Letters from the December 11, 2004, issue of Science News

Mover Earth

I would have thought that it is more likely that Earth’s hum creates the weather patterns (“Humming Along: Ocean waves may cause global seismic noise,” SN: 10/2/04, p. 212: Humming Along: Ocean waves may cause global seismic noise) than the other way around.

Judy Angel
Glasgow, Scotland

Nuclear fallout

“Hurrying a nuclear identity switch” (SN: 10/9/04, p. 238: Hurrying a nuclear identity switch) dealt with the alteration of the nuclear decay rate of beryllium-7. I believe you may have misinterpreted the researchers to be saying they had found “the largest such artificial hastening of an atom’s decay rate ever observed.” Whereas you report the authors observing a 0.83 percent change, I published a paper in Physical Review Letters in 1965 that demonstrated a 3.6 percent change in the decay rate of the niobium-90 meta-stable state.

John A. Cooper
Portland, Ore.

Shooting the breeze

Because the purpose of wind machines is to take energy out of the wind, it is counterintuitive to find the wind’s average velocity increases inside the wind farm (“Change in the Weather? Wind farms might affect local climates,” SN: 10/16/04, p. 246: Change in the Weather? Wind farms might affect local climates). This is not what I learned in Aerodynamics I. Some clarification, please.

John Toomay
Carlsbad, Calif.

Remember boundary layers. The wind speed at windmill level is higher than it is at ground level. The turbine is extracting energy from that high-altitude wind, and its rotating blades are sending some of that faster airflow down to ground level, where it increases the average wind speed.—S. Perkins

The title, headline, and photo caption of “Change in the Weather?” create the false impression of large-scale weather effects from wind turbines unsubstantiated in the article. For instance, the text explains a daily average increase in ground wind speed of 1.3 miles per hour.

Chris Carter
Graham, N.C.

The weather effects were averages estimated over the entire wind farm. The slight increase in wind speed may be a smaller concern than the boost in the evaporation of ground moisture.—S. Perkins