Daniel and Kelly’s Extraordinary Universe - What are virtual particles?

Episode Date: March 26, 2020

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This is an I-Heart podcast. December 29th, 1975, LaGuardia Airport. The holiday rush, parents hauling luggage, kids gripping their new Christmas toys. Then, everything changed. There's been a bombing at the TWA terminal. Just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged, terrorism. Listen to the new season of Law and Order Criminal Justice System

On the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. My boyfriend's professor is way too friendly, and now I'm seriously suspicious. Wait a minute, Sam. Maybe her boyfriend's just looking for extra credit. Well, Dakota, luckily, it's back to school week on the OK Storytime podcast, so we'll find out soon. This person writes, my boyfriend's been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now he's insisting we get to know each other, but I just want or gone. Now, hold up.

Isn't that against school policy? That seems inappropriate. Maybe find out how it ends by listening to the OK Storytime podcast and the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. I'm Dr. Scott Barry Kaufman, host of the Psychology Podcast. Here's a clip from an upcoming conversation about how to be a better you. When you think about emotion regulation, you're not going to choose an adaptive strategy, which is more effortful to use.

unless you think there's a good outcome. Avoidance is easier, ignoring is easier, denial is easier, complex problem solving, takes effort. Listen to the psychology podcast on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts. Hey, this is Daniel and Jorge from Daniela Jorge Explain the Universe. We interrupt this podcast for a special announcement. This Friday, March 27th,

we were having our first ever Daniel and Jorge Explain the Universe live stream event. So join us as we record an episode in real time and take questions from listeners like you. You can submit your questions live on air or send them to us ahead of time at questions at danielanhorhead.com. To tune in, just go to YouTube.com slash ph.D. Comics this Friday, March 27th at 10 a.m. Pacific.

That's 1 p.m. Eastern, 6 p.m. Europe. That's 2 a.m. in Tokyo and 4 a.m. in Australia. What time it's out on Mars, Daniel? You know, in case aliens want to tune in. Do you think aliens want to ask us questions? Maybe not you. They might have engineering questions, you know? Well, I got questions for them.

So tune in this Friday, March 27th at 10 a.m. Pacific at YouTube.com slash PhD comics. And bring your questions about the universe. Hey, Daniel, are you a fan of virtual reality? I'm still trying to get my head around this reality. What do I need another one for? You know, you can use it to walk on the surface of the moon without ever leaving your couch. That does actually sound pretty good. But isn't it expensive?

I hear it's virtually free. I think that means it's expensive. Actually, I think it is. Can I borrow some cash from you? Yeah, sure. I'll send you some virtual money. I am Horhammy cartoonist and the creator of PhD comics. Hi, I'm Daniel. I'm a particle physicist, and I'm the co-author of our book.

We Have No Idea, a guide to the unknown universe. It's available in paperback, hardcover, and also virtual reality. You can put on goggles and experience being inside our minds. Oh, man, that sounds terrifying. Is that a horror show? But welcome to our podcast, Daniel and Jorge Explain the Universe, a production of IHeart Radio. In which we take mental tours all over the universe

and talk about the biggest things, the smallest things, the fastest things, the craziest things in the universe, and explain all of them to you in a way we hope you find educational and entertaining. Yeah, that's right. We talk about all the real things out there in the universe and the cosmos and the furthest reaches of the galaxies and galaxies, and galaxy clusters. But we also like to talk about things

that don't yet exist or may not even exist. That's right. We want to take you inside the minds of scientists and tell you how they think about the universe. What models are going on in their head? And can we distill those in a way that makes sense to you? Because we want you to understand

sort of the forefront of human thinking about how the universe works. Yeah, because there are the things that are around us that we can see and touch and feel and holding our hands. But there's sort of another universe out there that we can't see and that is maybe not quite as real as you might imagine. Yeah.

Well, we're always sort of building a universe in our minds to map what's going on outside. Like we can do experiments, we can make measurements, we can see things, and then we try to understand them. And that understanding requires building a model in our head of what we think is happening. And some of those things we can experience, some of those. those things we wonder. Are they real or are they just our imagination? Yeah. So Daniel and I, we wrote a book, Daniel, called, You know, We Have No Idea. I don't know if you know we wrote a book, by the way. I had no idea. Yeah, it's called We Have No Idea. And then we talk about all the things

we don't know about the universe, all the unanswered questions out there. To those of you listening, please check it out if you are interested. But I was sort of surprised to get today's topic in an email from you this morning because I don't think we covered this topic in that book. No, this is a really tricky topic, and it really has to do with how physicists think about particles, what they mean, are they real? How do they talk to each other? What happens when one electron pushes against another electron? And what happens inside the mind of a physicist when she thinks about that? So this topic that we're going to talk about today, was it just too maybe extreme for our book? What did you think? Why didn't we talk about it in our fun and interesting book, now available for purchase? Well, we totally could have. And, you know, in the book, we had to make some pretty hard choices about what topics to cover. We talked about what is space and what is time and what is matter and how will the universe end.

And we could have gone on forever and talked about all the things we don't understand about the universe. It's a pretty long list. But we had to make some choices. I see. The book wasn't called, we have lots of no ideas. We have absolutely zero ideas about a lot of things. But anyway, so today's topic is pretty interesting because I think everyone has heard of particles. I mean, we all know that we are made out of molecules and atoms and atoms are made out of particles

and they form the basis for matter in all of the universe. But I think maybe not a lot of people have heard about this particular type of particle. Yeah, this is a concept that people talk about when they think about, you know, empty space and particles popping in and out of the vacuum. and it's a topic that's really important for thinking about forces and how things push and pull against each other and how that actually works at the microscopic level. So it's a really important concept in particle physics,

but it's sort of slippery to get your head around. But recently some listeners wrote in and asked us to explain this. So on the podcast, we'll be asking the question, What is a virtual particle? Is it a particle wearing virtual? reality goggles? Is it one particle imagining another particle? Is it a virtuous particle who has a stance up for its principles? These particles all follow rules, actually. That's a really good point because there's a lot of sort of pop science misinformation about virtual particles. People

say, oh, virtual particles don't follow the laws of physics, but they do. They follow the laws of physics, absolutely, just like all the other particles. And as far as we know, everything in our real the universe. Interesting. I like how you associate virtue with following the rules. It's some deep psychological things going on there, Daniel. Today on the podcast, Therapy of Daniel. How are you feeling today?

Virtually good? Particularly virtual. Well, so it's an interesting topic. I have to say I've never heard of these virtual particles. I guess because they're virtual. Is that part of what we're going to talk about today? about today? Yeah, a little bit. They're not real. Are they not real? Well, they are real. They're just not really particles. They're a thing that's out there in the universe. They're responsible for important

physical effects that we can see, but we can never see them directly. So one way to think about them is that there's sort of a calculational tool in our minds, a way that we think about what's happening out there in the universe, but not something that we can ever observe directly. Sort of like we think about quantum mechanical wave functions. We never observe the wave function itself. We only observe its consequences, its influence on things. But it's important for us to predict those experiments, to predict those consequences that we can use that in our calculations. All right. Well, let's get into it here today. But first, we were wondering, as usual, how many people out there knew what a virtual particle was. So I walked around

campus at UC Irvine and I asked people this kind of crazy esoteric question. So before you hear these answers, think about it for a second. If someone asked you on the street, what is a virtual particle, what would you answer? Here's what people had to say. Not in the slightest. An imaginary article used in light theories or something like that. A virtual state is a state, kind of a transitory state where if you're going to do like a two-photon excitation, it's that state in the middle.

That is a virtual state where it's not really, you can't describe, I can't describe it very well. I'm not into physics, but that's the best I can do on that one. It's a particle of matter? I don't. Something that's made of based on technology, maybe? All right. Virtually, no one said yes. There were some creative answers, though.

I really like the person that said something that's made up based on technology. That sounds pretty good. I wish I could use technology to create new particles. That's sort of my job. Isn't that what you do? Did you create new particles? That's what I'm supposed to be doing, and I'm using a lot of technology

and spending a lot of government money. But instead, you're here recording a podcast. Shh, don't tell anybody. That's right. Nobody knows about this, Daniel, don't worry. But, you know, in my... Only a few hundred thousand people listening. In my 20 years of searching for new particles,

I've never really found one. So I'm using technology to try to find new particles. I just haven't been successful yet. You're like, forget particles. I'm just going to have a particle. party. It's virtually easier. But, you know, this wasn't too surprising.

It's a sort of esoteric topic. And I think a lot of people know why virtual particles are important without knowing the concept itself. So I think you'll find that the things we talk about, the role virtual particles play will be familiar to a lot more people than actually know what virtual particles are and can explain it. Oh, I see. It's not a crazy concept.

It's just maybe kind of a naming convention or sort of like how physicists see some of these particles. Yeah, precisely. All right, well, let's get into it, Daniel. What is a virtual particle, and why is it called virtual, and is it not real? Well, I think first let's get a clear picture for, like, what do we mean by a particle and a real particle? Because as you talked about earlier, like, we are made of stuff, I'm made of stuff, you're made of stuff, we think we are real, I imagine, I'm real, and we think that we're made of particles. And those particles have an existence.

they like stick around, they have persistence, they can move through space, all this kind of stuff. And we feel substantial. And so you and I, we are made of real particles. But those particles, they're not like a little ball of stuff and they're not like a tiny dot, right? It's not like we're built out of little tinker toys. As we've talked about in the podcast several times, each of these particles should be seen as like a ripple in a quantum field. It's like you have this field that fills space and at some points it has energy and it's vibrating. and that's what each of these particles are.

It's like a little perturbation in reality, kind of. Yes, it's a little perturbation in reality, and the key thing to know is that real particles are special perturbations. There's not like any perturbation in the quantum field is a real particle. If that perturbation follows certain rules and has certain behaviors and obeys certain equations, then it's a real particle. You're saying there are perturbations that are not particles, that don't form particles in quantum fields.

Yes, and you just gave away the ghost because some perturbations are real particles and some perturbations are virtual particles. So some small fraction of the perturbations in quantum fields are what make up real particles that are you and me. I guess my question is, what makes a real particle real? What makes that perturbation real and special?

Well, it can do various things, like it can travel forever. You shoot a real particle through, space, it will just keep going until it bounces into something. It has this sort of self-sustaining nature to it. It doesn't just like spread out into nothing or cancel itself out. And it's propagating, right, through the feel. It's not like it's moving. It's like it's, I'm a perturbation here, and then I'm perturving the space next to me, and that's what we call moving. That's right. And you need to keep two pictures in your head at once. One is sort of the quantum field theory view. Like,

think about the whole universe is just space filled with quantum. fields and as you say a particle moving through them is the wiggle in the field is here and then the wiggle in the field is there so that wiggle is the thing that's propagating is the energy moving at the same time you like to associate that will with a particle you have maybe this image in your head of like a little ball that's moving from here to there and in fact if you shoot an electron out of an electron gun that's sort of what you imagine the most mathematically accurate the way to think about it is in terms of a little ripple in the field that's moving through the field. But you like to associate that with a real electron because it has properties like

mass and it can fly forever if it doesn't touch anything. And that's a real particle because it satisfies various rules. Like it has a specific mass and its kinetic energy makes sense. You know, you can interpret that ripple as a particle. Did it have to do with like the shape of it or? Yes, it has to do with the shape of it. What makes it special? Is it just like a set of conditions that made it is special, or there's something about the combination of things that went into it that caused ripple to be

special in the shape of it? It has a lot to do with how it was made. You can imagine, for example, a guitar string. Take a guitar string, if you pluck it carefully, it has various modes that it likes to wiggle at, right? And those are the various notes of the guitar string. And you can, you know, make the string

shorter or longer to change those modes. But just for like an open string, you play it, it likes to play. It likes to at a certain frequency. But you could also do other things on that string that aren't like a nice oscillation. You know, if your toddler comes in the room and hits your guitar with something crazy,

it doesn't make a nice sound. So you can imagine the difference between like a careful, clean plucking of the string that sends one well-behaved wave propagating down the string and a sort of chaotic tumble of ripples that can't be interpreted the same way. Because you're saying quantum fields

can be disturbed in any number of ways. Yes. But like if you disturb it just right, it'll create this kind of like perfect, self-sustaining, you know, bump in it. Yes, and precisely. And the thing that it has is it has a definite mass. So an electron always has an electron's mass

and it moves to the universe, always having the same mass. And so a real particle, something that has a definite mass, that has that stuff to it. That's the thing that makes it real, that it has a specific mass. mass, and you can interpret things about it that we're familiar with, right? You like to think,

well, things have energy, like kinetic energy. A real particle has a positive kinetic energy that makes sense. Later, when we talk about virtual particles, you'll see that they don't obey these same rules. They can't be interpreted in the same way. There's still ripples in the quantum field, but they're not nice, clean ripples that follow these rules. They're not that virtuous. I don't make any judgments. I'm a particle physicist. All particles are welcome in my mind. except the ones that break rules, apparently. Well, they don't break the rules. They don't call them real particles.

They don't break the rules. It's a category, right? These are, these that, you know, satisfies some restrictions. We call those real. They do certain things. It's just a label in our mind. It's a distinction in our head. Some of them have a mass that sticks around forever and, you know, and follow these, I guess they are rules.

Yes. I'm trying to avoid saying that, but you're right. I do like rules for it. we'd be nothing without rules all right well let's get into then what are virtual particles and whether or not they're real or whether you can only see them on a VR headset but first let's take a quick break

December 29th 1975 LaGuardia Airport The holiday rush, parents hauling luggage, kids gripping their new Christmas toys. Then, at 6.33 p.m., everything changed. There's been a bombing at the TWA terminal. Apparently the explosion actually impelled metal, glass. The injured were being loaded into ambulances, just a chaotic, chaotic scene.

In its wake, a new kind of enemy emerged, and it was here. to stay. Terrorism. Law and order criminal justice system is back. In season two, we're turning our focus

to a threat that hides in plain sight that's harder to predict and even harder to stop. Listen to the new season of Law and Order criminal justice system on the IHeart Radio app,

Apple Podcasts, or wherever you get your podcasts. My boyfriend's professor is way too friendly. and now I'm seriously suspicious. Oh, wait a minute, Sam. Maybe her boyfriend's just looking for extra credit. Well, Dakota, it's back to school week on the OK Storytime podcast,

so we'll find out soon. This person writes, my boyfriend has been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now, he's insisting we get to know each other, but I just want her gone. Now, hold up. Isn't that against school policy?

That sounds totally inappropriate. Well, according to this person, this is her boyfriend's former professor, and they're the same age. And it's even more likely that they're cheating. He insists there's nothing between them. I mean, do you believe him? Well, he's certainly trying to get this person to believe him

because he now wants them both to meet. So, do we find out if this person's boyfriend really cheated with his professor or not? To hear the explosive finale, listen to the OK Storytime podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. I had this, like, overwhelming sensation that I had to call her right then. And I just hit call. I said, you know, hey, I'm Jacob Schick. I'm the CEO of One Tribe Foundation. And I just wanted to call on and let her know, there's a lot of people battle.

some of the very same things you're battling. And there is help out there. The Good Stuff podcast, Season 2, takes a deep look into One Tribe Foundation, a non-profit fighting suicide in the veteran community. September is National Suicide Prevention Month, so join host Jacob and Ashley Schick as they bring you to the front lines of One Tribe's mission.

I was married to a combat army veteran, and he actually took his own life to suicide. One Tribe saved my life twice. There's a lot of love that flows through this place, and it's sincere. Now it's a personal mission. I don't have to go to any more funerals, you know. I got blown up on a React mission.

I ended up having amputation below the knee of my right leg and a traumatic brain injury because I landed on my head. Welcome to Season 2 of the Good Stuff. Listen to the Good Stuff podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. All right, Daniel, we're talking about virtual particles, And you're saying that a real particle is like a perturbation in a quantum field, which surrounds us all around. But it's like a perfect perturbation.

That's what a real particle is. It's like something that somehow the field really likes and doesn't just kind of like destroys or dissipates. Yeah. There are lots of different kinds of perturbations, and some of them satisfy additional constraints. Some of them satisfy a subset of them also satisfy some equations, some wave equations that tell us. about how they move. And those real particles... The universe likes them.

They're like, hey, I like this sound. I like this note. I'm just going to let it keep on going. You're speaking for the universe now? Dude, that's a bit presumptuous. Maybe the universe likes the other kind of particles. It thinks the real particles are like boring rule followers. Oh, I see.

Well, somehow it allows the real particles to be as special, right? Yes. They must sort of like them. Well, the real particles can do something that virtual particles can't. But virtual particles can do lots. of things real particles can't so you know what can real particles do that virtual can't well real particles can propagate across the universe they have a fixed mass and that carries them sort of through space you're saying forever nothing they don't degrade they don't degrade like you look up at

the sky and a photon hits your eye from a far away star that's a real photon it's propagated through space and it could have got another billion light years if your eye hadn't blocked it so yeah these things can travel forever but there are real particles that also that don't last. Like, weren't you telling me that some of the higher energy particles, like the, you know, some of these heavy quarks,

they, at some point, they break apart? Yes. Higher mass particles are unstable, but they're still real. They're real particles, but they can decay into lower mass particles. So not every particle has an infinite lifetime, like an electron or a photon,

but they are still real. You can interact with them. You can see them. They can propagate through space. All right. Well, then let's get into, what a virtual particle is. So I guess it means it's not a real particle.

Yeah. It's not a clean ripple. It's like everything else. You know, it's any other kind of disturbance in the quantum field, right? And it's like a transferer of energy from one place to another in the field. I mean, that's what the disturbance is.

But it's not something you can coalesce together and say, oh, this is a nice little packet of energy that moves in a tight way through the field and will stay that way. It, like, diffuses out. It spreads out. it fades away pretty quickly. Wait, so it's possible for fields to be disturbed, not in particles? It's possible for field to be disturbed in a way that makes a real particle.

It's also possible for fields to be disturbed in a way that doesn't make a real particle. What do we call that? We call that a virtual particle. Don't they break sort of the rule of quantum mechanics, like the minimum amount of energy and things like that? Is it possible to have a ripple that's smaller than an electron, for example? You have ripples in the electron field that don't have the mass of an electron, yes, but they're not breaking any of the rules. This is a common misunderstanding. They follow the rules of physics, but, you know, those rules have fuzziness in them.

So, for example, if you do something in a very short amount of time, then the energy these particles is very uncertain, because there's an uncertainty relationship between time and energy, like there is between momentum and space. And so there are a lot of things they can do that seem like they're breaking the rules, but isn't actually. Wait, so you can't have a ripple that's smaller than an electron then? You can have a ripple in the electron field that doesn't correspond to one real electron. It's a smaller ripple than one real electron. You might be thinking, hold on, the field is supposed to be quantized, and that's true. But that applies to real particles. And in the case of virtual particles.

You just broke open my head, Daniel. All this time, I thought it was like a fundamental. rule of the universe that quantum fields can't ripple with anything smaller than the quantum particles, but you're saying they can't.

They're just not real. Those are different. They're just not sustainable. They're not sustainable ripples, yeah. And, you know, the thing you're talking about are self-sustaining real particles create one, you can create two, you can create three, you can't contain two and a half,

right? There's no self-sustaining mode that can do that. But if you're going to have chaotic fluctuations of the field, then you can have all sorts of crazy stuff. And so, yeah, that releases you from a lot of those requirements. Okay, and these ripples are saying they don't propagate or they do propagate? They propagate, but they don't propagate as far.

They don't hold themselves together, so they don't sustain themselves. They sort of just like spread out and diffuse, and eventually they sort of cancel themselves out. What do you mean? What happens to them? They, like, separate? They become, you know, incoherent? Well, they're very short-lived. They're transient.

And so, for example, a virtual particle might be like a little blob of energy that one electron sends to another electron to push it away. Like two electrons, they push each other apart, right? How does that happen? Well, it happens through ripples in the electromagnetic field. And you can, that's not really a photon. Like, it's not a flash of light that goes between the electrons to push them apart. But there is a transfer of energy, a transfer of momentum.

And that you can associate with a particle. You can say, oh, that's like a virtual photon. Wait, you're saying that when an electron pushes another electron because they're both negative charge, I thought they always use photons. You're saying that doesn't happen through photons? They do, but it's a virtual photon. It's not a real photon.

It's not a photon that you could like see you with your eye. It's a virtual short-lived photon. Not a photon that could propagate across the universe and hit another star. That's a special photon, but there's non-special photons. Yes. Real photons are special photons in Jorge's universe, though. I love all particles equally, but there are two kinds of particles.

There's the real particles that can propagate through the universe forever without interacting. And then there are these transient short-lived virtual particles that we could argue about whether they really are particles. But we call them virtual particles. I feel like it would be like telling you your two kids. I think one of you is real, one of you is not. But I think you're both special to me. I like you both. If one of your kids only lasts for 10 to the minus 23 seconds,

you're not even going to be able to finish that sentence. Oh, man. Well, okay, so when an electron pushes another electron, they're not interchanging photons. They're interchanging wiggles in the field that are like photons, but not photons. They're not real photons. They are virtual photons. And when we draw little Feynman diagrams to describe this between physicists,

we draw a wiggly line just like a photon. but that photon is created inside the interaction it's emitted and then absorbed it's never seen externally like you never see that nobody says oh look at a little soft flash of light that only exists between the two electrons and so these virtual particles

are not ever directly observed they're just sort of used in our calculation and inferred oh I see but could someone intercept them could you know like let's say when an electron is pushing another electron and suddenly another electron sweeps in and would they be able to catch that photon and say,

yes, there was a photon here. Yeah, but that's going to blow your mind because then the photon becomes real. Then it becomes real. Then it becomes real. And you might ask, well, how does it know, right? Well, remember in quantum mechanics, there's no like propagation.

It's not like this is a thing which goes somewhere, it goes from here to there. If you have an initial state and a final state, your initial state is like an electron is flying off, and the final state is some, some photon from that electron is now observed by your camera, all the possible things that could explain that sort of can happen all at once, right?

And only some of them survive. And so if there's a camera there to observe it, then the virtual options disappear. They can't exist anymore. But if there's not a camera there to observe it, then it can interact in sort of its unobserved state with other electrons and push them along and stay a virtual particle.

I totally understood that virtually. in my VR headset here. All right, it sort of sounds like it's one of these quantum mechanical things where they're sort of virtual until you open the box, kind of. Yes, they're virtual until you open the box. And if you open the box and interact with them,

then only real particles can satisfy that set of constraints. And so then the virtual particles sort of never happened. And if you're worried about like, you know, causality there, you know, the whole interaction is not like a flowing in time in that same way. The whole interaction is sort of understood as one thing. You know, like there's this emission and absorption, and we're understanding this whole sort of process

in terms of one calculation. And we think about all the ways that it can happen simultaneously. Only some of those survive based on what the constraints are. When you open the box. When you open the box, yeah. All right, well, tell me you were saying that virtual particles break rules. So what are some of the rules that virtual particles,

particles can break. Right. So they don't violate like deep laws of physics, but they can do things that real particles can't do. For example, if you try to interpret these wiggles in the quantum fields as a particle, you get weird answers. Like, you do the calculations to get, what's the kinetic energy of this thing? Well, it can be negative. Negative kinetic energy. And that's weird if you're used to thinking about kinetic energy is like energy of motion, because like energy of motion, no matter which direction you're going is always positive, right? There's a V squared in there. So any velocity gives you positive energy. But in physics, we calculate this energy, you know, as a relationship between mass and momentum. And it gets wonky because it's not like an individual localized little

particle that's moving through space in the way you're familiar with. It's like this weird disturbance and you're trying to force this sort of particle view onto it and it doesn't quite work. It's like a little void of energy almost. It's sort of like you're asking an inappropriate question, and so you get a nonsense answer. Oh, I see. It's like a wiggle, you know, and that wiggle can give you weird answers when you try to measure it.

Yeah, and you're not measuring the energy. You're like, well, here's the wiggle. If I sort of try to squeeze this into the particle framework and then ask what would be the energy if this was a particle, you get sort of a nonsense answer. You know, like if you asked how popular would Daniel be if he was a famous movie star? But you're like, well, that's nonsense.

sense is no way he'd be a famous movie star, so he'd be like negative popular or something. And the other thing is that these virtual particles aren't restricted to have the same mass as the particles you're familiar with. Like, you know the photon is no mass. Photons that hit your eye from stars very, very far away, they have no mass because those are real photons. But virtual photons can have mass. A special disturbance in the electromagnetic field can have mass?

Yes. Yes, it can carry some mass with it. Where does it carry it that the other photons don't have room for? In its back pocket, of course. I mean, where do you carry your mass? That's where all mine seems to go. It's just another way to interpret this in the light of a particle. It sort of breaks one of those rules.

And that's actually the thing that distinguishes a virtual particle from a real particle. A real particle is a little packet of energy that has definite mass and propagates forever. And the virtual particle doesn't have that definite mass. It can have high mass. It can have low mass. For a photon, it can have non-zero mass. Does that mean that the photon is going slower than the speed of light? So virtual particles can go slower than the speed of light?

Well, all the information transfer in the electromagnetic field always happens at the speed of light. But when you talk about the speed of a particle, you usually want to define it in terms of like, how fast is this packet moving? And in terms of the virtual particle, it's like more diffused. It's like spreading out everywhere. And so I'm not even sure it makes sense to define the speed. of a virtual particle. Yeah, I feel like it's getting into this weird quantum realm.

Yeah, and that's exactly the problem is that we want to interpret things happening on the microscopic scale in terms of things we're familiar with, in terms of things we know. And so we ask these questions like, what is its mass? What is its kinetic energy?

But those are not always appropriate questions. Just like if you ask, where is the electron and where is it going, you know, that doesn't really always have a satisfactory answer. And so virtual particles are less satisfactory than real particles. They have, like, fewer answers to cough up.

All right, let's get into then the question of whether or not they're actually real. Can something be virtual and real at the same time? But first, let's take a quick break. December 29th, 1975, LaGuardia Airport. The holiday rush. Parents hauling luggage. kids gripping their new Christmas toys. Then, at 6.33 p.m., everything changed.

There's been a bombing at the TWA terminal. Apparently, the explosion actually impelled metal, glass. The injured were being loaded into ambulances. Just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged, and it was here to stay. Terrorism. Law and Order Criminal Justice System is back. In season two, we're turning our focus to a threat that hides in plain sight.

That's harder to predict and even harder to stop. Listen to the new season of Law and Order Criminal Justice System on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. My boyfriend's professor is way too friendly, and now I'm seriously suspicious. Oh, wait a minute, Sam. Maybe her boyfriend's just looking for extra credit. Well, Dakota, it's back to school week on the OK Storytime podcast, so we'll find out soon. This person writes, my boyfriend has been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her.

Now, he's insisting we get to know each other, but I just want her gone. Now, hold up. Isn't that against school policy? That sounds totally inappropriate. Well, according to this person, this is her boyfriend's former professor, and they're the same age. And it's even more likely that they're cheating. He insists there's nothing between them. I mean, do you believe him? Well, he's certainly trying to get this person to believe him because he now wants them both to meet.

So, do we find out if this person's boyfriend really cheated with his professor or not? To hear the explosive finale, listen to the OK Storytime podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. Hola, it's Honey German, and my podcast, Grasasas Come Again, is back. This season, we're going even deeper into the world of music and entertainment, with raw and honest conversations with some of your favorite Latin artists and celebrities. You didn't have to audition. No, I didn't audition.

I haven't auditioned in like over 25 years. Oh, wow. That's a real G-talk right there. Oh, yeah. We've got some of the biggest actors, musicians, content creators, and culture shifters sharing their real stories of failure and success. You were destined to be a start.

We talk all about what's viral and trending with a little bit of chisement, a lot of laughs, and those amazing vivas you've come to expect. And of course, we'll explore deeper topics dealing with identity, struggles, and all the issues affecting our Latin community. You feel like you get a little whitewash because you have to do the code switching? I won't say whitewash because at the end of the day, you know, I'm me.

But the whole pretending and code, you know, it takes a toll on you. Listen to the new season of Grasasas Come Again as part of My Cultura Podcast Network on the IHartRadio app, Apple Podcast, or wherever you get your podcast. All right, Daniel, so we've defined virtual particles as being the non-particle wiggles in the quantum fields of the universe. But are they actually real? Can we say that they're real if it sounds like you're saying they're not real? And that's why you call them virtual. Yeah.

Well, they're not real in the sense that we define them, right? Particle physicists have a very specific definition of what real is. You know, when you say real, you mean like it actually exists. It's out there. In that sense, absolutely, virtual particles are real. But, you know, we took this word real, and we redefined it to mean it has a specific mass. It can propagate infinitely through its quantum field. Oh, I see.

They exist, but they're just not real particles. It's like a, you have to keep the two words together. Yeah. They're not real, the capital R, I guess. Or they're not physics real, you know, or like real or whatever you would call it. But they have real, but they have actual effects on the universe. You know, we talk about. empty space, but we know that space has energy in it.

And that energy can be converted into short-lived virtual particles. You have energy. It's kind of like saying, like, it'd be different if I said, Daniel, it's not real, than if I said Daniel is not a real movie star. That's kind of where we're at. That's a perfect analogy. Daniel exists, but he's not a real movie star. Just like these wiggles exist, but they're not real particles.

That works perfectly except I'm not even a virtual. movie star so you can that's the whole point of virtual reality then I'm going to pop into your movie

and then pop right back out again all right so they're real but they're not particles so why even

call them particles why don't just call them you know squigglys or or ripples

because we like to categorize things and we like to find connections between things and so we

like to sort of say these real particles and the virtual particles are sort of two sides of the same coin. And they are, you know. Real particles are very closely related to virtual particles. It's not like a hard wall you can put between them and say they're totally different. Real particles are like a special case of virtual

particles. And so we call them particles because, hey, we're particle physicists. Everything's a particle. And we just sort of try to categorize them together. Hmm. When you have a hammer, when you have a $16 billion hammer, everything looks like a particle. Everything looks like a particle. And, you know, we even describe forces in terms of particles. We like to think about electromagnetism and the strong force and the weak force operating in terms of particles. And that can be confusing sometimes if you try to think about it like microscopically, how can particles be responsible for forces? All forces are done through virtual particles? All the forces that we can describe quantum mechanically, like gravitation, we still don't know.

But all those quantum mechanical forces, yeah, they're described using virtual particles. And the way you might have heard it described is like one electron comes along and pushes on the other electron by throwing a photon at it. But it's actually throwing a virtual photon. It's a virtual wiggle in the field and it's not thrown from one to the other, right? It's not something that's moving and flying in a well-defined way through space. It's a little disturbance in the field. That's causing, that's pushing on the other electron. Yeah.

And that's a key thing to understand because fields can do more than just push, right? If you and I are throwing a ball back and forth, all we can do is push each other. I can't throw the ball at you and then attract you somehow. That doesn't make any sense. I'm transferring momentum to you and pushing you away. So I can't throw a ball at you with negative momentum. So that's why that analogy breaks down, Because real forces, like electromagnetism,

they're also responsible for electrons attracting to protons. Yeah, pulling. It's the same deal. So to understand how that works in terms of virtual particles, you have to let go of particles as these little balls that were throwing back and forth. And just think about them in terms of weird ripples. And the key thing to think about there is, like,

you are exchanging a virtual photon. If it has a certain amount of energy to it, Heisenberg tells us, If you're well defined in terms of momentum, you're not well defined in terms of location. So that particle, that virtual photon that's being passed back and forth, doesn't really exist anywhere. It sort of exists everywhere. It's like, if its momentum is very specific, then its location is flat. It's like can exist through the whole universe.

So like if I have a magnet, let's say I'm holding two magnets here in the table in front of me, and I try to bring them together and they're pushing each other apart. these magnets. Before, I was thinking like maybe they're swapping photons so that they can repel each other. But really, they're not. They're just sort of like, just sort of like

perturbing each other's fields. Yes, they're perturbing each other's fields and transmitting energy back and forth, but not in the sense of like little particles that are actually flying back and forth, like real particles. Like you can't put a piece of cardboard between two magnets to block the magnetism, right? And you'd be like, well, look, photons

can't get through my cardboard, so how can magnetism get through, right? The reason is that electromagnetic fields definitely can get through your cardboard, right? You can hear a radio through cardboard. More like you're bending the fields around you and that's what's pushing the other one. Yes, yes.

It's just not in a way that you can characterize as a little ball, is like a little self-propagating nice package of field. And so that's how these things interact. They interact with the fields, and you can, if you want, interpret those in terms of virtual particles, is sort of like looser definition of what a particle is

than just the narrow definition of what real particles are. You sort of expanded the definition to include more of these weird things. Yeah, by relaxing some of the rules. Say you don't have to have the right mass, you don't have to have a kinetic energy that makes sense. It's a ripple in the field. You don't have to be a particle to be a particle, that's what you're saying. And you could also just get rid of the particle picture entirely.

Be like, you know what, that doesn't make any sense to me. I'm just going to think about the fields. And you can do that. It's just, it's really hard because calculations in field theory are very, very complicated. And so to simplify it, Feynman introduced this idea. He said, well, let's just think about it in terms of like the simplest interaction. And he drew these diagrams that showed like, well, if it was exchanging one thing you would call a particle, then it would look like this.

And then let's think about it in terms of the second simplest and the third simplest. And then they just ignore everything else. So he developed this framework for approximating quantum field theory calculations by using these like number of virtual particles. The most likely thing to happen is one virtual particle. The second most likely is two and then three. And as you go on, there's more and more possibilities, they get less and less likely so you can ignore them.

It just lets you sort of understand these complex field interactions. Yeah, it lets you quickly approximate it and get mostly the right answer in a way that sort of makes sense. And you know, physics is all about like making sense. We know these are the rules of the universe. What do they mean to us? This interpretation step is important. It's the physics part of it, right?

The rest of it's sort of mathematics. And it's like, how do we use this to build up a picture of the world that makes sense to us? And you're always teasing me that I like rules, but like, that's what physics is. You know, we're trying to figure out what the rules are and how they limit us and whether they actually do limit us. All right. Cool. Well, I feel my mind virtually blown a little bit to learn that. There are particles that are not particles.

But they're very much real and they very much kind of make everything work, right? Because without virtual particles, you can't have forces. And without forces, nothing happens. The universe would be pretty boring without any forces. So stay tuned for Daniel's future virtual career in the movie about virtual particles. But it's sort of interesting to think that, you know, there's more to the universe and what we can see and feel and touch. That there's all this sort of, you know,

underlying chaos happening in between what we imagine to be matter and electrons and quarks. Yeah, and that always our descriptions of it are lacking, right? That we are limited by the way our mind's work and the way that we think about the universe. We're trying to map that onto this crazy insane chaos that's going on on a microscopic level. And it's never completely satisfactory. It's always running into contradictions and seeming nonsense. And that's because the universe at that scale is weird and alien. and very difficult to translate into sense for the human brain.

But, hey, I think it's worth trying. So we hope that made a little bit more sense to all of you, and then now you know what a virtual particle is, or what it's not, or what it is not is. Or that you virtually understand it. So thanks for listening. We hope you enjoyed that. See you next time.

you still have a question after listening to all these explanations, please drop us a line. We'd love to hear from you. You can find us at Facebook, Twitter, and Instagram at Daniel and Jorge. That's one word. Or email us at Feedback at danielandhorpe.com. Thanks for listening. And remember that Daniel and Jorge Explain the universe is a production of iHeartRadio. For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows. December 29th, 1975, LaGuardia Airport. The holiday rush, parents hauling luggage, kids gripping their new Christmas toys. Then everything changed. There's been a bombing at the TWA terminal. Just a chaotic, chaotic scene.

In its wake, a new. new kind of enemy emerged. Terrorism. Listen to the new season of Law and Order Criminal Justice System on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. My boyfriend's professor is way too friendly, and now I'm seriously suspicious. Wait a minute, Sam. Maybe her boyfriend's just looking for extra credit. Well, Dakota, luckily, it's back to school week on the OK Storytime podcast, so we'll find out soon. This person writes, my boyfriend's been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now he's insisting we get to know each other, but I just want her gone.

Hold up. Isn't that against school policy? That seems inappropriate. Maybe find out how it ends by listening to the OK Storytime podcast on the Iheart radio app, Apple Podcasts, or wherever you get your podcasts. Every case that is a cold case that has DNA. Right now in a backlog will be identified in our lifetime. On the new podcast, America's Crime Lab, every case has a story to tell, and the DNA holds the truth. He never thought he was going to get caught, and I just looked at my computer screen. I was just like, ah, gotcha.

This technology's already solving so many cases. Listen to America's Crime Lab on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. This is an IHeart podcast.