Why do matter particles come in threes? | Hacker News Reader

Why do matter particles come in threes?

quantamagazine.org

99 pointstheafh56 comments

Unlike what the title lead me to believe, it is not the number 3 that is special. It could have been 2 or 42, the question would have remained the same.

The real question is "why are there N copies of each fundamental matter particles?", where N is a seemingly arbitrary number that happens to be 3.

This comment is just saying that some numbers can be other numbers in physics experiments. There is something special about 3 because that's what is observed.

This recent discussion comes to mind here https://news.ycombinator.com/item?id=22706459

Hmm. I dunno, I think there's something to three specifically. One is singular; AFAIK two (and any even number) has a symmetry; so three is the smallest number of things you can have in a set and have it be a set, instead of a unity or symmetry.

> so three is the smallest number of things you can have in a set and have it be a set, instead of a unity or symmetry.

Three is the smallest number of things you can have in a [non-empty] set and have it not be a set of one or a set of two? You don't say. :)

Okay, I'll try again.

AFAIK, the number 1 shows up in nature, it actually represents either an everything (this entire atom) or a 0-1 continuum.

When the number 2 shows up in nature, it's always balanced opposing somethings. Newton's third law, matter / antimatter, negative/positive electric charge, n/s on a magnet.

When the number 3 shows up in nature, you actually get a set of things. Proton, neutrons, electrons; and perhaps this theory now runs into a problem because I'm not thinking of another trinity.

So, if you have two things, and they're not opposites, they imply more things in the category. If you have one thing in a category, and it's not an everything or a spectrum (of the everything), it implies more things in the category. If you have three things in a category, they only imply more things if two of them have a symmetrical relationship (resistors, inductors, capacitors). The category may still have more things. but it's not otherwise implied.

Every multiple of every prime number has a symmetry.

It's unfathomable to me that anything about the universe would be pinned at some integer value.

My intuition is that particles come in infinite numbers of "generations" and we just so happen to be only able to measure three of them right now.

Everything in the universe is pinned at integer values. That's the reason quantum mechanics is called what it is.

Our model for everything in the universe is pinned at integer values. I think that's gp's point.

No, the physical evidence shows that everything in the universe is pinned at integer values in point of actual physical fact. It's not just our models. It goes all the way back to blackbody radiation and the ultraviolet catastrophe of the late 19th century. The evidence for QM is overwhelming. It's not just an artifact of our modeling.

The ultraviolet catastrophe is for sure a good example of this phenomenon.

What's the spin of an electron?

Yeah, so that's a core part of the unintuitiveness of Quantum Mechanics. Nature itself, it turns out, is fundamentally quantized. And also random too.

It objectively cannot be broken down into a continuum.

Neither of these are scientific conclusions — they’re philosophical positions built around an interpretation.

The sloppy way people present the Copenhagen interpretation as a scientific conclusion is likely what’s stalling science: it’s fundamentally built on an extraneous assumption, but everyone pretends their assumed interpretation is a conclusion.

We’re not gonna get progress until people assuming an extraneous assumption drop it and redo the last couple generations of physics to not depend on it.

“Unfathomable”? Why would you expect your uninformed amateur speculation (“intuition”) to be more plausible than the best modeling and experimental observation of generations of the world’s foremost experts?

We all have our own mental models of the world and expectations that derive from them. I don’t think that the parent is trying to say that their intuition is more plausible, only stating their surprise.

Cardinality is fundamentally integral, so if the basal layer of reality consists of discrete non-infinite configurations it should not be surprising that you see it resolve in some integral constants. Also, physical infinities have never actually been observed so you should definitely be more skeptical of that notion just on a prior basis.

Also, even if we take as given your supposition r.e. infinite types of particles, a variant of the question is just as interesting: why are only threes of them observable and why do our models seem to do a decent job of explaining reality with only threes of these infinite variants?

Would you say the same for the number of dimensions? :-)

BTW, related to your idea... IIRC, Schuster and Toro had some work using continuous spin particles (just a special representation of Lorentz algebra) with a similar motivation. Can’t recall the details right now, but feel free to check out their papers/talks.

PS: To all the uptight commenters pooh-poohing parent... relax, and lay off it... this is a legitimate research question/direction that physicists think about. We just don’t have satisfactory or appealing answers yet.

Evidence suggests that's not the case, however. Consider the neutrinos, which also are observed to come in three generations. Cosmological evidence suggests that the sum of the three masses is ~1 eV. Detector experiments suggest that the lightest neutrino must be at least 0.05 eV.

Now suppose there's a fourth generation of neutrinos. Per the weak interaction, the Z boson can decay into a neutrino/antineutrino pair through the following diagram:

  Z -> 2 v

(one of these neutrinos v would be an antiparticle). Therefore so long as the decay is kinematically permitted, ie m_Z > 2 m_v, we will eventually see the decay.

But just what is the mass of the Z? Well, experiment has its value pinned ~45 GeV -- at least 10^10 times larger than the heaviest of the three lightest neutrinos. If there is a fourth generation of quarks, then the mass the mass hierarchy must be something like*

  v_1 :  0.00000000005 GeV 
  v_2 :  0.00000000010 GeV 
  v_3 :  0.00000000100 GeV 
  v_4 : 22.50000000000 GeV

And of course, v_4 could be larger! There's nothing physically preventing a fourth generation of quarks from being so massive (at least, that we know of), but to a particle physicist that would be a highly unintuitive discovery.

* The mass splittings for the quarks is known, but not their actual values. Don't quote me on these values -- they're just for illustration!

There is common trick in designing reliable systems out of unreliable components: replicating the unreliable component 3 times. When one of the three behaves differently from the other two, it's declared faulty and replaced. This wouldn't work with 2 copies as it wouldn't be possible to say which copy is faulty. So roughly speaking, for an outsider, the HN website appears as a single entity, but under the hood it's 3 replicas. This is an analogy to a proton that consist of 3 quarks.

But not a good analogy.

Could it be that just like having extra neutrons in an atom make it more massive, but still have nearly the same reactive properties - that the particles themselves are made up of something else that can have extra "higgs" that make them more massive?

If that were the case you would expect there to be some change in how upper particles behave compared to lower ones, but as best as anyone can tell they act identical other than being heavier.

Well, identical except for weak force interactions.

The rule of three is also a decorating rule. You should always clump picture, vases, etc. in clumps of three. The reason always given is balance. Three esthetically produces the best visual balance. Maybe the universe has an esthetic sense?

Hacker News is not the correct venue to discuss mysticism, occultism, and esotericism more generally.

What I'll say on the matter is that both religious and esoteric texts place high importance on groupings like this. Certain texts may provide explanation for the generations of particles.

They are worth investigating with an independent mind, while assuming that what you're reading is incorrect.

What is an "independent mind"?

Some people view those texts as infallible sources of information. Other people view those texts not as sources of information at all but as lunacy. The reality is somewhere in the middle, but it's also a spectrum.

Science verifies information. The issue with these texts is that it's very, very hard to verify anything being said. It's much easier to provide counterexamples to disprove it.

By using the phrase "independent mind," I mean: it's worthwhile investigating these texts, but go in with a truth-seeking mentality, not a disproving mentality.

I question the universality of this rule. What makes two vases on a table less "balanced" than three? What about a single vase? Four? Five? Symmetry in physics isn't really about aesthetics.

For that matter, some people find asymmetry to be more aesthetically pleasing than symmetry.

> What makes two vases on a table less "balanced" than three?

Perhaps two points create an implied line that cuts across the table, where as three or more create a polygon that fits -within- the table with some balanced amount of space between the polygon sides and the table sides.

Alternatively (but perhaps similarly), it's the same reason why two-legged tables don't really exist.

Two-legged tables don't exist because the minimum number of points to define a plane is 3.

Three is actually the only choice for harmony.

> What makes two vases on a table less "balanced" than three?

Two leads to dialectic competition between them.

> What about a single vase?

Static world

> Four? Five?

Chaos

Indeed. In my experience of vases, which comes entirely from the BBC's "Antiques Roadshow", they famously come in pairs.

Yes, of course that number is sacred! Just ignore all the following examples: there are four bases in our DNA. Most animals have four feet. The vallancy of carbon (basis of life on earth) is four. We have four fundamental forces. The New Testament has four evangelists. Our economy runs on $, which happens to be above the number 4! Obviously, four is the universal balancing number! \s

Ah, a fellow disciple of the Time Cube I see.

omg, that brings back memories!

The universe also has 3 spatial dimensions.

In photography it's called "The Rule of Thirds".

This really depends on culture.

China/Chinese, for example, emphasises balance via symmetry. Hanzi are balances by layout into 4 grids (even practice books have a 2x2 grid for a character) - yes I am aware some characters have 1, 3 or 5 particles however these also fit within this grid.

Design of architecture is based around 2s and 4s, leading to relatively 'square' stuff (easy example, see the layout of the Forbidden City) and, sometimes, within this, the concept of non-uniformity.

I think the rule-of-three is quite culturally specific.

An entertaining introduction into the zoo of subatomic particles: http://enwp.org/Atom_%28Asimov_book%29

It's because of the 3 Fates.

j/k

More seriously, this is an interesting coincidence.

Perhaps we are on track to implementing the three seashells.

And the 3 dimensions.

Somebody voted down a joke? Seriously?

Wow. Some people must not be enjoying their quarantine as much as I am. LOL!!

In related news, the existence of biscuits and triscuits hints at a third food known as monosquits.

I read somewhere that the origin of the name 'triscuit' is because they were originally baked "with electricity" from turbines in/near Niagara Falls.

They had a picture of some period promotional material with the "baked with electricity" line, but who knows, in this era of deepfakes it easily could have been just a photoshop job done for fun amidst pandemic boredom.

Snopes [0], which is for the most part what passes for fact these days, says it's legit.

[0] https://www.snopes.com/fact-check/triscuits-electric-biscuit...

https://twitter.com/sageboggs/status/1242968530250870786 is a Twitter timeline thread of an investigation into this.

https://twitter.com/TheRealTriscuit/status/12431774024921620... is Nabisco's response through the brand account.

https://twitter.com/TheRealTriscuit currently says "elecTRIcity biSCUIT…but you can just call us Triscuit #ifykyk High voltage sign" in the bio field.

Other theories have been that the original recipe has only three ingredients, but Nabisco quashed that, and that it's named for triticum since it's a wheat snack.

Amazon is currently out of quadsquits.

Perhaps they would be known as unisquits?

Monoscuits, right? Or is it uniscuits or unoscuits?

As though a) we actually know that particle flavors come in threes and b) any human being's opinion on this is worth more than that of the schizophrenic on the corner who at least believes he is talking to God.

"Please don't post shallow dismissals, especially of other people's work. A good critical comment teaches us something."

https://news.ycombinator.com/newsguidelines.html

Yes, I think I was in a particularly bad mood when I wrote this.

But I also stand by the sentiment that a schizophrenic is in a better position than Weinberg because the schizophrenic hears God directly and so has reason for believing what he hears. Weinberg doesn't believe in God but somehow has convinced himself that his aesthetic preferences have something to do with the intrinsic nature of the universe.

Weinberg has been out of the physics game in and in the world of letters for my entire lifetime. He won a Nobel Prize (which is generally a tombstone for careers) before I was born. I don't want to say that his insights are completely worthless, but they're already conventional wisdom (so they don't add much to what we already commonly think) and he's just gotten so used to talking about the nature of the universe that he isn't trouble by the fact that he has nothing more than a hunch to back him up.

In this case, I have to be ad hominem because there's nothing but the man to discuss. He has a hunch. His hunch is worth printing because he's a Great Physicist (or whatever the original title was). To point out that the hunch is just a hunch, I have to point out that the Great Physicist is just a person and the hunch has no grounding whatsoever.

This includes much more information and so is less shallow, and therefore much a much better post than upthread. There's an interesting phenomenon where people often reply to moderation comments with a post that says what they meant in the first place.

The personal aspect is arguably still a problem. But it's also true that critiquing celebrities isn't the same thing as garden-variety personal attack, since they represent more than just themselves individually, and you make it clear that the intention isn't personal.

There's at least one revision a comment like this could go through to get better: a little more information about what the specific ideas are. For example, which insights are already conventional wisdom? Readers who are not steeped in the field could learn something from that.

three-dimensional space => three particle families ;-)

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