Why are neutrinos so light?

Published Jun 2, 2020, 4:00 AM

Daniel and Jorge talk about how the weirdest particle gets its mass

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Hi.

I'm David Ego from the podcast Inner Cosmos, which recently hit the number one science podcast in America. I mean neuroscientists at Stanford, and I've spent my career exploring the three pound universe in our heads.

Join me weekly to explore the relationship.

Between your brain and your life, because the more we know about what's running under the hood, better we can steer our lives. Listen to Inner Cosmos with David Eagleman on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts.

Hey, Daniel, do you think anti particles feel bad?

What do they have to feel bad about? I think anti particles are super cool.

Yeah, But you know, who wants to be labeled anti anything? Nobody wants to be the bummer in the room, you know.

I guess that's true. If you're a cartoonist, does that make me an anti cartoonist? That doesn't sound very cool.

What do you have against cartoons? Does that make me the anti physicist?

I don't know. I guess it's like with twins, right, there's always one evils win.

I think that's only true in soap operas, Daniel.

Maybe I'm watching too many telenovelas. But you know, in particle physics there is one particle like the photon, which is its own anti particle. Really, it's its own evil twins. That's right from the mouth of an anti physicist.

Hi am more Hammad, cartoonist and the creator of PhD comics.

Hi.

I'm Daniel. I'm a particle physicist, and I'm not sure yet whether I'm a physicist or an evil physicist.

Am I a physicist or am I a pro physicist?

I guess it depends on who destroys the world first.

Well, I am definitely anti destroying the world, Daniel, I know that for sure.

I am pro learning about the universe while destroying it.

Okay, you need a while of prefix.

Although you know, if somebody gave you the option, like what if you could learn all the secrets of the universe, but in doing so destroy it, that would be a difficult choice.

That would be a difficult choice. Oh my god, somebody take this man's finger off the button and away from any responsibility. Please.

I second that said.

But welcome to our podcast, Daniel and Rhead hopefully don't destroy the universe, a production of iHeartRadio.

In which we avoid destroying the universe instead take it apart gently, piece by piece, and put it back together in a way that makes sense to you.

Yeah, And we like to talk about the galaxies out there, the stars and the planets and all of the incredible nebula out there in the Cosmos book. But we also like to talk about the small things, the little things in life and in the universe, the things that we are all made out of, like the particles.

That's right, and the things that everybody is puzzling about. We think that everybody wants to know how the universe works, and you deserve an explanation that's not just the very basics, the dumbed down version, but an answer that takes you all the way to the forefront of knowledge, that helps you understand what science doesn't know right now.

Yeah, because scientists have this standard model of matter in the universe, is sort of collection of particles and force particles that they call the standard model of physics.

Yeah, what do you think about that name? The standard model? You give that an A rating.

It's pretty standard, I guess for physicists to claim something as standard.

Yeah, I guess so. And next I'm going to tell you it's not.

Actually said great, it's non standard.

Now, we have this standard model and it has particles in it that make up stuff. Those are matter particles like electrons and quarks and that kind of stuff. And we have particles that represent forces, like photons represent electromagnetism, and the W and Z particles represent the weak force, and the glue ones represent the strong force. And then in twenty twelve, we found the missing particle, the Higgs boson. And you'll hear a lot of people describe the standard model as finally complete, like the Higgs boson is the cap on the top of the pyramid.

Yeah and so, and you haven't found anything new since even though you've been like colliding particles with higher and higher energy, you haven't found anything new since twenty twelve.

Jesus sound like sort of demanding, like, hey, what do you discovered for me lately? Yo?

Well, yeah, we're my tax dollars are going to your salaries.

That's true. But remember that searching for new discoveries in particle physics is like exploring. We're like wandering around the surface of Mars, turning over rocks, hoping to find the little green men or weird new kinds of life. And it's true that since twenty twelve we have not found any new particles at the large had dun Collider, and that gives some people the feeling like, well, maybe the Standard Model is all wrapped up. Maybe that's all there is. Maybe we can just tighten the bow and move on. But there are lots of really weird little problems with the Standard Model, lots of interesting discoveries we've made along the way.

Yeah, it seems like a lot of big physics projects in the US and internationally have sort of turned inwards to look at one particular particle in the Standard Model, which is the new trino.

That's right, often described as the weirdest little particle, but not because they're rare.

Really, Yeah, you call it the weirdest little particle.

Yes, in a totally positive way, in a very loving we love you, little Neutrino's No, seriously, he's.

A weird.

We like you anyways, Is that kind of what you're saying.

Yes, Physicists love the weird, the strangely unexplained. That's where the clues are, right, That's where the hints are that tell you how to unravel the secrets of the universe. If you look at everything and it just sort of like makes sense instantly, Well, that's boring. We want a puzzle. We want something strange and weird, and so neutrinos are fascinating, but again not because they're rare. They're everywhere. There's one hundred billion neutrinos passing through my fingers nil every second. But there's so much that we still don't understand about them, really basic questions that just don't have answers to.

Yeah, we are a wash in neutrinos. There's no lack of neutrinos in the world around you. But there is one question about them that still puzzles physicists, and that's the topic of today's episode. So today on the podcast, we'll be tackling the question why are neutrinos so light? Not why are they light, they're not light, but just why is their mass so little?

That's right, it's not like they've been on a diet. Now, it's not about why neutrinos are bright or not bright. It's about why they don't have a lot of masks.

No, it's not their low calorie like coke light.

They are actually low calorie. You could eat like a cubic light year of neutrinos and gain no weight.

It just goes right through you.

That's right. There's zero points on the Weight Watchers diet. So go have your cheap day, eat as many neutrinos as you want. Maybe I should invent like a neutrino based snack food.

It sounds like toastinos, but.

It'd be a little neutral snack food, right. No, yeah, there you go, you know, speaking about snack foods and quantum physics. We did get a hilarious email from a listener today who suggested a really fascinating snack food based physics experiment.

A snack foods these days like a physic experiment, like how fluorescent can we make a snack?

Or flaming hot, glowing particles?

How can we delay entropy of my snack as much as pondible?

Yeah, and it's not about flame and hot neutrinos though, that's the snack food I want to develop now. This listener writes in and he says, I make a sandwich and I shoot it into deep space. Then I make a second sandwich, and instantaneously the first sandwich is converted from new sandwich to old sandwich. And so he's suggesting that this is a version of sort of quantum sandwich entanglement because the original sandwich is out there in deep space and suddenly becomes the old sandwich and he's made the new work.

Oh man, this is funny that this is funny to you. This is even a joke.

There's just some words that are funny, and I think sandwich is one of the weasels. Also that if this was a weasel sandwich, that would be even funnier.

I see, I see, Oh, I see it's it's there's kind of a joke about how name naming things is kind of like transmitting information at the speed of light faster.

Than exactly exactly. The universe recognizes that that's no longer the latest sandwich instantaneously, its status has changed.

Wow, it's a sandwich teleportation.

Anyway, back to the topic of neutrinos.

Back to the topic of today's podcast. Yeah, wh are neutrinos so light? So I guess, first of all, neutrinos are light.

Neutrinos are very low mass. We identify particles essentially by their mass. We look at the particles, we say how much mass does it have? And there's a huge spectrum of values, but neutrinos are on the very very bottom end of it. We measure these things in terms of electron volts, and a typical value like for an electron is half a million electron volts or a muon is one hundred million electron volts.

How much is intrino?

Neutrino is less than one electron volts?

What? Yeah, it's like wow, it's like a percentage of a percentage.

Yeah, it's like one millionth and they even go higher, like quarks are billions of electron volts up to almost two hundred billion electron volts. And you know, this is weird. There's a huge spectrum here from me very very very heavy to very very light, and even between the eleftons and the quarks, the electrons and the top quark example, there's a big range. But neutrinos are all on their own at the very very bottom of this scale. And that looks weird. That puzzles us.

Really, it's the only light particle, or I guess the only low mass particle. Yeah, because do you have particles that have that's right.

We have photons that have no mass, but neutrinos are the only fermion that have this small amount of mass. Neutrinos are matter particles, right, And we didn't know for a long time whether they had any mass, but we recently discovered that they do have masks, but it's a very very small amount. So zero makes sense to us. A number similar to the other masses makes sense to us. But a really weird, super tiny mass. That's a clue. That's like there's something going on here that you could figure out.

Right, yeah, all right, So that's a mystery. Why are neutrinos so much lighter or have so much less mass than all the other particles? And so, as usual, Daniel went out there into the wild of the internet, the pandemic Internet, to figure out how many people out there knew about this mystery and why they think that maybe neutrinos have such little mass.

That's right, So thanks to everybody who volunteered for these person on the Internet interviews and listen to these fun answers and thinks to yourself, do you know why neutrino's are so light?

What people had to say.

I'm not sure.

Why neutrinos are so as light as they are, as they're like not zero like photons. Neutrinos get their mass, I would assume by interacting with the Higgs field, like I think everything else is supposed to. So why they are so light would be because they interact very weekly with the Higgs field. Though they do these interacts some so they have some mass. Now why they interact so weekly with the Higgs field is another question.

I honestly don't know.

Neutrinos are light because they interact weekly with the Higgs.

Field because of how little they interact with the Higgs field, Oh man, I don't know.

They billions of them flowing through space all the time, and hardly any of them interact with us big detectors on the ground filled with bleach or something like that, if you rememory. I imagine they get their mass by the Higgs field.

So I think that nutrinos are made of dark matter, and they are paired in such a way that they almost cancel out in each other. That means they don't show gravitation attraction. Maybe something to do with inertia.

All right, some pretty knowledgeable answers here. There's a lot of references to the Higgs field, Like, wow.

Yeah, some listeners to this podcast have learned something about the Higgs field. That's awesome.

Yeah. So a lot of people say it's because it doesn't interact as much with the Higgs field.

Right, And that's a totally solid answer because most particles out there, that's how they get their masks, like the top quark, the electron, the bottom cork, the mew on, all those particles get their mass by interacting with the Higgs field.

It's almost like a synonym, right, It's almost like the same thing, like how much mass you have is how much you interact with the Higgs field.

Yeah, precisely, before we discovered the Higgs boson and understood this mechanism, we didn't really understand like where mass came from, Like it was just a description. When you try to push something, this happens that it tends to take a force in order to accelerate it. That's really what mass is, inertial mass what we're talking about. And then we discovered this mechanism, this weird feel that if it existed, would have exactly that property as you push on particles. It would mean that when you pushed on a particle, it would take a force to give it acceleration because of the way this field interacts with those particles. So that by itself is pretty super cool to take this like very intuitive macroscopic experience of stuff having inertia and explain it in terms of this weird microscopic particle interaction. You know. I love when you can make that connection between the big, the every day and the tiny microscopic. But hey, maybe that's why I'm a particle physicist and even an evil one.

All right, So maybe Daniel step us through here. Let's talk about mass and particles and just in general, like how do particles get mass? And before we can even talk about what one in particular has such little mass?

Yeah, and remember first of all that most of your mass, the stuff that makes you up, doesn't come from the Higgs field. What makes up mass is not just the sum of all the masses of all the particles inside you, but also the energy that holds them together. Because inertial mass comes not just from those particles, but from any energy that's stored with.

Any interesting because it equals mc squared. Like if you have energy stored, that's like having mass stored.

Yeah, mass essentially is a representation, it's a feature of having energy. Any energy that's stored has inertia. It takes some force to get it up to speed. And that's not something we totally understand, and we could do a whole other podcast about, you know, the mysteries of mass and how it works and whether it's connected to this whole other concept of gravitational mass, which is the force of gravity between objects. But the thing to understand is that the mass is this mysterious thing, and most of it is stored in the energy of your bomb ones, but about one percent of it is stored actually in the mass of those part of more.

Wow. So wait, ninety nine percent of my mass, like how much I weigh and how much I'm attracted by gravity to this planet is from the energy inside of me, not from the actual particles.

Yes, but you just refer to gravitational mass, right, which is a separate concept from inertial mass. Gravitational mass is how much you're attracted by the gravitational force of the Earth. Inertial mass is how much force does it take to give you an acceleration. It's the mn F equals m right.

But they're the same, right, It.

Turns out they're the same. I mean, they're different physical concepts, right, One is inertial on the other's gravity. Turns out the number turns out to be the same. But it's a whole fascinating topic we can dig into another time, but today we're mostly talking about inertial mass.

Okay, well, yeah, how hard I am to sort of move, and most of it comes from the energy I have, It's stored inside of me.

That's right.

If I'm feeling low energy, I should weigh less.

Yeah, And as you absorb energy from the sun, for example, you do weigh more. Like you go out and you suntan, you actually gain a tiny little bit of weight.

Is that true?

No, that is true. Yeah, No, it's not measurable, but every time you absorb a photon, you're getting more energy. Even though photons have no mass, you absorb a photon, you go up in mass.

One more reason to wear a hat when you're out in the sun.

That's right. Daniel Whitson's stay in the dark diet, you should market that eating blame it hot neutrino snack chips and staying in the dark. That's the particle physics.

Dies anti diet, and I'm sure it'll be anti profitable as well.

I just gave it away for free anyway.

So all right, so that's kind of wild to think about, just that, you know, like we're like batteries almost, Like most of what makes us us is the energy we have stwar it inside of us.

Yeah, and we talked about that a lot of times that most of what makes you you is not the actual nature of the particles that are used to build you, but how they're put together, and that includes the energy of those bonds. Right, You're like a bunch of lego pieces bound together really tightly, and it's all about how those lego pieces grip together. That's what gives you most of your mass. But the lego pieces themselves, those electrons and quarks that make you up, they also have their own mass.

And that's kind of what we're talking about here today, which is like, what's the intrinsic mass by itself of the neutrino.

That's right. And for electrons, for example, they get their mass by interacting with a Higgs field. And what that means microscopically is an electron can be flying along and it can emit a Higgs boson and then it can reabsorb that Higgs boson and that's what interacting with the Higgs field means. It can create virtual Higgs bosons.

Right, we talked about virtual particles last time.

Yeah, this is not like a real Higgs boson that you could ever see. Only the electron creates it and can reabsorb it. But the key thing is that in order for an electron to be able to emit a Higgs boson, it has to have an anti particle. The electron can't do that if the positron doesn't also exist.

All right, let's dive deep into these particle physics, phenomenons and processes. But first let's take a quick break.

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All right, so, Daniel, we're talking about the nutrino, and wide has such little mass, and we know that most particles get their mass from the Higgs field. You're telling me that this mass that comes from creating virtual Higgs particles and anti particles. So every time my particles feel mass, you're saying they're creating anti Higgs and Higgs boson.

It's more about the electron itself has to have an anti particle. We'll dig into the details in a moment, but the short version of the story is that any particle that gets its mass from the Higgs boson also has to have an anti particle. The kind of interaction that it does with the Higgs field means that to be consistent, it also has to be possible for a Higgs to decay into the particle and its anti particle. So if you don't have an anti particle, this interaction can't happen, and you just can't get your mass from the Higgs boson. The Higgs boson doesn't have an anti Higgs boson, but in order for the electron to be able to emit a Higgs boson and then later reabsorb it, it has to have an anti particle. There has to be a positron. Why every particle that gets mass from the Higgs boson to have an anti particle and the reason why it is fascinating. The way we think about these particle interactions is three lines intersecting. So for this interaction where an electron emits a Higgs boson, you have one initial particle, the electron, that's one line, and two outgoing particles, the electron and the Higgs bosons the other two lines. So maybe make a little diagram in your mind of an electron line splitting into an electron and Higgs boson. That's like a mini Fine Men diagram. Now, to be consistent with special relativity. For this interaction to exist, then others also have to exist. If you move an incoming particle from this diagram to the outgoing side, it becomes an anti particle. So this little interaction means you should also have another one where the Higgs comes in and outgoes an electron and a positron. But that interaction can only happen if there is a positron on Nature's menu.

WHOA. I feel like maybe an audio is maybe not the best place to use a schematic to explain something, so maybe let's break it down. I think what you're saying is that, you know, if we want an electron to be able to split into an electron plus a Higgs boson, which is kind of what happens when you try to move an electron. Then that process needs to be kind of like reversible, or you have to be able to get that process from any sort of order. Is that kind of what you mean?

Yeah, that's exactly what I mean. And some of those reversals turn electrons into anti electrons, and so the anti electron has to be a possibility in or for this interaction to work.

It has to be like a thing that can exist.

Yeah, if the electron didn't have an antiparticle, then it couldn't emit a Higgs boson.

Oh what because h I see, if it didn't have if there wasn't an anti version of the electron, that means that the whole process has to be canceled. You can't have that process.

Yes, yes, exactly, because this process also requires this other prom a Higgs boson turning into the particle and its antiparticle. But if the antiparticle doesn't exist, this process can't happen in any shape or form.

It's like everything has to balance out cosmically kind of.

That's right, Because this process an electron emitting a Higgs boson and then continue along its path. Somebody else from another perspective could see it differently. They could see it as a Higgs boson creating a particle an antiparticle because of special relativity. Remember, everybody can see the same thing from a different perspective, and so that process has to also.

Be possible, and that actually happens in the universe, right, Like sometimes a Higgs boson will hit a what an anti electron and become an electron.

Yes, sometimes we create Higgs bosons, for example the Large Hadron Collider real ones, not virtual ones, and they turn into a particle antiparticle pair like an electron and a positron or a bottom corkin anti bottom cork. This totally happens. It's how we discovered the Higgs boson.

Okay, So it's almost like a prerequisite for having mass is that there needs to be an anti version of you to have mass.

Right, in order to get mass from the Higgs boson, you have to have a partner. You can't dance without a partner. You want to dance with the Higgs, you have to have an anti particle.

It doesn't have to actually exist, it just has to be possible.

Yeah, it has to be sort of on Nature's list, on the menu of things that could exist.

All right, Yeah, yeah, I guess for me to exist, there has to be a for me to have mass, there has to be the possibility of an anti Horhe out there, even if one doesn't exist.

That's right. And so if you can get rid of the anti Horges, that means that you're not going to get any mass from the Higgs boson. There's a whole other particle physics diet for you.

There you go, the anti anti a twin diet. All right. So then but then neutrino's that's that's kind of where the mystery of neutrino's come in, because neutrinos don't have an anti version necessarily, right.

Well, that's the question. We don't know either. Neutrinos are just like the other particles electrons and top quarks and whatever, and they have anti particles and they get their mass from the Higgs boson, or they're not. There's some other weird kind of particle that doesn't have an anti particle that is its own anti particle. So those are the sort of the two possibilities, and we don't know currently which it is.

Wait, what are the two possibilities?

Said?

Neutrinos don't have an anti version and so they're just weird and they somehow violate this you know, sort of karmic requirement of the universe, or like the neutrino, it's so zen with itself that it satisfies its own anti requirement.

Well, yeah, the two possibilities are one that it's a normal particle like the electron. It has an anti particle and it gets its mass from the Higgs. But in that case we don't understand, like why does it get so little mass? Well, the other possibility is that it doesn't have an anti particle, so it can't dance with the Higgs, so it can't get its mass from the Higgs, and it gets its mass in a totally different way.

Oh, I see, those are the two possibilities.

Yeah, either it has an antiparticle and it gets its mass from the Higgs, or it doesn't. It's its own anti particle and that makes it this other weird kind of particle called a mayorana fermia.

Wow.

All right, well it sounds like two appealing options to enough physicists. But what have we measured, we've met. Have we measured or found an anti neutrino.

We haven't, right, We have not ever established whether anti neutrinos themselves exist. We've seen neutrinos, but remember that's always very indirect like neutrinos hardly ever interact. This is one of the things that makes them so weird is that they mostly ignore the rest of the universe. You have one hundred billion neutrinos flying through your fingertip right now, and you don't notice because they don't interact with you. And so it's very difficult to feel neutrinos. And the reason is that they only interact via one of the forces that we know, and the weakest one, the weak nuclear force. And so we have been able to see neutrinos. In the last twenty or thirty years, we've discovered that they do have mass. But you can't like get a pile of neutrinos and measure them. You can't like say, here's a spoonful of neutrinos and put them on a scale. They're very very light and very difficult to interact with. So we have these very subtle experiments that can't actually measure the masses themselves. They just measure the difference in masses between these kinds of neutrinos, like electron neutrinos and muon neutrinos and town nutrients.

Oh right, because we found different types of neutrinos, that's right.

We know there are three types of neutrinos, and we've seen them change back and forth from one to the other. We did a whole fascinating podcast episode about how neutrinos change flavor from electron to muon to flame it hot no to town neutrinos. And so what we do know is this is sort of the differences between the masses, and those are very very small numbers, and so.

We only know that their differences. We don't know they're like absolute masses.

That's right. We only know their differences. We don't know their absolute values. We've tried to measure their values, and we know that they're less than some number, But we don't know what the masses actually are. But we have measured the differences between them, so we know like the difference between one and two and two and three, But that doesn't even tell us like the order, like which one is heavier and which one is lighter. We can only measure these two differences.

We know that whatever they are, they're really small compared to other particles.

That's right, They're really small, and they're not zero. And so, for example, if they do have anti particles and they do get their mass from the Higgs boson, then it's a question of like why such a small number. Every particle that gets this mass from the Higgs boson gets a different amount of mass because it interacts with the Higgs boson more or less, Like the top core interacts a lot with the Higgs boson, the electron not nearly as much. So there's just like a parameter, like a number, like a dial on the universe that says how much you interact with the Higgs boson. And we want to know, like why are these numbers all different? Why are the values for neutrinos so small. It's not an explanation to say, oh, neutrinos get their mass because they hardly interact with their Higgs, Like why why neutrino's different or weird or special. It's a totally unanswered question.

But it could be that there's no answer, right, Like it could be that maybe the like the mass of the patrino. It's just like a basic constant in the universe that it's just is because it is.

But that's not an answer. I don't know. I find that totally unsatisfactory to say that the universe has like nineteen different numbers and they just are what they are, Like, why are they that and not something else? Was there a moment in the beginning of the universe when these were randomly chosen? Could they actually be any value? I feel like sometime in the future of physics will discover a reason why these numbers are what they are. We just don't know it yet. You know, there must be some pattern, some simplification, some way that we can explain this. So it's very unsatisfying to say, well, neutrinos get their mass from the Higgs, and they just don't interact with it very much for some reason we don't know. Right, that's weird and unexplainable.

And that's just option A. Option B is that it's a totally different kind of particle that maybe doesn't even get a mass from the Higgs.

That's right, And early on in the days of particle physicists, there were two competing ideas for how particles could exist, one from Paul Durak, a famish English physicist who predicted anti particles, and another from Ettore Mayorana, an Italian physicist who predicted that particles could be their own anti partiles.

All right, let's get into what neutrinos could be and how that would explain why they have such little mass. But first, let's take a quick break.

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Hi, I'm David Eagleman from the podcast Inner Cosmos, which recently hit the number one science podcast in America. I'm a neuroscientists at Stanford, and I've spent my career exploring the three pound universe in our heads. We're looking at a whole new series of episodes this season to understand why and how our lives looked the way they do. Why does your memory drift so much? Why is it so hard to keep a secret, When should you know trust your intuition? Why do brains so easily fall for magic tricks? And why do they love conspiracy theories. I'm hitting these questions and hundreds more because the more we know about what's running under the hood, better we can steer our lives. Join me weekly to explore the relationship between your brain and your life by digging into unexpected questions. Listen to Inner Cosmos with David Eagleman on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts.

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All right, Daniel Natrino's we know they're weird because they have such little mass, but We don't know if it's because that's just how they interact with the Higgs boson, or whether they get their mass from a totally different way. Is that an impossible Can you get mass from not the Higgs field?

Yeah? There are other ways to get mass, and the one was predicted by Mayorana and he came up with a whole different way to think about particles. Remember, most of the particles that we think about today were envisioned by Paul Durach. He was trying to put together a theory of quantum mechanics that worked well with relativity, and he came up with an equation called, of course, the Diract equation that described how particles moved through space. And it's when he put that equation down on paper and he looked at it and he noticed he said, wait a second. This equation suggests not just that particles can move through space, but that they should each have a partner. There's like a symmetry in that equation that says, if there's a particle, there should be an anti version, a version with the opposite charge. That's what the whole idea of anti particles came from from this guy, Paul Durrak And then of course we discovered electrons do have anti particles and protons have anti particles and all that. Dirac was right.

I wonder if he had come up with a second equation what he would have called.

It, or the rise of Skywalker, probably the.

Rise of my second equation.

Dirac strikes back.

All right, So that's one way that particles can be. They can have anti verse of itself. But then Majorana came up with another way.

Yeah, he came up with a different equation. He wrote his mathematics differently, and he thought about the way you could have quantum mechanics and relativity, and he put the math together in a different way, and he came up with a way to describe particles moving through space that didn't imply anti particles. And it totally works mathematically, Like, there's no reason we know of why particles should be like Diract particles instead of like Marana particles.

Wow, but it still predicts to antiparticles.

No, Marianas particles don't have anti particles. WHOA, yeah, they work without anti particles. So his equation is different. It doesn't have this symmetry. It doesn't require there to be the opposite particle.

But it's still right and true.

Well, it works mathematically, but we've never seen one in the universe. So before we discovered the positron, nobody knew whether every particle was like the ones described by directs equation or by the ones described by Marana's equations. And then we discovered, Oh, all the particles we know they do have antiparticle, so we'll put them on direct tut And so far Mayorana has won zero of these battles, Like every single particle we've discovered so far has been a direct type. Oh, I see, but it's possible that some of them could be Marona particles. We don't know. We have no reason to understand why the universe likes direct particles and not Mayorana particles. I mean, Marana was a cool dude, all right.

So then the idea is that maybe Neutrino's are maybe one of these Mayorana particles that don't have anti versions of itself.

Yes, exactly, Neutrino's could be their own anti particles. They could be Mayorna particles, so there's not like a separate particle that's the anti electron neutrino. And if that's the case. If they are Mayorana particles, this special, weird kind of particle nobody's ever seen before, then there's a very nice explanation for why they would be so light, why they would have such a small man.

Interesting because I guess Mayorana's equation kind of allows for some particles have very little mass.

Yeah. If you take his equations and you say, well, what if there aren't three neutrinos, there are six, and three of them are super dup or heavy, like cosmically heavy, like you know, each one weighs as much as like a planet or something crazy. Then if you do that, then because of the way the equations work out, you get three really low mass neutrinos that pop out of the equation.

So he pauses, said, neutrinos don't have maybe an anti version, they just have a heavy version.

Yeah, there's instead of there being three, there's like six, and three of them are super duper cosmically heavy. And that it's called the seesaw mechanism because those guys like steal all the mass essentially in these neutrino fields and leave only a tiny little bit left over to the neutrinos that we know and love, and so this imbalance comes from the way the matrices are diagonalized, et cetera, et cetera, falls out of the math. But essentially it's a very natural, simple way to solve his equations and to get a set of very heavy and very light neutrinos. See, so it'd be sort of elegant.

Instead of like flipping the charges, you kind of almost flip the mass kind of.

Yeah. Yeah, that's a good way to think about it. And unlike with the Higgs boson, you don't have to just like put a number in by hand. It's just like it comes out of the math naturally. If you have six of these particles and half of them are heavy, then the other ones just come out naturally to be very very light. And that's what we look for. We look for sort of natural explanations where you don't have to say, this is just a number. I don't know what it is. I'm just gonna stick it in there and see that it works without any explanation. We look for ways that it's a natural consequence of the math. The way that anti particles are a natural consequence of direct math. That tells us directs math is probably right about most of the universe. Interesting, maybe Mayorana's math is right about neutrinos, you know, maybe finally he can get one on his tally card.

But I feel like Mayerana's equation would require there to be like these crazy particles, like a neutrino with the mass of a planet that that doesn't sound like something we've found.

And it's not something we found absolutely and it's.

Not less Daniel. What if it's dark matter?

What if the whole Earth is just one big neutrino.

There you go.

But it's a classic trick in particle physics. To explain something we see, you add a bunch of crazy stuff that happens with particles that are really heavy. Because we can't see those particles, we can't create them in our colliders, we don't have enough energy. They're too rare would they haven't been around since the Big Bang, and so it's sort of like sweeping stuff under the rug I see. You know, you push up all your problems into the really heavy particles which nobody ever sees and are never.

Created and so can't be found kind of.

And can't be found exactly.

Right, because to like create a planet size Nutrina would require a crazy particle collider.

Yeah, particle collider the size of a galaxy probably to create that much energy.

Or like require conditions like the Big Bang, right because right now today it would be very unlikely for us to see something like that if it existed or could.

Yeah, essentially impossible. Nothing is technically impossible when you're talking about quantum mechanics, but essentially, but there are ways for us to figure out if neutrinos are their own anti particles or not.

M all right, that would settle the question of what kind of particle nutrinos are.

That would settle a question because if neutrinos have their own anti particles, then they're direct particles and he basically runs the board and wins everything. But if they do not have their own antiparticles, if they are their own anti particles like the photon is, then Mayorana wins one. You know, if people get confused, we're only talking about matter particles here. There are there are some particles like the Higgs and the photon, which are their own anti particles, but they're not matter particles, so they're not governed by this direct versus Myron and his distinction.

I feel like, now there are steaks.

Well, I really like the math of the Mayorana particles, and so I'm sort of rooting for him. I also like the underdog, you.

Know, It's like, let's give him one. Guys, come on, throw them a bone.

That's right, let's give them one. Also, let's give them the weirdest, best, awesomeess one. Neutrinos are fascinating, So if you have to pick one to win, it would be neutrinos.

All right, So you're saying, even if neutrinos are their own anti particles, that would still put them in the direct column.

No, if neutrinos have an antiparticle, that would put them in the direct column.

Right right, the opposite of what I just said.

Yeah, if the anti what you just said, if neutrios are their own antiparticles, then they're in the mayron a Carlo. Oh, I see, and we have a possibility to maybe even see this, to discover to tell the difference between those two hypotheses, to figure out if neutrinos are their own antiparticles or if they have anti particles.

Oh all right, it sounds like we have overtime penalty goal here, So maybe real quaintly describe what this experiment is.

Well, it involves beta decay. Beta decay is the process where you take a neutron and it turns into a proton, and it happens all the time. It's radioactive decay. And what you get is a neutron turns into a proton plus an electron and a neutrino. And this is actually how neutrinos were first discovered, because we saw that neutrons turned into protons and electrons, but there was some missing information because we can't see the neutrino itself, and so people thought, oh, well, there must be some little neutral particle carrying off some energy. That's the origin of the name neutrinomainder. Yeah, like a little remainder. Now, sometimes there's some nuclei they can't do this, But what they can do is they can do double beta decay. They can take two neutrons simultaneously turn them into two protons, which should give you also two electrons and two neutrinos. So what people are looking for is neutrino lists double beta decay. The idea that these two neutrinos that are produced one from each of the neutrons might combine and annihilate each other. If they are their own antiparticle, then they can do that. They can just like slurp into each other, disappear, disappear.

Yes, but it sounds like maybe the idea is that there's an experiment in which two neutrinos are created at the same time, and if we suddenly see these two neutrinos disappear, then that means that they are their own antiparticles and they did sort of cancel each other out.

Yeah, exactly. So if neutrinos are mayorana particles, then double bata decay can happen without any neutrinos flying out, be like neutrino list double beta decay. And you might ask like, well, how is it possible to even tell, Like you can't see neutrinos directly, so how can you tell, like if there weren't two neutrinos.

There, if there were over or if there weren't.

Yeah, well, if there's a neutrino there, it carries off some of the energy. Like that's how neutrinos were discovered. Remember, you add up the energy of everything else, and it doesn't add up like all the energy that came out doesn't equals with the energy that went in. That's the evidence for the existence of a neutrino. So if you see this happen and there's no missing energy, no energy is lost, then that tells you that there probably was no neutrinos created, and neutrinos annihilated themselves. That you have neutrino lists double bataca.

It sounds kind of impossible, right, Or what if the natrinos were created, they took some of the energy, but then they canceled each other afterwards.

Yeah, well it could be that they like just go off in opposite directions and so they do cancel each other. It's a very hard experiment to do. So far, nobody's ever seen neutrino list double beta decay. Nobody's ever seen this happen. But it's difficult, right to have evidence for this not happening. You have to create the situation where you think it could happen, and then prove that you would see it if it did happen, and then not see it. So it's a very subtle experiment. It's hard, but I totally.

Probably lost me a few steps back there. But it's like you have to see something that's not there, or you have to you have to, you have to not see something that is there but not there at this time.

It's a very subtle experiment and total props to the folks looking for a new tree, needless double bated. Akay. It's a fascinating question in particle physics, but it connects to this much bigger, deeper question of like how do particles get masked? And do particles have their own anti particles? And you know, why are there anti particles anyway, which is a question I've never really wrapped my mind around.

Interesting. So it's like a little detailed question that's subtle, but it might sort of upend the whole basis for the Standard model and our whole sort of understanding of what particles are and what's possible exactly.

And so the discovery of the Higgs boson is not the crowning achievement of the Standard model. It doesn't put the last piece into place and answer all of our questions. We don't step back and go, oh, yes, beautiful, we're done.

We've done it.

No, we're like, well, there are so many weird little bits that don't make any sense, hanging ugly things off the back of it that we want to try to understand and smooth over and figure out, because hey, we like the weird stuff, not the shiny and cool stuff.

All right, Well, it sounds like there's still big questions out there about our understanding of particles in the universe, and I think it's time for people to decide. You know, are you pro Dirac or anti Niurana? And is that the same thing?

And what would happen if Durak and Marana went to a conference together? Would the annihilate each other?

That's right, with the same energy and the opposite direction. Would we even be having this conversation?

That's right? Well, I'm on team Mayerana because I hope that the universe is weird and then we find new stuff. See if it turns out that neutrinos have anti particles and get their mass from the Higgs just like all the other particles, that's much less exciting than discovering a whole new kind of particle that does something.

So you're pro weird or anti standards.

That's right. I'm rooting for the weird model of physics, not the standard model.

All right. Well, we hope you enjoyed that and think a little bit differently. The next time you look up into the sky and realize that you're bathed in these weird, mysterious neutrinos did are maybe something totally different than the rest of the universe.

And maybe they hold a clue to something even deeper about the nature of matter and reality and the whole universe.

Thanks for joining us, See you next time.

Thanks for listening, and remember that Daniel and Jorge Explain the Universe is a production of iHeartRadio. For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows. When you pop a piece of cheese into your mouth, you're probably not thinking about the environmental impact. But the people in the dairy industry are. That's why they're working hard every day to find new ways to reduce waste, conserve natural resources, and drive down greenhouse gas emissions. House US dairy tackling greenhouse gases. Many farms use anaerobic digestors to turn the methane from maneure into renewable energy that can power farms, towns, and electric cars. Visit you as dairy dot COM's last sustainability to learn more. Hi.

I'm David Eagleman from the podcast Inner Cosmos, which recently hit the number one science podcast in America. I'm a neuroscientists at Stanford, and I've spent my career exploring the three pound universe in our heads.

Join me weekly to explore the relationship.

Between your brain and your life, because the more we know about what's running under the hood, that or we can steer our lives. Listen to Inner Cosmos with Savid Eagleman on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts.

Parents looking for a screen free, fun and engaging way to teach your kids the Bible. As a mom, I was looking for the same thing, so I created Kids Bible Story podcast. Thousands of families are raving about it, and kids actually request to listen. With captivating sound effects, voices, and an apply section at the end to spark meaningful conversations, It's a hit with both kids and parents. Listen to Kids Bible's Choice podcast on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts.

Daniel and Jorge Explain the Universe

A fun-filled discussion of the big, mind-blowing, unanswered questions about the Universe. In each e 
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