Speaker 1: Ythaniel. Do you ever get caught using a word that
Speaker 1: you don't really understand? Do you actually always know what
Speaker 1: you're talking about? I don't think I'm willing to devote
Speaker 1: that here on the podcast, and maybe we can have
Speaker 1: that conversation over a beer sometimes. But the thing that
Speaker 1: I love is that there are some topics in physics,
Speaker 1: some idea, some words that I'm pretty sure nobody actually
Speaker 1: really understands. I feel like this is taking us to
Speaker 1: another episode about quantum physics that's right and wrong at
Speaker 1: the same time. No, I mean, yes, exactly what at
Speaker 1: the same time. Hi'm Jorge. I'm a cartoonist and the
Speaker 1: creator of PhD Comics. Hi I'm Daniel, I'm a particle physicist,
Speaker 1: and Welcome to our podcast, Daniel and Jorge Explain the Universe,
Speaker 1: a production of I Heart Radio in which we take
Speaker 1: crazy and fascinating and amazing and hot and wet and
Speaker 1: nasty things about the universe and try to explain them
Speaker 1: to you. Today's episode is dedicated to a Lana, whose
Speaker 1: boyfriend Nick is a local fan of the podcast here
Speaker 1: in Irvine. Happy Birthday, Alana. Today's topic is a really
Speaker 1: fun one, and in preparation for it. Not only did
Speaker 1: I go and do the normal street interviews I usually
Speaker 1: do with random people, but I actually went around the
Speaker 1: halls of my physics department and I asked a bunch
Speaker 1: of grad students if they could explain today's topic for me,
Speaker 1: and they found it pretty tough. Wow, that's a pretty
Speaker 1: interesting spin on the topic in our process. That's right,
Speaker 1: that's right to be on the podcast. We're going to
Speaker 1: be talking about quantum spin exactly. Quantum spin? What is it?
Speaker 1: What does it mean? Are things actually spinning? Why is
Speaker 1: it quantum um? We've got a lot of people sending
Speaker 1: in requests to talk about this topic. And I think
Speaker 1: when people are interested in physics and digging around in
Speaker 1: videos on the internet and listening to podcast you hear
Speaker 1: this come up a lot. It comes up in quantum entanglement,
Speaker 1: It's in science fiction everywhere, and of course people want
Speaker 1: to know what does it mean, what's going on? Why
Speaker 1: is it so important? That's right? What is spin? How
Speaker 1: fast is it spinning? What's the spin on it? Exactly?
Speaker 1: Is it's spinning out of control? That's right? Is it
Speaker 1: different from political spin? Um? It's definitely a thing, right,
Speaker 1: It's something fascinating and more importantly, if you're an expert
Speaker 1: in this field, does that make you a spin doctor
Speaker 1: doctor of spin? Yes, exactly. You know, we have sort
Speaker 1: of a bad track record in physics of naming things
Speaker 1: um naming things using familiar words, like we give corks flavors, right,
Speaker 1: the up cork and the charm cork and the top
Speaker 1: cork a different flavors of corks, colors and colors, right
Speaker 1: when they don't really have color, they don't really have color,
Speaker 1: and they don't really taste different. I mean, I don't know,
Speaker 1: I've never actually tasted a top cork, So there you go.
Speaker 1: I'm speaking on something I don't really understand, but we
Speaker 1: don't mean it in that way. So sometimes we're like
Speaker 1: adopting existing words and just using them totally inappropriately. Other
Speaker 1: times we're trying to use words that are similar to
Speaker 1: some other concepts because specifically because we want to call
Speaker 1: up structures and ideas from those concepts. Like color is
Speaker 1: actually a pretty cool one because while the particles are
Speaker 1: not colored, there's something about quantum color which is similar
Speaker 1: to color, and so we want to express that. You're
Speaker 1: sort of trying to grab onto an intuitive idea, even
Speaker 1: if you're trying to like a reference, you're trying to
Speaker 1: reference an intuitive idea in our everyday experience and and
Speaker 1: kind of latch that onto a physics concept exactly. And
Speaker 1: we do that all the time, right, That's basically what
Speaker 1: physics is is try to explain the unknown in terms
Speaker 1: of the known, right, Like when we try to talk
Speaker 1: about particles, we're doing that all the time. You know,
Speaker 1: we're saying, oh, it's a particle, No, it's a wave. Right,
Speaker 1: It's really neither, and it's both and it's something else
Speaker 1: more complicated, And we're just trying to patch together a
Speaker 1: description of using ideas in your head, right, we weave
Speaker 1: these together into some sort of understanding. Here's such a
Speaker 1: suggestion for you guys. Maybe you should just instead of
Speaker 1: calling being bold and calling it like colors or flavors,
Speaker 1: just at the word, like at the beginning in your
Speaker 1: official definition. So the announcement should be like, like we're
Speaker 1: calling this color, I mean, like let's call flavor. No,
Speaker 1: I just call it like a quantum light color. It's
Speaker 1: light color. It has a color like property or a
Speaker 1: spin like property, or you know, I mean, if you
Speaker 1: want to get mathematically, just with a little Tilda in
Speaker 1: the front right, and then nobody would be confused. Yeah,
Speaker 1: I like that idea a lot good. You like like it? Yeah,
Speaker 1: I totally like it, and I think, um, I hope
Speaker 1: on Twitter it gets a lot of likes. There you go.
Speaker 1: I think I want to something. I think I think
Speaker 1: you should be nominated onto the secret International Physics Naming Committee.
Speaker 1: I don't know where it meets or when it meets,
Speaker 1: or who's in charge of it, but they have been
Speaker 1: making some dubious decisions recently and they need some fresh blood. Well,
Speaker 1: I think if I was in charge, I would just
Speaker 1: put the tilt in front of physics itself. You know,
Speaker 1: what are you study till the physics? Physics? I'm studying
Speaker 1: something like physics, but it's not actually, I mean, isn't
Speaker 1: everything like physics? Pretty next thing, you're gonna be calling
Speaker 1: me like a physicist, not actually a physicist, but something
Speaker 1: like approximating a physicist. You know, you're gonna spread this
Speaker 1: Tilda Daniels sort of like a Daniel into it. Lee,
Speaker 1: You're Daniel. You know I'm actually a Daniel. I am
Speaker 1: the definition of me, right, You're Daniel sub zero exactly.
Speaker 1: I'm not like me I am me, right, you are,
Speaker 1: I think therefore I am Daniel. Well, anyways, before we
Speaker 1: spin out of control here on this um side conversation, um,
Speaker 1: we're talking about quantum spin, and so it's it. It
Speaker 1: plays a big deal in quantum physics and quantum entanglement, right,
Speaker 1: and atomic orbitals. I mean it's it's sort of it's
Speaker 1: important in everybody's atoms, which um which are a kind
Speaker 1: of important to people, that's right. I like my atoms,
Speaker 1: you know, they're not like atoms. I just like them.
Speaker 1: But exactly, spin is everywhere, and you hear come up,
Speaker 1: and especially when you're hearing explanations of quantum entanglement or
Speaker 1: quantum computing or or orbitals and this kind of stuff,
Speaker 1: you hear about it. And when I was a student
Speaker 1: and I was learning about quantum spin, I was like, okay,
Speaker 1: but what is it like? Are these things actually spinning?
Speaker 1: Why do we call it spin? Right? How could a
Speaker 1: particle spin? And so let's dig into all that today. Well,
Speaker 1: as usual, Daniel went out there and asked people in
Speaker 1: the street if they knew what quantum spin was. And
Speaker 1: you actually have kind of an interesting spin twid this time, right, Yeah,
Speaker 1: I went out and I asked people on the U
Speaker 1: C Irvine campus and then a few other folks at
Speaker 1: the at an Irvine mall Um what they thought quantum
Speaker 1: spin was, if they could describe it, and if they
Speaker 1: did understand quantum spin. I also asked them, are these
Speaker 1: particles actually spinning or is that just like spin? Is
Speaker 1: that just like a word we use. Well, here's what
Speaker 1: people had to say, um, so energy, I just think
Speaker 1: of energy. Oh yes, what's the quantum spin? Uh? Like
Speaker 1: quantum spin as an like spin up, spin down with
Speaker 1: within molecular orbitals and electrons um. So are those particles
Speaker 1: like actually spinning gesa Uh No, I haven't quantum spin? No?
Speaker 1: Uh yeah, it's electron spin um that it can be
Speaker 1: positive or negative um. And then how's it different from
Speaker 1: normal spin? Like a tennis ball can spin? Is electron
Speaker 1: spain the same thing? Are they physically spinning? Uh? I'm
Speaker 1: not sure. I know some stuff about Polly's principle that
Speaker 1: the spin should be in a specific way, and they're prepared,
Speaker 1: so I know some way in distunt stuff, but I'm
Speaker 1: not sure about the people. Right. Yeah, isn't because um
Speaker 1: every electron has a different type of spin. It's like
Speaker 1: either a plus one half a minus one half. I
Speaker 1: forgot what it would Yeah, and are they like actually spinning.
Speaker 1: Is it like the same thing as a tennis ball spinning?
Speaker 1: Or is it's um? No, because it's not like because
Speaker 1: you can't treat it like it's a particle, right, because
Speaker 1: it's um like an electron is a mix of a
Speaker 1: particle and a way. I've heard of it, but I'm
Speaker 1: not familiar with the meaning. Okay, No, I don't know
Speaker 1: what that is, all right. Yes, there's up and down spin, right,
Speaker 1: and it's in me. Uh well, I don't know much
Speaker 1: more than that, Okay, all right. It seemed very binary.
Speaker 1: Some people had had no idea, never even heard of it,
Speaker 1: and some people had a lot to say about this topic. Yeah,
Speaker 1: and some people knew some stuff sort of in the
Speaker 1: vicinity of the topic, but not actually like reluing to
Speaker 1: the question the vicinity. Yeah, yeah, exactly. I like when
Speaker 1: when I asked somebody question and I can tell they
Speaker 1: haven't thought about this in a long time, and they
Speaker 1: have sort of like a free association going off in
Speaker 1: their mind that wait, this is connected to that idea,
Speaker 1: to that idea of that idea, and then they go no, Actually,
Speaker 1: I don't know. I don't know the answer. That's really fun,
Speaker 1: but you can see their process. Yeah, because a lot
Speaker 1: of people to be heard about it or read about
Speaker 1: it a long time ago, maybe in high school physics
Speaker 1: or something, and so you sort used to feel like
Speaker 1: it's in there in your brain. You just need some
Speaker 1: time to you know, boot up the hard drives. Yeah, exactly.
Speaker 1: But I think my favorite part of this experience asking
Speaker 1: people these questions was that one gentleman after I asked him, um,
Speaker 1: if you knew about quantum spin, he then asked me,
Speaker 1: he said, is this some thing you need for your dissertation?
Speaker 1: Said yes, yes, sir, Yes, sir, I am a twenty
Speaker 1: five year old graduate student. Absolutely, are you saying that
Speaker 1: you can be a grad student at forty something? There
Speaker 1: are fewer of them. Yes, there are a few or
Speaker 1: forties something year old grad students. But I have to
Speaker 1: say the ones that are forty years old, like folks
Speaker 1: that went out into the real world and worked in
Speaker 1: real estate or law or something and then came back
Speaker 1: to do physics grad school, they're really good students. They
Speaker 1: really want it. Yeah, it takes a it's a lot
Speaker 1: of work to divert from a path in the real
Speaker 1: world back into academia. It's much harder than just like
Speaker 1: going from undergrad to grad school. So I really respect that.
Speaker 1: You know, you gotta really want it cool. So if
Speaker 1: there are any there, any listeners out there who want
Speaker 1: to change careers and get a PhD, they should contact you,
Speaker 1: right and you have a spot for them. I'm not
Speaker 1: sure I just offered anybody funding, but I would encourage you.
Speaker 1: If you have a deep passion for physics and you're
Speaker 1: finding yourself in a dead end job and you wish
Speaker 1: you had gone to physics grad school to unraveled mr
Speaker 1: of the universe, I encourage you, sir and ma'am, if
Speaker 1: you'd like to be in another dead end of of
Speaker 1: awesome knowledge, then be a cartoonist. Is that what you're
Speaker 1: gonna say? Yes? Yes, alright, So Daniel, let's break it
Speaker 1: down for people. What is quantum spin? We don't know?
Speaker 1: Done podcast over, why we had to diversely so much?
Speaker 1: Just do fill fill in the air time? Um, So
Speaker 1: people don't know because I don't know what quantum spin is.
Speaker 1: We don't really know what it is. Now we know
Speaker 1: it's a thing, right, So there's this thing, this property
Speaker 1: of particles. We don't really understand what it is, what
Speaker 1: it's doing. But there's this thing we've observed and we
Speaker 1: call it quantum spin. So let's do that. Let's talk
Speaker 1: about what this thing is that we can observe, and
Speaker 1: then we'll talk about why we call it quantum spin.
Speaker 1: And you know whether it's actually spinning and stuff. Right, Well,
Speaker 1: what's the origin of this? How did this come to
Speaker 1: be a thing? And it came to be a thing
Speaker 1: basically because of magnets, right, and you remember that charged particles.
Speaker 1: So a little particle with the charge on it, like
Speaker 1: an electron, if you move it in a circle, right,
Speaker 1: like through a wire loop or something, then it makes
Speaker 1: a magnetic field. Right, you can turn it on and
Speaker 1: off like electro magnets. This is how they work, right,
Speaker 1: like motors everyday electric motors, motors in your car and
Speaker 1: in your electric car, and you're um even your phone, right,
Speaker 1: there's probably a little motor of solenoid doing the vibrations
Speaker 1: when you put it on vibrate mode. That that's the principle.
Speaker 1: Like they just pump electrons through a coil a little loop,
Speaker 1: and then that creates a magnetic magnetic field which moves something.
Speaker 1: That's right. And the cute cool thing there is you
Speaker 1: have a magnet you can control electronically or digitally. So
Speaker 1: that's pretty awesome. But the important concept there is that
Speaker 1: things moving in a circle. Charges moving in a circle
Speaker 1: give you a magnetic field. Right, So that's something we
Speaker 1: know about, right, something we understand. And so then people
Speaker 1: were asking the question, um, well, do electrons themselves like
Speaker 1: individual particles? Do they have little magnets on them, like
Speaker 1: not just moving in a circle, but is there a
Speaker 1: magnetic field just due to the particle? And this is
Speaker 1: the kind of thing physicists do. They're like, well, we
Speaker 1: don't expect this to be this way, but let's just check, right,
Speaker 1: let's see if this happens. Because back then maybe they
Speaker 1: thought particles were like little little balls, right maybe yeah,
Speaker 1: well they didn't know. Right, this is in the nineteen twenties,
Speaker 1: this is almost a hundred years ago. The whole idea
Speaker 1: of a particle was still pretty new. People discovered electrons
Speaker 1: and neutrons and you know, it was a crazy era
Speaker 1: of discovery. They were maybe asking, like, is one electron
Speaker 1: maybe like a magnet itself? Yes, exactly right, And that's
Speaker 1: what they were wondering about. And so if it's a magnet,
Speaker 1: it would have a direction, right, like a field exactly
Speaker 1: what it have its own little magnetic field. So that
Speaker 1: was the question they were trying to answer, like does
Speaker 1: an electron or a silver atom or whatever, a little
Speaker 1: particle have its own magnetic field. So what they did
Speaker 1: is they built this device that would um that. Basically,
Speaker 1: they put particles in this device and the device has
Speaker 1: a magnet nick field on it, and they move the
Speaker 1: particles through the device, not in a circle, just in
Speaker 1: a straight line. And the idea is that the device
Speaker 1: has magnets in it. So if the particles have their
Speaker 1: own magnetic field, then they'll get pushed to one side
Speaker 1: because the magnets on the particle would interact with the
Speaker 1: magnets um from this device and would push the particles
Speaker 1: to one side or the other, kind of like like
Speaker 1: if you not through an electron, but if you through
Speaker 1: like an actual magnet, like a fridge magnet, if you
Speaker 1: threw it at some other magnets, it would get deflected, right, yeah, exactly,
Speaker 1: it would get deflected. Now, most magnets are balanced, right,
Speaker 1: Most magnets have a north and a south. So say
Speaker 1: you set up like a really strong pair of magnets
Speaker 1: and then you threw a fridge magnet through it, probably
Speaker 1: wouldn't get deflected because it has a north and a south,
Speaker 1: and so the polls would get balanced. So what they
Speaker 1: did was they set up one really big magnet and
Speaker 1: then a weaker magnet on the other side, so there's
Speaker 1: like an uneven magnetic field through it, so that if
Speaker 1: your fridge magnet goes through it, depending on the angle
Speaker 1: of the magnet, depending on the angle of the north
Speaker 1: and the south, they'll get pulled the one direction or
Speaker 1: the other. So they build the particle version of this, Right,
Speaker 1: They an uneven magnetic field, and they shot some particles
Speaker 1: through it, and what they found was really surprising, Right,
Speaker 1: it was really shocking what they discovered. They found that
Speaker 1: particles do have magnetic fields. Yeah. Well, first of all,
Speaker 1: they found two things that were surprising. One, particles do
Speaker 1: have their own little magnetic fields. I mean, first they
Speaker 1: did it with silver atoms, which is sort of the
Speaker 1: easiest thing they could do to to make a beam.
Speaker 1: Then this is a long time ago before you could
Speaker 1: easily make like a beam of particles. They just put
Speaker 1: a bunch of silver in an oven and like some
Speaker 1: of it boiled off and they collimated it and got
Speaker 1: a beam of silver atoms. And then later they did
Speaker 1: the same thing with electrons, and they found that these
Speaker 1: things have their own little magnets. Like an electron is
Speaker 1: a magnet, which is kind of perplexing, like what does
Speaker 1: that mean? Like where does this magnet come from? Right?
Speaker 1: But what does it mean that it's a magnet? Like
Speaker 1: if I just look at an electron, it has like
Speaker 1: a north and south poll to it. Yes, exactly. Electrons
Speaker 1: have their own little magnetic fields, even when they're not
Speaker 1: moving in a circle, even if they're not moving at all,
Speaker 1: Like if you suspended a like current, can you can
Speaker 1: you do it? Yeah? Yeah, exactly. If you have an
Speaker 1: electron just floating motionless in mid air, it will have
Speaker 1: its own little magnet. And that's really weird to us now, right,
Speaker 1: because we know that part of electrons and particles, they're
Speaker 1: not like little balls or just points. Yes, exactly, and
Speaker 1: so the question of where does that magnet come from?
Speaker 1: That's where this whole idea of spin came from. But
Speaker 1: the other really weird thing they found was that the
Speaker 1: magnets didn't point in every direction, Like if you just
Speaker 1: throw a bunch of magnets through this device, if they're
Speaker 1: all pointed in different directions. Right is just randomly oriented,
Speaker 1: you'd expect them to get deflected in random directions. This
Speaker 1: one goes left, this one goes right, this one goes
Speaker 1: a little bit up, this one goes a little bit down.
Speaker 1: But you know, if they're randomly organized, they should go
Speaker 1: in all sorts of directions, right, But what they found
Speaker 1: was that they either went left or they went right.
Speaker 1: There was not nothing in between, Like it's either left
Speaker 1: or right and nothing else, like, those are your two options, really,
Speaker 1: and no variations and how much right or how much left? Yeah,
Speaker 1: they all went exactly the same amount left or this
Speaker 1: exactly the amount right? What, Yeah, exactly. And that's why
Speaker 1: we call it quantum. Right, they have this little quantum
Speaker 1: magnetic field. The amazing thing is that, say, then you
Speaker 1: rotate the device, you're like, okay, rotated ninety degrees. Maybe
Speaker 1: you were measuring it on the X axis. Now you're
Speaker 1: measuring on the y axis, right, so you're imagining, okay, well,
Speaker 1: maybe these particles just you know, we're somehow weirdly oriented
Speaker 1: along the x axis, so they either go left or right.
Speaker 1: So then rotate your device ninety degrees. Then all the
Speaker 1: particles either move up or down right. No matter how
Speaker 1: you orient the device, the particles either go along the
Speaker 1: magnet or against it. Right. So it's not like a
Speaker 1: it's not like a real magnetic field, right, it's something weirder.
Speaker 1: It's not like a real magnetic field. Exactly like a
Speaker 1: magnetic it's like a magnetic field. And that's that's exactly
Speaker 1: where we what they struggled with. They're like, Okay, this
Speaker 1: has some property. It's something is generating this magnet, and
Speaker 1: it's definitely quantum mechanical in some weird way because we
Speaker 1: have all these weird properties. Like another weird thing about
Speaker 1: this magnetic devices. So you send a bunch of electrons
Speaker 1: through and you split them um left and right. Okay,
Speaker 1: then you take the left beam, only the left beam,
Speaker 1: and you split them through a device that's rotated ninety
Speaker 1: degrees that goes up and down. Then they split up
Speaker 1: and down right, even though beforehand they would only split
Speaker 1: left and right. Wait, what if you take the left beam,
Speaker 1: the one that the ones that went left? What if
Speaker 1: you try to split them up again? Horizontally. Do they
Speaker 1: all go left again, Yes, they do. But if you
Speaker 1: split them left right, and you take the left beam,
Speaker 1: then you split them up down, you take the upbeam,
Speaker 1: and then you try to split it left and right again,
Speaker 1: then they mix they go both left and right. And
Speaker 1: that's why it's quantum mechanical, yeah, because you can't you
Speaker 1: can't measure this weird little quantum magnet that the electron has.
Speaker 1: You can't measure it both in X and in y
Speaker 1: at the same time. It's the old Heisenberg uncertainty principle.
Speaker 1: You can't know too much information about the universe. So
Speaker 1: when you measure it in up, down, it mixes it
Speaker 1: up again and left right. Whoa. It's like, oh, I see,
Speaker 1: you can't measure the up and down and the left
Speaker 1: and right at the same time. It's like them that
Speaker 1: you can't know a particle where it is and where
Speaker 1: it's going at the same time. The same thing applies
Speaker 1: to the magnet exactly. And that's how we knew it
Speaker 1: was a quantum mechanical property. Right, So we discovered this
Speaker 1: weird thing about particles that they have their own little magnets,
Speaker 1: and somehow this magnet is quantum mechanical, and so they
Speaker 1: were like, what could this be? All right, let's get
Speaker 1: into what it could be and some of the weird
Speaker 1: things about that. But first let's take a quick break, okay, Daniel.
Speaker 1: So people were measuring electrons and they found that they
Speaker 1: have sort of like an inherent and inherent magnet inside
Speaker 1: of electrons, and that it's quantum mechanical, meaning that it's
Speaker 1: like really weird and you can't measure up and down
Speaker 1: and left and right. That's right um, and so people
Speaker 1: that's why people decide to call quantum spin. Yeah, even
Speaker 1: though it's not really spinning, they just went for that name.
Speaker 1: That's right. They call it quantum spin. And so let's
Speaker 1: try to figure out what do they mean by quantum spin?
Speaker 1: What why did they call it quantum spin? Alright, Well,
Speaker 1: quantum is pretty straightforward. It's definitely it's a property of particles,
Speaker 1: and it behaves like other quantum things that you can't
Speaker 1: know too much about it at the same time or
Speaker 1: you can't measure the x and the y um direction
Speaker 1: of at the same time. And also it's either up
Speaker 1: or down, right, there's no in between, So it's quantized.
Speaker 1: So the quantum stuff all right, I buy it. Right,
Speaker 1: you should definitely call this quantum something. If you're gonna
Speaker 1: call it quantum spin or quantum banana, you know, that's
Speaker 1: another question. But it should definitely have the quantum label. Okay, Well,
Speaker 1: I feel like maybe they should have called it quantum
Speaker 1: pole or something, you know, like something that references that,
Speaker 1: because really you're trying to you're trying to capture this
Speaker 1: kind of the magnetic the direction of the magnetic field
Speaker 1: of the electron, right, which is kind of like the pole. Yeah, well,
Speaker 1: what they what they did is they thought about what
Speaker 1: generates magnetic polls, right, what generates magnetic fields. And we
Speaker 1: know that a particle moving in a circle, right, like
Speaker 1: orbiting for example, will generate a magnetic field. So then
Speaker 1: they thought, maybe the particle is spinning. Maybe it's like
Speaker 1: physically spinning. And if you imagine electron like it has
Speaker 1: charge on it, think about the surface of the electron
Speaker 1: has like little bits of its charge distributed across the surface.
Speaker 1: This is the image they had back then, not the
Speaker 1: image that we use now. If that was spinning, then
Speaker 1: you can imagine that the spinning surface of the electron
Speaker 1: could be basically particles moving in a circle and now
Speaker 1: would generate a magnetic field. So they were like, ah,
Speaker 1: maybe we've discovered that electrons can spin, right, but why
Speaker 1: didn't they just call it like quantum poles and that?
Speaker 1: Because because you were born a hundred years too late. Man,
Speaker 1: I know, that's what I'm saying. Totally. I'm officially nominating
Speaker 1: you to be on the Secret Physics Naming Committee. I
Speaker 1: think you're you're great at this. I mean in the
Speaker 1: sense of people out there who might be trying to understand,
Speaker 1: is you know, I mean they're enough is they don't
Speaker 1: really um care what they call it a perthennial thing.
Speaker 1: But if if they had called the quantum the quantum
Speaker 1: magnetic pole or something like that, would that still be
Speaker 1: accurate and also maybe be easier to understand. I don't
Speaker 1: think it's accurate because it's describing the effect and not
Speaker 1: the cause. Right. We think something is happening which generates
Speaker 1: the magnetic field and these other properties. But what we'd
Speaker 1: like to do is figure out what the cause of
Speaker 1: it is, Like, what is the particle doing that generates
Speaker 1: the magnetic field? Right? What is the source of it?
Speaker 1: And does that give us insight into other stuff? And um,
Speaker 1: it turns out it does. Right, If we like to
Speaker 1: think about the particles having this thing we call spin,
Speaker 1: and we call it spin because it generates the magnetic field,
Speaker 1: but also because the way the mathematics of the spin
Speaker 1: is really similar to the mathematics of electrons in orbit.
Speaker 1: M What do you mean it's similar? Well, the like
Speaker 1: the mathematical language we use to like to describe it
Speaker 1: is very very similar, right, And when you see it's
Speaker 1: like some phenomenon A and you describe it mathematically, and
Speaker 1: you see phenomenon being you describe mathematically and you notice
Speaker 1: how look they're described by the same math, then you
Speaker 1: have to wonder are they two sides of the same
Speaker 1: coin or are they really the same thing? And so
Speaker 1: people's people thought, oh, look at all this release relationships
Speaker 1: between quantum between this thing we call quantum spin and
Speaker 1: orbital angular momentum, you know, the angular momentum of something
Speaker 1: moving around in a circle. And it was a lot
Speaker 1: of connections there, but they turned out to be wrong, right,
Speaker 1: Like I know, I know we were trying to do,
Speaker 1: but you sort of missed kind of well, yes and no, right,
Speaker 1: that's the first way you think about quantum mechanics like
Speaker 1: theoretically it does work, Physically it doesn't. So like theoretically
Speaker 1: it does, it works in this beautiful, really deep way
Speaker 1: because um, what we know, for example, is that angular
Speaker 1: momentum is conserved. Right, Like momentum is this property of
Speaker 1: particles to keep going in the direction they're going. Angular
Speaker 1: momentum is property particles to keep spinning the way they
Speaker 1: were spinning, right, And we know that angler momentum is conserved.
Speaker 1: If you start something spinning, it's going to keep spinning
Speaker 1: until you stop it. Now, what's what's conserved is total
Speaker 1: angle momentum, not the anglementum of like one thing. So
Speaker 1: you spin a top right, and you can stop it
Speaker 1: by touching it against another top, which then takes its
Speaker 1: spin right. So the total spin of those two tops
Speaker 1: is conserved. Well, the fascinating thing is that while we
Speaker 1: don't know what spin is, we know that orribital, angular
Speaker 1: momentum and spin are conserved together, like the some of
Speaker 1: them is conserved, so you can change the spin of
Speaker 1: some particle and and it will influence its angular momentum. Right,
Speaker 1: what do you need to conserve is the some of
Speaker 1: those two things, which tells you that spin really is
Speaker 1: like a kind of angular momentum. Fundamentally, theoretically, these really
Speaker 1: are related thing, Like a particle has that kind of
Speaker 1: quite angular momentum, and so it's approble to call it spin. Yes,
Speaker 1: it's some kind of intrinsic angular momentum. Like you can
Speaker 1: transfer angular momentum from orbital from the orbital kind to
Speaker 1: the spin kind and back right, which tells you that
Speaker 1: they really are two kinds of the same thing, that
Speaker 1: in some way the division between them is just in
Speaker 1: our minds. It's just mathematical. Oh, I see, So you're
Speaker 1: saying it's some kind of spin, it's some kind of
Speaker 1: a rotation. Yes, exactly. So it's like spin. It's like
Speaker 1: spin exactly. And so it's really I got you, I
Speaker 1: got you. Yeah, you admit it on air that horror
Speaker 1: Chand was right. They should be called like spin. It
Speaker 1: should be called like spin. I completely in totally agree
Speaker 1: with you. There you go. But I guess that the
Speaker 1: question is, like, so they called they decided to call
Speaker 1: it spin because it's sort of like it, like real spin.
Speaker 1: But I guess the question is are these particles actually spinning? Right?
Speaker 1: And that's the fascinating part is that they can't I
Speaker 1: mean particles are points, right, they have no volume. We
Speaker 1: were talking earlier about the idea of a particle with
Speaker 1: a surface and maybe bits of it on the surface
Speaker 1: we're spinning like the surface was rotating and the bits
Speaker 1: of charge removing in a circle to generate a magnetic field.
Speaker 1: That's hogwash, Like that can't happen because particles don't have
Speaker 1: a size. Right, Electronics, as far as we know, has
Speaker 1: zero size. Like the one side of it is exactly
Speaker 1: the same place as the other side of it, so
Speaker 1: there's nothing to spin. You can't turn around a point
Speaker 1: and has no direction. It's like a vector of zero length,
Speaker 1: Like there's no the distance between one end of the
Speaker 1: particle and the other end of the particle for them
Speaker 1: to be sort of moving at different in different directions. Right,
Speaker 1: exactly because it's a point particle. Yeah, you spin the
Speaker 1: particle and it's exactly the same as it was before. Right,
Speaker 1: there's no direction to it. Right, But what isn't it
Speaker 1: kind of maybe a philosophical question, like maybe a particle
Speaker 1: a point can't spin? Who's is a point can't spin?
Speaker 1: You just can't see it. I just said it. That's
Speaker 1: not enough for you. I'm only a like physicist. You're liked.
Speaker 1: You're well liked, Daniel. Um. No, imagine a imagintive vector right,
Speaker 1: imagintive vector right, which is a length and a direction. Okay, Um,
Speaker 1: that can spin right, you can turn it ninety degrees
Speaker 1: or degrees or whatever like an arrow. Like an arrow exactly.
Speaker 1: But if an arrow has zero length, what direction is
Speaker 1: it pointing in the one that I told, the one
Speaker 1: that it decides to have. I don't know this quantum stuff. No,
Speaker 1: it has no directive, has no length. It can't have
Speaker 1: a direction, right, because the direction would imply a length. Right,
Speaker 1: But you're sort of telling me that it does kind
Speaker 1: of have a direction, right, It kind of has like spin, Yeah,
Speaker 1: it has some property. It can't spin physically, like, it
Speaker 1: can't spin in the way that we would spin a
Speaker 1: tennis ball. Right. It definitely cannot do that. Also, these
Speaker 1: other problems, like if you imagine an electron, if you say, well,
Speaker 1: we don't really know. Maybe an electron does have a size, right,
Speaker 1: you haven't seen it. It maybe does. Well, you know,
Speaker 1: if you say, we know the size of electron has
Speaker 1: to be less than like ten to the minus twenty meters,
Speaker 1: because that's the most best resolution we have we have
Speaker 1: on our biggest particle accelerators, and then you calculate, like, well,
Speaker 1: how fast would the service the electron be spinning? Will
Speaker 1: it be spinning faster than the speed of light? So
Speaker 1: it's definitely not happening. And these are not tiny, little
Speaker 1: actually spinning balls, right. But this always happens when we
Speaker 1: try to describe something quantum mechanical in terms of something
Speaker 1: that's not right. You have the tennis ball or the
Speaker 1: baseball spinning in your head and you're trying to use
Speaker 1: that as a model, and it works for a while
Speaker 1: until it doesn't. And it doesn't work because this thing
Speaker 1: is not a tiny ball, right, It's some weird thing
Speaker 1: and it has some weird property. The amazing thing is
Speaker 1: this spin property is really similar to this other thing
Speaker 1: we do understand, right. I think maybe the problem is
Speaker 1: that you're saying that um like precision wise, like where
Speaker 1: it's constituent matter is can't rotate in space, right, But
Speaker 1: you're saying that it has other properties other than position
Speaker 1: of its constituent matter that do sort of have a
Speaker 1: preferred direction. Yes, exactly, it has. That's why we call
Speaker 1: it intrinsic spin because it has some property which is
Speaker 1: very similar mathematically to spin, but we know it's not
Speaker 1: actually spinning. So like intrinsic is like is the physics
Speaker 1: version of like right, because well, it's intrinsic spin. It's
Speaker 1: like some kind of spin. Right, So you're saying that
Speaker 1: that it's a point, but it is kind of spinning.
Speaker 1: I'm saying it's a point and it has some weird
Speaker 1: property which is related to physical spin, but it's not.
Speaker 1: But mathematically it's kind of equivalent. Before we keep going,
Speaker 1: let's take a short break. It's really quite fascinating, and
Speaker 1: you know it's amazing too. It's to look at the
Speaker 1: history because they did these experiments in twenties and the
Speaker 1: twenties was also when they were figuring out quantum mechanics,
Speaker 1: like they're like, how does this thing work? And they're
Speaker 1: still trying to put the math together. And when they
Speaker 1: were trying to put together the math for relativistic quantum mechanics,
Speaker 1: I was like the quantum mechanics of tiny particles moving
Speaker 1: really fast, they discovered it didn't work. It only worked
Speaker 1: if you added some new hidden variable to the electrons,
Speaker 1: like there had to be two kinds of them, not
Speaker 1: just anti particles and particles, but every electron also had
Speaker 1: to have this other weird hidden property and then they
Speaker 1: called it spin, and it's the same. It turned out
Speaker 1: to be the same spin that the other physics we're
Speaker 1: looking at, Yes, exactly. It all converged beautifully, and they
Speaker 1: were like to ching, look at this, Oh my god,
Speaker 1: it all makes sense now we understand those experiments, right,
Speaker 1: and so you need spin, like quantum mechanics doesn't work
Speaker 1: without spin, Like the Lorenz group and quantum field theory,
Speaker 1: all that has has been deeply built inside of it,
Speaker 1: so we know it's a thing and theoretically it makes sense.
Speaker 1: Do you mean it needed like a hidden variable? What
Speaker 1: does that mean? Like it needed needing it like an
Speaker 1: extra space, like an extra variable attached to it for
Speaker 1: the math to like. Yeah, think about an electron is
Speaker 1: having labels, right, like it has certain mass, that has
Speaker 1: a certain position, has certain direction whatever. Every electron also
Speaker 1: has to have this other label. You know, it's either
Speaker 1: up or down. Right, Remember this is spin, so it's
Speaker 1: not like you're spinning at some random speed. It's quantum spin.
Speaker 1: So there's only two options up or down. And so
Speaker 1: every electron has to have this weird label you're spinning
Speaker 1: up or you're spinning down, and that makes a difference,
Speaker 1: like when you fill out atomic orbitals. Right, No, two
Speaker 1: electrons can be in the same orbital because their fermions
Speaker 1: they don't like to share. But an electron that spin
Speaker 1: up is different from an electron that spin down. So
Speaker 1: you can have two electrons in the ground state because
Speaker 1: they have this weird sort of hidden thing that's different
Speaker 1: about them, like black on the red or it's like
Speaker 1: the exception to the probably exclusion, right, it's like it
Speaker 1: lets you go around it, right. It's why you can
Speaker 1: have two atoms in the ground state where otherwise the
Speaker 1: poll exclusion principle, well tell you can't. It's because, well,
Speaker 1: they're not really in the ground state. There's two ground states.
Speaker 1: You can have a ground state for up and a
Speaker 1: ground state for down. Right, But it's not really up
Speaker 1: and down, right, it's only up and down if you
Speaker 1: measure it up and down. It's up and down along
Speaker 1: whatever direction you measure. So if you measure it in X,
Speaker 1: every electron will say I'm up or I'm down. If
Speaker 1: then you measure it in why, every electron will say, oh,
Speaker 1: I'm up or I'm down, but they get mixed up. Right,
Speaker 1: So there are the quantum mechanically confusing because they're either
Speaker 1: up or down in X and then later your upper
Speaker 1: down and why which makes misses up your upper downness
Speaker 1: and X. It's very complicated. So you're saying that electrons
Speaker 1: can like talk essentially it's a way to communicate. Yeah, um.
Speaker 1: And and this is why um. This comes up all
Speaker 1: the time in like quantum computing, because you can use
Speaker 1: electrons as sort of a cube bit. Right is it
Speaker 1: spin up or is it spin down? Electron can be
Speaker 1: in two states and it's like a nice map from
Speaker 1: a classical bit which is zero or one. So these
Speaker 1: quantum mechanical properties are nice because they have two states. Right,
Speaker 1: So electrons are spin up or spin down. Um. So
Speaker 1: that's why it comes up all the time. And also
Speaker 1: in quantum entanglement, like you you have some particle, create
Speaker 1: two electrons, well to conserve anglo momentum, one has to
Speaker 1: be spin up and one has to be spinned down.
Speaker 1: Oh really Yeah, when you when you create them out
Speaker 1: of nothing or out of something else, they can they
Speaker 1: can't both come out the same spin. Yeah. Well, for example,
Speaker 1: z bosons can have spin zero. WHOA, what does that
Speaker 1: even mean, Daniel? It has no things, which is not
Speaker 1: really like spin. It's actually it's actually even more complicated.
Speaker 1: Z Bosons have a total spin of one. That's like
Speaker 1: the length of their spin. But this is a vector,
Speaker 1: so it can point in different directions, which means they
Speaker 1: have three waves to spin. So particles like electrons are
Speaker 1: called spin one half particles. They have one half of
Speaker 1: a unit to spin, which means they can be spin
Speaker 1: up one half or down one half. Z Bosons have
Speaker 1: spin one, right, so they can be spinned plus one
Speaker 1: or minus one or zero. So z bosons have three
Speaker 1: different ways to spin, whereas electrons have two ways to spin.
Speaker 1: It's pretty weird it considered like spin one way or
Speaker 1: the other way or not at all. Yes, exactly. But
Speaker 1: if you have a z boson with spin zero and
Speaker 1: it decays into an electron and a positron, then one
Speaker 1: of them has to be spin up and the other
Speaker 1: one has to be spinned down so that they add
Speaker 1: up to the original angular momentum of the z boson,
Speaker 1: which was zero. What if a plus one then it
Speaker 1: turns into an electron and a positron which are spinning
Speaker 1: in the same direction. So they add those two one
Speaker 1: halves add up to one. I'm gonna pretend I understood that. Well,
Speaker 1: that's the cool thing about it is that the math
Speaker 1: of this is really similar. You can use all the
Speaker 1: math you developed for like angler momentum and understanding spin
Speaker 1: orbitals and stuff like that, you can use that same
Speaker 1: math to understands been which is really compelling to me.
Speaker 1: Tells me that theoretically we're dealing with a very similar topic, right,
Speaker 1: or maybe the math we had to understand angular momentum
Speaker 1: matches the physics of quantum particles, right, yes, exactly when
Speaker 1: the Mathew describing matches the physics, then that success, right,
Speaker 1: that says, oh, look I've described it. I've gotten some inside.
Speaker 1: I mean, that's all we can ever do writ is
Speaker 1: hope that the math describes the physics, right, You know
Speaker 1: what I mean is like um, maybe maybe if you
Speaker 1: hadn't called it spin, you called it quantum blukity book, right,
Speaker 1: and then reconsidering nominating you for that committee after that?
Speaker 1: What do you have against the blukaty books? I don't
Speaker 1: even know how to spell it anyway. All right, So
Speaker 1: let's say we had quantum blukaty blok. Yeah, and then
Speaker 1: later you find out that angular momentum behaves like quantum
Speaker 1: blukity bluk, then that would be which one would be
Speaker 1: more correct? Right? We don't work correct? Well, if you're
Speaker 1: using the same math for both of them, then you're done.
Speaker 1: And there it's really just a question of how you
Speaker 1: name it. Right. In the end, it's the math, right,
Speaker 1: Then the physics is really about the math and not
Speaker 1: the names. In the end, it's about the equations on
Speaker 1: the paper and and and they're the structures and however
Speaker 1: about it. So really you could have called it anything,
Speaker 1: but you picked spin because it's sort of related to
Speaker 1: something that we people had knowledge about, or people have
Speaker 1: kind of intuitive understanding about, that's right, And because we
Speaker 1: think it really is a kind of angular momentum. What
Speaker 1: kind is it? And are these things really spinning? And
Speaker 1: why do electrons have intrinsic angle momentum? That we have
Speaker 1: no idea, but it seems to be necessary to make
Speaker 1: quantum field theory work. It seems to be a kind
Speaker 1: of angular momentum. It's definitely a real thing, but it's
Speaker 1: kind of a mystery, and it's something I like to
Speaker 1: think about like, why are you doing the electron, why
Speaker 1: are you spinning this way? What? What is making you
Speaker 1: generate that magnetic field? Yeah, exactly exactly, Well I guess so.
Speaker 1: And then the answer is what it's quantum? Say, it's um.
Speaker 1: It's some property of electrons um that sort of behaves
Speaker 1: similar to rotation. But we don't really know what it is,
Speaker 1: but it's there, it's real, and it's definitely not actually spinning.
Speaker 1: And it's not just electrons, right, All particles have some
Speaker 1: kind of spin. There's particles with half integer spin we
Speaker 1: call them fermions, and all the matter particles and like that,
Speaker 1: electrons and quarks, and then there's particles with integer spin,
Speaker 1: like bosons, like photons and ws and zs and gluons
Speaker 1: and those kind of particles. And that's actually the way
Speaker 1: we distinguish them. Right, Fermions have half endeger spin and
Speaker 1: bosons have integer spin. So it's a it's a it's
Speaker 1: an important deal. Like in the particle world, it's a
Speaker 1: big deal. Right, And you meet a new particle, you
Speaker 1: want to know what is its spin. The Higgs, for example,
Speaker 1: is spin zero. It's the only particle we know that
Speaker 1: has no spin at all and never can spin. It's
Speaker 1: the only particle we've ever found that can never spin. Wow,
Speaker 1: now you're just messing with basic arithmetic. Man. You're like,
Speaker 1: if it's zero, can only be zero. If it's one,
Speaker 1: it can be zero when mine is you know what
Speaker 1: I mean, Like you're using the same words to describe
Speaker 1: things that means anyways, Okay, I should be more careful
Speaker 1: when I say what it means for a particle have
Speaker 1: a certain amount of spin. When we say a particle
Speaker 1: spin one, what we mean is that the length of
Speaker 1: its spin vector is one, and that vector can point
Speaker 1: in different directions, and the individual particle can have spin
Speaker 1: plus one, zero or minus one if it's a spin
Speaker 1: one particle. If a particle spin one half, that's like
Speaker 1: the length of its spin vector, then it's spin vector
Speaker 1: con point either plus one half or minus one half.
Speaker 1: Those guys can't be zero. It's like, it's like arithmetic.
Speaker 1: It's not really Yeah, that's what I mean. It would
Speaker 1: just be so much easier to understand, you guys if
Speaker 1: you just said, instead of saying it's quantum spin, it's
Speaker 1: it's like spin. All right, I'm gonna say it's like
Speaker 1: spin from now on, and we'll see how many weird
Speaker 1: eyebrow races I get in my physics conversations. Yeah, totally.
Speaker 1: Well you'll probably get weird eyebrows in your physics department.
Speaker 1: But I'm saying, if you're talking to people out there
Speaker 1: in the street, are you suggesting there's like more unibrows
Speaker 1: in the physics department than in your average street more unibrows,
Speaker 1: one weird eyebrows man. All right, well, that's what quantum
Speaker 1: spin is. I know it's confusing and it's complicated, but
Speaker 1: we hope we at least brought you up to speed
Speaker 1: to where the physics community is. And remember, even physicists,
Speaker 1: we don't really know what quantum spin is. And all
Speaker 1: those grad students I asked, what, how would you explain
Speaker 1: quantum spin to a random person on the street, They
Speaker 1: got themselves tangled up and by their tongues as well.
Speaker 1: So it's a confusing topic. But if you still have
Speaker 1: questions about quantum spin, send us an email to feedback
Speaker 1: at Daniel and Jorne dot com. That's right. You can
Speaker 1: even send us like emails or like questions or emails
Speaker 1: that about how much you like us. See you next time.
Speaker 1: If you still have a question. After listening to all
Speaker 1: these explanations, please drop us a line. We'd love to
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