Speaker 1: Hey, this is Daniel and Jorge from Daniel and Jorge
Speaker 1: Explained the Universe. We interrupt this podcast for a special announcement.
Speaker 1: This Friday March We're having our first ever Daniel and
Speaker 1: Jorge Explained the Universe live stream event. So join us
Speaker 1: as we record an episode in real time and take
Speaker 1: questions from listeners like you. You can submit your questions
Speaker 1: live on air, or send them to us ahead of
Speaker 1: time at questions at Daniel and Jorghead dot com. To
Speaker 1: tune in, just go to YouTube dot com slash PhD
Speaker 1: Comics this Friday March at ten am Pacific. That's one
Speaker 1: pm Eastern, six pm Europe. That's two am in Tokyo
Speaker 1: and four am in Australia. What time it's out of Mars, Daniel,
Speaker 1: You know in case aliens want to tune in? Do
Speaker 1: you think aliens want to ask us questions? Um? May not,
Speaker 1: you may they might have engineering questions. You know, well
Speaker 1: I got questions for them. So tune in this Friday,
Speaker 1: March twenty seven at ten am Pacific at YouTube dot
Speaker 1: com slash PhD Comics and bring your question about the universe. Hey, Daniel,
Speaker 1: are you a fan of virtual reality? I'm still trying
Speaker 1: to get my head around this reality? What do I
Speaker 1: need another one for? You know you can? You can
Speaker 1: use it to walk on the surface of the Moon
Speaker 1: without ever leaving your couch. That does actually sound pretty good.
Speaker 1: But isn't it expensive? Here? It's virtually free. I think
Speaker 1: that means it's expensive. Actually, I think it is. Can
Speaker 1: I can I borrow some cash from you? Yeah? Sure,
Speaker 1: I'll send you some virtual money. I am or had
Speaker 1: any cartoon is and the creator of PhD comments, Hi,
Speaker 1: I'm Daniel. I'm a particle physicist, and I'm the co
Speaker 1: author of our book, We Have No Idea, A Guide
Speaker 1: to the Unknown Universe. It's available in paperback, hardcover and
Speaker 1: also virtual reality. You can put on goggles and experience
Speaker 1: being inside our minds. Oh man, that sounds terrifying. Is
Speaker 1: that a horror show? But welcome to our podcast Daniel
Speaker 1: and Jorge Explain the Universe, a production of I Heart
Speaker 1: Radio in which we take mental tours all over the
Speaker 1: universe and talk about the biggest things, the smallest things,
Speaker 1: the fastest things, the craziest things in the universe and
Speaker 1: explain all of them to you in a way we
Speaker 1: hope you find educational and entertaining. Yeah, that's hard. We
Speaker 1: talked about all the real things out there in the
Speaker 1: universe and the cosmos and the furthest reaches of the
Speaker 1: galaxies and galaxy clusters, but we also like to talk
Speaker 1: about things dad don't yet exist or may not even exists.
Speaker 1: That's right. We want to take you inside the minds
Speaker 1: of scientists and tell you how they think about the universe,
Speaker 1: what models are going on in their head, and can
Speaker 1: we distill those in a way that makes sense to you,
Speaker 1: because we want you to understand sort of the forefront
Speaker 1: of human thinking about how the universe works. Yeah, because
Speaker 1: there are the things that are around us that we
Speaker 1: can see and touch and feel and hold in our hands,
Speaker 1: but there's sort of another universe out there that we
Speaker 1: can't see, and that is maybe not quite as real
Speaker 1: as you might imagine. Yeah. Well, we're always sort of
Speaker 1: building a universe in our minds to map what's going
Speaker 1: on outside. Like we can do experiments, we can make measurements,
Speaker 1: We can see things, and then we try to understand them,
Speaker 1: and that understanding requires building a model in our head
Speaker 1: of what we think is happening. And some of those
Speaker 1: things we can experience some of those things we wonder
Speaker 1: are they real or are they just our imagination? Yeah,
Speaker 1: So Daniel and I we wrote a book Daniel called
Speaker 1: you know, We Have No Idea. I don't know if
Speaker 1: you know we wrote a book by the way, I
Speaker 1: had no Idea? Is that right? Yeah? Yeah, it's called
Speaker 1: We Have No Idea? And uh. And then we talk
Speaker 1: about all the things we don't know about the universe,
Speaker 1: all the unanswered questions out there. Um of those of
Speaker 1: you listening, please check it out if you are interested.
Speaker 1: But I was sort of surprised to get today's topic
Speaker 1: in an email for me this morning, because I don't
Speaker 1: think we covered this topic in that book. No, this
Speaker 1: is a really tricky topic, and it really has to
Speaker 1: do with how physicists think about particles, what they mean,
Speaker 1: and are they real? How do they talk to each other,
Speaker 1: what happens when one electron pushes against another electron, and
Speaker 1: how does that end? What happens inside the mind of
Speaker 1: a physicist when she thinks about that. So this topic
Speaker 1: that we're going to talk about today, was it just
Speaker 1: too maybe extreme for our book? What did you think? What?
Speaker 1: Why didn't we talk about it in our fun and
Speaker 1: interesting book? Now? Available for purchase what we totally could have.
Speaker 1: And you know, in the book, we have to make
Speaker 1: some pretty hard choices about what topics to cover. We
Speaker 1: talked about what is space and what is time? And
Speaker 1: what is matter? And how will the universe end? And
Speaker 1: we could have gone on forever and talked about all
Speaker 1: the things we don't understand about the universe. It's a
Speaker 1: pretty long list, but we had to make some choices.
Speaker 1: I see, the book wasn't called we have lots of
Speaker 1: no ideas. We have absolutely zero ideas about a lot
Speaker 1: of things. But anyway, so today's talpic. It's pretty interesting
Speaker 1: because I think everyone has heard of particles. I mean,
Speaker 1: we all know that we are made out of molecules
Speaker 1: and atoms, and atoms are made out of particles, and
Speaker 1: they form the basis of for matter in all of
Speaker 1: the universe. But I think maybe not not a lot
Speaker 1: of people have heard about this particular type of particle. Yeah,
Speaker 1: this is a concept that people talk about when they
Speaker 1: think about you know, empty space and particles popping in
Speaker 1: and out of the vacuum. And it's a topic that's
Speaker 1: really important for thinking about forces and how things push
Speaker 1: and pull against each other and how that actually works
Speaker 1: at the microscopic level. So it's a really important concept
Speaker 1: in particle physics, but it's sort of slipper and you
Speaker 1: get your head around. But recently some listeners wrote in
Speaker 1: and asked us to explain this to be on the podcast,
Speaker 1: we'll be asking the question what is a virtual particle?
Speaker 1: Is it a particle wearing virtual reality goggles? Is it
Speaker 1: one particle imagining another particle? Is it a virtuous particle
Speaker 1: who has a Stanza for its principles? These particles all
Speaker 1: follow rules. Actually, that's a really good point because there's
Speaker 1: a lot of sort of pop science misinformation about virtual particles.
Speaker 1: People say, oh, virtual particles don't follow the laws of physics,
Speaker 1: But they do. They follow the laws of physics absolutely,
Speaker 1: just like all the other particles and as far as
Speaker 1: we know, everything in our real universe. Interesting. I like
Speaker 1: how you associate virtue with following the rules. Some deep
Speaker 1: psychological things going on there. Daniel today on the podcast
Speaker 1: Therapy of Daniel, How are you feeling steep virtually good?
Speaker 1: Particularly virtual particular? Well, so it's an interesting topic. I
Speaker 1: have to say, I've never heard of these virtual particles.
Speaker 1: I guess because they're virtual. Is that part of what
Speaker 1: we're gonna talk about today. Yeah, a little bit. They're
Speaker 1: not real, Are they not real? Well, they are real,
Speaker 1: they're just not really particles. There are a thing that's
Speaker 1: out there in the universe. They're responsible for important physical
Speaker 1: effects that we can see, but we can never see
Speaker 1: them directly. So one way to think about them is
Speaker 1: that they're sort of a calculational tool in our minds,
Speaker 1: a way that we think about what's happening out there
Speaker 1: in the universe, but not something that we can have
Speaker 1: ever observed directly, sort of like we think about quantum
Speaker 1: mechanical wave functions. We never observe the wave function itself.
Speaker 1: We only observe its consequences, it's influence on things. But
Speaker 1: it's important for us to predict those those experiments, to
Speaker 1: predict those consequences, that we can use that in our calculations.
Speaker 1: All right, well let's get let's get into it here today.
Speaker 1: But first we were wondering, as usual, how many people
Speaker 1: out there and you what a virtual particle was. So
Speaker 1: I walked around campus that you see Irvine, and I
Speaker 1: asked people this kind of crazy as a terror question.
Speaker 1: So before you hear these answers, think about it for
Speaker 1: a second. If someone asked you on this treet, what
Speaker 1: is a virtual particle? What would you answer? Here's what
Speaker 1: people had to say, not in the slowest an imaginary particle,
Speaker 1: Houston light theories or something like that. Virtual state is
Speaker 1: a state, kind of a transitory state where if you're
Speaker 1: going to do like a two photon excitation, it's that
Speaker 1: state in the middle that is a virtual state where
Speaker 1: it's not really you can't describe I can't describe it
Speaker 1: very well. I'm not into physics, but that's that's the
Speaker 1: best I can do on that one. It's a particle
Speaker 1: of matter. I don't know, something that's made up based
Speaker 1: on technology. Maybe all right? Virtually no one said yes,
Speaker 1: there was some creative answer, though. I really like the
Speaker 1: person that said something that's made up based on technology.
Speaker 1: That sounds pretty good. Like I was, I could use
Speaker 1: technology to create new particles. That's sort of my job,
Speaker 1: isn't that what you do? Did you create new particles?
Speaker 1: That's what I'm supposed to be doing, and I'm using
Speaker 1: a lot of technology and spending a lot of government money,
Speaker 1: but instead you're here recording a podcast. Don't tell anybody
Speaker 1: that's right, nobody knows about this, Daniel, don't worry. But
Speaker 1: you know, an attempt only a few thousand people listen.
Speaker 1: In my twenty years of searching for new particles, I've
Speaker 1: never really found one. So I'm using technology to try
Speaker 1: to find new particles. I just haven't been successful yet.
Speaker 1: You're like, forget particles. I'm just gonna have a party.
Speaker 1: It's a virtually easier But you know, this wasn't too surprising.
Speaker 1: It's a sort of esoteric topic, and I think a
Speaker 1: lot of people know why virtual particles are important without
Speaker 1: knowing the concept itself. So I think you'll find that
Speaker 1: the things we talk about the role virtual particles play
Speaker 1: will be familiar to a lot more people than actually
Speaker 1: know what virtual particles are and can explain. It's not
Speaker 1: a crazy concept. It's just maybe kind of a naming
Speaker 1: convention or sort of like how this is to see
Speaker 1: some of these particles? Yeah, precisely. All right, Well let's
Speaker 1: gett into it, Daniel. What is a virtual particle and
Speaker 1: why is it called virtual? And is it not real? Well?
Speaker 1: I think first let's get a clear picture for like
Speaker 1: what is what do we mean by a particle in
Speaker 1: a real particle? Because as you talked about earlier, like
Speaker 1: we're made of stuff. I made of stuff, You're made
Speaker 1: of stuff. We think when we are real, like I
Speaker 1: imagine I'm real, and we think that we're made of particles,
Speaker 1: and those particles have an existence. They're like stick around,
Speaker 1: they have persistence, that can move through space, all this
Speaker 1: kind of stuff, and we feel substantial, and so you
Speaker 1: and I we are made of real particles. But those particles,
Speaker 1: they're not like a little ball of stuff, and they're
Speaker 1: not like a tiny dot, right, It's not like we're
Speaker 1: built out of little tinker toys. As we've talked about
Speaker 1: in the podcast several times, each of these particles should
Speaker 1: be seen as like a ripple in a quantum field.
Speaker 1: It's like you have this field that feels space and
Speaker 1: at some points that has energy and it's vibrating, and
Speaker 1: that's what each of these particles are. It's like a
Speaker 1: little perturbation in in reality. Kind of yes, it's a
Speaker 1: little perturbation in reality. And the key thing to know
Speaker 1: is that real particles are special perturbations. There's not like
Speaker 1: any perturbation in the quantum field is a part is
Speaker 1: a real particle there if that perturbation follows certain rules
Speaker 1: and has certain behaviors and has and obeys certain equations.
Speaker 1: Then it's a real particle. You're saying, there are perturbations
Speaker 1: that are not particles that or that don't form particles.
Speaker 1: There aren't quantum fields. Yes, And that's uh, you just
Speaker 1: gave away the ghosts. Because some perturbations are real particles
Speaker 1: and some perturbations are virtual particles. So some small fraction
Speaker 1: of the perturbations and quantum fields are what make up
Speaker 1: real particles. That are you and me. I guess my
Speaker 1: question is what makes a real particle real? What makes
Speaker 1: that proturbation real? Well, it can do various things, Like
Speaker 1: it can travel forever. Right, you shoot a real particle
Speaker 1: through space, it will just keep going until it bounces
Speaker 1: into something. It has this sort of self sustaining nature
Speaker 1: to it. It doesn't just like spread out into nothing
Speaker 1: or cancel itself out and and and it's propagating right
Speaker 1: through the field. It's not like it's moving. It's like
Speaker 1: it's I'm a perturbation here, and then I'm proturbing the
Speaker 1: space next to me, and that's what we call moving.
Speaker 1: That's right, And you need to keep two pictures in
Speaker 1: your head. At once. One is sort of the quantum
Speaker 1: field theory view, like think about the whole universe is
Speaker 1: just space filled with quantum fields, and as you say,
Speaker 1: a particle moving through them. Is the wiggle in the
Speaker 1: field is here, and then the wiggle in the field
Speaker 1: is there, So that wiggle is the thing that's propagating.
Speaker 1: Is the energy moving At the same time, you like
Speaker 1: to associate that will with a particle. You have maybe
Speaker 1: this image in your head of like a little ball
Speaker 1: that's moving from here to there. And in fact, if
Speaker 1: you shoot an electron out of an electron gun, that's
Speaker 1: sort of what you imagine. The most mathematically accurate way
Speaker 1: to think about it is in terms of a little
Speaker 1: ripple in the field that's moving through the field. But
Speaker 1: you like to associate that with a real electron because
Speaker 1: it has properties like mass and it can fly forever
Speaker 1: um if it doesn't touch anything and that and that's
Speaker 1: a real particle because it satisfies various rules like it
Speaker 1: has a specific mass and it's kinetic energy. Makes sense,
Speaker 1: you know, you can interpret that ripple as a particle.
Speaker 1: Did you have to do with like the shape of
Speaker 1: it or yes, it has What makes it special is
Speaker 1: it just like a set of conditions that made it
Speaker 1: is special, or there's something about the combination of things
Speaker 1: that went into it that caused ripple to be special.
Speaker 1: In a like the shape of it. It has a
Speaker 1: lot to do with how it was made. And you
Speaker 1: can imagine, for example, a guitar string. Take your guitar string.
Speaker 1: If you plug it carefully, it has various modes that
Speaker 1: it likes to wiggle at, right, and those are the
Speaker 1: various notes of the guitar string. And you can, you know,
Speaker 1: make the string shorter or longer to change those modes.
Speaker 1: But just for like an open string, you play it,
Speaker 1: it makes it. It likes to play it a certain
Speaker 1: a certain frequency. But you could also do other things
Speaker 1: on that string that aren't like a nice awcole shan.
Speaker 1: You know, if your toddler comes in the room and
Speaker 1: hits your guitar with with something crazy, it doesn't make
Speaker 1: a nice sound. So you can imagine the difference between
Speaker 1: like a careful, clean plucking of the string that sends
Speaker 1: one well behaved wave propagating down the string, and a
Speaker 1: sort of chaotic tumble of ripples that don't that can't
Speaker 1: be interpreted the same way and because you're saying quantum
Speaker 1: fields can be disturbed in any number of ways, but
Speaker 1: like if you disturb it just right, it'll create this
Speaker 1: kind of like perfect self sustaining um, you know, bumping it, yes,
Speaker 1: and precisely. And the thing that it has it has
Speaker 1: a definite mass. So an electron always has an electron's mass,
Speaker 1: and it moves through the universe always having the same mass.
Speaker 1: And so a real particle something that has a definite mass,
Speaker 1: that has that stuff to it. That's the thing that
Speaker 1: makes it real that it has a specific mass, and
Speaker 1: you can interpret things about it that we're familiar with. Right,
Speaker 1: You like to think, well, things have energy, like kinetic energy.
Speaker 1: Are particle has a positive kinetic energy? That makes sense.
Speaker 1: Later and we talk about virtual particles, you'll see that
Speaker 1: they don't obey these same rules. They can't be interpreted
Speaker 1: in the same way. There's still ribbles in the quantum field,
Speaker 1: but they're not nice, clean ripples that follow these rules.
Speaker 1: They're not that virtuous judgment. I'm a particle physicists. All
Speaker 1: particles are welcome in my mind, except they want that
Speaker 1: break rules. Apparently, well, they don't break. They don't break
Speaker 1: the rules. It's a category, right, These are these that
Speaker 1: you know satisfy some restrictions we call those. Really they
Speaker 1: do certain things. It's just a label in our minds.
Speaker 1: It's a distinction in our head Some of them have
Speaker 1: a mass that sticks around forever and and and you know,
Speaker 1: and follow these um these I guess they are rules. Yes,
Speaker 1: I'm trying to I'm always saying that, But you're right,
Speaker 1: m I do like rules for it. We'd be nothing
Speaker 1: without rules. All right, Well, let's get into then, what
Speaker 1: are virtual particles and whether or not they're real or
Speaker 1: whether you can only see them on a VR headset.
Speaker 1: But first let's take a quick break. All right, Daniel,
Speaker 1: we're talking about virtual particles, and you're saying, a real
Speaker 1: particle is like a perturbation in a quantum field which
Speaker 1: surrounds us all around. And but it's like a perfect perturbation.
Speaker 1: That's what a real particle is. It's like something that
Speaker 1: somehow the field really likes and doesn't just kind of
Speaker 1: like destroys or dissipates. Yeah, there are lots of different
Speaker 1: kinds of perturbations, and some of them satisfy additional constraints.
Speaker 1: Some of them satisfy a subset of them also satisfy
Speaker 1: some equations, some wave equations that tell us about how
Speaker 1: they move, and those real part of universe likes them.
Speaker 1: They're like, hey, I like this sound, I like this note.
Speaker 1: I'm just gonna let it keep on going. You're speaking
Speaker 1: for the U niverse, now, do that's a bit presumptuous.
Speaker 1: Maybe the universe likes the other kind of particles. It
Speaker 1: thinks the real particles are like boring rule followers. Oh,
Speaker 1: I see, well, somehow it allows the real particles to
Speaker 1: to be a special right, yes, sort of like them. Well,
Speaker 1: the real particles, real particles can do something that virtual
Speaker 1: particles can't. But virtual particles can do lots of things
Speaker 1: real particles can't. So what can real particles do that
Speaker 1: virtuals can't. Well, real particles can propagate across the universe.
Speaker 1: They have a fixed mass, and that carries them sort
Speaker 1: of through space. You're saying forever nothing. They don't degrade.
Speaker 1: They don't degrade. Like you look up at the sky
Speaker 1: and a photon hit your I from a far away star.
Speaker 1: That's a real photon. It's propagated through space and it
Speaker 1: could have got another billion light years if your eye
Speaker 1: hadn't blocked it. So, yeah, these things can travel forever.
Speaker 1: But there are real particles also that don't last, like
Speaker 1: don't we Are you telling me that some of the
Speaker 1: higher energy particles, like the you know, some of these
Speaker 1: heavy cords, they at some point they break apart. Yes, um,
Speaker 1: higher mass particles are unstable, but they're still real. They're
Speaker 1: real particles, but they can decay into lower mass particles.
Speaker 1: So not every particle has an infinite lifetime like an
Speaker 1: electron or a photon, but they are still real. You
Speaker 1: can interact with them, you can see them, they can
Speaker 1: propagate through space. All right. Well, then let's get into
Speaker 1: what a virtual particle is. So I guess it means
Speaker 1: it's not a real particle. Yeah, it's not a not
Speaker 1: a clean ripple. It's like everything else, you know, it's
Speaker 1: any other kind of disturbance in the quantum field, right,
Speaker 1: And it's like a transfer of energy from one place
Speaker 1: to another in the field. I mean, that's what the
Speaker 1: disturbance is. But it's not something you can coalesce together
Speaker 1: and say, oh, this is a nice little packet of
Speaker 1: energy that moves in a tight way through the field
Speaker 1: and we'll stay that way. It like diffuses out, it
Speaker 1: spreads out, it fades away pretty quickly. Wait, so it's
Speaker 1: possible for feels to be disturbed, not in particles. It's
Speaker 1: possible for people feel to be disturbed in a way
Speaker 1: that makes a real particle. It's also possible for fields
Speaker 1: to be disturbed in a way that doesn't make a
Speaker 1: real particle. What do we call that? We call that
Speaker 1: a virtual particle. Do they break sort of the rule
Speaker 1: of quantum mechanics, like the minimum amount of energy and
Speaker 1: things like that, Like, is it possible to have a
Speaker 1: ripple that's smaller than an electron? For example, you have
Speaker 1: ripples in the electron field that don't have the mass
Speaker 1: of an electron. Yes, but they're not breaking any of
Speaker 1: the rules. This is a common misunderstanding. They follow the
Speaker 1: rules of physics, but you know those rules have fuzziness
Speaker 1: in them. So, for example, if you do something in
Speaker 1: a very short amount of time, then the energy these
Speaker 1: particles is very uncertain because there's an uncertainty relationship between
Speaker 1: time and energy, like there is between momentum and space,
Speaker 1: and so there are a lot of things they can
Speaker 1: do that seem like they're breaking the rules, but isn't
Speaker 1: actually Well, wait, so you can't have a ripple in
Speaker 1: that's smaller than an electron. Then you can have a
Speaker 1: ripple in the electron field that doesn't correspond to one
Speaker 1: wheel of drown it's smaller, it's a smaller ripple than
Speaker 1: one real electron. You might be thinking to hold on.
Speaker 1: The field is supposed to be quantized, and that's true,
Speaker 1: but that applies to real particles and in the case
Speaker 1: of virtual part and you just broke over my head, Daniel.
Speaker 1: All this time I thought it was like a fundamental
Speaker 1: rule of the universe that that quantum fields can't ripple
Speaker 1: with anything smaller than than than the quantum particles. But
Speaker 1: you're saying they can't. They're just not real. Those are different,
Speaker 1: not sustainable, they're not sustainable ripples. Yeah, and you know
Speaker 1: the thing you're talking about are self sustaining. Real particles
Speaker 1: create one, you can create two, you can create three.
Speaker 1: You can't contain two and a half. Right, there's there's
Speaker 1: no self sustaining mode. They can do that. But if
Speaker 1: you're gonna have chaotic fluctuations of the field, then you
Speaker 1: can have all sorts of crazy stuff. And so yeah,
Speaker 1: that releases you from a lot of those requirements. Okay,
Speaker 1: and these ripples you're saying, they don't propagate, or they
Speaker 1: do propagate. They propagate, but they don't propagate as far.
Speaker 1: They don't hold themselves to get other and so they
Speaker 1: don't sustain themselves. They sort of just like spread out
Speaker 1: and diffuse and eventually they sort of cancel themselves out.
Speaker 1: When you mean what happens to them, They they like separate,
Speaker 1: they become you know, inquirent or well, they're very short lived,
Speaker 1: they're transient. And so for example, a virtual particle might
Speaker 1: be like a little blob of energy that one electron
Speaker 1: sends to another electron to push it away, Like two
Speaker 1: electrons they push each other apart. Right, how does that happen, Well,
Speaker 1: it happens through ripples in the electromagnetic field. And you
Speaker 1: can that's not really a photon, Like it's not a
Speaker 1: flash of light that goes between the electrons to push
Speaker 1: them apart. But there is a transfer of energy, a
Speaker 1: transfer of momentum, and that you can associate with a particle.
Speaker 1: You say, oh, that's like a virtual photon. Wait, you're
Speaker 1: saying that when an electron pushes another electron because they're
Speaker 1: both negative charge. They I thought they always use photons.
Speaker 1: You're saying that doesn't happen through photons. They do, but
Speaker 1: it's a virtual photon. It's not a real photon. It's
Speaker 1: not a photon that could like see you with your eye.
Speaker 1: It's a virtual, short lived photon, not a photon that
Speaker 1: could propagate across the universe and hit another star. That's
Speaker 1: a special photon. But there's non special photons. Yes, real
Speaker 1: photons are special photons. And Jorges universe though, I love
Speaker 1: all particles equally, but there are two kinds of particles.
Speaker 1: There's a real particles that can probably through the universe
Speaker 1: forever without interacting, and then there are these transient, short
Speaker 1: lived virtual particles that don't that you know, we could
Speaker 1: argue about whether they really are particles, but we call
Speaker 1: them virtual particles. I feel like it's be like telling
Speaker 1: you your two kids. I think one of you is real,
Speaker 1: one of you is not, but I think you're both
Speaker 1: special to me. If one of your kids only lasts
Speaker 1: or ten to the mine is twenty three seconds, you're
Speaker 1: not even gonna be able to finish that sentence. Well, um, okay,
Speaker 1: So so when an electron pushes another electron, they're not
Speaker 1: interchanging photons. They're interchanging choosing the field that are like photons,
Speaker 1: but not photons. They're not real photons. They are virtual photons.
Speaker 1: And when we draw a little Feynman diagrams to describe
Speaker 1: this between physicists, we draw a wiggly line just like
Speaker 1: a photon. But that photon, you know, it is created
Speaker 1: inside the interaction. It's emitted and then absorbed. It's never
Speaker 1: seen externally, like you never see that. Nobody says, oh, look,
Speaker 1: I will soft flash of light that only exists between
Speaker 1: the two electrons. And so these virtual particles are not
Speaker 1: ever directly observed. They just sort of used in our
Speaker 1: calculation and inferred. Oh I see, But could someone intercept them?
Speaker 1: Could you know, like let's say, when an electron is
Speaker 1: pushing another electronic and suddenly another electron sweeps in in between,
Speaker 1: would they be able to catch that photone and say, yes,
Speaker 1: there was a photon here. Yeah, but that's going to
Speaker 1: blow your mind because then the photon becomes real. Then
Speaker 1: it becomes real. Then it becomes real, and you might ask, well,
Speaker 1: how does it know? Right? Well, remembering quantum mechanics, there's
Speaker 1: no like propagation. It's not like this is a thing
Speaker 1: which goes somewhere. It goes from here to there. If
Speaker 1: if you have an initial state and a final state,
Speaker 1: your initial state is like an electron is flying off
Speaker 1: and the final state is um some some photon from
Speaker 1: that electron is now observed by your camera. All the
Speaker 1: possible things that could explain that sort of can happen
Speaker 1: all at once, right, and and only some of them survive.
Speaker 1: And so if there's a camera there to observe it,
Speaker 1: then the virtual options disappear. They can't exist anymore. But
Speaker 1: if there's not a camera there to observe it, then
Speaker 1: they can interact and sort of it's unobserved state with
Speaker 1: other electrons and push them along and stay a virtual particle.
Speaker 1: I totally understood that. Virtually my VR heads in here,
Speaker 1: all right. It sort of sounds like, um, it's one
Speaker 1: of these quantum mechanical things where there's sort of virtual
Speaker 1: until you open the box. Kind Of, yes, they're virtual
Speaker 1: until you open the box. And if you open the
Speaker 1: box and interact with them, then only real particles can
Speaker 1: satisfy that set of constraints since and then the virtual
Speaker 1: particles sort of never happened. And if you're worried about
Speaker 1: like you know causality there, you know, the whole interaction
Speaker 1: is not like a flowing in time in that same way.
Speaker 1: The whole interaction sort of understood is one thing. You know,
Speaker 1: like there's this emission and absorption, and we're understanding this
Speaker 1: whole sort of process in terms of one calculation, and
Speaker 1: we think about all the ways that it can happen simultaneously.
Speaker 1: Only some of those survive based on what the constraints
Speaker 1: are when you open the box. When you open the box, Yeah,
Speaker 1: all right, Well tell me you're saying that virtual particles
Speaker 1: break rules. So what are some of the rules that
Speaker 1: virtual particles can break? Right, So they don't violate like
Speaker 1: deep laws of physics, but they can do things that
Speaker 1: real particles can't do. For example, if you try to
Speaker 1: interpret these wiggles in the quantum fields as a particle,
Speaker 1: you get weird answers. Like you do the calculations to
Speaker 1: get what's the kinetic energy of this thing? Well, it
Speaker 1: can be negative negative kinetic energy. Negative kinetic energy, and
Speaker 1: that's weird if you're used to think about kinetic energy
Speaker 1: is like energy of motion, because like energy of motion,
Speaker 1: no matter which direction you're going, is always positive, right,
Speaker 1: there's a V squared in there, so any velocity gives
Speaker 1: you positive energy. But in physics we calculate this energy,
Speaker 1: you know, as a relationship between mass and momentum, and
Speaker 1: it gets wonky because it's not like an individual, localized
Speaker 1: little particle that's moving through space and the way you're
Speaker 1: familiar with. It's like this weird disturbance and you're trying
Speaker 1: to force this sort of particle view onto it and
Speaker 1: doesn't quiet work. It's like a little void of energy almost.
Speaker 1: It's sort of like you're asking an inappropriate question and
Speaker 1: so you get a nonsense answer. Oh, I see, it's
Speaker 1: like a it's like a wiggle, you know, and that
Speaker 1: wiggle and can give you weird, weird answers when you
Speaker 1: try to measure it. Yeah, and you're not measuring the energy.
Speaker 1: You're like, well, here's the wiggle. If I sort of
Speaker 1: trying to squeeze this into the particle a work, and
Speaker 1: then ask what would be the energy if this was
Speaker 1: a particle. You get sort of a nonsense answer, you know,
Speaker 1: like if you asked how popular would Daniel be if
Speaker 1: he was a famous movie star. But you're like, well,
Speaker 1: that's nonsense. There's no way he'd be a famous movie star,
Speaker 1: so he'd be like negative popular or something. And the
Speaker 1: other thing is that these virtual particles aren't restricted to
Speaker 1: have the same mass as the particles you're familiar with.
Speaker 1: Like you know, the photon is no mass. Photons that
Speaker 1: hate your eye from stars very very far away, they
Speaker 1: have no mass because those are real photons. But virtual
Speaker 1: photons can have mass. A special disturbance in the electromagnetic
Speaker 1: field can have mass. Yes, yes, it can carry some
Speaker 1: mass with it. And where does it carry it that
Speaker 1: the other photons done? In its back pocket? Of course,
Speaker 1: I mean where do you carry your masks? That's where
Speaker 1: all minds these ago. It's sort of just another way
Speaker 1: to interpret this in the light of a particle. It
Speaker 1: sort of breaks one of those rules. And that's actually
Speaker 1: the thing that distinguishes a virtual particle from a real particle.
Speaker 1: A real particle is a little packet of energy that
Speaker 1: has definite mass and propagates forever, and the virtual particle
Speaker 1: doesn't have that definite mass. It can have high mass,
Speaker 1: it can have low mass um for a photon, it
Speaker 1: can have nonzero mass. You can do that mean that
Speaker 1: the photon is going slower than the speed of light.
Speaker 1: So virtual particles can go slower than the speed of light. Well,
Speaker 1: all the information transfer in the electromagnetic field always happens
Speaker 1: at the speed of light. But when you talk about
Speaker 1: the speed of a particle, you usually want to define
Speaker 1: in terms of like how fast is this packet moving,
Speaker 1: And in terms of the virtual particle, it's like it's
Speaker 1: more diffused, it's like spreading out everywhere, and so I'm
Speaker 1: not even sure it makes sense to define the speed
Speaker 1: of a virtual particle. Yeah, I feel I feel like
Speaker 1: it's getting to this weird quantum realm. Yeah, And that's
Speaker 1: exactly the problem is that we want to interpret things
Speaker 1: happening on the microscopic scale in terms of things were
Speaker 1: familiar with, in terms of things we know, and so
Speaker 1: we ask these questions like what is its mass? What
Speaker 1: is its kinetic energy? But those don't those are not
Speaker 1: always appropriate questions, just like if you ask where is
Speaker 1: the electron and where is it going? You know that
Speaker 1: doesn't really always have a satisfactory answer, and so virtual
Speaker 1: particles are less satisfactory than real particles. They have like
Speaker 1: a fewer answers to cough up. All right, let's get
Speaker 1: into then the question of whether or not they're actually real.
Speaker 1: Can something be virtual and real at the same time?
Speaker 1: But first, let's take a quick break, all right, Daniel,
Speaker 1: So we we've defined virtual particles as being the wiggle
Speaker 1: non particle wiggles in the quantum fields of the universe.
Speaker 1: But are they actually real? Can we say that they're real?
Speaker 1: If if it sounds like you're you're saying they're not real,
Speaker 1: that's that's why you call them virtual. Yeah, Well, they're
Speaker 1: not real in the sense that we define them, right.
Speaker 1: Particle physicists have a very specific definition of what real is.
Speaker 1: You know, when you say really, you mean like it
Speaker 1: actually exists, is out there in that sense. Absolutely, virtual
Speaker 1: particles are real. But you know, we took this word
Speaker 1: real and we redefined it to mean it has a
Speaker 1: specific mass, it can propagate infinitely through this quantum field. Oh,
Speaker 1: I see, they exist, But they're just not real particles.
Speaker 1: It's like a you have to keep the two words together. Yeah,
Speaker 1: they're not really the capital R, I guess or if
Speaker 1: they're not physics real you know, or like real or
Speaker 1: whatever you would call it. But they but they have
Speaker 1: real but they have actual effects on the universe. You know,
Speaker 1: we talk about empty space, but we know that space
Speaker 1: has energy in it, and that energy can be converted
Speaker 1: into short lived virtual particles. You have energy. It's kind
Speaker 1: of like saying like, um, it would be different if
Speaker 1: I say Daniely is not real. Then if I said
Speaker 1: Daniel is not a real movie star, that's kind of
Speaker 1: perfect psychology. Daniel exists, but he's not a real movie star,
Speaker 1: just like these wiggles exist, but they're not real particles.
Speaker 1: That works perfectly, except I'm not even a virtual movie star,
Speaker 1: so you can that's the whole point of virtual reality.
Speaker 1: Then I'm gonna pop into your movie and then pop
Speaker 1: right back out again. All right, So the um, they're
Speaker 1: they're real, but they're not particles, And so why even
Speaker 1: call them particles? Why even have they? Why why not
Speaker 1: just call them, you know, squigglies or or ripples. Because
Speaker 1: we like to categorize things, and we like to find
Speaker 1: connections between things, and so we like to sort of say,
Speaker 1: these real particles and the virtual particles are sort of
Speaker 1: two sides of the same coin. And they are. You know,
Speaker 1: real particles are very closely related to virtual particles. It's
Speaker 1: not like a um, a hard wall you can put
Speaker 1: between them. And say they're totally different. Real particles are
Speaker 1: like a special case of virtual particles, and so we
Speaker 1: call them particles because hey, we're particle busicists. Everything is
Speaker 1: a particle and we just short sort of try to
Speaker 1: categorize them together. M when when you have a hammer,
Speaker 1: when have a sixteen dollar hammer, everything, let's take a particle.
Speaker 1: Everything looks like a particle. And you know, we even
Speaker 1: describe forces in terms of particles. We like to think
Speaker 1: about electromagnetism and the strong force and the weak force
Speaker 1: um operating in terms of particles, and that can be
Speaker 1: confusing sometimes if you try to think about it like microscopically.
Speaker 1: How can particles be responsible for forces? All forces are
Speaker 1: done through virtual particles. All the forces that we can
Speaker 1: describe quantum mechanically, like gravitation, we still don't know, but
Speaker 1: all those quantum mechanical forces, yeah, they're described using virtual particles.
Speaker 1: And the way you might have heard it described is
Speaker 1: like one electron comes along and pushes on the other
Speaker 1: electron by throwing a photon at it. But it's actually
Speaker 1: throwing a virtual photon. It's a virtual wiggle in the field,
Speaker 1: and it's not thrown from one to the other. Right,
Speaker 1: it's not something that's moving and flying in a well
Speaker 1: defined way through space. It's a little disturbance in the
Speaker 1: field that's causing that's pushing on the they're electron. Yeah,
Speaker 1: and that's a key thing to understand because fields can
Speaker 1: do more than just push. Right, if you and I
Speaker 1: are throwing a ball back and forth, all we can
Speaker 1: do is push each other. I can't throw the ball
Speaker 1: at you and then attract you somehow. That doesn't make
Speaker 1: any sense. I'm transferring momentum to you and pushing you away,
Speaker 1: So I can't throw a ball at you with negative momentum.
Speaker 1: So that's why that analogy breaks down. Because real forces,
Speaker 1: like electromagnetism, they're also responsible for you know, electrons attracting
Speaker 1: to protons. Yeah, pulling, it's the same deal. So to
Speaker 1: understand how that works in terms of virtual particles, you
Speaker 1: have to let go of particles as these little balls
Speaker 1: that were throwing back and forth and just think about
Speaker 1: them in terms of like weird ripples. And the key
Speaker 1: thing to think about there is like you are exchanging
Speaker 1: a virtual photon if it has a certain amount of
Speaker 1: energy to it. Heisenberg tells us, if you're well defined
Speaker 1: in terms of momentum, you're not well defined in terms
Speaker 1: of location. So that particle, that virtual photon that's being
Speaker 1: passed back and forth, doesn't really exist any where. It
Speaker 1: sort of exists everywhere. It's like if it's momentum is
Speaker 1: very specific, then its location is flat. It's like you
Speaker 1: can exist through the whole universe. So like if I
Speaker 1: have a magnet, but let's say I'm holding too man
Speaker 1: magnets here in the table in front of me, and
Speaker 1: you know, I try to bring them together, and they're
Speaker 1: pushing each other apart, these magnets. Um Before I was
Speaker 1: thinking like maybe they're swapping photons so that they can
Speaker 1: repel each other, but really they're they're not. They're just
Speaker 1: sort of like just sort of like perturbing each other's fields. Yes,
Speaker 1: they're perturbing each other's fields and transmitting energy back and forth,
Speaker 1: but not in the sense of like little particles that
Speaker 1: are actually flying back and forth like real particles. Like
Speaker 1: you can't put a piece of cardboard between two magnets
Speaker 1: to block the magnetism, right, and you'll be like, well, look,
Speaker 1: photons can't get through my cardboard, so how can magnetism
Speaker 1: get through right. The reason is that electromagnetic fields definitely
Speaker 1: can get through your cardboard, or you can hear a
Speaker 1: radio through cardboard. More like you're bending the fields or
Speaker 1: on you, and that's what's pushing the other one. Yes, yes,
Speaker 1: it's just not in a way that you can characterize
Speaker 1: as a little ball is like a little self propagating,
Speaker 1: nice package of field. And so that's how these things interact.
Speaker 1: The interact with the fields, and you can, if you want,
Speaker 1: interpret those in terms of virtual particles. It's sort of
Speaker 1: like looser definition of what a particle is than just
Speaker 1: the narrow definition of what real particles are. You sort
Speaker 1: of expanded the definition to include more more of these
Speaker 1: weird things. Yeah, by relaxing some of the rules, say,
Speaker 1: you don't have to have the right mass, you don't
Speaker 1: have to have a kinetic energy. That makes sense. It's
Speaker 1: a ripple in the field. Let's have to be a
Speaker 1: particle to be a particle, that's what you're saying. And
Speaker 1: you could also just get rid of the particle picture entirely,
Speaker 1: be like, you know what, that doesn't make any sense
Speaker 1: to me. I'm just going to think about the fields
Speaker 1: and you can do that. It's just it's really hard
Speaker 1: because calculations and field theory are very, very complicated, and
Speaker 1: so to simplify it, Fineman introduced this idea, said, well,
Speaker 1: let's just think about it in terms of like the
Speaker 1: simplest interaction, and drew these diagrams that showed like, well,
Speaker 1: if it was exchanging one thing you would call a particle,
Speaker 1: then it would look like this, And then let's think
Speaker 1: about in terms of the second simplest and the third simplest,
Speaker 1: and then they just ignore everything else. So he developed
Speaker 1: this framework for approximating quantum field theory calculations by using
Speaker 1: these like number of virtual particles. The most likely thing
Speaker 1: to happen is one virtual particle, the second most likeliest two,
Speaker 1: and then three, and as you go on, there's more
Speaker 1: and more possibilities, but they get less and less likely,
Speaker 1: so you can ignore them. It just lets you sort
Speaker 1: of understand these complex field interactions. Yeah, lets you quickly
Speaker 1: approximate and get mostly the right answer in a way
Speaker 1: that sort of makes sense. And you know, physics is
Speaker 1: all about like making sense. We know these are the
Speaker 1: rules the universe, what do they mean to us? Like
Speaker 1: this interpretation step is important, it's the physics part of it, right.
Speaker 1: The rest of it's sort of mathematics, and it's like,
Speaker 1: how do we use this to build up a picture
Speaker 1: of the world that makes sense to us? And you're
Speaker 1: always teasing me that I like rules, but like that's
Speaker 1: what physics is, you know, we're trying to figure out
Speaker 1: what the rules are and and uh and how they
Speaker 1: limit us and whether they actually do limit us. M alright, cool, Well,
Speaker 1: I feel feel my mind virtually blown a little bit
Speaker 1: to learn that there are particles that are not particles.
Speaker 1: They're very much real and they very much kind of
Speaker 1: make everything work, right, because without virtual particles you can't
Speaker 1: have forces, and without forces, nothing happens. The universe would
Speaker 1: be pretty boring without any forces, So stay tuned for
Speaker 1: Daniel's future virtual career in the movie about virtual particles.
Speaker 1: It's sort of interesting to think that, you know, there's
Speaker 1: more to the universe and what we can see and
Speaker 1: feel in touch, that there's all this sort of you know,
Speaker 1: underlying chaos happening in between what we imagine to be
Speaker 1: matter and electrons and courts. Yeah, and that always our
Speaker 1: descriptions of it are lacking, right, that we are limited
Speaker 1: by the way our minds work and the way that
Speaker 1: we think about the universe. We're trying to map that
Speaker 1: onto this crazy, insane chaos that's going on at a
Speaker 1: microscopic level, and it's never completely satisfactory. It's always running
Speaker 1: into contradictions and seeming nonsense. And that's because the universe
Speaker 1: at that scale is weird and alien and very difficult
Speaker 1: to translate into sense for the human brain. But hey,
Speaker 1: I think it's worth trying. So we hope that made
Speaker 1: a little bit more sense to all of you. And
Speaker 1: then now you know what a virtual particle is, or
Speaker 1: what it's not, or what it what it is not
Speaker 1: is virtually understand it. So thanks for listening. We hope
Speaker 1: you enjoyed that. See you next time. Before you still
Speaker 1: have a question after listening to all these explanations, please
Speaker 1: drop us a line. We'd love to hear from you.
Speaker 1: You can find us on Facebook, Twitter, and Instagram at
Speaker 1: Daniel and Jorge That's one word, or email us at
Speaker 1: Feedback at Daniel and Jorge dot com. Thanks for listening,
Speaker 1: and remember that Daniel and Jorge Explain the Universe is
Speaker 1: a production of I Heart Radio. For more podcast from
Speaker 1: my Heart Radio, visit the i Heart Radio app. Apple
Speaker 1: podcasts or wherever you listen to your favorite shows. Yeah.