Random Samples

Science  24 Aug 2007:
Vol. 317, Issue 5841, pp. 1013

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    Stalactites in Arizona's Kartchner Caverns. CREDIT: R. GOLDSTEIN/UNIVERSITY OF CAMBRIDGE

    One grows in caves over thousands of years; the other appears in the back of your fridge in a matter of hours. But new research suggests that for all their differences, the mathematics describing stalactites and icicles is the same.

    According to work presented last week at a meeting on natural complexity at the British Antarctic Survey in Cambridge, U.K., the rate of growth of either a stalactite or an icicle can be modeled by a simple power law based on the radius and the inclination of the surface at any given point. Raymond Goldstein, a theoretical physicist at the University of Cambridge, U.K., developed the model to describe the growth of stalactites, based on the rate at which calcium carbonate precipitates from water. Icicles grow by an entirely different mechanism: heat transfer from water to the surrounding air, which causes the water to freeze. “Despite the time scales and dimensions of molecules being very different in the two cases, out pops the same mathematical formula,” says Goldstein. “It's a big mystery why nature would select the same power law.”

    “Nobody had a good model for the global shape of either stalactites or icicles before this, so to find a solution for both is impressive,” says Stephen Morris, a physicist at the University of Toronto, Canada.

  2. NETWATCH: Polar Ice Watch

    A telling sign of climate change is the declining amount of Arctic sea ice that remains at the end of summer. And it's not just an indicator. Arctic ice also influences climate by cooling the planet.

    You can follow changes in sea-ice status at the Web site of the National Snow and Ice Data Center in Boulder, Colorado, which posts regular updates on ice conditions and analyses of trends. By mid-August, this year's melt had already broken the record set in 2005, when only 5.3 million square kilometers of ice were left at the end of the season, 31% below average. The site will provide fresh information until the melting halts, usually in September.


  3. The Many Facets of Soccer Ball Design


    No ball is a perfect sphere, but the closer it is to one, the smoother the trajectory. After goaltenders during the 2006 soccer World Cup in Germany complained that the latest design had an unpredictable trajectory, South African geologist Jos Lurie decided to use his expertise in polyhedra and his 15 years of studying soccer ball designs to come up with a better pattern. Lurie, a professor emeritus who teaches gemology part-time at the University of Johannesburg, South Africa, describes his design as an “equilibrium” combination: 12 panels of a pentagonal dodecahedron and 30 of a rhombic triacontahedron. That makes for 42 panels—10 more than the popular Buckminster design and 28 more than the newer 14-panel Adidas Teamgeist. “The more panels you have, the more spherical the ball becomes,” he says.

    “A better design would be welcome, considering that the balls used in 2006 moved at times unpredictably, like knuckle balls in baseball,” says Ken Bray, a theoretical physicist at the University of Bath, U.K. Lurie has sent his design to Adidas, hoping the company will test the ball for the next World Cup, which will be held in South Africa in 2010. Adidas has so far failed to express interest and has defended its Teamgeist as “a perfectly round ball allowing great accuracy and control.”


    Open savanna with termite mounds in Queensland.


    Northern Australia is gaining fresh attention as one of the less spoiled areas of the world. The region—which extends more than 3000 kilometers from the wet tropics of Cape York Peninsula to Broome on the Indian Ocean—” contains the largest and most intact tropical savanna woodland remaining in the world,” says Brendan Mackey of the Australian National University in Canberra. Mackey is a co-author of The Nature of Northern Australia, a report released in Darwin last week that aims to supply science-based guidance for conservation and development. Much of the north remains “intact,” the authors say. “Great flocks of birds still move over the land. … Rivers still flow naturally. Floods come and go.”

    But northern Australia is also being threatened by climate change, poor fire management, weeds, and feral animals (including the fast-moving cane toad scourge), according to the Pew Environment Group and The Nature Conservancy. This summer, the two groups launched the Wild Australia Program, a $14 million, 3-year conservation effort.