alt.hn

12/27/2025 at 3:00:00 AM

Inside the proton, the ‘most complicated thing you could possibly imagine’ (2022)

 https://www.quantamagazine.org/inside-the-proton-the-most-complicated-thing-imaginable-20221019/

by tzury

12/27/2025 at 4:39:21 PM

I've heard this quote before, and I don't get it. This article fails to show me just how complicated that is. When I think "complicated," I think of a multiplicity of interconnected chemical molecular processes like what must happen in the cell, or layers of recursively connected neurons in the brain. Not some mindless cloud of gluons. What they've described seems less "complicated" and more "confusing." "We don't understand this (yet?)" is a lot different than "it's possible to understand this, if your brain is really big."

by kornork

12/27/2025 at 9:38:17 PM

It's complex in a physicist's sense of the word: the equations are hopelessly complicated to solve even in very simple cases. This means it's hard to build intuition or describe in simple terms.

Quantum chromodynamics is actually pretty similar to Maxwell's equations of electromagnetism. The big difference is that unlike photos, gluons interact with each other. This means goodbye to linear equations and simple planewave solutions. One can't even solve the equations in empty space, and only recently have supercomputers become powerful enough to make good, quantitative predictions about things like the proton mass.

by qnleigh

12/31/2025 at 10:58:39 AM

A key property of QCD is that unlike electrodynamics, the forces between interacting objects increase with distance (quark confinement). This is what breaks the usual style of expansions used to simplify problems. It's hard to overstate how important this is.

One of the implications is that there are many interactions where most possible Feynman diagrams contribute non-negligibly. The advances in theory arguably have much more to do with improvements in techniques and the applied math used, such as in lattice QCD and Dean Lee's group for instance.

by yummypaint

12/28/2025 at 12:48:39 AM

I wonder if it is inherently complex in an information-theory framework, or that we simply haven’t yet found its “natural” basis under which its description is most succinct?

by xeonmc

12/28/2025 at 12:38:16 PM

My thinking as well.

How could something so remarkably stable and functionally indistinguishable among its peers also be so complex?

by jcims

12/28/2025 at 8:12:17 PM

Yeah it's a great question. I don't know the answer, but I suspect the people who study it strongly suspect that it is highly complex in this sense. Otherwise they would be looking for simpler representations instead of running massive simulations.

To your question, I think there is an elegant answer actually; most composite particles in QCD are unstable. They're either made out of equal parts matter and antimatter (like pions) or they're heavier than the proton, in which case they can decay into one (or more) protons (or antiprotons). If any of the internal complexities of the proton made it distinguishable from other protons, they wouldn't both be protons, and one could decay into the other. Quantum mechanics also helps to keep things simple by forcing the various properties of bound states to be quantized; there isn't a version of a proton where e.g. one of the quarks has a little more energy, similar to how the energies atomic orbitals are quantized.

by qnleigh

12/27/2025 at 7:11:21 PM

My non-physicist but curious-about-the-topic take is similar. Things at the quantum level are not "complex" in the systems-theory sense. They couldn't be, I think, since we're dealing with the most basic constituents of the universe. They are mysterious, confusing, wildly counterintuitive... but they are fundamental. The most basic stuff there is.

The study of these things, on the other hand, is genuinely complex and difficult. But that's epistemology, not ontology.

by rubslopes

12/27/2025 at 4:20:12 PM

>using machine learning to infer the motions of quarks and gluons inside the proton in a way that sidesteps theoretical guesswork.

Doing away with theory and just keep the guessing. But seriously very interesting, though I barely understand anything.

by tokai

12/27/2025 at 8:29:01 AM

> The results suggested that in even higher-energy collisions, the proton would appear as a cloud made up almost entirely of gluons. The gluon dandelion is exactly what QCD predicts.

I find the proton as a gluon dandelion cloud enthralling

by stevenjgarner

12/27/2025 at 4:22:10 PM

Non-physicst here. Hopefully someone can correct me or elaborate. My understanding is that what's being described is smaller scale decoherence inside the proton. Normally, the universe only asks protons the question: "are you a proton?" and it's like "Yep I'm a proton." (What's your baryon number? What's your charge? etc)

When we blast it with higher and higher energies, we're asking new questions: "What are the momenta of your quarks? What's your color field arrangement?" There are many possible answers to those questions and we're now starting to see the landscape of them.

So having different answers based on how you look is really answering different questions, just like asking an electron: What's your momentum? What's your location?

by 613style

12/27/2025 at 6:08:03 PM

> decoherence

This has a specific meaning and is not a word I would use here. For something to be "decoherent" the particle phases would need to be "uncorrelated" or "random", but given the internal wavelengths, masses, and strength of the interaction of the particles involved against the spatial dimension of the proton this is not the case under quantum field theory.

In some ways the problem of this being "complicated" is because it's intractably coherent with a fluctuating large number of particles interacting via three "colors" of self-interacting charge (very different from electric charge and not just "three" independent charges) to consider. I'd put money on any decoherence would likely simplify the problem.

> Normally, the universe only asks protons the question: "are you a proton?" and it's like "Yep I'm a proton." (What's your baryon number? What's your charge? etc)

Protons have internal structure (the quarks and gluons) and size. Those are relevant to its interactions. To consider a proton "by itself" and just reduced to quantum numbers is not "normal" if by "normal" you mean "protons at a scale in nature you deal with every day". Those protons are bound in nuclei and are modified by the fact they are bound. These effects have been explicitly measured and documented, the EMC effect being one of them. The "new questions" you are referring to are in fact relevant questions at low energies and are not "new". They are a large active area of research typically referred to as "medium energy" (despite the fact it extends into "low" energy traditional nuclear physics and high energy QCD physics).

Even in a hydrogen atom, the internal structure of the proton modifies the chemistry by small changes in the electronic shell energies, in particular contributions to the lamb shift which has been used to measure the radius of the proton.

Maybe most directly, if what you described were the case you wouldn't have so many decimals in atomic mass numbers of nuclei.

> So having different answers based on how you look is really answering different questions, just like asking an electron: What's your momentum? What's your location?

The problems of looking at quarks and gluons at different energy scales are also endemic to other forces (e.g. electromagnetic) and all particles (for example, look up the running of coupling constants and renormalization theory). Saying they are "different" questions is more akin to comparing questions of skyscraper engineering and concrete dust mechanics. They are not orthogonal as I would consider momentum and location. They're questions of scale and things like emergent effects at different scales.

There are orthogonal questions of internal structure to be considered, though. Deep inelastic scattering processes at high energies tend to ask the "what are the momentum" questions. Elastic nucleon form factors ask more the "location". They both exist in a unified framework of "generalized parton distributions".

by terminalbraid

12/27/2025 at 2:40:19 PM

[flagged]

by albatross79

12/27/2025 at 4:12:55 PM

When I was a physics student, there were four forces: strong, weak, EM, and gravity. That picture seemed neat and clean. Strong kept the nucleus together, EM kept molecules and atoms together (or broke them apart), gravity kept astronomical bodies together, weak was some kind of momentum-accounting device.

Recently, GPT informed me that the strong force is really a tiny after-effect of the "QCD force" (in the same way that the Van der Waals forces are after-effect of EM). Also, more and more questions about "dark matter" seem to be building up, suggesting that the standard Newton-Einstein story of gravity is far from the complete picture.

25 years ago it seemed like physics was mostly complete, and the only remaining work was exploring the corner cases and polishing out all the imperfections. It doesn't feel that way anymore! The confusing part is that modern physics is so unbelievably successful and useful for technology - if the underlying theory was way off, how could the tech work?

by d_burfoot

12/27/2025 at 7:14:35 PM

> Recently, GPT informed me that the strong force is really a tiny after-effect of the "QCD force"

Maybe you should not take everything GPT tells you at face value? I have no idea what this QCD force is supposed to be. The strong force is _the_ force of QCD. The Standard Model still considers the electromagnetic, weak and strong force. The description of the weak and EM force can be unified into the electroweak force and there are theories that try to also unify it with the strong force and even gravity, but there are issues on the theory side and no clear evidence on the experimental side as to which direction is the correct one.

The Standard Model and General Relativity are still our most successful theories. It is clear that they don't tell the whole picture, but (annoyingly?) it is not clear at all where this is going.

Just for dark matter there are probably a dozen proposed hypothetical particles, but so far we have found none. But maybe it's something completely different...

by HansHamster

12/27/2025 at 5:23:52 PM

> 25 years ago it seemed like physics was mostly complete, and the only remaining work was exploring the corner cases and polishing out all the imperfections

Around 125 years ago, many thought the same about physics, that physics is mostly complete and it just explaining and finishing some edge cases and polishing all our measurements. There was just two things that were a little bit puzzling, the "looming clouds" over physics (per Kelvin description) will later lead to both Quantum Theory and Theory of relativity (Black body radiation and Michelson–Morley experiment) and the fundamental change of our understanding for physics after that.

So I would not take this position. Does this mean we are in a similar moment? maybe, who knows?

by elashri

12/28/2025 at 12:08:33 AM

"QCD force" is the same thing as the "strong" force. There is no reason whatsoever to invent any new name.

There are several hierarchical levels at which the strong interaction and the electromagnetic interaction bind the components of matter.

The electromagnetic interaction attempts to neutralize the electric charge. To a first approximation this is achieved in atoms. The residual forces caused by imperfect neutralization bind atoms in molecules. Even between molecules there remain some even weaker residual attraction forces, which are the Van der Waals forces, which are thus at the third hierarchical level.

For the strong interaction, there are only 2 hierarchical levels, approximate charge neutralization is achieved in nucleons, which are bound by residual attractive forces into nuclei.

So the forces between the nucleons of a nucleus correspond to the inter-atomic forces from inside a molecule, not to the Van der Waals forces between molecules.

by adrian_b

12/27/2025 at 5:11:40 PM

> 25 years ago it seemed like physics was mostly complete, and the only remaining work was exploring the corner cases and polishing out all the imperfections. It doesn't feel that way anymore!

Physicists thought the same thing c. 1900, but then one of the "corner cases" turned into the ultraviolet catastrophe[1]. The consequences of the solution to that problem kept the whole field busy for a good part of the 20th century.

I'm highly skeptical of the idea that physics is anywhere near complete. The relative success of our technology gives us the illusory impression that we're almost done, but it's not obvious that physics even has a single, complete description that we can describe. We assume it does for convenience, in the same way that we assume the laws are constant everywhere in spacetime. I view this as both exciting and terrifying, but mostly exciting.

[1]: https://en.wikipedia.org/wiki/Ultraviolet_catastrophe

by bmgxyz

12/27/2025 at 9:16:20 PM

> Recently, GPT informed me that the strong force is really a tiny after-effect of the "QCD force"

This is kind of just semantics. QCD describes both the force binding quarks inside protons and neutrons, and the residual force binding protons and neutrons. This is all part of the Standard Model, which has been essentially unchanged for the last 50 years. The big theoretical challenge is to incorporate gravity into this picture, but this is an almost impossible thing to explore experimentally because gravity is very weak compared to the other 3 forces. That's why the Standard Model is so successful, even though it doesn't incorporated gravity.

You might enjoy https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_p...

by qnleigh

12/27/2025 at 8:23:13 PM

> The confusing part is that modern physics is so unbelievably successful and useful for technology - if the underlying theory was way off, how could the tech work?

Who says "way" off? It's not complete to explain everything, but it explains a lot correctly enough to use it for calculations, predictions and practical effects. Same way Newton was and remains useful, and how people have been using maths and technology to solve problems for a long time since before Newton was born.

by dxdm

12/27/2025 at 4:23:50 PM

I think physics has felt pretty incomplete since the confirmation of qm non-locality in the 60s.

by tacitusarc

12/28/2025 at 3:45:26 AM

Electrons are bits: Minimal structure, maximal fungibility.

Protons are WASM modules: Portable, sandboxed, rich internals, stable interface.

Neutrons are headless WASM: Same runtime, no external API, harder to drive or inspect.

Nuclei are Kubernetes: Orchestration, emergent behavior, scheduling, binding energy as overhead.

QCD is the runtime: One spec, wildly different behavior depending on scale.

Experiments are profilers: You never see the code, only traces, distributions, hotspots.

HN comments are undefined behavior and non-renormalizable noise: Unconstrained interactions, long-range correlations, destroyed predictability.

by DonHopkins

12/27/2025 at 11:17:49 PM

So if we understand the internal differences between protons and neutrons, what’s the practical application? Turning neutrons into protons with low energies - alchemy?

by aetherspawn

12/27/2025 at 11:47:37 PM

Neutrons turn spontaneously into protons, which is called beta decay, and which happens in any nucleus with too many neutrons. This includes the free neutrons, which decay into protons in minutes.

Neutrons and protons differ in their composition, a neutron being made of 2 d quarks + 1 u quark, while a proton is made of 1 d quark + 2 u quarks, much in the same way as a nucleus of tritium differs from a nucleus of helium 3, the former being made of 2 neutrons + 1 proton, while the latter is made of 1 neutron + 2 protons.

For the strong interactions, nucleons (i.e. protons and neutrons) and nuclei are analogous to what atoms and molecules are for the electromagnetic interaction.

The strong interaction attempts to neutralize the hadronic charge (a.k.a. color charge), while the electromagnetic interaction attempts to neutralize the electric charge.

To a first approximation, the hadronic charge is neutralized in nucleons and the electric charge is neutralized in atoms.

However, because of the movement of the quarks inside of a nucleon and of the electrons inside an atom, the neutralization of the charge is imperfect and there remain some residual forces of attraction, respectively strong and electromagnetic, which bind the nucleons into nuclei and the atoms into molecules. Because they are just residual forces, the binding forces between nucleons in a nucleus are much weaker than those between quarks in a nucleon, similarly to how the binding forces between atoms in a molecule are much weaker than those that bind most of the electrons to the nucleus in an atom.

by adrian_b

12/29/2025 at 12:01:45 AM

Do you think it’s possible that the periodic table is too simple of an abstraction and that quarkish elements exist which cannot be aligned on the table but perhaps are never seen in nature or extremely rare?

by aetherspawn

12/29/2025 at 9:00:02 AM

The so-called elementary particles, which are divided into leptons and hadrons, are all "achromatic", i.e. the color charge is null for the whole particle.

While the leptons may be considered as truly elementary, at least in the current state of knowledge, the hadrons are composed of quarks, and the quarks have non-null color charge.

At present there is no hope of being able to produce any particle where quarks are separated, i.e. any particle with non-null total color charge, because when the distance between quarks increases the attraction force between them also increases (like they would have been bound by an elastic spring), until the force becomes high enough so that a pair quark-antiquark is generated, so the original hadron may split into 2 hadrons, both of which have null color charge and no free quarks can be produced (e.g. the quark initially being pulled apart is split away, but it takes with it the antiquark newly generated, forming a meson particle instead of a free quark).

Attempting to separate the quarks of a hadron has a result somewhat analogous to the attempt of separating the north and south poles of a magnet, when breaking the magnet produces a new pair of north and south poles, so you get 2 new magnets, each with a north and a south pole, instead of getting a north pole separated from the south pole.

Therefore, because neither free quarks nor combinations of quarks where the color charge is non-null can be produced, no "quarkish" elements can exist.

Nevertheless, while the normal chemical elements have nuclei composed of nucleons, i.e. protons and neutrons, it is possible to have nuclei composed of other hadrons, i.e. nuclei where besides protons or neutrons there are one or more of the so-called hyperons, which have a similar structure to nucleons, but which contain some heavier quarks than the u and d quarks that compose nucleons (there are also extremely short-lived heavier hadrons that contain more than 3 quarks, as long as the total color charge is null).

However, all hyperons have an extremely short half-life, much shorter than a second, so if such an exotic element containing hyperons in its nucleus were formed due to a very unlikely sequence of collisions between particles with very high energy, it would decay extremely quickly.

At the huge scale of the Universe, even extremely unlikely events may happen somewhere, so perhaps a few atoms of such hyperonic chemical elements have a transient existence somewhere (during a small fraction of a second), but their quantity must be truly negligible.

While a few atoms of such elements can be produced artificially or naturally, there is no chance to ever produce a quantity great enough to make a piece of material that you could see with your eyes, much less take in your hand (ignoring the extreme radioactivity of such an element, which would destroy anything close to it).

The only possible exception might be in extremely high gravitational fields, i.e. inside neutron stars and black holes, where there may be a chance that such hyperons could become stable due to the extreme pressure, but we do not really know the possible structure of matter in such conditions and in any case at such pressures there would be no chemical elements in the normal sense, as there would be no free electrons.

by adrian_b

12/27/2025 at 6:34:09 PM

Reminds me of that silly string theory first surfaced (under my Christmas tree) some 51 years ago.

by egberts1

12/27/2025 at 4:43:27 PM

because the article says that it is a haze of probabilities that only takes concrete form when observed, could it be a part of a larger neural network?

by vivzkestrel

12/27/2025 at 9:05:43 AM

[flagged]

by m101

12/27/2025 at 9:14:38 AM

I get what you’re saying, but the measurements are real. In some sense they are the truth.

In the article this refers to the finding that the quark is more complex than three valence quarks.

The measurements indicating that the three-quark-model is incomplete are overwhelmingly conclusive, so some degree of certainty in the language is warranted in my view.

by ephimetheus

12/27/2025 at 11:22:35 AM

It's a pop sci magazine, of course they use language like that. Actual academic papers are different.

by asystole

12/27/2025 at 9:23:10 AM

Not sure what this has to do with the article, it just seems like a nitpick. What did science do to you?

by venturecruelty

12/27/2025 at 1:35:39 PM

[flagged]

by ndai

12/27/2025 at 8:03:00 PM

One thing I've always wondered about is why crazy people are always fixated on quantum physics and then vague musical terms like "resonances".

LLMs do the same thing when they develop psychosis* except GPT also starts talking about "recursion" and Claude starts trying to enter nirvana.

* historical term "going Rampant"

by astrange

12/28/2025 at 1:28:35 AM

Your personal insult aside, resonance is a fundamental term in physics and harmonic oscillators are fundamental to quantum field theory and modern physics. Music was a metaphor- this isn’t Nature.

by ndai

12/27/2025 at 2:09:07 PM

> processes over objects

this is correct, waves are a product of pressures, so, are emergent also, the real question is, where does the pressure originate

by dekken_

12/27/2025 at 2:19:07 PM

Waves don’t come from pressure. Pressure comes from constrained waves… constraints prevent oscillatory relations from freely satisfying their phases. Pressure is a local manifestation of the same idea behind gravity. When many interacting modes lock into a persistent configuration, they impose constraints on nearby modes. To us on the inside it looks like curvature and attraction. But the comment section on HN is a bloodsport…

by ndai

12/27/2025 at 3:23:17 PM

You're also trying to argue against a nonzero number of literal physicists who do this type of thinking for a living.

by terminalbraid

12/27/2025 at 3:47:08 PM

I’m sharing not arguing. This is the comment section of a website. I sold my autonomy for a wage doing other things, but I happily accept my affliction of contemplating the universe. Maybe it will spark something in the imagination of someone. Amateurs thinking is what led humanity to this point. I clearly stated my lack of domain expertise- but I reserve my right to unprofessionally question foundations and reject treating silence about first principles as intellectual virtue. I also accept, with grumbling, the downvotes.

by ndai

12/28/2025 at 2:28:19 AM

How complicated is it?

"Definitely complicated enough for us all to keep getting paid for a long time."

read hhgttg

by deIeted

12/27/2025 at 3:13:30 PM

> We’ve incorporated their animations into our own attempt to unveil its secrets.

And like the proton, this statement is somehow heavier than the entire article. What an absolutely bizarre, arrogant choice of words.

by gnarlouse

12/27/2025 at 7:54:16 AM

The implication of this framing is that neutrons are considerably simpler.

I find that rather surprising.

by zahlman

12/27/2025 at 9:11:11 AM

Neutrons are just as complex, they’re much harder to study though.

by ephimetheus

12/27/2025 at 3:54:06 PM

If i remember correctly Feynman said in one of his lectures that we know the mass of the electron with much greater precision than the proton, which may mean that it electrons are easier to study. I don't know if this is still true though.

by gozzoo

12/27/2025 at 5:14:52 PM

Oh yes and so much so! Electrons are point-like (not composite like a proton) and interact only electroweakly (not strongly).

by ephimetheus

12/27/2025 at 3:58:39 PM

And neutrons are neither.

by anamexis

12/27/2025 at 12:03:03 PM

If it was possible to build a direct neutron accelerator/collider, I suspect we'd get some new physics pretty quickly.

Analysing hand-me-down neutron events from indirect collisions isn't quite as useful.

by TheOtherHobbes

12/27/2025 at 1:08:30 PM

At ISIS (Oxford neutron source)…

Spallation generation: High-energy protons (~800 MeV) hit a heavy target, releasing a wide spectrum of fast neutrons up to hundreds of MeV. These are then moderated down to useful energies for experiments.

It’s not the LHC, sure. But I don’t see any reason (apart from “why bother”) why they can’t do spallation in Geneva. OK maybe there’s a cooling problem…

by librasteve

12/27/2025 at 3:53:44 PM

Spallation is the easy part

But neutrons can't go around a tube being guided by magnetic fields

by raverbashing

12/27/2025 at 5:50:26 PM

Well my point is that the energy of the spallation neutrons is monotonically related to the energy of the protons hitting the Tungsten target ... although somewhat lower. I would consider these 100s MeV partiles to be (quite) high energy in contrast to the thermal neutrons alluded to elsewhere. Sure the spallation is lossy, but the result is still pretty high. And the physics is somewhat different with neutron experiments vs. protons... iiuc

by librasteve

12/27/2025 at 12:50:40 PM

There absolutely are direct neutron experiments, but they are much lower energy and have a different focus, partly because neutrons being neutral means they’re very hard to accelerate.

There’s an ultra cold neutron source at Paul Scherrer that is used to measure if the neutron has an electric dipole moment. This is complementary to high energy experiments.

by ephimetheus

12/27/2025 at 12:17:19 PM

Neutrons are not that different from protons. The decay from neutrons to protons is pretty well understood, and there’s no reason to think that the nature of quark/gluon interactions in a neutron are significantly different from those in a proton. What kind of new physics are you imagining we’d get?

Of course more experimental data is a good thing, but in this case it doesn’t seem obvious that it would lead to anything really new.

by antonvs

12/27/2025 at 3:22:08 PM

Why do you say they're "pretty well understood" when there's been a long-standing unresolved discrepancy between lifetime measurement techniques?

by terminalbraid

12/27/2025 at 7:19:20 PM

I think they mean that what happens when a neutron decays is well understood. One of the neutron's down quarks change to an up quark, facilitated by a virtual W boson with negative charge. The W boson is very unstable and immediately decays into an electron and an electron anti-neutrino, both of which are ejected leaving behind the former neutrino which is now a proton because of that quark change.

When that happens is less understood, hence the discrepancies you mentioned.

by tzs

12/28/2025 at 1:41:20 AM

The same QCD theory that's used to model the proton models the neutron. Theoretically, our understanding of both is on the same footing.

The comment I replied to talked about "new physics". That's a term that's used in physics to describe physics beyond the Standard Model. Better experimental data about neutron internals could certainly help constrain the neutron lifetime, but that would be likely to be experimental constraints on existing physics, not new physics in the sense that the term is normally used.

by antonvs

12/27/2025 at 11:47:07 AM

Where are you getting that implication? I didn't see anything in the article suggesting that neutrons were simple and I would share your skepticism if someone claimed they were. The fact that neutrons can spontaneously decay into protons (plus other stuff) suggests otherwise.

by mcherm

12/27/2025 at 2:49:02 PM

The title implies it directly.

by creddit

12/27/2025 at 4:43:50 PM

If you saw an article titled “My Nana is the nicest person you could possibly meet”, would you interpret that to be a statement that your own grandmother is considerably less nice?

by dpark

12/28/2025 at 10:48:09 PM

That is what the author would be implying, yes. Though, you may quibble over "considerable".

by creddit

12/29/2025 at 2:21:06 AM

Pedantry is rarely a good look. But intentionally misreading intent barely even qualifies as pedantry.

I like to imagine that people this ridiculous get into fist fights on the street constantly.

Normal person: “My wife is the absolute best.”

Pedant: “Don’t you dare insult my wife!” fists fly

by dpark

12/27/2025 at 7:35:39 PM

Because the failure to write about neutrons is conspicuous considering that they're always together in nuclei, similarly composed of three quarks etc.

by zahlman

12/27/2025 at 8:45:52 AM

I don't expect that to be the case, it's likely that the article simply focuses on the proton.

by tsimionescu

12/28/2025 at 2:55:13 PM

Neutrons decay into protons, so no. They're less stable than protons. If we figure put the proton we can then use that to understand the neutron.

by petre