I just can't wrap my head around how non-inverse-square-laws are supposed to work for forces. Why doesn't this (and MOND) violate a fundamental law? I thought the point of inverse square laws was that we have a point source, area increases with r^2, energy is radiated symmetrically in space, and thus energy at any given point has to drop off with 1/r^2 in order for total energy to remain constant. So how is a non inverse square law supposed to work? How can we not be violating something fundamental like conservation of energy, number of dimensions in space, spherical symmetry, causality, etc.?
You can think of it, at a very high level, being the difference between a force mediator that has no self interaction (photon) and a force mediator that does have self-interaction (gluon). Gluons interact with each other, whereas photons don’t. Even this by itself isn’t naively enough to get all the strong force’s interesting behavior. But the math works out in such a way that when you start to pull two strongly bound particles apart, the color field forms a flux tube of gluons between the two particles, and the force required to pull them apart further remains approximately constant (in other words the energy stored per unit length in the flux tube is ~constant). This only happens because of the self interaction.
It doesn’t violate energy conservation at all! For the trivial reason that field itself is not the entity using energy to displace two bound particles ;)
Thanks for posting this comment, it was really entertaining to see how quickly it got wildly over my head and started sounding like sci-fi gibberish
> You can think of it, at a very high level, being the difference between a force mediator that has no self interaction (photon)
Don't really know what a force mediator is but I can somewhat imagine, and photons not interacting with themselves I think makes sense
> a force mediator that does have self-interaction (gluon)
I'm guessing these particles interact with themselves and maybe they're called gluons because they stick together or something, like glue
> Gluons interact with each other, whereas photons don’t.
I think I'm making progress
> Even this by itself isn’t naively enough to get all the strong force’s interesting behavior. But the math works out in such a way that when you start to pull two strongly bound particles apart,
Good so far
> the color field forms a flux tube of gluons between the two particles,
lost me, you just switched lanes into back to the future speak
A completely different way to think about it: it doesn't surprise you that spring forces get stronger as you stretch them. You expect it because there is material there.
In the case of strong force, you get virtual particles appearing when you separate particles. So the strength increases with distance. It doesn't become infinite because particles also attract their "opposites", and so the result is zero from a distance. (Like the way single charged particles usually are found in uncharged clumps.)
(Opposite is a harder concept in strong force, which has more symmetries than the electrical one.)
I think I could see how this could work, but I'm not sure. So it sounds to me like we have a situation where either (a) quark isolation would violate conservation of energy, or (b) isolated quarks (assuming we could at hypothetically have them in theory, even if not in practice) wouldn't actually exert this constant strong force on each other (at least until they're close together and the "link" can get established, so to speak), and instead only exert some sub-1/r^2 force on each other before then. Am I correct to guess the situation is more like (b)?
If you have an electric dipole with a positive and negative electric charge near to each other then the force drops off like 1/r^3, faster than 1/r^2. This result is for a single quark in isolation; in reality quarks come in pairs or triplets, and they each have different colour charges which cancel out the long distance behaviour of the strong force
> If you have an electric dipole [...] the force drops off like 1/r^3
> This result is for a single quark in isolation
Sorry, I'm confused. Doesn't this confirm what I'm saying? For multiple particles I get how it could be different from 1/r^2 (though only less than 1/r^2, not more!), but as you say, this is about a single quark in isolation, which is neither multiple particles nor less than 1/r^2, so the problem is still there right? (The fact that quarks aren't ever found in isolation in practice seems irrelevant to me, unless the claim is "quarks absolutely cannot be found in isolation due to conservation of energy", which I've never read.)
And what about something like MOND? I see the same problem, and it's about gravity!
> I thought the point of inverse square laws was that we have a point source, area increases with r^2, energy is radiated symmetrically in space, and thus energy at any given point has to drop off with 1/r^2 in order for total energy to remain constant.
This explains an inverse square law for intensity of radiation, but why would you expect it to apply to forces in general?
It can only work between pairs of particles that are bound together. Otherwise, the total forces between every pair of quarks (N^2 pairs) in the universe would be preposterously large.
Maybe things in _our_ perceivable universe follow the inverse-square-law because they exist in the 3 dimensions familiar to us, as you succinctly explain. But maybe the Strong force propagates in less, or more, or different, dimensions?
Does the Strong force propagate at C? Can we test that? It might give some hint.
It reminds of the alternative to dark matter that is MOND, stating that the law of gravity behaves as 1/r at large distances (as opposed to 1/r2 at our scale) [0]. I personally like it because it seems less ad hoc than to posit the existence of invisible matter, and similar in my mind to the special relativity adjustment. (Do not take this endorsement too seriously, of course.)
However: "The most serious problem facing Milgrom's law is that it cannot eliminate the need for dark matter in all astrophysical systems: galaxy clusters show a residual mass discrepancy even when analyzed using MOND. The fact that some form of unseen mass must exist in these systems detracts from the adequacy of MOND as a solution to the missing mass problem, although the amount of extra mass required is a fifth that of a Newtonian analysis, and there is no requirement that the missing mass be non-baryonic." [0]
The problem with dark matter is not that it is ad hoc. It is that it feels un-parsimonious to resolve a discrepancy in rotation curves by inventing five times more stuff than you had, all undetectable, and distributed just right to make all your curves come out right.
It turns out that the mass of neutrinos produced so far adds up to as much mass as all the rest of particulate matter. I guess neutrinos must be distributed about evenly throughout the universe. If we could not ever detect neutrinos, that would be awkward.
I have not heard of a mechanism by which these dark matter particles can cool and condense to clumps to seed galaxies. By contrast, baryonic matter gets to emit photons to give up kinetic energy.
Particle physics has a pretty good track record of inventing undetected particles to solve missing item problems, then finding that particle later. I'd guess we're up to hundreds of such particles like this so far, with really big finds being positrons (and all anti-partickes, needed when adding relativity to spin), neutrinos (needed to account for missing mass), all the quarks (needed for certain symmetries, among others), and the Higgs bison itself (needed to explain masses).
So don't discount adding currently undetected things as explanations for surprising measurements. It's been extremely fruitful.
My pet theory for gravity / general relativity (which is probably completely wrong, but fun to think about), is that space itself is created through particle interaction. Space will thus be denser and create a gravitational effect in places with lots of matter.
That means space also has to decay. And unless you want space to become non-existent far away from matter, the rate of decay must also fall off somehow as you get further away from matter.
I wonder if you could get such a space creation/decay process to match a curve that's 1/r2 at short distances and 1/r at long distances...
My pet theory is that let's say particles are the excitation of the field, imagine you come to a lake in a quest to understand water. The surface is field. You throw in a rock and the splashback is particle, you analyze the particle, you throw other things and analyze the other particles. Then you form a water theory based on these particles and you find out that boats shouldn't float at all.
It's because particles are exceptional things, not the normal, calm field they come from. If you base your theory on those exceptional thing it will be non representative or outright wrong.
That's why quantum physics is giving us weird results, because particles are exceptions, not the common state of the field.
Interesting idea. Although, if particle interaction creates space, shouldnt it counteract gravity? If the Earth, full of interacting particles, is hurling space outwards, stuff around Earth should fling into infinity, not fall towards it, or what am I missing?
There's also the issue that some galaxies don't violate our pre-dark-matter models as much or do so in a different way. With dark matter that's easily explained as an abnormal dark matter halo (eg maybe displaced due to an ongoing interaction with another galaxy or absent for an unknown reason). When abnormalities like that are considered, dark matter becomes the elegant solution while theories that tweak gravity start to seem somewhat ad hoc.
That's the fascinating thing to me: it doesn't matter! MOND is a successful pseudoskeptical meme despite not being a successful physical theory.
The narrative of MOND-the-meme is totally wrong but extremely compelling. That's enough to give it outsized fitness in its niche, and then that general compellingness (which comes from being really good at tricking us) is misinterpreted as scientific merit. Even by those who say they're interested in truth, not stories.
It's an excellent test-case for critical thinking because everything about it as a meme should set off alarm bells, but often it doesn't.
My understanding is the 1/r^2 behavior comes from solving for Green's function of a PDE. Gravity is similar to Gauss's law (i.e. 1/r^2 behavior of charged particles) in the underlying PDE. So something in that equation would have to change.
Apparently it makes very accurate predictions though, so it's not just a matter of ad hoc tweaking some law to fit reality... It does seem to capture some regularity/mechanics of nature.
it introduces more parameters to fit its arbitrary conception about how gravity is supposed to scale. even worse, since basic MOND disagrees with a ton of basic evidence since it just doesn't work except for the few problems it was created for, the actual MOND derivatives that do try to make it work introduce even more parameters to fit.
It introduces ONE parameter. And TWO, for the relativistic version. To simplify, LCDM introduces at a minimum one parameter (relative dark matter:visible matter ratio) for each galaxy to get the rotation curves correct. That's at least a billion parameters.
MOND has made successful predictions:. The EFE, for example (there are others). LCDM has not, as far as I can tell -- please correct me if I'm wrong [0]
> work except for the few problems it was created for
That's actually a poor heuristic. Suppose we hadn't discovered relativity yet (but had galactic rotation curves, which only depend on good telescopes and newton, and Doppler effect), and we observed mercury's precession. Would you then use precession as an argument for dark matter on the basis that there's a dark matter entity in our solar system pulling mercury around? I would think that would not be a good idea.
[0] ok I looked it up and actually LCDM predicted no galaxies with redshift greater than 7... And thanks to jwst we now know there are galaxies with much much greater redshift, a feature explicitly predicted by MOND.
This is like saying that the existence of precession in mercury's orbit detracts from the adequacy of a Newtonian analysis and so there must be a dark matter blob pulling mercury's orbit around.
I always wonder if this "missing mass" is just light. As in it is so close to zero mass to be undetectable at a normal scale, but at galaxy scale, it actually has mass.
I've wondered similarly, but I don't know why it would need mass. That just complicated things. It has energy, and we have an equation that tells us how much equivalent mass that would be. It's not missing mass, it's energy that's the cause of the extra gravity.
Is it possible that the gravitational discrepancies can be explained with dyson spheres? Or dyson spheres collected into grids (with a dyson sphere scale tech you can prob move suns by making the dyson sphere a giant fusion engine).
There is an advantage to arranging dyson spheres closer together in order to reduce latency between nodes.
If your dyson spheres were optimized enough, could absorb all known spectrums and recycle them. Wouldn’t that appear completely dark save for gravity?
I mean, isn’t it possible entire galaxies have been converted in this way? Seems like it could be a much simpler explanation within the confines of current understanding.
But I’m sure this has been thought about and accounted for.
> If your dyson spheres were optimized enough, could absorb all known spectrums and recycle them.
A really cool outcome of statistical mechanics and thermodynamics is that what you suggest is impossible. The dyson sphere can be as amazing as you want, using every single trickery permitted by physics, but at some point it will enter thermal equilibrium with its host start (or pipe that heat somewhere else where you would still be able to see its thermal radiation). Inherently, if they are optimized to be good absorbers, they will have to also be thermal emitters. There is no such thing as "recycle all spectrum".
Tangentially related to the fact that a "perfectly black body", i.e. a perfect absorber, is also the perfect emitter of thermal radiation of its own.
My layman understanding is that the dyson spheres would occlude objects behind them if they happen to be in line of sight to us. Given that things in the universe are not static, other (visible) bodies would move in and out of occlusion, allowing us to detect the DS.
For this to match observations, all galaxies visible outside the milky way would have to be Dyson sphered through their whole extent. If they weren't, it would be obviously visible, as an expanding civilization that had only spread throughout half a galaxy would be a totally lopsided galaxy. And for some reason, all of those civilizations must have decided to leave a certain percentage of stars un-sphered even though they have the capacity to sphere them all.
And the Milky way would have to be un-dyson sphered, because if it were, we would be able to notice these spheres close up. e.g. if dark matter is 5x regular matter, we would expect there to be 5 Dyson spheres of stars the size of the alpha centauri system all within 4ly of Earth. This would be easy to detect through occlusion. Also, gravitational interactions between sphered stars and unsphered stars would be easily observable in our own galaxy. So for this to work, at minimum, the whole observable universe must by Dyson sphered, except for our own galaxy.
This baffles me, both gravity and electromagnetic forces drop off with increasing distance. Anyone familiar with the theoretical basis for this? I assume this has really weird consequences for unification of all forces. I believe when I was studying physics they said that strong and electromagnetic were very similar (at short distances).
The fundamental equations for QED (electromagnetic force) and QCD (strong force) are similar, but the solutions are radically different as gluons interact with themselves in a peculiar way. And we only know how to solve QCD equations at short distances where the force is small. Solving QCD at large distances is one of the unsolved "Millenium problems" [1].
It is mostly to do with color. If something is not a color singlet, gluons attach to it. Trying to separate the two quarks of a meson it is thought that a tube of gluons forms between them of which the energy is linear in the length of the tube. Since force is the derivative of energy, this leads to a constant force.
It's been more than a decade since I 've been out of High Energy Physics.
The mediator of the strong force, the gluon, is a different beast compared to photons. It can directly interact with itself and create more of it. Add in the math that describe it and you get an emerging behavior vastly different from the one you get for photons.
I'm brushing up. One tidbid is that "coupling" has a specific non-intuitive meaning which differs from "action-reaction pair." Since a couple acts on the system, and the action need-not be always-centering, it produces a torque, but exerts no force.
The article also mentions mass-growing at a distance, I wonder if
- they really mean "with displacement, mediated by speed"
- there's some interaction under which two gluons can enter a binary, uniform rotation about one-another
The introduction to the full text identifies a subset of the theories under comparison, and hints at the techniques the theories deployed to arrive at their predictions, for example by "light-front quantized QCD" [1]
To understand the strong force coupling look up the concept of asymptotic freedom.
This running of the coupling constant would in principle allow unification with the electroweak force in most theories e.g. supersymmetry - we just have not worked out the exact framework.
I believe you're confusing the strong with the weak force. Elecromagnetism does indeed join with the weak force and form electroweak at high energies. The strong force is a very different beast.
Simply put, the biggest difference is that gluons, the interaction particles of the strong force can in contrast to photos, which mediate the electromagnetic force, interact with each other. That gives rise to a lot of strange phenomena, such as the long-distance behaviour of the strong force.
This work has provided improved experimental confirmation, but that the force remains constant with distance was assumed already many decades ago.
The fact that the force between hadrons does not decrease with distance like the electromagnetic or gravitational forces explains why it is impossible to obtain free quarks.
When you have a system of particles which is bound by electromagnetic forces, e.g. the electrons bound to a nucleus, and you come with an external force and you pull the electron away from the opposite charge, the force retaining the electron becomes weaker and weaker while the distance increases, until the electron becomes free when the work of the pulling force exceeds the binding energy.
On the other hand, when you have a system of bound quarks, e.g. 3 quarks that compose a proton, and you come with an external force and you pull away one quark, the force remains constant while the distance increases, keeping the quark bound, until the work of the pulling force exceeds the energy of generation of a quark-antiquark pair.
At that threshold, a quark-antiquark pair is generated and the antiquark sticks to the quark that is pulled away, while the quark sticks to the other 2 remaining quarks.
Thus the effect of pulling one quark away is not the appearance of a free quark, but the appearance of a free quark-antiquark pair, which is named pion, a.k.a. pi meson, while the original proton may either transform into a neutron or remain a proton, depending on what kind of quark-antiquark pair happened to be generated.
To prevent the existence of free quarks, it would be enough for the force to decrease very slowly with the distance, but a model where the force is actually constant is the simplest and the most elegant, so it is good that the experimental data match this.
The reason why the interaction through electromagnetic or gravitational forces has a force decreasing with distance is that the force is the same in all directions and it is constant per solid angle, so the ratio of force per area decreases proportional to the area of the sphere centered on the source of the field.
This can be visualized with the Faraday's lines of force as equidistant radii going from the center of the sphere, and the density of lines of force per area decreases for greater spheres.
On the other hand the force between quarks can be visualized with the Faraday's lines of force not being towards all directions but being confined inside a tube that connects 2 quarks. When the distance between 2 quarks increases, the tube of lines of force becomes longer, but its cross-section remains constant, so the density of lines of force per area, i.e. the intensity of the force, remains constant.
When the distance increases over the threshold for generating a quark-antiquark pair, the tube of lines of force breaks into 2 tubes, with the 2 new ends of tubes being terminated on the newly generated antiquark and quark.
So visualizing a force that is constant with distance is not difficult and there are many materials that have the same behavior when they are extended over their elastic limit, i.e. their elongation increases continuously while the force is constant, until the material breaks.
There is actually a simple way to obtain a force between two objects that does not decrease with distance: simply connect them with an (idealized) string. And it is indeed not entirely inaccurate to say that the strong force produces some kind of quantum mechanical string between two quarks.
Historically the study of exactly these strings for the strong force led to the idea of string theory. Only later was it realized that it can be useful as a theory of quantum gravity as well.
Question for physics types: in a hydrogen atom, each quark feels a force from the other two quarks. But if the force really is constant over all distances, would it not feel an equal, or even greater force, from all the other quarks in the entire universe? If there was any imbalance, even one more quark on one side of the Hydrogen atom than the other, wouldn't the quark be pulled toward that?
Or does the strong force go back to zero at distances say larger than an atom?
The charge of the strong force is called color, and outside particles like protons the total color charge seen from the outside is zero.
It stays zero because of color confinement - at some point, it's less energetic to create color-anticolor pair instead of allowing color imbalance.
It's only constant force for quarks in isolation. A good mental model is that between the oppositely charged particles, a string of gluons forms and pulls them together with constant force. The resulting composite particle no longer has a color charge, so it does not interact as much with other particles through the strong force.
Of course there are also residual forces from a color-neutral bound state to quarks which are a bit further away, but those are not nearly as strong. They are for instance responsible for holding nuclei together.
The important property of the strong force here is that it interacts with itself. The field of two quarks together is not the sum of their individual fields, because the force-carrying gluons are also color charged and thus interact with each other.
I had the same thought. Perhaps the bound quarks are never far enough apart for the strong force to be constant?
My understanding is that if you do manage to pull two quarks apart the energy of separation is eventually enough to form two new quarks, thus pairing them up again.
My question is whether this pair production happens before or after the strong force reaches the region where it is constant?
I'm not a professional physicist, so take this with a grain of salt. But first of all: the same question could be asked about "everyday" electric forces, and the answer is simple: positive and negative particles bond together and neutralize each other; their fields get overlapped. All the remaining force due to small physical distance(?) or quantum jiggle(?) is very small residues. (But it is enough to beget molecular dynamics.)
I think (guess?) that the strong force does the same, in the sense that there is a "neutralizing tendency", anyway, but the mechanism is different. Protons and neutrons, and pions too, are neutral when you watch them from far away. (But not so, when you are trying to explain why atomic nuclei are formed, protons and neutrons _like_ to clump together.)
The difference between a photon field and a gluon field is that gluons are attracted to each others in a way that I, as a non-nuclear-physicist don't quite understand (as the symmetry between them is not something I've actually studied); but as photons form "beams" (you can think of them in a linear algebra sense of vectors, almost!) that propagate in a very geometrically uniform way, gluons, being attracted to each others, form "tubes", which behave, as any self-interacting system would, in a very dynamic way.
Imagine a cellular simulation (like the Game of Life, but more... floating point instead of of integers & squares) where each quark sends gluons but they tend to clump together and form tubes? These tubes can't be super long, because quantum physics and the universe works in a way that energy gets minimized, and anything that could happen to make that happen, tends to happen. That means that if there's enough energy stored in the tube, it becomes "cheaper" for the universe to sever that connection and instead, produce new, separate particles that have their own, internal "tubes". That means that no long "tubes" of gluons are allowed in the universe, and thus, the strong force of the Strong Force is contained.
So the mechanism seems to be really super different from "overlapping +/- fields", in a sense, but the result is the same: no forces (albeit small residues) seen from afar.
As I understood, it's constant only after some distance, meaning that the force to its very close quarks is still much stronger than the constant force from the rest of the universe.
After reading a bit more I think I got it all backwards. The force increases with distance, up to a constant, but it seems this is only applicable to already bound quarks, so there's no strong force from rest of the universe.
But that's my point. If the strength of the force is constant, independent of distance, then the farther away quarks contribute the same as the nearer quarks. In other words, distance doesn't matter, whether something's farther away or closer has no bearing on the strength of the force.
Wikipedia's discussion seems pretty good. Fundamentally, force calculations in classical physics tend to be replaced by perturbation calculations in quantum mechanics.
> "A coupling plays an important role in dynamics. For example, one often sets up hierarchies of approximation based on the importance of various coupling constants. In the motion of a large lump of magnetized iron, the magnetic forces may be more important than the gravitational forces because of the relative magnitudes of the coupling constants. However, in classical mechanics, one usually makes these decisions directly by comparing forces. Another important example of the central role played by coupling constants is that they are the expansion parameters for first-principle calculations based on perturbation theory, which is the main method of calculation in many branches of physics."
Perturbation theory and calculations depend heavily on the coupling constant. If I recall correctly, in quantum electrodynamics (Feynman diagrams) the coupling constant is ~ 1/137. If you raise this number to higher powers (adding terms in the pertubation process) it quickly falls off towards zero, so you can get very accurate calculations using this approach in QED.
With the strong force, this coupling constant is much larger and so the higher powers in the perturbative calculation are significant, meaning it's much harder to calculate accurately with QCD compared to QED. From the paper, this reference:
* Improving our knowledge of αS is crucial, among other things, to reduce
the theoretical “parametric” uncertainties in the calculations of all perturbative QCD (pQCD) processes whose cross sections or decay rates depend on powers of αS , as is the case for virtually all those measured at the LHC. *
(2021) "The strong coupling constant: State of the art and the decade ahead"
Unfortunately this is usually plotted as momentum vs coupling, which, if you wave your hands around the uncertainty principle enough, is sort of the reciprocal of the same thing.
If it's the maximum value and constant at all distances, wouldn't the strong force be dominated by all other objects everywhere else? Or does this force only apply to particles matched up together? If so, how does this matching occur?
Readit News
It doesn’t violate energy conservation at all! For the trivial reason that field itself is not the entity using energy to displace two bound particles ;)
> You can think of it, at a very high level, being the difference between a force mediator that has no self interaction (photon)
Don't really know what a force mediator is but I can somewhat imagine, and photons not interacting with themselves I think makes sense
> a force mediator that does have self-interaction (gluon)
I'm guessing these particles interact with themselves and maybe they're called gluons because they stick together or something, like glue
> Gluons interact with each other, whereas photons don’t.
I think I'm making progress
> Even this by itself isn’t naively enough to get all the strong force’s interesting behavior. But the math works out in such a way that when you start to pull two strongly bound particles apart,
Good so far
> the color field forms a flux tube of gluons between the two particles,
lost me, you just switched lanes into back to the future speak
But the overall story around colour confinement, flux tubes and so constant force required to separate quarks is the right explanation.[1]
It is not the self interaction per se that leads to confinement, but that colour seem to be confined.
[0] https://physics.stackexchange.com/questions/293873/do-gravit...
[1] https://en.wikipedia.org/wiki/Color_confinement#Origin
In the case of strong force, you get virtual particles appearing when you separate particles. So the strength increases with distance. It doesn't become infinite because particles also attract their "opposites", and so the result is zero from a distance. (Like the way single charged particles usually are found in uncharged clumps.)
(Opposite is a harder concept in strong force, which has more symmetries than the electrical one.)
> This result is for a single quark in isolation
Sorry, I'm confused. Doesn't this confirm what I'm saying? For multiple particles I get how it could be different from 1/r^2 (though only less than 1/r^2, not more!), but as you say, this is about a single quark in isolation, which is neither multiple particles nor less than 1/r^2, so the problem is still there right? (The fact that quarks aren't ever found in isolation in practice seems irrelevant to me, unless the claim is "quarks absolutely cannot be found in isolation due to conservation of energy", which I've never read.)
And what about something like MOND? I see the same problem, and it's about gravity!
This explains an inverse square law for intensity of radiation, but why would you expect it to apply to forces in general?
Does the Strong force propagate at C? Can we test that? It might give some hint.
However: "The most serious problem facing Milgrom's law is that it cannot eliminate the need for dark matter in all astrophysical systems: galaxy clusters show a residual mass discrepancy even when analyzed using MOND. The fact that some form of unseen mass must exist in these systems detracts from the adequacy of MOND as a solution to the missing mass problem, although the amount of extra mass required is a fifth that of a Newtonian analysis, and there is no requirement that the missing mass be non-baryonic." [0]
[0] https://en.wikipedia.org/wiki/Modified_Newtonian_dynamics
It turns out that the mass of neutrinos produced so far adds up to as much mass as all the rest of particulate matter. I guess neutrinos must be distributed about evenly throughout the universe. If we could not ever detect neutrinos, that would be awkward.
I have not heard of a mechanism by which these dark matter particles can cool and condense to clumps to seed galaxies. By contrast, baryonic matter gets to emit photons to give up kinetic energy.
So don't discount adding currently undetected things as explanations for surprising measurements. It's been extremely fruitful.
Deleted Comment
I don't believe that's true? The energy density in neutrinos today is < 0.5% (baryonic matter is ten times that.)
That means space also has to decay. And unless you want space to become non-existent far away from matter, the rate of decay must also fall off somehow as you get further away from matter.
I wonder if you could get such a space creation/decay process to match a curve that's 1/r2 at short distances and 1/r at long distances...
It's because particles are exceptional things, not the normal, calm field they come from. If you base your theory on those exceptional thing it will be non representative or outright wrong.
That's why quantum physics is giving us weird results, because particles are exceptions, not the common state of the field.
The narrative of MOND-the-meme is totally wrong but extremely compelling. That's enough to give it outsized fitness in its niche, and then that general compellingness (which comes from being really good at tricking us) is misinterpreted as scientific merit. Even by those who say they're interested in truth, not stories.
It's an excellent test-case for critical thinking because everything about it as a meme should set off alarm bells, but often it doesn't.
The answer is most likely MOND + dark matter.
it introduces more parameters to fit its arbitrary conception about how gravity is supposed to scale. even worse, since basic MOND disagrees with a ton of basic evidence since it just doesn't work except for the few problems it was created for, the actual MOND derivatives that do try to make it work introduce even more parameters to fit.
MOND has made successful predictions:. The EFE, for example (there are others). LCDM has not, as far as I can tell -- please correct me if I'm wrong [0]
> work except for the few problems it was created for
That's actually a poor heuristic. Suppose we hadn't discovered relativity yet (but had galactic rotation curves, which only depend on good telescopes and newton, and Doppler effect), and we observed mercury's precession. Would you then use precession as an argument for dark matter on the basis that there's a dark matter entity in our solar system pulling mercury around? I would think that would not be a good idea.
[0] ok I looked it up and actually LCDM predicted no galaxies with redshift greater than 7... And thanks to jwst we now know there are galaxies with much much greater redshift, a feature explicitly predicted by MOND.
I also assume this has been accounted for though
There is an advantage to arranging dyson spheres closer together in order to reduce latency between nodes.
If your dyson spheres were optimized enough, could absorb all known spectrums and recycle them. Wouldn’t that appear completely dark save for gravity?
I mean, isn’t it possible entire galaxies have been converted in this way? Seems like it could be a much simpler explanation within the confines of current understanding.
But I’m sure this has been thought about and accounted for.
A really cool outcome of statistical mechanics and thermodynamics is that what you suggest is impossible. The dyson sphere can be as amazing as you want, using every single trickery permitted by physics, but at some point it will enter thermal equilibrium with its host start (or pipe that heat somewhere else where you would still be able to see its thermal radiation). Inherently, if they are optimized to be good absorbers, they will have to also be thermal emitters. There is no such thing as "recycle all spectrum".
Tangentially related to the fact that a "perfectly black body", i.e. a perfect absorber, is also the perfect emitter of thermal radiation of its own.
And the Milky way would have to be un-dyson sphered, because if it were, we would be able to notice these spheres close up. e.g. if dark matter is 5x regular matter, we would expect there to be 5 Dyson spheres of stars the size of the alpha centauri system all within 4ly of Earth. This would be easy to detect through occlusion. Also, gravitational interactions between sphered stars and unsphered stars would be easily observable in our own galaxy. So for this to work, at minimum, the whole observable universe must by Dyson sphered, except for our own galaxy.
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[1] https://www.claymath.org/millennium-problems/yang%E2%80%93mi...
The mediator of the strong force, the gluon, is a different beast compared to photons. It can directly interact with itself and create more of it. Add in the math that describe it and you get an emerging behavior vastly different from the one you get for photons.
The article also mentions mass-growing at a distance, I wonder if - they really mean "with displacement, mediated by speed" - there's some interaction under which two gluons can enter a binary, uniform rotation about one-another
The introduction to the full text identifies a subset of the theories under comparison, and hints at the techniques the theories deployed to arrive at their predictions, for example by "light-front quantized QCD" [1]
[1] https://www.mdpi.com/2571-712X/5/2/15
This running of the coupling constant would in principle allow unification with the electroweak force in most theories e.g. supersymmetry - we just have not worked out the exact framework.
The fact that the force between hadrons does not decrease with distance like the electromagnetic or gravitational forces explains why it is impossible to obtain free quarks.
When you have a system of particles which is bound by electromagnetic forces, e.g. the electrons bound to a nucleus, and you come with an external force and you pull the electron away from the opposite charge, the force retaining the electron becomes weaker and weaker while the distance increases, until the electron becomes free when the work of the pulling force exceeds the binding energy.
On the other hand, when you have a system of bound quarks, e.g. 3 quarks that compose a proton, and you come with an external force and you pull away one quark, the force remains constant while the distance increases, keeping the quark bound, until the work of the pulling force exceeds the energy of generation of a quark-antiquark pair.
At that threshold, a quark-antiquark pair is generated and the antiquark sticks to the quark that is pulled away, while the quark sticks to the other 2 remaining quarks.
Thus the effect of pulling one quark away is not the appearance of a free quark, but the appearance of a free quark-antiquark pair, which is named pion, a.k.a. pi meson, while the original proton may either transform into a neutron or remain a proton, depending on what kind of quark-antiquark pair happened to be generated.
To prevent the existence of free quarks, it would be enough for the force to decrease very slowly with the distance, but a model where the force is actually constant is the simplest and the most elegant, so it is good that the experimental data match this.
The reason why the interaction through electromagnetic or gravitational forces has a force decreasing with distance is that the force is the same in all directions and it is constant per solid angle, so the ratio of force per area decreases proportional to the area of the sphere centered on the source of the field.
This can be visualized with the Faraday's lines of force as equidistant radii going from the center of the sphere, and the density of lines of force per area decreases for greater spheres.
On the other hand the force between quarks can be visualized with the Faraday's lines of force not being towards all directions but being confined inside a tube that connects 2 quarks. When the distance between 2 quarks increases, the tube of lines of force becomes longer, but its cross-section remains constant, so the density of lines of force per area, i.e. the intensity of the force, remains constant.
When the distance increases over the threshold for generating a quark-antiquark pair, the tube of lines of force breaks into 2 tubes, with the 2 new ends of tubes being terminated on the newly generated antiquark and quark.
So visualizing a force that is constant with distance is not difficult and there are many materials that have the same behavior when they are extended over their elastic limit, i.e. their elongation increases continuously while the force is constant, until the material breaks.
There is actually a simple way to obtain a force between two objects that does not decrease with distance: simply connect them with an (idealized) string. And it is indeed not entirely inaccurate to say that the strong force produces some kind of quantum mechanical string between two quarks.
Historically the study of exactly these strings for the strong force led to the idea of string theory. Only later was it realized that it can be useful as a theory of quantum gravity as well.
Gauss's law (which is purely mathematical). Or basically, the area the force "sees" as it gets farther or closer.
Or does the strong force go back to zero at distances say larger than an atom?
The charge of the strong force is called color, and outside particles like protons the total color charge seen from the outside is zero. It stays zero because of color confinement - at some point, it's less energetic to create color-anticolor pair instead of allowing color imbalance.
Of course there are also residual forces from a color-neutral bound state to quarks which are a bit further away, but those are not nearly as strong. They are for instance responsible for holding nuclei together.
The important property of the strong force here is that it interacts with itself. The field of two quarks together is not the sum of their individual fields, because the force-carrying gluons are also color charged and thus interact with each other.
My understanding is that if you do manage to pull two quarks apart the energy of separation is eventually enough to form two new quarks, thus pairing them up again.
My question is whether this pair production happens before or after the strong force reaches the region where it is constant?
I think (guess?) that the strong force does the same, in the sense that there is a "neutralizing tendency", anyway, but the mechanism is different. Protons and neutrons, and pions too, are neutral when you watch them from far away. (But not so, when you are trying to explain why atomic nuclei are formed, protons and neutrons _like_ to clump together.)
The difference between a photon field and a gluon field is that gluons are attracted to each others in a way that I, as a non-nuclear-physicist don't quite understand (as the symmetry between them is not something I've actually studied); but as photons form "beams" (you can think of them in a linear algebra sense of vectors, almost!) that propagate in a very geometrically uniform way, gluons, being attracted to each others, form "tubes", which behave, as any self-interacting system would, in a very dynamic way.
Imagine a cellular simulation (like the Game of Life, but more... floating point instead of of integers & squares) where each quark sends gluons but they tend to clump together and form tubes? These tubes can't be super long, because quantum physics and the universe works in a way that energy gets minimized, and anything that could happen to make that happen, tends to happen. That means that if there's enough energy stored in the tube, it becomes "cheaper" for the universe to sever that connection and instead, produce new, separate particles that have their own, internal "tubes". That means that no long "tubes" of gluons are allowed in the universe, and thus, the strong force of the Strong Force is contained.
So the mechanism seems to be really super different from "overlapping +/- fields", in a sense, but the result is the same: no forces (albeit small residues) seen from afar.
https://en.wikipedia.org/wiki/Coupling_constant
> "A coupling plays an important role in dynamics. For example, one often sets up hierarchies of approximation based on the importance of various coupling constants. In the motion of a large lump of magnetized iron, the magnetic forces may be more important than the gravitational forces because of the relative magnitudes of the coupling constants. However, in classical mechanics, one usually makes these decisions directly by comparing forces. Another important example of the central role played by coupling constants is that they are the expansion parameters for first-principle calculations based on perturbation theory, which is the main method of calculation in many branches of physics."
Perturbation theory and calculations depend heavily on the coupling constant. If I recall correctly, in quantum electrodynamics (Feynman diagrams) the coupling constant is ~ 1/137. If you raise this number to higher powers (adding terms in the pertubation process) it quickly falls off towards zero, so you can get very accurate calculations using this approach in QED.
https://en.wikipedia.org/wiki/Perturbation_theory
With the strong force, this coupling constant is much larger and so the higher powers in the perturbative calculation are significant, meaning it's much harder to calculate accurately with QCD compared to QED. From the paper, this reference:
* Improving our knowledge of αS is crucial, among other things, to reduce the theoretical “parametric” uncertainties in the calculations of all perturbative QCD (pQCD) processes whose cross sections or decay rates depend on powers of αS , as is the case for virtually all those measured at the LHC. *
(2021) "The strong coupling constant: State of the art and the decade ahead"
https://arxiv.org/pdf/2203.08271.pdf
You can find a plot in the preprint: https://arxiv.org/abs/2205.01169