Daniel and Kelly’s Extraordinary Universe - Do photons bump into each other?

Episode Date: June 28, 2022

Daniel and Jorge bump brains and talk about whether beams of light interact or pass through each other. See omnystudio.com/listener for privacy information.

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All right. What is it? How close are we to having real-life lightsabers? You're asking a physicist, that question? I would ask the same question to my favorite engineer. Wait, do you think it's an engineering solution? Don't we need, like, a super? kind of breakthrough in theoretical physics first? Not. I mean, the science fiction authors have done their job already, and they passed it on to the physicists. Oh, yeah, and the physicists have figured out how to do it? Well, you know, we've been smashing photons together to see what happens. And how does that give us a lightsaber?

Well, so far it makes a really awesome sound, like, ooh, but can it cut through swords and deflect light guns? That's the engineering problem. Hi, I'm Jorge. I'm a cartoonist and the creator of PhD comics. Hi, I'm Daniel. I'm a particle physicist and a professor at UC Irvine. And until a moment ago, I had never made a lightsaber sound with my mouth. Yeah, we could tell. That was terrible, Daniel. All right, let's hear your lightsaber sound. Right? That sounds a lot more agglaber.

Well, we'll let the listeners vote. I think the coolest sound, though, is when they clash, you know, because they're like, and then it's zzzed or something when they hit against each other. Oh, boy, that's even worse, Daniel. Everyone knows it's, kash, kach, kish. Oh, that was much better. All right, you're right. That's definitely better.

Those movies are ingrained, are burning into my brain for better or for worse. Like somebody inscribed them with a lightsaber. Like somebody waved their hand and said, I would only remember these movies for the rest of my life. It would be pretty awesome if the movies themselves, were a Jedi mind trick. What I think they were. They certainly got a lot of my money out of my pocket. These are the movies you want to pay for.

But anyways, welcome to our podcast, Daniel and Jorge, Explain the Universe, a production of IHeart Radio. In which we pull off the physics mind trick of attempting to understand the universe. We convince ourselves and hopefully convince you that the crazy cosmic mysteries, the grandest questions of the existence of humanity, the things that philosophers have been wondering about for thousands of years, very nature of our reality and its meaning can be understood by tiny little squishy brains living on a little rock orbiting a very normal star. We talk about all of these questions and we explain

all the answers to you. That's right. We use the force to understand the forces of the universe and to look out to galaxies far, far away and actually also a long, long time ago to understand how it's all put together and why it's all hanging there the way it is. Because everything around us presents mysteries. How do these things work? What happens when they bump into each other? And as a particle physicist, my favorite way to understand how things work is to do exactly that. Smash them into each other or collide them into each other or blow them up, whatever you prefer. Yeah, because the universe has a dark side and also a light side. And it seems to be in constant struggle with itself, bumping into each other, colliding, fields, interacting with each other,

all of it to create this amazing spectacle that we can see just by looking out into the night sky. And we've made remarkable progress in understanding the very nature of the universe by describing space itself and everything out there in terms of oscillating quantum fields, these things which fill the whole universe with their energy and slide and smush against each other to come together to describe the reality that you and I experience. Wait, Daniel, you mean it's not all made out of midichlorians, little tiny beings that, you know, bind everything together? I think Middiclorians were biological, not quantum mechanical. They never described it in Star Wars. Maybe they are quantum mechanical. Ooh, maybe they are quantum biology. Yeah, maybe, right?

Well, in a way, it seems almost the same. I mean, you're saying that the universe is made of these fields that are bound together with these little tiny things that bump around each other and somehow direct the cosmos. That's kind of what George Lucas was saying. That's kind of what everybody was saying, if you're going to say, kind of, and be really generous about it, you know. Yeah, kind of. But I love this picture of the universe as all these different quantum fields. You have like a field for the photon.

You have a field for the electron. You have a field for the quarks. And you know, those fields we can think about as having particles in them which slide around and keep a little discrete blob of energy. And we've talked in the podcast about how particles are these little ripples in the quantum fields. But one of the most interesting things that these fields can do is talk to each other. The photon field and the electron field don't just fill the space of the universe and ignore each other. they interact, they touch, they bind together, they transfer energy back and forth.

Yeah, and thankfully, I guess, right? Because if all the fields ignored each other, like nothing would ever happen. We wouldn't be here. We're here because of those interactions in a way. Every interaction between two different kinds of particles, the way the electron is bound to the nucleus of the atom, the way chemical bonds form, the reason you don't fall through your chair is all because those quantum fields don't ignore each other. It's because they interact with each other because they pass energy back.

and forth. In some sense, it's a bit of an artificial distinction to say we have two different fields. You might want to think of them holistically as one bundle of fields. One force with the dark side and the light side, right? I think you're kind of saying the same thing. One force to rule them all. Now I'm mixing our mythologies. We need to have like a Lord of the Ring, Star Wars crossover event. Who would win? Oh my goodness. Fan fiction writers, get on it. Are those owned by like different corporate conglomerates, in which case it'll never happen? Not on the internet. Anything can happen on the internet.

That's true, until Disney's lawyers come after you. No, if Disney buys Lord of the Rings, then we might get like a Marvel, Star Wars, Lord of the Rings, Frodo crossover, right? Oh, my goodness, we'd throw Iron Man in there, and I'm all in. Gandalf versus Iron Man, wow. Who would win?

Dr. Strange or Gandalf? The War of the Wizards. I don't know. Who's got a better grasp on the quantum fields? But it is interesting in things like Star Wars, they use lasers, right? Laser guns to shoot at each other and also lightsavers to cut through appendages and also doors and walls. And it's interesting to think that light can interact with matter. Like if you shoot a laser, it's going to burn a hole through your wall, right?

And you can even use light to push a solar sail to push a spaceship off of the solar system. Exactly. Light is really weird. It has energy. It has momentum, but it doesn't have any mass. And yet, of course, it can influence our world. because of that energy and that momentum. A laser will deposit a lot of energy in a very small spot and burn right through it.

And that exactly happens because those photons can interact with charged particles. The quantum field of photon and the quantum field of those electrons or muons or quarks can interact and pass energy back and forth. I always wondered when I watched those lightsaber battles, I thought, how does that work? How do two lightsabers, two beams of light hit each other?

Well, this is getting a little philosophical You know, are lightsavers beams of light actual, like light that just stands there and sits there? Or are they like some kind of material like, you know, like a plasma beam? Well, wouldn't they be called plasma sabers then? I mean, they are called lightsabers. And I imagine George Lucas knows his quantum mechanics. Yeah, but maybe they're called lightsabers because they give off light. I guess that's a good point.

You know, light bulbs are not made of light. Yes, we're getting deep here. This is very stimulating, illuminating conversation here. Well, two bright minds, you know, let's see what we can do. I guess we were talking about things interacting, and, you know, it's kind of interesting that electrons can definitely interact with other electrons, right? Like an electron will repel another electron and like a proton will repel another proton. Like, things seem to be able to interact with it themselves.

But not directly, actually. Electrons do not interact directly with other electrons. Electrons interact with photons, and photons interact with electrons. Sort of like having an interpreter, right? You can talk to the photon and the photon can talk to the other electron, but electrons don't interact with each other directly. I see. You got to go through their agents. Like talk to my people. Exactly. It's like electrons are celebrities. They don't just email you. Their people email your people. But I guess this brings up an interesting question, which is what do photons interact with specifically?

Yeah, exactly. When those two lightsabers are about to cross and to make that sound that I can't make, what exactly is going on at the microscopic level in Georgia? Lucas's mind. Yeah, so to the end of the podcast, we'll be asking the question. Do photons bump into each other? And Daniel, this seems a little risque. Like, what do you mean bump into each other? Like, they bump and grind or they like casually like, oops, sorry, bump into each other. Yeah, well, you know, photons can do all sorts of things. They can be circularly polarized. So I guess they can do like spins on the dance floor. And, you know, I'm not one to tell you what's appropriate and what's not appropriate. talk to your parents about that.

But this is more of a physics question. You know, what happens when two beams of light cross each other? Do the photons ignore each other? Do they hit each other? Do two photons push against each other? You know, what happens when you cross the streams? Oh, man. Now we're getting to another mythology, Ghostbusters.

Do not cross the streams. Exactly. I want to see Venkman versus Gandalf versus a Jedi now. Oh, obviously, Agerman would win. I mean, the smart engineer always wins. I don't know. Vinkman's quite the smart professor. Yeah, because I think this is something that I wondered about as a kid. Like if you take a flashlight and you take another flashlight and you point them, not even at each other, but just like pointing them in the same direction or cross their beams, like what's happening there?

Like what's happening to the light? Do the light beams ignore each other or do they kind of interfere or somehow scatter each other? So you're saying you wanted to understand light and so you make light collisions. Well, I don't know. Is it possible for light to collide? That's the question of today's episode. Can you create a collite? A photon collider. So that's the big question we're asking today is, can light bump into each other?

Does light interact with itself? Because not every particle interacts with other particles. Neutrinos, for example, ignore most of the matter in the universe sliding right by as if it wasn't even there. Each particle, each ripple in the quantum field, can either see other fields or ignore the other fields. And it's not like an option. It's not like it depends on its mood. Some of these fields couple with each other and other fields just don't.

couple with each other at all. Well, it's kind of interesting because I know we talked about this a lot before, how there are two kinds of particles. There are matter particles, like the stuff that we think of with stuff. Then there are force particles. And so a photon is a force particle. And so the question, I guess maybe a larger question is, do force particles interact with themselves? It is a really interesting and deep question. Some of the force particles can actually interact directly with themselves and others interact indirectly with themselves. But as we'll learn today, there's several layers of nuance to the answer. All right. Well, we'll get right on it. But as usual, we were wondering how many people had thought about this light question, this question of whether light can interact with itself. And so as usual, Daniel, went out there into the internet, Daniel, or to your campus? These are questions from our cadre of internet volunteers. So thanks very much for everybody who continues to participate and fill my inbox with these really fun answers. I greatly appreciate it. And if you'd like to hear your voice on the podcast, please don't be shy. Write to us to questions at Danielanhorpe.com.

Yeah, so we ask folks, do you think that photons bounce off of each other? Here's what people had to say. Since photons do not have electric charge and mass, I think they do not bounce of each other. I think that photons should bounce off each other because in physics, we learn that photons are particles that act as waves because they have a particle wave kind of duality to them. So if they're particles, they should be able to bounce off each other. But also at the same time, they're very small, so the rate that they do bounce off each other is so small

because it's very hard to hit two very small particles together. I would think not. I think they'd pass right on by each other. Yes? Yes? Yes. Yes? Why or how? Wait. Because...

Oh, maybe they don't. Wait, proton. Maybe they need neutrons. Do you know what a photon is? Wait, a photon? What's a photon? Wait, a photon will need to stick to a proton. What is a photon?

Wait, is it two protons? I would say the photons can bounce off each other because I know my understanding is the photons don't have mass, but I know the idea of a light sail requires bouncing, photons off of them. So it's something about the momentum or energy of a photon can actually impart some momentum into an object. So I would say because of that, photons probably can bounce off each other if shot at each other just right. If I remember rightly, you've said on some prior episode that photons do not bounce off each other but just pass right through. One might think they would

bounce off because of their particle nature, but they also have wave nature. And I guess that's what lets them pass right through each other. I don't believe photons can directly interact with each other, being waves as well as particles. They just pass through interfering or not on their way through, but then continuing on their happy ways. I really don't know. I suppose they could. I know if they hit hard enough, they'll break into other things. All right. I like that kid's answer. That was pretty funny.

Yes, yes, of course. Wait, what? I love hearing people think about it on the fly. They have their initial reaction and then their physics brain engages. And they're like, hold on a second. Is that really the way this works? Really? They have two brains.

I have lots of small brains all wrapped up together into my... Oh boy, that's a weird picture. Like if we open your skull, we wouldn't find a brain. We just find a whole bunch of little brains. Yeah, I'm like 19 little brains in a trench coat, not actually a full person. Boy, that's a bit disturbing, I guess. You know, you've got different parts of your life. And so you've got to engage like, oh, I need dad brain or oops, I need husband brain.

Or it's physics brain time. I find that having split personalities is a bit of a problem. I see. So everybody's always just getting the same cartoon as brain all the time. Yeah, everyone's just getting the Jorge brain. There's no menu option. you get what you get and you don't get upset

but yeah pretty interesting answers here from people some people think they yes definitely they do and some people think they definitely don't and here's an interesting answer because they're waves like can two waves interact with each other yes right

no reason why not like two waves definitely can interact with each other if you've seen waves in the ocean you know they can add up together they can even cancel each other out so waves can definitely interact with each other and photons can do that as well You know, we've seen like the double slit experiment is interference between photons.

And so waves can definitely interact with each other. That's not an issue. But I guess in water in the ocean, if you get like one wave going one way and another wave going the other way, they do sort of mix in the middle, but afterwards they just keep going as if they hadn't interacted, right? Yeah, the effect that you see is a superposition of the two waves. And so there isn't necessarily direct coupling between the waves, but what you see is the addition of the two waves. In that sense, you experience the combination of them, but the individual waves can still be thought of as individual waves.

Yeah, but then they keep going as if they hadn't interacted, right? Yeah, no, that's a good point. They don't interact with each other the way they would interact with, for example, a boundary or a wall where they really would reflect. Yeah, they just sort of ignore each other. I mean, in the moment, if you're sitting in the middle, you would experience both waves and they would add or subtract, but eventually the waves just keep going, right? Yeah, that's true. And so the question is, does the same happen to photons? That is indeed the question of the episode.

And what happens when two photons get near each other? Do they ignore each other or do they bounce off each other or do they do something else? All right. Well, let's dig into it, Daniel. I guess, first of all, what does bouncing off actually mean? Like, what does it mean for one particle to bump into another particle? Do they actually bump? Yeah.

So the microscopic view of bumping into things on the dance floor or sitting in your chair or whatever is not sort of the conceptual view that you might have. You probably imagine that the reason that you don't pass through a wall is that like the surface of your body is touching the surface of the wall and it's pushing back, right? But what do we really mean by touching, like microscopically, zoom in, what's happening? Well, you know, the surface of your body is a bunch of atoms and those have electrons around them. So really the tip of your finger, for example, is a bunch of electrons. And the edge of the wall, the surface of the wall is also a bunch of electrons. And what happens when you push one against the other?

The electrons themselves don't have to touch, right? They can repel each other without actually touching. So this microscopic view of the world from a physics point of view, there's no actual contact between these particles. It all happens via the fields between them, or equivalently the particles that they're passing between each other. So when your finger pushes against the wall, it's ripples in the electromagnetic field or equivalently photons

that are transmitting that information that are pushing, back on you. Yeah, but I, you know, I think we have, everyone has this intuitive feeling that the things touch each other because, like, my finger has a volume and the table has a volume and that two objects can sort of occupy the same space at the same time. And so if I press my finger against the table, like somehow the universe is resisting my finger being in the same place as the table. But two things can occupy the same place at the same time. Your body is full of neutrinos right now as well, and they're passing right through you and ignoring you. They are taking up your volume. The only reason you perceive a volume, the reason you think there's

a boundary between your particles and the other particles is when there's a force between them. Neutrinos don't feel a force, so they just trapes right through the edge of Jorge and then out the other side. No big deal. The reason the table and the chair doesn't is because there's a force that prevents them. So it's really all about the force. You can imagine things that sort of like with virtual springs between them, preventing them from getting too. close. But there's no actual contact. Contact doesn't really mean anything. All there is is force between particles. Right. I think that's what you were saying is that this idea that my finger can't occupy the same space as the table is really just kind of an illusion, right? Because they could,

I guess, but something is somehow preventing my cluster of atoms in my finger from somehow being or, you know, penetrating or infringing upon the volume of the atoms clustered together on the table. Yeah. And I wouldn't say the volume is an illusion. You know, people talk about like atoms being mostly empty space. And I think that's cool to give you the sense that like it's made of tiny particles, but it's also a little bit misleading. That space isn't empty. It's filled with fields or with virtual photons that are zooming around and keeping everything in its position. You can define what your volume is, but that volume, the edge of it is not defined by like the stuff that you're made out of, but the fields from that stuff, the forces of that stuff. And the volume also depends. on what you're touching, right? You want to touch a blob of neutrinos, then your volume is different. Then you want to touch something like a table or a chair. Right.

So because the volume depends on the fields and not everything feels those fields, then the volume is a little bit dependent on what you're touching. Right. I think you're saying that, you know, instead of thinking of our fingers or at the table as collections of stuffy particles, maybe it's better to think of them as like clusters of ripples

in the fields of the universe. Like my finger is not really a finger. It's just a whole bunch of ripples kind of tightly clustered together. And so this whole bunch of ripples doesn't want to just go through the bunch of ripples of the table. There are forces that push my group of ripples against the table's group of ripples. That's right. And I like the sound of the word ripples. And yeah, you are made of little matter ripples, right?

Your particles you can think of as like little ripples in quantum fields of matter. And the way those things stay apart, again, is not that they are. basically touching each other, but that they exchange other kinds of ripples, these force ripples between them. So you can think of yourself as like a cloud of these little matter ripples that are maintaining their distance from each other by passing back and forth these other little ripples and also maintaining their distance from other things. But there's no microscopic equivalent of touching.

The surfaces are not like actually coming into contact. Right. But in a way sort of like my ripples, like my wave functions of my ripples are touching the wave functions of the other. ripples. And so that's kind of like touching, right? They're getting into each other's business. Another way to say it instead of saying there is no touching is to say that's exactly what touching is. That's how touching works. Your experience of touching means these particles are communicating with the other particles, but they don't have to be on top of each other.

And this is something that physicists struggle to understand for a long time. They call this spooky action at a distance because we like to think of physics as local that you only affect things that are right next to you. You can't like do something here and instantly affects things in Andromeda. So we like to think of physics is only happening in like a very close vicinity to an object. And so this idea that like an electron could push another electron without actually touching it was a little bit weird for physicists for a while. And then they invented this concept of a field that the electron creates this field around it, which then pushes on other electrons. Right. And like you said, it sort of all depends on which fields you're talking about. Like some

fields do interact with each other and some don't. Like there could be a whole house made out of neutrinos falling on top of me right now, but it'll just keep going and won't touch or interact with any of my ribbles. Exactly. And each particle that's out there has a different set of ways to interact. Like the electron can interact via photons. It can also interact with the weak force. So it can interact using Ws and interact using Zs, for example. So it's got like two ways to talk to other particles. You can like speak two different languages. Whereas the quarks, they can speak a third language, right? They can interact via gluons because they feel the strong force. And the neutrino only speaks one language, just the weak force.

So depending on which kind of particle you are, you see the universe very differently, right? Either it's filled with stuff that wants to talk to you or it's filled with people speaking gobbledygook that you can't understand and mostly just ignore. All right. Well, let's touch on this a little bit more and we'll speak to what some of these forces are up to. But first, let's take a quick break. Hello, it's Honey German. And my podcast, Grasias Come Again, is back. This season we're going even deeper into the world of music and entertainment

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And these are just a few of the profound and powerful stories I'll be mining on our 12th season of Family Secrets. With over 37 million downloads, we continue to be moved and inspired by our guests and their courageously told stories. I can't wait to share 10 powerful new episodes with you, stories of tangled up identities, concealed truths, and the way in which family secrets almost always need to be told.

I hope you'll join me and my extraordinary guests for this new season of Family Secrets. Listen to Family Secrets Season 12 on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Hey, sis, what if I could promise you you never had to listen to a condescending finance, bro, tell you how to manage your money again. Welcome to Brown and Vision. This is the hard part when you pay down those credit cards. If you haven't gotten to the bottom of why you were racking up credit or turning to credit cards, you may just, recreate the same problem a year from now when you do feel like you are bleeding from these high interest rates, I would start shopping for a debt consolidation loan, starting with your local

credit union, shopping around online, looking for some online lenders because they tend to have fewer fees and be more affordable. Listen, I am not here to judge. It is so expensive in these streets. I 100% can see how in just a few months you can have this much credit card debt when it weighs on you. It's really easy to just like stick your head in the sand. It's nice and dark. in the sand. Even if it's scary, it's not going to go away just because you're avoiding it and in fact, it may get even worse. For more judgment-free money advice, listen to Brown Ambition on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. All right, we're talking about the question of what's going on in Star Wars when a

lightsaber hits another lightsaber. Daniel, is the light actually touching it? itself? Is it colliding or is that actually something that's impossible in the universe? Did George Lucas make all that stuff up then? You know, he has a huge budget. So I'm sure he did all the R&D necessary to make sure that Star Wars is realistic. But actually, didn't Star Wars happened a long time ago? So in principle, all this stuff has already been developed. Yeah, well, it depends on who the movie's for, you know? Like the movie could be for aliens who are really far away, in which case, it will have happened a long time ago for them. Wow, I wonder if he wrote that into his contracts, you know,

future kinds of revenue from alien galaxies. He was pretty savvy, I heard. I'm sure those contracts say everywhere in the known universe. And some lawyer out there is like, ooh, what if we discover a new universe? Does this contract extend to merchandise sold in the multiverse? Yeah, although actually, George Lucas sold everything Star Wars to Disney. That's right. So Disney owns the universe.

That's right, yeah. Well, we're talking about whether photons interact with photons, whether light can hit light, I guess, or interact with itself. And so we talked about what it actually means for particles to interact with each other, and it sort of all depends on what fields they're in and how they interact with each other.

One thing I think that's interesting that you said is that sometimes particles don't actually interact with each other, but they have sort of intermediary fields that they talk through. Like an electron doesn't actually interact with another electron. Exactly. Electrons can interact with a very small number of particles directly. They can interact with photons, Ws, and Zs. And that's it. Like electrons can only interact with force particles.

They can't interact with other matter particles, not directly. Like if you look at the equations of the standard model, we have all of these fields and we say very specifically which fields can talk to the other fields. And the electron can only talk to the photon field, the W field, the Z field, and actually also the Higgs field. Wait, are you saying that like an electron can actually be on top of another electron? Isn't there some sort of like universe rule that says no two electrons can be in the same place? There certainly is that rule. And so quantum mechanics prevents that from happening. But that would never happen anyway because electrons, though they can't talk to each other directly,

they can talk to each other via the photon. And so the way we build up our description of the universe is we have these little basic building blocks. Like what are the simplest things that can happen? And then from that you can build up more complex things. You can say, well, an electron can only talk to a photon. But that means a photon can talk to an electron. So then you put together this two-step process when an electron talks to a photon, which passes the information to another electron. Sort of like when the parents are arguing and they interact via the kids, you know, tell your mother that dinner will be ready at 6 p.m.

I don't know what you're talking about, Daniel. What sort of household are you running there? I mean, I've just seen that in the movies. I've never had an argument with my spouse. Well, tell our agent that I don't agree with that. All right. And remember that this is like our description of the universe. We try to boil it down to the simplest set of it.

interactions, and then we can use those to try to describe all the complex phenomena that we see out there, some of which can be described with just the basic pieces, and some of which requires us to put two or three of these pieces together to describe everything that happens. But it's kind of weird to think that if there wasn't a photon field, then you could have electrons kind of running into each other, kind of, right? Occupying the same field in the same spot. It's pretty hard to think about a universe without a photon field, because it would break a lot of our laws.

Remember, we have this episode about gauge and variance. We actually need photons around for electrons to behave properly, to conserve electric charge and all that stuff. Remember, forces aren't everything in physics. They're also just rules of quantum mechanics. Electrons can't be in the same state as another electron. And that's not like due to a force. It's just something electrons don't do.

All right. So then all electrons have to go through the photon field to talk to each other. What about things like quarks? So quarks can do the same thing. corks interact with all the same particles that electrons do plus gluons so if two quarks are approaching each other they have a lot of different ways to talk to each other they can exchange w's they can exchange zes they can exchange photons or they can exchange those crazy particles with gluons and so again quarks don't talk to each other directly right matter

particles and never interact directly with matter particles what they do is they interact via the fields they create which is equivalent to saying that they interact via these force particles. Again, just to be totally clear, you can imagine like the electromagnetic field that a quark generates because a quark has electric charge, like two-thirds or minus one-third, and another quark is flying through that field and fields of force. That's what the field is. Another equivalent way of thinking about it is that thinking of that field is a bunch of virtual particles being created by the first quark. Those are two equivalent ways of thinking about particles interacting, either via fields or via virtual particles.

But I guess maybe like a philosophical question is, could you have a universe without a photon field or a gluon field and still like makes sense mathematically? Like is it just coincidence that somehow corks can talk to each other via the gluon field or is it not even possible for quarks to exist without gluons? I mean, philosophically, you can put together all different kinds of universes. You can put together universes with just quarks in them or with just electrons in them. Of course, you wouldn't get any interesting complex structure. Like everything that we know and love about the universe comes from the fact that these particles do interact and make protons and neutrons and atoms and chemistry and ice cream and all that good stuff. So you wouldn't get anything interesting and if you had these fields and they couldn't talk to each other, you couldn't form really any kind of complex structure. Also without these forces, remember these forces exist to preserve symmetries that we observe in nature between these particles.

So there are symmetries among the quarks and symmetries among the electron and the other particles that are preserved by these. forces. Check on our episode on Gage Symmetry to explain a little bit more what I mean. You have to have these forces if the universe has these symmetries. Though we don't know why the universe has these symmetries. So you could in theory create other universes without these symmetries and without the forces. But they would be pretty boring. Yeah, there wouldn't be there would be any sequels probably. Well, I guess it's sort of a, it's sort of an interesting philosophical thing to think about like, you know, there are matter particles and those matter because that's what they make stuff out of, but the force particles, you know, they seem to only be there so that the matter

particles can talk to each other. And so like, are they there just to make the other ones interact or are they there because they have to be there or are they there by coincidence? It is an interesting philosophical question. You know, we observe these things in the universe. That doesn't answer the question of why they are there. What we can do is think about like what other possible universes could you put together and then think about why we have this one. And we do see these amazing mathematical symmetries that tell us that the force particles really do complement the matter particles in this way that they preserve these internal mathematical symmetries. But you know, you could also have other kinds of universes. We can imagine other kinds of universes that do follow their own self-consistent laws, you know, like universes with just photons in them or universes with just gluons in them.

You can imagine those universes. They could exist. You can write down the equations for them on paper. You can think about them in your mind. you can do computer simulations. That doesn't tell you why we have corks. So much of what we do in particle physics is just observation. We see this out here in the universe.

We try to describe it mathematically. We don't know why it's this universe and not another universe. We just don't know. You're just describing what you see. We are. We're describing what we see. We're trying to boil it down to as few rules as possible to describe all of the complexity. And then we're trying to look at those rules and say, hey, does this make sense?

Could it have been different? Why is it this way and not another way? mostly we're still pretty clueless by the answers to those questions. There's so many things about the particles that just don't make any sense and don't seem to have any reason at all. You know, why are there three kinds of electrons? We have no idea. All sorts of interesting questions.

All right. Well, what seems to be observed is that matter particles don't interact with each other. They do it through force particles. And so the question is, what do force particles interact with? Can they interact with themselves? Like the photon. Can the photon interact with itself? So again, not directly, right?

a photon only interacts with particles that have electric charge. So the photon can interact with the electron or the muon or any of the quarks. It can also interact with the W boson, which is not a matter particle. The rule for the photon is that it only interacts directly with particles that have electric charge. Particles like the Z and the neutrino, it cannot see, it cannot interact with them. And interestingly, the photon itself doesn't have electric charge. It's neutral. So the photon cannot directly bump into another photon.

Well, okay, so you're saying that a photon can't interact with it itself. Can any particle? Can any force particle interact with itself? Or can any particle in general interact with itself? Actually, yes, some of them can. Like a gluon interacts only with particles that have strong charge color, right? Like the quarks, for example, and not the electrons. But the gluons themselves have color. So gluons can interact with themselves.

Two gluons who find each other in the universe can bounce directly off each other without using some other intermediate particle. Wait, they can. Like, they can bounce off, but they don't use an intermediary to bounce off. They can just bounce off. Gluons can talk directly to each other. And that's one of the reasons why the strong force is so strong and so weird and so much of a pain in the butt to do any calculations with. Because gluons just can't stop talking to each other. You know, corks are constantly generating gluons and those gluons talk to each other and the other corks.

and it's a huge tangled mess. Photons are much easier because once you make them, they don't talk to each other. They can fly alongside each other and hardly interfere with each other. So gluons are very chatty and that's kind of a pain.

Are you saying they're very sticky? That's the problem. They are indeed very sticky, absolutely. Are you sure there's no hidden particle that they're using to interact with it themselves? Like, isn't that weird that electrons can interact with electrons, but gluons can interact with gluons?

It is weird. and the mathematics you need to describe gluons becomes very different from the mathematics you need to describe photons and w's and z's. And that's another thing that makes a strong force so weird and so powerful. It's a very different kind of particle. Another example is the Higgs boson. The Higgs boson can also interact directly with itself. Like a Higgs boson flying through space can bounce into another Higgs boson.

Or it can radiate a Higgs boson. It can like pop off one of itself. Whoa. But then, so what's the difference between the Higgs boson and, like, say, the electron or the photon that ignores itself? Well, the rule is the photon can only interact with particles that have electric charge, because that's a photon's job, is to preserve electric charge in the universe. Higgs boson interacts with anything that feels the weak force, and that includes the Higgs boson itself. The Higgs boson has this weird ability to talk to itself. And again, this is not something where we understand why it is this way.

But if it wasn't this way, the Higgs boson couldn't do its job. We talked to the podcast about the Higgs boson and its relationship to Mexican hats, how it has this weird vacuum energy that gives it the power to apply mass to particles. And that comes partially from its interaction with itself. That's what makes the Higgs boson weird in just the right way that it can give mass to these particles. So it's, again, not something we totally understand. So I guess you're saying, as far as we know, the photon can't interact with itself, at least directly. And so that kind of answers the question of the episode, right?

Light can't interact with itself directly. Yeah, directly. Although, you know, how we organize these things in our minds doesn't necessarily determine what happens out there in the universe. We have this strategy of let's make the simplest possible basic ideas and then build everything out of it, like the way you might describe the universe in terms of Legos and say, I only need these Lego pieces to describe anything I can build out of Legos.

That doesn't necessarily limit what you can make out of Legos. And it would be like artificial to say, say, what can I make out of only these pieces? Nobody really cares, right? What's out there in the universe is all sorts of crazy combinations of those pieces. So while it's true that in our model, two photons can't bump against each other directly, there are definitely ways for photons to interact indirectly, and we see that in the universe. But I guess just to be clear, like if I take a flashlight and I cross the beam with another flashlight's beam, like nothing happens, zero. Well, two photons don't touch each other directly, but they do have ways of passing information

information against each other. So effectively, photons can interact. Again, not directly. They have to like use an intermediary like other electrons or other particles. But in the same way that my electrons can't interact with your electrons directly, they do it via photons. My photons can't interact with your photons directly. They have to do it via electrons. But does that mean that I can just pile photons on top of each other? Can photons just be like in the two photons? Can they be in the same place at the same time? Photons actually can because they don't follow the same rules as electrons. They have different spin. There's integer spin, which means they are bosons. And quantum mechanics says that matter particles, fermions, cannot be in the same state at the same time. But no rule like that exists for bosons. So you compile as many bosons as you want on top of each other. And that's why, for example, we've been able to do things like make Bose Einstein condensates,

which is a bunch of bosons on top of each other that have the same wave function, macroscopically act like a quantum object. You can do the same thing with photons. You can have as many photons as you want in the same state. That's why I like lasers work, for example. Yeah, I hear you can stick a bunch of bozos too in a small cart. They do that in some particle collider, a circuses. Particle collider does feel like a circus sometimes.

It is a ring, right? It's a ring. It's a three-ring circus out there in Geneva. We do our best to keep the energy high. So you're saying that photons cannot interact with themselves directly. What does that mean? Does that mean they can interact indirectly? Yes, they can interact indirectly.

The process is a little bit different than electrons interacting. Like when electrons come by, one of them can just radiate a photon, which is absorbed by the other electron and go on its business, right? It doesn't cost anything but energy to radiate a photon. Now imagine the case with photons. Two photons are approaching each other. Can one of them just radiate an electron, which is then absorbed by the other one? Can't actually do that? because that would violate conservation of electric charge.

The photon can't just create an electron out of nothing. In order to interact with that other electron, it has to do something slightly different. It has to die. Wait, wait, the light has to die. Yeah, the light has to die. In order for it to interact with the other photon, it has to convert into an electron and a positron. So the photon doesn't just like emit an electron, which is then absorbed by the other photon. It converts into a new pair of particles, an electron and a positron.

And then those guys can interact with the second photon. Can they or does the other photon also have to turn into a pair of electron and an anti-electron? No, that electron and positron pair, they can interact directly with a photon because photons can interact with charged particles. And so if you have a photon coming in, it could convert into this pair, one of which or both of which can interact then with that photon. And so you can deflect that other photon with the first photon. But the first photon doesn't just like emit something go on. its way, it has to kill itself as to transform into an E plus E minus pair. Okay, so let me see if I'm understanding the picture.

You have two photons heading towards each other, right? Darth Vader is swinging his lightsaber. Luke Skywalker is, you know, moving to Perry. And one of the photons turns into an electron, anti-electron pair. And then those somehow deflect the other photon that's still alive? Is that what you're saying? Like, it can actually bump it? That's exactly what happens.

because the electron and positron can interact with a photon. What, they can absorb the photon, or they can deflect the photon, all sorts of things can happen there. Now, is this dependent on the first photon doing that split, splitting off into a pair of electron anti-electron particles, or is this like a quantum mechanical thing where a photon is always kind of splitting into a pair of these particles all the time, but with a certain, you know, probability? Yes, exactly. A photon isn't just a little packet.

of energy in the photon field flying through space, it's constantly creating E plus E minus pairs and then going back to being a photon. And sometimes it creates E plus E minus pairs. And those things radiate their own photons, which create more E plus E minus pairs, which then collapse back. So it's just like buzzing swarm of particles all the time. So what happens when two photons come near each other is that sometimes they pass right through each other and ignore each other. Sometimes one of the photons will interact with one of these E plus E minus pairs is that briefly exists. So it's sort of probabilistic what happens when two photons come near each other.

But the way that they can interact is through the creation of this matter, anti-matter pair momentarily. Wait, what? Like sometimes that photon will bump into another photon and sometimes not? Or does it always happen but just a little bit? Like, is it quantum in that way? Or does one photon feel a little bit of force? Or does it only sometimes feel a force?

Well, there's an infinite number of possibilities because it's an infinite number ways that a photon can split into these pairs, which can then split into the pairs. And so technically what happens when a photon passes to another photon is it has an infinite number of possibilities. And so then if you measure that photon, then you're going to get one of those possibilities. And in principle, one of those possibilities is zero deflection, though in practice actually measuring zero deflection is probably impossible because you're measuring things with physical systems. And so you're never going to get the photon at exactly the angle. that it came in at.

I see. You're saying there's always some sort of interaction, but it's quantum mechanical. So there's sort of a probability range of things that can happen. Like if I shoot a photon at another photon, it is going to bump into each other through the split of the particle antiparticle pair.

But what actually happens is sort of probabilistic. Like it can be deflected a little bit or a lot or maybe not at all. Exactly. And sometimes crazy things happen. Like sometimes the two photons come together. They both create the, the E plus E minus pair.

Two of those then annihilate and, like, destroy each other. And you end up with just an E plus E minus pair, which comes out. So it's like two photons come together and then an electron and positron come out. So it's like light gets converted into matter. Wait, what? So if I collide two photons, I'm going to get some bits of matter out of it. Sometimes, yeah. Don't those two things annihilate each other also instantaneously?

Well, you know, there's possibilities for lots of different things to happen. But if they've come in opposing each other and then the electron and positron fly out the other, the other direction that they're not likely to then annihilate each other. But yeah, that's also a possibility. Whoa. So like if I point my flashlight at another flashlight, stuff is happening. Like stuff can happen. The light is going to

bump into the other light. And also, I could be creating matter out of my flashlights. Yeah, you are creating matter and antimatter if you cross the stream. So be careful out there, folks. Yeah, it sounds kind of dangerous. Little did I know. I could have ended the universe

as a kid crossing some flashlights together. The other thing to understand is that, you know, we build up this picture of how particles interact using these basic like tinker toys. You know, this one can talk to this one. And then you can chain those things together to make more complex interaction. The more pieces of the chain you need to use,

the less likely it is for things to happen because it's like two quantum mechanical things have to happen, both of which are not that likely. So particles interacting directly is more likely than particles interacting indirectly. If you have to have multiple steps in your chain, it's less and less likely. So light by light scattering, for example, is less likely than light scattering off of electrons because that's more direct. All right. So it sounds like the answer is actually a little bit complicated.

Like everything in particle physics. And so let's get into how we have actually observed this in experiments and seen light bump into other kinds of light. So let's get into that. But first, let's take another quick break. Hey, sis, what if I could promise you you never had to listen to a condescending finance, bro, tell you how to manage your money again. Welcome to Brown Ambition. This is the hard part when you pay down those credit cards. If you haven't gotten to the bottom of why you were racking up credit or turning to credit cards, you may just recreate the same problem a year from now. When you do feel like you are bleeding from these high interest rates, I would start shopping for a debt consolidation loan, starting with your local credit union, shopping around online.

online, looking for some online lenders because they tend to have fewer fees and be more affordable. Listen, I am not here to judge. It is so expensive in these streets. I 100% can see how in just a few months you can have this much credit card debt when it weighs on you. It's really easy to just like stick your head in the sand. It's nice and dark in the sand. Even if it's scary, it's not going to go away just because you're avoiding it. And in fact, it may get even worse. For more judgment-free money advice, listen to Brown Ambition on the IHeart Radio app, Apple or wherever you get your podcast. I had this overwhelming sensation that I had to call it 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 battling 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's, shick 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 don't want to 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 the traumatic brain injury because i landed on my head welcome to season two of the good stuff listen to the good stuff podcast on the iheart radio app apple

podcast or wherever you get your podcast. Your entire identity has been fabricated. Your beloved brother goes missing without a trace. You discover the depths of your mother's illness, the way it has echoed and reverberated throughout your life, impacting your very legacy. Hi, I'm Danny Shapiro. And these are just a few of the profound and powerful stories I'll be mining on our 12th season of Family Secrets.

With over 37 million downloads, we continue to be moved and inspired by our guests and their courageously told stories. I can't wait to share 10 powerful new episodes with you, stories of tangled up identities, concealed truths, and the way in which family secrets almost always need to be told. I hope you'll join me and my extraordinary guests for this new season of Family Secrets. Listen to Family Secrets Season 12 on the IHeart Radio, app, Apple Podcasts, or wherever you get your podcasts. Hola, it's HoneyGerman. 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 audition 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. I feel like this is my destiny. 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 Vibras 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 what I'm me? Yeah. But the whole pretending and cold, you know, it takes a toll on you.

Listen to the new season of Grasas Has Come Again as part of My Cultura Podcast Network On the IHartRadio app, Apple Podcasts, or wherever you get your podcast. All right, we're talking about the question of whether photons can bump into each other. Like if I point a flashlight and I cross its beam with another flashlight, what's going to happen? Is it just going to keep going or is it going to bump into each other? And it sounds like the answer is they're going to bump into each other. Like not directly. Like the photons can interact with the other photons, but they kind of do through these other quantum

mechanical possibilities. Exactly. Everything in your body is a constant swarm of particles turning into other particles. And so if you want to interact with something else, you got sort of lots of options being presented simultaneously. So the fact that photons don't interact directly with other photons is not really limitation because they can talk to each other via electrons or via other charged particles. Yeah, I'm not feeling quite myself today.

Is it because of my quantum mechanical nature? Hormé, just the fact that I didn't sleep enough last night. Well, I thought you said everybody always gets the same Jorge. Yeah, and sometimes that horace is sleepy and sometimes less sleepy, but it's still the same Jorge. Maybe we need to put you in the particle beam and charge you up a little bit. Yeah, yeah. That's my answer to everything.

That's what I need, a suntan bed. I feel like you're telling me that if I take a flashlight and I cross, faucets beam with another flashlight, they're going to interact with each other. Like the light beam is going to hit the other light beam and matter can come out or light's going to get scattered. But that's kind of not my experience. You know, I feel like if you point two flashlights at each other, like the beams just go through each other. Yeah, mostly that's not your experience because it's pretty rare because it has to have two steps to happen. It's less likely than particles interacting directly. It's also very strongly a function of the energy. The higher

energy the photons, the more likely this is to happen. So photons in the visible spectrum don't actually have that much energy. And so it's harder for them to create these E plus E minus pairs because electrons have mass. And so it costs more of their energy to make the E plus E minus pair. So it's less likely for them to happen. So if you want to see this happen, you need really high energy photons. That's where it's more likely for photons to bounce off each other. Oh, I see. So you're saying when I cross my flashlight beams, they are mostly going through each other, mostly ignoring each other, but they are maybe in a very low scale, like very improbable. There are little photons here and there that are scattering with each other or creating matter and

antimatter. Almost certainly because there are a huge number with the photons. So even if the probabilities are tiny, one or two photons are probably doing something crazy in those beams. You won't notice it because it's such a tiny fraction and it's impossible and they're drowned out by the other photons. But almost certainly some of those photons are dancing together. Wow, that's pretty cool.

That means I can make matter and antimatter, like in my house. I just take two flashlights and cross the beams. Yeah, and you're making positrons momentarily. And you're saying, like, the higher the energy. So if I take x-ray flashlights, then they would interact more. Yeah, x-rays would interact more. And this is something we've actually done. We've studied this.

We have created matter just from colliding light. Though in order to do it, we need higher energy beams of light than even x-rays can provide. Yeah, these are like real experiments you've done in colliders. So tell us about this. So first of all, how do you make two light beams into matter? So your first thought might be like, let's take two lasers and shoot them at each other and see what happens, right? Or cross them at least. Yeah, or two lightsavers, light savers, that would be even cooler.

Yeah, that's the closest thing we can do to lightsabers, right? The issue is that while lasers are really good at making coherent sources of monochromatic light, photons all with the same phase and all with the same wavelength, they're not actually great at making very high energy photons. Like you can have an intense beam where you've got lots of photons per second from lasers, but you can't make photons with a lot of energy per photon because there's limitations on the cavity and how you can actually make lazing happen, which requires reflections and resonances. Even x-ray lasers are hard to do.

We need things like well above x-rays, well above gamma rays, like super high energy photons. So the way we do that is not by creating light sources at all, but by going to our colliders. and using the photons radiated from the other particles that we're smashing together. So to make high energy light, you use colliders. But isn't it doesn't get scattered all over the place? Like, isn't it hard to, like, harness that or aim those photons at another source of photons? It is tricky, and we don't actually create photons in our colliders. You know, at the LHC, for example, we're colliding protons, right?

But protons have electric charge, which means that they're constantly radiating photons, especially when they're flying really fast and bending. So protons, and the LATC, for example, is surrounded by a swarm of photons, which have really high energy. And to get even higher energy, what you need is not a proton, which just has one electric charge. You need something with even more electric charge because it'll generate higher energy and higher number of photons. So for that, we don't collide protons.

We collide gold or lead nuclei. Like you take gold, you strip off all. All of the electrons, so now you have something with like a very, very strong positive charge. You put that in the collider instead of protons and you swing those around and they generate huge numbers of photons, which can then smash into each other. Meaning they glow like the ring glows, but then how do you like how do you focus these so that they, you know, collide with another set of photons? Yes, you can't focus them at all.

We do this anyway because we're interested in collisions of heavy nuclei for other. things like cork glue on plasma and we're going to do an episode about that soon so we already have this program to put gold in the collider accelerate it and smash it into other gold particles because that's really cool and fun to do but sometimes the gold particles miss each other so say for example you have the gold particle swinging around the collider and they don't actually smashing each other they miss they call this an ultra peripheral interaction as they pass by each other because both of them are surrounded by these glowing swarms of photons then those photons smash into each other.

So like two gold atoms do a near miss, then their photon swarms will bang into each other. And that's how you study photon photon collisions at very high energy. You actually like miss the gold particles. And you're hoping that their glow, their relative, respective glow, then collides. Yeah, exactly. It's like you have two celebrities moving through a party and their entourages smash into each other. Get into a fight.

Yeah, that's what always seems to happen, right? Exactly. That makes the most exciting videos the next day anyway. And so remember, we can't like aim these gold particles very precisely. It's just that sometimes we miss and then we don't get a gold gold collision. But hey, we can look at that and see if we saw a photon photon collision instead. So it's like the accidents, the mess-ups from the gold-gold physics gives us interesting photon photon physics. And you can tell that it was two photons crashing into each other?

It's a big mess and it's really hard to analyze. but sometimes they do. And in fact, they've seen electrons fly out. Like they've seen these gold atoms miss each other and then pairs of electrons and positrons fly out. And they've analyzed it and they're convinced that this is due to the photons smashing into each other and creating matter.

Wow. Cool. Yeah, because that's the only thing that could explain where these electron pair came from. Exactly. It also has to do with the angles. Like sometimes you get electrons just flying out randomly. And so to really convince yourself that this is due to the process that you think it is, like you understand the quantum mechanics of it, you calculate and say, what are the probabilities for the electrons to fly out at this angle or

that angle? And you measure a bunch of them and you see them at the angles you expect. And then you can convince yourself that you haven't been fooled. So this is an experiment. This is something was just done last year. In 2021, the Star Collaboration did this, not the Large Hadron Collider, but at Rick in Brookhaven. Rick is RHIC. It stands for the relativistic, heavy ion Collider, and they specialize in gold collisions and all sorts of other crazy stuff. Now, I guess the question is, do they actually have to use gold, or is that just how they roll? You don't have to use gold. It's just sort of awesome. It's funny, though, at the LHC on the European side, they tend to use lead. So it's gold on the American side and lead on the European side.

And, you know, sometimes you smash lead together and gold comes out. You can make gold from lead at the collider, though it's not economical. That sounds very American. Like, you know, The Germans are like, no, let's use lead. Of course, that's more practical. And the Americans are like, whatever, it's used gold. You know, I think Rick is on Long Island and, you know, maybe they like their glam. You know, they like their bling out there. What are you saying about Long Islanders, Daniel?

I think I just said it, you know, they like things shiny. And, hey, who doesn't? I'm all into shiny stuff. I think you're saying that's how Rick rolls. I think we all just got Rick rolled. I'm never going to let you down. But anyway, at the LHC, they do the same. kinds of studies where instead they use lead ions and they see interesting things they've seen

light by light collisions where you get two photons coming out at weird angles so at rick they've seen two photons turn into two electrons and at atlas the experiment i work on at the lhc they've seen photons bounce off each other deflect each other and go out at weird angles wow yeah because i guess so you had these lead particles miss each other and you saw light coming off with weird like strange angles. Yeah, I guess, right? But they didn't actually bump with each other. They turned into an electron, anti-electron pair,

and then those maybe bumped into each other, and then created photons that sped off in weird directions. Exactly. And we can only explain those weird directions using that description you just gave, which is photons interacting with each other via this weird box of electrons and positron. So that's pretty cool because it's a rare process. It's hard to reproduce.

it's a really good test of like do we actually understand the quantum mechanics and it's something that was predicted you know decades and decades ago physicists like in the 30s were thinking about this they're like huh is this possible i think it might be possible it would be really hard to do and it's one of these like open questions that stood for decades is this really happening out there in nature the amazing thing about the standard model is that it seems like an ugly clude sometimes like there's so many things we don't understand and yet it works so well every time we go to check it on the details. It's exactly right. It really nails it down to the decimal places. Cool. All right. So that means that you've done that experiment. You've shown two light beams

at each other and you see that light does collide with itself, right? Although we missed an amazing opportunity. We don't have microphones in the collider. So we can't tell what sound it made when those two photons smashed into each other was like a zh or like a k-k or like what sound do lightsabers really make. I can't tell you're joking or not. Would light actually make sound? No, it all happens in a vacuum, so it wouldn't make sound. But that would be awesome. Oh, geez, Daniel, that's the cardinal sin of Star Wars.

It's the sounds of explosions in space. Now you're trying to tell people that sounds happening at the large Hadron Collider. Tis-tis-tis-tis. Yeah, science disinformation right here on the podcast. But, you know, there could have been surprises. It could be that we didn't see it. Or that the photons came out at even weirder angles, which would mean that maybe the photons interact in different ways from the way we expect.

You know, maybe there's some other particle that appears that lets photons talk to each other, like the axion particle or something else weird and new that we don't know if it's out there. That's one of these reasons that we do, these really high precision cross-checks of these little details of particle physics, because it could be in one of those details, we find something weird in that unraveling that thread is exactly how we create a whole new understanding of the universe. You know, that's how we discovered quantum mechanics, understanding. why the photoelectric effect wasn't exactly as we expected it to. So we never know which little cross-check is going to reveal the right thread to pull on.

Cool. Or the right lightsaber to turn on. That makes just the right sound. I guess it's kind of interesting to think now that photons can interact with each other, although not directly. Does that mean, though, I have a question of whether all particles in? Does that mean that all particles can interact with themselves just indirectly? Like, everything's a fair game in the universe? Yes, everything is.

fair game in the universe. Photons can interact with themselves indirectly, right? They can generate E plus E minus pairs, which can then interact back with them. Could neutrinos, like neutrinos interact with regular electromagnetic things through these quantum transformations? Absolutely. A neutrino feels the weak force and it can generate a W particle, right? And that W particle can interact with electrons. And that's exactly how the neutrino feels the rest of the universe. And a neutrino could indirectly interact with quarks in the same way or other things. stuff. The only thing we don't know about is dark matter. Is dark matter a particle? Which forces does it feel? Does it feel any forces at all other than gravity? Dark matter might be

out there totally inert, unable to interact with anything except for gravity as far as we know. We don't know if it's fair game or not, but it could be. It could be just be super rare, maybe. It could just be super rare. There could be some other kind of force that dark matter can use to interact with itself. Like the whole universe could be split into different sectors. This whole group of particles that can talk to each other with forces, the ones we know and love, and another separate sector that can only talk to each other and can't interact with us except through gravity. That's possible. What about midichlorians? Can they interact with themselves? Only if they make sound, right? Do they scream in space?

Maybe that's a sound that lightsabers actually make when they crash into each other. It's a billion midichlorians screaming at the same time. Oh, wow. Now that I understand the true cost of using the force, I will be more careful about it. Yeah, it's pretty tragic, actually. Why, that puts a whole different spin on Star Wars, isn't it? It really does, yeah. I wonder, is any of this canon, do you think? Yeah, because you're a physicist, right?

Right, absolutely, yeah. This is all official now, folks. Yeah, yeah. But the question is, can Midichlorians feel, not just forces, but feelings? Well, we'll have to have one on the podcast as a guest and ask it. Yeah, or George Lucas, whichever one will come first. All right, George, give us a call. All right, well, I guess.

Again, an interesting look into how the universe surprises you. Sometimes you think that two things can interact with each other, but through quantum mechanical magic, they sort of do. And it's almost the same thing, as if they were interacting with each other. Yeah, and the universe out there is a crazy, swarming quantum mechanical nightmare of complexity, but somehow we can pull together these beautiful, simple stories about particles interacting with each other and use those as Lego bricks to describe all the amazing complexity out there, even gold, gold near misses at very high energies.

It's incredible what physics has been able to do. Yep. So I think this is the part where we thank people for joining us and this is the part where we turn off our lightsabers. Thanks for joining us. See you next time. Thanks for listening. And remember that Daniel and Jorge Explain the Universe is a production of I Heart

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