# Does sound travel in space?

1. Jun 30, 2015

### Josh S Thompson

As far as I know sound is vibrating matter. Does that mean it could not exist in a vacuum?

In outer space there is much less matter for sound to interact with so my question is, how does a sound generated in high matter places change as it travels to low matter places?

For example, if you could create a sound loud enough to be heard from orbit, would someone the same distance away on earth hear the sound at the same volume?

2. Jun 30, 2015

### Borg

Yes. Sound needs to travel through a medium of some sort.

3. Jun 30, 2015

### Borg

4. Jun 30, 2015

### Josh S Thompson

Thanks much appreciated.

So is he saying the speed of sound will increase with less matter and that's where the energy goes?

Also, does the sound frequency change in mediums?

That's crazy that sound travels the same speed no matter how much you force molecules and atoms to vibrate, don't get it.

5. Jun 30, 2015

### Borg

Again, the situation that marcus refers to is very different from normal sound waves on earth. Sound normally travels through a medium and its speed is dependant on the physical properties of that medium which is made up of many, many particles. "Sound" in space is not the same because you essentially only have one particle. Any measurement on that particle is just going to be a snapshot of the energy that was imparted on it at a particular moment. The sound that we are used to is based on energy imparted over a period of time. It's like the difference between a picture and a movie.

6. Jun 30, 2015

### Staff: Mentor

No, that's not what he's saying. While the speed of sound does vary with density, Marcus was saying that as the expelled matter travels, the energy in the sound wave is spread out over a larger distance until it is too low to detect. And really, 'sound wave' probably isn't the best way of describing that situation. It's more like a shock wave.

I want to say it's the wavelength that changes, not the frequency, but I'm not 100% certain on that.

A sound wave is a collective motion involving trillions upon trillions of atoms/molecules. Since the random motion of the atoms and molecules tend to cancel themselves out, their magnitude has little effect on the speed of the sound wave.

7. Jun 30, 2015

### Josh S Thompson

First of all, how did you split my comment into separate lines to reply to that's nice.

But the last part, are you saying the magnitude of force can increase the speed of sound, regardless of medium, if it can overcome the random motion of atoms

8. Jun 30, 2015

### Josh S Thompson

Right, I get that so my question is will the force imparted on that one molecule cause a stronger vibration for that molecule compared to sound in a denser medium?
i.e. force imparted on 2 molecules makes each molecule oscillate with wavelength = 3, so same force imparted on one molecule should have wavelength with some higher factor of three maybe 3*2=6. Causing the sound to be different

or
You have dense area of molecules that get in the way of sound movement and when you dilute the medium the sound can travel faster because it bumps into less molecules.

9. Jun 30, 2015

### Staff: Mentor

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No, the speed of sound is mostly independent of the magnitude of the force or the amplitude of the sound wave. This holds true until the force is so large that it generates a shock wave, which is a different kind of wave with different properties from a sound wave.

10. Jun 30, 2015

### Josh S Thompson

Ok thank you Drakkith

But does sound affect each individual molecule more in space, in the solar systm, or is that wrong and there is a ton of molecules in space as well as earth.

11. Jun 30, 2015

### Staff: Mentor

The density of molecules/atoms in space is so low that each one can travel a huge distance before ever impacting another. In such a case it is hard to say that sound can even travel.

12. Jun 30, 2015

### rootone

Yes, it would be interesting to measure the speed of sound in a container which gradually had the air pumped out of it.
(I imagine somebody must have done this.)
Will the speed of sound decrease as the air density decreases until the speed is zero?
or, speed of sound remains the same but it travels less far before becoming undetectable?
Something else?

13. Jun 30, 2015

### cosmik debris

"In space, no-one can hear you scream".

14. Jun 30, 2015

### Staff: Mentor

It appears I was somewhat mistaken. The speed of sound appears to depend a great deal on temperature. See the following picture from wiki's article on the speed of sound:

15. Jun 30, 2015

### Josh S Thompson

Wow, thanks for all the answers, I was looking at it much too simple, I need to up my knowledge on sound before asking any more questions

16. Jun 30, 2015

### Staff: Mentor

See the earlier thread, Interstellar Speed of Sound.

Even though a shock wave differs from a sound wave, there must exist a speed of sound to have a shock wave.

Supernova Remnant and Shock Wave
Credit: Chandra: NASA / CXC / GSFC, U.Hwang et al.; ROSAT: NASA/GSFC/S.Snowden et al.