Physicist here. I don’t buy some of these distinctions, like the chirality. Chirality is an observable, it’s like saying there are two photons because they can come in two polarizations, but polarization is not an inherent property: it depends on how we measure it. So I could describe any photon in the left/right chiral basis just as well as in the vertical/horizontal basis or any two antipodal points in the Poincaré sphere, so which is the “right one”? Neither. Spin on the other hand (which is where polarization comes from) is well-defined for any photon and it’s always 1 (the astute reader will wonder why the projection of spin 1 does not take 3 eigenvalues 1,0,-1 and it’s because photons are massless so the 0 projection never occurs because there is no rest frame for massless particles).

• gus_massa

  today at 6:23 PM

  Chirality is a real property of (most) elementary particles. For example the electron with left chirality has a weak hypercharge of -1, but the electron with right chirality has a weak hypercharge of 0. https://en.wikipedia.org/wiki/Weak_hypercharge#Definition In some sense, they are very different particles. Also, only the left version interact with the weak interaction.

I'm not a physicist (so take this with a grain of salt) but I have spent a lot of time trying to find an answer to this question. If you interpret the physics before Spontaneous Symmetry Breaking as more fundamental, and you treat the antimatter fields as distinct, then I think you can reasonably claim that there are 30 fundamental fermion fields. Specifically, in each of the 3 generations, you have:

1. The left-handed lepton doublet field, and the antimatter equivalent. 2. The left-handed quark doublet field, and the antimatter equivalent. 3. The right-handed electron singlet field, and the antimatter equivalent. 4. The right-handed up-quark singlet field, and the antimatter equivalent. 5. The right-handed down-quark singlet field, and the antimatter equivalent.

The bosons are more confusing to me, but I think a reasonable person might say that there are 16 fundamental boson fields:

1. The four scalar boson fields. 2. The eight gluon fields. 3. The three W boson fields. 4. The B boson field.

The B boson couples to every fermion (via hypercharge), while gluons only couple to quarks (via color) and W bosons only couple to the doublets (via weak isospin).

I feel like you ought to be go lower than 17, down to 9, by not counting the 3 generations of fermions as distinct (so you've just got up-type quark, down-type quark, electron-type particle, and neutrino). After all, if they can mix with one another, should they really be considered entirely different particles?

• ndsipa_pomu

  today at 5:36 PM

  There's different behaviour between the 3 generations though as a muon will decay whereas an electron won't.

  • aeonik

    today at 5:45 PM

    We don't know that electrons don't decay for sure.

    If we live in a false vacuum, for example, that could allow them to decay.

    • ndsipa_pomu

      today at 5:53 PM

      > We don't know that electrons don't decay for sure.

      However, we don't expect electrons to decay as we don't know what they would decay into i.e. there doesn't seem to be anything plausible with a lower energy configuration.

      > If we live in a false vacuum, for example, that could allow them to decay.

      Possibly, but that's quite speculative and if our vacuum does decay, then there's a good chance we wouldn't be around to see the differences.

Not being a Physicist, I have to wonder if all these particles are somehow manifestations of a simpler thing.

Might there have been a point in time (long ago) where the “wave photon” and the “particle photon” seemed like possibly different things?

• jerf

  today at 2:45 PM

  You don't have to wonder, because they are. They're manifestations of fields.

  I think it is a reasonable answer to tell people "if you're looking for the short list of simplest things, the number of types of fields there are is probably what you're looking for".

  That doesn't invalidate this question in general, though the number of different answers from people looking at the same thing suggests it may be underspecified.

  • HarHarVeryFunny

    today at 3:34 PM

    But of course one can then question why are there exactly N different types of fields, with their specific types of interaction (at least in our universe)? Why should we suppose that this is the most fundamental description of reality, rather than being emergent from something else?

    • frutiger

      today at 4:18 PM

      > But of course one can then question why are there exactly N different types of fields, with their specific types of interaction (at least in our universe)?

      Even that has a (still unsatisfactory) answer.

      Poincaré symmetry imposes constraints on the kinds of fields we can have. Gauge symmetry shows us how they may couple.

      There are still some arbitrary selections of the possible permutations that nature has “picked”.

      • HarHarVeryFunny

        today at 5:45 PM

        Interesting, but (way out of my depth here) why do these symmetries have to exist?

        It would be much more satisfying (not that nature exists to be satisfying) if we could explain our universe starting from some universal constraints on things that must be true of any non-random mechanistic universe, plus some set of (< N) non-forced "it must be A or B" additional constraints, then be able to derive everything known about our universe - fields and symmetries etc - (& ideally predict something unknown) as resulting from some particular selection of those additional constraints.

        This seems about as close as we could get to explaining our universe... Basically saying that god flipped a coin marked A and B, and it come down A so here we are. Maybe god kept on flipping sets of coins and created a whole bunch of other universes too, whose physics we could also derive.... and maybe one day visit and confirm.

        • behringer

          today at 6:13 PM

          You might not want to visit because it's probable you would explode or have some other horrific death due to incompatibility between your fields and theirs.

    • today at 4:18 PM

    • jerf

      today at 4:12 PM

      I completely agree that's a reasonable question.

      I'd also observe that between dark matter and dark energy, there's good reason to believe that we may not have a full accounting of all fields.

      I am just observing that if you have a non-scientist asking the question "how many fundamental particles are there", with the expectation that "995.5" is not really the right answer, "the number of fields" is a reasonable response that probably gets closer to what they are looking for. Even if someday someone does get them to all be some manifestations of a single field it would arguably still be the case that people are more interested in the answer of the current number of fields then being told "1", because "1" is in many ways not a helpful answer to "how many types of things are there". Even if there is a profound sense in which it was true, there would still be a profound sense in which it was false, too.

    • tsimionescu

      today at 3:49 PM

      Well, why would there be fewer than N? There is no general principle that we can impose on the world, it just is, we can only discover what the laws and components of the world are (hopefully). I'm not claiming it's impossible for there to be fewer fields than we think right now. But there is no reason to believe there should be.

      • GistNoesis

        today at 5:15 PM

        Elegance. It's Occam's razor. If we can do with only one field, it's probably it.

        It's inductive and abductive reasoning. The one field, and it has lot of mathematical characteristics which makes it unique on its own, and also it is the only one that has a chance to fit, is the e8 field popularized by Garrett Lisi.

        If a universe were to be designed based using the e8 Lie algebra as an elemental field, it would look a lot like our universe.

        Currently the standard model is a patchwork of field added as experiments for observing particles were possible to realize. The big picture's view is a unified theory which fits perfectly all existing data.

        • tsimionescu

          today at 5:29 PM

          Occam's razor has nothing to do with this, it only applies once you have multiple competing theories - you can't use Occam's razor to decide that a theory "should" exist.

          Currently, we don't have any theory that works that's any simpler than the SM. So that's the theory that Occam's razor currently tells us must be true, as it's the simplest alternative that actually works.

      • HarHarVeryFunny

        today at 4:13 PM

        I'm not saying fewer fields, but perhaps a more fundamental substrate to reality than fields that fields emerge from. Maybe the N fields are just vibrational modes or attractor dynamics of something simpler.

        It seems there has to be a reason WHY there are exactly N fields, and WHY they interact in the ways they do.

        Edit: As I noted in another comment, the best explanation may come down to "there are only 100 viable types of universe, and ours is type 42". I'd be happy with that.

    • api

      today at 4:41 PM

      To me it looks like the periodic table. There's an underlying set of levers in terms of quantum characteristics of fields, but not all settings of these levers are stable. This is just like how only atoms with certain combos of protons and neutrons and electrons are neutral and stable.

      If you look at histogram plots of protons, neutrons, and stability, it's not a perfectly idealized form. It's a rocky plot. This emerges from the quantized nature of reality.

      So a periodic table of particles (fields) that looks kind of weird and ad-hoc to us is the expected result.

      What we don't yet fully understand is really two things as far as I know. First, we know less about why these particular values are special. For the periodic table we actually understand this pretty well. Second, we do not know if there are other islands of stability or particles-fields we cannot see (e.g. WIMPS). For the periodic table we are pretty sure there are no large islands of stability at higher weights. Not 100% sure, but if they do exist there's probably only a few exotic mega-atoms that could be stable, not many.

  • rwmj

    today at 3:03 PM

    To me that raises the opposite question, why are there so few fields? (Compared to what I'd imagine, infinite)

    [Edit: I suppose I'm imagining waves or frequencies of waves, rather than fields, hence why in my imagination there would be an infinite variety]

    • Filligree

      today at 3:08 PM

      Not all fields interact with all other fields. You can think of them as a loosely coupled graph…

      There might be any number of graph components with no connectivity to our fields at all, and we’d never know. Assuming, of course, that we’re including gravity in this logic.

      There’s also might be any number of arbitrarily complex components which are only connected through gravity. That’s a decent candidate for what the dark sector actually is.

  • TheOtherHobbes

    today at 3:15 PM

    In QFT every particle type has its own field.

    • nine_k

      today at 4:01 PM

      ...and a field is just a value that behaves in a particular way. An example outside QFT: phonons [1] behave like particles, but there is no "palpable" sound field, there's only local distribution of implulses of the molecules of air (or whatever medium) where the sound propagates.

      Other fields can be seen as attributes of the space itself, and "elementary particles" as wrinkles on it. Gravity is special because it bends the very geometry of space.

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

    • antonvs

      today at 3:27 PM

      Every particle type has its own field, but the OP article is counting a single particle type multiple times based on properties like spin and polarization. At one point the article reaches the number 118. That corresponds directly to 37 quantum fields once you take the "double counting" into account.

      • dpark

        today at 4:54 PM

        Where are you getting 37? The standard model has 17 fields.

        If you pick and choose which properties to select as unique fields, maybe you can get the number 37, but at that point why not 118 fields?

  • today at 3:42 PM

  • Noaidi

    today at 2:55 PM

    > They're manifestations of fields.

    Or wave. Everything is a quantum wave.

    https://www.vlatkovedral.com/everything-in-the-universe-is-a...

    • GroksBarnacles

      today at 3:08 PM

      A wave is already what we call a manifestation of a field, maybe I skimmed too quickly but I don't get the author's breakthrough point.

      • dpark

        today at 6:31 PM

        I am not sure there’s any breakthrough here, but this article is about a different QM interpretation (as opposed to Copenhagen or Many Worlds). Interesting but seems irrelevant to the discussion here of particles and fields.

      • Noaidi

        today at 3:32 PM

        Yes, the field is the substrate.

        "I insist upon the view that 'all is waves'."

            Letter to John Lighton Synge (9 November 1959), as quoted by Walter Moore in Schrödinger: Life and Thought (1989) ISBN 0521437679 
        

        It is not a breakthrough, it is just something we refuse to see, something that was known for a century.

        "All is a wave" is the unifying principle. I am no mathematician, but the math needs to start with that fundamental principle.

        The very notion of calling it "qunatum" physics is probably wrong since quantum is "a discrete quantity of energy proportional in magnitude to the frequency of the radiation it represents."

        And if everything is a wave there are no discrete quantities beyond our definition of what constitutes the end, or borders, of the wave.

        • dpark

          today at 5:18 PM

          > I am no mathematician, but the math needs to start with that fundamental principle.

          This is a weird sort of hubris. “I’m not qualified to do this job but I can certainly tell you how it needs to be done.”

          > And if everything is a wave there are no discrete quantities beyond our definition of what constitutes the end, or borders, of the wave.

          This is not true in multiple ways. First, it’s known that these particles exhibit quantum behavior. This is measured and confirmed over and over. Many measures are in fact quantized.

          Second, existing as a wave does not mean no discrete quantities. Even in everyday materials we observe situations like standing waves that are effectively quantized.

          https://en.wikipedia.org/wiki/Standing_wave

    • andrewflnr

      today at 3:42 PM

      > Now, when I told my editor at Allen Lane about my own interpretation, he immediately said “It’s Many Worlds on steroids!” There is a grain of truth in that, ...

      Dude, this is an answer to an entirely different question. He's proposing an interpretation of QM, which is independent from "how many fundamental particles".

    • antonvs

      today at 3:30 PM

      A wave is a phenomenon that propagates through a field - i.e. the field is what allows the wave to exist.

      (The philosophy of that admittedly gets messy, though, e.g. "are fields real objects?")

  • antonvs

    today at 3:25 PM

    > if you're looking for the short list of simplest things, the number of types of fields there are is probably what you're looking for

    Definitely. It's rather strange that the OP article doesn't even mention the word "field". It seems that people in general have a hard time letting go of the idea of particles as fundamental.

    A good overview of this is "There are no particles, there are only fields" (https://arxiv.org/abs/1204.4616) by physics prof Art Hobson.

    Fields collapse the zoo described in the article significantly, because particles and antiparticles arise from the same field, and similarly, spin, polarization, and helicity are properties of the same field. Taking this into account, the 118 particles number that the article reaches at one point drops to 37 fields.

    • AnimalMuppet

      today at 3:56 PM

      You've said that "37 fields" at least twice. It doesn't seem to come from the arxiv article you linked, though. And it seems rather high to me. (Of course, 118 seems ridiculously high...)

      Anyway: Would you list them? Or supply a link to somewhere that does?

  • taylodl

    today at 4:38 PM

    [dead]

• colejohnson66

  today at 2:38 PM

  That's what the various string theory proponents start from. There's "too many" different subatomic particles, so there surely must be something smaller that they're composed of?

  • Noaidi

    today at 2:58 PM

    How long can you break something apart until you cannot any longer? The things we are breaking apart are illusions in a sense. There will always be a smaller particle because that is what we are looking for.

    When we understand that everything that we see is a manifestation of a probability wave, then we will understand everything is a wave and end these foolish experiments.

    • GroksBarnacles

      today at 3:10 PM

      Do you have a meaningful quantitative explanation with some math we can start building tech on, or will that require some... experiments?

    • krapp

      today at 3:00 PM

      I'll be sure to inform all of the physicists that @Noaidi on Hacker News has solved physics and that they can go home.

      • Noaidi

        today at 3:14 PM

        https://www.vlatkovedral.com/about/

• jiug

  today at 3:31 PM

  Even if we use "wave photon" and "particle photon" alternatively, they are only convenient ways of talking about the behavior of the "photon field". The same way when we say "it is raining" we don't mean there is an "it" that "rains" we should try to avoid giving too much litteral meaning to these descriptions.

  That said, I get it is difficult, especially because we are using everyday language to talk about very-much-not-everyday stuff. We all needental hooks to anchor new knowledge and most of our intuition comes from the classical (not-quantum) world around us.

  As a physicist, I feel the art is in learning when to use what description, what Sean Carrol calls "poetic naturalism".

• today at 4:56 PM

• slashdave

  today at 4:47 PM

  > I have to wonder if all these particles are somehow manifestations of a simpler thing

  Yes, theorists have been working on a similar idea for decades.

  > the “wave photon” and the “particle photon” seemed like possibly different things?

  No. Wave vs particle is just a different description of the same thing.

• jiug

  today at 3:14 PM

  Even though "particle photon" and "wave photon" are used alternatively, they are just convenient ways of talking about the behavior of the same "photon field". The same way when we say "it is raining" we don't mean that there is a "it" that "rains", we should try avoid taking these descriptions too literally.

  That being said, is difficult because we are using language to describe very-much-not-everyday stuff. We all need mental hooks to anchor new knowledge and most of our intuition is based on the classical (not-quantum) world aroud us.

• RobotToaster

  today at 3:44 PM

  Unified field theory https://en.wikipedia.org/wiki/Unified_field_theory

• antonvs

  today at 3:32 PM

  > I have to wonder if all these particles are somehow manifestations of a simpler thing.

  Someone else already mentioned that yes, they're manifestations of quantum fields. This is well established - the dominant theory of particle physics, the Standard Model, is a theory of quantum fields.

  In that context, a particle is simply the smallest excitation of a quantum field that can be detected. Fields can be "excited" (fluctuate) in many different ways, and the OP article is interpreting each one of those as a different type of particle. It's misleading.

There are also 17 wallpaper groups. That always seemed like a funny number. I know it's a long shot, but is there a relation?

• slashdave

  today at 4:45 PM

  Funny to who? The decimal system, for example, is a human invention.

  • d4ng

    today at 4:47 PM

    It's a reasonably sized prime number regardless of base.

    • sva_

      today at 5:15 PM

      > reasonably sized prime number

      I feel like you're alluding to something but won't say to what? Maybe something like the 'fine-tuned universe' hypothesis?

      • d4ng

        today at 5:48 PM

        Actually I’m not alluding to anything specific. I just wondered whether the 17ness of wallpaper groups and fundamental particles was some sort of mapping from a related common object. Obviously a long shot as previously mentioned.

As usual, the hard problem is how you define "Elementary" which is why the posters always show 17, and then you get numbers that go as high as 995.5 (and the .5 is an interesting result as well).

• rwmj

  today at 3:16 PM

  Isn't it just a thing that cannot be broken into / explained as a combination of more elementary things? ie. as far as we know an electron is an elementary particle because it can't be split into smaller components nor is there any evidence that it contains something smaller (unlike, say, an atom or a proton).

going in the opposite direction, as few as two

https://en.wikipedia.org/wiki/Preon

Some powerof two many actual states + a fractal deterministic random generator for particle Explorers?

The answer is 42.

D

• eximius

  today at 4:31 PM

  Hmm if a particle is a quantized packet of a field, then if multiple quantizations are possible in a field, then it's possible for more particles than fields?

  • tlogan

    today at 4:48 PM

    I somehow deleted my original comment.

    I actually made mistake. There are 16 fields:

    * 12 matter fields (6 quarks + 6 leptons)

    * 1 gluon field (an 8-component SU(3) field)

    * 1 weak field (a 3-component SU(2) field)

    * 1 hypercharge field (a 1-component U(1) field)

    * 1 Higgs field (SU(2) x U(1))

    We have 17 particles is because W+, W-, Z are combination on 2 fields.

    I think counting particles is just going to confuse people because they are really not “balls”.

There are no particles. Everything is a wave.

The Everything-Is-a-Quantum-Wave Interpretation of Quantum Physics

https://www.mdpi.com/2624-960X/5/2/31

Stopped reading after "Yet in the mathematical equations that define the Standard Model, the eight gluons are distinct from one another in the same way that the W and Z bosons differ."

W and Z bosons, photons, etc have fixed masses, charges, interaction strengths with other particles. These properties can exactly be listed and looked up in a table of elementary particles with discrete rows.

Gluon color is continuous property in a vector space. Gluons can have any color in that space, with any combination of the 8 basis vectors (and that choice of basis is also completely arbitrary). The color |g1> is no more valid than the color (|g1> + |g2> + |g8> / √3) or any other of infinite combinations.

Calling this "8 gluons" is like saying there's "3 photons" because they can have momentum in 3 dimensions. If you want to argue there's infinite kinds of gluons, go ahead, but there aren't 8.

• pdonis

  today at 4:19 PM

  > W and Z bosons, photons, etc have fixed masses, charges, interaction strengths with other particles.

  But you can form a continuous set of linear combinations of these things, just as you can with gluons. Indeed, what the article calls W and Z bosons (and photons) are just such linear combinations--the ones that appear in the low energy limit after the electroweak phase transition occurs. Before that phase transition, different linear combinations (i.e., a different basis of the electroweak vector space) are the ones that naturally appear. So saying that there are two W, one Z, and one photon is really counting basis vectors in the electroweak vector space, just as saying there are 8 gluons is really counting basis vectors in the gluon sector of the strong interaction vector space.

  • unholiness

    today at 4:49 PM

    In a hypothetical scenario where we were inventing the standard model in the first 10^-11 seconds after the big bang, you're right there would be an analogy there. But in that scenario, our standard model would say there was one electroweak particle, not that there were 8 gluons.

    In our own universe, the fact that electroweak symmetry breaks ensures there are 4 electroweak particles and not other combinations. There's no corresponding thing to contain gluons to individual particles, you'd need laws of physics we don't have to add that constraint.

• yccs27

  today at 4:32 PM

  The gluon with color (|g1> + |g2> + |g8>) / √3 is just a superposition of the gluons with colors g1, g2 and g8, the same way you can make superpositions of any other particles. You are right that the choice of basis vectors is arbitrary, but that doesn't make it wrong to count the number of dimensions. It also doesn't make it fundamentally different than, say, polarizations of photons or even flavors of quarks. You can have superpositions of photon polarizations or quark flavors.

  All of these are continuous properties in an n-dimensional vector space.

• today at 4:23 PM

• slashdave

  today at 4:45 PM

  And the different charge W bosons are just the same particle, via time reversal symmetry.

• usuckatphysics

  today at 4:47 PM

  8 color indices, why not call that 8 particles what is the point of commenting like you are better than the article when you so clearly show you are not in one sentence never speak on physics again please

• LearnYouALisp

  today at 4:24 PM

  Huh, I didn't even know we had sub-species ID of gluons now