In the cold heart of a pure crystal, electrons flow like a viscous fluid — an idea predicted by Lev Landau. But the vortices of this fluid remained invisible, like a painting inferred from the noise of a crowd. Now scientists have created a nanostring: a semiconductor tuning fork with a circular cavity. When an electron vortex swirls inside, a magnetic moment arises. An external magnetic field makes this moment tremble, and the tuning fork sings — its vibration directly reveals the structure of the vortex.

The sensitivity of the method is comparable to detectors of gravitational waves, which catch the trembling of space. This allowed them to distinguish two regimes: ballistic (electrons fly apart without collisions) and hydrodynamic, where viscosity sets the rules. The paradox: the more friction in the fluid, the louder the tuning fork sounds. Viscosity, linked to entropy, does not dampen the oscillations but amplifies them — transforming from an enemy of precision instruments into the main tool.