Popular Science

Sunburn and mosquito bites go together in the summer like a hot dog and ketchup. To keep from becoming a mosquito buffet, most of us turn to bug sprays with DEET.  An acronym built from its scientific identification (diethyltoluamide), DEET was developed for the United States Army in 1946 and entered civilian use in 1957. It is generally considered safe when used as directed. 

However, mosquitoes can learn to associate the repellant with food. They may even become attracted to it. The findings are detailed in a study published today in the Journal of Experimental Biology.

“If someone applies DEET and the concentration fades over time, but a mosquito still manages to feed, the insect may begin associating that smell with a reward,” Clément Vinauger, a study co-author and biochemist at Virginia Tech, said in a statement. “That’s a possibility we should take seriously when we think about how repellents are used in the real world.”

Ace processors

Like it or not, Earth’s over 3,500 known mosquito species are pretty smart and an evolutionary wonder. They use sensory information to find hosts and can adapt to changing environments.

In previous studies, Vinauger’s team has shown that the insects remember and avoid hosts who swat them away, can combine smell and vision to precisely track humans, and even gravitate toward and away from the smell of certain soaps.

“Mosquitoes are remarkable at processing information about their environment,” Vinauger said. “What we are trying to understand is not only how they detect us, but how their brains interpret those cues and turn them into behavior.”

A DEET-covered dinner bell?

In this new study, the team focused on the yellow fever mosquito (Aedes aegypti). This species spreads several diseases to tens of millions of people each year, including dengue fever, Zika, yellow fever, and chikungunya.

The team trained mosquitoes using a form of Pavlovian conditioning. Often called “Pavlov’s dogs,” this training method developed by neurologist and physiologist Ivan Pavlov in the early 20th century was used to teach dogs to associate the sound of a bell ringing with food. 

The mosquitoes were restrained behind a piece of fabric mesh. They then offered the mosquitoes a bag of warm blood (yum) that was just out of the insects’ reach to see how enthusiastically the insects stabbed at it with their proboscises. As expected, the mosquitoes were interested in the blood, particularly when the team rewarded them by lowering the bag within reach. Things changed a bit once DEET entered the experiment. When the team offered the insects blood when surrounded by the scent of DEET, they initially stayed away from the potential feast.  

A female yellow fever mosquito (Aedes aegypti), feeding on a bag of warm blood. Image: Romina Barrozo.

To see if they could be trained to associate that smell with the dinner bell, the team fed the mosquitoes warm blood for 20 seconds, squirting the scent of DEET into the enclosure in the final 10 seconds of dining. They repeated the procedure three more times before noting how the mosquitoes responded to only the scent of DEET. In this trial, over 60 percent of mosquitoes tried to bite when they smelled DEET.  

To examine further, the mosquitoes were given a choice between two human hands. The hand belonged to study co-author Ayelén Nally of the University of Buenos Aires. One of Nally’s hands was coated with DEET at normal concentrations and the other was bare. The untrained mosquitoes avoided the DEET-treated hand, while the trained mosquitoes were drawn to it.

Interestingly, the mosquitoes could form that same association when sugar, instead of blood, was used as the reward. 

According to the team, they are seeing how the mosquito’s brain can rewrite its response based on their experiences. What they have learned matters just as much as what a chemical like DEET does. 

“If mosquitoes are repeatedly exposed to DEET, it becomes less effective as a repellent,” study co-author Claudio Lazzari from University of Tours in France added.

Keep the bug spray

Importantly, this does not mean you should stop using DEET completely. It is still one of the most effective ways to keep the dangerous insects away, particularly where mosquito-borne disease is common.

“If you’re in tropical regions where disease risk is real, you should use it,” Vinauger said. “Instead of applying a lot at once, you may want to reapply regularly so it’s always active and providing continuous protection.”

Treated clothing may also be a challenge since DEET concentrations in fabric decline over time. Additional study to understand their behavior is crucial for public health as mosquito-borne illnesses increase due to climate change. 

“We need to understand how mosquitoes keep outsmarting our control strategies,” Vinauger concluded. “And that takes understanding how they work—at the molecular level, the neural level, the behavioral level.”

The post Mosquitoes can learn that DEET means dinner is served appeared first on Popular Science.

Everyone who has ever owned a hamster knows the sound: the small, relentless squeak of the exercise wheel, usually starting around two in the morning.

As you watch your cute furball running toward no destination whatsoever, you might wonder: What’s going on here? Is little Hammy acting out of restlessness or boredom? 

For decades, scientists assumed it was exactly that: a neurosis, an artifact of captivity, the hamster equivalent of doing push-ups in prison. 

But in 2014, researcher Johanna Meijer conducted a study that suggested a less depressing scenario. When wild mice came across a wheel in their natural habitat, they got on the wheel and ran—sometimes for up to 18 minutes at a stretch.

So if it’s not boredom or neurosis (wild mice surely have plenty of more important tasks than wheel running), what is it? 

Dr. Theodore Garland Jr., a professor of biology at UC Riverside, has spent more than 30 years trying to figure that out. 

“There’s still a lot of controversy about what, exactly, wheel running means to an organism,” Garland says. “What is it? What is the organism trying to do?”

Why wild mice run on wheels just like your hamster

In Meijer’s 2014 study, published in Proceedings of the Royal Society B, she and her colleagues placed exercise wheels in two different locations: a green urban area and a dune area not accessible to the public. For more than three years, they recorded wildlife activity at both locations.

They found that wild mice closely mirrored the behavior of their cage-dwelling counterparts. At both locations, the mice frequently ran on the wheels—often for lengths of time equal to the “workout” durations of captive mice.

Although food was initially used to attract animals to the wheel, the researchers found that wheel running continued even after the food was removed. This suggests that the animals not only ran voluntarily on the wheel, but did so without any external reward. 

The wheels attracted more than just mice, too. Shrews, frogs, and even slugs were recorded using the equipment (a few snails were excluded from the study due to “haphazard” movements on the wheel). But wild mice used the wheel far more than another animal, accounting for 88 percent of all wheel runners. 

Hamsters aren’t the only creatures that like running on wheels. Video: Wild Animals Caught On Hamster Wheel, Live Science

So, why do rodents specifically enjoy a run to nowhere? Are slugs simply less committed to their cardio?

According to Garland, rodents are simply built for it—bigger home ranges, faster metabolisms, and the aerobic capacity to sustain speed over distance.

“A toad isn’t going to be running 10 kilometers in a day,” Garland says. “Whereas a chipmunk could be.”

Dopamine keeps mice and hamsters coming back for more

But that’s only part of the story. The more interesting question is why any animal would choose to do it at all.

According to Garland, the drive to run on wheels among free-ranging animals is not fully understood, but the behavior is likely tied to the reward centers of the brain. 

“Dopamine is viewed as the final common denominator,” Garland says, referencing the neurotransmitter that delivers a sense of pleasure to the brain’s reward system. Similar to a human working out at the gym, mice get a dopamine boost every time they run on their trusty wheel. 

In Garland’s own lab, mice placed in larger, rat-sized wheels will sometimes slow down mid-run and rather than jumping off as the wheel keeps spinning, complete a full 360, and keep going. It serves no obvious purpose. It looks, for all the world, like a bit of acrobatics, as if the little mouse is creating its very own roller coaster.

“I’m hesitant to use the ‘F-word’ about lower vertebrates,” he says, “but it’s hard to ignore the idea that they’re getting some sort of pleasure or enjoyment out of it.” 

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The reward system may explain the drive, but Garland sees something even more elemental at work—something similar to the “zoomies” dogs and other young animals get. 

A baby horse, Garland notes, will sometimes just tear around a field for no apparent reason—solo, unprompted, burning energy for the sheer joy of it. “We used to call it nip-norting,” he says, “just going crazy, even without another individual to egg it on.”

Exercising at a young age leads to lifelong habits, even for hamsters

Rodents’ love of running on wheels might even have implications for humans. Some of Garland’s work suggests that, when introduced at a young age, wheel running can become a lifelong habit.

In his study, Garland found that mice given access to a running wheel immediately after weaning, at just three weeks old, ran significantly more as adults.

“It’s got to be something up here,” Garland says, indicating the brain. “Their reward system has been permanently tweaked.”

Whatever it is keeping these little guys running, an early start seems to predict an ongoing practice. The implications, Garland believes, extend well beyond mice. For instance, cutting physical education from school curricula, he says, could be “a huge public policy disaster,” leading to adults who aren’t used to exercising.

“If you’re a kid who never gets to play basketball or tennis,” he says, “and then you get to college, and your friends are playing pickup games, it’s probably not even on your radar to do that kind of thing.”

Of course, none of this is on your hamster’s radar at all. They’re just galloping away, keeping you awake with the endless rotation of their squeaky wheel. But all that running can also lead to some good: Recently, a resourceful young YouTuber rigged his brother’s hamster wheel to charge his phone.  

But no need to worry—the clever teen isn’t exploiting the toil of a joyless captive. Hammy, it seems, is just doing what comes naturally. 

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 Hamsters run on wheels for a surprisingly joyful reason appeared first on Popular Science.

This article was originally featured on The Conversation.

On May 22, 2026, the Pentagon released a second batch of previously classified photos and videos showing what appear to be unexplained flying objects. These file dumps were the culmination of a process that was set in motion back in July 2023, when a group of government whistleblowers testified before Congress that the U.S. government was secretly in possession of extraterrestrial spacecraft and suspected alien body parts.

That congressional hearing marked the beginning of a cultural shift in which UFO reports are increasingly treated as a matter for serious discussion, both within the government and the scientific community.

The Pentagon released over 200 previously classified UFO files in May 2026. Image: Department of Defense

But is this newfound legitimacy deserved? As an aerospace scientist who studies aircraft and spacecraft design, I approach this question using math, physics and the principles of engineering. To assess the plausibility of alien visitors, it’s necessary to understand the obstacles that an extraterrestrial vessel would need to overcome to reach Earth.

The tyranny of distance

There is no evidence of intelligent alien life in our solar system. So any extraterrestrial visitors would likely have to come from another star system within our Milky Way galaxy.

Proxima Centauri, the star closest to our Sun, is located 4.25 light-years (about 25 trillion miles or 40 trillion kilometers) away.

For perspective, if Earth were the size of a pea, the distance to Proxima Centauri would roughly equal the distance between New York and Sydney, Australia.

Even the stars closest to Earth are incredibly far away.

Since only a fraction of stars are thought to host intelligent life, the nearest alien civilization – if one exists – is surely much farther away than Proxima.

A need for speed

Given the scale of interstellar distances, it’s inevitable that any alien voyage to Earth would span many years and possibly several centuries. But as the time spent in transit increases, so does the risk of catastrophic accidents or system malfunctions that could jeopardize the mission. So it’s important to avoid an overly lengthy journey by traveling as fast as possible.

No object can reach or exceed the speed of light (roughly 186,000 miles or 300,000 kilometers per second). But well before approaching that threshold, engineering constraints begin to assert themselves. Limited fuel availability and the potential for structural damage will restrict the spacecraft’s peak velocity.

There is no universally accepted upper limit on interstellar flight speeds, but studies tend to converge around 19,000 miles per second (30,000 km/s) – 10% of the speed of light – as a realistic cruise velocity. At this speed, a journey of 10 light-years will take approximately 100 years to complete.

Fueling the dream

Finding a way to accelerate the ship to its target cruise speed is the central challenge facing any would-be alien explorers.

Interstellar space is unforgivingly vast, but the emptiness has some advantages. The lack of atmosphere means there is no aerodynamic drag. So when the ship reaches its cruise speed, it can shut down its propulsion system and coast toward the final destination. Unfortunately, the lack of atmosphere also means there is nothing to slow the ship down prior to arrival. So ideally, the propulsion system would be used for both acceleration at the start of the trip and deceleration at the end.

One of the more exotic propulsion strategies employs high-powered laser beams to push the ship through space. The beam is projected from a stationary array near the travelers’ home planet and directed toward a thin reflective sail attached to the ship. The beam’s photons exert radiation pressure on the sail, propelling the ship forward.

This approach has a major advantage in that it requires no onboard fuel. But the amount of energy and infrastructure needed to operate the laser would be staggering. Also, beamed propulsion provides no mechanism for deceleration. At best, this method could be deployed as part of a hybrid strategy that uses a separate system for deceleration.

A more practical approach is to use rocket propulsion. Rockets generate propulsive force, also known as thrust, by expelling high-velocity exhaust in a rearward stream. By reversing the direction of the exhaust, rockets can also be used to slow the ship down.

Their main disadvantage is that rockets must carry their own fuel in addition to carrying the passengers, the habitat and other life-sustaining systems. The extra load necessitates even more fuel. In other words, you need fuel to transport your fuel. The result is a costly snowball effect that can cause the total fuel requirement to balloon to absurd proportions.

Rocket propulsion can be divided into three broad categories.

Chemical propulsion uses chemical reactions – typically combustion – to extract energy from the bonds between atoms. All human space missions thus far have used chemical propulsion. The problem with this method is that it accesses only a tiny fraction of the energy contained within the fuel.

Consequently, using chemical propulsion on a spacecraft with a cruise velocity of 19,000 miles per second (30,000 km/s) would require more fuel than all the mass in the observable universe.

Antimatter propulsion is theoretically the most efficient option. When antimatter comes into contact with ordinary matter, the two undergo mutual annihilation and 100% of their combined mass is converted into energy. This makes it possible to achieve the same cruise velocity – one-tenth the speed of light – with fuel accounting for less than a quarter of the ship’s total mass. This is science fiction-level fuel efficiency, which makes antimatter an attractive option for interstellar propulsion.

The downside is that antimatter is extremely unstable and difficult to make. To date, particle physicists have produced less than 20 billionths of a gram of antimatter. Moreover, these particles had lifespans lasting only fractions of a second and a price tag in the hundreds of millions of dollars.

Nuclear fusion offers a more viable alternative to antimatter. This approach harvests energy stored inside the nucleus of an atom using the same process that powers the Sun. With current technology, fusion engines remain aspirational, but they could, in theory, produce 10 million times more energy per kilogram than chemical rockets.

NASA has been working to develop nuclear propulsion. This artist’s impression shows what a nuclear-powered rocket could look like. Image: Public Domain, John Frassanito & Associates/Wikipedia

Still, a fusion-powered ship with a cruise velocity of 19,000 miles per second (30,000 km/s) would require fuel equivalent to 150 times the mass of the ship itself.

A delicate balancing act

These numbers assume that our extraterrestrial visitors have figured out how to efficiently convert the energy released by their reactor – whether nuclear fusion or antimatter – into thrust.

Just as importantly, they must be able to create optimized fuel tank structures that are ultra lightweight yet highly secure. Designing the structure of the ship, from the fuel tanks to the hull, would be one of the biggest engineering challenges of the entire mission.

Interstellar space contains a sparse smattering of hydrogen atoms and microscopic grains of cosmic dust. At 19,000 miles per second (30,000 km/s), dust particles would smash into the ship’s hull with the energy of a .22-caliber bullet. The bombardment of hydrogen atoms would produce a violent cascade of radiation that could erode even the most resilient engineering materials.

Surviving the onslaught would require no less than a flying fortress with complex magnetic shielding. This would increase the total mass of the ship, which further drives up the demand for fuel.

This example is just one of the hundreds of delicate design trade-offs that would plague any interstellar vessel. Each individual design requirement acts as a filter, reducing the number of feasible solutions.

Finding a single system that simultaneously satisfies all the requirements is analogous to shopping for a car online. With each new filter you apply – four-wheel drive, black exterior, less than 10,000 miles on the odometer – the number of available options dwindles.

When design requirements are in tension with one another – for example, requiring a structure that is lightweight but also supremely durable – the number of feasible solutions can drop to zero.

No single law of physics prohibits an interstellar voyage to Earth. But the combined effects of hundreds of extreme, often conflicting engineering requirements may render it physically infeasible.

It’s also possible that alien civilizations have discovered novel technologies that outperform anything currently known to humans. But like the examples discussed here, any such technology will inevitably encounter its own engineering hurdles.

The trillion-dollar question

Ultimately, engineering challenges are just some of the many barriers to interstellar travel. Any prospective alien visitors must also have sufficient cognitive ability, technological maturity, physical resources, collective desire and proximity to Earth.

That said, if the stars were to align and an alien vessel made it to Earth intact, it would trigger a torrent of burning questions: Where are they from? What do they want? What are they made of?

But the question that would go furthest in shedding light on the deeper mysteries of the universe is, “How on Earth did they get here?”

The post Could aliens ever visit Earth? An aerospace scientist unpacks the challenges of interstellar spaceflight. appeared first on Popular Science.

Animals are not the only stinky living things on this planet. The putrid corpse flower blooms with  the stench of rotting flesh, as does the lesser-known (but equally pungent) Bulbophyllum phalaenopsis. Then there is the elegant stinkhorn (Mutinus elegans), a fungus known for its phallic appearance and spores that give off the odor of rotting meat.

Also called the devil’s dipstick, elegant stinkhorns are found across most of eastern North America, particularly from spring to the earliest days of winter. It has also been found in parts of Europe and Asia. They typically prefer temperate climates and looser soils, springing up in gardens, mulch beds, forests, and wood debris during warm and wet weather. They can grow to about four to six inches tall, and a mature mushroom will only last a day or two before subsiding. 

The sticky (and stinky) brown spore substance attracts insects to help the fungi spread. Image: Tina Shaw/USFWS.

All of that stench comes from the dark and slimy coating on the mushroom’s tip called the gleba, and it serves an important purpose. The fungi uses this dark and stinky spore mass to get the flies and other insects buzzing. Once they get a whiff of that rotten flesh smell, they will land on the stinkhorn and get covered in spores. As the bugs fly away, they spread the stinkhorn’s spores far and wide, so that more stinkhorn can pop up elsewhere.  

During the Victorian era, their penis-like appearance was reportedly distressing to some ladies. According to one story, naturalist Charles Darwin’s daughter Henrietta (or Etty), was openly combative towards the elegant stinkhorn. She would roam the woods armed with a spear, following her nose to the offensive mushrooms. Her niece recalled that Etty would find the fungi and “poke his putrid carcass into her basket.” After cleansing the territory, Etty would then secretly burn it to protect “the morals of the maids.”

Henrietta “Etty” Darwin (1843-1927) was the eldest of Charles Darwin’s daughters to reach adulthood. Image: Cambridge University Library. 

If you encounter this bizarre fungus in the wild like Etty Darwin, don’t worry. Beyond offending your nostrils, it is not poisonous or dangerous to your health. But you still probably shouldn’t eat it anyway. 

The post This phallic fungus also smells like rotting flesh appeared first on Popular Science.

When Sachita Shah sent her cardiologist brother an ultrasound of her patient’s heart, he was very confused. The heart was huge, and the left ventricle incredibly muscular. His confusion was warranted, as the ultrasound was not of a human heart. It belonged to another primate—a gorilla. Shah, emergency physician and VP of Global Health at medical equipment manufacturer Butterfly Network, tells Popular Science that if she had shown an ultrasound of a gorilla fetus to a radiologist, they would have assumed it was a human baby. 

Shah is on the gorilla care team currently looking after Jamani and Olympia, two western lowland gorillas (Gorilla gorilla gorilla) mothers at Woodland Park Zoo in Seattle, Washington. Jamani gave birth on Monday May 18, and Olympia is expected to deliver her new baby imminently. Shah and her colleagues’s work involves conducting ultrasounds of Jamani and Olympia’s baby bump—though now probably just Olympia’s—to keep an eye on the baby’s growth and position. 

“We got a really pretty baby face,” Shah says, speaking of the ultrasounds. “We could see nose and lips and fetal breathing movements and heartbeat and drinking fluid, opening mouth and swallowing. For all intents and purposes, it was very much the same [as a human baby].” 

The endangered gorilla mothers were trained to take part in the exams and procedures conducted by the gorilla care team, and they could choose whether to participate or not. The gorillas put their bellies against the edge of the enclosure for the scan (and received snacks), where there is a small opening through which the care team can reach through with the ultrasound probe. 

As such, the zoo needed a small and portable imaging device. That’s where Butterfly Network and their all-in-one ultrasound probe came in. 

“When you think of an ultrasound, you might think of a big cart with lots of different probes—a different probe if you wanted to do a pregnancy scan, or a heart scan, or a pediatric scan might have a tiny probe,” Shah says. 

Instead, the Butterfly probe they use at Woodland Park Zoo is a handheld ultrasound that plugs into a smart phone. It is around as big as an electric shaver, and it functions with a number of different softwares for either veterinarian or human health use. Notably, an app allows the team to use it for different types of scans—from a pregnant gorilla to a child’s lungs—that would traditionally require distinct probes and machines. 

Jamani’s baby was born on May 18 at 5:50 a.m. Image: Jeremy Dwyer-Lindgren / Woodland Park Zoo.

Shah and her colleagues also used the Butterfly ultrasound device to scan the heart of Nadaya, the silverback gorilla father of both babies. In fact, the heart ultrasound Shah sent to her brother belonged to Nadaya.  They used human software for that scan, even though their vet software is optimized for fur. Fortunately, Nadaya’s chest isn’t very furry. 

Shah, who has gone through a pregnancy herself, was most moved by working with the gorilla mothers. 

“We could tell the baby’s head had dropped and we thought, ‘oh man, she must be so uncomfortable.’ And she was waddling and walking a little differently. I was like, ‘oh, I remember that, girl.’ It was just amazing to remember that we’re all connected in that way,” she says. 

Western lowland gorillas are critically endangered, so babies are always excellent news.

UPDATE May 27 8:19 a.m EDT

On Sunday, May 24, at 1:44 p.m. PDT, Olympia’s baby was delivered by an emergency C-section performed by a medical team who typically works on humans. This 5.4-pund boy is the western lowland gorilla’s second baby.

The post Pregnant gorillas undergo ultrasounds and the results might look familiar appeared first on Popular Science.

While a holiday weekend has come and gone, May 26 is not without a cause for celebration. It’s National Paper Airplane Day! 

The annual day commemorates the homemade aeronautical toy that has fascinated (and frustrated the less crafty) children and adults for generations. According to National Day, the practice of constructing paper planes is sometimes called aerogami, after origami, the Japanese art of folding paper. Building paper planes that can soar through the air like a bird is believed to have originated in ancient China, where paper was invented around 105 CE. However, the art of folding it into an airplane may have been perfected in Japan, as it is similar to origami.

Here in the United States, instructions for folding the Basic Dart were included in a children’s book published in 1859, so it is safe to say kids and adults alike have been making them for over 167 years. The term paper airplane was then coined in 1907 and replaced paper dart as the dominant term by the 1950s. In 2022, Kim Kyu Tae nabbed the Guinness World Record for the Longest Paper Airplane Throw Ever with a flight of 252.6 feet. According to Guiness World Records, the longest time flying a paper aircraft is 31.2 seconds and was achieved by Rao Chongyi and a team in China in February.  

If you’re inspired to create the world’s best paper airplane, we have you covered. You can also look to the great minds at NASA for inspiration. After all, the first letter “A” in NASA stands for aeronautics. Their step-by-step NASA Space Crafts tutorial will not only help you make a colorful paper airplane, but also NASA’s X-57 Maxwell and the X-59 Quiet SuperSonic Technology.

May your National Paper Airplane Day be free of paper cuts.

The post It’s National Paper Airplane Day: How to make a NASA-approved plane appeared first on Popular Science.

Small as a grain of rice, polka-dotted, and everything nice. These are some of the ingredients that come together to make Thecacera sesama, a newly identified species of sea slug, or nudibranch, found swimming in Taiwan.

“Taiwanese divers call it ‘sesame’ in Chinese and it is also small like a sesame seed, hence the name,” researchers explain in a statement. Indeed, T. sesama is less than 0.12 inches long. The tiny bugger is also translucent and speckled black and yellow, and Ho-Yeung Chan “accidentally discovered” it while diving in 2019. 

A sketch of Thecacera sesama showing its appearance and morphological features. Image: Chen-Lu Lee.

Chan is a researcher at the National Taiwan Ocean University’s Institute of Marine Biology and Center of Excellence for the Oceans, but was an undergraduate student when he made the discovery. Chan didn’t realize he’d found a previously unknown species until after he’d spoken with sea slug identification expert Hsini Lin via Facebook. Chan is now lead author of a recently published ZooKeys study officially introducing T. sesama to the world. 

The new sea slug seems to enjoy a simple life. It displays just four main actions: feeding, searching, mating, and laying eggs on bryozoans. Also known as moss animals, bryozoans are a group of small aquatic invertebrates. The bryozoan that hosts T. sesama might also be a previously unknown species. 

Living specimens of Thecacera sesama. Image: Ho-Yeung Chan et al., 2026

While you might assume that the most difficult aspect of researching T. sesama is its miniscule size, the hardest part of the study for the team was the explosive weather of Taiwan’s Keelung coast. The island as a whole often has summer typhoons and large waves in the winter monsoon season, during which the sea is frequently colder than 60.8 degrees Fahrenheit. 

With these challenging conditions, researchers can only dive to investigate sea slugs for around a third of the year. The narrow window means that spotting the sesame-sized slugs is completely a toss-up.

“Nudibranchs are one of the key players in the marine food web,” the team explained. “They are extremely colourful and can be spotted on coral reef ecosystems. However, many nudibranchs are very small in size and are extremely difficult to spot underwater with the naked eye.”

Chan and colleagues believe that Taiwan’s marine environment is probably home to many other unknown tiny species. It remains to be seen what new strange creature will emerge from the island’s turbulent waters. 

The post Seed-size sea slug looks like an everything bagel appeared first on Popular Science.

An extremely rare piece of Olympics history hits the auction block this week. Sports enthusiasts with deep pockets have the chance to own an original gold medal from the 1924 Paris Summer Olympics. 

The harp on this side of the medal represents the Cultural Olympiad, an artistic and cultural program that ran alongside the athletic competition. Image: Nate D. Sanders Auctions.

The 1924 Paris Games were a hallmark of Olympics and sports history. More than 3,000 athletes from 44 countries competed in the first Olympics to include a Closing Ceremony. American swimmer Johnny Weissmuller won three gold medals and later went on to play Tarzan in 12 films. Swiss tennis player Richard Norris Williams won gold, after surviving the sinking of the RMS Titanic in 1912. He almost lost both his legs after jumping into the freezing water, but made a full recovery. The Paris Games were also featured in the award-winning film Chariots of Fire.

The 1924 Paris Games were also the first to officially feature the iconic five-ring Olympic symbol. The rings were designed by Baron Pierre de Coubertin, the founder of the modern Olympics and symbolize five continents and athletic unity. 

This symbol of sportsmanship set the standard for future medals. Image: Nate D. Sanders Auctions. 

The medals were designed by sculptor André Rivaud. The obverse side shows a winning athlete reaching out to help a fallen competitor, an image of sportsmanship that set the standard for future Olympic medal design. The five Olympic rings are beneath this scene. The reverse side features sports equipment alongside a harp, a nod to the Cultural Olympiad. This artistic and cultural program ran alongside the athletic competition to explore the links between art and sport and the values they both share.

The medal is about 2 inches in diameter and weighs 2.7 ounces. It is listed as “near fine condition,” is made from gold-plated gilt silver and has the “2ARGENT” stamp on the rim as a mark of authenticity. Only 304 gold medals were originally produced, making them one of the   rarest and most coveted pieces of Olympic history in existence. The auction will take place on May 28 with a minimum bid of $14,000.

Only 780 days to go until the 2028 Summer Olympic Games in Los Angeles, California. 

The post Extremely rare 1924 Olympic gold medal up for auction appeared first on 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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