[HN Gopher] Why the weak nuclear force is short range
___________________________________________________________________
Why the weak nuclear force is short range
Author : sohkamyung
Score : 276 points
Date : 2025-01-11 23:43 UTC (3 days ago)
(HTM) web link (profmattstrassler.com)
(TXT) w3m dump (profmattstrassler.com)
| somat wrote:
| There is an interesting video essay by the Huygens Optics channel
| where some simulations of these field effects are considered.
|
| Turning Waves Into Particles
| https://www.youtube.com/watch?v=tMP5Pbx8I4s
|
| And if unfamiliar, that channel constantly delivers high quality
| thought provoking content on the nature of light.
| mmcnickle wrote:
| One thing I'm not clear on when watching his videos is whether
| what he's describing is an established scientific
| interpretation, or his own thoughts as someone who has
| extensive knowledge on optical engineering (vs theory).
|
| Very enjoyable and thought provoking stuff though!
|
| Edit: spelling
| mecsred wrote:
| When he provides sources, then it's the first one, otherwise
| the second.
| pomian wrote:
| That's great. Thanks. When you start watching it you think, it
| will be too long, but it gets better and better. Everything
| goes back to Einstein. YARH! Yet another rabbit hole! It's
| amazing we have any time left to do anything after reading HN.
| randomtoast wrote:
| TLDR; It is short range primarily because the underlying fields
| (those of the W and Z bosons) are "stiff," causing any
| disturbance to die off exponentially at distances much smaller
| than an atom's diameter. In quantum language, that same stiffness
| manifests as the nonzero masses of the W and Z bosons, so their
| corresponding force does not effectively propagate over long
| distances--hence it appears "weak" and short-range.
| hammock wrote:
| So it's like a stiff spring /strut vs a loose one? Doesn't a
| loose suspension dampen and stiff propagate quicker though?
| XorNot wrote:
| Urgh, I'm half way through this and I hate it.
|
| The problem is it's upfront that "X thing you learned is wrong"
| but is then freely introducing a lot of new ideas without
| grounding why they should be accepted - i.e. from sitting here
| knowing a little physics, what's the intuition which gets us to
| field "stiffness"? Stiff fields limit range, okay, but...why do
| we think those exist?
|
| The article just ends the explanation section and jumps to the
| maths, but fails to give any indication at all as to why field
| stiffness is a sensible idea to accept? Where does it come from?
| Why are non-stiff fields just travelling around a "c", except
| that we observe "c" to be the speed of light that they travel
| around?
|
| When we teach people about quantum mechanics and the uncertainty
| principle even at a pop-sci level, we do do it by pointing to the
| actual experiments which build the base of evidence, and the
| logical conflicts which necessitate deeper theory (i.e. you can
| take that idea, and build a predictive model which works and
| here's where they did that experiment).
|
| This just...gives no sense at all as to what this stiffness
| parameter actually is, why it turned up, or why there's what
| feels like a very coincidental overlap with the Uncertainty
| principle (i.e. is that intuition wrong because actually the math
| doesn't work out, is this just a different way of looking at it
| and there's no absolute source of truth or origin, what's
| happening?)
| andyferris wrote:
| I agree this doesn't gel well with the pop-science approach.
|
| However, it is actually a similar approach to how De Broglie,
| Schrodinger, and others originally came up with their equations
| for quantum behavior - we start with special relativity and
| consider how a wave _must_ behave if its properties are going
| to be frame-independent, and follow the math from there. That
| part is equation (*), and the article leads with a bit of an
| analogy of how we might build a fully classical implemenation
| of it in an experiment (strings, possibly attached to a stiff
| rubber sheet) so we get some everyday intuition into the
| equation's behavior. So from my point of view, I found it very
| interesting.
|
| (What the article doesn't really get into is why certain fields
| might have S=0 and others not, what the intuition for the cause
| of that is, etc. It also presupposes you have bought into
| quantum field theory in the first place, and wish to consider
| the fundamental "wavicles" that would emerge from certain field
| equations, and that you aren't looking closely at the EM force
| or spin or any other number of things normally encountered
| before learning about the weak force).
| Y_Y wrote:
| I had very much the same feeling. Honestly this might be all
| true, but it's got a vibe I don't like. I did QFT in my PhD and
| have read plenty of good and bad science exposition, and it
| doesn't feel right.
|
| I can't point at any outright mistakes, but for example I think
| the dismissal of the common interpretation of virtual particles
| in Feynman diagrams is not persuasive. If you think the
| prevailing view among experts is wrong then the burden of proof
| is high, perhaps right than you can reach in am article pitched
| so low, but I don't feel like reading his book.
| lokimedes wrote:
| In all honesty, this gives a delightful if frightening look
| into how physicists are thinking amongst themselves. As a
| (former) particle physicist myself, I can't remember the number
| of times an incredulous engineer has confronted me with "the
| truth" about physics. But you see, for practicing physicists,
| the models and theories are fluid and actually up for
| discussion and interpretation, that's our job after all. The
| problem is that the official output is declared to be immutable
| laws of nature, set in formulae and dogmatic conventions. That
| said, I agree that he is trading one possible fallacy for
| another here, but the beauty of the thing is that the
| "stiffness" explanation is invoking less assumptions than the
| quantum one - which physicists agree is a "good thing" (Occam's
| razor).
| xigency wrote:
| There definitely seems to be a modern trend of over
| complication in physics along with the voodoo-like worship of
| math. Humbly enough, people have only come to understand the
| equations for an apple falling out of a tree within the last
| 500 years, and that necessitated the invention of Calculus.
|
| What's more distressing than the insular knowledge cults of
| modern physics is the bizarre fixation on unfalsifiable
| philosophical interpretation.
|
| That just makes it incomprehensible to outsiders when they
| quibble over the metaphors used to explain the equations that
| are used to guess what may happen experimentally. (Rather
| than admitting that any definition is an abstraction and any
| analogies or metaphors are merely pedagogical tools.)
|
| My kneejerk reaction: Give me the equations. If they are too
| complicated give me a computer simulation that runs the
| equations. Now tell me what your experiment is and show me
| how to plug the numbers so that I may validate the theory.
|
| If I wanted to have people wage war over my mind concerning
| what I should believe without evidence, I would turn back to
| religion rather than science.
|
| Anyway, I hope this situation improves in the future. Maybe
| some virtual particle will appear that better mediates this
| field (physics).
| selecsosi wrote:
| Having studied undergraduate physics, I think this
| viewpoint is inverted from the realities of the matter. It
| is less that the math is complicated and more so these are
| the relevant tools invented for us to model the
| experimental results we obtain post discovery/formalization
| of SR/GR/Quantum experiences. There are computers that can
| run these simulations but they are infeasible to model
| large scale processes. That is the reason people are
| looking for more than numerical solutions to problems, but
| laws and tools that can simplify modeling large scale
| emergent behavior that it would be infeasible or
| unnecessarily complicated to do with numerical simulation.
| These tools are the more straightforward approach
| dist-epoch wrote:
| > introducing a lot of new ideas without grounding
|
| The grounding is 3 years of advanced math.
| SpaceManNabs wrote:
| > This just...gives no sense at all as to what this stiffness
| parameter actually is, why it turned up, or why there's what
| feels like a very coincidental overlap with the Uncertainty
| principle
|
| Because not everyone has the prerequisite math or
| time/attention to go into quantum field theory for a rather
| intuitive point about mass and fields.
|
| This reminds me a bit of how high school physics classes are
| sometimes taught when it comes to thermodynamics and optics.
| You learn these "formulas" and properties (like harmonics or
| ideal gas law) because deriving where they come from require
| 2-3 years of actual undergraduate physics with additional
| lessons in differential equations and analysis.
| Timwi wrote:
| What makes me skeptical here is that the author claims that
| fields have a property that is necessary to explain this, and yet
| physicists have not given that property a name, so he has to
| invent one ("stiffness"). If the quantity appears in equations, I
| find it hard to believe that it was never given a name. Can
| anyone in the field of physics elucidate?
| sigmoid10 wrote:
| The author isn't inventing anything. He's just dumbing it down
| in an extreme way so that non-physicists could have the
| faintest hope of understanding it. Wich seems odd, because if
| you actually want to understand any of this you should prepare
| to spend two or three years in university level math classes
| first. The truth is that in reality all this is actually a lot
| more complex. In the Higgs field (or any simple scalar field
| for that matter) for example, there is a free parameter that we
| could immediately identify as "mass" in the way described in
| the article. But weirdly enough, this is not the mass of the
| Higgs boson (because of some complicated shenanigans). Even
| more counterintuitive, fermionic (aka matter) fields and
| massive bosonic fields (i.e. the W and Z bosons mentioned in
| the article) in the Standard Model don't have any mass term by
| themselves at all. They only get something that looks (and
| behaves) like a mass term from their coupling to the Higgs
| field. So it's the "stiffness" of the Higgs field (highly
| oversimplified) that gives rise to the "stiffness" of the other
| fields through complex interactions governed by symmetries. And
| to put it to the extreme, the physical mass you can measaure in
| a laboratory is something that depends on the energy scale at
| which you perform your experiments. So even if you did years of
| math and took an intro to QFT class and finally think you begin
| to understand all this, Renormalization Group Theory comes in
| kicks you back down. If you go really deep, you'll run into
| issues like Landau Poles and Quantum Triviality and the very
| nature of what perturbation theory can tell us about reality
| after all. In the end you will be two thirds through grad
| school by the time you can comfortably discuss any of this. The
| origin of mass is a really convoluted construct and these low-
| level discussions of it will always paint a tainted picture. If
| you want the truth, you can only trust the math.
| azalemeth wrote:
| I think perhaps the 'maths' at the bottom is a bit of a
| retelling of the Yukawa potential which you can get in a
| "relatively understandable" way from the Klein-Gordon
| equation. However, the KG equation is very very wrong!
|
| Perhaps an approach trying to actually explain the Feynman
| propagators would be more helpful? Either way, I agree that
| if someone wanted to understand this all properly it requires
| a university education + years of postgrad exposure to the
| delights of QED / electroweak theory. If anyone here wants a
| relatively understandable deep dive, my favourite books are
| Quantum Field Theory for the Gifted Amateur [aka graduate
| student] by Stephen Blundell [who taught me] and Tom
| Lancester [his former graduate student], and also Quarks and
| Leptons by Halzel and Martin. It is not a short road.
| awanderingmind wrote:
| I haven't read the other two, but I'll second 'Quarks and
| Leptons'. I do believe it's Halzen though, rather than
| Halzel...
| sigmoid10 wrote:
| The Yukawa potential is also just a more "classical" limit
| of an inherently quantum mechanical process. Sure you can
| explain things with it and even do some practical
| calculations, but if you plan on going to the bottom of it
| it'll always fail. If you want to explain Feynman
| propagators correctly you basically have to explain so many
| other things first, you might as well write a whole book.
| And even then you're trapped in the confines of
| perturbation theory, which is only a tiny window into a
| much bigger world. I really don't think it is possible to
| convey these things in a way that is both accurate (in the
| sense that it won't lead to misunderstandings) and simple
| enough so that people without some hefty prerequisites can
| truly understand it. I wish it were different. Because this
| is causing a growing rift between scientists and the normal
| population.
| specialist wrote:
| IIRC, Feynman said something like "I can't explain
| magnetism to a layperson in terms they can understand."
|
| > _...causing a growing rift between scientists and the
| normal population._
|
| True.
| pdonis wrote:
| _> the KG equation is very very wrong!_
|
| How so? It's the standard equation for a scalar (spin zero)
| field.
| awanderingmind wrote:
| Fortuitously the author of the posted article also has a
| series on the Higgs mechanism (with the math, but still
| including some simplifications):
| https://profmattstrassler.com/articles-and-posts/particle-
| ph...
| sigmoid10 wrote:
| Those posts would really benefit from some math typesetting
| in latex.
| awanderingmind wrote:
| I wholeheartedly agree.
| kridsdale1 wrote:
| Can an LLM reliably re-format it for us?
|
| EDIT: yes I tried pasting it in to Gemini, 4o, and
| Claude. Only Claude was able to zero-shot create the
| latex and an html wrapper that renders it, and open the
| html preview on iOS. It worked great.
| UltraSane wrote:
| I love Claude Sonnet 3.5 so much. DeepSeekv3 is also very
| good.
| Zondartul wrote:
| At some point our understanding of fundamental reality will
| be limited not by how much the physicists have uncovered but
| by how many years of university it would take to explain it.
| In the end each of us only has one lifetime.
| rachofsunshine wrote:
| He addresses this in the comments. The term that corresponds to
| "stiffness" normally just gets called "mass", since that is how
| it shows up in experiments.
|
| Roughly put:
|
| - A particle is a "minimum stretching" of a field.
|
| - The "stiffness" corresponds to the energy-per-stretch-amount
| of the field (analogous to the stiffness of a spring).
|
| - So the particle's mass = (minimum stretch "distance") *
| stiffness ~ stiffness
|
| The author's point is that you don't need to invoke virtual
| particles or any quantum weirdness to make this work. All you
| need is the notion of stiffness, and the mass of the associated
| particle and the limited range of the force both drop out of
| the math for the same reasons.
| pdonis wrote:
| _> The term that corresponds to "stiffness" normally just
| gets called "mass", since that is how it shows up in
| experiments._
|
| Then why not just call it "mass"? That's what it is. How is
| the notion of "stiffness" any better than the notion of
| "mass"? The author never explains this that I can see.
| kridsdale1 wrote:
| Undergrad-only level physics person here:
|
| I think stiffness is an ok term if your aim is to maintain
| a field centric mode of thinking. Mass as a term is
| particle-centric.
|
| It seems these minimum-stretching could also be thought of
| as a "wrinkle". It's a permanent deformation of the field
| itself that we give the name to, and thus "instantiate" the
| particle.
|
| Eye opening.
| pdonis wrote:
| _> I think stiffness is an ok term if your aim is to
| maintain a field centric mode of thinking._
|
| "Stiffness" to me isn't a field term or a particle term;
| it's a condensed matter term. In other words, it's a name
| for a property of substances that is not fundamental;
| it's emergent from other underlying physics, which for
| convenience we don't always want to delve into in detail,
| so we package it all up into an emergent number and call
| it "stiffness".
|
| On this view, "stiffness" is a worse term than "mass",
| which does have a fundamental meaning (see below).
|
| _> Mass as a term is particle-centric._
|
| Not to a quantum field theorist. :-) "Mass" is a field
| term in that context; you will see explicit references to
| "massless fields" and "massive fields" all over the
| literature.
| timewizard wrote:
| In the unit analysis it appears as if it's just kinematic
| viscosity.
| fermisea wrote:
| It's nonsense. The fact that the particle is massive is a
| direct cause of the fact that the interactions are short
| ranged.
|
| The nuance is this: Naturally, in a field theory the word
| "particle" is ill-defined, thus the only true statement one can
| make is that: the propagator/green function of the field
| contains poles at +-m, which sort of hints at what he means by
| stiffness.
|
| As a result of this pole, any perturbations of the field have
| an exponential decaying effect. But the pole _is_ the mass, by
| definition.
|
| The real interesting question is why Z and W bosons are
| massive, which have to do with the higgs mechanism. I.e., prior
| to symmetry breaking the fields are massless, but by
| interacting with the Higgs, the vacuum expectation value of the
| two point function of the field changes, thus granting it a
| mass.
|
| In sum, whoever wrote this is a bit confused and just doesn't
| have a lot of exposure to QFT
| fermisea wrote:
| Actually upon further reading I realize that the author
| actually goes deeper into what I thought, so it's not
| nonsense, it's actually a simplified version of what I tried
| to write.
|
| But I don't particularly like the whole "mass vs not mass"
| discussion as it's pointless
| aghilmort wrote:
| that & pointless is an amazing pun intentional or
| otherwise; well-done, just absolutely
| whatshisface wrote:
| It does have a name, it's called "coupling." A spring (to
| physicists all linkages are springs :-) ) couples a pair of
| train cars, and a coupling constant attaches massive fields to
| the higgs field.
| kridsdale1 wrote:
| Even capacitors and thermal models in solids are springs.
| pdonis wrote:
| _> If the quantity appears in equations, I find it hard to
| believe that it was never given a name._
|
| It does have a name: mass!
|
| What I'm skeptical of is that this "stiffness" is somehow
| logically or conceptually prior to mass. Looking at the math,
| it just _is_ mass. The term in the equation that this author
| calls the "stiffness" term is usually just called the "mass"
| term.
| brabel wrote:
| > Only stiff fields can have standing waves in empty space, which
| in turn are made from "particles" that are stationary and
| vibrating. And so, the very existence of a "particle" with non-
| zero mass is a consequence of the field's stiffness.
|
| It's really difficult to reconcile "standing waves in empty
| space" with "stiff fields". If the space is truly empty, then the
| field seems to be an illusion?
|
| If we think about fields as the very old concept of aether, then
| it actually makes more intuitive sense. Stiffness then becomes
| simply the viscosity of the aether.
|
| But I don't think this is where this article is trying to get
| us!!
| mjburgess wrote:
| fields are a non-mechanical aether, more precisely they are
| lorentz invarient (ie., their motion is the same for all
| observers)
| keepamovin wrote:
| And if you can hop from each standing wave node to the next,
| you can teleport, or move ridiculously fast by moving
| discretely instead of continuously. What if you could tune the
| wavelength of these standing waves with particles stationary
| and vibrating?
|
| I like the speaker on water / styrofoam particle demonstration
| of standing waves.
| hammock wrote:
| Or change the frequency of the wave you are standing on (or
| those around you, I'm not sure which) and move forward like
| an inchworm
|
| I believe this is not dissimilar to the mechanics suggested
| by the ZPE/antigravity people like Ashton Forbes
| jagrsw wrote:
| If we wanted to model the universe as a set of equations or a
| cellular automaton, how complex would that program be?
|
| Could a competent software engineer, even without knowing the
| fundamental origins of things like particle masses or the fine-
| structure constant, capture all known fundamental interactions in
| code?
|
| I guess I'm trying to figure out the complexity of the task of
| universe creation, assuming the necessary computational power
| exists. For example, could it be a computer science high school
| project for the folks in the parent universe (simulation
| hypothesis). I know that's a tough question :)
| dmos62 wrote:
| Stephen Wolfram has been taking a stab at it. Researching
| fundamental physics via computational exploration is how I'd
| put it. https://www.wolframphysics.org/
| cjfd wrote:
| He is basically a crackpot. Any attempt at fundamental
| physics that doesn't take quantum mechanics into account
| is.... uhm.... how to put this.... 'questionable'.
| russdill wrote:
| That really seems to be mischaracterizing his work. The
| idea is that the quantum effects we see will eventually
| emerge.
|
| Most people in the field don't think his research will be
| fruitful, but that doesn't make him a crack pot
| momoschili wrote:
| most people in the field believe his research isn't even
| capable of being wrong
| dmos62 wrote:
| Someone seems to say something demeaning like that about
| him whenever he comes up, and I don't really know why.
| Which is fine, maybe it's a subjective thing. For what it's
| worth, the few times I read something of his, I loved it.
| cjfd wrote:
| Well, one can love playing chess and that is all fine and
| good and so on but if someone says that chess is the
| fundamental theory of the universe, how much sense does
| that make? There might even even be truth in that
| statement, who could possibly know? All we can be quite
| certain about is that to actually demonstrate the
| hypothetical truth of the statement 'chess is the
| fundamental theory of the universe' some number,
| presumably larger than 5, of nobel price level of physics
| discoveries need to take place.
| gowld wrote:
| You are making an unscientific criticism.
|
| Wolfram's claim is that Cellukar Automata can provide as
| good or better mathematical model of the universe than
| current current theories, by commonly appreciated metrics
| such as "pasimony of theory" (Occam's Razor). He's not
| making claims about metaphysical truth.
| 7thaccount wrote:
| It's a complex issue. He is obviously extremely
| intelligent and at least a decent business man. If you've
| never used Wolfram Mathematica before, I implore you to
| pick up a raspberry pi and play with the educational
| version. It's nothing short of magical in many ways. I
| still prefer Python in a lot of ways (least of all with
| Python being free/open), but Mathematica notebooks are
| nuts. You can do anything from calculus to charts,
| geographic visualizations, neural networks, NLP, audio
| processing, optimization, text processing, time series
| analysis, matrices, and a bazillion other things with a
| single command or by chaining them together. It has its
| warts, but is very polished.
|
| He also did some important early work on cellular
| automata if iirc.
|
| Then he wrote "A New Kind of Science", which reads like
| an ego trip and was not received well by the community
| (it is a massive tome that could have been summarized
| with a much smaller book). He also tried to claim
| discoveries from one of his workers due to some NDA
| shenanigans (or something along these lines iirc). The
| latter doesn't make him a crank, just a massive egotist,
| which is a trait nearly all cranks have. Sabine
| Hossenfelder did a video on him and how he only publishes
| in his own made up journals and generally doesn't use the
| process used by all other scientists. I think a lot
| believe where there is smoke, there is fire. To his
| credit, she also mentioned that some physicists gave him
| some critical feedback and he did then go and spend a
| bunch of time addressing the flaws they found.
| UltraSane wrote:
| I sympathize with your opinion of him being a crackpot but
| he is also a genius and the idea is that the graphs in his
| theory are more fundamental than quantum mechanics and it
| would emerge from them.
| xwkd wrote:
| I'm not even able to hold a candle to Wolfram
| intellectually- the guy is a universe away from me in that
| regard. But: Given a cursory look at his wiki page and
| Cosma Shalizi's review of his 2002 book on cellular
| automata [1], I feel fairly comfortable saying that it
| seems like he fell in the logician's trap of assuming that
| everything is computable [2]:
|
| >There's a whole way of thinking about the world using the
| idea of computation. And it's very powerful, and
| fundamental. Maybe even more fundamental than physics can
| ever be.
|
| >Yes, there is undecidability in mathematics, as we've
| known since Godel's theorem. But the mathematics that
| mathematicians usually work on is basically set up not to
| run into it. But just being "plucked from the computational
| universe", my cellular automata don't get to avoid it.
|
| I definitely wouldn't call him a crackpot, but he does seem
| to be spinning in a philosophical rut.
|
| I like his way of thinking (and I would, because I write
| code for a living), but I can't shake the feeling that his
| physics hypotheses are flawed and are destined to bear no
| fruit.
|
| But I guess we'll see, won't we?
|
| [1] http://bactra.org/reviews/wolfram/ [2]
| https://writings.stephenwolfram.com/2020/04/how-we-got-
| here-...
| Aardwolf wrote:
| I do wonder if you'd want to implement a sort of 3D game engine
| that simulates the entire universe, if somehow the weird stuff
| quantum physics and general relativity do (like the planck
| limit, the lightspeed limit, discretization, the 2D holographic
| bound on amount of stuff in 3D volumes, the not having an
| actual value til measured, the not being able to know momentum
| and speed at the same time, the edge of observable universe,
| ...) will turn out to be essential optimizations of this engine
| that make this possible.
|
| Many of the quantum and general relativity behaviors seem to be
| some kind of limits (compared to a newtonian universe where you
| can go arbitrarily small/big/fast/far). Except quantum
| computing, that one's unlocking even more computation instead
| so is the opposite of a limit and making it harder rather than
| easier to simulate...
| jules wrote:
| The universe is already modeled that way. Differential
| equations are a kind of continuous time and space version of
| cellular automata, where the next state at a point is
| determined by the infinitesimally neighboring states.
| mannykannot wrote:
| My first thought was 'ah, yes.' My second thought was 'but
| what about nonlocality?'
| harha_ wrote:
| How complex? I'm no physicist nor an expert at this, but AFAIK
| we aren't really capable of simulating even a single electron
| at the quantum scale right now? Correct me if I'm wrong.
| kergonath wrote:
| We can simulate much more than that, even at the quantum
| scale. What we cannot do is calculate things analytically, so
| we only have approximations, but for simulation that's more
| than enough.
| whatshisface wrote:
| Our present best guess is that cellular automatons would be an
| explosively difficult way to simulate the universe because BQP
| (the class of problems that can be related to simulating a
| quantum system for polynomial time) is probably not contained
| in P (the class of problems Turing machines can solve in
| polynomial time).
| zmgsabst wrote:
| The scales get you:
|
| You can't simulate a molecule at accurate quark/gluon
| resolution.
|
| The equations aren't all that complex, but in practice you have
| to approximate to model the different levels, eg
| https://www.youtube.com/playlist?list=PLMoTR49uj6ld32zLVWmcG...
| jcranmer wrote:
| > Could a competent software engineer, even without knowing the
| fundamental origins of things like particle masses or the fine-
| structure constant, capture all known fundamental interactions
| in code?
|
| I don't think so.
|
| In classical physics, "all" you have to do is tot up the forces
| on every particle and you get a differential equation that is
| pretty easy to numerically work with. Scale is a challenge all
| of its own, and of course you'd ideally need to learn about all
| the numerical issues you can run into. But the math behind
| Runge-Kutta methods isn't that advanced (really, you just need
| some calculus to even explain what you're doing in the first
| place), so that's pretty approachable to a smart high schooler.
|
| But when you get to quantum mechanics, it's different. The
| forces aren't described in a way that's amenable to tot-up-all-
| the-forces-on-every-particle, which is why you get stuff like
| https://xkcd.com/1489/ (where the explainer is unable to really
| explain anything about the strong or weak force). As an
| arguably competent software engineer, my own attempts to do
| something like this have always resulted in my just bouncing
| off the math entirely. And my understanding of the math--as
| limited as it is--is that some things like gravity just _don 't
| work at all_ with the methods we have at hand to us, despite us
| working at it for 50 years.
|
| By way of comparison, my understanding is that our best
| computational models of fundamental forces struggle to model
| something as complicated as an atom.
| cjfd wrote:
| Horribly complex and/or impossible.
|
| (1) quantum mechanics means that there is not just one
| state/evolution of the universe. Every possible state/evolution
| has to be taken into account. Your model is not three-
| dimensional. It is (NF * NP)-dimensional. NF is the number of
| fields. NP is the the number of points in space time. So, you
| want 10 space-time points in a length direction. The universe
| is four-dimensional so you actually have 10000 space-time
| points. Now your state space is (10000 * NF)-dimensional. Good
| luck with that. In fact people try to do such things. I.e.,
| lattice quantum field theory but it is tough.
|
| (2) I am not really sure what the state of the art is but there
| are problems even with something simple like putting a spin 1/2
| particle on a lattice.
| https://en.wikipedia.org/wiki/Fermion_doubling
|
| (3) Renormalization. If you fancy getting more accuracy by
| making your lattice spacing smaller, various constants tend to
| infinity. The physically interesting stuff is the finite part
| of that. Calculations get progressively less accurate.
| russdill wrote:
| To go down this rabbit hole, the deeper question is about the
| vector in Hilbert space that represents the state of the
| universe. Is it infinite dimensional?
| cjfd wrote:
| Yes, but that is not saying very much. Just one single
| harmonic oscillator already has a state space that is an
| infinitely dimensional Hilbert space. It is L^2. Now make a
| tensor product of NF * NP of these already infinitely
| dimensional Hilbert spaces defined above to get quite a bit
| more infinite.
| IIAOPSW wrote:
| Well, Newton thought he could do it with just 3 lines, and
| we've all been playing code golf ever since.
| mrguyorama wrote:
| To be fair, his universe was much simpler than ours. He
| didn't need a nuclear reactor or particle accelerator to
| transmute lead into gold in his theory.
| UltraSane wrote:
| Stephen Wolfram is trying to model physics as a hypergraph
|
| https://www.wolframphysics.org/universes/
| gus_massa wrote:
| You (sorta) can! https://en.wikipedia.org/wiki/Lattice_QCD
|
| The trick is (as the sibling comments explain) that it involves
| an exponential number of calculations, so it's extremely slow
| unless you are interested only in very small systems.
|
| Going more technical, the problem with systems with the strong
| force is that they are too difficult to calculate, so the only
| method to get results is to add a fake lattice and try solving
| the system there. It works better than expected and it includes
| all the forces we know, well except gravity , and it includes
| the fake grid. So it's only an approximation.
|
| > _Could a competent software engineer, even without knowing
| the fundamental origins of things like particle masses or the
| fine-structure constant, capture all known fundamental
| interactions in code?_
|
| Nobody know where that numbers come from, so they are just like
| 20 or 30 numbers in the header of the file. There is some
| research to try to reduce the number, but I nobody knows if
| it's possible.
| Jach wrote:
| http://oyhus.no/QuantumMechanicsForProgrammers.html gives a
| flavor of one possible shape of things. It's pretty intractable
| to actually compute anything this way.
| jfengel wrote:
| The formulas are really not very complex. The Standard Model is
| a single Lagrangian with a couple of dozen constants.
|
| https://visit.cern/node/612
|
| You can expand that Lagrangian out to look more complex, but
| that's just a matter of notation rather than a real
| illustration of its complexity. There's no need to treat all of
| the quarks as different terms when you can compress them into a
| single matrix.
|
| General relativity adds one more equation, in a matrix
| notation.
|
| And that's almost everything. That's the whole model of the
| universe. It just so happens that there are a few domains where
| the two parts cause conflicts, but they occur only under
| insanely extreme circumstances (points within black holes, the
| universe at less than 10^-43 seconds, etc.)
|
| These all rely on real numbers, so there's no computational
| complexity to talk about. Anything you represent in a computer
| is an approximation.
|
| It's conceivable that there is some version out there that
| doesn't rely on real numbers, and could be computed with
| integers in a Turing machine. It need not have high
| computational complexity; there's no need for it to be anything
| other than linear. But it would be linear in an insane number
| of terms, and computationally intractable.
| baxtr wrote:
| _> The Standard Model is a single Lagrangian with a couple of
| dozen constants._
|
| I hear it's a bit more complex than that!
|
| https://www.sciencealert.com/this-is-what-the-standard-
| model...
| l33tman wrote:
| It's a single lagrangian with a couple of dozen constants,
| in their pics there as well. It's just expanded out to
| different degrees.
| baxtr wrote:
| Through smart definitions I can contract any longer term
| as much as I want.
| ajkjk wrote:
| Nah it really is simpler than that, that picture has
| exploded the summations to make it look complicated.
| Although it is strangely hard to find the compressed
| version written down anywhere...
|
| the thing about Lagrangians is that they compose systems by
| adding terms together: L_AB = L_A + L_B if A and B don't
| interact. Each field acts like an independent system, plus
| some interaction terms if the fields interact. So most of
| the time, e.g. on Wikipedia[0], people write down the terms
| in little groups. But still, note on the Wikipedia page
| that there are not that many terms in the Lagrangian
| section, due to the internal summations.
|
| [0]: https://en.wikipedia.org/wiki/Mathematical_formulation
| _of_th...
| xyzzy_plugh wrote:
| I can't help but wonder if, under extreme conditions, the
| universe has some sort of naturally occurring floating-point
| error conditions, where precision is naturally eroded and
| weird things can occur.
| jfengel wrote:
| I doubt it. Even the simplest physical system requires a
| truly insane number of basic operations. Practically
| everything is integrals-over-infinity. If there were
| implemented in a floating-point system, you'd need umpteen
| gazillion bits to avoid flagrant errors from happening all
| the time.
|
| It's not impossible that the universe is somehow
| implemented in an "umpteen gazillion bits, but not more"
| system, but it strikes me as a lot more likely that it
| really is just a real-number calculation.
| xyzzy_plugh wrote:
| Right, I don't mean literally floating-point errors, but
| something similar.
| Hextinium wrote:
| That could very well be what the quantum uncertainty
| principal is, floating point non deterministic errors. It
| also could just be drawing comparisons among different
| problem domains.
| yyyk wrote:
| >These all rely on real numbers, so there's no computational
| complexity to talk about.
|
| There's a pretty decent argument real numbers are not enough:
|
| https://www.nature.com/articles/s41586-021-04160-4/
|
| https://physics.aps.org/articles/v15/7
| jekude wrote:
| I've always thought that gravity exists because without it,
| matter doesn't get close enough for interesting things to
| happen.
| tmiku wrote:
| I'm surprised that more sibling comments aren't covering the
| lack of a unified theory here. Currently, our best
| understanding of gravity (general relativity) and our best
| understanding of everything else (electromagnetism, quantum
| mechanics, strong/weak force via the standard model) aren't
| consistent. They have assumptions and conclusions that
| contradict each other. It is very difficult to investigate
| these contradictions closely because the interesting parts of
| GR show up only in very massive objects (stars, black holes)
| and the interesting parts of everything else show up in the
| tiniest things (subatomic particles, photons).
|
| So we don't have a set of equations that we could expect to
| model the whole universe in any meaningful way.
| whatshisface wrote:
| At the level of writing a program to simulate the universe as
| we see it, ideas like classical gravity (see Penrose) would
| probably work.
| abecedarius wrote:
| Less ambitiously, how small and clear could you make a program
| for QED calculations? Where you're going for code that can be
| clear to someone educated with only undergrad physics, with
| effort, to help explain what the theory even is -- not for
| usefulness to career physicists.
|
| Maybe still too ambitious, because I haven't heard of such a
| program.
| whatshisface wrote:
| Wolfram actually got his start writing these.
| antonvs wrote:
| Rephrasing what some of the other answers have said, with a
| decent knowledge of math you could write the program, but you
| wouldn't be able to run it in a reasonable time for anything
| but the most trivial scenarios.
| at_a_remove wrote:
| How I learned it, as a mere undergrad, was that the mass of the
| virtual particle for the field in question determined exactly how
| long it could exist, just by the uncertainty principle -- much
| like the way the virtual particles drive Hawking radiation.
|
| In short, a massive virtual particle can exist only briefly
| before The Accountant comes looking to balance the books. And if
| you give it a speed of _c_ , it can travel only so far during its
| brief existence before the books get balanced. And therefore the
| range of the force is determined by the mass of the force carrier
| virtual particle.
|
| There's probably some secondary and tertiary "loops" as the
| virtual particle _possibly_ decays during its brief existence,
| influencing the math a little further, but that is beyond me.
| not2b wrote:
| And the article we are discussing explains why this is
| incorrect.
| nyc111 wrote:
| "For the subtleties of different meanings of "mass", see chapters
| 5-8 of my book.]"
|
| Isn't this called "equivocation" in logic?
| mtreis86 wrote:
| The top of fig 3 doesn't accurately represent a string pulled
| down in the middle. A string pulled down in the middle would have
| no curve to it in the legs unless some force is acting on it, it
| would look like a V.
| seeekr wrote:
| To me it seems like it's depicting a situation where the string
| hasn't been pulled fully, so some of its slack hasn't
| straightened out into the otherwise resulting triangle yet.
| SpaceManNabs wrote:
| This particular article has a prelude on the same website
|
| https://profmattstrassler.com/2025/01/10/no-the-short-range-...
| halyconWays wrote:
| PSA: it's "fib," not "phib"
| not2b wrote:
| No, his use is intentional. It's a portmanteau for "physics
| fib".
| metacritic12 wrote:
| Doesn't this "explanation" just shift the question to what is
| stiffness? Like it refactored the question but didn't actually
| explain it.
|
| Previously, we had statement "the weak force is short range". In
| order to explain it, we had to invent a new concept "stiffness"
| that is treated as a primitive and not explained in terms of
| other easy primitives, and then we get to "accurately" say that
| the weak force is short due to stiffness.
|
| I grant the OP that stiffness might be hard to explain, but then
| why not just say "the weak force is short range -- and just take
| that as an axiom for now".
| pishpash wrote:
| Because you may get something else out of stiffness besides
| this explanation? Usually that's how a level deeper explanation
| works.
| drdec wrote:
| If you read far enough into the math-y explanations, stiffness
| is a quantity in the equations. That makes it more than a hand
| waving explanation in my book.
| ajkjk wrote:
| I think it's a big improvement. Stiffness is something you can
| picture directly, so the data -> conclusions inference
| "stiffness" -> "mass and short range" follows directly from the
| facts you know and your model of what they mean. Whereas
| "particles have mass" -> "short range" requires someone also
| telling you how the inference step (the ->) works, and you just
| memorize this as a fact: "somebody told me that mass implies
| short range". You can't do anything with that (without
| unpacking it into the math), and it's much harder to pattern-
| match to other situations, especially non-physical ones.
|
| It seems to me like the right criteria for a good model is:
|
| * there are as few non-intuitable inferences as possible, so
| most conclusions can be derived from a small amount of
| knowledge
|
| * and of course, inferences you make with your intuition should
| not be wrong
|
| (I suppose any time you approximate a model with a simpler one
| ---such as the underlying math with a series of atomic notions,
| as in this case---you have done some simplification and now you
| might make wrong inferences. But a lot of the wrongness can be
| "controlled" with just a few more atoms. For instance "you can
| divide two numbers, unless the denominator is zero" is such a
| control: division is intuitive, but there's one special case,
| so you memorize the general rule plus the case, and that's
| still a good foundation for doing inference with)
| lilyball wrote:
| Besides the fact that stiffness shows up as a term in the
| equations, stiffness is a concept that can be demonstrated via
| analogy with a rubber sheet, and so lends itself to a somewhat
| more intuitive understanding.
|
| Also, the math section demonstrated how stiffness produces both
| the short-range effect and the massive particles, so instead of
| just handwaving "massive particles is somehow related to the
| short range" the stiffness provides a clear answer as to why
| that's the case.
| exmadscientist wrote:
| In addition to what the sibling comments have said, the "axiom"
| is actually the term in the equations. That is, fundamentally,
| where this all comes from. "Stiffness" is just a word coined to
| help describe the behavior that arises from a term like this.
| Everything flows from having that piece in the math, so if you
| start there and with nothing else, you can reinvent everything
| else in the article. (Though it will take you a while.)
|
| You might also ask where that term comes from. It really is
| "axiomatic": there is no _a priori_ explanation for why
| anything like that should be in the equations. They just work
| out if you do that. Finding a good explanation for why things
| have to be _this_ way and not _that_ way is nothing more and
| nothing less than the search for the infamous Theory of
| Everything.
| UniverseHacker wrote:
| This is often I think a really unsatisfying thing about
| physics. Usually the qualitative descriptions don't quite
| make sense if you think very hard about them- and if you dig
| deeper it's often just "we found some math that fits our
| experimental data" - and ultimately that is as much as we
| know, and most attempts at explaining it conceptually are
| conjecture at best.
|
| When I was a physics undergrad, most of my professors were
| fans of the "shut up and calculate" interpretation of quantum
| mechanics.
|
| Ultimately, this is probably just a symptom of still not
| having yet discovered some really important stuff.
| bnetd wrote:
| As an aside, is there conclusive evidence to say that no aether
| exists, or are we just saying it doesn't exist because a handful
| of tests were conducted to match what we thought this aether
| would behave like and the tests came back negative?
| aidenn0 wrote:
| For a strict enough definition of "conclusive," there is never
| conclusive evidence that something doesn't exist.
|
| On top of that, if we find something that behaves nothing like
| what people meant when they said aether, then is it really
| aether?
| LegionMammal978 wrote:
| Lorentz formulated his ideas in terms of a motionless aether.
| But his aether theory yielded predictions identical to special
| relativity, so later physicists ditched his interpretation in
| favor of Einstein's theory that didn't need an undetectable
| global reference frame.
|
| Overall, we can't really have 'conclusive evidence' against any
| mechanism, as long as our observations might possibly be
| simulated on top of that mechanism. So as far as evidence goes,
| 'what really exists' might be higher-dimensional strings, or
| cellular automata, or turtles all the way down, or whatever.
|
| Instead, physics has some number of models (either
| complementary or competing) that people find compelling, and
| mechanisms on top of those models to explain our observations.
| If you did come up with a modern aether theory, you'd have to
| come up with a mechanism on top of it to explain all the
| relativistic effects we've observed.
| pdonis wrote:
| We say the "aether" as it was originally conceptualized in the
| 19th century doesn't exist for the same reason we say that
| Russell's teapot or Carl Sagan's invisible dragon in the garage
| doesn't exist: we have a model of the world that makes all the
| same predictions without it, so it gets scraped right off by
| Occam's Razor.
| akomtu wrote:
| Magnetic field is that aether.
| aidenn0 wrote:
| It seems to me that there is a 1:1 correlation between mass of
| virtual particle and field stiffness. Given that fact, why isn't
| it equally correct to say "The field stiffness is caused by the
| mass of the virtual particle" and "The virtual particle
| necessarily has mas because the field is stiff"
|
| The author states that "it is short range because the particles
| that "mediate" the force, the W and Z bosons, have mass;" is
| misleading as to causality, but I missed the part where they
| showed how/why it was misleading.
| sojuz151 wrote:
| Because in a classical theory, where there are no particles,
| there is still the same short range potential.
| aidenn0 wrote:
| This arises from a parameter in the elementary field
| equation. If that parameter is non-zero than it is both true
| that the field is stiff and it must be mediated by a particle
| with non-zero rest mass. This says nothing about causality.
| nimish wrote:
| This is a lot of words to say that the field oscillations (i.e.,
| particles) require very high energy. This shows up as the
| mass-(energy) of the particle, or stiffness of the field; take
| your pick.
|
| Whether you call that stiffness or mass is a little beside the
| point IMO -- it shows up in the Yukawa force as an exponential
| dependence on that parameter which means the force quickly decays
| to zero unless the parameter is 0.
| bawana wrote:
| The effect of stiffness can also be represented by stretchability
| of the string. Picking up a string with a free end will result in
| the same shape described by adding stiffness. A fanciful analogy
| might be a chain of springs with constant k2 where each spring
| junction is anchored to the ground with a spring with constant
| k1. If k2>>k1 the entire spring chain lifts in a gentle arc when
| a spring is lifted. If k1>>k2, only the springs near the pulling
| point really stretch and displace. It's these kinds of simple
| analogies that engage our intuition. I still however cannot
| envision a mechanical analogy to demonstrate wavicles.
| gweinberg wrote:
| One thing that confused me at the very beginning is, the author
| says the weak force is weak because it is short range. But the
| strong force is also short range.
| lilyball wrote:
| The weak force is weak not because it has "short range" but
| because its range "dies off at distances ten million times
| smaller than an atom".
| MathMonkeyMan wrote:
| The strong force is short range for a different reason. It's
| called [confinement][1]. The strong force gets stronger as you
| pull color charges apart. At some point the energy is so high
| that it's very likely that corresponding matching-color
| particles will exist, and so now there two pairs of close
| charges, instead of one pair of far charges.
|
| [1]: https://en.wikipedia.org/wiki/Color_confinement
| JumpCrisscross wrote:
| > _Google's AI, for instance, and also here -- that the virtual
| particles with mass actually "decay"_
|
| Do virtual particles decay?
| vonneumannstan wrote:
| The real answer is we don't know or otherwise some kind of
| anthropic argument, i.e. the weak force has the range it does
| becuase otherwise we wouldn't have this kind of universe with
| people in it pondering why the weak force is the way it is.
|
| Seems generally unhelpful to say 'the weak force is short range
| because it's field is stiffer!' When you can then immediately say
| 'well why is the weak force's field stiffer?'
| atoav wrote:
| Got you, but I am unsure if moving to the next question isn't a
| success as well. You understood a thing and move on, rinse and
| repeat.
|
| Or: consider where science would be had it operated under your
| proposed maxime for the past 3 centuries.
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