Speaker 1: Hey, Jorge, I'm wondering how you feel about the Midi Chlorians,
Speaker 1: those little critters that give Jedi the ability to interact
Speaker 1: with the Force.
Speaker 2: You mean in Star Wars. I mostly try to ignore them.
Speaker 2: They're a bit of an awkward retroactive continuity or redcon
Speaker 2: of the original series.
Speaker 1: Mm so you prefer the original approach where it's like
Speaker 1: more democratic. Anybody can learn the force like yoga.
Speaker 2: You mean, like Yoda or yoga.
Speaker 1: I mean like Yoda doing.
Speaker 2: Yoga, and like downward facing Jedi.
Speaker 1: That conjured of a pretty awkward mental image.
Speaker 2: How flexible is Yoda? We may never know.
Speaker 1: Well, I'm a fan of the Midichlorians. I feel like
Speaker 1: they're more scientific.
Speaker 2: Oh are you a fan of jar Jar Binks too?
Speaker 2: Because I think most people who are in that camp
Speaker 2: are also in the jar Jar Binks camp. But you're
Speaker 2: not tall made up right? It's not real science.
Speaker 1: I know it's not real science, but it's science. You know.
Speaker 1: It's a better microscopic explanation than just like hand waving
Speaker 1: yoga magic.
Speaker 2: I think the magic in Star Wars is literally handwaving,
Speaker 2: like waving your hands in front of your face, going,
Speaker 2: does this not the signs you're looking for.
Speaker 1: I need the old physics mind trick instead.
Speaker 2: That's right, redcon our real universe, not my childhood fantasy.
Speaker 1: That's my job.
Speaker 2: Hi'm Jorhem, a cartoonist and the author of Oliver's Great
Speaker 2: Big Universe.
Speaker 3: Hi.
Speaker 1: I'm Daniel. I'm a particle physicist, and that means my
Speaker 1: job is to explain away all the apparent magic in
Speaker 1: the universe.
Speaker 2: You have to understand it first, though, don't you. Isn't
Speaker 2: that step one? Or are you just making stuff up?
Speaker 2: Are you? George Lucas seing it?
Speaker 1: I think explaining it away is understanding it. Describing how
Speaker 1: something works in terms of its like tiny little bits
Speaker 1: and how they bump and dance together. That's basically explanation.
Speaker 2: Or maybe I think you're maybe saying your job is
Speaker 2: to look for explanations.
Speaker 1: Yeah, and sometimes we actually find them.
Speaker 2: Yeah, and then explain it to other pe books like
Speaker 2: we do in this podcast. So welcome to Daniel and
Speaker 2: Jorge Explain the Universe, a production of iHeartRadio.
Speaker 1: In which we try to take everything in the universe
Speaker 1: that seems unexplainable, that seems magical, and figure out how
Speaker 1: it comes to be. Drill down into its tiny little
Speaker 1: bits and particles and explain how they bump and dance
Speaker 1: and push on each other to weave themselves together into
Speaker 1: our reality, to explain why yoga feels so good or
Speaker 1: so bad.
Speaker 2: That's right, because it is a marvelous universe out there,
Speaker 2: with giant gaxies moving across at cosmos and stars exploding
Speaker 2: and black holes sucking stuff in, and we're interested in
Speaker 2: knowing what are some of the forces that bind it
Speaker 2: all together, that flow through us and make it all
Speaker 2: make sense.
Speaker 1: And is it even possible to explain all of that craziness,
Speaker 1: all the amazing things we experience in the universe, from
Speaker 1: leaves swirling in the fall to black holes collapsing in
Speaker 1: terms of tiny particles. Is it really possible to break
Speaker 1: it all down and say it's just a bunch of
Speaker 1: electrons passing particles back and forth.
Speaker 2: I feel like you're minimizing electrons. You said, only a
Speaker 2: bunch of electrons. But electrons are pretty pretty special, aren't they.
Speaker 2: Each one is a tiny snowflake in the universe.
Speaker 1: They're all actually identical right in a way snowflakes aren't
Speaker 1: even But I think the job of particle physics is
Speaker 1: literally to minimize the universe, to say, everything that's big
Speaker 1: can be explained in terms of everything that's small.
Speaker 3: Yeah.
Speaker 2: I guess that's a job of physics to break things down.
Speaker 2: And I guess throughout the history of humans and signs,
Speaker 2: that's what you have been doing, right, first breaking things
Speaker 2: down into types of elements, and then atoms and then
Speaker 2: atomic particles.
Speaker 1: Yeah. We hope that breaking things down will give us explanations,
Speaker 1: will reveal the true nature of the universe, and that
Speaker 1: we could go the opposite direction also from the little
Speaker 1: bits tooing and frowing, that we can weave those little
Speaker 1: bits back together. All their tooing and frowing can be
Speaker 1: sewn together to explain everything that happens, the way like
Speaker 1: water droplets eventually could explain a hurricane, and the way
Speaker 1: quantum particles somehow make up your classical body. We hope
Speaker 1: that by drilling down we can expose the most fundamental
Speaker 1: layer of the universe and then build back up to
Speaker 1: explain everything.
Speaker 2: Yeah, and so, little by little, scientists have come up
Speaker 2: with a picture of the universe that can be broken
Speaker 2: down into subatomic particles called electrons and quarks, and also
Speaker 2: force particles. So the question is does it all make sense?
Speaker 2: Does it all stick?
Speaker 1: We have a mathematical description of how this all works,
Speaker 1: which is incredibly precise. We can predict the outcomes of
Speaker 1: experiments to ten or fifteen decimal places and mostly get
Speaker 1: it right. But is it possible to get an intuitive
Speaker 1: understanding to tell ourselves, like a little story about what's
Speaker 1: happening down there in the quantum realm in a way
Speaker 1: that gives us some insights, some understanding. Is it really
Speaker 1: true that particles are zipping around tossing force particles back
Speaker 1: and forth together or is something deeper happening?
Speaker 2: Yeah, so we're here to force out the truth. So
Speaker 2: today on the podcast, we'll be asking the question how
Speaker 2: do particles carry force? This is generic force, not the force, right.
Speaker 1: This is science force, not science fiction force or magical force.
Speaker 2: Who Science Force? I want to be part of that team.
Speaker 2: Do you wear uniforms? Do you have like a secret base?
Speaker 1: Absolutely, they're snappier than the Space Force.
Speaker 2: Also, yeah, well I'll join either one. To be honest,
Speaker 2: anything that has a base and involves space or science
Speaker 2: and laser guns.
Speaker 1: I mean, I think we settle this already. The Science
Speaker 1: Force is going to elect you to be part of
Speaker 1: the space Force and send you up to meet the aliens?
Speaker 4: Wait?
Speaker 2: Wait, when do we settle this? I didn't sign any
Speaker 2: agreements here.
Speaker 1: Oh sorry, we had a meeting of the Science Force.
Speaker 1: I guess you weren't there.
Speaker 2: Yeah, yeah, I guess it depends on how much you're
Speaker 2: paying me. How much are you paying me to do this? Daniel?
Speaker 2: And or am I surviving relatives?
Speaker 1: Yeah? You get paid on your return? Is that all right?
Speaker 2: What do you mean I pay or I get paid?
Speaker 1: You get paid if you survive.
Speaker 2: That sounds like a terrible deal. Do you get paid
Speaker 2: only if you discover something in physics Daniel? Or do
Speaker 2: you get paid either way?
Speaker 1: I'm getting paid and I never discovered anything?
Speaker 2: Then the answerds yes, so far, so far right. There's
Speaker 2: always an optimism.
Speaker 1: That's right and over yet.
Speaker 2: That's right, your careering over yet? But maybe have a
Speaker 2: podcast long enough and who knows what you'll say, day
Speaker 2: tuned folks. But anyways, it's an interesting question because we
Speaker 2: tend to think of matter and the things around us
Speaker 2: is being made out of particles. That kind of makes sense.
Speaker 2: But the idea that maybe the forces between those particles
Speaker 2: the things that make you stand here on Earth or
Speaker 2: that makes all your atoms stick together, or your hair
Speaker 2: stent when they're theirs static electricity, those things could be
Speaker 2: due to particles also is kind of confusing, right.
Speaker 1: It is confusing, and yet it's something you hear a
Speaker 1: lot in popular science without a sort of deeper explanation
Speaker 1: for what the limits are of that description. You know,
Speaker 1: everything in the end is an analogy, and those analogies
Speaker 1: always break down at some point. So which parts of
Speaker 1: that story are true and which parts of that story
Speaker 1: are just a cartoon?
Speaker 2: That's right. You don't want to force a force analogy
Speaker 2: that's too deep, all right? Well, as usual, we were
Speaker 2: wondering how many people out there I thought about the
Speaker 2: idea of particles caring force and how they might do that.
Speaker 1: So thanks to everybody who volunteers for this audience participation
Speaker 1: segment of the podcast. We'd love if you participated. Since
Speaker 1: you are part of the audience. Don't be shy write
Speaker 1: to me two questions at Daniel and Jorge dot com
Speaker 1: and in the future you'll hear your voice on the podcast.
Speaker 2: So think about it for a second. How do you
Speaker 2: think particles carry forth? Here's what I be glad to say.
Speaker 4: I think technically, they carry force by exchanging particles. I know,
Speaker 4: all the matter particles are called fermions, and they exchange
Speaker 4: force by passing around their boson counterparts. For example, the
Speaker 4: strong force I think passes around gluons, and so the
Speaker 4: mental model that I have is fermians passing their bosons around,
Speaker 4: sort of like playing catch. But I'm sure that's not
Speaker 4: even close to an accurate representation, but it's kind of
Speaker 4: what I've.
Speaker 2: Thought of boson's carry force, because there's a way paint
Speaker 2: qui fermions, just in the way light light steams up.
Speaker 5: I think particles carry forces by interacting with fields, or
Speaker 5: they might also carry a force by being like a
Speaker 5: part of them, like shaking in that dimension. Sort of.
Speaker 6: Particles carry force in their pockets, and when they want
Speaker 6: to transmit a force, they reach into their pocket and
Speaker 6: they pull out a boson and they lob it at
Speaker 6: another particle to push it out of the way.
Speaker 7: I assume particles carry force through velocity, mass, and spin,
Speaker 7: and they transfer force as they translate one of those
Speaker 7: upon interaction with something else.
Speaker 6: I thought that the forces were transmitted when the force
Speaker 6: particles were transferred from one particle to another, but Having
Speaker 6: just listened to your podcast on energy, I imagine the
Speaker 6: answer is probably just momentum.
Speaker 2: All right, a lot of pretty science the answers. Are
Speaker 2: you also recruiting them for the science force? Is there
Speaker 2: a pledge to be in the science force?
Speaker 1: Did you like the answer where the're pulling bosons out
Speaker 1: of their pockets?
Speaker 7: Yeah?
Speaker 2: What's it required? What kind of gadgets do you get?
Speaker 1: You get a pocket full of bosons and you set free,
Speaker 1: go go forth in science.
Speaker 2: Nice. Nice, that sounds like a ninety song pocket full
Speaker 2: of bosons. But anyways, interesting answers from our listeners here.
Speaker 2: None of them mentioned Yoda doing yoga or Medei Chlorians disappointed. Yeah,
Speaker 2: step it up, listeners. We have some interesting answers having
Speaker 2: to do with velocity and mass and colored matter and
Speaker 2: maybe extra dimensions. So I'll have to explore here. So
Speaker 2: let's break it down, Daniel, what is the technical definition
Speaker 2: of a force? Let's start with that.
Speaker 1: So all of these explanations in the end are trying
Speaker 1: to describe things we have experience with. That's what physics does, right,
Speaker 1: give labels to things and then try to explain them.
Speaker 1: And so a force is something we're familiar with. Right,
Speaker 1: somebody pushes you, or you press down the accelerator in
Speaker 1: your car. These are things that involve forces. Mathematically and
Speaker 1: in physics, we think about a force as anything that
Speaker 1: changes the momentum of an object. So a ball flying
Speaker 1: through space at the same velocity, there's no force on
Speaker 1: it. It just continues. If you want to change its velocity,
Speaker 1: its direction, or its overall momentum in any way, you
Speaker 1: have to apply a force.
Speaker 2: Right. It also goes back to basically f equals ma
Speaker 2: a right, like, if you have a mass, something with
Speaker 2: mass and it's change it's velocity, then there must be
Speaker 2: a force involved. And that's kind of maybe what you're
Speaker 2: saying is the definition of it.
Speaker 1: Yeah, you can actually even rewrite eth eqals ma as
Speaker 1: the change in momentum, and that really helps you understand
Speaker 1: the connection between forces and momentum because remember that in
Speaker 1: our universe, momentum is conserved, So if something has a
Speaker 1: certain momentum, it's just going to keep that momentum unless
Speaker 1: you add in momentum from somewhere else. That's what a
Speaker 1: force is. You have a particle flying through space, you
Speaker 1: want to change its direction, change its momentum, you have
Speaker 1: to bring in some external momentum, you have to have
Speaker 1: another particle come by and give it a push or pull.
Speaker 1: That's what the force is. It's the change of momentum
Speaker 1: of an object.
Speaker 2: But the objects ever really change mass, And if they
Speaker 2: never do, then what's the point of saying momentum? Why
Speaker 2: did you say ethicals?
Speaker 1: When things are moving slowly, you can think of momentum
Speaker 1: as just mass times velocity. But as things approach the
Speaker 1: speed of light, when they get relativistic, there's another term
Speaker 1: that creeps in there that changes the relationship between momentum
Speaker 1: and velocity. They're no longer just linear. We whole episode
Speaker 1: on the concept of like relativistic mass and whether that
Speaker 1: makes any sense, and you remember, we decided that the
Speaker 1: real concept is relativistic momentum. That momentum has a simple
Speaker 1: relationship with velocity when you're moving slowly, but when you
Speaker 1: move fast, it's much more complicated, And it's momentum that's
Speaker 1: really the more fundamental concept. That's the thing that the
Speaker 1: universe cares about, that's the thing the universe conserves. So
Speaker 1: it's really sort of the more pure idea is momentum.
Speaker 2: So when you say force is a change in momentum.
Speaker 2: Are you also talking about its relativistic momentum?
Speaker 7: Yeah?
Speaker 1: Absolutely. Relativistic momentum is the more general concept. You only
Speaker 1: really need it near the speed of light. Mostly you
Speaker 1: can use the old classical momentum, which is just mass
Speaker 1: times velocity, and it gets things mostly right. But it
Speaker 1: is the relativistic momentum that the universe conserves. And that's
Speaker 1: one way we know that relativity is right is that
Speaker 1: it's this relativistic momentum that the universe keeps track of.
Speaker 2: I see all right, So then to change your momentum,
Speaker 2: you can increase it or decrease it. So forces can
Speaker 2: push and pull.
Speaker 1: Right, yeah, exactly. The intuitive description of a force is
Speaker 1: a push or a pull. And what happens there is
Speaker 1: you're changing your momentum. When you hit the brakes on
Speaker 1: your car, you're changing your velocity. When you hit the accelerator,
Speaker 1: you're changing your velocity. A change in your velocity is
Speaker 1: an acceleration. It's a change in momentum, and there's always
Speaker 1: a force involved there. Like the fastest way to slow
Speaker 1: down is like hit a brick wall. There the wall
Speaker 1: is applying a force on you and your car changing
Speaker 1: your momentum.
Speaker 2: And it's kind of a weird feature of the universe
Speaker 2: that it has this conservation of momentum, right, or that
Speaker 2: you need a force to change momentum. It could have
Speaker 2: been that the universe was different, right. It could have
Speaker 2: been that the universe maybe preferred mass time's acceleration to
Speaker 2: be conserved.
Speaker 7: Right.
Speaker 1: Maybe yes, and no, it's not true that we have
Speaker 1: no idea why the universe conserves momentum. It comes from
Speaker 1: a deeper symmetry. We know because of Nuther's law, which
Speaker 1: tells us that every time the universe can serves something,
Speaker 1: it's because of a symmetry of the universe. In this case,
Speaker 1: the symmetry of the universe is a symmetry of space itself.
Speaker 1: The laws of physics are the same at every point
Speaker 1: in space, the momentum is conserved. That step there seems
Speaker 1: like a big leap, but that's exactly the leap from
Speaker 1: Nuther's law. I mean Nuther, this mathematics from about one
Speaker 1: hundred years ago made this deep realization that there's a
Speaker 1: connection between symmetry and conservation laws. So this law conservation
Speaker 1: momentum comes from the fact that space is the same everywhere,
Speaker 1: and so you're right, it doesn't have to be true
Speaker 1: that space is the same everywhere in our universe. It
Speaker 1: seems to be, and that's why we have conservation and momentum.
Speaker 1: But there could be other universes where the laws of
Speaker 1: physics change as you move through space and their momentum
Speaker 1: would not be conserved.
Speaker 2: I feel like you. You spend a minute agreeing with me.
Speaker 1: Awesome, can we agree?
Speaker 2: Well, this is the universe we live in, and it
Speaker 2: seems to conserve momentum. And there's several ways that you
Speaker 2: can do that, right, Several forces that will allow you
Speaker 2: to change particle's momentum, maybe depending on what kind of
Speaker 2: particle it is and what its properties are.
Speaker 1: Yeah, and so we can take the same concept of
Speaker 1: a force that applies to your car and applied also
Speaker 1: to particles. Particles have momentum, and if you want to
Speaker 1: change your momentum, you have to apply a force. And
Speaker 1: you're right, there's several ways to do that. We've observed
Speaker 1: several ways, and again this is just descriptive. We've noticed
Speaker 1: several things happened to particles, and we've categorized them as
Speaker 1: much as we can. We've tried to like weave them
Speaker 1: together into one concept, but haven't totally succeeded. We call
Speaker 1: these things the fundamental forces. So there's like electricity and magnetism.
Speaker 1: Charged particles will push or pull on each other. That's
Speaker 1: definitely a force. Electrons will change each other's momentum. They'll
Speaker 1: change their direction entirely, right, that's a change in momentum.
Speaker 1: Even if your velocity is the same but your direction
Speaker 1: is different, it's still a change in momentum.
Speaker 2: M So that's maybe the most familiar force to people,
Speaker 2: like your magnetism. That's basically what keeps our atoms together, right,
Speaker 2: and our molecules stuck together with the different atoms in it. Right.
Speaker 2: Without the electromagnetic force, it would be a big deal.
Speaker 2: We would all fall apart, exactly. We all need electromagnetism.
Speaker 2: So you truly acknowledge the electromagnetic force in like every
Speaker 2: book or paper you write, because you totally rely on it.
Speaker 2: That's right, every acceptance speech you give, every thank you
Speaker 2: card you write.
Speaker 1: There you go, yeah, you sent a holiday card to
Speaker 1: the electromagnetic force this year.
Speaker 2: Have put it on the holidays, and thanks again to
Speaker 2: the electromagnetic force.
Speaker 1: Thanks for all the photons but it's not the only
Speaker 1: force that's out there. There's another force called the weak force,
Speaker 1: which US physicists actually have managed to stitch together into
Speaker 1: one force we call the electro week. But traditionally people
Speaker 1: talk about the weak force as responsible for like radioactive
Speaker 1: decay and interactions of neutrinos and stuff like that. So
Speaker 1: it's sort of a shyer force.
Speaker 2: What does it mean that it's related to radioactive decay?
Speaker 2: Like when something decays radioactively, the weak force is there
Speaker 2: to split things apart or to hold things together. What
Speaker 2: is it doing there?
Speaker 1: Lots of radioactive decay can be explained by one kind
Speaker 1: of quark changing into another kind of quark, and it
Speaker 1: does so using the weak force. So the weak force
Speaker 1: can change, for example, like an upcork into a down
Speaker 1: cork if you emit a w boson, and the w
Speaker 1: boson is intimately connected to the weak force, as we'll
Speaker 1: talk about more later. Without the weak force, that can't happen.
Speaker 1: And so that's what we mean when we say the
Speaker 1: weak force is responsible for radioactive decay. It like opens
Speaker 1: up a channel for this to happen.
Speaker 2: But is it pushing or pulling on anything?
Speaker 1: That's a tricky question the weak force can push and
Speaker 1: it can pull. The whole podcast episode inspired by a
Speaker 1: question from an organic chemistry professor, but whether the weak
Speaker 1: force can push and can pull? The answer is that
Speaker 1: it can do both, but it's more complicated than the
Speaker 1: electromagnetic force.
Speaker 2: Well or right, what are some of the other forces
Speaker 2: in nature?
Speaker 1: So the last thing that's really a force is the
Speaker 1: strong force. This is the thing that quarks feel, but
Speaker 1: like electrons don't. Two electrons can pass near each other
Speaker 1: and not push or pull on each other with the
Speaker 1: strong force. But quarks or gluons, these things do feel
Speaker 1: the strong force. They have another kind of charge, the
Speaker 1: way an electron has an electric charge, which allows it
Speaker 1: to feel electric fields and electromagnetic force, but neutrinos don't.
Speaker 1: Quarks and gluons have a color charge, a strong force
Speaker 1: charge lets them interact using the strong force in a
Speaker 1: way that electrons just don't. And so that's the last force.
Speaker 1: And this is the one that holds quarks together into
Speaker 1: protons and neutrons, and the residual little forces bind those
Speaker 1: protons and neutrons together into nuclei. So we also rely
Speaker 1: on the strong force to build our world.
Speaker 2: So they're all pretty necessary.
Speaker 1: It seems they all have role to play exactly the
Speaker 1: top billing to the extras in the back.
Speaker 2: What about gravity? Is in gravity also a force.
Speaker 1: So we sometimes think of gravity as a force, and
Speaker 1: we talk about the force of gravity, and Newton describes
Speaker 1: his force law or gravity. But now we know that
Speaker 1: gravity isn't actually a force. Things move in a way
Speaker 1: that makes it look like there's a force there, but
Speaker 1: that's actually just because they are free falling in curved space.
Speaker 1: There's no actual change in momentum there. And you can
Speaker 1: tell the difference between gravity and these other forces because
Speaker 1: gravity doesn't cause a change in momentum. You can't measure
Speaker 1: acceleration due to gravity.
Speaker 2: Wait, what do you mean If I hold a bowling
Speaker 2: ball above you and I let it go, isn't it
Speaker 2: going to gain some dangerous momentum for you there?
Speaker 1: So if you're falling with the bowling ball and you
Speaker 1: have like an accelerometer, you're not going to measure any
Speaker 1: acceleration there. The bowling ball is in freefall, there are
Speaker 1: no forces on it.
Speaker 2: Right, But here it is going to measure a pretty
Speaker 2: big acceleration, isn't it.
Speaker 1: Yeah, Because in that scenario I'm actually doing the accelerating.
Speaker 1: I'm accelerating towards the bowling ball. The bowling ball is
Speaker 1: in freefall. The surface of the Earth or my chair
Speaker 1: or whatever is accelerating me against the natural curvature of
Speaker 1: space time towards the bowling ball. So that's actually my
Speaker 1: acceleration due to the structure of the Earth or my
Speaker 1: rocket ship or whatever that I'm measuring. There's no acceleration
Speaker 1: there due to gravity.
Speaker 2: Wait, so if I drop a bowling ball on you,
Speaker 2: it's not my fault, it's you're saying it's your fault.
Speaker 1: Yeah, I basically rear ended you.
Speaker 2: Yeah, basically would that work in a court of law? Daniel,
Speaker 2: can I bring you in as an expert physicist?
Speaker 1: I definitely recommend you hire a particle physicist instead of
Speaker 1: a lawyer next time you're in court. See how that
Speaker 1: works out, well, your honor, I want to upend thousands
Speaker 1: of years of legal tradition.
Speaker 2: That's right. Let me bring out some charts here.
Speaker 1: And the truth is that Einstein did say something really
Speaker 1: interesting about this. The equivalence principle that a lot of
Speaker 1: people have heard about says that any experiment you do
Speaker 1: is the same whether or not. You're in curved space
Speaker 1: that you basically can't ever measure locally the curvature of space.
Speaker 2: Wait, so I feel like I'm a little bit confused, Beau.
Speaker 2: If I drop a bowling ball on you, and you're
Speaker 2: saying the only bob doesn't accelerate to the gravity, You're
Speaker 2: saying you're accelerating. Your head is accelerating due to the
Speaker 2: you know, the forces that the ground is pushing up
Speaker 2: on you with exactly.
Speaker 1: So it looks to me like the bowling ball is
Speaker 1: accelerating towards me, but I'm actually accelerating towards it.
Speaker 2: I see.
Speaker 1: An acceleration is not just relative, right, unlike velocity, and
Speaker 1: velocity is equivalent to say, I'm moving in this speed
Speaker 1: relative to you, and you're moving in this speed relative
Speaker 1: to me, But acceleration is not relative. We can both
Speaker 1: hold accelerometers and we can tell who's being accelerated.
Speaker 2: Right. Does that mean that if I'm just sitting here
Speaker 2: doing nothing, my momentum is changing.
Speaker 7: Yeah?
Speaker 1: Absolutely, Right now you are being accelerated.
Speaker 2: So you're saying my momentum is changing, Yeah, absolutely, even
Speaker 2: though I'm just sitting here.
Speaker 1: Momentum is defined relative to your axis. So you can
Speaker 1: always define an access in which you're at rest and
Speaker 1: that doesn't change, and so your momentum is not changing,
Speaker 1: but that frame of reference is accelerating. So from an
Speaker 1: inertial reference frame, you are definitely accelerating, but you are
Speaker 1: not in an inertial reference frame. You're an accelerating reference
Speaker 1: frame on the surface of the Earth.
Speaker 2: So my reference frame is like off into space or what.
Speaker 1: If you define your reference frame to be you, then
Speaker 1: you have no momentum and you never will right by definition, hmm.
Speaker 1: If you pick some reference frame of a distant observer
Speaker 1: looking at the Earth, then yes, you are definitely accelerating.
Speaker 1: You're accelerating against the curvature of space time from the Earth,
Speaker 1: and you're accelerating against the curvature of space time from
Speaker 1: the Sun.
Speaker 2: I see this requires us to kind of think in
Speaker 2: space time, not just space.
Speaker 1: I don't know that you need space time, but you
Speaker 1: do have to think about inertial reference frames, ones that
Speaker 1: are not accelerating and accelerating reference frames.
Speaker 2: So then how do you explain the fact that I
Speaker 2: don't feel like I'm moving?
Speaker 1: Why don't you feel like you're moving? If you stand
Speaker 1: on a scale, you measure something that tells you that
Speaker 1: there's a force being applied. You're just used to it.
Speaker 2: I don't feel like I'm moving.
Speaker 1: Motion is relative, right, You can just define a reference
Speaker 1: frame at yourself and then you're not moving, But acceleration
Speaker 1: is not, and that's why you can measure it.
Speaker 2: M I think maybe what you say is you said
Speaker 2: relativity is complex, and if you sort of think about
Speaker 2: the curvature space or of space time, then technically even
Speaker 2: if you're just sitting there, you're changing momentum.
Speaker 1: If you want to dig deep into these questions relativity,
Speaker 1: we had an episode recently about inertial versus gravitational mass
Speaker 1: that laid it all out in detail. I think the
Speaker 1: big picture here is that gravity is not a force.
Speaker 1: It doesn't apply in acceleration the way the other fundamental
Speaker 1: forces do, at least not in our current understanding of gravity, right.
Speaker 2: Right, Because some people think maybe gravity is a force, right,
Speaker 2: and there might be gravit cons perhaps.
Speaker 1: There might be in future theories of quantum gravity might
Speaker 1: change our entire picture of how gravity works.
Speaker 2: All right, Well, let's dig into the larger question we're
Speaker 2: trying to answer here, which is how particles can carry
Speaker 2: forces for the things that we do call forces for now,
Speaker 2: I guess, And so let's dig into that. How to
Speaker 2: force particles work? And is that really the picture of
Speaker 2: how the universe actually is? So let's dig into that.
Speaker 2: But first let's take a quick break. All right, we're
Speaker 2: talking about Yoda doing yoga. Now do you think Yoda
Speaker 2: does hot yoga or some other kind of yoga?
Speaker 1: I think Yoda's pretty hot already. I don't think he
Speaker 1: has to do any yoga.
Speaker 2: Oh yeah, yeah, you're into the ears and the wrinkles.
Speaker 1: Well, you know, there's also baby Yoda, right for those
Speaker 1: of you who are interested in the smoother skin.
Speaker 2: Oh yeah, yeah, he does like cute yoga, adorable adorbs yoga. Well,
Speaker 2: it's hard to keep track of yoga and yoga at
Speaker 2: the same time. Now, can Yoda drink yogurt doing yoga?
Speaker 1: You got me?
Speaker 2: Yeah, yo got me? All right, Well, we're talking about
Speaker 2: how particles can carry force? Do they carry force? What
Speaker 2: does it mean for a particle to carry force? Because
Speaker 2: I feel like we're used to forces being just some
Speaker 2: sort of invisible thing in the universe. It makes us
Speaker 2: want to go towards something, we're away from something, But
Speaker 2: I feel like you're saying. Physicists have this view where
Speaker 2: a force, when something's pulling or pushing you, it's actually
Speaker 2: some sort of exchange of particles.
Speaker 1: Yeah, this microscopic picture is compelling because it helps connect
Speaker 1: with our macroscopic understanding, our like intuitive experience of what
Speaker 1: a force is, and that's basically touching. You know, when
Speaker 1: the brick wall slows your car down, it does so
Speaker 1: because you hit the brick wall. Or when you lap
Speaker 1: that baseball into a home run, you do so because
Speaker 1: the baseball hit the bat. Right, And we have this
Speaker 1: sense that in order to change something's momentum, you got
Speaker 1: to touch it, that it comes from contact, from like
Speaker 1: literally pushing on something or pulling on something to apply
Speaker 1: that force.
Speaker 2: Well, not necessarily like a magnet, Like I think people
Speaker 2: are familiar with a magnet kind of pushing pulling things
Speaker 2: without actually touching it.
Speaker 1: Yeah, that's a great example. I think that's probably why
Speaker 1: magnets feel so spooky and weird to a lot of people,
Speaker 1: because it is action at a distance. Right, it's things
Speaker 1: pushing and pulling out each other without touching.
Speaker 2: Or Oh well, I don't want to get into this again,
Speaker 2: but you know, reused to gravity making things move towards
Speaker 2: each other without any kind of contact.
Speaker 1: Also, yeah, there, what's happening is you're interacting with curved.
Speaker 2: Space, all right, So then what do you mean by
Speaker 2: this macroscopic view?
Speaker 1: Just basically that things feel like they're local. You know,
Speaker 1: if you want to push on something, you got to
Speaker 1: touch it. And often when we're telling stories about what's
Speaker 1: happening on the microscopic scale, when we're trying to tell
Speaker 1: ourselves a story about the particles, we rely on our
Speaker 1: intuition from the macroscop it from like the big scale stuff.
Speaker 1: So then the question is, when particles are pushing on
Speaker 1: each other, are they coming into contact in some way?
Speaker 1: Is this interaction like a local thing? And that's where
Speaker 1: the story of two particles exchanging some particle helps us
Speaker 1: sort of fill in that gap. It tells us a
Speaker 1: local story. Now, like one particle is flying along and
Speaker 1: it throws a particle, pulling it out of its boson pocket.
Speaker 1: Add another particle which catches it. In that story, everything
Speaker 1: is always local.
Speaker 2: M Yeah, I'm all about eating local and theorizing locally.
Speaker 2: But maybe let's paint a picture, more concrete picture for
Speaker 2: folks Let's say you have two electrons a meter part
Speaker 2: and according to what we know, they feel that electromagnetic
Speaker 2: force and they have the same charge. So they're repelling
Speaker 2: each other, meaning if you just leave it for a while,
Speaker 2: they're going to move away from each other. Yep, okay,
Speaker 2: So then how is that force being transmitted if they're
Speaker 2: not touching each other.
Speaker 1: Yeah, So there's a lot of different ways to think
Speaker 1: about it. One story, which I'm not a big fan of,
Speaker 1: but is a sort of common story you hear, is
Speaker 1: that they do it by exchanging a particle. That one
Speaker 1: electron transmits momentum to the other electron basically by shooting
Speaker 1: a photon at it. Because electrons can emit photons and
Speaker 1: they can also absorb photons, it's like an interaction that's
Speaker 1: allowed in the universe. So the story is like, electron
Speaker 1: one shoots off a photon and in doing so, it
Speaker 1: recoils against that photon. Right, maybe it was going straight,
Speaker 1: now it's going left, shoots that photon off to the right.
Speaker 1: The other electron, which was going straight, absorbs that photon
Speaker 1: which was going right, and now it's going right. And
Speaker 1: so it's sort of like two cars driving in parallel,
Speaker 1: and one of them throws a ball at the other one,
Speaker 1: and some momentum gets carried along with that ball.
Speaker 2: Or like if I toss a bowling ball at you,
Speaker 2: you know, when I toss it at you, I'm going
Speaker 2: to move back a little bit because it takes some
Speaker 2: effort to toss it your way, and then when you
Speaker 2: catch it, you're going to recoil back also a little bit,
Speaker 2: because the ball had some sort of momentum to it
Speaker 2: and it pushes you back.
Speaker 1: Yeah, exactly the same way you feel a literal recoil
Speaker 1: when you shoot a gun, and then the target also
Speaker 1: feels that momentum transfer.
Speaker 2: Absolutely, I feel like this view is something that you
Speaker 2: would get it if you were already a little bit
Speaker 2: familiar with science, right, like if you're take in a
Speaker 2: maybe a college little physics course. I don't know, maybe
Speaker 2: they teach it also in high school. But maybe for
Speaker 2: the everyday person, this might be a new story that
Speaker 2: they had never heard before, right, Like, maybe to then
Speaker 2: average person, they're just thinking, well, those two electrons, one
Speaker 2: of them is exerting a force on the others through
Speaker 2: the magic of magnetism.
Speaker 1: Yeah, and then the question is, how do you actually
Speaker 1: explain that. How do you come up with like a
Speaker 1: coherent theory that says what's really happening? And one way
Speaker 1: to do that is to say, oh, these forces are
Speaker 1: actually being carried by particles, right, because particles are things
Speaker 1: we know in the universe can carry momentum, and so
Speaker 1: if you want to push on something or pull on something,
Speaker 1: you've got to use particles to carry that momentum. So
Speaker 1: this is just like a way to try to explain
Speaker 1: these forces that we see. Maybe what's happening microscopically is
Speaker 1: that particles are being exchanged the same way you might
Speaker 1: wonder like, well, what's everything made out of around me?
Speaker 1: And you drill in on the tiny details and you discover, oh,
Speaker 1: the surface of my table is not smooth. It's actually
Speaker 1: a bunch of particles. I just don't see them because
Speaker 1: they're so tiny. So maybe the forces between two and
Speaker 1: the forces between two electrically charged objects are actually particles
Speaker 1: being transmitted between them. That's sort of how the story goes.
Speaker 2: Right, Like if people see me and you moving away
Speaker 2: from each other, they might think, oh, there's some sort
Speaker 2: of invisible magical force, but no, really, actually it's because
Speaker 2: Orhea tossed a bowling ball to Daniel.
Speaker 1: Yeah, exactly, do you have invisible bowling balls? By the way,
Speaker 1: that sounds pretty cool.
Speaker 2: Well, no, it doesn't have to be invisible. It could
Speaker 2: just be a black bowlling ball at night. But I
Speaker 2: think what you're trying to get at is like, this
Speaker 2: is a view that's maybe popular out there if you
Speaker 2: consume a lot of science and physics, but maybe this
Speaker 2: view doesn't quite work. So does it work or not?
Speaker 1: It definitely doesn't work for me, and I get the
Speaker 1: sense that it doesn't work for a lot of people
Speaker 1: out there because they get a lot of questions about it.
Speaker 1: People absorb this idea and then they do what we're
Speaker 1: always telling them to do on this podcast, which is well,
Speaker 1: think about whether that makes sense. Does it explain other
Speaker 1: things you see? Can you understand it in other circumstances,
Speaker 1: does it click together with the other parts of your understanding.
Speaker 1: And there's a bunch of pretty typical questions that this
Speaker 1: picture raises and can't really answer. For example, For example,
Speaker 1: we can tell a nice story about electrons repelling each
Speaker 1: other by tossing photons back and forth, but how do
Speaker 1: things attract each other if an electron and a positron.
Speaker 1: Electromagnetism says they should be pulled together. How does an
Speaker 1: electron or a positron throw a ball at the other
Speaker 1: one and pull it towards itself. It have to be
Speaker 1: like a ball with negative momentum somehow.
Speaker 2: Yeah, I was about to say that.
Speaker 1: Why not, because if it's negative momentum, it's going the
Speaker 1: other direction, right?
Speaker 2: Is that a requirement? Can I just come up with
Speaker 2: a magical bowling ball it has negative momentum.
Speaker 1: Having negative momentum really makes no sense. It's sort of
Speaker 1: like having a negative mass or negative length, right. It
Speaker 1: really just means momentum in the other direction. So if
Speaker 1: you're going to throw a ball to the right with
Speaker 1: negative momentum, you're really throwing a ball to the.
Speaker 2: Left right, which would push me towards the you right,
Speaker 2: And so it would make sense.
Speaker 1: But that's not an exchange of particles. Right. Maybe the
Speaker 1: electron throws off a ball in one direction, the positron
Speaker 1: throws off the ball in the other direction. They move
Speaker 1: towards each other. But now you also have these photons, right,
Speaker 1: and we don't see those photons when electrons and positrons
Speaker 1: are try and then there's no exchange there, the electron
Speaker 1: and positron not actually exchanging particles there.
Speaker 2: Well, I feel like you know, I'm new to this,
Speaker 2: so to me, it could all be magical. Daniel, lets
Speaker 2: you make stuff up. I'm relying on YouTube. Tell me, like, no,
Speaker 2: that's a fundamental law of the universe that you're breaking.
Speaker 2: So like, let's you have a magical bowling ball with
Speaker 2: native momentum and you're you're standing in front of me,
Speaker 2: so to toss it to you, I actually have to
Speaker 2: push it back behind me, and then the ball would
Speaker 2: go towards you, and then when you catch it, it has
Speaker 2: negative momentum, which would actually pull you towards me. When
Speaker 2: am I breaking there?
Speaker 1: Okay, well then I'll just tell you that that's not allowed.
Speaker 1: You can't have particles with negative momentum. It just doesn't
Speaker 1: make any sense.
Speaker 2: Hmmm, it says to you. But let's move on.
Speaker 1: You just have to me to tell you when you're
Speaker 1: breaking the rules, you breaking the rules. But there's also
Speaker 1: other parts of the story that don't really make sense,
Speaker 1: like how does the electron know the positron is there?
Speaker 1: Has it no to admit a photon in one direction
Speaker 1: to attract the positron.
Speaker 2: M Yeah, That's one thing I've always wondered about this
Speaker 2: picture is like, does that mean that electrons are just
Speaker 2: throwing a photons in all their all the time, and
Speaker 2: then it just happens to interact with another elect what
Speaker 2: happens to catch it? Then they're going to repel each other?
Speaker 1: Yeah, exactly is that what you mean?
Speaker 2: Like that doesn't make sense.
Speaker 1: That doesn't make sense. And then you would see those photons, right,
Speaker 1: And if you stick your head between two particles that
Speaker 1: are supposedly exchanging photons, why can't you see them? When
Speaker 1: magnets are floating above each other? Why can't you see
Speaker 1: flashes of light there? So there's all sorts of questions
Speaker 1: that are raised by this particle exchange model that don't
Speaker 1: really have good answers.
Speaker 2: Okay, so this view doesn't seem to make sense. Where
Speaker 2: did it come from? Who came up with this? And
Speaker 2: then didn't they think of these things when they came
Speaker 2: up with it.
Speaker 1: They didn't have a cartoonist keeping them in check. That's
Speaker 1: really the problem.
Speaker 2: Yeah, that's really the problem. They're missing their cartoonists in
Speaker 2: their science force.
Speaker 1: Yeah, exactly. Every physicists should have adult supervision in the
Speaker 1: form of a cartoonist. That's what we're learning today.
Speaker 2: But then who supervises the cartoonist and we're off the rails?
Speaker 1: Yoda, I think, yoda. But yeah, where does this come from?
Speaker 1: It comes from You won't be surprised to learn the
Speaker 1: unfortunate naming of another idea. So what's really happening here
Speaker 1: is not the There are literal photons being exchanged between
Speaker 1: electrons or electrons and positrons. But there's something else happening.
Speaker 1: There's an interaction that we describe using the phrase virtual
Speaker 1: particles and virtual particles because it has the word particle
Speaker 1: in it sounds like maybe it's a kind of particle,
Speaker 1: but really they're not particles at all.
Speaker 2: Which you're saying, like the first person who came up
Speaker 2: with this idea really meant virtual particles. But then at
Speaker 2: some point people stop using the word virtual.
Speaker 1: Yeah, exactly when it transitions over into popular science, people
Speaker 1: are like, you know, it's kind of like they're throwing
Speaker 1: photons back and forth. They're virtual particles, but you can
Speaker 1: think of them as particles, And that's exactly where it
Speaker 1: breaks down. If you think of them as particles, they're
Speaker 1: not really because they don't do all these other things
Speaker 1: you would expect particles to do.
Speaker 2: All right, well, let's dig into what is actually going
Speaker 2: on virtually and for reals in this universe and see
Speaker 2: if we can make sense of this picture of what
Speaker 2: a force is. So tostig into that. But first let's
Speaker 2: take another quick break. All right, we're asking the question
Speaker 2: how do particles carry force? And there's a view that
Speaker 2: maybe they exchange force particles. But Daniel, you're saying that
Speaker 2: actually they're not really exchanging particles. They're exchanging virtual particles,
Speaker 2: which is kind of like bitcoin.
Speaker 1: It's nothing. Well, I mean if you say bitcoin is
Speaker 1: nothing like money, then yes, virtual particles are like bitcoin.
Speaker 2: Yeah, there you go. They're not real. They're just like
Speaker 2: a concept.
Speaker 1: I mean, you're going to bring all the crypto bros
Speaker 1: down on us, dude.
Speaker 2: Bring it on. Yeah, maybe they like to fund us
Speaker 2: in bitcoin or dorsche coin.
Speaker 1: Well, we can only pay virtual bills with virtual dollars,
Speaker 1: so I'm not sure how helpful that is.
Speaker 2: I feel like I have a virtual job anyways. But anyway,
Speaker 2: so explain it to us. What's the difference between a
Speaker 2: particle and a virtual particle, and how to virtual particles
Speaker 2: create forces.
Speaker 1: So what is a particle anyway? A particle is actually
Speaker 1: a ripple in a field, like what is a real photon.
Speaker 1: A photon is a ripple in the electronnetic field. The
Speaker 1: whole field fills the universe, and a photon is a
Speaker 1: very regular disturbance in that field. It's a very particular,
Speaker 1: very special kind of disturbance that's sort of self sustaining.
Speaker 1: Like you point your flashlight up at Alpha Centauri. Those
Speaker 1: photons can go across light years and make it to
Speaker 1: Alpha Centauri. They don't get tired, they don't run out
Speaker 1: of steam. All that energy is compact in this perfect way.
Speaker 1: It's slashing through the electromagnetic fields in this very special
Speaker 1: particular way that lets it propagate through the universe. That's
Speaker 1: what a particle is, So like a very special kind
Speaker 1: of disturbance in the field that satisfies a bunch of
Speaker 1: equations for how those field works.
Speaker 2: Okay, it's a particle, not like a real object. It's
Speaker 2: a little ripple, special ripple in the giant cosmic universe
Speaker 2: spanding field.
Speaker 1: Yeah, exactly. Now, a virtual particle is also a disturbance
Speaker 1: in that field, but doesn't have any of those same properties.
Speaker 1: Virtual particles are like basically everything else that field can do.
Speaker 1: If that field is disturbed by the presence of some
Speaker 1: other particle, then the field will slasher and oscillate a
Speaker 1: little bit, and then that'll die out, and that we
Speaker 1: can describe as virtual particles if you like, or you
Speaker 1: can just think about it as oscillations in the field.
Speaker 1: But virtual particles are basically a way of thinking about
Speaker 1: what else fields can do other than having particles in them.
Speaker 2: Now is the difference that that one is sustainable or
Speaker 2: sustained and the other one kind of fades away like
Speaker 2: an electron. It's special in the electron field because it's
Speaker 2: there and it doesn't go away.
Speaker 1: Yeah, exactly. All these fields have equations to describe how
Speaker 1: they wiggle. The fields are always wiggling. They have kinetic energy,
Speaker 1: which means they're moving. They have potential energy, which means
Speaker 1: they have energy of their configuration. It's sort of like
Speaker 1: a kid on a swing. Right, they're swinging back and forth.
Speaker 1: And for a kid on a swing, you give them
Speaker 1: just the right push, they can swing really nicely. Right,
Speaker 1: if you push them at the right frequency, they can
Speaker 1: swing in a really nice regular way. But there's also
Speaker 1: other crazy things that that swing can do that aren't
Speaker 1: so nice and self sustaining. Like you give that kid
Speaker 1: random pushes at random times, it's going to get a
Speaker 1: very chaotic sort of oscillation. So if you wiggle a
Speaker 1: field in just the the right way, you can set
Speaker 1: up these self sustaining perturbations that will move through space.
Speaker 1: If you don't do it in just the right way,
Speaker 1: then they sort of peeter out and the energy dissipates
Speaker 1: instead of like moving in a little compact blob.
Speaker 2: And so virtual particle is any wiggle of the field
Speaker 2: that is not self sustaining, which is not special like
Speaker 2: the wiggle that is an electron exactly.
Speaker 1: So an electron is a special wiggle, and you can
Speaker 1: see it, you can interact with it, same with a photon.
Speaker 1: A virtual particle is any other sort of disturbance in
Speaker 1: the field that fades away really quickly. And there's sort
Speaker 1: of an argument in particle physics about what's the best
Speaker 1: way to describe them. Some people think, look, let's just
Speaker 1: talk about the fields. Everything is a field. Particles are
Speaker 1: actually wiggles in fields when they interact with each other.
Speaker 1: That's just fields interacting other people like this virtual particle story.
Speaker 1: They say, no, particles are the basic thing, and let's
Speaker 1: talk about how they interact in terms of virtual particles.
Speaker 1: So in some sense, virtual particles are just the story
Speaker 1: we tell ourselves to describe some things that fields can do.
Speaker 1: But fields are really the more fundamental element of the universe,
Speaker 1: according to lots of physicists.
Speaker 2: Okay, so then it has to if it feels. But
Speaker 2: then I guess what do you call these particles virtual?
Speaker 2: They seem as real as the other kinds of particles,
Speaker 2: like the electron.
Speaker 1: We call them virtual for a few reasons. Number one
Speaker 1: is they don't obey the rules that particles obey. These
Speaker 1: real particles. They have like the same mass, right, so
Speaker 1: a real electron always has the same mass, and real
Speaker 1: photons always have zero mass. These other wiggles in the field,
Speaker 1: you can try to describe them in terms of a
Speaker 1: particle like story, but it breaks down because they don't
Speaker 1: follow the same rules. And so like, what is the
Speaker 1: mass of this virtual photon? Well, if you try to
Speaker 1: calculate a mass, you end up with weird numbers. Sometimes
Speaker 1: they have really huge mass, sometimes it's even negative. It's
Speaker 1: because it doesn't really apply. You're trying to describe a
Speaker 1: bowling ball as a car, and you're asking, like, you know,
Speaker 1: what's it like to drive? Well, it's not really anything
Speaker 1: like to drive a bowling ball.
Speaker 2: Oh, how do you know. I'm just trying to ask
Speaker 2: the tough questions here today, Daniel.
Speaker 1: No, these are great questions. I love that you can't
Speaker 1: be flat footed with questions like what is it really
Speaker 1: like to drive a bowling ball?
Speaker 2: I mean, for making blanket statements here about the nature
Speaker 2: of bowling balls, we need to back it up with
Speaker 2: real science.
Speaker 1: The point is that we have these weird disturbances in
Speaker 1: the field that we can describe mathematically, but they don't
Speaker 1: have the same behavior as normal particles, and so we
Speaker 1: can't interpret them in the same way.
Speaker 2: Okay, so they're weird wiggles in the field. They're not
Speaker 2: as as special as the particles. You call them virtual particles. Now,
Speaker 2: how do they actually the transmit a force?
Speaker 1: All these fields contain energy, right, An electron is a
Speaker 1: little pulse in the field, still vibration of the fields.
Speaker 1: It's an excited state of the field. It has energy.
Speaker 1: So in this field picture, how do two electrons push
Speaker 1: on each other? They do so through the electromagnetic field.
Speaker 2: So we're talking about multiple fields now, right. So there's
Speaker 2: an electron field and then there's a photon field, which
Speaker 2: is the electromagnetic force field. Yes, and you're saying, like,
Speaker 2: the two electrons are in the same field, the electron field.
Speaker 2: They're sharing the same field, but to talk to each
Speaker 2: other they have to go through another field.
Speaker 1: Yeah, that's exactly right. The field doesn't interact with itself. Right.
Speaker 1: You have these two fields that feel space, the electromagnetic
Speaker 1: field and the electron field. These are two separate fields, right.
Speaker 1: For one of them, the excited state of that field
Speaker 1: is an electron. For the other one, for the electromagnetic field,
Speaker 1: the excited state of it is a photon.
Speaker 2: Right now, why can't they interact within the same field,
Speaker 2: Like if I have the ocean like a way will
Speaker 2: interact with another wave.
Speaker 1: Some fields will do that, like the strong force. Gluons
Speaker 1: can interact directly with themselves, but photons can't interact with photons,
Speaker 1: and electrons can't interact with other electrons.
Speaker 2: It's just a weird happenstance of the universe that the
Speaker 2: electron field can't do that.
Speaker 1: That's right. Some fields are allowed to interact directly with themselves.
Speaker 1: But the electron field doesn't do that, and you might
Speaker 1: ask why, and it's just description, this is what we
Speaker 1: see in the field.
Speaker 2: Do Okay, So they talked through the photon field, and
Speaker 2: so what's going on. Where are the virtual particles in
Speaker 2: the photon field or the electron field.
Speaker 1: They're in the photon field, So these are virtual photons,
Speaker 1: and again they're not real particles. They're like weird disturbances
Speaker 1: in the field. So electron number one causes a disturbance
Speaker 1: in the photon field, and it does that all the time,
Speaker 1: like electron can't exist without disturbing the photon field. It's
Speaker 1: doing it all the time. It's constantly interacting with the
Speaker 1: photon field, and the photon field is constantly interacting with
Speaker 1: electron fields, like a photon flying through space is constantly
Speaker 1: interacting with the electron field. It's not like it just
Speaker 1: sometimes does. And so the electron is causing these disturbances
Speaker 1: in the photon field. And if those disturbances interact with
Speaker 1: another electron, then that's effectively momentum transfer from one electron
Speaker 1: to another through the photon field, which you could also
Speaker 1: say is the exchange of a virtual photon, but it's
Speaker 1: not really a particle. It's not a particle you could
Speaker 1: like see with your eyes or if you put a
Speaker 1: detector in there, because it's not a real photon. It's
Speaker 1: just a ripple in the photon field that we call
Speaker 1: a virtual particle to connect with this story about electrons
Speaker 1: passing particles back and forth.
Speaker 2: But I feel like this all sounds great, but I
Speaker 2: feel like you're just going to run into the same
Speaker 2: question as you did with the real particles picture right,
Speaker 2: because you might say this is not a bowling balls,
Speaker 2: there's a virtual bowling ball, or it's a tennis ball,
Speaker 2: but you're still you're still run into the same questions
Speaker 2: like if I toss a virtual a tennis ball to you,
Speaker 2: how did I know where you were? And how did
Speaker 2: you know to catch it? And why am I not
Speaker 2: shooting tennis balls in all directions? And what if you're
Speaker 2: and I'm an electron, how do we repel each other?
Speaker 2: How do we throw a negatively momentum a tennis ball?
Speaker 1: Yeah, okay, great questions, and we can actually answer all
Speaker 1: of them now, right, So an electron is constantly creating
Speaker 1: these ripples in the field. It doesn't have to know
Speaker 1: that the positron or the other electron is there. It's
Speaker 1: constantly creating these ripples in the electromagnetic field. That's just
Speaker 1: what it does. The two fields are constantly interacting, so
Speaker 1: you don't have to know the other particle is there.
Speaker 2: So it's constantly in all directions shooting virtual photons. Yes,
Speaker 2: but where does this energy come from? And wouldn't you
Speaker 2: be able to see them? It's the same question you
Speaker 2: have with the photons, right, mm hmm.
Speaker 1: The energy dissipates, right, So virtual photons are not like
Speaker 1: real particles that you could interact with. It's not like
Speaker 1: it's shooting a light bulb at Alpha centauri and eventually
Speaker 1: it will be seen. These fade away really quickly, and
Speaker 1: if you try to think about them in terms of
Speaker 1: a particle, it's really just part of the story. There's
Speaker 1: lots of complicated ripples going on. You can describe them
Speaker 1: in terms of one virtual photon or two virtual photons
Speaker 1: or seventeen virtual photons. That's really just an attempt to
Speaker 1: describe what's happening to the field. But to get back
Speaker 1: to the question, basically, the two fields are constantly interacting,
Speaker 1: So if a positron comes by then the fact that
Speaker 1: there's an electron there. The electron is affecting the electromagnetic
Speaker 1: field that the positron is also constantly interacting with. So yeah,
Speaker 1: basically you're constantly shooting these virtual particles. Answered the other
Speaker 1: question of like, well, then how do you attract virtual particles?
Speaker 1: Don't have to obey that law I told you about
Speaker 1: earlier about what because they're not really particles. There you go, yes, exactly.
Speaker 3: He's told me that it was not possible, Daniel, for particles,
Speaker 3: or for bowling balls, or for tennis balls. Particles have
Speaker 3: to obey that law. Virtual particles are not particles. It
Speaker 3: feels like a cop out because we're saying, oh, you
Speaker 3: put virtual on it. You don't have to obey the rules.
Speaker 3: Like if I'm driving my virtual car, can I ignore
Speaker 3: the speed limits. It's not really a particle. It's just
Speaker 3: a ripple in the field. And these fields can have
Speaker 3: all sorts of weird.
Speaker 1: Ripples in them that don't obey the rules of normal particles,
Speaker 1: like negative mass or crazy high mass photons. That feels
Speaker 1: like a contradiction.
Speaker 2: So it is like I'm shooting a negative momentum tennis
Speaker 2: ball at you, right, that's what you're saying.
Speaker 1: Sort of, except that these are not particles, right, They're ripples.
Speaker 1: They're ripples exactly.
Speaker 2: Just like a particle is.
Speaker 1: A particle is a special kind of ripple that like
Speaker 1: satisfies the wave equation of the field. Virtual particles do
Speaker 1: not satisfy that, and so you can't even ask the
Speaker 1: question like, what is the mass of this thing? There
Speaker 1: are energy and they are flowing through the field, but
Speaker 1: they're not particles.
Speaker 2: Hmmm. I feel like you're trying to get me on
Speaker 2: a technicality here.
Speaker 1: Physics is technicalities, man.
Speaker 2: But I guess the main question is, so you're saying
Speaker 2: that if we've put the word virtual in front of it,
Speaker 2: then this whole picture of exchanging particles work. You just
Speaker 2: have to call them virtual so that they can break
Speaker 2: the rules of regular particles.
Speaker 1: Yeah, but they're not even really particles, right. I feel
Speaker 1: like it's really misleading to just say, oh, it's a
Speaker 1: kind of particle. It's not a kind of particle. It's
Speaker 1: a totally different thing. Virtual particles are kinds of particles
Speaker 1: the way bowling balls are types of cars.
Speaker 2: Well, I see, Really the name should be a non
Speaker 2: particle ripple.
Speaker 1: Yes, exactly, come up with a better name than virtual
Speaker 1: particle because that has misled millions of people.
Speaker 2: Now, is that the best name for it, non particle ripple.
Speaker 1: I feel like that's confusing because you're still using the
Speaker 1: word particle.
Speaker 2: No, but it's a non particle ripple. It's a ripple
Speaker 2: that doesn't mean all the requirements of a particle.
Speaker 1: Should I describe my bowling ball as a non car
Speaker 1: bowling ball.
Speaker 2: It causes confusion. Yeah, for sure.
Speaker 1: It has nothing to do with cars. I should also
Speaker 1: describe it as a non banana ball and a non
Speaker 1: chocolate ball.
Speaker 2: Well, no, I mean the difference is that of this
Speaker 2: virtual particle in this particle have something common, which is
Speaker 2: that they're both ripples in the field.
Speaker 1: Yeah, that's true. Bowling balls and cars both can roll
Speaker 1: down the road, right, very different things. I feel like
Speaker 1: you're trying to get me in a technicality here.
Speaker 2: No, just trying to understand you're confusing nomenclature here. But
Speaker 2: I mean, just so we can reach an understanding maybe
Speaker 2: with our listeners, would you say that a better way
Speaker 2: to call these things is as non particle ripples in
Speaker 2: the field, because I feel like that's what you just
Speaker 2: explained it as.
Speaker 1: Yeah, that's definitely better than virtual particles because they're not particles.
Speaker 1: And there are ripples in the field, yes, there you go.
Speaker 2: But some ripples are particles, but those are special m
Speaker 2: and so these are not those kinds exactly.
Speaker 1: And we often describe these in terms of virtual particles
Speaker 1: because we like to think about particles particles are the
Speaker 1: things we observe. We never see the field directly, right,
Speaker 1: You never observe a field. You only see the effect
Speaker 1: of the field on a particle. So a lot of
Speaker 1: people like to think of the particles as the sort
Speaker 1: of basic stuff that we're using to describe the universe,
Speaker 1: and in order to describe how they interactly, think about
Speaker 1: that in terms of particles. And we draw these cute
Speaker 1: little finement diagrams that include like little wiggles in the
Speaker 1: paper that we say are virtual particles. So it's a
Speaker 1: compelling story, but we should always remember these are not
Speaker 1: really particles. They're really just different kinds of ripples in
Speaker 1: a field.
Speaker 2: Well, and I mean to be a pain, but it's
Speaker 2: a little bit like says you kind of right, like
Speaker 2: you're saying that the boundary of the definition of a
Speaker 2: particle is that it meets all these rules. Now, is
Speaker 2: that something that's totally accepted by every physicist or would
Speaker 2: some physicists say, well, I would say any ripple is
Speaker 2: a particle.
Speaker 1: No, I think that's totally acceptable. And also, you can
Speaker 1: see real particles. You can't ever see virtual particles. They're
Speaker 1: just a part of the description. This feels very complicated ripples,
Speaker 1: and you can describe part of it using a virtual particle,
Speaker 1: but to describe it fully you need like an infinite
Speaker 1: number of virtual particles. So the virtual particles are just
Speaker 1: like a component of the story. They're not a real
Speaker 1: thing in any sense. You can't see or interact with
Speaker 1: a virtual particle.
Speaker 2: Would you sort of see them? When two electrons repel
Speaker 2: each other, aren't you sort of seeing them?
Speaker 1: Not directly? I mean, if you had like a photon counter,
Speaker 1: you wouldn't register any photons there. You're right, you can
Speaker 1: see the effect on two electrons. Absolutely well.
Speaker 2: You can't see in the photon either without interacting with it.
Speaker 1: Right, Yeah, but here you're one more step removed. Right here,
Speaker 1: you're seeing its effect on the electron. You're not even
Speaker 1: interacting with a photon because you can't because it's not
Speaker 1: a real photon a virtual photon.
Speaker 2: Now, okay, so then you're saying that forces happen in
Speaker 2: the universe between two particles with a capital P because
Speaker 2: they interchange virtual particles or non particle ripples in the
Speaker 2: quantum field. Yes, does that mean that everything's explained now?
Speaker 2: That works?
Speaker 1: That works. That is a very effective description of how
Speaker 1: particles interact and allows us to ditt what particles will
Speaker 1: do with extraordinary accuracy, which makes us feel like maybe
Speaker 1: we got it right.
Speaker 2: And in this picture, like an electron is just sitting
Speaker 2: there in space and it's shooting an infinite number of
Speaker 2: ripples in all directions all the time.
Speaker 1: Well, the two fields are interacting with each other. The
Speaker 1: electromagnetic field and the electron field are interacting with each other.
Speaker 1: The energy is kind of going back and forth, right,
Speaker 1: it's a constant interaction. You can describe that as like
Speaker 1: the electron creeds virtual photons which it then absorbs, or
Speaker 1: maybe those virtual photons interact with a passing positron or electron,
Speaker 1: or you can just think about it as fields sort
Speaker 1: of pulsing back and forth together.
Speaker 2: Oh, I see, there's no like energy being generated. It's
Speaker 2: like the electron puts some energy into the photon field,
Speaker 2: and maybe that energy doesn't like dissipate, it goes back
Speaker 2: to the electron. But unless maybe there's another electron nearby,
Speaker 2: or a positron, in which case some of that energy
Speaker 2: goes to the other particles exactly. All right, that was
Speaker 2: not a forced conversation at all. You got very real,
Speaker 2: not virtual.
Speaker 1: And somewhere out there in some universe, Yoda is driving
Speaker 1: his bowling all down the road and this all makes
Speaker 1: sense to him. That's right on his way to his
Speaker 1: yoga class.
Speaker 2: Hot yoga class. Yes, Now, do you think both Jedis
Speaker 2: and Sith practice yoga or is this something only the
Speaker 2: Jedi would do?
Speaker 1: I wonder if there's dark yoga there you.
Speaker 2: Go, Yeah, evil yoga. All yoga is evil. Maybe what's
Speaker 2: the other one? Pilates? Maybe pilates is what the Sith practice.
Speaker 1: Yeah, forever he will dominate their strenchiness.
Speaker 2: That's right? All right? Well, I think this has been
Speaker 2: an interesting exploration of how physicists view the universe and
Speaker 2: how particles interact. But again, this is just kind of
Speaker 2: your view of it, right, who knows what's really happening underneath?
Speaker 1: Yeah, philosophically, this is just a story we tell that
Speaker 1: explains experiments. Is any of it true? Do the elements
Speaker 1: of our ideas actually correspond to real physical things happening
Speaker 1: out there in the universe. That's for philosophers to decide.
Speaker 2: All right, well, we hope you enjoyed that. Thanks for
Speaker 2: joining us. See you next time.
Speaker 1: For more science and curiosity, come fine us on social
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Speaker 1: and Jorge Explain the Universe is a production of iHeartRadio.
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