we have to talk about the fact that while we were making this episode, NASA sent four astronauts into space, headed to the dark side of the Moon for the first time, and then their toilet basically immediately broke.

LB: Immediately. I mean, that poor crew.

SD: I know. Yeah, Artemis II embarks on this historic mission around the Moon, and then just a few hours into the mission, NASA’s like, “Ooh, guys, quick update, the space toilet fan broke.”

LB: Guessing that’s a sentence that probably caused, you know, some stress at Mission Control.

SD: Yeah, just, you know, a little bit, especially because there was only one toilet on board for four astronauts on a 10-day mission.

LB: Yeah, that toilet had a lot riding on it.

SD: Yeah. And unlike airplane toilets, space toilets can’t really rely on gravity because, you know, space.

LB: Space. In microgravity, nothing naturally goes down, which means space toilets use fans to pull waste in the correct direction, and in this case, the fan stopped doing that, which would have meant urine floating around the cabin. Ew.

SD: Yeah. The good news is NASA fixed it pretty quickly. Astronaut Christina Koch worked with Mission Control to get the system back online within a few hours.

LB: And apparently the astronauts had backup emergency urine bags, just in case. 

SD: Which, fun fact, is basically how Apollo astronauts handled this back in the 1960s. No luxury Moon bathroom, just Neil Armstrong peeing and pooping in a bag.

LB: What an image.

SD: I mean …

LB: I know, right? Humanity can build giant rockets, fly hundreds of thousands of miles through space, and still end up improvising bathroom solutions.

SD: Honestly, it all feels very, very human.

LB: It does. And on that note…

SD: May all of your toilets, earthly or cosmic, function correctly.

LB: And that’s it for this episode, but don’t worry, we’ve got more episodes of Ask Us Anything live in our feed right now. Follow or subscribe to Ask Us Anything by Popular Science wherever you enjoy your podcasts, and if you like our show, leave us a rating and review.

SD: Our producer is Alan Haburchak, and this week’s episode was based on an article written for Popular Science by Tom Hawking, with a link in the show notes if you wanna learn more about airplane bathrooms.

LB: Thank you, team. Thank you, toilets, and thanks everyone for listening.

SD: And one more time, if you want something you’ve always wondered about explained on a future episode, go to popsci.com/ask and click the “Ask Us” link. Until next time, keep the questions coming and close those toilet lids.

LB: And watch out for the blue ice…

The post Why airplane toilets are tiny engineering marvels appeared first on Popular Science.