Thanks to Einstein’s special theory of relativity, we know that the speed of light in space is the limit of the ultimate speed of the universe, but other waves also expected to have limitations. Of particular interest are sound waves. Now, the maximum speed limit for moving through solid and liquid dense materials has calculated for the first time. As reported in the journal Science Advances, the team estimates that sound waves can propagate at a maximum speed of 36 kilometers (22 miles) per second, with twice the speed of sound in diamonds and twice the speed of sound through the wind. This is about 8,000 times less than the speed of light in space.
A sound wave is a type of vibration that propagates through medium, whether solid, liquid or gas. In solids and liquids, the speed of sound is much faster due to the higher density. Their material particles allow the vibrations to spread more quickly together. Researchers began calculating from the general consideration of how the speed of sound is calculated using the physical properties of a substance. The standard formula shows how much speed can distort your material and how dense it is. The team realized that they could extend this calculation to create an ideal case, reaching a formula that depended on three physical constants: the speed of light in space, the ratio between the mass of electrons and the mass of protons, and the fine-structured constant, which is electromagnetic in particles, identifies interaction energy.
They believe that this theoretical formula can predict the upper limit of the speed of sound since you do not need the properties of the material as a whole (with its imperfections) but you are only considering its elemental particles and how they interact with one another. “Soundwaves in solids are already very important across many scientific fields. For example, seismologists use seismic formulas to understand the nature of seismic events and the characteristics of the earth’s composition,” said Chris Pickard, a professor of physics at Cambridge University. “These are also of interest to physicists because sound waves are related to important elastic properties, including stress resistance.”
The team tested a variety of materials on a variety of materials to make sure that their assumptions – with increasing mass of molecules in a substance that would reduce the maximum speed of sound in a solid – were correct. The limited case is hydrogen, the lightest atom, in its solid form. Unfortunately, hydrogen is not an easy material to harden. The team suspects that this higher limit can achieved in a real substance when hydrogen is in its rare metallic state due to the incredible pressure at the center of planets like Jupiter.
“We believe that the results of this study may have scientific applications to understand and further understand the limitations of various properties relevant to our high-temperature superconductivity, quark-gluon plasma and even black hole physics, such as viscosity and thermal conductivity limitations,” said the author. Professor Costa Trachenko has finished.