APRIL'S ISSUE TANGLED WITH quantum braids in “Computing with Quantum Knots,” by Graham P. Collins. Readers also learned about new vaccines coming to market that promise to conquer childhood diarrhea caused by rotavirus, a frequent killer of young children in the developing world, in “New Hope for Defeating Rotavirus,” by Roger I. Glass.
Most interesting were reader responses to another health problem, depicted by Madhusree Mukerjee, about public health scientist Smarajit Jana's work in organizing sex workers to fight HIV in India [“The Prostitutes' Union,” Insights]. Some letters demonstrated that there are those who prefer to draw a sharply defined line between science and medicine, culture and politics—an impossible luxury when scientific knowledge is applied to ameliorating human ills. Robert L. Teeter e-mailed: “Do you really think that articles on prostitution are appropriate for what used to be a dignified and respected scientific magazine?” More opinions were closer to Andy Benton's, who wrote from Flourtown, Pa.: “Thank you for sharing Jana's story. He is truly a hero of our times.”
CARPING ABOUT CONGRESS
Steve Mirsky's application of “tiny backbone living in corrosive swamp” in “Short Takes” [Anti Gravity] to describe both a kind of carp and any member of the House ethics committee surely deserves at the least a tiny Pulitzer Prize for its succinctness, completeness and brevity.
“The Prostitutes' Union,” by Madhusree Mukerjee [Insights], betrays an irony: India, a country with one of the oldest and deepest-rooted organized religions in history, is perhaps the first to successfully apply a purely secular solution to a problem that may be older than religion itself. Imagine if the U.S. surgeon general came up with this idea. I think the firestorm of revulsion from the religious right would overwhelm all the public health considerations. And yet in India, religious leaders became part of the solution. How sad that we have not made life better for our own sex workers because of belief systems infected with pride. I guess that is the contradiction of “scientific” America.
Palm Harbor, Fla.
AERODYNAMIC AIR OUT
As magazine editors dedicated to educating the public about scientific and technological issues, you should not perpetuate misleading descriptions, as was the case in “Big Squeeze,” by Mark Fischetti [Working Knowledge]. The article described how an airplane wing produces lift thus: “...because the wing top is curved, air streaming over it must travel farther and thus faster than air passing underneath the flat bottom.” If so, how could a plane fly upside down with the flat surface on top and the curved surface on the bottom?
In fact, if a winglike object, such as a flat plate, is inclined with respect to the airflow (relative wind), the air will travel much faster over the surface away from the wind and slower over the other surface, giving rise to a pressure differential. This difference is dependent on the wing's angle of attack (angle of the wing with respect to the relative wind) but not on one surface being more curved than the other.
A better explanation of lift is: as a wing angled up with respect to the relative wind moves through a volume of air, it deflects downward a large amount of air above and below the wing. Thus, the wing exerts a downward force to accelerate this mass of air downward (Newton's second law). The air exerts an equal but opposite force upward on the wing (Newton's third law). This upward force by the deflected volume of air is the lift. (This force also produces drag.)
Department of Physics
John Carroll University
University Heights, Ohio