Discover的November 2016目录

Humans have observed supernovas — the violent explosions that herald death for massive stars — for millennia. Now, using precise chemical measurements of seafloor rock and moon samples, scientists have shown that nearby supernovas rained down radioactive iron and potentially influenced life on Earth. Anton Wallner of the Australian National University led a team that measured 60Fe — a kind of iron ejected by supernovas — in sediment and rock samples from the bottom of the Indian, Pacific and Atlantic oceans. The team found that 60Fe levels spiked some 40 times higher in seafloor material that was roughly 2 million years old, with another significant rise 7 million years ago. The researchers suspect each iron spike happened when the fallout from a supernova explosion hit Earth. Another team of researchers…

→“She’s back.” Jackie, our seen-it-all triage nurse, gave me the look. A wave of moaning, a basso profundo, found my body’s frequency and set it vibrating. The source, a 28-year-old woman, lay on the ambulance gurney, clutching her belly. The rumble filled the space around her. The husband, gamely standing by her side, quickly answered the registrar’s questions. Jackie filled me in. “Belly pain. Lots of Dilaudid [an opioid pain medication] last night. Abdominal CT negative.” She raised her eyebrows. “Good luck.” The patient had landed in our hospital the day before in extreme pain, and here she was again. Uppermost in my mind was that 15,000 Americans died last year from narcotic overdoses — most originally hooked by a doctor’s prescription. Ten minutes later, I stood at the foot…

“For the first time in human history, we can do more than just gaze at the stars,” declared philanthropist and high-tech entrepreneur Yuri Milner on April 12. “We can actually reach them.” Milner, a Russian native, was named after cosmonaut Yuri Gagarin, who exactly 55 years earlier became the first man in space and the first to orbit Earth. Milner was hoping to bring another historic first to fruition. At a press conference held atop New York City’s One World Trade Center, he unveiled Breakthrough Starshot, a program with a bold agenda: to launch, within 20 years, a fleet of spacecraft that would within another 20 years reach the nearest star system, Alpha Centauri, 4.37 light-years away. Milner wasn’t just talking a good game; he was backing it with his…

IIt is impossible to fully appreciate the value of a trail until you have been forced to walk through the wilderness without one. There is a practical reason why, for more than a thousand years, after the fall of Rome and before the rise of Romanticism, little was more abhorrent to the European mind than the prospect of a “pathless” or “tangled” wilderness. Pathless wildernesses still exist in the modern world, and at least some have retained their power to elicit dread. I have visited one such place. It lay on the northern rim of a glacial fjord called Western Brook Pond, on the island of Newfoundland, in Canada’s easternmost province. If you want to be taught (however harshly) the blessing of a well-marked trail, go there. To cross the…

Eight years ago, a young male wolverine from Idaho surprisingly showed up near Truckee in California’s Sierra Nevada range. Wolverines had been absent there for 80 years. Discover profiled the animal in March 2014, in the article “Where’s Buddy?” “Buddy” was the nickname given by wildlife biologist Amanda Shufelberger, who works for Sierra Pacific Industries, a lumber company. Young wolverines migrate to empty territories to find mates and start new populations. Buddy set up shop on a snowy mountaintop owned by the timber company. It turned into an odd kind of love triangle. Each winter, Shufelberger kept tabs on Buddy with motion-sensitive trail cameras, which she set near trees baited with raw chicken. She never saw him during the summer or, for that matter, in the flesh. Also, she never…

An iconic example of the Ice Age megafauna of North America, the mammoth went extinct soon after humans arrived on the continent — except for isolated populations. WOOLLY MAMMOTH PHOTO BY STEPHEN WILKES, COURTESY OF THE ROYAL BC MUSEUM AND ARCHIVES, VICTORIA, BC, CANADA One day thousands of years ago, on a tiny island in the middle of the Bering Sea, a woolly mammoth made a fatal misstep. It fell into a pitlike cave with no escape, and there it died. In 2003, another animal entered the cave — with a ladder. As he explored the space with his colleagues, Russell Graham, a paleontologist from Pennsylvania State University, lifted a rock near the back. There he found a single, pristine tooth from the mammoth, oblong and bumpy and as big…

→It’s a chapter of history nearly forgotten: Intrepid merchants and explorers traveled thousands of miles, not along storied caravan routes, but across the great blue expanse of the Indian Ocean, exchanging goods and ideas, forming bonds and challenging our notions about the ancient world. “People think that it must have taken a long time to get anywhere, that it must have been difficult to travel long distances, but that is not true,” says archaeologist Marilee Wood, whose research focuses on the network’s glass bead trade. “This [field of study] is about opening that all up.” In fact, by the time Marco Polo set out to explore East Asia in the 13th century, communities across Africa, Asia and the Mediterranean had been exchanging their wares for thousands of years in a…

IN HIS OWN WORDS It was about 10:30 or 11 at night. Everyone was getting a little tired. We were about to head back, and I saw a frog. It was this little brown frog, pretty nondescript. I jumped into the mud and totally missed it. For the next half-hour, I proceeded to crawl around in the river. Eventually I gave up. It was gone. In 2008, I had one chance to get back to this same location. I couldn’t believe my eyes when I got there. On that very same rock was a little brown frog. I thought I was hallucinating. I dove down and caught it. It was Craugastor milesi, the Miles’ Robber Frog. At that time, only two species of frogs had been declared extinct in Honduras,…

Imagine drilling a hole through Earth, hopping on a train powered by gravity alone and traveling through from one end to the other. How long would you spend on that “gravity train” before popping out on the other side? It’s a question physics professors have been asking students for decades, and they always expect the same answer: 42 minutes, 12 seconds. One graduate student claims to have shaved a few minutes off that traditional travel time. In Science Smackdown, we let a prof and the grad student duke it out. Earth’s Density Is Equal All the Way Through In 1966, physicist Paul Cooper calculated how long the train would spend falling from one side of Earth to the other. People have been thinking about this hypothetical scenario — pondering the…

→One pound a week It’s a common weight-loss goal thought by experts to be reasonable. By that reckoning, I should have lost 780 pounds in the 15 years I tried to lose weight. But I didn’t. Instead, I lost a paltry 25 — an inglorious rate of a half-ounce per week. Or that would’ve been the rate, had I used the entire 15 years to shed those 25 pounds. But that’s not how it happened. I couldn’t lose them, I couldn’t lose them, I couldn’t lose them. And then, suddenly, I could. What flipped the switch wasn’t a diet or an exercise plan. It was a book contract. Because the day I signed it, I quit my job. Working from home, I’d be out of reach of the doughnuts in…

→When you hear that Mississippi is a red state, you think politics, but red also applies to the toll of its cardiovascular disease. Look at the Centers for Disease Control and Prevention’s map of the death rates from heart disease down to the county level across the U.S. Colors range from a healthy pale pink to deep red — those areas are the sickest. Mississippi is bathed almost entirely in crimson. Among Americans 35 and older, Mississippians have the highest mortality from heart disease in the nation, ranging between 450 and 850 deaths per 100,000. By no coincidence, this state also has the greatest portion of African-American residents, close to 40 percent of the total population. Ervin Fox, a Harvard-trained cardiologist and epidemiologist, knows these statistics from multiple perspectives. Fox,…