Scientists Reach the Upper Limit of the Speed of Sound

The scientists of Queen Mary University in London, and the University of Cambridge, have just discovered the fastest possible speed of sound.



Measuring the sound waves.

Measuring the sound waves

The study found that it was possible to set an upper limit on the speed of sound, by measuring two fundamental dimensionless constants: the fine structure constant and, the proton-to-electron mass ratio.

These fundamental constants have been observed to affect a wide range of scientific fields, including nuclear reactions and habitable zones in space. Apparently, they can also help us determine the speed of sound.

The researchers tested sound waves with a range of materials to find the answer to a specific theory. The speed of sound will slow down with a lower mass of the atom. As they state, the sound will be fastest in solid atomic hydrogen.



Solid atomic hydrogen.

Solid atomic hydrogen.

However, solid atomic hydrogen is very difficult to find, as it only appears at very high pressures above 1 million atmospheres.

At these pressures, comparable to those found in the heart of gas giants like Jupiter, hydrogen forms a metallic solid, similar to copper, and should act as a superconductor at room temperature.

Scientists have been using quantum mechanical calculations to calculate that the speed of sound in solid atomic hydrogen should be around the theoretical fundamental limit.

According to the University of Cambridge, the result of the study is approximately 36 km per second. This is double the speed of sound in diamond, the strongest material known in the world.

Chris Pickard, professor of the Cambridge Department of Materials and Metallurgy Sciences, explained that the sound waves in solids are already extremely important in many fields of science.

For example, seismologists use sound waves triggered by earthquakes deep inside the Earth to understand the nature of seismic events and the properties of the Earth’s composition.

Professor Kostya Trachenko, professor of physics at Queen Mary said that the results of this study could have further scientific applications, in helping them find and understand the limits of different properties such as viscosity and, conductivity.