Physicists capture 'second sound' for the first time — after nearly 100 years of searching

Scientists directly imaged 'second sound,' where heat behaves like sound waves in superfluids, using a new heat-mapping technique on cold lithium-6 atoms. They observed heat moving as a wave and bouncing in its container. This discovery could aid in predicting heat flow in neutron stars and high-temperature superconductors, potentially enabling near-lossless energy transmission. The method tracks fermion pairs through resonant frequencies, visualizing the transition from normal fluid to superfluid behavior. This research advances the study of extreme objects and superconductor designs.