Researchers suggest phonons may have mass and perhaps negative gravity

sound wave
Credit: CC0 Public Domain

A trio of physicists with Columbia University is making waves with a new theory about phonons—they suggest they might have negative mass, and because of that, have negative gravity. Angelo Esposito, Rafael Krichevsky and Alberto Nicolis have written a paper to support their theory, including the math, and have uploaded it to the xrXiv preprint server.

Most theories depict waves as more of a collective event than as physical things. They are seen as the movement of molecules bumping against each other like balls on a pool table—the energy of one ball knocking the next, and so on—any motion in one direction is offset by motion in the opposite direction. In such a model, sound has no mass, and thus cannot be impacted by . But there may be more to the story. In their paper, the researchers suggest that the current theory does not fully explain everything that has been observed.

In recent years, physicists have come up with a word to describe the behavior of at a very small scale—the phonon. It describes the way sound vibrations cause complicated interactions with molecules, which allows the sound to propagate. The term has been useful because it allows for applying principles to sound that have previously been applied to actual particles. But no one has suggested that they actually are particles, which means they should not have mass. In this new effort, the researchers suggest the phonon could have negative , and because of that, could also have negative gravity.

To understand how this is possible, the researchers use a fluid-filled container as an example. In a cup of water, the water particles are denser in the bottom of the cup than are those at the top—this is because gravity is pulling them down. But it is also commonly known that sound moves faster when moving through denser material. So what happens to the as it encounters this difference? The researchers suggest it would deflect upward, exhibiting qualities of negative gravity. They suggest further that the same thing could be happening with sound in the air around us, causing it to rise slightly. They acknowledge that such a rise would be too small for current equipment to measure, but note that improvements in technology could someday soon prove their to be correct.


Explore further

Unusual sound waves discovered in quantum liquids

More information: The mass of sound, arXiv:1807.08771 [hep-th] arxiv.org/abs/1807.08771

Abstract
We show that the commonly accepted statement that sound waves do not transport mass is only true at linear order. Using effective field theory techniques, we confirm the result found in [Phys. Rev. B97, 134516 (2018), 1705.08914] for zero-temperature superfluids, and extend it to the case of solids and ordinary fluids. We show that, in fact, sound waves do carry mass—-in particular, gravitational mass. This implies that a sound wave not only is affected by gravity but also generates a tiny gravitational field. Our findings are valid for non-relativistic media as well, and could have intriguing experimental implications.

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Citation: Researchers suggest phonons may have mass and perhaps negative gravity (2018, August 15) retrieved 25 May 2019 from https://phys.org/news/2018-08-phonons-mass-negative-gravity.html
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Aug 15, 2018
{Cough...} Refractive index ??

Aug 15, 2018
No, it's about behaviour in a single medium, no refraction happening.

Aug 15, 2018
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Aug 15, 2018
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Aug 15, 2018
Even if sound is effectively repelled by higher media density towards lower media density, that does NOT make this negative gravity. Similarly, a north pole of one magnet repelling upward a linearly aligned south pole of a second magnet is NOT negative gravity either. In the given example, freeze the water in the cup to lock in the density difference (or use a solid material with a density gradient) then flip the ice upside down. Now the force is directed downward instead of upward and adds to gravity instead of subtracting from it.

Aug 15, 2018
This comment has been removed by a moderator.

tpb
Aug 15, 2018
If gravity is changing the density, then it is changing the refractive index.

Aug 15, 2018
{Cough...} Refractive index ??

You nailed it, Nik_2213.

No, it's about behaviour in a single medium, no refraction happening.

It may be a single medium but it doesn't have a uniform density. Refraction is inevitable.
You weren't paying attention Ojorf.

If gravity is changing the density, then it is changing the refractive index.

Correct. No anti-gravity required.

@Mark Thomas: You are kinda correct but freezing the water won't lock in the density difference. (Ice floats).

@Whart1984 - you talk a load of bollocks.

Aug 15, 2018
This comment has been removed by a moderator.

Aug 15, 2018
This comment has been removed by a moderator.

Aug 15, 2018
@andyf I'm just looking for connections and linking sources. Their interpretation is on another readers.

But you are still talking a load of bollocks. That applies to your subsequent post too. You should easily get a job on a fake news channel, because you are absolutely full of it.


Aug 15, 2018
This comment has been removed by a moderator.

Aug 15, 2018
Congrats, Whart, you've made it onto my ignore list.

By the way, I have just come back inside from my observatory.


Aug 15, 2018
This comment has been removed by a moderator.

Aug 15, 2018
Can Anti-matter be used to create anti-gravity ?

https://drive.goo...HxpxPJhb


Aug 15, 2018
A phonon is a wave frequency travelling through the atomic lattice by virtue of the oscillating atoms
Can we get anti-gravity simply by setting an atom in motion with frequency and wave by virtue of oscillatory motion?

Aug 15, 2018
{Cough...} Refractive index ??

You nailed it, Nik_2213.

No, it's about behaviour in a single medium, no refraction happening.

It may be a single medium but it doesn't have a uniform density. Refraction is inevitable.
You weren't paying attention Ojorf.

If gravity is changing the density, then it is changing the refractive index.

Correct. No anti-gravity required.

@Mark Thomas: You are kinda correct but freezing the water won't lock in the density difference. (Ice floats).

As a layman I need some guidance. To me the article seems to be suggesting that the increase in density from top to bottom increases in discrete values thereby causing the phonon to 'jump' along then 'hit a barrier' because the discrete value becomes to large. Wouldn't there be a (more or less) smooth gradual density gradient?

Aug 15, 2018
Oh holoman, please! No experimenting with anti-gravity. Fortuitously all the utubed claims of anti-grav effect are poorly F/Xed frauds and hoaxes.

Cause, in my unsubstantiated, wildly speculative interpretation of Gravity? Any realistic attempt to produce an anti-gravity device, will result in a spectacular explosion!

What? You are not satisfied with a Nuclear Arsenal that has the present ability to kill every human being six times? In addition to destroying the Earth's Biosphere?

The Modern American National Motto is "If it is worth doing? It is worth overdoing! Excess is never enough!"

Mimath 224. Good Question! I wonder if there is some sort of "Phase Change" occurring between each discrete value?

Aug 15, 2018
@Mark Thomas: You are kinda correct but freezing the water won't lock in the density difference. (Ice floats).


Andyf, you may be right, but I still think we are on the same page. That's why I wrote, "or use a solid material with a density gradient."


Aug 15, 2018
@andyf
Congrats, Whart, you've made it onto my ignore list.

By the way, I have just come back inside from my observatory.

in case you didn't guess it, Whart1984 is the latest incarnation of zephir the aether pseudoscience believer in his umpteenth sock-puppet

In would post you a list to watch for but there is a 1K character limit

Aug 20, 2018
Captain Stumpy is sooooo correct.

Anti gravity ... there has never been an honest substantial discussion of Gravity. PLEEEEZZZZZZEEE get it together folks.

Aug 21, 2018
Well phonons are not exactly a new concept--they are quantum particles. Further, I really think what is being considered is their effective mass, not actual mass. The phonons do carry energy, ergo do have positive actual mass.

I can't say for sure, but it appears to be an analogy of saying that air bubbles in water, or helium balloons in air, have "negative gravitational mass." I apologize if I am misinterpreting the original research, but this is what the reading here seems to imply.

Aug 21, 2018
Oh holoman, please! No experimenting with anti-gravity. Fortuitously all the utubed claims of anti-grav effect are poorly F/Xed frauds and hoaxes.

Cause, in my unsubstantiated, wildly speculative interpretation of Gravity? Any realistic attempt to produce an anti-gravity device, will result in a spectacular explosion!

What? You are not satisfied with a Nuclear Arsenal that has the present ability to kill every human being six times? In addition to destroying the Earth's Biosphere?

The Modern American National Motto is "If it is worth doing? It is worth overdoing! Excess is never enough!"

Mimath 224. Good Question! I wonder if there is some sort of "Phase Change" occurring between each discrete value?

my anti gravity machine is no fraud
https://www.youtu...g68VE-Ys

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