Daniel and Kelly’s Extraordinary Universe - What are paraparticles?

Episode Date: August 19, 2025

Daniel and Kelly talk about recent mathematical innovations that suggest a third category of particles beyond matter and forces.See omnystudio.com/listener for privacy information.

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Brought to you by Novartis, founding partner of IHeart Women's Sports Network. How does the universe work? What are the rules that govern its most microscopic nature? For a few hundred years, we've been making progress on this question, mostly by taking things apart. And when we zoom into the universe at the smallest level, it seems so far like there are two different categories of particles. Matter particles like quarks and electrons and force particles like photons and gluons.

For a long time, it seems like that has to be all. all there is? What else could there possibly be? But experiments aren't the only way to reveal the secrets of the universe. Another very fruitful path is to follow the math. When we ask what else the math allows, we sometimes get predictions for very weird phenomena like antimatter or black holes or Higgs bosons, which turn out to be real in the universe. So can the math show us another kind of particle? A weird third way beyond matter and forces? Welcome to Daniel and Kelly's extraordinary mathematical universe. Hello, I'm Kelly Wienersmith.

I study parasites and space, and I think there are four kinds of particles. Are parasites the fourth particle? I mean, if physics were any good, the answer would be. Yes. See, what I think is that y'all like symmetry, and I think if you decide there's three kinds of particles, that will be an odd number, and you'll have to decide there's another kind, so that it's even. Hi, I'm Daniel.

I'm a particle physicist, not a paraparticle physicist, or a parasitical particle physicist, or any of those other varieties, but I do love understanding the nature of the universe and finding symmetry in it all. Amazing. So are you one of those physicists who feels like that? like there needs to be symmetry in these answers, or does it just kind of depend on the topic? Wow, what a deep question to drop on me at the top of the episode. I think what we've learned so far is that there is symmetry in the universe. Like all the rules we've discovered about physics

seem to follow symmetric patterns. There's like reflections and translations, and you can generalize this into abstract algebra called group theory. So the universe seems to be well described by symmetries in mathematics. Does that mean the universe is symmetrical? or that's just the way we like to think about it? I mean, that's a deep question of philosophy. We're not going to answer it today. But I appreciate symmetry. I love it.

I love the mathematical beauty of what we've learned about the universe. Why should the universe be symmetrical instead of just a mess? Like, as an evolutionary biologist, like, it all being held together with, like, duct tape and zip ties, makes more sense to me than it being beautifully symmetrical. But why is it symmetrical? I think I have a natural preference for explanations that are simple. that are harmonious and parsimonious, right? Like, we think that the universe should be, in the end, described by one simple idea.

And so we're constantly looking for that. And symmetry helps us restrain that. It helps us reduce the number of options. You know, like, instead of having to come up with 10 numbers, what if there's a symmetry that tells you that those numbers are all related? So there really is just one number that turns into 10. But you might also ask the basic question,

like, well, why do we expect the universe to be? simple and parsimonious. And I don't have an answer for that. You know, just so far, that seemed to work. You know, looking for the simplest explanation, so far has found us things that work in the universe. They predict experiments. They describe things we haven't seen yet. So many times in the history of science, we followed the symmetry in mathematics to make discoveries, like antiparticles, or like electromagnetism, you know, Maxwell looking at these equations and seeing a lack of symmetry and penciling in the piece he needs. to make the equation symmetrical, discovering something real in the universe, or Peter Higgs

finding a piece that clicks together with all the other pieces to answer why symmetry is broken. So it seems to work is the only real answer I can give you. Interesting. You know, so I was, I'm reading this book called The Remedy right now, and it is about how, like, Koch and Pasteur determined that microorganisms caused disease. And the author was arguing that actually this kind of flew in the face of, we should look for the simplest answer because the simplest answer at the time

was that bad air causes all of these maladies. And so having one cause that explained all of this stuff seemed much simpler than, you know, tuberculosis is caused by this tiny organism and smallpox is caused by that tiny organism that we can't even see. And so the fact that bad air was simpler sort of made people cling to it a little bit longer

than this more complicated answer that tended to be right. And so I think in almost every case it makes a lot more sense to look for the simplest explanation first. but you should not let it close your eyes to the more complex answers that might actually be the reality of the situation. Yeah, you should choose the simplest answer that works that actually describes the universe.

Yes. Not the simplest answer that doesn't describe the universe. That's right. But you're right. You don't know in advance what's going to work and what isn't. And so we often start from the simplest thing because why not, right? And if that doesn't work, then we move on to something more complicated. And that's how we get chemistry and biology and all sorts of other delicious, beautiful messes.

of science that have yet to pull themselves together into a single parsimonious explanation. And that's also one reason why I am a physicist, because physics, I feel like, is closer to getting to a single answer than chemistry is, for example. I was always frustrated in chemistry with like, this rule for this thing, and this rule for that thing, and this other rule except for this other scenario. And maybe I just have a bad memory and it's hard to hold all those things in my head. But I just really like to look, here's one equation. Start from that.

You can get to anything. That just always appealed to me. That's so interesting. I think we live on very different sides of this gradient. So, like, for me, you know, you said biologists and chemists have yet to come up with a simple theory. I don't feel like that's what we're trying for at all. Maybe that's why you haven't found one. Why would you assume that there is one? Like, life is beautifully complex.

You know, the it depends is where all the fun lives, I think. You know, you're like, oh, that's frustrating. And I'm like, no, that's the exciting part. Like, what, it depends on what? Life is complicated and messy. And that's what makes it beautiful. But isn't it beautiful when you find things that are true across all of life, right? Like DNA, for example, undergirds a lot of life on Earth.

And that's really powerful to discover that and to understand it, right? Yeah. It's not as fascinating. It's like, this one kind of frog does this one kind of thing on random Tuesdays, in my opinion. Well, I will politely disagree with you. I think what the frogs are doing on Tuesdays I am deeply interested in. But yes, you know, I think it's beautiful that, you know, blueprint for life is stored in the same material, no matter what organism you're looking at.

But we all do very different things with that material. You know, bacteria do horizontal gene transfer. They're swapping genes back and forth. And, you know, we have to have sex to swap genetic material. And we've got recombination. And I don't know. Anyway, that's where the It Depends gets fun again. Well, we have made a lot of hay in physics, at least, in looking for symmetries and then

trying to understand when there are holes, is there something to fill that hole, right? The way we did with antiparticles and the way we did with all the quarks. And so often, mathematical beauty really does lead us to new discoveries. And that's what we're talking about today on the podcast, whether there is another bucket, another kind of thing out there in the universe that we can use to describe how everything works. Maybe it explains why those toads do that thing on Tuesday. At the end of all of our banters, I'm like, how are we going to get back on track? and you always get us there.

Okay. It's sometimes a bigger step than I expect. But you're good at jumping that chasm. All right. So today we're talking about paraparticles. And I had never heard of paraparticles before. And so let's see if our audience is on the same page as Kelly. So we asked, what are paraparticles?

And here are the answers we got. I wonder if it's something to do with larger things showing particles. light behavior in certain circumstances. I'm so glad there isn't an exam at the end of the podcast. Piece of a particle, like a very small part of the particle. Some sort of entity that exists alongside the traditional particles. Somewhere between a real particle and a ghost particle. Like a virtual particle in that it's enabling interactions with others.

I think it's like a super, super position. and it's one of those weird things about quantum mechanics that if you look at it, it just disappears off. They may be particles that we believe exist but have no proof for yet. Kind of like a particle, but not quite. Something that acts like a particle when certain conditions are met. It's something that's almost a particle. Paraparticles rely on their neighboring particle for existence.

I'm completely stunned by this one. The virtual particle pairs that spring to existence in a vacuum. Is a paraparticle something that lives off of or takes advantage of another particle? Is it a paralyzed particle? So lots of playing with what para means in other contexts. I like it. You all are very clever. But they missed the obvious.

Nobody went for the connection to parasites. Guys, guys, I worked so hard. So hard. Oh, wait, no, no, no, that's not true. Somebody said relying on their neighbors for existence. That's, they're parasitizing. You're right. Parasitical particles.

That's right. Way to go, that particular audience member. Thank you for paying attention all this time. I was just glad that nobody went for the sort of anti-academic grifter line. The, like, academics are just parasites on society and they're sucking money and scams and don't really believe anything they're doing, all that bad faith nonsense. You sometimes see in various. corners of the internet. Oh, wow. Are you, I feel like there's a bit of insecurity today. What? I just want to address the reality. You know, that kind of stuff is out there in the universe.

It's true. Anyway, I was very happy to hear all of these positive and constructive answers. Thanks, everybody. If you'd like to contribute your ideas for future episodes, don't be shy. Write to us to questions at daniel and kelly.org. You can hear your voice on the podcast. Amazing. All right, so let's dig in. So paraparticles. So you said in the introduction that there are maybe three kinds of particles. Can we start by reviewing the first two kinds? Because I'm sure that you've mentioned in the past that particles come in matter and force flavors. But every once in a while at the end of an episode, I'll discover my brain has reached capacity and maybe some stuff overflowed out the top. And so remind me, what are matter particles? What are force particles? And then we'll

get into this third kind. Yeah, sure, no problem. Be careful with the word flavor, though. Flavor has a particular meaning in particle physics. It means something else. And it's not like, you know, cookie dough and mint chocolate chip. It's like the difference between electrons and muons and tau's or different flavors of leptons. Like that's an actual like physics jargon term is flavors. Oh, absolutely. And there's a whole subfield of particle physics called flavor physics. And then the people who work on the flavor of particles that have a lot of mass that's called heavy flavor physics, which sounds like it should be a hip hop group. But it really is a bunch of nerds.

Well, you know, nerds can have hip-hop groups. You don't have to be so judgy. Yeah, heavy flavor-flaves. Let's hear it. Love it. All right. So today we're talking about one way to distinguish particles, and that's by their spin. So there are particles that make up matter, me and you and everything that's out there.

And everything you've ever eaten are made out of corks and leptons. So the up quark and the down quark make up protons and neutrons. You add electrons, which are kind of lepton, and you can make any atom, right? And from that, you can make any molecule and anything anybody has ever seen or thrown at their sister is made out of this kind of stuff, right? Okay. So this is what we call matter particles. And all these particles have something in common, which is their quantum spin has units of one half, which means they can have spin up one half or spin down one half. So all these particles, which we call fermions after Enrico Fermi, these are matter particles.

They're particles with one half spin. spin. Can you help me, like, visualize that? Like, are they actually spinning? Hmm. You know the answer to that question, Kelly, is nobody knows. Quantum spin is a super fascinating topic, because on one hand, it's very different from real spin, like normal spin. Like, you take a ball and you spin it. We can talk about the angular momentum. We can talk about the velocity on the surface. A classical object has spin, and it has angular momentum, right? And we know that that angular momentum is important to the universe because it's preserved. Like, if you spin a ball in space, it keeps spinning. And the reason that, like, our galaxy is spinning is because

of conservation of angular momentum. The reason the solar system has the shape that it does, it's like sort of flat the way the galaxy is a disk is because of angular momentum. Angle momentum is a really big important thing in the universe. Things really do spin. Quantum particles don't spin in the same way because electrons are not tiny little balls. And like 100 years ago, when they were thinking about this, they were like, well, what if they spin? How fast would they be spinning? They tried to calculate like how fast the surface of an electron is spinning. And you get an answer that's like higher than the speed of light. So it's obviously nonsense. Whenever you do physics and you get an answer that doesn't make sense. Like something has gone wrong along the way, right? Or you've created a

new field. In this case, the answer is that these are quantum particles. They're not classical. So you can think of them as existing physically the same way where every part of them has a location, every moment in time. So they don't physically spin. You shouldn't think about these quantum particles as like little balls that are spinning. And so you might ask, well, if it's not spinning, why do you call it spin? We call it spin because it has a lot of the same properties as classical object spin. For example, it's conserved, right? And it's conserved together with other kinds of angular momentum, meaning that what the universe cares about is the total angular momentum, including spin. So you can convert like normal angular momentum like the Earth is spinning

into quantum angular momentum spin and back and forth. The universe requires you to conserve the sum of those two, which tells you they're like the same kind of thing. The same way that like energy is often conserved, but it's the sum of kinetic and potential energies, which tells you like, okay, these are two kinds of the same thing because what the universe cares about is the some of them, not the individual ones. So we know that quantum spin is similar to real spin, classical spin, because the universe conserves the sum of those things. And quantum spin has other similar properties, like things that have quantum spin and

electric charge have little magnetic fields because charges in motion give magnetic fields. So like an electron, which is spinning, has a little magnetic field. And that's why it's like bent by magnetic fields, et cetera, et cetera. So we don't really know what it is, but we know. know that it acts a lot like spin, so we call it quantum spin, which I think is a pretty good name, even though it's not spinning. Okay. All right.

So I usually need to hear things like four times before they stick in my brain. I think we're at like two. So be prepared to repeat that. But so to try to help me, all right, so fermions, they're, these are the mass or the matter particles. Yes. And so I'm going to think of fermions as like it's firm, matter. It makes up me.

Although, you know, now you're going to misspell fermions from here on out because it's not spelled like firm. But anyway, all right, that's how I'm remembering it. And so now let's talk about force. And so I always thought force was like a field and I didn't think of it as a particle. Anyway, so let's go on. So the bosons are our force particles. Yes. And let me also elaborate on the comments you made about field versus particles.

There are two ways of thinking about what stuff is and how it's pushed. One is the field picture, which is really natural to a lot of particle physicists. There's an electron field, and the electron is actually just a ripple in that field. And there's an electromagnetic field, and photons are ripples in that field. And in that view, the fields are the fundamental thing, and particles are just ripples in those things. They're like emergent phenomena from the fields, and the fields can interact. And we talk about that picture a lot on the podcast. There's another way to think about things and say, you know, fields are just like a construct in our minds.

we never see them directly. We only see them acting on particles. And the particles are the things we can see. We see dots on the screen. We see electrons moving through wires, et cetera. So particles are the real things. And so from that point of view, we have electrons, and they're little particles, and we have quarks and they're little particles.

And then the forces, we can talk about other particles. So we have, like, the photon. What happens when two electrons repel each other? They exchange photons. So this is the particle picture of the universe. everything is made out of little particles, and it can explain matter. It's a little bit more awkward, but it can also explain forces, right? In that picture, like electrons exchange photons.

That's the way they attract or repel each other. And it's a little bit awkward because, like, how exactly do electrons and positrons attract each other by exchanging photons? It's hard to imagine you could, like, attract Zach by throwing a ball at him, right? It feels like it would only push him away. But, you know, this is the quantum world, and you can do weird things like you can throw a photon with negative momentum. So when Zach catches it, he's pulled towards you.

It's like a tractor beam photon. Yeah, biology is too complicated. It doesn't make sense. What are you guys thinking? Yeah, yeah. And this is one reason why I think the field picture is a little bit more natural. But anyway, we can talk about these forces as mediated by particles. And these particles have a property, which is that they don't have half integer spin, like

one-half or negative one-half. They have integer spin. So a photon, for example, can have spin-war. spin zero or spin negative one. And the W boson and the Z boson and the Higgs boson and the gluons, all the particles that correspond to the forces and how matter particles exchange momentum, they all have this same property that their spin is integer values. You know, no halves.

It's like plus two minus one, this kind of stuff. So those are particles we call bosons. So the fermions and the matter particles, the bosons are the force particles in this picture. All right. So now we've got through the two kinds of particles. And let's bring a little bit of pep into this conversation after the break. So we'll talk about the Pauley Exclusion Principle when we get back. echoed and reverberated throughout your life, impacting your very legacy. Hi, I'm Danny Shapiro, and these are just a few of the profound and powerful stories I'll be mining on our 12th season of Family Secrets. With over 37 million downloads, we continue to be moved and inspired by our guests and their courageously told stories.

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I ended up having amputation below the knee of my right leg and a traumatic brain injury because I landed on my head. Welcome to Season 2 of the Good Stuff. Listen to the Good Stuff podcast on the IHeart Radio app, Apple Podcast, or wherever you get your podcast. All right, so we've established that we have two kinds of particles. We've got the fermions, which are the matter particles, and the bosons, which are the force particles. Why does it matter that we divide them in this way? Why can't they all just be particles?

They are all just particles or fields equivalently. But they have very different behaviors, and that behavior is really important. Specifically, bosons can do something fermions will never, ever, ever do. Which is, bosons can be in the same quantum state, and fermions never will. So you made this joke about PEP, the Polly Exclusion Principle named after Wolfgang Polly, says that no two fermions can ever be in the same quantum state. So if you have two identical particles, like two electrons, they can't have all the same quantum description. which would be like their location, their momentum, their spin, their energy, all this kind of stuff.

They can't be identical. They have to be unique. Every fermion has to have a different quantum state. Does it make sense to think of that? So our fermions are our matter particles? Does it make sense to think of it as like two pieces of matter can't take up the same space? Or this is like a totally different thing than thinking about it that way? Two pieces of matter can take up the same space as long as they have something.

to differentiate them. So, for example, electrons have two possible spins, right? Spin up and spin down. So in the ground state of an atom, for example, you can have two electrons with exactly the same energy, the same momentum, the same location, the same energy, the same everything, but one is spin up and the other is spin down. That's why you have two electrons in the lowest state. That's where that two comes from because there are two options for spin.

You can't have two electrons both spin up and you can't have two electrons both spin down, Because of this poly exclusion principle, it says you can never have two electrons in the same state. And that's why you don't get all of the electrons in the ground state. If you already have two electrons in that ground state, it's full. It can't take anymore. There's no third spin, right? So when another electron comes along, it has to have a higher energy. It has to be the next energy level because the lowest rungs are filled and it's one electron per unique state.

So the lowest energy level has two of those. The next one, because has more energy, has more option. options for like where the electron it is around the atom, this P state, now we're getting deep into chemistry, so I'm beyond my expertise. Right away. But that's why you can have more electrons in that second one. And then more in the third level and more in the fourth because there's more options for differentiating exactly which version of that energy level you're in.

And this is why we have chemistry. This is why gold looks the way it does. This is why we have water. This is why atoms bind together. This is why our whole universe looks the way that it does because Fermions cannot be in the same state. Now, is this an observation of what's happening? Or do we understand why it has to be that way? It's still a little bit mysterious.

Like, it's definitely an observation, and we've never, ever seen it violated. And if it was violated, like, the whole universe would look different. Like, if somebody turned this rule off and said, hey, fermions, no problem. You can now share a state. All of matter would collapse. Bad news. Exactly. It would be bad news.

So I don't recommend it if you're sitting in the universe control room and you have your finger on that knob, call me, please, before you do anything. We do have some hand wavy explanations for why it is. We don't have a really full formal proof. We can't go from like, here are the fields. Here's how fermions will behave. What we can do is prove the negative. Like, we can show why fermions can't do this thing. We can show that if fermions did this thing, it would lead to some contradictions.

I'm going to try to walk you through a hand-wavy version of that proof in a minute, but we couldn't have started from scratch and really shown how this happens. And Feynman famously said that we don't have a full proof, and also it's really challenging to give an intuitive explanation for this, because, quote, we do not have a complete understanding of the fundamental principle involved. Feynman was big on this theory that, like, if you can't accept, Explain it simply, you don't really understand it, which I think is really interesting as a hypothesis, because it kind of lines up with like what we were talking about earlier. And it touches on something we were talking about, I think, on the Discord of like how on this pod we're constantly trying to explain complicated stuff in an intuitive way without all the math.

You can't just be like, here's a bunch of math. This math tells you what the answer is. We want to like tell a story that connects with the ideas in your head. So you go, oh, that makes sense. I get it. Why it's this way and not the other way. And that's very different from the mathematical explanation or concepts that we often have in academia. We teach in college and in graduate school and that most physicists have in their minds.

This is like an intuitive grasp of something you have to develop in order to explain it. And Feynman is saying that without that extra piece, this like parallel explanation that's intuitive, you don't really understand it. And I think that's fascinating. It may be correct, but it's a pretty strong statement of philosophy for a guy who was famously against philosophy. Yeah. And how do you think he would feel about the current state of things today? Although I'm going to go ahead and admit that I hate questions where they're like, what do you think Benjamin Franklin would think about blah blah? It's like, I'm not Benjamin Franklin. And if he was raised in our time, he might feel totally different about things. Yeah, Feynman is a complicated character because on one hand, super genius dude, lots of important insights, also lots of great explanations. And he did something which I think is really impressive that I've never seen before, which is he He came up with an explanation of a concept, in this case, Nother's Theorem, in one of his popular books, like, for a popular audience. And that explanation then got transformed into a full rigorous proof, which is now the go-to rigorous proof you find in, like, formal physics books. Usually things go the other way.

You, like, start with a full rigorous proof, and then you develop the intuitive explanation. But he actually came up with it for the general public, and then it turned into a rigorous proof. So that's pretty cool. Like, the guy definitely had talents in lots of different directions. he's also famously kind of a jerk and so he's sort of a problematic figure in that sense I think if finally were a lot today he probably would feel grumpy

that people had come up with stuff without him I don't know hard to say well he's in our past he's in the rearview mirror okay so we have observed that fermions don't occupy the same state we kind of understand why it would be nice to understand better

and we've observed that bosons can right we see this all the time. Like you put two photons in a box, they're very happy to sit right on top of each other to be in exactly the same state. And this lets you do things like make Bose-Einstein condensates and macroscopic objects that have quantum properties because all the photons are in the same state. And you can't do that with electrons. You put too many electrons together. They get this degeneracy pressure. They don't want to be in the same lowest state. So some of them have to be in a higher energy state. And that's where you get like pressure. That's why like white dwarves don't

collapse because the electrons inside them, if they collapsed, would have to end up being in the same lower energy state. And they resist that. They can't do it. And so, like, this has real impact in the universe and it affects how we do experiments and all sorts of stuff. And so this is definitely real. And we have some understanding of how it works. All right. So fermions are our introverts and the bosons are our extroverts. That's right. Electrons just want to be in their own house, like watching their own TV show at night by themselves, and photons are always up for a party. Okay, so now we have a pretty good understanding of fermions and bosons and what they can

and can't do. How do we get from here to para particles? All right, so to understand how para particles might fit into this picture, because it sounds like there are only two options, either you have half integer spin, you know, one half, three halves, five halves, or you have integer spin, zero, one, two, three, whatever. What's another option? How could you possibly have a third category, right? And that was the prevailing wisdom for a long, long time until very recently.

But to understand where the loophole is, we've got to dig one level deeper into understanding why fermions behave this way and why bosons behave the other way. So we're going to go through this sort of rough and imperfect proof of the poly exclusion principle to explain why fermions behave one way and bosons the other way. Daniel's got pep. All right, let's do that. All right. So imagine two particles. particle one and particle two. In typical physicist's fashion, those are very boring names for them, but okay.

Okay, let's make them exciting names. What would be exciting names for these particles? I'm feeling if we name them like Frank and Rita, it's going to be hard to keep track. Maybe one and two was a good idea. Okay, wow. Backed off your criticism pretty quickly there, didn't you? All right, you got me. All right.

So particle boring one and particle boring two. All right. Now, each of them can do one thing right now. They have two different options. They can be in state A or state B. So particle A can do two things. It can be in state A or it can be in state B. Particle 2 can also be in state A or state B.

And then we can describe the full quantum state of the pair of the particles as saying like 1A 2B. That means particle 1A is in state A and particle 2 is in state B, right? You could also have 1B and 2A, right? Am I understanding? Yes, absolutely. Cool. Exactly. And so let's do that.

Let's take our particles 1A to B and let's swap them. These are identical particles. There's nothing different about them. Every electron in the universe, for example, is the same. And so let's just swap them. So we go from 1A to B to A to A. Okay. Now the quantum field theory of fermions, the math of fermions,

because they have spin one half, when you do this, you get a minus sign. So you can't go from 1A to B just to 1B, B, 2A. you go to minus 1B2A. You get a negative sign in front of the quantum state. And this has to do with what happens when you're swapping them. And you're making a face that tells me I need to pause so you can ask a question. Okay, so we said that you can have 1A2B as one state. And you can have 1B2A as another state.

Yes. But I thought that you were saying that actually you can't have 1B2A. It has to be negative 1B2A. You can have 1B2A. Oh, okay. But if you start with 1A2B and then you swap them, you don't end up at 1B2A. What you end up with is negative 1B2A. Okay.

That's like saying, you know, take your driver's license and flip it around, right? You don't necessarily get it in exactly the same orientation depending on how you spin it, right? Some things, like a sphere, doesn't matter how you spin it, you end up with exactly the same sphere as perfect symmetry. Other things have like a handedness or an orientation, right? Or take your left hand and turn it around. It doesn't look exactly like your right hand, right? Maybe it looks like a mirror image of your right hand. It's like negative of your right hand.

So this is the part where we're being like a little bit fuzzy and sloppy. But fermions, because there's spin one half, when you swap them, you get a negative sign in the quantum state. Okay, so that only happens with fermions, not with bosons. Only with fermions, not with bosons. And that's what makes this impossible. That's where we have a contradiction, right? Because say you have these two particles in the same state. Say you started with 1A, 2A, right?

Both particles in the same state. You can't do that? Okay. Oh, no, you can with bosons. You can with bosons. Well, let's say we have fermions, and we try to do that. Let's try to do that and see what happens. Okay, so we have 1A2A.

We're like, we put two fermions in the same place, in the same state. Okay, well, now let's swap them. Well, what happens? Quantum Field theory says we get negative. 1A, 2A. Okay. Right? Because when we swap fermions, we get a negative sign.

But these are supposed to be indistinguishable particles. So if you swap them, you shouldn't get any change because there's no real difference. You're swapping 1A2A. You have to get 1A2A. But quantum field theory says, no, you have to get negative 1A2A. So we have two different rules, one that says, if you have particles in the same state and they're indistinguishable and you swap them, nothing happens. And the other rule from field theory that says if they're fermions and you

swap them, you get a negative sign. Boom, that's a contradiction. So that tells us you just can't do this. You can't have fermions in the same state because then if you swap them, you'd get a contradiction. Quantum field theory says you're supposed to get a negative sign. Common sense says you can't get a negative sign if you swap things that aren't different. Okay, so the poly exclusion principle is a result of what happens with quantum field theory. Yes, exactly. And you might think, well, what's this negative sign? What is going on there? Remember that this negative sign is part of the quantum state, it's not something we observe, right? A negative sign in a quantum state is not observable, because every observable you make is only sensitive to the quantum state

squared. Remember, quantum states can also be like complex numbers. You can have like a way function that has like four plus two I in it, and you can't observe those things, but when you square it, the imaginary part goes away. So we can't observe this. It's like a hidden internal part of the quantum state. We can't observe. And yet the math is there and it's real and it tells us, that fermions cannot do this thing because it leads to an inherent contradiction. Now, spin one particles, bosons are different. Their rules when you swap them are different. If you swap 1A2B, and now you're talking about bosons, you don't get the negative sign.

You just get 1B2A. Everybody's happy. So if you started with 1A2A and you swap them, quantum field theory says you get 1A2A. Common sense says you get 1A2A. No contradiction. Everybody's cool. It's that negative sign that unobsurable. negative sign in the quantum state that appears for fermions when you swap them that causes them

to never be allowed to be in the same quantum state if they're indistinguishable fermions. Okay. So just to make sure that I'm understanding. So like negative one and one, they cancel each other out when you add them together. Or when you square them, you get the same answer. Okay. And so I should be keeping that in my head. This isn't like we arbitrarily identified that some state is negative one and you could have called the states A, B, and C. Like there is actually something about negative one and one that is different in an important mathematical way. Exactly. And the important thing here is fermions have a different kind of spin, and that changes what happens when you swap them. It introduces this negative sign.

And if you're curious about why that is exactly, this is the bit that's famously impossible to explain with intuition. We have math for it. It's called the spin statistics theorem. And even Richard Bindman couldn't come up with an intuitive explanation for it. So I hope you're going to excuse me for not having one either. But if you take us out of word for that, the fermions, when you swap them, you get a negative sign that's not observable, but it does prevent them from ever being in the same quantum state that you can go from there to understand why the Fermi exclusion principle happens. And it's going to lead us to think about the third way that paraparticles might behave. And if you are excited about that, then stick with us because we're going to get to it after the break. Your entire identity has been fabricated. Your beloved brother goes missing without a trace.

You discover the depths of your mother's illness the way it has echoed and reverberated throughout your life, impacting your very legacy. Hi, I'm Danny Shapiro. And these are just a few of the profound and powerful stories I'll be mining on our 12th season of the first. Family Secrets. With over 37 million downloads, we continue to be moved and inspired by our guests and their courageously told stories. I can't wait to share 10 powerful new episodes

with you, stories of tangled up identities, concealed truths, and the way in which family secrets almost always need to be told. I hope you'll join me and my extraordinary guests for this new season of Family Secrets. Listen to Family Secrets, Season 12. on the IHeartRadio app, Apple Podcasts, or wherever you get your podcasts. I had this, like, overwhelming sensation that I had to call it right then. And I just hit call. I said, you know, hey, I'm Jacob Schick. I'm the CEO of One Tribe Foundation, and I just wanted to call on and let her know.

There's a lot of people battling some of the very same things you're battling. And there is help out there. The Good Stuff Podcast Season 2 takes a deep look into One Tribe Foundation, a nonprofit fighting suicide in the veteran community. September is National Suicide Prevention Month, so join host Jacob and Ashley Schick as they bring you to the front lines of One Tribe's mission. I was married to a combat army veteran, and he actually took his own life to suicide. One Tribe saved my life twice. There's a lot of love that flows through this place, and it's sincere.

Now it's a personal mission. Don't want to have to go to any more funerals, you know. I got blown up on a React mission. I ended up having amputation below the knee of my right leg and a traumatic brain injury because I landed on my head. Welcome to Season 2 of the Good Stuff. Listen to the Good Stuff podcast on the Iheart Radio app, Apple Podcasts, or wherever you get your podcasts. A foot washed up a shoe with some bones in it. They had no idea who it was.

Most everything was burned up pretty good from the fire that not a whole lot was salvageable. These are the coldest of cold cases, but everything is about to change. Every case that is a cold case that has DNA. Right now in a backlog will be identified in our life. lifetime. A small lab in Texas is cracking the code on DNA. Using new scientific tools, they're finding clues in evidence so tiny you might just miss it. He never thought he was going to get caught, and I just looked at my computer screen. I was just like, ah, gotcha. On America's Crime Lab, we'll learn about victims and survivors, and you'll meet the team behind the scenes

at Othrum, the Houston Lab that takes on the most hopeless cases, to finally solve the unsolvable. Listen to America's Crime Lab on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Hey, sis, what if I could promise you you never had to listen to a condescending finance, bro, tell you how to manage your money again. Welcome to Brown Ambition. This is the hard part when you pay down those credit cards. If you haven't gotten to the bottom of why you were racking up credit or turning to credit cards, you may just recreate the same problem a year from now. When you do feel like you are bleeding from these high interest or. I would start shopping for a debt consolidation loan, starting with your local credit union,

shopping around online, looking for some online lenders because they tend to have fewer fees and be more affordable. Listen, I am not here to judge. It is so expensive in these streets. I 100% can see how in just a few months you can have this much credit card debt when it weighs on you. It's really easy to just like stick your head in the sand. It's nice and dark in the sand. Even if it's scary, it's not going to go away just because you're avoiding it. And in fact, it may it even worse. For more judgment-free money advice, listen to Brown Ambition on the Iheart radio app, Apple Podcasts, or wherever you get your podcast. Okay, so we teased you before the commercial break that we're going to explain to you how

periparticles behave. Your weight is over. Daniel, tell us about paraparticles and how they behave. So for a long time, decades and decades, people thought that fermions and bosons were the only options. Not only because, hey, look, spin one-half and integer spin seem like the only choices, because like spin one-third or spin-two-thirds is impossible, but also in terms of the explanation we just gave, it feels like there are two options. Either you add a negative sign when you swap them, like fermions, which means you can't be in the same quantum state, or you don't, like bosons, which means you can be in the same quantum state. So it's seems like there's no crack there. Seems like there's no room for another direction. And in the

1970s, somebody went through a bunch of math to prove that there is no third option under certain conditions. So like if you live in a universe where space has three dimensions, then there is no other option. You have fermions and you have bosons and that's it zip and period. So people sort of put this away for a long time. They were like, yeah, well, that's done. Somebody proved it. Dot, dot, dot. Nobody should ever spend time thinking about it again. And that's like a famous. misplaced to make a big discovery, because I'm sure this happens in biology also. You have a paper which makes a big advance, and then it gets sort of summarized in a short-handed sort of way that ignores some of the assumptions that went into it. And the conclusions just sort of get

broadened a little bit. And then people treat the lore as if it was real and complete. And people rarely go back and read the original paper to discover, ooh, actually, there are caveats here. So there are loopholes. And people who do and discover those loopholes and then explore them can, like, crack open a whole new area of physics sometimes. That's why it is so critical to read and to read the original papers. And for those of you wondering what that sound is in the background, that's a big rainstorm in Virginia right now. I love rain. Is that, was that a dig on Virginia? Why do you assume that's a dig? That's definitely not a dig. Because I know you. This week, I'm in Aspen for the Aspen Center for Physics. And it,

It rains every afternoon, and I love it. The smell of it in the mountains is just wonderful. The thing I do love about mountain rain is that it ends also quickly. Yeah. Well, our rainstorms don't last very long, and I am, the reason you can hear it is because I converted the tack room in the barn, the horse barn that we have on our property into my office, and so there's a metal roof above me, and so the metal roof really sort of makes the sound of rain much louder, which I love when I'm sleeping up here at night, everyone so

while I have sleepovers up here with my daughter on Friday nights. But anyway, sorry about the background noise, everyone. No problem. And we now have enough background to understand para-particles because very recently, two physicists at Rice University, which we both know and love, found some loopholes in this 1970s no-go theorem, the one that famously said,

it's impossible to have anything but a fermion and a boson. And the loophole is, what if you give these particles some other kind of properties? things that like a minus sign are not observable directly and disappear when you square it. So like a minus sign is a great example because if you square it, you get plus one. If you didn't have a minus sign, you can't tell. Plus one squared and minus one squared have the same answer. But they came up with another thing you can add to this particle, like another category, another part of the description.

Not a minus sign, but like a new dimension to this quantum field, a new attribute, new label you can give it. And this kind of thing, also when you square it, it goes away. So there's some technical details here, but the sort of way to understand it intuitively is that these internal states depend on the observer a little bit. So like you and I might see this electron differently because we're different observers and we might make different observations. So there's a little bit of like relativity there. So if you add this to some particle states in a weird mathematical way,

you can create a new kind of behavior. So it sort of like fuzzes up a little bit, this notion of indistinguishable particles. Are the particles indistinguishable or not? So you might be wondering, well, we have electrons and we have photons. Are there things out there in the universe that follow this new weird quantum math?

The answer is we don't know, not yet at least. What they've done is show that there is another mathematical description of fields and particles that you can construct that has like a third kind of behavior. It's not a fermion and it's not a boson, but it is self-consistent and mathematical. Nobody's built one, but they've just sort of like mathematically shown that as far as we know, the rules of the universe don't disallow this.

So I don't want to ever question the amazing research that comes out of Rice University, but it sounds like, okay, so they're like, well, there's this one thing we can't see and can't measure. And so let's add another thing we can't see or we can't measure. It's just like, like, biologists can't be like, well, what if the viruses were wearing hats? Maybe we should look for what's a good combination of hat and viruses? You're right. This is like taking the quantum particles and saying, hey, we've only been thinking about them wearing cowboy hats. What if they wear other kinds of hats?

What if choice of hats is another, like, degree of freedom for describing these particles? And it turns out if you do that, it cracks. this open a little bit, and it lets you have another category. And so that's interesting mathematically. It's only interesting physically if it describes the universe, if the universe does this in the same way that, like, you know, Dirac looked at the solutions to the Schrodinger equation, and he was like, oh, this is interesting. This allows you to have electrons, but it also allows you to have positively charged particles. That doesn't mean the universe does it, right? It could have just been like a mathematical oddity, like, oh, the math allows this, but does the universe choose it? And

turns out, yes, the universe does choose to make antiparticles, and the universe, in many other cases, chooses to explore all the avenues of symmetries. We don't know if it does in this case. What we've shown is that the mathematics of our description of the universe do allow for a third category of particles, para-particles, but we don't know if they do ever exist in the universe. And if they do, we don't think they would be fundamental particles the way that like photons electrons are, because there aren't no fundamental particles we know of that fall into this category. You'd have to make like quasi-particles, the way you make like anions or plasmons or phonons. These are things that follow the math of particles, but are waves

not in a fundamental field like the electromagnetic field or the electron field, but a wave in something else, like a wave in air or a wave in water, or a wave in electron gas in some weird meta-material that solid-state physicists cook up in their dark little labs. And so it might be something that people can create in the lab someday in the future and show, oh, look, we've created this new quasi-particle that has a different kind of mathematical behavior than fermions or bosons. So that would be cool, and something nobody had seen before, doesn't mean we can make hoverboards or we can make wormholes or anything like that yet. But you never know with fundamental physics, like, what's this going to lead to? It's very deep. It's very much at the foundation

of quantum field theory and our understanding of, like, the mathematics of it. So it's exciting when anybody makes any progress in that area. And it's a great example to push back on the nonsense you might hear online that, like, physics hasn't made any progress since the 1970s. Like, dude, we're making progress all the time. And here's a great example. So are people currently working on experiments to try to find these particles? Yeah, more create than find. People are trying to engineer weird exotic materials that might have these behaviors. And this is the kind of stuff solid state physicists love to do. You know, they're like, what if we made super thin layers of graphene and then super thin layers of this? And could we force the electrons to act as if

they're in a 2D universe or can we see superconductivity or whatever? So they're very clever at engineering materials to make quantum states behave in new ways. And that's the most promising way we might see something that's a periparticle, it would be an emergent phenomenon, a quasi-particle that comes out of the behavior of these weird exotic systems. And not exotic and like impossible or wrong in any way, just like not something we find in nature usually. But that's the cool thing about being humans. We're like constantly pushing the boundaries and saying, hey, can the universe do this? What happens if we do that? And it teaches us things about the universe. This is how we learn where the boundaries are by pushing them, right?

Yeah. Yeah. So when we have a guest on our show, you usually end the interview by asking them if an alien were to visit our planet from an advanced civilization and you asked them if their thing exists on their home planet. That's your way of testing how confident they are that the thing actually exists. So, Daniel, if aliens from an advanced civilization landed on Earth, do you think they would know about periparticles and would think that periparticles existed? This is a great question and a fair one since I just wrote a whole book. on how aliens might think about the universe. Y'all should check it out.

It's coming out in November. It's called Do Aliens Speak Physics? I'm really excited about it. Two thumbs way up. My personal suspicion is that particle physicists are too up in their own heads, and they think that the whole universe uses their mathematical description of how things work, and that's just, like, too self-centered to put ourselves at the heart of the understanding of the universe, and likely there's a bunch of arbitrary sense.

assumptions we've made, and probably aliens have a completely different description of how the universe works. And they're like, what? Why are you even using quantum fields that makes no sense? Here's a much simpler way. But if they are using quantum fields, then I think this is an inevitable discovery they would make. And they might have even found other ways. Like there might be four, 17, or 92 different kinds of particles. And they're like, what? Y'all have only found three. Come back to us. You can join the cosmic society when you're up to 10. When you found para, para, para, para particles, then talk to us. Exactly.

Yeah, and maybe they'll listen to this podcast. Oh, oh, particles and parasites. Maybe these guys were on the right track. Oh, my gosh. Yeah, and at least they'll think that we're interesting. Aliens, if you are listening, please don't zap us from outer space. Come talk to us. Tell us about your secrets and tell us about your parasites, but keep them to yourselves.

All right. Thanks, everyone for going on this journey with us into the heart of particle physics, how it works, what we know, what we don't know, and the hints that mathematics is giving us about what we might learn about the fundamental nature of space and time and matter and energy and aliens. See you all next time. Daniel and Kelly's Extraordinary Universe is produced by IHeart Radio. We would love to hear from you.

We really would. We want to know what questions you have about this extraordinary universe. We want to know your thoughts on recent shows, suggestions for future shows. If you contact us, we will get back to you. We really mean it. We answer every message. Email us at Questions at Danielandkelly.org. Or you can find us on social media.

We have accounts on X, Instagram, Blue Sky, and on all of those platforms, you can find us at D and K Universe. Don't be shy. Write to us. Hi, it's HoneyGerman, and I'm back with season two of my podcast. Thank you. We got you when it comes to the latest in music and entertainment with interviews with some of your favorite Latin artists and celebrities. You didn't have to audition? No, I didn't audition.

I haven't auditioned in like over 25 years. Oh, wow. That's a real G-talk right there. Oh, yeah. We'll talk about all that's viral and trending with a little bit of cheesement and a whole lot of laughs. And of course, the great bevras you've come to expect. Listen to the new season of Dacias Come Again on the IHeart Radio app, Apple Podcast, or wherever you get your. podcast. Every case that is a cold case that has DNA right now in a backlog will be identified

in our lifetime. On the new podcast, America's Crime Lab, every case has a story to tell, and the DNA holds the truth. He never thought he was going to get caught, and I just looked at my computer screen. I was just like, ah, gotcha. This technology's already solving so many cases. Listen to America's crime lab on the iHeart radio app, Apple Podcasts, or wherever you get your podcasts. I'm Dr. Scott Barry Kaufman, host of the psychology podcast. Here's a clip from an upcoming conversation about how to be a better you. When you think about emotion regulation, you're not going to choose an adaptive strategy which is more effortful to use unless you think there's a good outcome. Avoidance is easier. Ignoring is easier. Denials easier. Complex problem

solving takes effort listen to the psychology podcast on the iHeart radio app apple podcasts or wherever you get your podcasts get fired up y'all season two of good game with sarah spain is underway we just welcomed one of my favorite people an incomparable soccer icon megan ripino to the show and we had a blast take a listen sue and i were like riding the lime bikes the other day and we're like we're like people ride bikes because it's fun we got more incredible guests like Megan in store, plus news of the day and more. So make sure you listen to Good Game with Sarah Spain on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Brought to you by Novartis, founding partner of IHeart Women's Sports Network. This is an

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