A superfluid gas is like a crowd of people marching in step: each atom knows where to go and doesn't fall out of the common rhythm. But this crowd has three 'valleys'—three different directions it can take. In a new experiment, physicists made one valley slightly more 'favorable' than the others and watched how the crowd darted between them.

It turned out that when the imbalance is small, the two 'losing' valleys start trembling in antiphase: if one gains people, the other loses them. This is like two communicating vessels, as much water as arrives in one, so much leaves the other. And when the imbalance was increased, one of the valleys suddenly 'locked': its oscillations became like a pendulum in a narrow funnel: it swings back and forth but can't escape.

The scientists built a simple model that explains this behavior: the three valleys exchange atoms in pairs, and this exchange sets the stiffness of the whole system. When stiffness is low, the barriers between valleys 'soften' and atoms roam freely. When stiffness is high, one valley becomes a trap, and atoms in it oscillate like a weight on a spring. Such measurements open a new way to peer into the hidden life of quantum liquids, where order and disorder constantly argue with each other.