Sommaire pour July - August 2016 de Discover

As we age, the brain gets packed. Sometimes it feels as if it’s just stuffed to the brim. I remember thinking as a new parent about how my son’s brain was primed to soak up everything around him, all his senses firing as he learned things like crazy. It’s fascinating to watch him now at 12, drawing connections between seemingly disparate ideas. And, of course, I already see signs of that common adolescent belief that he does know everything. This special issue — Everything Worth Knowing — isn’t intended to take you back to those middle school hallways. But I’ll bet that for many of us, our knowledge of basic biology or paleontology topped out in high school. While some things we learned about, say, cellular structure, still apply, what…

During the run-up to the Super Bowl in early February, physician Mitchell Berger, the lead consultant to the National Football League on the long-term effects of brain and spine injury, met with the news media. It didn’t go well. Several reporters quarreled with Berger’s assessment of the neurological injury known as chronic traumatic encephalopathy, or CTE. Asked if playing football was “linked” to CTE, Berger hedged on the meaning of link. One newspaper called his statements “shameful.” Even as he spoke, the Hollywood movie Concussion was faulting the NFL for having disputed the discovery of CTE in a retired player 10 years earlier. A book about the controversy, League of Denial, had come out in 2013, and yet here the facts — as reporters understood them — were being challenged…

When it comes to determining the age of stuff scientists dig out of the ground, whether fossil or artifact, “there are good dates and bad dates and ugly dates,” says paleoanthropologist John Shea of Stony Brook University. The good dates are confirmed using at least two different methods, ideally involving multiple independent labs for each method to cross-check results. Sometimes only one method is possible, reducing the confidence researchers have in the results. And ugly dates? “They’re based on ‘it’s that old because I say so,’ a popular approach by some of my older colleagues,” says Shea, laughing, “though I find I like it myself as I get more gray hair.” Kidding aside, dating a find is crucial for understanding its significance and relation to other fossils or artifacts. Methods…

Every embryo begins as a single fertilized egg, which develops into a human body consisting of trillions of cells, each one specialized to carry out specific functions. Since embryonic stem cells can differentiate into any type of tissue, they have the potential to treat an almost unending array of medical conditions — replacing damaged or lost body parts or tissues, slowing degenerative diseases, even growing new organs. Researchers working to understand how to manipulate this powerful tool get their supply from stem cell lines, groups of stem cells derived from animal or human tissue that can reproduce themselves indefinitely. What Are They? Stem cells can morph into all manner of specialized tissue cells. They are prized for their potential to treat many different kinds of medical conditions, as well as…

Inside a dim laboratory at Oregon State University, a glass tank full of living corals glows like a slice of sky during the grand finale of a fireworks display. These species would never share the same stretch of ocean in real life, but they have one important thing in common. “All of these corals are symbiotic,” says Virginia Weis, who chairs the Department of Integrative Biology, peering into the tank with me. “Every single one of them has algae, and without that interaction they would bleach and die.” The corals eat but don’t digest these singlecelled photosynthetic algae, which then reside inside the corals and feed them the carbon sugars created during photosynthesis. In return, the corals not only give the algae a safe berth but also feed the algae…

1 SHAAARK! Did you just get a mental image of a gaping mouth and pointy teeth? Think again. The roughly 500 known species of shark vary in size, shape, environment and diet. 2 Living shark species range from a few that could fit in your hand, such as the dwarf lanternshark, to a few you could fit inside, including the whale shark, which grows up to 40 feet long. 3 Angelsharks are nearly flat, like the rays and skates to which sharks are closely related, while sawsharks have a toothy snout that can be almost as long as their cylindrical bodies. 4 Sharks ply the waters of every ocean, from shallow, brackish estuaries to depths of nearly 10,000 feet. 5 Deep-sea dwelling Mitsukurina owstoni, the goblin shark, is the oldest…

Named after Aeolus, the Greek god of wind, aeolian processes pertain to the godlike ways wind can sculpt a landscape. Over time, fine sediments such as silt or sand are picked up and deposited, building dunes or scouring rock bare. These processes play a major role in shaping exposed areas in deserts and along coastlines. They can be observed on other planets, too: Many of the formations on the surface of Mars are a result of aeolian processes.…

The Birth of Sleep Medicine In 1925, University of Chicago physiologist Nathaniel Kleitman began observing sleepdeprived subjects in a makeshift lab. William Dement joined Kleitman in 1952, using new electroencephalograms to monitor sleeping volunteers. Dement’s wife, Pat (above), was one of the first women to participate. In 1952, when medical student William Dement started measuring brain waves and eye movements of slumbering volunteers at the University of Chicago, the world still held two deep-seated assumptions about sleep: It was a passive state — merely the absence of wakefulness — and if you had trouble sleeping, the cause was probably worry. “We’ve learned that it’s more complicated,” says Dement, now 87, who later founded the world’s first sleep disorders clinic at Stanford University in 1970. He still teaches a class there.…

Imagine the Statue of Liberty, water lapping at her skirts. Or the Sydney Opera House, seawater filling its seats. Coastal areas around the globe are losing ground to the sea — and faster than ever. In the past quartercentury alone, the ocean has risen an average of almost 3 inches. With nearly half the world’s population living within 93 miles of a coast, and much of the globe’s commerce concentrated there, sea level rise looms as one of the greatest of all climate change threats. Given the vastness of the oceans, it may be hard to imagine that warming seas and melting glaciers could raise sea levels enough to inundate thousands of miles of coastline. But adding an inch of water to a full bathtub can still soak the floor…

The Germanic god Odin tended a smorgasbord of divine duties — healing, death, poetry and knowledge among them — but he might have been a somewhat less powerful one-eyed immortal without his animal helpers. According to Norse texts, ravens named Thought and Mind sat on the god’s shoulders, departing every morning to spy on humans for him. The old myths about clever animals may have been closer to the truth than science has been for much of its history. Until fairly recently, animals were considered to be unthinking machines and humans the only truly intelligent species. But aided by new tests that allow animals to show their smarts unhobbled by human preconception, scientists have discovered that there may be more similarities between human and animal intelligence than differences. To paraphrase…

Astronomers are at nature’s whim. They study what they can see on the silk screen of the night sky, and must interpret that as a threedimensional universe. Stars that appear next to each other on the sky’s visual plane could actually be hundreds of light-years apart along that hidden third dimension, depth. Astronomers have done their best to compensate, but sometimes they don’t succeed. It’s been a particular challenge in understanding a specific kind of stellar explosion. For decades, astronomers treated the final bursts of tiny white dwarf stars known as type Ia supernovas like identical blasts, occurring the same way everywhere in the universe. Because of their identical intrinsic brightness, they earned the nickname “standard candles.” Scientists use them as a kind of mile marker for cosmology, measuring our…

Venus’ flytraps evolved in rough neighborhoods where soil didn’t always provide enough nutrients. To survive, they supplement their diets with insects, using a clever counting scheme to snap the trap shut and digest the meal. When a critter bumps into one of the flytrap’s sensitive hairs, the pressure sends an electrical signal racing from cell to cell, priming its jaws to close. Wary of false alarms, however, the plant waits for a second touch. That one snaps the trap shut. As the bug struggles, it keeps bumping into trigger hairs, producing a hormone that activates digestion. Larger, more active insects, with more nutrients to offer the flytrap, hit more triggers. German biophysicist Rainer Hedrich of the University of Würzburg and his colleagues found that flytraps count the triggers to size…

GRUNT: The Curious Science of Humans at War By Mary Roach “For every general and Medal of Honor winner, there are a hundred military scientists whose names you’ll never hear,” writes veteran science journalist Roach. These are the brave men and women toiling to make tastier rations and more hygienic field latrines, among other unsung but much-needed achievements. With her usual dry wit and relentless curiosity, Roach investigates the novel ways some very passionate people try to make war a little less hellish. — ALL REVIEWS BY GEMMA TARLACH COYOTE AMERICA: A Natural and Supernatural History By Dan Flores Historian Flores has written about the American West for decades, so it’s no surprise his gaze should turn to the region’s scrappy mascot. Over the past 500 years, the original desertdweller…

Every month we promise you “science for the curious,” but there’s simply too much happening to cover it all. Albert Einstein himself gave up on the quantum side of physics, and nowadays microbiologists and nanobiologists barely speak the same language. What chance does anyone have of keeping up? That’s where this issue comes in. We’ve taken the liberty of distilling the latest and most important essentials in various disciplines of science: everything from black holes to stem cells to dinosaurs, aimed to keep you in the loop and informed. It is, in short, everything worth knowing. But this guide certainly isn’t the last word. As you wander through the following pages, discovering new facts or remembering old tidbits, drop us a line about what else you want to know at…

350 B.C. Aristotle writes in De Anima (On the Soul) that people are born with a mind like a blank slate onto which experiences are carved. 1885 German psychologist Herman Ebbinghaus creates about 2,300 nonsense syllables, forces himself to memorize lists of them, and tests how quickly he forgets the lists. He compiles his data into an equation that can be plotted on a graph as a “forgetting curve.” His project launches the study of learning. 1920s Psychologist Karl Lashley is among the first to study learning by testing how rats navigate mazes. Before and after training the rats, he randomly removes different parts of their cortices to see which areas are responsible for remembering the maze. Since many of his lesions disrupt memory, he reasons that memories live throughout…

There’s a dirty little secret in paleoanthropology: What we know about human evolution is that we don’t know much of the story. Let’s be clear: That Homo sapiens evolved from earlier hominin species isn’t in question. Although the fossil record is incomplete, we have more than enough to see that, in broad terms, our big-brained, long-limbed, built-for-distance-walking species evolved from arboreal ancestors with smaller brains, larger teeth and broader chests. We can also say, more confidently than even a few decades ago, that our family tree isn’t a tall pine, with a single trunk progressing upward to a lone pinnacle (us). Instead, the story of hominin evolution is a gnarly tree with multiple branches, some of them tangled through interbreeding. “Our provisional family tree shows typically several hominids were living…

Up until last year, mathematician Peter Bierhorst had hoped the physicists he works with would fail. It was nothing personal. He just found their worldview a little disturbing. Like most physicists, his co-workers believe that our universe’s particles can influence each other using a sort of telepathy. Called “entanglement,” this connection allows two particles separated by vast distances to behave as a single entity. Both instantly react to something that happens to one of them. If you find this very weird and counterintuitive, you’re not alone. “I find this very weird and counterintuitive,” says Bierhorst, a postdoc at the National Institute of Standards and Technology. Albert Einstein felt the same way. Unfortunately for them, experiments have finally showed beyond a reasonable doubt that entanglement exists. The current record for largest…

Medical imaging, at its very core, is about your very core. It allows physicians to view anatomical structures throughout your body to find disease or injury — or better yet, rule them out. This function is so basic to medical practice that The New England Journal of Medicine named body imaging one of the most important developments of the previous millennium. And just look how far we’ve come. ➊ Anatomical Drawings INVENTED: circa 275 B.C. BACKGROUND: Human dissections were taboo in ancient Greece, the birthplace of Western medicine. That changed briefly after the founding of Alexandria, a heady time and place for cultural and scientific exploration. When the ban on human dissections was lifted for a few decades, a doctor named Herophilus opened up hundreds of bodies and made detailed…