Field of Science

Oil on the waters

Newsweek's Blogwatch highlights PZ Myers' Pharyngula blog and his altercation with George Gilder. While that post might have inflamed the blogosphere, the same issue considers a publication that recommends casting some calming "oil upon the waters".

A short text box highlights a recent paper (Barenblatt, Chorin, Prostokishin in PNAS Natl Acad Sci. 2005 Jul 27, pre-publication on web) by three mathematicians: "A note concerning the Lighthill "sandwich model" of tropical cyclones". The authors try to show that the maximum wind speeds that can be obtained above water depend on the turbulence of the flow. If you reduce the turbulence of the flow, the winds increase dramatically. They speculate that large water droplets thrown into the air reduce the turbulence and thus result in increased winds. The last paragraph of the article notes that in the distant past, sailors poured oil onto the waters to calm storms. Newsweek notes that a surfactant might work, and you might leave with the impression that oil is a surfactant.

Surfactants (from "surface active agents) reduce the surface tension of a liquid. When the surface tension is reduced, the size of droplets formed from the solution also decreases. So surfacants in theory could reduce the formation of large wind-blown droplets. Oil forms a physical barrier, since oil and water are immiscible, that prevents the water from being touched by the waves. Oil molecules are much heavier than water and less likely to form large stable droplets in the air. So both might work to calm a storm, but in chemically different ways.

My father spent much of his scientific career making surfactants. They see uses from the prosaic (read the back of your shampoo bottle, see something like sodium lauryl sulfate?) to the exotic (surfactants are used to treat premature babies' lungs).

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