What can neutrinos teach us about supernovas?

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Speaker 1: Or Hey, did you ever wish you had a different kind of eyeball? Well, that's a weird question. I guess I'm pretty happy with my eyeballs right now. I like, I wouldn't want it to be cubic or you know, any other shape rather than it's around. How about you? I mean, my eyeballs are great, but there's just so much that they miss them at the universe. You know, they can't see infrared or ultra violet, or dark matter or neutrinos or dark energy or all that great stuff. But you can't see that you can, and you've been holding out on us. Well, I guess I don't get it. I mean, do you want your eyeballs to see more things? Or do you want more eyeballs? Like, would you want extra eyeballs for each of those types of light or things? I wonder if I look more like a physics professor, if I had four sets of eyeballs and even eat glasses, you know, you would wouldn't just have four eyes, you would have sixteen eyes, which would make me look like four times as smart. Art. Well, it would definitely raise your eye. Que Hi am r handmaker tennis and the creator of PhD comics. Hi, I'm Daniel. I'm a particle physicist and a professor at U C Irvine, and I will always fund a grand proposal that tries to build a new kind of eyeball. I thought you were gonna say, you're gonna say you would find any proposal that makes you want to have more eyes. Yeah, exactly, that's what I mean. They don't have to be orbs implanted in my physical wet wear. If we build a new kind of technology that's sensitive to something new about the universe and translates those signals into something we can understand, that's kind of like an eyeball. Interesting. So if I sent you an email proposing a seven billion dollar new kind of eyeball, you would you would send me the money. I will go to bout for you with the funding agencies to fund that proposal, that they send it to me for review, I will say fund fund fund No no, no. That you said you would fund whatever proposal propos and you kind of eyeball Yeah, absolutely, yeah. Please wait for your check. Thanks. I look for it with my prototype eyeballs. The Daniel Science Foundation might be in your junk mail folder. Is that what the foundation does it just sends junk mail encouraging people to make more eyeballs. Somebody's got to do the hard work around here. But anyways, welcome to our podcast. Daniel and Horror explain the universitate production of My Heart Radio, in which we connect your eyeballs and your earballs do all the interesting things going on out there in the universe, the incredible cosmic rays streaking nearly the speed of light through the universe, carrying with them messages from the distant reaches of the cosmos, and bearing secrets about strange physical processes. We try to digest all of that information that's coming here to Earth and explain all of it to you. Yeah, because it is a pretty incredible universe full of things happening all the time, every second of the day, every second of the night. There is something going on in the universe, and it's screaming for us to learn and discover it. That's right, And almost everything out there in the universe produces some kind of message. Is it a proton, is an electron? Is it a photon, Is it a neutrino? Is it dark matter? It always produces some kind of impact rippling through the universe. And if clever apes on this third planet from the Sun learned to listen to those messages, they might just deduce some secrets of the universe. Yeah, because I think that's an interesting thing about the universe, is that there's stuff happening all the time, and it all has an effect on the rest of the universe, right, Like, almost nothing happens that it doesn't affect anything else. Energy is always flashing back and forth. Stars shootout energy, which gets absorbed by other stuff, which heats up, which radiates out energy. They're all these flows in the universe of energy being released and captured and re released, an incredible cosmic swirl. Yeah, there's stuff happening, and it's it's shooting out stuff all the time, and we and we are literally kind of bathd in information about the universe. All that stuff is coming to us, passing through us. And if we can only learn to see it, or at least hear it in the right way with our earballs, I guess we would learn a lot about the universe. I think a lot about how our mental picture of reality is determined by the senses that we have. A lot of people are very visual, and so their mental picture of how the universe looks depends on what they are seeing, and they imagine that what they see is what's there, and things they don't see aren't there. But we know that there's a lot more going on in the universe, that there are plenty of things out there that we can't see with our eyeballs but are just as real as the things that we can see. What if you're more sort of touch oriented, what kind of picture of the universe would you feel? I wonder about that. For people who can't see, for example, what kind of mental model of the universe they have. They must still have some sort of three D model where they build up shapes based on sound and touch and all sorts of other clues. But I wonder if it's a very different experience on their I really know, well, it is a pretty incredible and exciting and active universe, and with all sorts of things happening in it, and not more so, are more fantastic or incredible than stars exploding or supernovas. It's one of the most dramatic and least well understood things that happened in the universe. At the end of the life cycle of a star, sometimes they just go kaboom, and they can shine briefly as bright or brighter than the entire galaxy that they are in. Yet it's one of the most explosive I guess events that can happen in the universe, and it's kind of hard to believe that we don't know a lot about them. I mean, when they happen, they're pretty bright, right, we can see them all the way across from the next galaxy. They're so bright, and they're really unusually transient. Most of the things in the night sky just sit there and burn and they're the same every day, every year. But supernova are short lived that I light up the sky briefly and then disappear. It's the kind of thing that's so dramatic that you can actually find records of it in ancient history. People like hundreds are even up to US thousand years ago writing stories about these strange things that appeared in the night sky. Wow. Can you imagine being born at the time and looking up and then suddenly this star starts burning super bright? What would you think is going on? Would you freak out? It's hard to imagine it because it's hard to put yourself in the place of somebody who has no idea what the sky means, right, They don't even know what a star was. I had that same experience when I saw the eclipse birthand in the path of totality. It was really an incredible experience, and it made me wonder what it must have been like twenty thousand years ago for stone age man to look up and see this thing happening, and I thought the world was ending. Clearly something important was going on right right right, Or maybe they just thought that like, oh, look it's Zeus, or look it's mercury taking off its start. Yeah, or somebody out there knows what I did, right, Every guilty person on the planet was like, oh, I've been caught. This is my fault. It's shining a spotline exactly. And so in the same way, if you look the nights guy, you see a supernova, what do you think? It depends on what you think a star is. And those folks are so ignorant they had no idea what they were looking at, And of course that makes me project forward. You know, what weird things are we seeing in the sky that we just don't really understand at all. And in a thousand years, people will look back and be like, wow, Daniel was so clueless. He had no idea what he was looking at. Like yeah, Like if you extrapolate the progress of science since human knowledge into the future, like who knows what we're going to know in the future, right, maybe everything? Yeah, And who knows what ideas we have today that we take for granted will be overturned by some crazy discovery. Maybe in ten years, maybe in a hundred years, our entire picture of the cosmos could be totally upended. Are you gonna be able like one of those science fiction movies where you go like, oh, in fifteen years, we'll be riding around in flying cars and know the secrets of the universe. And then fifteen years go by and nothing has happened. I hope not. But you know, it is research, and so it's hard to predict. It doesn't really align with quarterly reports and predictions and this kind of stuff. You just never know. The frustrating thing about research, and this is what my grad students have to learn, is that time spent is not equal to progress made. Right, You can be busy, busy, busy, busy, and get nowhere and then one afternoon, boom, it all clicks together, and that's why research is not for everybody. Yeah, I guess past performance is no indication of future returns, right, definitely not, definitely not. But the exciting thing about astrophysics and cosmology is that we do know that we know very little about the universe. We know that most of the things going on out there are things we don't understand, which gives us you no hope that we will figure something out. At least there is something out there to learn, even if we're not quite sure exactly the way to unravel the mystery. Yeah, And so it's interesting that we don't know a lot about its supernova. It's a kind of a big explosion, but it's it's there's still a lot that we don't know about them, and it might be because maybe we're not looking at them in the right way. Yeah, the way that we look at the universe with eyes and ears and touch and telescopes to see mostly pote Hans, it's just one slice of the universe, and if you look at it in other ways, you see a totally different universe. Yeah. But just to make sure we haven't touched any supernose happening, there's a big sign on it says do not touch, and I always try to follow the rules. You're kind of pedantic in that way, Yeah, exactly. But you know, depending on the eyeball you use to look at the universe, even when it comes to photons, if you look in the infrared or the ultra violet or the visible light, you see a very different kind of universe because the different processes. The stuff you were talking about earlier, the stuff that's always going on in the universe, shines in different kinds of light. But going beyond that, stuff in the universe can shine in things that are not even light. Yeah, And so supernova do that. They produce not just visible light, but all kinds of light and all kinds of particles that might be able to tell us what's going on during those crazy events. And so today on the podcast, we'll be asking the question what can nutrinos ellas about super novas? And how do we get a neutrino to appear on the program to answer these questions? Would you have any opinions or would you be neutral about everything? They're so weak? Oh boy, that is a deep physics joke right there. We won't even bother explaining it until later, But I had a more basic question, Daniels, it's supernovas or super nova? I think those who have learned Latin will write in and say it's super nova with an a E at the end. But I'm pretty sure I hear physicists say supernovas all the time. I'm not sure it's a good idea to correct them. Why not? Physicists don't like to be corrected. So what you're saying not on the pedantic actually it's pronounced supernovae doesn't meanly go over very well in a seminar. Well. I've recently discovered that, you know, fungas, you can say fun guy, or you can just say funguses. Fungus is that is a terrible sounding word. Yeah, it's optional in the English language at least, But fun guy is so much funner because it sounds like you're a fun guy. I know, right, But you know, but if your name is Gus, then it's also good to be one of the fun Gusses. I see. I guess that could be the name of a band made all of gusses, right, ten fun Gusses, the Fuses. I'm sure that they'll sell out in no time. I'm sure they'll be opening for the Grateful Dads sometime soon. Oh hey, they're probably better anyways, so we might be the opening act. But anyways, it is kind of interesting to think that a supernova not just produces visible light in a big flash that we can see with our eyes, but it also produces a whole bunch of other things that maybe we can use to learn what's inside of him. And so Daniel went out there into the wilds of the internet to ask listeners what do neutrinas teach us about supernova? Thank you very much to everybody who volunteered, and if you are a listener who has never participated, please write to us two questions at Daniel and Jorge dot com. We would love to have your voice on the podcast. Think about it for a second. What do you think we can learn about supernova from neutrinos. Here's what people had to say. I remember seeing a documentary or something a few years back about using trinos to see on the to see what goes on on the inside of stars image And when a supernova explodes, it puts out just massive amounts of neutrinos and they sail through everything. So if we could detect them and read their states. That probably give us a lot of really good information about what's going on inside of a supernova. I guess they'd tell us the direction of the supernova because they both fly through anything in spice and arrive at protector, and they would car light in an energy sense with the size of the bluff in some way. Putrinos probably come in slightly different frequencies and different energy levels, different so other qualities perhaps, and depending on exactly the type of supernova that occurs, perhaps the new trino's can give us a bit of information about how big these star wars that exploded, or if it was a particular type of explosion. I imagine they can probably give us quite a bit of information. Maybe they tell us what kind of nuclear reactions have occurred during this explosion, which would tell us the composition and size of the star. From what I know, the no can tell us what happened after the supernova, if we have a neutron star, if we have a black hole. Probably, but for sure I know that it can tell us if we have a neutron star after a supernova. So what I know about supernova first of all is that they're basically a star that exploded, and it sends off thousands of solar masses of particles and material, and it also sends out a lot of energy, like a lot of energy. And what I'm imagining is since neutrinos are so incredibly small and they could go and travel through even all of Earth without even hitting a single atom and Earth, then that means they're moving incredibly fast and there's a lot of them. So if neutrinos, which we know quite a bit about and how they're given off from certain particles, reach us from supernova, I guess it could tell us what was in that star and what that explosion was. Like, these are some amazing answers. Yeah, they're pretty specific and pretty um physics sounding to meaning I mean like did they actually like give you a good ideas there? They're not just physics sounding their physics containing. I mean, these are really insightful answers. After I got these, I thought, Wow, did I accidentally email like a neutrino physics conference, Like these folks know what they're talking about? Wow? Cool? And then you wrote down the ideas and you're going to use them for research and not credit that. That's right. I got seven billion dollars neutrino telescope funded based on these ideas. Good is it all because of my letter that I sent you? That's right, I want to cut them. I'm still waiting for the first check from the Daniel Science Foundation hasn't arrived. Yeah, and got a junk mail from yourself, he said, so, but it's so easy. I have very serious doubts about this foundation. Now you can't even send itself its own junk mail. I'm starting to get the same feeling. But anyways, supernova are pretty incredible events, and so maybe let's just take it back to the basic level and it's still our listeners. What a supernova is. Supernova is an exciting moment in the life cycle of a star. It's a huge explosion that blows out most of the matter and releases an enormous amount of energy that was stored in the star. And depending on the kind of star that you have that you start with, you can get supernova's in two basic ways. One is you can just have like a really big star, and remember that what happens at the heart of stars because of incredible gravitational pressure and high temperatures, is that you're fusing lighter elements into heavier elements. At some point, those elements get so heavy that when you fuse them, you don't get energy. You lose energy, and the heart of the star starts to cool and can no longer support itself against gravity, and then it collapses and you get this huge supernova that's called a core collapse supernova. And there's another kind where it doesn't quite have enough mass in order to have a core collapse supernova. It sits there as a white dwarf for a little while, and then somebody comes along and gives it some extra fuel triggers the supernova, and then it collapses. And so you get this gravitational collapse towards the heart of the star, which creates this incredible high temperature and pressure situation and boom, all the fuel very quickly undergoes fusion, and you get an incredible explosion of all that energy in a very very short amount of time. Yeah, but I guess, just to be clear, not every star goes supernova, right, Like, it's actually kind of a rare thing for us are to explode, that's right. It doesn't happen very often. If you have a galaxy of about a hundred billion stars, you'll only get about one to three supernova's per century, so it's an unusual outcome. A lot more often, for example, a red dwarf will just turn into a white dwarf and not go supernova, or like, our son is not gonna explode, it's just gonna kind of puff up and then kind of go out, and just similar for forever. You know, our star's endpoint is likely to be a white dwarf, which is just hot lump of metal, you know it just like with a core collapse supernova. It's burned, it's fused, and then the byproducts of that fusion are things it can no longer burn, and then eventually it just goes out. By going out, we mean it's no more fusion. It's still like a big hot lump. And that's what a white dwarf is, is just like a big glowing blob of fusion remnants which can no longer burn anymore, but it sits there glowing for like a trillion years until eventually becomes a black dwarf. Right, our son has headed to be a hot mess, just like most stars here on Earth as well. That's right, you're turn that your career can end without a huge explosion and just sort of fezzle out. Yeah, I thank you hopefully. You know, I always hope for an uninteresting life, right. Something I think is super interesting is that it's very hard for us to predict when a star will go supernova. So it's the kind of thing we usually just see afterwards. It's not like we can say, oh, that star over there is going to go supernova in seventeen days, let's all point our telescopes at it. It's the kind of thing we're like, whoa, look at that star. It just went supernova. Quick point your telescope so we can catch the last bits of it. Right. It's kind of unpredictable when it happens, but it's it's not like it's random either, right, Like it only happens in certain kinds of stars. Like if you can something see a star and no, oh that one's not gonna go supernova, or you can see another star and say, oh that one can and might one day go supernova. Yeah, but of the hundred billion stars, it's not easy to predict which one is going to go supernova. Part of that is because we don't understand the life cycle of stars. Well enough to know like which ones are going to go supernova, and it's not easy to predict when they're going to go super nova. So even if you're pretty sure that this star is big enough and it's eventually going to go supernova, knowing when that's going to happen is hard to predict. And that's because we don't have a grasp on a lot of the complex physics, and it depends a lot on these physics. It's like predicting a hurricane. You know, can you predict the path of a hurricane. There's no like weird new quantum physics going on. It's just a lot of calculations and the result is very sensitive to the details. In the same way like can you predict when a star is going to collapse? It depends on so much crazy nuclear physics and really high density, high temperature situations that we just can't describe yet, but I guess you can. What I'm saying is you can sort of rule out whole categories of stars from going supernova, and so there is a certain category of stars that can go supernova. That's true, although even the ones that you think can't go supernova, like our son could eventually go supernova, Like our son is gonna be a white dwarf if it later acquired a binary star partner, like some other star came nearby and they're orbiting near each other, and our son, the white dwarf, stole a bunch of gas from this new partner. It could then become a Type one A supernova. So sometimes it's like this ramp them back to supernovas, which is pretty hard to predict, but those are extraordinary events, Like you need a whole another star to be to come to our solar system. Yeah, that's true, you need a whole of the star. Remember though, that a lot of stars out there are in binary systems, and so there's a lot of white dwarfs out there that could potentially go Type one A supernova. I think it's super cool because we have never seen the progenitor of a supernova like we've seen them after the fact. We've never had like a zoomed in, close up study of a star just before it goes supernova because we've never been able to predict when it was going to happen. M M, I see interesting, all right, Well, just because they're rare doesn't mean they're not cool. In fact, that just makes them more special, right, and harder to to spot and to study them. And these extreme events are sort of the perfect laboratory for understanding what's going on inside the star, Like how do you trigger a collapse? When does the collapse? What's going on in the collapse? Can you understand how our shock wave of propagates through this crazy material? What we're interested in understanding is like what happens when all these forces are at play, Like inside a supernova you have gravity, you have the strong force from the quirks, you have the weak force producing neutrinos. You have electromagnetism because everything's charged, so you have all the forces sort of at play at the same time. It's a great opportunity to understand those things or to probe those things if you can get enough data, if you can say, like what's going on inside the star? That's why it's a very exciting thing to study. Yeah, it's always a surprise, I guess, I mean, is he kid? And you never know when they're gonna happen. All right, let's dig into a little bit more into supernova and how many we've seen over the course of human history, and then let's talk about what neutrinos can tell us about them. But first let's take a quick break. All right, we're talking about the neutrinos that come from a supernova and what they could tell us about what a supernova is all about, because they're surprising events in the universe and we've never actually seen one, I guess close up or in slow motion because they just happened, like trying to catch a close up film of a popcorn popping kind of you never know which which colonel is gonna pop exactly after it pops, you can then point your camera at it, right or yes. And one of the issues is that supernova are so rare that they don't happen very close to us very often. It's also good news because if a supernova went off, you wouldn't be hearing this podcast. You know, we'd be fry. Yeah, you don't want to too close up of a supernova, right, It would be the last thing you see exactly, which means that if you want a close up view of a star that's about to go supernova, you have to focus one of our space telescopes at it, and they can only look really really deep at a very small patch of the sky, and so you basically have to know where to look or build like zillions more space telescopes to look at the whole sky simultaneous, which, of course you know the Daniel Science Foundation would be very excited to fund. Well, you really tuned this foundation. But do you admit it's all a scamp. So I'm not sure what it's just my fantasy foundation. You know, maybe some billionaire who's listening will think that guy really knows how to do science. I'm going to write him a check for fifty billion dollars. Maybe that guy really clearly knows how to run a foundation. I'll put him in charge. Exactly. This guy is confidence inducing. Let me just write him a check. I see most people play fantasy football, but physicists play fantasy foundation. Is that what it is? What you're saying. So you get together, you you make imaginary bets and on what science is going to get funded? Yeah, but you know, the most tantalizing and frustrating part of that is, while you might never be a pro athlete, like you fantasize all of these dreams about understanding the universe are really attainable, Like Jeff Bezos really could buy us knowledge about the universe. The only thing standing between us and understanding so many things about the universe is a couple of dudes, right, a couple of big checks. We know what to do, we know how to do it, we just need the cash. So it's frustrating to me that these fantasies are actually attainable. Well, I'm confused, Daniel. Earlier you were saying that you can't promise that you're going to get results with research, that time doesn't equal results, But now you're saying money does equal results. Or is that is that just what the foundation says. Let's do the experiment and find out, you know, send me the money. We'll see. Now, it's true that you can't promise anything, and we could build like a hundred new hubbles and seeing nothing interesting. But every time we look out into the universe, we always find something weird and surprising and bonkers that up ends our ideas. And so I'm pretty confident that continued research will reveal something. But yes, I won't make any actual promises any you won't sign any legal contract now, but I'm all forced off of funding science for sure, and it teaches incredible things like the about supernovas, which is kind of interesting to think that most are all supernovs really come from a collapse, you know, like we tend to think of explosions that's just things that react and then spew out a bunch of energy. But actually all supernovaus, all right, start off as as collapsing stars. The collapse, and the key thing to understand there is that what happens inside of the star depends on the temperature and the pressure, like can you fuse hydrogen or can you fuse all the way up to carbon or even further up the periodic table. It just depends on the pressure and the temperature. So the higher the temperature, the higher the pressure conditions that you create, the more crazy things that could happen inside that star. And so typically sort of steady state, but as supernova, as you say, starts with the collapse, which creates this incredible high temperature and high pressure inside the star, and you can like burn a huge fraction of the fuel inside the star in just seconds instead of millions or billions of years. And that's why they're so luminous, right, because that's kind of what's going on. It's like in this when the star is just burning. It doesn't have enough pressure and deeed to to fuse some of the heavier elements. But when collapses, then you have those conditions and then it all happens at the same time, like in the type one a supernova. Typically these are blobs made of carbon and oxygen, and they're not hot enough to fuse carbon. But as soon as they get over the tipping point, they get it just enough gravity, it collapses and then all of a sudden, boom fuses like a huge fraction, like a half or a third of that carbon in a very brief amount of time. And that's basically an explosion. Right. The difference between a nuclear reactor and a nuclear bomb is whether it's like a chain reaction and runaway explosion. And that's what happens at the heart of a supernova when you create conditions from the collapse, So you got to collapse inwards and then a shock wave outwards. Yeah, it's like a bounce, almost like a super bounce. It's a super bounce. And people who do modeling of this stuff they try to understand exactly what is happening. It's really complicated physics. You know, are the photons getting absorbed by the iron. Is it breaking up the iron which is causing this? You know, whenever we do physics modeling, we can never describe everything that's going on. It's just too many crazy details. We always have to make judicious choices, like we think it's a combination of these things and those things. And so what they do is they develop these complicated models and then they make predictions and they say, okay, well the supernova should be this brighter, should last this long. But the problem is we don't have that many observations of supernova and we can't see inside them. We can only basically see the light that they admit, well maybe illuminate us. And what are some of the things we don't know about supernova? Like we there's a lot we don't understand about them, and what are some of these things? So a lot of the things we don't understand us about supernova involved what triggers that collapse, you know, what is going on there, what makes that happen? How exactly does that shock wave propagate to the core, how far in does it get before the core starts to ignite? And pushes back this question about when that turns around, when them bounce exactly happens that we don't really understand. But you know, more deeply than that, we just don't understand matter at this density. You know, we think we understand, for example, what happens when you take three quarks and you put them together you get a proton or a neutron. What hapens when you squeeze those protons and neutrons are really really close together, so that it's more like a six cork particle. Now do that with like a billion quarks. What does that look like. It's the same kind of question we ask about what's going on inside a neutron star or what form of matter is happening inside a black hole? These are all the same kinds of questions. What happens when you squeeze things are really high temperatures and pressures, and at lower energies. You know, we have some ideas of the kind of things that happened, like structures emerge. You get crystals of one temperature, and you get gas at other temperatures, and you get fluids at other temperatures. So there might be like whole new states of matter that can be described by interesting new equations that we've just never seen before, and this is the way to probe it, to like say, what's going on inside there? Well, create a shock wave that passes through it, and let's understand how that chock wave propagates. And they can tell you something about the phase of matter inside. Right. It can maybe even tell us a little bit about the Big Bang, right, because during the Big Bang you also have these crazy conditions kind of like maybe what do you see inside of a supernova? Yeah, the Big Bang is like a huge supernova exactly. And it's very hard for us to model those very early moments of the universe because the forces are very very strong, very powerful. And usually when we do modeling, we'd like to make assumptions like we can ignore this, and we can ignore that, we can ignore this other piece because it'd be too complicated to model. But when everything is dense and all the forces are at play, you can't ignore any of those details, and the details really matter. You get them a little bit wrong and your whole model is wrong. So it's a very very challenging kind of thing to model, and it's a kind of thing we'd really like to learn about because we want to understand what the universe was like in its first moments and what happens when you squeeze matter to incredible densities. Yeah, and sometimes, like you know, studying matter under those extreme conditions tell you a lot about the matter itself, right like, your theories can only go so far. There's a lot you can learn about even like a person under extreme conditions, right Like, it gives you a bigger picture about the matter. Absolutely, And that's exactly why we have our series of podcast about extreme conditions, like how strong can a magnet we'll get? Or how fast can you get something spitting? And the reason is those extremes tell you what the rules are, and they tell you what the boundary conditions are for the universe. That says you can't go faster than this, or you can't have something denser than this, And those are the places when the universe illuminates the edge cases. Right it tells you exactly how things operate. Well, one thing we do know about supernovas or supernova is that they produced neutrinos and a lot of neutrinos, and then those neutrinos might tell us kind of about what's going on inside of the explosion. Yeah, I love neutrinos. They are fascinating particle. They appear in all the like core mysteries of the universe, not even just talking about like astrophysics and supernovas. Just from a pure particle physics point of view, neutrinos are super fascinating. That's sort of the least well understood particle of all the particles that we have discovered. Yeah, they're pretty mysterious and ghostily. But so maybe tell us what do we know about neutrinos? What are they? For those of those who, um, maybe I don't know. The trinos are fascinating little particle. You're probably familiar with the up cork and the down cork, which make up the proton and the neutron that's in the nucleus of the atom, and then around the atom you have electrons of course, so those are the three particles you need to make up like normal matter. But there's another particle out there that's part of this core set, and that's the neutrino that's paired with the electron. And it's not part of the atom, like you are not made out of neutrinos in any sense, but it's a particle that sort of can exist in nature's menu and it turns out there's lots of particles out there which can exist. There's sort of like on the menu of the universe, but don't exist under normal circumstances. Neutrinos are especially weird kind because they ignore most of the forces in the universe. Like they don't feel electromagnetism because they're neutral, right, No trino means little neutral particle in Italian. And they don't feel the strong force, right, they don't have a color. Those the two most powerful forces in universe. So all they're left with is the weak force. And of course gravity, which is like so ridiculously weak we don't even think about it when it comes to particles. So neutrinos are these little neutral particles that only feel the weak force. It's almost like they're ignoring the rest of the universe in a way, right, Like most of the universe, like our particles talked to each other through these other forces. But Newtinas are like, Nope, I'm just not gonna check Twitter or Facebook. I'm just gonna only accept handwritten letters unless they're junk male from the Daniel Foundation. Yeah, and you know, the neutrino was actually discovered by a professor here at UC Irvine, for which he won the Nobel Prize. And in my office I can often hear tours of campus going by, and as they pass the physics building, they say, and this is Ryness Hall, named after Fred Ryness, who discovered the neutrino, the smallest fundamental particle. That always makes me cringe because I'm like, the neutrino is not smaller than the electron or the quirk. They're all the same size, they're all points. But they call it the smallest particle because of its ability to pass us through stuff. Because it only feels the weak force, it can pass through an incredible amount of matter without interacting with it. Well, it's also small in this sense that it has very little mass, right, Like it does feel gravity, but it's just has very little mass for it to kind of obey gravity. That's right. It does have non zero mass. Like we know neutrinos have some mass, but we don't know exactly what their masses. But they are very very small, especially compared to the electron. Wait, did you say neutrinos are very small? Their mass is very small, especially compared to the electron. But you know they're not the lowest mass particle right photons and zero mass blue ones have zero mass. The reason people call them small, I think, is because they're trying to understand how it is. And neutrino can like pass through the entire Earth without even noticing. They wanted to like slip through all those particles and like slide around them without interacting. But a better way to think about it is in terms of like transparency. You know, light can go through your window without interacting with glass. It can pass through right or through the air. The air is transparent to light. It's not like the lightest sliding around and avoiding all those molecules. It just doesn't interact with them. It doesn't have the right frequency to get absorbed by those molecules. And so those molecules just ignore each other. They pass right through each other. And that's what's happening with neutrinos. Neutrinos see the whole universe as almost transparent, right, so they just pass right through without even noticing. Yeah, they're just ignoring everyone. Everyone's like, hey, talk to us with this strong force or the electroman game for us, and they're like, nope, which is cruising through you said, they're related to the electron. What does that mean? Or they're paired with the electron, what does that mean. We have all these rules and particle physics about like what can decay into what? And for example, a W boson it can decay into an upcork and a down cork. You can also decay into an electron and an electron neutrino. So the electron and electron neutrino sort of like paired together by the W. W can't for example, to came into an up cork and a neutrino or a down cork and an electron, and so they have this sort of relationship in the weak force of the electron and the neutrino have exactly one electric charge step between them negative one and zero, just like the down cork and the upcork have an exactly one electric charge between them. So we group them together into these pairs for that reason. They're sort of like made together or they go well together. Yeah, And for those of you who think quantum mechanically and in terms of quantum fields, you know, the W particle sort of like raises an electron into a neutrino, or the other W can turn in a neutrino into an electron. It's sort of like converts these fields from one to the other. Or if you remember our episode about gauge symmetry, like the whole reason we have forces and force particles is to preserve these weird symmetries that fill all of space. Well, the w particle does that, and it pairs the neutrino and the electron together. They have a symmetry together, the electron and the neutrino. I see the like the neutrino doesn't pair us well with others. It somehow kind of in the same category as electrons. Yeah, and we have this thing called electron number, which is conserved, Like you can't increase or decrease the number of electrons in the universe, but neutrinos are a counted as electrons for that category. Interesting, it's like a non non electron electron and the muon and the tow which is like the weird heavy versions of the electron. They have their own neutrino. There's a muon neutrino and a tow neutrino, and there's a number of muons that's conserved in the universe, and a number of towels, and so each of those is paired with their own lepton in that way, all right, So they're ghostly particles that go through the universe, ignoring everybody else, it seems. But what's weird is that they're produced um not just in supernova, but they're produced by our son. Like our son produces a huge amount of neutrinos, and so it's weird to think that something in our universe that likes to talk to us, that has electromagnetic forces and all the other forces make make things that then ignore the forces. Yeah, our Sun, it turns out, produces an incredible number of neutrinos. It's like you know, you're following somebody on Instagram and then you discover, oh my god, they're huge on TikTok and I never even knew. Our son produces so many new trinos that even here on Earth there are a hundred billion passing through your fingernail every second. So a hundred billion per square centimeter per second is the flux on Earth. Now, imagine like how many neutrinos passed through a square centimeter if you're right on the surface of the Sun. It's just mind boggling. How many there are because, as you said, like during in these sort of like quantum or particle reactions, they just get produced along with all the other stuff that gets produced in these reactions. Yeah, the fusion that happens inside the Sun, and this is not even during a supernova, just normal everyday burning of the Sun also involves the weak force, which means that neutrinos are produced. Can't remove an electron without producing a new trino for example, because of this conservation of the number of electrons, which includes neutrinos, weirdly do you end up with lots of neutrinos produced in those reactions. And one thing I think is super cool is that if you only have a neutrino detector, you can use it to take a picture of the Sun. In neutrinos. You can make like an image of the Sun in neutrinos. If you didn't have eyeballs and you couldn't see photons, you could still tell that the Sun was there just by using neutrinos, right, Yeah, I mean it's sort of like if you couldn't see visible light, but you could see other frequencies of light, you would still know the Sun is there because it's producing across all these frequencies. Absolutely, Remember it's a different kind of particle. It's not just a different frequency photon. It's like a completely different way to get information. It's like seeing a car versus hearing a car. You're using a completely different sense to now detect it. And if you google, you can actually google like picture of the Sun in neutrinos, and you can see this image that was made of the Sun using neutrinos. I think it's super cool. Oh so it's almost in a good way that we can then turns don't interact with us. Like if neutrinos interactive with us, they might fry us from all the nutrin just coming out of the Sun, Like we would get into trino sunburned, neutrino cancer. That's something I've never heard of before, but you're right, it's an incredible amount of rediation. On the other hand, maybe we could build like neutrinos solar panels and that would solve our energy problems. Oh. Interesting, that's a science fiction story for you right there. All right, Well, um, so the Sun produces a lot of neutrinos, and supernovas produce a lot of the trinos. So let's get into what we can learn from them about what's going on inside of these stellar explosions. But first, let's take another quick break. All Right, we're talking about supernovas and what can neutrinos tell us about them, because I guess um, a lot of trinos get produced in the supernova, a lot of neutrinos get produced in a supernova. In fact, neutrinos carry away most the energy of a supernova. You thought a supernova was bright and visible light, and it is. That's nothing compared how bright it is in neutrinos. What do you mean as bright? Like? As much more energy is produced in the ne trinos than are made in a supernova than act than regular light. A hundred times of the energy produced in a supernova is carried away in new trinos. So if you're just looking at a supernova in the visible light, you're getting one percent of its energy. WHOA, that's like a lot. That's like supernova is mostly a a trino explosion. Yes, it's mostly a neutrino explosion. It's like autrino explosion. Yeah, we've been following it on Twitter, but it's been on TikTok this whole time. And you know these supernovas, they're not small even in the visible light. And there's some of these that are just mind bogglingly bright in the visible light, like one called a s A S S N fifteen l H was a trillion times brighter than our sun momentarily. That's like ten times as bright as our entire galaxy. And that's in the visible light. Multiplied that by a hundred, and that's the intensity of the energy carried away by the neutrinos. WHOA, So I guess what's going on? Like how you're saying, like for every little explosion that's happening inside of supernova, it's producing a hundred times more neutrinos than any anything else. Absolutely, the number of neutrinos produced by supernova is something like ten to the fifty. That's ten with fifty zeros after it, and some models go up to predicting ten to the sixty. So it's an incredible number. What's happening is that the nucleus of this star is getting compressed, and so you have protons in there, and you have some electrons that are in there, and they get squeezed down to the electron and the proton actually fused together and they turn into a neutron. So that's called electron capture. But remember there's this conservation of the number of electrons. You can't just delete an electron from the universe. What happened is the proton and the electron turn into a neutron, but they also pop out a neutrino, so it's called the neutron ization of the core. You make this thing super duper dense. You squeeze the electrons and protons together to make neutrons. Plus you make a neutrino every time that happens. Wait what Wait, so you you can squeeze an electron and a proton together, but they're like plus and minus. Wouldn't that like that's how intense things are. They can overcome that basic repulsion. Well, they're plus a mindus, so they're attracted to each other. Right, That's how the electron is bound around the proton. But typically electrons don't like to get squeezed down into the nucleus because a quantum particle has a minimum energy. Like you can find a quantum particle, it can't go down to zero energy. You know have for example, if you have a bowl and you put a marble in it you can just sit at the bottom of the bowl with no energy. It was a quantum marble. It couldn't go to the bottom of the bowl. It would have like a minimum energy level in which it would be buzzing around. That's why electrons don't collapse into protons, and normally they resist this because the Heisenberg and certainty principle says, if you localize the electron, if you squeeze it down to a small space, then it's gonna have a lot of energy, has a lot of uncertainty in its momentum. And so what's happening here is you're overcoming that with the pressure. You're squeezing these electrons down into the proton where they don't actually want to go, and turning it into a neutron. A neutron and a neutrino, I guess because the plus and the minus canceled out, but some of that energy has to go somewhere. Yeah. It's really interesting because you go from two charged particles a plus a negative to two neutral particles. So it's like the neutralization of the core. You get a neutron and a neutrino, but a proton is really just made out of quarks, and so it's it's actually more complicated, right, it's like a minus one plus a two thirds minus two one third or something like that. Yeah, what's actually happening is that you have one of the quarks inside the neutron emits the W changing into a different kind of quirk. So that changes the proton into a neutron, and then that W interacts with the electron and converts into a neutrino. So that's what's putting sort of microscopically from the particle physics point of view. All right, So then you push together the electron on the proton and creates a neutrino, and it creates a whole bunch of neutrinos in this supernova explosion, and so that's really useful because, like neutrinos are then easier to see kind of through the explosion, so you could sort of get a trans X ray picture almost of the supernova. One of the reasons that you have so much energy released in terms of neutrinos is that the star is mostly transparent to those neutrinos. So when the neutrino is produced, it can fly out from the star it's this crazy, incredible intense explosion that's happening. But once you've made the neutrino is mostly able to just escape and fly out into the universe. So every time you get energy dumped into a neutrino boom, that's released. On the other hand, if it turns into a photon, that photon is created inside a really incredibly high dense environment with all sorts of charged particles that it will interact with, and so it gets reabsorbed very quickly. So neutrinos fly right out of the superno of a, whereas photons are mostly reabsorbed. If you see a photon from the supernova, it was only emitted from the surface of the supernova, not from the core. Interesting and in fact, you're saying that because matrinos are can fly through the explosion, they sort of get here first before any actual light from the explosion. That's really counterintuitive, but supernova neutrinos arrived here before photons. You might think, how is that possible. Photons travel with the speed of light. Neutrinos have a little bit of mass, so they don't travel at the speed of light. But the answer is that they are released first. Supernova. Neutrinos can leave the core of the supernova and fly immediately towards the Earth, but photons don't get released immediately when the supernova starts. You need like that shock wave to travel through the star and then emit at the edge of the star. So that sort of limited first by the speed of sound propagating that chock wave, and then when the shock wave hits the surface of the star, then photons from the surface can leave, and they'll spend their whole time trying to catch up to those neutrinos us and not quite making it. It's almost like the supernova in a way traps the visible light so it can leave. We can't see the explosion until afterwards, but the trinos can just fly out and tells like, hey, supernova happened. Yeah, And it's the similar things what happens inside our sun. You sometimes hear people say that it takes a photon thousands of years to travel from the center of the Sun to the surface. It's a bit misleading because you know, what's actually happening is a photon created at the center is just reabsorbed and then the whole sun heats up and later it emits a photon at the surface, but the principle is the same that a photon created the heart of our Sun also can't just leave the Sun and shine out to Earth. Only photons from the surface can make it from the Sun and hit the Earth. So you can actually use new trinos as like an early warning system for supernovas. But it wouldn't that depend on how far away the supernova is, Like, if it's far enough away, the photons will catch up eventually. Yes, if it is far enough away, the photons will catch up because they're going fat saster than the neutrinos. Yeah, but neutrinos are really really light. Their mass is very very small, and so they travel an incredibly high fraction of the speed of light, you know, like point and so you're right, photons are traveling faster, and so eventually they will overtake it. But they'd have to come from extremely distant supernova for that to happen, and all the supernovas we see are pretty distant. You know, we haven't seen one in our galaxy since sixteen hundreds, Like the last person to see a supernova in the Milky Way was Kepler, whoa in sixteen o four, like it's been a while, and that's sort of a puzzle, like not we don't really understand it. We're supposed to get like one to three per century, and it's been like four hundred years and we've gotten zero. So that's something nobody understands about supernova Like, if something one happens in our Milky Way, it would be more than just like a light shining getting brighter. It would maybe be super bright light light up the nights. Guy, it would And we saw a supernova in seven, not from our actual gaxe or from like a nearby blob from the Magellanic cloud. And this is in seven. They saw this supernova it's called Supernovae A, and they actually saw neutrinos from it before they saw the light from it. WHOA, meaning like we had some lutrino detectors ready to go, and we saw a spike before we saw the actual flash exactly. We have particle physicists studying neutrinos just because we want to understand like how often does an electron neutrino turn into a muan neutrino or this kind of like basic particle physics questions. So we have these neutrino telescopes, like the when we talked about earlier that took a picture of the Sun in neutrinos. So these things are always running, they're always sensitive. In the late seventies, a couple of theorists had this prediction. They said, you know what, we did this calculation. We predict that when a supernova happens, there will be an incredible flux of neutrinos. Nobody had ever thought that before. And then ten years later, after these neutrino telescopes were built, they saw one. They saw this flux, this momentary flash of neutrino knows that nobody was expecting. And a few hours later they saw a bright light from the same direction, and so that was the supernova. In two different kinds of signals, we got the preview, like the Trader kind of for the for the main event exactly, or I guess not, because in the Trina explosion is the main event of the event, Yeah, exactly. The supernova itself is like the post credit scene. Yeah, it's just it's just the the event, just sitting around eating schwarma. But we only saw like twenty five neutrinos, and that's a lot that's a lot of neutrinos. In order to detect twenty five neutrinos, you need to have billions and trillions of neutrinos passing through your detector, because remember it's very rare that they interact, so most of the neutrinos will pass right through you. So they saw like twenty five neutrinos over a span of like thirteen seconds, which is like nobody ever sees a new Trina detector lighting up like that. They were going crazy. But this is the only time it's ever happened. This is the only supernova we've ever seen neutra arinos from. But I mean, we have these neutrino telescopes running all the time, and aren't there supernovs happening all the time. Shouldn't we see these neutrino events then as all the time as well? Yeah we should, But a lot of these supernovas are very distant. Was sort of unusually close. It was in this blob that orbits the Milky Way to Magel in a cloud. Most of the supernovas we see are in much more distant galaxies, And so the number of neutrinos we get and the number we can detect is very, very small, but we do expect that all these neutrinos from all these distant supernovas sort of add up to be like an overall supernova neutrino background, which we hope the next generation of telescopes will be able to see. So even if you can't like individually identify neutrinos from one supernova, you might be able to tell that there are a lot of supernovas out there producing a lot of neutrinos that you can pick up. Interesting. Well, I guess maybe to answer the question of the episode, then, what can neutrinos tell us about supernova? What do you think they'll tell us if we can maybe see these a little bit better or a better resolution, and they can tell us a lot about what's going on inside the supernova. Because neutrinos have three different flavors electrons, muans, and towels, And while most of the neutrinos produced in the heart are electron neutrinos, as they fly through the star, they change from electron to muan to taw, this process called neutrino oscillation. We have a whole podcast episode about that, and that happens based on the density of the material and the kind of the material. So by looking at like the ratios of electrons and muans and town neutrinos, you can tell something about the density of the material. It's sort of like X raying the supernova. You can see what happened on the inside, not just on the surface. I see because maybe in this signal, this explosion of neutrinos, you can tell, oh, first there was this kind and then it changed into this other kind of neutrino, and then that would tell you kind of how the explosion um evolved. Can tell you something about the density and the layers of what's going on inside the supernova. And so there's sort of like the messenger of the core of the supernova mechanism. You're saying, like, right now we have we can have a neutrino telescope look at our son and get a picture of our son. But right now we don't have the technology too and get a picture of a supernova in neutrinos, not most of them, because neutrinos are so poorly interacting. Even supernovas that are super duper bright, we can't resolve most of them. It's just like how there are lots of black holes out there and meeting lots of gravitational waves. But it's not always easy to pick out one gravitational wave from one black hole because there's so many and they're so distant, so they all add up to sort of like a buzz. You want to pick out one specific supernova, it's got to be kind of bright and kind of nearby. But we're building the next generation of new trino detectors which should be even more sensitive to neutrinos, so we should be able to see supernovas and other galaxies in neutrinos, and they'll give us the information we need to start like answering some of these questions about what's going on when this core collapses. You're saying, like, right now we have more like a micro like a neutrino microphone was in a way, but maybe in the future will have more like a telescope natrino telescope, like a focused scope for it exactly. And the Daniel Science Foundation very excited to find that when junk mail and we could have a supernova early warning system. Right if we could detect these things happening before they shine in the visible light, then we can point our telescopes to them hours before they become luminous, and we can really see what happens just before the shock wave reaches the surface, which would be super fascinating interesting, be like having a third eyeball looking out for the next supernova. Yeah, you can also turn it the other way around. Not only can new trinos tell something about supernovas, but this one supernova also told us something about new trinos. Oh yeah, you mean, like there's still a lot we don't know about neutrinos, right, Yeah, And in the nineteen eighties we have no idea what the massive neutrinos was, like, how small was it? Exactly? The very difficult experiments to do. So when we got this pulse of neutrinos from that supernova, actually used it to figure out roughly how much mass does the neutrino have based on the difference in arrival times of neutrinos, Like two neutrinos are produced in the supernova at the same time but with different energies, which means slightly different velocities, and we can measure the arrival time on Earth and the energy on Earth, and then you do a bunch of math and you can figure out exactly what the mass of that neutrino had to be if it had this energy and this velocity. So we're able to figure out roughly what the mass of the neutrino was because we got a nice big blob of them from this supernova. And what you've learned is that it's a really small or really light. It's really really small mass exactly. The electron neutrino is some mass less than like twenty five e v, and in comparison, the electron has a mass of five hundred thousand ev. So the neutrino is much much, much, much much lower mass than even the electron, which is very low mass compared to lots of other particles. It's interesting that you know, so much a the energy of a supernova is trying into neutrinos. But then neutrinos are you know, ghostly and super light, so they're almost like impossible to see. Yeah, Like photons, they carry their energy mostly in their motion, not in their mass. Right, Photons are pure motion, they're just kinetic energy to have momentum but no mass. Neutrinos also have momentum and they have a very very small amount of mass, all right, So stay tuned for these new neutrino telescopes funded by the Daniel Junk Mail Foundation, which my one day gave everyone a next eyeball, at least internal eyeball for us to see the universe in other types of energies. That's right, and if you would like to support the mission of the Daniel Science Foundation, please send us a check or at least send us some junk mail. Daniel will recycle it and use that to make more junk mail. I guess it's just a junk mail making operations. You caught me. It's just a big spam. It's a hobby, Daniel. Let's let's face it. One day I want to build a junk male detector. That would be my next kind of eyeball. I'll focus on the Anverse to find the greatest sources of junk male in the universe. I see, yeah, well, I think every house is a junk male detector, or at least a junk male collector. But maybe you could do like a citizen science project where you coordinate, you know, different households, and then you could pinpoint the source of these junk males junk male telescope network. I might tell you a lot about the postal universe. Yeah, all right, we'll stay tuned. And again just another reminder that there's a lot going on in this universe that is maybe not apparent to the naked eye. You know, there's a lot of interesting science and physics and incredible energy is being released out there that are regular human eyes can't see. So we're sort of in our everyday lives kind of ignorant about all of this amazing and miraculous processes going on in in nature. Yeah, and those are the things that we know we don't know about. There might even be more things, the unknown unknowns, that we don't even know that we can see. And it could be going on right under our very eyeballs. You could be getting a lot of junk bill and not even know it. That sounds like a good situation actually, but it's there, Daniel, it's clearing up your background and so I have questions. That's right, there's a huge pile in your backyard. You just haven't cleaned that part of it. All right. Well, we hope you enjoyed that. Thanks for joining us, see you next time. Thanks for listening, and remember that Daniel and Jorge explained 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. Yeah.