To most people, the sound of a “perfect fluid” might be the gentle trickling of water into a cup or the satisfying splash of waves crashing onto a beach. However, for physicists, a perfect flow has the least amount of viscosity within the laws of quantum physics. Recently, Massachusetts Institute of Technology (MIT) researchers have created a near-perfect fluid for the first time in history that very closely satisfies this requirement. It sounds something like this.

Martin Zwierlein, the Thomas A. Frank Professor of Physics at MIT, and his team utilized fermions in their creation of their perfect fluid. Fermions are elementary particles like electrons, neutrons, and protons and are considered the building blocks of matter. 

“A fermion is defined by its half-integer spin, a property that prevents one fermion from assuming the same spin as another nearby fermion,” said Jennifer Chu from the MIT News office.

The researchers configured a complex laser system to trap lithium-6 atoms in the form of gas, so that whenever the fermions hit an edge of the contraption, they would be reflected back into the gas. In addition, the atoms were controlled so that they collided with each other as strong as allowed by quantum mechanics. 

After sending a variety of sound waves through the fluid, the scientists took thousands of snapshots and made a sonogram (much like an ultrasound), allowing them to observe clear resonances, to calculate the sound diffusion of the fluid. This was calculated to be equivalent to the value generated from using a constant of nature known as Planck’s constant and the average fermion mass in the gas. Thus, Zwierlein’s team realized that they had just created a perfect fluid, with the lowest viscosity allowed by physics.

Fluid behavior similar to this is not commonly observed in everyday life, but it is thought to occur in the universe, normally beyond reach of even the brightest scientists. 

“Scientists can now use the fluid as a model of other, more complicated perfect flows, to estimate the viscosity of the plasma in the early universe, as well as the quantum friction within neutron stars—properties that would otherwise be impossible to calculate. Scientists might even be able to approximately predict the sounds they make,” reported Chu.

In conclusion, although the research and new data derived from the formation of this perfect fluid would not be applicable to daily life, it is certainly a significant breakthrough for astrophysicists and their future research.

Photo courtesy of BERKELEY.EDU