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News and Trends
April 16, 2007


Sinkholes
Follow the Money
Drawing Lines in the Sand
Navy SEALs Get Backup
Byzantine Podcasts
Space Junk

Sinkholes
They gobble up people, trucks, roads, buildings, even entire lakes. The insatiable monsters known as sinkholes occur when water erodes underground rock and causes the ground above to collapse. Increasingly, the culprit is bad pipes, as many of America's century-old water and sewer lines spring leaks. Water utilities are trying to educate the public and urge elected officials to allot more money for repairs. Stephen P. Allbee of the Environmental Protection Agency says neglect can be as fatal to a water system as a terrorist attack. "You can lose the system all at once because of terrorism," he says, "but you can lose it over time by just not taking care of it."

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Follow the Money
Do you know where that crumpled dollar bill in your wallet has been? Dirk Brockmann, a physicist at the Max Planck Institute in Germany, might be able to tell you. Brockmann was looking for a way to track human travel patterns—the paths people trace when moving around byfoot, car, train, or plane. An American friend told him about Wheresgeorge.com, a popular Web site that tracks U.S. paper currency. Users enter the series and serial numbers of bills along with their ZIP code. As more people do this, it creates a record of where each bill has traveled. And where the bills travel, so do people. Using data from the site, Brockmann and his team were able to create a mathematical model for predicting the probability of a bill—and its spenders—staying within a10-kilometer radius over a period of time, compared with the probability of traveling 100 or 1,000 kilometers over the same period. These patterns may help scientists predict how epidemic diseases like avian flu and measles spread.

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Drawing Lines in the Sand
Brazilians say the beach is their "most democratic space." But class and racial divisions are still there. Rio de Janeiro's beaches are subdivided by 12 lifeguard stations, or postos. Each has its own culture and may be hostile to outsiders. At the top is Posto 9, with its celebrity "in" crowd. Middle-class families stay between Postos 11 and 12. Posto 7 is a surfer hangout, but it also attracts people who arrive by bus from working-class suburbs. Surfers often make fun of their drab straw mats and picnic lunches. "Most people treat you OK," says one man who occasionally visits the beach with his wife and children, "but some are really prejudiced, even racist."

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Navy SEALs Get Backup
The U.S. Navy may soon deploy sea lions and dolphins to patrol a naval base in Washington State. The animals would help guard ships and submarines at the Kitsap-Bangor Naval Base on Puget Sound from attacks by swimmers and divers. Sea lions carry cuffs attached to long ropes in their mouths, and can attach the cuffs to a swimmer's leg. The person can then be reeled in. With their keen sonar abilities, dolphins are able to detect people in the water. Animal-rights activists object to military use of marine mammals, saying that the animals are being deprived of their natural habitat and social structure, and do not provide a reliable defense system.

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Byzantine Podcasts
By day, Lars Brownworth teaches high school history at the Stony Brook School in Long Island, N.Y. By night, he writes and stars in his own series of podcasts—12 Byzantine Rulers—covering 1,200 years of Byzantine history, from the reign of Diocletian in 284 to Constantine XI in 1453. Brownworth's series has routinely been in the top five educational podcasts on iTunes, and the top 50 over all. Last December, when Wired magazine cited it as one of the nation's most influential podcasts, 12 Byzantine Rulers drew 141,000 hits. "I can't believe it's that many people," Brownworth says of his global audience. "I always thought the only one listening was going to be me."

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Space Junk
Dead satellites, rocket stages, cameras, hand tools—those are just a few examples of space junk. Early this year, the number of "observable objects" (four inches wide or larger) orbiting the Earth reached 10,000. On January 11, China added to the clutter when it tested an anti-satellite rocket, which blew an old satellite into hundreds of fragments. As the debris increases, so does the danger to spacecraft. Experts have long worried that a piece of debris will smash a large spacecraft to bits and start a chain reaction. This series of collisions could continue to expand for centuries, putting billions of dollars worth of satellites at risk.

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