Maximum sound speed limit determined by British and Russian scientists

The ultimate speed of light has been known to us for many years, but the maximum speed of sound waves remained a mystery till now. Scientists from Queen Mary University of London have discovered that sound waves might travel as fast as 36 kilometres per second. It is 8000 times slower than the speed of light in the vacuum.

There were two significant physical constants that the calculations were based on: one is the ratio of proton mass to electron mass, the other one was the fine-structure constant, also known as Sommerfeld’s constant, which determines the strength of interactions between electrically charged particles.

By now, it was known that the speed of sound depends on the density of the material and the pattern of particles connections, hence it propagates best in solids – the highest speed of sound so far was found in a diamond. It is believed now that it is just half of the maximum speed that sound waves can theoretically achieve.

Full article can be accessed in Science Advances magazine: https://advances.sciencemag.org/content/6/41/eabc8662