Physicists have for the first time measured how our “perfect” fluid travels soundwaves to the nearest object, in an ideal case where the liquid is only by its density and pressure. This can further help the researcher to study and understand the interior of the neutron star and the extreme environment like the first few fractions of one second after the Big Bang. You can think of a liquid as just a liquid, but a liquid is a substance that adheres to its container (research on whether cats are liquids won the IG Nobel Prize in 2017), including gas and plasma. The three fluids experience friction in their layers the higher the friction, the thicker or viscous the liquid.
In the science report, the MIT team created a perfect liquid using Fermi gas. It is a specific state matter where each constituent is fermions, in a specific class of particles that include electrons, protons and neutrons. Firms do not like to interact with each other because of the quantum mechanical laws, but it is possible to force them to interact. When this happens, the resulting liquid has very little viscosity or very little friction, which is an important step towards what known in physics as a perfect liquid. The team firmly used fermions atoms and used lasers to trap the gas and create an optical box. If an atom moves to one side of the box, the laser light can return it.
To create a sound wave, the team varied the brightness of one side of the box. It creates mechanical waves through the gas. They recorded these thousands of snapshots so they could understand which soundwaves was the most broadcast, the resonance frequency.
“All of these snapshots together give us a sonogram and that’s exactly what happened when we took the ultrasound to the doctor’s office,” senior author Professor Martin Zwierlein said in a statement. “Resonance properties tell me about the viscosity or sound uniqueness of a liquid. If the viscosity of a liquid is low, it can produce very strong sound waves and can be very loud, if only hit at the right frequency. If it is a very viscous liquid, it does not resonate well.”
The distribution of resonance frequencies gives a way to calculate the sound amplitude of their fluid. This is where things got very interesting. One of the most important basic physical constants for quantum mechanics is to obtain the same value using the mass of individual atoms and Planck’s constant. The properties of the liquid depend solely on the limits imposed by quantum mechanics. This gas was as perfect liquid as it could get.
“This work connects directly to the resistance of the materials,” Zwierlein added. “Determining what your minimum resistance to a gas is tells us what can happen to electrons in materials and where an element can form where it can flow in a proper way. It’s exciting.” Sound reproduction is definitely something: a bit like old school sci-fi and a bit like an alarm. In addition, it certainly needs a full explanation for the praise.
