Daniel and Kelly’s Extraordinary Universe - The mystery of the missing neutrinos

Episode Date: November 28, 2019

How did physicists lose trillions of neutrinos?  Learn more about your ad-choices at https://www.iheartpodcastnetwork.comSee omnystudio.com/listener for privacy information.

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Grazias, come again. We got you when it comes to the latest in music and entertainment with interviews with some of your favorite Latin artists and celebrities. You didn't have to audition? No, I didn't audition. I haven't audition in, like, over 25 years. Oh, wow. That's a real G-talk right there.

Oh, yeah. We'll talk about all that's viral and trending, with a little bit of cheesement and a whole lot of laughs. And of course, the great bevras you've come to expect. Listen to the new season of Glasses Come Again on the IHeartRadio app, Apple Podcasts, or wherever you get your podcast. Hey, Jorge, have you seen a particle lying around here? Yeah, I had this neutrino actually more than one. And what happened? You lost them?

Yeah, it was here. I turned around, you know. Exactly how many particles are you missing, Daniel? Let's see. One, two. It was about sextillion. How do you lose a sextillion particles? Well, actually, it was one sextillion particles per second? Daniel, you expect us to believe that you're not going to destroy the world with your physics experiments? Hi, I'm Jorge, I'm a cartoonist and the creator of Ph.D. Comments. Hi, I'm Daniel. I'm a particle physicist, and I have not yet destroyed the world.

And welcome to our new true physics crime podcast. Daniel and Jorge uncover mysteries of the universe and explain them. in which we hunt down those responsible for the missing particles. That's right. And it's always the last person you expect. Or the last force, the last fundamental force you expect. That's right. It was the butler in the library with the strong force. It was the butler with a particle collider using the strong force.

But welcome to our podcast in which we explore everything that's amazing about the universe from space physics to particle physics. and basically everything in between, including comics. That's right. Welcome to Daniel and Jorge Explain the Universe, a production of iHeart Radio. That includes apparently even comics. I guess comics are part of the universe. Comics are made of particles, just like everything else.

Oh, are they, though? Aren't they more like an idea? Or an art? Is art made out of particles? Art is just a concept in your brain. Your brain is made of particles, so yeah, basically. Is math made out of particles? Okay.

That's a deep question. Let's put our philosophy degrees to you. here, Daniel and Jorge expound ignantly on philosophy. Daniel and Jorge get derailed in the first few minutes of every podcast. Daniel and Jorge can't get to the topic of explaining the universe

within 10 minutes. Well, let's get into it. So today's podcast we'll be talking about a big mystery in physics. Apparently, one of the biggest mysteries in particle physics for a long time. You guys were wondering about this for a while, it seems. Yeah, we're always looking for mysteries in particle physics,

and a lot of people in our field are focused on the heavy particles, the new, the big, the fat stuff, the Higgs boson, the top cork, the kind of stuff you need a lot of energy to make in particle colliders. But there are also a lot of really interesting, fascinating puzzles about the tiniest, the lightest, the weirdest little particles out there. Right, yeah. I'm not on a diet. I just need to decay some heavy particles in my body.

That's right. So this week we are cutting back on the rich diet of heavy particles we've been feeding you and we will be sprinkling you some salad of light particles. So this was a mystery for a long time that you guys couldn't figure out, right? And it's a huge mystery. It's like a 16illion of these particles are missing every second.

Yeah, I had to look that up, sextillion. That's 10 to the 20. And so... 10 to the 20. 10 to the 20. It's a big number. It's a hard number to even wrap your head around. But that's the number of neutrinos

that hit the earth every second. So then the podcast will be tackling the topic. The mystery of the missing neutrinos. And this is a classic story in experimental physics when people thought they understood something, basically how many neutrinos the sun makes and how many we should see here on Earth. And then they went out to measure it.

And they didn't get the answer they expected. And so that was a big puzzle for a long time. Right. I mean, you guys basically deal with mysteries, right? Like when things go missing, that's when you guys get excited. Well, I like to think that most of science is like a detective story. You're trying to put the pieces together. You're looking for the evidence.

You see if it fits. Sometimes you think maybe somebody's lied to you and you have to try to understand, did you miss here? Is the evidence wrong? Do you need to remeasure? So a lot of science is sort of like trying to unravel a detective story. That's what's fun about it for me. Now, do you guys see yourselves more like, you know, Humphrey Bogart type of detectives

or more like a Jim Carrey, Ace Ventura type of detectives? More like the Woody Allen. You know, not really understanding, worrying about imposter syndrome, you know, trying to pretend to fit in. You think of yourself as Humphrey Bogart, but you dress like Ace Jim Carrey, but you look like Woody Allen. Is that kind of what I'm getting for me? And I get paid like none of them. You get paid.

No, but you're right. We are detectives of the universe. we are trying to understand the story of the universe, how this whole thing came together, how the whole thing fits together, does it make sense? And you know, remember that science is of the people,

by the people, and for the people. And so the things we work on are the things that get us interested so that we can tell a story, so that we can try to find an interesting mystery to unravel so that we can tell the story of the universe.

And so sometimes things go missing in this universe, right? Like you think that there's something or you, according to your math or your theories, you think that there should be something there or you should see a lot of something, but you don't. And so that kind of throws everything into question. Yeah, and it's sort of good news and bad news.

And we do this a lot in science. We say, well, we predict that if we make some measurement, we know what we'll see. Like if you say, let's go count the number of red stars versus white stars. We think we know the answer. Let's just go check. And usually it's a totally on.

You get the answer you expected. You move on. But sometimes you don't get the answer you expected. And that's either an amazing opportunity to learn something new about the universe or a huge headache. Yeah. And so the mystery that we're talking about here today is that you guys were expecting there to be a lot of neutrinos somewhere, but they're not there. You're missing. Yeah, exactly. We know the sun makes a huge number of neutrinos in its fusion furnace. And a guy went out to measure these things and they're really hard to spot. And he saw a lot of neutrinos,

but not nearly the number he expected. There was an enormous number of neutrinos missing. And so that was a mystery for a long time. Yeah, like you had some physics and some math about the sun that it should be spewing out a ton of neutrinos, but where are they? That was the mystery. That was the mystery.

And so I was wondering, are people aware of this mystery? Do people know how this works? And, you know, here at UC Irvine, we have a special relationship with a neutrino. Do you know why? I do, because I'm an avid listener of Daniel and Jorge explained the universe.

But for those of you who are, and maybe you should explain. Well, the guy who discovered the neutrino, Fred Rhinis, was a professor at UC Irvine, and he won the Nobel Prize in 1995. Yeah, and the building you work in, Daniel, is called after this. Yeah, it's called Rines Hall. And it's a bust of the guy in the lobby. And, you know, there's a huge picture of his experiment on the wall. And so I figured, well, most folks at UC Irvine must be aware. It's not like we're winning physics Nobel Prizes every week around here.

And so I You got one You should expect people to know Yeah, exactly And so I thought people should know about this Probably everybody around here knows all about neutrinos So I walked around campus to ask people

If they knew what a neutrino was And if they knew about the mystery The missing neutrinos Yeah, so before you listen to these answers Think about it for a second If someone asked you what a neutrino is And whether you knew That a lot of them are missing apparently

Think about what you would answer Here's what people had to say. Do you know what a neutrino is? No. No, I have not. Do you know they were discovered by a professor here at UC Irvine? No, I didn't. Wouldn't know about it?

No, I had never heard of it. Yeah, neutrino, yeah, I heard about it. I read about it. I mean, I read something about that in a physics building, a lecture hall. But I can't remember. I read that someone discovered it from here as an anti-nutrino or something. I have not. I've heard of it. I don't know what it is. I've heard of it. I don't know the specifics of what it is. I have. Do you know whether neutrinos can turn into other kinds of

neutrinos? No, I don't. All right, Daniel. It sounds like you need to do a lot more branding work there at the university. I got to say I was a little disappointed. I mean, I love the fact that these students are willing to answer a question, that they're game for it. Total respect for that. But almost nobody had even heard of a neutrino. There was one guy who was like, something in the physics building maybe I think I read about it somewhere it sounds like he was waiting for the bathroom and killing time by reading a poster or something

oh that's what you should do you should go around campus putting little like bumper stickers on the inside of bathroom stalls that's where people do the most reading probably if they look up from their phone nowadays which is kind of gross if you think about it but let's not think about that yeah so if you're listening to this podcast in a bathroom stall

you know hey think about neutrinos instead. But hey, actually, you're listening to this podcast about neutrinos, so you're doing both at the same time. But yeah, maybe it would help if you change the name of your building to the neutrino, something like that, you know? Yeah, perhaps. Perhaps. Anyway, I apologize to Fred Rines and the Fred Rhinis family because all the students walk around campus have no idea about this incredible discovery made by a physicist here on campus. But that's okay. We are going to educate everybody today about the amazing particle that is the neutrino and the mystery of why they went missing. And don't feel too bad. I didn't, I don't think I knew what a neutrino

was until, you know, I started talking to you a couple of years ago. So it's not an essential part of your diet, I guess. No, you can mostly get on with your life without knowing when neutrino is. That's true. But you are sort of bombarded by them a lot. Yeah, they're everywhere around you. There are 100 billion neutrinos pass through every square centimeter of the earth per second. So you hold out your fingernail, that's like, the size of your thumbnail. It's $100 billion per second. Wow. That's a lot of neutrinos in my thumb. It is a lot of neutrinos and they're all pumped out from the fusion in the sun. Like the sun, when it does all that fusion, it combines all those elements to make heavier and heavier elements. It pumps out a lot of energy. A lot of that is in terms of photons, but also neutrinos because this is fusion reaction. So a lot of neutrinos are produced. Yeah. All right. So let's get down into the details of it. So let's talk about what a neutrino even is.

before and then we'll talk about why people thought they were missing so many of them were missing so daniel what what is a neutrino how would you describe what it is it's a really weird little particle because it's an essential part of our sort of periodic table of particles but it's not part of the atom like to make an atom you need quarks to make protons and neutrons and then you need an electron to go around it to balance it then there's this neutrino particle what is it for we don't really know why it exists we found it we see that it's there it sort of bounces things out a little bit but it's not part of the atom like you are not made of neutrinos you aren't there are no neutrinos in you so it's something that can exist right basically and does exist a lot

in the in the universe but it doesn't really interact with anything that we're made out of right like it doesn't um you can't really feel them that's right neutrinos are very snobby and so you remember that there are several ways for particles to interact. They can interact via electromagnetism, that's light, and they can interact via the strong force. That's gluons that holds the nucleus together. And then there's this other force, the weak nuclear force, which is really, really weak.

That's the only force that neutrinos feel. Right. And it's both really weak and only really works if you're really, really close to it, right? Like if your neutrino just happens to pass very, very near the nuclear of your atoms, then it might react with you. Yeah, and you can think of the weak nuclear force is sort of like another version of electromagnetism,

but with a really heavy photon. Like the photon, the real one, the one that makes up light has no mass. It flies across the universe. It can go forever, right? You shine a flashlight from here. Your photons can still be traveling billions and billions of miles away. But the weak nuclear force is like a version of that with a really heavy, slow photon. And so it's really weak. I don't think I've ever heard of that term before, Daniel. A heavy photon. Yeah. It's like, a heavy photon. And in fact, the weak forces... Like you can have heavy light. Yeah.

I feel like that would be a great science fiction novel title. Heavy light. Somebody out there copyright that for us. Yeah, it's like slow heavy light. And so it's weak and it's very short range. And so as you were saying, a neutrino can pass through an enormous amount of matter without interacting. Like if it passes through a light year of lead that has a 50% chance of interacting. Like you send 100 neutrinos through a light year of lead, you get about 50 of them coming out the other side, not even noticing.

Right. It doesn't feel the electromagnetic force, which is what you would sort of need to feel in order to push my particles or even for me to really sort of feel them in the traditional sense of the word of feeling or touching something. That's right. If you shoot an electron at a light year of lead, it'll bounce off the surface of it or get absorbed because it will interact with the other electrons or it'll interact with the atomic nucleus. and if you shoot a proton at a piece of lead it'll interact with the atomic nucleus via the strong force but the neutrino doesn't feel the strong force and it doesn't feel electromagnetism too so the two strongest ways particles can interact the neutrino doesn't feel at all

it's like a little ghost particle flying through the universe and it's both a ghost and apparently a multifaceted ghost yeah it comes in three flavors fruity ghosts and chocolate ghost and cookie cromel ghosts No, they're all diet flavors, right? Remember, this thing has no mass, right?

It's heavy. It's heavy, like, there's romaine, there's iceberg, and there's alfalfa flavored. Calorie-wise, it's the lettuce of particles. Yes, it's the lettuce of particles. Yeah, it's interesting because we have, we talked on the program once about how there's different kinds of electrons. It's the electron, the one you know and love that's part of you that makes up electricity. And then it has these cousins, the muon and the tau. So together, there's three.

particles, we call them leptons, the electron, muon, and tau. The weird thing is, the neutrinos also have three versions. The electron neutrino, the muon neutrino, and the tau neutrino. So there's three kinds of neutrinos, just like there's three kinds of electrons. Now, why are they tied to the electron and the muon and the tau? Couldn't just call them, you know, remain neutrino, iceberg neutrino. You know, I was at the meeting, and I totally suggested that, and I was shot down, you know, they were like, you're just a lobbyist for big salad. And, hey, I am a lobbyist for a big salad. I'm a big pro-salid person.

All right. But, yeah, why are they sort of tied? Why do we associate them with electrons? That's really fascinating because it turns out that each neutrino is a different kind. And if you take a neutrino, we call an electron neutrino and you interact with it using this slow photon, the W boson, then it can turn into an electron. But a muon neutrino can only turn into a muon. And a tau neutrino can only turn into a tau. And so these two talk to each other.

They're like paired. Like the electron and the electron neutrino come together somehow. They're like part of a grouping. You know, we're always looking in particle physics for patterns and organizations. And it turns out that these two are related. And the muon and the muon neutrino are related. In the town, the town neutrino related, there's something about the universe that requires them to be connected. Right.

And you're associating them with electrons because they can sort of turn into electrons or they sort of come from electrons. something, there's something that ties them together as opposed to like tying them to like quarks or something. Yeah, precisely. You can use a W boson to turn an electron neutron to turn an electron, but you can't turn it into a muon neutrino. And there's something really weird about this, like the universe keeps count. For example, you can't turn a muon into an electron. The universe like has a count, like the number of muons in the universe, the number of electrons in the universe. And you can't just like take one from here and put it in the other column. The universe doesn't let you do that. You can't makes a match.

You can't mix a match. Like, you might imagine, hey, take a muon and turn it into an electron and a photon, get rid of that extra mass. There's nothing physically wrong with that. We have no reason why that doesn't happen. We just don't see it, right? We've never seen that happen. And so for some reason, the universe likes to keep the same number of electrons and muons.

They just can't turn into each other. And we thought for a long time that the same was true of neutrinos, that if you had an electron neutrino, it had to be an electron neutrino forever. You couldn't just turn it. into a muon neutrino. We thought the same rule that applied to electrons also applied to neutrinos.

Oh, I see. Because electrons can't mix and match, you thought neutrinos couldn't mix a match between these three different kinds that it can take the form of. Yeah, that's what we're doing all the time in physics. We're saying, here's a rule.

How broadly does that rule apply? Right. This rule seems to apply to electrons, muis, and tau's for reasons we don't understand. Like, we have no understanding for why you can't turn, a muon into an electron or photon.

We just don't see it. It's a description of what we haven't seen, not like a deep understanding of the universe. Maybe someday somebody will come up with an explanation, like, oh, it makes perfect sense because these things are built out of different little, you know, sub-muons or something. I don't know.

So we see that happening for electron and muis and tals, and we thought maybe the same thing applied. Right. All right. So that's the neutrino. It's this kind of snobby particle that Cam doesn't want to bother with us, apparently. It doesn't really like us, apparently.

And so it's kind of, it's there in the universe, floating all around us, but it doesn't really interact with us. And I think if you want to learn more, we have an episode on the neutrino, right? If you kind of scroll through our archives, you'll find the neutrino episode, just on the neutrino. Yeah, sometime late last year, we put out a whole episode on the neutrino

and how it was discovered and what it means and how it interacts and gory details about neutrinos. Right. All right. So let's get into how you guys lost a six-dillion of them per second in this universe. It was before my time. So I don't know why you're putting a blame on me. That's right. We'll lay out the clues and the hints and the spoilers of this mystery. But first, let's take a quick break. at airport. The holiday rush, parents hauling luggage, kids gripping their new Christmas toys.

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Oh, that's the run right. I'm looking at this thing. Listen to no such thing on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. A foot washed up, a shirt. shoe with some bones in it. They had no idea who it was. Most everything was burned up pretty good from the fire that not a whole lot was salvageable. These are the coldest of cold cases, but everything is about to change. Every case that is a cold case that has DNA right now in

a backlog will be identified in our lifetime. A small lab in Texas is cracking the code on DNA. Using new scientific tools, they're finding clues in evidence so tiny you might just miss it. He never thought he was going to get caught. And I just looked at my computer screen. I was just like, ah, gotcha. On America's Crime Lab, we'll learn about victims and survivors, and you'll meet the team behind the scenes at Othrum, the Houston Lab that takes on the most hopeless cases to finally solve the unsolvable. Listen to America's Crime Lab on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. All right, so we're surrounded by neutrinos,

and they're all around those, but they can't touch it. But at some point, you guys, physicists, you guys lost a lot of them. Like, you didn't know where they were. I know. I had them in my hand, and then I put my keys down, and I turned around, and, you know, they were gone. Like, doesn't that happen to you? I mean, it's totally reasonable, right? Did you guys try posting an ad in the back of, like, milk cartons or something?

Yeah, we just drew a blank box. Have you seen these neutrinos? Have you seen this? Actually, you can't see them. Have you detected any with some heavy water by any chance? Well, it's funny because, you know, we are surrounded by neutrinos, but they're not just sitting around. It's not like we're swimming through them. We're not like in a pool of neutrinos.

It's more like we're in a wind of neutrinos. Oh, I see. They're going through us. You know, they're not even stopping. They're not even hanging out. Yeah, they're produced by the sun, and they shot out. at great energies something like 3% of the energy of the sun is pumped out just in terms of neutrinos so that's a lot of energy right the sun is a big a plob it produces a lot of energy

and these are shot out from the sun and you know neutrinos are very light the way almost nothing and so they're traveling at nearly the speed of light probably like looking at the sun even 3% is enough to blind you you know yeah if neutrinos could interact with your eyeballs they would blind you so So one more reason to not be like President Trump and look at the sun. Especially on an eclipse. Okay, so you guys calculated that the sun should be making a lot of neutrinos,

100 billion per square centimeter per second on Earth. But we didn't see that. Like that's how much your model of the sun predicted should be pumping out of the sun, how many neutrinos should be pumping out of the sun, but you're saying that the mystery was that we didn't see any neutrality. neutrinos like that here in Earth.

Yeah, and this started from like, do we understand the sun? Like, we think we understand what's going on. There's all these different elements in there. They're fusing. The fusion process produces this and that and heat and neutrinos. So if we understand the sun, we should be able to check those calculations. We should be able to run a calculation that says how many neutrinos does the sun produce per second and then go out and measure it.

And this is not because people were interested in like the deep particle physics of neutrinos. People thought, oh, yeah, we understand neutrinos. they just wanted to understand the sun and so they predicted how many neutrinos the sun should produce it was 100 billion per square centimeter per second and then a guy named something like looking at the chemistry of it right

like you know that it's fusing hydrogen and so you know what comes out of that fusion should have these percentages of stuff coming out yeah and there's different mixtures and each element produces neutrinos of different energies and all this stuff and so put that all

together it's called the standard solar model. That's a model for like what's cooking in the sun and what it's pumping out. A guy named John Bacall calculated that. He had his model of the sun and he predicted a hundred billion per square centimeter per second. And then his colleague Ray Davis said, well, I'm going to go check. And so he built an experiment to go see neutrinos and try to measure these things and calculate how many neutrinos were actually flying into the earth. And he found, what, a bloody knife or crime scene? He has this crazy experiment which involved. a hundred thousand gallons of dry cleaning fluid.

And, you know, when they're a physicist, you have to sort of make do. Like, there's the experiment you wish you could do. And then there's the experiment you can afford to do. And usually what you can afford to do relies on what's commercially available cheap. And, you know, Americans use a lot of dry cleaning fluid. So it's not that expensive to buy a hot, it's not that expensive to buy a big volume of dry cleaning fluid, which contains a lot of chlorine. Oh, the chlorine was important. Yes, because when an electron neutrino hits a chlorine atom, it turns it into argon.

This is like alchemy, right? There's a neutron inside the chlorine nucleus, and when the neutrino hits it, it turns it into a proton and an electron. The proton stays behind, so the chlorine turns into argon. So if you have a huge vat of this dry cleaning fluid, then very occasionally one chlorine atom will get turned into argon. Wait, so 100,000 gallons of dry cleaning fluid. was not his first choice. He had in mind something even crazier. Oh, man, it's super toxic.

You want to imagine working with that stuff? He probably killed off a bunch of grad students in that experiment. Oh, geez. But they, you know, the bodies were dissolved, so it was an evidence. Yeah, and the living ones never had children, so. What do you mean, dry, clean, fluid? Is it like chlorophyll, whatever? What am I, what chemical I do you think about here?

Yes, it's chlorophyll, exactly. No, it's a pyrochloro-florocarbano. No, I'm not sure exactly what it was, but it's some hydrocarbon that has a lot of chlorine in it, and it's used typically in commercial applications for dry cleaning. But he just had this enormous vat of it, 100,000. And remember that neutrinos, there's a lot of them, but each one is a very small chance of interacting. So the bigger your volume, the more likelihood you are to get one of these, chlorine atoms to turn into argon so he was just looking at a handful of things a year of these events yeah

it's not like you know you turn this thing on and you got chlorine popping into argon every two seconds you know it's more like once a month maybe if you're lucky it's kind of like laying out a giant net right that's what these this giant vat was right which is like a like a catcher's mid for neutrinos yeah because neutrinos don't really interact with the walls or the you know the the ground of the earth or the the clouds or the atmosphere, but they do interact kind of with chlorine atoms in a way that you can observe. Yeah, they interact with all that other stuff too, but just really rarely. In chlorine atoms, you can get a really pure sample that has almost no argon in it. And the only way to turn chlorine into argon basically is to hit it with a neutrino.

So any argon in there, you can mostly assume came from neutrinos. So that's why he chose that substance. And then he could bubble it out every once in a while and see if he found argon in there. And how do you think he sourced that 100,000 gallons of dry clean? I think he had a front probably. He just called the local fashion cleaners and we're like, hey, can you do this tomorrow? No, he probably just drove around to the dumpster behind the local dry cleaners and just used theirs, you know? All right.

So that's how you measure. He measured. He put out a giant vat of it, try to catch them. And he didn't see enough, he didn't catch enough to kind of justify the model of the sun that we had. Yeah, John McCall's calculation predicted 100 billion percent. square centimeters per second and he did his calculation and integrated it all and he got about a third of that value so he was so two thirds of the neutrinos were missing like an enormous number 66 billion per square centimeter per second were just gone just missing just uh not there just not there and so

he went back to his friend and said did you check your calculations are you sure the sun is pumping all those numbers out you know were they friends were they yeah they were friends they were you know this is a scientific collaboration, and they both ended up with Nobel Prizes, so everybody's happy. But he went back to check his numbers, and, you know, with the sun, there are things you can observe. The solar model predicts also light and other things. And so there's a lot of ways to check that his model of the sun was right. And he went back, and he double-checked everything, and he was like, you know, I'm pretty

sure my model of the sun is correct. And we had a pretty solid understanding of solar physics and astrophysics at the time. So the question was then, like, did you, did you take that? Did you make a mistake in your... How many grad students did you dissolve in this dry cleaning fluid? Yeah. Did you use used dry cleaning fluid or brand new dry cleaning fluid, you know? Well, that's why it's sometimes an amazing opportunity, but also sometimes a headache.

Like, sometimes the explanation is prosaic. You know, like, oops, you jiggled the cable and it wasn't connected correctly, and that's the source of every problem. Remember that neutrino experiment that thought they discovered neutrino is going faster than light? And then the answer was, they didn't jiggle the cable correctly. So often the mistake is just that it's simple, it's a calculation or some other small bug. But sometimes it's a big clue that gives you insight into how the universe works. And what do you think that moment was like? Like, you know, like if you expect to see, you know, if you expect your three kids to come home one day and when only one of them comes home, you know, that's a big.

Well, it depends on which kid, I guess. Not your favorite one. No, I think it must have been exciting. I think probably at first it was frustrating. Oh, man, something's wrong. You know, but we are detectives in the end. We like to unravel this stuff. We like to think about ways to double-check your answers

and let's check this and let's check that and let's check this other thing. And everybody double-checked it. And then other people did experiments, you know, not just this one guy with his vat of fluid. Other people did experiments with other substances and everybody agreed. We were seeing about one-third of the neutrinos

that we expected to see. So somewhere between the sun that you know is spewing out all of these neutrinos and your vat of dry cleaning fluid, two-thirds of those neutrinos go missing. Disappear. Exactly. They have no alibi.

All right. So that was a big mystery in physics. And it was a big deal, right? Because it sort of, you know, there's a lot in this theory, in this prediction, right? There's your understanding of the sun. There's your understanding of particles. There's your understanding of how particles interact with other particles.

And so, like, if this is not jiving, then that's kind of a big deal. Yeah, and it was an outstanding mystery for decades. It was like, here's something we don't understand. Maybe someday somebody will figure it out. For decades, really? For decades, yeah. David started his experiments in the 60s. And so this is something which was an outstanding problem in physics for a while.

And, you know, we have those problems today. We have, like, the list of things we don't understand. and like, what is dark matter? Eventually, that'll be a history problem. We'll know the answer. We'll look back. But at the time, it's just a question mark. And so this was an open question for a long time.

I feel like it's one of those primetime specials, you know. Years later, the mystery still bothers him. I wish sometimes we could just like fast forward, do a musical montage. Like a musical montage my way to the answer, what is dark matter? She has some physicists hitting the boxing, what do you call the boxing ball? putting on a lab coat, standing at the chalkboard, looking confused, having a moment of inspiration, you know, running to the streets. Running up to Philadelphia courthouse deaths. Exactly. Lowell, please provide the sound music for that musical montage.

But, yeah, and then finally the mystery was solved, right? Finally, you guys figured it out. They found the missing neutrinos. We did find the missing neutrinos. All right, let's get into how they found these missing neutrinos. But first, let's take another quick break. December 29th, 1975, LaGuardia Airport. The holiday rush, parents hauling luggage, kids gripping their new Christmas toys. Then, at 6.33 p.m., everything changed.

There's been a bombing at the TWA. terminal. Apparently, the explosion actually impelled metal glass. The injured were being loaded into ambulances, just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged, and it was here to stay. Terrorism. Law and order, criminal justice system is back. In season two, we're turning our focus to a threat that hides in plain sight. That's harder to predict and even harder to sort. Listen to the new season of Law and Order Criminal Justice System on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. 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 this. they could land the plane with the help of air traffic control. And they're saying like, okay, pull this, until this. Do this. Pull that. Turn this. It's just... I can do my eyes close. I'm Mani. I'm Noah. This is Devin. 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. Listen to no such thing on the Iheart radio app,

Apple Podcasts, or wherever you get your podcasts. Your entire identity has been fabricated. Your beloved brother goes missing without a trace. You discover the depths of your mother's illness the way it has echoed and reverberated throughout your life, impacting your very legacy. Hi, I'm Danny Shapiro. And these are just a few of the profound and powerful stories

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

Listen to Family Secrets Season 12 on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. All right, Daniel, so how did they find the missing sextillion neutrinos per second that were somehow misplaced by physicists? Well, they had this idea. They thought, well, maybe the interiors. neutrinos aren't missing. Maybe they're just hiding. And maybe they're hiding because they turned into other types of neutrinos. And we talked earlier about how there's three kinds of neutrinos, electrons, muons, and tau's. And they thought, well, what if some of these are turning into muon neutrinos or some of these are turning into tau neutrinos?

Oh, my God. They fake their death. That is such a standard soap opera plot point. Should have been the first thing we thought of, right? Did you look for neutrino with a weird mustache on it? check to see if they had any large outstanding debts or something? Yeah, well, we thought, remember, well, we're sure that electrons and muons can't turn into each other. We know that doesn't happen. We don't know why, but we've never seen

it happen. Dedicated experiments looking for that, haven't seen it. But people thought, you know, we could explain this mystery if electron neutrinos were turning into muons and tauz. Wouldn't another kind of neutrino interact with the chlorine also? Like, how does that explain? No, it wouldn't. So a muon neutrino is, that comes and hits the chlorine doesn't turn it into argon. Oh, does it do something different or it just doesn't interact with the chlorine? It doesn't interact with the chlorine in a way that turns into argon. So you can't measure muon neutrinos or tau neutrinos by looking at chlorine.

And so what people did was they built another experiment, one that was sensitive to muons and one that was sensitive to tau neutrinos. So there's this experiment called the Snow Experiment. It was at Sudbury Neutrino Observatory and it could detect separately the rates of electron, muon, and town neutrinos. And then they found them. And then they found them. They're like, oh, there they are. We saw them.

These neutrinos. So you use your credit card. You're still alive. Precisely, they were able to spot them. And so those neutrinos are there. They're just a different flavor. So there's a bunch of neutrinos coming from the sun. Some of them turn into different kinds of neutrinos, and then they go through us and the earth.

And you're saying that they were only missing because we weren't looking for the right kind of neutrino. Precisely. And it's important to understand the sun only makes electron neutrinos. There's three different kinds, but the sun just makes electrons. It's like a pure source of electron neutrinos because you have electrons in fusion, right? Electrons are the lightest ones, and so electrons are the thing that's in the atom. And so electron neutrinos are what's made in the sun.

So the sun produces all these electron neutrinos, but then there's three kinds. And so by the time they get here, they sort of slosh around and some of them become muons and some of them become tau neutrinos. Right. And they do this randomly? Or is it like a, they're decaying from like an energy, high energy state to a lower energy state? Or is it just kind of random? Like, hey, today I want to, I feel like more like a tau.

Is that how you get dressed every day? Just sort of randomly? Quantum mechanical wardrobe. Today I feel like a working cartoon is. Tomorrow I don't know if I'll feel. You just invented quantum fashion, Jorge. Yeah. No, it's not entirely random.

There's some random. element to it, but it's actually really fascinating and reveals something really deep about neutrinos. You see, the weak force, the thing that can interact with neutrinos, it sees neutrinos differently than the Higgs boson does. So those W bosons and the Higgs bosons are sort of disagreeing about how to talk to the neutrinos. Wait, what do you mean? Yeah, well. Say that, say that again. So the weak force says, okay, there's three kinds of neutrinos. There's electron neutrinos, muon neutrinos, and town neutrinos. And like I said earlier, the difference between those is that the weak force can turn an electron neutrino into an electron or a muon neutrino into a muon.

That's how the weak force sees neutrinos. But the Higgs boson comes along and it says, no, no, no, there's three neutrinos. There's numbers one, two, and three. The lightest one, the medium one, and the heaviest one. And you're like, okay, that's cool. Which one is which? But it turns out they don't overlap. It's not like neutrino number one is the electron neutrino.

And two is the muon neutrino. The Higgs boson, when it says electron number one, it means a weird mixture of electron muon and tau. And the Higgs boson neutrino number two is a different mixture of electron muon and tau. So it's like these things look at it totally differently. They see a different mixture. Are they still different things?

Or does it depend on who's interacting with them? It depends on who's interacting with it. So if you're just flying through space, what you need is to have a certain mass. Like for a particle to fly through space, you need to be a thing. You need to have a fixed mass. Your mass can be zero or whatever, like for a photon, but for any particle to propagate through space, it needs to have its mass specified.

Remember, that's how you get mass is by moving through the Higgs field. So the sun makes you using the weak interaction, you're an electron neutrino. You're flying through space. You have mass because of the Higgs boson. And then you're either electron one, two, or three, right? But the electron neutrino is a weird mixture of one, two, and three. So as it's flying through space, these things. fly through space differently. The electron one, electron two, electron three parts of the electron

neutrino fly through space differently. So by the time they get to Earth, you have a different mixture of electron one, two, and three, and maybe you're a muon neutrino, or maybe you're a town neutrino. Wow. That makes no sense, Daniel. So I start off as one kind of neutrino, and you're saying that on the way, the universe just kind of like looks at me differently. And by the time I get to my destination and two different things. Say your family goes on a trip together and one of you is thirsty and one of you is hungry and one of you is totally satisfied. Now, along the way, maybe you get some food and drink.

So by the time you get to your location, the different people in your family are feeling different than when they left because the trip has been a different experience for each of you. So by the time you get there, it's kind of like you're a different family. But that's because time has passed and maybe I got thirstier or hungrier or I drank some water on the way. Is there something actually happening on the way for these neutrinos? Or is it just kind of like the universe sort of corrects itself? The different parts of the electron neutrino fly through space differently because they have different masses. The electron neutrino doesn't

actually have like a mass. You can say what the mass of the electron is, but the electron neutrino doesn't have a mass. It's a weird mixture of three neutrinos that do have masses. So there's a different categorization? Like a different set of names based on the Higgs. Yes, there's different ways to categorize neutrinos, and the Higgs boson categorizes them one way, and the weak force categorizes them differently. They don't agree. And the Higgs force decides how you get mass, and so it says, you get this mass, you get that mass, you get this other mass, and the weak force decides what particle you turn into, like you turn into electron, you turn into muon, you turn into a tau. And because they don't agree, you get these really weird

behaviors. But then what comes out what arise here on Earth is actually two different. Is it still the same electron neutrino? Or is it now something that's been changed because of the what happens when you go through the actual universe? It's something that's

been changed. And so electron neutrino starts out with some mixture of neutrino one, two, and three. And then those fly through space differently because they have different masses. And by the time it gets here, it's a different mixture. And that different mixture can be more likely to be a muon neutrino. So then when it gets to Earth, it can be like, oh, you know what?

Now I'm a muon neutrino. But when it interacts with like argon, then it does care whether it's precisely. Then it does care. And so when the, like it cares at the beginning at the end, but somewhere in the middle, the universe is like, no, no, no, no. I don't like what you're starting out with. I'm going to change up your identity. Yeah, it's like it spins all the knobs in flight. And then when you get here, you're like, huh? You're totally different. You know, it's like if everybody got on an airplane. And then in flight, you, like, swapped heads and legs of all the passengers, right? And then when you got the other side of the flight, you'd be like, wow, I don't recognize anybody.

That is both disturbing and also confusing. Is it more like kind of like, you know, like shooting light through a prism or something? Like somehow going through the medium separates out the nature of it. Yeah, it's a lot like that. And for those people who are like really good with linear algebra, it's essentially what you're doing is you're rotating the basis set. You have a different eigenvectors that describe the sort of space of particles and the Higgs boson uses one set of eigenvectors and the weak force uses a different set

and they don't agree so you can rotate from one to the other. And why is there such a discrepancy between what the universe sees or thinks and what the math and the physics and the collisions all predict? We don't know. We don't know why the weak force and the Higgs boson sees. these things differently. It's fascinating. We just don't know why they don't agree. They're very different forces, right? And so they, I guess they have the right to make whatever choice they like, but we don't know. We don't know why they're rotated in this way, like why neutrinos

one, two, and three are not aligned with the electron muon and tau neutrinos. Because it's not the case for the other particles. Like the e-mue and tau, the weak force interacts with them the same way the Higgs boson does. Like the electron has a specific mass. The muon has a specific mass. And so does the tau. So it's a weird twist that only happens for neutrinos. It's like in the murder mystery, it's like, no, actually it turned out nobody killed Mr. Green. Actually, he turned into Mrs. Plum. Turns out Mr. Green has two identical twins.

He's a member of an identical triplets and they all speak weird accents. And due to some magical or unexplainable quantum phenomenon of the universe, that's what happened. Yeah, and it's not something we understand. And we actually don't even understand how the neutrinos talk to the Higgs boson. Like most particles get their mass from the Higgs boson, but we don't actually know the neutrinos do. Because to get your mass from the Higgs boson, you have to have a particle and an antiparticle, like the electron and the anti-electron. But we don't know if neutrinos have antiparticles or if they are their own antiparticles the way a photon is. So there's a lot of mysteries about neutrinos.

I feel like we started out with such a simple mystery, where are they? And we've turned out, like, it turned into a fundamental mystery of the universe that we don't know. Precisely. And that's what's amazing about these experimental checks, you know. They go out to like, yeah, we think we understand this. Let's just go double check. Huh, didn't work. I wonder what that means.

Dot, dot, dot, crack open deep mystery of the universe, right? That's the possibility every time you're about to do a boring experiment, is that it could be the thread that unravels your entire understanding of something fundamental about the universe. And you wouldn't maybe think that was the case just because these particles are, are so inconsequential to our everyday lives, right? So non-interactive with everything else, but it turns out that maybe cracking them open would tell us a lot about the universe.

Yeah, there are a lot of them, and they ignore us, but they have a lot of tiny little clues. And when you add them all up, they tell you something really fascinating about how the universe works. And there's a lot of mysteries there we still don't know the answer to. There might be CP violation in neutrinos.

Detrinos do all sorts of weird stuff, but they're really challenging to measure because they mostly ignore you. And so you have to build really big detectors and wait a long time just to do anything, basically, with neutrinos. Is this going to drive out the price by dry cleaning, Daniel? Is how I want to know. Let's bring this back to me, right?

Yeah. I have seen sort of a lot of, like a lot of particle physics, I know in your field, is sort of turning towards neutrinos because it is sort of like a place where there are still a lot of big open questions. Yeah, the entire United States high-energy community is turning towards neutrinos, focusing their energy on these questions, because we think that there are a lot of mysteries there that might be open. In fact, there probably are still questions we don't even know how to ask about neutrinos.

It's like the beginning of a field of neutrino physics. So there's a bright future. There's a lot of people working on it, a lot of really fascinating questions. And I think in 10 years we'll know a lot more about the way the whole universe works just from these tiny little ghostly particles. All right. So we figured out the mystery, Daniel. We will take credit. What fraction the Nobel Prize did we get? I don't remember. John Raines with the weak force in the mysterious force in the universe. In the underground lab.

In the unknown, deep mystery of the universe. It was Ray Davis with 100,000 gallons of dry cleaning underground. So the next time you look out into the universe or see, well, not see the sun, but be out in a sunny day and look at the sunlight. all around you, maybe think about all the mysterious little neutrinos that are going through you and everything else. And what secrets of the universe they are hiding? We hope you enjoyed that.

Thanks for joining us. See you next time. If you still have a question after listening to all these explanations, please drop us a line we'd love to hear from you. You can find us at Facebook, Twitter, and Instagram at Daniel and Jorge. word, or email us at

Feedback at danielandhorpe.com. Thanks for listening, and remember that Daniel and Jorge Explain the Universe is a production of iHeartRadio. For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows. Do we really need another podcast? with a condescending finance brof, trying to tell us how to spend our own money.

No, thank you. Instead, check out Brown Ambition. Each week, I, your host, Mandy Money, gives you real talk, real advice with a heavy dose of I feel uses, like on Fridays when I take your questions for the BAQA. Whether you're trying to invest for your future, navigate a toxic workplace, I got you. Listen to Brown Ambition on the IHeart Radio app, Apple Podcast, or wherever you get your podcast. I'm Dr. Scott Barry Kaufman, host of the psychology podcast. Here's a clip from an upcoming conversation about how to be a better you.

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