Tabla de contenidos para Jul-Aug-10 en Science Illustrated

Italian scientists have found a way to map a city—despite the fact that it's been buried for centuries. The ancient Roman city of Altinum was abandoned between A.D. 400 and 600, when invaders drove out its inhabitants. As the city's residents moved onto the islands of a nearby lagoon, founding the city of Venice, Altinum was covered by floodwaters and soil. Although archaeologists have long known that Altinum existed just north of Venice, they haven't been able to get a good look at the remains of the city until now. In 2007 researchers at the University of Padua took aerial photos of the area during a drought using near-infrared radiation. Healthy plants appeared as a different color than crops struggling in the dry conditions. The photos revealed the outlines of…

A Greek explorer, Eudoxus of Cyzicus, made the first known attempt to sail the entire perimeter of Africa in the 2nd century B.C. His first boat ran ashore, and his second expedition was lost. No one tried again until the late 1400s. The word comes from the verb “compute,” meaning to determine, especially by mathematical means. That word comes from the Latin computare. “Computer” was first written in 1646 by English author Thomas Browne to describe a person who computes. Peter Henlein, a German locksmith, is thought to have invented the first watches in the early 1500s. Unlike clocks, these used springs instead of drive weights, allowing them to be small and portable.…

Brad Norman has loved the ocean since he was a little boy, but after a surreal encounter with a feeding whale shark, he decided to dedicate his life to protecting the species. The Australian marine conservationist encountered the massive fish in 1995 while conducting master's-degree research at Murdoch University in Australia. As it passed, the whale shark ignored Norman completely. “I was laughing into my snorkel,” he says, recalling “a mix of excitement and relief.” Soon he was diving with the species regularly, intrigued by how little researchers knew. These gentle giants, which can grow to 60 feet long during their lifetime, sport glowing white spots on their skin. Norman thought the markings might be used to identify individuals just as fingerprints identify humans. Before a 1986 review, Norman soon…

The tides are controlled by the gravitational pull of the moon and the sun. The moon is the major player, causing water to collect at the points on the Earth that are closest to it and opposite it. This results in high and low tides approximately two times a day. Features on the Earth's surface can affect the height and speed of the tides as well. The tides flow over an uneven ocean floor and around uneven landmasses, sometimes spreading out over an especially deep or wide body of water and sometimes funneling into especially shallow or constricted areas such as bays, inlets or even rivers. This funneling often causes choppy waves, whirlpools and fast-moving currents—like the nearly 9mph stream at the European Marine Energy Center's Eday test site in…

When a nerve signal causes a muscle to contract, it begins to produce chemicals called myokines, such as IL-6, which have many beneficial effects on the body. 1. An increase in muscle calcium (Ca2+) activates transcription factors to go to the cell nuclei, where they may turn on genes that produce myokines. 2. Increased energy production by mitochondria in muscle cells creates chemically reactive waste products, ROS, which could stimulate the generation of myokines.…

July of 1913 was not an especially hot month in California, but one day, in a little valley hidden behind tall mountains, the mercury climbed to an incredible 134°F—the highest air temperature that had ever been recorded anywhere in the world. That blast furnace of a place is called Death Valley, now part of a national park. (The record has since been eclipsed, but just barely: The Libyan desert once reached 136°.) Because of Death Valley's very special geological conditions, it remains one of the hottest, driest and lowest pieces of land on Earth. On average, temperatures soar above 90° for seven months of the year. Some years are even hotter. In the summer of 2001, there were 154 consecutive days of 100° or higher, and 1996 saw a stretch…

A nearly century-old dream of space exploration is moving closer to reality as the Planetary Society in Pasadena, California, plans its second attempt to send a spacecraft sailing toward the stars powered entirely by energy from light particles. In the 1920s, Russian scientists Fridrich Tsander and Konstantin Tsiolkovsky first contemplated solar sails. In the 1950s and '60s, a number of researchers theorized that the pressure from light, or photons, reflecting off an ultrathin foil sheet on a spacecraft would push the craft forward. The Planetary Society attempted the world's first launch of a solar sail into space in 2005, but the Russian rocket carrying it exploded over the Barents Sea. Shortly after the failed launch, the Society took over Nanosail, NASA's solar-sail R & D program, which was about to…

Q How big can carnivorous land mammals grow? A Theoretically, around 2,425 pounds for terrestrial mammals, according to models developed by researchers at the Institute of Zoology in London. That number takes into account the fact that larger animals need to eat more, and that carnivores spend much more time and energy looking for (and killing) food than herbivores do. Carnivores face energy-based challenges related to their size: The larger a predator becomes, the more difficult it becomes to take in enough calories. Once mammals exceed about 44 pounds, they can generally meet their energy needs only by eating prey of their own size or larger. Large prey provides significant food and energy but also takes more energy to hunt, and this imposes a limit on the maximum size of…

On December 2, 1989, a private twin-engine plane traveling from San Diego crashed near a regional airport in Ruidoso, New Mexico, killing the pilot and his wife. Investigators found no defects in the engines and attributed the crash to pilot error before storing the wreckage in a yard outside the airport. Attorneys for the children of the couple later salvaged some of the plane parts and conducted their own investigation, turning up a small mass of plant matter in one engine's fuel lines. They sued the plane's manufacturers, asserting that the engine sucked in the vegetation during the aircraft's flight or approach, clogging the fuel line and causing power loss. Filters, they claimed, would have prevented the crash. In an unusual move, the defense attorneys called in palynologists—experts on pollen…

Wave power has always lagged behind tidal power, which takes advantage of the slightly more predictable nature of currents and has more similarities to wind power. Wave power suffered a setback in 2008, when a principal investor in a wave farm off the coast of Portugal—the first ever to deliver power to the grid—went bankrupt, forcing the farm to shut down after just a few months at sea. But supporters of wave power haven't been discouraged. “We learned a huge amount from the Portugal project,” says Max Carcas of Pelamis Wave Power, the Scottish company responsible for the design and manufacture of the equipment used at the Portugal farm. “We're keen to move forward,” he says. The company is partnering with the English energy supplier E.ON UK to install and…

Scientists can't weigh a star on a scale, but they can, with the help of gravitational formulas, find a star's mass, or the amount of matter it contains. (Weight is a different measurement: the force that gravity exerts on a mass.) This knowledge helps astronomers and cosmologists understand how bright a star shines, plus when and how it will die. The mass of celestial objects, like planets and stars, can be determined by calculating how much gravity one exerts on the other. For example, the mass of the sun can be found by looking at its gravitational pull on the Earth using Newton's version of Kepler's Third Law of Planetary Motion: a3 / P2 = Gm. Here a represents the semimajor axis—the longest radius of an elliptical orbit—of the Earth…

The easiest way to reach the valley is by flying to McCarran International Airport in Las Vegas and renting a car. Taking NV-160 W from the airport should get you there in just over two hours. There are plenty of camping sites in the area, but if you prefer the great indoors, check out Furnace Creek (furnacecreekresort.com) or Stovepipe Wells (stovepipewells.com), the valley's only lodgings. Hydrate: On average, at least one person dies of heat exhaustion every summer in Death Valley, so stock up on water. Death Valley public information officer Terry Baldino recommends at least a gallon per person per day, plus an extra gallon in the car. And don't forget moisturizer and lip balm. Stay Cool: Light-colored clothes and protective gear like hats, sunglasses and sunblock will keep…

Q What gives bird feathers their colors? A Birds can see a larger spectrum of colors than most of us, and they flaunt a variety of eye-catching plumage. Pigments called melanins, carotenoids and porphyrins made in the birds' skin produce most feather colors. Melanins produce black feathers, but depending on the concentration of the pigment granules, they can also range to reddish browns and pale yellows. Bright red, yellow and orange feathers are produced by carotenoids, which birds generally get from eating plants. These pigments can interact with melanins to produce even more colors, like olive green. The final group, porphyrins, appear as a wide range of colors, including brown, pink, red and green. Certain birds, such as parrots, get their bright colors from less-common pigments produced directly in their…

These fish contain special cells called electroplaques that produce electricity through the excitation of nerves. Large numbers of electroplaques in the tail region of the eels form the electric organs, which the animals use to stun their prey. The organs can discharge up to 650 volts, nearly four times the peak voltage produced by a household outlet. English astronomer James Bradley calculated the speed of light in 1725 by measuring changes in the position of stars. He correctly concluded that the movement of the Earth along its orbit, and the fact that light had a finite speed, caused the stars' apparent orbital movement. Squirrels favor acorns from red oaks because they last through the winter without sprouting. Once they sprout, the acorns are less valuable as food.…

Water crashes against the steep, rocky cliffs on the western coast of Mainland, the largest of the Orkney Islands north of Scotland. The waves rolling in from the Atlantic are typically 6 to 10 feet high in the summer. In winter, they can reach 30 feet. It's a perfect home for the European Marine Energy Center (EMEC), a testing ground for wave- and tidal-power installations. Ocean-power generators are simple in theory. Like conventional hydro-electric power plants, which are often located in river dams, marine plants rely on moving water—either from strong tidal currents or big waves—to turn a mechanism such as the blades in a turbine, driving a generator to produce electricity. But ocean-power stations must be able to withstand the heavy currents and unpredictable weather of the open seas.…

Exercise is the cornerstone of good health—it strengthens the heart and lungs and helps us keep our weight under control. Staying active also benefits the body in more-subtle ways, reducing the risk of obesity, diabetes and cardiovascular disease. For example, physical activity seems to ward off insulin resistance, which occurs when cells become less sensitive to the ability of the hormone insulin to decrease blood glucose levels. This resistance can cause a buildup of blood sugar, which may lead to several illnesses, including cardiovascular disease. Sedentary adults are more likely to suffer insulin resistance, a condition that could eventually lead to Type 2 diabetes. And people who don't exercise are more likely to suffer atherosclerosis, a condition in which plaques form on the walls of arteries. The deposits can become…

For most animals, life is a balance between periods in which food exists in surplus and periods of scarcity. The better a species is at dealing with the hungry times, the better its chances of survival. Some animals are hunger artists, so superbly adapted that they can last months or even years without food. Others are at risk of death after just a few days without eating. Efficient energy conservation is the key to surviving long periods of hunger. In order to preserve vital energy, some animals reduce their body temperature. Many of them also cut back on the blood supply to their organs and put their digestive tract and immune system on standby. The tiny Arctic ground squirrel takes energy savings especially seriously. It allows its body temperature to…

atomic number: 79 density: 316.3 grams/cubic inch melting point: 1,947.5°F boiling point: 5,172.8° 42.5 lbs. The weight of a one-liter milk carton filled with gold. That's around the weight of the average five-year-old. 0.0004 ounce of gold may be found in the body of an average adult male—presumably from dietary intake. $1,215.70 At press time, the record high price for gold per ounce, set on December 2, 2009 158 lbs. The weight of the Welcome Stranger, the world's largest gold nugget 2/3 The fraction of the gold supply between 2003 and 2008 that was newly mined. Much of the remaining third was recovered from scrap, such as connectors in circuit boards. 2,485 tons of gold are produced from 400 mines worldwide every year. 0.000000000004 ounce of gold is in each…