Speaker 1: Hey, Katie, how do your particles feel today? I guess
Speaker 1: it depends on which particle you ask. All right, well,
Speaker 1: let's start with your protons. How are they feeling this morning?
Speaker 1: They're feeling pretty positive. And your electrons any negativity there? Well,
Speaker 1: I would say they're all charged up. And what about
Speaker 1: those neutrons. We don't want to overlook them? How are
Speaker 1: they doing? There? Come scums? All right, well, let's see
Speaker 1: if this podcast can get them excited. Well, I'm excited
Speaker 1: even if my neutrons are kind of just meth. Hello.
Speaker 1: I'm Daniel. I'm a particle of physicist and a professor
Speaker 1: at UC Irvine, and I contain multitudes of particles. And
Speaker 1: I am Katie Golden. I host the podcast Creature feature
Speaker 1: about animals and my particles. Uh, I think I've got
Speaker 1: at least ten of them. You know, really, your podcast
Speaker 1: is also about particles, since all animals are also made
Speaker 1: of particles. That's right, So who's the physicist? Now? We're
Speaker 1: all physicists. That's the point. Every podcast is really about particles,
Speaker 1: even those true crime podcasts, even the Bigfoot podcast, even
Speaker 1: those paranormal e sp podcasts that consistently outrank ours in
Speaker 1: the natural science category, but welcome to the podcast. Daniel
Speaker 1: and Jorge explain the universe in which we treat the
Speaker 1: entire universe as a crazy swarm of particles. Particles that
Speaker 1: are mysterious, particles that are weird, particles that follow very
Speaker 1: strange quantum rules, but particles that do follow rules in
Speaker 1: the end, rules that we think we can understand, we
Speaker 1: can digest, that we can explain to you. On this podcast,
Speaker 1: we hope to wrap our minds around everything in the universe,
Speaker 1: break it down to its time little particles, and feed
Speaker 1: them to you one by one. My co host and friend,
Speaker 1: Jorge Champ can't be here today, but we are very
Speaker 1: lucky to have our regular co host, Katie. Katie thanks
Speaker 1: a lot for joining us. Of course, I am ready
Speaker 1: to learn about particles because you know, they seem important,
Speaker 1: given that I need them in me to make me, me,
Speaker 1: to make you you. Indeed, but you know what is
Speaker 1: the units of you? Diving right into the philosophical questions
Speaker 1: at the heart of particle physics, one thing we have
Speaker 1: learned recently about particles and the universe is that we
Speaker 1: all seem to be made up of the same kinds
Speaker 1: of particles. I'm made of protons, neutrons, and electrons. You're
Speaker 1: made of protons, neutrons and electrons. What's the difference? Are
Speaker 1: there Katie particles and Daniel particles? No, it turns out
Speaker 1: that the only different it's between Daniel and Katie fundamentally,
Speaker 1: or between an apple and a banana, or between kittens
Speaker 1: and lava, is how those particles are put together. You
Speaker 1: take that same basic set of building box and you
Speaker 1: can make anything. You're blowing my mind. So if we
Speaker 1: sort of melted down Katie and Daniel into just the
Speaker 1: particles and then rearranged all the Katie particles into Daniel
Speaker 1: particle like the Daniel blueprints, then now would just create
Speaker 1: a Daniel even though uh, those were originally my particles.
Speaker 1: That's exactly right. It seems like our universe follows the
Speaker 1: same principles as legos, that the same basic building blox
Speaker 1: can be used to make anything. Right, if your little
Speaker 1: brother used your legos to make a huge dinosaur and
Speaker 1: then you smashed it and used it to build a
Speaker 1: pirate boat, you could reuse those dinosaur legos to make
Speaker 1: your pirate hip. Now Here, of course, I have to
Speaker 1: quibble with the fundamental flaw of Lego toys. The original Legos,
Speaker 1: We're just the basic building blocks, and I love that
Speaker 1: simplicity that I had no bias to them. You you
Speaker 1: could use them to make anything. These fancy new modern Legos,
Speaker 1: you know, they come with stuff printed on the sides
Speaker 1: or specific shapes, right, so the sort of like predetermine
Speaker 1: what you have to build. I'm talking about the true
Speaker 1: original Legos. Yeah. I usually just built the tallest tower
Speaker 1: I could make out of my Legos, and then usually
Speaker 1: put a bunch of guys on it, so it's like
Speaker 1: just this big tower of Babel. I don't know what
Speaker 1: that says about me, but yeah, I agree, Although I
Speaker 1: do like that modern legos do have different kinds of Legos.
Speaker 1: Like it started out, I think, with just the one
Speaker 1: Lego block unit, but now you have all sorts of
Speaker 1: different types of Legos. You have like the sort of
Speaker 1: o G blocks, but you also have these long, skinny ones,
Speaker 1: you have ones that can rotate, you have like connector legos.
Speaker 1: But is that at all similar to how the universe works?
Speaker 1: Seems to be very similar to how the universe works.
Speaker 1: You know, I'm made of protons and neutrons and electrons
Speaker 1: and store are you and so is basically everything that
Speaker 1: you've ever eaten, everything you've ever tripped over, everything you've
Speaker 1: ever thrown at your sibling. They're all made of the
Speaker 1: same ingredients. And if you look at the periodic table,
Speaker 1: you can see that that's true, right, Every element on
Speaker 1: the periodic table is just made of protons and neutrons
Speaker 1: and electrons arranged in different numbers. You start with one
Speaker 1: proton and electron, you have hydrogen. You added another proton,
Speaker 1: you get helium. Keep adding protons, do you get different elements?
Speaker 1: You're just adding more of the same basic building blocks,
Speaker 1: but you make fundamentally different elements. But those different elements
Speaker 1: are not really fundamentally different. The only difference between carbon
Speaker 1: and neon, or between lead and gold is the number
Speaker 1: of protons inside those nuclei. So really you can build
Speaker 1: anything with the same basic building blocks. It's so hard
Speaker 1: to wrap my head around that. So, you know, just
Speaker 1: like it's just seems that it's a numbers game, because
Speaker 1: like usually with legos, if you just have like five legos,
Speaker 1: it doesn't suddenly turn into from like you know, a
Speaker 1: sugar into like gold or something like that. But with
Speaker 1: these on the atomic levels. When you change just the
Speaker 1: number of these these tiny particles, it turns from you know,
Speaker 1: something that if you eat nothing would happen to you,
Speaker 1: to something if you eat it it would be bad
Speaker 1: and drive you crazy, like eating lead versus drinking air.
Speaker 1: I guess we don't really drink air, but you get
Speaker 1: the idea. Yeah. Absolutely. It might seem like a small difference.
Speaker 1: You're just adding a proton, what's the big deal, But
Speaker 1: it completely changes its emergent behavior. All these characteristics that
Speaker 1: were familiar with the way metals are shiny and conduct electricity,
Speaker 1: the way some of these elements are float around and
Speaker 1: ignore the other ones that are not very active. All
Speaker 1: of those properties are determined by how many protons and
Speaker 1: how many electrons there are in each atom, and so like,
Speaker 1: the fact that metals are metallic and conductive comes from
Speaker 1: the fact that their electron shells are not filled, which
Speaker 1: is determined by the number of protons inside the nucleus.
Speaker 1: So it's not just an relevant detail, it's a totally
Speaker 1: determining fact. But it's fascinating they're all made out of
Speaker 1: the same bits. The other fascinating thing to me is
Speaker 1: that we're all made out of roughly the same ratios
Speaker 1: of bits, Like any given atom has basically a one
Speaker 1: to one to one proton to neutron to electron ratio.
Speaker 1: So lead has more protons than hydrogen, but it also
Speaker 1: has more neutrons and also has more electrons. That means
Speaker 1: that not only are we all made out of the
Speaker 1: same three basic building blocks, but we're made out of
Speaker 1: them in the same proportions. It's not like Katie has
Speaker 1: more electrons and Daniel has more protons, right, where the
Speaker 1: same building blocks in the same proportions just rearranged differently.
Speaker 1: So you you mentioned that the number of protons sort
Speaker 1: of changes the element. In the number of electrons, it's
Speaker 1: kind of changes the characteristic of these elements, But you
Speaker 1: didn't mention neutrons too much being sort of the determinant
Speaker 1: of what these elements are. Why are neutrons different in
Speaker 1: terms of pro tons and electrons. Yeah, it's a good point,
Speaker 1: and neutrons are sadly often overlooked, which is why we
Speaker 1: are dedicating almost our entire podcast today to talking about
Speaker 1: these mysterious, funny particles. But you're right that neutrons don't
Speaker 1: really determine as much the identity of the atom, and
Speaker 1: that's because they are electrically neutral. Like if you add
Speaker 1: another proton to the atom, then in order to make
Speaker 1: it electrically neutral, you have to add another electron in
Speaker 1: orbit around it, and that really changes the chemical properties.
Speaker 1: It changes how this thing interacts, whether or not it's
Speaker 1: electron orbitals are filled, or whether it's got an opening
Speaker 1: that very strongly affects the behavior of the atom. You
Speaker 1: add another neutron, then you don't need to add another electron.
Speaker 1: So you can add neutrons, no big deal. You can't
Speaker 1: just add neutrons anytime you like to any atom. It
Speaker 1: doesn't make them heavier, and it makes these other versions
Speaker 1: of the elements. These are called isotopes. So, for example,
Speaker 1: you can have hydrogen, which is just a proton, but
Speaker 1: you can also have deuterium, which is a proton and
Speaker 1: a neutron. So you put those together inside the nucleus,
Speaker 1: you have an electron around it. It's still called hydrogen,
Speaker 1: but it's like a heavy version of hydrogen. For example,
Speaker 1: if you put that together into H two O, but
Speaker 1: instead of the hydrogen, you have this heavy version of
Speaker 1: hydrogen with a neutron also in the nucleus. Then you
Speaker 1: get what's called heavy water, which we sometimes use in
Speaker 1: nuclear experiments. Right, so it does change a little bit
Speaker 1: sort of the flavor of the element to add neutron,
Speaker 1: sort to take them away, but it doesn't change its
Speaker 1: fundamental identity, which is determined by the charged objects of
Speaker 1: proton and the electron. So that's really interesting to me.
Speaker 1: Why is the neutron involved at all in the atomic
Speaker 1: structure if it's just kind of this It seems like
Speaker 1: this neutral fluff particle just this like dead weight, But
Speaker 1: is that really true. No, the neutron often overlooked, but
Speaker 1: it does play a vital role in keeping the nucleus together.
Speaker 1: We're gonna dig into it a bit more on the podcast,
Speaker 1: but very briefly, think about how the nucleus stays together. Right,
Speaker 1: If you have the nucleus of an atom that has
Speaker 1: like twenty five protons in it, those things are all
Speaker 1: positive of lee charged. Why don't they just like bust apart?
Speaker 1: You know, why don't they repel each other because they
Speaker 1: all have the same positive charge. The answer is that
Speaker 1: the nucleus is held together by the strong force, which
Speaker 1: is much more powerful than electromagnetism and neutrons. Even though
Speaker 1: they are neutral electromagnetically, they do involve the strong force.
Speaker 1: Turns out, the nucleus is a bit of a delicate
Speaker 1: puzzle keeping those protons from flying apart. You need the neutrons.
Speaker 1: It's a little bit of a spacer, and so it's
Speaker 1: easier to make stable nuclei if you include the neutrons.
Speaker 1: I see, So without the neutrons, the protons would not
Speaker 1: be able to stand each other's presence. I know people
Speaker 1: like that and like in group dynamics, that kind of
Speaker 1: keep the peace. So that's that is really interesting. So
Speaker 1: I guess without neutrons we wouldn't exist, we would not
Speaker 1: be held together. But it's odd to me though, that
Speaker 1: that neutrons have. It seems like they're fundamentally different from
Speaker 1: like a proton or an election because they don't have
Speaker 1: this charge. So you know, how did that even really happen? Yeah, well,
Speaker 1: these are deep questions about the universe, like why do
Speaker 1: we have neutrons anyway? Right, it's just sort of how
Speaker 1: the universe coalesces. Remember, we go back to the very
Speaker 1: early part of the universe where everything is just energy,
Speaker 1: and the universe then expands and cools and as it cools.
Speaker 1: It's sort of like crystallizes into lower energy states. Things
Speaker 1: sort of like come together and form stable particles. And
Speaker 1: by looking around in the universe and seeing sort of
Speaker 1: what was made, we can tell sort of like what
Speaker 1: the options were. We don't know like why it's possible
Speaker 1: to build neutrons necessarily, but we see that a lot
Speaker 1: of them sort of emerged from the chaos of the
Speaker 1: early universe. And that's another really fascinating aspect of these
Speaker 1: particles is their age. Like protons, we think that protons
Speaker 1: probably live forever. Like you make a proton, you can
Speaker 1: just hang out forever and stick around till the end
Speaker 1: of time. Same with an electron. Electron is stable, right,
Speaker 1: you have an electron sitting in empty space, it will
Speaker 1: just stay an electron for a billion years, maybe a
Speaker 1: trillion years, a quadrillion years. And what that means is
Speaker 1: that the protons and electrons inside your body were probably
Speaker 1: made during the Big Bang. So you are made of
Speaker 1: ancient multitudes. I mean, you know, thank you for that,
Speaker 1: thank you for calling me old. So neutrons weren't necessarily
Speaker 1: made during the Big Bang. You're saying, so neutrons were
Speaker 1: also made during the Big bang, right as the universe cooled,
Speaker 1: we got protons, we've got electrons, we've got neutrons. But
Speaker 1: there's a difference between protons, electrons, and neutrons that goes
Speaker 1: beyond just their electric charge. Neutrons don't seem to last
Speaker 1: forever the same way that protons and electrons do. In fact,
Speaker 1: they don't last very long at all. So that makes
Speaker 1: them fundamentally weird and different. And by studying the details
Speaker 1: of how long the neutron lives and what it turns into,
Speaker 1: we might get some clues to these questions about like
Speaker 1: why are there neutrons after all? What's going on inside
Speaker 1: the neutrons? Are they irrelevant little particles? Are they the
Speaker 1: most important clue we have to the nature of the universe?
Speaker 1: So yeah, no, I'm really curious, like what does it
Speaker 1: mean for a neutron to be alive? And then how
Speaker 1: does it die? And how long does that process take?
Speaker 1: And so today on the podcast we'll be answering the
Speaker 1: question how long does a neutron live? Alright, Katie, and
Speaker 1: you've already called me out, I see for using the
Speaker 1: word live in the title, because our neutrons alive after all,
Speaker 1: and you know, as a particle physicist, I think about
Speaker 1: these particles as sort of having a lifetime. But you're right,
Speaker 1: neutrons are not alive, nor are they dead in any
Speaker 1: sort of biological sense. I mean, if you corner a
Speaker 1: biologist and try to get them to answer the question
Speaker 1: what is life, They're gonna start sweating and giving you
Speaker 1: a really complex answer. So it's not a simple question.
Speaker 1: But but no, I get it. So it's like a
Speaker 1: neutron does not always remain a neutron in the sense
Speaker 1: that it does not stay the same forever, and so
Speaker 1: that could be seen as it, you know, essentially decaying
Speaker 1: or dying. Right exactly, When we talk about particle lifetimes,
Speaker 1: we're talking about how long the particle exists before it
Speaker 1: turns into something else. So some particles in the universe
Speaker 1: are stable, like electrons and protons and the corks that
Speaker 1: make up those protons and photons. For example, you can
Speaker 1: create a photon with a flashlight, shoot it out into space,
Speaker 1: and it might fly for billions or trillions of years.
Speaker 1: Some of the photons received by your eyeballs when you
Speaker 1: look up at night have been crawling across the universe
Speaker 1: for billions of years. It's incredible how long they have survived.
Speaker 1: So some particles sort of live forever. And again we're
Speaker 1: using to live in a sort of anthropomorphic biological analogy
Speaker 1: to life. Really we just mean exists, but other particles don't.
Speaker 1: Other particles are not stable, and the neutron is one
Speaker 1: of those. That's really interesting. So yeah, I didn't really
Speaker 1: think of neutrons as being an impermanent thing. I think
Speaker 1: about the building blocks of life. I mean I pictured
Speaker 1: them as these like little permanent speares that you know,
Speaker 1: make everything and just stay the same, and you know
Speaker 1: that is just this kind of like solid foundation to everything.
Speaker 1: But now you're shaking that all up. What if I
Speaker 1: told you that one of your legos a specific kind
Speaker 1: of lego, if you didn't use it, it would just
Speaker 1: like evaporate or turn into other kinds of legos. That
Speaker 1: sounds like an excuse a little brother would give when
Speaker 1: you're stealing all my legos. All right, but this is
Speaker 1: not a family therapy podcast, at least not yet. So
Speaker 1: I was curious if other people had thought about the
Speaker 1: lifetime of the neutron, if people were aware that neutrons
Speaker 1: don't live forever, and how long they thought it might live.
Speaker 1: So I went out there to our cadre of Internet
Speaker 1: volunteers who are willing to answer hard physics questions without
Speaker 1: any opportunity to prepare themselves. Thank you very much, and
Speaker 1: if you would like to join this hearty group, then please,
Speaker 1: they'll be shy right to me. Two questions at Daniel
Speaker 1: and Jorge dot com. So think about it for a moment.
Speaker 1: Do you know how long a neutron lives? Here's what
Speaker 1: people had to say. I guess. My guess would be
Speaker 1: that it would live indefinitely until some other force overpowers
Speaker 1: the forces that hold it together. Tron lives um like
Speaker 1: a free nel tron shouldn't been that long, but I
Speaker 1: don't know, probably not more than a few minutes. I
Speaker 1: think that actually this is something that's really confused me
Speaker 1: as I've started to look into and tried to understand
Speaker 1: particle physics and quantum physics and everything, and I think
Speaker 1: that possibly it's just an instant. Yeah, neutrons, just like
Speaker 1: like a lot of particles, just exists for an instant.
Speaker 1: On the other hand, it could be they could last
Speaker 1: for by entire lifetime, so yeah, it could be a
Speaker 1: long time as well. Well. Neutrons makeup part of stomic nuclei,
Speaker 1: so they live for at least as long as the
Speaker 1: longest lived elements UM, so at least a few million years.
Speaker 1: But I think UH universe skills tend to be quite extreme,
Speaker 1: so I guess since they don't live for only fractions
Speaker 1: of a millisecond, I'm going to guess they live for
Speaker 1: billions of years. I don't know if a neutron lives forever,
Speaker 1: and I think the answer to that question is we
Speaker 1: don't know if neutrons live forever. I know that proton
Speaker 1: decay is still actively being studied and debated, and I
Speaker 1: don't think a neutron would be much different. And as
Speaker 1: of now, I believe we do not know how long
Speaker 1: they live or if they decay away. I know that
Speaker 1: protons decay inter neutrons UM because they emit a positron,
Speaker 1: so I'm gonna wonder whether neutrons can also emit an
Speaker 1: electron and in a sense decay into protons. But this
Speaker 1: process doesn't happen, so all the proton has a lifetime
Speaker 1: of I don't know if the order of a few
Speaker 1: seconds UM, and you'tron. I know it's a number of
Speaker 1: years and I think it's the amount amount of time
Speaker 1: is comfortable to the age of the universe something like that.
Speaker 1: I really like the answer, probably just an instant, or
Speaker 1: maybe my entire lifetime, because even though that seems funny,
Speaker 1: like how could you compare an instant to an entire lifetime?
Speaker 1: How could you be so equivocal? On the universal scale,
Speaker 1: those are almost the same in a certain way, right,
Speaker 1: Like when you look at the entire lifetime of the universe,
Speaker 1: an instant in one human lifetime or not that different exactly.
Speaker 1: And that's the incredible thing about all of these numbers
Speaker 1: in physics that when you're talking about how long something lives,
Speaker 1: it could be some crazy, tiny tiny number ten to
Speaker 1: the minus twenty seconds, or it could be cosmic the
Speaker 1: scale of the lifetime of the universe, right, which is like,
Speaker 1: you know, six tillions of seconds, and so it's hard
Speaker 1: to know, like on that huge scale where to put
Speaker 1: these numbers, And so if you don't have any information,
Speaker 1: then you're right, his entire lifetime does feel sort of
Speaker 1: like an instant. And that's one of my favorite things
Speaker 1: about physics that it may think about these cosmic sweeps
Speaker 1: of time and recognize the fact that something that might
Speaker 1: take our entire lifetime is basically meaningless on the time
Speaker 1: scale of the universe. Well, way to make me feel
Speaker 1: both old and small. So in terms of neutrons, like
Speaker 1: it is interesting, like if they live like a human lifetime,
Speaker 1: that makes me feel a little less alone, or if
Speaker 1: they live like an instant, that almost makes me feel
Speaker 1: sorry for them. It's really hard not to anthropomorphize something
Speaker 1: once we're talking about how long it lasts, as if
Speaker 1: the neutron particularly cares. But I guess I want to know, like,
Speaker 1: what what is the neutron? Should I feel sorry for it? Well,
Speaker 1: I'm not going to tell you how to feel about
Speaker 1: the particles, but I'm happy to tell you how they're
Speaker 1: put together and what they mean. And so in the
Speaker 1: case of a neutron, we've been talking about it as
Speaker 1: if it was a particle in itself, like atoms. We
Speaker 1: said are made out of protons and neutrons in the
Speaker 1: nucleus surrounded by electrons. And that's true, but we can
Speaker 1: also drill one step deeper to understand what is the
Speaker 1: neutron itself made out of? Now, in the case of
Speaker 1: some fundamental particles like the electron, we don't know if
Speaker 1: they're actually fundamental or made out of even smaller lego
Speaker 1: building blocks. So far, the electron just looks like it's
Speaker 1: only made out of itself, but that might just be
Speaker 1: because we haven't zoomed in far enough. We don't have
Speaker 1: colliders capable of blowing up electrons and seeing what's inside them.
Speaker 1: In the case of protons and neutrons, we actually have
Speaker 1: been able to break them up and see what's inside.
Speaker 1: For about the last fifty years or so, we have
Speaker 1: had colliders capable of smashing these particles and showing us
Speaker 1: what they are made out of. And fascinatingly, the proton
Speaker 1: and the neutron are made out of the same two
Speaker 1: building blocks, up quarks and down corks, so there are
Speaker 1: two funny little particles. They have weird fractional electric charges,
Speaker 1: which allows them to get added up to make a
Speaker 1: neutron or a proton. So, for example, a neutron is
Speaker 1: an up cork which is charged two thirds, and then
Speaker 1: two down corks, each of which are charged minus one third.
Speaker 1: So neutron is an up, down, down Three of these
Speaker 1: corks put together, and you get zero electric charge. So physicists,
Speaker 1: when you're asked what's up cork? Do you just say
Speaker 1: not much what's up cork with you? Or do you
Speaker 1: have an actual answer to what's an up cork? And
Speaker 1: I guess what's a down cork? I don't know what's
Speaker 1: up is down, what's down is up? Sometimes in physics,
Speaker 1: you know, as I always say, I'm not going to
Speaker 1: be held responsible for the names of these particles, but
Speaker 1: you know, there are some reasons why we called them
Speaker 1: up corks and down corks. They're organized together by the
Speaker 1: weak force into this pair, this up and down pair
Speaker 1: that get linked together by the w boson, which we're
Speaker 1: going to talk about in just a minute. But actually
Speaker 1: in the nucleus, the upcorks and down corks are not
Speaker 1: held together by the weak force. They're held together by
Speaker 1: the strong force. So quarks have electric charges, but that's
Speaker 1: not what's holding them together. Like you think about the
Speaker 1: way molecules are held together, they're held together because of
Speaker 1: the electric charges. These electrons are like whizzing around and
Speaker 1: making these ionic bonds or covalent bonds. The electric charges
Speaker 1: are basically irrelevant once you get inside the proton and
Speaker 1: the neutron because there's a much more powerful force at play.
Speaker 1: And that's the strong nuclear force, which totally overwhelms the
Speaker 1: electromagnetic force, is able to hold all of these particles together.
Speaker 1: And the strong nuclear force does that by using gluons.
Speaker 1: So your mental picture of a neutron shouldn't be like
Speaker 1: three little lego pieces that clicked neatly together and that's it. Instead,
Speaker 1: it's more like three tiny little dots surrounded by a
Speaker 1: swarm of these gluons that are holding it together. So
Speaker 1: it's more like a bag of gluons with three hard
Speaker 1: dots in it. So, oh my gosh, so gluons. It's
Speaker 1: just this sort of like swarm of these things that
Speaker 1: hold together the up quarks and down corks. So like,
Speaker 1: the more we split things apart and try to think
Speaker 1: about like the even smaller thing that holds the smaller
Speaker 1: things together, it gets really difficult for my brain not
Speaker 1: to start hurting. But all right, So, so do we
Speaker 1: know like how many gluons are in a neutron or
Speaker 1: is it just kind of this mass of stuff that
Speaker 1: we know holds together of corks and down corks, But
Speaker 1: we can't necessarily quantify how many of these things there are. Yeah,
Speaker 1: that is a great question because probably you're wanting to
Speaker 1: put together a model of what's going on inside the
Speaker 1: neutron that has like a basic recipe, and those things
Speaker 1: clicked together to make a neutron way like pieces of
Speaker 1: a jigsaw puzzle get clicked together to make a bigger picture. Right,
Speaker 1: But that's not really the way we think about these gluons.
Speaker 1: Luans in this case are force particles. They're not matter particles.
Speaker 1: What that means is that they don't really exist in
Speaker 1: the same way that the matter particles do. They exist
Speaker 1: as a representation of the force between the matter particles.
Speaker 1: So you have the up cork and the two down corks.
Speaker 1: They're sitting there and they're pulling on each other, the
Speaker 1: strong forces holding them together there. How do you think
Speaker 1: about that force, Well, there's a few different ways of
Speaker 1: doing it. One is to think about them exchanging particles
Speaker 1: like zooming gluons back together. That's how they hold themselves together.
Speaker 1: And you can use that same strategy to think about
Speaker 1: how other particles talk to each other, Like what happens
Speaker 1: when two electrons push against each other because they have
Speaker 1: the same electric charge. How does that actually work microscopically, Well,
Speaker 1: you can think of them as shooting photons towards each
Speaker 1: other because photons are the force particle for the electromagnetic force.
Speaker 1: So inside the neutron, these corks are holding onto each
Speaker 1: other by shooting gluons at each other. That's one way
Speaker 1: of thinking about how the forces are working inside the neutron.
Speaker 1: There's another way of thinking about it, which doesn't use
Speaker 1: this sort of like virtual particles, these gluons sipping back
Speaker 1: and forth. You just think about fields. Like if you're
Speaker 1: more comfortable thinking about an electron being surrounded by its
Speaker 1: electric field and the way that it pushes on other
Speaker 1: electrons is that it's electric field pushes on it, then
Speaker 1: you can think about the interior of the neutron that
Speaker 1: same way as having three quarks each surrounded by a
Speaker 1: field from the strong force, and those fields are tugging
Speaker 1: on each other. Those are gluonic fields. You can think
Speaker 1: about them as either like a huge tower or virtual
Speaker 1: gluons which appear and disappear very quickly, or you can
Speaker 1: think about them in terms of fields. Are two equivalent
Speaker 1: mental pictures for the same fundamental process that's going on.
Speaker 1: But you can't really like count the number of gluons
Speaker 1: because they're not particles that exist in the same way
Speaker 1: as the corks. So, Okay, in my recipe that I'm
Speaker 1: writing for home baked neutrons, I'm just gonna put down
Speaker 1: a pinch of gluons. So you said that this is
Speaker 1: these are strong, uh, strong forces holding this neutron together.
Speaker 1: But we were just talking about how maybe these neutrons
Speaker 1: break apart. So how would they break apart if you
Speaker 1: have these really strong forces holding them together? Great question,
Speaker 1: and it reveals something about the way I think a
Speaker 1: lot of people think about particles and their decay. What
Speaker 1: happens when a particle decays? Is it breaking apart? Are
Speaker 1: you taking its pieces and they're reassembling them to build
Speaker 1: something else? Right, Well, what's happening when a neutron decays
Speaker 1: is not actually that is breaking apart at all. It's
Speaker 1: that one piece of its internal structure, one of those corks,
Speaker 1: changes its nature. So remember that a neutron is up, down,
Speaker 1: down right tow down corks and an up cork. Well,
Speaker 1: what happens if one of those down corks changes its
Speaker 1: flavor and becomes an up cork? Then you have two
Speaker 1: upcorks in a down instead of two down corks and
Speaker 1: an up. Remember that up coorks are charged plus two
Speaker 1: thirds and a down cork is charged minus one third,
Speaker 1: So now you have plus two third plus two third
Speaker 1: minus one third gives you a charge of plus one.
Speaker 1: That's a proton. So what happens when a neutron decays
Speaker 1: is that one of its down corks converts into an
Speaker 1: upcork and the neutron becomes a proton. So it doesn't
Speaker 1: break apart. It flips from being a neutron to being
Speaker 1: a proton. That's amazing. So it's less of a death
Speaker 1: of a particle in more of a tram information of
Speaker 1: a particle. Do we have any idea of why a
Speaker 1: down cork would become up cork? Yeah, Like you know,
Speaker 1: why does it down cork decide it wants to be
Speaker 1: an upcork one day? You know, like why isn't it
Speaker 1: just happy being an upcork. It's a great question, and
Speaker 1: it's a really deep question. It's like why does any
Speaker 1: particle decay? You know, why do muance just hang out
Speaker 1: and be muance? Why do they decay to electrons and
Speaker 1: a couple of neutrinos? Why does anything decay? And the
Speaker 1: reason is that the universe is constantly getting colder and
Speaker 1: spreading out. Entropy and statistical mechanics tells us that the
Speaker 1: universe doesn't like to have energy localized in a little spot.
Speaker 1: It likes for it to spread out. Sort of fascinating
Speaker 1: quantum mechanical, the universe likes to occupy multiple quantum states
Speaker 1: instead of like being focused on a single quantum state.
Speaker 1: What that means essentially is that any particle will always
Speaker 1: decay into a lower mass particle. If it's possible for
Speaker 1: you to take a step down the mass ladder to
Speaker 1: break up into smaller particle with less mass than you,
Speaker 1: always will the universe is its constant pressure. It's the
Speaker 1: same as if you have like a hot object sitting
Speaker 1: on a surface, it's going to spread its energy out
Speaker 1: to the neighboring stuff. The same way you have a
Speaker 1: very high mass particle. It wants to break up into
Speaker 1: lower mass particles. And it turns out that the neutron
Speaker 1: is heavier than the proton just by a little bit,
Speaker 1: and so the neutron can do this. It can take
Speaker 1: a step down into a lower energy configuration. So the
Speaker 1: neutron is a higher energy state, which means it has
Speaker 1: a little bit more mass. And decays down into a proton.
Speaker 1: It does this by flipping one of the down corks
Speaker 1: into an upcorp. So it's my freshly biked neutron. It's
Speaker 1: kind of like a hot soup flay. And then if
Speaker 1: I leave that out, it's going to cool down and
Speaker 1: then collapse into a proton. I got it. Oh, speaking
Speaker 1: of su fla, I did leave one out, so we're
Speaker 1: gonna need to take a quick break while I go
Speaker 1: check on that. I'm sure it's fine, uh, And then
Speaker 1: we hopefully will come back and I'll still have my
Speaker 1: neutron soup fla attack and we'll continue talking about how
Speaker 1: long do these neutrons live? How do I resuscitate my
Speaker 1: neutron souflay? So we'll be right back. Okay, So bad
Speaker 1: news is that my soup fla did collapse. The good
Speaker 1: news is I guess it's now our proton, so all
Speaker 1: isn't lost. That's always the backup plan for your neutron souflay.
Speaker 1: Turns out, charge it up to a proton south lag.
Speaker 1: Like you know, a sou flay that collapses is still
Speaker 1: gonna taste pretty good. So a neutron that decays into
Speaker 1: a proton is still a particle. It'll still build things
Speaker 1: like delicious soufleas exactly. And so we were talking about
Speaker 1: how neutrons decay and how they turn into protons, and
Speaker 1: people might be wondering, like what's going on with the
Speaker 1: electric charges? Like can you just turn a down cork
Speaker 1: which is charged minus a third into an upcork, which
Speaker 1: is charged plus two thirds? Like charge doesn't just come
Speaker 1: for fruit. You can't just like create charge. How do
Speaker 1: you just convert a neutron into a plus one charged proton? Right?
Speaker 1: The answer is that the universe does do the accounting
Speaker 1: quite carefully. And when a downcourt converts into an upcork,
Speaker 1: it also emits a W particle. Okay, now you're just
Speaker 1: making up particles. What's the W particle? So a W
Speaker 1: particle is the force particle for the weak nuclear force. Right,
Speaker 1: we got all these different forces. We have electromagnetism, we
Speaker 1: have a strong force, we have the weak force. Each
Speaker 1: one we think of as carried by a particle. So
Speaker 1: photons carry the electromagnetic force, gluons carry these strong force.
Speaker 1: W particles carry the weak nuclear force. The weak nuclear
Speaker 1: force is like the weirdest, strangest, most amazing sporce there is.
Speaker 1: It's not very powerful, but it can do all sorts
Speaker 1: of really strange stuff. And we have a couple of
Speaker 1: podcast episodes dedicated just to under standing the weak force
Speaker 1: and parity violation and all that crazy stuff. But in
Speaker 1: this case, the weak force is here to help balance
Speaker 1: the books. When a down cork becomes an upcork, that
Speaker 1: sort of costs one electric charge. You've gone from a
Speaker 1: neutron to a proton. So to balance the books, you
Speaker 1: also need to create something with negative charge. The amazing
Speaker 1: thing about these W particles is that they do have charge,
Speaker 1: so the W can have a positive or a negative charge.
Speaker 1: In this case, you emit a W minus which balances
Speaker 1: the charges. So have you've gone from a neutron to
Speaker 1: a proton and a W minus. So the proton is
Speaker 1: plus one, the W minus is minus one. That all
Speaker 1: adds up to zero. The W minus itself doesn't live
Speaker 1: for very long and it turns into an electron and
Speaker 1: an anti neutrino. Okay, so an electron does have a
Speaker 1: negative charge, so it still retains that negative charge. What
Speaker 1: is an anti neutrino? Yeah, and anti neutrino is one
Speaker 1: of these little ghostly particles. So you and I are
Speaker 1: made of protons and neutrons and electrons, which are made
Speaker 1: of upcorks and down corks. But there's this other particle,
Speaker 1: this neutrino, which exists in the universe and can be made,
Speaker 1: and the Sun is pumping out like jillions of them
Speaker 1: every second. But they're very strange little particles because they
Speaker 1: don't appear normally inside matter, Like I am not made
Speaker 1: out of neutrinos, and you're not made out of neutrinos
Speaker 1: in any way. But it's something that the universe can exist.
Speaker 1: It's like a Lego building block that's never used in
Speaker 1: making anything bigger or larger. It's just sort of like
Speaker 1: floating around in the universe. Yeah, I remember those Lego blocks.
Speaker 1: They're usually like these like weirdly shaped, clear little ones,
Speaker 1: and they would just kind of not be used in anything,
Speaker 1: get quickly lost or eaten exactly. And neutrinos are strange
Speaker 1: because they're very very low mass, they're almost massless but
Speaker 1: not entirely, and they also hardly interact. They don't have
Speaker 1: any electric charge, they don't have the strong force, so
Speaker 1: they basically just fly through everything. So neutrino when it's produced,
Speaker 1: can fly through like a star without blinking an eye
Speaker 1: into a neutrino. The whole universe is transparent, and so
Speaker 1: that just sort of flies out. And so to summarize them,
Speaker 1: when a neutron decays, it turns into a proton, an electron,
Speaker 1: and then an anti neutrino, and so that's what happens
Speaker 1: when a neutron decase. That's spooky. So neutron does kind
Speaker 1: of create a ghost when it decays scientifically speaking exactly.
Speaker 1: And we should also be clear about what we mean
Speaker 1: about neutron decay because people might be wondering, like, does
Speaker 1: that mean that the neutrons that are in my body
Speaker 1: right now are going to like break up, like they
Speaker 1: don't last for long? Like, am I dying because my
Speaker 1: neutrons are decaying? Yeah, I want to know if I
Speaker 1: will spontaneously turn into a pile of protons, electrons and
Speaker 1: ghost particles in my best interest to know. And that's
Speaker 1: one of the really fascinating mysteries about neutron decay is
Speaker 1: that neutrons do decay, but only sort of like when
Speaker 1: they're on their own, floating out in the universe. When
Speaker 1: a neutron is inside a nucleus when it's hanging out
Speaker 1: with other protons. When it and it's proton brethren have
Speaker 1: built something larger, then he can last forever. You know,
Speaker 1: you have a stable nucleus like iron, right, iron can
Speaker 1: live forever. We think if you have an iron atom
Speaker 1: sitting alone in the universe, it's made of protons and
Speaker 1: neutrons and electrons, it can sit there, we think forever.
Speaker 1: We think it's stable. If it's not perturbed, it will
Speaker 1: just hang out until the end of time. That includes
Speaker 1: the neutrons inside the iron right there there. They're neutrons.
Speaker 1: They will hang out forever. Their down corks are not
Speaker 1: going to flip into up corks, turning them into protons.
Speaker 1: This is like the ultimate ziplock bag techniques. So keeping
Speaker 1: neutrons fresh forever. I love that technology for my strawberries.
Speaker 1: They're so good, but they go bad so fast. Exactly so,
Speaker 1: the neutrons in your body are in atoms, and so
Speaker 1: they are likely to last as long as those atoms last.
Speaker 1: But if you take a neutron out of the atom
Speaker 1: and you have it by itself hanging out in free space,
Speaker 1: now we can talk about the lifetime of that neutron.
Speaker 1: What does it do when it's left alone? Well, the
Speaker 1: neutrons sitting there in empty space last till end of
Speaker 1: time or will it decay? So if you put like
Speaker 1: a proton and then a neutron and electron, you have
Speaker 1: them just hanging out in free space and you just wait.
Speaker 1: The proton will last forever, we think, the electron will
Speaker 1: last forever, we think, but the neutron will not. The
Speaker 1: neutron by itself will decay. One of those down corks
Speaker 1: will flip. That's the actual sound it makes, and it
Speaker 1: will turn into a proton electron and an anti neutrino.
Speaker 1: So when we talked about the neutron last time, we're
Speaker 1: talking about the isolated neutron, not a neutron that's inside
Speaker 1: the nucleus. So, when it's inside the nucleus, what is
Speaker 1: that zip block effect that is keeping it from decaying. Yeah,
Speaker 1: it's a great question, and there's a lot of mysteries
Speaker 1: there because we don't really understand very well how the
Speaker 1: strong force works. We talked about it briefly a little earlier,
Speaker 1: but when protons and neutrons are locked together inside a nucleus,
Speaker 1: it's not like you just have these particles and they're
Speaker 1: stuck together like legos. They're also talking to each other
Speaker 1: because remember a proton and a neutron, they're not just
Speaker 1: linked together quarks, they're little bags of gluons. When you
Speaker 1: get a proton and neutron close enough together, then their
Speaker 1: gluons talk to each other. Those bags leak a little bit.
Speaker 1: They're not totally separate from each other, and really they
Speaker 1: sort of like weave themselves into a larger mosaic. You
Speaker 1: might wonder inside a heavy hydrogen atom, where you have
Speaker 1: not just a proton, but a proton or a neutron,
Speaker 1: what's making the proton and neutron stick to each other? Right,
Speaker 1: the proton is positively charged, the neutron is negatively charged.
Speaker 1: Why did they stick together at all? Why don't they
Speaker 1: just float apart? The answer is their gluons. When you
Speaker 1: get them that close together, then the gluons inside each
Speaker 1: other's bags talk to each other, and they click together
Speaker 1: into sort of a larger object which is not really
Speaker 1: anymore just and isolated proton, not really any more isolated neutron,
Speaker 1: but this combined object that has these linkages together. So
Speaker 1: is that why when you keep adding neutrons to an
Speaker 1: atom that it becomes maybe less stable because you start
Speaker 1: to weaken those gluon forces. Yeah, you can make it
Speaker 1: less stable or more stable. Right, The way that you
Speaker 1: organize the protons and the neutrons inside the nucleus totally
Speaker 1: determined whether something is stable or not. We have a
Speaker 1: fun podcast episode about the islands of stability and how
Speaker 1: heavy you can make something and keep it stable. We
Speaker 1: don't know the answer to that because the strong force
Speaker 1: is very difficult to do calculations with, Like we can't
Speaker 1: sit down with pencil and paper and solve the quantum
Speaker 1: mechanics of the nucleus the way we can with the
Speaker 1: hydrogen atom. Folks who have done physics in college have
Speaker 1: done like the shortening your equation for the hydrogen atom.
Speaker 1: When we know those equations, we can solve them, we
Speaker 1: can find the states of the electron. We don't know
Speaker 1: how to do those calculations for the strong force because
Speaker 1: it's much more powerful and much more sensitive to tiny details,
Speaker 1: So we don't actually know like the answer to those
Speaker 1: We can't do it with pencil and paper. We have
Speaker 1: massive computers trying to do those calculations, but it's really challenging,
Speaker 1: So mostly it's experimental. We try to like build heavier
Speaker 1: stuff and see if we can keep it together. People
Speaker 1: shoot like neutrons at atoms and see like, oh, can
Speaker 1: I get one to stick in there and make something
Speaker 1: which lasts longer. So it's a whole area of research.
Speaker 1: How do weave protons and neutrons together into stable objects?
Speaker 1: We think that they organize themselves in terms of these shells.
Speaker 1: Is this nuclear shell model that tells you how to
Speaker 1: build protons and neutrons together into a stable nucleus sort
Speaker 1: of analogous to the way electrons organize themselves in shells
Speaker 1: on the outside of the atom. It's really fascinating. So
Speaker 1: I am feeling more and more like a physicist based
Speaker 1: on my childhood because I would try to just build
Speaker 1: the biggest thing out of legos and then kind of
Speaker 1: hold it up and see if it could sustain and
Speaker 1: self for if it would fall apart. And it sounds
Speaker 1: like that's what you guys are doing, just with more
Speaker 1: expensive equipment. But yeah, so that that is interesting is
Speaker 1: you're saying that, like maybe they arrange themselves into shells.
Speaker 1: When you're talking about shells, I'm assuming this is not
Speaker 1: like a mollusk shell or something. So what is a
Speaker 1: shell in terms of particle physics. Yes, when we talk
Speaker 1: about shells we think of like spheres and other arrangements.
Speaker 1: We think of The protons and neutrons inside the nucleus
Speaker 1: have somehow found stable ways to organize themselves into these
Speaker 1: like little mosaics. Instead of thinking about them really as
Speaker 1: protons and neutrons anymore, you really should think about them
Speaker 1: as components of this fabric, this nuclear fabric, which likes
Speaker 1: to weave itself together. And the incredible thing is that
Speaker 1: it's stable, like in many configurations, even for very very
Speaker 1: heavy elements, these things are quite stable. Again, we don't
Speaker 1: really understand it. And so there's two different communities of
Speaker 1: physicists here, the ones that like to make really big
Speaker 1: blobs of protons and neutrons and understand like how are
Speaker 1: they working together? And then there's the folks who just
Speaker 1: want to like dig inside one neutron and say, well,
Speaker 1: let's just study the neutron by itself. Let's zoom inside
Speaker 1: the neutron and see if we can understand what makes
Speaker 1: that cork flip from one to the other. How often
Speaker 1: does that happen? How long does it take? And what
Speaker 1: does that mean about the neutron. So you've got like
Speaker 1: the nuclear physicists studying like huge blobs of neutrons and
Speaker 1: protons inside the nucleus, and they have us particle physicists
Speaker 1: looking to break it apart and see what's inside. That's
Speaker 1: really interesting. So now that we have isolated the neutron,
Speaker 1: it's we've broken apart that atom. It's outside, it's vulnerable.
Speaker 1: Now what happens? So now we can see how long
Speaker 1: it takes to pop into a proton and electron and
Speaker 1: a neutrino. And so this is a really interesting question,
Speaker 1: just like how long does it take? Remember, protons will
Speaker 1: live for trillions of years. There's two amazing things about
Speaker 1: the neutron lifetime how long a neutron will survive on
Speaker 1: its own. First is that it's very short. It's like
Speaker 1: fifteen minutes. The neutron does not last very long. The
Speaker 1: person is that it's basically instantaneous on a cosmic timescale.
Speaker 1: That's right, you know, neutron's last for like fifteen minutes.
Speaker 1: It's it's nothing. You know, cosmically, do you make a neutron?
Speaker 1: You leave it there, you go to get a coffee
Speaker 1: and you come back it's gone. You know, that's kind
Speaker 1: of sad to me. I don't know why. Again, I'm
Speaker 1: like attributing emotions to these things in the universe that,
Speaker 1: as far as I know, don't feel emotions, but it does.
Speaker 1: It seems very um disconcerting. That's something as fundamental as
Speaker 1: a neutron, less about as long as it takes for
Speaker 1: my soup to cool down. Yeah, So if you want
Speaker 1: to build something out of neutrons, and you make yourself
Speaker 1: a big pile of neutrons, you better get to work.
Speaker 1: No time for a coffee break, you know, before you
Speaker 1: get started. Like you got to use them or lose them.
Speaker 1: The other fascinating thing about the neutron lifetime is we
Speaker 1: don't actually know what it is. We've tried to measure it,
Speaker 1: and we have two very different ways of measuring the
Speaker 1: neutron lifetime, like two very different experimental setups, and they
Speaker 1: get different results. Like one group put a bunch of
Speaker 1: them in a bottle and wait to see how many
Speaker 1: they have like ten minutes later, and they get an
Speaker 1: answer of like fourteen minutes and thirty nine seconds. And
Speaker 1: other folks use a beam of neutrons and count how
Speaker 1: many protons come out, and they get a different answer.
Speaker 1: They get fourteen minutes and forty eight seconds, So there's
Speaker 1: like a nine second difference, so we don't even actually know. Well,
Speaker 1: I see what the problem is. Probably one group is
Speaker 1: using one Mississippis and the other group is using one
Speaker 1: potato to potato. You have solved this mystery. It is
Speaker 1: funded physicists for decades and today you have figured it out. Katie. Wow,
Speaker 1: thank you so much your contributions to particle physics. So
Speaker 1: you're welcome everyone for me solving this physics problem. And
Speaker 1: when we get back, um, I'm sure Daniel will make
Speaker 1: some kind of argument that no, it's not as simple
Speaker 1: as one Mississippi or one potato, but you know all
Speaker 1: of them have a short break to work that one out,
Speaker 1: because I think my argument is prettier tight. Okay, And
Speaker 1: so we're back and we've got this. Two teams of
Speaker 1: I would assume, very smart, very professional scientists, but they're
Speaker 1: coming to slightly different answers on how long it takes
Speaker 1: for a neutron on to decay. One group fourteen minutes
Speaker 1: thirty nine seconds, the other group fourteen minutes and forty
Speaker 1: eight seconds. So what the heck is going wrong? Is
Speaker 1: one group just wrong? We don't know. It's really fascinating
Speaker 1: to have watched this series of experiments over a couple
Speaker 1: of decades. You know, whenever you do something in physics,
Speaker 1: you try to do it a couple of ways because
Speaker 1: it's easy to make mistakes. You're doing something hard, you're
Speaker 1: making assumptions, you're doing the best you can, but it's
Speaker 1: very easy for mistakes to creep in, and so it's
Speaker 1: great practice to have two different groups of people doing
Speaker 1: it two different ways, making different mistakes. In the end,
Speaker 1: we're supposed to be measuring the same thing about the universe.
Speaker 1: The neutron should just have a certain lifetime and we
Speaker 1: should be able to measure it and get the same answer.
Speaker 1: And if we don't, that means that one of our
Speaker 1: assumptions is wrong, where somebody is making a mistake, or
Speaker 1: there's something deeper going on. Right, something is happening in
Speaker 1: one of these experiments that we don't understand, which could
Speaker 1: be like a clue as to how the universe works.
Speaker 1: So originally these two groups made these measurements and they
Speaker 1: didn't get the same answer, But nobody was worried because
Speaker 1: their airbor were pretty large. You know, the difference was
Speaker 1: like eight or nine seconds, but the uncertainty was like
Speaker 1: thirty seconds. So people have thought, we'll just keep working
Speaker 1: and maybe the numbers will creep together as they get
Speaker 1: more precise. The opposite has happened. Both groups have been
Speaker 1: working hard to reduce those uncertainties, you know, figure out
Speaker 1: the sources of error and potential bias in their experiments,
Speaker 1: shaving them off, calibrating them, cross checking them. And as
Speaker 1: the uncertainties have decreased, and now those uncertainties are like
Speaker 1: less than a second or two, the size of the
Speaker 1: difference between the two experiments has stayed the same. In fact,
Speaker 1: it's even crept up a little bit, from like eight
Speaker 1: to almost ten seconds. Okay, so we have Team Bottle,
Speaker 1: I'm going to say, and then Team Beam. So what
Speaker 1: are these teams doing? Because they have very different methods
Speaker 1: going on here, which that may somewhat explain why they're
Speaker 1: getting different results. So first let's go over like Team Bottle.
Speaker 1: What is Team Bottle doing just you know, shaking up
Speaker 1: some neutrons and a bottle, seeing what happens to them.
Speaker 1: That's basically, yeah, they have a new tron source. This
Speaker 1: is actually at Los Alumos, New Mexico, where I grew up.
Speaker 1: I was wasn't involved in this experiment. It's a huge
Speaker 1: facility there. As far as you know. Anyways, go on,
Speaker 1: I may have been unwittingly roped into this experiment. They
Speaker 1: have a bunch of neutrons there and basically they put
Speaker 1: them in a bottle. They get them ultra cold, so
Speaker 1: they're not moving very fast, and neutrons are a bit
Speaker 1: hard to store because they don't have electric charts, so
Speaker 1: you can't use magnetic fields or electric fields to control them.
Speaker 1: You have to use gravity to get them cold. So
Speaker 1: they slow down and let them just like fall into
Speaker 1: this container. They call it the bathtub, And basically they
Speaker 1: just collect a bunch of neutrons. They very carefully count
Speaker 1: how many introns they start with, and then they measure
Speaker 1: the number of neutrons in their bottle, and then they
Speaker 1: come back ten minutes later, measured again. And they come
Speaker 1: back ten minutes later and they measure it again. And
Speaker 1: that's the essence of the experiment, is like, if you
Speaker 1: think something doesn't last very long, put a bunch of
Speaker 1: them in a bottle. Count how many you have come
Speaker 1: back later and count them again. So it's very simple
Speaker 1: experiment in that way. So you've got this this ice
Speaker 1: cold bottle of delicious new atron's man that makes me thirsty.
Speaker 1: And so they would measure these and they would find
Speaker 1: that they are sort of disappearing at a certain rate,
Speaker 1: and that is how they got at fourteen minutes and
Speaker 1: thirty nine seconds exactly. The important thing to understand is
Speaker 1: that the neutron lifetime doesn't mean that every neutron has
Speaker 1: a clock in it and it expires exactly after fourteen
Speaker 1: minutes and thirty nine seconds. It's an exponential decay. Every
Speaker 1: neutron has a probability to decay in any moment. And
Speaker 1: if some fraction of your neutrons will decay in shorter time,
Speaker 1: and a fraction of the neutrons will last longer, just
Speaker 1: like radioactive decay, it's the same fundamental process. In fact,
Speaker 1: it is that process protons turning into neutrons, which drives
Speaker 1: also radioactive decay. So you don't like watch one neutron,
Speaker 1: just ask how long did it live. Have a whole
Speaker 1: population of neutrons, and you count how many you have
Speaker 1: over time, and you fit that to a function and
Speaker 1: exponential decay, and you measure sort of the parameter the
Speaker 1: slope of that function. So it's a bit more than
Speaker 1: just watching one neutron decay. That's why you have a
Speaker 1: population of them. So they have these in a little
Speaker 1: bathtub and then every once in a while they're trying
Speaker 1: to count all of them. They pushed them against this
Speaker 1: counter which is covered in boron and zinc, and that
Speaker 1: makes the neutrons give off a little flash of light,
Speaker 1: and they count how many flashes of light they saw,
Speaker 1: and that tells them how many neutrons they have left
Speaker 1: I see. So these two experiments would be like two
Speaker 1: groups of alien scientists measuring the average lifespan of a human. Like, sure,
Speaker 1: our lifespans are going to differ, but they're not going
Speaker 1: to differ by like hundreds of years. They're going to
Speaker 1: differ by a matter of a few years. And so
Speaker 1: you should in theory, even if these two alien scientists
Speaker 1: groups have different methods of measuring our lifespan, they should
Speaker 1: in theory be able to both come up with the
Speaker 1: same average lifespan. But in this case they're not. So
Speaker 1: then what is what is Team Beam doing? The Team
Speaker 1: Beam is taking the opposite approach, where his team Bottle
Speaker 1: is saying, let's count how many neutrons we still have left,
Speaker 1: Team Beam is asking how many neutrons disappear. So they
Speaker 1: have a beam of neutrons that they create, and they
Speaker 1: count how many protons are created within these beams, because
Speaker 1: remember a neutron decays and it decays into a proton,
Speaker 1: So to count how many neutrons have disappeared, they count
Speaker 1: how many protons are created. And so instead of counting
Speaker 1: how many neutrons they still have, like the Bottle guys
Speaker 1: are doing, they're counting how many neutrons have left the room.
Speaker 1: So in the analogy you were talking about with human lifetime,
Speaker 1: instead of counting how many humans do we still have left,
Speaker 1: they're counting graves. I see. I mean it makes me wonder.
Speaker 1: And again this is probably you know, me strolling in
Speaker 1: without having done the rigorous testing that Team Beam has done.
Speaker 1: But like, could there be like some infiltration of protons,
Speaker 1: like protons coming from some other source that is messing
Speaker 1: with their results. Absolutely, that's the kind of thing that
Speaker 1: they've been thinking about for like the last twenty years.
Speaker 1: So you're right, it's something to be worried about, but
Speaker 1: they're very careful. They shield their experiments that magnetic fields
Speaker 1: to prevent anything from creeping in, and they filter these
Speaker 1: protons out using magnetic fields and very careful to only
Speaker 1: count the protons that they think come from their beam.
Speaker 1: So each experiment has like a long list of ways
Speaker 1: that they can get it wrong. And over the last
Speaker 1: ten years they've been like going down that list and thinking,
Speaker 1: how can we check this, How do we really know
Speaker 1: this is true? Can we do this another way just
Speaker 1: to verify, just like as a sanity check, maybe there's
Speaker 1: something going wrong here. And they've gone down that list
Speaker 1: and nobody's found any basic mistakes, and as a result,
Speaker 1: they've been able to shave down their uncertainty because now
Speaker 1: they have like multiple ways of doing every step of
Speaker 1: their experiment to convinced themselves that their number is correct.
Speaker 1: So we still have Team Bottle and Team Beam doing
Speaker 1: very careful work. Nobody has an idea for what might
Speaker 1: be different where the mistake could be, but they're still
Speaker 1: getting different answers. Also, bringing it back to the aliens
Speaker 1: observing Earth analogy, I mean, I wonder if maybe there
Speaker 1: could like these teams could be doing everything perfectly and
Speaker 1: executing the experiments perfectly, still getting the different results, but
Speaker 1: not because they made an error, but because there's something
Speaker 1: else going on. So, for instance, maybe if the Team
Speaker 1: Alien one is just counting the number of humans left
Speaker 1: after a certain amount of time and average getting the
Speaker 1: lifespan average from that, they may not be taking into
Speaker 1: account like a new births or something. And then for
Speaker 1: Team Alien just measuring the graves. You know, what if
Speaker 1: you have a grave that has like more than one
Speaker 1: person in it, So could there be something going on
Speaker 1: where these these two you know, let's not blame the
Speaker 1: groups of scientists or the intern or the janitor. Nobody's
Speaker 1: doing anything wrong. But they are actually correct. But just
Speaker 1: because their method of measurement is different, there is some
Speaker 1: some mysterious mechanism going on that is creating that difference. Yes, absolutely,
Speaker 1: that is sort of the hope, right. The boring answer
Speaker 1: is like, oh, it turns out the cable wasn't plugged
Speaker 1: in right, or this temperature was set to the wrong number,
Speaker 1: and like you know, from an experimental point of view,
Speaker 1: that would be satisfied to figure it out. More exciting
Speaker 1: would be is if it reveals that one of the
Speaker 1: assumptions that are made that suggests that these two experiments
Speaker 1: should be getting the same answer are fundamentally wrong. So
Speaker 1: people have been very creative about this, and there is
Speaker 1: one cool idea floating out there that maybe when the
Speaker 1: neutron decays, it doesn't always decay into a proton. Maybe
Speaker 1: sometimes it decays into something else like dark matter. Some
Speaker 1: tiny fraction of time, the neutron turns into dark matter,
Speaker 1: and that would explain this difference because remember that the
Speaker 1: beam folks, they won't see it if the neutron decays
Speaker 1: into something else. They only count the number of times
Speaker 1: the neutron decays into a proton because they assume it
Speaker 1: always decays into a proton. Now the bottle folks, they
Speaker 1: will see that neutron disappear because they're counting the neutrons themselves.
Speaker 1: So if the neutrons sometimes decay into something which is
Speaker 1: not a proton, then these two groups will get different numbers.
Speaker 1: So this is fun idea out there about how maybe
Speaker 1: neutrons will sometimes decay into dark matter instead of into protons.
Speaker 1: That is really cool. I love that when in science,
Speaker 1: like if you get an unexpected result bolt or something
Speaker 1: that seems like a mistake, it could actually lead you
Speaker 1: to an even bigger, even more interesting discovery. And there's
Speaker 1: so many times in the history of science when you
Speaker 1: do that, When people do experiments, they think just like
Speaker 1: wrapping up everything, tying up the loose ends. We're pretty
Speaker 1: sure we understand what we're gonna see. And then there's
Speaker 1: a discrepancy and it's persistent and it won't go away,
Speaker 1: and sometimes you tug on that thread and it unravels
Speaker 1: like everything we thought we knew about the universe. You know,
Speaker 1: the whole discovery of quantum mechanics was from people like
Speaker 1: m that's weird. You don't really understand what's going on
Speaker 1: with the photoelectric effect. So these little discrepancies are very important.
Speaker 1: They're very powerful ways to test your assumptions and to
Speaker 1: maybe get a clue that there's something new going on
Speaker 1: in the universe we don't know. And the dark matter
Speaker 1: idea is just sort of like a category of possibilities.
Speaker 1: The specific theory that was bounced around for a few
Speaker 1: years about the neutrons decay in the dark matter doesn't
Speaker 1: look like it works. They made this very specific prediction
Speaker 1: that it would decay into a new state, and in
Speaker 1: that state, we decay into dark matter, and along the
Speaker 1: way it would make a tiny little lash, a very
Speaker 1: specific light. And so the bottle folks looked for this
Speaker 1: flash of light, but they didn't see it. But that
Speaker 1: doesn't mean that it's wrong. There might be some other
Speaker 1: explanation in the same vein the neutrons could be turning
Speaker 1: into something else. We don't expect a new kind of
Speaker 1: dark matter or even something else weirder, So, are are
Speaker 1: they looking into new experiments that they could potentially do
Speaker 1: to sort of find out what's going on here exactly?
Speaker 1: They're trying to develop like a third way to measure
Speaker 1: the neutron lifetime, because that will give us a handle.
Speaker 1: It's like a vote, right, we develop a third, totally
Speaker 1: independent way with different assumptions than either the first two.
Speaker 1: It will tell us which of those first two is
Speaker 1: correct and which one is not. Actually measuring the neutron
Speaker 1: lifetime the way we thought it was. A third way
Speaker 1: to measure this is actually in space because one way
Speaker 1: to make neutrons is to smash protons against the Earth's atmosphere,
Speaker 1: which happens all the time out there in space because
Speaker 1: space is filled with high energy cosmic rays. Protons from
Speaker 1: the center of the galaxy or from other solar systems
Speaker 1: smashing into Earth's atmosphere, creating these showers of particles, including
Speaker 1: neutron on. Now, most of these neutrons then like rain
Speaker 1: down on the Earth's surface, and as they do, because
Speaker 1: they're by themselves, they're not inside atomic nuclei, they turn
Speaker 1: into protons. So if you can count like the number
Speaker 1: of neutrons created at the edge of the atmosphere with
Speaker 1: a number of protons you then see raining down, you
Speaker 1: can get a sense for how many of those neutrons
Speaker 1: have converted from neutrons into protons. And that's a way
Speaker 1: to measure the neutron lifetime. It's a bit tricky and
Speaker 1: it's more complicated, which is why it wasn't like the
Speaker 1: first option or the second option. But now we need
Speaker 1: a third option and we need to figure this out.
Speaker 1: And so people are even talking about like building probes
Speaker 1: that an orbit Venus, because Venus might have the perfect
Speaker 1: atmosphere to do this kind of experiment, because it's got
Speaker 1: so much C O two in it, So it's using
Speaker 1: a whole planet as a test tube exactly. Particle physicists
Speaker 1: are not content to just do experiments in one tiny
Speaker 1: little lab. We want to use the whole universe as
Speaker 1: our experiment. I see you're just trying to use your
Speaker 1: research budget for travel. I get it, exactly. What's this
Speaker 1: first class ticket to Venus? Daniel? Can you explain this charge?
Speaker 1: But this is something that's really important, you know, not
Speaker 1: just because we want to understand what's inside the neutron
Speaker 1: and how does it work and is the neutron turning
Speaker 1: into something else? The neutron lifetime is a really important
Speaker 1: component of our universe. You know, in the early universe,
Speaker 1: neutrons were made, as we talked about, but if they
Speaker 1: didn't last for long enough, they couldn't get served up
Speaker 1: into atomic nuclei. So the length of the neutron lifetime
Speaker 1: sort of determines how many isotopes are made, how much
Speaker 1: helium is made, and so it's important to get this
Speaker 1: number right. You know. They determines like the hydrogen to
Speaker 1: helium ratio that's made during the Big Bang, but also
Speaker 1: determines like how long stars will live, because the more
Speaker 1: helium you get, the smaller and heavier the stars are
Speaker 1: that are made, which don't burn as long. So this
Speaker 1: is like a fundamental ingredient to the early universe calculations.
Speaker 1: It's something we really need to understand. So even a
Speaker 1: discrepancy of a few seconds is very important to determine
Speaker 1: what is causing that and what the answer is to
Speaker 1: this right, and it goes to really deep questions in
Speaker 1: particle physics about the strong force. You know, this is
Speaker 1: something that we can't sit down and predict very confidently.
Speaker 1: It takes massive calculation to try to get a sense
Speaker 1: for how corks talk to each other because the forces
Speaker 1: are so strong and so difficult to calculate with. It's
Speaker 1: something physicists called non perturbative, which means that we can't
Speaker 1: make many of our typical assumptions and simplifications when we
Speaker 1: do these calculations. So this is a great laboratory to
Speaker 1: force the universe to teach us something about how the
Speaker 1: strong force actually works, to force it to like tell us,
Speaker 1: here's how this happens. Here's the result of this calculation.
Speaker 1: So it's a really powerful way to try to get
Speaker 1: some inside how these little particles are talking to each other.
Speaker 1: And in the end, I got neutrons and you got neutrons.
Speaker 1: So this should be important to all of us. Yeah,
Speaker 1: it is interesting. It's such a humble particle that you
Speaker 1: think of this like neutral doesn't seem to have such
Speaker 1: a big role to play, But really it's so important
Speaker 1: to not only to keep us together apparently, like I
Speaker 1: don't want to fall apart into a bunch of protons
Speaker 1: and w minuses and then which turns into ghost particles
Speaker 1: and electrons. I want to stay me for as long
Speaker 1: as possible, but also just it seems like it's really
Speaker 1: important to understand them, to understand the universe. Yeah, and
Speaker 1: it's an enduring mystery. We're gonna stay tuned to figure
Speaker 1: out what's going on with these neutrons, how long they live,
Speaker 1: and whether Team Bottle or Team Beam got it right.
Speaker 1: This is exciting. I want to print shirts Team Bottle,
Speaker 1: Team Beam and see we're the dialay. Thank you everybody
Speaker 1: for joining us on this journey, the journey inside our
Speaker 1: atoms and your atoms and the universe's atoms, where tiny
Speaker 1: little clocks determine the fate of neutrons and the fate
Speaker 1: of stars. And thanks very much Katie for joining us
Speaker 1: on this very particular podcast. Thanks for having me, and
Speaker 1: good luck with your neutron soup. Flay tune in next time. Everybody,
Speaker 1: thanks for listening, and remember that Daniel and Jorge Explain
Speaker 1: the Universe is a production of I heart Radio. For
Speaker 1: more podcast from my heart Radio, visit the i heart
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