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Speaker 1: Ity, Daniel, you cook a lot. Are you the kind

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Speaker 1: of person who keeps their kitchen clean? I don't think

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Speaker 1: I'm excessive, you know, clean, but in a normal way.

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Speaker 1: I think usually your definition of normal is different than

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Speaker 1: most normal people. As a picture, they leave the dishes

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Speaker 1: in the sink. What dishes in the sink? This isn't

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Speaker 1: the frat house? I guess that's it. What about the counter?

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Speaker 1: Do you have any of you know, stuff in it?

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Speaker 1: I mean, we have cabinets and drawers. There's no reason

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Speaker 1: to leave stuff on the counter. That's another no, I guess.

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Speaker 1: So I'm getting the sense that you keep a pretty

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Speaker 1: tighty kitchen. I mean we do our best to keep

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Speaker 1: it need and organized right. And your office, how need

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Speaker 1: do you keep that one? I think I focus my

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Speaker 1: energies on the kitchen and not your work. You know,

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Speaker 1: my priorities are the kitchen is sterile and the office

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Speaker 1: is a disaster. I am for him and cartoonists and

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Speaker 1: the co author of frequently asked Questions about the universe. Hi,

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Speaker 1: I'm Daniel. I'm a particle physicist and a professor you

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Speaker 1: see Irvine, And my office is a mess, but I

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Speaker 1: promise you my mind is organized. What is that saying

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Speaker 1: you're a mess in the office but a neat freak

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Speaker 1: in the kitchen. Barack Obama said, physical discipline, mental discipline,

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Speaker 1: and he's pretty good at what he does, so we

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Speaker 1: should all follow his example. I mean, I've never read

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Speaker 1: one of his physics papers, but he does seem like

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Speaker 1: a smart dude. I think he probably funded a lot

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Speaker 1: of your research indirectly, so maybe you should be a

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Speaker 1: little bit more thankful. That's true. He used to be

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Speaker 1: my boss's boss's boss's bosses boss's boss's boss's boss's boss. Yeah,

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Speaker 1: there you go. He used to be a part of

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Speaker 1: the administration practically. I mean you were right there. I

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Speaker 1: mean you weren't in the white House, but you were

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Speaker 1: in the white sun House. That's true, which, because I

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Speaker 1: live in Irvine, is actually beige. But welcome to our podcast.

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Speaker 1: Daniel and Jorge explained the Uni Verse, a production of

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Speaker 1: I Heart Radio, in which we want to defeat all

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Speaker 1: of the levels of the universe. We want to kill

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Speaker 1: the lower minions and we want to work our way

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Speaker 1: up to the boss levels of understanding of the universe.

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Speaker 1: We want to break down all of those barriers. Talk

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Speaker 1: about the deepest hardest, most confusing, trickiest questions about the

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Speaker 1: nature of reality and show you what science does and

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Speaker 1: does not understand about all of it. Yeah, because it

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Speaker 1: is a pretty big universe, a pretty complicated with a

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Speaker 1: kind of a complicated or chart. I guess a lot

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Speaker 1: of middle management levels here in the universe that you

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Speaker 1: have to go through, Daniel in in order to understand it.

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Speaker 1: We are trying to make sense of it, and we're

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Speaker 1: hoping that if we have a complete picture of everything

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Speaker 1: that's out there and how they all talk to each other,

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Speaker 1: that some patterns will emerge, that some sense will be

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Speaker 1: a parent, that we will gain some understanding about how

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Speaker 1: it all makes sense, or maybe the whole thing is

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Speaker 1: just a big mess. What do you think is the

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Speaker 1: universe's management style? Do you think it's pretty flat or

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Speaker 1: is it kind of curved or is it multidimensional. It's

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Speaker 1: definitely not Obama's management style. I mean, he was no

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Speaker 1: drama Obama, but there's a lot of drama in the

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Speaker 1: universe supernovas, that's pretty dramatic. Yeah, there's always those troublemakers

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Speaker 1: in your organization, I guess who like to blow up exactly.

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Speaker 1: But sometimes when things blow up they actually give us

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Speaker 1: clues about how things work. When stars do go supernova,

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Speaker 1: they give us a peek into the inside of those

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Speaker 1: cosmic fusion reactors, so we can understand the crazy, intense

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Speaker 1: forms of matter that are being created at their center.

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Speaker 1: Because there are still a lot of incredible and tantalizing

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Speaker 1: mysteries out there for us to discover. And that's just

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Speaker 1: only on the things that we can see and detect.

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Speaker 1: There's a lot about the universe that is actually hidden.

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Speaker 1: You have these little windows into the universe through your senses.

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Speaker 1: You can see some things, you can feel some things,

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Speaker 1: you can taste a few things. But we know the

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Speaker 1: universe is much richer and more complicated than the things

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Speaker 1: we can detect directly with our senses. And over the years,

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Speaker 1: we have built all sorts of technological eyeballs and ears

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Speaker 1: and noses and tongues to experience the hidden parts of

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Speaker 1: the universe. We can now see ultra violet and infrared.

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Speaker 1: We can detect crazy particles that are invisible to our eyeballs.

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Speaker 1: We know that there's a lot more going on out

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Speaker 1: there than we can see directly. Wait. Wait, you're building

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Speaker 1: like an electronic tongue. Is that what you're saying in

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Speaker 1: a in a physics lab somewhere, or is this part

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Speaker 1: of your kitchen endeavors. Well, the standard analogy is to

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Speaker 1: talk about new technological eyeballs, like we are seeing the universe.

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Speaker 1: I wonder sometimes why we always use the analogy of vision,

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Speaker 1: because you could, in principle, translated to any of our senses.

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Speaker 1: I don't know if people heard recently that the soonification

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Speaker 1: of a black hole where they took like the oscillatory

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Speaker 1: waves and the gas around the black hole and they

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Speaker 1: turned it into sound. All these things are just an

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Speaker 1: attempt to describe something that is unexperienceable into something that

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Speaker 1: you know how to experience. Translate the unfamiliar into the familiar,

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Speaker 1: so you can choose any of our senses, vision, hearing, taste, smell, right,

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Speaker 1: what do electrons smell like? Are you trying to bring

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Speaker 1: back to smell a vision? Are you trying to build

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Speaker 1: the incredibly expensive smell atron. I think it's a whole

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Speaker 1: new frontier for science communication. You know, people are making

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Speaker 1: false color images of the James Webb pictures, people are

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Speaker 1: making soonifications of black holes, but nobody's doing smellification of particles.

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Speaker 1: Until we are today. I think if you made people

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Speaker 1: smell physicists, they might be turned off by signs. So

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Speaker 1: I'm not sure that's the best science communication strategy here. Yeah,

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Speaker 1: I think we want to keep that in the office.

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Speaker 1: But it is a pretty incredible universe because a lot

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Speaker 1: of it is hidden. In fact, we've figured out that

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Speaker 1: of the universe is totally invisible and we have no

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Speaker 1: idea what it is. And stuff being invisible is not

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Speaker 1: that unfamiliar. I mean, you are surrounded by air, but

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Speaker 1: you can't see it, right, it's invisible to your eyes. Now,

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Speaker 1: of course, you can touch it and you can tell

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Speaker 1: that it's there, you can breathe it. But there are

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Speaker 1: other things out there that are not just invisible. They're

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Speaker 1: also intangible particles out there that fly right through your

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Speaker 1: body and fly right through the Earth without even noticing.

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Speaker 1: Does that mean they're also intasteable? Like? What does the

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Speaker 1: neutrino taste like? I don't know, But we do have

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Speaker 1: three flavors of neutrino, even though we have no idea

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Speaker 1: which ones are delicious, So basically we can make up

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Speaker 1: flavors for them, right, one one could be spicy, the

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Speaker 1: other one could be sweet, the other one could be mommy, right.

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Speaker 1: I was hoping you were gonna say, O, mommy neutrinos,

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Speaker 1: because that's the most mysterious flavor. You know, it's the

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Speaker 1: most delicious one, I guess if you're a savory kind

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Speaker 1: of person. But there are a lot of mysterious things

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Speaker 1: out there, some that are we are still trying to

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Speaker 1: figure out, and so let's talk about one of them.

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Speaker 1: So to be on the podcast, we'll be tackling the

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Speaker 1: question what are sterile neutrinos, or for our UK fans,

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Speaker 1: what are sterile neutrinos? They're apparently pronounced differently, although Daniel,

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Speaker 1: you I think you have to pronounce it with the

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Speaker 1: British accent sterile neutrinos. You want the full phrase with

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Speaker 1: with that's kind of like a cockney accident maybe, or

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Speaker 1: I don't know. And it's embarrassing that my UK accent

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Speaker 1: is so bad because I actually am a citizen of

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Speaker 1: the UK and my father grew up in London and

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Speaker 1: my grandmother, who recently passed lived in London for fifty years,

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Speaker 1: so I should be able to do it, but I can't. Yeah,

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Speaker 1: I'm sure you're a big disappointment to Brits. Everywhere other.

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Speaker 1: If you are British, doesn't that mean that any accent

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Speaker 1: you have is a British accent? There you go, Yes,

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Speaker 1: I define Britishness in just existing. Yeah, you're a pretty

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Speaker 1: dear fellow. But this is an interesting question. Sterile neutrinos.

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Speaker 1: Does that mean there are fertile neutrinas. Yeah, I think

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Speaker 1: we're gonna have a lot of fun talking about the

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Speaker 1: meaning of sterile and what physicists intended it to mean

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Speaker 1: and how people interpreted. But no, there are not neutrinos

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Speaker 1: out there that are becoming parents. Or is it more

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Speaker 1: like sterile like clean, like bacteria free? Does that mean

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Speaker 1: there are dirty neutrinos? Dirty fertile neutrinos sort of in

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Speaker 1: the clean sense. These are more neutrinos that are totally

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Speaker 1: isolated from everything else. They don't interact. They're more like

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Speaker 1: standoffish neutrin learn or neutrinos. There you go. See, you

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Speaker 1: should just put me in charge of naming things. Things

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Speaker 1: would go a lot easier example number four seventy seven.

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Speaker 1: But anyways, as usually, we were wondering how many people

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Speaker 1: out there had heard of sterile neutrinos or have any

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Speaker 1: idea about what they could be. So thanks very much

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Speaker 1: to everybody who volunteers to answer these questions for the podcast.

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Speaker 1: We really appreciate it, and everybody out there loves hearing

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Speaker 1: what you think. So if you would like to hear

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Speaker 1: your voice on the podcast for a future episode, please

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Speaker 1: don't be shy. Right to us two questions at Daniel

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Speaker 1: and Horre dot com. So think about it for a second.

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Speaker 1: What do you think a sterile neutrino is? Here's what

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Speaker 1: people have to say sterile neutrinos. I don't know what

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Speaker 1: they are. I feel like a neutrino can turn into

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Speaker 1: a different type of particle, though, so maybe a sterile

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Speaker 1: neutrino cannot for some reason. And so I think that's

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Speaker 1: as a sterile environment is an environment way there is

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Speaker 1: no interaction between sales and bacterias or other um micro organism.

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Speaker 1: I think the right neutrinos don't want to interact with

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Speaker 1: um other particles like they should do. From what I've

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Speaker 1: heard about sterile neutrinos, and like the word itself, um,

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Speaker 1: I think they're just neutrinos that don't really interact with anything,

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Speaker 1: so they're just existing. But I don't really serve much

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Speaker 1: of a purpose sterile little trinos. They are very clear,

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Speaker 1: probably they washed their heads, very awful. Keep social distance well.

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Speaker 1: A neutrino, as far as I know, is um a

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Speaker 1: particle that doesn't interact with anything, so it flies straight

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Speaker 1: through and apparently it's flying through me right now, So

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Speaker 1: that already seems pretty sterile. So I'm not sure how

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Speaker 1: it could get more sterile because it doesn't really interact

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Speaker 1: with matter, and I've not heard of sterile neutrinos. I

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Speaker 1: feel like I have heard that term before. I know

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Speaker 1: neutrinos come in three flavors, but I'm not sure what

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Speaker 1: would make one st or how we would know. I mean,

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Speaker 1: who's checking anyway. Ordinary neutrinos can only interact with other

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Speaker 1: particles by means of the weak interaction. Sterile neutrinos don't

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Speaker 1: interact with other particles at all. I assume that sterile

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Speaker 1: neutrinos are neutrinos that are even more neutral than regular neutrinos,

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Speaker 1: but I have no idea, all right, I am totally

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Speaker 1: with the person here who says that this combination of

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Speaker 1: words doesn't make any sense to me. I think that's

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Speaker 1: a direct message to you, Daniel and to all physicists

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Speaker 1: to maybe take words that make more sense. There are

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Speaker 1: a lot of people who were totally misled by this phrase,

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Speaker 1: but a couple of people actually got it right on

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Speaker 1: the nose. So this pair of words did lead a

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Speaker 1: few people to the right idea. Who got it right

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Speaker 1: The people who said it doesn't make any sense, the

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Speaker 1: people who doubted the ability of physicists to name things accurately. No,

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Speaker 1: it's all about the interactions, right. What can particles do?

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Speaker 1: They can fly through the universe and they can interact,

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Speaker 1: So sterility refers to whether or not they interact with

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Speaker 1: other particles. Well, let's dig into it, and let's start

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Speaker 1: with the basics. First of all, what is an netrino?

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Speaker 1: So neutrino is a really fun, very weird little particle.

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Speaker 1: It's unusual because it's one of the sort of base

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Speaker 1: particles we think of in the universe. There are four

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Speaker 1: of them, the up cork, the down cork, the electron,

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Speaker 1: and then the fourth one is the neutrino. The weird

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Speaker 1: thing is that the neutrino, unlike the other three, does

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Speaker 1: not appear in the atom. It's not technically a sub

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Speaker 1: atomic particle because it's not part of the atom. Take

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Speaker 1: the atom apart has electrons around it, and inside our

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Speaker 1: protons and neutrons. You take those apart, you get up

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Speaker 1: corks and down corks. So to make everything in the universe,

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Speaker 1: you have upcorks, down corks, and electrons. But then there

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Speaker 1: is this other particle out there, the neutrino. It definitely exists.

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Speaker 1: It's created in the heart of the sun during fusion.

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Speaker 1: There's a lot of them out there, but they're not

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Speaker 1: part of the atom, and they're especially weird because they

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Speaker 1: don't have any electric charge and so they don't give

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Speaker 1: off any light, they don't absorb any light. They're essentially invisible. Yeah. Well,

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Speaker 1: I mean, there are a lot of other particles besides

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Speaker 1: the electron and the corks, but this one, is it

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Speaker 1: a different type of particles out there? Is it like

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Speaker 1: a whole different quantum field and it's hold own classification

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Speaker 1: or is it kind of like a cousin of one

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Speaker 1: of the other particles, So it's its own different type

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Speaker 1: of particle at the same level as the upcork, the

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Speaker 1: down cork, and the electron. There are other particles out there,

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Speaker 1: you're right, like the charm cork and the top cork,

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Speaker 1: but those are like reflections of the up cork. And

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Speaker 1: there are muons and towels, but those are reflections of

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Speaker 1: the electron. They're really like four base matter particles, the upcork,

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Speaker 1: the down cork, the electron, and then the new trino,

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Speaker 1: of which there are also three kinds. Now we do

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Speaker 1: group them together, like the two corks we grouped together,

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Speaker 1: and the electron we grouped together with the new trino,

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Speaker 1: because then trino is related to the electron like the electron.

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Speaker 1: It also doesn't feel the strong force, So the neutrino

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Speaker 1: is super weird because it doesn't feel the strong force

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Speaker 1: like corks do. It also doesn't feel electromagnetism like electrons do.

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Speaker 1: The only force that it feels is the weak interaction.

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Speaker 1: So like a neutrino can fly through a magnetic field

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Speaker 1: and not get bent. If you've applied an electric field

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Speaker 1: to a neutrino, it doesn't pull on it. A neutrino

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Speaker 1: can fly through the heart of an atom without interacting

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Speaker 1: with any of the corks and luons inside of it

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Speaker 1: ignores almost all the interactions that make the universe the

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Speaker 1: way that it is. Right, it doesn't feel any charge

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Speaker 1: because I guess the corks feel a positive charge, right,

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Speaker 1: and the electrons feel a negative charge, but the nutrina

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Speaker 1: doesn't feel any charge at all. Right, Yeah, the corks

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Speaker 1: actually do. The corks have really weird charges. The upcork

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Speaker 1: has a charge of plus two thirds it's a fraction,

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Speaker 1: and the down cork has a charge of minus one third.

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Speaker 1: So the upcork is a positive charge to down cork

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Speaker 1: is a negative charge. Really interesting is that their charge

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Speaker 1: difference is one, is exactly one, between two thirds and

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Speaker 1: negative one third. It's the same for the electron and

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Speaker 1: the neutrino. They also have a charge difference of one.

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Speaker 1: In this case, the electron has charged negative one and

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Speaker 1: the neutrino has charged zero. So then trino is the

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Speaker 1: only fundamental matter particle that has no electric charge. And

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Speaker 1: you're pretty sure about that. I guess could it be

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Speaker 1: that it just feels it, but just super weakly or something.

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Speaker 1: That's a super good question. How well do we know it?

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Speaker 1: It's definitely part of the theory that it's exactly zero.

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Speaker 1: How well do we know that experimentally? In the end,

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Speaker 1: we never know anything perfectly well, Right, there's some limit

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Speaker 1: on the charge of the neutrino. It's got to be

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Speaker 1: something super duper duper tiny. Even a very small charge

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Speaker 1: in the neutrino would upset all sorts of things because

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Speaker 1: charge is conserved in the universe. That would mean, for example,

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Speaker 1: if the neutrino had even a little bit of charge,

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Speaker 1: would make it more complicated to keep charge conserved when

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Speaker 1: you produce it together with an electron. For example, like

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Speaker 1: we have a W boson that has charged positive one

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Speaker 1: elects to decay into an electron and a neutrino. But

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Speaker 1: if the neutrino has a little bit of charge, that

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Speaker 1: has to come from somewhere, and that W only has

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Speaker 1: charged one, so it can't create an electron and a

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Speaker 1: neutrino if the neutrino has charged so we're pretty confident

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Speaker 1: has zero charge, but you can never know absolutely for sure.

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Speaker 1: But it does feel the weak force, which is part

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Speaker 1: of the electromagnetic force, but it's kind of not it's

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Speaker 1: like a sister force kind of yeah, it's not part

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Speaker 1: of electromagnetism. It's part of a combined idea called electroweak,

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Speaker 1: which puts electromagnetism and the weak force together into a

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Speaker 1: single concept. It shows that mathematically, they obey some larger symmetries,

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Speaker 1: some rules that tie them together, the same way that

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Speaker 1: we think electricity and magnetism don't make as much sense

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Speaker 1: separate as they do together, because we see that magnetic

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Speaker 1: fields create electric fields and electric fields create magnetic fields.

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Speaker 1: In that same way, it makes more sense to put

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Speaker 1: the weak force together with electromagnetism into one holistic thing

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Speaker 1: called electroweak. Right, and you said neutrinos are matter particles,

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Speaker 1: which means they do actually have mass. Right, They do

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Speaker 1: feel it, right, and they it does take them some

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Speaker 1: time to accelerate. Right. That's a really interesting topic because

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Speaker 1: it's actually one of the few hints we have that

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Speaker 1: the standard model of particle physics is wrong. Neutrinos in

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Speaker 1: our theory are perfectly massless. O. Our theory does not

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Speaker 1: allow for them to have any mass, and yet in

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Speaker 1: our experiments we measure them to have some mass. We

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Speaker 1: know that they do have very tiny little masses, so

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Speaker 1: you're right, they don't travel at the speed of light,

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Speaker 1: but it's not something that we yet understand the masses

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Speaker 1: of neutrinos. Wait, we've measured that they have mass, but

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Speaker 1: in our theory they don't have mass. Don't you have

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Speaker 1: to revise your theory. We do have to revise our theory.

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Speaker 1: We know that the standard model is not correct and

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Speaker 1: we need to somehow modify it to accommodate neutrino masses.

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Speaker 1: But it's pretty tricky, and one way to do that

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Speaker 1: actually is to add a new kind of neutrino called

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Speaker 1: a sterile neutrino, which helps solve the problem, because that's

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Speaker 1: a big question of the day. And just to clarifying,

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Speaker 1: nutrients are not rare in the universe, right There's like

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Speaker 1: a whole bunch of them going through us right now. Yeah,

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Speaker 1: Our Sun is a huge neutrino factory. Fusion produces an

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Speaker 1: enormous number of neutrinos, so many that they carry like

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Speaker 1: one percent of the Sun's energy output in neutrinos. So

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Speaker 1: the Sun isn't just a star that pumps out photons

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Speaker 1: and light. It also pumps out neutrinos. Like you could

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Speaker 1: use neutrinos to navigate around the Solar system because you

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Speaker 1: can use it to see the Sun. There's so many

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Speaker 1: that by the time they get to Earth, there's a

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Speaker 1: hundred billion passing through a square centimeter per second. So

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Speaker 1: if you like, hold out your hands and you count

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Speaker 1: one Mississippi, a trillion neutrinos have passed through your fingernails. Wow.

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Speaker 1: Unfortunately they don't interact with the electrons and the corks

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Speaker 1: in my body. Otherwise would be a toast. Right, Yeah,

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Speaker 1: you'd all get neutrino cancer or we'd be putting on

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Speaker 1: neutrinos screen every time we go outside. All right, Well,

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Speaker 1: those are neutrinos, and it seems like there's a different

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Speaker 1: kind of neutrino called the sterile neutrino, which it sounds

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Speaker 1: like solves a lot of problems in our theory of

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Speaker 1: the universe. So let's get into that. But first let's

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Speaker 1: take a quick break. All right, we're talking about neutrinos,

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Speaker 1: which are plentiful in the universe. They're made in the Sun.

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Speaker 1: The account for one percent of the Sun's output. So

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Speaker 1: it's kind of a big deal in the universe, right,

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Speaker 1: I mean, the universe seems to like making them. Yeah,

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Speaker 1: the universe certainly pumps out a lot of them. They

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Speaker 1: produced also in supernovas. We have a whole episode about

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Speaker 1: how neutrinos let us see what's going on inside Supernova's

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Speaker 1: one of My favorite applications of neutrinos, though, is that

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Speaker 1: it lets us see that the sun is still there

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Speaker 1: at nighttime because neutrinos hardly interact with anything, so they

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Speaker 1: can pass all the way through the Earth. So if

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Speaker 1: you're like up at three am and you're worried that

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Speaker 1: the sun has disappeared, we can actually verify that the

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Speaker 1: sun is still there on the other side of the

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Speaker 1: Earth by looking for its neutrino signal, because that neutrino

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Speaker 1: signal will pass all the way through the Earth to

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Speaker 1: your neutrino detector. You could also just like call your

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Speaker 1: friend in Japan, but that's less cool, or you could

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Speaker 1: wait a few hours. I mean, the sun will rise tomorrow,

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Speaker 1: isn't that what the song said, unless it's like disappeared

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Speaker 1: or been blown up by aliens. And how would you

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Speaker 1: even know if it's three am? Right? This keeps some

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Speaker 1: people up at night, so this is a way for

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Speaker 1: them to feel comfortable, or how how would it matter?

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Speaker 1: You know, we'd all be toast if the sun disappeared,

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Speaker 1: so you might as well sleep peacefully for the last

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Speaker 1: couple of hours of life that you have. If I

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Speaker 1: told you that aliens had blown up the sun, you'd

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Speaker 1: go take a nap. Is that what you're saying? Yeah, basically,

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Speaker 1: I mean what else would you do? Worry about it?

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Speaker 1: Panic called Bruce Willis. So there's something called that's a

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Speaker 1: sterile neutrino, which I guess it's a different kind of

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Speaker 1: new trino. I mean you said there are different kinds

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Speaker 1: of nutrinos already, right, there's three flavors of neutrinos, but

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Speaker 1: this is something different. Yeah, it is something very different.

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Speaker 1: We have three flavors of neutrinos. We call them electron,

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Speaker 1: muan in town neutrinos because they are produced with electrons,

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Speaker 1: muans and towns. Like when a W boson decays into

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Speaker 1: an electron and a neutrino, it doesn't just decay into

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Speaker 1: any random neutrino decays into an electron neutrino, which is

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Speaker 1: different from a muon neutrino. Muon neutrinos the kind produced

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Speaker 1: when a W boson decays into a muon and a neutrino.

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Speaker 1: In that case it produces a muon neutrino. So there's

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Speaker 1: three different kinds electron, nuon, and town neutrinos. Those we

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Speaker 1: know exist. We've definitely seen them. They interact with the

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Speaker 1: weak force. We've measured each of their various kinds. We're

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Speaker 1: sure that they exist. But the idea is maybe there's

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Speaker 1: a fourth kind of neutrino, a sterile neutrino, which doesn't

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Speaker 1: even feel the weak interaction. It doesn't have the strong force,

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Speaker 1: it doesn't have electromagnetism, and it also doesn't have the

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Speaker 1: weak force. It's totally without interactions, which is why they

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Speaker 1: call it sterile. So it's kind of like a fourth

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Speaker 1: kind of nutrio. Maybe step us through this first, though,

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Speaker 1: like the three other kinds of neutrinos, how are they different?

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Speaker 1: Because I think I've heard that we don't actually know

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Speaker 1: their masses or we're not sure what their masses are,

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Speaker 1: So how do we know they're different? So we know

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Speaker 1: that they are different because we know that the universe

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Speaker 1: keeps count of how many electrons there are, how many

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Speaker 1: muons there are, and how many towels there are. Particle physics,

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Speaker 1: we do this all we look for rules that the

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Speaker 1: universe seems to follow, like conservation of momentum. We notice

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Speaker 1: that in particle interactions, the amount of momentum afterwards is

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Speaker 1: the same as the momentum beforehand and we go, oh,

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Speaker 1: that's cool, what does that mean. We have a whole

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Speaker 1: podcast episode about what that means about the universe. So

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Speaker 1: we're always on the lookout for are the rules that

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Speaker 1: are being followed, because then we can try to figure

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Speaker 1: out what that means. And one thing we've noticed is

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Speaker 1: that the universe keeps track of the number of electrons,

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Speaker 1: so you can't just create one electron. If you do so,

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Speaker 1: you have to also create an anti electron. But the

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Speaker 1: electron neutrino is sort of in the same column. So

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Speaker 1: when you produce an electron, if you produce an anti

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Speaker 1: electron neutrino, then the universe is happy and all the

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Speaker 1: accounts balance. That's why we think that there are different neutrinos.

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Speaker 1: That's what it means. Means for these to be different neutrinos.

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Speaker 1: There's the one that balances the electron book, another one

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Speaker 1: that bounces the muon book, another one that balances the

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Speaker 1: tao's books, which so you only think there are three

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Speaker 1: different neutrinos. I mean, it sounds like what if just

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Speaker 1: the one neutrino helps balance all the other electron, muon

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Speaker 1: and tow particles, and it's not a universal currency. Well,

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Speaker 1: if we produce just one kind of neutrino, for example,

427
00:22:25,960 --> 00:22:29,320
Speaker 1: you start with muans. You can produce muon neutrinos from

428
00:22:29,359 --> 00:22:32,240
Speaker 1: their decays, and then we smash it into a bunch

429
00:22:32,280 --> 00:22:35,280
Speaker 1: of stuff. It tends to only interact with muans, and

430
00:22:35,359 --> 00:22:38,600
Speaker 1: the same with electrons. You produce an electron neutrino beam

431
00:22:38,680 --> 00:22:40,639
Speaker 1: and you smash it into a bunch of stuff. It

432
00:22:40,720 --> 00:22:43,840
Speaker 1: tends to bounce off only electrons because those like to

433
00:22:43,880 --> 00:22:46,120
Speaker 1: talk to each other. So we're pretty sure that those

434
00:22:46,160 --> 00:22:49,320
Speaker 1: different flavors exist. Also, it would be very very weird

435
00:22:49,440 --> 00:22:52,240
Speaker 1: in our theory if we had three kinds of charge

436
00:22:52,320 --> 00:22:55,720
Speaker 1: lectons e. Mutao and only one kind of neutral lecton.

437
00:22:55,880 --> 00:22:58,520
Speaker 1: That's not an argument for it not existing it being weird,

438
00:22:58,960 --> 00:23:01,359
Speaker 1: but theoretically that to be very strange. But we do

439
00:23:01,520 --> 00:23:03,960
Speaker 1: have experiments where we can isolate each different kind of

440
00:23:04,040 --> 00:23:06,879
Speaker 1: neutrino and see that they really do have different properties.

441
00:23:07,080 --> 00:23:09,680
Speaker 1: And we also know that there are three kinds of

442
00:23:09,760 --> 00:23:13,280
Speaker 1: neutrinos because we have made measurements of their masses. We

443
00:23:13,440 --> 00:23:17,959
Speaker 1: know that there are three different neutrino masses, all right,

444
00:23:18,320 --> 00:23:20,760
Speaker 1: But I think you don't know exactly what those masses

445
00:23:20,800 --> 00:23:22,840
Speaker 1: are right, we don't know what those masses are. In fact,

446
00:23:22,840 --> 00:23:25,800
Speaker 1: we've only ever measured the mass differences. We know that

447
00:23:25,880 --> 00:23:28,720
Speaker 1: there are differences between the masses of neutrinos because those

448
00:23:28,800 --> 00:23:32,280
Speaker 1: mass differences help the neutrinos change flavor. So, for example,

449
00:23:32,400 --> 00:23:35,960
Speaker 1: neutrinos produced in the Sun are all electron neutrinos because

450
00:23:36,040 --> 00:23:38,400
Speaker 1: the Sun has electrons in it and almost no muans.

451
00:23:38,800 --> 00:23:41,240
Speaker 1: By the time those electron neutrinos get to the Earth,

452
00:23:41,359 --> 00:23:43,920
Speaker 1: a huge fraction of them have turned into something else

453
00:23:44,280 --> 00:23:47,280
Speaker 1: like muon neutrinos, and that comes directly from the mass

454
00:23:47,359 --> 00:23:50,439
Speaker 1: differences in the neutrinos. But it sounds like maybe it's

455
00:23:50,440 --> 00:23:53,000
Speaker 1: a little bit hypothetical. Still, there's a lot we don't

456
00:23:53,119 --> 00:23:57,240
Speaker 1: understand about neutrino mixing and oscillation and how this all works,

457
00:23:57,320 --> 00:23:58,760
Speaker 1: and there's a bunch of things in the theory that

458
00:23:58,800 --> 00:24:00,800
Speaker 1: don't quite fit together. Yeah, and there's also a bunch

459
00:24:00,800 --> 00:24:03,119
Speaker 1: of experiments that all contradict each other and have had

460
00:24:03,160 --> 00:24:06,680
Speaker 1: people arguing for about two decades. That's a physicist favorite activity,

461
00:24:06,760 --> 00:24:09,400
Speaker 1: so they're pretty happy about that. But you said there's

462
00:24:09,560 --> 00:24:12,320
Speaker 1: maybe a fourth kind of neutrino, or we know for

463
00:24:12,400 --> 00:24:14,520
Speaker 1: sure there is a fourth kind of matrino called a

464
00:24:14,640 --> 00:24:18,640
Speaker 1: sterile neutrino, or as they say in England, sterile neutrino.

465
00:24:18,920 --> 00:24:20,680
Speaker 1: So we don't know for sure if there is a

466
00:24:20,760 --> 00:24:24,359
Speaker 1: sterile neutrino. We have good reasons to suspect it, both

467
00:24:24,440 --> 00:24:27,959
Speaker 1: theoretically and experimentally. We have a lot of hints from

468
00:24:28,000 --> 00:24:31,000
Speaker 1: both directions. We definitely do not know for sure. Sterile

469
00:24:31,040 --> 00:24:34,600
Speaker 1: neutrinos are still hypothetical, and there's a lot of very strong,

470
00:24:34,920 --> 00:24:38,200
Speaker 1: very different opinions about the strength of the evidence for them.

471
00:24:38,800 --> 00:24:44,000
Speaker 1: They're more hypothetically the other nutrina. Yeah, exactly, they're more hypothetical.

472
00:24:44,040 --> 00:24:46,639
Speaker 1: And these things are really hard to observe because the

473
00:24:46,760 --> 00:24:50,080
Speaker 1: only interaction they have is gravity, right, which, as we know,

474
00:24:50,280 --> 00:24:52,520
Speaker 1: is the weakest force, And so that makes it very

475
00:24:52,600 --> 00:24:55,720
Speaker 1: very difficult to like study sterile neutrinos directly or to

476
00:24:55,840 --> 00:24:58,440
Speaker 1: discover them. All Right, well, it sounds like they're double

477
00:24:58,520 --> 00:25:01,720
Speaker 1: they're hypothetical. Well, what makes us think they might exist

478
00:25:01,880 --> 00:25:03,680
Speaker 1: or why did we give him a name and think

479
00:25:03,760 --> 00:25:06,200
Speaker 1: that they are out there? So they started out in

480
00:25:06,280 --> 00:25:08,440
Speaker 1: the theory, it's an idea of people were playing with.

481
00:25:08,680 --> 00:25:11,920
Speaker 1: One of the central mysteries is why neutrino masses are

482
00:25:12,040 --> 00:25:14,840
Speaker 1: so small, and actually how they get mass in the

483
00:25:14,960 --> 00:25:17,479
Speaker 1: first place. Like most of the particles that are out

484
00:25:17,520 --> 00:25:20,480
Speaker 1: there in the standard model, the electron, the corks, we

485
00:25:20,640 --> 00:25:23,760
Speaker 1: think they get their masses by interacting with the Higgs boson.

486
00:25:23,920 --> 00:25:27,160
Speaker 1: The electron flies through this field which fills the universe,

487
00:25:27,240 --> 00:25:29,560
Speaker 1: the Higgs field, and it interacts with it a little bit,

488
00:25:29,640 --> 00:25:32,920
Speaker 1: and that changes how it moves. The pure theoretical electron

489
00:25:32,960 --> 00:25:35,920
Speaker 1: by itself has no mass, but the effective electron, the

490
00:25:35,960 --> 00:25:38,479
Speaker 1: one that moved through the Higgs field, moves as if

491
00:25:38,560 --> 00:25:41,280
Speaker 1: it had mass, and that's actually what we call mass.

492
00:25:41,680 --> 00:25:43,679
Speaker 1: So that's how an electron gets mass, and that's how

493
00:25:43,680 --> 00:25:46,200
Speaker 1: an upcork gets mass. But we don't think that happens

494
00:25:46,240 --> 00:25:48,720
Speaker 1: for neutrinos. What do you mean you don't think neutrinos

495
00:25:48,960 --> 00:25:51,880
Speaker 1: interact with the Higgs field. I thought we knew for sure,

496
00:25:52,080 --> 00:25:54,800
Speaker 1: or that they have mass, or you're just talking about

497
00:25:54,800 --> 00:25:56,840
Speaker 1: stole neutrinos. We're just talking about the standard model of

498
00:25:56,840 --> 00:25:59,840
Speaker 1: neutrinos right now, we don't understand how they get mass.

499
00:26:00,320 --> 00:26:03,440
Speaker 1: In our theory, they shouldn't have any mass, and that's

500
00:26:03,480 --> 00:26:05,800
Speaker 1: because in order to interact with the Higgs field, and

501
00:26:05,840 --> 00:26:08,600
Speaker 1: to get mass the way that electrons do and corks do,

502
00:26:08,920 --> 00:26:10,679
Speaker 1: you have to have two different kinds of the particle.

503
00:26:10,760 --> 00:26:12,720
Speaker 1: One time we talked about how the Higgs field can't

504
00:26:12,800 --> 00:26:15,920
Speaker 1: give masses to particles that are their own antiparticle, because

505
00:26:15,920 --> 00:26:18,119
Speaker 1: the Higgs field has to talk to two different sides

506
00:26:18,160 --> 00:26:20,119
Speaker 1: of the particle, has to talk to the particle and

507
00:26:20,200 --> 00:26:23,040
Speaker 1: the anti particle. But even more than that, particles have

508
00:26:23,080 --> 00:26:26,640
Speaker 1: another quality to them. It's called holicity or chirality. Particles

509
00:26:26,680 --> 00:26:29,240
Speaker 1: can be left handed or right handed, and to talk

510
00:26:29,280 --> 00:26:30,720
Speaker 1: to the Higgs field, to get your mass from the

511
00:26:30,800 --> 00:26:33,320
Speaker 1: Higgs field, you have to have both right and left

512
00:26:33,359 --> 00:26:36,000
Speaker 1: handed versions of the particle. And that's true for the

513
00:26:36,040 --> 00:26:38,240
Speaker 1: electron and for the up cork and for the down cork,

514
00:26:38,440 --> 00:26:41,719
Speaker 1: but it's not true for the neutrino. Neutrinos only ever

515
00:26:41,840 --> 00:26:45,600
Speaker 1: exist as left handed versions of the particle. Well, it's long,

516
00:26:45,800 --> 00:26:48,560
Speaker 1: I'm not underhanded, it's I guess it's all right, But

517
00:26:48,680 --> 00:26:50,440
Speaker 1: I think I'm getting a little loss in all this

518
00:26:50,720 --> 00:26:53,840
Speaker 1: term anology. Here. You're saying that in neutrinos are do

519
00:26:54,040 --> 00:26:57,520
Speaker 1: have mass, right, you confirmed that with experiments, it seems

520
00:26:57,560 --> 00:27:00,600
Speaker 1: like and but it's very little mass. But that's weird

521
00:27:00,680 --> 00:27:03,800
Speaker 1: because your theory says that they should have zero mass.

522
00:27:04,119 --> 00:27:06,000
Speaker 1: Why does the theory say they should have zero mass,

523
00:27:06,200 --> 00:27:09,119
Speaker 1: because neutrinos only interact via the weak force, and the

524
00:27:09,160 --> 00:27:12,600
Speaker 1: weak force only talks to left handed particles. We have

525
00:27:12,680 --> 00:27:15,800
Speaker 1: an episode about parody violation, how the weak force doesn't

526
00:27:15,880 --> 00:27:18,200
Speaker 1: look the same in the mirror, and that's because the

527
00:27:18,240 --> 00:27:21,080
Speaker 1: weak force has this really weird property where it ignores

528
00:27:21,240 --> 00:27:24,040
Speaker 1: right handed particles and only talks to left handed particles.

529
00:27:24,560 --> 00:27:27,000
Speaker 1: And this handedness refers to like the direction of the

530
00:27:27,080 --> 00:27:30,520
Speaker 1: particle's motion relative to the direction of its quantum spin,

531
00:27:31,000 --> 00:27:33,200
Speaker 1: and those two things translate differently in the mirror, so

532
00:27:33,320 --> 00:27:35,480
Speaker 1: like a left handed particle in the mirror becomes a

533
00:27:35,600 --> 00:27:38,639
Speaker 1: right handed particle. And so neutrinos are only left handed,

534
00:27:38,680 --> 00:27:41,800
Speaker 1: and the weak force only talks too left handed particles,

535
00:27:42,320 --> 00:27:45,679
Speaker 1: and so in our theory, only left handed neutrinos should exist,

536
00:27:45,920 --> 00:27:48,160
Speaker 1: which means there should be no right handed neutrinos, which

537
00:27:48,200 --> 00:27:50,040
Speaker 1: means they don't talk to the Higgs field, so they

538
00:27:50,080 --> 00:27:53,080
Speaker 1: should have zero mass, and yet we see that they

539
00:27:53,200 --> 00:27:56,320
Speaker 1: do have mass. So there's definitely some gap in the theory.

540
00:27:56,440 --> 00:27:59,920
Speaker 1: Right the theory is not describing the universe that we see. Well,

541
00:28:00,080 --> 00:28:02,720
Speaker 1: maybe you're just you know, wrong about that. Maybe you

542
00:28:02,840 --> 00:28:05,359
Speaker 1: can interact with the Higgs field with the other kind

543
00:28:05,400 --> 00:28:07,399
Speaker 1: of particle, you know, like what made you think that

544
00:28:07,560 --> 00:28:09,720
Speaker 1: it can only the Higgs can only interact with one

545
00:28:09,880 --> 00:28:12,680
Speaker 1: type of spinning particle and not the other if you

546
00:28:12,760 --> 00:28:14,879
Speaker 1: have experimental evidence that it does. Well, we know that

547
00:28:15,000 --> 00:28:17,680
Speaker 1: it has mass, but the Higgs field really mathematically just

548
00:28:17,800 --> 00:28:20,399
Speaker 1: cannot give mass to particles that don't have a right

549
00:28:20,480 --> 00:28:23,080
Speaker 1: handed component. But it does right well. We don't know

550
00:28:23,160 --> 00:28:24,639
Speaker 1: that it gets its mass from the Higgs field. We

551
00:28:24,680 --> 00:28:27,000
Speaker 1: know that it has mass. There are other ways for

552
00:28:27,119 --> 00:28:29,359
Speaker 1: particles to get mass. We talked once about whether the

553
00:28:29,440 --> 00:28:33,320
Speaker 1: neutrino is a myorona particle. Maybe it is its own antiparticle,

554
00:28:33,400 --> 00:28:35,800
Speaker 1: so that's a different way to get mass. That's one

555
00:28:35,840 --> 00:28:38,640
Speaker 1: possibility that maybe the neutrino gets mass but not from

556
00:28:38,720 --> 00:28:41,440
Speaker 1: the Higgs field. Or maybe we're wrong about the neutrino

557
00:28:41,600 --> 00:28:44,120
Speaker 1: not having a right handed component. Maybe there is a

558
00:28:44,320 --> 00:28:47,360
Speaker 1: right handed neutrino out there. The weak force doesn't create

559
00:28:47,400 --> 00:28:49,680
Speaker 1: it or talk to it, but maybe it still exists,

560
00:28:50,120 --> 00:28:52,680
Speaker 1: and so that allows the neutrino to get mass from

561
00:28:52,680 --> 00:28:55,320
Speaker 1: the Higgs field, all right, So that's one mystery how

562
00:28:55,400 --> 00:28:57,760
Speaker 1: does the neutrino get its mass? And it's also kind

563
00:28:57,760 --> 00:29:00,800
Speaker 1: of a mystery why that mass is so small, right,

564
00:29:00,800 --> 00:29:03,280
Speaker 1: because it's a lot lighter than all the other particles.

565
00:29:03,560 --> 00:29:06,120
Speaker 1: It would be really weird if the neutrino got its

566
00:29:06,200 --> 00:29:07,960
Speaker 1: mass from the Higgs field and then it got such

567
00:29:08,000 --> 00:29:11,160
Speaker 1: a tiny little serving of mass. Right, The neutrinos are

568
00:29:11,200 --> 00:29:14,480
Speaker 1: like less than one millions the mass of the electron,

569
00:29:14,600 --> 00:29:17,400
Speaker 1: which is already very very light compared to like the proton.

570
00:29:17,600 --> 00:29:19,760
Speaker 1: So we have this really deep question in particle physics

571
00:29:19,800 --> 00:29:22,640
Speaker 1: about why particles are interacting with the Higgs field at

572
00:29:22,640 --> 00:29:25,920
Speaker 1: different strengths. And the neutrino would be like the outlier,

573
00:29:26,120 --> 00:29:29,080
Speaker 1: be even crazier than all the other particles. So to

574
00:29:29,160 --> 00:29:32,600
Speaker 1: make it sort of hang together more crisply mathematically, people

575
00:29:32,680 --> 00:29:36,360
Speaker 1: like adding another neutrino. They say, what if there's another

576
00:29:36,440 --> 00:29:39,120
Speaker 1: kind of neutrino and this one is only right handed,

577
00:29:39,280 --> 00:29:41,520
Speaker 1: so it doesn't interact with the weak force at all.

578
00:29:42,120 --> 00:29:44,719
Speaker 1: So this idea that maybe they're right handed neutrinos out

579
00:29:44,760 --> 00:29:48,480
Speaker 1: there gets extended to like creating a pure right handed neutrino,

580
00:29:48,560 --> 00:29:51,960
Speaker 1: a sterile neutrino. If you put that in and calculate

581
00:29:52,000 --> 00:29:54,320
Speaker 1: all your equations, then it tends to pull on the

582
00:29:54,440 --> 00:29:57,760
Speaker 1: masses of the other neutrinos and make them small. So

583
00:29:57,800 --> 00:29:59,920
Speaker 1: the idea of a stero neutrino would explain how new

584
00:30:00,000 --> 00:30:03,160
Speaker 1: trinos get mass and why they are so small. All right,

585
00:30:03,200 --> 00:30:05,840
Speaker 1: So we have those two mysteries, why it neutrinos have

586
00:30:06,000 --> 00:30:09,080
Speaker 1: mass and why they are so light. But you're saying

587
00:30:09,120 --> 00:30:11,680
Speaker 1: the solution is to create a whole different kind of neutrinos.

588
00:30:11,720 --> 00:30:14,000
Speaker 1: How would it hold different kind of natrino explain the

589
00:30:14,040 --> 00:30:16,440
Speaker 1: mysteries and the other kinds of neutrinos. Well, it would

590
00:30:16,440 --> 00:30:19,480
Speaker 1: demonstrate that right handed neutrinos exist, and that helps us

591
00:30:19,600 --> 00:30:22,760
Speaker 1: understand how neutrinos get mass, because maybe we were wrong

592
00:30:23,120 --> 00:30:25,600
Speaker 1: that neutrinos are only left handed. Maybe they all do

593
00:30:25,840 --> 00:30:28,600
Speaker 1: have a little bit of a right handed component. It's

594
00:30:28,640 --> 00:30:30,600
Speaker 1: possible for them to then talk to the Higgs field

595
00:30:30,640 --> 00:30:32,360
Speaker 1: and to get mass. Then if you have a special

596
00:30:32,480 --> 00:30:36,280
Speaker 1: fourth kind of neutrino through some mathematical mixing, it turns

597
00:30:36,320 --> 00:30:38,720
Speaker 1: out that it gets most of the mass and it

598
00:30:38,760 --> 00:30:41,840
Speaker 1: becomes very very heavy. And because the seesaw mechanism with

599
00:30:42,000 --> 00:30:43,760
Speaker 1: like it sits on one side very very heavy, it

600
00:30:43,800 --> 00:30:46,960
Speaker 1: makes the other particles very very light. Oh, I see,

601
00:30:47,120 --> 00:30:49,920
Speaker 1: you've made up this new kind of neutrino because just

602
00:30:50,120 --> 00:30:53,520
Speaker 1: to like balance out the weirdness of the other ones.

603
00:30:53,600 --> 00:30:55,520
Speaker 1: It's like, all the other ones seem to be left handed.

604
00:30:55,600 --> 00:30:58,800
Speaker 1: Maybe there's a huge ginormous right hand in the trin

605
00:30:58,920 --> 00:31:01,320
Speaker 1: on the other side that's uh, you know, kind of

606
00:31:01,840 --> 00:31:04,200
Speaker 1: taking up all of the neutrino mass in the universe.

607
00:31:04,320 --> 00:31:06,320
Speaker 1: Is that kind of what you mean? Yeah, that's exactly it.

608
00:31:06,840 --> 00:31:09,080
Speaker 1: And it's sort of a weird idea, but it also

609
00:31:09,400 --> 00:31:11,600
Speaker 1: kind of works. Like this is part of the process

610
00:31:11,720 --> 00:31:14,160
Speaker 1: of physics. It's just being creative and being like, well,

611
00:31:14,240 --> 00:31:16,480
Speaker 1: what about this crazy idea? Now that doesn't work, And

612
00:31:16,560 --> 00:31:18,680
Speaker 1: this is a crazy idea somebody had one day and

613
00:31:18,720 --> 00:31:20,480
Speaker 1: they cranked it through the math and dot com. This

614
00:31:20,600 --> 00:31:23,840
Speaker 1: actually kind of works. It's not that complicated, and it

615
00:31:23,880 --> 00:31:26,800
Speaker 1: would explain what we're seeing. So it became sort of

616
00:31:26,840 --> 00:31:30,880
Speaker 1: attractive theoretically for that reason. But I guess if there

617
00:31:31,120 --> 00:31:36,200
Speaker 1: does exist humongous right handed netrino out there and tun

618
00:31:36,240 --> 00:31:38,800
Speaker 1: when you have seen it already, wouldn't be like extra obvious.

619
00:31:39,000 --> 00:31:41,720
Speaker 1: So that's the other fun clue. But Darren neutrinos is

620
00:31:41,800 --> 00:31:44,960
Speaker 1: that maybe they are the dark matter. Maybe we have

621
00:31:45,280 --> 00:31:49,120
Speaker 1: been seeing them right. We know that there is some

622
00:31:49,320 --> 00:31:52,520
Speaker 1: sort of particle out there that only feels graft. It

623
00:31:52,640 --> 00:31:55,240
Speaker 1: has no other kinds of interactions. We've been calling it

624
00:31:55,360 --> 00:31:57,960
Speaker 1: dark matter on the podcast for years, and people have

625
00:31:58,000 --> 00:32:00,200
Speaker 1: been talking about in physics for decades. We know that

626
00:32:00,560 --> 00:32:02,160
Speaker 1: most of the mass in the universe is this new,

627
00:32:02,240 --> 00:32:05,800
Speaker 1: weird kind of thing, and so sterile neutrino really fits

628
00:32:05,920 --> 00:32:09,040
Speaker 1: that bill right. One reason we don't think that normal

629
00:32:09,160 --> 00:32:13,120
Speaker 1: neutrinos e. Mute town neutrinos are the dark matter is

630
00:32:13,160 --> 00:32:15,760
Speaker 1: because they have very very low mass because they fly

631
00:32:16,040 --> 00:32:19,000
Speaker 1: through the universe very very fast, and so they would

632
00:32:19,000 --> 00:32:21,320
Speaker 1: have given a different shape to the universe. It wouldn't

633
00:32:21,360 --> 00:32:23,560
Speaker 1: get like the clumpiness that we see in the universe today.

634
00:32:23,840 --> 00:32:26,720
Speaker 1: They're too hot, is what we say. But this could

635
00:32:26,760 --> 00:32:29,240
Speaker 1: be cold dark matter. They could be very massive and

636
00:32:29,320 --> 00:32:31,400
Speaker 1: just sort of like hanging out there. So the universe

637
00:32:31,440 --> 00:32:34,080
Speaker 1: could be filled with these sterile neutrinos. You ask, why

638
00:32:34,160 --> 00:32:36,360
Speaker 1: wouldn't we have seen them, Well, maybe we have been

639
00:32:36,720 --> 00:32:39,320
Speaker 1: Maybe they are the dark matter. What it's like a

640
00:32:39,440 --> 00:32:42,480
Speaker 1: huge plot twist if it turns out the dark matter

641
00:32:42,680 --> 00:32:45,880
Speaker 1: was just a big neutrino in the universe. So let's

642
00:32:45,880 --> 00:32:48,520
Speaker 1: get into this idea a little bit more and whether

643
00:32:48,840 --> 00:32:51,800
Speaker 1: or not we've seen these in experiments. But first let's

644
00:32:51,840 --> 00:33:06,400
Speaker 1: take another quick break. We're in the third act of

645
00:33:06,440 --> 00:33:08,840
Speaker 1: the movie here, which just revealed the big plot twist

646
00:33:09,080 --> 00:33:12,080
Speaker 1: in our story here. It turns out the dark matter

647
00:33:13,520 --> 00:33:15,320
Speaker 1: of the universe that we have no idea what it is.

648
00:33:15,440 --> 00:33:17,160
Speaker 1: Maybe we do know what it is, and it could

649
00:33:17,200 --> 00:33:20,480
Speaker 1: be maybe a fourth kind of neutrino, which kind of

650
00:33:20,560 --> 00:33:23,240
Speaker 1: totally fits the bill right. It's like an almost invisible

651
00:33:23,320 --> 00:33:25,920
Speaker 1: type of matter. It's heavy, and that white did means

652
00:33:25,920 --> 00:33:30,880
Speaker 1: you think of this before. It's been a candidate for

653
00:33:31,040 --> 00:33:34,360
Speaker 1: dark matter for a while, but it's become more popular

654
00:33:34,480 --> 00:33:36,800
Speaker 1: in the last couple of decades because we have a

655
00:33:36,840 --> 00:33:41,280
Speaker 1: bunch of really confusing experimental results in neutrino physics that

656
00:33:41,360 --> 00:33:44,440
Speaker 1: have been hinting towards a sterile neutrino, but then also

657
00:33:44,600 --> 00:33:47,040
Speaker 1: kind of contradicting other experiments. So it's a bit of

658
00:33:47,080 --> 00:33:49,840
Speaker 1: a confusing landscape right now about whether the experiments are

659
00:33:49,880 --> 00:33:53,000
Speaker 1: consistent with a sterile neutrino or not? Wait, which experiments?

660
00:33:53,040 --> 00:33:55,280
Speaker 1: The dark matter experiments tell us there is dark matter

661
00:33:55,360 --> 00:33:57,080
Speaker 1: out there. We know that it's out there, we know

662
00:33:57,200 --> 00:33:59,160
Speaker 1: how much it is, but we don't know what particle

663
00:33:59,200 --> 00:34:01,440
Speaker 1: it's made out of, or if it is even made

664
00:34:01,480 --> 00:34:03,560
Speaker 1: out of a particle. The dark matter experiments have never

665
00:34:03,640 --> 00:34:06,360
Speaker 1: seen a particle of dark matter. But there are people

666
00:34:06,440 --> 00:34:11,000
Speaker 1: studying neutrinos in great detail, watching them change from one

667
00:34:11,080 --> 00:34:13,919
Speaker 1: kind to another, electrons to muans, two towers to back,

668
00:34:14,320 --> 00:34:17,440
Speaker 1: and they've been seeing some weird things that suggest maybe

669
00:34:17,520 --> 00:34:20,239
Speaker 1: there's another kind of neutrino out there that would help

670
00:34:20,320 --> 00:34:24,960
Speaker 1: explain these weird neutrino experiments. And that could also maybe

671
00:34:25,200 --> 00:34:27,239
Speaker 1: be the dark matter that we're seeing. Right, that's the

672
00:34:27,320 --> 00:34:30,720
Speaker 1: idea exactly. Maybe it all come together into a beautiful

673
00:34:30,760 --> 00:34:33,160
Speaker 1: resolution at the end of the movie, right, Yeah, bring

674
00:34:33,239 --> 00:34:35,839
Speaker 1: together the A B storylines. That's that's always the coal.

675
00:34:36,280 --> 00:34:38,200
Speaker 1: But um, I guess one question is why are they

676
00:34:38,239 --> 00:34:41,160
Speaker 1: called sterile matrinos or sterile if you're in England, are

677
00:34:41,200 --> 00:34:45,719
Speaker 1: there neutrinos who are not sterile or reproductive or fertile

678
00:34:45,960 --> 00:34:49,719
Speaker 1: or dirty? Well, there are neutrinos that interact electron muan

679
00:34:49,760 --> 00:34:53,000
Speaker 1: in town neutrinos do feel the weak force, so we

680
00:34:53,080 --> 00:34:56,200
Speaker 1: are capable of detecting them. If you send a bunch

681
00:34:56,320 --> 00:34:59,839
Speaker 1: of electron neutrinos into a huge vat of liquid, one

682
00:35:00,080 --> 00:35:02,239
Speaker 1: out of a billion of them will bang into an

683
00:35:02,280 --> 00:35:04,880
Speaker 1: electron and will give it some recoil. So you can

684
00:35:04,960 --> 00:35:07,960
Speaker 1: see that if you send muon neutrinos into a huge

685
00:35:08,120 --> 00:35:10,160
Speaker 1: vat of liquid, one of them will bang into a

686
00:35:10,239 --> 00:35:12,360
Speaker 1: muan if it happens to be created as a virtual

687
00:35:12,440 --> 00:35:15,960
Speaker 1: particle temporarily, so we can see electron muan and town

688
00:35:16,000 --> 00:35:19,600
Speaker 1: neutrinos sort of indirectly. But sterile neutrinos don't have any

689
00:35:19,680 --> 00:35:22,440
Speaker 1: interaction at all other than gravity, so we can't do

690
00:35:22,640 --> 00:35:25,719
Speaker 1: particle physics experiments with them. But what we can do

691
00:35:25,920 --> 00:35:27,759
Speaker 1: is try to see if there's a missing part of

692
00:35:27,880 --> 00:35:30,640
Speaker 1: the story. We watch electron Muan and town and Trina

693
00:35:30,760 --> 00:35:33,040
Speaker 1: sort of turn into each other back and forth, and

694
00:35:33,120 --> 00:35:35,640
Speaker 1: we try to notice if somebody accounting doesn't seem to

695
00:35:35,719 --> 00:35:38,160
Speaker 1: be adding up, is like a missing person. It sounds

696
00:35:38,200 --> 00:35:40,800
Speaker 1: sort of like the definition of a sterile metrino is

697
00:35:40,880 --> 00:35:43,239
Speaker 1: the same definition is dark matter. I mean you're saying

698
00:35:43,280 --> 00:35:46,440
Speaker 1: asteria lutrino is massive, it has mass, it feels gravity,

699
00:35:46,680 --> 00:35:49,880
Speaker 1: but it doesn't feel the weak force, which is a

700
00:35:50,280 --> 00:35:52,799
Speaker 1: sort of kind of what devolves. It's turn about about

701
00:35:52,880 --> 00:35:55,560
Speaker 1: dark matter, and so you can't see this potential type

702
00:35:55,600 --> 00:35:58,640
Speaker 1: of neutrino, and so you're saying there might be other

703
00:35:58,680 --> 00:36:00,520
Speaker 1: ways to see it. Yeah, there might be other ways

704
00:36:00,520 --> 00:36:02,439
Speaker 1: to see it. There are various candidates for dark matter.

705
00:36:02,520 --> 00:36:04,880
Speaker 1: You know, some generic particle out there that only feels gravity.

706
00:36:05,200 --> 00:36:08,560
Speaker 1: This is a special type of dark matter candidate because

707
00:36:08,600 --> 00:36:10,960
Speaker 1: it's not just a generic particle. It's a neutrino, and

708
00:36:11,000 --> 00:36:14,040
Speaker 1: it actually does mix with the other kinds of neutrinos.

709
00:36:14,360 --> 00:36:16,520
Speaker 1: See neutrinos do this really weird thing, which is that

710
00:36:16,600 --> 00:36:18,960
Speaker 1: they mix with each other. We've been talking about neutrinos

711
00:36:19,000 --> 00:36:23,120
Speaker 1: in two different ways. There's different flavors of neutrinos Electron, Muan,

712
00:36:23,200 --> 00:36:26,319
Speaker 1: and tao. And then this is the different masses of neutrinos,

713
00:36:26,680 --> 00:36:29,000
Speaker 1: like call those one, two, and three. The super duper

714
00:36:29,080 --> 00:36:31,840
Speaker 1: confusing thing about neutrinos is that those are not the

715
00:36:31,920 --> 00:36:34,759
Speaker 1: same things. Like we know there are three different mass neutrinos,

716
00:36:34,840 --> 00:36:37,320
Speaker 1: and we know there are three different flavor neutrinos. But

717
00:36:37,360 --> 00:36:40,320
Speaker 1: it's not the case that electron neutrino has one specific

718
00:36:40,440 --> 00:36:43,440
Speaker 1: mass and the muon neutrino has another specific mass and

719
00:36:43,480 --> 00:36:46,759
Speaker 1: the town neutrino has a third specific mass. Instead, they're

720
00:36:46,760 --> 00:36:49,719
Speaker 1: all mixtures of each other. So the electron neutrino is

721
00:36:49,719 --> 00:36:52,840
Speaker 1: a mixture of the three different neutrino masses. Wait, what

722
00:36:52,840 --> 00:36:54,880
Speaker 1: do you mean? What? How can something have different masses?

723
00:36:54,960 --> 00:36:59,000
Speaker 1: What even the words different masses have mean? Make some

724
00:36:59,280 --> 00:37:01,800
Speaker 1: one thing having three different masses? What does that mean? Yeah, So,

725
00:37:01,920 --> 00:37:05,200
Speaker 1: as you fly through the universe, your mass determines how

726
00:37:05,320 --> 00:37:07,560
Speaker 1: you move, right, So that's the property of a particle.

727
00:37:07,760 --> 00:37:09,880
Speaker 1: It doesn't determine how you move. It determs how you

728
00:37:10,000 --> 00:37:11,879
Speaker 1: speed up or slow down. Right, If you're just moving

729
00:37:11,920 --> 00:37:15,239
Speaker 1: through the universe, your mass is kind of irrelevant. Yeah,

730
00:37:15,320 --> 00:37:17,800
Speaker 1: that's what I mean. It determines how you're creative, determines

731
00:37:17,880 --> 00:37:20,560
Speaker 1: how fast you go based on your energy. This kind

732
00:37:20,600 --> 00:37:23,400
Speaker 1: of stuff. The mass is part of the property determines

733
00:37:23,600 --> 00:37:26,160
Speaker 1: how you move through the universe and includes acceleration and

734
00:37:26,280 --> 00:37:28,560
Speaker 1: momentum and all that kind of stuff. So neutrinos have

735
00:37:28,680 --> 00:37:31,680
Speaker 1: different kinds of masses. Yeah, normally particles are created with

736
00:37:31,719 --> 00:37:33,600
Speaker 1: a definite mass. You create an electron, it has a

737
00:37:33,640 --> 00:37:36,399
Speaker 1: certain mass. It flies through the universe. Happy you create

738
00:37:36,400 --> 00:37:40,000
Speaker 1: an electron neutrino, it's a combination of three different masses.

739
00:37:40,440 --> 00:37:43,400
Speaker 1: This is super duper weird, and so as it flies

740
00:37:43,440 --> 00:37:47,760
Speaker 1: through the universe, those masses do move differently. And because

741
00:37:47,800 --> 00:37:51,120
Speaker 1: the muon neutrino is a different combination of those masses,

742
00:37:51,600 --> 00:37:55,279
Speaker 1: that's how electron neutrinos can turn into muon neutrinos as

743
00:37:55,360 --> 00:37:58,240
Speaker 1: they fly through space. It's sort of like two different

744
00:37:58,320 --> 00:38:01,600
Speaker 1: ways to see the neutrinos. Imagine you have like you know,

745
00:38:01,640 --> 00:38:04,560
Speaker 1: an X and Y axis that's like the masses, and

746
00:38:04,600 --> 00:38:07,080
Speaker 1: now you have like a rotated version like X prime

747
00:38:07,160 --> 00:38:10,720
Speaker 1: and y prime. You create something along the y prime axis.

748
00:38:10,960 --> 00:38:13,000
Speaker 1: It's like a mixture of X and y and so

749
00:38:13,080 --> 00:38:16,080
Speaker 1: in the same way, electron neutrinos are a mixture of

750
00:38:16,120 --> 00:38:19,400
Speaker 1: the three different masses. Muon neutrinos are a different mixture

751
00:38:19,480 --> 00:38:21,560
Speaker 1: of those masses. He lost me a little bit there

752
00:38:21,600 --> 00:38:24,520
Speaker 1: with the rotating xs that, but I guess I'm trying

753
00:38:24,520 --> 00:38:26,920
Speaker 1: to understand what you mean by like having a combination

754
00:38:27,000 --> 00:38:28,959
Speaker 1: of different masses. What does it mean like I'm heavy

755
00:38:29,000 --> 00:38:30,640
Speaker 1: and I'm light at the same time. Or are these

756
00:38:30,719 --> 00:38:33,480
Speaker 1: like types of masses. No, that's exactly what it means.

757
00:38:33,520 --> 00:38:36,480
Speaker 1: Electron neutrinos. These are quantum particles, right, so they are

758
00:38:36,480 --> 00:38:40,520
Speaker 1: a superposition of three different masses. I'm heavy and light

759
00:38:40,600 --> 00:38:42,560
Speaker 1: at the same time. What does that mean? Doesn't energy

760
00:38:42,640 --> 00:38:44,919
Speaker 1: need to be conserved? How can I switch back and forth?

761
00:38:44,960 --> 00:38:47,920
Speaker 1: Willy Nili, Well, the different states have different energies, right,

762
00:38:48,200 --> 00:38:50,600
Speaker 1: They have different masses and different energies in the same

763
00:38:50,640 --> 00:38:52,440
Speaker 1: way the particle can be like, Oh, I'm a combination

764
00:38:52,480 --> 00:38:55,440
Speaker 1: of spin up and spin down. Electron neutrinos are a

765
00:38:55,480 --> 00:38:58,680
Speaker 1: combination of three different masses, and muon neutrinos are a

766
00:38:58,800 --> 00:39:04,239
Speaker 1: different combination of those masses. Oh, you mean quantum mechanically combined, right,

767
00:39:04,280 --> 00:39:07,000
Speaker 1: like probabilistically combined. Like it could be when I measure

768
00:39:07,040 --> 00:39:10,160
Speaker 1: it could be heavy, light, or medium. But since it's

769
00:39:10,280 --> 00:39:12,960
Speaker 1: quantum and I haven't measured it, you say that it's

770
00:39:12,960 --> 00:39:15,480
Speaker 1: a combination of the three. Yeah, But there's another layer

771
00:39:15,480 --> 00:39:18,000
Speaker 1: of nuance, which is about how you measure it. If

772
00:39:18,040 --> 00:39:20,040
Speaker 1: you measure it, if you try to measure its mass,

773
00:39:20,160 --> 00:39:22,400
Speaker 1: then you get either mass one, two, or three. If

774
00:39:22,400 --> 00:39:24,600
Speaker 1: you're trying to measure using the weak force, then you

775
00:39:24,719 --> 00:39:27,640
Speaker 1: get electron, muan or tow. Right, So the weak force

776
00:39:28,120 --> 00:39:32,280
Speaker 1: looks at these neutrinos differently than mass looks at these neutrinos.

777
00:39:32,320 --> 00:39:35,000
Speaker 1: There's like a rotation between them. There's like offset. The

778
00:39:35,040 --> 00:39:38,400
Speaker 1: weak forces like twisted in this strange way, so the

779
00:39:38,480 --> 00:39:41,440
Speaker 1: neutrinos it likes to create are not lined up with

780
00:39:41,560 --> 00:39:44,600
Speaker 1: the masses of the neutrinos. There this weird twist you mean,

781
00:39:44,719 --> 00:39:47,400
Speaker 1: like they're not correlated. It's not like the tow is

782
00:39:47,560 --> 00:39:51,000
Speaker 1: always one type of mass and the men is another

783
00:39:51,040 --> 00:39:53,360
Speaker 1: type of mass. It's like each of the three kinds

784
00:39:53,840 --> 00:39:57,880
Speaker 1: have different you know, probabilities of being three different masses exactly.

785
00:39:57,960 --> 00:40:00,200
Speaker 1: So we do these experiments where we see one count

786
00:40:00,200 --> 00:40:02,279
Speaker 1: of neutrino turning into another one. What I mean, it

787
00:40:02,360 --> 00:40:04,480
Speaker 1: turns into another one, like it flies through the air

788
00:40:04,560 --> 00:40:06,719
Speaker 1: and it turns into a muon or a tower or

789
00:40:06,760 --> 00:40:10,400
Speaker 1: something like that. That's exactly right. An electron neutrino produced

790
00:40:10,520 --> 00:40:12,640
Speaker 1: in the Sun, by the time it gets to the Earth,

791
00:40:12,760 --> 00:40:16,240
Speaker 1: a big fraction them are now muon neutrinos. Why, because

792
00:40:16,239 --> 00:40:19,480
Speaker 1: they're created with these superposition of different masses and those

793
00:40:19,520 --> 00:40:22,759
Speaker 1: different masses moved through the universe differently, right, because they

794
00:40:22,800 --> 00:40:25,080
Speaker 1: have different masses, and so by the time it gets

795
00:40:25,200 --> 00:40:26,640
Speaker 1: to the by the time it gets to the Earth,

796
00:40:26,880 --> 00:40:29,960
Speaker 1: it's a different combination of those masses which has a

797
00:40:30,000 --> 00:40:32,720
Speaker 1: good chance to line up with the Muon kind of neutrino.

798
00:40:32,960 --> 00:40:34,680
Speaker 1: So that's how they can change. They can change from

799
00:40:34,680 --> 00:40:37,200
Speaker 1: one flavor into another because the masses are not all

800
00:40:37,239 --> 00:40:40,040
Speaker 1: the same, so they fly through the universe differently. Wait

801
00:40:40,120 --> 00:40:42,440
Speaker 1: do they actually change or is it again one of

802
00:40:42,520 --> 00:40:45,520
Speaker 1: these quantum mechanical tricks where it's like it has the

803
00:40:45,600 --> 00:40:49,359
Speaker 1: probability of being one of the three, but it's one

804
00:40:49,440 --> 00:40:51,560
Speaker 1: depending on how you measure it. Well, it's created, it

805
00:40:51,600 --> 00:40:54,680
Speaker 1: has chance to being an electron neutrino as it flies

806
00:40:54,719 --> 00:40:57,680
Speaker 1: through the universe. That probability changes when you measure it

807
00:40:58,040 --> 00:41:01,239
Speaker 1: after one a U it has like a sixty chance

808
00:41:01,280 --> 00:41:04,279
Speaker 1: of being a Muan neutrino or in a five chance

809
00:41:04,320 --> 00:41:06,279
Speaker 1: of being a town neutrino. And so yes, it's a

810
00:41:06,360 --> 00:41:09,120
Speaker 1: quantum mechanical trick, but also that's the trick that describes

811
00:41:09,200 --> 00:41:11,800
Speaker 1: our universe. But then you say, these things have to

812
00:41:11,880 --> 00:41:14,440
Speaker 1: be conserved, so like if one of them changes from

813
00:41:14,480 --> 00:41:17,640
Speaker 1: a meal into a tower or something. Doesn't that, you know,

814
00:41:17,760 --> 00:41:19,799
Speaker 1: throw the balance sheet of the universe off, like if

815
00:41:19,840 --> 00:41:22,440
Speaker 1: a dollar turned into a British pound exactly. And that's

816
00:41:22,440 --> 00:41:25,320
Speaker 1: why it was such a huge discovery because it breaks

817
00:41:25,360 --> 00:41:27,839
Speaker 1: the standard model. In the standard model, these things are

818
00:41:27,880 --> 00:41:31,000
Speaker 1: totally conserved, but in the universe they are not. This

819
00:41:31,239 --> 00:41:34,840
Speaker 1: breaks that rule. You're exactly right, very sharp point. And

820
00:41:34,920 --> 00:41:37,600
Speaker 1: so we know that the standard model is violated, right,

821
00:41:37,680 --> 00:41:41,520
Speaker 1: because neutrino oscillations, that's what this is called, breaks the

822
00:41:41,600 --> 00:41:44,720
Speaker 1: conservation of lefton number. And that's why people won several

823
00:41:44,760 --> 00:41:47,680
Speaker 1: Nobel Prizes for these discoveries because it's a hint that

824
00:41:47,800 --> 00:41:50,279
Speaker 1: the standard model is wrong. I feel like Daniel, this

825
00:41:50,320 --> 00:41:52,640
Speaker 1: whole episode has been us saying there's a rule, but

826
00:41:53,160 --> 00:41:56,719
Speaker 1: you know, it turns out that rule doesn't work. So

827
00:41:56,800 --> 00:41:59,520
Speaker 1: why even have rules? Maybe you shouldn't call them rules

828
00:41:59,680 --> 00:42:02,479
Speaker 1: such a questions. Yeah, there you go. We were looking

829
00:42:02,560 --> 00:42:04,640
Speaker 1: for the suggestions of the universe, not the laws of

830
00:42:04,719 --> 00:42:07,640
Speaker 1: the And to me, the really fascinating part experimentally is

831
00:42:07,719 --> 00:42:10,040
Speaker 1: that we look at all these experiments that see one

832
00:42:10,120 --> 00:42:12,839
Speaker 1: kind of neutrino changing into another, and they don't all

833
00:42:12,960 --> 00:42:15,880
Speaker 1: make sense. Like there was one experiment in Los Almos

834
00:42:15,920 --> 00:42:18,680
Speaker 1: in the nine nineties they trying to see muon neutrinos

835
00:42:18,719 --> 00:42:21,120
Speaker 1: turning into electron neutrinos, and they saw way too many.

836
00:42:21,200 --> 00:42:23,759
Speaker 1: We couldn't explain them even with a modified version of

837
00:42:23,840 --> 00:42:26,360
Speaker 1: the standard model that had three neutrino types in it.

838
00:42:26,520 --> 00:42:28,680
Speaker 1: But you can explain it if you add a fourth

839
00:42:28,840 --> 00:42:32,960
Speaker 1: type of neutrino, a sterile neutrino, would explain that experiment.

840
00:42:33,120 --> 00:42:36,640
Speaker 1: It like helps participate in this weird mixing that neutrinos

841
00:42:36,760 --> 00:42:39,560
Speaker 1: do with each other and would change those rates of

842
00:42:39,640 --> 00:42:42,600
Speaker 1: mixing and would explain that experiment. Wait, so I guess

843
00:42:42,680 --> 00:42:45,080
Speaker 1: this helps us get back on the topic of sterile

844
00:42:45,120 --> 00:42:49,200
Speaker 1: neutrinos because we think it's maybe an interesting possibility that

845
00:42:49,239 --> 00:42:51,560
Speaker 1: could explain maybe dark matter. But I guess then the

846
00:42:51,640 --> 00:42:53,560
Speaker 1: question is if they're so hard to see, just like

847
00:42:53,680 --> 00:42:55,480
Speaker 1: dark matter is hard to see, how are we trying

848
00:42:55,520 --> 00:42:58,080
Speaker 1: to see this kind of neutrino. And you're saying that

849
00:42:58,200 --> 00:43:00,880
Speaker 1: maybe you can see it by looking at experiments with

850
00:43:00,960 --> 00:43:03,560
Speaker 1: regular neutrinos, right, I think that's what you're saying, because

851
00:43:04,440 --> 00:43:07,680
Speaker 1: this fourth potential kind of neutrino can also turn into

852
00:43:07,719 --> 00:43:10,400
Speaker 1: the other three kinds of neutrinos you can't directly, but

853
00:43:10,520 --> 00:43:13,080
Speaker 1: it's also a weird mixture of the mass states. If

854
00:43:13,120 --> 00:43:15,920
Speaker 1: it turns out there's four different masses of neutrinos, and

855
00:43:16,040 --> 00:43:19,800
Speaker 1: stero neutrinos are a weird mixture of those four mass states.

856
00:43:20,120 --> 00:43:22,200
Speaker 1: So the short version is it changes how the other

857
00:43:22,239 --> 00:43:25,239
Speaker 1: two neutrinos turned into each other. Like stero neutrinos can

858
00:43:25,320 --> 00:43:28,960
Speaker 1: turn sometimes into electron neutrinos, muon neutrinos could be turning

859
00:43:29,000 --> 00:43:32,759
Speaker 1: into stero neutrinos because of this weird mixing that neutrinos

860
00:43:32,840 --> 00:43:34,600
Speaker 1: can do with each other. So it's sort of like

861
00:43:34,680 --> 00:43:37,320
Speaker 1: discovering that there's a fourth person in your conversation but

862
00:43:37,400 --> 00:43:39,760
Speaker 1: you haven't been hearing them, but it explains what everybody

863
00:43:39,800 --> 00:43:41,920
Speaker 1: else has been doing, you know, why they've been acting

864
00:43:42,000 --> 00:43:45,080
Speaker 1: sort of strangely. So the muon, electron and town atrinos

865
00:43:45,120 --> 00:43:47,880
Speaker 1: have been acting kind of weird. We can't explain how

866
00:43:47,920 --> 00:43:50,600
Speaker 1: they're turning into each other and back and forth without

867
00:43:50,680 --> 00:43:54,360
Speaker 1: invoking this other fourth neutrino I see. So in the

868
00:43:54,440 --> 00:43:56,960
Speaker 1: experiments that you've have been doing with neutrinos, there's something

869
00:43:57,200 --> 00:44:00,040
Speaker 1: maybe missing some unexplainable things, and you think that me me,

870
00:44:00,160 --> 00:44:02,319
Speaker 1: this new neutrino would fix it. But I mean, if

871
00:44:02,360 --> 00:44:04,480
Speaker 1: it is kind of part of dark matter, wouldn't that

872
00:44:04,600 --> 00:44:06,960
Speaker 1: mean there are there's a lot of this fourth kind

873
00:44:07,000 --> 00:44:09,080
Speaker 1: of a netrino, Like, wouldn't that just totally throw the

874
00:44:09,120 --> 00:44:12,560
Speaker 1: balances off because there is of the universe that is

875
00:44:12,760 --> 00:44:15,040
Speaker 1: supposed to be dark matter. Wouldn't that be a huge

876
00:44:15,040 --> 00:44:18,160
Speaker 1: amount of sterile neutrinos. Yes, absolutely, it would be a

877
00:44:18,239 --> 00:44:20,239
Speaker 1: huge amount of steril neutrinos, and it would throw a

878
00:44:20,320 --> 00:44:22,800
Speaker 1: lot of other things off. Like people who study the

879
00:44:22,880 --> 00:44:26,000
Speaker 1: early universe, they can actually measure how many different kinds

880
00:44:26,040 --> 00:44:29,120
Speaker 1: of neutrinos there are because it would affect like how

881
00:44:29,239 --> 00:44:33,360
Speaker 1: the universe expanded very very early on, and those measurements

882
00:44:33,400 --> 00:44:36,200
Speaker 1: are very conclusive. There are exactly three kinds of neutrinos

883
00:44:36,239 --> 00:44:38,279
Speaker 1: and no more and no room for any other kind,

884
00:44:38,360 --> 00:44:41,040
Speaker 1: thank you very much. So the very early universe picture

885
00:44:41,080 --> 00:44:44,759
Speaker 1: from like studying the cosmic microwave background says there's absolutely

886
00:44:44,920 --> 00:44:47,200
Speaker 1: only three kinds of neutrinos. But then we have this

887
00:44:47,320 --> 00:44:50,360
Speaker 1: weird experiment from Los Almos that can only be explained

888
00:44:50,480 --> 00:44:53,960
Speaker 1: using a sterile neutrino or maybe they messed it up.

889
00:44:56,640 --> 00:44:59,759
Speaker 1: That's the other possibility. I guess maybe they just didn't

890
00:44:59,800 --> 00:45:01,799
Speaker 1: care at the zero or something. Well, you know, these

891
00:45:01,840 --> 00:45:04,120
Speaker 1: experiments are very very hard to do, and they were

892
00:45:04,160 --> 00:45:06,600
Speaker 1: doing something nobody had ever done before, and it was

893
00:45:06,640 --> 00:45:08,720
Speaker 1: a big puzzle. And so they actually did a follow

894
00:45:08,800 --> 00:45:12,000
Speaker 1: up experiment like ten years later. It was called Mini Boon,

895
00:45:12,480 --> 00:45:14,360
Speaker 1: where they used like a lot of the same devices,

896
00:45:14,440 --> 00:45:15,880
Speaker 1: but they made it a little bit more clever to

897
00:45:15,920 --> 00:45:18,280
Speaker 1: see if they could like nail this down. They changed

898
00:45:18,320 --> 00:45:20,759
Speaker 1: it so they weren't just looking at muon neutrinos, they

899
00:45:20,800 --> 00:45:23,680
Speaker 1: were looking also at anti muon neutrinos. And I remember

900
00:45:23,800 --> 00:45:26,160
Speaker 1: being in the room at Fermilab when they unveiled the

901
00:45:26,320 --> 00:45:29,120
Speaker 1: results of this experiment. It's like fifteen years ago, and

902
00:45:29,160 --> 00:45:31,560
Speaker 1: everybody was wondering, like, are we going to see conclusive

903
00:45:31,600 --> 00:45:34,439
Speaker 1: evidence us there on neutrinos, And unfortunately what they saw

904
00:45:34,840 --> 00:45:38,160
Speaker 1: doesn't agree with the original Los Almos experiment, but it

905
00:45:38,320 --> 00:45:41,600
Speaker 1: also doesn't agree with the standard model. So it's like

906
00:45:41,719 --> 00:45:44,719
Speaker 1: they saw something else weird that they can't explain. So

907
00:45:44,800 --> 00:45:47,520
Speaker 1: then we had like two mysteries that were inconsistent with

908
00:45:47,600 --> 00:45:52,040
Speaker 1: each other. But from the same group of people. So yeah,

909
00:45:52,040 --> 00:45:53,480
Speaker 1: it was a bit of a puzzle what was going

910
00:45:53,520 --> 00:45:57,680
Speaker 1: on there, and they didn't carry the two this time. Yeah,

911
00:45:57,760 --> 00:46:00,520
Speaker 1: And you know, sociologically it's fascinating because there's some very

912
00:46:00,640 --> 00:46:04,920
Speaker 1: prominent neutrino physicists in the community, very fancy universities, so

913
00:46:05,040 --> 00:46:07,400
Speaker 1: they have a lot of credibility. But you know, if

914
00:46:07,440 --> 00:46:09,279
Speaker 1: you ask neutrino physicists, what do you think is the

915
00:46:09,320 --> 00:46:11,880
Speaker 1: most likely explanation. Do you think it's star on neutrinos

916
00:46:11,960 --> 00:46:14,120
Speaker 1: or do you think they've like misunderstood some of the

917
00:46:14,160 --> 00:46:16,759
Speaker 1: background or mess something up. They start off talking about

918
00:46:16,760 --> 00:46:18,600
Speaker 1: stering neutrinos, but in the end, I think a lot

919
00:46:18,640 --> 00:46:21,320
Speaker 1: of people are convinced that these experiments there's something missing

920
00:46:21,320 --> 00:46:23,920
Speaker 1: about our understanding of them. Well, I mean, the trinos

921
00:46:23,920 --> 00:46:25,600
Speaker 1: are kind of a big deal right now in physics,

922
00:46:25,640 --> 00:46:27,760
Speaker 1: and so there are a lot of ma trino experiments

923
00:46:27,800 --> 00:46:30,640
Speaker 1: going on. Haven't have any of them found any indication

924
00:46:30,719 --> 00:46:33,440
Speaker 1: that sterling neutrinos exist? Or have they all just been

925
00:46:34,160 --> 00:46:37,319
Speaker 1: telling us the same picture. All the other experiments are

926
00:46:37,400 --> 00:46:41,239
Speaker 1: consistent with each other and inconsistent with these two experiments

927
00:46:41,360 --> 00:46:44,240
Speaker 1: that point to sting netrinos. So Without these two experiments,

928
00:46:44,480 --> 00:46:47,880
Speaker 1: everything fits together very very nicely. Wait, without these two experiments,

929
00:46:47,920 --> 00:46:50,920
Speaker 1: we wouldn't even be talking about sterl netrinos. Yeah, that's right.

930
00:46:51,040 --> 00:46:53,880
Speaker 1: I mean, theoretically they're very attractive and they could explain

931
00:46:53,920 --> 00:46:56,480
Speaker 1: the dark matter. But the early universe says no to

932
00:46:56,520 --> 00:46:59,160
Speaker 1: star on the trinos. All the other neutrino experiments out there,

933
00:46:59,239 --> 00:47:01,520
Speaker 1: not led by the group of people, are all consistent

934
00:47:01,560 --> 00:47:03,520
Speaker 1: with each other and say no to stare on neutrinos,

935
00:47:03,560 --> 00:47:06,879
Speaker 1: even very specifically cross checking the exact kind of stare

936
00:47:06,920 --> 00:47:09,640
Speaker 1: on the trino predicted by this Los Almos experiment and

937
00:47:09,719 --> 00:47:12,920
Speaker 1: the miniboon experiment. But these two other experiments, you know,

938
00:47:13,360 --> 00:47:16,080
Speaker 1: we don't understand their results. Oh man, I feel a

939
00:47:16,080 --> 00:47:17,600
Speaker 1: little bit let down. I feel like they shouldn't be

940
00:47:17,640 --> 00:47:19,600
Speaker 1: called ster on lutrinos. Maybe they should just be called

941
00:47:19,800 --> 00:47:24,200
Speaker 1: futile because it sounds like I'm not really believe that

942
00:47:24,320 --> 00:47:26,800
Speaker 1: these exists, Right, You're not painting a very convincing picture

943
00:47:26,880 --> 00:47:29,239
Speaker 1: from me here. Well, I'll say, you know, personally, I'm

944
00:47:29,280 --> 00:47:31,520
Speaker 1: not convinced by these things at all. When I was

945
00:47:31,560 --> 00:47:33,040
Speaker 1: in the room and they unveiled the results of this

946
00:47:33,120 --> 00:47:35,760
Speaker 1: second experiment, the follow up one, I thought the results

947
00:47:35,800 --> 00:47:38,440
Speaker 1: look pretty wonky. Not just the actual results sometimes you

948
00:47:38,480 --> 00:47:40,320
Speaker 1: see a surprise from the universe, but they had a

949
00:47:40,360 --> 00:47:42,920
Speaker 1: bunch of control regions where they were supposed to be

950
00:47:43,000 --> 00:47:44,759
Speaker 1: able to understand the results if they knew what they

951
00:47:44,800 --> 00:47:47,960
Speaker 1: were doing, and those also looked wonky. So immediately I

952
00:47:48,040 --> 00:47:50,640
Speaker 1: was like, I'm just not sure that these folks understand

953
00:47:50,680 --> 00:47:54,799
Speaker 1: the backgrounds. It's very personal, my personal opinion about these

954
00:47:54,840 --> 00:47:57,279
Speaker 1: experimental results. And you know, these things are really really

955
00:47:57,400 --> 00:47:59,400
Speaker 1: hard to do. I'm not saying I know how to

956
00:47:59,440 --> 00:48:01,880
Speaker 1: do these things better than those experts. I'm just not

957
00:48:02,000 --> 00:48:03,960
Speaker 1: sure that we really understand everything that's going on in

958
00:48:04,000 --> 00:48:07,000
Speaker 1: those experiments. Well, I would hear about what happened, and

959
00:48:07,239 --> 00:48:09,480
Speaker 1: I think that pretty much explains it. Yeah, I think

960
00:48:09,520 --> 00:48:12,759
Speaker 1: their kitchens were just dirty and not though, and that

961
00:48:12,920 --> 00:48:16,600
Speaker 1: probably uh you know, ended up correcting their data. Right, Yeah,

962
00:48:16,680 --> 00:48:20,080
Speaker 1: maybe that's it. Actually, these experiments are amazing technological feats

963
00:48:20,160 --> 00:48:23,640
Speaker 1: involved like a hundred and sixty tons of pure mineral

964
00:48:23,760 --> 00:48:27,279
Speaker 1: oil in these vats underground. They're very difficult. You have

965
00:48:27,360 --> 00:48:29,920
Speaker 1: to be very careful and exacting about your cleanliness to

966
00:48:30,000 --> 00:48:32,719
Speaker 1: even do these experiments. So I'm pretty sure their kitchen,

967
00:48:32,840 --> 00:48:36,480
Speaker 1: metaphorically speaking, is pretty clean. Maybe that you said the

968
00:48:36,600 --> 00:48:39,080
Speaker 1: oven wrong, All right, Well, it sounds like it's another

969
00:48:39,120 --> 00:48:42,480
Speaker 1: one of these interesting mysteries in physics, as as they

970
00:48:42,520 --> 00:48:45,440
Speaker 1: seem to be everywhere and where you have some experiments

971
00:48:45,520 --> 00:48:49,560
Speaker 1: that point to something interesting and some that don't, and

972
00:48:49,800 --> 00:48:52,040
Speaker 1: if one of them is correct, and Mike tell us

973
00:48:52,040 --> 00:48:54,840
Speaker 1: a lot about a huge portion of the universe, right Like,

974
00:48:54,960 --> 00:48:57,040
Speaker 1: if something like this could explain dark matter, it would

975
00:48:57,040 --> 00:48:59,920
Speaker 1: be a humongous deal. It would be twenty seven per

976
00:49:00,080 --> 00:49:02,399
Speaker 1: end of the universe. It would be a humongous deal.

977
00:49:02,920 --> 00:49:06,040
Speaker 1: And even without these experiments, even without sterio neutrinos, we

978
00:49:06,200 --> 00:49:09,799
Speaker 1: know there's something weird going on with neutrinos, right because

979
00:49:09,920 --> 00:49:12,560
Speaker 1: we can't explain why they have mass, why they seem

980
00:49:12,600 --> 00:49:14,719
Speaker 1: to be right handed neutrinos, why they have such a

981
00:49:14,760 --> 00:49:18,759
Speaker 1: little mass. Neutrinos themselves are very very strange objects. And

982
00:49:18,960 --> 00:49:21,640
Speaker 1: in the physics community, a lot of people are persuaded

983
00:49:21,840 --> 00:49:24,080
Speaker 1: that this is the next frontier, this is where we're

984
00:49:24,120 --> 00:49:26,520
Speaker 1: going to make big discoveries. And that's actually why the

985
00:49:26,640 --> 00:49:29,200
Speaker 1: United States has decided to make a big bet on

986
00:49:29,320 --> 00:49:33,000
Speaker 1: neutrino physics. We're not going after like Energy Frontier super

987
00:49:33,120 --> 00:49:35,840
Speaker 1: high energy colliders were letting the Europeans and the Chinese

988
00:49:35,880 --> 00:49:37,759
Speaker 1: do that, but the U S community is betting big

989
00:49:37,840 --> 00:49:41,239
Speaker 1: on neutrino experiments. Alright, well, stay tuned as we learn

990
00:49:41,280 --> 00:49:45,000
Speaker 1: more about neutrinos, or maybe not learn much about neutrinos.

991
00:49:45,120 --> 00:49:47,880
Speaker 1: Either way, it would point to some big mysteries in

992
00:49:47,920 --> 00:49:50,080
Speaker 1: the universe. And we definitely know that the universe seems

993
00:49:50,080 --> 00:49:52,719
Speaker 1: to be sort of a hot, delicious mess. Doesn't seem

994
00:49:52,760 --> 00:49:54,719
Speaker 1: to make any sense to us, but maybe one day

995
00:49:54,760 --> 00:49:57,200
Speaker 1: if we rotate our internal matrice is the right way,

996
00:49:57,480 --> 00:50:02,000
Speaker 1: it'll all click into place and hopefully be delicious. That's

997
00:50:02,040 --> 00:50:04,480
Speaker 1: the taste I'm going for in life. Let's open an

998
00:50:04,480 --> 00:50:07,040
Speaker 1: ice cream shop called Neutrino Flavor. Well, we hope you

999
00:50:07,120 --> 00:50:09,680
Speaker 1: enjoyed that. Thanks for joining us, See you next time.

1000
00:50:17,400 --> 00:50:20,240
Speaker 1: Thanks for listening, and remember that Daniel and Jorge explained.

1001
00:50:20,239 --> 00:50:23,120
Speaker 1: The Universe is a production of I Heart Radio. For

1002
00:50:23,280 --> 00:50:26,200
Speaker 1: more podcast from my Heart Radio, visit the I Heart

1003
00:50:26,280 --> 00:50:29,839
Speaker 1: Radio app, Apple Podcasts, or wherever you listen to your

1004
00:50:29,920 --> 00:50:32,600
Speaker 1: favorite shows. H