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17 Jun 2002
At last week's joint meeting of the Acoustical Societies of America and Japan in Honolulu, researchers presented the latest results on sonoluminescence (SL), the mysterious phenomenon in which acoustic waves aimed at a water tank create oscillating bubbles which collapse and release ultrashort light flashes representing trillion-fold concentrations of the original sound energy.
Presenting new experimental results, groups at Yale, the University of Washington (UW), and UCLA bolstered the front-running explanation for SL, namely, that a collapsing bubble creates an imploding shock wave which heats up gas inside the bubble and generates light.
The three groups all recorded sharp acoustical pops during the SL process, suggesting the creation of shock waves. UW's Tom Matula presented preliminary results of SL experiments on a NASA astronaut-training plane showing that the same maximum light output was produced in high gravity, microgravity, and normal gravity. These results weakened recent speculations that SL occurs when an imploding bubble forms a needle-like spike or "jet" on one side which punctures the other side of the bubble to produce a flash of light, since different gravity conditions would surely vary the shape of the bubble and the formation of any resulting jets.
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