DiscoverJuly/August 2019的目錄

When day-to-day life grinds along in its own way for each of us, it can feel like we’re rolling through in the muddled-up middle. No clear definition, not much stark contrast. But slow down and look a little closer, and it’s apparent that life is full of extremes. Often, they’re just too big or small to catch our eye. Some of these extremes we take for granted. For others, we aren’t even aware they’re chugging along, invisible to us. A theme of extremes runs through this annual special issue — consider it the Everything Worth Knowing section on life at the edge. Take the sun, certainly an extreme environment. Or the moon, which is extreme in a much different way. Or the nature of flight, and how it manifests in…

IT WAS 1975 on the Caribbean island of Basse-Terre, part of Guadeloupe. Beyond a green stretch of jungle, the volcano La Soufrière de Guadeloupe loomed. The island’s capital, also called Basse-Terre, lay nestled between the ocean and the towering peak, which hadn’t had a major eruption since around 1530. But that July, La Soufrière began showing signs of life. Debate ensued among seismologists over the chances of a major eruption; some saw evidence that molten magma below the Earth’s crust was rising. By November, authorities were scrambling to craft an emergency plan for the city and the surrounding area, then home to roughly 75,000 people. In August of the following year, at least 72,000 residents were evacuated. But no magma came. The evacuation itself proved more destructive, costing $342 million…

The Power of Representation Thanks to advances in big data, health experts and researchers can glean genetic insights from large populations of people. To do this, they conduct what are called genome wide association studies (GWAS). GWAS rely on databases that house huge amounts of information. However, most of the information in these databases comes from people of European ancestry — a feature that doesn’t translate well if you’re studying other populations. Researchers from the Broad Institute of MIT and Harvard and Massachusetts General Hospital demonstrated this phenomenon in a recent paper in Nature Genetics. The team analyzed information from one of the largest publicly available genetic data sets, the UK Biobank. Specifically, they looked at polygenic scores, which can predict someone’s risk for developing conditions like breast cancer or…

WHETHER HUNG ON CLASSROOM WALLS, put up in dorm rooms or screen-printed on T-shirts, the periodic table of elements screams, “Science!” like no other image. And why not? At 118 members and counting, the table lists every known chemical element, the (mostly) immutable building blocks of all materials in the universe. But it’s not just a random list of elements. The organization of the periodic table reveals an element’s behaviors and characteristics: from atomic size, density and abundance, to how it would likely interact with others. Take this opportunity to gaze upon the periodic table and see for yourself some of its hidden insights. Elements 101 Everything is made up of atoms, and atoms are made up of their own tiny particles: Electrons flit semi-randomly around a central nucleus, which…

A WHOLE NEW WORLD Saturn’s moon Titan may be an alien landscape, but as this artist’s rendering suggests, it can still be a familiar one: The world has its own analogs for Earthly weather, such as dust storms and lakes of liquid methane. Now scientists are investigating whether Titan may be home to its own version of life, too. Read about these efforts, which include other moons and exoplanets, on page 80. And starting on page 86, see the coins that suggest humans have been memorializing solar eclipses for millennia.…

Titan’s thick haze at lower altitudes is the result of chemical reactions between incoming energy (sunlight and energetic particles from Saturn) and molecules in the moon’s upper atmosphere such as nitrogen and methane. These reactions — which incorporate elements such as carbon, hydrogen, and nitrogen — create lighter carbon chain molecules (middle box) that eventually form larger organic molecules that scientists believe sink to the moon’s surface. However, not all of these reactions are known or understood yet, and the signs of life may be buried within data yet to be analyzed from the Cassini mission.…

Moral vs. Material (“The Happiness Dilemma,” March 2019) Maybe what evolution is telling us is that we are looking for happiness in all the wrong places. The examples used in von Hippel’s article — the next mastodon, the new car, the next raise, winning the lottery — all play into the fallacy that true happiness resides in the material, the ephemeral. Ask Buddha, Aristotle or even Thomas Jefferson. They would probably tell us that happiness is the result of a moral, well-lived life. Stuart Lynn Worcester, Mass. Lidar’s Past (“A Lost World Emerges,” March 2019) This story was very enlightening and illustrated how light detecting and ranging (lidar) is used to look through vegetation and reveal details invisible to explorers. However, I was surprised the author didn’t mention previous uses…

FOR MOST OF US, WHEN THE SUN’S UP, WE’RE UP. Other critters are nocturnal, operating mainly at night. But not everything falls into those two camps. Many creatures are crepuscular — most active at dusk and dawn — including some species of butterflies, bees, deer, rabbits, even house cats. The trait can allow these animals to avoid extreme temperatures, predators and competition with others over resources. Meteorologists also use the term to describe some types of light rays from the sun, such as the ones that pierce through clouds like spotlights.…

VIRUSES ARE NOT ALIVE, at least in the classical sense. While they’re made of proteins and genes like living things, they need to interact with living host cells to reproduce. These agents of cellular mayhem have been the cause of history-altering outbreaks and pandemics, from smallpox and polio to HIV and Ebola, but were only discovered at the turn of the 20th century. Since then, we’ve found them in nearly every ecosystem worldwide. Viruses are, and always will be, the world’s experts at going viral. So … What Is a Virus? Viruses are ultra-tiny packages of genetic material. A single particle, or virion, of influenza is up to 100 times smaller than common bacteria; you could fit some 15,000 end-to-end across the head of a pin. The outer layer is…

THE UNIVERSE IS FULL OF WEIRD OBJECTS, but pulsars take the prize as the strangest things scientists can study directly. The shriveled remains of once-mighty stars, they’re around a dozen miles across, have approximately the mass of a sun and can spin hundreds of times per second. They’re also made of a poorly understood particle soup for which researchers don’t have the recipe. Here’s what we do know: Pulsars are a type of neutron star, the dense core left over after a supernova — a stellar explosion. Astronomers can see pulsars only because electromagnetic radiation, especially radio waves, streams from their magnetic poles. As the pulsars spin, these streams point, once per goaround, at Earth. They sweep over our planet like transient lighthouse beams, and telescopes pick up each one…

WHETHER ANIMAL, vegetable, mineral or machine, everything experiences stress — broadly defined as challenges to equilibrium, a balanced state of being. The Human Stress Story In biology, stress is the body’s response to perceived threats to our physical or mental well-being. Moderate amounts are healthy and normal. But too much — or too little — causes problems. Chronic stress is linked to cardiovascular disease, anxiety and depression. Stress associated with extreme events such as combat can lead to post-traumatic stress disorder (PTSD). Symptoms of PTSD, which affects over 7 million Americans, include flashbacks and hypervigilance long after a trauma. Meanwhile, recent studies show that people who underreact to stress are more likely to have impulsive behavior and substance addiction. The Adaptive Stress Response A 1936 Nature paper launched the field…

The Great American Eclipse of August 21, 2017, certainly was one for the record books. It became a huge media event, and hotels and even state and national parks were booked to capacity in anticipation. But total solar eclipses have not always been seen with the same kind of awe and wonder. In ancient times, people often experienced great fear and trepidation, and they viewed such events as omens or portents of change. The earliest verifiable eclipse observation was made June 15, 763 b.c., by the Assyrians. This was soon followed by well-documented viewings recorded by the Chinese and Greeks. But it was the Chaldean astronomers of the Neo-Babylonian Empire who first deduced the sun-moon eclipse connection known as the saros cycle. This period, 6,585.3211 days, is the length of…

RESEARCHERS HAVE LONG STUDIED TRANSGENDER PEOPLE — those who don’t identify as the gender that aligns with their biologically determined sex at birth. But until recently, most of the research has focused on adults. Kristina Olson, a psychologist at the University of Washington, is helping to change that. Since 2013, she’s spearheaded the TransYouth Project, a 20-year study following kids who have socially transitioned, a process that effectively transforms them into their selfi dentified gender. This often includes using pronouns that correspond to their identified gender, and altering fashion and hairstyles to match as well. More than 300 children from the U.S. and Canada are participating, all between the ages of 3 and 12 when they started the study. Already, Olson and her team have found that the kids’ gender…

THE FIRST WAY WE LEARN TO COMMUNICATE is through body language — our facial expressions, our gestures and, when we’re older, our postures. Even after we figure out how to speak, this non-verbal communication still exerts a powerful and often unconscious influence over our interactions, people’s first impressions of us and even our impressions of ourselves. A Learned Body Language? David Matsumoto, a San Francisco State University psychologist, led a 2008 study to determine whether body language is innate or learned in childhood. He and his team examined Olympic and Paralympic athletes from over 30 countries. Specifically, they studied judo competitors who could see and those who’d been blind since birth. It turned out all athletes made similar gestures when they won — arms raised wide, chest out, head tilted…

WHEN THE WRIGHT BROTHERS took to the skies in 1903, they were relative latecomers — insects already had been buzzing around for 325 million years. But in a little over a century, our species has more than made up for its Earth-bound origins, visiting every planet in the solar system and even penetrating interstellar space. FEATHERS Like modern bird plumage, the feathers of Archaeopteryx are asymmetrical, a geometry that can generate aerodynamic lift by pushing air under the wing. BREAST Archaeopteryx lacked the modern bird’s prominent breastbone, which anchors flight muscles and guides the tendons that facilitate a rapid upstroke. Arm muscles appear to be more broadly distributed in Archaeopteryx, even running along the belly, probably making flying more arduous than it is for modern birds. SHOULDER The shoulder joint…

CHRONOSTRA-WHAT? The long word may be new to you, but you’ll find the concept familiar. Case in point: Jurassic Park. You can thank chronostratigraphy for the name, even though any dino nerd will tell you it should have been called Cretaceous Park. That’s because most of the animals in the park, including T. rex, lived around the end of the Cretaceous, tens of millions of years after the Jurassic. How do paleontologists know that? Thank chronostratigraphy for that one, too. During 18th-century mining explorations and early 19th-century fossil digs, expeditioners noticed similarities in rocks over large geographic areas. And so stratigraphy — the study of layers (strata) of rock in relation to each other — was born. Chronostratigraphy is a modern offshoot of this discipline, organizing these dateable rock layers…

Iceland, which sits atop the geologically active Mid-Atlantic ridge between tectonic plates, generates about 27 percent of its electricity from geothermal energy. Deep wells tap underground reservoirs of pressurized water, providing steam to power turbines at Iceland’s six geothermal plants. If you’ve ever grabbed a self-service meal or eaten at a buffet, you’ve seen a steam table, which keeps prepared food warm on the bottom and four sides of a food pan. Steam transfers heat five times more efficiently than water and 12 percent better than air. Heron of Alexandria is thought to have invented the first steam engine in the first century A.D. His aeolipile, or “wind ball,” consisted of a sealed spherical container filled with water and heated over an open flame. Steam jetting from two pipes on…

Water is a polar molecule consisting of two hydrogen atoms and one oxygen atom. The oxygen atom in one water molecule tends to be attracted to a hydrogen atom in a neighboring water molecule, and vice versa, giving water its unique properties. These properties are essential for the chemistry of life on Earth. For the chemical processes of life to happen, molecules must be able to connect, separate, and reconnect in specific ways. Think about DNA replication, for instance. The base pairs that make up the genetic code bond when their negatively charged hydrogen atoms are attracted to positively charged atoms in another nucleotide. Those bonds hold the two strands of the double helix together, but because the hydrogen in water molecules also bonds this way, it’s relatively easy for…

“Our lifestyles are killing microbial diversity.”—Maria Gloria Dominguez-Bello, microbiologist In the Amazon rainforest of Venezuela, Yanomami huntergatherers subsist on cassava, palm hearts and wild banana. They also hunt frogs, monkeys and tapirs, using techniques that probably would have been familiar to their ancestors 11,000 years ago. The extraordinary continuity of their culture, and the fact that some of the groups have had scant contact with outsiders, led biologists to wonder whether the Yanomami might reveal what the human digestive system looked like before industrialization supplied the world with processed foods and antibiotics. In 2009, researchers had a chance to find out in a previously unknown Yanomami village. Health workers collected fecal and skin samples from about 30 villagers. When researchers cultured and analyzed microbes in the feces, the scientists discovered…