Number 168 (Story #3), March 10, 1994 by Phillip F. Schewe and Ben Stein SONOLUMINESCENCE CAN BE CHAOTIC . Previously, researchers have observed sonoluminescence to be remarkably stable: when applying sound waves to a liquid and thereby creating light flashes from collapsing bubbles, they observed that the time between successive flashes remained constant. However, new experiments, performed by R. Glynn Holt of JPL (818-393-6946) show that slight adjustments in experimental parameters (such as sound wave frequency and intensity) away from these stable conditions can lead to variations in the time between successive flashes. Taken as a sequence, the variations in successive flashes exhibit chaotic or other non-periodic characteristics. For example, the experimenters observed quasi- periodic behavior in which the timing between flashes could be broken down into two frequencies. Such behavior suggests, according to the experimenters, that the bubbles in sonoluminescence may change shape as well as volume, complicating the current theoretical picture whereby the bubbles are assumed always to have a spherical geometry. (R. Glynn Holt et al., Phys. Rev. Lett, 28 February 1994.)