Liquid helium can act like a superfluid when cooled to temperatures just a few degrees above absolute zero.

However, this view began to change when scientists investigated a very slippery kind of fluid known as a superfluid, which flows with virtually zero friction or viscosity. In classical physics, their energy can make matter move back and forth, but they were not thought to possess mass. Sound waves are fluctuations of density within materials. 'It's surprising in this day and age that it is still possible to find new results in classical Newtonian physics,' said particle physicist Ira Rothstein at Carnegie Mellon University in Pittsburgh, who did not take part in this study. Still, the finding challenges long-held assumptions about how sound works.

'It is a tiny, tiny effect,' said study lead author Angelo Esposito, a high-energy physicist at the Swiss Federal Polytechnic School of Lausanne. However, these new findings suggest that even in regular conditions that ignore relativity, sound possesses gravitational mass.Īny sound waves on Earth would have extraordinarily weak gravitational effects on their surroundings compared to the effect of the Earth itself, which has a mass of about 6 trillion trillion kilograms. One consequence of this relationship according to Einstein's theory of relativity is that matter traveling near the speed of light will get heavier. One might assume these findings are related to Einstein's famous equation E=mc 2, which revealed that anything with energy could be converted to an equivalent amount of mass and vice versa. Oddly, the findings also suggest the pull is in the opposite direction of the gravitational pull generated by normal matter, meaning sound waves might fall up instead of down in Earth's gravitational field. (Inside Science) - The sound of a sonic boom may produce about the same magnitude of gravitational pull as a 10-milligram weight, a new study finds.

Soundwaves definition