Why do some particles die?

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Speaker 1: Or Hey, just starting a new decade? Make you feel young or old? What? It's a new decade. It's gonna be very soon when this podcast comes out, it will well, you know, it makes me feel a little bit of both. I guess I feel you old? You old? Is that a quantum superposition of young and old kids? It's both in neither. Well, here's something that might make you feel kind of young. Oh, this is this invent the Fountain of Youth. Still running a grand application for that project. But I know it's more a sense of perspective. All right, well, what is it? I'll take it. Well, did you know that the particles in your body are more than thirteen billion years old? Compared to that, you're like a baby. Wait, you're telling me that I'm a billion years old and that's supposed to make me feel young. Maybe it just means you need a n APP. Sounds good, calculatory. Hi. I'm Jorge. I'm a cartoonists and the creator of PhD Comics. Hi I'm Daniel. I'm a particle physicist and I've seen many many particles pass away. Welcome to a new decade of our podcast. Daniel and Jorge explain the Universe, a production of I Heart Radio, in which we venture forth into a whole new decade and try to understand the universe, a decade perhaps in which we will reveal new secrets about the universe that nobody in human history has ever understood. That's right. We like to talk about the planets and the stars and the cosmos, but also the little tiny things in the universe, the particles that we're all made out of and that are all around us all the time. I'm glad that you said we like to talk about a particle. Sometimes I think it's just me. Well, I'm using the Royal We, the Physicist podcast Arial We. But yeah, well, I do like to talk about particles because I feel like, in the end, we're all made of particles, and if we want to understand the universe, we got to start at the beginning, the smallest, the littlest nuggets. And if we understand the way the universe works at these smallest scales, then we have a chance to maybe understand the way things work at larger scales. Yeah, you know, I think that as human as we tend to kind of forget that fact. You know, we're made out of tiny, little molecules and atoms and tiny little particles. We I think we love to think of ourselves as as these sort of ethereal thinking beings, but really we're just like a giant lego set of particles, right, Yeah, And ever since I learned about quantum mechanics and the frothing vacuum and how particles are popping in out of existence at all times, it gives a different sense for what you are. You are a collection of particles, but that set of particles is changing, so you're more like a storm, like a cloud. You're like an excitation of the space in which you were living. He gives a different sense for what it means to be you. And that's why I want to understand the universe from the smallest scale, because it tells us what it's like to be us, what it means to be a thing. Well, I am definitely hopefully a thing, and I'm definitely in a state of excitation. And I have to say that I did get a fronting vacuum for Christmas, so I'm glad you. Does that mean that it makes phone for your coffee while it cleans the kitchen? Yeah, it's it's it's a multitasker's dream. I'll have the cappuccino vacuum please. Yeah. So, so today we'll be talking about the things that everyone is made out of. You, me, this, this um microphone that I'm speaking to, those speakers that are broadcasting our voices. Everything is made out of particles. And some people might be surprised, maybe or maybe not, that particles don't last forever. That's right, particles are not forever as far as we know. But there are kind of two different kinds of particles. There's the particles that make up me and you, and as we've talked about in the podcast, those are mostly three different particles up quarks, down quirks, and electrons. But then we talk about all these other particles higgs bosons, top quarks, w bosons, and those particles aren't around. You don't like find a pile of them under rock somewhere, and that's because they don't last very long. They flash into existence and then they die very quickly. Hey, can I choose what kind of quarks I'm made out of? Like? Can I be up corks all the time. I don't know what kind of special powers you have as a cartoonist, but if you're made of protons and neutrons, and there's not a whole lot of flexibility, so some of them disappear and some of them are born all the time. Um, And so to be on the podcast will be sort of tackling that crazy phenomenon of what makes particles come into and out of existence. Why is it that some particles were born in the Big Bang and are still around, whereas other particles only get to lie tend to the minus twenty three seconds in our universe. So to be on the podcast, we'll be talking about why do particles die? It make it sound so sad, you know, Oh, I see? Why do particles move on? We talk about why particles are born and what they've accomplished in their brief, beautiful lives. You know, why do particles go to Grandpa's farm where they're running happily and jumping over streams streams of particles? They go to the particle reserve where they're well taken care of. And here's another example of where we're sort of anthropomorphizing particles. Right, Particles definitely don't have feelings and emotions and families and Thanksgiving dinners, but we talk about them as if they are born and as if they die, and I think it just helps us connect to them, it helps us think about them. So some particles decay and others don't. So some particles die and some of them live forever? Is that true? Can some particles live from the beginning of time till the end of time? We can never say for sure. All we can say is what we've seen and were in. Some particles, like electrons, we have never seen them decay, so we can estimate how long the lifetime of an electron is based on never having seen any of them decay and having looked at a lot of them, And the current estimate is like seventeen ga jillion years. Now it might be is that is that? The is? What that in a paper? Actually I rounded up at six point nine gajillion years. But the point is we make some statistical statement and say it must be longer than this very very big number, much longer than the age of the universe, or we would have seen when decay. But we can never be sure. And it's the same with a proton. They're pretty stable. Like if you put an electron in a jar, it's just gonna sit there. It's never gonna turn into anything. It's never going to I guess collide with something and turn into something else. Is that possible? Oh, it certainly could actually could get absorbed and then disappeared. But an electron in isolation could you to sit there forever, the same way a photon can fly across the universe for billions of years and still be a photon. But other particles, you know, you put a neutron in a jar or a top cork in a jar, and it will spontaneously decay, will turn into other stuff. Some of the particles that I am made out of might be zillions of years old, and some of them could be, you know, three years old. Yeah, Unfortunately, most of them are billions of years old. If you were looking to feel young, that's not the way to do it. I'd like to focus on the young part of me, Daniel, I'm young inside. Yeah. And so in particle physics, the technical term we use is that some particles are stable. We think they just hang out forever, they don't do anything, and other particles are unstable because they decay into other particles. And so this is kind of an interesting word, decay and particle using them for particles, and so we were wondering, as usual, how many people out there associate the two works together and know about this process that all particles go through or don't go through. Yeah. So I walked around campus a UC Irvine and I asked people if they knew that heavier particles can decay into lighter particles and why it happens. So think about it for a second. How much do you know about particle decay? And what would you be able to answer if Daniel appros you on the street one day. Here's what people had to say. Do you know that particles decay? No? I didn't. Yes. Do you know why that happens? No? Yes? Do you know why that happens? I'm gonna say energy emissions? Yes? Do you know why that happens? A great active decay? You know what is it? I just know that if as too many neutrons and it's center, it's like unstable, so they can't I'll stay they shut off. No, I did not know that. I don't know because like there's some kind of potentials high for them. I'm actually not sure. Do you know why that happens? Uh? No, but I do know, like the half life of particles, and so all right, a couple of yes and no answers. None of the answers changed, none of the answers decayed. They're all stable in their ignorance of this question. You know, some people said yes, and are you saying they maybe they said yes, but they didn't really know. Some people said yes, they know that it does happen, but they weren't really clear on why. And when I pressed them, they just sort of described the process that happens, you know, like they have short lifetimes. That's like asking, you know, why does something I have a short lifetime? Because it has a short lifetime. There isn't really there wasn't really much understanding for why it happens, Like why can these heavy particles not just stick around forever? I see? Well, some people said radioactive decay, But that's that's a little bit different, right, that's when a whole atom sort of breaks down, not a particular particle. Yeah, it's a little bit different, but it's actually the same thing because what's going on inside radioactive decay is just a particle decay. It has an impact on the rest of the Atomate changes the automate changes a neutron into a proton and that changes what the atom is. But radioactive decay is actually just an example of one of the particles inside the atom decay. Oh wow, so it's like a Russian doll. Yeah, precisely. Well that's what reality is. It's like Russian dolls, right, you get these layers and layers of reality. Yeah, it all leads back to Russia. We were going to try to avoid politics on the show, but it's the new in the New decade. We're not doing politics, all right, So pretty good answers. And I have to admit I don't know why particle decay. I know that they decay, and they sometimes spontaneously trying to do other things, but I also don't know why some of them don't decay. That's kind of puzzling to me. So let's get into a Daniel. Well, let's maybe define for people first, what is particle decay. Yeah, decay is a funny word because it implies like you've died and your bits are sort of falling apart and blowing away in the winds really dramatically, right, But really, by decay, we just mean that a particle turns into other particles like it's it was kind of particle and then an instant later it's like it's broke apart. Did break apart or does it transform? Yeah, that's exactly it. It doesn't break apart. It transforms like when a higgs boson turns into a pair of bottom corks, which it likes to do. It's not like it was made out of a pair of bottom quarks and it broke up into those. This is not like you're taking a molecule of water and splitting it into the hydrogen and the oxygen that you can do. But when particles decay, they transform from one kind of matter to another. It's really it's alchemy. So the higgs boson was not made of bottom quarks. It transformed from higgs boson into a pair of bottom corks. It's kind of like when the Beatles broke up. It's not that they it's almost up. Good, I'm glad, I'm right, Okay. So it's not like a case like it breaks down, but it's more like, um, it just decide it to be something else totally. Yeah. And it's not like it's making a decision, right, It's like it's alive and his moods and it's like today I'm not feeling it. I just want to be be corks today. How do you know, Daniel, how do you know his bosons? I've interviewed them. They're not very insightful. You talk to them to find out that they don't talk. Is that what you're saying. I try to interview them. You know, their agent never calls me back, so you know they're super important or they have nothing to say. And we see the same process happened for lots of other particles and not to the Higgs boson. Right, Really, the neutron decays into a proton, and when it does so, it kicks out an electron and some neutrino um. The top cork decays into a W and a B corks. This kind of stuff happens all the time. Like, what do you mean It kicks out like it transformed into one thing and another thing, but one of the things flies away. Yeah, a particle can turns. We'll get into this a little bit later. There are a lot of rules for how particles decay, but one of the most important one is that a particle cannot decay into one other single particle. It can only decay into multiple particles. So when a neutron decase, It decays into a proton and an electron and an anti neutrino. And this is what we called beta decay. This is actually what happens inside the nucleus when an atom radioactively decays, is that one of the neutrons is turned into a proton. And this is all kind of that quantum mechanical magic. Don't say magic, not magic, quantum mechanical wizardry. Science. Man's you used to word alchemy? How is that any different? Alchemy is science. For a long time people thought it was nonsense, impossible, but then it turns out it's actually possible. We do it all the time, so it's been brought back into science. Well maybe he'll disabill happen for a wizardry. Okay, alright, alright, I'll compromise. We'll call it quantum witching about that in one way? Is that a compromise? I don't quite understand, But all right, it's quantum something. Yes, yeah, yeah, yeah, I guess what it's. What I mean is that it's not like things are like you said. They don't break apart into into the parts that they're made out of. They literally sort of like become a ball of for more deal energy, and then that energy transforms into other things. Yeah, precisely, you're converting one kind of matter into another kind of matter. And that seems really strange, right, like where did it go? But remember all of these things are particles, and particles are just excited states of the quantum fields. Space is filled with these fields, and sometimes they ripple, and those ripples are particles. So we're really talking about is moving energy from one quantum field, like the Higgs field, into another quantum field, like the field for bottom corks. It's like the excitation passes from one field to the other. Yeah, exactly, just like a wave can move from one kind of fluid into another kind of fluid. Or when you strum a guitar string, you're changing the shaking of the guitar string into the shaking of the air. Interesting, and so we go back to the Beatles because it's it is sort of like the loneliest guitar. All right, Yeah, go you win. You're right, it's just like the Beatles. But that's kind of what we call particle decay or particle death. I guess that. I mean, that's what we mean when when we asked the question why do some particles die because basically the elect the first particle that was there basically stops existing, stops existing, and something else exists. Yeah, and it's and it's bits are no longer there. We don't know if the Higgs boson is made of smaller bits right now we think of it. It's just fundamental. But whatever it is is no longer around. It's not just getting taken apart and rearranged like Jigsaw puscles into something else, like Lego pieces into something else. It's really getting transformed. And that's what we mean. You mean the Higgs is not made out of little Higgy's um. I think the Lego company has a copyrun on that name, so we should avoid using it, all right, So that and so it really dies, right, it's like it's no longer in the universe. Yeah, it's gone. And so we make particles like this in collisions all the time. We collide protons together, we make some heavy particle z W a top cork, Higgs boson, something else, and they live for like ten to the minus twenty three seconds before they turn into something else. And you know, that's what makes it so hard to study these particles that they're not around for very long, so it's hard to talk to them. Wow. Well, it seems like some particles are alive quote unquote for ten to the minus twenty three seconds, and some of them are live for seven bizillion years. It seems unfair, doesn't it. All right, so let's get into why that is and what causes a particle to decay or not. But first let's take a quick break, all right, Daniel, So why does it happen? Why the particles have to die? The key thing to understand is that there's a difference in the mass of these particles. So higher mass particles like the Higgs, like the top they decay into lower mass particles. And this makes simple sense because of conservation of energy. If you have a high mass particle just at rest all of its energies in its mass. If it turns into other particles, those particles have to have lower mass, otherwise you'd be violating conservation of energy. Oh, I see, And it's a it's a spontaneous event, right, Like nothing triggers it. It's not like it bumped into something and it broke up, or you shot you shot a particle at it and then that caused the transformation. It's like it was just sitting there and because it had too much, too much mass, it just suddenly breaks up. Yeah, it's spontaneous. It doesn't need to be triggered from anything from the outside. And it's also random. So if you have like a hundred Higgs bosons and you have them all in an array somewhere and you watch them, some of them would decay very quickly and some of them would live a little bit longer, and it's a distribution there. So we can predict the probability of the Higgs boson decaying after a certain time. You can't predict it for an individual one because it's quantum mechanical. But we know, like what the average lifespan is a Eiggs boson, where the average lifespan is of a top cork, and it's totally random, Like what what I guess? What triggers a death the death of a particle. That's the deepest question in quantum mechanics, right. We know that physics predicts the probability of things happening at various times, but we don't know how the universe makes a decision about what's going to happen when you know in which Shortinger's boxes the cat alive or dead. This is exactly that question, because the way the Shortinger's box works, if you have an atom inside the box that can decay or not decay, and it has a certain lifespan, and if it's already decayed, that's killed the cat. And if it hasn't decated, hasn't killed the cat. And what makes a decision for an individual box We don't know. The universe has some mysteriously not magical um which he dies somewhere that makes those decisions. I see, it's not magic, it's just mysterious. It is mysterious. Now. It's one of my deepest questions about the universe is how it picks random numbers. Where is the universe's random numbers generator? How's that work? Um and and way. That's a deep fascinating question. But the key thing to understand is that higher mass particles decay into lower mass particles. Right that that you're saying, that's like the Golden rule of particle decay. Yeah, there is actually something called the Golden rule, and it helps you sort of do that do onto other particles. As other particles we do onto you. Yeah, I don't know how particles behave and if they're nice to each other or not, but firm me. The golden rule helps you understand sort of why lower mass particles are more likely to exist in the universe than higher mass Like, why don't higher energy, lower mass particles turn into high mass particles all the time. Why does it mostly go the other way? Why do things sort of move down the mass ladder? Well, to to make something heavier rooting, you need to collide with something else and then from that you can like join together. Yeah, and that's exactly what we do in particle collisions. We make these heavy particles very briefly by smashing lower mass particles with a lot of energy together, So we have enough energy to create these high mass particles. But then you might wonder, like, why don't they just stick around? Why don't high mass particles just sit there being high mass particles forever? Right? And is that also a rule? I mean, so, the one rule is that you can only decay do things that are less massive than you, so kind of basically smaller, lighter things. That's one rule. The other rule seems to be that maybe the like the more mass you have, the more the quicker you are you're going to decay. Is there a correlation also in like if you have more mass, the less life you have. Yes, that's certainly true. The more mass you have, the more likely you are to decay quickly. Also, the more ways you have to decay, the more ways you're allowed to decay, the more rapidly you're going to decay. So if you have a really heavy particle but it can only decay via like the weak force, then it's gonna be around for longer because the weak force doesn't act for often. It's very weak. Where if you can decay via the strong force hydronically, then you can decay very very quickly because the strong force is very powerful. Oh so it's kind of like if it has a lot of options, then it's going to take one of those options sooner or later precisely. And the way I like to think about it is that these particles sort of like to relax. They start out in these very high mass states, and you think of it like having a lot of tension, and it wants to relax down to the lower mass the way it's sort of water likes to flow downhill, right, and everything in the universe likes to spread out and cool down and and sort of smooth out, and being in lower mass states is more smooth, has less energy sort of concentrated in one place. So maybe we should rename this episode why the particles like to relax? Why are particles so smooth? All right? So what you're saying, um, this death of this decay, this transformation is really just like the universe kind of reverting or going towards the lowest possible energy state. Yeah, imagine what happens, for example, when you strum a guitar string, right, let's go back to that. You have a lot of energy stored in the guitar string. But then that guitar string interacts with other stuff, right, It can bump into air molecules and give it some of its energy, and then the sound spreads out through the air and you enjoy the music of the Beatles. This is just energy dissipating, right. Why it is energy dissipated. It dissipates because of entropy, because things like to spread out, things like they get more smooth, and so in the same way, you can think of a particle sort of like as the strumming of a quantum field, it's like a field that's oscillating, and if that field can talk to other fields, like the Higgs field can talk to the bottom core field, that it has a way to sort of spread out into those other fields. It's like it's louder and so it it can reach other fields better. Yeah, Or it's like, you know, it's in a box and there are more holes in the box, so it can spread out. If there are lots of really big holes in the box, that it can get out, whereas if you put it in a box and there's almost no holes and it's gonna take a long time for that energy to leak out. And so the lower the mass, then the more stable you are. Precisely, and if there's no particle with or mass than you, than your stable because you can't spread out anymore. So the particles at the bottom of the rungs that have no particles below them, then they can't decay to anything else and so they are stuck. And that's the situation with the electron, because there's nothing with a less mass then you or or do you have to do also with the rules of particles, like an electron can just turn into a super light I don't know, quark or higgs or something. Yeah, there has to be something with less mass than you that you are also allowed to decay into. So, for example, a muan can decay into an electron, it also has to create two neutrinos at the same time for other rules, but the opposite can't happen. Electrons don't decay into muans because muons are heavier than electrons and the electrons are the are the lightest ones, right Tows and muans can both decay into electrons electrons the bottom of the ladder, but electrons can't decay into corks and whatever. And there's all sorts of rules preventing some kind of decays from happening. So um, as long as you're not breaking one of the rules, you always decay into the lightest particle around. Oh I see. So, like a muon can't decay into something that's not an electron, muans almost always decay into electrons. Sometimes a particle will have several things that can decay into. So for example, the higgs can decay into a pair of bottoms, but it can also decay into a pair of photons or a pair of w bosons or something else, or a pair of charm corks or even a pair of electrons. So sometimes a particle will have lots of different places it can go, all right, So there are sort of rules to these decays, but generally they follow that rule, like if you decay, you're going to decay into lower mass particles until you hit the bottom, until you're like the gopher, and then working in the mail room. You can't get fired demoted more than that. Yeah, it's just like that. It's like getting fired down the hierarchy. And once you're at the bottom, you know, um, then you can hang on forever. I guess it's not like having a job, because you could get kicked down this street. But I guess maybe stable particles are the unemployed ones in this analogy. Right, Oh, there you go. You don't have a job, so you can't get fired, all right. And so then that's why some particles never never decay like electrons. You're saying, they can't decay in to anything lighter, and so they just hang around forever. As far as we know, they hang around forever. I mean, we don't know that we know all the list of particles that are out there but for the electron to decay into a lighter particle, there would have to be another particle out there that we hadn't heard it before, and it would have to interact with the electron. So it has to be some force that couples the electron to this particle to allow to decay, to create sort of that hole in the box, to let the electron turn into that other particle. Um. And you know, there are other particles like neutrinos, but electrons can't decay into neutrinos because that violates one of the rules, like electrons have a charge, neutrinos don't. So you can't turn electron into a neutrino because then where does the charge go. There has to be conservation not just of mass, but also all these other quantum magical quantities. Yeah, and we have this whole list and we'll go into it in a minute for all the rules of particles have to follow in the decay. And the things to understand about that is that this is just a list of rules we invented um to sort of describe the things that don't happen. We're like, well, this doesn't happen. Why not, Well, let's make a rule that says it can happen. That doesn't mean we know why the rule is there, right, It's just we've noticed this never happens, and so there must be a reason. We just don't know yet. It's not it's not so it's not it's less rules, but more like trends or you know, things we've never seen happen. Yeah, and our goal is to make the sort of minimal set of trends, like what's the minimal set of rules you need to describe everything we've seen. And then we look at those and we say, well, do this makes sense? And what does it mean about the universe? And can we find a reason why these rules have to exist and stuff like that, And so what are some of the other particles that also live forever? The quarks lift forever. The up corks and the down corps do live forever. Yes, there are no lighter quarks, right. The charm cork and the strange cork, those are heavier, and so they decay into the up and the down and the top cork. In the bottom cork they're even heavier, so they decay also down the ladder to charm and strange and then into up and down. So literally every particle in my body then is is as old as time itself. All the particles in your body are just three different kinds of particles up quarks, down quirks, and electrons. And I think that those particles have been around since just after the Big Bang. None of my particles have were created more recently than that. It's not because you can create those particles. You know, if for example, one of the electrons in your body hits a piece of antimatter coming from a cosmic ray, it can get annihilated into a photon, and then that photon lives very briefly and turns back into an electron and positron, so then it's been reborn. Right in that sense, These particles are always having interaction and and sometimes they get they disappear and come back. So some of these electrons have been born more recently, but it's possible for an electron to stick around the whole lifetime in the universe. Yeah, every particle that I am made out of was made at the Big Bang, or you know, it was there when it all happened. It's got stories to tell around. Yeah. Oh, if you could interview particles, if only they could talk. Part If these particles could talk, these particles could talk, they probably tell stories like in old folks homes, you know, while when I was a kid and I have an onion on my belt and the universe was young. You think you have it bad now? We had to live through the hot plasma. Yeah, I think. I think about what it was like in the Big Bang. We have to walk up hill both ways, all right, So that is kind of what happens is when particles die. And so let's get into a little bit more of what these rules are in more detail and what they mean for us as billion of year old beings. But first let's take a quick break. Yeah, all right, Daniel. So particles die, unfortunately, is just the way of the universe. Uh. And then, and that means that particles sometimes, if they're too heavy, they will transform into lower energy particles until you get to a certain types of particles which apparently never decay, like quorcs and electrons. Yeah, and not just lower energy particles, lower mass particles or lighter particles. As we have this rung of particles and they decay down, down down the rung, and they get to the bottom of the ladder, and they can't decay any further. And the particles ever spontaneously go up the ladder. Absolutely they do. If they get a burst of energy, they absorb some energy, then they can go up the ladder. And that's exactly the kind of thing we do in particle collisions, is that we bring particles together with a lot of energy and low mass, and we create we push them up the ladder briefly, because our question is like what particles are on the ladder, how far up the ladder can you go. It's like we're swimming in very cold, cold universe and we're trying to climb up the ladder to see like what could exist, what used to exist. So we create these pockets, momentary pockets of density to push a particle up the ladder to see like, oh look you can make top quarks. Oh look you can make Higgs bosons. Yeah, And so that kind of answers the question why the particles die is that that's just kind of the way of the universe. Nothing heavy last forever. That's the kind of caveat right, like something's last forever. But if you're too heavy, you're not gonna last for a long time. I feel like that should be on your tombstone. Nothing heavy lads forever, or maybe the you know, the motto of the universe would be like only electrons and quarks last wherever. Yeah, it's true that nothing heavy last forever. It's a deep principle of the universe that things spread out. You know, it's connected to entropy that things tend to like to transform into more relaxed states and the ones with more disorder, and the things that lower mass particles, they just have a lot of different ways to be. Like a higher mass particle, it can basically just sit there. It's used up all of its energy to create this particle. But if it decayed into lower mass particles, then there's a zillion different arrangements for it, and the universe prefers that. It prefers configurations with lots of different arrangements. It's more disorder, and so that's just the way the universe flows. Even for an electron. I guess I'm curious. Even for an electron, you're saying, we'll probably never decay, but but it can, Like can is one of its possibilities that it just one day disappears for no no reason and transform into I don't know, fluton or something. Yeah, potentially, I mean, electrons are stable. But again, all these statements that we make are statistical. We've never seen an electron decay and so, and there are a bunch of rules that prevented from turning into the particles that are lighter than it, things like charge conservation and electron number concert ration, all sorts of other rules we invented just to sort of describe the fact that we never see them decay. But in principle, there could be some lighter particle of the electron that's connected to the electron with some very very weak force that we haven't discovered yet, and eventually, after sixty two chillion years, electrons will decay into those other particles. It's possible. Was that time you used their chillion chilion just invented it. But it's technically like the Chilian it's it represents the flow of the universe. Man, Oh dude, yeah, alright, So I let's getting through these rules because I feel like that's where the meat of this is, right, Like, it's not like any particle can just die spontaneously. It has to follow some rules that the universe seems to follow or maybe not rules. Are these more like we've never seen these things happen, but maybe they but they they're not absolute rules. Maybe. Well, it's that way with all the physics. We see stuff happen. We write down rules that we think describes what happens, and that we hope those rules are fundamental to the universe. But we could be wrong. There could be exceptions to these rules we just haven't observed yet. So in the same way, we're like, you know, let's write down all the results of particle physics experiments, and then let's try to simplify that into a set of rules that we think describes all those experiments, and then we try to understand those rules, like do they make any sense? And why this rule and why of that other rule? Er what are the patterns among the rules. That's sort of the stage we're ad in particle physics. So it's it's interesting to think about what these rules are and what they might mean. I see. So it's kind of like you if you dropped an egg and it broke on the floor, and you dropped an egg again, and it broke on the floor, and you dropped another egg and it's broken the floor, and so and your mom is like, why did I have an experimentalist as a kid? And so you made a rule that set if you drop an egg it'll break. Yeah, and that describes what you've seen and and then of course you should test your prediction and try dropping eggs in other people's houses and tom toomps the mountains and to see if it is a deep rule of the universe or just something specific like if you drop an egg on the space station doesn't break. So it turns out your rule needs to qualifier, right, I see this is a special egg breaking rule only in whore his kitchen, or only on Earth, or only near objects with gravity. If you drop egg, does this break? Yeah, there's a difference between general eggcticity and special eggticity. All right, So what are some of the rules that govern particle decay and just I guess real quickly here. Yeah. Well, one of them we talked about already is that they have to decay from heavier particles in the lighter particles because of conservation of energy. The other is that electric charge has to be conserved, so electrons, for example, can't decay into neutrinos um muans have to decay into electrons. They can't decay into positrons. You have to conserve because the universe can't do anything with that extra charge. Is that it it's like it has to do thing with it. Yeah, precisely, electric charge is conserved. The universe cannot create or just destroy electric charge. It sticks around, and that's not something we understand why. But we've noticed that that it's the case that electric charge is always conserved. I guess my question is where did all this charge come from? Ymtanu the Big Bang? And you know electric charge comes in positive and negative, right, So you can create a positive charge if you also create a minus or photon can turn into an electron and a positron, because the total electric charge is then conserved, all right, So that's a that's another rule you have to concern And that also works for the other charges I imagine, right, like the color charge and the the smelly charge and all the other charges. Yeah, for the other charges, there are similar conservation rules. And you know these charges also are important, for example, because the photon can only interact with charge particles. So for example, the photon can turn into a electron impositron, but it can't decay into neutrinos and interact with neutrinos at all because it only talks to the electron and the positron. Can it kind of do like a three point turn like kind of decay into an electron which then decase into a neutrino. Well, remember electrons are stable, so if a photon decase and electrons, it can't then turn into neutrinos. But if a photon decayed into like a muon and an anti muon, that muant an antimu and could then turn into a pair of electrons and positrons and produce neutrinos at the same time. So yeah, photons can eventually produce neutrinos, but not directly. I think what I'm getting here is that if you are a person who likes rules and memorizing rules, then particle physics is for you. And we've got fewer rules than like organic chemistry. You know, we're trying to keep it simple. That's true that organic chemistry is all rules, and that it's just a list of rules that nobody understands and it's an exception for every single case. That's that's why I didn't do organic chemistry. Didn't see what I mean because the list is shorter. That's the only difference. Actually, totally Pegg, dude, I'm interested in particle physics because it has the smallest list of things to memorize. Did I ever tell you why I became an engineer? No, because you wanted to work with cockroaches. Because my dad said to me in high school, He's like, engineering is the best. Man. You don't have to memorize anything. If anyone asks you a question, you just look it up in a book. And I was like, that's for me when your classes or when your homeworkers due or no to turn out, you don't need those things either. Um, but maybe we should just round it up with my favorite rule of particle decay. Okay, okay, you have a favorite favorite is that a particle cannot decay into one other particle has to decay into at least two. Yeah. You can't just have like a Higgs Boson decay into a bottom cork, or you can't even just have like a Muon decay into an electron. Why not? We're not exactly sure why not, but we know that if it could happen, it would break another rule, which is conservation of momentum. Imagine you have a heavy particle it's just sitting there, has no momentum, and it turns into a lower mass particle. Now, now that energy that from the difference in mass has to go somewhere, and usually that goes into the motion of the particle. Okay, So if a muon, for example, turned into an electron, there's extra energy there from the mass difference, so the electron is moving. But then that violates conservation the momentum because the muon originally had no momentum and now the electron has momentum. So you have to create another particle to balance out the momentum that the electron is getting to go the other direction. But wait, what if the muan, the first one, was moving a little bit, can it decay to a smaller particle that's moving faster, because then you can still conserve momentum. They can't because there's some of potentially some observers moving to the same speed as the muan, and they also need to see something that makes sense. And so that's true for all particles that have mass, that there's always the potential to catch up to it and see it motionless. And so you have to have a rule that works also for those observers. You can always look at it in a way that had that it has zero momentum because it's not moving. And in that frame where has no momentum, it can't just spontaneously turn into an electron that's moving, because then you've created momentum. And conservation momentum is another one of those rules about the universe. We don't know why it exists. Um, we don't know why it's there. We show a whole podcast episode about these rules because they're really fascinating, and they highlight a famous woman in physics who has long been overlooked, Emily Nurther, who invented sort of the symmetry that that describes all these things. H interesting. Well, I feel like you're saying that every particle is that a stand still for somebody, every particle that has mass. Yes, photons are never to stand still because they have no mass and if they were to stand still, they'd be nothing. Okay, So you always need to decay to two particles because everything is particles, right, even sort of like energy? Whoa man? That was deep? Did I tell you I didn't have a banana today? So I am running on fubes man, everything is energy and energy particles. Let's go with that. You're like, let me take a puff here? Yeah, man, what did you said? Go for it? I'm smoking my banana appeals. But it's I think it's fascinating that every particle when it decays has to turn into two others. It can't just turn into one. That means that the number of particles increases, so there's no conservational rule and like the overall number of particles in the universe, that's not a problem, all right, Maybe just to wrap it all up then, um, you know, I feel like we started off with the question why do particles die? And I feel like I feel like we arrived at a good answer. You know, I feel like it what is the meaning of last of particles or two? It's it's like, that's the way the universe is, you know, nothing, Um, most particles don't last forever. You know. That's just the way. That's a constant truth truth of the universe, unless you're you get to the bottom rung, in which case you can last forever. You can last, right, you can hang on forever at that bottom rung. But yeah, the universe just likes to spread out. That's what it means for time to move forwards in some sense is that pockets of energy density spread out and diffused themselves across the universe. The whole universe is spreading out and getting colder and more dilute, and so the same thing happens on the particle level. So in that way, we have that in common with particles. And I think it's amazing to think about that, the idea that every particle in my body, like every single one potentially or most of them, they were all there at the Big Bang, right, and maybe part with the Big Bang? Is that true? No, we think they were. That matter was created just after the Big Bang. Oh, I see, okay, so it was there in the Big Bang. All of these particles that are made out of the journey fourteen billion years just for the privilege of being part me. And I hope they're not disappointed. Yeah, I hope this is not their peak moment here. You know, they've been in the heart of stars, they've flown through the universe, but this is where it is, This is where it's good. Maybe maybe the answer to why particles eyes that they realized they travel all this way just to be part of For here sously the aspultaneously decay, because why even go on? Man. Yeah, but it's cool, even if this is not their peak. It's cool to think that every particle in my body may be here until the end of time, right like it. It was there the Big Bang, and now it's part of me and it they'll still be around buzillions of years into the future most likely. Yeah, because, like we've talked about on this podcast several times, the thing that is you is not the things that make you up. It's the arrangement of those bits. Because you could take your bits and rearrange them and to make a star or lava or kittens. It's all the same stuff when the same proportions. It's just how it's put together, so you can put it together to make a whorehey, or a Daniel or you know, BMW or whatever you like. It's all the same stuff, and it's been around for a long time, and it's gonna be here for sixty two chillion years. I think what you're saying, Daniel is that my particles are old, but I can be as young as I want to be. That's right, That's exactly what I'm saying. Your particles are fourteen billion years old, but you're as fresh as a breath of air. But then that that air is also made out of old particles. Yeah, precisely, but we don't know, and we can tell where it's been based on how it smells. All right, Well, we hope you enjoyed that discussion about death, the death of particles, the death and birth and rebirth sometimes of particles, and the eternal life of other particles, and all the rules in between. And we are struggling to understand these rules. And the more we smash particles together and see the rules for new particles, the more we can understand why we have these rules and not those rules. And are these rules really universal? And do they only exist in our part of the universe or for for the particles that we have seen so far. And one day we hope to have a very simple, concise set of rules that we totally describe everything in one line, and hopefully we'll be around to explain that line. So stay tuned, keep listening, subscribe and follow us on Instagram and Twitter, and have a great twenty everybody. See you next time. Before you still have a question after listening to all these explanations, please drop us a line. We'd love to hear from you. You can find us on Facebook, Twitter, and Instagram at Daniel and Jorge That's One Word, or email us at Feedback at Daniel and Jorge dot com. Thanks for listening, and remember that Daniel and Jorge Explain the Universe is a production of I Heart Radio. For more podcast from my heart Radio, visit the i heart Radio app, Apple Podcasts, or wherever you listen to your favorite shows. Two