The universe is beautiful and amazing and strange and confusing, and we struggle sometimes or a lot of times, to make sense of it. One reason is that we have a limited vocabulary to explain it to ourselves, not just limited to the words that we choose, but the concepts that we find familiar, the things we accept as explanations.
Most of physics is about explaining the weird, bonkers rules of our universe in terms that do make sense to us, like eating some new, weird fruit nobody's ever tasted before, and then describing it in terms of familiar childhood staples. It's a little bit like an orange, but with hints of cherry and BlackBerry. That's what we try to do.
For example, with photons, we say, oh, they're kind of like waves, they're kind of like particles, even though we know that neither of those fully capture the alien of the photon. But today's episode isn't about oranges or about photons, at least not directly. We're going to dig into another basic concept and try to understand what it really is. Electric charge. What is it? Where is it? Why do some particles have it? Why do some have more than others?
How is it connected to electric forces? And once we have something of a handle on that, we're going to see if we can extend it to something less familiar, the weak force. How do charges work for those other forces? And why, oh why did physicists call the charge for the weak force hypercharge? Is it weak or is it hyper? Make up your minds, physicists. Welcome to Daniel and Kelly's hyper Extraordinary Universe.
Hello, what smith? I am a parasitologist and weak hypercharge is a phrase that makes really no sense to me.
Huh. I'm Daniel Watson. I'm a particle physicist, and so I should understand weak hypercharge, but it still gets scrambled up in my head.
Well that's all right, we're going to clear it all up today. And so you and I are very well organized people, so we record our episodes a few months before they actually come out. So for you and I, it actually has recently become the new year, So welcome to twenty twenty five. Do you believe in resolutions?
I believe in self improvement. You know, I think people can take positive steps to change their life. I'm not one of those naysayers who says people never change, because my life has changed significantly in various ways over the years. So yeah, I think it's good for people to have introspection, think about their life, think about how it could change in the new year, especially when you're reaching out to folks who are in your community or used to be
in your community. You know, personal connection is the thing that makes life wonderful. So reach out to somebody you haven't talked to in a while and make that connection again.
That is a way deeper answer than I was expecting. Like, so, my resolutions aren't usually like think about how you could improve your personality and do something better, or reach out to an old friend. It's like, I want to get done this five resolution. I want two little baby ducks.
That's not a resolution, that's a wish list.
I resolved to build their habitat and make time in my life for you know, a happy, relaxing pens.
I'm going to improve myself by adding ducks.
Hell, that will make me happy. That's a happiness improver. Getting baby ducks and renovating my kitchen. Those are my twenty twenty five I guess they're goals now instead of resolutions. Do you have a resolution you want to share, then or a goal.
I do have a resolution for the year, and it's about the podcast and its response to an email I got on January first at eight am, where somebody wrote in and says Happy New Year. Unfortunately, I can't listen to the show anymore because of the perpetual giggling, which of course just made me giggle. And I thought to myself, man, who doesn't like a podcast with giggling in it? And so this year, I'm gonna lean into the giggling.
I resolve to giggle with you a lot over we hypercharges and strong forces and all sorts of other things. We're gonna have a blest.
But it made me wonder about giggling, because you know, I have a bit of a deeper voice, and I've always thought myself as more of a chuckler than a giggler. And so I don't know, what are your thoughts, where's the distinction between giggling and chuckling.
After we record an episode, our editor does the editing, he sends it to us. We listened to it to make sure we didn't get anything wrong, and I was listening to my laugh and I was like, I've got a really like sort of obnoxious, dude ish kind of laugh, But I don't care. It's unique. I'm happy and that's all I care about.
Your laugh is not obnoxious. It's expressive. You know, you are really showing us how funny you think something is. It's very it's very New Jersey also though it is.
Yeah, yeah, well I was born in New Jersey and am proud of that. Yeah. I don't hold back it. So I don't feel like either one of us do what I would call giggling. But whatever, we're having fun and let's resolve to lean into it absolutely.
And I think a key to understanding difficult concepts is to giggle a little bit, right. You can't just always go deep on these concepts. You got to lighten the mood a little bit. That's kind of our brand, right, Like, make a few mom jokes along the way, throwing a few dad ponds, keep it light as we go deep on the topics.
A couple jokes about Urinus.
So hey, if you're here to learn some deep concepts about the universe and you are allergic to giggling, you might have found the wrong podcast.
Sorry, there's got to be something else out there for you.
But we are going to go deep into topics, and especially today, we're going to dig into one of my favorite concepts in physics, not just because it tells you something about how the universe works, but it shows you the mechanics of how physics as a field struggles with
try to grapple with something alien. How we start from intuitive concepts and we build this precarious scaffolding to help us understand something even weird or and translate it back into something we might be able to make sense of.
And I'm super excited today because you sent me the outline for this topic and there's a bunch of things when I was reading it through that made me think, oh gosh, I thought I knew the difference between like charge and force, but maybe I really don't. And I think a bunch of that's going to get cleared up today, and I'm glad that I'll be giggling along the way. And you know what's good for giggles.
What's good for giggles, Kelly.
The hilarious answers we get from our audience. I mean, we get lots of great, serious answers, but we also usually get some pretty funny ones when folks don't know what it is. So let's go ahead and giggle at lots of amazing answers.
So today we're talking about electric charge and the weak fours, and specifically weak hypercharge. So I went out there to our volunteers and I asked them if they knew what weak hypercharge was. Think about it for yourself. Do you know what a weak hypercharge is? Here's what audience members had to say, All right, sort of.
A permeter of property. It might even be a mathematical concept to describe the weak force. The week hypercharge is the value assigned to a particle participant.
It's either some extortionate tax imposed by a cowardly government, or it's something associated with the weak field, which mirrors the electric charge in the electromagnetic field.
Hypercharge combinds with isospin to somehow give a charge under the electro weak force.
A charge state of the weak force.
I have no idea weaknd hyper sounds like my childhood Nope, it's related to.
Quantum physics.
I have no idea what the hypercharge part would be and how I would tie it to the weak force. The weak hypercharge is the charge of the weak force.
Encapsulates a particles in some particular force along with its spin and maybe mother information. I don't know what the weak Harper charge is, but it sounds like there's a stronger version of it somewhere.
Well, that's pretty easy. That's when you try to do a hypercharge CAU and it's so weak it doesn't really.
Charge a single factor that enumerates both like a particle's electric charge. It's weak charge and I don't know it's magnetic.
All right, So I chuckled at sounds like my childhood and the one about attacks put on by a cowardly governmental agency. So thank you everyone for the giggles and the serious answers as well.
Yes, and some of these serious answers are right on the money, so I was really impressed.
Well, I'm not surprised.
We have a brilliant and good looking too. Wow, that's right.
That's what I think. It's called the halo effect. When somebody is good at one thing and then you just assume they're good at everything else. They're probably also like fits and fast.
They smell good.
Yeah, way to go, guys. All right, so let's start like super back at the beginning. Let's make sure we're all on the same page. With just even what is charge?
Yeah? Oh wow, I'm supposed to answer that question. Whate'relie physicists?
Yea, what is charge?
So yeah, let's begin with charge, and let's just talk about charge descriptively first before we get into the philosophy of like what is it? Man? We know that electrons have negative charge, Protons have positive charge, right, electrons or minus one protons or plus one. So already we know something about charge, which is that it's associated with the number line. Right, it's a number. It can be zero, it can be positive, it can be negative, right, It
also can be fractional. Quarks have two thirds of a charge or minus one third of a charge, so it's not an integer, right, So it's associated with the real number line. We don't know if they're rational or irrational charges. We've only ever seen fractional charges. But this tells us something that charge lies along this spectrum. It's important to keep that in mind because later on, when we get to the week four the strong force, that's no longer true.
But let's stay on the safe ground of electricity. Particles have this thing we call charge. It can be positive, it can be negative, and there are mirrored versions of it like there's the electron that has negative one charge, and then there's another particle, the anti particle of the electron, which is a version of it with positive charge. We call that the positron. And every particle we've observed that has a charge, there's also a partner particle that has
the opposite charge. The anti matter version of it has the opposite charge. So a cork might have one third charge, but the anti cork would have minus one third.
For example, I'm thinking of like a number line, and we've got electrons with negative one and we've got protons with one. Are the magnitude of those charges the same in the different directions? Even though electrons are smaller and protons are bigger, they still have opposite charges.
Yes, And when to put your finger on one of the deepest mysteries in physics right there. Because electrons and protons have opposite sign charges and exactly the same magnitude. It's like electrons are minus one point zeros or zeros z z is their infinite zeros and protons are plus one point zero zero. And how do we know they match exactly? Well, if they didn't match, you couldn't have
neutral atoms. Right. You use a proton and an electron to make hydrogen, and then it's neutral, and it's crucial that hydrogen is neutral, right, Like hydrogen gas clouds are what forms most of the universe and the dynamics of that and the reason they gravity can pull them together to form stars is because it's neutral. Electricity, which is much more powerful than gravity, has been literally neutralized because these things cancel each other out. But as you say,
the electron is much smaller than the proton. The electron is, we think fundamental, made of nothing but electron. The proton is made of three quarks. Two of them have two thirds charge, one of them has minus one third charge, which add up to plus one. Why is that? Why
does the electron exactly balance this combination of quarks. Why isn't it like off by a little bit, Because in our theory those are just two different numbers, like there are parameters in our theories, knobs that you could change, and we think still have a valid universe, but a very different universe. We don't know why these two knobs happen to be set in exactly the way, so that the charge of the proton and the charge of the
electron balance. It's like if I asked you to pick two random numbers between zero and a zillion and you picked the same number twice, or the number and its opposite, Like, what are the chances of that? So it's a screaming clue that there's a deep connection between the quarks and the electrons, but we don't know what it is.
Okay, So a positron is an electron with a positive charge, and that positive charge is that positive charge now plus one, like the same quantity of charges a proton. Yes, you're shaking your head exactly, but it's not done with that's right, right.
Yeah, So an electron doesn't switch its charge to become a positron. The universe can do two things. The universe can make electrons. The universe can also make positrons. And remember, electrons are ripples in a field, right the way like photons are ripple in the electromagnetic field. Electrons are also ripples in a field. They're ripples in the electron field. So we have two different fields that sound very similar. Bad naming becausists the electron field and the electromagnetic field.
Ripples in the electron field are called electrons. Or it turns out that same field, not a different field. The same field can ripple in another way, and that way is a positron. So the electron field can ripple to make electrons, or can ripple slightly differently to make positrons. And this is something to Rack noticed years and years and years ago when he was looking at the math for electrons in field theory. He was like, hmm, if the universe can do this, why can't it also do that?
In fact, I predict that it does. Then a couple of years later, boom, we found positrons. So you're right, positrons have the same electric charge as protons, but they're fundamentally very different. Positrons, we think, are fundamental particles ripples in the electron field that are different from the way electrons make that field ripple, and protons are a combination of three quarks, each of which is a ripple in its own field.
Okay, all right, so this is.
All descriptive, right, we're talking about what we've seen in the universe. We've seen this charge, we've seen that charge, and explaining in terms of fields makes us wonder like, well, what is this thing anyway? Like, why is it that some fields have charge, Like the electron field when it ripples, it has a charged particle, but when the photon field ripples, it doesn't have a charge, Like photons aren't neutral, right, So makes us wonder like what is charge anyway? Fundamentally?
Yeah, go on, what's the answer?
I was curious because I was like, is that just me? Like interested in philosophy and physics? Is a biologist like, well, we just grind it and we've given it a name. So let's move on.
No, no, I following you. Let's go down the rabbit hole. Let's go one more level of why.
And so we don't fundamentally know what charge is, but we have a bunch of interesting clues. And when I was growing up thinking and learning about charge, I used to think about charge as a property of a particle that could be like removed from it, you know, or it's like a description of how the particle is. You know, Like if you paint something red, Okay, now it's red, but you could also paint it blue and it's still the same thing. Right, Like you take an apple and
it's red, you paint a blue. It's blue now, but it's still an apple, right? Or is it a fundamental part of the thing that helps define what it is. Is it something that you can take off of it, like you can peel an apple and then you still have an apple, right even though it's peeled. Can you take an electron and remove the charge from it and have like an peeled electron an uncharged electron, you know?
Or is the charge fundamentally part of the electron? This is something I was always wondering about as I was learning about particle physics as a kid, and it's not something we have a solid answer for, but thinking about it in terms of fields helps. And so let's go back to thinking about particles in terms of ripples of fields, and I'll show you the role the charge plays in the field picture and it gives you a very different feel for what charge is fundamentally.
My first thought was, Okay, is charge going to be just like an arbitrary thing that humans use in our definition for an electron, like charge in mass or is it going to be like do you use the example of painting it red or blue? And that doesn't change anything fundamental about it. But I think the fact that when you change the charge and you get like a positron, but they annihilate each other. They're behaving totally different, and so that feels different than just painting it red or blue.
But okay, now let's talk about fields and see if we can dig into that.
Deeper, because the field's picture of physics is going to tell us that charge is not a property of particles. It's actually a relationship between fields.
I should have seen that coming. The field's always throw me off.
So remember in the field picture, we still have particles. There are things we call particles. We have a different mental image for what they are. They're not little bits of stuff. There are ripples in these fields, and these fields fill the universe, and sometimes these fields can interact
with each other. So now let's talk about forces. What happens to an electron when it's flying through space and it encounters an electric field, Well, it accelerates, either it slows it down or it speeds it up, but it changes its velocity. That's what an electric field is. That's what electric field does, right, And that means that there's a force on it. You accelerate something, you have to put a force on it. That's f equals ma A. But a neutral particle like a neutrino flying through the
same electric field totally ignores it. Right, it will fly right through. It has no charge, and it ignores the electric field. Yeah, it's there, but it doesn't interact with it. It doesn't matter to It does not accelerate the neutrino. So you shoot an electron to an electric field, it accelerates. You shoot a neutral particle through electric field, nothing happens.
So electric fields exert force on electrons, but electric fields don't exert force on neutrons exactly.
Electric fields exert force on any particles with charge.
Okay.
And you might think, okay, well that's a useful way to describe what an electric field does. It's actually a description of what charge is. Charge is a label we put on particles that are accelerated by electric fields.
Okay, So charge is the ability to be sped up or slowed down. Can you get slowed down by an electric field too?
Yeah? Absolutely, you can get slowed down. Yeah, if you flip the direction of it. So charge is a label we put on it. Like let's say I give you an electric field and they give you a bunch of particles. I don't tell you anything about them. You throw them all into an electric field. Some of them slow down, some of them don't. The ones that slow down, you say, oh, this notices the electric field. I'm gonna put a label on that one. This notices the electric field in the
opposite direction. I'm gonna put the negative label on that one. This one, it ignores the electric field. I'm putting a zero on that one. All right, So charge is a label we put on on particles that sense electric fields. So now let's go back to the fields. Picture what's happening there. The electron is flying through space. It's a ripple in the electron field. Now, an encounter is an
electric field, which is energy in the electromagnetic field. What happens is those two fields are coupling with each other. Energy is going from the electromagnetic field to the electron field. Right, it's accelerating the electron or it's decelerating whichever, but energy is passing. These two fields are coupling together. So instead of just having like one field slashing through space doing its own thing and another field slashing through space doing
its own thing, think of them as like tied together. Right, there's a connection between them. It's like having two guitar strings. But now you have like a rubber band connecting them. So when one oscillates, the other one's gonna oscillate. Also, that's what charge is. Charge is a coupling between two fields for two different fundamental particles. So when the electron moves through space, it makes ripples in the electromagnetic field, and if there's a field there, it pushes on the electron.
It slashes back and forth between electrons and the electromagnetic field, and charge tells us how that works. If you have a zero, then there's no coupling. If you have a one, then they are coupled. If you have a mindus one, you couple the opposite direction.
Okay, all right, so first we're talking about strings, but it has nothing to do with string theory.
Now we talk about strings because strings follow the wave equation, and so do the fields. The wave equation is everywhere.
Okay, great, perfect. When we're talking about electron fields, we're talking about a bunch of electrons acting together. When we talk about electric fields, what is an electric field made of?
Electric field is energy in the electromagnetic field, which is just another field in the universe, the same way the electron field is, and ripples in the field are photons, right, And so in the particle picture, you have electrons which shoot photons back and forth at each other, and that's how electrons repel each other. In the field's picture, you have ripples in the electron field which couple to the electromagnetic field and exchange energy that way.
Okay, all right, I've caught up.
So that's another way to think about charge. Charge. Here is a coupling between fields, right, it says this field connects to that field. This field connects to that field. These two fields don't connect at all. You put a zero. So instead of thinking of charge as something attributed to the particle, like the charge is the electrons, it's the relationship between the electron and the photon, or the electron field and the electromagnetic field. Are they connected? If so,
put a one. Are they anti connected or do they ignore each other? So charge is how the fields couple. But it might not just be our description. It might be something important to the universe, because this is something the universe respects.
And let's talk about RSPCT. After the break, we're back and we're talking about fields respecting each other. And where are we going with this?
So you might think all right, Well, if we are just putting label on particles and it's just a relationship between fields, then these are just numbers. We made them up and they shouldn't have any special properties, right. But we know that charge has a really interesting special property, which is if you count up all the charges on all the particles in some system and then you let
it do its thing. Let physics happened for a second, for a billion years whatever, and you come back and you count up all the charges again, and you might have you know, some of the electrons are gone, and now you've made protons or whatever. The particles have all changed, but the total number of charge has not changed. Charge is conserved in the universe. Every microphysical process and electron radiates a photon, or electron and positron annihilate. None of
those violate electric charge. So you can do zillions of them and they don't add up to any violation of the electric charge. It's exactly conserved in the universe in a way, very very few things are exactly conserved. And for a physics that's like whoa, that's a big screaming clue that this might be an important thing to the universe, not just something we made up.
So first of all, I'm finding myself wondering if there are more religious people in physics than there are in biology, because the more we get into this, it feels like
something is making these things be symmetrical. Maybe you've hinted at the fact that the universe could not be otherwise, like when we were talking about the Big Bang and why are there electrons and we've lost the positrons and if we had equal numbers, everything would annihilate, there'd be nothing, right, So this is the only thing that could have arisen from the chaos, this symmetry. Is that the right way
to be thinking about it? Or are we going in a different direction with this conversation.
No, this is definitely the right part of your brain to be using here, because the whole juice of physics for me is like, let's reveal what the rules are, and then let's be odd that the rules are what they are and wonder if they could have been different, right, And my whole fantasy is that we will work hard to unify all of our understanding of the universe and be left with an equation and then it will be
self evident. We're like, oh, yeah, I can see how this is the only way you could put a universe together. There is no other way to do it. Of course, it's got to be this way. The alternative is you get to some equation and you're like, huh, well, I mean, I see how that works. But you could have also made this a six or that a nine, Like why don't we live in that universe? Then you got a bunch of open questions. I don't know which is going
to be the outcome. But along the way you have these moments where something emerges from the math that you didn't build in. Right. You didn't say I'm going to create this concept of charge and I'm going to insist that it's conserved. You just discover that, right. It's like it comes out in our experiments. We notice that charge is concerved, and then we also see it in the mathematics, and that seems like ooh. You are digging deep into the firmament of the universe and you clanged onto something
hard and you're like, whoa, there's something here. Let's dig out this corner and see what this is. And it turns out there is a really interesting, very very deep realization here which I don't think has penetrated nearly enough into like the broader culture of what it means for something to be conserved. And it also connects to our goal of uplifting overlooked women who've contributed to science, because there's a very influential theorem from the mind of Emmy Nuther.
She was a mathematician working around the same time as Einstein, and she just like dabbled occasionally in physics on her coffee breaks and came up with these incredible realizations, you know, just while gooving around before going back to real stuff
like mathematics. And her theorem tells us that every time something is conserved in the universe, like electric charge or momentum for example, that's because there's a symmetry in the universe, there's something the universe respects, and so for momentum, it's very straightforward. We have momentum conservation in the universe because the universe doesn't care where something happens. The rules are the same everywhere. So you set up some physics experiment,
you do it, you get an answer. If you could set it up ten meters to the right or ten thousand meters to the left, it shouldn't matter. The rules of the universe should be the same no matter where you are. There's no like absolute origin to the universe. You can't tell where you are in the universe. That makes sense, right, there's a symmetry there. That symmetry is why we have conservation of momentum. So notre connected these
two ideas of symmetries and conservations. And we can do a whole other episode where I try to explain the mathematics of that and intuitive way, but today's episode just accept like every symmetry means a conservation, and now we have a conservation of something electric charge. So you're like, okay, well, you know they're telling me, what's the symmetry, right, what is the universe respecting here? And it turns out this is incredible that what is respecting is some weird internal
angle that electrons have. Like when we say electrons are ripples in the field, that's true, but the mathematics gives us another degree of freedom, like electrons ripple through the field, but they also have an angle to them as they go, and this angle is mostly unimportant, like you can't measure it doesn't matter, you can't see it, and you could have a universe whether the electron angles are just like
willy nilly. But if you insist that the universe respects this angle, that it's symmetric with respect to this angle, that you can change this weird internal electron angle and not change any of the physics the same way you can change the location or direction of an experiment and always get the same answer. The only way to do it if you have electrons in the universe and you want that symmetry preserve this weird internal angle is to have photon. You could only preserve this symmetry, this weird
electron angle if you add photons to the universe. Electrons can't do it by themselves, so it's sort of like you derive the existence of photons. You're like, Okay, I have electrons and they have charge, and they have this weird angle inside them. If I insist for whatever reason that this weird internal electron angle has a symmetry, that the universe is the same if I spin that angle, then I got to add photons. Otherwise it doesn't work. You can like derive the existence of photons just from
this requirement. And of course we know that photons are what do the thing that charges do right, they're there to provide the forces. So there's this deep connection between charge and photons and this bizarre internal angle that electrons have and we don't quite understand it, but we know that for some reason, the universe really wants to be symmetric with respect to this internal angle that electrons have, and that's why we have charge conservation in the universe.
And you have to have photons to make that whole thing work.
All right. So first, when we were talking about symmetry, I was thinking that positrons where the symmetrical thing with electrons, and so that's a symmetrical thing with electrons, but there's another symmetrical thing with electrons, which is this angle. Absolutely, you said, we can't measure the angle, So how do we know this?
You can't measure an electrons angle directly. It has to do with like what fraction of its wave function is real and what fraction is complex? And you can't measure complex properties of an electron. But it exists and affects how the wave function propagates, so we can make predictions based on it in a statistical way. So you're asking, like, how do we know this angle is real? Well, it's sort of like asking, how do we know the wave function is real? We can't see it directly, but it's
an important part of our model. So yeah, it's a deep question in philosophy, like is this real? It's a necessary component of the model which predicts the outcome of experiments, since that makes it feel real ish. But is anything that's complex valued act? I don't know. I mean technically mathematicians are like, real numbers are real. Complex numbers are not real. But I think we mean real philosophically there So anyway, that's a long way of saying, yeah, we don't know.
Okay, Yeah, I feel like fifty percent of the conversations you and I have gets down to what is real, what exists?
So I don't know.
So you could have symmetry with respect to charge and with respect to angle. Are there other features of electrons that have symmetries?
Yeah? So there are lots of these pairings from Notther's theorem. You know. One of them is like where are you in the universe doesn't matter? That gives you conservation and momentum. There's also angles, like hey, what if you send your X axis this direction or that direction doesn't matter? No, the universe has no preferred angle that gives you angular momentum conservation. And there's also symmetries with respect to time, like due to the laws of physics change over time, we
don't think, So that's where energy conservation comes from. So all the big conservation laws can be translated into symmetries or vice versa, and you can actually think of them as sort of two sides of the same coin. And all those I think are clues. They tell us like how the universe works, Like if energy is concerned, that means that the laws of physics don't change with time.
That's kind of a big deal. And in fact, it turns out energy not exactly conserved in our universe because the laws of physics are changing slightly with time as the universe expands and dark energy is increasing, and that changes a factor that we conclude in the laws of physics. So that's a whole other rabbit hole. But this one
is exactly conserved. The universe conserves electric charge exactly, which means this weird internal electron angle that seems bizarre and just sort of like abstract is important to the universe. The universe respects it. It's built in deep, deep to the mechanics of the universe. I feel like that's a clue, that's something hard we're clinging on in the firmament of physics.
So protons and electrons have opposite charges of the same magnitude, but they don't have the same mass. Does that tell us something about mass not being conserved or am I clinging to a not relevant factor here?
The mass of these particles is a totally separate topic, And you're right, mass is not conserved. Electrons and positrons do have the same mass because of the ripples in the same fundamental field. But yeah, mass is definitely not conserved in the universe. I mean we destroy mass all the time in the large Hadrunk glider unilate protons you use their mass to make new stuff that has lower mass and higher velocity. You also gain mass all the
time from energy. You go out and feel the sun, the photons that your body absorbs, increase the internal energy of your molecules and gain mass. You charge your tesla, it gains mass. So yeah, mass is definitely not conserved in the universe. But this concept of charge turns out to be a little bit more general than even electric charge. We've talked about charge as a way that the photon the electric fields coupled to each other, right, but also
somehow deeply connected to the universe. And that turns out to be the simplest way to thy think about it, because you have just like one kind of charge can be positive or negative, and just one field, the photon field, that it couples to. And you know, muans coupled to the photon field, and quarks couple to the photon field.
Anything with electric charge couples to the photon field. But the other charges for the other forces that are mediated by other fields and particles turned out to be an generalization, a more complex version of the same basic idea thinking about how fields couple to each other.
Okay, so how is that a more subtle point than what we had talked about before. So we had already talked about how protons have two two thirds quarks and then a negative one third quark or something. And so with what you just said, what did we learn that was different than what we had known before? Because I think I didn't catch it.
No, we didn't learn anything new. I'm just now trying to set us up to think about the other forces. In terms of this framework. So we introduced this new way of thinking about the electric charge, like not as paints you put on some part and other particles, but as a relationship between fields. Right now, let's try to use that same sort of intellectual framework and think about the other forces, the other kinds of charges in the same way, because implicit there is the idea that forces
and charges are linked. Right. Electric charges are how we used to label particles that feel forces in electric fields. There are other forces in the universe, and some particles ignore them. Some particles don't. So, for example, the strong force strongest force out there, electrons totally ignore it. Electrons
that have electric charge have no strong charge. So if I'm going to give you a bunch of particles and you're going to throw them through a what we call a color field, that's the field for the strong nuclear force. Electrons fly right through, it doesn't matter. But if you throw a QRK through there all sorts of crazy interactions. Oh my gosh, it gets accelerated like crazy. So now we have another kind of label, right like, okay, well, every particle has a label for whether it ignores electric
fiel fields or not. It also has a label for whether it ignores color fields fields from the strong force. But instead of thinking about as a label in the particle, think about it as a way those fields interact. So the electron field does not interact with the gluon field. That's the analogy in the strong nuclear force of the electromagnetic field. Right, we have these gluons, and so electrons just don't interact with gluon fields. You kind of intense
buzzing energy in the gluon field. Electron field is not linked to it at all. They oscill it completely independently. But a quark field in that same region of space where the gluon fields a lot of energy, those are tied very strongly together, and so they buzz together.
Okay, so we talked about charge as the direction of the response to the electromagnetic field. That's our baseline. And now when you move on to strong force, it's no longer really helpful to think of negative and positive because it's just like do they respond to these forces or not.
You're right that we shouldn't think about strong nuclear charges as zero, positive or negative, but it's not truth that they're simpler. It's not just like a yes or no In fact, they're more complicated. There are three different axes along which you can have a color charge. So for electric forces it's just one axis, right, and you're the zero, positive or negative. For the strong force, there are three different ones and they call them red, green, and blue.
And so for example, you can have a quirk that's green or an anti green cork, or you can have a red cork or an anti blue cork, and so it's more complicated than the electromagnetic field. It's a generalization of it. The fundamental ideas are the same, but instead of like a single number zero, negative one, whatever, you have like a vector, you have like three different numbers. You have a green, a red, and a blue charge, and if you're zero in all of those, that's what
we call colorless or white. So, for example, the proton has quarks inside of it, and each of those quarks has a charge. But if you have a red, a green, and a blue, the math works out that they add up to zero, and.
So electrons have a red, a green, and a blue.
You mean protons, Well, I thought you said.
Protons do respond to the force, but electrons don't.
So quarks respond to the force. Quarks are charged right, But quarks can add up to neutralize themselves to have zero color charge, the same way that like an electron positron together have zero electric charge. Three quarks that make a proton have zero color charge. So if you have a red, a green, and a blue cork together, the math adds up that they add up to zero total charge, so they're not three totally independent directions in this weird way.
So there's two different ways that you can have zero color charge. You can either have one red, one green, one blue, or you can have red and anti red. So for example, a quark and an antiquark can come together to make a colorless object, which is like a pion. All these particles we call masons are two quarks together in a colorless state. They have no strong charge total, same with a proton and a neutron. There's lots that
you can make it with three quarks. You can also make it with six quarks for really crazy particles, but most of the stuff we see in the universe is either three quarks together colorless or two quarks together overall colorless. And there's not just one gluon field because there's so
many different colors. You need eight different gluon fields, and the glue on fields each have two colors, so you could have like a red green gluon or a blue anti red gluon, and the math is very complicated, it's really crazy, but it's an analogy to the way we think about electric charge and electric forces and the interactions between the fields. So you have these eight gluon fields filling the universe with all their color, and they interact with quarks, but not with electrons.
Okay, they interact with quarks, but at the level of a proton they usually cancel out full proton usually doesn't respond to the strong force, and electrons don't usually respond to the strong force.
Yes, that's exactly right. And these quarks also have weird internal angles to them, and the universe likes to conserve those. It's more complicated than just conserving one number because a three dimensional color thing. But the universe can serves strong nuclear color, which means it's symmetric with respect to all those weird internal quark angles. So that's all. I'm still very similar to electromagnetism.
All right, so I think I've followed all that. After the break, let's talk about the weak force. We're back, all right. So we've talked about charge and force as it relates to electromagnetic forces and the strong force, and so now let's let's get to the weak force. We're two thirds of the way through the episode. We're at the weak force of our goal of talking about the weak hyperforce. So tell me about the weak force, right, So.
The weak force super fascinating because it touches everything in the universe. Like, there are some particles out there with zero electromagnetic charge, right, like neutrons or neutrinos. They ignore electric fields. There are particles out there with no strong charge. Right, Electrons ignore the strong force. There's nothing in the universe that ignores the weak force. Everything out there except maybe dark matter, which we haven't figured out yet. It might
not be a particle. Da da da da feels the weak force. It's fascinating. It's like unavoidable, but it's also super duper feeble. Right, It's the weakest force out there except for gravity. Probably not a force anyway, but it's much weaker than electromagnetism and the strong force. But it's pervasive.
Even neutrons are responding to the weak force.
Yes, neutrons respond to the weak force. Protons respond to the weak force, neutrinos respond to the weak force. Absolutely yes, And we can think about the weak force in the same sort of framework as we thought about electromagnetism and generalize it in the way we did also for the strong force. So the weak force, like the strong force, doesn't just have one charge. It has multiple charges. Right, So remember electromagnetism, which seemed complicated at the time, was
actually nice and simple because it was just a number. Right, It's like negative one plus two thirds, what's the big deal? Well, weak forces have two charges, and because they were discovered at different times and then like adapted from different theories historically, the names for the mer disaster. We don't just have like week charge one, week charge two or whatever, or even the strong force is like nice colors which unify it.
So that's why we have two different charges and they're called weak isospin in weak hypercharge.
I hate you, guys, it's.
Terrible, and I hate the word weak hyper charge because to me, hyper suggests like it's strong, it's intense, it's powerful, it's overwhelming, but then it's weak, So you're like, what is it more powerful? Is what's powerful. I can't even tell. Well, it's like super big tiny something what And.
I'm not sure I understand what isospin either.
Means Oh, that's even worse.
And the colors were throwing me too. I think you guys need to start back at the drawing board. But all right, all right, let's work with what we've got.
Isospin comes from another theory which kind of failed and then was adapted later on. It was like, maybe this could be reused, Like this happens in physics all the time. Somebody studies something for like twenty years, it seems like it's going to work out in the universe, says no, thanks, that was a nice idea, but no, and then somebody else comes along, so well, maybe I could adapt that actually to answer this other question. That's what happened with
string theory. String theory was originally an attempt to explain color forces and the strong nuclear force, and it failed. But then it turns out to explain much more deep things, so that can work sometimes. But you know, come up with a new name. Yeah, so the's two different charges,
and every particle it now has two numbers. Right, you have your isospin number and your hypercharge number, and these numbers are a little weird, like isospin Electrons have minus a half and neutrinos have plus a half, and so muons, for example, of minus a half tows of minus a half, but all the neutrinos have plus a half. And hypercharge is just like another number, and electrons and neutrinos both have hypercharge minus one, whereas quarks have hypercharge plus a third.
Could you have predicted what these charges would be once you knew about the weak force or these things where you had to measure it and then you were like, huh, negative a half, wouldn't I guess that? But now we know that's a feature of the universe, Like, can you predict these things or did you just measure them and then work with that?
Yeah, great question. Electric charges we definitely just measured. Week charges are much harder to measure because the weak force is very weak, and these are numbers that we came up with later to explain particles we've already seen. Because there's a deep connection between the weak force and the electromagnetic force. These things are not totally separate. We've unified them into one theory called electro week and This is really interesting because it turns out that electromagnetism is just
part of the weak force. So remember how the strong force had like a bunch of different gluon fields to handle all the complexity. There are four fields in the electroweak force, and one of them is the photon, and the other three are fields that we call the weak force, two W fields, and then the Z field. And the electric field is like the weird sibling in the electroweak
force because it's so simple and well preserved. Like the universe preserves the electric charge and respects this weird symmetry. But more broadly, the weak charges are not conserved. So for example, isospin not conserved in the universe, hypercharge not conserved in the universe. The universe doesn't respect this symmetry. This is how Higgs made his discovery, because he saw that the weak force does not respect these things. His whole theory is in a contact we call electroweak symmetry.
Breaking the weak force is kind of a big, sloppy mess. But electric charge turns out to be a weird combination of isospin and hypercharge. You have this big, messy weak force when nothing is conserved everything is very weak and flimsy in sloshing around. But if you look at it from just one angler, you take one slice of it, you say, oh, this is beautiful. This is the photon field on electromagnetism, and everything is perfectly concerned in this one weird slice of a larger, messy field. So it
turns out electric charge is connected to weak hypercharge. It's like a combination of hypercharge and isospin together.
Okay, so the weak force is actually measured in four different ways, one of which is the electromagnetic field, and that is conserved, yes, But the other three are a freaking mess. Yes, And we don't understand why, and we don't think that we are misunderstanding something. It's just actually not conserved, which maybe tells us something about what's important about the universe. Was the conservation for the strong force, Yes,
conservation for the strong force. These three kinds of weak forces, you don't get conservation because.
Of the Higgs. The Higgs and messes up those other fields. In fact, that's how Higgs knew the Higgs was there. He's like, oh, how do you mess up these three fields and not the photon. I'm gonna invent this thing to mess up those three fields and not mess up the photon. That's the Higgs boson, and that's how we knew that that was there, because the weak field is messed up in this weird particular way that preserves one
corner of it. It's like if you have four siblings sharing a room and three of them are total Slavs, and somehow one of the siblings is like military corners on the bed, not a piece of dust on the floor, and you're like, all the way down to the edge and you measure it, like down to the micron. You have like an electron microscope, and you can't find a tiny little bit of dust that goes past that barrier, and you're like, wow, there's something going on here. That's
what Higgs saw. He's like, all right, I'm going to invent this mechanism that messes up this part of the universe and not that part at all and doesn't even touch it.
Okay, So Higgs has a field and a boson, right.
Yes, that's right. The boson is a ripple in the field. So it's really just one concept.
So we've got the Higgs field. What is the connection between the field and the weak force.
So the Higgs field is another field, and it interacts with all of these fields, and it messes up the symmetry of the Week field. So if you didn't have the Higgs field, the weak charges would be perfectly conserved and the internal angles of the weak field would be crystal and beautiful, just like the other forces. But the Higgs field messes up the weak field. It breaks electroweek symmetry in a way that messes up those fields and
breaks the conservation of weak hypercharge and weak isospin. So separately, these two things are not conserved, but this one combination of them is preserved by the Higgs boson.
Okay, so the Higgs field messes up the three different measurements for the weak force. And remind me of what a weak hypercharge now that I've got that in my head.
All right, and we hypercharge is one of these charges of the weak force. So the electro week force week plus electromagnetism has three charges. Electric charge, weak hypercharge, weak isospin. Electric charge is actually a special combination of those two. The Higgs field messes up the conservation of it. Generally, right, they're not separately conserved, but this combination of them. Electric
charge is conserved in the universe. So we have this fields description of all the ripples of energy in the universe, and we know which fields talk to which other fields, and that's what we call charge. And fields can talk to each other in different ways. Right. They can talk to each other through the photon field, in which case they both have electric charge, because that's what it means
to send energy through the photon field. It means you have an electric charge you're coupling to the photon field. Or they can talk to each other through weak fields because all particles have weak hypercharge or weak isospin. Or they can talk to each other through the gluon field if they couple to the gluon fields, and that's what
it means to have color charge. So we hypercharge is an example how matterfields fields to describe electrons and muons and quarks and all this kind of other stuff can interact with each other through these force fields, through the electromagnetic field and the gluon fields and the W field and the Z field and all these other fields that help particles interact with each other. And so it's fascinating that electric charge is conserved and strong charge is concerned,
but we hypercharge is not right. The universe mess that up created the Higgs boson gave it this weird energy. But I hope that this gives you like a different view of like what charge is. It's not just about electricity. It's not a label we put on particles. It's about how fields talk to each other. And a lot of particle physics is understanding how energy slashes back and forth between these fields. And like you can ask the philosophical
questions like what is an electron anyway? And our description of electron isn't just a particle flying through space. It's a buzzing and a rippling in the electron field that's also constantly coupled to the photon field, and energy is slashing back and forth between them. And that's what we mean by the electron we measure in the lab. And when we talk about a cork, it's got a cloud of gluons around it, or you can think about it as a ripple in the quark field, constantly slashing energy
back and forth via gluon fields. That's really what charges about. It's about coupling of the fields and the weak hypercharge is that a great example because it shows off how the universe can be beautiful and symmetric and crystalline, and then sometimes it can just be the messy sibling leaving dirty dishes under its bed.
Yeah, a total disaster. Yeah. So I feel like I thought that I understood charge and force going in, and it's totally different. I'm thinking about it now in a totally different way than I had before, which is really exciting. One quick step back, isospin is also not conserved.
Isospin is also not concerved?
Yeah, and so did we decide that we wanted this episode to be about the weak hypercharge because it's a funny name. Why are we emphasizing that charge as opposed to talking about isospin? Yeah, and the weak hypercharge because they seem to be telling us the same thing. As far as I can tell.
You're right, week isospin and week hypercharge are on the same footing. Two reasons why this episode started out about hypercharge and not isospin. One is it has the word charge in it, So I thought I would at least give the listeners a clue when we're asking them about it, Like, otherwise, what is this thing? It's just a bunch of words physicists invented. And also because at least one person wrote in and said, I was reading the Wikipedia page on
week hypercharge and what is this? Can you explain it? So I thought, all right, let's try to dig into.
This perfect Those are two great reasons. Okay, now I'm with you, and I'm never going to see the world the same way again.
And for those of you who want to learn more, all the mathematics of these fields and how they interact is described with this beautiful piece of theory called group theory, which shows you how these things rotate and how energy flows between them. It's a great example also of how mathematicians will develop a new branch of mathasthematics just for fun. They're like, hey, this is cool. Let's create these rules and then just play games with them for one hundred years,
and they totally did that. Then one hundred years later physicists are like, oh my gosh, these games you've been playing, just like you know, sipping tea and being nerds, turns out to be perfect description of this complex mathematics of these fields we discovered, thanks guys, and just plugged it right in. And now group theory is like at the heart of our understanding of the universe.
Were the mathematicians just devastated when they found out their work was applied and then like, oh, I have.
To move on and invent another irrelevant game.
Yeah, oh, it must have been a bad day for the mathematicians.
I think there are two kinds of mathematicians, those who are disappointed in, those who are excited yeah yeah, yeah, those who have a little bit of physicist in them, and those that don't. Yeah yeah, because in the end, you know, the dotted lines we draw between math and physics and philosophy, these are just the way humans like to categorize people, right as you always say, this a spectrum.
Yep, agree, Nature and humanity don't like to be in categories.
All right, Well, thank you for joining us for this tour along the spectrum of complexity of all the forces, from the crisp, beautiful nature of electromagnetism to the messiness of the week force. So I hope that helped you get a new view of how the universe worked. And I hope we giggled just the right amount.
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