Physicists see heat move as a wave after 90 years of theory

Physicists at MIT have, for the first time, directly observed and filmed the quantum phenomenon known as "second sound," a theory predicted in 1938 but never before visually confirmed. Unlike normal heat diffusion, second sound occurs in superfluid states where heat propagates as a wave, similar to sound, with the surrounding fluid remaining stationary. The team overcame significant experimental challenges by cooling gases to near absolute zero and using lithium-6 atoms, whose resonance frequency shifts with temperature, allowing them to track heat movement via radio wave-induced resonance. This breakthrough enabled real-time visualization of heat waves in a superfluid, marking a major advance in studying quantum states of matter. The ability to observe second sound has important scientific and technological implications. It offers new insights into extreme states of matter such as those found in neutron stars, potentially improving astrophysical models. On Earth, the findings could advance research into high-temperature superconductors, which are crucial for energy-efficient technologies like lossless power transmission and magnetic levitation.