In "Chunk of Death-Dealing Asteroid Found" (SN: 11/21/98, p. 324), how do we switch from "This is really the first thing we can say is a piece of a meteorite from the K-T boundary" to "pretty good circumstantial argument that this was a piece of the meteorite that was the culprit . . ."? How do we know that the Kyte meteorite didn't strike the Tuesday before or after the "death-dealing asteroid"? Or a year or more before or after?

David Jones
St. Paul, Minn.

"Self-motion perception heads for home" (SN: 11/21/98, p. 324) reports on some truly unsurprising Caltech research showing that the cognitive functions involved in keeping a constant sense of one's position while moving past other objects require processing an interplay of data from one's brain, from one's body, and from the environment.

The researchers also noted that empirical evidence remains sparse regarding these mechanisms. Instead of conducting artificial experiments in the lab, these researchers should have talked to some baseball outfielders, or better yet, tried outfielding themselves. There is no other way for an outfielder to note the direction of a hit ball, turn and race in its direction, and jump up and bounce off the back wall, catching the ball behind his head, without his brain processing internal information (the flight arc of the ball), feedback from his body (where he is on the field, what his angle of momentum is), and feedback from the environment (as he nears the wall).

Peter B. Newman
San Rafael, Calif.

See SN: 6/15/96, p. 372, and SN: 5/13/95, p. 297, for scientific examples of Outfielding 101.

—B. Bower

I read your article "Laser interplay stokes fusion uncertainty" (SN: 11/28/98, p. 326), and I disagree completely with the way the sentence "This is very bad for fusion" is used in the text.

Experiments at LULI (Laboratoire pour l'Utilisation des Lasers Intenses) at École Polytechnique, France, have shown that the overlap of two or three laser beams produces an unexpected rise in stimulated Raman scattering associated with a decrease in stimulated Brillouin scattering. Those two instabilities are of concern to reach a good coupling efficiency and quality between the laser beams and the plasma. Our group is working in collaboration with researchers from LLNL and the University of Alberta to understand the physics of these couplings and to identify the potential problems in interaction physics in order to know how to fight them. Although there is still some work to be done, some solutions are already proposed for laser fusion.

Christine Labaune
Directeur de Recherche au CNRS
Palaiseau, France