Letters from the April 23, 2005, issue of Science News

The shark as red herring

I’m sure you published “A Fishy Therapy,” (SN: 3/5/05, p. 154) in good faith, but I believe that claims for shark cartilage are not made seriously by anyone who studies the role of natural substances in cancer prevention. It was proved ineffective long ago. I think your article does a disservice to honest people who are trying to fight the drug-industry prejudice against natural (profitless) substances to prevent and treat many diseases. Shark cartilage is a red herring.

James Street
Oakland, Calif.

On the bubbles

The article “Brutal Bubbles: Collapsing orbs rip apart atoms,” (SN: 3/5/05, p. 147) didn’t specify how strong the ultrasonic waves were or if any special conditions were required for these bubbles to form. I am curious to know if there’s a difference between the ultrasonic waves mentioned in your article and those in ultrasound exams of pregnant women.

Andrea Bikfalvy
Dowagiac, Mich.

The article made me wonder whether the ultrasonic waves of naval sonar can “rattle” an aquatic mammal’s brain. If so, it bears some serious investigation.

Debbie Butler
Vashon, Wash.

The shorter duration and higher frequency of diagnostic ultrasound make bubble formation less likely than with the ultrasound used in sonoluminescence experiments. As for marine mammals, some investigators suspect that bubbles may form in blood and tissues exposed to sonar and that the result can be animals stranded on beaches. Deep-diving marine mammals may be particularly vulnerable to ultrasonic-bubble formation because they have large amounts of dissolved gas in their bodies.—P. Weiss