Can the popping of tiny bubbles trigger nuclear fusion, a potential source of almost unlimited energy? This controversial idea is back on the table, because its main proponent has new results that, he claims, will silence critics.

The idea: blast a liquid with waves of ultrasound and tiny bubbles of gas are created, which release a burst of heat and light when they implode. The core of the bubble reaches 15,000 degrees C, hot enough to wrench molecules apart. Physicists have even suggested that the intense conditions of this sonoluminescence could fuse atomic nuclei together, in the same process that keeps our Sun running.