Daniel and Kelly’s Extraordinary Universe - Can neutrinos explain why we have matter?

Episode Date: July 16, 2020

Daniel and Jorge explore how the new DUNE experiment could unravel secrets of neutrins... and the Universe! Learn more about your ad-choices at https://www.iheartpodcastnetwork.comSee omnystudio.com/listener for privacy information.

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Okay, Jorge, I have a physics game for you. Is that all physics is to you, Daniel? A game. I thought you took particles in black holes seriously. Well, this is a game about taking place. being seriously. It's called, would you worry? Oh, man, I'm worried already. Sounds like a meta game. All right. Would you worry if CERN created a black hole?

Yes. Even after all those times, I told you not to worry? I mean, you said it's unlikely that they would create a bad black hole. But if you ask me if I'm concerned that they created a black hole, the answers, yes. All right. Would you worry if we shot a beam of high energy particles through your backyard? Yes. Also, yes. High energy particles can never be good. My kids play in that yard.

What if we shot it through the yard as in like underground? They won't come up. They will not come up. But I'm still a little bit worried because, you know, why would you do that? Why not? Hi, I'm Jorge. I'm a cartoonist and the creator of Ph.D. Comics. Hi, I'm Daniel. I'm a particle physicist and I don't shoot particles at your children. Not usually. Only if they're in your lawn. Is that what happens?

Only if they're deep, deep underground your lawn. Do you have a little particle shooter in your porch? Well, you know, sometimes particle physicists build accelerators underground. And in the U.S., you own the land all the way to the center of the earth. And so you have to get permission from people to build underneath their land. But in other countries, like in Europe, you only own the earth down to like 50 meters below your land. So the government can build whatever accelerator they want under your property. Wow. Are you telling me that I own my land all the way to the center of earth?

That's right. All the way down to the center of the earth, U.S. land law says that you are the owner of that entire, what is it, cone or pyramid of earth? Wow. I should build the biggest bunker humanity has ever seen. A very long, very thin bunker with very low gravity near the center. Multi-tiered pools, you know, be a great apocalypse. But anyways, welcome to our podcast, Daniel and Jorge Explain the Universe, a production of IHeartRadio. In which we take you all the way down to the center of the earth to understand what's going on underneath your feet.

Are there bunkers down there? Are particle physicists doing experiments you aren't aware of? And we zoom out to the wider universe to help you understand why we're here, what we're doing, and what the future holds. That's right, all the way to the far corners of the universe to explore all the things that we can barely see and we can see and that we might one day see. And we also take you down to the very core of you, to your atoms and to your particles and to all the things that make you who you are. That's right, because we think the biggest game in town is trying to understand what the world is made out of. You look around and you have to wonder, why is the world this way and not some other way? What are the basic rules that make everything up?

How do they explain the reason why cats are so weird and dogs are so friendly? In the end, it has to all come down to the tiny little particles. That's right. And the even deeper question, why are we made of the particles that we're made out of? Why aren't we made out of other particles? That's right, because scientists have discovered lots of really weird symmetries. We have a certain set of particles, but there are other possible. particles out there, particles that you can create in high-energy collisions, but you just don't

see very often. And some of those particles are weird reflections of the particles we are made out of matter, but it's also possible to create antimatter. Yeah, because we have this standard model, right, Daniel, that explains or that maps out all the particles that we know about. And so there's a big question of whether or not that model is like done. Is it wrapped up that all the matter there is. You know, now that we found the Higgs boson, what's left to learn about the particles that make up matter in the universe, but there's still sort of one unanswered question about it, right? That's right. I got more than one unanswered question. Well, I only have one. What is this podcast about? But you're right, there's sometimes the perception that because we have

this standard model of physics, and for a long time, we said there was one missing piece, the Higgs boson. And that's true. We thought that piece existed and it was missing, and then we did find it. But that doesn't mean that questions are over. We don't just tie a bow on it and walk away and say, that's it, we're done. We look at it and we ask questions about it and we say, why is it this way and not some other way? We look at things in our universe that don't have explanations like why is there so much matter and not antimatter. That's something we can't currently explain using even the complete standard model of particle physics. Yeah, it's a very big question that basically determines everything because the whole universe could have gone the anti-matter.

way, right? Everything could have been made out of matter, but somehow, for some reason, everything is made out of matter, not antimatter. And so a big question is whether or not we can explain that with some of the particles that we have, namely the neutrino. That's right. One of the least explored areas of the standard model are these weird neutrinos. You might have heard of them because the sun is pumping them out at an incredible rate. There's like a hundred billion of them passing through your fingernail every second as we sit here on the surface. of the earth. And they can do a bunch of really weird stuff.

They come in three different flavors. They turn from one into the other. But their mysteries are only beginning to be cracked. And they could have the answers to some of these really big questions that are still open in particle physics. Yeah. Why do neutrinos only come in three flavors? Is it like vanilla, chocolate, and strawberry? Can you make Neapolitan neutrinos?

Is it neapolitan ice cream from Italy also? That's where neutrinos were discovered or named at least, right? So many connections being made today. But, you know, if there were only three flavors in the world, would you want them to be chocolate, vanilla, and strawberry? No, because I'm allergic to strawberry. But that's probably the only reason, to be honest. Be careful what you wish for then, man. I would be like chocolate, darker chocolate, and super dark chocolate.

And pure chocolate. Pure chocolate. Forget the ice cream part. I just want a block of chocolate. Who needs cream and ice? Just give you the chocolate. They're just delivery mechanisms. But yeah, we don't know why neutrinos come in three flavors.

And in the last 20 years, we learned some weird things about neutrinos. Like sometimes they're made in one flavor and they can, while flying through space, turn weirdly into a different flavor, which isn't something other particles can do. They have these really tiny little masses. Not zero. They definitely have some mass. They're not like photons. But their masses are much smaller than anything else we've ever seen.

They have a very subtle flavor, neutrinos. But yeah, that's the question. for today is whether or not neutrinos could, you know, explain one of the biggest questions in particle physics. And so today on the podcast, we'll be answering the question are neutrinos the reason why we have matter and not

antimatter in the universe? That's a big question, Daniel. It's a big question, yeah. To hang on one little poor particle. I know. And we often think like, well, neutrinos hardly have any matter to them. I mean, there's almost no mass there. So how can they matter? so much. But remember that there are lots of them, right? There are billions and billions of them

in every cubic centimeter of our solar system. So even though there are very few of them, they really add up. You know, they're like votes. Every neutrino counts. Yeah. And right now there's a big experiment, right, Daniel, that's trying to answer this question. And it has a pretty cool name, at least if you're a sci-fi fan, or a fan of sand. I'm a fan of science fiction and sand, so I love this experiment. Because the United States has made a sort of political, strategic choice to not try to have the highest energy collider in the world anymore. We've sort of given up and let CERN take over.

Instead, the United States communities decided, we're going to focus on neutrinos. We think neutrinos are the place to discover the new secrets of the universe. So the biggest particle physics experiment in the United States right now is not a huge collider to smash particles together at the highest energy's ever seen. But instead, it's a neutrino experiment to try to understand the mysteries of these neutrinos. And it's called Dune, D-U-N-E. The deep underground neutrino experiment. And it's outside of Chicago and Fermilab, right?

That's right. It actually stretches part of the way across the country. What? Yes, we'll get into all of that. But it shoots neutrinos from one part of the country through a bunch of backyards to another part of the country. It's pretty amazing. All right. Well, we were wondering how many people out there in the internet?

that had heard of this experiment, the Dune experiment, and again, it has nothing to do with the spice or giant worms. You don't know that. They could discover giant worms. They are underground, aren't they? That's right. Who knows what's out there? You've got to keep an open mind every time you do an experiment.

It could be a giant water reservoir down there. But anyways, we're wondering how many people out there had heard of this. So as usual, Daniel went out into the wilds of the internet to ask this question. So thank you to everybody who volunteered to answer these random questions. If you would like to hear your random speculation on our podcast, please volunteer to questions at Daniel and Jorge.com. So before you listen to these answers, think about it for a second. Have you heard of the Dune experiment? Here's what people had to say.

That's another one unfortunately have not heard of unless it's referring to the Dune novels by Frank Herbert. Hmm, I don't know if this is an acronym, and I'm not sure what the letter stand for. but since I'm in the microbiology field, I'm going to say that it involves testing for some kind of extraterrestrial microbes in sand or soils from other planets. I don't know. Never heard of that one?

I'm blank on that one. I live five miles from Fermilab and I take advantage of their lecture series and things so I know the Dune experiment. Fermilab is shooting streams. of neutrinos and antineutrinos through the earth to a detector in a mile deep in South Dakota.

I have no idea what the Dune experiments is. Maybe I should know this, but I hope that they will answer everything. Well, I've definitely never heard of the Dune experiments. I hope that they would be looking for a spice, to extend human life and make space travel more feasible. So mostly blanks on that one. Yeah, except for that one person who lives near it.

I guess they're probably pretty aware of it and maybe a little concern. Who knows? They did sound very concerned. They sound more happy with themselves to have heard of it. But I like the one that's suggesting that maybe it was looking for a spice to extend human life. Ooh, that would probably get more funding more easily. Yeah, let's fund every science fiction novel as a particle. physics experiment.

There you go, lightsabers and transporter beams. Let's get on it, Daniel. Send me the money. I'll get started. All right, well, let's step through this. What is Dune, the deep underground neutrino experiment? So this is a really awesome new massive experiment. It's being

built right now. It's not finished yet. It's going to be finished in the next five, ten years. And it's going to try to unravel some of these mysteries. Try to understand the relationship between neutrinos and anti-neutrinos and help us understand how they could potentially give us a clue about how anti-matter all got disappeared from the universe. And it starts at Fermilab, which is this collider facility outside

of Chicago. It's actually where I did my PhD work. It's out in the suburbs of Chicago near Naperville and Batavia. Interesting. And nothing bad happened to you. At least not if you count a PhD. Yeah, well, there were some adventures there, but not appropriate for this podcast. Oh, wow. Well, maybe they are actually. Like, for example, the first year that I worked at Fermilab, it was Halloween, and I thought, hey, Fermilab is a kooky place. Probably everybody shows up at work in costume, right?

Uh-huh. So I showed up a work in a clown costume. Are you serious? Only person in the entire facility to wear a costume to work on Halloween. Like makeup wig, the whole thing? Makeup wig, the whole thing. Wow. That was pretty goofy.

And so 10 minutes in, when I realized nobody else was wearing a costume, I pulled out the bits that I could, washed off the makeup, but I was still walking around all day in oversized blue shoes. Oh, man. Did you become famous on campus for that? Infamous. I thought really my academic career had tanked at that point.

I would have thought nobody paid attention to you. You think you'd blend in, but, you know, among the khaki shorts and stained t-shirts, I really did kind of stick out. Well, that sounds like a pretty appropriate story. But, yeah, so you guys are smashing neutrinos, catching neutrinas, you're looking for neutrinas. What's involved in the experiment?

Well, what they're doing is they're making a beam of neutrinos at Fermilab, and then they're shooting it into a detector. And Fermilab used to be the place where you had the highest energy collisions in the world. Back in 2000 to 2010, it was the energy frontier. There were no higher energy collisions, and it was smashing protons and anti-protons together. But then it sort of lost the race to CERN, and it's been repurposed. And they're taking that beam of protons, and they're turning it into a neutrino beam. or an anti-neutrino beam.

Or, you speak as if you don't know what's coming out. No, they do both. They have like a knob. They can produce a beam of neutrinos or a beam of anti-nutrinos. Yeah. I'm confused because I thought neutrinos were its own anti-nutrinos. Well, we don't know, right? We can produce neutrinos and we can produce anti-nutrinos.

We don't know if they're the same particle or not. What? I guess how do you know you're making anti-nutrinos if you don't know if they're the same thing as regular neutrinos? Yeah, that's a great question. Well, typically, neutrinos, which are matter, are produced from decays of other matter. And anti-nutrinos, which are anti-matter, are produced from decays of other antimatter. And in these collisions, we can make both kinds and we can select for matter or we can select for antimatter. And then we can

just sort of let it decay. So the way it works is we smash protons at some target, which makes a big mess. You get lots of crazy particles out, pyons and caons and all sorts of stuff. And And that stuff usually has electric charges. So we can separate it using a magnet. We can say, all right, the positive ones over here and the negative ones over here. So that gives us like mostly matter or mostly antimatter. That travels through a long space where the caons and pyons, they all decay into lighter particles like neutrinos that we're looking for and then also electrons and muons.

And the earth absorbs all of it except for the neutrinos. And so we don't specifically produce neutrinos or anti-nutrinos. We produce stuff which turns into neutrinos or stuff which turns into anti-nutrinos. And then we just let the earth filter it all the way. And so that's the knob you can dial. You can dial like smash matter or smash antimatter. Like we can produce antimatter that well? We can produce antimatter.

Absolutely. You just smash protons into a big heavy block of matter, graphite in this case. And you get a huge spray of stuff, both matter and antimatter. I mean, a proton smashing into graphite, it starts out with just plus one electric charge, right? because of the proton. Then you get a huge bunch of particles, but you can get like plus 500 electric charge over there and minus 499 electric charge over here. So you get a combination of matter and antimatter.

Oh, I see. The antimatter has like the negative charge? Yeah, in some cases. In the same way, for example, a photon can turn into an electron and a positron, right? So it can turn into matter and anti-matter. And then you could separate them and say, oh, give me all the matter or give me all the anti-matter. And so that's what you do here.

The super cool thing is that you're not interested in any of it except for the neutrinos. So you've got to filter everything out like a sieve where you want to get everything out of the way except for the neutrinos. Neutrinos are the only thing you basically can't bend or turn or stop. So the way you get everything else out of your beam is you just slam it into the earth and let the earth absorb all of it except for the neutrinos. Interesting. So you produce them at Fermilab, but then you catch them somewhere else. Like, you don't catch them right away. That's right.

We produce them a Fermilab, and we're interested in how these neutrinos change over time. Like, do they turn muon neutrinos into electron neutrinos or into tau neutrinos or into anti-nutrinos or what do they do? So we got to get them time to do that. So we want to watch this beam. We take a snapshot of it immediately as soon as it's measured to get a sense for what was in there. And then we take a snapshot that's 1,300 kilometers away in South Dakota. What? You shoot them in Chicago and you catch them in South Dakota? Yeah. They're made in the cybers of Chicago and then they're just aimed through the earth, like the earth curves.

And we shoot them in a straight line sort of under the curve of the earth so they come into this mine in South Dakota. What? And nobody cares? Like you can just shoot stuff through the earth like that? You can just shoot stuff under people's property because, you know, neutrinos do nothing. You know, you're not going to give anybody cancer shooting neutrinos under their house. Right. That you know of. We know of. It's sort of amazing because usually when you make a beam of particles, you very carefully shoot it through a vacuum because you don't want to lose any of your particles.

Like the beam that's at the LHC, the Large Hadron Collider is through a very, very low vacuum tube. But here you specifically shoot neutrinos through rock and rubble and all sorts of crazy stuff to get rid of all the other particles. So it's sort of awesome. Wow. All right, let's get into why we're shooting this beam of neutrinos 1,300 miles to South Dakota and what we're going to learn from them. But first, let's take a quick break. Imagine that you're on an airplane, and all of a sudden you hear this.

Attention passengers. The pilot is having an emergency, and we need someone, anyone, to land this plane. Think you could do it? It turns out that nearly 50% of men think that they could land the plane with the help of air traffic control. And they're saying like, okay, pull this, until this. Pull that. Turn this. It's just... I can do my eyes close.

I'm Mani. I'm Noah. This is Devon. And on our new show, no such thing. We get to the bottom of questions like these. Join us as we talk to the leading expert on overconfidence. Those who lack expertise lack the expertise they need to recognize that they lack expertise. And then, as we try the whole thing out for real, wait, what?

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But the whole pretending and cold, you know, it takes a toll on you. Listen to the new season of Grasasas Come Again as part of My Cultura Podcast Network on the IHartRadio app, Apple Podcast, or wherever you get your podcast. All right, Daniel. So about a trillion neutrinos per second are being shot out of Chicago and they're being caught in South Dakota. So these are going, how far underground are these neutrinos going?

Like underneath me, how far would I be able to catch them? Well, when they hit in South Dakota, they're about a mile underground. About halfway through their trip, they're even further because the curvature of the earth piles above them. So they're produced in Chicago and they're just above ground there when they're made and they're shot into the earth. And then they go deeper and deeper and deeper. And then the curvature of the Earth sort of curves back towards them, but they end up about a mile underground where there's a mine, an old mine that was used for, you know, mining, and has now been taken over by particle physics experiments where people want to look for really rare stuff.

And they do these experiments underground so that they're not constantly drowned out by the noise from cosmic rays, particles from space that would otherwise fill your experiments. And you were telling me earlier that, you know, I technically owned the ground underneath me. from my house down to the core of the earth. So did the U.S. get permission from everyone along the way, or did they just did it? Nope, they just did it. Lawsuit, anyone? They can't build a facility

under your house because you own it, but they can shoot particles through it underground. Really? That was a loophole. Yeah, they don't need your permission to send cell phone signals through your house, for example. Or radio waves. It's the same deal. I guess. Did they slip that in under the same regulations? Like, did

this. FTC, approved this experiment? SCC. I don't know if the SCC or the SOC or the POC or anything approved this, but they're doing it. And, you know, remember the neutrinos, they hardly ever interact. Like, they'll go through a light year of lead and have a 50% chance

of interacting. So there are trillions of neutrinos produced per second, but only a handful of them are seen. And it takes a really, really specialized, very sensitive detector to see any of them. All right, so tell us about that what's on the other side in South Dakota in that mine? Is it like a big detector or a little detector? What's there? It's ridiculously big detector. Because to see neutrinos, you have to have

something very, very quiet because neutrinos are really shy. They hardly ever interact with the detector and they're very light. So when they do interact, all they do is they like bounce off a nucleus, maybe kick off an electron or so. But that happens all the time. Like if you just look for electrons being kicked off of nuclei, you would see it all the time around you from cosmic rays and from other processes. So to see it from neutrinos, you have to get a very quiet environment where nothing else is happening and then listen for these little buzzes from the electrons. And you want to see it as often as you can so you get a really big volume. So what they have is like basically a big bath of very cold liquid. They use liquid argon. Argon is a noble gas that doesn't interact very much. It's

very quiet. And if you chill it down to like minus 186 Celsius, it turns into a liquid. And they have these enormous containers of this liquid argon just sitting there waiting for neutrinos to fly through them. Interesting. And when they fly through, do they create like a ping or like an image? Because they used to measure these with images, right? Like you might see the trail of bubbles that the particles make, but I'm guessing these don't use that. These use a very cool new technology. Older neutrino experiments like the ones in Japan, you may have seen those, they're like a huge cylinder of water surrounded essentially by cameras, photomultiplier tubes. And those use Cherenkov light, like a neutrino comes in and turns into a muon which gives off this cone of light that's then imaged on the side of the detector.

These are even fancier because there's an electric field that's put through the liquid argon. So when a neutrino comes in, it actually can kick off a bunch of electrons and you can get the whole trail of the neutrino. You can get like a track of the neutrino. because you can pull off those electrons from deep inside this detector. The electric field sucks out any of these electrons and registers them sort of on the side. Like single electrons. Single electrons, exactly. And so it has to be very quiet and very clean, but it also has to be really big.

And so experimentally, that's a big challenge, right? Like you can build something small that performs really well, but to scale it up is really difficult. And these tanks have 10 kilotubut. of liquid argon. Like, these are not small devices. Well, I guess my question is, why shoot them through the earth? Wouldn't that, you know, kind of corrupt signal or, you know, dampen the signal? Why not shoot them kind of straight into a detector?

Well, they do that also. So they have a detector immediately after the neutrinos are produced to sort of sample the beam there. Like, well, what did we make? Did we make mostly electron neutrinos? Do we make mostly muon neutrinos, et cetera? But then you also want to see them change. And that's really the question we're asking. It's like, do we understand how neutrinos change from one kind into another?

That's the thing that's going to help us connect to this question of antimatter and the deeper questions of the universe and even, you know, maybe understand some things about exploding stars in faraway galaxies. Wow. The key is to understand how the neutrinos change from when they're created to further down the road. So you want to sort of corrupt them. You want them to interact, to change in flight, to do the things they're going to do, the weird stuff they're. can do so then you can catch them having done it down the road. But wouldn't you want a clear line of sight? Why would you want it to go through rock? Wouldn't that, you know, give you a lot of things that could have happened or unexplained phenomenon along the way? Well, if you discover

that somebody, for example, built a bunker all the way down to the center of the earth, that could really, like, corrupt your measurements with all their cascading pools and banana plantations and stuff. Yeah. What if a giant sandworm like walks right into the beam? That wouldn't be good. The first thing is you want all that earth there to filter out all the other particles. You need to get rid of all the muons and the caons and all the other stuff. So you have a pure neutrino beam. So you need the earth there for that also. But then you want it to interact.

And you might be thinking, well, usually particle physicists, they like things to be simple. Like, let's interact it with a block of graphite or a perfect cube of argon or something, right? And rock and dust and rubble seems sort of messy. But we're not very sensitive to the details of like, is it, you know, marble or is it graphide or is it dense or is it loose because we're integrating over like 1300 miles of stuff and so we're not very sensitive to like exactly what happens where we're not going to get like a picture of the center of the earth we just want the neutrinos to do something and they have to pass through matter in order for that to happen all right well my guess the question is what

are we going to learn from this experiment and how does this how do you relate neutrinas to matter and antimatter because I guess you know you hear the word neutrino you think they're neutral they don't care. But maybe they do care. And maybe they had a lot to do with the fact that we have matter. Yeah. Well, there's this deep question, right? Like, why is there matter and not antimatter?

And we think that in the beginning of the universe, we suspect that matter and antimatter were made at the same rate. We don't know why it would be anything different. And that's just an assumption. Like, it could be at the very beginning of the universe, there was just more matter made than antimatter for some weird other deep reason we don't understand. But we assume, because we like to make sense,

simple assumptions, that it was made in a symmetric way, and that something exists that can turn matter into antimatter, some process, something that prefers to create matter over antimatter. Because I guess in the equations that we have now, there's nothing in them that says, oh, obviously matter is more likely to be made. There's nothing. Like, in the equations, they're totally equal, just opposite. They're not 100% equal. Like, for a long time, we thought they're totally equal. Obviously, things have to be symmetric. And there's this principal charge conservation that says if you see a process in nature,

you should be able to flip all the charges, all the particles to antiparticles and see exactly the same thing happen. It should be exactly the same. But then we discovered that didn't actually hold true. That that's not really true, that there are some asymmetry. For example, the weak nuclear force breaks this rule. And especially when you combine it with this other rule about putting things in the mirror. So together, it's called CP violation. charge and parity.

You flip the charges of something and you put it in the mirror. You should see the same effect, but you don't often. We have a whole podcast episode digging into discovery of CP violation. But this CP violation, it does give you a reason to have more matter than antimatter, but not nearly enough. It explains it by like 1% of it. So there are some asymmetries. The equation do predict that you get more matter than antimatter,

but it's not big enough to explain what we see. Interesting. What does that mean? Like the violation means that it's 1% more likely to get matter than antimatter from like a random explosion of energy? We've calculated how much imbalance you need between matter and antimatter in order to get the universe we have now. If they're exactly matched, then you get no matter left or antimatter left over in the universe because they all annihilate into nothing. You need some process which will create matter more often than antimatter in order to get extra matter. left over. So when all the annihilation happens, you have matter, which is the universe that we have now. And so we've calculated like how much of that do you need to happen? And we can explain

about 1% of that process. So it's not like any given particle has a 1% chance of turning into antimatter, but we're looking for, you know, a way, a channel for this to happen. And we found a few, but they're really small. They'd explain just like 1% of what we need to explain the universe we see. So there's a big missing process. Something out there. really prefers turning antimatter into matter rather than matter into antimatter and we don't know what it is and maybe it's neutrinos.

Well, so then the idea is that matter turns into antimatter but not symmetrically. Is that kind of what you just said? Yeah, exactly. So you have these processes where matter can turn into antimatter can turn into matter

most of the time it's symmetric. So stuff just sloshes back and forth and you don't overall change the balance. Right. But there are a few. things that preferentially produce matter that prefer to go from antimatter to matter. And then they don't

go back as easily, I guess. Exactly. They don't go back as easily. So you don't get an equilibrium, you gradually build up an excess of matter. But they don't explain what we've seen. You need more processes. We're looking for the rest of them. We've seen CP violation. These processes that produce more

matter than antimatter. You've seen it in caons. We've seen it in B mesons. But those are very, very small. They're like not big enough. It's like we're handing for gold and we know there's a lot of gold in the stream, but we just keep getting dust and we know that there are big nuggets out there. All right. And so is the picture then that, you know, we had the Big Bang and a whole bunch of both matter and antimatter got made equally, but then over time somehow everything flipped over to matter? Is that kind of what we're looking for? That's the

scenario we're trying to figure out? Yeah. And not everything flipped over to matter. Just like some fraction of it flipped over to matter. And then you had more matter than antimatter. But, you know, the antimatter all annihilated with matter. But since you had more matter than antimatter, some matter was left over. All right. And that's where we came from. That's us. We are the matter that's still here.

All right. Well, let's get into then how neutrinos could explain this in balance and also what it means for astrophysics. But first, let's take another quick break. Imagine that you're on an airplane and all of a sudden you hear this. Attention passengers. The pilot is having an emergency, and we need someone, anyone, to land this plane. Think you could do it? It turns out that nearly 50% of men think that they could land the plane with the help of air traffic control. And they're saying like, okay, pull this, pull that, turn this. It's just... I can do my eyes close.

I'm Mani. I'm Noah. This is Devon. And on our new show, no such thing. We get to the bottom of questions like these. Join us as we talk to the leading expert on overconfidence. Those who lack expertise lack the expertise they need to recognize that they lack expertise. And then as we try the whole thing out for real. Wait, what? Oh, that's the run right. I'm looking at this thing.

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Well, there's so many open questions about neutrinos and antimatter. Like, for example, as you said earlier, we don't even know if neutrinos are there antiparticle, or if there are two different particles there, like, is a neutrino and an antinitrino different? It's so hard to tell because neutrinos hardly ever interact. Right. Like for a neutral particle, what does it mean to have an antiparticle? It's like they're both charge zero, right? Electric charge zero, but they, and neutrinos have other charges, right?

Exactly. In terms of the quantum charges. Exactly. Neutrinos, like every other particle, have charges for every single force. You have a charge for their electromagnetism. You have a charge for the strong force. and you have a charge for the weak force. And sometimes those charges are zero.

Like the electron has a minus one charge for electromagnetism, but has no strong charge. We call that color. But neutrinos, the only charge they have is for the weak force. And so the antiparticle would have the anti-charge. But the weak force is so weak that it's very difficult to study. That's what makes these experiments so difficult. And Dune doesn't measure neutrinos turning into anti-nutrinos directly.

Instead, what it does is, ask whether muon neutrinos turn into electron neutrinos the same way that anti-muon neutrinos like to turn into anti-electronutrinos. So it flips the whole process and measures the antimatter version of it. These effects are very subtle. You can't like look at one particle and see what's happening. It's a build it up over time and takes a lot of experiments before you can actually see these effects. Right, because it's the weak force.

Because it's the weak force. What is the weak force charge call? It's called the weak hypercharge. Hypercharge. Okay, so then neutrinos have a charge, a weak hypercharge. And so if there are antineutrinos, then are you saying those would be flipped or those would not be flipped? Or we don't know. We don't know. If they are their own antiparticle, they wouldn't be flipped. If they aren't, if there is a separate antineutrino, then it would be flipped. And what we're interested in is how do neutrinos turn into anti-nutrinos and back?

If there's a big asymmetry there, if antineutrinos like to turn into neutrinos, more than neutrinos like to turn into anti-nutrinos, if they even are as ever particles. I know. I'm so confused. You're asking like, could an anti-neutrino turn to neutrino if an anti-neutrino is not the same as a neutrino? There's so many things we don't understand about this. It's like a big black box. We don't know what's going on inside. And because we don't know what's going on inside, it gives us a lot of options for things it could explain. Like if they are not the same. So matter and antimatter are not the same for neutrinos. And antineutrinos like to turn into neutrinos more than neutrinos like to turn into anti-nutrinos. That could account for

why we have more matter than antimatter. It could have been essentially that a bunch of neutrinos are being made. And the neutrinos can turn into other kinds of matter. Like a neutrino can turn into an electron and a W boson. What? So like we could have come from neutrinos. Yeah, absolutely. Some of our Particles certainly did come from neutrinos. I always thought there was a little Italian in me. Just a little bit. Just 1%. Just 1%.

You're Jorgeino. Well, I guess what I don't understand is, a neutrino does have hypercharge for the week fours. You know, why can I just flip that charge and call it an anti-nutrino? Like, it's possible. Why would you think that flipping the hypercharge would make it the same thing? Well, we don't know necessarily what the universe thinks about this symmetry. We don't know that the opposite particle can exist.

Why is there an opposite to the electron? It's not like you're allowed to demand that every opposite particle exists. We see the opposite particle for the electron and for the proton and for quarks, but we don't know why they exist. So it's not like we can claim that every particle should have its antiparticle. And we're doing these experiments to try to figure out. We do a whole different set of experiments called neutrino-less double beta decays, where they try to see neutrinos and anti-nutrinos annihilating or not.

So I guess you're asking, like, if I make neutrinos from antimatter, does it make the same neutrinos as regular matter? Or does it make like the one with the charge flip? Exactly. Can we tell any difference? And that's why they do this experiment in two modes where they produce neutrinos and then they look to see what happens. And then they produce anti-nutrinos and they look to see what happens. And one thing they're curious about is do they see any difference?

do neutrinos and anti-nutrinos turn into different stuff as they fly through the earth or do they act exactly the same way? And the exciting thing is that there were some experiments done in Japan that saw a hint, that saw a clue that suggested maybe there was a difference. Really? What did they see? They saw that neutrinos do like being matter, not antimatter?

Yeah, they saw a hint of exactly this. And they weren't powerful enough to really detect it. It was just like a little glimmer or it could have been a fluctuation. But this is a sort of similar experiment in Japan where they produce neutrinos in a collider and then they send it underground to this other experiment, which originally was looking for neutrinos from the sun, but now they're piling neutrinos into it through the Japanese bedrock. And it's that experiment where they have a big heavy water container surrounded by cameras

looking for flashes from the neutrinos turning into muons or electrons or whatever. And they saw a hint. And it was not significant. like they didn't have enough data to really say they found it. But they had enough data to suggest that it might be real. And that's the kind of motivation you need when you're spending, you know, a billion dollars on an underground experiment in South Dakota. All right.

So if we find that neutrinos like matter more than antimatter or becoming matter more than antimatter, then that would explain the whole universe, right? It totally could. Because there are so many neutrinos in the universe that might explain why. Because we have more matter than antimatter. That's right. Because it all came from neutrinos who would like more matter than antimatter. That's right.

And the other particles are like to make matter versus antimatter. The caons and the bees, they just do it a tiny little bit. It could be the neutrinos do it a lot, like all the time. Like they really heavily prefer making matter versus antimatter. So it could be a massive effect. It's exciting because we really just don't know. Like we don't know what the answer is going to be. It could be a very small effect and explain nothing.

It could be zero. It could be huge. You could be like, what? these things are all turning into neutrinos all the time and anti-nutrinos aren't even really a thing. So it's exciting for us as particle physicists when we don't know the answer. It's much less exciting when like the theorists tell us,

here's the Higgs boson, we know what it looks like, go find it, we know what to do, we just do it. It's like box checking, you know? Oh, man. So when the Higgs was found, you're like, eh, I hate it when you're right. I hate it when you're right, theorist. Out of principle, I will not support this.

Well, you know, there is a lot of drama and political intrigue and uncertainty in the quest for the Higgs boson, which we'll dig into us soon in an episode. But a little bit, yeah, it would have been more exciting to not see the Higgs and to see something else crazy

which made the theorists go, what? So as an experimentalist, it's more fun to discover something unexpected. So it's nice here when we don't know the answer and we've got to go and measure it because to me, that's the excitement, right? That's what's interesting about being an experimentalist.

You're exploring the universe. You're asking you questions and you don't always know what the answer is going to be. Interesting. All right, well, let's take this conspiracy theory to the next level, Daniel, and ask, could neutrinos even be responsible for dark matter? How do you tie those two together? Well, you know that dark matter is something that's out there. It's massive.

There's a huge amount of it. It's like an explanation for all the gravity that we see out there that we can't explain otherwise. There's no mass that can explain all the gravity that we see. So naturally, people thought for a long time, well, what if it's just a bunch of neutrinos? We know there are neutrinos everywhere. We can hardly see them. They're basically dark and there's a lot of them. What if there's just like a huge, ridiculous amount of neutrinos and that would be enough

to explain the dark matter. Right. Or not just a lot of neutrinos, but maybe like really, really massive neutrinos. Yeah. See, originally people thought, what if it's just a lot of the vanilla neutrinos, the strawberry neutrinos, the ones we're familiar with, right? But they ruled that out because neutrinos are very, very light and move way too fast. And so they can't explain all the structure we see in the universe to see how galaxies formed and stars get pulled together.

We need the gravity from dark matter to be sort of slow moving. It can't be zooming everywhere in the universe or we just would have spread everything out. So we know that if it is a neutrino, it has to be a new kind of neutrino, like a weird new, heavy neutrino, like very massive neutrino. Like pure chocolate neutrinos, like just a chunk of chocolate. Are you saying that chocolate are not a good weight loss technique, if so? then I'm in trouble over here. I'm saying dark matter could be dark chocolate. New theory.

Hey, what are you doing, Daniel? I'm just eating dark chocolate to get an idea of a dark matter, right? It's research. Filling myself up with a potential hypothesis. There you go. That's right. It's intellectual food. So, yeah, it could be that there's a new kind of neutrino, like a fourth kind of neutrino.

We currently know about electron, muon, and town neutrinoes, but there could be another kind out there, a heavy one. that we don't even know about. We don't know about it. Yeah, we haven't seen. And there are a few other places in physics where we've seen hints that suggest maybe there is one, but they're not conclusive. Like there was an experiment in Los Alamos, actually my hometown, that saw neutrinos sort of disappearing in a way that we couldn't explain.

And they explained it in terms of a weird new sterile neutrino that is really hard to make and is very heavy and very occasionally neutrinos sort of disappear into that sector. Interesting. And so, an experiment like this, like Dune, that very precisely makes a huge number of neutrinos and studies them and their antimatter, if sterile neutrinos are a thing and are possible, then they could see some of these neutrinos sort of disappearing into the dark sector, you know, because they can count the number of neutrinos they expect to see. And if they see too few, then they might be evidence that these things are turning into something else, something invisible to them. Interesting. It's basically like a really fancy and upgraded neutrino gun kind of. Yes, it's a neutrino gun and a neutrino camera.

And they point the gun at the camera. And it's a more powerful gun than anybody's ever built and a more sensitive camera than anybody's ever built. And so we're going to get a new window into neutrinos. And another cool thing is that we're not the only people who have built neutrino guns. Like it turns out that the universe is filled with neutrino guns. And this new power. Alien? Maybe.

And this new powerful neutrino camera will let us see neutrinos produced by other sources, is not just, you know, conspiracy theories in Chicago. Oh, interesting. So the same camera under South Dakota, a mile down, could see neutrino bursts from other things in the universe, like supernova, as you were telling me? Yeah, supernovas are these amazing events where an entire star collapses and then explodes.

And we really want to understand how that happens and do they turn into black holes and how often and, you know, the details, the blow by blow of what happens in those events. And there's a lot of mystery because we can't see them very, directly. They're very far away. And one big problem is that they're complicated. And so like light is produced in the first moments of the supernova, but then it gets reabsorbed. So you don't see it. And it takes a while for the light to sort of like make it out through the shockwave before it comes to us. But neutrinos are a great way to see supernovas because supernovas make a huge number of them. And they're not reabsorbed by the

supernova. They come right through. They shoot right out from the heart of that event. That crazy cosmic collapse and tell us about the very first few moments of what's happening in a supernova. Wow. We can use this neutrino camera basically to take pictures of the insides of supernovas. Wow. Do you have to like point it to this supernova? We're not pointing this 10 kilotone of liquid argon at anything, dude. Yeah, that's what I was asking.

Like, I guess is it easier to move to Earth then? Like, do you rotate the Earth in a different way? Or what do you do? Yeah, we've got a knob over here. We can just turn the Earth any way we like. It's in a pivot, right? I'm sure. Yeah, when you're late with a deadline, you're just like, could you just stop the earth at 458, please?

You don't do anything like that. You just sort of like, look. What you do is you turn off the neutrino gun at Fermilab, and you just let the experiment be quiet. So basically, any time the beam is not on, you can use it to observe the universe. And you can't point it at anything, but we think that these sources come from everywhere,

and we're shielded by a mile of rock that prevents anything but neutrinos from getting down through the earth to this camera. camera. And so you just, you know, basically point your camera up at the sky straight up and see what you see. All right. Well, it sounds like neutrinos could hold the key to the universe somehow. And conveniently, that's where a lot of our funding is going in physics in the U.S. But when is this experiment going to go online, Daniel? Well, they're building it now. And they hope to have the first part of it done in 24. Nobody's ever built one this big or this complicated before. So they built like a mini version, a

proto version, which worked well. But they think the first full scale piece will be done in 2024, and the whole thing will be complete in 2027. And then you have to run it for a few years. So like, we might be looking at an answer in like 2030. And it's an exciting place to look, mostly because it's a hard place to look. And that's also the reason why it's still a place to look. You know, we look for obvious answers. We do the easiest things first. Neutrinos are the hardest things to study. And that's why they still have these mysteries, because they're sort of shrank. And so we had to up our game and like figure out ways to see them and to study this deep, dark, hidden sector of the standard model to see if it has any of the secrets, any of the answers to these open questions. I guess my question is if neutrinos turn out to be the key to the matter and antimatter mystery, which means that they're not neutral, do you have to rename them, Daniel?

Well, they could. Because they're not neutral anymore. They're still neutral from the point of view of electromagnetism, but you're right, they're not totally neutral. I mean, they do even have mass, which gives them an effect a gravitational charge. But neutrino is such a cute word that if we're going to rename any of the particles, that's not renewing neutrinos. It's got a special place in your heart. How about the spice? We could call it the spice, or the chocolate spice.

That sounds good, chocolate spice ons. All right. Well, we hope you enjoyed that. And maybe as you look up and imagine those trillions of neutrinos going through you right now, maybe they have the key to understanding why we're here and why the universe is the way it is. That's right. And we're always interested in exploring something we have not yet looked at because under every rock we haven't turned over could be the answer to an open question in physics or it could be something else, something new, something totally unexpected. The history of science is filled with people building an experiment to answer one question, but accidentally stumbling over the answer to a totally different question, they might not have even known to ask. Either way, it's fun. And we learn a lot about the U.S. That's right. And it gives the U.S. Particle Physics community.

something to do. Because you don't want them pointing any other kinds of particle guns at anybody else's backyard. That's right. Your children are safe. All right. Well, thanks for joining us.

See you next time. Thanks for listening. And remember that Daniel and Jorge Explain the Universe is a production of IHeart Radio. For more podcasts from IHeart Radio, visit the IHeart Radio app. Apple Podcasts, or wherever you listen to your favorite shows.

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