Random Samples

Science  28 Sep 2007:
Vol. 317, Issue 5846, pp. 1839

    If you're itching to visit other stars, better zip over to London first. On 15 November, the British Interplanetary Society (BIS) will host a workshop titled “Warp Drive, Faster Than Light: Breaking the Interstellar Distance Barrier.”

    Warp bubble.


    “Warp” refers to the fact that space and time can bend, stretch, and shrink. The conference is based on work by theoretical physicist Miguel Alcubierre, now at the National Autonomous University of Mexico in Mexico City, who in 1994 showed that Einstein's general theory of relativity, which equates gravity with the bending of space and time, could allow for faster-than-light propulsion. He noted that because the universe is expanding, two distant galaxies can move apart faster than light without either one's moving that fast relative to the space around it. Run the film backward, and the galaxies rush toward each other. Combining the effects, Alcubierre showed that in theory, one could move a patch of ordinary space superfast by shrinking space in front of it and stretching space behind it to make a “warp bubble.”

    There's a hitch, however. The scheme requires “negative energy,” which does not exist as far as anyone knows. “The idea was to make a fine point about general relativity, not really to have any practical means of traveling faster than light,” says Alcubierre, who will not attend the conference. Physicist Richard Taylor, a consultant to BIS, says it's still “quite exciting to let real scientists talk about things that are almost off-limits.”


    Following up on an intriguing clue from Vietnam, researchers in Florida are studying whether guava trees can control a devastating plant disease called citrus greening. Spread by aphidlike insects called psyllids, the bacterial disease makes fruit taste nasty and then kills trees. It was first spotted in Florida 2 years ago, but citrus growers have yet to figure out how to beat it (Science, 28 April 2006, p. 523).

    U.S. Department of Agriculture (USDA) researchers recently learned that in Vietnam, orange groves planted with guava trees were disease-free. So they went to look for themselves. “It was pretty much incredible,” says entomologist David Hall. “I never found a psyllid in the interplanted fields.” The USDA team is now planting some 10,000 guava saplings in test orchards. Hall says it will take at least a year to see if these guava varieties, different from those in Vietnam, ward off psyllids in Florida orange trees, which are not planted as densely as they are in Vietnam. Denise Feiber, a spokesperson for the Florida Department of Agriculture, says she's cautiously optimistic but points out that guava trees attract fruit flies, which could complicate the picture. Ultimately, the scientists say, compounds from guava extracts might be used as sprays.


    “Old Man” Patrick Nanudjul, one of the last three speakers of Magati Ke.


    Of 6900 languages spoken in the world today, 6300 are in danger of going extinct, say two linguists who have mapped the world's “language hot spots.”

    Gregory Anderson and K. David Harrison, a visiting professor at Swarthmore College in Pennsylvania, have taken the concept of “biodiversity hot spots” and applied it to languages, using criteria that include “genetic diversity”: the ratio of languages to language families. Bolivia, for example, has as many language lineages as Europe but far fewer languages, which means its language diversity is threatened. Other hot spots are in North America, Siberia, and Australia.

    The pair, who are documenting languages with high-tech equipment from the National Geographic Society, have just returned from northern Australia, whose 231 aboriginal languages—from 50 different language families—are almost all endangered. They found a lone speaker of Amurdag, a language that had been thought extinct, and three known speakers each of two other languages, Magati Ke and Yawuru.

  4. NETWATCH: Keeping Tabs on Aliens

    When you think of an invasive species, the freshwater jellyfish Craspedacusta sowerbyi probably isn't what comes to mind. But the Chinese native has a firm tentacle-hold in the United States and now lives from coast to coast.

    To find out more about this and other aquatic interlopers, visit the NISbase Web site from the Smithsonian Environmental Research Center in Edgewater, Maryland. The site allows you to simultaneously scan nine databases that cover areas as far apart as the Gulf of Mexico, the Mediterranean Sea, and Australia. There are links to images, fact sheets, museum records, and species accounts from the taxonomy hub ITIS. C. sowerbyi, you can learn, probably hitched a ride to the United States in ornamental water plants shipped from the Yangtze River valley.


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