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Humans kill large carnivores—a category of animals that includes wolves, bears, lions, tigers and pumas—at more than nine times their mortality rate in the wild. Although they may not be our prey in the traditional sense, new research shows that some of the world’s biggest carnivores are responding to humans in a way that resembles how prey animals react to predators. Biologists at the Santa Cruz Puma Project, an ongoing research effort in the mountains of California’s central coast, report that even the formidable puma, or mountain lion, shows its fearful side when people are around....

The plume darkened the skies in Puerto Rico earlier this week, causing some of the highest atmospheric aerosol concentrations the island had ever seen. By yesterday morning, the cloud had begun to creep over the Gulf Coast. Meteorologists say the hazy skies could last into the weekend. This particular plume is among the most extreme on record, scientists have noted. The thickness of dust particles in the atmosphere is the highest observed in 25 years of satellite measurements....

Many scientists are loath to involve themselves in policy debates for fear of losing credibility. They worry that if they participate in public debate on a contested issue, they will be viewed as biased and discounted as partisan. That perception then will lead to science itself being branded as partisan, further weakening public trust in research. But lately some commentators and scientific leaders have argued that scientists should overcome this unease and contribute to urgent debates from climate change to gun control, alerting people to relevant scientific evidence and, in some cases, endorsing particular policies where their data provide support....

COPENHAGEN—Pleasure yachts and tall ships line the wharves and quays of Nyhavn here in the Danish capital. Shipping in Denmark goes back to the Vikings and their long ships that made perilous sea crossings even beyond Greenland. Now what may be the future of shipping is docked around the corner from Nyhavn at Kvaesthusmolen pier, a bright orange and yellow North Sea supply ship from Norway dubbed “Viking Lady”—the first ship to employ a fuel cell in history....

A lot of things we never thought would happen over the last four years have happened. On September 23, when President Trump publicly refused to commit to a peaceful transition of power after the election, once again, many in the nation were shocked. It was a troubling enough statement that the next day, the U.S. Senate unanimously passed a resolution affirming that “there should be no disruptions by the president or any person in power to overturn the will of the people of the United States....

I was riding a bus recently and noticed an older man sitting outside a coffee shop on a busy sidewalk. He had set up a chessboard on the table in front of him, and he watched as people passed by, mostly engrossed in their phones. His eyes kept jumping from person to person, searching for someone to notice and join him for a game of chess. Right before the traffic cleared and my bus moved on, he reached over to make the first move, and then resumed his searching....

Two winters ago, after a spell of burnout landed her in the hospital, Ann began having disturbing dreams. Visions of her father turned into distressing flashbacks from her childhood—scenes of physical and psychological abuse. A single mother of three daughters, Ann, whose name has been changed for privacy, grew up in a town in eastern Germany, an hour’s drive from the country’s capital, Berlin. She spent her childhood surrounded by alcoholics, including her father and her grandfather....

The following essay is reprinted with permission from The Conversation, an online publication covering the latest research. The question of when people first arrived in Australia has been the subject of lively debate among archaeologists, and one with important consequences for the global story of human evolution. Australia is the end point of early modern human migration out of Africa, and sets the minimum age for the global dispersal of humans....

With this week’s bellicose boasting about who has the bigger red button on his desk, an alert Thursday from the Centers for Disease Control and Prevention felt more than a bit on the nose. With the prospect of actual nuclear war breaking out between North Korea and the United States seeming ever more real, the CDC is moving to prepare health professionals and others on what the public health response would be to a nuclear detonation....

During the most recent conference of my professional organization, my colleague Amanda Dilger and I encouraged our fellow clinicians in attendance to offset the carbon cost of their travel. This was in addition to a panel in which we explained to a small crowd of surgeons that climate change is a health issue. Amanda and I are otolaryngologists, but we are also climate activists. Before starting the panel, I was unsure about how it would be received by my fellow surgeons, as climate change had rarely been discussed at these meetings....

Two moons in the outer solar system—Jupiter’s Europa and Saturn’s Enceladus—are becoming the undisputed top targets in the search for life elsewhere in the solar system, scientists and NASA officials said at a press conference Thursday. Beneath their icy crusts both moons have deep, global oceans of liquid water, kept warm by tidal tugs from the gas-giant planets they orbit. Whether anything swims in those oceans remains unknown—but perhaps not for long....

In the 1960s and 1970s, the United States and the Soviet Union conducted unprecedented lunar exploration programs that remain unmatched to this day. The American crewed Apollo landings were complemented by uncrewed Soviet landings, with both yielding revolutionary bounties of scientific data, such as the hundreds of kilograms of lunar rock and soil that the missions returned to Earth. Oddly missing from all those samples, however, was any material that indisputably originated from the moon’s rocky mantle....

Giant, razor-sharp claws seen on herbivorous dinosaurs may have been used for digging, grasping or piercing, a researcher says. The new findings shed light on the changes in claw form and function that occurred as birds evolved from their ancient dinosaur ancestors, the scientist added. Meat-eating dinosaurs such as Tyrannosaurus rex and Velociraptor were all reptiles known as theropods; they relied on sharp teeth and claws to capture and kill prey....

Climate change is warming the Arctic more than twice as fast as anywhere else on the planet. One of the most serious consequences is sea level rise, which threatens nations from Bangladesh to the U.S. But exactly how does melting Arctic ice contribute to sea level rise? Scientific American asked Eric Rignot, professor of earth system science at the University of California, Irvine, and Andrea Dutton, assistant professor of geology at the University of Florida, how changes in this particular northern region are driving the oceans to dangerous heights....

Earth is under constant bombardment by space rocks. When they crash and burn through the atmosphere, most of the debris gets lost to the oceans, while some is buried or gradually weathered away. Nonetheless, plenty of chunks of fallen meteors, or meteorites, are strewn across the accessible parts of the planet. So far, more than 40,000 meteorites have been found and catalogued, and countless more are still out there, waiting to be chanced upon....

On October 4, 2019, the Polarstern, a German icebreaker the length of a football field, sidled up to a thick ice floe above the Arctic Circle and turned off its engines. Soon the sun would set for months. The remaining open ocean around the boat would ice over, and three million square miles of liquid would turn solid in the span of a few short weeks. Were you to have peered down on the ship then, it would have looked like an almond lodged in a bar of white chocolate the size of Australia....

In the African bush in southern Kenya, Lucy King watched an elephant nicknamed Mohican rest under an acacia tree, seemingly nonplussed by an overhead beehive. It was 2007, and King had just published a behavioral study confirming a belief, widely held by Indigenous communities for thousands of years, that elephants are terrified of bees. “I was completely thrown by this,” King says, recalling the day she sat watching the untroubled matriarch....

Plug-in electric cars such as the Chevy Volt and the Nissan Leaf have only just begun to penetrate the U.S. consumer market, but already automakers are thinking ahead to the next technological advance: a car that can recharge itself anytime and (almost) anywhere. Consumers are perfectly happy to plug in phones and game controllers, but many have not yet adapted to the idea of plugging in a car at the end of a commute....

From Nature magazine First, the vet inserts his arm in a shoulder-length plastic glove. Next, he grips an ultrasound probe and slides both arm and probe deep into the rectum of a 500-kilogram rhinoceros. All eyes of those present, including his, are on the ultrasound image on the laptop monitor nearby. As the vet moves the probe over the animal’s intestinal wall, her uterus comes into view on the screen. Even to the untrained eye, it is clear that there is something seriously wrong: marble-sized cysts fill the space where there should be a smooth uterine lining....

Five Western nations late last week announced they would fork over $1.5 billion to an effort designed to speed delivery of vaccines to developing countries. As Scientific American reported earlier this month, officials from Italy, the U.K., Canada, Norway and Russia met in Rome on February 9, where they announced that their governments would commit the funds for vaccines against pneumococcus, which causes pneumonia and meningitis that kill up to a million children every year....