Scientists just engineered the perfect friction-less fluid and here’s what it sounds like! – SYFY WIRE

It's not often we pause in the middle of our day and think about the nature of viscosity, unless perhaps we're on our way to Oil Can Henry's for an oil change onthe 'ol family truckster. But thanks to some fluid-friendly physicists, now we've got a reason!

According to Princeton University's official definition, "Viscosityis a measure of a fluid's resistance to flow.It describes the internal friction of a moving fluid. A fluid with large viscosity resists motion because its molecular makeup gives it a lot of internal friction." Got that?

Now that we're all in agreement as to what constitutes resistant flow, imagine a free-moving substance, call it a "perfect fluid" that operates with the least possible amount of friction allowed by the immutable laws of quantum mechanics, and you'll grasp what scientists at MIT have just created. Far from just a friction-less environment, the results of the experiments might aid physicistsin theirpursuits to investigatethe viscosity in cores of neutron stars, the plasma of the ancientuniverse, and additional forcefulinteracting fluids.

To create this universal magic, scientists made a recording of sound waves delivered through a controlled gas of basic particles called fermions. This rising scale, known as a glissando, can be heard in the clip below, which demonstrates the distinct frequencies that the gas resonates like a guitar string when sound waves are injected.

By analyzingthousands of sound waves shootingthrough this gas to calculateits sound diffusion, or how fastsound dissipates, the team was able to determine thematerials viscosity, or internal friction. Theresults of their effortswere published this week in the online journal, Science.

Its quite difficult to listen to a neutron star, says study co-author Martin Zwierlein, the Thomas A. Frank Professor of Physics at MIT. 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.The stars resonant frequencies would be similar to those of the gas, and even audible if you could get your ear close without being ripped apart by gravity.

So low was the value of the sound diffusion that it could only be measuredby a molecular-level of friction. Itconfirmed that thisstrongly interacting fermion gas demonstrates propertiesofa perfect fluid, and is considered universal in nature. This marks the first instance ofscientistsmeasuringsound diffusion in a perfect fluid.

Fermions are elementary particles likeelectrons, protons, and neutrons, and areregarded asthe building blocks of all matter.Normally content to exist as loners, fermions display characteristics of low viscosity when aroused and made to strongly interact.To manufacture this unflawedfluid, the researchers employeda system of lasers to entrap a gas of lithium-6 atoms, which are recognized asfermions.

By configuringlasers to form an optical box around the fermion gas, scientists were able to tune them to causefermions to ricochet back into the box when they collided with the edges of the optical enclosure.

All these snapshots together give us a sonogram, and its a bit like whats done when taking an ultrasound at the doctors office, Zwierlein added. The quality of the resonances tells me about the fluids viscosity, or sound diffusivity. 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. If its a very viscous fluid, then it doesnt have any good resonances.

Zwierlein and his colleagues are confident that thesenew tools can be harnessed toestimate quantum friction withincosmicmatter likeneutron stars, and also allowfor a greaterunderstanding of howdiversematerials can be manipulatedto portrayperfect, superconducting flow.

This work connects directly to resistance in materials, Zwierlein notes. Having figured out whats the lowest resistance you could have from a gas tells us what can happen with electrons in materials, and how one might make materials where electrons could flow in a perfect way. Thats exciting.

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Scientists just engineered the perfect friction-less fluid and here's what it sounds like! - SYFY WIRE