Sound has a speed limit. Under normal conditions, its waves cannot travel faster than about 36 kilometers per second, physicists propose on October 9 in scientific progress.
Sound gypsum at different rates in different materials – for example moving faster in water than in air. But under conditions found naturally on Earth, no object can host sound waves that exceed this final limit, which is 100 times faster than the normal speed of sound traveling in the air.
The rationale of the team lies in the well-known equations of physical and mathematical relations. “In terms of the simplicity of the argument, it suggests that (researchers) are pointing the finger at something much deeper,” says Kamran Behnia, an oppressed material physicist at the Ecole Superior de Physic and de Simi Industries in Paris.
Equation for speed range Basic constants, special numbers governing the universe. Such a number sets the speed of light, the ultimate speed limit of the universe – nothing can go fast. The other is called the elegant structural constant, which determines the force at which electrically charged particles push against each other. When combined with another constant in the correct arrangement – the ratio of the masses of protons and electrons – these numbers give the speed limit of sound.
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Sound waves, which are vibrations of atoms or molecules, travel through an object as one particle stimulates another particle. The speed of the waves depends on various factors, including the chemical bonds that hold the substance together and how large its atoms are.
None of the previously measured sound velocities in various liquids and solids exceeded the proposed limit, as discovered by compressed material physicist Kostya Drochenko and colleagues. The velocity measured in diamond is only half the theoretical maximum.
The limit applies only to solids and liquids at the pressures normally found on Earth. At pressures millions of times higher than Earth’s atmosphere, sound waves can move faster and exceed the limit.
An object that is expected to boast a high sound speed exists only at such high pressures: hydrogen compresses hard enough to form a solid metal (SN: 6/28/19). The metal was never reliably developed, so the researchers calculated the expected speed instead of using a gauge. Estimates suggest that the sound speed limit will be broken at about 6 million times the Earth’s atmospheric pressure.
The role of fundamental constants at the maximum speed of sound is derived from how the waves move through objects. Sound thanks to the electromagnetic interactions of the electrons of neighboring atoms, which is where the elegant structural constant comes into play. The proton-electron mass ratio is important because even though the electrons interact, the nuclei of the atoms move as a result.
The elegant-structural constant and the proton-electron mass ratio are dimensionless constants, i.e. no units are attached to them (so their value does not depend on any particular unit). Such dimensionless constants appeal to physicists because, as we know, values are important to the existence of the universe (SN: 11/2/16). For example, stars, planets, and life could not have formed if the elegant structural constant had changed significantly. But no one can explain why all these important numbers have their values.
Trochenko of Queen Mary University in London says, “When I have sleepless nights, I sometimes think about it. So he and colleagues extend this puzzle to general concepts such as the speed of sound from the cosmos. Trochenko and co-founder of the Institute for High Pressure Physics in Troitsk, Russia, also announced the minimum viscosity of fluids in scientific advances on April 24.
That viscosity range depends on the Planck constant, a number at the heart of quantum mechanics, the mathematics that governs physics on very small scale. If the Planck constant is 100 times larger, Drachenko says, “water will be like honey, and this will be the end of life, because the processes of the cells will not run efficiently.”