Submitted by full_hammer t3_10eku2h in askscience

I know that sound doesn't travel through space because it is a vacuum and has no medium for the vibrations to travel through. But where does the energy go? If I yell really loud, I expend energy to make my voice travel, but if I yell in space, where does that energy get transferred?



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ellipsis31 t1_j4s9a0a wrote

If you yell in space the energy goes into the gases that you are expelling as heat. If you tap a tuning fork in space the energy pretty much stays in the tuning fork as heat until it can be radiated away as infrared.


full_hammer OP t1_j4sclec wrote

Ah that makes sense, thanks for the tuning fork example. That really helped it click


quaste t1_j4u5j45 wrote

Just think about it as: the dampening effect of the surrounding air doesn’t exist, so energy stays within its source longer.

Or think about water instead of air and moving in water (sound is just movement or created by movement) vs outside.


wastedintime t1_j4slhdq wrote

So, since the tuning fork doesn't have the resistance from the air, which it moves to make sound, will it vibrate for a very long time?


Chemomechanics t1_j4sm8iq wrote

A while, but not forever. Even elastic deformation dissipates a little heat (termed internal friction or sometimes mechanical hysteresis).


[deleted] t1_j4swaiu wrote



zebediah49 t1_j4t72hl wrote

Minimally faster. Without the air resistance it'll sit a bit closer to ideal resonance -- but even in air it's extremely close. The mechanical properties of the fork are what dictate the frequency, and those remain unchanged.


aspheric_cow t1_j4tpg0p wrote

A tuning fork would not vibrate measuralby faster in vacuum. If air resistance changed its vibration frequency (pitch) by a measurable amount, it would also vibrate slower when its vibration amplitude is less - i.e. its pitch would go down as the vibration decays.


Mord42 t1_j4u2r5i wrote

> A tuning fork would not vibrate measuralby faster in vacuum.

I'm being incredibly pedantic rn but since a vacuum slightly decreases the damping, the damped frequency would be ever so slightly higher than if the air was there.


Force3vo t1_j4u9qtb wrote

Which is why they said measurably faster.

It would be faster but not in a way that's really meaningful.


Force3vo t1_j4u9tl7 wrote

What's up with people with zero knowledge about things talking like they are specialists lately?


Saidear t1_j4sww6h wrote

That would imply continuously increasing energy in the fork. While the initial vibration might be faster, and it will fall off slower.. the energy will be decreasing and thus, any material fatigue minimum


Mord42 t1_j4u2u2x wrote

Even if you increase the energy the vibration frequency would not change. The frequency is not related to amplitude


TerminationClause t1_j4u2ek4 wrote

You know, I woke up this morning and didn't have a sudden urge to take a tuning fork into a vacuum, thanks. That's what my life has been missing. I actually have a couple of large tuning forks if someone can supply me with a vacuum chamber.


DragonKnightAuroran t1_j4uup7d wrote

So you're telling me, if I was loud enough in space I could breathe fire?


Baalthoros t1_j4vfrz4 wrote

You would expell a fine dusting of ice crystals and gas which would cause you to start spinning from the force of the gas expelled. You would then die painfully over a few minutes from exposure to vacuum.


GolfballDM t1_j4vta9j wrote

> You would then die painfully over a few minutes from exposure to vacuum.

If you're unconscious, is it really pain? Is it pain all the time, or just when it can be perceived?


Baalthoros t1_j4x4il7 wrote

From what ive read it take about a minute for curculation to stop. So you dont instantly black out, however the process you go through would be painful the second it started. So lots of fun pain there. Also, the body and brain respond to pain stimuli even when you are not concious. So yes, still pain until you die. Plus, if you are in open space in a solar system within a certain distance from the local star while it happens you get to experience one half of you boiling from sunlight while the other half freezes.


skurk t1_j4vgrsu wrote

This may be a silly question, but why infrared?


the_agox t1_j4vqzs4 wrote

The short answer is blackbody radiation. Everything naturally glows a little bit, and that glow changes with its temperature. At "room temperature", it's in the infrared (Planck's Law). As temperature increases, so does that frequency of the radiation. If the tuning fork was heated to 500ish degrees Celsius, it would glow a dull red.


[deleted] t1_j4up4z5 wrote

As well as the vibrations through your own body. The sound has to travel through something and given the lack of air except that which you expel, most of it just moves through you.


roosty_butte t1_j4uszj7 wrote

If you moved that tuning fork directly into a pocket or air, would it produce its tone?


Buddahrific t1_j4wfdcw wrote

A "pocket" of air would want to dissipate from it's own pressure in a vacuum/near vacuum. If one were to exist long enough to stick a tuning fork into it, it would dissipate faster. Think like a pile of sand on a vibrating table (not a resonating table with high and low energy standing waves, but just a table where the whole thing is vibrating at the same rate).


roosty_butte t1_j4wi5a2 wrote

Nah, I mean as a purely theoretical situation. The bubble of air is not affected by the vacuum of space.


Buddahrific t1_j4wma2y wrote

Pressure plays an essential role in sound (sound is pressure), so it's hard to separate the two. A vibrating tuning fork would transfer kinetic energy to anything that gets close enough to touch it, including a pocket of air that is somehow held together in a vacuum. If you had a microphone inside that, I think it would pick up those vibrations as sound.


Vicorin t1_j4wvjrs wrote

So in space, could I beat on a tuning fork until it was red hot? How long does it take for the energy to radiate out?


ellipsis31 t1_j4xha2n wrote

Almost certainly yes, heat dissipation is a huge problem in space/space travel.


zamach t1_j4vcstt wrote

Unless it's slightly asymmetrical and over time some of the vibration turns into rotation.


LampardNK t1_j4vflip wrote

so if you yell loud enough can you spit fire like a dragon?


10113r114m4 t1_j4u5wd4 wrote

I read that second sentence as "if you fap a tuning fork" and I was like "yes, yes, then what?" Just to realize I misread


vox_mechanika t1_j4uj4dj wrote

Wouldn't you just end up with an extremely satisfied tuning fork... and a sticky mess??


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.


Prak_Argabuthon t1_j4vh8to wrote

Do you want to have your mind blown? Because: actually THERE IS sound in space - really, really, REALLY quiet. Because - deep space is not really a perfect vacuum - there is about 1 atom of hydrogen per cubic centimetre. So, explosions such as a supernova DO create a sound wave - they are very quiet and very slow moving, but they definitely exist.


Redwoo t1_j4vjhjk wrote

Exactly! Sound does travel through the vacuum of space, just not at a high enough frequency for human hearing to perceive. The frequency is very low; so low that it might be hard to describe it as sound at all. And sound travels very slowly in space, slower than a typical walking pace.


Coomb t1_j4vz73x wrote

Sound, as it is conventionally understood, requires a medium to propagate which can reasonably be approximated as a continuum. That isn't true in the vast majority of space. Events like supernovas create shocks, not sound.


Prak_Argabuthon t1_j4wwvc3 wrote

Oh well if you want to get really technical, geez. Haha just kidding yes you're right of course. Thanks for clarifying.


BNeutral t1_j4styf0 wrote

Nowhere, things are just more efficient. Or less efficient. Depends on how you want to look at it.

Yelling is a very bad example for your question thought because the mechanics are a bit harder to follow? On earth, if you hit something, the molecules of that move around, and eventually some of them at the borders push on the air and sound is created. In a vacuum, the molecules of what you hit don't push any air, and either more of that is converted to heat, or the molecules oscillate longer as the wave propagates through them, or more kinetic energy ends up propelling what you hit, or some combination of all of this.


brandude87 t1_j4tsvs8 wrote

If you still had air in your lungs and yelled directly into someone else's ear with your dying breath, it may still be audible to the other person. However, your mouth must completely encapsulate the other person's ear to prevent the air gases from instantly vaporizing into tiny liquid droplets and ice crystals. Furthermore, the air bubble exhaled from your mouth into their ear will be traveling far slower than the speed of sound, so the sound waves will have bounced around the bubble quite a bit before reaching their eardrum, causing your yell to sound muffled, but possibly still intelligible.


nog642 t1_j4unp9g wrote

Sound energy either stays in the medium (the boundary with space basically reflecting the sound back), or becomes kinetic energy of the molecules of the medium that are flung into space (and are just moving at a constant speed, not vibrating, so it can't really be called sound anymore). You'd get the former if the medium is a solid, the latter if the medium is air that is escaping into space.


Plane_Pea5434 t1_j4u08ws wrote

The energy dissipates in other forms, if you yell (assuming no spacesuit) the air will just go out and keep travelling trough space, if you do have a suit the the vibrations will eventually become heat that will be radiated in to the vacuum, remember that sound is how we perceive the movement of the air and not exactly a kind of energy


MoodiusJ t1_j4uy70q wrote

The energy is contained in the wave motion of matter. To set up this problem you need some Region of matter ie fluid or solid then a boundary with vacuum. This boundary will have conditions imposed on the pressure, fluid velocity or lattice displacement wave equation of the sound. With a solid-vacuum boundary it will cause a full reflection of the wave at the boundary and the energy will remain constrained in the matter region and eventually be dissipated in the solid.

With a fluid vacuum boundary things are a bit more interesting because typically that boundary will not be sharp because of diffusion. For exampke,, in the upper atmosphere of earth you will get a gradient of air density with altitude. The sound's wavelength and speed will be a function of density and temperature and therefore altitude as will its impedance per unit length so if you launch a wave up from the surface it will both spread out transversely and some of the power will be reflecting back toward the surface as it moves per unit length.


gramoun-kal t1_j4uhoyz wrote

When something vibrates, in air or in vacuum, the flexing of the molecular structure itself robs energy away from the movement and turns it into internal heat. So anything that vibrates will eventually come to a rest (ang get slightly warmer) even in a vacuum.

In air, the vibration is slowed down slightly faster with energy from the movement being robbed by air molecules and it becomes sound waves.

So, unsurprisingly, vibrating stuff will lose its energy faster in air than in vacuum.

To answer your question, the energy that would have gone into the sound remains in the vibrating material and goes to keeping it vibrating a little longer.


DucksVersusWombats t1_j4v2ooo wrote

But space is filled with gasses of varying degrees of rarefaction. How dense does gas have to be to propagate sound waves?

Space is filled with periodic and aperiodic events; can't some of them be interpreted as sound?

What frequency or amplitude of vibration in a gaseous medium do we decide isn't sound?


ISvengali t1_j4v9inl wrote

That a good point, though the answer is rarely. Theres something like 1 molecule / cm3 (though places can be less and more)

Every now and then one of those atoms will get close enough and the tuning fork will knock it away making 'noise'. Presumably if one hits at the right time itll add energy also.

Both events are going to be fairly rare.


yak-broker t1_j4yygy9 wrote

There isn't going to be an abrupt cutoff between sound and not-sound, of course. But there'll be a range of pressures where it stops being as useful to think of the phenomenon as "sound" and starts being more useful to think of it as a vibrating thing occasionally imparting more/less energy to individual gas molecules.

My semi-educated guess is that's around when the mean free path of the gas molecules stops being small compared to the wavelength of the sound. But that's just a guess.


Relevant_Lychee_8428 t1_j4uk0l3 wrote

Sound cannot travel through a vacuum, such as the empty space between stars and planets, because there is no medium to carry the sound waves.

This means that if you were to yell in space, your voice would not travel and the energy you expended to make the sound would not be transferred as sound waves.

It will not transfer anywhere, it will remain in your mouth.


Cheekybants t1_j4vn19n wrote

More thermometer space, plane and simple, they need to take advantage of the PS5 which allows for better memory, fidelity, performance, most games I play don’t have too much replayability despite being fantastic in their many regards. An open world game can focus on driving physics for example but has to give a pass on open worlds details or dynamics which could easily be enabled if there was more space to allow for these components and details