# apart from affecting the density of matter, does gravity affect sound?

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Are sound waves pulled down? Also as a bonus question, does gravity affect anything other that matter?

In: Physics

Gravity affects anything with energy, including matter with mass (mass is a form of energy) but also light/electromagnetic waves/photons, which don’t have rest mass but do have energy and momentum. This is why light from distant galaxies can be bent and distorted during its travel from there to here — it is being affected by the warped spacetime aka gravity.

I don’t believe gravity directly affects sound waves. Like you said, it does affect the medium in which they travel, though, so for example a change in gravity can cause a change in the density of air and alter the properties of sound waves. It won’t make them fall down towards the source of gravity, though.

EDIT: According to the article shared by another commenter, this might be wrong, and sound waves may actually possess *negative* mass. Interesting!

sound is just a specific way matter moves. if the matter is pulled down, the sound being carried by the matter is too. if the source of the sound is pulled down, the sound it emits gets distorted similar to how the sound of a car distorts when it drives past you

and gravity affects light. when light passes close to a black hole or very large star, astronomers notice it bend through what they call a gravity lens

Interesting question.

I would expect that since gravity is the curvature of spacetime, that sound waves traveling through spacetime would have to follow the curve of space just like everything else.

Just pointing out that density isn’t directly dependant on gravity, it’s simply mass (amount of material)/volume: the density of water is the same here and in the moon. Liquid water always (more or less) has a density of ~1 kg/L: every 1 liter of water contains a mass of 1 kg.

Weight, on the other hand, is the force that acts upon an object under gravity.

Yes in the sense that the medium they travel through is.

No in… any other sense.

Sound is just a wave of stuff being pushed together and pulled apart. It’s not exactly a thing, but a way in which something behaves. Not a what, but a how.