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Superfluid liquids—ultracold, zero-viscosity liquids that creep over vessel walls—manifest a kind of Bose–Einstein condensation. They are subject to quantum constraints that might be thought to thwart both the onset and dissipation of turbulence. Before superfluid turbulence was first seen in 1958, Richard Feynman posited the generation and reconnection of quantized vortex lines, tornadolike topological defects that would allow turbulent eddies to form and dissipate in superfluids. The quantized line integral of the fluid velocity around any loop enclosing a single vortex line would be h/m, where m is the mass of the relevant boson. For the next half century, the existence of such vortex lines was assumed but never directly seen. But techniques recently developed in Daniel Lathrop’s lab at the University of Maryland render the vortex lines and their reconnection events visible in superfluid helium-4. Injected hydrogen gas forms micron-sized hydrogen-ice particles that attach themselves to the vortex lines and scatter illuminating light, allowing the Maryland team to film reconnections.

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Category: Science