One cable holds the bridge up.
San Francisco has its share of massive earthquakes, but the Bay Bridge, one of the city’s main transit arteries, is not as quake-safe as you’d hope. That’s why, alongside it, the state is building a massive new replacement structure—the largest self-supporting suspension bridge ever built. Jim Giles at New Scientist went to visit the bridge and provides a primer on its engineering:
In a regular suspension bridge, the cables that support the roadway are hung between two or more towers, like a hammock between trees, and anchored at each end by a connection to land. The new bridge is more like a sling. A single cable loops under the roadway, over the tower and beneath the roadway on the other side of the tower. The enormous forces placed on the cable by the road cancel out, leaving a structure that is balanced but not directly supported by a land anchor…
As the [road] segment fell into place it revealed the full length of tower that stands behind it, an elegant structure made up of four concrete pillars. These drop into enormous steel foundations, parts of which were built in Texas and shipped to California via the Panama canal. The pillars are connected by “shear beams”—relatively weak steel components that are designed to break if the towers move. The two roadways, one each for east and westbound traffic, hang from the cables but are not attached directly to the tower. This arrangement means that the four pillars and two roadways will sway when a quake hits, but remain intact even through the strongest shaking that geologists expect the region to experience over the next 1500 years.
Read more at New Scientist.
Image courtesy of Bay Bridge Information Office.
What’s the News: Scientists have already bent light to make invisibility cloaks and manipulated sound to hide underwater objects from sonar. Now, researchers have come up with a preliminary design for a mesh shield that would let submarines stealthily maneuver through the seas without leaving any wake, they report in a study published online last week.
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What’s the News: Keeping track of what’s happening inside the body often requires a great deal of equipment outside it: Just think of the tangle of sensors in any hospital room. Now, though, engineers have developed an ultra-thin electrical circuit that can be pasted onto the skin just like a temporary tattoo. Once it’s served its purpose, you can simply peel it off. These patches could be provide a simpler, less restrictive way to monitor a patient’s vital signs, or even let wearers command a computer with speech or other slight movements.
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Most archaeologists dig up the past, examining artifacts for clues—but experimental archaeologists build the past from the ground up, testing out what they can make and do using the same tools and techniques ancient peoples did. Brandon Keim at Wired Science has compiled a fascinating collection of these studies, following scientists as they sail the South Pacific on rafts of balsa wood, hunt deer with flint-tipped spears, and build smoky fires to keep warm through the Scandinavian winter (above).
[See the rest at Wired Science.]
Image: Liedgren & Östlund, Journal of Archaeological Science, 2011
Scanning electron micrograph images of the nut (A,B)
and screw (C, D) in the leg joint of a Papuan weevil
What’s the News: Biologists spend lots of time poring over nature’s nuts and bolts. Now, for the first time, they’ve found a biological screw and nut—previously thought to be an exclusively human invention. The legs of beetles called Papuan weevils, researchers report today in Science, have a joint that screws together much like something you’d find in the hardware store.
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The National Palace in Port-au-Prince
after the 2010 Haiti earthquake
What’s the News: To dampen structural vibrations from earthquakes, engineers often place a flexible layer of rubber bearings in between buildings and the soil. Now, scientists are learning that Mother Nature uses a similar technique. A research team has found that a buried layer of mangrove in the Caribbean island of Guadeloupe absorbs earthquake energy, shielding the above ground from soil liquefaction. This discovery could be exploited to help protect new buildings in the Caribbean islands.
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This week China unveiled a new supercomputer that’s pretty darn quick.
The Tianhe-1A machine housed at the National Supercomputing Center in Tianjin reportedly works at the rate of 2.5 petaflops (a petaflop being about a thousand trillion operations per second), and reportedly will take the top spot in the rankings of world supercomputers when the people who attend to this list release the new version next month. That will bump the top U.S. machine down to number 2.
Personally, I’m not going to panic until China leapfrogs the United States on the Princeton Review list of top party countries or People Magazine’s sexiest countries in the world. But the announcement brought talk of American unease about being bested by China, and American alarm over China’s growing technological expertise. So is the vague, festering worry about the Chinese supercomputer justified? Let’s look at both sides of the argument.
Yes
Putting aside the issue of our wounded national pride, some experts say the real concern is whether the United States has the organization to match what China has done. CNET interviewed Jack Dongarra of Oak Ridge National Laboratory, keeper of the former fastest supercomputer, who called China’s achievement a “wake-up call.”
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Worrying about water (and fighting over it, and creatively diverting it) is a way of life in the arid American West. However, according to reports out this week, the ever-precarious water level is nearing a breaking point where the states of the West might have to put emergency plans into place.
Lake Mead, the giant reservoir formed by the Hoover Dam near Las Vegas Nevada, is fast approaching its all-time low level of 1,083 feet set more than half a century ago. Should the level dip below 1,075, things will get serious.
That will set in motion a temporary distribution plan approved in 2007 by the seven states with claims to the river and by the federal Bureau of Reclamation, and water deliveries to Arizona and Nevada would be reduced. This could mean more dry lawns, shorter showers and fallow fields in those states, although conservation efforts might help them adjust to the cutbacks. California, which has first call on the Colorado River flows in the lower basin, would not be affected. [The New York Times]
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The fourth nation to put a person in space, after Russia/USSR, the United States, and China, could be… Denmark?
Denmark indeed. Kristian von Bengtson and Peter Madsen, the leaders of Copenhagen Suborbitals, plan to fire a test flight of their HEAT-1X rocket from the European nation early next week.
This upcoming flight will be an unmanned test flight, but if all goes well, Madsen hopes to be inside the single-passenger capsule named Tycho Brahe for a manned flight in the near future [Universe Today].
The capsule stands about 10 yards tall, and its top is a clear glass dome through which the standing passenger can enjoy the trip to space. (Or at least, try to enjoy it: The cramped passenger will have only minimal arm movement, just enough to operate necessities like a camera, escape hatch, and vomit bag.) The rocket would carry the capsule to the edge of space, where the passenger will be temporarily weightless, and then it will fall in a parachute-slowed descent.
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The National Highway Traffic Safety Administration’s full report on Toyotas and their “sudden unintended acceleration” problem has yet to see the light of day, but the first wave of information from it suggests that driver error—not some mysterious mechanical problem in the electronic throttle control—could be to blame in many, if not most, of the reported accidents.
NHTSA has been studying data recorders from wrecked Toyotas—dozens of them—in their investigation, which will go on for months to come. Those data recorders show that the cars had their throttles open and brakes disengaged at the times of the crashes.
The early results suggest that some drivers who said their Toyotas and Lexuses surged out of control were mistakenly flooring the accelerator when they intended to jam on the brakes [Wall Street Journal].
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When scientists talk up learning about transportation networks from nature, it’s often ants that get the praise for being so much more organized and efficient than we humans with our silly gridlock. But a team of Japanese researchers found, for a new study in Science, that you don’t even need a brain to be to a traffic genius. Single-celled slime molds, they found, can build networks as complex as the Tokyo subway system.
The yellow slime mold Physarum polycephalum grows as a single cell that is big enough to be seen with the naked eye. When it encounters numerous food sources separated in space, the slime mold cell surrounds the food and creates tunnels to distribute the nutrients [Science News]. To test how efficient the mold could be, Toshiyuki Nakagaki’s team duplicated the layout of the area around Tokyo: They placed the slime mold in the position of the city, and dispersed bits of oat around the “map” in the locations of 36 surrounding towns.
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Forget the myths about massive numbers of slaves or Jews building the great pyramids, Egypt‘s chief archaeologist argues this week. He says Egyptian researchers have found the tombs of more pyramid builders, and in those tombs more evidence that free men erected these monumental tributes to the ancient pharaohs.
Zahi Hawass this week unveiled new research on 4,000-year-old tombs found near the pyramids—tombs he says belonged to pyramid builders. Graves of the pyramid builders were first discovered in the area in 1990 when a tourist on horseback stumbled over a wall that later proved to be a tomb [Canadian Press]. These new ones stretch beyond those previously-discovered tombs, and contain a dozen skeletons.
What matters for the historical interpretation, Hawass stressed, is location, location, location. “These tombs were built beside the king’s pyramid, which indicates that these people were not by any means slaves,” said Mr Hawass. “If they were slaves, they would not have been able to build their tombs beside their king’s” [The Times]. In addition, Hawass says that the walls of the tombs (which the builders probably built for themselves) bear graffiti like “friends of Khufu (a pharaoh).”
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1. A tower in Dubai that opens today has earned the title of world’s tallest building with a height of 2,717 feet (828 meters). That’s more than half a mile high. Actually, it grabbed that title during construction back in July 2007 when it passed Taipei 101, which stands 500 meters tall.
2. Until its official opening today, the building’s exact height was a closely held secret known by only a few people. The building’s architects, Chicago-based Skidmore, Owings, and Merril, speculated last week that someone might try to steal the thunder from the big announcement by measuring the building’s shadow to figure out its height.
3. The opening ceremony included another surprise. The tower, which had been known as the Burj Dubai, was renamed the Burj Khalifa, in honor of Sheik Khalifa bin Zayed Al Nahyan, the president of the neighboring emirate Abu Dhabi. The last-minute switch carries a symbolic weight in light of the billions of dollars oil-rich Abu Dhabi has poured into Dubai in order to cover its debts [The New York Times].
4. The Burj is not only the tallest building in the world, it’s also home to the highest observation deck, swimming pool, elevator, restaurant, and fountain in the world.
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