In sonoluminescence, intense sound waves in water cause bubbles to form, which then collapse emitting a brief flash of light. We know that the collapse heats the trapped gas, but not why light is emitted. A technique that could help answer this question is laser-induced bubble collapse, in which much bigger bubbles are produced. Time-resolved measurements of the flash have been used to constrain emission mechanisms — for example, if it is ordinary thermal radiation, the central temperature in the bubble must be at least 70,000 K.
