Letters from the April 9, 2005, issue of Science News

Big ideas

Your article “Life on the Scales” (SN: 2/12/05, p. 106) reminded me that taking a bird’s song and transposing it down four octaves makes it sound like a whale’s song. The opposite is also true. To hear this, go to http://www.mind.net/music/birdwhaleDemo.mp3.

Todd Barton
Ashland, Ore
.

The article would imply that the only anomaly to the theory that mass equates to longevity is that large-dog breeds live shorter lives than small ones do. I would suggest that there are many more discrepancies. For example, humans outlive elephants, horses, and cows, and tortoises outliving humans. And amoebas outlive us all.

McClellan Blair
Indiana, Pa
.

This is tremendously interesting. The scaling law is evidently expressible in a single formula. Why not present it?

Patrick J. Roache
Socorro, N.M.

Here’s the equation, I = i0 M3/4e–E/kT. I is an individual’s metabolic rate, i0 is a normalization constant, M is mass, E is the activation energy, k is Boltzmann’s constant, and T is body temperature in kelvins.—E. Klarreich

No bargain

“High costs of CT screening” (SN: 2/19/05, p. 125) overlooks an immeasurable long-term cost of whole-body computed tomography scans: the potential cancers induced by high-dose radiation. Aggressive marketing of CT scans without full disclosure of the risk is unethical and should be illegal.

Nancy Evans
San Francisco, Calif
.

Pressure point

“Against the Migraine” (SN: 2/19/05, p. 119) mentions several possible triggers for migraines, with a patent foramen ovale being one. There is also the change-in-weather trigger, from which I suffer. All the symptoms mentioned in the article could cause a fairly sudden change in blood pressure. A weather-related change in barometric pressure might have the same effect. I wonder if there’s a common mechanism in how migraine victims’ bodies handle changes in pressure.

Dotti Lydecker
Lake San Marcos, Calif
.