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TheJasonKientz t1_j4to0cc wrote

A sound doesn’t have any energy of its own, it’s all kinetic energy of interacting matter. So when a sound wave from earth reaches the edge of the atmosphere, the molecules will just not bump into another molecule and the sound wave ceases to exist. But the molecules all still have their kinetic energy. And eventually that will dissipate as heat.

The person who talked about the tuning fork is right. I’ll add, though, that that tuning fork in space technically never made any sound because there was no medium for the vibration of the tuning fork to propagate through.


origami_alligator t1_j4u0rtj wrote

Wouldn’t the medium of the tuning fork propagate the sound within itself? Sound doesn’t propagate only through gas.


WeaponizedKissing t1_j4ukxh8 wrote

If a tuning fork is dinged in space, but there's no atmosphere to hear it in, does it make a sound?

The fork will continue to vibrate. But there's no "sound". It's just a wobbly fork. No matter how close you hold it to your ear, you won't hear anything.


raff7 t1_j4unzfj wrote

Well.. technically if you get it close enough so that you physically touch the for you will eat it, because sound can be carried by the fork and then your own body


Buddahrific t1_j4whq4h wrote

That's assuming you didn't blow your eardrum completely in the transition to a vacuum. Which is possible if the pressure differential was maintained (pressure reduced on the inner ear at the same rate as outer).


origami_alligator t1_j4w5obs wrote

I think you asked the equivalent of “If a tree falls in the forest, and no one is around to hear it, does it make a sound?”

There are vibrations propagating through the medium of the tuning fork. Thus, sound is being propagated. In space it doesn’t have a medium to transfer that wave to, and thus it cannot be perceived by the human ear. That doesn’t mean the vibrations aren’t functionally the same as if we hit the tuning fork in a place with some sort of atmosphere. Sound doesn’t need to be perceived to be functionally the same thing as sound that is perceived. Technically any vibration through a medium is considered sound, whether you can hear it or not.


rdrunner_74 t1_j4vq4gl wrote

It is the natural frequency of the fork, so it will not waste (much) energy swinging at it.


And yes, it makes a sound - You can press it against your skull to hear it (via Bone propagation)


Acceptable_Visit604 t1_j4veluu wrote

Only if you find a way for the tuning fork to be in direct contact with your eardum

So just mold one while the shape is right against your ear 😁


SweetNeo85 t1_j4vfzhc wrote

And why shouldn't indirect contact be suitable? Hold it in your teeth for example. I imagine something would even get through merely holding it in your hand.


kerbaal t1_j4vuioz wrote

> And why shouldn't indirect contact be suitable? Hold it in your teeth for example.

Don't do that, you don't need to do that. Just hold it to your temple, or any nearby area where there is bone just under the skin.


Baalthoros t1_j4vg1m9 wrote

If it was touching the skin near the ear youd hear it. Just like bone induction earbuds. The sound would travel through the skin, then bone, to your eardrum.


Froggmann5 t1_j512hmv wrote

There are toothbrushes like this that play the radio when you brush your teeth. If you put a wobbly fork to your teeth in space wouldn't you still hear it that way?


MoonKnighy t1_j4tswn6 wrote

So with the tuning fork. It could be cold but if you gave it kinetic energy it would warm up so to speak?


Flappyhandski t1_j4u66x0 wrote

Yeah, it would get hotter as the vibrations turn into heat, then the heat would radiate out into spcae


MoonKnighy t1_j4w22xr wrote

And if this happens on Earth it wouldn’t do it that much since molecules aren’t no where near as spread as in space correct?

Interesting… in fiction like Star Wars and Metal Gear Solid there exist “Vibro Blades” that vibrate so fast they glow white hot. So I know vibration creates heat but I didn’t know how it differs in space.


KmartQuality t1_j4uirvb wrote

There is sound in the tuning fork. You just have to put your ear drum directly on it.


TheJasonKientz t1_j4xkc76 wrote

It’s not actually sound. It’s vibration. Sound is a propagating wave. The fork oscillates and when you put your face on it you’ve given the vibrations a medium to propagate through. Even if you put your ear drum directly on the fork the vibration would cause the ear drum to oscillate and then a sound wave would form in your cochlea (inner ear).


KmartQuality t1_j4xko1u wrote

Isn't that what I said?


TheJasonKientz t1_j4xm8sz wrote

I’m trying to make the distinction that it is not sound in a vibrating fork. The sound is what happens when the vibration of the fork is translated into a medium as a pressure wave. So there is no sound in the fork.


Butterfly-greytrain t1_j4uhwtk wrote

So basically, there’s no sound in space? To take OP’s example, if I yelled, would I hear nothing?


soul1001 t1_j4ujofk wrote

Exactly. Astronauts will put their helmets together if they want to talk and can’t get a radio signal through (the helmets touching gives them something for the sound to travel through)


Poopster46 t1_j4urj22 wrote

If you were wearing a space suit, you would hear yourself but others wouldn't. If you did not have a space suit, the air would rush out of your lungs the moment you opened your mouth. You might hear your voice up until the moment your lungs were empty (from inside your head), but no one else would.


TheJasonKientz t1_j4xkx66 wrote

Definitely no sound in space. If you watched an explosion in space, it would be silent until the moment the edge of the explosion reached you and then it would be chaos. Because explosions are (usually, depending on what exploded) made of gas that will carry sound.


Just_Berti t1_j4ullp3 wrote

if kinetic energy "will dissipate as heat" what will the heat dissipate into when there are no particles that could receive energy and get heated?


TanteTara t1_j4uptz8 wrote

Photons, mostly in the infrared energy range. Photons make up the vast majority of what we can actually "see" from the universe outside of the earth/moon system, though since recently we can measure some gravity waves too.


ISvengali t1_j4v7hsp wrote

I mean, photons make up everything we can see, inside and out right?


ThetaReactor t1_j4vb5y4 wrote

They make up the image that we see, but they don't constitute the actual objects.


Machobots t1_j4uobcv wrote

it would make sound if you put your ear against the fork - even better - your skull


Fortisimo07 t1_j4v50qt wrote

This isn't really right, the wave in the fork will reflect off the boundary, it doesn't just disappear. In atmosphere, most of the energy in a running fork reflects off the boundary with air as well, but in space essentially all of the energy stays in the fork, so the sound wave will just keep bouncing around and around inside. It's an impedance matching problem, and the acoustic impedance of space is essentially zero


TheJasonKientz t1_j4xih46 wrote

The fork is vibrating. It’s never causing a pressure wave through any adjacent medium. The fork itself has energy but if it was truely in a vacuum it would never make any sound. Vibration is not the same as sound.

I wasn’t saying that the fork energy ceases to exist at the boundary of the fork, it’s just not translated into any matter as the fork oscillates back and forth through empty space. It is the atomic structure of the tuning fork itself that will cause the vibration of the fork to eventually stop. With every oscillation of the forks tines the amplitude gets a little bit smaller and the energy witching the fork translates to head which is radiated away. Or conducted away through whatever is holding the fork.

None of this is sound though. Sound is a pressure wave propagating through a medium, by definition. A tuning fork normally makes sound when there is air around it because the oscillating of the fork causes alternating low and high pressure in the adjacent air. This is the part that can’t happen in a vacuum.


Fortisimo07 t1_j4xoykj wrote

Yeah and those "vibrations" are pressure waves traveling through a medium (the metal that the fork is made of). It's sound.


TheJasonKientz t1_j4xseg1 wrote

It’s not a pressure wave. It’s an entirely different mechanism.

The fork tines oscillate back and forth as the metal bends at the base of the tines. There is no propagating wave through the metal. It’s really more like the motion of a spring.

Not all vibration crates sound and vibration is never sound in and of itself.

All atoms are vibrating all the time. But they are so small and there are so many of them vibrating out of sync with one another that a pressure wave never develops in any given direction.

Noise canceling headphones cancel the noise by oscillating out of phase with a sound wave so that the sound wave is canceled. So that’s a case where vibration actually eliminates sound.

Vibration is not sound.


Competitive_Way_5485 t1_j4u3hrp wrote

Ok, i understand. But how do we Communicate in the Vacuum of Space from Earth to Moon. How do the Signals move without any chance to form a Wave? And why do we freeze in Space?


gab_r95 t1_j4u45u9 wrote

The signals are electromagnetic waves (light, microwave, radio...). They don't need a medium, and actually in a vacuum they go as fast as possible (speed of light). We freeze in space by radiating the energy away (thermal infrared).


Jai84 t1_j4uhxzz wrote

Also, (I see people going back and forth on this a lot, but here’s my understanding….) you wouldn’t freeze super fast like you see in movies. There might be ice forming on your skin, but in general there’s not really any matter (there’s an infinitesimal amount even in the “vacuum of space”) for your body to interact with, so the only heat your body is loosing is from slow radiation. I’m assuming you’re also gassing off water vapor and other things into the vacuum from your skin, eyes, mouth, lungs, etc. which would cause a loss in temperature locally I think? I haven’t done a lot of research in this, but I think the general understanding is you’d take awhile to actually “freeze up”. You’d be dead and floating around and looking stiff because there’s minimal forces acting on your limbs etc., which could give the impression you’re frozen.


Jarlentium t1_j4uk8n8 wrote

Yeah decompression is what will kill you not freezing

And spacecraft don't have freezing issues, they have overheating issues because there's no medium to transfer heat out of the ship


Poopster46 t1_j4usgbv wrote

> I’m assuming you’re also gassing off water vapor and other things into the vacuum from your skin, eyes, mouth, lungs, etc. which would cause a loss in temperature locally I think?

Absolutely. Due to the extremely low pressure in space, any liquid water would immediately evaporate, as the boiling point is inversely related to pressure. This will cause your surface temperature to drop. But as soon as that's over, your core temperature would probably offset that again.


Thundahcaxzd t1_j4u4794 wrote

Sound is molecules bumping into each other, so it needs a medium. Electromagnetic radiation such as light or radio or microwaves etc are something else entirely and dont need a medium.


TheJasonKientz t1_j4xlz53 wrote

The other answers about communicating are correct, we use radio wave which are light and which do not require a medium to propagate.

We freeze in space because there are no molecules in the air (there’s no air) bumping into our skin. On earth, air molecules are constantly bumping into you and transferring the energy they have picked up from the suns rays or from other air molecules. When this happens your badly stays warm.

But if you go to the top of a mountain, even in a sunny day it’s really really cold because the air is very thin. Actually you might be warm on the top of the mountain if you were in the sun because the suns rays would heat you up but if you were in the shade you’d get real cold. Even the back side of you body, the part not facing the sun would get real cold.

This is what happens in space as well. Things that are in direct sunlight are very hot and things that are in the shade are extremely cold. Because the only natural heat source when there is no air are the rays from the sun.

The James Webb Space telescope is over 200 degrees Fahrenheit on the sun lit side and is less that -350 degrees Fahrenheit on the dark side. There is almost a 600 degree difference. All because there is no air.