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/sci/ - Science & Math

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2527042 No.2527042 [Reply] [Original]

legit question from a stupidfag. if space is a vacuum, why arent gasses in space and surrounding planets and whatnot sucked outward to fill the vacuum as much as possible?

>> No.2527045

Gravity

>> No.2527051

gravity

Hydrogen gas can sometimes escape our atmosphere though.

>> No.2527052

basically, it's because of their own gravity. Big nebulous clouds of gas in space are really quite enormous, containing insane amounts of mass. All this mass pulls on each other quite evenly and thus it just kind of sits there. Unless something disturbs it, and that's how you get stars! Or at least one way.

>> No.2527053

Because it's all about pressure. They are expanding (if there is very low gravity) because the particles are bumping into each other, but they are being "sucked" anywhere because there is no pressure to force them apart faster than through natural collisions.

>> No.2527056

>>2527045
Pretty much this. Matter tends to stick around other bits of matter.

>> No.2527058

yes, gravity.

also, space isn't really a vacuum. there is about 1 particle per cubic centimeter in space.

which brings up the point that there is in fact sound in space!

just not sound you would hear with your puny, tiny ears. to be able to hear the low amplitude sound created by the few particles out there you would need a gianormous ear.

>> No.2527059

even though gases try to fill as much space as the atoms can't dissociate or break off from their molecules, so there is a finite amount of space a gas can fill, and then theres also gravity

>> No.2527060

>>2527053
I was talking about gasses in space, like clouds, and all the gravity people are talking about gasses near planets/stars/sources of large gravity.

>> No.2527062

>>2527058
>there is sound in space

There goes another broken misconceived notion. You never cease to amaze me, /sci/ence.

>> No.2527074

>>2527062
Wait what?

Are you disagreeing that there are pressure waves (sound) that travel through even the most rarefied interstellar space?

>> No.2527076

>>2527062
>>2527058
no, there is no sound in space. Indeed, there is a very very small number of molecules floating around; however, that is nowhere near enough to actually get a sound wave to travel through it.

one atom every centimeter is not a medium

>> No.2527088
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2527088

>>2527074
Er, no, I should've worded that better. I intended to mean that it broke the notion that I held.

>> No.2527095

>>2527076

okay stupid. then how does a supernova produce a shock wave?

to produce a SHOCK you have to move faster than the SOUND speed.

like i said before, you couldn't hear this sound because of it's low amplitude, but it is still sound because it is a compressional wave.

god, you suck so hard. let me guess, you took one university physics course and now you're a fucking expert? die in a fire.

>> No.2527092

>>2527058
>gianormous ear.

We need to build this and listen to the sounds in space. Because space-whales.

>> No.2527091

>>2527060
Well a small cloud would diffuse.

but a gigantic cloud of gas like the nebula in OP's pic has a huge amount of mass and therefore a lot of gravity

>> No.2527107
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2527107

>>2527092

>> No.2527113

>>2527095
Uh . . . wow, some underage B& is a little buttmad at being told. You are completely wrong on the shock point and as already stated, a few molecules floating around in diffusely in space a "sound medium" does not make.

>> No.2527116

>>2527095
supernovas produce "shock" waves of superheated material. Due to the force of the explosion of the star, the gases ejected retain their shell shape and do not diffuse into the vacuum due to gas pressure.

sage for having to deal with unnecessary belligerence

>> No.2527149

>>2527116
correction: the shock wave of a supernova is the shock wave traveling through the interstellar medium

however, this is possible due to the scale of the event

>> No.2527154

>>2527149
another correction: I have no fucking idea what I'm talking about

it has to do with plasma physics

>> No.2527156

>>2527116
>>2527113

this is a quote from the abstract of a scientific aritcle that can be found here: http://arxiv.org/pdf/0811.3747v3

"Our simulations have a sufficiently high spatial resolution (1.95 pc) to follow the hydrodynamic interactions among multiple supernovae that structure the interstellar medium. At a given supernova rate, we find that the mean mass-weighted sound speed and velocity dispersion decrease as the inverse square root
of gas density."

they use hydrodynamic (fluid) simulations to predict the behavior of the ISM (interstellar medium).

fluid is a medium. space has a sound speed.

you're both still stupid.

>> No.2527172

>>2527156
Please link in the article where they said that sound travels in space, not just that they use fluid dynamic laws to judge how the interstellar medium works, which is very thinly dispersed, not like an atmosphere that supports sound. I'm sure you being as smart as you are realize those are two separate things.

>> No.2527188

>>2527172

on page four just above equation #3 they use the phrase "local sound speed"

please explain the difference between using the fluid equations to model a system and that system having a sound speed (and hence sound).

>> No.2527201

>>2527172

and again, i'm not claiming you could hear this sound ( not with the size of your ear because then the fluid approximation would be inappropriate). as i said before with a larger ear you could hear this sound and this is because then the fluid approximation would be appropriate and the particles in space would behave as a fluid.

sound is simply a compressional wave, the compression and ratification of matter because of pressure gradients.

there is sound in space.

>> No.2527209

>>2527188
Earth's atmosphere is a good medium for sound (vibrations in frequency of matter). Now, take half the matter out of the atmosphere. Would you still call it a sound medium? Now half that. Now half that. Now half that. Now, for every centimeter, have there be one, count it, ONE atom. Is that a good sound medium? How about a single atom? Does that striking an object make it a good sound medium? At what point does something stop becoming a sound medium? I say, for all intents and purposes, the chances of one atom per cubic centimeter colliding enough and causing a sound to be picked up by a detector, which by the way has to be sensitive enough to detect a few atoms, is so small that it cannot be considered a sound medium. I thought this was pretty straightforward, but please, argue over the semantics some more.

>> No.2527212

>>2527201
well, okay then

last question is: why do you have to be such a sandy cunt about it?

>> No.2527221

>>2527209

did you even read what i just wrote? or even look at the article?

you're right, almost, the fluid approx. becomes less useful for a constant physical scale with lower densities. however, for larger physical scales, the lower density mediums can still be described by the fluid equations. they'll still behave as a fluid.

considering that the conditions ( pressure and density) are very rare for the universe, i think you're being small minded to say that only the physical for which we experience sound is really sound.

it's not just semantics, you're excluding the possibility of using the fluid equations for situations in which they are appropriate and useful to understanding our universe.

>> No.2527235

>>2527212

because so many tards on /sci/ have had this same stupid argument with me and i'm pretty fucking sick of you all being so ignorant about something that you could look up yourselves.

you're supposed to be rational thinkers, but so many of you just believe whatever nonsense you heard on some discovery channel half hour special and then argue for it like it was something you derived yourself.

>> No.2527237

>>2527221
well I don't think that something that we can't experience as sound could really be described as sound

like how electromagnetic waves outside of the visible spectrum are still light, right, but it's not like we can experience them

they're still there, yes, and it's still light, yes, but it's confusing to call it all the same thing when you're trying to take into account how humans experience things

it may be a sound wave, but it's not a sound wave that a human can experience, so I think it would be wise to differentiate it somehow, just like how gamma, microwave, x-ray, etc. electromagnetic radiation is differentiated from the visible spectrum

>> No.2527249

>>2527235
well, I'm sorry that you lack patience, it is indeed a virtue that not many hold. As I'm sure you'll understand, when a concept that has been accepted as fact for a very long time is attacked and declared as false, it causes a great deal of stress. This is a very natural thing to do. The worst way to deal with someone who is having his or her beliefs attacked is to verbally attack them. Calling someone stupid for being ignorant is only going to keep them ignorant. And isn't that exactly opposite of what science is about?

I'd like to thank you for broadening my understanding of the interstellar medium and how it acts as a fluid

>> No.2527251

>>2527221
I'm just pointing out how unlikely it is to pick up a sound of something, at any scale, that has perpetuated itself through the medium. If the large scale stuff still acts like a fluid, wouldn't the original "sound" that was moving through teh medium be drowned out by other physical events that contact the atoms?

Also, when someone says sound, of course they would be referring to the human expirience. When you say color I assume you know about infrared and ultraviolet, but are talking about red, blue, orange, and the likes. Same thing here. When we say sound, it is something that we are used to, not all encompassing.

>> No.2527264

so global warming is that simple?

all we need to do is somehow reverse gravity and all carbon dioxide will escape our atmosphere

>> No.2527266

>>2527264
here I was, waiting for a reply from the guy talking about sound in space, and this shows up

fuck it, I'm going to bed

>> No.2527270

>>2527237
>>2527251

i made it clear from my initial post that this was a sound you couldn't hear, and i explained why.

also, the fact the the atoms collide with each other only bolsters the fluid approximation, it is required for them to collide. which is why greater physical scales are needed for the fluid approximation with low density mediums.

>>2527249
i'm sorry, you're right. i'll be politer next time.

>> No.2527275

>>2527270
I understand what you're saying now, I guess I was just trying to pick up the scraps of my pride

>> No.2527286

>>2527275
it's okay, i was getting really butt hurt too. but now you know something cool and i know to stop getting so worked up over internet arguments.

>> No.2527293

>>2527270
It really seems like it's coming down to semantics. We are talking about the same thing, but I'm not calling it sound because it's not sound that we are used to and you are calling it sound even though you say it is very small/difficult to detect.

>> No.2527302

>>2527249

FOR ALL PRACTICAL PURPOSES

the interstellar medium IS NOT a fluid.

semantically, sure. but practically, no.

(aerospace engineer (hint: rocket scientist)

>> No.2527316

>>2527293

this depends on what you mean by 'detect'.

sound waves are actually how overpressurized regions of space (like supernova remnants) reach equilibrium with their surrounding medium (space) . since we observe this kind of thing, we observe sound in space.

you're arguing that since you can't hear it, it must not be sound, which i'm saying is small minded since the conditions are earth are only a very small subset of all physical conditions.

>> No.2527334

>>2527302

okay, so i'm guessing you're new to this thread and haven't checked out this article: http://arxiv.org/pdf/0811.3747v3

and if you're going to pull "expert on the internet", i beat you in cred for this thread topic. i'm a PhD grad student in astrophysics studying MHD (magnetofluid dynamics)

but the all caps really proved your point.

>> No.2527345

>>2527316
No, I'm saying that sound has been given a definition by humans to be what humans can hear, so it is incorrect to classify something that doesn't fit our human senses as sound to be sound. Like the example of color. What color are x-rays? They are a form of electromagnetic radiation, but we don't see it, so it's not color.

And then I'm not saying that just because we can't hear it doesn't make it sound, my point has been that it would be so difficult to detect with an instrument and then distinguish from interference that it is just bad practice to give it such a referential name as sound.

>> No.2527364

just gonna quickly pop in this thread to say that the main argument has become infinitely trivial

okay bye

>> No.2527370

>>2527042
Gravity. There is a "pressure" or "force" trying to push the outer atmosphere up further, and there is a "force" of the Earth's gravity pulling it back down. Right now, they're equal. (Yes I know I'm likely ignoring a bunch of shit, and simplifying greatly, but that's the jist of it.)

>> No.2527371

Could OP please delete this thread?
It has devolved into people trolling the guy who was nice enough to take some time to share some real knowledge.

>> No.2527373

>>2527345
the definition of sound is not "what humans can hear" because that would mean that dog whistles are magic.

sound is defined by science (oh look we're on a science board) as a compressional wave and it's speed is given as:

cs = sqrt(gamma * pressure/ density)

where gamma is the adiabatic index

the only time there isn't sound is when there is absolutely nothing (density = 0), which we've all already agreed is not the case in space since there is stuff there even if there isn't a lot of it.

so again, there is sound in space, but you can't hear it with the size of your ears, but that doesn't mean it isn't sound or it doesn't exist, just like the sounds your dog can hear are still sound even though you can't hear them.

>> No.2527392

>>2527373
Again it really feels like stupid semantic bullshit as we are talking about the same thing. Does one atom striking an object count as being a compressed wave? How many atoms per cubic centimeter does it take to not be called a sound medium?

Just say, it's so close to not being sound that I can see where it could potentially not be considered sound.

>> No.2527398

>>2527334

like i said, you're arguing semantics. there's NO PRACTICAL REASON to treat the interstellar medium as a fluid, and there never will be.

>> No.2527416

>>2527392
fine, it's semantics. you win. you can say it's not sound, while i, and the rest of the astrophysical fluid dynamicists, will call it sound and use the fluid equations to understand the motions of matter in the ISM, stellar formation, black hole accretion disc and supernova explosions.

you win the wonderful prize of continued ignorance. congrats.

>> No.2527424

>>2527416
Here. This. Answer it. Come on. All of you and everyone else.
>Does one atom striking an object count as being a compressed wave? How many atoms per cubic centimeter does it take to not be called a sound medium?

There is none and it is up to the observer to define it. Check fucking mate with your dumb subjective ass.

>> No.2527433

>>2527416

wow... go to sleep man.

you're talking about the interstellar medium being a fluid right???

WRONG... astrophyisical fluid dynamicists deal with the gasses that MOVE through the medium, not the medium itself.

i mean, you guys use numerical methods to approximate solutions to fluid laws right? and those laws apply to the gasses, right? i mean, since the gasses are the fluid.

and I also thought that you guys assume that the medium is a vacuum right?

i mean, i could be wrong, but...

nah, i'm not wrong. and i don't need to say anything more to qualify my statements.

>> No.2527464

>>2527424
compare the mean free path length (avg distance between collisions) to the physical size you are interested in. as long as the mean free path is smaller, the the fluid approximation works.

so two atoms colliding could be a fluid if they will collide often enough that the distance between their collisions is smaller than the physical scale you're interested in.

it's not really subjective.

>> No.2527473

>>2527433

please be a troll. what do you think the medium is? you've seen the heated soda can up-ended into water bit yes? what do you think gasses (with pressure) would do when they encounter a vacuum?

>> No.2527505

>>2527424
i answered. what happened to you?