Popular ScienceApril 2014的目錄

PAGE 62What's living inside this sponge? Feed 06 From the Editor 08 A Bit About Us 10 Peer Review Now 13 The amateur telescope, perfected 14 Data-crunching sports gear 16 Ten things we love this month 18 Headlights with lasers! 19 The science behind ABC's Mind Games 20 A lightbulb that can set your circadian rhythm 23 Using iBeacon for good, not evil Next 25 The new age of microscopy 26 How climate change alters spring 28 Nuclear fuel rods for the post-Fukushima world 30 Meet the man who translates animal motion into robots 32 A heartbeat-powered pacemaker 34 Why it's time to stop studying “male” vs. “female” brains Manual 67 A life-size LEGO hot rod powered by air 68 A deadly crossbow crafted from trash 70 Make a pinhole…

Q: WHAT DO YOU THINK IS THE GERMIEST THING IN YOUR HOME? 1. The dark, dank closet that contains my boiler. 2. It's probably my kitchen sponge. I'm terrified of it. 3. Statistically? I suspect it's me. (But I prefer to call them microbes.) 4. Doorknobs. The answer is always doorknobs. 5. The freezer, where I store my collection of heirloom bacterial cultures. 6. My dog, Lola. But I will continue to let her lick me. 7. The refrigerator! I have well-developed science projects at times. 8. Definitely nothing. I was raised by a mother who was obsessed with cleaning. 9. My toaster's crumb tray … that I just discovered existed.…

It's an upcoming type of USB connector that can be plugged into a port in either direction. Hallelujah. Expected in mid-2014, the new standard will deliver the same transfer speed (up to 10 gigabits per second) as its predecessor, with a couple of notable improvements: The plug will be smaller—about the size of current micro USBs—and reversible. Once the standard is complete, device manufacturers will be free to integrate it, and accessory makers will release the inevitable slew of adapters for current-generation connections.…

We like to think of ourselves as rational beings, but there are many ways we can be subconsciously influenced. At least, that's the premise of ABC's new series Mind Games. Christian Slater and Steve Zahn star as consultants who use psychological techniques to manipulate their clients' bosses, co-workers, and family members. Writer and executive producer Kyle Killen pored over scientific research in marketing, psychology, and consumer behavior and found a number of real-world methods the characters can use to bend minds. BY INTRODUCING A DECOY OPTION Coined by Duke professsor Joel Huber, asymmetrical dominance … (a.k.a. the decoy effect) … is a technique Killen borrowed from real-estate marketing. Say you're torn between two very nice but different homes. Hoping you'll choose House A, your Realtor shows you a similar yet…

Cells live in a three-dimensional world, but until recently, scientists using fluorescence microscopes could see them well in only two dimensions. With advances in confocal microscopes, which use pinhole apertures to focus light on several planes, scientists can now view samples with depth, like these human prostate-cancer clusters. Source: Louisa Windus, at Griffith University in Queensland, Australia, studies how cancer cells grow and spread.…

Most gridlock strikes when the quick braking of one driver ripples rapidly down a string of cars. “There is no accident, there is no bottleneck—it is a phantom blockage,” says Berthold K. P. Horn, a computer scientist at MIT. Horn recently developed an algorithm that shows traffic can flow more smoothly when people follow certain rules. Here's what you can do to help: Pay attention to the car behind you, and maintain an equal distance between it and the car ahead. With a buffer, if the driver in front briefly brakes, you won't pass the hiccup along. Drive at the same speed as the cars around you. Accelerating to catch up to the vehicle ahead will result in braking or switching lanes, which may force another driver to slow suddenly.…

On April 8, Bonhams will auction more than 300 pieces of space memorabilia. We have our eyes on these items: Buzz Aldrin used the list—complete with handwritten notes—in preparation for his flight home from the moon. Est. price: $35,000–45,000 Still covered in moon dust, this strap held equipment in place on Intrepid, the second manned lunar lander. $25,000–35,000 An aerospace company built this 1:7 model of Lunokhod 2, a Russian rover that roamed the moon in 1973. $10,000–15,000 The pressure suit dates to Project Mercury, the first U.S. human spaceflight program. $8,000–12,000…

Plate tectonics—the theory that explains the sinking, spreading, and slip-sliding of big chunks of Earth's surface—is a bedrock of geology. But it can't explain what happens to plates once they sink, or account for the forces that drive many of the planet's volcanic hotspots. Today, advances in seismology, geochemical analysis, and computer modeling have enabled researchers to collect a wealth of new geological data about our planet and form a complementary theory of what's going on beneath its surface.…

Next year, robots will land on the moon, competing for the Google Lunar XPRIZE. The contest offers $40 million in rewards, including a $20 million grand prize. Winning is fairly straightforward: Safely land a privately funded spacecraft, move it a third of a mile, and beam back HD-video “mooncasts.” Completing the challenge by December 31, 2015, however, is anything but easy. Organizers have already extended the deadline by a year, and of the 33 teams that initially registered, only 18 remain. Astrobotic, an offshoot of Carnegie Mellon University, survives as a leading contender. The group has finished a two-spacecraft design—Griffin, a car-size lander, and a surface explorer called Red Rover. It has also booked space aboard a rocket that's scheduled to launch in October 2015. Here's how Astrobotic plans to…

There can be up to 25 pounds of lean meat in the fat trimmings of the average beef cow. BPI, a meat-processing company, pioneered the process of extracting it. Meat-product manufacturers use this lean finely textured beef—a.k.a. pink slime—to create packaged ground beef with specific lean-to-fat ratios. Inspect Metal detectors and workers scan fat trimmings for bone and other debris. Grind A machine cuts the trimmings into small, uniform pieces. Refine A second, finer grinder removes sinew and cartilage. Temper A series of tubes warm the product to 102.5°F, a live cow's normal body temperature. Separate A centrifuge spinning at 4,800 rpm separates meat from fat. Sanitize A puff of ammonium hydroxide raises the surface pH of the meat to inhibit microbial growth. Freeze The meat is frozen and formed…

Since electronic cigarettes hit the market in 2007, yearly sales have reached $1 billion in the U.S. Although they're popular, it's still unclear how safe they are. Last year, a study from an international group of scientists showed that the toxins in e-cigarette vapor are 9 to 450 times lower than in tobacco smoke. The Food and Drug Administration is still determining its regulatory stance. It's sponsoring more research while sorting out its position. LED: When the e-cigarette is active, an indicator light glows like a tobacco ember. SENSOR: Some versions have a pressure sensor that detects the airflow of an inhalation. The sensor then turns on the battery, which triggers the heating element. Other e-cigarettes are turned on and off with a button. BATTERY: A slim lithium-ion battery, usually…

Equipped with short-range walkie-talkies programmed to specific frequencies, cartel informants called hawks report the movements of Mexican police, soldiers, and rival cartels from positions along streets and near border crossings. A string of antennas concealed on rooftops, towers, and in trees—and often hijacked from legitimate businesses—receive and transmit walkie-talkie transmissions from Zetas personnel. A repeater receives radio traffic, then amplifies the signal to travel over greater distances or obstacles like mountains, allowing cartel members to communicate across dozens of miles. By separating incoming and outgoing signals, a duplex repeater lets different units—hawks, drug runners, gunmen—talk over a single channel. Semiautonomous regional communications centers—at least one of which was hidden in a suburban home—are equipped with networked laptops, central processors, and digital receivers to help coordinate the Zetas' local communications traffic.…

EACH YEAR, an estimated 250,000 children worldwide are born infected with HIV. What if hundreds, maybe even thousands, of them are now free of the virus and don't know it? This is the hope that the case of a baby in Mississippi offers. The baby was born to an HIV-positive mother and received antiretroviral drugs within 30 hours. Normally, when a baby is diagnosed as HIV-positive, he or she begins treatment and continues it indefinitely. But the Mississippi baby stopped getting the drugs when she was about 15 months old. By the time she returned to the health care system, she had been off therapy for about a year. Instead of being desperately sick, she showed only a faint trace of HIV. This discovery has led to speculation that the…

The Super Awesome Micro Project, a full-size car made of 500,000 LEGOs, sprung from an unlikely partnership between Romanian tinkerer Raul Oaida and Australian investor Steve Sammartino. The two met over Skype in 2012, and since then, Sammartino has helped Oaida raise money for his ambitious projects, including a jet-powered bicycle. After they saw a video of a Ferrari 599 GTB made of LEGOs, they set out to build something grander. “If you're going to make a LEGO car,” Sammartino says, “you might as well make it a hot rod.” Oaida spent 18 months constructing the compressed-air-powered vehicle and then shipped it to Australia for a test drive. The throttle and steering wheel snapped off, and a few high-pressure air hoses blew, scattering LEGOs everywhere. Oaida's quick fixes got it…

In January, a key patent expired for an ultrahigh-resolution 3-D–printing technology. It isn't a household term now, but it could be after future (and more capable) generations of consumer 3-D printers make it to market. Here's one way it's already being used. CUSTOMIZED SPLINT Three graduate students at the University of California at Los Angeles used selective laser sintering to print a lightweight, breathable nylon splint that provides support where an injured wrist needs it most.…

Wind chill? Heat index? Can't we combine them? Short answer Scientists have—but they don't yet know if it will work. AMore than 100 weather indices have been proposed over the past century in an effort to translate environmental conditions—how cold it is, how windy, how sunny, how wet—into felt experience and physiological risk. Many of these, like the wind chill and the heat index, focus on specific subsets of the variables in play. (The wind chill uses ambient temperature and wind speed; the heat index uses temperature and humidity.) But in the past few years, a group of 45 scientists from 23 countries, led by German meteorologist Gerd Jendritzky, devised what they call the Universal Thermal Climate Index (UTCI)—a simple, single-number weather reading that could estimate how an average person…

Albert Einstein had no shortage of colorful quotes, but my favorite is perhaps his best known. In a letter to the biographer Carl Seelig in 1952, he wrote, “I have no special talents. I am only passionately curious.” When Einstein penned those words, he was already the world's most celebrated scientist, the winner of the 1921 Nobel Prize, and one of the creators of modern physics. Yet he fobbed off his achievements on something as seemingly pedestrian as curiosity. He wasn't alone. Scientists from Newton on have waxed poetic about curiosity's role in discovery. Books extol the virtues of the childlike mind. There's even a design conference dedicated to the power of play. I'm not one to judge, but despite coming from famously scientific minds, this all strikes me as…

For non-astronomers, stargazing may seem simple: Just plop down a scope, and peer toward the heavens. It's usually not quite that easy. Scopes can be tricky to set up and celestial objects elusive. The Celestron Cosmos 90 GT uses a Wi-Fi connection with a smartphone to do the hard work for you. To align it, users point it at any three bright objects in the sky; the scope uses them to triangulate its precise location. Through an app, users then select the celestial body they want to see from Celestron's 120,000-entry database. Motors in the base position the scope in seconds. Telescope aperture 3.5 inches Magnification high-power eyepiece, 91x; low-power eyepiece, 36x Astronomical database 120,000 objects Price $400…

There are headlights that sync to your steering, ones that shift their aim when the road curves, even ones that dim their glare when they sense other cars. But with the new Laserlight system, Audi is returning to the basics: making beams brighter. Engineers replaced standard high beams with blue laser modules. Laser diodes shine through a phosphor plate, which turns the glow white. This creates brights that are three times as powerful as LEDs and can illuminate beyond 500 yards. Brighter lights means better visibility and safer driving. (Don't worry, they also dim when another car approaches.) The lights are already on Audi's R18 e-tron Quattro LMP1 racecar, but because of U.S. safety regulations, their stateside appearance may take a few years. Range 1,640 feet Laser Lens Yellow phosphorus…

It might shine like any other bulb, but the Rhythm Downlight LED from Lighting Science (price not set; available summer) can make users feel energized or sleepy on cue. NASA plans to deploy similar technology on the International Space Station to help astronauts regulate their sleep. (At 17,500 mph, they see 16 sunrises and sunsets every 24 hours.) Scientists at Thomas Jefferson University and the Uniformed Services University of the Health Sciences recorded how volunteers responded to different wavelengths of light from 440 nanometers (nm) to 600 nm. The spectrum they used ranges in color from indigo to orange. Subjects underwent exposure in 90-minute intervals, while researchers recorded melatonin levels in each participant's blood. The team found that blue light measuring 446 nm to 477 nm suppressed production of melatonin,…

As the planet warms, the temperatures that trigger spring arrive earlier. But not everything's adjusting on the same schedule. Flowers open before their insect pollinators come out, and birds return from migration too late to find their usual bug meals. Detailed study of ecological mismatch requires equally meticulous observations of historical timing—and a Boston University lab has found a trove in the journals Henry David Thoreau kept in Massachusetts in the mid-1800s. “They're probably the oldest detailed records of flower and bird-migration times in the United States,” says Richard Primack, a conservation biologist who runs the BU lab. The diaries, together with more recent data, reveal an ecological system in flux. In 2012, plants leafed out a full month early in some parts of the Northeast, as measured by satellite…

Daniel Goldman spends his days working with venomous rattlesnakes, baby sea turtles, and a dozen other types of animals. But he isn't a zookeeper, or even a biologist. He's a physicist, studying locomotion at Georgia Tech. In order to test his hypotheses, he builds robots that mimic the ways animals move. Jealous yet? Popular Science: Why do you have so many sandboxes? Daniel Goldman: No one has ever studied the complexities of a sidewinder rattlesnake's movement on sand, its natural substrate. In principle, you can understand how a hummingbird stays aloft or how a shark swims by solving fluid-dynamics equations. We don't yet have fundamental equations for complex terrain—sand, leaf litter, tree bark. To figure that out, we built giant sandboxes that are equipped with high-speed cameras and can tilt…

In December, a highly publicized study declared that distinctive wiring in the brain explains different skill sets in men and women. After scanning hundreds of participants' brains, the researchers reported that men have stronger connections within a given hemisphere, whereas women have stronger connections between the two. This makes sense, they speculated, because same-side connections are responsible for carrying out focused tasks, such as map reading, at which men excel, whereas cross-brain connections underlie the multitasking and social graces that are most often associated with women. Finally, evidence that men are from Mars and women are from Venus! The trouble is, the study is riddled with faulty assumptions and methodological flaws. Worse still, problems like these taint just about every study that claims to show a “hardwired” explanation for why…

When one tectonic plate is forced beneath another, forming a subduction zone—the cause of many earthquakes—its leading edge sinks deeper into the mantle. The slab descends slowly, mixing molten rock as it goes, and as it nears the core, it partially melts. Most volcanoes begin in the relatively cool upper mantle and shoot up along the rims of tectonic plates. But geologists now think many of Earth's hotspots (in Iceland, for example) are powered by mantle plumes. These plumes rise in columns from the very bottom of the mantle, some 1,800 miles down, and carry heat from near the core to the crust. Plumes originate along the edges of two vast areas—commonly known as piles—that lie opposite one another on the equator, one under Africa and the other under the…

The Wiffle ball has been fooling batters since its invention in 1953, but scientists only recently learned why. Mechanical engineer Jenn Stroud Rossmann at Lafayette College placed the ball in a wind tunnel, measured airflow around it, and concluded that the shifting balance of forces inside and outside the ball is what makes it so devilishly hard to hit. The holes are on just one side. They disrupt airflow, increasing turbulence over that half of the ball. More turbulence means less drag on that side, resulting in an upward “lift” force. Air rushing into the holes creates vortices that whirl inside. The ball's orientation, spin, and velocity all affect how those vortices develop. Vortices create a force that can change the ball's direction.On faster pitches, the interior force typically overpowers…

Surgery has always been synonymous with incisions. But the new snake-inspired Flex System from Medrobotics could reduce bloodshed and hasten healing by traveling through a convenient (if unsettling) alternative: a natural orifice, such as the mouth. During a Flex procedure, the surgeon stands or sits within arm's reach of the patient and a video console, and alternates between steering the robot with a joystick and manually operating the instruments threaded through its tip. Since the bot curves and pivots to maneuver around tissue and organs, Medrobotics claims it's more versatile than laparoscopy, which often requires multiple punctures to insert a camera and tools. The company is now submitting Flex for approval in the U.S. and Europe for head and neck procedures, such as the removal of throat tumors. But the…

Last year, evidence emerged that rockets containing sarin, a clear, odorless, and tasteless nerve agent, had been used in the Syrian conflict, killing hundreds and injuring thousands more. Intelligence agencies are still investigating who launched the attack, but in September, Syria signed the Chemical Weapons Convention—an international post-Cold War agreement prohibiting the manufacture and stockpiling of these arms. The Geneva Protocol had already banned their use, and with good reason: Chemical weapons are classified by the U.S. military as weapons of mass destruction because they're nothing less than airborne poison—delivered by rocket—capable of killing thousands of people in minutes. In Syria, sarin was probably mixed in a mobile lab and loaded into a rocket before firing. Some Cold War-era rockets created sarin by combining two nonlethal chemicals in flight. When…

IN 2007, a little-known German doctor applied to speak at a prestigious AIDS conference, claiming to have cured a single case of the disease. He described a 41-year-old man, dubbed the “Berlin patient,” who had had both AIDS and leukemia. The patient received a bone-marrow transplant from an HIV-resistant donor and no longer showed any sign of the virus. Perhaps the conference organizers didn't know what to make of the case. They asked the doctor, Gero Huetter, to present the results on a poster instead of in a talk. So he did. The poster ended up hidden toward the back of a room. “I ran into the poster by mistake. No one was paying attention to it; there was no buzz,” says Stephen Deeks, professor of medicine at the University…

On a recent morning, Noah Fierer, a professor of ecology and evolutionary biology at the University of Colorado, Boulder, found himself standing 1,000 feet above the farmland of eastern Colorado. He was perched near the pinnacle of the Boulder Atmospheric Observatory, a cellphone-tower-like spire built in 1977 to conduct climate and weather research. To reach the top, Fierer and his colleague Joanne Emerson had taken a five-minute ride in the tower's cramped elevator to an even more cramped catwalk 90 stories up. Dressed in hard hats and safety harnesses, the two leaned over to check a small device strapped to a latticework platform. The machine, which they'd installed several months earlier, sucked in air every night, filtered it, and stored the contents for collection every two weeks. It was basically…

English philosopher Thomas Hobbes believed that men living in anarchy would lead “solitary, poor, nasty, brutish, and short” lives. So as much as I'd enjoy rebuilding civilization from piles of trash after an apocalypse, I'd first worry about a way to send petrol-marauding punk rockers scrambling and make infectious zombies take a dirt nap. A gun would do the trick. That is, until my ammunition ran out. Then I'd just have an awkward club. A crossbow, on the other hand, would mean business: The weapon has a fierce reputation for raw power and accuracy, and ammo can be made or retrieved with relative ease. Going into this build, my crossbow knowledge was limited, but I knew I wanted something quiet, compact, and powerful enough to punch through our contemporary version…

Ultralight tents don't have to lighten your wallet.Save a bundle of cash by making one from Tyvek. The breathable, water-resistant material, a favorite of home contractors, weighs less than two ounces and costs about $2 per square yard. Here's how to fashion a featherweight bivouac from the stuff. Materials & Tools: Two 6-foot by 9-foot sheets of Tyvek Home-Wrap, hammer, 1/2-inch grommet kit, 8 lengths of 12-foot-long parachute cord (or thin rope) INSTRUCTIONS: Approximate time: 1 hour Cost: About $25 Difficulty: WARNING: Bad weather could send this temporary shelter sailing. Build and use at your own risk. Lay one Tyvek sheet on the ground, and fold over three inches of each edge. Hammer a grommet into each corner and the center of each folded edge. Tie a parachute cord to…

Why do some birds chirp while others gobble? Short answer It depends on how big they are and where they live. ADifferent bird sounds have different functions. Songbirds use elaborate music to attract a mate or to let rivals know the limits of their territory; other kinds of birds will chirp for food or to communicate a message to their peers, such as the presence of a predator. But there are other factors that determine why songs and calls may not sound so much alike from one species to the next. First of all, there's body size. The sound a bird makes depends on the size of its syrinx, the avian organ for making sounds. A big turkey can make its membranes vibrate at lower frequencies, to form a deeper…

For his feature “Radio Tecnico” (page 48), Damon Tabor spent four years investigating Jose Luis Del Toro Estrada, the man behind a massive, covert radio network used by the Zetas drug cartel. Tabor traveled to Texas and Mexico to interview sources, venturing into cartel-controlled regions. What kept him going? “The fact that [Del Toro Estrada] had built something of such a grand scale and few even knew about it. No one had seen anything like this before.” In 2009, Rebecca Boyle wrote her first story for Popular Science about the moon. This issue, Boyle returns to the subject with a story about the Google Lunar XPRIZE, a moon-exploration competition (page 40). “I was most struck by the idea of this being the robot derby on the moon. There's probably going…

Sports have always been about numbers. We obsessively rank and handicap athletes based on averages and percentages. But while we can tally jump shots or backhands, we've never been able to fully understand why some are successful and others aren't. Now manufacturers are releasing equipment embedded with data-gathering capabilities, allowing a first look into the dynamics of any shot. By and large, the gear will appear unchanged. The Babolat Play tennis racket, for example, has the same weight (300 grams) and balance as the base Pure Drive model—even with a circuit board in the handle. The difference is the mountain of data the equipment collects, much of which can help players improve. For instance, the app for the 94Fifty basketball may offer advice on how to get more arc on…

Speaker maker Bose released a chip that can run noise-canceling software on most cars, not just those with Bose sound systems. It generates sounds that cancel out noise from the engine and exhaust. In January, Mercedes-Benz began retrofitting QR codes on all models from 1990 onward. In a crash, the codes will direct first responders to rescue plans, including the best way to pry the vehicle apart. Husky Corporation, a Missouri company, will introduce a program to test a line of robotic gas pumps in St. Louis. The pumps use a suction cup to open gas caps and a motorized nozzle to deliver the fuel.…

Last June, Craig Federighi, Apple's senior vice president of software, sneaked something big into his Worldwide Developers Conference keynote. On a slide listing features that would debut in iOS 7, an unfamiliar word appeared: iBeacons. An iBeacon is a small module that makes a spontaneous Bluetooth connection with a nearby smartphone to deliver packets of information. In December, stores, arenas, and other venues began to test the hardware, pushing coupons and other location-based information to customers. Like any technology, iBeacon is not inherently good or bad; it's how we use it that will make the difference. To understand iBeacon, it's important to understand the underlying technology, Bluetooth Low Energy (BLE). Unlike previous Bluetooth devices, BLE ones don't need to maintain a constant (and battery-draining) connection in order to share data.…

For more than 50 years, engineers have built the rods that hold nuclear fuel the same way, out of zirconium-based metal alloys. They maintain structural integrity at high temperatures and allow uranium neutrons to escape in order to produce nuclear reactions. But, as Fukushima demonstrated, they have a very serious drawback: At about 2,000°F, the stuff quickly reacts with steam, releasing heat and hydrogen gas that can easily ignite—and then explode. 1 Silicon carbide (SiC) ceramic rods can do everything that zirconium-based ones do. 2 But they are far less reactive with hot water. 3 And they're still strong at 2,900°F and higher. 4 Several companies have been working on SiC rods, including Maryland-based Ceramic Tubular Products, which tested them under accident conditions last year.…

A pacemaker's battery needs to be swapped out about every five to eight years, requiring surgery. Engineers are now working on a device that converts the mechanical energy of a beating heart into electrical energy and could last indefinitely. A prototype tested in farm animals has generated a microwatt of power, enough to keep a pacemaker going. AFlexible polymer holds system in place. BPiezoelectric ribbons harvest energy. CRectifier switches current. DMicrobattery stores energy. ELeads connect battery to pacemaker. FPacemaker controls heart rhythm. Source: John A. Rogers, professor of materials science and engineering, University of Illinois at Urbana-Champaign…

This year, the first fully electric racing series will debut in cities around the globe. Called Formula E, the new Fédération Internationale de l'Automobile (FIA) championship is the zero-emissions complement to the Formula One (F1) international racing series. Formula E will be open to any vehicle that meets FIA technical specifications, an effort to motivate manufacturers to push the bounds of electric-vehicle technology. But for the inaugural season, all 10 teams (each with two drivers) will race just one model: the Spark-Renault SRT_01E. With oversight from Renault, the French company Spark Racing Technology will build 42 of them, incorporating parts from F1 heavyweights Dallara (chassis), Williams (batteries), and McLaren (powertrain and electronics). When the first race starts, in Beijing in September, the SRT_01E will show bystanders just what electric vehicles…

The relatively thin and cool crust forms Earth's surface. TEMPERATURE: Ranges from surface temperature near the top to 1,600°F at the bottom THICKNESS: About 5 miles under the oceans and 25 miles under the continents COMPOSITION: Silicates that take the form of granite and basalt rocks Two thirds of the planet's mass, the mantle is the source of molten rock that rises to the surface during volcanic eruptions and when plates spread apart. TEMPERATURE: About 1,600°F at the top and 4,000°F at the bottom THICKNESS: Approximately 1,800 miles COMPOSITION: Largely silicate rocks containing more iron than those in the crust The ultrahot, metallic core sits at the planet's center. TEMPERATURE: About 4,000°F at the outer edge to 9,000°F at its center THICKNESS: The outer core is 1,400 miles thick. The…

Solar cells typically convert just 20 percent of incoming energy into electricity, in part because they capture only certain wavelengths of light. Researchers at Germany's Fraunhofer Institute for Solar Energy Systems have developed a solar cell that converts 44.7 percent—a new record. It consists of a lens that concentrates sunlight onto four stacked subcells, each designed to absorb a distinct portion of the spectrum. The team estimates it will take them another two to three years to scale up the 5.2-millimeter prototype for use in solar-power plants. Sunlight passes through a multifaceted lens known as a Fresnel. The lens focuses direct sunlight, delivering the power equivalent of 297 suns to the solar cell below. The first subcell, made from gallium indium phosphide, captures photons from the shortest wavelengths of light.…

For more than a decade, the only robot cleared for general surgery has been Intuitive Surgical's da Vinci Surgical System. It costs up to $2.3 million and uses remote-controlled manipulators for precise operation inside the body—but it needs as many as six entry points to reach a tumor. The Flex System builds on bio-inspired research from the lab of Carnegie Mellon University roboticist Howie Choset, a co-founder of Medrobotics. Choset's snakebots can crawl, climb, swim, and roll through different terrains to do inspections and search and rescue.…

ON SEPTEMBER 16, 2008, Carl Pike, the deputy head of the Drug Enforcement Administration's Special Operations Division, watched live video feeds from a command center outside Washington, D.C., as federal agents fanned out across dozens of U.S. cities. In Dallas, a team in SWAT gear tossed a flash-bang grenade into a suburban home and, once inside, discovered six pounds of cocaine behind a stove, and a stockpile of guns. At a used-car dealer's house in Carmel, Indiana, agents pulled bricks of cocaine from a secret compartment in his Audi sedan, while state troopers dragged a stove-size safe onto the lawn and went at it with a sledgehammer. In the coming weeks, the net widened to include caches of assault rifles, a Mexico-bound 18-wheeler with drug money hidden in fresh produce,…

HIV attacks immune cells that express a surface receptor called CD4. The best known is the CD4+ T cell. First, the gp120 portion of a protein protruding from the viral envelope, or virus's outer coat, latches onto CD4. The binding triggers a structural change that exposes another viral protein, gp41. This protein docks with a second surface molecule called CCR5 (or for some cell types, another co-receptor called CXCR4), which enables HIV to penetrate the cell's membrane. The virus then releases its genetic material, which embeds itself in the cell's DNA. The infected cell either begins churning out copies of HIV or silently waits to be activated. Immune cells that carry a mutant form of CCR5 don't allow HIV to bind. Several research groups are trying to mimic this natural…

One morning about a year and a half ago, at my home in Brooklyn, New York, I woke up the usual way: My dog leapt into bed and plopped his face on my pillow. That day, I wondered what came with him. Did living with an animal influence my apartment's microbial composition? To answer that question, I signed up for the Wild Life of Our Homes project, run by Rob Dunn at North Carolina State. Volunteers swab prescribed locations in their living spaces to collect microbial DNA, which is then sequenced to reveal which species appear where. Here's how I compare with 18 other people in the U.S. SWAB LOCATIONS KITCHEN COUNTER FRONT DOOR, OUTSIDE FRONT DOOR, INSIDE PILLOW OTHER PARTICIPANTS My outer doorNot much evidence of soil or plants,…

In a world of digital cameras and instant gratification, photographer Justin Quinnell embraces pinhole photography, a technique hundreds of years old. He uses beer cans and photographic paper to record the gradual shift in the sun's path over the course of several months. Quinnell originally designed his simple beer-can solargraph camera for students at Falmouth University in England, but early experimentation quickly blossomed into a personal obsession. “The indestructibility of a pinhole camera opens up some fun possibilities,” he says. “The only viewfinder you need is your imagination.” Build and deploy your own by following these steps. MATERIALS: INSTRUCTIONS: 15 MIN.Approximate time to build this project Cost: Less than $1 per photo Difficulty: TOOLS: Can opener, pin, scissors, red light, blow-dryer, computer, flatbed scanner WARNING: Wear protective gloves when cutting…

Sean Hodgins enjoys ring smithing, a hobby he adopted from his grandpa, and loves building small electronic gadgets. So he combined his passions to make a ring that turns body heat into light. Hodgins milled a two-finger band out of aluminum—an excellent thermal conductor—to cradle a 6-millimeter by 3-millimeter Peltier module and custom circuit board. The Peltier module converts heat flowing from the ring into a small voltage, and the circuit board amplifies the current. For now, cold weather best illuminates an LED on the ring, but Hodgins is designing a new circuit to make it blink brightly at any temperature. Approximate time: 150+ hours Cost: $200–$250 Heat flows into one side of the Peltier module … … through semiconductors in the middle … … and is rejected by the…

In 1926, the Sunbeam Tiger racecar set the land-speed record at 152.33 mph. But it wasn't the Tiger's speed that secured its spot on the August cover of Popular Science that year, it was the efficiency. The car produced less than one tenth the horsepower of its competitors, but a lightweight body allowed it to reach high speeds on less fuel. Today, some races are abandoning traditional fuel altogether. In September, the FIA will launch the all-electric Formula E Championship. The first car to compete, Spark-Renault's SRT_01E, hits an estimated 140 mph without any gas. Turn to page 36 to learn how it works. 1894 The first organized automobile competition was a nearly 50-mile test drive from Paris to Rouen, France. The winner drove an average speed of 10.2 mph.…