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Choose a legend: The Great Wall of China is the one of the few man-made structures visible from orbit. Or, more remarkably, it’s the only human artifact on Earth visible from the moon. Both are false, say astronauts and remote-sensing specialists. Although the Great Wall spans some 4,500 miles (7,200 kilometers), it’s constructed from materials that make it difficult to discern from space. The unglamorous truth is that the wall is only visible from low orbit under a specific set of weather and lighting conditions....

Ian Wilmut, famed for creating Dolly the cloned sheep, announced recently that he is abandoning the technique to concentrate on a popular new approach: making induced pluripotent stem (iPS) cells. Such cells would get around the ethical and legal issues surrounding embryonic stem cell work, of which cloning, or somatic cell nuclear transfer, has been an integral part. For the Insights story, “No More Cloning Around,” in the August 2008 Scientific American, Sally Lehrman asked Wilmut about his change in focus, whether somatic cell nuclear transfer is still relevant, and what lessons he learned in his experience with Dolly....

In the eyes of many planetary scientists, the surface of Mars’s northern hemisphere has long looked like it once contained an ocean. Now it is “sounding” that way, too. A European spacecraft equipped with sounding radar that bounces radio waves off the Red Planet to investigate its makeup has identified what appear to be sedimentary deposits in the Martian north. The sediments, which could be mixed with ice, would represent the remains of a shallow ocean that existed some three billion years ago, according to a study published in January in Geophy­sical Research Letters....

Is a cure for Alzheimer’s just years away? German researchers report in Science that they developed a drug that may combat Alzheimer’s disease, a neurodegenerative disorder that affects some five million Americans. The new therapy targets beta-secretase, an enzyme on neurons around which plaques (buildups of a protein called beta-amyloid) cluster in the brain. (Such plaques are a hallmark of the disorder and their discovery in a postmortem brain is the only way to confirm that a person had the illness....

AGING MEMORIES Thank you for an outstanding issue with many intriguing articles. In “The Engine of Memory,” by Donald G. MacKay, one anecdote triggered a long-forgotten memory of my own. When Henry Molaison, MacKay’s famous subject, replied “compass” when the answer was supposed to be “protractor,” he may have been answering correctly, depending on what was taught in school. In the early 1950s, when I was in elementary school in Louisiana, we were asked to bring in some math supplies, which included a “compass....

America is an absurdly backward country when it comes to passenger trains. As anyone who has visited Europe, Japan or Shanghai knows, trains that travel at nearly 200 miles per hour have become integral to the economies of many countries. With its celebrated Tokaido Shinkansen bullet trains, Central Japan Railway has for the past five decades carried billions of passengers between Tokyo and Osaka in half the time it would take to fly....

Editor’s Note: This story was originally posted in the January 2004 issue of Scientific American. Thirteen years ago, in an article for Scientific American, the late Mark Weiser, then my colleague at Xerox PARC, outlined his bold vision of “ubiquitous computing”: small computers would be embedded in everyday objects all around us and, using wireless connections, would respond to our presence, desires and needs without being actively manipulated. This network of mobile and fixed devices would do things for us automatically and so invisibly that we would notice only their effects....

Given the billions of food items that are packaged, purchased and consumed every day in the U.S., let alone the world, it is remarkable how few of them are contaminated. Yet since the terrorist attacks of September 11, 2001, “food defense” experts have grown increasingly worried that extremists might try to poison the food supply, either to kill people or to cripple the economy by undermining public confidence. At the same time, production of edible products is becoming ever more centralized, speeding the spread of contaminants—natural ones or those introduced purposely—from farms or processing plants to dinner tables everywhere....

How to Build a Dinosaur: Extinction Doesn’t Have to Be Forever by Jack Horner and James Gorman. Dutton, 2009 A more accurate title would be How to Genetically Modify a Chicken. But How to Build a Dinosaur is definitely catchier—and harmless. The subtitle is less sanguine. Extinction, certainly of really ancient creatures, is forever, as the authors themselves make clear. But back to that chicken. Horner, a well-known paleontologist (his co-author is a writer for the New York Times), confides that he has kept a chicken skeleton at hand wherever he has worked, because it looks like a dinosaur....

A mysterious disease that is turning sea stars to goo has taken off along the Oregon coast, with up to half or more of the creatures being infected in just the last few weeks, scientists say. Until now, Oregon was the one state along the U.S. West Coast essentially spared from the disease. In April, researchers estimated less than 1 percent or so of the purple ochre sea stars (Pisaster ochraceus) living within 10 sites along Oregon’s intertidal zones — which provide an easily accessible place to monitor sea stars — were affected by the wasting disease....

“The records kept by the Hartford Steam Boiler Inspection and Insurance Company show that 170 steam boilers exploded in the United States last year, killing 259 persons and injuring 555. The classified list shows the largest number of explosions in any class to have been 47, in sawing, planing and woodworking mills. The other principal classes were in order: paper, flouring, pulp and grist mills, and elevators, 19; railroad locomotives and fire engines, 18; steam boats, tugboats, yachts, steam barges, dredges and dry docks, 15; portable engines, hoisters, thrashers, piledrivers and cotton gins, 13; ironworks, rolling mills, furnaces, foundries, machine and boiler shops, 13; distilleries, breweries, malt and sugar houses, soap and chemical works, 10....

Nearly 100 years ago, a physician opened a school in a poor section of Rome. In doing so, Maria Montessori went beyond being the first female doctor in Italy and became the pioneer of a new method of education. A curriculum based on close observations of children, the Montessori method includes an individualized curriculum and no grades, among other innovations. And a new study among children from Milwaukee seems to show that it delivers significant benefits over traditional public schools for the youngest students....

We all multitask, but some of us are especially good at it. This test helps researchers identify “supertaskers,” those rare individuals who can execute several mental tasks at once without missing a beat. Are you one of them? To understand your multitasking mind, read “Top Multitaskers Help Explain How Brain Juggles Thoughts.” For the full version of the supertasker test, click here. The GateKeeper test was created by Andrew Heathcoate of the University of Newcastle and David Strayer of the University of Utah and developed by David Elliot of the University of Newcastle....

HUMAN FAMILY TREE used to be a scraggly thing. With relatively few fossils to work from, scientists’ best guess was that they could all be assigned to just two lineages, one of which went extinct and the other of which ultimately gave rise to us. Discoveries made over the past few decades have revealed a far more luxuriant tree, however—one abounding with branches and twigs that eventually petered out. This newfound diversity paints a much more interesting picture of our origins but makes sorting our ancestors from the evolutionary dead ends all the more challenging, as paleoanthropologist Bernard Wood explains in the pages that follow....

Having spent the better part of a decade looking out from our solar system to survey the Milky Way’s population of exoplanets, NASA’s Kepler space telescope is easing into retirement by turning around and taking a photo of home. On December 10, if you look near the constellation Capricornus, the aging, venerable spacecraft will be gazing back from some 100 million miles away. To raise awareness of the event and as a kind of tribute, some astronomers have started a “#waveatkepler” social media campaign—hoping people around the world will pause, look up and salute the space telescope that since its launch in 2009 has revolutionized astronomy with its search for Earth-like exoplanets....

The case of the Saturn moon Titan’s bizarre “magic islands” has taken an intriguing turn. These strangely shifting island-like features, which NASA’s Saturn-orbiting Cassini probe has spotted in several of Titan’s hydrocarbon seas, may actually be rafts of fizzing nitrogen bubbles, a new study based on laboratory experiments suggests. “Thanks to this work on nitrogen’s solubility, we’re now confident that bubbles could indeed form in the seas and, in fact, may be more abundant than we’d expected,” study co-author and Cassini radar team co-investigator Jason Hofgartner, of NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, said in a statement....

At the height of the drought that gripped the southeastern United States between 2005 and 2007, the water level of the massive reservoir that provides Atlanta’s drinking water dropped 14 feet below normal. The dry spell intensified an ongoing legal battle among Georgia, Florida and Alabama over fresh water supplied by the Apalachicola-Chattahoochee-Flint River Basin, which runs through the three states. But a new study suggests things could have been far worse....

Researchers may have glimpsed a means by which the tuberculosis bacterium could adapt itself to different human populations. The loss of a gene from one strain of tuberculosis (TB) allows the bug to subvert the immune response of its host, potentially explaining why the strain caused an unusually severe outbreak at a U.K. school, researchers report. Related strains are a major cause of the disease in India and among Asians living in the U....

Under stress, we fight or flee, or so scientists have long preached. But this response may really be just a guy thing. New evidence shows how, unlike men, women under stress “tend and befriend,” engaging in nurturing and social networking. At the Cognitive Neuroscience Society 2010 annual meeting in Montreal, psychologist Mara Mather of the University of Southern California and her colleagues asked male and female volunteers to place their hand in ice water, which makes the stress hormone cortisol shoot up....

A private Orbital Sciences-built cargo launch to the International Space Station ended in a fiery explosion just seconds after liftoff Tuesday night (Oct. 28). Orbital’s unmanned Antares rocket exploded in a brilliant fireball shortly after launching from NASA’s Wallops Flight Facility in Virginia at 6:22 p.m. EDT (2222 GMT), crashing back down to the launch pad in a flaming heap. The Antares was carrying Orbital’s unmanned Cygnus spacecraft, which was toting 5,000 pounds (2,268 kilograms) of food, scientific experiments and other supplies on this flight — the third cargo mission to the space station under a $1....