Surprising Discovery Hints Sonic Waves Carry Mass (scientificamerican.com) 191
jbmartin6 shares a report from Scientific American: In a paper published in Physical Review Letters, a group of scientists has theorized that sound waves possess mass, meaning sounds would be directly affected by gravity. They suggest phonons, particle-like collective excitations responsible for transporting sound waves across a medium, might exhibit a tiny amount of mass in a gravitational field. "You would expect classical physics results like this one to have been known for a long time by now," says Angelo Esposito from Columbia University, the lead author on the paper. "It's something we stumbled upon almost by chance."
Esposito and his colleagues built on a previous paper published last year, in which Alberto Nicolis of Columbia and Riccardo Penco from Carnegie Mellon University first suggested phonons could have mass in a superfluid. The latest study, however, shows this effect should hold true for other materials, too, including regular liquids and solids, and even air itself. And although the amount of mass carried by the phonons is expected to be tiny -- comparable with a hydrogen atom, about 10^-24 grams -- it may actually be measurable. Except, if you were to measure it, you would find something deeply counterintuitive: The mass of the phonons would be negative, meaning they would fall "up." Over time their trajectory would gradually move away from a gravitational source such as Earth. "If their gravitational mass was positive, they would fall downward," Penco says. "Because their gravitational mass is negative, phonons fall upwards." And the amount they would "fall" is equally small, varying depending on the medium the phonon is traveling through. In water, where sound moves at 1.5 kilometers per second, the negative mass of the phonon would cause it to drift at about 1 degree per second. But this corresponds to a change of 1 degree over 15 kilometers, which would be exceedingly difficult to measure.
Esposito and his colleagues built on a previous paper published last year, in which Alberto Nicolis of Columbia and Riccardo Penco from Carnegie Mellon University first suggested phonons could have mass in a superfluid. The latest study, however, shows this effect should hold true for other materials, too, including regular liquids and solids, and even air itself. And although the amount of mass carried by the phonons is expected to be tiny -- comparable with a hydrogen atom, about 10^-24 grams -- it may actually be measurable. Except, if you were to measure it, you would find something deeply counterintuitive: The mass of the phonons would be negative, meaning they would fall "up." Over time their trajectory would gradually move away from a gravitational source such as Earth. "If their gravitational mass was positive, they would fall downward," Penco says. "Because their gravitational mass is negative, phonons fall upwards." And the amount they would "fall" is equally small, varying depending on the medium the phonon is traveling through. In water, where sound moves at 1.5 kilometers per second, the negative mass of the phonon would cause it to drift at about 1 degree per second. But this corresponds to a change of 1 degree over 15 kilometers, which would be exceedingly difficult to measure.
Negative mass (Score:2)
If it turns out that sound has a negative amount of mass, does this fix many of the problems with dark matter and the weight of the universe? Is dark matter just ... sounds?
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Is dark matter just ... sounds?
Yes, it's BSharp
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Is dark matter just ... sounds?
Yes, it's BSharp
No, its C-Pound
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If it turns out that sound has a negative amount of mass, does this fix many of the problems with dark matter and the weight of the universe? Is dark matter just ... sounds?
No, but we can use phonons to make a really cool anti-gravity hoverboard. Just be sure to wear hearing protection, because it will be loud.
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In space, no one can hear you revolutionize physics.
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Since we're talking about antigravity, I'm more curious if it's possible to use sound as a means of atmospheric propulsion. If the phonons have upward force it might be possible to create an efficient echo chamber that generates lift. That could revolutionize aerospace. I recall research on a 'sonic engine' to power cars, containing echoing sounds "so loud they would start your hair on fire," so there's already been some research done on such vessels.
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It would be fun to try, anyway.
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"so loud they would start your hair on fire,"
That's exactly it; you would require so much sound that you'd heat the air to an uncomfortable level without creating enough force to lift more than a sheet of paper.
And how are you going to generate sound that vibrates preferentially in one direction? How much motion can you generate that isn't immediately reversed by the oscillating signal? 1 Planck's constant in a rounding error?
You can't. And so, you have to simply use less speed on the return of the voice coil. But that screws your duty cycle, and now
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you would require so much sound that you'd heat the air to an uncomfortable level without creating enough force to lift more than a sheet of paper.
So, like putting a fart can on a Honda.
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For something to exist, it has to be observed.
For something to exist, it has to have a position in time and space.
And this explains why nine-tenths of the mass of the universe is unaccounted for.
Nine-tenths of the universe is the knowledge of the position and direction of everything in the other tenth. Every atom has its biography, every star its file, every chemical exchange its equivalent of the inspector with a clipboard. It is unaccounted for because it is doing the accounting for the rest of it, and
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Makes me glad didn't read it, yikes.
Superman (Score:2)
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While we often represent sound as a Sine wave, and sound experts use the sine function to create sounds. It is actually a compression wave, think of spreading a slinky horizontally on a table, then quickly pressing and releasing one end in.
Atomically everything is squishy, so atoms are bouncing around all the time, when a force is applied those atoms will be less random in their bouncing and let the force affect them. That is why we have the speed of sound that is different for the material. In Air is is
Re: Negative mass (Score:1)
Makes sense to me (Score:5, Insightful)
Sound travels through matter, so consists of, well, "phonons" that are really just the slightly altered movements of the matter the sound travels through. Sound exists for as long as that extra movement exists, and for it to exist, the matter needs to be excited, ie possess energy, over and above ambient. So that means sound waves traveling perpendicular to a gravity field have a tendency to be a little less affected by that field than ambient matter. So it looks like phonons have negative mass.
So this apparent mass is an artifact of the way you look at it.
Says I, who is so very much not a physicist. Nor a patent examiner.
The only competent comment here. (Score:3, Informative)
Given the idiocies all the other commenters wrote at this point, including TFS, you're the only one here who hit the nail on the head.
It seems people don't get that infomation is not a physical object (matter/energy) itself, but only the *structure* of matter/energy. So it's a meta level. In a medium. With different meta laws.
Hence the whole "intellectual property" oxymoron confusion.
TL;DR: Sound does not have mass. The particles that form the medium of sound, do.
Sound is a meta level, so it can only have m
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The mass is real. It is the idea that the sound "has" the mass that is meta.
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The particles are moved from additional energy, is this the mass? Are they treating the transfer of this from particle to particle as some kind of virtual particle?
virtual particle (Score:2)
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To quote from the paper's introduction:
The researchers are looking at net masses and the mass of the total material transported. These masses can be negative.
Contrary to the above summary, the resea
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Let's look at the traditional definition of "mass":
Mass is both a property of a physical body and a measure of its resistance to acceleration (a change in its state of motion) when a net force is applied. The object's mass also determines the strength of its gravitational attraction to other bodies.
so what definition of "mass" is this nons
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"The net mass transported by a sound wave vanishes" is a result based on conventional simplifying assumptions that are frequently used in the field.
Dig deep enough in any physics paper and eventually you'll find the spherical cows in a vacuum.
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Right, a small amount of energy is stored inside the phenomena and so if you interrupt it, you notice a tiny transient spike in a variable.
It is like a slight inductance.
Re:Makes sense to me (Score:5, Informative)
Sound travels through matter, so consists of, well, "phonons" that are really just the slightly altered movements of the matter the sound travels through. Sound exists for as long as that extra movement exists, and for it to exist, the matter needs to be excited, ie possess energy, over and above ambient. So that means sound waves traveling perpendicular to a gravity field have a tendency to be a little less affected by that field than ambient matter. So it looks like phonons have negative mass.
So this apparent mass is an artifact of the way you look at it.
This is explicitly not what the paper is saying. I'll just quote the introduction:
Now, this effect is completely equivalent to standard refraction: in the presence of gravity, the pressure of the superfluid depends on depth, and so does the speed of sound. As a result, in the geometric acoustics limit sound waves do not propagate along straight lines. Because of this, one might be tempted to dismiss any interpretation of this phenomenon in terms of “gravitational mass”. However, since in the formalism of [1] the effect is due to a coupling with gravity in the effective Lagrangian of the phonon, the same coupling must affect the field equation for gravity: the (tiny) effective gravitational mass of the phonon generates a (tiny) gravitational field. The source of this gravitational field travels with the phonon.
In other words, if you look at the phonons path, the effect of gravity on it looks just like standard refraction because, well, this is a sound wave. But the phonon itself couples to gravity, which means the phonon produces a gravitational field (albeit an extremely tiny one) as if it has negative mass. That is interesting (although probably not very interesting, as phonons are still quasiparticles, not real particles: a real particle with negative mass would revolutionize physics. A quasiparticle with negative mass might revolutionize a few scientists CVs).
Interesting (Score:2)
https://en.wikipedia.org/wiki/Alcubierre_drive [wikipedia.org]
"Thus, in a very physical sense, the phonon carries (negative) mass."
https://arxiv.org/pdf/1807.08771. [arxiv.org]
Vacuum (Score:3)
Wouldn't this then imply that sound should be able to pass, at least in part, through a vacuum? If sound itself has mass, then sound itself isn't a vacuum...
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Re:Vacuum (Score:5, Informative)
"Mass" isn't the same thing as "matter".
The kinds of particles, like for example electrons, that travel through vacuum, are waves in quantum fields. There is an electron field everywhere, some amount of "electron-ness" everywhere, and an electron particle is an excitation of that field. That particle would be massless, like all particles would be, if it weren't for some of its kinetic energy being bound up in interactions with other fields; in the case of free-travelling electrons, the Higgs field. Mass is just energy that's bound up doing something other than moving; most of the mass of a proton, for instance, is the binding energy of the color force holding its quarks together, way way way more than the rest-mass of those quarks (again, from the Higgs field) contributes.
Phonons are "quasiparticles" in that they are excitations of something other than a quantum field; they're compression waves in a medium like air or water. Quantum fields are everywhere, but air and water aren't everywhere, so phonons can't travel through a vacuum. To say that they have mass is, most likely (not having read all this new research yet), to say that some of their energy is bound up doing something other than moving the constituent particles of their medium. Or perhaps, since their mass is negative, that they are constantly drawing energy from their medium? In any case, it's definitely not to say that they are made of some kind of matter, which can then carry itself through the vacuum.
FWIW though, sound can travel through what we normally think of as "vacuum", since true vacuum doesn't actually exist. The space between planets is filled with a thin gas called the interplanetary medium; the space between stars is likewise filled with an even thinner interstellar medium; and the space between galaxies with an even thinner intergalactic medium. A very high-amplitude long-wavelength compression wave in this medium can travel through it, just so long as the wave moves the constituent particles hard enough and far enough that they can actually reach their nearest neighbor particles, quite some ways away in such a thin medium, and induce a similar motion in those.
Separate forces (Score:1)
The problem is you have a mass of separate forces. Each force needs a binding particle to connect it to other forces, so you have a model full of mediating particles, including this phonon. Quasi particles to connect things together that somehow magically interact via force X and Y but not Z, and other particles connects Y and Z but not X....
These are not real particles, they're simply mechanisms to describe an unknown set of properties at a pinch point.
If you think of the EM Drive, it likely oscillates the
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I'm not sure that we would be able to hear the supernova, for the same reason I'm not sure you'd be able to hear a gunshot in a hurricane. A given star system's interplanetary medium is generally comoving with the star, and blowing outward with that star's solar wind. That star is then moving quite rapidly through the interstellar medium, and there's a "bow shock" where the two meet, where an object traveling through the interplanetary medium would suddenly be hit by the different speed and direction of the
Re: Vacuum (Score:1)
This sounds like a disguised attempt at bragging about your stereo equipment. Queue Spinal Tap reference.
So? (Score:3)
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Circular reasoning. Sound, by definition, travels through matter.
Energy and mass (Score:3)
Wouldn't this then imply that sound should be able to pass, at least in part, through a vacuum?
No. By definition sound cannot pass through a vacuum. Oversimplifying here but sound is defined as a pressure wave through a medium. No medium = no sound.
If sound itself has mass, then sound itself isn't a vacuum..
Probably an imprecise statement. It's not that sound has mass so much as that it carries energy which has an effect on mass of the medium through which it travels. I've never really thought about it explicitly but it makes some sense that sound and mass would have some relationship. (E=mc^2 and all that)
If you get into the weeds of it, mass doesn't a
PBS Space Time Video (Score:2)
The rest mass of an electron is pretty much a single value... in fact it's a fundamental constant you could say.
Not what I'm talking about. PBS Space Time has a very good video [youtube.com] which explains what I'm talking about far more eloquently than I probably could. Totally worth watching.
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Not real mass.
Because phonons aren't real elementary particles. They are artifacts of the structure of real elementary particles that make up the medium.
It's a nice useful construct, but don't confuse information meta-space with real space.
And we have a winner. And if you calculate the mass of the medium out, then waves of lower density which temporarily thins the medium, will carry a negative mass if perceives as particles.
This ... ahem ... sounds ... (Score:2)
... like someone got his fundamentals mixed up. I'm sure mass in motion (sound) is hampered/influenced by gravity as it should, but that doesn't mean it itself has mass. I expect this guy's findings to be dismissed any time soon
Difficult to Measure by Inept Layman (Score:1)
But this corresponds to a change of 1 degree over 15 kilometers, which would be exceedingly difficult to measure.
If the speed of light was first measured by shining light through a spinning shutter in front of a hole in a box, to a mirror on a tower miles away, I highly doubt that measuring sound over 15 kilometers is beyond the reach of scientists over a century later.
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Measuring the speed of the wave is indeed trivial.
Where is the relevance to the stated problem.
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So would any movement then? (Score:2)
Let's say you grab the end of a cable tied down at the other end, and you give it a thwap - send a pulse down that chord, that bounces as it hits the end, reducing much like a sound wave. No sound, but a propagating wave in a physical medium that can also make sound if you plucked it instead of whipping it.
Does that add mass?
If so, is there anything special about sound in this? Or would any chain reaction propagation of kinetic energy do the same?
The actual article seems to emphasize that the wave is more
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It is like electrical inductance; the negative value comes from the mass already being stored inside the phenomena before the part where you're counting it.
Like when you shut off an electric motor and get an inductive spike as the stored power bleeds out.
Action/reaction, all that jazz, but with a slight temporal buffer.
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Does compressed spring have more mass than uncompressed one?
Per inch? Yes. Overall? No. It has more potential energy, though. Same for a gas being compressed in a cylinder. It's got more mass per cubic inch, but not more mass of gas overall. One would expect the same from sound, since it's a compression wave passing through a medium.
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What is "directly affected by gravity. "? (Score:2)
Everything is affected by gravity including light and other massless particles. That is how they first proved relativity.
What is surprising here?
And a sound wave is a movement in particles with mass, so I think relativity also says something about changing their mass.
God Continuously Invents Science (Score:2)
ðY
huh? (Score:2)
Or (Score:1)
15km in 1 second at 1.5km/s? (Score:4, Informative)
In water, where sound moves at 1.5 kilometers per second, the negative mass of the phonon would cause it to drift at about 1 degree per second. But this corresponds to a change of 1 degree over 15 kilometers, which would be exceedingly difficult to measure
Uh, if sound moves at 1.5 km/s, and drifts by 1 degree/s, then in 1 second it should have drifted by 1 degree and travelled 1.5 km, not 15km? After 10 seconds it will have travelled 15 km and drifted by 10 degrees, which surely would be measurable. (PS: I read the article, the summary quotes the article correctly.)
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Yes... journalism math. Decimal points are just decoration.
I don't think it would be easily measurable though. It's easy enough to measure sound in water at 15 km distance (or 150 km) but it would be very difficult to determine whether the average direction had changed since the wave would have dispersed so much.
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Details.... First sentence starts with 'in water'. Presumably, the next sentence is not 'in water'.
I think it must have been a decimal point problem instead, because the speed of sound in air is only 0.3km/s. Even in metals like steel it's only 5 - 8km/s. I'm not a materials scientist, but I don't know any solid that transmits sound at 15km/s. Wikipedia says it's 12km/s in diamond, for whatever that's worth as a reference.
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Good. So I'm not the only one who hasn't had enough coffee yet.
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deduct from classical physics? (Score:2)
In how far can this be deducted from 'classical' physics? Because phonons are not real, but quasiparticles, only quantised because of the geometrical setup.
Meaning: sonic waves have differences in pressure in them. Something of low pressure tends to go up (helium balloons) in a material, and vice versa.
What if these do not eliminate each other exactly within one wavelength?
Probably an annaccounted EM interaction (Score:1)
What about sonar? (Score:2)
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They may very well have - but my guess would be error in the known temperature of thermal gradients within the ocean would contribute far greater error. Temperature, salinity, and currents all contribute far more than gravity.
When can I get the cables (Score:2)
The Alcubierre Drive (Score:2)
https://en.wikipedia.org/wiki/Alcubierre_drive [wikipedia.org]
"Thus, in a very physical sense, the phonon carries (negative) mass."
https://arxiv.org/pdf/1807.08771. [arxiv.org]
This is a surpise? (Score:2)
Sonic waves carry energy. Energy is mass. We've known this for about a century.
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You made the same mistake I initially did. They are saying phonons carry *negative* mass, which to me is very counter-intuitive.
explains (Score:1)
Sound lift (Score:2)
Does that mean that the noisier the plane engines the better the plane flies? :P
Witches should fly on vacuum cleaners, not brooms.
You get the idea.
Simple way to view this (Score:2)
the ratio of the sines of the angles of incidence and refraction of a wave are constant when it passes between two given media.
So basically the sound kind of bounces off the pressure gradient caused by gravity, lifting the mass of the medium with it (slightly). The authors themselves discuss
One degree over 15km (Score:2)
Is about 250 meters, following the 1:60 rule used in navigation. I would've thought a 250m offset is large enough to measure, but maybe not with sound in water.
I’m no physicists, but... (Score:2)
You flunked math, huh? (Score:2)
Wow....it would also correspond to a change of 1 degree over 1 millimetre. And a change of 1 degree over 1 billion parsecs.
The rest of this pathetic post is similarly utter ignorant nonsense babble from someone who doesn't understand the most
Pick the right cables (Score:2)
For the correct delivery of phonons to your eardrums, use Siltech Royal Signature Emperor Double Crown Loudspeaker cables [analogueseduction.net]. The have elegant self-shielding topology.
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I'm having trouble with the concept of negative mass, too. The phonons would not just move away from the earth, but also from the sun, from the center of the galaxy, etc... Where do you stop? And would they also move opposite to other mass in the accelerating expansion of the universe? Relative to what center?
It also seems quite difficult to reconcile this with General Relativity where, for example, you are not supposed to be able to tell whether an elevator is in a field of gravity or accelerating without
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I'm having trouble with the concept of negative mass, too. The phonons would not just move away from the earth, but also from the sun, from the center of the galaxy, etc... Where do you stop? And would they also move opposite to other mass in the accelerating expansion of the universe? Relative to what center?
I'm having trouble with the concept of positive mass, too. The phonons would not just move towards the earth, but also towards the sun, toward the center of the galaxy, etc... Where do you stop? And would they also move opposite to negative mass in the accelerating expansion of the universe? Relative to what center?
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I'm having trouble with the concept of negative mass, too. The phonons would not just move away from the earth, but also from the sun, from the center of the galaxy, etc... Where do you stop?
I'm having trouble with the concept of positive mass, too. The phonons would not just move towards the earth, but also towards the sun, toward the center of the galaxy, etc... Where do you stop?
For positive mass this is no problem. The earth is attracted to the sun, and so is everything on earth, so the relative acceleration between objects on earth and the earth due to the gravity of the sun is zero (apart from small tidal forces). Same for the center of the galaxy which attracts the sun, the earth, and everything on earth. This is unnoticeable because the whole system gets the same acceleration towards the center of the galaxy. And the same goes for whatever acceleration we get from the accelera
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Ultimately we knew to start with these assumptions because positive gravity obviously does work and we achieve at least some form of localized stability for a reasonable measure of time. Either the same be assumed of negative mass or we can assume it is so unstable as to not impact the stability of other systems or it may well be that it has been a factor all along and we've accounted for it with constants or other small adjustments in the formulas across many other measurements causing them to give functio
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I'm having trouble with the concept of negative mass, too. The phonons would not just move away from the earth, but also from the sun, from the center of the galaxy, etc... Where do you stop?
You don't have to stop. The force due to gravity is F=GMm/r^2. Make the little m negative, it becomes a repulsive force inversely proportional to the square of the distance (instead of the attractive force for positive mass).
It also seems quite difficult to reconcile this with General Relativity where, for example, you are not supposed to be able to tell whether an elevator is in a field of gravity or accelerating without gravity. Both situations ought to be equivalent (apart from tidal forces), but clearly result in opposite accelerations when negative mass is involved.
Not if the inertial mass and gravitational mass are both negative. If they are, then F=ma means acceleration is opposite the applied force, which while weird still gives equivalence between gravitational and inertial mass.
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But if the gravitational force is repulsive and the acceleration is also opposite to the force, they would fall down rather than up, wouldn't they?
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Helium balloons don't have negative mass, they still have weight and are attracted by the earth. It's the heavier surrounding air that pushes the balloon up (pressure gradient provides more force than gravity).
So you're saying that phonon traveling through some medium (like air) is pushed up by the rest of the medium? That's not really "negative mass", just "less mass than the surrounding medium".
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If you understood classical physics, you'd understand that there is no difference between the statements. The wind cannot push the tree without the tree swaying. The tree cannot sway without pulling the wind. Pulling and pushing are identical; we call one an "action" and the other a "reaction" because it is easier for humaans to understand, but they're not separate; you can't have only one, which would be required for it to be causal.
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No matter how many people lean to the west, they will not cause a west wind to blow. They'll just fall over and feel silly.
Don't confuse an immediate local interaction with causality.
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You seem to have entirely missed the point what you quoted; the subject of what you quoted is not even physics. In the quote, "west wind" and "leaning" are not contextually connected. Whereas, what you replied to was referring to Newton's 3rd Law, which narrowly covers interactions between things.
And that said, yes, when you lean to the west, you do blow some wind that way.
But regardless, Newton's 3rd Law prevents cause and effect from having meaning when it comes to the action and reaction. Forces act equa
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I didn't quote anything. My words were my own. You seem to have not understood them.
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This has been understood by Metallica for a long time now.
I mean, why do you think they call them "Heavy Metal" bands?
CAP === 'contempt'
Already predicted by E=MC^2 (Score:2)
Anything that stores energy has mass doesn't it? So a sound wave which is a melange of oscillations of kinetic and potential energy has mass. So this is already known.
Additionally, if it's like a photon, then it is not going to have any additional mass on top of that I believe though I might be wrong.
Negative mass and the mass defect (Score:2)
oops... accidentally deleted half my post when I submitted it.
Anyhow, so how do we get to negative mass? I think there are two ways that are essentially realted.
in a nutshell, this is like an airbubble in water. The air bubble is made of air so it has mass. But it floats up like it has negative mass.
Consider the mass defect effect. That's the reason why isoptopes weigh less than they should. the reason is that the attractiv forces in the nucleous create abinding energy well the neutrons are in. So they
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I predict that an article like this is going to bring the cranks out of the woodwork. Two obvious flaws in this "journalistic impression" of the actual research: 1) The original article has nothing to do with antigravity, it discusses an effect more like buoyancy. 2) A change of one degree is not hard to measure, regardless of the distance it is measured over, because angles do not change with distance. These obviously nonsensical inventions are the result of some journalist's wild imagining about a topic t
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Sorry, but this is plausible. It would need careful calculation, but it's plausible. My reasoning is thus:
Sound (in air) originates as a wave of compression, which squeezes things away from it, followed by a wave of de-compression, which allows things to return. If the sound encounters a barrier (necessary to create a phonon), then the pressurization still squeezes molecules out, but the barrier prevents easy return, so the mass of the air within the phonon will be less than the mass of the air away from
Re:Theoretical physics isn't science (Score:5, Insightful)
Come on now. Science is not limited to the domain of experimental science.
Science broadly construed is the search for hypotheses that unite various phenomena. Experimental science merely attempts to falsify these hypotheses.
If anything, experimental science is the ugly stepsister here ...
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Theory is a part of the process. It is not enough by itself to be "science", being only the first step in the scientific method. Or, put differently, theory that never gets tested never becomes science.
Theory alone is just story telling within a rigorous framework, and the vast majority of published theoretical work is eventually disproven. Heck, there have been 20ish years of published theory about "inflation", and there will likely be decades more, thousands upon thousands of speculations. At most one
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You should stop worrying about big-picture stuff like 'science' and instead concentrate on reading comprehension.
In response to dude who said that theoretical physics is not science, I said science is both the positing and the empirical testing of hypotheses.
Re:Theoretical physics isn't science (Score:5, Informative)
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Also, I would be more surprised if quasiparticles *didn't* have mass associated with them - would be a violation of matter energy conservation. With inelastic scattering you can map out phonon energy distribution as well. Not belittling any of their work, always neat to see things confirmed experimentally.
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Disregard comment below - went full /.'er and just skimmed the summary. Missed "negative" mass - now I can safely say I don't understand the results at all.
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But negative mass (according to TFA). And so negative energy.