[Paleopsych] Economist: Materials science: Pasta alla fisica

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Materials science: Pasta alla fisica
http://www.economist.com/science/PrinterFriendly.cfm?Story_ID=4269826

    Aug 11th 2005

    Physicists have solved the long-standing puzzle of how spaghetti
    breaks

    IT WAS a problem that baffled the master himself. Richard
    Feynman--maverick physics genius, Nobel laureate and father of modern
    quantum theory--could not work out why, when a strand of dried
    spaghetti is snapped, it almost never breaks in half but instead
    fragments into three or more pieces. At dinner with Daniel Hillis, an
    old friend and computer scientist, the two became obsessed with this
    and spent hours theorising and experimenting. In the end, they left
    with a kitchen full of pulverised pasta and no reasonable answer.

    Basile Audoly and Sébastien Neukirch of the University of Paris VI
    think, however, that they have succeeded where Feynman failed. Their
    calculations, revealed in a forthcoming paper in Physical Review
    Letters, suggest that the key to the problem lies in so-called
    flexural waves. Each time part of a bent strand breaks, a series of
    these waves ripples down the length of the pasta. The mistake Feynman
    probably made was to assume that the strain released when a bent
    strand breaks allows the two half-strands to relax and become straight
    again. Instead, according to their equations, the passing waves cause
    parts of the daughter strands to curve even further. This triggers
    other breakages which, in turn, trigger further waves, causing the
    strand to fragment.

    To put their mathematical solution to the test, they devised a
    rigorous experiment. And, like all good researchers, they describe
    their materials and methods in a way that allows others to repeat what
    they did: "A Barilla no. 1 dry spaghetti pasta of length L=24.1cm was
    clamped and bent into an arc of circle," they write. "Twenty-five
    experiments were carried out with various pasta diameters." By
    snapping 1,000 photos per second as they released the bent strands,
    they were able to see the travelling waves and to show that the motion
    of the strands followed their equation exquisitely. Videos of all this
    can be viewed [4]here.

    Dr Audoly's and Dr Neukirch's research does have a serious point, of
    course. The steel struts that help to hold up skyscrapers and bridges
    are slightly less trivial examples of thin rods whose tendency to
    break needs to be understood. Knowing the mechanisms by which these
    rods fragment is important not only for designing such structures but
    also for reconstructing what has gone wrong when one fails.

    Having out-thought Feynman, though, it is hard to see what should be
    next on the pasta research agenda. Perhaps a suitably profound problem
    is that of the slowing down of time--a well-established part of the
    theory of relativity. Or, to put it in pasta terms, does a watched pot
    take longer to boil?