Letters from the October 28, 2006, issue of Science News

Slow down a minute

“Braking news: Disks slow down stars” (SN: 8/12/06, p. 109) says that a magnetic linkage between spinning stars and the charged particles in the dusty disks that surround them slowed the spin of the stars, but says nothing about its effect on the disk. The law of conservation of angular momentum dictates that the angular momentum lost by the star would be transferred to the charged particles in the disk, presumably raising their orbits around the star. Did the researchers comment on this or the potential effects that it might have on planet formation?

John A. Black Jr.
Tempe, Ariz.

Astronomer Luisa Rebull of the California Institute of Technology in Pasadena says that angular momentum is indeed being transferred from a star to its disk. However, she adds that her team, as a “humble observer,” was concerned only with the effect on the stars.—R. Cowen

Who’s watching whom?

I wonder if the researchers in “Underage Spiders: Males show unexpected interest in young mates” (SN: 8/26/06, p. 133) have made any observations of the prevalence of males mating with juvenile females when mature females are present in the environment.

Carolyn Cramoy
Lake Placid, N.Y.

Maydianne Andrade of the University of Toronto at Scarborough says that no information on that is available yet. She and her team didn’t know about juvenile-spider mating when they did earlier field research that might have offered insight.—S. Milius

Cooling trend

From literature I’ve reviewed, there can be significant differences between small-building cooling towers and large cooling towers—at a power plant, for instance (“Pathogen Preference: Infected amoebas flourish in cooling towers,” SN: 8/26/06, p. 133). A large cooling tower is designed with significantly more water circulation, flushing, and chemical treatment that reduce the potential for pathogens. The researchers should be encouraged to not lump all “cooling towers” in the same category.

Sara Head
Ventura, Calif.