Scientists have long thought of soundwaves as massless, and this image of the sound waves surrounding a supersonic jet sure look that way. But new research suggests that isn't quite the case. Credit: Shutterstock
The objects’ motion we see in our everyday lives are governed by Newton’s Laws of Motion and gravity. But according to scientists at the Columbia University have suggested something else. They suggested that there might actually be particles with negative mass – which under gravity, move up, instead of down – and they’re all around us.

Scientists in their paper say that the particles of sound we hear and produce every day – phonons – that are rebelling against the force of gravity. The sound has negative mass, and all around you, it’s drifting up, up and away albeit very slowly.

The phonons, a quantum mechanical description of an elementary vibrational motion, that can potentially describe the sound at very small scales have a very slight negative mass. Means, sound waves travel upward ever so slightly.

Rafael Krichevsky, a graduate student in physics at Columbia University explained, “When sound moves through the air it vibrates the molecules around it, but that vibration can’t be easily described by the movement of the molecules themselves.”

“Instead, just as light waves can be described as photons or particles of light, phonons are a way to describe sound waves that emerge from the complicated interactions of the fluid molecules.”

Scientists during the study found that the phonons have a tiny mass and thus they move in opposite direction when gravity tugs on them.

Krichevsky explained, “To understand how this might work, imagine a normal fluid in which gravity acts downward. Fluid particles will compress the particles below it, so that it’s slightly denser lower down. Physicists already know that sound typically moves faster through denser media than through less-dense media — so the speed of sound above a phonon will be slower than the speed of sound through the slightly denser particles below it. That causes the phonon to “deflect” upward.”

The effect is too small to measure with existing technology, and there are also other potential explanations for this trajectory that have nothing to do with gravity. But scientists suggest that it is not impossible.

They believe that a very precise measurement could be made using super-precise clocks that would detect the slight curvature of a phonon’s path.

Although this paradox is at the heart of the new hypothesis, yet there are real consequences to this discovery.

The paper is published in arXiv:1807.08771.

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