Answers are grounded in this paper and cite their sources.
Physicists have known for decades that ultrasound beamed into a flask of water can spark brief bursts of visible and ultraviolet light from a bubble, but the phenomenon is still a mystery. In a flurry of theorizing, physicists are trying to explain it by invoking everything from miniature implosions to tiny lightning storms to energy stolen from empty space.
No takes yet. Share an insight, caveat, or question.
James Glanz (1996) studied this question.
Synapse has enriched 10 related papers. Consider them for comparative context: