An Australian magpie. Image Credit: NAPARAZZI, Flickr

<p>During a recent study, a group of magpies removed their GPS trackers, astounding their observers. But were the birds actually trying to help each other?</p>

How magpies outwitted researchers in Australia

A person in the first stages of multiple sclerosis may have trouble gripping objects or experience dizziness, fatigue, and vision problems. Symptoms may get progressively worse. Image Credit: © Minerva Studio/Shutterstock

<p>The underlying cause of multiple sclerosis is not yet known, but Epstein-Barr virus is a possible culprit, Harvard researchers say.</p>

Epstein-Barr infection found to increase risk of multiple sclerosis

Animal Care Supervisor Lisa Dijenno bottle-feeds a manatee named Tober. Image courtesy of ZooTampa

<p>As Florida’s seagrass beds die off, manatees are starving. Can the seagrass–and the manatees–make a comeback?</p>

A day at a Florida manatee hospital

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<p>NOVA Next is NOVA’s award-winning digital publication that provides answers from the cutting edge of science and technology. Launched in 2012, we feature in-depth articles and commentaries from some of the most respected journalists, scientists, and engineers. NOVA Next explores the ideas that are changing the future, from the frontiers of synthetic biology to the politics of personalized medicine.</p><p>Let us know what you think. We’re listening on <a href="http://www.facebook.com/NOVAonline">Facebook</a>, <a href="http://twitter.com/novapbs">Twitter</a>, and email.</p><p>If you’re a journalist and have an idea for a story, send it our way.</p>

NOVA Next is NOVA’s award-winning digital publication that provides answers from the cutting edge of science and technology.

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<p>NOVA Next is NOVA’s award-winning digital publication that provides answers from the cutting edge of science and technology.</p>

Cluster of three purple fireworks exploding against a black sky

Image Credit: Matthew Bellemare, Wikimedia Commons

The science of fireworks

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<p>Fireworks are part of countless celebrations around the world—including United States Independence Day festivities dating back to the very first bash in 1777. But how do those glittering displays actually work? It turns out that the firework shows that dazzle crowds across the country each year are backed up by millennia of engineering—and science that continues to evolve.</p><h3><b>The boom</b></h3><p>The basics of fireworks have remained the same for a thousand years, starting with a recipe believed to have been devised by <a href="https://www.americanpyro.com/history-of-fireworks">Chinese alchemists</a> around 800 CE. The “black powder” they dreamed up is three quarters potassium nitrate and the rest charcoal and sulfur. Stuff that in a paper container, and you’ve got the beginning of a firework. </p><p>When you light that baby, the sulfur melts first, flowing over the potassium nitrate and charcoal and setting them alight. This flame releases gas and energy: an explosion. If there is a conveniently placed hole in the container, the gas escapes and launches the firework skyward before it blasts apart. </p><p>In modern aerial fireworks, black powder is packed into a container connected to a fuse. When the fuse is lit, it burns for a set amount of time to allow the firework to reach a desired altitude, at which point it reaches the “bursting charge.” Inside, all that black powder has been packed with “stars,” small spheres or cubes made of metal salts, in a particular pattern. The exploding powder throws those stars outward, creating intricate spheres or flowers of sparkling light with names like “palm,” “willow,” and “chrysanthemum.” More complicated “multibreak” shells can even burst in two or three phases, sometimes including shells-within-shells, fuses that ignite each other, or explosives that break each section into pieces.</p><h3><b>The ooh and ahh</b></h3><p>We’ve come a long way from the simple Chinese launch-and-boom fireworks of a thousand years ago. These days, modern firework designers can use computer programs to choreograph their shows—sometimes along with music—down to a fraction of a second. They use a mix of virtual modeling, precisely engineered launching brackets, and circuits equipped with computer chips to map out and execute the timing of each firework, its launch angle, and how high it should sail in the air before exploding.</p><p>Plus, 21st century fireworks have something the original Chinese inventors could only dream of: color. In the original versions, which used potassium nitrate as a base of the black powder, the sulfur’s electrons would get excited, jumping into a further orbital away from each atom. When they fell back to their original state, that extra energy would be released as yellow light. </p>
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<p>But in the 1830s, Italian firework makers discovered that using potassium chlorate instead of nitrate opened up a huge realm of sparkling possibilities. The new material delivered oxygen more quickly to the powder, increasing combustion temperature from 1,700 to 2,000 C. And that increased temperature created an opportunity to add a new set of chemicals with higher burn temperatures that could create brighter light—and new colors.</p><p>More specifically, Italian firework innovators began adding metal salts to their works of explosive art. Each of these ionic compounds emits light from a different part of the spectrum when its excited electrons bounce from their outer orbital neighborhood back to home base. Strontium and lithium both make deep reds; calcium blooms orange; sodium glitters yellow; barium radiates green.</p><h3><b>Greener greens, safer reds, and the elusive blue</b></h3><p>All that is good for creating a visual masterpiece—but the new chemicals adding to our oohs and ahhs have some drawbacks. The strontium chloride that creates beautiful red blooms in the night sky can also create carcinogenic fallout. In 2015, researchers looking for more environmentally friendly, chlorine-free options found possibilities in materials like hexamine, a preservative, and 5-amino-1H-tetrazole, an airbag propellant, <a href="https://cen.acs.org/articles/93/web/2015/08/Red-Fireworks-Green.html?ref=search_results">Chemical &amp; Engineering News reported</a>. That could be helpful in military contexts, since red flares used in training can be a regular source of harmful fallout.</p><p>And in 2011, a U.S. Army team of pyrotechnics experts found that boron carbide, “a compound long dismissed as inert” could help replace the toxic, barium-based chemicals currently used in green fireworks, <a href="https://www.nature.com/articles/news.2011.222">Nature reported</a>.</p><p>Environmental and safety concerns aren’t the only challenge left for pyrotechnic artists. There’s still the firework holy grail: the perfect blue. Blue fireworks have always been among the most difficult to develop. They must stand out against the dark night sky, but their signature color is created using a copper gas that burns at a very high temperature. The firework maker's task is to help the color come out without overheating it and causing the color to wash out, turning from blue to white. That makes a really vivid blue firework an aerial feat of chemistry that marks a true master.</p>
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An elderly woman in a red sweatshirt runs down a path in a park

Image Credit: David Tett via Centre for Ageing Better

How exercise may help prevent Alzheimer's

<p>Your brain loves it when you exercise. Of course, you yourself may not love every sweaty minute of your kickboxing class or Saturday afternoon run—but your brain revels in it. That’s because exercise doesn’t just increase muscle tone. It doesn’t just goose energy levels and enhance mood, fighting <a href="https://www.pbs.org/wgbh/nova/video/depression-memory-alzheimers/">depression</a> and anxiety. It also heightens problem-solving skills and memory. And, research has increasingly shown, it protects against <a href="https://www.pbs.org/wgbh/nova/video/determined-fighting-alzheimers/">Alzheimer’s disease</a>—both delaying onset of the disease and slowing decline in patients who have already been diagnosed.</p>
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<p>As baby boomers age and more Americans live longer, Alzheimer’s is on the rise. In 2020, some 5.8 million people in the U.S. were living with this most common form of dementia, in which inflammation and tangles of misformed proteins in the brain accompany progressive <a href="https://www.pbs.org/wgbh/nova/video/alzheimers-screening-test/">memory loss</a> and inability to perform day-to-day tasks.</p><p>Despite decades of research, effective treatments for Alzheimer’s have eluded researchers; even a full explanation of what happens inside an Alzheimer’s patient’s brain has remained out of reach. This is in part because the disease is incredibly knotty and multifaceted, says Fang Yu, a researcher at Arizona State University who specializes in applying new dementia science to human trials. Alzheimer’s affects myriad processes in the brain, our most complicated organ, but most treatments developed thus far have only been able to tackle one aspect of the disease at a time, she says. “Even if there is a medication that can help target certain pathways, there are many pathways needed.” </p><p>That’s why Yu’s Alzheimer’s studies have often focused on the power of moving our bodies. Exercise is unique in that it also affects the body and brain in many ways, she says, making it an important intervention for addressing the complexity of Alzheimer’s. </p><p>It’s “something quite special,” agrees Christiane Wrann, a neuroscientist at Harvard University and Massachusetts General Hospital. While you’re dancing, bicycling, or running, it may seem like “you’re doing something that doesn’t have anything to do with the brain,” she says. “But you’re actually getting improvement in cognitive function.”</p>
<h3><b>How does it work?</b></h3><p>Perhaps the most straightforward way in which exercise safeguards against Alzheimer’s is by improving cardiovascular health. The effects of a good sweat session don’t stop at our hearts—they help improve the condition of our other organs and blood vessels as well. Those healthier vessels deliver an upgrade in the connections among brain cells called neurons, Wrann says. With reinforced wiring, it’s easier for nourishing oxygen to get in, for waste products to get out, and for the neurons to talk to one another. And improved fitness of the heart and lungs also seems to help the brain take up glucose more efficiently, which helps keep neurons healthy.</p><p>Plus, <a href="https://www.pbs.org/wgbh/nova/video/cannabis-reverses-brain-aging/">research on mice</a>—a common, if imperfect, source of new Alzheimer’s science, since it’s not possible to ethically conduct some kinds of research on living humans—has shown that exercise is a rare cause of “adult neurogenesis,” or the growth of new neurons in adulthood. Although it’s difficult to prove fully that the same happens in humans, it seems like <a href="https://www.researchgate.net/publication/323624428_The_Role_of_FNDC5Irisin_in_the_Nervous_System_and_as_a_Mediator_for_Beneficial_Effects_of_Exercise_on_the_Brain">one key player is irisin</a>, a hormone manufactured in the muscles in response to exercise, Wrann explains. Irisin is special because it carries a pass to get through the blood-brain barrier, the barricade of tissue and blood vessels that keeps harmful substances from reaching the brain. </p><p>Once inside, <a href="https://www.researchgate.net/publication/354038429_Exercise_hormone_irisin_is_a_critical_regulator_of_cognitive_function">irisin helps the brain</a> create a neurotransmitter called BDNF, which is important to hippocampus health. The hippocampus is a center of learning and memory in the brain, and Alzheimer’s patients’ hippocampi tend to shrink as their health declines, Yu says. The ability to sprout new cells in the hippocampus, and to prune away connections that aren’t needed anymore—two processes that BDNF supports—is key to stabilizing and protecting it.</p>
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<p>A series of studies at Wrann’s lab in Boston has also shown that, at least in mice, irisin produced during exercise has powerful anti-inflammatory effects in the brain. That could be an important insight because some new research points to <a href="https://www.pbs.org/wgbh/nova/article/brain-inflammation/">inflammation</a>, rather than previously implicated amyloid plaques, as a possible cause of neuron death in Alzheimer’s. Inflammation is caused by the immune response to negative stimuli—not just viruses or bacteria but also, for example, misfolded proteins in the brain. In an Alzheimer’s patient, the immune system may respond to the presence of these plaques by attacking them, Wrann explains, and in its enthusiasm, it may also attack the synapses that connect neurons. “If it gets completely out of control, you have this ‘friendly fire’ that causes damage to the neurons,” she says. But her research indicates irisin may bind to receptors on specialized cells deep within the brain, calming that inflammatory response.</p><p>And one last piece of the puzzle is <a href="https://www.pbs.org/wgbh/nova/article/healing-sleep/">sleep</a>—not a type of exercise in itself, but caught up in something of a love triangle with exercise and Alzheimer’s disease. When it comes to dementia prevention, sleep and exercise may work together, says neuroscientist Miranda Chappel-Farley, a Ph.D. candidate at University of California, Irvine. Studies have shown that more exercise leads to better quality sleep, which is an important protective factor itself against Alzheimer’s. And people getting better sleep are more likely to feel up to exercising. Together, they create a powerful bulwark against dementia and represent a lifestyle factor ignored at your peril, says Chappel-Farley, who cautions against “targeting exercise but not paying attention to sleep.” </p>
<h3><b>What kind of exercise is best?</b></h3><p>Aerobic exercise seems to be the champion when it comes to protection against Alzheimer’s and maintaining executive function. Of course, most of the mice participating in Alzheimer’s trials run on their wheels, but that doesn’t mean you have to. Biking, dancing, swimming, or any activity that gets your heart rate up is a good candidate, Yu says. That’s because it has the potential to increase BDNF levels; spur blood flow and shore up blood vessels; and decrease “white matter hyperintensities,” abnormal changes that affect how the brain transmits electrical signals.</p><p>Newer research also indicates that resistance-based muscle-building exercise may support a broad spectrum of cognitive functions. That effect seems especially promising in patients who have already been diagnosed with Alzheimer’s, where it may help slow their decline, adds Yu, who often works with dementia patients. There, the goal is not improvement but slowing deterioration. “And that’s basically what my research has shown: that exercise can level and stabilize,” she says.</p><p>Tai chi and other types of movement that incorporate mindfulness also decrease stress and inflammation and improve sleep, she adds. And some research suggests that a mix of many types of exercises may provide stronger improvement than a single activity. In a review of <a href="https://europepmc.org/article/med/34004389">71 studies of exercise and dementia</a>, Yu and her colleagues found the most consistently effective exercise was “mixed component,” a blend of muscle-building and aerobic workouts.</p><p>Still, “it’s important to highlight that there’s a lot we don’t know yet,” says Chappel-Farley, since exercise comes in so many forms and can be adjusted by duration, intensity, frequency, and timing. “It’s not totally clear which might be best.” Does it take a certain amount of exercise for our brains to reap the benefits? Are there any findings in the extensive mouse research on this topic that can’t be transferred to humans? </p><p>Wrann says that data is encouraging so far, indicating that the more you exercise the more benefit you’ll experience. And really, what’s the risk? “My big message is that exercise is good for you,” Yu agrees. “Even if in the future we find that it doesn’t prevent Alzheimer’s for everyone, it’s still good for your health and quality of life.”</p><p>But Wrann also remains mindful of people who can’t exercise because of a disability or physical limitations, or who may develop Alzheimer’s despite getting plenty of exercise; there’s still no silver dementia bullet. While it’s unlikely that researchers could develop a drug that can affect the body in as many ways as exercise can, she’s hopeful about irisin’s potential as a source of new drug therapies. Because it’s a powerful anti-inflammatory that can already wriggle through the blood-brain barrier, she wonders if it might be possible to use irisin to create a drug that goes even beyond the positive effects of exercise. Inflammation in the brain seems to be central to many neurological conditions. That way, she says, “we could reach people with Alzheimer’s disease—or beyond.”</p>
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<p data-block-key="eldwf">Exercise could be a powerful defense against Alzheimer’s disease. Three dementia researchers explain how it works.</p>

6 stinking cool facts about dog noses

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<p>Did you know that dogs can use their cold, wet (and cute!) noses to sense sources of heat and thermal radiation? </p><p>That discovery, via a <a href="https://www.science.org/content/article/new-sense-discovered-dog-noses-ability-detect-heat">2020 study from Sweden</a> that challenged dogs to choose between a warm and cool object across a room, makes them only the second mammal known to possess that superpower. (The other is a vampire bat.)</p><p>And that’s not all dogs' noses can do. Read on for six reasons why dog noses are among nature’s most amazingly engineered instruments—instruments whose power humans are <a href="https://www.pbs.org/wgbh/nova/video/electronic-nose-imitate-dog-nose/">now trying to recreate</a>:<br/><br/> 1. Dogs' <a href="https://www.pbs.org/wgbh/nova/article/dogs-sense-of-smell/">sense of smell</a> is between 10,000 and 100,000 times as potent as humans’. This power comes in part from the up to 300 million olfactory receptors dogs carry around in their noses, compared to our mere 6 million. And the part of the canine brain that is dedicated to smells is 40 times larger than ours, proportionally speaking.<br/><br/>2. Dogs can smell continuously, even while they’re breathing in and out. In contrast, when a human smells a scent (sniffs a rose, for example) we inhale that odor and breathe in oxygen through the same passage. But if a dog smells the same flower, air “splits into two different flow paths, one for olfaction and one for respiration," Brent Craven, a Pennsylvania State University bioengineer who has modeled <a href="https://anatomypubs.onlinelibrary.wiley.com/doi/full/10.1002/ar.20592">canine olfaction anatomy</a> using high-resolution MRIs, <a href="https://www.pbs.org/wgbh/nova/article/dogs-sense-of-smell/">told NOVA</a>.</p><p>Craven and his colleagues found that a portion of the air dogs inhale gets ushered into a specialized area at the back of the canine nose reserved for odor detection, while the rest of it continues rushing toward the lungs. And when dogs exhale, that air departs through nose slits in a unique aerodynamic pattern that also guides new air in, creating a cycle of breath that continuously supplies the in-house laboratory in the back of the canine nose with new material. In <a href="https://pubmed.ncbi.nlm.nih.gov/8735662/">one study from the University of Oslo</a>, a dog on a hunt sniffed continuously for a full 40 seconds, across 30 respiratory cycles!</p><h4><b>Watch: This Device Smells Diseases by Imitating a Dog's Nose</b></h4>
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<p>3. Dogs can <a href="https://vcahospitals.com/know-your-pet/how-dogs-use-smell-to-perceive-the-world">wiggle their nostrils independently</a>, which helps them figure out which direction a scent is coming from. Humans can only wiggle their nostrils simultaneously. (Try it. We’ll wait.)</p><p>4. Dogs are great at interpreting all the information coming in through their noses in fine detail. In her book “Inside of a Dog,” canine cognition researcher Alexandra Horowitz writes that humans might taste a teaspoon of sugar added to a cup of coffee. But a dog could detect the same teaspoon of sugar in a million gallons of water—enough to fill two Olympic-sized pools.</p><p>And to take the sugar metaphor further, “if we humans walk into a bakery, we can say, ‘someone’s baking a pie in here,’” canine search specialist Lynne Engelbert <a href="https://www.pbs.org/wgbh/nova/article/cremation-ashes-sniffing-dogs-california-wildfire/">told NOVA</a>. “A dog would walk in and say, ‘Oh, someone’s baking a pie in here, and it has apples, and butter, and cinnamon, and nutmeg.”</p>
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<p>5. Dogs can connect a human with the scent they leave behind with exceptional precision—and even help diagnose sick humans with a variety of diseases. Forensic chemist Ken Furton, who has studied dog olfaction for more than 25 years, once blew up a car with colleagues and then asked detection dogs to pick out human scent from the resulting debris. The dogs were able to sniff the small amount of shrapnel and correctly identify the people who had been in contact with the bomb pre-explosion 82% of the time.</p><p>More recently, Furton and his colleagues looked at whether dogs might be trained to identify COVID-19 patients—and found they could do so with 97.5% accuracy. “I was shocked,” he told NOVA. And <a href="https://faseb.onlinelibrary.wiley.com/doi/abs/10.1096/fasebj.2019.33.1_supplement.635.10">one 2019 study</a> indicated humans’ best friends can sniff out cancer with a similarly high 97% accuracy rate.</p><h4><b>Watch: Cannabis-Sniffing K-9's: Out of a Job?</b></h4>
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<p><br/>6. Dogs can not only identify human remains–they can sniff out <i>already cremated</i> remains from among other ashes. Dogs in the American West are now being trained to <a href="https://www.pbs.org/wgbh/nova/article/cremation-ashes-sniffing-dogs-california-wildfire/">look for the cremated remains</a> of homeowners’ loved ones when those homes are lost to the region's increasingly fierce wildfires. The non-profit Alta Heritage Foundation brings specially trained search dogs and archaeologists to the site of a house destroyed by fire, using canine colleagues to narrow down where the lost ashes might be buried and then archeological techniques to excavate them. </p><p>The ashes are often the only thing his clients want to recover from their houses, Alta Heritage founder Alex DeGeorgey told NOVA. So being able to find their loved ones’ ashes within the ashes of a house is both powerful and continually surprising. “I’ve done this hundreds of times,” DeGeorgey says of cremation ash recovery, “and I still marvel that we’re able to do it.”</p>
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<p data-block-key="dc0rk">Dogs can sniff out disease and analyze new odors even as they exhale. But how?</p>

Human fossil footprints at White Sands National Park in New Mexico. Image Credit: Courtesy of the National Park Service

Human tracks may be earliest evidence of people in North America

<p>In southern New Mexico lies the Tularosa Basin, an oblong bowl that’s home to a natural sandbox: White Sands National Park.</p><p>In 2005, David Bustos came to White Sands to work as a National Park Service biologist. The following year, he took notice of odd animal footprints that would appear only when the ground was wet. (The first of these footprints was reported in the 1930s.) The markings, which would disappear as the earth dried up, became known as ghost tracks.</p><p>Then in 2009, Bustos came across tracks he thought belonged to ancient humans walking alongside mammoths. But few scientists agreed, he says, rebutting with “No, no, those are the prints of camels that were slipping in the mud,” referring to now-extinct North American camels. And the tracks would disappear with changes in the weather. Heavy rainfall drowned them; periods of drought dried them up. It would take more than a decade—and cooperative weather—for scientists to agree that the tracks belonged to humans. </p><p>Then, says U.S. Geological Survey (USGS) Research Geologist Kathleen Springer, “What everyone was asking is, ‘How old are these things, really?’”</p>
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<p>In September 2021, Bustos, Springer, and a group of other researchers published their findings in the journal Science: The team identified 61 human tracks within multiple levels of earth belowground, and between layers of these tracks were seeds from an ancient aquatic plant. Analyses of these seeds—and the footprints they were embedded within—are now challenging scientists’ understanding of when and how people arrived in the Americas.</p><p>Archaeologist Joe Watkins, who was not involved in the study, believes the findings have potentially massive implications. “I think, outside the next big migration of going to the Moon or Mars, the migration to the Americas was the last great migration humanity had,” he says. Upending the timeline of this journey could have implications for both science and Native American cultures, Watkins, who is a member of the Choctaw Nation of Oklahoma, believes.</p><h3>Visiting the tracks</h3><p>At first light on a cold January morning in 2020, Bustos set out with Springer and her USGS colleague Jeff Pigati on all-terrain vehicles to visit White Sands’ ancient tracks. The team wore parkas to keep warm amid a prevailing wind. Springer recalls the hour-and-a-half journey through the dunes being like a “Disney ride.” It was the “funnest thing in the world,” she says. “Just being out there is surreal.”</p><p>Eventually, after passing through a large swath of national park that borders the site of the first atomic bomb test, Springer, Pigati, and Bustos fell upon thousands of tracks. They belonged to packs of dire wolves, giant sloths, 13-foot-tall mammoths, and other animals. And, Springer says, “there’s a person track right smack dab in the middle of them.”</p>
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<figcaption><p>Gypsum sand dunes at White Sands National Park, New Mexico. Image Credit: NOVA/GBH</p>
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<p>“When Dave showed us these things and we had our eyes trained on them, we were almost afraid to step down,” Pigati says. “It looks like a painting in some places.”</p><p>Bustos recalls the conditions that day being perfect for identifying tracks. The trio saw human footprints going underneath the sediment in places, illustrating that there was more than a surface layer of them. “We were seeing seed layers popping out all over the place,” Bustos says. To determine how old the footprints were, Springer and Pigati’s team would collect these ancient seeds from different layers of footprints. The overwhelming evidence of ancient plant life excited Bustos.</p><p>About 36,000 to 19,000 years ago, lakes filled the Tularosa Basin. The largest of these was Lake Otero, which fluctuated in size and activity based on rainfall. Plants like spiral ditchgrass (<i>Ruppia cirrhosa</i>), whose seeds are now embedded in layers of earth, grew along Otero’s edges. About 23,000 years ago, the southwestern U.S. became drier and the lake shrank. This exposed a large area of land that was once underwater, whose clays and silts became overtopped by gypsum sand and silt. People began walking around these surfaces, which “were kind of squishy in some areas,” Springer explains. And the people weren’t alone: The impressions from mammoths, ground sloths, and camels, sit alongside—and sometimes right on top of—human prints. </p><p>“This can only happen if they are in the area at the same time,” Pigati said in an email. “Exactly how they may have interacted in the vicinity of our [research site] is unknown, but there is definitive evidence that humans were harassing or stalking a giant ground sloth on the west side of the basin.”</p><p>In many other cases, interactions between humans and animals seem peaceful. “What’s interesting to me,” Bustos says, “is it’s not just a mammoth and a hunter. It’s families. You see a baby mammoth turning around and spinning. We have the juvenile and adult megafauna prints with the babies and adult [humans].”</p>
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<figcaption><p>A footprint from a Harlan's ground sloth at White Sands National Park. Image Credit: Courtesy of the National Parks Service</p>
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<p>Having about 10 hours of daylight, the team got to work “trenching” the human footprints, Springer says. With ground-penetrating radar, they were able to determine that footprints were present within layers of sediment. They then dug a trench to view the layers in cross-section. If Springer and Pigati’s cross-section was a sandwich, the footprints would be the filling and the dateable material around the footprints would be the bread. </p><p>Dating tracks only at the surface would yield inaccurate results, Pigati explains. “You can look in every direction and there are trackways everywhere in every horizon,” he says. But if you calculate the age of these footprints on the surface layer of earth only, you’ll just find that they’re younger than the ground they’re upon, he says. By looking at layers of sediment below the surface, the team set out to document how many layers contained footprints and find datable material above and below each layer. Each of these layers would contain footprints from a unique time period, the team posited. “The footprints are imprinted at the top of a given layer of sediment—they don’t really pass through the layers,” Pigati wrote in an email.</p><p>As the sun rose higher in the sky, the white sand reflected a near-blinding light, and the day quickly grew warm. The researchers shedded their parkas and worked in t-shirts until the January sun fizzled and it was time to ride back through the dunes, chunks of sediment layers in hand.</p><p>The team later extracted 40 to 60 ditchgrass seeds from every level of footprints in every sample. In a USGS lab in Golden, Colorado, they cleaned each set of seeds with a chemical treatment and began combusting them.  </p><p>The combustion process, automated by a machine in the lab, didn’t obliterate the seeds but turned them into a gas. From this gas, a machine turned the once-seeds back into solids: graphite pellets about the size of a pencil tip. This technology of making “graphite targets” dates back to the 80s, Pigati says. “Every lab does it the same way in the world.”</p><p>The team then took these pellets, tapped them down into cartridges, and sent them off to a lab to measure the amount of a radioactive isotope of carbon, called carbon-14, they contained. Then they waited for results.</p><h3>What the tracks mean</h3><p>Months later, they came. The seeds revealed that the footprints they were embedded within are between 21,000 and 23,000 years old—thousands of years older than what scientists generally consider to be the earliest evidence of people in the Americas.</p><p>“For forever, people thought Clovis were the first people to cross over [the Bering Strait] about 13,000 years ago,” Pigati says, referring to the commonly-held view among archaeologists. As the story goes, ice sheets in what is now Canada blocked passage between what is now Alaska and the rest of the Americas. Once these ice sheets began retreating, people came south through an ice-free corridor, Pigati explains. His team’s findings now challenge this belief. Carbon dating of the seeds within the White Sands footprints suggest that people were in the Americas while ice sheets still covered much of northern North America. “A lot earlier” than previously thought, Pigati says. </p><p>“When we got the final dates back, it was very…” Springer pauses over Zoom, choosing her words carefully. “The arrows were going to start flying. We knew we needed an [evidence-supported] explanation why these findings were really robust.”</p>
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<p>Archaeologist Joe Watkins says that if the dating of the seeds, and therefore footprints, is correct, “it puts us at 20% older than the dates we have from the rest of America.” Therefore, ages of other important archaeological sites like Meadowcroft Rockshelter in Pennsylvania, where scientists have found 16,000-year-old evidence of human life, may need to be reconsidered. (In 2014, Nikhil Swaminathan <a href="https://www.archaeology.org/issues/145-1409/features/2369-peopling-the-americas-meadowcroft-rockshelter">wrote for Archaeology Magazine</a> that Meadowcroft Rockshelter is “the longest-occupied site in the Americas.”)</p><p>Watkins first heard about the White Sands tracks years ago while working in Washington D.C. as the chief of the Tribal Relations and American Cultures Program of the National Park Service. But he didn’t see them until after he’d retired, visiting White Sands during a NOVA shoot for the film “<a href="https://www.pbs.org/wgbh/nova/video/ice-age-footprints/">Ice Age Footprints</a>.” Seeing human footprints intermingling with those of ground sloths was overwhelming and “tremendously exhilarating,” he says.</p>
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<img alt="Archaeologist Joe Watkins holds a clovis point" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/Joe_Watkins.width-990_4i0j7w4.jpg"/>
<figcaption><p>Watkins pictured with a replica Clovis point. His interest in archaeology was piqued at 10 years old when he found an archaic point on his family’s Oklahoma homestead. Watkins, who’s now 71, showed the point to his grandmother. The artifact didn’t come from modern Choctaw, but was much older, she explained in her native language. From that moment, Watkins became “more interested in looking into the unwritten past,” and, with his grandmother’s support, began pursuing a career in archaeology, a field he recognizes isn’t always “in advantage to the Native American community,” he says. Image Credit: NOVA/GBH</p>
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<p>But Watkins cautions that, with no other aspects of culture present but footprints, scientists like him can only speculate how ancient humans were using the land. “Were they just walking? Were they hunting? Did they have a camp nearby?” he asks. Archaeology may not hold all the answers to these questions: “I do think it’s important for American Indians to be involved so they can offer their insights so we can better understand who these people were,” Watkins says, reflecting on his own Choctaw roots.</p><p>As Native American identity is tied to the land, Watkins believes, “the Native peoples will say we’ve always been here,” he says. “I usually say [the first Americans] weren’t Native Americans. They weren’t Siberians. They were whatever they called themselves.” Combining this philosophy with science is a way to integrate belief systems, he says.</p>
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<p>The White Sands findings, Watkins says, “forced us to reconsider the most cherished ideas of the people of North America.”</p>
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<p>Watkins recites his people’s story about two stiff-legged bears that meet in a black-loam prairie and have a battle. Only one survives; it becomes the last of its species. “Some Choctaw interpret ‘stiff-legged bear’ as being a mammoth,” Watkins says. If humans did once walk alongside mammoths in New Mexico’s Tularosa Basin 20,000 years ago, he adds, there’s a chance these people gave birth “to any number of tribal people across the U.S.” </p><h3>Racing against time</h3><p>Bustos, Springer, Pigati, and fellow researchers visited the ghost tracks again in January and April 2022. They extended their trench, identifying more footprints from potentially before and after the original set they excavated. To bolster their findings, Bustos explains, the team won’t rely solely on dating seeds. They’ll date pollen, too. “This work is not done,” Pigati says. “We have a window from 21,000 to 23,000 [years]. We don’t know if people were here before then.” </p><p>But the clock is ticking. Erosion in White Sands is exposing and destroying the tracks, Springer says. Though the Tularosa Basin has been eroding for nearly 12,000 years, climate change is likely exacerbating erosion today, she explains. “The layers, they’re finite,” Bustos adds. “We’re losing thousands of tracks to erosion. It’s a race to document them before they’re gone.”</p><p>Already, some tracks reveal clues about ancient daily life in the Tularosa Basin.</p><p>“There’s something about the children,” Bustos says. “You see these toddlers running and jumping, and the story really comes alive.” Watkins agrees. “When we look at the tracks of children playing in perhaps puddled water surrounded by ground sloths,” he says, “it takes us back to childhood memories of children playing in puddles all around the world.”</p>
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<p data-block-key="arqov">Footprints in New Mexico’s White Sands National Park challenge scientists’ timeline of when humans first came to North America.</p>

The second-ever direct image of a black hole features Sagittarius A*, the supermassive black hole at the center of our galaxy. Image Credit: Event Horizon Telescope collaboration

Scientists capture first-ever image of our galaxy’s supermassive black hole

<p>On Thursday morning, an international team of astrophysicists and other researchers released the world’s first image of the supermassive black hole at the center of our galaxy, 27,000 light-years from Earth. </p><p>The event marks “the dawn of a new era of black hole physics,” the team<a href="https://twitter.com/ehtelescope/status/1524737908892049408"> announced on Twitter</a>.</p><p>More than 4 million times the mass of our sun, the black hole, named Sagittarius A* (or Sgr A*, pronounced “sadge ay star,” for short) is so dense and massive that no light can escape its gravity. The visible light in the new image comes from bright stars, gas, and other space matter swarming around the black hole itself.</p>
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<p>The image is the first visual evidence of Sgr A*’s existence; the black hole was previously only indirectly confirmed by observations of stars in orbit around it. The image comes from the Event Horizon Telescope’s (EHT) international consortium. A group of more than 300 scientists helped with the effort to capture it, “compiling information from radio observatories around the world,” Bill Chappell <a href="https://www.npr.org/2022/05/12/1098472567/image-black-hole-milky-way">reports for NPR</a>. (The EHT, named for the event horizon, or “point of no return” from a black hole, consists of eight radio telescopes scattered across the globe.)</p><p>In 2019, the EHT team compiled an <a href="https://www.pbs.org/wgbh/nova/article/first-black-hole-image/">image of Pōwehi</a>, a supermassive black hole 55 million light-years away in the galaxy Messier 87. Similar in appearance to Sgr A* but much more massive, Pōwehi is 6.5 billion times the mass of our sun.</p><p>The much smaller Sgr A* proved difficult for scientists to visually capture: It’s a “dynamic environment” full of burbling and gurgling, Feryal Özel, a professor of astronomy and physics at the University of Arizona, told NPR. And the necessity to look through both the Earth’s atmosphere, gas clouds, and interstellar dust near the Milky Way’s center added to the challenge, Özel said. “It took several years to refine our image and confirm what we had, but we prevailed," Özel told NPR. And, despite its meager distance from Earth compared to Pōwehi, Sgr A* is far enough away to appear “to us to have about the same size in the sky as a donut on the Moon,” the EHT team stated <a href="https://eventhorizontelescope.org/blog/astronomers-reveal-first-image-black-hole-heart-our-galaxy">in a press release.</a></p><p>Hot gas whirling around Sgr A* at nearly the speed of light made capturing an image of this black hole considerably more difficult than Pōwehi, the EHT team said in the press release. “The brightness and pattern of the gas around Sgr A* was changing rapidly as the EHT was observing it,” EHT scientist Chi-Kwan Chan said in the press release.</p>
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<p>Images of Pōwehi captured by astronomers across the EHT were visually similar to one another, allowing scientists to compile a sharp composite image of Messier 87’s black hole. “That was not the case for Sgr A*,” the EHT team said in the press release. But despite these initial inconsistencies, the scientists were eventually able to compile an image of Sgr A*.</p><p>Now, having images of such differently sized black holes provides a better look into the behavior of swirling gas around supermassive black holes, a phenomenon that’s not yet fully understood, but thought to play a key role in how galaxies, like our own, came to be. "Now we can study the differences between these two supermassive black holes to gain valuable new clues about how this important process works," EHT scientist Keiichi Asada said in the press release. </p>
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<p data-block-key="qta1u">The Event Horizon Telescope team has captured the first image of Sagittarius A*, the black hole at the center of the Milky Way. </p>

Russian spacewalkers explore the spherical Prichal docking module, which is attached to the Nauka multipurpose laboratory module of the International Space Station. Image credit: NASA Johnson, Flickr

Daily life on the International Space Station: A Q&A with a space archaeologist

<p>Soon after photos started arriving from the International Space Station (ISS), Justin Walsh spotted something unexpected: frosting. Tucked into a plastic bag hanging off the station wall, near a can opener and bottle of ketchup, were telltale red, yellow, and green tubes. Walsh was mystified. “What does frosting imply? Baking,” he said recently over Zoom. But baking in space is pretty much impossible. </p>
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<p>He got his resolution when astronaut Kayla Barron <a href="https://www.instagram.com/reel/CZmgSeupMuq/?utm_source=ig_web_copy_link">posted on Instagram</a> that she’d made a birthday cake for a colleague. “They did it by cutting the tops off of muffins and gluing them together with honey, then covering the whole thing with icing and frosting,” Walsh says. To Walsh, an art historian and archaeologist at Chapman University, the frosting was physical proof of something less concrete: astronauts’ bond with one another. Cooking and eating “is not only about sustenance; it's about social relations,” he says—even 250 miles above Earth. </p><p>He, fellow space archaeologist Alice Gorman, and their colleagues received the frosting photo as part of the Sampling Quadrangle Assemblages Research Experiment, known as SQuARE. The ISS, which is administered by multiple space agencies, is essentially a <a href="https://www.nasa.gov/audience/forstudents/5-8/features/nasa-knows/what-is-the-iss-58.html">network of modules</a> for cooking, sleeping, science research, and other uses that’s slightly larger than a six-bedroom house. Between January and March, astronauts on board took daily photos of six carefully chosen sites around their temporary home first at the same time each day, then at random times. The project was an interstellar version of the archaeological technique known as quick testing, in which archaeologists divide a new site into a grid of one-meter squares and dig “test pits” that provide a basic sense of what they might find. </p><p>In SQuARE, those “pits” are one-square-meter areas marked off with tape, scattered across the American, European, and Japanese modules of the ISS in areas used for work, science experiments, cooking, and hygiene. The team will analyze the resulting photos in hopes of understanding how each area is used over time and, from there, identify opportunities to improve space habitat design. </p><p>NOVA talked with Walsh about the challenges of space archaeology and why astronauts eat so many tortillas. </p>
<p><b>Alissa Greenberg: Usually, archaeologists excavate sites because it’s the only way to learn about life in those places—all the people are long dead. But we can talk to these astronauts. Why not do that?</b></p><p><b>Justin Walsh:</b> It's true that, for the most part, archaeologists do study the distant past. Contemporary archaeology developed starting in the 1970s. The first example of it was a project called the Tucson Garbage Project by a guy named William Rathje at the University of Arizona. He got the City of Tucson sanitation department to drop off samples of neighborhood garbage on a regular basis, and he and his graduate students went through it to understand the patterns of usage of different items.</p><p>What's really fascinating about it is that they then went and interviewed people from the neighborhood about their consumption habits. So first of all, he found that people were throwing out lots of meat that they weren't using. So he was able to show that people were being wasteful with this particular commodity. But then he went to talk to people about these things, and he found out some interesting facts. Such as when you ask people questions, the way sociologists and anthropologists often do, they are not necessarily really good at articulating the realities of their lives—or they don't want to. Which is also perfectly fair and understandable! I would not blame them for that. But what it shows is that what archaeology can do is provide additional insights into human practices and that those insights don't have to be about the distant past.</p><p>So, you can say, “Well why don't you just talk to the crew and ask?” or “Doesn't NASA document all that stuff?” Okay, we can absolutely do that, but that doesn't always work well—especially for astronauts, who are 100% good at staying on message and will not say anything to jeopardize their next flight to space. And as for the space agency, they don't do any forensic work on what's happened on the space station before. They're in the present and the future—and the past is <i>gone</i>. They're not thinking about what they can learn.</p>
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<img alt="Mesh bags full of condiments and food items hang from a space station wall" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/iss066e130191_1.width-990_qW6eQSP.jpg"/>
<figcaption><p>One of the SQuARE sample locations, in a U.S. module galley area, marked by yellow tape at each corner. On the wall, mesh bags hold ketchup, Sriracha sauce, chocolate, and other food items. In the upper right corner are plastic bags holding tubes of frosting, which indicated that a kind of “space cooking” activity was happening in this location. Image courtesy of Justin Walsh</p>
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<p><b>AG: Why do you find space culture so compelling?</b></p><p><b>JW:</b> Because humans are doing things there in an environment that we are 100% not adapted for. We literally cannot survive. So, we have to come up with all these technologies that allow us to survive in that environment, living in microgravity. And on top of that, there's the other issues of confinement and isolation: the bad food, the distance from family and friends. How do they work together and live together? </p><p>One of the phrases that I like is that a crewed spacecraft is “<a href="https://nap.nationalacademies.org/read/12387/chapter/1">a microsociety in a miniworld</a>.” You have the transmission of culture and traditions—"this is how we do things, this is how this is laid out”— being handed down almost from generation to generation. For example, on the ISS they have dinner together every Friday. Most of the time it's in the Russian service module; sometimes it's in the American service module. Or on ISS their food is carefully designed, and there are different kinds of traditions associated. Things like there's no bread, because crumbs are bad in space. If you inhale a crumb, that could really be a problem, so instead they use tortillas for everything. Tortillas don't make crumbs.</p><p><b>AG: Can you talk about this most recent study? What’s the goal here?</b></p><p><b>JW:</b> We've been doing this study of historic photos that document life on the space station over 21 years. We've got this body of photographs, both published photographs from Flickr and also unpublished photographs that NASA has now given us—thousands and thousands of photographs. We've been working for the last three years to develop machine learning techniques that would allow the automated tagging of people, places, and objects in the photos. But they were taken essentially randomly. They weren't taken at precise intervals. How do we even characterize what the potential problems might be with that? One way is by doing an actually systematic survey of the material culture of the space station over the short term. That's what SQuARE is.</p>
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<img alt="Photo of 3 astronauts with numbers labeling objects and people in the scene" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/iss018e043629_9452806214_o_v3.width-990_xdqMU3n.jpg"/>
<figcaption><p>A NASA astronaut, a JAXA astronaut, and a Hungarian-American space tourist pose in the Russian service module Zvezda in 2008. The wall behind them is decorated with items including flags, mission patches, portraits of Soviet space heroes, and Russian Orthodox religious objects such as painted icons. Image courtesy of Justin Walsh</p>
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<p>In archaeology, we take soil that’s all the same type, same color, same consistency, and different from what's above it and what's below it or what's adjacent to it, as a group that reflects a particular period of time. We take all of those items as relating to one another, and therefore they are separate from and need to be interpreted differently from what’s above or below. So we're treating each photo that way, because it is a slice of time, separate from the next day or the previous day.</p><p>The fact that we're doing this one picture a day for each of six squares for 60 days, 360 images that were taken systematically at precisely defined locations, will allow us to better understand what the historic photos are all about. And likewise, what's happening in the historic photos—because there's so many of them and such a variety of things going on in them—will help us to interpret what we're seeing in the systematically recorded images.</p>
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<p><b>AG: What have you found so far?</b></p><p><b>JW:</b> We thought that the two experimental areas that we selected probably were not going to show very much change over time because they're basically just racks with scientific equipment. In fact, we were asked, “Are you sure you want to use those areas? Don’t you want to see where more activity is happening?” We had to say no because archaeology is not a treasure hunt. We want to actually see the full range. How would we be able to tell the difference between low activity and high activity if we’re only looking at high-activity areas?</p><p>It turns out that one of those areas <i>is</i> seeing hardly any change. But in one of the other areas, we actually have seen a lot of things moving around. Things are being stored there, like laptops and a video camera. It seems to be kind of a staging area for what's happening next door, a veggie experiment. So that's really interesting, because that shows that when things aren't happening in the location, it can be repurposed.</p><p>Another thing we’ve been seeing in the eating area is books. In one case there's been an actual physical book on the wall, just kind of stuck there for the time being—somebody put it down. But we've also seen an iPad with an e-book that was on. So, in a leisure moment, when you're eating by yourself, maybe you read a book or a magazine.</p><p>The way it works right now is that there's this kind of plate hooked to an adjustable arm. And the plate has some Velcro on the front of it, so that the back of the iPad that has Velcro on it can be stuck to it. And that's fine, maybe that's a good enough solution. But now we have evidence of a different way in which the space is being used. And in future space habitat designs you might want to accommodate it in order to make a better experience. If nobody had evidence that this is how this is being done, we wouldn't even be able to think of solutions.</p>
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<img alt="Two astronauts take a photo of themselves in a small mirror hanging on a cluttered wall of the space station" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/iss066e146542.width-990_gLFl5hC.jpg"/>
<figcaption><p>In an image of a SQuARE sample in a U.S. hygiene area, NASA astronauts Mark Vande Hei and Kayla Barron take a self-portrait in the mirror. Image courtesy of Justin Walsh</p>
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<p>Another aspect of the photo study—we placed a <a href="https://osf.io/preprints/socarxiv/ra4c3/">preprint of this on SocArXiv</a>—is we had all these images from Flickr, 8,000 of them, and helpfully NASA has captioned all of them. We were able to scrape them and peel out particular words: the names of the crew members and the locations. Just with those two pieces of data from each item, for the first time it's possible to map out where men and women are across the International Space Station by module. </p><p>And if we look at nationality by module, it does seem like there are some real results. In the Russian segment, unsurprisingly, Russians make up the majority of people. And unsurprisingly, in the U.S. segment Americans make up the majority of people who are in those modules. So this indicates that in what claims to be an international space station, there are national zones. That's not something anybody has ever been able to show data for. Again, anecdotally you might have expected that to be the case. But we're able to show the reality. And this is because of the way the ISS is managed. Those are official designations. Each agency decides what happens in its own module and what their own crew do. So as a result, you end up with inefficiencies.</p><p><b>AG: You’ve mentioned the future design of space habitats. Do you know if people doing that are watching your project? What kind of questions are they hoping you’ll answer?</b></p><p><b>JW:</b> The ISS is maybe the most expensive building project humans have ever undertaken. A staggering amount of money for one piece of architecture, and $3 billion or $4 billion on NASA alone to maintain it each year. I think that we're looking to be able to give more accurate and more precise descriptions of the functions of different areas and how that relates to what the originally designed and planned functions of those spaces are. It's really important to be able to understand whether people are using spaces the way they're intended. If they're not, how are they being used?</p><p>We have at the moment four different commercial organizations that are planning, designing, building their own space stations, partly funded by NASA. And NASA and the other space agencies in ISS—except for the Russians—are currently already building a new space station that's going to go into orbit around the moon: Lunar Gateway. There are key problems that they're already focused on sorting out. But also, how do astronauts and designers create the conditions that mimic, or are as my colleague Alice says, are surrogates for, gravity? That is to say, handrails, bungee cords, Velcro, resealable bags. Where do we see Velcro building up over time? Those are areas where it might not have been foreseen, where it ended up that the crew realized that they were going to need more “gravity.” First of all, we have to identify those areas. And, second of all, then we have to understand <i>why</i> those areas are requiring “gravity,” because of the kinds of activities that are going on there. And then third, how do we anticipate that for future designs? </p><p>Those kinds of questions, the space station companies really want to know that. Even when they have astronauts on their staff or in their executive boardroom, they still realize that there's a difference between anecdotes and data. So the really amazing thing about this is that, as (terrible pun) out of this world as this project is, it's the rare archaeological project that can actually have concrete and practical implications for the future.</p><p><i>This interview has been edited for length and clarity.</i></p><p><i>Correction: Due to a punctuation error, a previous version of this article indicated that the Russian space agency was building Lunar Gateway. It is actually a project of the four non-Russian ISS space agencies.</i></p>
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<p data-block-key="ahv45">Archaeologists are working to understand how astronauts really use their space on the ISS—and help improve space habitats of the future.<br/></p>

Quinn Brett hikes with her Bomber off-road handcycle on Walter's Wiggles, a steep trail named for its many switchbacks, in Zion National Park. Image Courtesy of Quinn Brett

Adapting national parks for wheelchair hiking

<p data-block-key="y4wi5">The trails through our public lands weren’t designed for wheelchairs, but new wheelchairs are designed for those trails. National Park Service accessibility specialist Quinn Brett wants parks to catch up with wheelchair technology, increasing access to American wilderness.</p>

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