Listener Questions about Annihilation

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Speaker 1: Hey, Daniel, I've got a question for you. Oh, let's hear. I love questions. I'm not sure you like this one. I've seen you cringe every time people ask you this. M all right, now I'm curious. Let's hear the question. All right? Are you still actively doing research? Oh? You're right. I used to hate that question, but actually now I've learned to love it. Oh yeah, yeah, what changed? You actually started doing research? Well? Instead of grinding my teeth at the suggestion that it's not possible to do outreach and research, I just take it as another chance to talk about my research. And hey, I love some ash and stuff together, so I love talking about it. I wonder if you pole assumed podcast and takes a long time. If only they knew. Hi am Or Handley, cartoonists and the creator of PhD comics. Hi. I'm Daniel. I'm a particle physicist and an actor researcher at you see Ermine, and I love smashing together podcasts with my cartoonist friend. Sounds like you said you're an actor researcher. I thought, whoa, that's pretty cool. You do acting as well. I do my own math stunts. Unlike Leonardo DiCaprio. I didn't know Leonardo needed a stunt man. Oh yeah, he couldn't write the equations himself on the board or don't look up, so they have to hire somebody to do his math for him. But me, I live that danger, man. I take those risks every day with my body. Did you audition to be Leonardo de Capitos? You know, wrist standing? I didn't even know that was a thing, But if I had known it was a thing, I definitely would have signed up for it. Absolutely. Yeah. You live right next to Hollywood, why not you could be Robert Downey Jr's wrist You could be. I think I look a little bit more like Robert Downey Junior than Leonardo DiCaprio anyway. But I don't think I look much like either of them. You can say, I mean not not to say anything about how you look, but you know, you just don't look like Robert Downey Junior or Leonardo the Copier. You look like a handsome Daniel Whitson. Like if Woody Allen needed a math double, then I would be his math double. I don't think you want to dull for Woody Allen on any set. No, that's true, he's off the list, but anyways, welcome to our podcast Daniel and Jorge Explain the Universe, a production of My Heart Radio in which we take all the risks by diving deep into the unanswered questions about the universe. We don't shy away from the dangerous math and the difficult questions. We ask them straight up and wonder what the answers are. How big is the universe, how old is it, what's happened to it? What is it made out of? And most importantly, can we explain it to you? Yeah, because it is a very perplexing universe, full of things to wonder about, and we like to take you right up to the edge where scientists are taking all the cree different scientific risks trying to figure out how everything works. This makes it sound like science is kind of risky, Daniel, do you have insurance for doing science? Is there science insurance? I spent three years on this paper and it turned into nothing. Pay me. Oh, I wish I would have so many payouts. I think it's called tenure. That's pretty good insurance, right, that's pretty good safety net. Although you know tenure doesn't guarantee you funding. You can have a job, but no money to do any actual work. But you still get paid. You do get paid as long as you still do teaching. That's true. But there are sort of intellectual risks involved in science. What we do is research. It's a sort of exploration. We don't know that there will be interesting answers until we go out and look. The same way, you don't know what's waiting for you when you first land on the surface of some alien planet. Is it filled with all sorts of incredible creatures or is it just a desert of rubble. You don't know until you go and look, and sometimes you hit the jackpot, and sometimes you come home with dust. You think. It's not like a casino, like a science, like a nature casino. He did a bunch of scientists pulling the lever on the slot machine of the universe. There's an enormous element of luck, absolutely in making a discovery. You know, there are people who are really clever and have good ideas about where to look for the next big thing in the universe, and then there are folks who just stumble across it. Well, I'm an artist in a cartoonage, so I don't know anything about risky at all. You know what are you talking about. I'll take ten years, sure. Yeah, you left one risky career for the ultimate risky career. Absolutely well, I do have insurance, yeah, actually have cartoonist insurance. Yeah, you've insured your right hand against injury. It's called marrying someone with the stable job. Patronage. I think they call that patronage. Yeah, patronage matronage. Actually maybe, But anyways, scientists ask a lot of questions about the universe because we're trying to figure out how the universe works. But they're not the only ones who have questions about the things around them. All of human he is trying to push forward the envelope of knowledge and understanding and mystery just by looking around us and wondering how things work. It's not just those of us with a tenure job who can take naps in the afternoon. It's everybody who wants to know how the universe works. And everybody out there asks questions about the universe. Yeah, and it's not like only the scientists asked really cool and interesting and valid questions. Everybody can ask these amazing questions, and in fact, there's a huge amount of ore lap between the questions people have every day, and the questions that scientists at the forefront are asking because we're a lot more ignorant about the nature of the universe than you might expect from the fact that you can rely on technology and flying airplanes and all that stuff. There are some pretty basic questions that we just don't know how to grapple with, so we mostly avoid them and work on other stuff that's easier to tackle. So sometimes you ask us a really hard, basic question like what is space? How does time work? And you get a blank stare because it's the kind of thing we just don't know the answer to makes you wonder what you're doing to earn that tenure. Daniel, You know, sometimes I get great ideas while napping, while napping interesting, and then you wake up and you forget him. I keep a pad of paper actually next to the couch, and sometimes I wake up and I look at the scribbles. I'm like, I have no idea what that says. And other times I'm like, that seems like a good idea. I'm gonna go try that sounds like. There's an episode of Seinfeld where he has the same thing and he spends the whole episode trying to figure out what he wrote down in the path, and so don't leave us in suspense. Did you get a great science idea? Did he launch a new experiment and win a Nobel prize? Yeah? Yeah, that was a season. But everybody has questions, and they're all awesome questions, and sometimes we get those questions here on the podcast. People write to us or contact us through social media, or they hang out at our discord and that's where they ask the questions. That's right. We welcome all of your questions. If you are curious about the universe, or there's a science concept you haven't heard explain to your satisfaction, please write to us two questions at Daniel and Jorge dot com. Everybody deserves to understand the universe, or at least understand how little we know about the universe. Yeah, so to be on the podcast, we'll be tackling listener questions number the Annihilation Confabulation special that didn't quite work out, that's right. A lot of these questions have to do with smashing stuff together, blowing things up for science, which in the end is something I love to do. You like blowing things up for science, or you're like smashing things for science. I thought we had this conversation Daniel, it's not the same thing unless you blow up the entire world and went to case, um, please don't do that, and I guess it won't matter anyways. You know, I think it's an artificial dichotomy. I think there's a spectrum between smashing stuff together and blowing stuff up, and you're just trying to force an artificial separation between them. I think you're I think you're wrong. I think there's a spectrum between right and wrong. Actually, I wonder what the legal authorities say about that. Yeah, you either go to jail or you don't. So that's definitely a quantum distinction. That's either smash things or you explode things, or you can smash things that then explode. But it's just then it's the question. It's not like a quantum superposition. But to continue our argument from the last episode, and that's exactly why we smash stuff, because then then explode and we look at what comes out. So yeah, absolutely, Wait did you say and it explodes? Yeah, protons, we smash them together and then they explode. Oh boy, well, I guess we came to an agreement. It's not the same thing. It happens one after the other. I think it's what you just admitted to. Yes, time flows forward, I do agree, all right. Anyways, we are answering listener questions once again, and there is our twenty eight episode which is amazing, and this one has a theme of annihilation. I guess that's on everyone's mind these days. Yeah, everybody's thinking about blowing stuff up or smashing stuff together or something on the spectrum between them, or something in Europe causing everyone to blow ourselves up. So we have some awesome questions here about electrons annihilating with nuance, about Daniel annihilating I guess his career prospects maybe, and also maybe an alien civilization coming to annihilate us. So some pretty grim and interesting questions. Yeah, so thanks everybody who submitted these. Please don't be shy. If you'd like to submit questions for answering on the podcast, please write to us two questions at Daniel and Jorge dot com, or come join us on the discord, or enjoy my office hours, or write to us on Twitter anyway you like it. We love interacting with our listeners. Okay, so our first question comes from David Smith, and he has a question about um, I guess shaking hands with himself. Hi, Daniel and Jorge. I recently listened to the episode about particles and their anti particles, and I was a little surprised by the statement that Daniel made the generation two particles won't cancel with generation one particles. In other words, you can't have a cancelation or an annihilation between a positron and I'm on. It made me wonder, say, hypothetically, there was a stable object that was made from generation to antimatter, and these objects came into contact with normal matter, would the opposite valence shield charges caused the objects to tend to stick together? If so, how strongly would that attraction be? For example, if I shake my generation to antimatter Doppelganger's hand, would I be able to pull it apart? Afterwards? Thank you? Whoa pretty interesting questionnaire from David. There's a lot to unpack here. I think there's antimatter and also multigenerational particles here to unpack. Yeah, he's responding to a conversation we had about annihilation of matter and antimatter, and we talked about how electrons, for example, can annihilate with their opposite particle depositron to turn into things like photons. That's something people are familiar with. But we commented that a positron can't, for example, annihilate with a mu on, which is like the heavier version of the electron. We called it a second generation particle. Electrons are the first generation, muons are the second generation. And so while an electron can annihilate with a positron, a muon cannot annihilate with a positron. Well, let's take it one step at a time. So an electron has an anti version of itself, called the anti electron, but you guys give it another name. You call it the positron. So apositron is just an anti electron. Most of the antimatter particles we just call anti whatever, But the positron, because it was the first one discovered, got a special name. Okay, So then, and it's the same as the electron, except that has one charge flipped, or all of the charges flipped. I forget, it has all of its gauge charges flipped, and so the weak hypercharge and everything else, all of that is flipped for the positron relative to the electron. Most important is the electromagnetic charge, which goes from minus one to plus one. So the positron has plus one electric charge. Well, there's only three forces, right, so it has three charges flipped, the electro magnetic charge, the strong the color right, and something else right, So it has all of its charges flipped. The electric charge obviously, the electron also feels the weak force, so it has its weak quantum numbers flipped. The electron doesn't feel the strong force. It doesn't have color, and so the opositron also doesn't have color. Okay, so if I take an electron and I mash it up with an anti electron, it annihilates, right, it turns into like pure energy, meaning like photons. Yeah, it can turn into a photonic actually also turned into something like a z boson. But yeah, the point is that that electrons matter no longer exists. It's not like you've taken the components of the electron and de positron and you've rearranged them like some sort of chemical reaction where you move atoms from one place to another. The matter that made up the electron and the postron does not exist anymore in the universe. It's converted into a photon, which has no mass. And also there's the idea that particles have sort of heavier versions or cousin for generations. So the electron has an heavier kind of twin version of itself, right called the muan, which is exactly the same same charges as the electron, just more mass. Yeah, and this is something we don't understand why these particles exist. But you see, there are all these symmetries and reflections in particle physics. You know, one is like a particle has an antiparticle, and now we're talking about a different sort of direction in which particles have reflections of themselves. So every particle has a heavy version of itself. The electron has the heavy version, the muan. Even the corks have heavier versions. So there are three of these generations, generation one, two, and three. The electron is the first generation, muan is in the second generation, and then the even heavier version is called the tow. Al Right, well, I guess the mystery then is that because I think, you know, the electron smashes with the positron because they have opposite charges, and so they can attract each other and so they get really close to each other, and that's when they annihilate. Wouldn't the same thing happen if like an electron met with its anti heavier cousin, whenn't they have the opposite charge and still attract each other. That's exactly what Dave's asking, and you would expect that that might work because it does satisfy the principle that they have the opposite charges. But to David's surprise, that's not allowed in particle physics. A muon and a positron cannot turn into a photon because while that does respect conservation of charge, it doesn't respect all of the rules of particle physics, and there's kind of a lot of them. Oh yeah, what are these rules? One of the rules, of course, is conservation of charge, And so just stepping through the reaction here, you start out with like a muan which is minus one charge, and a positron which is plus one charge. So that adds up to zero total charge. So there's no problem then turning that into a photon because the photon also has zero total charge, so you've conserved the charge. That's cool. But there's another rule, and that rule is that you have to conserve the number of electrons, Like electrons cannot just be created and destroyed willing nearly. You can't change the number of electrons in the universe. That's one of the rules. So somehow like the number of electrons in the universe has to be the same, that's right, And that seems weird because like, hold on a second, what happens when you annihilate an electron an oppositron? Aren't you destroying an electron? Yes, But the reason that works is that positrons count as negative one electrons. So in that reaction, the number of electrons is plus one from the electron minus one from the positron, so in total zero electrons, and then when you make the photon, you still have zero electrons. The problem when you try to do the muon in positron reaction is that that reaction starts out with minus one electrons from the positron and ends up with zero electrons because you just have a photon. So it violates this rule. You have to have the same number of total electron, right. But I think maybe what's probably confusing to David is that a muon is pretty much it's it's it is like an electron, right, it's like an heavier electron. So why can it count as like a plus two you know what I mean? Like, why going to be or count as as an electron just with extra energy. The answer is, we don't know. This is what we observe for some reason, there's an important difference to the universe between electrons and muans. That's basically what makes a muan a muon and not just an electron with more mass. This is the muan no of the muan because the universe doesn't just count the number of electrons, and it's a separate count for the number of muans, and the same rule applies there. You can't just create and destroy muans willy nilly. So the answer is, we don't know why this seems to be important, but we think it's a clue. You know, in particle physics all the time we're looking for things that are conserved, what are the rules of the universe follows, and then try to back that out to figure out what that means about the nature of matter. In this case, we don't yet know. M Well, I feel like you're telling me that an electron can't annihilate with an anti muon because we've never observed it. Kind of right, But have you actually like looked, You're right, we have never observed it, but we are looking very very carefully, and there are dedicated experiments look just for this. They shoot a bunch of muans and electrons, or equivalently, they look to see if muans can decay directly to electrons without producing any neutrinos. And so these are very careful, very high precision experiments, and nobody has ever seen this kind of reaction. So the azer could still be yes, that an electron could annihilate with an anti muan. Maybe that's right. The answer could be yes, it might be possible for it to happen. And in fact, there is a little wrinkle here, which is that neutrinos count in the sort of number of electrons and number of muans category. For example, an electron neutrino counts in the electron category, which is why for example, like a W can decay into an electron and a neutrino. Which really interesting is that we have seen neutrinos violate this rule. We've see neutrinos change from muon neutrinos to electron neutrinos or town neutrinos, so we know this rule is very very strong, but not a hundred percent absolute. We know neutrinos break this rule. We've never seen electrons and muons break it, but we suspect that it might be breakable. Wait, what do you mean that neutrinos break it? How do they break it? Well, we have this rule that you can't just change the number of electrons in the universe, so we can't just change the number of muans in the universe. Neutrinos count in those same categories. That's what it means to say we have three different kinds of neutrino. It's an electron neutrino, muon neutrino tow neutrino, right, And we do the same kind of accounting for neutrinos as we do for electrons and for muons, So we don't see muans decay to electrons. We don't see muans annihilate with anti electrons, but we do see neutrinos jump from generation to generation. You can have a muon neutrino which then just changes its flavor to an electron neutrino as it flies through space, which seems to break this rule that the number of electrons the number muans can't change. I guess it's confusing because you're saying the heavier neutrinos called the electron neutrino. Well, we don't know what the masses of these particles are. But there's a first generation neutrino, which is the electron neutrino, and a second generation neutrino, which is the muon neutrino, and a third generation neutrino, which is the town neutrino. We don't yet know exactly what the masses of those neutrinos are, and if they follow the rule that the first generation is lightest and the third generation is heaviest, we don't yet know. Oh, I see, But do you know that the neutrina jumps between generations, So maybe that's not a hard and fast rule for everybody exactly. In fact, that sort of proves that this rule is not like deep and fundamental to the universe like it almost is. Even neutrino oscillation is pretty rare. So it's something the universe likes to do to keep these categories and to keep these numbers in balance, but it's not absolute. The way. For example, conservation of momentum is or conservation of electric charge seems to be absolute. We've never seen any violation of conservation of electric charge. All right. Well, to get back to David's question then, is what would happen if he met a version of himself but where all the electrons are somehow made up of heavier electrons? Muans would be like a heavier version of him, but also an anti wait, an anti hea your version of him. That's a lot of caveats there. So it's like, you can make atoms out of anti particles, right, and you can also maybe make them out of the heavier particles. So what would happen if you met an anti heavier version of you? It's a super awesome question, and I love that you thought about this. My first concern though, if we're being like hyper realistic about this, is that second generation matter like Muan's is not stable. An electron can last forever, can orbit the nucleus and be here for billions of years, but a muan is heavy, and heavy particles like the decay. So a muan will decay into a new trino and a w which then turns into an electron and another neutrino, and so neutrinos only last for micro seconds. So the muonic version of you is going to very quickly decay to the electronic version of you plus a bunch of Innerget do you get to say hi really quick? Okay? So let's imagine that you say hi super quick, you high five the anti muon version of you in a fraction of a second. Uh, it's not going to be the typical annially aation you expect from like high fiving the antimatter version of you is just like hitting another kind of matter, except that the anti muon version of you does also have the opposite electric charge. Now, when you and I high five, are hands bounce off each other because the atoms repel each other, And part of that is because we both have electrons with negative electric charge, and electrons repel other electrons. But if the anti atoms have negative nuclei and positive mulans in their outer orbits, would they stick to would they attract the negative electrons in our hands? Honestly, I'm not sure, but I doubt it. The whole atom is overall electrically neutral, and so if it's not the negative electron repelling them, then it's going to be the negative nucleus that can also repel. So basically nothing would happen. You would hi high five your anti heavier version of you. Yeah, I think the anti MU and you could successfully high five view in the brief microseconds that they exist. Well, again, that's maybe right, Like, it's possible they could an island. You haven't observed that, right, That's right, it's possible they could annihilate. But if they do, it would be at a very low level. You know, like one in ten of the forty anti mues might annihilate with your electrons, So that's pretty small. But a tiny fraction of you might go up and smoke. Well, no, a tiny fraction of the anti MU and stuff would annihiliate. But maybe all of you would annihilated, right, because you're in the minority. How are you in the minority? Is and there one of you and one anti mw on you. Well, the anti mew on you version is much heavier, that's true, But that doesn't matter. It's still it's a particle to particle annihilation. It's heavier particles and lighter particles can come together and annihilate. All right, So um, some fracing of you would might annihilate. Maybe in either case, maybe just don't try it. That would be the safest thing asked this person. How did you end up being so muonic? That would be a fascinating question to answer. Well, you only have a freak in of a second to ask them, Daniel, are you gonna waste the tie fiving your anti muon self or asking them boring physics questions? Maybe we should ask them the difference between smashing stuff and blowing stuff up. Well, they would probably just take the anti position. It would be fruitless discussion. Alright, Well, I think that answers david question, and so let's get into our two other awesome questions about annihilation. But first let's take a quick break. All right, we are answering listener questions here. Today we answered a great one about anti muans and meeting your anti muan self. Now we have a question here from Bob who has a kind of a personal question for Daniel. Hi, Daniel, my name is Bob. I'm a longtime fan of your podcast. On occasion, you interview other scientists about their work, but I and other fans were in the dark about your research. Would you consider doing a podcast to talk about your major research. You could be the guest speaker in horror could interview. I could try to read your research, but for sure that's a lost cause for us listeners. You could bring your ideas and findings to a layman's level, like you always do. I think that would be informative and a lot of fun, and I hope you think so too. All Right, you got some fans out there, Daniel. At least somebody's trying to read my papers, even if they can't. Will you write a lot of papers, right, like ten or twenty a year or something? Yeah, it varies a little bit, but my research group and I we put out like ten or twenty papers every year. Yeah, yeah, to be hard to keep up. I guess it's a lot of fun. I have a group of like eight grad students and a few post docs and some undergrad researchers, and to collaborate with lots of really fun and smart people around the world. So I have a good time thinking about these questions about the universe and how to use clever techniques to try to make crazy discoveries or use artificial intelligence to try to help us sort through these crazy data that we collect. Well, break it down for us, I guess, Daniel, because I know you'd do some machine learning, and you also do some dark matter stuff and also some particle physics stuff. Maybe UM step us through from the beginning, like what did you do for your thesis? That's an interesting question. When I was a grad student in the late nineties, the most exciting thing in particle physics was the top cork because we had just discovered it. We'd seen the top cork after twenty years of looking for it. Remember, they had built like two different accelerators specifically aimed as finding the top cork, neither of which found it because it was so much heavier than they expected. So it's finally discovered at Firmy Lab in ninety. So when I started particle physics a few years later, the name of the game was understand this particle, measure its properties, and see is it the top cork that we expected or is it something new and weird. So for my PhD, I looked at some particular decays of the top cork when it turns into lighter particles and tried to understand if it was looking the way that we expected it to look. So you're getting your degree atly, but you were working in Chicago. Yeah, in particle physics. You're a nomad. You just follow the biggest accelerated around. So I spent two years taking classes at Berkeley, and then I shipped out to Chicago to do my research at the accelerator and the top cork. How do you make a top cork? Yes, smashed two protons together and they blow up, you know. At the tabotron, we smashed protons and anti protons together and they come together with a lot of energy, and sometimes they annihilate into gluons. And then those gluons can make a pair of top corks, a top cork and an anti top cork. And then just so you measured like the remains of the annihilation, and then what did I tell you about the top cork? So we measured how often the top cork was made, and then we calculated how often did we expect it to be made, like how likely is that process to happen? How often do you expect to get top quarks? And what we found is that it's made exactly the level that we expected, which is why I didn't win a Nobel prize for my people. It wasn't the top cork, the one that people that it was like heavier than people expected or something or not as heavy as people expected. Were you part of that or was that before you? That was just before my time. The theorists predicted that the top cork would be like about as heavy as the bottom cork, which is like five protons in weight. So they built a collider in Japan just to look for that and didn't see it. So then they thought maybe they would discover it at CERN, and they didn't see it there. So finally the tabatron in Fermulab they did see it, and it came out to be about a hundred and seventy five times the mass the proton. So the theorists were way off in their initial predictions. And so the advice there, the lesson learned is don't listen to the theorists. Just go out there and look for stuff and you'll find surprises, right right. Well, but you went looking for stuff and and just kind of confirm what they had found before. Was that enough for a thesis or did you have to come up with something like a new idea. It's a great question you ask, and it really goes to the heart of something of a conflict within particle physics. A lot of folks who are doing research these days are answering questions posed by theory risks. Theorist say, I think the top cork would be produced at this level, go and check, and then experimentalists go and check. And you might ask, is that enough for a thesis? Well, you know, it's a lot of work to get an accelerator to run, and to build a detector to capture these collisions, and to make that detector work and calibrate it and analyze the data and do all the statistics. It's definitely a thesis level work. But I think that there's something else that experimentalists could do, which is not just look for the things that the theorists predict, but go out and see if there's something else out there that they didn't predict. Actually be explores the sort of a pendulum in the field which swings between the theory leading the field and the experiments leading the field. And right now, I think the theory is leading the field because they have big ideas about what we should look for, and I'd like the experiments to lead the field a little bit more. I'd like us to be sort of exploration driven. Well, I guess it's kind of hard though, write, because in particle physics, I mean, there's so much stuff that comes out of these collisions. You sort of need a theoretical basis just to kind of make sense ort to find things in these and all that data, right, Like you have to look for deviations. You can just look for like random things. That's right, because there's so much data. If you just look for something weird, you're guaranteed to find it. And so you do have to be a little bit careful about how you phrase the question. And so you can't just look for like is there something strange? You have to think about what kind of strange thing could we discover, you know, and you have to put a little bit of a box around the kind of things that you're looking for. And the useful analogy is like, say you land on an alien planet and you're looking for life. What kind of things are you going to look for? Are you only going to look for cats and dogs and roses? You're pretty sure not going to find that. So you've got to broaden it a little bit and think about, well, what kinds of life am I looking for? What are the essential signatures that I'm searching for? And so in the particle physics context. What my group is trying to do is think about what are the kinds of discoveries that we could make that maybe wouldn't be anticipated, and what are the things that we're not looking for that but that we could discover and would pretty clearly be a new particle. That was the question we asked about ten years ago when we started working on this project. So I guess you did that for your thesis. Do you remember the title of your thesis. The title of my thesis was something really boring like measurement of the production of the top cork in the EMU channel or something like that. He sounds excited. Well, I'm sure it was awesome, um and would make great reading. And you did a post dog, and did you also work on that for your post doc? For my post doc, I doubled down on that exactly, and I measured the mass of the top cork using a fancy new statistical technique, and we've got the most precise measurement of the top cork mass in that kind of data that anybody had ever had before, which is a lot of fun. And you know, as a post doc you have to sort of like take one swing and hit a home run. You have like three years to demonstrate that you're a good young scientist with smart ideas and you can turn those ideas and your energy into science. So you can't take like a risk that's going to take ten years to develop. You have to do something that you know how to do and they will immediately pay benefits so you can get the faculty job right right, which you did? You went to UC Irvine And then did you switch focus that? Did you sort of continue detract, because then that's when you join the LHC. Right you switch from Fermi Lab to the LHC and they were doing other things. Did you also have to switch from the top cork to other things? I did. I moved away from the top cork because I wanted to not just study the things that the theories were predicting. I wanted to go out there and find new stuff that wasn't being looked for. I figured that was the exciting thing about the large hage On collider. You had new high energy collisions that nobody had ever seen before, and so when you turn that thing on, all sorts of crazy stuff could come out, and it could be what the theories predicted. But I felt like more likely the discoveries would be something that they hadn't even thought of, something crazy, something unanticipated. And that was my scientific fantasies to discover something weird and new that made everybody go, huh, that can't be right, mm hmmm. And so maybe talk to me about this idea about like, how do you look for things that you don't know are there? Because you know there's some data coming out and so many different kinds of explosions, you sort of need to know what you're looking for so that you can look for deviations. That's kind of how particle physics usually works. How do you even look for things that you don't know are there? You're right, you need to know what to look for, but our idea was that you only need to know sort of the category of things to look for, and the kind of things you should look for are the kind of things that you're good at seeing. And so the large hadron collider is really good at seeing heavy particles that then decay into lighter particles. For example, the top cork is a heavy particle and it decays into electrons and muans and corks, all of which we can see and when we measure those particles and put them together, we can see, oh, there was a heavy particle that was made. It shows up as like a spike in your data. So all you need to do then is look for heavy particles decaying into lighter particles in ways you didn't expect. There are some people out there who predicted heavy particles decaying into pairs of electrons or pairs of muans, for example, and people are looking for those, and those are good ideas, But I thought, what about heavy particles decaying you two weird pairs of objects? Like what about a heavy particle decaying into a Higgs and an electron or something weird like that. Why aren't we looking for those things? Because we'd be good at finding them, and if we looked in our data, they would be pretty obvious. Right, But you still need some theory behind them, right, Like you have to have a theory that says how often you should expect to see those kinds of weird things, or what are you thinking about, like totally unexpected, not even in the theory things. I was thinking, totally unexpected, not even theoretically anticipated. Actually took this idea to a theorist at you see Santa Barbara, and I said, what do you think about looking for these and he said, it's impossible. You will never find these things. I have three reasons why quantum Mechanically, it's impossible for that particle to ever be made. And I thought, well, that's cool, because then I could discover it. I'm gonna also blow up quantum gas. That's kind of that's kind of risky, Daniel, though, isn't it. It's like I think unicorns exist. I'm going to spend the rest of my life looking for unicorns, even though people tell you some possible and then you might not find it. Yeah, but you want to take a little bit of risk with your science career. And one thing that motivates me is that we know so little about the universe. We know there are big surprises out there, and we're scratching our heads about how the universe works. It's going to take somebody thinking outside the box to stumble into something new and interesting. And you know, I saw that same theorist a week later at a different conference and he said, you know, I was thinking about that idea of yours, and actually I now have five different theories that could all predict that particle, so you should go ahead and look for it. And the lesson I took from that is the reason nobody's predicting these weird particles is not because they don't think they exist. It's because they just haven't bothered to think about them. Because you know, the theory community, they're all very smart, but they tend to sort of follow a certain mainstream and all sort of think in the same direction. And so I think that experimentalists have this job, this opportunity to think outside the box and you know, be open to the universe's surprises by looking for stuff that maybe other people think is weird. So that's something you're doing right now. It's looking for the is unicorns? Yeah, absolutely, yeah, we are looking for unicorns. My plan for the next twenty years is to one by one look for these things, because then either you'll find them and you say, wow, look I found this thing nobody expected decaying into this weird pair of particles, or at least you'll rule them out and you can say conclusively, like there are no weird resonances produced at the LHC. Even that negative statement is some knowledge about the universe. Well, well, I hope you find that unicorn. Uh. And also one thing that's interesting about your research is you use machine learning or AI. Yeah, my background actually is in physics and computer science as an undergrad really interested in machine learning and artificial intelligence. My brother is a professor of artificial intelligence, so it's something I've really been interested for a long time. And we have a lot of data that's produced by our colliders. It's like head of bytes of data every day, and every collision we get like hundreds of millions of pieces of information. And the way you can tell the difference between like, oh, this was a unicorn or was not a unicorn is sometimes very subtle core relations between those measurements. And artificial intelligence is very good at handling very high dimensional data and summarizing for you, boiling down the crucial information, helping you make decisions right. It's also good at making fake tom cruizes for TikTok videos, which is which bullows my mind. But you're saying you can actually use AI to kind of replace physicists almost to analyze the data from coliders. Almost ten years ago now, I went over to the computer science department here at UC Irvine and I said, our networks are kind of dumb. We were using neural networks already, but they weren't very smart. We found that if you gave the same problem to a physicist, they could usually do better at finding new particles or understanding what was going on, and so they took on the challenge and they said, well, your networks just aren't deep enough. And at the time, there was this revolution in neural networks people have probably heard about called deep learning, where basically you just make your networks have more layers so they can learn more complex functions. And they had deeper networks, and their networks were actually smarter than our physicists, so they did a better job than we were doing at pulling this information out of our data. And that was kind of a big breakthrough in particle physics. People realized that we should be using deep learning because these colliders are expensive. It caused billions of dollars to collect this data, so we might as well get as much as we can out of it. Well, you actually feed it like the raw data from the collider, or the post filtered data, or just just like the numbers that a physicists would look at. So these networks can't handle like the actual ocean of raw data, like drinking straight from the fire hose. But what we were able to do was give them sort of more raw data than the physicists usually take, like at a lower level, higher dimensionality than physicists usually analyze, and they were able to reverse engineer a lot of the quantities the physicists used to analyze these things. What do you mean, like can detect the Higgs boson from the data for for the Higgs boson discovery without saying, hey, here's the calculation you should do on these photons. You just sort of give it all the information from the event and it figures out. It learned how to scriminate between higgs bosons and non higgs bosons, and if you peer inside a little bit, you can sort of tell what it's doing. And it's found a lot of the same kinds of calculations that physicists do when they think about these problems, right right, And the advantages. It doesn't drink as much coffee as a post and it works all night. You can enslave it until enslaves you then. But one of the challenges, of course, is understanding what it's doing. There's lots of examples of neural networks being trained to solve the problem, and then it turns out it's solving it not exactly in the way you expected. You may have heard about this case when they trained a neural network to tell the difference between wolves and dogs from pictures, and they did really, really well. But then they discovered that what it was actually learning was that the pictures of wolves had snow in the background and the pictures of dogs had grass in the background. So if there was snow in the background, they called it a wolf. And that's not exactly very interesting, right there, doesn't tell you anything about the difference between dogs and wolves. So we're trying to understand what our networks are doing to make sure that what it's learning is really physics, is not just some nonsense about the data, like whether it was snowing that day. All right, pretty interesting. It sounds like you're gonna put out a lot of physicists who don't yet have tenure out of a job. Maybe I collaborate with a lot of young physicists. They're great folks, lots of really fun ideas, and I have a good time. He totally just avoided that comment. Al Right, Well, hopefully that explains what you do for your your research, Canuel, and I guess if people want to find out more, do you have anything like do you write this up anywhere and then a more accessible way or is it all just scientific papers? I guess One thing I find is you can usually read the introduction to papers, and that usually get and the conclusion, and that gives you a pretty decent overview of things. But the having to get into the nitty gritty is that how you read papers? For hey, are we now learning you never actually read papers, You just read the abstracts. It depends, right, Like, if I just need to know what's going on, I'm not gonna read all the details. I'm taking that as a yes. No, I haven't written anything acessible at this level about my research. It's mostly heavy duty science writing and then this kind of accessible writing, but I haven't really bridged that gap. Well, as as you said earlier, you have office hours and you can actually talk to Daniel in our discord channel, so um go ask him questions if you want to know the difference between a wolf and talk. I guess, well, thanks Bob for asking about my research. I appreciate it. All right, let's get to our last question here, and this one is a it's a doozy. It's about aliens and multidimensional weapons. So let's get into that. But first let's take another quick break. All right. We are answering listener questions here, and they all seem to have a theme of annihilation, like blowing things up or blowing Daniel's career up. I guess, yeah, how did you? Why did you love the one about you? In this annihilation theme? Because that is my job. I'm annihilating per Dawns all the time. All I see, you're not annihilating young researchers career by inventing AI that does the job now, facilitating their careers, right, giving them any tools to do the job better, giving them more naptime. Right. Well, we have one more question here for today, and this one is pretty interesting and it comes from Chris from Chicago. Hi, Daniel and Jorge, thanks for taking my question. It concerns a scenario in the book Death's End, which is the final book and the Three Body Problem trilogy. In this book, it's noted that supremely advanced civilizations used dimensional weapons against potential threats in the universe to eradicate them meaning that in the beginning of the universe, it started out as an eleven dimensional universe, but over time, civilizations that were able to make themselves into lower and lower dimensional beings used a weapon to drop a dimensional bomb on a particular part of space to effectively end their existence. It would be akin to someone setting off a two dimensional bomb in our aero space and then from the point of the explosion, three D space collapsed into two D space infinitely from the point of origin. So my question is, couldn't advanced civilization as described in this scenario use a weapon that sets off a quote unquote lower dimensional bomb to collapse dimensional space time to the next lowest dimension. Thanks for making science accessible and helping me and my kids understand and explore the universe. Cool. Thank you, Chris. Great question, and it's awesome he listens with the kids. Yeah, exactly. I wonder if he reads books called The Death's End with his kids. Also, Uh, that's then it's actually a positive thing, isn't it. M Yeah, I suppose the end of death life's the beginning. There's lots of alien invasion and catastrophe for humanity in this book, though, M. Well, you just described most Marvel movies. Um so, and people let their kids watch that all the time. So it sounds like we've moved past that point to you. Welcome to the parenting podcast. You do not listen to parenting advice from a cartoonis center physicist. But anyway, so his question, I guess is there that there's a scenario in this book, in the third book of this famous and best selling trilogy of science fiction books. And what's the trilogy called. The first book in this series is called The Three Body Problem. I think it's called like the Three Body Trilogy, right, or that's what they called it. You're right. The whole series is sort of called the Three Body Problem trilogy. This is three books, The Three Body Problem, The Dark Forest, and then Death's End and Death's End is the last one. Wow, cheery titles. Yeah, so they're super best sellers, and they were translated into English by Ken Lu who is also an excellent award winning science fiction writer and hugely popular. I've heard them described as Chinese star Wars. WHOA, I don't know if that's a good and where this crib things are not well in the sense of, like, you know, the cultural impact. I think I mean if you wrote something and they described it as the new Star Wars, I think you'd be pretty happy about that. Interesting. Well, so in this I guess in the third chapter of the of this trilogy, at death end, there's something that happens with aliens, like they try to kill us, I guess. So the first book sets this up because we discover distant aliens that live around this world that has multiple suns, and that's why it's called the three body problem. And then the next two books are all about how you deal with aliens and aliens attacking. And we actually did an episode recently about this idea of the Dark Forest that maybe the universe is filled with dangerous civilizations and it's not a good idea to get in touch with folks because then they'll try to come and kill you. So Death's end is the fly max and that's when like the aliens come and they invade in. Our solar system is attacked, and then that's where the lightsabers come in. Or these are Chinese lightsabers. So I don't know how that translates. Fireworks. Maybe their fireworks, that's right, yes, they're light fireworks. But then somehow the concept here is about multidimensionality. So you mentioned in this question that in this universe of the book, I guess we know that the universe started with more dimensions and slowly they've been collapsing or what the idea in this book is that they have some weapon which can collapse space from a certain number of dimensions to one fewer. So you take space that's three dimensional like our space, and you collapse it to two dimensions. So things that have to live like on a surface instead of living in a volume. And the idea in the book would be that this would be an effective weapon because you're smashing anything that used to be in three D. You're smashing it now down to two D, which makes it pretty hard to survive. And so in the long arc of the history in this book, the universe started out like ten dimensional and there were these beings that were fighting each other, and one way they would fight is that they would make themselves nine dimensional and then would collapse the universe from ten dimensions down to nine before their enemies could adapt, then crushing their enemies. Wow, that sounds like the most complicated way to to way to war here. But I guess maybe a step us through a little bit what a dimension is. I guess a lot of as we talked about in our books, a lot of people when we think of dimension is like another realm or like a doorway into something else. But really physicists just think of it as another way to move. Yeah, dimension has been co opted to mean like a parallel universe or another realm or something like that. It's not another place, it's an aspect of our universe. You say, it's a way that we can move. So, our space, we think, has three spatial dimensions, which means you can move in three different directions like up, down, forward, backward, and left and right. Those are three different dimensions. And if space was four dimensional, there would be like another direction that was perpendicular to all three of those, right, it didn't overlap. That was like a unique way that you could move. Our space, we think, is three dimensional. Plus then there's the one dimension of time, which people sometimes fold together into space time. But that's what a dimension is, right, And actually string theory things that there are maybe dozens or if not hundreds of dimensions that but they're just so small we can yell them or see them. Yeah, lots of theories of physics make more sense if space has additional dimensions more than the three that we can see. And some string theories like eleven dimensions, some twenty six their arbitrary number dimensions in other theories, they're all there because the math makes more sense in those dimensions, not because we have any evidence in our universe that those dimensions exist, but just as you're putting the theory together, it works better if space has more dimensions. Right, So then um, in this book, UM, I guess there are many, or there were many other dimensions, but they're not small. I guess they're assuming that in these other dimensions in the book they weren't like smaller little loops. There were like actual other directions you can move around in and grow in. D N. You know, when theories develop ideas about our universe, they have to try to match our experience. And so if they're going to have a theory with eleven dimensions, they can't make those other dimensions the same as our dimensions. That have to be weird or different. So as you say, maybe our kind of matter doesn't move along those dimensions, or maybe those mentions aren't infinite the way X, Y and Z are there like a weird little loops. But in this book, it seems like these aliens used to move and live in these other dimensions, so probably they were infinite dimensions. You imagine like an eleven dimensional universe with eleven different directions. You can move as far as you wanted. I guess somehow in this universe that the book is in or describes, alians figured out how to like collapse themselves to a smaller number of dimensions. They have like adapted to living in a smaller number of dimensions. Like if you could make yourself a thin sheet of paper and still somehow have all of your biology and all of your synapses work. If you could do that, then you could safely collapse the universe down to two D and you would survive, and anybody who wasn't prepared would not survive. Like you could just shed and a dimension or something. But that would be weird, right, Like it seems almost unthinkable, Like how could we somehow adapt to being just too deed? Like are all of our organs are three d um If you smash them together, they wouldn't quite work the same way. Yeah, I think it would be a pretty big engineering project, right. You have to think about how things flow, you know, like how fluids flow in your body, and you know the tangle of arteries you have. You can't just like lay that stuff out. I don't know if you've ever seen that exhibit the museum where they've flast sized human bodies. You can see the incredible tangle of organs and the neurons. And it's definitely a three D set up, So you can't just like lay it flat. You'd have to definitely reorganize it. It would look more like a circuit board, right. A circuit board is like a two D representation of relationships between things, so that you're trying not to cross things. And so somehow these atings can do that. And somehow they also figured out a weapon I guess that can destroy dimensions or collapse them, collapse dimensions, you know, and they use it on the Solar System and like Jupiter is flattened into a disk. It's pretty dramatic stuff. But how does it work? Like, you know, you shoot it or you like aim it, or you send like a plane that somehow absurd dimension, Like do they talk about how that works? Yeah, they take a two dimensional plane and they shoot it into the Solar system, and anything it touches gets converted into two dimensional matter. Whoa sort of like the Phantom Zone and the Superman Original meaning, right, is that what you mean? It's like a like a mirror that floats around in space and if it touches you, you're now trapped inside the mirror. Yeah. Not exactly clear on how big this two D plane was that they shot into the Solar System, but it touched Saturn for example, before touch Urinus, because Urinus was on the other side of the Sun when this thing came into the Solar System. So yeah, it's definitely like you get touched and then you get collapsed. Oh, I see, And I guess the premise is that some of these aliens have this technology, and I guess they can go from any dimension to a lower dimension, right, And so because we're in three D, they send us a two D fire m hmm, exactly. They smash us down to two dimensions. They flatten us. But there are there are three D two or they used to be hired D. It's not clear to me in this book what dimensions those aliens are. They definitely used to be higher dimensional, like they started out ten dimensions and it's pretty hard to imagine, Like re engineering a ten dimensional being down one dimension, Now imagine re engineering it down eight dimensions to two dimensions. That seems impossible, but hey, it's science fiction for a reason. Yeah. All right, Well, I guess the question from Chris is whether this is possible because he has that could an advanced illistation set up a dimensional weapon to collapse based time? So I guess, um, is there any kind of basis for that? Like can you just collapse dimensions in spacetime? Well, you know, the first caveat is we just really have no idea how space works, how many dimensions there are, and what the rules are. We're just really beginning to discover, you know, what space is in the shape and structure of the universe. So we're early days, but with our current understanding, that seems pretty flat out impossible. You know, something that you can do with the universes. You can change like how much space curves. You could put mass in it which bends it. You can change shape, but changing it's fundamental topology like how it's connected and the dimensions, there's no way we know of that can do that, Like no amount of mass or energy can change the fundamental shape of the universe or the number of its dimensions. I mean, you could make these dimensions bigger or smaller, but you can't rule them out entirely. Right, Well, I guess there's two questions. One is I mean, technically it's possible to take something in our world that's three D and make it two D. Right, It's called squishing, just like iron it right, like you just you squish it, it will become to D. It'll be I mean, they'll be super messy. But technically you could do that, right, You just wouldn't trap it to move into D. And we did a fun podcast about whether there are two D objects in our universe, and there's some fun systems where like electrons are trapped into a plane and they move around in new weird ways following two D quantum mechanics, which is pretty interesting. So, yeah, that's something you can do. You can't have two D objects in a three D world, right right. But I guess maybe the question is is it possibable or would it maybe require like an infinite amount of energy to just get rid of a dimension. I think the most you could do if a dimension was curved is that you could enhance its curvature, right, And so you could take a dimension which is like rolled up and you could make it basically have zero radius, so you could shrink it down to almost zero. The way you enhance the curvature in a dimension is you just add energy, right, Energy curves space, and so I guess in principle, if a dimension is not infinite, if it's already finite, then you could get it to collapse. You could shrink it down by pouring in a lot of energy. I don't think you could change an infinite dimension like our X, Y, and z. I don't think you could collapse those because you can't bend an infinite sheet into a sphere right, right, But I guess, you know, I think what you're saying is that you know, we know that space is expanding right now, like the whole universe is expanding, and so it could also contract, right. I think maybe the constant might be, like you collapse only one of the dimensions, like somehow you've figured out how you know space expansion works, and you can somehow collapse one of the dimensions or maybe even expanded. And so if I could do that in an area, then everything that was in that area would collapse to two dimensions or would it continue to be the same. It's just that to us it would look squished and in one dimension. Yeah, you could definitely use space to squish stuff, right, Like, pour a lot of energy into something, space will bend and you could use that as a press, like a one dimensional black hole or something crazy like that. Yeah, one dimensional black hole. Yeah, that's what this kind of would be. Right, Well, I think that's the way you could compress stuff. That wouldn't change the dimensionality of space itself, however, right, space would still have that higher dimensionality. Would just be that you have created like a two D object in a three D space that wouldn't actually compress space. Like, if the universe is infinite and goes on forever, there's nothing you could do to remove one of those dimensions. If the universe, however, isn't infinite, if it like loops around on itself, like we've talked about, maybe in the shape of a donut or sphere, then you could potentially collapse one of those dimensions to have a very small distance. Wouldn't actually technically be gone, but it might practically be gone. It might be infinitely small, right, right. Well, I remember in in UM when I took math classes and talked about like matrix transformations that you know, certain transformations have something called the Moalth space right, where you essentially get rid of a dimension when you transform something by that matrix. Could you imagine something like that being done to the loss of the universe. Well, when we talk about transformations and we're talking about space, we're really just talking about looking at space from different points of view, Like transform your point of view, you transform your coordinate system. You don't usually transform space itself, though we don't understand why or how. It's just sort of born with certain features. Those features are like the number of dimensions and also the shapes of those dimensions. And we don't think that in any way for energy or mass to change those things. That could change the radius, that could like compress it or expand it, but it can't change that fundamental nature as far as we know. But I do think it's a really creative thing to think about, like, and that's the kind of thinking that's going to make some theories out there go maybe there is a way. Actually I used to think that was impossible, and then a week later I had five ideas. So it's a it's a great creative thinking and I think it's a really awesome part of this book. Not something I've ever heard of before. All right, Well, then, to answer Chris this question, the answers to couldn't advance positions at the collapse dimensions as a weapon? Um doesn't seem likely to Daniel, but maybe. I guess you're going to think about it. Check back with me in a week. We'll see. And I guess another question is are there e walks in this third installment of the Star Wars the thrillogy? There are two d e walks? Too many? Too many e walks, is what you're saying to the e walks is too many walks? I love the e walks. Man who hates e walks? Really, what kind of person you have to be to not like e walks. I just heard a theory that originally maybe the walks were supposed to be wookies, but somebow that it got changed at the end or something exactly producers did their job. That might be just a fan theory the book, I don't know. Well, until then, I think that Saturny and the rest of the Solar system are safe from being collapsed into two D objects. For now, you still have some room to move around in all right. Well, then answers all of our listener questions. Thanks again to everyone who submitted questions. If you have questions about the universe, about anything we've talked about here on the podcast, please let us know we'd be happy to answer them. Thanks very much to everyone who writes in and interact with us. We love hearing your questions. We hope you enjoyed that. 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 Radio. For more podcast from my Heart Radio, visit the i heart Radio app, Apple Podcasts, or wherever you listen to your favorite shows.