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What is weak hypercharge? · Daniel and Kelly’s Extraordinary Universe

0:05
Speaker 1: The universe is beautiful and amazing and strange and confusing,
0:11
Speaker 1: and we struggle sometimes or a lot of times, to
0:14
Speaker 1: make sense of it. One reason is that we have
0:17
Speaker 1: a limited vocabulary to explain it to ourselves, not just
0:21
Speaker 1: limited to the words that we choose, but the concepts
0:25
Speaker 1: that we find familiar, the things we accept as explanations.
0:30
Speaker 1: Most of physics is about explaining the weird, bonkers rules
0:34
Speaker 1: of our universe in terms that do make sense to us,
0:38
Speaker 1: like eating some new, weird fruit nobody's ever tasted before,
0:42
Speaker 1: and then describing it in terms of familiar childhood staples.
0:46
Speaker 1: It's a little bit like an orange, but with hints
0:48
Speaker 1: of cherry and BlackBerry. That's what we try to do.
0:51
Speaker 1: For example, with photons, we say, oh, they're kind of
0:54
Speaker 1: like waves, they're kind of like particles, even though we
0:56
Speaker 1: know that neither of those fully capture the alien of
1:00
Speaker 1: the photon. But today's episode isn't about oranges or about photons,
1:05
Speaker 1: at least not directly. We're going to dig into another
1:08
Speaker 1: basic concept and try to understand what it really is.
1:12
Speaker 1: Electric charge. What is it? Where is it? Why do
1:16
Speaker 1: some particles have it? Why do some have more than others?
1:19
Speaker 1: How is it connected to electric forces? And once we
1:22
Speaker 1: have something of a handle on that, we're going to
1:25
Speaker 1: see if we can extend it to something less familiar,
1:28
Speaker 1: the weak force. How do charges work for those other forces?
1:31
Speaker 1: And why, oh why did physicists call the charge for
1:34
Speaker 1: the weak force hypercharge? Is it weak or is it hyper?
1:39
Speaker 1: Make up your minds, physicists. Welcome to Daniel and Kelly's
1:43
Speaker 1: hyper Extraordinary Universe.
1:58
Speaker 2: Hello, what smith? I am a parasitologist and weak hypercharge
2:03
Speaker 2: is a phrase that makes really no sense to me.
2:08
Speaker 1: Huh. I'm Daniel Watson. I'm a particle physicist, and so
2:10
Speaker 1: I should understand weak hypercharge, but it still gets scrambled
2:13
Speaker 1: up in my head.
2:15
Speaker 2: Well that's all right, we're going to clear it all
2:16
Speaker 2: up today. And so you and I are very well
2:19
Speaker 2: organized people, so we record our episodes a few months
2:22
Speaker 2: before they actually come out. So for you and I,
2:24
Speaker 2: it actually has recently become the new year, So welcome
2:27
Speaker 2: to twenty twenty five. Do you believe in resolutions?
2:33
Speaker 1: I believe in self improvement. You know, I think people
2:36
Speaker 1: can take positive steps to change their life. I'm not
2:39
Speaker 1: one of those naysayers who says people never change, because
2:42
Speaker 1: my life has changed significantly in various ways over the years.
2:45
Speaker 1: So yeah, I think it's good for people to have introspection,
2:48
Speaker 1: think about their life, think about how it could change
2:51
Speaker 1: in the new year, especially when you're reaching out to
2:54
Speaker 1: folks who are in your community or used to be
2:56
Speaker 1: in your community. You know, personal connection is the thing
2:59
Speaker 1: that makes life wonderful. So reach out to somebody you
3:02
Speaker 1: haven't talked to in a while and make that connection again.
3:05
Speaker 2: That is a way deeper answer than I was expecting. Like, so,
3:09
Speaker 2: my resolutions aren't usually like think about how you could
3:12
Speaker 2: improve your personality and do something better, or reach out
3:15
Speaker 2: to an old friend. It's like, I want to get
3:16
Speaker 2: done this five resolution. I want two little baby ducks.
3:22
Speaker 1: That's not a resolution, that's a wish list.
3:26
Speaker 2: I resolved to build their habitat and make time in
3:29
Speaker 2: my life for you know, a happy, relaxing pens.
3:32
Speaker 1: I'm going to improve myself by adding ducks.
3:36
Speaker 2: Hell, that will make me happy. That's a happiness improver.
3:40
Speaker 2: Getting baby ducks and renovating my kitchen. Those are my
3:42
Speaker 2: twenty twenty five I guess they're goals now instead of resolutions.
3:45
Speaker 2: Do you have a resolution you want to share, then
3:47
Speaker 2: or a goal.
3:48
Speaker 1: I do have a resolution for the year, and it's
3:50
Speaker 1: about the podcast and its response to an email I
3:53
Speaker 1: got on January first at eight am, where somebody wrote
3:57
Speaker 1: in and says Happy New Year. Unfortunately, I can't listen
4:01
Speaker 1: to the show anymore because of the perpetual giggling, which
4:06
Speaker 1: of course just made me giggle. And I thought to myself, man,
4:10
Speaker 1: who doesn't like a podcast with giggling in it? And
4:13
Speaker 1: so this year, I'm gonna lean into the giggling.
4:16
Speaker 2: I resolve to giggle with you a lot over we
4:19
Speaker 2: hypercharges and strong forces and all sorts of other things.
4:23
Speaker 2: We're gonna have a blest.
4:24
Speaker 1: But it made me wonder about giggling, because you know,
4:26
Speaker 1: I have a bit of a deeper voice, and I've
4:28
Speaker 1: always thought myself as more of a chuckler than a giggler.
4:31
Speaker 1: And so I don't know, what are your thoughts, where's
4:33
Speaker 1: the distinction between giggling and chuckling.
4:35
Speaker 2: After we record an episode, our editor does the editing,
4:38
Speaker 2: he sends it to us. We listened to it to
4:39
Speaker 2: make sure we didn't get anything wrong, and I was
4:41
Speaker 2: listening to my laugh and I was like, I've got
4:43
Speaker 2: a really like sort of obnoxious, dude ish kind of laugh,
4:48
Speaker 2: But I don't care. It's unique. I'm happy and that's
4:51
Speaker 2: all I care about.
4:52
Speaker 1: Your laugh is not obnoxious. It's expressive. You know, you
4:55
Speaker 1: are really showing us how funny you think something is.
4:59
Speaker 1: It's very it's very New Jersey also though it is.
5:02
Speaker 2: Yeah, yeah, well I was born in New Jersey and
5:04
Speaker 2: am proud of that. Yeah. I don't hold back it.
5:05
Speaker 2: So I don't feel like either one of us do
5:07
Speaker 2: what I would call giggling. But whatever, we're having fun
5:10
Speaker 2: and let's resolve to lean into it absolutely.
5:12
Speaker 1: And I think a key to understanding difficult concepts is
5:16
Speaker 1: to giggle a little bit, right. You can't just always
5:18
Speaker 1: go deep on these concepts. You got to lighten the
5:20
Speaker 1: mood a little bit. That's kind of our brand, right, Like,
5:23
Speaker 1: make a few mom jokes along the way, throwing a
5:26
Speaker 1: few dad ponds, keep it light as we go deep
5:29
Speaker 1: on the topics.
5:29
Speaker 2: A couple jokes about Urinus.
5:34
Speaker 1: So hey, if you're here to learn some deep concepts
5:36
Speaker 1: about the universe and you are allergic to giggling, you
5:39
Speaker 1: might have found the wrong podcast.
5:41
Speaker 2: Sorry, there's got to be something else out there for you.
5:46
Speaker 1: But we are going to go deep into topics, and
5:48
Speaker 1: especially today, we're going to dig into one of my
5:50
Speaker 1: favorite concepts in physics, not just because it tells you
5:53
Speaker 1: something about how the universe works, but it shows you
5:55
Speaker 1: the mechanics of how physics as a field struggles with
5:59
Speaker 1: try to grapple with something alien. How we start from
6:03
Speaker 1: intuitive concepts and we build this precarious scaffolding to help
6:06
Speaker 1: us understand something even weird or and translate it back
6:09
Speaker 1: into something we might be able to make sense of.
6:12
Speaker 2: And I'm super excited today because you sent me the
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Speaker 2: outline for this topic and there's a bunch of things
6:16
Speaker 2: when I was reading it through that made me think,
6:17
Speaker 2: oh gosh, I thought I knew the difference between like
6:20
Speaker 2: charge and force, but maybe I really don't. And I
6:24
Speaker 2: think a bunch of that's going to get cleared up today,
6:26
Speaker 2: and I'm glad that I'll be giggling along the way.
6:28
Speaker 2: And you know what's good for giggles.
6:29
Speaker 1: What's good for giggles, Kelly.
6:31
Speaker 2: The hilarious answers we get from our audience. I mean,
6:33
Speaker 2: we get lots of great, serious answers, but we also
6:35
Speaker 2: usually get some pretty funny ones when folks don't know
6:38
Speaker 2: what it is. So let's go ahead and giggle at
6:40
Speaker 2: lots of amazing answers.
6:41
Speaker 1: So today we're talking about electric charge and the weak fours,
6:44
Speaker 1: and specifically weak hypercharge. So I went out there to
6:48
Speaker 1: our volunteers and I asked them if they knew what
6:50
Speaker 1: weak hypercharge was. Think about it for yourself. Do you
6:54
Speaker 1: know what a weak hypercharge is? Here's what audience members
6:58
Speaker 1: had to say, All right, sort of.
7:00
Speaker 3: A permeter of property. It might even be a mathematical
7:03
Speaker 3: concept to describe the weak force. The week hypercharge is
7:07
Speaker 3: the value assigned to a particle participant.
7:10
Speaker 4: It's either some extortionate tax imposed by a cowardly government,
7:16
Speaker 4: or it's something associated with the weak field, which mirrors
7:20
Speaker 4: the electric charge in the electromagnetic field.
7:23
Speaker 1: Hypercharge combinds with isospin to somehow give a charge under
7:30
Speaker 1: the electro weak force.
7:32
Speaker 3: A charge state of the weak force.
7:34
Speaker 1: I have no idea weaknd hyper sounds like my childhood Nope,
7:40
Speaker 1: it's related to.
7:42
Speaker 3: Quantum physics.
7:43
Speaker 1: I have no idea what the hypercharge part would be
7:46
Speaker 1: and how I would tie it to the weak force.
7:48
Speaker 1: The weak hypercharge is the charge of the weak force.
7:51
Speaker 3: Encapsulates a particles in some particular force along with its
7:57
Speaker 3: spin and maybe mother information. I don't know what the
8:01
Speaker 3: weak Harper charge is, but it sounds like there's a
8:03
Speaker 3: stronger version of it somewhere.
8:05
Speaker 1: Well, that's pretty easy. That's when you try to do
8:07
Speaker 1: a hypercharge CAU and it's so weak it doesn't really.
8:11
Speaker 3: Charge a single factor that enumerates both like a particle's
8:15
Speaker 3: electric charge. It's weak charge and I don't know it's magnetic.
8:22
Speaker 2: All right, So I chuckled at sounds like my childhood
8:27
Speaker 2: and the one about attacks put on by a cowardly
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Speaker 2: governmental agency. So thank you everyone for the giggles and
8:33
Speaker 2: the serious answers as well.
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Speaker 1: Yes, and some of these serious answers are right on
8:37
Speaker 1: the money, so I was really impressed.
8:39
Speaker 2: Well, I'm not surprised.
8:40
Speaker 1: We have a brilliant and good looking too. Wow, that's right.
8:45
Speaker 2: That's what I think. It's called the halo effect. When
8:47
Speaker 2: somebody is good at one thing and then you just
8:48
Speaker 2: assume they're good at everything else. They're probably also like
8:51
Speaker 2: fits and fast.
8:52
Speaker 1: They smell good.
8:53
Speaker 2: Yeah, way to go, guys. All right, so let's start
8:57
Speaker 2: like super back at the beginning. Let's make sure we're
9:01
Speaker 2: all on the same page. With just even what is charge?
9:03
Speaker 1: Yeah? Oh wow, I'm supposed to answer that question. Whate'relie physicists?
9:08
Speaker 2: Yea, what is charge?
9:10
Speaker 1: So yeah, let's begin with charge, and let's just talk
9:12
Speaker 1: about charge descriptively first before we get into the philosophy
9:15
Speaker 1: of like what is it? Man? We know that electrons
9:19
Speaker 1: have negative charge, Protons have positive charge, right, electrons or
9:23
Speaker 1: minus one protons or plus one. So already we know
9:27
Speaker 1: something about charge, which is that it's associated with the
9:30
Speaker 1: number line. Right, it's a number. It can be zero,
9:33
Speaker 1: it can be positive, it can be negative, right, It
9:36
Speaker 1: also can be fractional. Quarks have two thirds of a
9:41
Speaker 1: charge or minus one third of a charge, so it's
9:44
Speaker 1: not an integer, right, So it's associated with the real
9:46
Speaker 1: number line. We don't know if they're rational or irrational charges.
9:51
Speaker 1: We've only ever seen fractional charges. But this tells us
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Speaker 1: something that charge lies along this spectrum. It's important to
9:57
Speaker 1: keep that in mind because later on, when we get
9:59
Speaker 1: to the week four the strong force, that's no longer true.
10:02
Speaker 1: But let's stay on the safe ground of electricity. Particles
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Speaker 1: have this thing we call charge. It can be positive,
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Speaker 1: it can be negative, and there are mirrored versions of
10:10
Speaker 1: it like there's the electron that has negative one charge,
10:13
Speaker 1: and then there's another particle, the anti particle of the electron,
10:17
Speaker 1: which is a version of it with positive charge. We
10:20
Speaker 1: call that the positron. And every particle we've observed that
10:24
Speaker 1: has a charge, there's also a partner particle that has
10:27
Speaker 1: the opposite charge. The anti matter version of it has
10:31
Speaker 1: the opposite charge. So a cork might have one third charge,
10:34
Speaker 1: but the anti cork would have minus one third.
10:37
Speaker 2: For example, I'm thinking of like a number line, and
10:40
Speaker 2: we've got electrons with negative one and we've got protons
10:43
Speaker 2: with one. Are the magnitude of those charges the same
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Speaker 2: in the different directions? Even though electrons are smaller and
10:49
Speaker 2: protons are bigger, they still have opposite charges.
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Speaker 1: Yes, And when to put your finger on one of
10:55
Speaker 1: the deepest mysteries in physics right there. Because electrons and
10:59
Speaker 1: protons have opposite sign charges and exactly the same magnitude.
11:03
Speaker 1: It's like electrons are minus one point zeros or zeros
11:06
Speaker 1: z z is their infinite zeros and protons are plus
11:09
Speaker 1: one point zero zero. And how do we know they
11:13
Speaker 1: match exactly? Well, if they didn't match, you couldn't have
11:16
Speaker 1: neutral atoms. Right. You use a proton and an electron
11:19
Speaker 1: to make hydrogen, and then it's neutral, and it's crucial
11:23
Speaker 1: that hydrogen is neutral, right, Like hydrogen gas clouds are
11:27
Speaker 1: what forms most of the universe and the dynamics of
11:30
Speaker 1: that and the reason they gravity can pull them together
11:32
Speaker 1: to form stars is because it's neutral. Electricity, which is
11:35
Speaker 1: much more powerful than gravity, has been literally neutralized because
11:40
Speaker 1: these things cancel each other out. But as you say,
11:42
Speaker 1: the electron is much smaller than the proton. The electron is,
11:46
Speaker 1: we think fundamental, made of nothing but electron. The proton
11:50
Speaker 1: is made of three quarks. Two of them have two
11:52
Speaker 1: thirds charge, one of them has minus one third charge,
11:56
Speaker 1: which add up to plus one. Why is that? Why
12:00
Speaker 1: does the electron exactly balance this combination of quarks. Why
12:03
Speaker 1: isn't it like off by a little bit, Because in
12:06
Speaker 1: our theory those are just two different numbers, like there
12:10
Speaker 1: are parameters in our theories, knobs that you could change,
12:13
Speaker 1: and we think still have a valid universe, but a
12:16
Speaker 1: very different universe. We don't know why these two knobs
12:19
Speaker 1: happen to be set in exactly the way, so that
12:23
Speaker 1: the charge of the proton and the charge of the
12:25
Speaker 1: electron balance. It's like if I asked you to pick
12:28
Speaker 1: two random numbers between zero and a zillion and you
12:32
Speaker 1: picked the same number twice, or the number and its opposite, Like,
12:36
Speaker 1: what are the chances of that? So it's a screaming
12:39
Speaker 1: clue that there's a deep connection between the quarks and
12:42
Speaker 1: the electrons, but we don't know what it is.
12:45
Speaker 2: Okay, So a positron is an electron with a positive charge,
12:50
Speaker 2: and that positive charge is that positive charge now plus one,
12:54
Speaker 2: like the same quantity of charges a proton. Yes, you're
12:57
Speaker 2: shaking your head exactly, but it's not done with that's right, right.
13:01
Speaker 1: Yeah, So an electron doesn't switch its charge to become
13:04
Speaker 1: a positron. The universe can do two things. The universe
13:08
Speaker 1: can make electrons. The universe can also make positrons. And remember,
13:12
Speaker 1: electrons are ripples in a field, right the way like
13:15
Speaker 1: photons are ripple in the electromagnetic field. Electrons are also
13:19
Speaker 1: ripples in a field. They're ripples in the electron field.
13:22
Speaker 1: So we have two different fields that sound very similar.
13:25
Speaker 1: Bad naming becausists the electron field and the electromagnetic field.
13:30
Speaker 1: Ripples in the electron field are called electrons. Or it
13:33
Speaker 1: turns out that same field, not a different field. The
13:35
Speaker 1: same field can ripple in another way, and that way
13:39
Speaker 1: is a positron. So the electron field can ripple to
13:42
Speaker 1: make electrons, or can ripple slightly differently to make positrons.
13:47
Speaker 1: And this is something to Rack noticed years and years
13:49
Speaker 1: and years ago when he was looking at the math
13:51
Speaker 1: for electrons in field theory. He was like, hmm, if
13:54
Speaker 1: the universe can do this, why can't it also do that?
13:57
Speaker 1: In fact, I predict that it does. Then a couple
13:59
Speaker 1: of years later, boom, we found positrons. So you're right,
14:02
Speaker 1: positrons have the same electric charge as protons, but they're
14:06
Speaker 1: fundamentally very different. Positrons, we think, are fundamental particles ripples
14:10
Speaker 1: in the electron field that are different from the way
14:13
Speaker 1: electrons make that field ripple, and protons are a combination
14:17
Speaker 1: of three quarks, each of which is a ripple in
14:20
Speaker 1: its own field.
14:21
Speaker 2: Okay, all right, so this is.
14:23
Speaker 1: All descriptive, right, we're talking about what we've seen in
14:25
Speaker 1: the universe. We've seen this charge, we've seen that charge,
14:28
Speaker 1: and explaining in terms of fields makes us wonder like, well,
14:31
Speaker 1: what is this thing anyway? Like, why is it that
14:35
Speaker 1: some fields have charge, Like the electron field when it ripples,
14:38
Speaker 1: it has a charged particle, but when the photon field ripples,
14:42
Speaker 1: it doesn't have a charge, Like photons aren't neutral, right,
14:45
Speaker 1: So makes us wonder like what is charge anyway? Fundamentally?
14:50
Speaker 2: Yeah, go on, what's the answer?
14:52
Speaker 1: I was curious because I was like, is that just me?
14:56
Speaker 1: Like interested in philosophy and physics? Is a biologist like, well,
14:59
Speaker 1: we just grind it and we've given it a name.
15:01
Speaker 1: So let's move on.
15:03
Speaker 2: No, no, I following you. Let's go down the rabbit hole.
15:05
Speaker 2: Let's go one more level of why.
15:07
Speaker 1: And so we don't fundamentally know what charge is, but
15:10
Speaker 1: we have a bunch of interesting clues. And when I
15:13
Speaker 1: was growing up thinking and learning about charge, I used
15:15
Speaker 1: to think about charge as a property of a particle
15:19
Speaker 1: that could be like removed from it, you know, or
15:22
Speaker 1: it's like a description of how the particle is. You know,
15:25
Speaker 1: Like if you paint something red, Okay, now it's red,
15:27
Speaker 1: but you could also paint it blue and it's still
15:29
Speaker 1: the same thing. Right, Like you take an apple and
15:31
Speaker 1: it's red, you paint a blue. It's blue now, but
15:33
Speaker 1: it's still an apple, right? Or is it a fundamental
15:37
Speaker 1: part of the thing that helps define what it is.
15:39
Speaker 1: Is it something that you can take off of it,
15:41
Speaker 1: like you can peel an apple and then you still
15:43
Speaker 1: have an apple, right even though it's peeled. Can you
15:46
Speaker 1: take an electron and remove the charge from it and
15:49
Speaker 1: have like an peeled electron an uncharged electron, you know?
15:54
Speaker 1: Or is the charge fundamentally part of the electron? This
15:57
Speaker 1: is something I was always wondering about as I was
15:59
Speaker 1: learning about particle physics as a kid, and it's not
16:03
Speaker 1: something we have a solid answer for, but thinking about
16:05
Speaker 1: it in terms of fields helps. And so let's go
16:08
Speaker 1: back to thinking about particles in terms of ripples of fields,
16:12
Speaker 1: and I'll show you the role the charge plays in
16:13
Speaker 1: the field picture and it gives you a very different
16:16
Speaker 1: feel for what charge is fundamentally.
16:19
Speaker 2: My first thought was, Okay, is charge going to be
16:21
Speaker 2: just like an arbitrary thing that humans use in our
16:24
Speaker 2: definition for an electron, like charge in mass or is
16:27
Speaker 2: it going to be like do you use the example
16:29
Speaker 2: of painting it red or blue? And that doesn't change
16:32
Speaker 2: anything fundamental about it. But I think the fact that
16:34
Speaker 2: when you change the charge and you get like a positron,
16:37
Speaker 2: but they annihilate each other. They're behaving totally different, and
16:41
Speaker 2: so that feels different than just painting it red or blue.
16:44
Speaker 2: But okay, now let's talk about fields and see if
16:46
Speaker 2: we can dig into that.
16:47
Speaker 1: Deeper, because the field's picture of physics is going to
16:50
Speaker 1: tell us that charge is not a property of particles.
16:52
Speaker 1: It's actually a relationship between fields.
16:56
Speaker 2: I should have seen that coming. The field's always throw
16:59
Speaker 2: me off.
17:00
Speaker 1: So remember in the field picture, we still have particles.
17:02
Speaker 1: There are things we call particles. We have a different
17:05
Speaker 1: mental image for what they are. They're not little bits
17:07
Speaker 1: of stuff. There are ripples in these fields, and these
17:09
Speaker 1: fields fill the universe, and sometimes these fields can interact
17:13
Speaker 1: with each other. So now let's talk about forces. What
17:16
Speaker 1: happens to an electron when it's flying through space and
17:19
Speaker 1: it encounters an electric field, Well, it accelerates, either it
17:23
Speaker 1: slows it down or it speeds it up, but it
17:25
Speaker 1: changes its velocity. That's what an electric field is. That's
17:28
Speaker 1: what electric field does, right, And that means that there's
17:31
Speaker 1: a force on it. You accelerate something, you have to
17:33
Speaker 1: put a force on it. That's f equals ma A.
17:36
Speaker 1: But a neutral particle like a neutrino flying through the
17:38
Speaker 1: same electric field totally ignores it. Right, it will fly
17:42
Speaker 1: right through. It has no charge, and it ignores the
17:45
Speaker 1: electric field. Yeah, it's there, but it doesn't interact with
17:48
Speaker 1: it. It doesn't matter to It does not accelerate the neutrino.
17:51
Speaker 1: So you shoot an electron to an electric field, it accelerates.
17:54
Speaker 1: You shoot a neutral particle through electric field, nothing happens.
17:58
Speaker 2: So electric fields exert force on electrons, but electric fields
18:02
Speaker 2: don't exert force on neutrons exactly.
18:05
Speaker 1: Electric fields exert force on any particles with charge.
18:09
Speaker 2: Okay.
18:09
Speaker 1: And you might think, okay, well that's a useful way
18:11
Speaker 1: to describe what an electric field does. It's actually a
18:14
Speaker 1: description of what charge is. Charge is a label we
18:18
Speaker 1: put on particles that are accelerated by electric fields.
18:23
Speaker 2: Okay, So charge is the ability to be sped up
18:25
Speaker 2: or slowed down. Can you get slowed down by an
18:27
Speaker 2: electric field too?
18:28
Speaker 1: Yeah? Absolutely, you can get slowed down. Yeah, if you
18:30
Speaker 1: flip the direction of it. So charge is a label
18:33
Speaker 1: we put on it. Like let's say I give you
18:35
Speaker 1: an electric field and they give you a bunch of particles.
18:37
Speaker 1: I don't tell you anything about them. You throw them
18:39
Speaker 1: all into an electric field. Some of them slow down,
18:42
Speaker 1: some of them don't. The ones that slow down, you say, oh,
18:45
Speaker 1: this notices the electric field. I'm gonna put a label
18:48
Speaker 1: on that one. This notices the electric field in the
18:50
Speaker 1: opposite direction. I'm gonna put the negative label on that one.
18:53
Speaker 1: This one, it ignores the electric field. I'm putting a
18:55
Speaker 1: zero on that one. All right, So charge is a
18:59
Speaker 1: label we put on on particles that sense electric fields.
19:02
Speaker 1: So now let's go back to the fields. Picture what's
19:04
Speaker 1: happening there. The electron is flying through space. It's a
19:07
Speaker 1: ripple in the electron field. Now, an encounter is an
19:10
Speaker 1: electric field, which is energy in the electromagnetic field. What
19:14
Speaker 1: happens is those two fields are coupling with each other.
19:17
Speaker 1: Energy is going from the electromagnetic field to the electron field. Right,
19:22
Speaker 1: it's accelerating the electron or it's decelerating whichever, but energy
19:26
Speaker 1: is passing. These two fields are coupling together. So instead
19:29
Speaker 1: of just having like one field slashing through space doing
19:32
Speaker 1: its own thing and another field slashing through space doing
19:35
Speaker 1: its own thing, think of them as like tied together. Right,
19:38
Speaker 1: there's a connection between them. It's like having two guitar strings.
19:42
Speaker 1: But now you have like a rubber band connecting them.
19:44
Speaker 1: So when one oscillates, the other one's gonna oscillate. Also,
19:48
Speaker 1: that's what charge is. Charge is a coupling between two
19:52
Speaker 1: fields for two different fundamental particles. So when the electron
19:57
Speaker 1: moves through space, it makes ripples in the electromagnetic field,
20:00
Speaker 1: and if there's a field there, it pushes on the electron.
20:03
Speaker 1: It slashes back and forth between electrons and the electromagnetic field,
20:07
Speaker 1: and charge tells us how that works. If you have
20:10
Speaker 1: a zero, then there's no coupling. If you have a one,
20:14
Speaker 1: then they are coupled. If you have a mindus one,
20:16
Speaker 1: you couple the opposite direction.
20:18
Speaker 2: Okay, all right, so first we're talking about strings, but
20:22
Speaker 2: it has nothing to do with string theory.
20:23
Speaker 1: Now we talk about strings because strings follow the wave equation,
20:27
Speaker 1: and so do the fields. The wave equation is everywhere.
20:29
Speaker 2: Okay, great, perfect. When we're talking about electron fields, we're
20:32
Speaker 2: talking about a bunch of electrons acting together. When we
20:36
Speaker 2: talk about electric fields, what is an electric field made of?
20:41
Speaker 1: Electric field is energy in the electromagnetic field, which is
20:45
Speaker 1: just another field in the universe, the same way the
20:47
Speaker 1: electron field is, and ripples in the field are photons, right,
20:52
Speaker 1: And so in the particle picture, you have electrons which
20:55
Speaker 1: shoot photons back and forth at each other, and that's
20:58
Speaker 1: how electrons repel each other. In the field's picture, you
21:01
Speaker 1: have ripples in the electron field which couple to the
21:04
Speaker 1: electromagnetic field and exchange energy that way.
21:08
Speaker 2: Okay, all right, I've caught up.
21:12
Speaker 1: So that's another way to think about charge. Charge. Here
21:15
Speaker 1: is a coupling between fields, right, it says this field
21:19
Speaker 1: connects to that field. This field connects to that field.
21:21
Speaker 1: These two fields don't connect at all. You put a zero.
21:24
Speaker 1: So instead of thinking of charge as something attributed to
21:27
Speaker 1: the particle, like the charge is the electrons, it's the
21:30
Speaker 1: relationship between the electron and the photon, or the electron
21:34
Speaker 1: field and the electromagnetic field. Are they connected? If so,
21:38
Speaker 1: put a one. Are they anti connected or do they
21:40
Speaker 1: ignore each other? So charge is how the fields couple.
21:44
Speaker 1: But it might not just be our description. It might
21:46
Speaker 1: be something important to the universe, because this is something
21:49
Speaker 1: the universe respects.
21:50
Speaker 2: And let's talk about RSPCT. After the break, we're back
22:13
Speaker 2: and we're talking about fields respecting each other. And where
22:17
Speaker 2: are we going with this?
22:19
Speaker 1: So you might think all right, Well, if we are
22:22
Speaker 1: just putting label on particles and it's just a relationship
22:25
Speaker 1: between fields, then these are just numbers. We made them
22:28
Speaker 1: up and they shouldn't have any special properties, right. But
22:32
Speaker 1: we know that charge has a really interesting special property,
22:35
Speaker 1: which is if you count up all the charges on
22:38
Speaker 1: all the particles in some system and then you let
22:41
Speaker 1: it do its thing. Let physics happened for a second,
22:44
Speaker 1: for a billion years whatever, and you come back and
22:46
Speaker 1: you count up all the charges again, and you might
22:48
Speaker 1: have you know, some of the electrons are gone, and
22:50
Speaker 1: now you've made protons or whatever. The particles have all changed,
22:53
Speaker 1: but the total number of charge has not changed. Charge
22:57
Speaker 1: is conserved in the universe. Every microphysical process and electron
23:02
Speaker 1: radiates a photon, or electron and positron annihilate. None of
23:06
Speaker 1: those violate electric charge. So you can do zillions of
23:09
Speaker 1: them and they don't add up to any violation of
23:11
Speaker 1: the electric charge. It's exactly conserved in the universe in
23:15
Speaker 1: a way, very very few things are exactly conserved. And
23:19
Speaker 1: for a physics that's like whoa, that's a big screaming
23:22
Speaker 1: clue that this might be an important thing to the universe,
23:25
Speaker 1: not just something we made up.
23:26
Speaker 2: So first of all, I'm finding myself wondering if there
23:29
Speaker 2: are more religious people in physics than there are in biology,
23:33
Speaker 2: because the more we get into this, it feels like
23:35
Speaker 2: something is making these things be symmetrical. Maybe you've hinted
23:39
Speaker 2: at the fact that the universe could not be otherwise,
23:42
Speaker 2: like when we were talking about the Big Bang and
23:44
Speaker 2: why are there electrons and we've lost the positrons and
23:49
Speaker 2: if we had equal numbers, everything would annihilate, there'd be nothing, right,
23:51
Speaker 2: So this is the only thing that could have arisen
23:54
Speaker 2: from the chaos, this symmetry. Is that the right way
23:57
Speaker 2: to be thinking about it? Or are we going in
23:59
Speaker 2: a different direction with this conversation.
24:01
Speaker 1: No, this is definitely the right part of your brain
24:03
Speaker 1: to be using here, because the whole juice of physics
24:07
Speaker 1: for me is like, let's reveal what the rules are,
24:11
Speaker 1: and then let's be odd that the rules are what
24:13
Speaker 1: they are and wonder if they could have been different, right,
24:17
Speaker 1: And my whole fantasy is that we will work hard
24:20
Speaker 1: to unify all of our understanding of the universe and
24:23
Speaker 1: be left with an equation and then it will be
24:26
Speaker 1: self evident. We're like, oh, yeah, I can see how
24:29
Speaker 1: this is the only way you could put a universe together.
24:31
Speaker 1: There is no other way to do it. Of course,
24:33
Speaker 1: it's got to be this way. The alternative is you
24:35
Speaker 1: get to some equation and you're like, huh, well, I mean,
24:38
Speaker 1: I see how that works. But you could have also
24:40
Speaker 1: made this a six or that a nine, Like why
24:42
Speaker 1: don't we live in that universe? Then you got a
24:44
Speaker 1: bunch of open questions. I don't know which is going
24:46
Speaker 1: to be the outcome. But along the way you have
24:50
Speaker 1: these moments where something emerges from the math that you
24:54
Speaker 1: didn't build in. Right. You didn't say I'm going to
24:56
Speaker 1: create this concept of charge and I'm going to insist
25:00
Speaker 1: that it's conserved. You just discover that, right. It's like
25:03
Speaker 1: it comes out in our experiments. We notice that charge
25:06
Speaker 1: is concerved, and then we also see it in the mathematics,
25:09
Speaker 1: and that seems like ooh. You are digging deep into
25:12
Speaker 1: the firmament of the universe and you clanged onto something
25:15
Speaker 1: hard and you're like, whoa, there's something here. Let's dig
25:18
Speaker 1: out this corner and see what this is. And it
25:20
Speaker 1: turns out there is a really interesting, very very deep
25:24
Speaker 1: realization here which I don't think has penetrated nearly enough
25:28
Speaker 1: into like the broader culture of what it means for
25:31
Speaker 1: something to be conserved. And it also connects to our
25:34
Speaker 1: goal of uplifting overlooked women who've contributed to science, because
25:38
Speaker 1: there's a very influential theorem from the mind of Emmy Nuther.
25:41
Speaker 1: She was a mathematician working around the same time as Einstein,
25:45
Speaker 1: and she just like dabbled occasionally in physics on her
25:48
Speaker 1: coffee breaks and came up with these incredible realizations, you know,
25:53
Speaker 1: just while gooving around before going back to real stuff
25:56
Speaker 1: like mathematics. And her theorem tells us that every time
26:00
Speaker 1: something is conserved in the universe, like electric charge or
26:04
Speaker 1: momentum for example, that's because there's a symmetry in the universe,
26:09
Speaker 1: there's something the universe respects, and so for momentum, it's
26:12
Speaker 1: very straightforward. We have momentum conservation in the universe because
26:16
Speaker 1: the universe doesn't care where something happens. The rules are
26:20
Speaker 1: the same everywhere. So you set up some physics experiment,
26:23
Speaker 1: you do it, you get an answer. If you could
26:26
Speaker 1: set it up ten meters to the right or ten
26:28
Speaker 1: thousand meters to the left, it shouldn't matter. The rules
26:30
Speaker 1: of the universe should be the same no matter where
26:32
Speaker 1: you are. There's no like absolute origin to the universe.
26:36
Speaker 1: You can't tell where you are in the universe. That
26:39
Speaker 1: makes sense, right, there's a symmetry there. That symmetry is
26:41
Speaker 1: why we have conservation of momentum. So notre connected these
26:45
Speaker 1: two ideas of symmetries and conservations. And we can do
26:48
Speaker 1: a whole other episode where I try to explain the
26:50
Speaker 1: mathematics of that and intuitive way, but today's episode just
26:53
Speaker 1: accept like every symmetry means a conservation, and now we
26:57
Speaker 1: have a conservation of something electric charge. So you're like, okay, well,
27:00
Speaker 1: you know they're telling me, what's the symmetry, right, what
27:03
Speaker 1: is the universe respecting here? And it turns out this
27:07
Speaker 1: is incredible that what is respecting is some weird internal
27:11
Speaker 1: angle that electrons have. Like when we say electrons are
27:16
Speaker 1: ripples in the field, that's true, but the mathematics gives
27:19
Speaker 1: us another degree of freedom, like electrons ripple through the field,
27:23
Speaker 1: but they also have an angle to them as they go,
27:25
Speaker 1: and this angle is mostly unimportant, like you can't measure
27:29
Speaker 1: it doesn't matter, you can't see it, and you could
27:31
Speaker 1: have a universe whether the electron angles are just like
27:33
Speaker 1: willy nilly. But if you insist that the universe respects
27:38
Speaker 1: this angle, that it's symmetric with respect to this angle,
27:42
Speaker 1: that you can change this weird internal electron angle and
27:45
Speaker 1: not change any of the physics the same way you
27:47
Speaker 1: can change the location or direction of an experiment and
27:51
Speaker 1: always get the same answer. The only way to do
27:53
Speaker 1: it if you have electrons in the universe and you
27:55
Speaker 1: want that symmetry preserve this weird internal angle is to
27:59
Speaker 1: have photon. You could only preserve this symmetry, this weird
28:03
Speaker 1: electron angle if you add photons to the universe. Electrons
28:06
Speaker 1: can't do it by themselves, so it's sort of like
28:10
Speaker 1: you derive the existence of photons. You're like, Okay, I
28:13
Speaker 1: have electrons and they have charge, and they have this
28:16
Speaker 1: weird angle inside them. If I insist for whatever reason
28:20
Speaker 1: that this weird internal electron angle has a symmetry, that
28:23
Speaker 1: the universe is the same if I spin that angle,
28:26
Speaker 1: then I got to add photons. Otherwise it doesn't work.
28:29
Speaker 1: You can like derive the existence of photons just from
28:32
Speaker 1: this requirement. And of course we know that photons are
28:35
Speaker 1: what do the thing that charges do right, they're there
28:37
Speaker 1: to provide the forces. So there's this deep connection between
28:41
Speaker 1: charge and photons and this bizarre internal angle that electrons
28:46
Speaker 1: have and we don't quite understand it, but we know
28:49
Speaker 1: that for some reason, the universe really wants to be
28:52
Speaker 1: symmetric with respect to this internal angle that electrons have,
28:56
Speaker 1: and that's why we have charge conservation in the universe.
29:00
Speaker 1: And you have to have photons to make that whole
29:02
Speaker 1: thing work.
29:02
Speaker 2: All right. So first, when we were talking about symmetry,
29:04
Speaker 2: I was thinking that positrons where the symmetrical thing with electrons,
29:09
Speaker 2: and so that's a symmetrical thing with electrons, but there's
29:12
Speaker 2: another symmetrical thing with electrons, which is this angle. Absolutely,
29:16
Speaker 2: you said, we can't measure the angle, So how do
29:18
Speaker 2: we know this?
29:20
Speaker 1: You can't measure an electrons angle directly. It has to
29:22
Speaker 1: do with like what fraction of its wave function is
29:25
Speaker 1: real and what fraction is complex? And you can't measure
29:27
Speaker 1: complex properties of an electron. But it exists and affects
29:30
Speaker 1: how the wave function propagates, so we can make predictions
29:33
Speaker 1: based on it in a statistical way. So you're asking, like,
29:37
Speaker 1: how do we know this angle is real? Well, it's
29:40
Speaker 1: sort of like asking, how do we know the wave
29:41
Speaker 1: function is real? We can't see it directly, but it's
29:44
Speaker 1: an important part of our model. So yeah, it's a
29:47
Speaker 1: deep question in philosophy, like is this real? It's a
29:50
Speaker 1: necessary component of the model which predicts the outcome of experiments,
29:54
Speaker 1: since that makes it feel real ish. But is anything
29:58
Speaker 1: that's complex valued act? I don't know. I mean technically
30:02
Speaker 1: mathematicians are like, real numbers are real. Complex numbers are
30:04
Speaker 1: not real. But I think we mean real philosophically there
30:07
Speaker 1: So anyway, that's a long way of saying, yeah, we
30:09
Speaker 1: don't know.
30:10
Speaker 2: Okay, Yeah, I feel like fifty percent of the conversations
30:12
Speaker 2: you and I have gets down to what is real,
30:15
Speaker 2: what exists?
30:16
Speaker 1: So I don't know.
30:17
Speaker 2: So you could have symmetry with respect to charge and
30:19
Speaker 2: with respect to angle. Are there other features of electrons
30:23
Speaker 2: that have symmetries?
30:24
Speaker 1: Yeah? So there are lots of these pairings from Notther's theorem.
30:28
Speaker 1: You know. One of them is like where are you
30:30
Speaker 1: in the universe doesn't matter? That gives you conservation and momentum.
30:34
Speaker 1: There's also angles, like hey, what if you send your
30:37
Speaker 1: X axis this direction or that direction doesn't matter? No,
30:40
Speaker 1: the universe has no preferred angle that gives you angular
30:43
Speaker 1: momentum conservation. And there's also symmetries with respect to time,
30:47
Speaker 1: like due to the laws of physics change over time, we
30:50
Speaker 1: don't think, So that's where energy conservation comes from. So
30:54
Speaker 1: all the big conservation laws can be translated into symmetries
30:58
Speaker 1: or vice versa, and you can actually think of them
31:00
Speaker 1: as sort of two sides of the same coin. And
31:02
Speaker 1: all those I think are clues. They tell us like
31:04
Speaker 1: how the universe works, Like if energy is concerned, that
31:08
Speaker 1: means that the laws of physics don't change with time.
31:11
Speaker 1: That's kind of a big deal. And in fact, it
31:13
Speaker 1: turns out energy not exactly conserved in our universe because
31:17
Speaker 1: the laws of physics are changing slightly with time as
31:20
Speaker 1: the universe expands and dark energy is increasing, and that
31:24
Speaker 1: changes a factor that we conclude in the laws of physics.
31:27
Speaker 1: So that's a whole other rabbit hole. But this one
31:30
Speaker 1: is exactly conserved. The universe conserves electric charge exactly, which
31:34
Speaker 1: means this weird internal electron angle that seems bizarre and
31:39
Speaker 1: just sort of like abstract is important to the universe.
31:42
Speaker 1: The universe respects it. It's built in deep, deep to
31:46
Speaker 1: the mechanics of the universe. I feel like that's a clue,
31:49
Speaker 1: that's something hard we're clinging on in the firmament of physics.
31:52
Speaker 2: So protons and electrons have opposite charges of the same magnitude,
31:57
Speaker 2: but they don't have the same mass. Does that tell
32:00
Speaker 2: us something about mass not being conserved or am I
32:03
Speaker 2: clinging to a not relevant factor here?
32:06
Speaker 1: The mass of these particles is a totally separate topic,
32:08
Speaker 1: And you're right, mass is not conserved. Electrons and positrons
32:12
Speaker 1: do have the same mass because of the ripples in
32:15
Speaker 1: the same fundamental field. But yeah, mass is definitely not
32:18
Speaker 1: conserved in the universe. I mean we destroy mass all
32:21
Speaker 1: the time in the large Hadrunk glider unilate protons you
32:24
Speaker 1: use their mass to make new stuff that has lower
32:27
Speaker 1: mass and higher velocity. You also gain mass all the
32:30
Speaker 1: time from energy. You go out and feel the sun,
32:32
Speaker 1: the photons that your body absorbs, increase the internal energy
32:36
Speaker 1: of your molecules and gain mass. You charge your tesla,
32:39
Speaker 1: it gains mass. So yeah, mass is definitely not conserved
32:43
Speaker 1: in the universe. But this concept of charge turns out
32:47
Speaker 1: to be a little bit more general than even electric charge.
32:50
Speaker 1: We've talked about charge as a way that the photon
32:53
Speaker 1: the electric fields coupled to each other, right, but also
32:56
Speaker 1: somehow deeply connected to the universe. And that turns out
32:59
Speaker 1: to be the simplest way to thy think about it,
33:00
Speaker 1: because you have just like one kind of charge can
33:02
Speaker 1: be positive or negative, and just one field, the photon field,
33:06
Speaker 1: that it couples to. And you know, muans coupled to
33:08
Speaker 1: the photon field, and quarks couple to the photon field.
33:10
Speaker 1: Anything with electric charge couples to the photon field. But
33:14
Speaker 1: the other charges for the other forces that are mediated
33:17
Speaker 1: by other fields and particles turned out to be an generalization,
33:22
Speaker 1: a more complex version of the same basic idea thinking
33:25
Speaker 1: about how fields couple to each other.
33:29
Speaker 2: Okay, so how is that a more subtle point than
33:32
Speaker 2: what we had talked about before. So we had already
33:34
Speaker 2: talked about how protons have two two thirds quarks and
33:39
Speaker 2: then a negative one third quark or something. And so
33:43
Speaker 2: with what you just said, what did we learn that
33:45
Speaker 2: was different than what we had known before? Because I
33:47
Speaker 2: think I didn't catch it.
33:48
Speaker 1: No, we didn't learn anything new. I'm just now trying
33:51
Speaker 1: to set us up to think about the other forces.
33:53
Speaker 1: In terms of this framework. So we introduced this new
33:55
Speaker 1: way of thinking about the electric charge, like not as
33:58
Speaker 1: paints you put on some part and other particles, but
34:01
Speaker 1: as a relationship between fields. Right now, let's try to
34:04
Speaker 1: use that same sort of intellectual framework and think about
34:07
Speaker 1: the other forces, the other kinds of charges in the
34:11
Speaker 1: same way, because implicit there is the idea that forces
34:14
Speaker 1: and charges are linked. Right. Electric charges are how we
34:17
Speaker 1: used to label particles that feel forces in electric fields.
34:21
Speaker 1: There are other forces in the universe, and some particles
34:24
Speaker 1: ignore them. Some particles don't. So, for example, the strong
34:27
Speaker 1: force strongest force out there, electrons totally ignore it. Electrons
34:32
Speaker 1: that have electric charge have no strong charge. So if
34:36
Speaker 1: I'm going to give you a bunch of particles and
34:38
Speaker 1: you're going to throw them through a what we call
34:40
Speaker 1: a color field, that's the field for the strong nuclear force.
34:44
Speaker 1: Electrons fly right through, it doesn't matter. But if you
34:48
Speaker 1: throw a QRK through there all sorts of crazy interactions.
34:50
Speaker 1: Oh my gosh, it gets accelerated like crazy. So now
34:53
Speaker 1: we have another kind of label, right like, okay, well,
34:57
Speaker 1: every particle has a label for whether it ignores electric
34:59
Speaker 1: fiel fields or not. It also has a label for
35:02
Speaker 1: whether it ignores color fields fields from the strong force.
35:06
Speaker 1: But instead of thinking about as a label in the particle,
35:09
Speaker 1: think about it as a way those fields interact. So
35:12
Speaker 1: the electron field does not interact with the gluon field.
35:16
Speaker 1: That's the analogy in the strong nuclear force of the
35:20
Speaker 1: electromagnetic field. Right, we have these gluons, and so electrons
35:24
Speaker 1: just don't interact with gluon fields. You kind of intense
35:27
Speaker 1: buzzing energy in the gluon field. Electron field is not
35:30
Speaker 1: linked to it at all. They oscill it completely independently.
35:32
Speaker 1: But a quark field in that same region of space
35:35
Speaker 1: where the gluon fields a lot of energy, those are
35:37
Speaker 1: tied very strongly together, and so they buzz together.
35:41
Speaker 2: Okay, so we talked about charge as the direction of
35:45
Speaker 2: the response to the electromagnetic field. That's our baseline. And
35:49
Speaker 2: now when you move on to strong force, it's no
35:52
Speaker 2: longer really helpful to think of negative and positive because
35:55
Speaker 2: it's just like do they respond to these forces or not.
35:58
Speaker 1: You're right that we shouldn't think about strong nuclear charges
36:01
Speaker 1: as zero, positive or negative, but it's not truth that
36:04
Speaker 1: they're simpler. It's not just like a yes or no
36:06
Speaker 1: In fact, they're more complicated. There are three different axes
36:11
Speaker 1: along which you can have a color charge. So for
36:14
Speaker 1: electric forces it's just one axis, right, and you're the zero,
36:17
Speaker 1: positive or negative. For the strong force, there are three
36:20
Speaker 1: different ones and they call them red, green, and blue.
36:24
Speaker 1: And so for example, you can have a quirk that's
36:27
Speaker 1: green or an anti green cork, or you can have
36:29
Speaker 1: a red cork or an anti blue cork, and so
36:33
Speaker 1: it's more complicated than the electromagnetic field. It's a generalization
36:37
Speaker 1: of it. The fundamental ideas are the same, but instead
36:41
Speaker 1: of like a single number zero, negative one, whatever, you
36:44
Speaker 1: have like a vector, you have like three different numbers.
36:48
Speaker 1: You have a green, a red, and a blue charge,
36:50
Speaker 1: and if you're zero in all of those, that's what
36:53
Speaker 1: we call colorless or white. So, for example, the proton
36:57
Speaker 1: has quarks inside of it, and each of those quarks
37:00
Speaker 1: has a charge. But if you have a red, a green,
37:03
Speaker 1: and a blue, the math works out that they add
37:06
Speaker 1: up to zero, and.
37:08
Speaker 2: So electrons have a red, a green, and a blue.
37:10
Speaker 1: You mean protons, Well, I thought you said.
37:12
Speaker 2: Protons do respond to the force, but electrons don't.
37:14
Speaker 1: So quarks respond to the force. Quarks are charged right,
37:18
Speaker 1: But quarks can add up to neutralize themselves to have
37:22
Speaker 1: zero color charge, the same way that like an electron
37:24
Speaker 1: positron together have zero electric charge. Three quarks that make
37:29
Speaker 1: a proton have zero color charge. So if you have
37:32
Speaker 1: a red, a green, and a blue cork together, the
37:34
Speaker 1: math adds up that they add up to zero total charge,
37:37
Speaker 1: so they're not three totally independent directions in this weird way.
37:42
Speaker 1: So there's two different ways that you can have zero
37:45
Speaker 1: color charge. You can either have one red, one green,
37:47
Speaker 1: one blue, or you can have red and anti red.
37:51
Speaker 1: So for example, a quark and an antiquark can come
37:55
Speaker 1: together to make a colorless object, which is like a pion.
37:59
Speaker 1: All these particles we call masons are two quarks together
38:02
Speaker 1: in a colorless state. They have no strong charge total,
38:07
Speaker 1: same with a proton and a neutron. There's lots that
38:09
Speaker 1: you can make it with three quarks. You can also
38:11
Speaker 1: make it with six quarks for really crazy particles, but
38:15
Speaker 1: most of the stuff we see in the universe is
38:17
Speaker 1: either three quarks together colorless or two quarks together overall colorless.
38:22
Speaker 1: And there's not just one gluon field because there's so
38:26
Speaker 1: many different colors. You need eight different gluon fields, and
38:29
Speaker 1: the glue on fields each have two colors, so you
38:32
Speaker 1: could have like a red green gluon or a blue
38:34
Speaker 1: anti red gluon, and the math is very complicated, it's
38:39
Speaker 1: really crazy, but it's an analogy to the way we
38:42
Speaker 1: think about electric charge and electric forces and the interactions
38:47
Speaker 1: between the fields. So you have these eight gluon fields
38:49
Speaker 1: filling the universe with all their color, and they interact
38:52
Speaker 1: with quarks, but not with electrons.
38:55
Speaker 2: Okay, they interact with quarks, but at the level of
38:57
Speaker 2: a proton they usually cancel out full proton usually doesn't
39:01
Speaker 2: respond to the strong force, and electrons don't usually respond
39:04
Speaker 2: to the strong force.
39:05
Speaker 1: Yes, that's exactly right. And these quarks also have weird
39:10
Speaker 1: internal angles to them, and the universe likes to conserve those.
39:15
Speaker 1: It's more complicated than just conserving one number because a
39:18
Speaker 1: three dimensional color thing. But the universe can serves strong
39:21
Speaker 1: nuclear color, which means it's symmetric with respect to all
39:24
Speaker 1: those weird internal quark angles. So that's all. I'm still
39:27
Speaker 1: very similar to electromagnetism.
39:29
Speaker 2: All right, so I think I've followed all that. After
39:32
Speaker 2: the break, let's talk about the weak force. We're back,
39:51
Speaker 2: all right. So we've talked about charge and force as
39:55
Speaker 2: it relates to electromagnetic forces and the strong force, and
39:58
Speaker 2: so now let's let's get to the weak force. We're
40:01
Speaker 2: two thirds of the way through the episode. We're at
40:03
Speaker 2: the weak force of our goal of talking about the
40:05
Speaker 2: weak hyperforce. So tell me about the weak force, right, So.
40:08
Speaker 1: The weak force super fascinating because it touches everything in
40:12
Speaker 1: the universe. Like, there are some particles out there with
40:15
Speaker 1: zero electromagnetic charge, right, like neutrons or neutrinos. They ignore
40:19
Speaker 1: electric fields. There are particles out there with no strong charge. Right,
40:23
Speaker 1: Electrons ignore the strong force. There's nothing in the universe
40:27
Speaker 1: that ignores the weak force. Everything out there except maybe
40:30
Speaker 1: dark matter, which we haven't figured out yet. It might
40:32
Speaker 1: not be a particle. Da da da da feels the
40:35
Speaker 1: weak force. It's fascinating. It's like unavoidable, but it's also
40:39
Speaker 1: super duper feeble. Right, It's the weakest force out there
40:43
Speaker 1: except for gravity. Probably not a force anyway, but it's
40:46
Speaker 1: much weaker than electromagnetism and the strong force. But it's pervasive.
40:51
Speaker 2: Even neutrons are responding to the weak force.
40:53
Speaker 1: Yes, neutrons respond to the weak force. Protons respond to
40:56
Speaker 1: the weak force, neutrinos respond to the weak force. Absolutely yes,
41:00
Speaker 1: And we can think about the weak force in the
41:02
Speaker 1: same sort of framework as we thought about electromagnetism and
41:06
Speaker 1: generalize it in the way we did also for the
41:08
Speaker 1: strong force. So the weak force, like the strong force,
41:11
Speaker 1: doesn't just have one charge. It has multiple charges. Right,
41:15
Speaker 1: So remember electromagnetism, which seemed complicated at the time, was
41:18
Speaker 1: actually nice and simple because it was just a number. Right,
41:20
Speaker 1: It's like negative one plus two thirds, what's the big deal? Well,
41:24
Speaker 1: weak forces have two charges, and because they were discovered
41:27
Speaker 1: at different times and then like adapted from different theories historically,
41:31
Speaker 1: the names for the mer disaster. We don't just have
41:33
Speaker 1: like week charge one, week charge two or whatever, or
41:36
Speaker 1: even the strong force is like nice colors which unify it.
41:39
Speaker 1: So that's why we have two different charges and they're
41:41
Speaker 1: called weak isospin in weak hypercharge.
41:45
Speaker 2: I hate you, guys, it's.
41:47
Speaker 1: Terrible, and I hate the word weak hyper charge because
41:51
Speaker 1: to me, hyper suggests like it's strong, it's intense, it's powerful,
41:55
Speaker 1: it's overwhelming, but then it's weak, So you're like, what
41:57
Speaker 1: is it more powerful? Is what's powerful. I can't even tell. Well,
42:00
Speaker 1: it's like super big tiny something what And.
42:04
Speaker 2: I'm not sure I understand what isospin either.
42:06
Speaker 1: Means Oh, that's even worse.
42:08
Speaker 2: And the colors were throwing me too. I think you
42:10
Speaker 2: guys need to start back at the drawing board. But
42:12
Speaker 2: all right, all right, let's work with what we've got.
42:14
Speaker 1: Isospin comes from another theory which kind of failed and
42:18
Speaker 1: then was adapted later on. It was like, maybe this
42:22
Speaker 1: could be reused, Like this happens in physics all the time.
42:24
Speaker 1: Somebody studies something for like twenty years, it seems like
42:27
Speaker 1: it's going to work out in the universe, says no, thanks,
42:30
Speaker 1: that was a nice idea, but no, and then somebody
42:33
Speaker 1: else comes along, so well, maybe I could adapt that
42:36
Speaker 1: actually to answer this other question. That's what happened with
42:38
Speaker 1: string theory. String theory was originally an attempt to explain
42:41
Speaker 1: color forces and the strong nuclear force, and it failed.
42:44
Speaker 1: But then it turns out to explain much more deep things,
42:46
Speaker 1: so that can work sometimes. But you know, come up
42:49
Speaker 1: with a new name. Yeah, so the's two different charges,
42:52
Speaker 1: and every particle it now has two numbers. Right, you
42:56
Speaker 1: have your isospin number and your hypercharge number, and these
43:00
Speaker 1: numbers are a little weird, like isospin Electrons have minus
43:04
Speaker 1: a half and neutrinos have plus a half, and so muons,
43:08
Speaker 1: for example, of minus a half tows of minus a half,
43:11
Speaker 1: but all the neutrinos have plus a half. And hypercharge
43:14
Speaker 1: is just like another number, and electrons and neutrinos both
43:18
Speaker 1: have hypercharge minus one, whereas quarks have hypercharge plus a third.
43:23
Speaker 2: Could you have predicted what these charges would be once
43:28
Speaker 2: you knew about the weak force or these things where
43:30
Speaker 2: you had to measure it and then you were like, huh,
43:33
Speaker 2: negative a half, wouldn't I guess that? But now we
43:35
Speaker 2: know that's a feature of the universe, Like, can you
43:37
Speaker 2: predict these things or did you just measure them and
43:39
Speaker 2: then work with that?
43:40
Speaker 1: Yeah, great question. Electric charges we definitely just measured. Week
43:44
Speaker 1: charges are much harder to measure because the weak force
43:47
Speaker 1: is very weak, and these are numbers that we came
43:50
Speaker 1: up with later to explain particles we've already seen. Because
43:54
Speaker 1: there's a deep connection between the weak force and the
43:57
Speaker 1: electromagnetic force. These things are not totally separate. We've unified
44:02
Speaker 1: them into one theory called electro week and This is
44:06
Speaker 1: really interesting because it turns out that electromagnetism is just
44:09
Speaker 1: part of the weak force. So remember how the strong
44:12
Speaker 1: force had like a bunch of different gluon fields to
44:15
Speaker 1: handle all the complexity. There are four fields in the
44:19
Speaker 1: electroweak force, and one of them is the photon, and
44:22
Speaker 1: the other three are fields that we call the weak force,
44:26
Speaker 1: two W fields, and then the Z field. And the
44:29
Speaker 1: electric field is like the weird sibling in the electroweak
44:32
Speaker 1: force because it's so simple and well preserved. Like the
44:36
Speaker 1: universe preserves the electric charge and respects this weird symmetry.
44:41
Speaker 1: But more broadly, the weak charges are not conserved. So
44:44
Speaker 1: for example, isospin not conserved in the universe, hypercharge not
44:49
Speaker 1: conserved in the universe. The universe doesn't respect this symmetry.
44:53
Speaker 1: This is how Higgs made his discovery, because he saw
44:55
Speaker 1: that the weak force does not respect these things. His
44:58
Speaker 1: whole theory is in a contact we call electroweak symmetry.
45:01
Speaker 1: Breaking the weak force is kind of a big, sloppy mess.
45:05
Speaker 1: But electric charge turns out to be a weird combination
45:10
Speaker 1: of isospin and hypercharge. You have this big, messy weak
45:14
Speaker 1: force when nothing is conserved everything is very weak and
45:16
Speaker 1: flimsy in sloshing around. But if you look at it
45:19
Speaker 1: from just one angler, you take one slice of it,
45:21
Speaker 1: you say, oh, this is beautiful. This is the photon
45:24
Speaker 1: field on electromagnetism, and everything is perfectly concerned in this
45:28
Speaker 1: one weird slice of a larger, messy field. So it
45:31
Speaker 1: turns out electric charge is connected to weak hypercharge. It's
45:36
Speaker 1: like a combination of hypercharge and isospin together.
45:40
Speaker 2: Okay, so the weak force is actually measured in four
45:44
Speaker 2: different ways, one of which is the electromagnetic field, and
45:49
Speaker 2: that is conserved, yes, But the other three are a
45:53
Speaker 2: freaking mess. Yes, And we don't understand why, and we
45:56
Speaker 2: don't think that we are misunderstanding something. It's just actually
46:01
Speaker 2: not conserved, which maybe tells us something about what's important
46:04
Speaker 2: about the universe. Was the conservation for the strong force, Yes,
46:08
Speaker 2: conservation for the strong force. These three kinds of weak forces,
46:11
Speaker 2: you don't get conservation because.
46:13
Speaker 1: Of the Higgs. The Higgs and messes up those other fields.
46:16
Speaker 1: In fact, that's how Higgs knew the Higgs was there.
46:18
Speaker 1: He's like, oh, how do you mess up these three
46:20
Speaker 1: fields and not the photon. I'm gonna invent this thing
46:23
Speaker 1: to mess up those three fields and not mess up
46:26
Speaker 1: the photon. That's the Higgs boson, and that's how we
46:30
Speaker 1: knew that that was there, because the weak field is
46:32
Speaker 1: messed up in this weird particular way that preserves one
46:36
Speaker 1: corner of it. It's like if you have four siblings
46:39
Speaker 1: sharing a room and three of them are total Slavs,
46:42
Speaker 1: and somehow one of the siblings is like military corners
46:45
Speaker 1: on the bed, not a piece of dust on the floor,
46:48
Speaker 1: and you're like, all the way down to the edge
46:50
Speaker 1: and you measure it, like down to the micron. You
46:52
Speaker 1: have like an electron microscope, and you can't find a
46:54
Speaker 1: tiny little bit of dust that goes past that barrier,
46:57
Speaker 1: and you're like, wow, there's something going on here. That's
47:01
Speaker 1: what Higgs saw. He's like, all right, I'm going to
47:02
Speaker 1: invent this mechanism that messes up this part of the
47:05
Speaker 1: universe and not that part at all and doesn't even
47:07
Speaker 1: touch it.
47:08
Speaker 2: Okay, So Higgs has a field and a boson, right.
47:10
Speaker 1: Yes, that's right. The boson is a ripple in the field.
47:13
Speaker 1: So it's really just one concept.
47:15
Speaker 2: So we've got the Higgs field. What is the connection
47:18
Speaker 2: between the field and the weak force.
47:20
Speaker 1: So the Higgs field is another field, and it interacts
47:22
Speaker 1: with all of these fields, and it messes up the
47:25
Speaker 1: symmetry of the Week field. So if you didn't have
47:28
Speaker 1: the Higgs field, the weak charges would be perfectly conserved
47:31
Speaker 1: and the internal angles of the weak field would be
47:34
Speaker 1: crystal and beautiful, just like the other forces. But the
47:36
Speaker 1: Higgs field messes up the weak field. It breaks electroweek
47:40
Speaker 1: symmetry in a way that messes up those fields and
47:42
Speaker 1: breaks the conservation of weak hypercharge and weak isospin. So separately,
47:47
Speaker 1: these two things are not conserved, but this one combination
47:50
Speaker 1: of them is preserved by the Higgs boson.
47:53
Speaker 2: Okay, so the Higgs field messes up the three different
47:56
Speaker 2: measurements for the weak force. And remind me of what
47:59
Speaker 2: a weak hypercharge now that I've got that in my head.
48:01
Speaker 1: All right, and we hypercharge is one of these charges
48:04
Speaker 1: of the weak force. So the electro week force week
48:07
Speaker 1: plus electromagnetism has three charges. Electric charge, weak hypercharge, weak isospin.
48:14
Speaker 1: Electric charge is actually a special combination of those two.
48:17
Speaker 1: The Higgs field messes up the conservation of it. Generally, right,
48:22
Speaker 1: they're not separately conserved, but this combination of them. Electric
48:26
Speaker 1: charge is conserved in the universe. So we have this
48:29
Speaker 1: fields description of all the ripples of energy in the universe,
48:33
Speaker 1: and we know which fields talk to which other fields,
48:36
Speaker 1: and that's what we call charge. And fields can talk
48:39
Speaker 1: to each other in different ways. Right. They can talk
48:41
Speaker 1: to each other through the photon field, in which case
48:43
Speaker 1: they both have electric charge, because that's what it means
48:46
Speaker 1: to send energy through the photon field. It means you
48:48
Speaker 1: have an electric charge you're coupling to the photon field.
48:51
Speaker 1: Or they can talk to each other through weak fields
48:53
Speaker 1: because all particles have weak hypercharge or weak isospin. Or
48:57
Speaker 1: they can talk to each other through the gluon field
49:00
Speaker 1: if they couple to the gluon fields, and that's what
49:02
Speaker 1: it means to have color charge. So we hypercharge is
49:06
Speaker 1: an example how matterfields fields to describe electrons and muons
49:10
Speaker 1: and quarks and all this kind of other stuff can
49:12
Speaker 1: interact with each other through these force fields, through the
49:16
Speaker 1: electromagnetic field and the gluon fields and the W field
49:19
Speaker 1: and the Z field and all these other fields that
49:22
Speaker 1: help particles interact with each other. And so it's fascinating
49:26
Speaker 1: that electric charge is conserved and strong charge is concerned,
49:29
Speaker 1: but we hypercharge is not right. The universe mess that
49:32
Speaker 1: up created the Higgs boson gave it this weird energy.
49:36
Speaker 1: But I hope that this gives you like a different
49:37
Speaker 1: view of like what charge is. It's not just about electricity.
49:41
Speaker 1: It's not a label we put on particles. It's about
49:43
Speaker 1: how fields talk to each other. And a lot of
49:45
Speaker 1: particle physics is understanding how energy slashes back and forth
49:50
Speaker 1: between these fields. And like you can ask the philosophical
49:53
Speaker 1: questions like what is an electron anyway? And our description
49:57
Speaker 1: of electron isn't just a particle flying through space. It's
49:59
Speaker 1: a buzzing and a rippling in the electron field that's
50:02
Speaker 1: also constantly coupled to the photon field, and energy is
50:05
Speaker 1: slashing back and forth between them. And that's what we
50:07
Speaker 1: mean by the electron we measure in the lab. And
50:11
Speaker 1: when we talk about a cork, it's got a cloud
50:13
Speaker 1: of gluons around it, or you can think about it
50:15
Speaker 1: as a ripple in the quark field, constantly slashing energy
50:18
Speaker 1: back and forth via gluon fields. That's really what charges about.
50:22
Speaker 1: It's about coupling of the fields and the weak hypercharge
50:25
Speaker 1: is that a great example because it shows off how
50:27
Speaker 1: the universe can be beautiful and symmetric and crystalline, and
50:31
Speaker 1: then sometimes it can just be the messy sibling leaving
50:34
Speaker 1: dirty dishes under its bed.
50:36
Speaker 2: Yeah, a total disaster. Yeah. So I feel like I
50:39
Speaker 2: thought that I understood charge and force going in, and
50:42
Speaker 2: it's totally different. I'm thinking about it now in a
50:45
Speaker 2: totally different way than I had before, which is really exciting.
50:48
Speaker 2: One quick step back, isospin is also not conserved.
50:51
Speaker 1: Isospin is also not concerved?
50:53
Speaker 2: Yeah, and so did we decide that we wanted this
50:55
Speaker 2: episode to be about the weak hypercharge because it's a
50:58
Speaker 2: funny name. Why are we emphasizing that charge as opposed
51:02
Speaker 2: to talking about isospin? Yeah, and the weak hypercharge because
51:06
Speaker 2: they seem to be telling us the same thing. As
51:08
Speaker 2: far as I can tell.
51:08
Speaker 1: You're right, week isospin and week hypercharge are on the
51:10
Speaker 1: same footing. Two reasons why this episode started out about
51:14
Speaker 1: hypercharge and not isospin. One is it has the word
51:17
Speaker 1: charge in it, So I thought I would at least
51:19
Speaker 1: give the listeners a clue when we're asking them about it, Like, otherwise,
51:22
Speaker 1: what is this thing? It's just a bunch of words
51:24
Speaker 1: physicists invented. And also because at least one person wrote
51:28
Speaker 1: in and said, I was reading the Wikipedia page on
51:30
Speaker 1: week hypercharge and what is this? Can you explain it?
51:33
Speaker 1: So I thought, all right, let's try to dig into.
51:36
Speaker 2: This perfect Those are two great reasons. Okay, now I'm
51:39
Speaker 2: with you, and I'm never going to see the world
51:41
Speaker 2: the same way again.
51:42
Speaker 1: And for those of you who want to learn more,
51:44
Speaker 1: all the mathematics of these fields and how they interact
51:47
Speaker 1: is described with this beautiful piece of theory called group theory,
51:51
Speaker 1: which shows you how these things rotate and how energy
51:54
Speaker 1: flows between them. It's a great example also of how
51:57
Speaker 1: mathematicians will develop a new branch of mathasthematics just for fun.
52:02
Speaker 1: They're like, hey, this is cool. Let's create these rules
52:04
Speaker 1: and then just play games with them for one hundred years,
52:07
Speaker 1: and they totally did that. Then one hundred years later
52:09
Speaker 1: physicists are like, oh my gosh, these games you've been playing,
52:12
Speaker 1: just like you know, sipping tea and being nerds, turns
52:14
Speaker 1: out to be perfect description of this complex mathematics of
52:18
Speaker 1: these fields we discovered, thanks guys, and just plugged it
52:21
Speaker 1: right in. And now group theory is like at the
52:23
Speaker 1: heart of our understanding of the universe.
52:26
Speaker 2: Were the mathematicians just devastated when they found out their
52:29
Speaker 2: work was applied and then like, oh, I have.
52:32
Speaker 1: To move on and invent another irrelevant game.
52:35
Speaker 2: Yeah, oh, it must have been a bad day for
52:38
Speaker 2: the mathematicians.
52:39
Speaker 1: I think there are two kinds of mathematicians, those who
52:40
Speaker 1: are disappointed in, those who are excited yeah yeah, yeah,
52:43
Speaker 1: those who have a little bit of physicist in them,
52:45
Speaker 1: and those that don't. Yeah yeah, because in the end,
52:49
Speaker 1: you know, the dotted lines we draw between math and
52:52
Speaker 1: physics and philosophy, these are just the way humans like
52:55
Speaker 1: to categorize people, right as you always say, this a spectrum.
52:59
Speaker 2: Yep, agree, Nature and humanity don't like to be in categories.
53:02
Speaker 1: All right, Well, thank you for joining us for this
53:04
Speaker 1: tour along the spectrum of complexity of all the forces,
53:07
Speaker 1: from the crisp, beautiful nature of electromagnetism to the messiness
53:11
Speaker 1: of the week force. So I hope that helped you
53:13
Speaker 1: get a new view of how the universe worked. And
53:16
Speaker 1: I hope we giggled just the right amount.
53:20
Speaker 2: Fick everyone. Daniel and Kelly's Extraordinary Universe is produced by
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