Letters from the April 28, 2007, issue of Science News

Long ago gas

Finding CO2 levels that are 2,500 times higher in 5,000-year-old fulgurites than in modern samples, scientists have speculated that the extra CO2 resulted from vaporization of organic material by lightning (“Stroke of Good Fortune: A wealth of data from petrified lightning,” SN: 2/17/07, p. 101). Could some of this gas reflect elevated atmospheric CO2? And if so, could current laments regarding “unprecedented levels” of CO2 be insupportable?

John M. Corboy
Mililani, Hawaii

Other archives of preindustrial carbon dioxide, such as ice cores and corals, don’t indicate that concentrations of the greenhouse gas were abnormally high 5,000 years ago.—S. Perkins

Fractal fairy tales?

Fractal characteristics associated with Jackson Pollack’s paintings are interesting (“Fractal or Fake?” SN: 2/24/07, p. 122), but to determine authenticity, it would seem that two propositions would have to be proved: first, that Pollack’s paintings always had fractal character; and second, that only Pollack’s paintings had fractal character. Both seem highly dubious.

Steve Johnson
Prairie Village, Kan.

In doing drip or splash painting, the artist defines the overall upper-level structure of the image, but the higher-magnification patterns are the result of the physics of liquids falling on a solid surface, only slightly affected by the artist’s intention. Any drip painting that looks like a Pollack overall will look in details like one as well.

Bruce McIntosh
Madrid, N.M.

Not planning on it

In regards to “Bird Plans: Jays show foresight in breakfast menus” (SN: 2/24/07, p. 117), I find it hard to rule out an interpretation that would not require anything similar to planning. This could simply be pattern completion, similar to building a nest or bower. The animal is not necessarily planning, but simply filling in missing pieces.

Robert Fizzell
Beloit, Wis.

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