/sci/ - Science & Math

[Anonymous No.2113333]

Is sound mass?

[Anonymous No.2113349]

No, but I think what you're asking is "does sound have mass."

The answer is no. I could take the time to explain why, but I'm too stoned, so I'll just say that sound doesn't have mass because it isn't Catholic.

[Anonymous No.2113950]

Why is it that music generally sounds smooth with four beats?

[Anonymous No.2113987]

>>2113950
because anything in pairs sounds good, and that can always be broken into fours
threes sound good too, which covers most numbers out there

[Anonymous No.2113984]

>>2113333
>wave
>mass
>nope

[snoɯʎuouɐ No.2113996]

Sound is the propagating wave caused by a source, such as a speaker.

Its basically the compression and decompression of air at different pressures and frequencies, causing what you hear to be sound, the more palpitations and compressions and decompression = the higher the frequency = the higher the sound you hear.

Kind of like on a car, with a big Diesel truck, you can hear the oscillations of the cylinders, you can hear the slow frequency of it, it also has a low sound.

And then you have one of those cool sports cars, its frequency of oscillations is very high, so it sounds very high pitched

[Anonymous No.2113999]

>>2113984

but...but....waves have energy some energy E, right?

and they can be wave packets, right?

so if <span class="math">E \psi = H \psi[/spoiler]

and <span class="math">E = f h[/spoiler]

and <span class="math">m = \frac {E}{c^2}[/spoiler]

then why can a quantum particle like an electron have mass but a sound phonon can't?

fuckin' bollocks mate. Seems to be that phonons and in fact the whole damn sonic field can have mass if the inertial observer relative to the sonic field (that is, the listener) is located in a time-like dimension.

[Anonymous No.2114006]

>>2113999
>>2113333

QUADS AND TRIPS. QUADS AND TRIPS EVERYWHERE.

[snoɯʎuouɐ No.2114015]

>>2113999
because sound waves occur with lots of atoms at one time, the physics for a lepton are different on that super small scale compared with the massive result of a sound wave from a speaker or something

[snoɯʎuouɐ No.2114018]

>>2114015
also for your "time" dimension statement

4th dimension is time, we live in a 3rd dimensional setting using time as a reference point

[Anonymous No.2114029]

>>2114015

>because sound waves occur with lots of atoms at one time,

then use maxwell Boltzmann statistics instead. In that way, one can determine the amount of thermal-kinetic energy the sound wave-front is carrying and then find the "mass" ofthe wave front via <span class="math">\frac {E}{c^2}[/spoiler]

This would be theoretically sound but it would be highly unconventional way to think about it, literally a "wall of sound", and engineers would laugh at you about it.

[Anonymous No.2114036]

>>2114018

someone "standing in the 4th dimension" would observe all time-dependant energy transfers are massive "objects"

[snoɯʎuouɐ No.2114039]

>>2114029
and at the same time, you can argue other waves such as microwaves stimulate water molecules making your food hot.

In fact you could argue that soundwaves can stimulate other objects making them more hot because of the heat transfer

[Anonymous No.2114053]

Sound isn't mass, but sound waves, like light waves, contain energy, and so have a mass equivalent.

[Anonymous No.2114060]

>>2114039

sound waves will most def heat something up, and relativity theory tell us that if two bodies of otherwise identical mass are of different temperature, then the hotter object will be more massive

[Anonymous No.2114073]

sound wwaves are slight disturbances in the density of the medium (air), after they pass the lower pressure on the back pulls the air back so no mass is really transported. once it goes in your ear i think it can't pile mass on or else your head would get very very heavy real fast

[Anonymous No.2114092]

>>2114060
No, heat is not mass. E=mc^2 doesn't mean that all energy is mass. It just has a mass equivalent.

[Anonymous No.2114114]

>>2114060
lol by this logic light can be very massive

[snoɯʎuouɐ No.2114123]

>>2114114
same way other photons like UV and Gamma rays can.

[Anonymous No.2114130]

>>2114123
>photons have mass
please, not this again

[Anonymous No.2114162]

>>2113950

Because the human heart has four chambers.

[Anonymous No.2114169]

>>2114092
>mass
>mass equivalent energy

same thing according to General Relativity

>>2114130
photons have a very small but finite mass. Accodring to the standard model this small but finite mass is statistically insignificant, to the point of decalreing that for all proctical purposes photons are massless. But as I've just states, because light has a mass equivalent energy, it can act as mass in some circumstances. If light were truly and literally massless, then gravitational lensing would not occur.

[Anonymous No.2114183]

>>2114092

>mfw the Unruh effect

http://en.wikipedia.org/wiki/Unruh_effect

[Anonymous No.2114215]

>>2114183
wtf do you think the Unruh Effect has to do with anything?

[No.2114228]

energy has a mass equivalent
sound is kinetic energy

[Anonymous No.2114237]

>>2114169
>same thing according to General Relativity
GR says no such thing

>>2114130
>photons have a very small but finite mass
Photons are massless, you complete fuckwit. Gravitational lensing has absolutely NOTHING to do with photons having mass, which they do not. Photons themselves generate a gravitational field, because gravitational fields are generated by all forms of energy, including forms which are not mass.

[Anonymous No.2114243]

>>2114215

The Unruh effect implies that thermal energy transfer and the deformation of space-time are intimately linked phenomenon, and perhaps one and the same on the quantum scale.

Therefore as "radiation conveys inertia" (to quote Einstein), then heat energy does in fact convey mass

In any event, the idea is that kinetic energy and "inertial mass" are equivalent when viewed from a co-ordinate transformed referenced frame. So Yes, OP, "sound has mass". You just have to think about it as (from your reference frame) non-inertial mass.

>mfw I just owned everyone on /sci/

[Anonymous No.2114260]

>>2114237
>because gravitational fields are generated by all forms of energy, including forms which are not mass.

This is news to me. I thought it was only the kinetic energy increase of a localized energy density (i.e. the acceleration of a mass) that caused gravitation.

Funny that.

[Anonymous No.2114271]

>>2113999
Make that <span class="math">m = \sqrt{E^2 - p^2}[/spoiler] but yes, sound has mass. Just not very much.

[Anonymous No.2114278]

>>2114260
Nope, gravitation is according to the mass equivalent, which includes ALL forms of energy.

[Anonymous No.2114301]

>>2114278
In general relativity, the metric is influenced by the density and flow of both energy and momentum. Mass has nothing to do with it.

[Anonymous No.2114307]

>>2114278

Thats fuckin DEEP, bro. Wait...wait a sec!

>mfw if thats true, then this guy >>2114237 just contradicted himself and proved this guy >>2114243 right

>gravitation is according to the mass equivalent, which includes ALL forms of energy
>ALL forms of energy
>Unruh radiation
>heat energy
>sound energy

So then sound waves have a gravitational field.

/thread

[Anonymous No.2114334]

>>2114307
>So then sound waves have a gravitational field.
Yes, but no mass.

>mfw if thats true, then this guy >>2114237 just contradicted himself and proved this guy >>2114243 right
No. Mass isn't defined by a gravitational field. Gravitational fields are caused by energy. Mass is defined in SR as the invariant mass or rest mass. In GR mass has no one definition.

[Anonymous No.2114349]

>>2114334

Ok I'll accept that. energy-momentum tensor and all that.

So then what the fuck is mass?

this thread is now about what the fuck mass is.

in b4 higgs boson

[Anonymous No.2114362]

>>2114334
We can meaningfully speak of the energy and momentum carried by a sound wavepacket. The momentum is less than the energy, so the wavepacket has mass.

[Anonymous No.2114381]

higgs boson did 9/11

[Anonymous No.2114382]

>>2114349
Mass is the magnitude of the energy-momentum vector:
<div class="math">m = \sqrt{E^2 - p^2}</div>
Or in unnatural units:
<div class="math">m = \sqrt{E^2/c^4 - p^2/c^2}</div>

Most of the mass of matter actually comes from QCD and not from the Higgs mechanism.

[Anonymous No.2114391]

>>2114362

[Anonymous No.2114398]

>>2114382

THEN WHO WAS HIGGS

[Anonymous No.2114403]

>>2114349
In the context of SR, mass is the energy stored in an object in its rest frame.

[Anonymous No.2114422]

>>2114362
But the energy in a sound wave IS the same as the energy of the momentum of the sound wave.

[Anonymous No.2114431]

>>2114422
The comparison is between its energy and its momentum, not between its energy and "the energy of its momentum."

[Anonymous No.2114433]

>>2114422

What is the sound of one hand clapping?

[Anonymous No.2114440]

>>2114422
>>2114362
In fact, the momentum of a wave is defined as p = E/c.

[Anonymous No.2114442]

>>2114398
The Higgs mechanism gives mass to electrons (also muons and tauons) and a little to the quarks that make up protons and neutrons.

[Anonymous No.2114446]

>>2114431
Energy has different terms than momentum, so you can't compare them directly. However, the energy of momentum is E = pc, where c is the wave speed. That is the full energy of a wave.

[Anonymous No.2114453]

>>2114446
Energy and momentum have the same units if you take c=1, which you should.

[Anonymous No.2114464]

>>2114453
c changes at different pressures and temperatures, so you can't set c=1.

[Anonymous No.2114466]

>>2114442

Thats balls. How the fuck do they figure that leptons wouldn't have any mass without the higgs mechanism? Charged leptons have fucking mass-energy right? I mean, wtf. Anyone who's been shocked can tell you that.

>mfw the higgs boson it's found at LHC becasue pic is related

fuckin' standard model. patchy as fuck theory.

[Anonymous No.2114465]

>>2114464
c is constant always. The speed of sound changes, but the speed of sound is not c.

[Anonymous No.2114477]

>>2114433
fap fap fap

[Anonymous No.2114479]

>>2114465
Yes, the speed of sound is c. c stands for the wave speed you are studying. In this case we are studying sound waves.

[Anonymous No.2114490]

>>2114479
In special relativity, c is a constant equal to 299792458 meters/second. If you want to use the variable for something else, that's your business, but don't try to claim that energy in momentum can't have the same units because you want the letter c to mean something else.

[Anonymous No.2114500]

>>2114490
LOL. Energy and momentum NEVER have the same units. c meant the speed of classical waves LONG before relativity was developed, and it still means the speed of classical waves when you are talking about classical waves. When talking about the energy of a sound wave, it is E = pc. p is the momentum of the wave, and c is the speed of sound.

[Anonymous No.2114505]

>>2114453

try again bra.

E=P^2/(2m)

units of momentum squared divided by mass.

[Anonymous No.2114508]

>>2114505
Taking c=1, momentum and mass have the same units.

[Anonymous No.2114514]

>>2114500
>Energy and momentum NEVER have the same units.
Just to elaborate on this part, when you use natural units, you can pretend energy and momentum are unitless, but this doesn't mean that energy and momentum have the same units.

[Anonymous No.2114526]

>>2114508
>Taking c=1, momentum and mass have the same units.
see >>2114508
No one ever takes c=1 for classical waves. But if you did, then a sound wave's energy equals its momentum.

[Anonymous No.2114528]

>>2114514
If two things are unitless in a particular unit system, they have the same units (in that unit system). Feel free to qualify anything you want with "pretend"; your feelings on what is "pretend" doesn't change any actual results.

[Anonymous No.2114534]

>>2114526
c=299792458 m/s in that statement. Not the speed of sound.

[Anonymous No.2114567]

>>2113333

OP's question is a bad question because mass as we normally understand it really doesn't apply in the grand scheme of wave energy.

[Anonymous No.2114569]

>>2114534
that's fine, but when talking about the energy and momentum of sound waves, they are related by the speed of sound, not the speed of light. So E=p only if you use units where the speed of sound = 1.

[Anonymous No.2114573]

>>2114500
Also, I'm fairly sure that that equation
>E = pc,
where c is the speed of the sound wave, is wrong. You should be able to get the momentum of a sound wavepacket in Newtonian mechanics by integrating the density of the medium minus its equilibrium density, then multiplying by the velocity of the packet. But that quantity needn't have any relationship with the energy of the wavepacket, as far as I can tell offhand.

[Anonymous No.2114588]

>>2114569
<span class="math">E \neq p[/spoiler] when you take c=299792458 m/s=1, which is what's relevant if you want to ask what the mass of the sound wavepacket is according to special relativity. Since <span class="math">E \neq p[/spoiler], the wavepacket has a nonzero mass.

[Anonymous No.2114616]

>>2114588

this

[Anonymous No.2114635]

>>2114588
Sound waves don't come in wave packets. Saying E=p or E=/=p is meaningless. If you are going to make energy and momentum directly comparable, then it's up to you to arbitrarily set your unit system so that either E=p or E=/=p.

[Anonymous No.2114638]

Come to think of it, even in Newtonian mechanics, a sound wavepacket can be reasonably said to have mass if it consists only of an overdense region, or if the overdense parts beat out the underdense parts when integrated over volume. You could have wave packets with negative mass, too. Maybe you'd prefer to say they carried positive/negative mass, but that's all semantics. Unless I've screwed up royally and such things aren't solutions to the wave equation.

[Anonymous No.2114649]

>>2114588
Also, if you're talking about special relativity, the only mass is the invariant mass (rest mass), so waves don't have mass.

[Anonymous No.2114651]

>>2113333
is a water wave, or a earthquake shockwave mass?

[Anonymous No.2114652]

>>2114635
I told you what the unit system was. And why don't you think we can have sound wavepackets? I'm not talking about sound quanta, mind you (although those exist too!).

[Anonymous No.2114659]

>>2114638
there aren't wavepackets in newtonian physics.

[Anonymous No.2114662]

>>2114635

>Sound waves don't come in wave packets

WRONG

http://en.wikipedia.org/wiki/Phonons

[Anonymous No.2114675]

STOP TALKING ABOUT SCIENCE ON /sci/!

[Anonymous No.2114671]

>>2114659
I think you're confusing wave packets with quanta.

[Anonymous No.2114670]

IF SOUND DOESNT HAVE MASS THEN HOW DOES GLASS COLLAPSE WHEN U SHOUT LOUDLY HA!

[Anonymous No.2114681]

>>2114652
Yes, you can use one unit system to say E=p. You can use another unit system to say E=/=p. If you try to derive any information from either statement, you're just not getting it.

[Anonymous No.2114685]

>>2114675
Shit, someone start an IQ thread!

[Anonymous No.2114687]

>>2114662
He wasn't talking about phonons.

[Anonymous No.2114707]

>>2114681
In the unit system where c = 299792458 m/s = 1, we have <span class="math">m = \sqrt{E^2 - p^2}[/spoiler] so we can conclude <span class="math">m \neq 0[/spoiler] directly from <span class="math">E \neq p[/spoiler].

In a unit system where that is not the case, we have to use <span class="math">m = \sqrt{E^2/c^4 - p^2/c^2}[/spoiler] (where c = 299792458 m/s). It's more work, but you get the same result.

[Anonymous No.2114744]

>>2113996
My god. It is just a fucking wave.

LONGITUDINAL WAVE. wtf. It is just the vibration of particles. Kinetic energy, with a frequency. COME THE FUCK ON.

[Anonymous No.2114750]

>>2114652
And I should add that I'm quite aware that sound is normally not in the form of wavepackets. But wavepackets are a solution to the wave equation, so we most certainly can make sound wavepackets. And it's a lot easier to analyze what the mass of a wavepacket is than to worry about realistic wavefronts which don't have an obvious place where they begin and end. (Although I suppose you could realistically talk about, for example, the momentum and energy of all the sound in a room. And that, taken collectively, most certainly has mass according to special relativity.)

[Anonymous No.2114759]

>>2114707
You can assume that m=0 for any wave energy, so you should get E=p.

[Anonymous No.2114767]

>>2114750
Then by all means, show me what the mass of a sound wave packet is.

[Anonymous No.2114774]

>>2114707
You realize that that's the equation for rest mass, right? So you're claiming that sound waves have rest mass?

[Anonymous No.2114778]

>>2114759
>You can assume that m=0 for any wave energy
And what ass did you pull that assumption out of?

[Anonymous No.2114795]

>>2114774
Yes. There is a frame of reference in which a sound wavepacket is at rest, and their energy (divided by c^2 in unnatural units) in that frame will equal their mass. I don't see what your objection is.

[Anonymous No.2114825]

You can express then energy density of a sound wave as
E = pv/c
where p = sound pressure, v = particle velosity, and c = speed of sound. The pv part is the sound intensity. You'll find that these two components, pressure and particle velocity account for all the energy in a sound wave. Mass is not involved.

[Anonymous No.2114829]

>>2114778
Because it's a wave. There's no rest mass.

[Anonymous No.2114846]

>>2114795
The energy of a wave is equal to its MASS EQUIVALENT. If you're comoving with a wave, the wave has energy in the form of pressure and particle velocity, although it has no group velocity. None of its energy is in the form of mass.

[Anonymous No.2114862]

>>2114846
Mass isn't a "form of energy"; it is energy (as measured in the rest frame of the object).

[Anonymous No.2114932]

>>2114862
I've never seen that definition of mass. I assume you mean an inertial frame. So by your definition, you can change the mass of an object by spinning it, but not by throwing it.

[Anonymous No.2114946]

>>2114932
> I've never seen that definition of mass.
It's what we use in particle physics.

> I assume you mean an inertial frame.
Yes.

> So by your definition, you can change the mass of an object by spinning it, but not by throwing it.
That's right.

[Anonymous No.2114951]

86 replies

you disappoint me /sci/

[Anonymous No.2114961]

>>2114946
It's acceptable to use that definition for particles. It's not acceptable to apply that definition to a wave moving through a field of particles. Then you end up taking readily-observed kinetic energy and calling it mass.

[Anonymous No.2114975]

>>2114961
Why would you consider a proton to be a particle but a sound wavepacket to not be? That's an arbitrary and meaningless distinction.

[Anonymous No.2115000]

>>2114975
Because a proton is composed of massive particles, whereas a sound wave is composed of motion.

If your definition is used in particle physics, why does a photon have zero rest mass, yet spin and angular momentum.

[Anonymous No.2115028]

>>2115000
In the end, we don't know what anything is made of (yet), so using "what it's made of" as a criterion is a bad idea.

As far as photons, something can have angular momentum without having mass. And photons can't have arbitrary angular momentum, it's always the same amount. So you can't increase the mass by changing the angular momentum.

By the way, the full definition is <span class="math">m = \sqrt{E^2/c^4 - p^2/c^2}[/spoiler] which obviously reduces to the energy in the rest frame. But the fuller definition allows you to define the mass of things like photons which don't have rest frames.

[Anonymous No.2115043]

>>2115028
>In the end, we don't know what anything is made of (yet), so using "what it's made of" as a criterion is a bad idea.

To elaborate on this, a sound wavepacket generally consists of some number of phonons (actually most likely a superposition of several different numbers).