Is the Speed of Sound Affected by Gravity?

In summary, the conversation discusses the effects of gravity on light and sound waves. While light waves are affected by the curvature of space-time, sound waves are primarily affected by the equation F=mg. However, this equation is only accurate for sound waves when the gravitational field is not too large. The conversation also touches on the different theories of gravity and how general relativity is correct for both types of waves. It is also mentioned that the density of the atmosphere can affect the bending of both light and sound waves towards the center of the Earth. Additionally, it is noted that gravity can produce stresses in bodies, but there is not always a simple relation between the stress field and the gravitational field.
  • #1
cottonkat5
2
0
Sorry if this is in the wrong thread (my first time posting),

I know that light is affected by gravity (gravitational lensing), but is sound affected in the same way?
 
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  • #2
The effect of gravity on a light wave is explained by general relativity, because gravity warps space-time.
Before general relativity, we had the equation F=mg, but of course light waves don't have mass, so this is why relativity was an important shift in the understanding of gravity.
Sound waves are made by the movement of molecules, these molecules have mass. so gravity effects sound waves in 2 ways: 1) F=mg causes the molecules to be pulled towards the source of the gravitational field. 2) the curvature of space-time has a similar effect on sound waves as it does on light waves.
For gravity sources with comparatively low density (such as the earth), the effect of gravity on the curvature of space-time is much smaller than the effect due to F=mg.
So, for sound waves, F=mg is the main effect of gravity on the molecules, but for light waves, the curvature of space-time is the effect of gravity.
Therefore sound and light waves are affected by gravity in different ways.
 
  • #3
Actually, I think I am wrong. Gravity effects sound waves in only one way. And that can either be modeled by the theory that gravity warps space-time or the theory that gravity is a force. for sound, these two theories should give the same result.
But for light, the theory that says gravity is a force is incorrect. The theory saying that gravity warps space-time is correct for light waves.
therefore general relativity is correct for both types of waves, but F=mg only works for sound waves, (when the gravitational field isn't too large)
 
  • #4
If we're talking about light and sound waves in the Earth's atmosphere, they are both bent towards the centre of the Earth because the density of the atmosphere is greater closer to the earth.
The effect of gravity on light and sound waves would be much less, but I think it would have the same effect
 
  • #5
From a practical standpoint, where we care only about Earth's gravity...no. The molecules will experience the same gravitational force as they would when there is no sound wave at all.

The exception is a sound wave with an extremely long wavelength that could move particles considerably closer or further from a large mass.
 
  • #6
Sound waves are vibrations in some medium (solid or fluid) and they are affected by the stress field in the medium. (Example - the speed of sound for transverse vibrations of a stretched string depends on the tension in the string, and therefore the vibration frequency depends on the tension).

So sound waves are affected by gravity is so far as gravity produce stresses.

Cleatly gravity CAN produce significant stresses in bodies, but there is not usually a simple relation between the stress field and the gravitational field that causes it. (Example - the tension in the string in the previous example could be produced by hanging a mass from one end of it).
 

1. How does gravity affect the speed of sound?

Gravity does not directly affect the speed of sound. The speed of sound is determined by the medium through which it travels, such as air or water. However, gravity can indirectly affect the speed of sound by influencing the density and temperature of the medium, which can alter the speed of sound.

2. Can sound travel in a vacuum due to gravity?

No, sound cannot travel in a vacuum regardless of gravity. Sound waves require a medium to vibrate and propagate, and in a vacuum, there is no medium for sound to travel through.

3. Does gravity affect the pitch of sound?

Yes, gravity can affect the pitch of sound. As sound waves travel through a medium, they can be affected by gravity, causing them to either compress or expand. This change in the wave's frequency can result in a higher or lower pitch.

4. How does gravity impact the direction of sound?

Gravity can affect the direction of sound by causing sound waves to bend or refract as they move through different mediums with varying densities. This phenomenon is known as sound refraction and can cause sound to travel in unexpected directions.

5. Is the loudness of sound affected by gravity?

No, the loudness of sound is not directly affected by gravity. However, as sound waves travel through a medium, they may lose energy due to gravity, resulting in a decrease in loudness. This decrease in loudness can also be affected by the distance the sound has to travel.

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