Physicists have discovered the ultimate speed limit of sound

 The universal regulation of any reasonably wave – be it electromagnetic or gravitational – travelling through a vacuum has been known since physicist developed his theory of Einstein's special theory of relativity in 1905. But the most speed of sound moving through a solid or a liquid has just been calculated for the primary time. it's about 36 kilometres per second, over 8000 times not up to the speed of sunshine during a vacuum.

To make this calculation, Kostya Trachenko at the Queen Mary University of London and his colleagues started with two well-known physical constants: the ratio of proton mass to the electron mass, and also the spectrum line constant, which characterises the strength of interactions between charged particles.

Trachenko says we've a fairly good idea of those values because if they were changed even touch, the universe wouldn’t observe all prefer it does. “If you modify these constants by some per cent, then the proton may not be stable anymore, and you would possibly not even have the processes in stars leading to the synthesis of heavy elements, so there would be no carbon, no life,” he says.

The sound may be a wave that propagates by making neighbouring particles interact with each other, so its speed depends on the density of cloth and the way the atoms within it are bound together. Atoms can only move so quickly, and also the speed of sound is restricted by that movement.

Trachenko and his colleagues used that fact together with the proton-electron mass ratio and therefore the spectrum line constant to calculate the most speed at which sound could theoretically travel in any liquid or solid: about 36 kilometres per second.

“The common wisdom was that diamond has the best speed of sound, because it's the toughest material, but we didn’t know whether there was a theoretical fundamental limit to that,” says Trachenko. The theoretical bound is about twice the speed of sound in a very diamond.

The speed of sound is additionally enthusiastic about the mass of the atoms within the material, therefore the researchers predicted that solid metallic hydrogen – a fabric that theoretically exists at the centre of giant planets, except for which laboratory evidence has been hotly contested – should have the best speed of sound. They calculated that it should be near the theoretical limit. They also checked out experimental data for 133 materials and located that none of them broke the limit.

However, Graeme Ackland at the University of Edinburgh within the UK says that it isn’t clear the calculations produce an ordinance. “You can use these fundamental constants to urge something with units of velocity, but I can’t quite see an honest fundamental reason for why it abounds. I’m not completely convinced.” He says that more work is critical to search out exactly how it applies to sound moving through heavier elements.