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Does the weak force attract or repel? · Daniel and Kelly’s Extraordinary Universe

0:08
Speaker 1: Hey, Jorge, do the mysteries of physics pull you in
0:12
Speaker 1: or do they make you runaway screaming? You mean, does
0:17
Speaker 1: physics attract me or repel me? That's right, you know
0:21
Speaker 1: if you want to think about it physically. Now, are
0:23
Speaker 1: we talking about physics or physicists? No, the whole shebang.
0:26
Speaker 1: You can't separate the physics from the physicists. Well, you know,
0:30
Speaker 1: I kind of like the big questions that physics as
0:32
Speaker 1: they're pretty exciting, but you know, it's phys the math
0:35
Speaker 1: and all the jargon. It's kind of a little bit
0:37
Speaker 1: hard to put up with. So it's a little bit
0:39
Speaker 1: of a push an pole. That's right. Every time I
0:41
Speaker 1: think I'm free of physics, it just pulls me back in.
0:45
Speaker 1: We're like the mob. You're the al Pacina of physics,
0:49
Speaker 1: and you are the pun father. Now you're more like
0:51
Speaker 1: the dawn coreole is physics. Hi am Jorge, I'm your
1:10
Speaker 1: cartoonists and the creator of PhD comics. Hi, I'm Daniel.
1:13
Speaker 1: I'm a particle physicist and a professor U c Irvine.
1:16
Speaker 1: And I'm still laughing about that. Don coriole with joke.
1:20
Speaker 1: Do you need a break here? No? But I do
1:23
Speaker 1: love the idea of somebody who's like a master of physics,
1:28
Speaker 1: you know, like the godfather of physics. But you know,
1:30
Speaker 1: we just lost somebody who many people consider the godfather
1:34
Speaker 1: of the weak force and the standard model. Stephen Weinberg
1:37
Speaker 1: and Professor Ut Austin, who won the Nobel Prize forty
1:40
Speaker 1: years ago, just passed away last week. So rest in
1:43
Speaker 1: peace to one of the giants of the twentieth century.
1:46
Speaker 1: Oh man, rest in peace. Yeah. So who's gonna take
1:49
Speaker 1: the mantle of the godfather now of physics? I don't know,
1:53
Speaker 1: because the stakes are high, right, you gotta win the
1:55
Speaker 1: Oscar for the sequel also, and then not flubb it
1:58
Speaker 1: on the third moviee on the third a prize. You know,
2:01
Speaker 1: it's got to be as good as the rest. But
2:03
Speaker 1: welcome to our podcast Daniel and Jorge Explain the Universe,
2:05
Speaker 1: a production of Our Heart Radio in which we try
2:08
Speaker 1: to make you the godfather of everything in the universe.
2:11
Speaker 1: We try to give you an understanding of how things
2:14
Speaker 1: work at the very smallest scale. We share with you
2:17
Speaker 1: what humanity has accomplished in terms of understanding the true
2:21
Speaker 1: nature of reality around us, the context of our lives,
2:25
Speaker 1: the long cosmic stretch of history, the crazy, violent events
2:30
Speaker 1: that have led to our existence, and everything in between.
2:33
Speaker 1: We ask questions about the very nature of time and space,
2:37
Speaker 1: and we do our best to answer them. That's right,
2:40
Speaker 1: because it is a pretty wonderful universe, full of amazing
2:43
Speaker 1: and incredible forces and energies, and places to explore and
2:48
Speaker 1: particles to discover, full of intriguing mysteries and sometimes weak questions.
2:54
Speaker 1: That's right. It really is incredible to me how varied
2:57
Speaker 1: and complex and gorgeous and strange the university is. You know,
3:03
Speaker 1: it's filled with bananas and movies and all sorts of
3:06
Speaker 1: silly things. And then when you take it apart, you
3:08
Speaker 1: find that at its microscopic level, it's nature is fundamentally
3:11
Speaker 1: totally different, which means that everything we know about the
3:14
Speaker 1: universe is not fundamental. It's instead, it's emergent. It's just
3:18
Speaker 1: like an accident of how things come together. And so
3:21
Speaker 1: the real majesty of the universe, the real like nature
3:24
Speaker 1: of the reality around us, is embedded in how the
3:27
Speaker 1: basic bits are put together, and so the rules that
3:30
Speaker 1: govern how those bits come together and how they interact
3:33
Speaker 1: or how they don't interact, is really what leads to
3:36
Speaker 1: things like ice cream and movies and bananas, and so
3:40
Speaker 1: it's fascinating to me how the world exists at these
3:42
Speaker 1: different scales and we can somehow pull them apart and
3:45
Speaker 1: understand them at all different levels. Yeah, I guess that.
3:48
Speaker 1: You know, the universe is pretty majestic at like the
3:50
Speaker 1: gaxy level, at the nebula level, it's pretty amazing, And
3:53
Speaker 1: it's also pretty fascinating at like the smallest, tiniest levels
3:57
Speaker 1: that you can possibly get right at the quant level. Yeah,
4:00
Speaker 1: And that's sort of a philosophical question, like why do
4:03
Speaker 1: we find the universe majestic and beautiful? Could it have
4:06
Speaker 1: been that we like look at galaxies and we're like
4:08
Speaker 1: kind of an ugly smear. But instead, you know, we
4:11
Speaker 1: look at them, were like wow, maybe evolution filtered for
4:15
Speaker 1: optimists or our internal physicists, you know, somehow made to survive. Yeah,
4:19
Speaker 1: because we also find a lot of the Earth beautiful.
4:22
Speaker 1: You know, we see vistas, were like, wow, we're lucky
4:24
Speaker 1: you'll live here. Could we have evolved on a planet
4:27
Speaker 1: where we're like, man, this place is a dump. It
4:29
Speaker 1: makes me wonder sometimes, right, or maybe like there are
4:32
Speaker 1: aliens who grew up in a totally turned planet. Who think,
4:34
Speaker 1: are you know beautiful mountains and trees and rivers are
4:38
Speaker 1: are ugly or boring? Yeah? Exactly. The aliens who grew
4:42
Speaker 1: up in Irvine and they prefer Beiji. They don't like
4:44
Speaker 1: color or liveliness. Oh man, that would be terrible if
4:48
Speaker 1: we met aliens and they're like, Wow, your suburbs are nice,
4:51
Speaker 1: but these forests make it all like Irvine. Right where
4:56
Speaker 1: did the aliens come and they tear down everything beautiful
4:58
Speaker 1: and they just build subdivision. Well, then we should move
5:00
Speaker 1: to their planet because then their their planet must be gorgeous.
5:04
Speaker 1: That sounds good. But rolling back up to what we
5:06
Speaker 1: were talking about, I think it's amazing how many incredible
5:09
Speaker 1: things there are in our universe and how it all
5:11
Speaker 1: just comes out of how the little bits interact. You know,
5:14
Speaker 1: the nature of your body is mostly determined by the
5:17
Speaker 1: strength of the electromagnetic force. The structure of the atom
5:20
Speaker 1: is mostly due to a combination of the strong force
5:23
Speaker 1: and electromagnetism. The structure of the galaxy comes from the
5:27
Speaker 1: nature of gravity. It's really the forces that shape the
5:30
Speaker 1: very fabric of reality as we experience it. Yeah, the
5:33
Speaker 1: forces are pretty good, because without forces, the universe would
5:36
Speaker 1: be pretty boring, right, I mean, the forces in the
5:38
Speaker 1: universe are what makes things stick together and do things
5:41
Speaker 1: right and move, Otherwise it would be a pretty um
5:44
Speaker 1: static universe. Yeah, you could say they forced it to
5:46
Speaker 1: be interesting. It was a bit of a force joke there.
5:48
Speaker 1: Then don't force my hand or I'll make some more. Yeah.
5:51
Speaker 1: We like to talk about the giant things in the universe,
5:53
Speaker 1: but we also like to talk about the little things,
5:55
Speaker 1: like the forces that keep our particles together or repel
5:58
Speaker 1: them or or make them do interesting things. And so
6:01
Speaker 1: today we'll be talking about one specific question about one
6:05
Speaker 1: of the fundamental forces. That's right. And this is a
6:07
Speaker 1: super fun question for me because it came from a
6:09
Speaker 1: listener who attended one of my public office hours when
6:12
Speaker 1: I just hang out on Zoom and answer physics questions
6:15
Speaker 1: from all comers. And this one came from an organic
6:17
Speaker 1: chemistry professor who asked me a pretty tough question that
6:21
Speaker 1: I didn't know the answer to. Wow, was that scary?
6:24
Speaker 1: Did you freeze the panic? No, those public office hours
6:27
Speaker 1: are pretty low key, and I often get asked questions
6:29
Speaker 1: I don't know the answer to, and I just try
6:31
Speaker 1: to figure them out on the fly. Hoping that people
6:33
Speaker 1: appreciate seeing a physicist like make mistakes and back up
6:36
Speaker 1: and hopefully figure it out. All right, Well, let's get
6:39
Speaker 1: to the question that Daniel at his office hours. So
6:42
Speaker 1: today on the program, we'll be asking the question does
6:50
Speaker 1: the weak force attract or repel? Now, Daniel, is that
6:55
Speaker 1: repel or repel? How exciting is the week? The weak
6:58
Speaker 1: force likes to go climbing, elects to bouldering. I don't
7:01
Speaker 1: know if it likes to repel down cliffs. Also, it's
7:03
Speaker 1: too weak to do it. It just lays in bed
7:07
Speaker 1: and complains until somebody brings it lunch. Well, that's a
7:09
Speaker 1: pretty interesting question. Does the weak force attract or repel?
7:12
Speaker 1: I guess are there only two options? Can the force
7:15
Speaker 1: only attract or repel? Or can it do something else like,
7:18
Speaker 1: I don't know, push you sideways or this interest you?
7:21
Speaker 1: That's an awesome question, and no forces can do other
7:23
Speaker 1: things than just attract or repel. Will dig into it
7:26
Speaker 1: in the podcast. Some forces can do things like change
7:29
Speaker 1: the nature of a particle. You know, change you from
7:31
Speaker 1: an electron to a neutrino, for example, so you know
7:34
Speaker 1: you might end up in a different direction and be
7:36
Speaker 1: a different particle, so it's more complex than just getting
7:39
Speaker 1: pushed or pulled. And the force of magnetism can do
7:42
Speaker 1: things like turn you doesn't change your overall speed, but
7:45
Speaker 1: it bends your path. So there's all sorts of complicated,
7:48
Speaker 1: amazing things that forces can do. But I think the
7:50
Speaker 1: fundamental thing they do seems to be either pull things
7:53
Speaker 1: together and hold them tights so they can build up
7:55
Speaker 1: and make complex things like bananas and ice cream, or
7:58
Speaker 1: push things apart keep them from forming complex structure. And
8:02
Speaker 1: this is a pretty fundamental question because the weak force
8:05
Speaker 1: is one of the four fundamental forces. Like there are
8:08
Speaker 1: only four forces in the entire universe, right, that four
8:11
Speaker 1: forces that make everything work, and this is one of them. Yeah,
8:14
Speaker 1: although stein Weinbergley Nobel Prize Laurier we just talked about,
8:17
Speaker 1: he's the guy who brought together the weak force with electromagnetism.
8:21
Speaker 1: He showed that really it's one force, which we now
8:23
Speaker 1: call electro week. So depending on how you count, there
8:27
Speaker 1: either three fundamental forces or four fundamental forces. In the
8:30
Speaker 1: case where it's three, there's gravity, the strong force, and
8:34
Speaker 1: the electro weak force. In the case where there's four,
8:37
Speaker 1: you break up electro week into the weak force and
8:40
Speaker 1: electricity magnetism. All right, well, we'll get into that, but
8:43
Speaker 1: first we were wondering how many people out there knew
8:46
Speaker 1: whether the weak force attracts or repel or hadn't even
8:48
Speaker 1: thought about this question. So Daniel went out there into
8:51
Speaker 1: the internet to ask people does the weak force attract
8:54
Speaker 1: or repel? So thank you everybody out there in the
8:56
Speaker 1: Internet who was willing to play this simply physics game.
8:59
Speaker 1: And if you would like to be asked questions that
9:01
Speaker 1: stumped physics professor and hear your answers on the podcast,
9:04
Speaker 1: please write to us two questions at Daniel and Jorge
9:07
Speaker 1: dot com. Think about it for a second. What would
9:09
Speaker 1: you answer? Here's what people had to say. I can't
9:12
Speaker 1: remember exactly what the weak force is all about, so
9:15
Speaker 1: I'm going to say maybe neither or both. On this one.
9:20
Speaker 1: I'm gonna have to say, I'm gonna guess that the
9:22
Speaker 1: weak force repels. And I'm going to say that because
9:29
Speaker 1: things in the universe seemed to be, for the most
9:32
Speaker 1: part stuck together, and I have kind of thought that
9:36
Speaker 1: the weak force and the strong force are working against
9:40
Speaker 1: each other. So if everything is stuck together, I'm going
9:44
Speaker 1: to say that the strong force overpowers that weak force,
9:48
Speaker 1: and uh, that's why you know we are in clumps
9:52
Speaker 1: of atoms instead of just spread out everywhere as gas
9:56
Speaker 1: all the time. I guess I think the strong force
9:59
Speaker 1: attract so that maybe the weak force repels. I genuinely
10:04
Speaker 1: don't know that's the weak force repellent tract. I want
10:08
Speaker 1: to say maybe both. Although it holds party together, is
10:12
Speaker 1: what would the structures? I guess it would also have
10:16
Speaker 1: to retell stuff that it doesn't want to react with
10:20
Speaker 1: and allow in. I don't know. I feel like I
10:23
Speaker 1: should know, but I just don't know. I've actually never
10:26
Speaker 1: understood if the week fourth attractor repelled or they know?
10:30
Speaker 1: Is that the fourth profable for sometimes a productive the
10:33
Speaker 1: key like the bit of the kyform me from particles
10:37
Speaker 1: into order particles, So like electronics tretrino. If I remember, well,
10:44
Speaker 1: the gravitational force is the only one that attracts. Only
10:52
Speaker 1: the rest of them attract and repose. So the weak
10:57
Speaker 1: force attracts any repels. Not sure if it's the same
11:03
Speaker 1: like an electromagnetic force, but I know that it detracts
11:07
Speaker 1: any pills. I gotta say I was pretty relieved that
11:11
Speaker 1: these folks also didn't know the answer they had. Would
11:14
Speaker 1: you feel inadequate as a physicist? Yeah, I would have
11:17
Speaker 1: to give up my professorship. I would have lost it
11:19
Speaker 1: in physics combat. Oh man, I gotta get like a
11:22
Speaker 1: Nobel Price winner to be one of your respondents just
11:25
Speaker 1: to sabotage you. You gotta get a ringer in there,
11:28
Speaker 1: just to set me up. But so this surprising, and
11:31
Speaker 1: this question came from an organic chemistry professor. That's pretty cool.
11:35
Speaker 1: Are you going to take revenge now and go to
11:36
Speaker 1: his office hours and give him a really tough organic
11:39
Speaker 1: chemistry question. I don't even understand organic chemistry well enough
11:42
Speaker 1: to ask a question, not to mention find one that's tricky.
11:45
Speaker 1: But I totally respect this question because it's so simple.
11:48
Speaker 1: It's so basic. Right, It's like, well, we know forces
11:51
Speaker 1: push and pull, so what about the weak force? Where
11:54
Speaker 1: does it fit in? And it's such a simple and
11:56
Speaker 1: basic question, but one I had never thought of before
11:59
Speaker 1: because I did to think about the weak force only
12:01
Speaker 1: in terms of like particle interactions, like particles colliding and annihilating,
12:05
Speaker 1: because there doesn't really play a tactile role in our lives, right,
12:08
Speaker 1: you don't feel the weak force pushing against you or
12:11
Speaker 1: pulling things together, and so I never really thought about
12:14
Speaker 1: it in this context. It was really a fascinating question.
12:17
Speaker 1: You just like to break things. You don't worry about
12:19
Speaker 1: putting things together. It's kind of my job to break
12:23
Speaker 1: things at high speed. It's like the top gear of
12:25
Speaker 1: particle physics, and you get to survive most of the time.
12:28
Speaker 1: So that's good most of the time, exactly. Well, let's
12:31
Speaker 1: warm up to the answer here and maybe let's you know,
12:34
Speaker 1: start at the basics here, So let's talk about what
12:36
Speaker 1: is the weak force and what does it mean in
12:39
Speaker 1: general to attract or repel something to step us through. Then. Yeah,
12:43
Speaker 1: so we have a few ways that particles can interact
12:46
Speaker 1: with each other, and that's really what forces are. They
12:49
Speaker 1: are particles feeling each other. And when we first discovered
12:52
Speaker 1: that particles can do this, it was sort of a
12:55
Speaker 1: question of like, wait, how does this happen? How do
12:57
Speaker 1: particles like push and pull on each other with out
13:00
Speaker 1: actually touching, right? How they like feel each other? Two electrons,
13:04
Speaker 1: for example, can push against each other. It doesn't mean
13:07
Speaker 1: that the surfaces of the electrons have come into contact
13:10
Speaker 1: like little tiny balls, and the way they do this
13:13
Speaker 1: is with the forces between them, so that each one
13:15
Speaker 1: has a field, right, each electron has an electric field
13:18
Speaker 1: around it. Where the electric field really is is a
13:21
Speaker 1: way for the electron to apply a force to other things.
13:25
Speaker 1: And so that's for electricity, and this is a a similar
13:27
Speaker 1: field for magnetism. And electricity and magnetism were then shown
13:31
Speaker 1: to be actually two sides of the same coin. It
13:33
Speaker 1: made more sense to think about them together. Some phenomena
13:36
Speaker 1: seemed like electricity if you're at rest, and they seem
13:39
Speaker 1: like magnetism if you're moving, and so it's pretty clear
13:42
Speaker 1: that's really just sort of one thing that we were
13:45
Speaker 1: seeing two sides of. And the weak force is in
13:47
Speaker 1: the category of electromagnetism. It's a force that particles can
13:51
Speaker 1: use to operate on each other. And so it's a
13:54
Speaker 1: little weirder than the other forces because it's not something
13:57
Speaker 1: you experience day today because it's so weak. And the
14:01
Speaker 1: reason that it's so weak and so weird is that
14:03
Speaker 1: the particles that communicate those forces, the fields that it uses,
14:08
Speaker 1: have a lot of mass. They're very very heavy, and
14:11
Speaker 1: so they don't last for very long. They don't make
14:13
Speaker 1: it very far, and that mass really weakens their impact.
14:17
Speaker 1: So electromagnetism and the weak force are very closely related,
14:20
Speaker 1: but the big difference is that these particles that communicate
14:23
Speaker 1: the weak force are very heavy, and so they really
14:26
Speaker 1: weaken the force. So maybe let's step back a little
14:29
Speaker 1: bit here, because you just went through a lot there.
14:31
Speaker 1: So I think what most people are probably familiar with
14:34
Speaker 1: is the electromagnetic force. And we know that like you know,
14:37
Speaker 1: if I have two magnets, they repel, or two magnetic
14:39
Speaker 1: can attract each other and pushing pool and it's all
14:41
Speaker 1: because of the electromagnetic force, Right, That's the one that
14:44
Speaker 1: people are most familiar with. And people are i think
14:47
Speaker 1: also familiar with gravity, which kind of attracts things together.
14:50
Speaker 1: So that's where I think maybe people expect that all
14:54
Speaker 1: forces attract or repel. Yeah, and it's really interesting because
14:57
Speaker 1: electromagnetism can do both of those things. Electromagnetism can attract
15:02
Speaker 1: or repel with the same force. And that's because in electromagnetism,
15:06
Speaker 1: the force depends on the charge of the particle. Right,
15:09
Speaker 1: So every particle we add this label like a minus
15:12
Speaker 1: or a plus, right, and each one we call the
15:15
Speaker 1: electric charge, and there's two possible values. This plus and
15:18
Speaker 1: this minus. And if two particles have the same charge
15:21
Speaker 1: like plus plus, then they repel each other. They have
15:24
Speaker 1: opposite charges, they attract each other. It's important to understand though,
15:27
Speaker 1: that this charge we're talking about, what it means is
15:30
Speaker 1: that the particles feel the field like a particle that
15:33
Speaker 1: has no charge is a particle that ignores the electromagnetic field.
15:37
Speaker 1: A particle has a positive or negative charge is a
15:40
Speaker 1: particle that does feel the field. We discover that there
15:43
Speaker 1: are two these different kinds of charges, and if you
15:46
Speaker 1: combine them in one way, they repel, and if you
15:48
Speaker 1: combine them in another way, they attract. So that's a
15:51
Speaker 1: really fascinating thing about electromagnetism is that it can do both. Well,
15:55
Speaker 1: maybe us through through an example. So let's say have
15:57
Speaker 1: two electrons and they're like sitting close to each other, right,
16:01
Speaker 1: so they both have negative charge. And then you talked
16:04
Speaker 1: about there being a field and this force being going
16:06
Speaker 1: through the field. Can you step us through what's happening?
16:09
Speaker 1: Like if I have an electron here, an electron there,
16:11
Speaker 1: and then they're both the same charge, they're gonna push
16:15
Speaker 1: each other away, right, That's right, That's exactly what's gonna happen.
16:18
Speaker 1: So you have electron one and it's just hanging out,
16:20
Speaker 1: but it also fills the space around it with an
16:23
Speaker 1: electromagnetic field. And so now you put another particle in
16:26
Speaker 1: that field, a second electron, and it's going to feel
16:29
Speaker 1: that field. That field exists just to apply forces to
16:34
Speaker 1: other charged particles, and the direction of the force depends
16:38
Speaker 1: on the charge of the two particles, and why it happens,
16:41
Speaker 1: why there's a push or a pull depends on the
16:43
Speaker 1: potential energy of the field. Things like to basically roll
16:47
Speaker 1: downhill to low potential energy, and these fields, they have
16:50
Speaker 1: a potential energy which varies with distance, and the potential
16:53
Speaker 1: energy tends to be slanted, so the particles like roll
16:57
Speaker 1: down the potential towards each other. Then the force that
17:00
Speaker 1: tracks sort of like if you put two rocks in
17:02
Speaker 1: a valley, they would roll towards each other. The gravitational
17:06
Speaker 1: potential minimizes when they're closer, or if the shape of
17:10
Speaker 1: the potential energy is such that it minimizes when the
17:13
Speaker 1: particles are far apart, like you put two rocks on
17:16
Speaker 1: the top of a mountain that tend to roll away
17:18
Speaker 1: from each other, then the force will push the particles apart.
17:21
Speaker 1: And so when you have two charges, the shape of
17:25
Speaker 1: this potential, which determines whether it's pushing or pulling, depends
17:29
Speaker 1: on the charges of the particles. If the charges are
17:32
Speaker 1: the same, then they repel. The charges are opposite, then
17:35
Speaker 1: they attract. And it all has to do with the
17:37
Speaker 1: shape of this potential energy created by the field of
17:40
Speaker 1: one of the particles. Right. But maybe I think what
17:42
Speaker 1: might be confusing to some people is you mentioned it's
17:45
Speaker 1: like an electric field. Now is that the same as
17:47
Speaker 1: a quantum field? Right, because so the electrons are we
17:51
Speaker 1: know there's sort of like fluctuations in the quantum field
17:53
Speaker 1: of electrons. Are you saying there's like a separate field
17:57
Speaker 1: that's quantum or or is this more of a mathematical
18:00
Speaker 1: When you say field, that's the same field we've been
18:02
Speaker 1: talking about forever, the electromagnetic field. You can actually talk
18:05
Speaker 1: about electricity magnetism without quantum mechanics. It was developed before
18:09
Speaker 1: quantum mechanics. We have a classical theory of electricity and
18:12
Speaker 1: magnetism that explains how electrons pulling each other. That was
18:15
Speaker 1: just before we understood that this field was quantum. What
18:19
Speaker 1: that means is that it just can't have any arbitrary value,
18:22
Speaker 1: but it's like chopped up into discrete bits. It's like
18:25
Speaker 1: if you are eating a cake, it's like you have
18:26
Speaker 1: to have one piece, or two pieces, or three pieces.
18:29
Speaker 1: You can't just nable on the cake all day long.
18:31
Speaker 1: And so before quantum mechanics, we thought that these fields
18:33
Speaker 1: were classical fields. It could just have any value. And
18:36
Speaker 1: then we discovered that they have a minimum value and
18:38
Speaker 1: they have steps to them, So it is a quantum field.
18:41
Speaker 1: This is a quantum field we're talking about. And so
18:43
Speaker 1: ripples in this electromagnetic field are, for example, the photon,
18:47
Speaker 1: which is one quantum of the electromagnetic field. So that
18:50
Speaker 1: the electron is a ripple in the electromagnetic field, or
18:53
Speaker 1: it's a ripple in its own quantum field, but they're
18:56
Speaker 1: sitting in another field, which is the electromagnetic force field. Right.
19:00
Speaker 1: The electron is a ripple in the electron field, right,
19:04
Speaker 1: and it generates ripples in the electromagnetic field, which is
19:08
Speaker 1: the field of the photon. And that's because these two
19:11
Speaker 1: particles talk to each other, electrons and photons talk to
19:14
Speaker 1: each other. Or in the language of fields, you could
19:16
Speaker 1: say these two fields couple. You could have a universe
19:19
Speaker 1: in which you have a particle and then another field
19:22
Speaker 1: and they don't interact at all. Right, For example, like
19:25
Speaker 1: neutrinos are wiggles in the neutrino field, but they don't
19:28
Speaker 1: affect the electromagnetic field at all. They have no charge.
19:32
Speaker 1: And so electrons are wiggles in the electron field as
19:35
Speaker 1: a quantum field, but they also create wiggles in the
19:37
Speaker 1: electromagnetic field because they have charged as a charge that
19:41
Speaker 1: connects these two fields. Charges, Like how much these two
19:44
Speaker 1: fields are connected for that one particle. Yeah, And interestingly,
19:48
Speaker 1: for electromagnetism, there's assigned to it. There's two different kinds
19:51
Speaker 1: of charges, and that determines the shape of the potential
19:54
Speaker 1: from the field and whether they attract or repel. All right,
19:57
Speaker 1: let's field more questions about this main question of does
20:01
Speaker 1: the weak force attractor repel? And so let's get into
20:03
Speaker 1: the weak force itself when we come back from the break.
20:06
Speaker 1: But first let's take a quick break. All right, we're
20:21
Speaker 1: talking about the weak force and whether or not it's
20:24
Speaker 1: attractive or repulsive. I guess, Daniel, is that the same
20:27
Speaker 1: as asking whether it's hot or not? Is it appealing
20:30
Speaker 1: or not appealing? Well, I find it mysterious, which makes
20:34
Speaker 1: me want to know more. And so I think the
20:37
Speaker 1: weak force is definitely pretty hot, but it's pretty weak.
20:40
Speaker 1: It can't heat anything up, so it leaves the universe
20:43
Speaker 1: kind of cold. We were talking about the first electromagnetic
20:46
Speaker 1: force and how the force of it is actually the
20:49
Speaker 1: interaction of two particles in the electromagnetic field, and that
20:53
Speaker 1: happens when they exchange photons, and it's all because of
20:56
Speaker 1: the charge of the particles. But I guess you know,
20:59
Speaker 1: that's the way to look at things. But another way
21:01
Speaker 1: to look at it things might be the same way
21:03
Speaker 1: that we look at gravity, right Like gravity, we look
21:05
Speaker 1: at at it in a totally different way right now, Yeah,
21:08
Speaker 1: gravity actually is really interesting, and you can look at
21:11
Speaker 1: it using the same sort of set of concepts. You
21:14
Speaker 1: can say, like, well, what does gravity do? Gravity only attracts,
21:19
Speaker 1: and you can think about it like call the mass
21:21
Speaker 1: I'm an object to be like the version of electric
21:25
Speaker 1: charge for gravity. And because objects only have positive mass,
21:29
Speaker 1: you only have one kind of charge for gravity. So
21:32
Speaker 1: when we say charge, we mean like a more general concept,
21:35
Speaker 1: not just for electromagnetism, we mean like for any kind
21:39
Speaker 1: of force. Does the particle field that field, it feels
21:43
Speaker 1: the field if it has the right charge. And so
21:45
Speaker 1: for electromagnetism, you say, well, electric charge tells you whether
21:49
Speaker 1: it feels the force or not. For gravity, it's mass.
21:52
Speaker 1: Mass is the charge for gravity. And this is what
21:55
Speaker 1: sort of blew my mind when I realized this years ago.
21:58
Speaker 1: And it's also a friend from electromagnetism because in electromagnetism,
22:03
Speaker 1: if you have the same charge, like two electrons, they
22:06
Speaker 1: repel each other. But in gravity, if you have the
22:09
Speaker 1: same charge two objects with positive mass had the same
22:12
Speaker 1: charge they're both positive, then they attract each other rather
22:16
Speaker 1: than repel. I see. So there are two main forces
22:19
Speaker 1: that people are most familiar with, gravity and electromagnetism. One
22:22
Speaker 1: of them pushes in pools, that's electromagnetism, and gravity only
22:27
Speaker 1: pulls things together. So that's kind of weird, right, It
22:31
Speaker 1: is weird, and it makes me wonder, like, what would
22:34
Speaker 1: happen if we had negative mass? Right? If we had
22:37
Speaker 1: negative mass, with two negative masses attract each other with
22:41
Speaker 1: a positive and negative mass repel each other, that would
22:43
Speaker 1: be super weird and fun. Yeah, I think a lot
22:46
Speaker 1: of people would love to have negative mass. These days
22:50
Speaker 1: after the toy, staying at homes for so long, eating
22:53
Speaker 1: things out of the fridge. But just to summarize, so
22:55
Speaker 1: the electromagnetic force attracts and repels and gravity attracts, so
22:59
Speaker 1: not now the question is what does the weak force do?
23:01
Speaker 1: Does it also attract and repel or one of the two. Yeah,
23:04
Speaker 1: it's really fascinating and kind of complicated. So the weak
23:08
Speaker 1: force is kind of a big mess. It's not as
23:11
Speaker 1: simple as electromagnetism or gravity. And one reason is that
23:15
Speaker 1: has three particles that mediated. So electromagnetism has the photon
23:20
Speaker 1: is everything. For electromagnetism, Gravity we don't know. Maybe it
23:24
Speaker 1: has the graviton. We're not sure if it's quantized, but
23:27
Speaker 1: it's pretty straightforward from that perspective. The weak force has
23:30
Speaker 1: three of these things, has three separate particles or three
23:33
Speaker 1: separate fields that mediate its forces. You have the W plus,
23:37
Speaker 1: the W minus, and the Z So these are like
23:41
Speaker 1: three different weird heavy photons that communicate it. So it's
23:45
Speaker 1: much more complicated than any of the other forces. Interesting.
23:48
Speaker 1: So it's like when two particles that feel the weak
23:51
Speaker 1: force talk to each other, they do it through three
23:54
Speaker 1: different ways. You're saying like, there's three different particles that
23:57
Speaker 1: can communicate this force. Yeah, exactly, So the weak force
24:00
Speaker 1: can do sort of three different things and they're all
24:03
Speaker 1: part of the same force. I mean, you might imagine
24:06
Speaker 1: like a different history of science where we had discovered
24:08
Speaker 1: these different parts of the weak force separately and called
24:11
Speaker 1: them different things, and then some other version of Steve
24:13
Speaker 1: Weinberg had realized, oh, this makes more sense. We should
24:16
Speaker 1: click them all together. And so it's sort of like
24:18
Speaker 1: three forces fit together into like the ultimate transformer force,
24:23
Speaker 1: and that makes more sense. And then you know, you
24:24
Speaker 1: plug in the photon, you get all the beautiful symmetry
24:27
Speaker 1: of having those four particles altogether. But these three, the
24:30
Speaker 1: W plus, the W minus, and the Z, we call
24:32
Speaker 1: these together the weak force. Now, are those separate three
24:36
Speaker 1: different quantum fields or is it one quantum field but
24:39
Speaker 1: three different ways to kind of activate it or to
24:42
Speaker 1: wiggle it. There are three quantum fields. There's a fields
24:45
Speaker 1: for the W plus, for the de W minus, and
24:47
Speaker 1: for the Z. The amazing thing is that they work together.
24:49
Speaker 1: There's like symmetries that they respect, Like something can move
24:52
Speaker 1: from one to the other, but it conserves this number,
24:55
Speaker 1: which is like the charge for the weak force. So
24:58
Speaker 1: it's definitely clear that they are three re separate things,
25:00
Speaker 1: but they work together as part of a whole. Interesting. Yeah,
25:04
Speaker 1: I guess that question would be why not call it
25:05
Speaker 1: three different forces? You're saying it's like three quantum fields,
25:08
Speaker 1: but they're all depending on each other so that they
25:11
Speaker 1: actually act as one. Yeah, it's like, why don't you
25:13
Speaker 1: call the heads and the tails two different coins? Well,
25:16
Speaker 1: it makes much more sense to call it one thing, because,
25:19
Speaker 1: for example, a coin is either heads up or tails up.
25:23
Speaker 1: It's never both, right, And so the two are definitely
25:25
Speaker 1: connected their sinc they fit together. These three fields are
25:28
Speaker 1: the same way. They connect together into one thing, which
25:31
Speaker 1: is much more simple mathematically than any of the individual parts.
25:35
Speaker 1: All right, so the weak force talks through three different
25:38
Speaker 1: quantum fields, or three different particles W plus, W minus
25:43
Speaker 1: and the Z. Now is there the equivalent of a
25:45
Speaker 1: charge in the weak force, like we have electric charge
25:49
Speaker 1: or mass? There is, Yes, it's got its own kind
25:51
Speaker 1: of charge. Has a really weird name. The name for
25:55
Speaker 1: it is weak iso spin, And every particle that feels
25:59
Speaker 1: the weak force has a value for weak isospin, which
26:02
Speaker 1: is either up or down. So just like the electromagnetic
26:06
Speaker 1: force can push or pull on everything with an electric charge,
26:09
Speaker 1: which is either plus or minus. The weak force can
26:12
Speaker 1: tug or push on things that have either up or
26:15
Speaker 1: down values of the weak isospin. I guess why call
26:19
Speaker 1: it the weak isso spin? Why not call it the
26:21
Speaker 1: weak charge. Yeah, that's a long story that comes from history.
26:25
Speaker 1: People tried to create this idea of isospin, which is
26:28
Speaker 1: like a generalized version of spin for the strong force,
26:31
Speaker 1: and it works really well there, and then when people
26:34
Speaker 1: were studying the weak force, they thought maybe there's something
26:36
Speaker 1: similar over here, so they created a version of that.
26:39
Speaker 1: It doesn't really work, but the name stuck. So yeah,
26:42
Speaker 1: it would be better if we called it like the
26:43
Speaker 1: weak charge or something. But the weak isso spin is
26:47
Speaker 1: the name we got. And these are actually numbers, but
26:50
Speaker 1: instead of just plus or mine, as you say, up
26:52
Speaker 1: or down, right, these are just numbers that the particles have.
26:55
Speaker 1: Just like the electron just happens to have negative charge.
26:58
Speaker 1: Some particles have up quantum week is spin, yeah exactly,
27:03
Speaker 1: And so we call them up or down so to
27:06
Speaker 1: by convention, because for example, of corks have up weak
27:10
Speaker 1: isospin and down corks have down weak isospin, and then
27:14
Speaker 1: the electron has down weak isospin and neutrinos have up.
27:20
Speaker 1: You can also map this if you're more comfortable with
27:22
Speaker 1: numbers to the number line, in which case we say,
27:25
Speaker 1: for example, that neutrinos have positive a half weak isospin,
27:29
Speaker 1: and electrons have minus a half. Up corks also have
27:33
Speaker 1: positive a half and down corks have minus a half.
27:36
Speaker 1: But this is like a different sort of dimension for
27:38
Speaker 1: every particle than electric charge, Like there's no relationship between
27:42
Speaker 1: the electric charge and the weak isospin. For example, neutrinos
27:46
Speaker 1: have no electric charge, but they do have weak isospin. Interesting,
27:50
Speaker 1: So like an up cork is just a cord that
27:52
Speaker 1: has up weak isospin exactly, and that's why we call
27:56
Speaker 1: it up because it sits at the top of weak isospin,
28:00
Speaker 1: and that's why we call it down corks down. And
28:02
Speaker 1: that's why top corks are called top corks because they
28:05
Speaker 1: have up weak isospin. So when we lay out these
28:08
Speaker 1: generation of particles, we group them into these pairs that
28:12
Speaker 1: are like up and down charming strange top and bottom.
28:14
Speaker 1: The top row there up charm top. They'll have up
28:18
Speaker 1: type weak isospin and the bottom row. I'll have down type.
28:22
Speaker 1: All right, Well, how would you even define this weak isospin?
28:25
Speaker 1: Is it just sort of like how much a particle
28:28
Speaker 1: interacts with the weak fields? Is that the equivalent of
28:32
Speaker 1: like electric charge? Yeah, exactly. It's the thing that tells
28:35
Speaker 1: you whether a particle feels the weak force, whether it
28:39
Speaker 1: interacts with the weak force. And in analogy with the
28:41
Speaker 1: other forces, if you have no electric charge, you don't
28:44
Speaker 1: feel electric forces. Like a neutrino can fly right through
28:48
Speaker 1: the most powerful electric fields and totally shrug it off
28:51
Speaker 1: because it doesn't have charge. And so weak isospin is
28:55
Speaker 1: the thing that tells you whether a particle feels the force.
28:58
Speaker 1: But it's something a little bit more than that, you know,
29:01
Speaker 1: because the fascinating thing is that there's a symmetry. Right,
29:04
Speaker 1: these forces, the W plus, the W minus, and the
29:06
Speaker 1: Z they have this really fascinating symmetry to them. It's
29:10
Speaker 1: not a physical symmetry. It's not like, you know, if
29:12
Speaker 1: you rotated it like a spear, it looks exactly the same.
29:15
Speaker 1: It's an internal symmetry. These forces all have like angles
29:19
Speaker 1: to them, and if you rotate the particles, they rotate
29:22
Speaker 1: together and they work together and the upshot is that
29:25
Speaker 1: they end up conserving this thing called weak isospin. So
29:29
Speaker 1: these particles and their interactions they conserve weak isospin the
29:33
Speaker 1: way the photon, for example, conserves electric charge. You can't
29:37
Speaker 1: just like create electric charge willy nilly, in the same
29:40
Speaker 1: way the weak force preserves weak isospin. If you have it,
29:43
Speaker 1: it's going to stick around. If you don't have it,
29:45
Speaker 1: you can't create it. Interesting, it's because sort of like
29:49
Speaker 1: a universal rule. Yeah, and it's you know, connected to
29:52
Speaker 1: this concept we've talked about a few times in the podcast.
29:55
Speaker 1: No those theorem that tells you that any symmetry in
29:58
Speaker 1: physics leads to conservation law. So there's some like internal
30:02
Speaker 1: symmetry between these particles that W plus the wus and
30:05
Speaker 1: the Z where like if you rotate them internally, they
30:08
Speaker 1: turned into each other. But they do it in this
30:11
Speaker 1: way that preserves a certain number and that leads directly
30:14
Speaker 1: to conservation of weak isospin the same way, for example,
30:18
Speaker 1: the photon is responsible for conserving electric charge. So it's
30:22
Speaker 1: really like a deep thing in physics. When you discover
30:24
Speaker 1: this number which doesn't change, it tells you you've found
30:28
Speaker 1: something about the universe. Which feels fundamental or important because
30:32
Speaker 1: it in its bookkeeping, it makes sure that this number
30:35
Speaker 1: doesn't yet changed. The universe has an accountant, and it
30:38
Speaker 1: has a special account for that weak iso spin is
30:40
Speaker 1: what you're saying exactly, and again, these are just sort
30:43
Speaker 1: of random numbers, right, Like, we don't know why. For example,
30:46
Speaker 1: some particles have you know, up half isospin or negative
30:51
Speaker 1: have isospin. Right, these are it's just sort of arbitrary almost. Yeah, well,
30:54
Speaker 1: we don't know if there's rhyme or reason to it,
30:57
Speaker 1: but you're right, our level of understanding is we're just
30:59
Speaker 1: sort like writing these things down in our lab notebook.
31:02
Speaker 1: We don't understand why particles have different values. We're just
31:05
Speaker 1: sort of tabulating it and looking for patterns. And you know,
31:08
Speaker 1: the numbers are pretty weird, Like weak eys of spin
31:11
Speaker 1: is actually pretty straightforward. Is either plus a half or
31:13
Speaker 1: minus a half. If you look at like electric charge,
31:16
Speaker 1: it's weird, you know, like neutrinos have zero, electrons have
31:20
Speaker 1: minus one. Up corks have plus two thirds, down corks
31:23
Speaker 1: have minus the third. It's kind of crazy, and we
31:26
Speaker 1: don't understand why those numbers are what they are. I mean,
31:30
Speaker 1: in some sense they're arbitrary, like you could make them
31:33
Speaker 1: twice what they are or half what they are, and
31:35
Speaker 1: then you could take that number and like you know,
31:37
Speaker 1: weekend or strengthen the feeling of the force. But the
31:40
Speaker 1: relationships between them and our arbitrary. Like that's just what
31:43
Speaker 1: we see in nature. And then also the name weak
31:46
Speaker 1: force you said, comes from this, not that it's not
31:49
Speaker 1: that the weak force is weak. It's just that it's
31:51
Speaker 1: doesn't have long range or something. Right, it's due to
31:55
Speaker 1: these particles, these force particles having mass. Yeah, these particles
31:58
Speaker 1: that W plus the W minus in the Z, they
32:00
Speaker 1: have a lot of mass. And that's actually really fascinating
32:03
Speaker 1: because it's what makes the weak force different from electricity
32:07
Speaker 1: and magnetism. We think back in the very early days
32:09
Speaker 1: of the universe, before the Higgs field, that all these
32:11
Speaker 1: particles were massless and they were flying all the way
32:14
Speaker 1: around the universe. And then the Higgs field came and
32:16
Speaker 1: it made three of these particles have mass. The W
32:19
Speaker 1: plus the W minus and the Z got a huge
32:21
Speaker 1: amount of mass from the Higgs field, and now they
32:24
Speaker 1: are very heavy, and as you say, that makes them weak,
32:27
Speaker 1: it means that it's much less likely for this interaction
32:30
Speaker 1: to happen, Like if you shoot two neutrinos at each other,
32:34
Speaker 1: they're much less likely to interact then if you shoot
32:36
Speaker 1: two electrons, because the weak force is weaker than electromagnetism.
32:40
Speaker 1: It's also shorter range, as you say, because the particles
32:43
Speaker 1: can't fly as far, but it's also weaker, it's less
32:46
Speaker 1: likely to sort of like come into play when you
32:49
Speaker 1: shoot two particles at each other. I guess the question
32:51
Speaker 1: is how as having mass make it less likely to
32:54
Speaker 1: interact or harder to interact and also a shorter range,
32:59
Speaker 1: you can think of them as nected, like imagine shooting
33:01
Speaker 1: two particles together, and you know, the probability of them
33:04
Speaker 1: interacting sort of depends on their relative distance. Like if
33:07
Speaker 1: you shoot them in the same direction but they're like
33:09
Speaker 1: a meter apart, there's gonna be no chance to interact.
33:12
Speaker 1: As they get closer and closer together, then there's a
33:14
Speaker 1: larger and larger chance that they interact. And we talk
33:17
Speaker 1: about the chance that interaction is being like the relative
33:19
Speaker 1: cross section, like a physical analogies, you throw like two
33:22
Speaker 1: balls at each other, the chance that they're gonna hit
33:24
Speaker 1: each other depends on their cross section, Like how big
33:27
Speaker 1: does one appear to the other, And so we have
33:29
Speaker 1: sort of a quantum analog of that, which we call
33:32
Speaker 1: again the cross section, And the cross section is smaller
33:34
Speaker 1: if the particle that mediate it has a lot of mass.
33:37
Speaker 1: The fact that it's a shorter range force means it
33:39
Speaker 1: has a smaller cross section when the particles coming the
33:42
Speaker 1: other direction. So you have to sort of like get
33:44
Speaker 1: right on the nose in order to have that interaction happen,
33:47
Speaker 1: Whereas if you're you're using photons, they can fly everywhere.
33:50
Speaker 1: You don't have to like shoot electrons to be as
33:52
Speaker 1: close to each other for them to feel each other. Yeah,
33:54
Speaker 1: but I guess you know, what does it mean to
33:56
Speaker 1: have short range Like what happens to the particle, Like
34:00
Speaker 1: it disappears or breaks up into other particles because it
34:03
Speaker 1: has mass, which means it has energy. Yeah, exactly, if
34:05
Speaker 1: you shoot a Z particle, for example, it can't just
34:08
Speaker 1: fly across the universe forever the way a photon can,
34:11
Speaker 1: Like a photon made billions of years ago can still
34:14
Speaker 1: just fly through the universe towards you. If you make
34:16
Speaker 1: a Z particle billions of years ago, it will decay
34:19
Speaker 1: pretty quickly into something else. Because it's so heavy it
34:22
Speaker 1: will turn into a pair of electrons or a pair
34:24
Speaker 1: of neutrinos or something. So they just don't last very long,
34:27
Speaker 1: right because it can, right, because it has this sort
34:30
Speaker 1: of internal energy from the mass, and so it tends
34:32
Speaker 1: to like disperse kind of exactly, whereas photons are stable
34:35
Speaker 1: and they can propagate forever, but these dissipated and turn
34:38
Speaker 1: into other fields. It's like throwing a snowball in a
34:41
Speaker 1: windstorm or something like the it just breaks up, yeah,
34:44
Speaker 1: or like throwing a snowball in death Valley. Right, it's
34:46
Speaker 1: just it's probably gonna melt before it gets to your
34:48
Speaker 1: friend's face, which sounds like a fun activity. But I
34:51
Speaker 1: guess maybe a question is is the week force, you know,
34:55
Speaker 1: weak in itself? Like if it could travel further, would
34:58
Speaker 1: it still be weak or would it have an inherently
35:01
Speaker 1: lower kind of interactive value or impact, Like is it
35:04
Speaker 1: as strong as the other forces? But because it decays
35:09
Speaker 1: and it has a short range, it's you call it
35:11
Speaker 1: weak because of that. Yeah, I would say so if
35:13
Speaker 1: for example, we lived in a universe where it didn't
35:15
Speaker 1: get mass right with the Z and the W propagated
35:18
Speaker 1: the same way as the photon, it would be as
35:20
Speaker 1: strong as electromagnetism. All right, I think we covered the
35:23
Speaker 1: basics and now let's get into the main question, which
35:26
Speaker 1: is does the weak force attract or repel? But first
35:31
Speaker 1: let's take another quick break. All right, does the weak
35:45
Speaker 1: force attract or repel? And Daniel, we talked about it
35:48
Speaker 1: being weak because it doesn't have a very long range.
35:52
Speaker 1: The particles that transmit this force decay before they get
35:56
Speaker 1: very far. But I guess the question is if it
35:58
Speaker 1: does reach their target. It like if you if two
36:01
Speaker 1: particles do interact with a W plus or W minus
36:04
Speaker 1: or Z force particle, are they gonna make each other
36:07
Speaker 1: come closer or further apart? Yes, so, because the weak
36:10
Speaker 1: force is a lot like electricity magnetism, and because actually
36:14
Speaker 1: they're just part of a larger force. In general, it
36:17
Speaker 1: follows the same rules as electricity and magnetism, which means
36:20
Speaker 1: if you have the same weak charge right weak isospin,
36:24
Speaker 1: then particles will repel each other. Via the opposite weak isospin,
36:28
Speaker 1: then particles will attract each other. So that makes it
36:31
Speaker 1: similar to electromagnetism and different from gravity. All right, well,
36:35
Speaker 1: then we answer the question, it does attract and repel.
36:38
Speaker 1: It does attract and repel, and there's some interesting wrinkles
36:41
Speaker 1: to it. Right. For example, you asked earlier, like what
36:44
Speaker 1: can a force do other than attract and repel? And
36:47
Speaker 1: the W particle is an example of that. Right, The
36:50
Speaker 1: W particle doesn't just attract or repel. In fact, you
36:53
Speaker 1: can't even really think of it as attracting or repelling
36:55
Speaker 1: because the W particle transforms a particle. It doesn't just
36:59
Speaker 1: like push it or pull it. It changes it into
37:02
Speaker 1: something else because the W particle itself, for example, has
37:06
Speaker 1: electric charge. Wait what so Like, let's have two particles,
37:11
Speaker 1: you know, to electrons in the electron field, and they
37:14
Speaker 1: interact through the week fource. You're saying, like, the exchange
37:17
Speaker 1: a W particle and then that doesn't move them, but
37:20
Speaker 1: it just changes one of them. It both moves them
37:23
Speaker 1: and changes both of them. So, for example, if an
37:26
Speaker 1: electron interacts with a W particle, what how does it
37:29
Speaker 1: do that? Well, to give off a W particle, it
37:31
Speaker 1: has to lose its electric charge because the W particle
37:34
Speaker 1: itself has electric charge. Like an electron can radiate a photon,
37:39
Speaker 1: photon is charge zero doesn't change the electron it's still
37:42
Speaker 1: an electron. It's just an electron with less energy now
37:45
Speaker 1: or something. But the electron radiates a W, the electric
37:48
Speaker 1: charge has to be conserved, and so that electric charge
37:50
Speaker 1: goes with the W and the electron is no longer
37:53
Speaker 1: an electron. It turns into a new trino. So for
37:56
Speaker 1: an electron to radiate a W, it has to become
37:58
Speaker 1: a new trino, And for neutrino to feel a W,
38:02
Speaker 1: it has to turn into an electron. So the W
38:05
Speaker 1: particles here do much more than just push or pull.
38:07
Speaker 1: They transform these particles. Interesting, but does that mean that
38:11
Speaker 1: an electron can talk to another electron through the W
38:14
Speaker 1: or it cannot? Absolutely, it can. It can read a W,
38:17
Speaker 1: and that W can interact with an electron because the
38:20
Speaker 1: W feels a charge and the electron feels a charge,
38:23
Speaker 1: and so then that W and the electron can like
38:25
Speaker 1: attract or repel each other based on their relative charges.
38:29
Speaker 1: So absolutely, and the electron can also interact with other
38:32
Speaker 1: electrons using the Z particle. So it's kind of like
38:35
Speaker 1: the electromagnetic force, but it's just like it has added
38:38
Speaker 1: complications because these force particles are have you know, more
38:42
Speaker 1: to them. They have energy and an electric charge, whereas
38:46
Speaker 1: the photon doesn't exactly, So it's out of this big
38:48
Speaker 1: complicated mess. It's got two of these charged bosons, a
38:52
Speaker 1: W plus and W minus, which can do these crazy things,
38:55
Speaker 1: you know, like change the charge of the particle that
38:57
Speaker 1: was radiating it. Oh wait, wait wait, that's what the
38:59
Speaker 1: plus means. The plus means it has positive electric charge. Yeah,
39:03
Speaker 1: for once the plus actually means something reasonable, It actually
39:06
Speaker 1: makes sense. Yeah, good job. All this time you thought
39:09
Speaker 1: the W plus were just like, well, it can't actually
39:12
Speaker 1: mean positive charge because that would make sense. I don't know.
39:15
Speaker 1: It seems like you guys use it kind of willy
39:17
Speaker 1: knee leak, right because even the up and do you
39:19
Speaker 1: use plus and minus for it? Right? Yeah, that's right.
39:22
Speaker 1: But no, the W plus has a plus one electric
39:24
Speaker 1: charge and the W minus has a minus one electric charge.
39:27
Speaker 1: That's exactly what it means. And the Z is neutral.
39:30
Speaker 1: The Z has no electric charge. So like, if too
39:32
Speaker 1: electrons exchange a Z, then they don't change, or they
39:36
Speaker 1: still change, or they push each other. What happens when
39:39
Speaker 1: they exchange a Z. Yeah, So if you have electrons
39:42
Speaker 1: and positrons, they can exchange photons and they can exchange
39:44
Speaker 1: Z particles. And now if they exchange photons, you know
39:47
Speaker 1: what the rules are. Right, If the charges are the same,
39:49
Speaker 1: they repel each other. The charges of the opposite they
39:53
Speaker 1: attract each other. The same rule applies for the Z,
39:56
Speaker 1: but if the charge is different, because the charge for
39:58
Speaker 1: the Z is the weak isospin, And so you can
40:02
Speaker 1: then ask the question like, due to electrons attract or
40:05
Speaker 1: repel each other using the Z and the answer is
40:08
Speaker 1: that the electrons have the same weak iso spin because
40:11
Speaker 1: it's just two electrons, and so they repel each other
40:14
Speaker 1: the same way like two positrons will repel each other.
40:17
Speaker 1: They have the same weak isospin, so they have to repel.
40:20
Speaker 1: But I guess maybe a difference is that the Z
40:23
Speaker 1: force particle doesn't go at the speed of light, right
40:25
Speaker 1: because it has mass, so it's like a slower force too. Yeah,
40:28
Speaker 1: and so the Z is weaker. And so usually if
40:30
Speaker 1: two electrons are interacting, it's just dominated by the photon
40:33
Speaker 1: interaction because that's much stronger and longer range. The Z contributes,
40:38
Speaker 1: but it's like almost ignorable, which is why in chemistry,
40:41
Speaker 1: for example, you're mostly thinking about like the electromagnetic interactions
40:45
Speaker 1: between electrons and atoms and electrons and neighboring atoms. There
40:49
Speaker 1: are some weak force interactions there, but they're mostly ignorable
40:53
Speaker 1: because the weak force is so much weaker than electromagnetism. Oh. Interesting,
40:58
Speaker 1: it's like it's always happening. They're just like electromagnetic forces,
41:02
Speaker 1: but they're just you know, so weak that nobody cares.
41:06
Speaker 1: But it's always happening. Like even within the particles in
41:08
Speaker 1: my body, there's a whole bunch of you know, weak
41:11
Speaker 1: stuff going on, but it's sort of negligible. Yeah, exactly,
41:15
Speaker 1: it's mostly just washed out by electromagnetism. And it's interesting
41:19
Speaker 1: to think about, like is it always pushing and pulling
41:22
Speaker 1: in the same direction or is it sometimes like opposing electromagnetism.
41:27
Speaker 1: And the answer is that it's always pushing and pulling
41:29
Speaker 1: in the same direction. And the reason is that it
41:32
Speaker 1: follows the same basic rule that like charges repel and
41:36
Speaker 1: opposite charges attract, and it just so happens that like
41:39
Speaker 1: electrons and neutrinos have opposite charges, and up corks and
41:44
Speaker 1: down corks have opposite electric charges and opposite weak isospin charges.
41:49
Speaker 1: So you know, for example, take an upcork and a
41:52
Speaker 1: down cork For example, an upcork and a down cork
41:55
Speaker 1: have opposite sign electric charges. One of them is plus
41:59
Speaker 1: two thirds the other one is minus one third, so
42:02
Speaker 1: they attract each other. They also have opposite week iso spin.
42:06
Speaker 1: One is plus a half, one is minus a half,
42:09
Speaker 1: so they attract each other. So in that case, the
42:11
Speaker 1: upcork and the down cork, the photon is pulling them
42:14
Speaker 1: together and the Z is pulling them together. I mean,
42:16
Speaker 1: like plus electric charge is always associated with up kind
42:20
Speaker 1: of or one of those two, like you never mix
42:22
Speaker 1: and match him that much. Plus electric charge is always
42:25
Speaker 1: associated with up week iso spin, and minus electric charge
42:29
Speaker 1: is always associated with minus weak isospin exactly. But there's
42:33
Speaker 1: one weird case, right, There's always a weird case, and
42:36
Speaker 1: the weird case is the neutrino. The neutrino has no
42:40
Speaker 1: electric charge, right, so the photon doesn't push or pull.
42:44
Speaker 1: So in the case of the neutrino, the Z is
42:46
Speaker 1: the only thing pushing and pulling. And so there are
42:49
Speaker 1: no other weird cases where like you know, it has
42:51
Speaker 1: a plus electric charge, but like a down that never happens.
42:55
Speaker 1: It's always of a line these two forces exactly. Because
42:58
Speaker 1: the anti particles have opposite values, but they flipped together.
43:02
Speaker 1: So for example, an up cork has positive electric charge
43:05
Speaker 1: and positive weak isospin, and an anti up cork has
43:10
Speaker 1: negative both values, negative electric charge and negative weak isospin.
43:14
Speaker 1: So they're always pointing in the same direction and they
43:16
Speaker 1: flipped together. But theoretically there could be particles maybe that
43:20
Speaker 1: have a weird combination. We just don't see them. Yeah. Absolutely.
43:24
Speaker 1: And the interesting thing about the weak force is everything
43:26
Speaker 1: feels it. Like the other forces, there's always some particle
43:30
Speaker 1: that ignores it, you know, the strong force. Electrons don't
43:33
Speaker 1: feel the strong force, totally ignore it, electromagnetism, neutrinos totally
43:37
Speaker 1: ignore it. Nothing ignores the weak force. The weak force
43:41
Speaker 1: feels everything. Wait, what do you mean? It feels everything,
43:44
Speaker 1: Like every particle in the universe feels the weak force.
43:46
Speaker 1: There is no particle out there that doesn't interact with
43:49
Speaker 1: the weak force. There are particles that don't interact with electricity, magnetism,
43:53
Speaker 1: and there are particles that don't interact with the strong force.
43:56
Speaker 1: But there's no particle we've discovered that doesn't interact with
43:59
Speaker 1: the weak force, sort of like gravity, right, Like, we
44:01
Speaker 1: don't know any particle that doesn't interact with gravity. Yeah,
44:04
Speaker 1: although we don't really understand you know, how particles and
44:07
Speaker 1: gravity interact, you know, what's going on there on the
44:10
Speaker 1: quantum level. It's not something we can really say specifically
44:13
Speaker 1: how that works. But you're right that, like everything we know,
44:16
Speaker 1: moves through space, and the curvature of that space depends
44:19
Speaker 1: on the massive stuff around it. But again we don't
44:21
Speaker 1: understand it at the quantum level. But I think it's
44:24
Speaker 1: fun to think about like two neutrinos. Like you shoot
44:26
Speaker 1: two neutrinos at each other, they actually do repel or
44:30
Speaker 1: attract each other based on their weak isospin. Like two
44:35
Speaker 1: neutrinos will repel each other, and a neutrino and an
44:38
Speaker 1: anti neutrino will attract each other because they have opposite
44:41
Speaker 1: weak isospin. Yeah, just like two electrons will repel each other. Now,
44:45
Speaker 1: you said that the weak force is sort of like
44:48
Speaker 1: part of the electromagnetic force, or they're all part of
44:50
Speaker 1: the same force. What does that mean? Like they're sort
44:53
Speaker 1: of coupled, they depend on each other, they're not independent.
44:56
Speaker 1: What does that mean? It means that it makes more
44:58
Speaker 1: sense mathematically when you plug them to gether. In fact,
45:00
Speaker 1: we don't think about weak isospin on its own. Usually
45:03
Speaker 1: what we do is we think about electricity and magnetism
45:06
Speaker 1: together and we make this new number which is a
45:09
Speaker 1: combination of electric charge and weak isospin, and we call
45:14
Speaker 1: it weak hypercharge. And then we have these two numbers
45:18
Speaker 1: week isso spin and weak hypercharge, and together these four
45:22
Speaker 1: particles conserve these numbers. Like, these four particles respect these values.
45:27
Speaker 1: They do what they can to make sure that in
45:29
Speaker 1: the bookkeeping of the universe, these two quantities weak hypercharge
45:33
Speaker 1: and weak isospin are conserved. And so we see them
45:36
Speaker 1: all working together to keep this symmetry in line, which
45:39
Speaker 1: is why we think they're all part of the same thing. Well,
45:42
Speaker 1: I see, you notice that they are sort of part
45:44
Speaker 1: of the same team, or they were, they weren't for
45:46
Speaker 1: the same company which has the same accounting you know, Ledger,
45:50
Speaker 1: and so you sort of group them together, unlike say,
45:52
Speaker 1: like the strong force or maybe gravity. Like gravity and
45:56
Speaker 1: the strong force don't care about the conservation of this
45:59
Speaker 1: hyper charge. That's exactly right. And you know, we tend
46:02
Speaker 1: to think about things that way, where like if things
46:04
Speaker 1: transformed together, if when you rotate the world, things move together.
46:09
Speaker 1: We think that there's part of the same thing. Just
46:11
Speaker 1: like if you pick something up and you turn it
46:13
Speaker 1: around and it holds itself together, and you look at
46:16
Speaker 1: it from different directions and it feels like it keeps
46:18
Speaker 1: the same shape, you think it's always one thing, whereas
46:21
Speaker 1: if you pick it up and it falls into pieces, like, oh,
46:24
Speaker 1: it's a bunch of different stuff. It just happened to
46:26
Speaker 1: be near each other. And in that same way, the
46:28
Speaker 1: photon like fits in with these other three particles to
46:31
Speaker 1: make one cohesive mathematical object, which if you rotate in
46:35
Speaker 1: this like mathematical way, keeps its same shape. It conserves
46:39
Speaker 1: these numbers. All right, Well, I think that answers the
46:42
Speaker 1: question does the weak force attract or repel? And the
46:44
Speaker 1: answer is yes. But it's a little bit more complicated,
46:47
Speaker 1: right because the force that transmits it also has charge
46:52
Speaker 1: and mass, and so it's it gets complicated. It's not
46:55
Speaker 1: a straight up relationship. It does get complicated. But I
46:57
Speaker 1: think it's pretty cool that we can use sort of
46:59
Speaker 1: the sim Miller ideas we used to think about electricity
47:02
Speaker 1: and magnetism, charges and potentials to think about whether these
47:06
Speaker 1: things push and pull, And it's even much richer than
47:09
Speaker 1: we've got to talk about on the podcast, because there's
47:12
Speaker 1: two kinds of particles. There are left handed particles and
47:14
Speaker 1: right handed particles, and only the left handed particles actually
47:18
Speaker 1: do this kind of interaction. The right handed particles don't
47:20
Speaker 1: do it. So it's even more complicated than we talked about.
47:23
Speaker 1: The weak force is like a huge mathematical headache slash
47:27
Speaker 1: delicious puzzle slash weak strong problem kind of yeah, it's
47:34
Speaker 1: sort of like attracts and repels physicists. All right, well, um,
47:37
Speaker 1: I guess maybe one last question is why did you
47:40
Speaker 1: find this question so hard? Like, you know, we broke
47:42
Speaker 1: it down and it seemed like something that you know,
47:46
Speaker 1: two things have the same week. I's just been the
47:48
Speaker 1: repellor or and if they don't they attract what was
47:51
Speaker 1: the thing that was stomping in? I think it's just
47:53
Speaker 1: because I've never thought about the weak force in terms
47:55
Speaker 1: of its potential you mean to push and pull, like
47:58
Speaker 1: its ability to push or pool things, just because it's
48:00
Speaker 1: so weak. Yeah, just because it's so weak, and also
48:02
Speaker 1: because frankly, there's some layers of mathematical complexity I'm hiding
48:05
Speaker 1: from you here, Like there's actually two different potentials that
48:08
Speaker 1: the z has has an axcel potential and an axial
48:11
Speaker 1: vector potential, and so I had to actually work through
48:14
Speaker 1: whether they're always working together or sometimes working apart from
48:17
Speaker 1: each other, as whether or not we need to dig
48:19
Speaker 1: into that. So one issue was like how deep to
48:22
Speaker 1: go into this? You know, we could do like ten
48:24
Speaker 1: podcast episodes of quantum field theory engage symmetry before we
48:27
Speaker 1: get to the answer. All right, let's do it. Daniel,
48:29
Speaker 1: I got ten hours. Alright, alright, well, thank you to
48:33
Speaker 1: the person who asked this question, the organic chemistry professor.
48:36
Speaker 1: I think you should watch out because Daniel might come
48:38
Speaker 1: to your office hours and lay down some tough organic chemistry.
48:42
Speaker 1: That sounds like a threat, man, an economic threat. He's
48:45
Speaker 1: going to be nervous every time he has office hours
48:47
Speaker 1: from now on. Oh man, he's gonna be looking out
48:49
Speaker 1: for you. All right. Well, we hope you enjoyed that
48:52
Speaker 1: and made you think a little bit about all the
48:55
Speaker 1: things that are happening inside of your body right now.
48:57
Speaker 1: There's a lot of stuff going on in between your articles,
49:00
Speaker 1: not just electromagnetic forces, but this really strange and complicated
49:05
Speaker 1: thing called the weak force. And all these forces working
49:08
Speaker 1: together are what create the fabric of reality that we
49:11
Speaker 1: experience around us. The world wouldn't be the same without
49:14
Speaker 1: just one of these forces. It would feel palpably different.
49:17
Speaker 1: It wouldn't be nearly as delicious. We might be those
49:20
Speaker 1: aliens that look at this landscape and go, if this
49:23
Speaker 1: had a weak force, it would be much cooler. That's right,
49:26
Speaker 1: it's too weak right now. It's a weak sauce. We
49:29
Speaker 1: should have called the weak force the spicy force to
49:31
Speaker 1: give it some pride, you know. Yeah, there you go,
49:33
Speaker 1: because it's not sort of not weak, right, it's it's
49:35
Speaker 1: it's sort of strong, and it's a mathematical complexity. Yeah,
49:39
Speaker 1: it's doing a lot. Man. Yeah, maybe weak is a
49:41
Speaker 1: new strong, and I just spin is a new plus
49:45
Speaker 1: or minus. I don't know anyways, Thanks for joining us,
49:48
Speaker 1: See you next time. Thanks for listening, and remember that
49:58
Speaker 1: Daniel and Jorge expl in the Universe is a production
50:01
Speaker 1: of I Heart Radio or more podcast from my heart Radio.
50:05
Speaker 1: Visit the I heart Radio app, Apple Podcasts, or wherever
50:08
Speaker 1: you listen to your favorite shows. Yeah,