For The First Time, Physicists Have Recorded The Flowing Sound of a 'Perfect' Fluid - ScienceAlert

For the first time, physicists have recorded sound waves moving through a perfect fluid with the lowest possible viscosity, as permitted by the laws of quantum mechanics, an ascending glissando of the frequencies at which the fluid resonates.

"But now you could mimic it in a lab using atoms, shake that atomic soup and listen to it, and know how a neutron star would sound." (You can listen to the recording here.).

And, since the viscosity of a fluid can be measured by the way sound dissipates through it - a property called sound diffusion - a team of researchers devised an experiment to propagate sound waves through a fluid of fermionic particles to determine its viscosity.

This allowed them to find ripples in the fluid's density analogous to a sound wave.

"The quality of the resonances tells me about the fluid's viscosity, or sound diffusivity," Zwierlein said.

"If a fluid has low viscosity, it can build up a very strong sound wave and be very loud, if hit at just the right frequency.

From these, they calculated the fluid's sound diffusion.

We could use fluids such as the team's lithium-6 gas to understand the diffusivity of neutron stars, which could, in turn, lead to a better understanding of their interiors, and the gravitational wave signals generated by merging neutron stars.