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How long does a neutron live? · Daniel and Kelly’s Extraordinary Universe

• 0:08
  Speaker 1: Hey, Katie, how do your particles feel today? I guess
• 0:11
  Speaker 1: it depends on which particle you ask. All right, well,
• 0:14
  Speaker 1: let's start with your protons. How are they feeling this morning?
• 0:16
  Speaker 1: They're feeling pretty positive. And your electrons any negativity there? Well,
• 0:21
  Speaker 1: I would say they're all charged up. And what about
• 0:25
  Speaker 1: those neutrons. We don't want to overlook them? How are
• 0:27
  Speaker 1: they doing? There? Come scums? All right, well, let's see
• 0:32
  Speaker 1: if this podcast can get them excited. Well, I'm excited
• 0:35
  Speaker 1: even if my neutrons are kind of just meth. Hello.
• 0:55
  Speaker 1: I'm Daniel. I'm a particle of physicist and a professor
• 0:58
  Speaker 1: at UC Irvine, and I contain multitudes of particles. And
• 1:03
  Speaker 1: I am Katie Golden. I host the podcast Creature feature
• 1:07
  Speaker 1: about animals and my particles. Uh, I think I've got
• 1:11
  Speaker 1: at least ten of them. You know, really, your podcast
• 1:16
  Speaker 1: is also about particles, since all animals are also made
• 1:19
  Speaker 1: of particles. That's right, So who's the physicist? Now? We're
• 1:23
  Speaker 1: all physicists. That's the point. Every podcast is really about particles,
• 1:28
  Speaker 1: even those true crime podcasts, even the Bigfoot podcast, even
• 1:31
  Speaker 1: those paranormal e sp podcasts that consistently outrank ours in
• 1:36
  Speaker 1: the natural science category, but welcome to the podcast. Daniel
• 1:42
  Speaker 1: and Jorge explain the universe in which we treat the
• 1:45
  Speaker 1: entire universe as a crazy swarm of particles. Particles that
• 1:49
  Speaker 1: are mysterious, particles that are weird, particles that follow very
• 1:53
  Speaker 1: strange quantum rules, but particles that do follow rules in
• 1:57
  Speaker 1: the end, rules that we think we can understand, we
• 2:00
  Speaker 1: can digest, that we can explain to you. On this podcast,
• 2:03
  Speaker 1: we hope to wrap our minds around everything in the universe,
• 2:07
  Speaker 1: break it down to its time little particles, and feed
• 2:10
  Speaker 1: them to you one by one. My co host and friend,
• 2:13
  Speaker 1: Jorge Champ can't be here today, but we are very
• 2:15
  Speaker 1: lucky to have our regular co host, Katie. Katie thanks
• 2:18
  Speaker 1: a lot for joining us. Of course, I am ready
• 2:21
  Speaker 1: to learn about particles because you know, they seem important,
• 2:27
  Speaker 1: given that I need them in me to make me, me,
• 2:31
  Speaker 1: to make you you. Indeed, but you know what is
• 2:34
  Speaker 1: the units of you? Diving right into the philosophical questions
• 2:38
  Speaker 1: at the heart of particle physics, one thing we have
• 2:41
  Speaker 1: learned recently about particles and the universe is that we
• 2:45
  Speaker 1: all seem to be made up of the same kinds
• 2:47
  Speaker 1: of particles. I'm made of protons, neutrons, and electrons. You're
• 2:51
  Speaker 1: made of protons, neutrons and electrons. What's the difference? Are
• 2:55
  Speaker 1: there Katie particles and Daniel particles? No, it turns out
• 2:59
  Speaker 1: that the only different it's between Daniel and Katie fundamentally,
• 3:02
  Speaker 1: or between an apple and a banana, or between kittens
• 3:05
  Speaker 1: and lava, is how those particles are put together. You
• 3:09
  Speaker 1: take that same basic set of building box and you
• 3:11
  Speaker 1: can make anything. You're blowing my mind. So if we
• 3:14
  Speaker 1: sort of melted down Katie and Daniel into just the
• 3:19
  Speaker 1: particles and then rearranged all the Katie particles into Daniel
• 3:22
  Speaker 1: particle like the Daniel blueprints, then now would just create
• 3:26
  Speaker 1: a Daniel even though uh, those were originally my particles.
• 3:30
  Speaker 1: That's exactly right. It seems like our universe follows the
• 3:33
  Speaker 1: same principles as legos, that the same basic building blox
• 3:37
  Speaker 1: can be used to make anything. Right, if your little
• 3:40
  Speaker 1: brother used your legos to make a huge dinosaur and
• 3:43
  Speaker 1: then you smashed it and used it to build a
• 3:45
  Speaker 1: pirate boat, you could reuse those dinosaur legos to make
• 3:49
  Speaker 1: your pirate hip. Now Here, of course, I have to
• 3:51
  Speaker 1: quibble with the fundamental flaw of Lego toys. The original Legos,
• 3:55
  Speaker 1: We're just the basic building blocks, and I love that
• 3:57
  Speaker 1: simplicity that I had no bias to them. You you
• 4:00
  Speaker 1: could use them to make anything. These fancy new modern Legos,
• 4:03
  Speaker 1: you know, they come with stuff printed on the sides
• 4:05
  Speaker 1: or specific shapes, right, so the sort of like predetermine
• 4:09
  Speaker 1: what you have to build. I'm talking about the true
• 4:11
  Speaker 1: original Legos. Yeah. I usually just built the tallest tower
• 4:16
  Speaker 1: I could make out of my Legos, and then usually
• 4:19
  Speaker 1: put a bunch of guys on it, so it's like
• 4:21
  Speaker 1: just this big tower of Babel. I don't know what
• 4:24
  Speaker 1: that says about me, but yeah, I agree, Although I
• 4:27
  Speaker 1: do like that modern legos do have different kinds of Legos.
• 4:31
  Speaker 1: Like it started out, I think, with just the one
• 4:34
  Speaker 1: Lego block unit, but now you have all sorts of
• 4:37
  Speaker 1: different types of Legos. You have like the sort of
• 4:41
  Speaker 1: o G blocks, but you also have these long, skinny ones,
• 4:44
  Speaker 1: you have ones that can rotate, you have like connector legos.
• 4:48
  Speaker 1: But is that at all similar to how the universe works?
• 4:53
  Speaker 1: Seems to be very similar to how the universe works.
• 4:55
  Speaker 1: You know, I'm made of protons and neutrons and electrons
• 4:58
  Speaker 1: and store are you and so is basically everything that
• 5:00
  Speaker 1: you've ever eaten, everything you've ever tripped over, everything you've
• 5:04
  Speaker 1: ever thrown at your sibling. They're all made of the
• 5:06
  Speaker 1: same ingredients. And if you look at the periodic table,
• 5:08
  Speaker 1: you can see that that's true, right, Every element on
• 5:11
  Speaker 1: the periodic table is just made of protons and neutrons
• 5:14
  Speaker 1: and electrons arranged in different numbers. You start with one
• 5:17
  Speaker 1: proton and electron, you have hydrogen. You added another proton,
• 5:21
  Speaker 1: you get helium. Keep adding protons, do you get different elements?
• 5:24
  Speaker 1: You're just adding more of the same basic building blocks,
• 5:26
  Speaker 1: but you make fundamentally different elements. But those different elements
• 5:30
  Speaker 1: are not really fundamentally different. The only difference between carbon
• 5:34
  Speaker 1: and neon, or between lead and gold is the number
• 5:37
  Speaker 1: of protons inside those nuclei. So really you can build
• 5:41
  Speaker 1: anything with the same basic building blocks. It's so hard
• 5:44
  Speaker 1: to wrap my head around that. So, you know, just
• 5:48
  Speaker 1: like it's just seems that it's a numbers game, because
• 5:51
  Speaker 1: like usually with legos, if you just have like five legos,
• 5:54
  Speaker 1: it doesn't suddenly turn into from like you know, a
• 5:57
  Speaker 1: sugar into like gold or something like that. But with
• 6:02
  Speaker 1: these on the atomic levels. When you change just the
• 6:06
  Speaker 1: number of these these tiny particles, it turns from you know,
• 6:10
  Speaker 1: something that if you eat nothing would happen to you,
• 6:13
  Speaker 1: to something if you eat it it would be bad
• 6:15
  Speaker 1: and drive you crazy, like eating lead versus drinking air.
• 6:19
  Speaker 1: I guess we don't really drink air, but you get
• 6:22
  Speaker 1: the idea. Yeah. Absolutely. It might seem like a small difference.
• 6:25
  Speaker 1: You're just adding a proton, what's the big deal, But
• 6:28
  Speaker 1: it completely changes its emergent behavior. All these characteristics that
• 6:32
  Speaker 1: were familiar with the way metals are shiny and conduct electricity,
• 6:36
  Speaker 1: the way some of these elements are float around and
• 6:38
  Speaker 1: ignore the other ones that are not very active. All
• 6:40
  Speaker 1: of those properties are determined by how many protons and
• 6:44
  Speaker 1: how many electrons there are in each atom, and so like,
• 6:48
  Speaker 1: the fact that metals are metallic and conductive comes from
• 6:51
  Speaker 1: the fact that their electron shells are not filled, which
• 6:54
  Speaker 1: is determined by the number of protons inside the nucleus.
• 6:58
  Speaker 1: So it's not just an relevant detail, it's a totally
• 7:01
  Speaker 1: determining fact. But it's fascinating they're all made out of
• 7:04
  Speaker 1: the same bits. The other fascinating thing to me is
• 7:07
  Speaker 1: that we're all made out of roughly the same ratios
• 7:10
  Speaker 1: of bits, Like any given atom has basically a one
• 7:13
  Speaker 1: to one to one proton to neutron to electron ratio.
• 7:17
  Speaker 1: So lead has more protons than hydrogen, but it also
• 7:20
  Speaker 1: has more neutrons and also has more electrons. That means
• 7:24
  Speaker 1: that not only are we all made out of the
• 7:25
  Speaker 1: same three basic building blocks, but we're made out of
• 7:28
  Speaker 1: them in the same proportions. It's not like Katie has
• 7:31
  Speaker 1: more electrons and Daniel has more protons, right, where the
• 7:34
  Speaker 1: same building blocks in the same proportions just rearranged differently.
• 7:38
  Speaker 1: So you you mentioned that the number of protons sort
• 7:43
  Speaker 1: of changes the element. In the number of electrons, it's
• 7:46
  Speaker 1: kind of changes the characteristic of these elements, But you
• 7:49
  Speaker 1: didn't mention neutrons too much being sort of the determinant
• 7:54
  Speaker 1: of what these elements are. Why are neutrons different in
• 7:58
  Speaker 1: terms of pro tons and electrons. Yeah, it's a good point,
• 8:01
  Speaker 1: and neutrons are sadly often overlooked, which is why we
• 8:05
  Speaker 1: are dedicating almost our entire podcast today to talking about
• 8:08
  Speaker 1: these mysterious, funny particles. But you're right that neutrons don't
• 8:12
  Speaker 1: really determine as much the identity of the atom, and
• 8:16
  Speaker 1: that's because they are electrically neutral. Like if you add
• 8:18
  Speaker 1: another proton to the atom, then in order to make
• 8:21
  Speaker 1: it electrically neutral, you have to add another electron in
• 8:24
  Speaker 1: orbit around it, and that really changes the chemical properties.
• 8:28
  Speaker 1: It changes how this thing interacts, whether or not it's
• 8:30
  Speaker 1: electron orbitals are filled, or whether it's got an opening
• 8:33
  Speaker 1: that very strongly affects the behavior of the atom. You
• 8:36
  Speaker 1: add another neutron, then you don't need to add another electron.
• 8:39
  Speaker 1: So you can add neutrons, no big deal. You can't
• 8:41
  Speaker 1: just add neutrons anytime you like to any atom. It
• 8:44
  Speaker 1: doesn't make them heavier, and it makes these other versions
• 8:47
  Speaker 1: of the elements. These are called isotopes. So, for example,
• 8:50
  Speaker 1: you can have hydrogen, which is just a proton, but
• 8:52
  Speaker 1: you can also have deuterium, which is a proton and
• 8:55
  Speaker 1: a neutron. So you put those together inside the nucleus,
• 8:58
  Speaker 1: you have an electron around it. It's still called hydrogen,
• 9:01
  Speaker 1: but it's like a heavy version of hydrogen. For example,
• 9:04
  Speaker 1: if you put that together into H two O, but
• 9:06
  Speaker 1: instead of the hydrogen, you have this heavy version of
• 9:09
  Speaker 1: hydrogen with a neutron also in the nucleus. Then you
• 9:11
  Speaker 1: get what's called heavy water, which we sometimes use in
• 9:14
  Speaker 1: nuclear experiments. Right, so it does change a little bit
• 9:16
  Speaker 1: sort of the flavor of the element to add neutron,
• 9:19
  Speaker 1: sort to take them away, but it doesn't change its
• 9:21
  Speaker 1: fundamental identity, which is determined by the charged objects of
• 9:25
  Speaker 1: proton and the electron. So that's really interesting to me.
• 9:28
  Speaker 1: Why is the neutron involved at all in the atomic
• 9:32
  Speaker 1: structure if it's just kind of this It seems like
• 9:35
  Speaker 1: this neutral fluff particle just this like dead weight, But
• 9:40
  Speaker 1: is that really true. No, the neutron often overlooked, but
• 9:44
  Speaker 1: it does play a vital role in keeping the nucleus together.
• 9:48
  Speaker 1: We're gonna dig into it a bit more on the podcast,
• 9:50
  Speaker 1: but very briefly, think about how the nucleus stays together. Right,
• 9:54
  Speaker 1: If you have the nucleus of an atom that has
• 9:56
  Speaker 1: like twenty five protons in it, those things are all
• 9:59
  Speaker 1: positive of lee charged. Why don't they just like bust apart?
• 10:02
  Speaker 1: You know, why don't they repel each other because they
• 10:04
  Speaker 1: all have the same positive charge. The answer is that
• 10:08
  Speaker 1: the nucleus is held together by the strong force, which
• 10:11
  Speaker 1: is much more powerful than electromagnetism and neutrons. Even though
• 10:15
  Speaker 1: they are neutral electromagnetically, they do involve the strong force.
• 10:19
  Speaker 1: Turns out, the nucleus is a bit of a delicate
• 10:21
  Speaker 1: puzzle keeping those protons from flying apart. You need the neutrons.
• 10:25
  Speaker 1: It's a little bit of a spacer, and so it's
• 10:27
  Speaker 1: easier to make stable nuclei if you include the neutrons.
• 10:31
  Speaker 1: I see, So without the neutrons, the protons would not
• 10:35
  Speaker 1: be able to stand each other's presence. I know people
• 10:38
  Speaker 1: like that and like in group dynamics, that kind of
• 10:41
  Speaker 1: keep the peace. So that's that is really interesting. So
• 10:43
  Speaker 1: I guess without neutrons we wouldn't exist, we would not
• 10:47
  Speaker 1: be held together. But it's odd to me though, that
• 10:50
  Speaker 1: that neutrons have. It seems like they're fundamentally different from
• 10:55
  Speaker 1: like a proton or an election because they don't have
• 10:57
  Speaker 1: this charge. So you know, how did that even really happen? Yeah, well,
• 11:01
  Speaker 1: these are deep questions about the universe, like why do
• 11:04
  Speaker 1: we have neutrons anyway? Right, it's just sort of how
• 11:07
  Speaker 1: the universe coalesces. Remember, we go back to the very
• 11:10
  Speaker 1: early part of the universe where everything is just energy,
• 11:13
  Speaker 1: and the universe then expands and cools and as it cools.
• 11:16
  Speaker 1: It's sort of like crystallizes into lower energy states. Things
• 11:20
  Speaker 1: sort of like come together and form stable particles. And
• 11:23
  Speaker 1: by looking around in the universe and seeing sort of
• 11:25
  Speaker 1: what was made, we can tell sort of like what
• 11:27
  Speaker 1: the options were. We don't know like why it's possible
• 11:30
  Speaker 1: to build neutrons necessarily, but we see that a lot
• 11:33
  Speaker 1: of them sort of emerged from the chaos of the
• 11:36
  Speaker 1: early universe. And that's another really fascinating aspect of these
• 11:39
  Speaker 1: particles is their age. Like protons, we think that protons
• 11:43
  Speaker 1: probably live forever. Like you make a proton, you can
• 11:47
  Speaker 1: just hang out forever and stick around till the end
• 11:50
  Speaker 1: of time. Same with an electron. Electron is stable, right,
• 11:54
  Speaker 1: you have an electron sitting in empty space, it will
• 11:56
  Speaker 1: just stay an electron for a billion years, maybe a
• 11:59
  Speaker 1: trillion years, a quadrillion years. And what that means is
• 12:03
  Speaker 1: that the protons and electrons inside your body were probably
• 12:07
  Speaker 1: made during the Big Bang. So you are made of
• 12:10
  Speaker 1: ancient multitudes. I mean, you know, thank you for that,
• 12:14
  Speaker 1: thank you for calling me old. So neutrons weren't necessarily
• 12:19
  Speaker 1: made during the Big Bang. You're saying, so neutrons were
• 12:22
  Speaker 1: also made during the Big bang, right as the universe cooled,
• 12:25
  Speaker 1: we got protons, we've got electrons, we've got neutrons. But
• 12:28
  Speaker 1: there's a difference between protons, electrons, and neutrons that goes
• 12:31
  Speaker 1: beyond just their electric charge. Neutrons don't seem to last
• 12:35
  Speaker 1: forever the same way that protons and electrons do. In fact,
• 12:39
  Speaker 1: they don't last very long at all. So that makes
• 12:42
  Speaker 1: them fundamentally weird and different. And by studying the details
• 12:47
  Speaker 1: of how long the neutron lives and what it turns into,
• 12:49
  Speaker 1: we might get some clues to these questions about like
• 12:51
  Speaker 1: why are there neutrons after all? What's going on inside
• 12:55
  Speaker 1: the neutrons? Are they irrelevant little particles? Are they the
• 12:58
  Speaker 1: most important clue we have to the nature of the universe?
• 13:02
  Speaker 1: So yeah, no, I'm really curious, like what does it
• 13:05
  Speaker 1: mean for a neutron to be alive? And then how
• 13:08
  Speaker 1: does it die? And how long does that process take?
• 13:11
  Speaker 1: And so today on the podcast we'll be answering the
• 13:14
  Speaker 1: question how long does a neutron live? Alright, Katie, and
• 13:23
  Speaker 1: you've already called me out, I see for using the
• 13:25
  Speaker 1: word live in the title, because our neutrons alive after all,
• 13:29
  Speaker 1: and you know, as a particle physicist, I think about
• 13:31
  Speaker 1: these particles as sort of having a lifetime. But you're right,
• 13:35
  Speaker 1: neutrons are not alive, nor are they dead in any
• 13:38
  Speaker 1: sort of biological sense. I mean, if you corner a
• 13:41
  Speaker 1: biologist and try to get them to answer the question
• 13:44
  Speaker 1: what is life, They're gonna start sweating and giving you
• 13:47
  Speaker 1: a really complex answer. So it's not a simple question.
• 13:50
  Speaker 1: But but no, I get it. So it's like a
• 13:52
  Speaker 1: neutron does not always remain a neutron in the sense
• 13:56
  Speaker 1: that it does not stay the same forever, and so
• 14:00
  Speaker 1: that could be seen as it, you know, essentially decaying
• 14:04
  Speaker 1: or dying. Right exactly, When we talk about particle lifetimes,
• 14:07
  Speaker 1: we're talking about how long the particle exists before it
• 14:10
  Speaker 1: turns into something else. So some particles in the universe
• 14:14
  Speaker 1: are stable, like electrons and protons and the corks that
• 14:18
  Speaker 1: make up those protons and photons. For example, you can
• 14:21
  Speaker 1: create a photon with a flashlight, shoot it out into space,
• 14:24
  Speaker 1: and it might fly for billions or trillions of years.
• 14:27
  Speaker 1: Some of the photons received by your eyeballs when you
• 14:30
  Speaker 1: look up at night have been crawling across the universe
• 14:34
  Speaker 1: for billions of years. It's incredible how long they have survived.
• 14:38
  Speaker 1: So some particles sort of live forever. And again we're
• 14:41
  Speaker 1: using to live in a sort of anthropomorphic biological analogy
• 14:45
  Speaker 1: to life. Really we just mean exists, but other particles don't.
• 14:49
  Speaker 1: Other particles are not stable, and the neutron is one
• 14:52
  Speaker 1: of those. That's really interesting. So yeah, I didn't really
• 14:56
  Speaker 1: think of neutrons as being an impermanent thing. I think
• 15:00
  Speaker 1: about the building blocks of life. I mean I pictured
• 15:02
  Speaker 1: them as these like little permanent speares that you know,
• 15:06
  Speaker 1: make everything and just stay the same, and you know
• 15:09
  Speaker 1: that is just this kind of like solid foundation to everything.
• 15:13
  Speaker 1: But now you're shaking that all up. What if I
• 15:15
  Speaker 1: told you that one of your legos a specific kind
• 15:17
  Speaker 1: of lego, if you didn't use it, it would just
• 15:19
  Speaker 1: like evaporate or turn into other kinds of legos. That
• 15:23
  Speaker 1: sounds like an excuse a little brother would give when
• 15:25
  Speaker 1: you're stealing all my legos. All right, but this is
• 15:28
  Speaker 1: not a family therapy podcast, at least not yet. So
• 15:32
  Speaker 1: I was curious if other people had thought about the
• 15:35
  Speaker 1: lifetime of the neutron, if people were aware that neutrons
• 15:38
  Speaker 1: don't live forever, and how long they thought it might live.
• 15:41
  Speaker 1: So I went out there to our cadre of Internet
• 15:43
  Speaker 1: volunteers who are willing to answer hard physics questions without
• 15:47
  Speaker 1: any opportunity to prepare themselves. Thank you very much, and
• 15:50
  Speaker 1: if you would like to join this hearty group, then please,
• 15:53
  Speaker 1: they'll be shy right to me. Two questions at Daniel
• 15:56
  Speaker 1: and Jorge dot com. So think about it for a moment.
• 15:59
  Speaker 1: Do you know how long a neutron lives? Here's what
• 16:03
  Speaker 1: people had to say. I guess. My guess would be
• 16:06
  Speaker 1: that it would live indefinitely until some other force overpowers
• 16:14
  Speaker 1: the forces that hold it together. Tron lives um like
• 16:19
  Speaker 1: a free nel tron shouldn't been that long, but I
• 16:22
  Speaker 1: don't know, probably not more than a few minutes. I
• 16:27
  Speaker 1: think that actually this is something that's really confused me
• 16:34
  Speaker 1: as I've started to look into and tried to understand
• 16:38
  Speaker 1: particle physics and quantum physics and everything, and I think
• 16:42
  Speaker 1: that possibly it's just an instant. Yeah, neutrons, just like
• 16:46
  Speaker 1: like a lot of particles, just exists for an instant.
• 16:49
  Speaker 1: On the other hand, it could be they could last
• 16:51
  Speaker 1: for by entire lifetime, so yeah, it could be a
• 16:56
  Speaker 1: long time as well. Well. Neutrons makeup part of stomic nuclei,
• 17:01
  Speaker 1: so they live for at least as long as the
• 17:05
  Speaker 1: longest lived elements UM, so at least a few million years.
• 17:10
  Speaker 1: But I think UH universe skills tend to be quite extreme,
• 17:14
  Speaker 1: so I guess since they don't live for only fractions
• 17:18
  Speaker 1: of a millisecond, I'm going to guess they live for
• 17:20
  Speaker 1: billions of years. I don't know if a neutron lives forever,
• 17:23
  Speaker 1: and I think the answer to that question is we
• 17:26
  Speaker 1: don't know if neutrons live forever. I know that proton
• 17:29
  Speaker 1: decay is still actively being studied and debated, and I
• 17:33
  Speaker 1: don't think a neutron would be much different. And as
• 17:36
  Speaker 1: of now, I believe we do not know how long
• 17:39
  Speaker 1: they live or if they decay away. I know that
• 17:41
  Speaker 1: protons decay inter neutrons UM because they emit a positron,
• 17:48
  Speaker 1: so I'm gonna wonder whether neutrons can also emit an
• 17:51
  Speaker 1: electron and in a sense decay into protons. But this
• 17:55
  Speaker 1: process doesn't happen, so all the proton has a lifetime
• 17:58
  Speaker 1: of I don't know if the order of a few
• 18:01
  Speaker 1: seconds UM, and you'tron. I know it's a number of
• 18:05
  Speaker 1: years and I think it's the amount amount of time
• 18:10
  Speaker 1: is comfortable to the age of the universe something like that.
• 18:13
  Speaker 1: I really like the answer, probably just an instant, or
• 18:17
  Speaker 1: maybe my entire lifetime, because even though that seems funny,
• 18:21
  Speaker 1: like how could you compare an instant to an entire lifetime?
• 18:24
  Speaker 1: How could you be so equivocal? On the universal scale,
• 18:28
  Speaker 1: those are almost the same in a certain way, right,
• 18:31
  Speaker 1: Like when you look at the entire lifetime of the universe,
• 18:35
  Speaker 1: an instant in one human lifetime or not that different exactly.
• 18:39
  Speaker 1: And that's the incredible thing about all of these numbers
• 18:42
  Speaker 1: in physics that when you're talking about how long something lives,
• 18:45
  Speaker 1: it could be some crazy, tiny tiny number ten to
• 18:49
  Speaker 1: the minus twenty seconds, or it could be cosmic the
• 18:52
  Speaker 1: scale of the lifetime of the universe, right, which is like,
• 18:55
  Speaker 1: you know, six tillions of seconds, and so it's hard
• 18:58
  Speaker 1: to know, like on that huge scale where to put
• 19:01
  Speaker 1: these numbers, And so if you don't have any information,
• 19:04
  Speaker 1: then you're right, his entire lifetime does feel sort of
• 19:06
  Speaker 1: like an instant. And that's one of my favorite things
• 19:09
  Speaker 1: about physics that it may think about these cosmic sweeps
• 19:12
  Speaker 1: of time and recognize the fact that something that might
• 19:15
  Speaker 1: take our entire lifetime is basically meaningless on the time
• 19:18
  Speaker 1: scale of the universe. Well, way to make me feel
• 19:22
  Speaker 1: both old and small. So in terms of neutrons, like
• 19:27
  Speaker 1: it is interesting, like if they live like a human lifetime,
• 19:31
  Speaker 1: that makes me feel a little less alone, or if
• 19:34
  Speaker 1: they live like an instant, that almost makes me feel
• 19:37
  Speaker 1: sorry for them. It's really hard not to anthropomorphize something
• 19:40
  Speaker 1: once we're talking about how long it lasts, as if
• 19:43
  Speaker 1: the neutron particularly cares. But I guess I want to know, like,
• 19:47
  Speaker 1: what what is the neutron? Should I feel sorry for it? Well,
• 19:52
  Speaker 1: I'm not going to tell you how to feel about
• 19:54
  Speaker 1: the particles, but I'm happy to tell you how they're
• 19:56
  Speaker 1: put together and what they mean. And so in the
• 19:58
  Speaker 1: case of a neutron, we've been talking about it as
• 20:00
  Speaker 1: if it was a particle in itself, like atoms. We
• 20:03
  Speaker 1: said are made out of protons and neutrons in the
• 20:05
  Speaker 1: nucleus surrounded by electrons. And that's true, but we can
• 20:08
  Speaker 1: also drill one step deeper to understand what is the
• 20:12
  Speaker 1: neutron itself made out of? Now, in the case of
• 20:15
  Speaker 1: some fundamental particles like the electron, we don't know if
• 20:18
  Speaker 1: they're actually fundamental or made out of even smaller lego
• 20:22
  Speaker 1: building blocks. So far, the electron just looks like it's
• 20:25
  Speaker 1: only made out of itself, but that might just be
• 20:27
  Speaker 1: because we haven't zoomed in far enough. We don't have
• 20:29
  Speaker 1: colliders capable of blowing up electrons and seeing what's inside them.
• 20:33
  Speaker 1: In the case of protons and neutrons, we actually have
• 20:36
  Speaker 1: been able to break them up and see what's inside.
• 20:38
  Speaker 1: For about the last fifty years or so, we have
• 20:41
  Speaker 1: had colliders capable of smashing these particles and showing us
• 20:45
  Speaker 1: what they are made out of. And fascinatingly, the proton
• 20:48
  Speaker 1: and the neutron are made out of the same two
• 20:50
  Speaker 1: building blocks, up quarks and down corks, so there are
• 20:55
  Speaker 1: two funny little particles. They have weird fractional electric charges,
• 20:59
  Speaker 1: which allows them to get added up to make a
• 21:00
  Speaker 1: neutron or a proton. So, for example, a neutron is
• 21:04
  Speaker 1: an up cork which is charged two thirds, and then
• 21:08
  Speaker 1: two down corks, each of which are charged minus one third.
• 21:12
  Speaker 1: So neutron is an up, down, down Three of these
• 21:16
  Speaker 1: corks put together, and you get zero electric charge. So physicists,
• 21:21
  Speaker 1: when you're asked what's up cork? Do you just say
• 21:25
  Speaker 1: not much what's up cork with you? Or do you
• 21:28
  Speaker 1: have an actual answer to what's an up cork? And
• 21:30
  Speaker 1: I guess what's a down cork? I don't know what's
• 21:32
  Speaker 1: up is down, what's down is up? Sometimes in physics,
• 21:35
  Speaker 1: you know, as I always say, I'm not going to
• 21:37
  Speaker 1: be held responsible for the names of these particles, but
• 21:39
  Speaker 1: you know, there are some reasons why we called them
• 21:42
  Speaker 1: up corks and down corks. They're organized together by the
• 21:45
  Speaker 1: weak force into this pair, this up and down pair
• 21:48
  Speaker 1: that get linked together by the w boson, which we're
• 21:51
  Speaker 1: going to talk about in just a minute. But actually
• 21:53
  Speaker 1: in the nucleus, the upcorks and down corks are not
• 21:55
  Speaker 1: held together by the weak force. They're held together by
• 21:58
  Speaker 1: the strong force. So quarks have electric charges, but that's
• 22:02
  Speaker 1: not what's holding them together. Like you think about the
• 22:05
  Speaker 1: way molecules are held together, they're held together because of
• 22:07
  Speaker 1: the electric charges. These electrons are like whizzing around and
• 22:10
  Speaker 1: making these ionic bonds or covalent bonds. The electric charges
• 22:14
  Speaker 1: are basically irrelevant once you get inside the proton and
• 22:17
  Speaker 1: the neutron because there's a much more powerful force at play.
• 22:21
  Speaker 1: And that's the strong nuclear force, which totally overwhelms the
• 22:24
  Speaker 1: electromagnetic force, is able to hold all of these particles together.
• 22:28
  Speaker 1: And the strong nuclear force does that by using gluons.
• 22:31
  Speaker 1: So your mental picture of a neutron shouldn't be like
• 22:33
  Speaker 1: three little lego pieces that clicked neatly together and that's it. Instead,
• 22:37
  Speaker 1: it's more like three tiny little dots surrounded by a
• 22:40
  Speaker 1: swarm of these gluons that are holding it together. So
• 22:44
  Speaker 1: it's more like a bag of gluons with three hard
• 22:47
  Speaker 1: dots in it. So, oh my gosh, so gluons. It's
• 22:51
  Speaker 1: just this sort of like swarm of these things that
• 22:55
  Speaker 1: hold together the up quarks and down corks. So like,
• 22:59
  Speaker 1: the more we split things apart and try to think
• 23:01
  Speaker 1: about like the even smaller thing that holds the smaller
• 23:04
  Speaker 1: things together, it gets really difficult for my brain not
• 23:08
  Speaker 1: to start hurting. But all right, So, so do we
• 23:11
  Speaker 1: know like how many gluons are in a neutron or
• 23:15
  Speaker 1: is it just kind of this mass of stuff that
• 23:18
  Speaker 1: we know holds together of corks and down corks, But
• 23:21
  Speaker 1: we can't necessarily quantify how many of these things there are. Yeah,
• 23:24
  Speaker 1: that is a great question because probably you're wanting to
• 23:27
  Speaker 1: put together a model of what's going on inside the
• 23:29
  Speaker 1: neutron that has like a basic recipe, and those things
• 23:32
  Speaker 1: clicked together to make a neutron way like pieces of
• 23:34
  Speaker 1: a jigsaw puzzle get clicked together to make a bigger picture. Right,
• 23:38
  Speaker 1: But that's not really the way we think about these gluons.
• 23:41
  Speaker 1: Luans in this case are force particles. They're not matter particles.
• 23:44
  Speaker 1: What that means is that they don't really exist in
• 23:46
  Speaker 1: the same way that the matter particles do. They exist
• 23:49
  Speaker 1: as a representation of the force between the matter particles.
• 23:53
  Speaker 1: So you have the up cork and the two down corks.
• 23:56
  Speaker 1: They're sitting there and they're pulling on each other, the
• 23:58
  Speaker 1: strong forces holding them together there. How do you think
• 24:00
  Speaker 1: about that force, Well, there's a few different ways of
• 24:03
  Speaker 1: doing it. One is to think about them exchanging particles
• 24:05
  Speaker 1: like zooming gluons back together. That's how they hold themselves together.
• 24:09
  Speaker 1: And you can use that same strategy to think about
• 24:12
  Speaker 1: how other particles talk to each other, Like what happens
• 24:15
  Speaker 1: when two electrons push against each other because they have
• 24:17
  Speaker 1: the same electric charge. How does that actually work microscopically, Well,
• 24:21
  Speaker 1: you can think of them as shooting photons towards each
• 24:24
  Speaker 1: other because photons are the force particle for the electromagnetic force.
• 24:28
  Speaker 1: So inside the neutron, these corks are holding onto each
• 24:31
  Speaker 1: other by shooting gluons at each other. That's one way
• 24:34
  Speaker 1: of thinking about how the forces are working inside the neutron.
• 24:38
  Speaker 1: There's another way of thinking about it, which doesn't use
• 24:41
  Speaker 1: this sort of like virtual particles, these gluons sipping back
• 24:43
  Speaker 1: and forth. You just think about fields. Like if you're
• 24:46
  Speaker 1: more comfortable thinking about an electron being surrounded by its
• 24:49
  Speaker 1: electric field and the way that it pushes on other
• 24:51
  Speaker 1: electrons is that it's electric field pushes on it, then
• 24:54
  Speaker 1: you can think about the interior of the neutron that
• 24:56
  Speaker 1: same way as having three quarks each surrounded by a
• 24:59
  Speaker 1: field from the strong force, and those fields are tugging
• 25:02
  Speaker 1: on each other. Those are gluonic fields. You can think
• 25:05
  Speaker 1: about them as either like a huge tower or virtual
• 25:08
  Speaker 1: gluons which appear and disappear very quickly, or you can
• 25:11
  Speaker 1: think about them in terms of fields. Are two equivalent
• 25:13
  Speaker 1: mental pictures for the same fundamental process that's going on.
• 25:17
  Speaker 1: But you can't really like count the number of gluons
• 25:19
  Speaker 1: because they're not particles that exist in the same way
• 25:22
  Speaker 1: as the corks. So, Okay, in my recipe that I'm
• 25:25
  Speaker 1: writing for home baked neutrons, I'm just gonna put down
• 25:29
  Speaker 1: a pinch of gluons. So you said that this is
• 25:34
  Speaker 1: these are strong, uh, strong forces holding this neutron together.
• 25:39
  Speaker 1: But we were just talking about how maybe these neutrons
• 25:43
  Speaker 1: break apart. So how would they break apart if you
• 25:46
  Speaker 1: have these really strong forces holding them together? Great question,
• 25:49
  Speaker 1: and it reveals something about the way I think a
• 25:51
  Speaker 1: lot of people think about particles and their decay. What
• 25:54
  Speaker 1: happens when a particle decays? Is it breaking apart? Are
• 25:58
  Speaker 1: you taking its pieces and they're reassembling them to build
• 26:00
  Speaker 1: something else? Right, Well, what's happening when a neutron decays
• 26:04
  Speaker 1: is not actually that is breaking apart at all. It's
• 26:07
  Speaker 1: that one piece of its internal structure, one of those corks,
• 26:11
  Speaker 1: changes its nature. So remember that a neutron is up, down,
• 26:15
  Speaker 1: down right tow down corks and an up cork. Well,
• 26:18
  Speaker 1: what happens if one of those down corks changes its
• 26:22
  Speaker 1: flavor and becomes an up cork? Then you have two
• 26:25
  Speaker 1: upcorks in a down instead of two down corks and
• 26:28
  Speaker 1: an up. Remember that up coorks are charged plus two
• 26:31
  Speaker 1: thirds and a down cork is charged minus one third,
• 26:35
  Speaker 1: So now you have plus two third plus two third
• 26:38
  Speaker 1: minus one third gives you a charge of plus one.
• 26:41
  Speaker 1: That's a proton. So what happens when a neutron decays
• 26:45
  Speaker 1: is that one of its down corks converts into an
• 26:48
  Speaker 1: upcork and the neutron becomes a proton. So it doesn't
• 26:51
  Speaker 1: break apart. It flips from being a neutron to being
• 26:54
  Speaker 1: a proton. That's amazing. So it's less of a death
• 26:58
  Speaker 1: of a particle in more of a tram information of
• 27:00
  Speaker 1: a particle. Do we have any idea of why a
• 27:05
  Speaker 1: down cork would become up cork? Yeah, Like you know,
• 27:08
  Speaker 1: why does it down cork decide it wants to be
• 27:11
  Speaker 1: an upcork one day? You know, like why isn't it
• 27:13
  Speaker 1: just happy being an upcork. It's a great question, and
• 27:16
  Speaker 1: it's a really deep question. It's like why does any
• 27:19
  Speaker 1: particle decay? You know, why do muance just hang out
• 27:22
  Speaker 1: and be muance? Why do they decay to electrons and
• 27:24
  Speaker 1: a couple of neutrinos? Why does anything decay? And the
• 27:28
  Speaker 1: reason is that the universe is constantly getting colder and
• 27:31
  Speaker 1: spreading out. Entropy and statistical mechanics tells us that the
• 27:35
  Speaker 1: universe doesn't like to have energy localized in a little spot.
• 27:38
  Speaker 1: It likes for it to spread out. Sort of fascinating
• 27:41
  Speaker 1: quantum mechanical, the universe likes to occupy multiple quantum states
• 27:45
  Speaker 1: instead of like being focused on a single quantum state.
• 27:48
  Speaker 1: What that means essentially is that any particle will always
• 27:51
  Speaker 1: decay into a lower mass particle. If it's possible for
• 27:56
  Speaker 1: you to take a step down the mass ladder to
• 27:58
  Speaker 1: break up into smaller particle with less mass than you,
• 28:01
  Speaker 1: always will the universe is its constant pressure. It's the
• 28:04
  Speaker 1: same as if you have like a hot object sitting
• 28:07
  Speaker 1: on a surface, it's going to spread its energy out
• 28:09
  Speaker 1: to the neighboring stuff. The same way you have a
• 28:11
  Speaker 1: very high mass particle. It wants to break up into
• 28:14
  Speaker 1: lower mass particles. And it turns out that the neutron
• 28:18
  Speaker 1: is heavier than the proton just by a little bit,
• 28:22
  Speaker 1: and so the neutron can do this. It can take
• 28:24
  Speaker 1: a step down into a lower energy configuration. So the
• 28:27
  Speaker 1: neutron is a higher energy state, which means it has
• 28:29
  Speaker 1: a little bit more mass. And decays down into a proton.
• 28:32
  Speaker 1: It does this by flipping one of the down corks
• 28:35
  Speaker 1: into an upcorp. So it's my freshly biked neutron. It's
• 28:38
  Speaker 1: kind of like a hot soup flay. And then if
• 28:40
  Speaker 1: I leave that out, it's going to cool down and
• 28:43
  Speaker 1: then collapse into a proton. I got it. Oh, speaking
• 28:47
  Speaker 1: of su fla, I did leave one out, so we're
• 28:50
  Speaker 1: gonna need to take a quick break while I go
• 28:52
  Speaker 1: check on that. I'm sure it's fine, uh, And then
• 28:55
  Speaker 1: we hopefully will come back and I'll still have my
• 28:58
  Speaker 1: neutron soup fla attack and we'll continue talking about how
• 29:01
  Speaker 1: long do these neutrons live? How do I resuscitate my
• 29:04
  Speaker 1: neutron souflay? So we'll be right back. Okay, So bad
• 29:20
  Speaker 1: news is that my soup fla did collapse. The good
• 29:24
  Speaker 1: news is I guess it's now our proton, so all
• 29:26
  Speaker 1: isn't lost. That's always the backup plan for your neutron souflay.
• 29:31
  Speaker 1: Turns out, charge it up to a proton south lag.
• 29:35
  Speaker 1: Like you know, a sou flay that collapses is still
• 29:38
  Speaker 1: gonna taste pretty good. So a neutron that decays into
• 29:41
  Speaker 1: a proton is still a particle. It'll still build things
• 29:45
  Speaker 1: like delicious soufleas exactly. And so we were talking about
• 29:50
  Speaker 1: how neutrons decay and how they turn into protons, and
• 29:54
  Speaker 1: people might be wondering, like what's going on with the
• 29:57
  Speaker 1: electric charges? Like can you just turn a down cork
• 30:00
  Speaker 1: which is charged minus a third into an upcork, which
• 30:04
  Speaker 1: is charged plus two thirds? Like charge doesn't just come
• 30:07
  Speaker 1: for fruit. You can't just like create charge. How do
• 30:09
  Speaker 1: you just convert a neutron into a plus one charged proton? Right?
• 30:13
  Speaker 1: The answer is that the universe does do the accounting
• 30:16
  Speaker 1: quite carefully. And when a downcourt converts into an upcork,
• 30:19
  Speaker 1: it also emits a W particle. Okay, now you're just
• 30:23
  Speaker 1: making up particles. What's the W particle? So a W
• 30:27
  Speaker 1: particle is the force particle for the weak nuclear force. Right,
• 30:32
  Speaker 1: we got all these different forces. We have electromagnetism, we
• 30:35
  Speaker 1: have a strong force, we have the weak force. Each
• 30:37
  Speaker 1: one we think of as carried by a particle. So
• 30:40
  Speaker 1: photons carry the electromagnetic force, gluons carry these strong force.
• 30:45
  Speaker 1: W particles carry the weak nuclear force. The weak nuclear
• 30:49
  Speaker 1: force is like the weirdest, strangest, most amazing sporce there is.
• 30:53
  Speaker 1: It's not very powerful, but it can do all sorts
• 30:55
  Speaker 1: of really strange stuff. And we have a couple of
• 30:57
  Speaker 1: podcast episodes dedicated just to under standing the weak force
• 31:01
  Speaker 1: and parity violation and all that crazy stuff. But in
• 31:03
  Speaker 1: this case, the weak force is here to help balance
• 31:06
  Speaker 1: the books. When a down cork becomes an upcork, that
• 31:09
  Speaker 1: sort of costs one electric charge. You've gone from a
• 31:12
  Speaker 1: neutron to a proton. So to balance the books, you
• 31:15
  Speaker 1: also need to create something with negative charge. The amazing
• 31:18
  Speaker 1: thing about these W particles is that they do have charge,
• 31:21
  Speaker 1: so the W can have a positive or a negative charge.
• 31:24
  Speaker 1: In this case, you emit a W minus which balances
• 31:29
  Speaker 1: the charges. So have you've gone from a neutron to
• 31:31
  Speaker 1: a proton and a W minus. So the proton is
• 31:34
  Speaker 1: plus one, the W minus is minus one. That all
• 31:37
  Speaker 1: adds up to zero. The W minus itself doesn't live
• 31:40
  Speaker 1: for very long and it turns into an electron and
• 31:42
  Speaker 1: an anti neutrino. Okay, so an electron does have a
• 31:46
  Speaker 1: negative charge, so it still retains that negative charge. What
• 31:49
  Speaker 1: is an anti neutrino? Yeah, and anti neutrino is one
• 31:52
  Speaker 1: of these little ghostly particles. So you and I are
• 31:54
  Speaker 1: made of protons and neutrons and electrons, which are made
• 31:57
  Speaker 1: of upcorks and down corks. But there's this other particle,
• 32:00
  Speaker 1: this neutrino, which exists in the universe and can be made,
• 32:04
  Speaker 1: and the Sun is pumping out like jillions of them
• 32:07
  Speaker 1: every second. But they're very strange little particles because they
• 32:10
  Speaker 1: don't appear normally inside matter, Like I am not made
• 32:14
  Speaker 1: out of neutrinos, and you're not made out of neutrinos
• 32:16
  Speaker 1: in any way. But it's something that the universe can exist.
• 32:19
  Speaker 1: It's like a Lego building block that's never used in
• 32:22
  Speaker 1: making anything bigger or larger. It's just sort of like
• 32:25
  Speaker 1: floating around in the universe. Yeah, I remember those Lego blocks.
• 32:29
  Speaker 1: They're usually like these like weirdly shaped, clear little ones,
• 32:33
  Speaker 1: and they would just kind of not be used in anything,
• 32:36
  Speaker 1: get quickly lost or eaten exactly. And neutrinos are strange
• 32:40
  Speaker 1: because they're very very low mass, they're almost massless but
• 32:43
  Speaker 1: not entirely, and they also hardly interact. They don't have
• 32:46
  Speaker 1: any electric charge, they don't have the strong force, so
• 32:49
  Speaker 1: they basically just fly through everything. So neutrino when it's produced,
• 32:52
  Speaker 1: can fly through like a star without blinking an eye
• 32:55
  Speaker 1: into a neutrino. The whole universe is transparent, and so
• 32:59
  Speaker 1: that just sort of flies out. And so to summarize them,
• 33:01
  Speaker 1: when a neutron decays, it turns into a proton, an electron,
• 33:05
  Speaker 1: and then an anti neutrino, and so that's what happens
• 33:08
  Speaker 1: when a neutron decase. That's spooky. So neutron does kind
• 33:12
  Speaker 1: of create a ghost when it decays scientifically speaking exactly.
• 33:18
  Speaker 1: And we should also be clear about what we mean
• 33:20
  Speaker 1: about neutron decay because people might be wondering, like, does
• 33:23
  Speaker 1: that mean that the neutrons that are in my body
• 33:26
  Speaker 1: right now are going to like break up, like they
• 33:28
  Speaker 1: don't last for long? Like, am I dying because my
• 33:31
  Speaker 1: neutrons are decaying? Yeah, I want to know if I
• 33:33
  Speaker 1: will spontaneously turn into a pile of protons, electrons and
• 33:37
  Speaker 1: ghost particles in my best interest to know. And that's
• 33:42
  Speaker 1: one of the really fascinating mysteries about neutron decay is
• 33:45
  Speaker 1: that neutrons do decay, but only sort of like when
• 33:48
  Speaker 1: they're on their own, floating out in the universe. When
• 33:51
  Speaker 1: a neutron is inside a nucleus when it's hanging out
• 33:54
  Speaker 1: with other protons. When it and it's proton brethren have
• 33:57
  Speaker 1: built something larger, then he can last forever. You know,
• 34:00
  Speaker 1: you have a stable nucleus like iron, right, iron can
• 34:03
  Speaker 1: live forever. We think if you have an iron atom
• 34:06
  Speaker 1: sitting alone in the universe, it's made of protons and
• 34:09
  Speaker 1: neutrons and electrons, it can sit there, we think forever.
• 34:12
  Speaker 1: We think it's stable. If it's not perturbed, it will
• 34:14
  Speaker 1: just hang out until the end of time. That includes
• 34:18
  Speaker 1: the neutrons inside the iron right there there. They're neutrons.
• 34:22
  Speaker 1: They will hang out forever. Their down corks are not
• 34:25
  Speaker 1: going to flip into up corks, turning them into protons.
• 34:28
  Speaker 1: This is like the ultimate ziplock bag techniques. So keeping
• 34:33
  Speaker 1: neutrons fresh forever. I love that technology for my strawberries.
• 34:38
  Speaker 1: They're so good, but they go bad so fast. Exactly so,
• 34:41
  Speaker 1: the neutrons in your body are in atoms, and so
• 34:44
  Speaker 1: they are likely to last as long as those atoms last.
• 34:47
  Speaker 1: But if you take a neutron out of the atom
• 34:49
  Speaker 1: and you have it by itself hanging out in free space,
• 34:52
  Speaker 1: now we can talk about the lifetime of that neutron.
• 34:54
  Speaker 1: What does it do when it's left alone? Well, the
• 34:57
  Speaker 1: neutrons sitting there in empty space last till end of
• 35:00
  Speaker 1: time or will it decay? So if you put like
• 35:02
  Speaker 1: a proton and then a neutron and electron, you have
• 35:05
  Speaker 1: them just hanging out in free space and you just wait.
• 35:07
  Speaker 1: The proton will last forever, we think, the electron will
• 35:10
  Speaker 1: last forever, we think, but the neutron will not. The
• 35:14
  Speaker 1: neutron by itself will decay. One of those down corks
• 35:17
  Speaker 1: will flip. That's the actual sound it makes, and it
• 35:20
  Speaker 1: will turn into a proton electron and an anti neutrino.
• 35:24
  Speaker 1: So when we talked about the neutron last time, we're
• 35:25
  Speaker 1: talking about the isolated neutron, not a neutron that's inside
• 35:29
  Speaker 1: the nucleus. So, when it's inside the nucleus, what is
• 35:32
  Speaker 1: that zip block effect that is keeping it from decaying. Yeah,
• 35:35
  Speaker 1: it's a great question, and there's a lot of mysteries
• 35:37
  Speaker 1: there because we don't really understand very well how the
• 35:41
  Speaker 1: strong force works. We talked about it briefly a little earlier,
• 35:44
  Speaker 1: but when protons and neutrons are locked together inside a nucleus,
• 35:47
  Speaker 1: it's not like you just have these particles and they're
• 35:50
  Speaker 1: stuck together like legos. They're also talking to each other
• 35:53
  Speaker 1: because remember a proton and a neutron, they're not just
• 35:56
  Speaker 1: linked together quarks, they're little bags of gluons. When you
• 36:00
  Speaker 1: get a proton and neutron close enough together, then their
• 36:03
  Speaker 1: gluons talk to each other. Those bags leak a little bit.
• 36:07
  Speaker 1: They're not totally separate from each other, and really they
• 36:09
  Speaker 1: sort of like weave themselves into a larger mosaic. You
• 36:12
  Speaker 1: might wonder inside a heavy hydrogen atom, where you have
• 36:16
  Speaker 1: not just a proton, but a proton or a neutron,
• 36:19
  Speaker 1: what's making the proton and neutron stick to each other? Right,
• 36:22
  Speaker 1: the proton is positively charged, the neutron is negatively charged.
• 36:26
  Speaker 1: Why did they stick together at all? Why don't they
• 36:28
  Speaker 1: just float apart? The answer is their gluons. When you
• 36:31
  Speaker 1: get them that close together, then the gluons inside each
• 36:34
  Speaker 1: other's bags talk to each other, and they click together
• 36:37
  Speaker 1: into sort of a larger object which is not really
• 36:40
  Speaker 1: anymore just and isolated proton, not really any more isolated neutron,
• 36:44
  Speaker 1: but this combined object that has these linkages together. So
• 36:47
  Speaker 1: is that why when you keep adding neutrons to an
• 36:51
  Speaker 1: atom that it becomes maybe less stable because you start
• 36:54
  Speaker 1: to weaken those gluon forces. Yeah, you can make it
• 36:57
  Speaker 1: less stable or more stable. Right, The way that you
• 37:01
  Speaker 1: organize the protons and the neutrons inside the nucleus totally
• 37:04
  Speaker 1: determined whether something is stable or not. We have a
• 37:07
  Speaker 1: fun podcast episode about the islands of stability and how
• 37:10
  Speaker 1: heavy you can make something and keep it stable. We
• 37:13
  Speaker 1: don't know the answer to that because the strong force
• 37:16
  Speaker 1: is very difficult to do calculations with, Like we can't
• 37:18
  Speaker 1: sit down with pencil and paper and solve the quantum
• 37:21
  Speaker 1: mechanics of the nucleus the way we can with the
• 37:24
  Speaker 1: hydrogen atom. Folks who have done physics in college have
• 37:27
  Speaker 1: done like the shortening your equation for the hydrogen atom.
• 37:29
  Speaker 1: When we know those equations, we can solve them, we
• 37:32
  Speaker 1: can find the states of the electron. We don't know
• 37:35
  Speaker 1: how to do those calculations for the strong force because
• 37:37
  Speaker 1: it's much more powerful and much more sensitive to tiny details,
• 37:41
  Speaker 1: So we don't actually know like the answer to those
• 37:44
  Speaker 1: We can't do it with pencil and paper. We have
• 37:45
  Speaker 1: massive computers trying to do those calculations, but it's really challenging,
• 37:49
  Speaker 1: So mostly it's experimental. We try to like build heavier
• 37:52
  Speaker 1: stuff and see if we can keep it together. People
• 37:55
  Speaker 1: shoot like neutrons at atoms and see like, oh, can
• 37:57
  Speaker 1: I get one to stick in there and make something
• 37:59
  Speaker 1: which lasts longer. So it's a whole area of research.
• 38:02
  Speaker 1: How do weave protons and neutrons together into stable objects?
• 38:06
  Speaker 1: We think that they organize themselves in terms of these shells.
• 38:09
  Speaker 1: Is this nuclear shell model that tells you how to
• 38:12
  Speaker 1: build protons and neutrons together into a stable nucleus sort
• 38:16
  Speaker 1: of analogous to the way electrons organize themselves in shells
• 38:20
  Speaker 1: on the outside of the atom. It's really fascinating. So
• 38:23
  Speaker 1: I am feeling more and more like a physicist based
• 38:25
  Speaker 1: on my childhood because I would try to just build
• 38:28
  Speaker 1: the biggest thing out of legos and then kind of
• 38:29
  Speaker 1: hold it up and see if it could sustain and
• 38:32
  Speaker 1: self for if it would fall apart. And it sounds
• 38:34
  Speaker 1: like that's what you guys are doing, just with more
• 38:36
  Speaker 1: expensive equipment. But yeah, so that that is interesting is
• 38:41
  Speaker 1: you're saying that, like maybe they arrange themselves into shells.
• 38:45
  Speaker 1: When you're talking about shells, I'm assuming this is not
• 38:48
  Speaker 1: like a mollusk shell or something. So what is a
• 38:51
  Speaker 1: shell in terms of particle physics. Yes, when we talk
• 38:54
  Speaker 1: about shells we think of like spheres and other arrangements.
• 38:58
  Speaker 1: We think of The protons and neutrons inside the nucleus
• 39:00
  Speaker 1: have somehow found stable ways to organize themselves into these
• 39:04
  Speaker 1: like little mosaics. Instead of thinking about them really as
• 39:07
  Speaker 1: protons and neutrons anymore, you really should think about them
• 39:10
  Speaker 1: as components of this fabric, this nuclear fabric, which likes
• 39:14
  Speaker 1: to weave itself together. And the incredible thing is that
• 39:16
  Speaker 1: it's stable, like in many configurations, even for very very
• 39:20
  Speaker 1: heavy elements, these things are quite stable. Again, we don't
• 39:23
  Speaker 1: really understand it. And so there's two different communities of
• 39:26
  Speaker 1: physicists here, the ones that like to make really big
• 39:29
  Speaker 1: blobs of protons and neutrons and understand like how are
• 39:32
  Speaker 1: they working together? And then there's the folks who just
• 39:34
  Speaker 1: want to like dig inside one neutron and say, well,
• 39:36
  Speaker 1: let's just study the neutron by itself. Let's zoom inside
• 39:39
  Speaker 1: the neutron and see if we can understand what makes
• 39:42
  Speaker 1: that cork flip from one to the other. How often
• 39:45
  Speaker 1: does that happen? How long does it take? And what
• 39:48
  Speaker 1: does that mean about the neutron. So you've got like
• 39:50
  Speaker 1: the nuclear physicists studying like huge blobs of neutrons and
• 39:54
  Speaker 1: protons inside the nucleus, and they have us particle physicists
• 39:57
  Speaker 1: looking to break it apart and see what's inside. That's
• 40:00
  Speaker 1: really interesting. So now that we have isolated the neutron,
• 40:04
  Speaker 1: it's we've broken apart that atom. It's outside, it's vulnerable.
• 40:08
  Speaker 1: Now what happens? So now we can see how long
• 40:11
  Speaker 1: it takes to pop into a proton and electron and
• 40:15
  Speaker 1: a neutrino. And so this is a really interesting question,
• 40:17
  Speaker 1: just like how long does it take? Remember, protons will
• 40:20
  Speaker 1: live for trillions of years. There's two amazing things about
• 40:23
  Speaker 1: the neutron lifetime how long a neutron will survive on
• 40:26
  Speaker 1: its own. First is that it's very short. It's like
• 40:29
  Speaker 1: fifteen minutes. The neutron does not last very long. The
• 40:33
  Speaker 1: person is that it's basically instantaneous on a cosmic timescale.
• 40:36
  Speaker 1: That's right, you know, neutron's last for like fifteen minutes.
• 40:40
  Speaker 1: It's it's nothing. You know, cosmically, do you make a neutron?
• 40:43
  Speaker 1: You leave it there, you go to get a coffee
• 40:45
  Speaker 1: and you come back it's gone. You know, that's kind
• 40:48
  Speaker 1: of sad to me. I don't know why. Again, I'm
• 40:51
  Speaker 1: like attributing emotions to these things in the universe that,
• 40:55
  Speaker 1: as far as I know, don't feel emotions, but it does.
• 40:58
  Speaker 1: It seems very um disconcerting. That's something as fundamental as
• 41:03
  Speaker 1: a neutron, less about as long as it takes for
• 41:07
  Speaker 1: my soup to cool down. Yeah, So if you want
• 41:09
  Speaker 1: to build something out of neutrons, and you make yourself
• 41:11
  Speaker 1: a big pile of neutrons, you better get to work.
• 41:13
  Speaker 1: No time for a coffee break, you know, before you
• 41:15
  Speaker 1: get started. Like you got to use them or lose them.
• 41:18
  Speaker 1: The other fascinating thing about the neutron lifetime is we
• 41:20
  Speaker 1: don't actually know what it is. We've tried to measure it,
• 41:24
  Speaker 1: and we have two very different ways of measuring the
• 41:27
  Speaker 1: neutron lifetime, like two very different experimental setups, and they
• 41:30
  Speaker 1: get different results. Like one group put a bunch of
• 41:34
  Speaker 1: them in a bottle and wait to see how many
• 41:36
  Speaker 1: they have like ten minutes later, and they get an
• 41:39
  Speaker 1: answer of like fourteen minutes and thirty nine seconds. And
• 41:42
  Speaker 1: other folks use a beam of neutrons and count how
• 41:45
  Speaker 1: many protons come out, and they get a different answer.
• 41:49
  Speaker 1: They get fourteen minutes and forty eight seconds, So there's
• 41:52
  Speaker 1: like a nine second difference, so we don't even actually know. Well,
• 41:56
  Speaker 1: I see what the problem is. Probably one group is
• 41:59
  Speaker 1: using one Mississippis and the other group is using one
• 42:02
  Speaker 1: potato to potato. You have solved this mystery. It is
• 42:06
  Speaker 1: funded physicists for decades and today you have figured it out. Katie. Wow,
• 42:10
  Speaker 1: thank you so much your contributions to particle physics. So
• 42:13
  Speaker 1: you're welcome everyone for me solving this physics problem. And
• 42:18
  Speaker 1: when we get back, um, I'm sure Daniel will make
• 42:21
  Speaker 1: some kind of argument that no, it's not as simple
• 42:24
  Speaker 1: as one Mississippi or one potato, but you know all
• 42:28
  Speaker 1: of them have a short break to work that one out,
• 42:30
  Speaker 1: because I think my argument is prettier tight. Okay, And
• 42:46
  Speaker 1: so we're back and we've got this. Two teams of
• 42:50
  Speaker 1: I would assume, very smart, very professional scientists, but they're
• 42:54
  Speaker 1: coming to slightly different answers on how long it takes
• 42:58
  Speaker 1: for a neutron on to decay. One group fourteen minutes
• 43:02
  Speaker 1: thirty nine seconds, the other group fourteen minutes and forty
• 43:05
  Speaker 1: eight seconds. So what the heck is going wrong? Is
• 43:08
  Speaker 1: one group just wrong? We don't know. It's really fascinating
• 43:12
  Speaker 1: to have watched this series of experiments over a couple
• 43:15
  Speaker 1: of decades. You know, whenever you do something in physics,
• 43:17
  Speaker 1: you try to do it a couple of ways because
• 43:20
  Speaker 1: it's easy to make mistakes. You're doing something hard, you're
• 43:22
  Speaker 1: making assumptions, you're doing the best you can, but it's
• 43:25
  Speaker 1: very easy for mistakes to creep in, and so it's
• 43:27
  Speaker 1: great practice to have two different groups of people doing
• 43:30
  Speaker 1: it two different ways, making different mistakes. In the end,
• 43:33
  Speaker 1: we're supposed to be measuring the same thing about the universe.
• 43:36
  Speaker 1: The neutron should just have a certain lifetime and we
• 43:38
  Speaker 1: should be able to measure it and get the same answer.
• 43:40
  Speaker 1: And if we don't, that means that one of our
• 43:42
  Speaker 1: assumptions is wrong, where somebody is making a mistake, or
• 43:45
  Speaker 1: there's something deeper going on. Right, something is happening in
• 43:48
  Speaker 1: one of these experiments that we don't understand, which could
• 43:51
  Speaker 1: be like a clue as to how the universe works.
• 43:54
  Speaker 1: So originally these two groups made these measurements and they
• 43:56
  Speaker 1: didn't get the same answer, But nobody was worried because
• 43:59
  Speaker 1: their airbor were pretty large. You know, the difference was
• 44:02
  Speaker 1: like eight or nine seconds, but the uncertainty was like
• 44:04
  Speaker 1: thirty seconds. So people have thought, we'll just keep working
• 44:07
  Speaker 1: and maybe the numbers will creep together as they get
• 44:09
  Speaker 1: more precise. The opposite has happened. Both groups have been
• 44:13
  Speaker 1: working hard to reduce those uncertainties, you know, figure out
• 44:16
  Speaker 1: the sources of error and potential bias in their experiments,
• 44:19
  Speaker 1: shaving them off, calibrating them, cross checking them. And as
• 44:22
  Speaker 1: the uncertainties have decreased, and now those uncertainties are like
• 44:24
  Speaker 1: less than a second or two, the size of the
• 44:27
  Speaker 1: difference between the two experiments has stayed the same. In fact,
• 44:30
  Speaker 1: it's even crept up a little bit, from like eight
• 44:32
  Speaker 1: to almost ten seconds. Okay, so we have Team Bottle,
• 44:38
  Speaker 1: I'm going to say, and then Team Beam. So what
• 44:41
  Speaker 1: are these teams doing? Because they have very different methods
• 44:44
  Speaker 1: going on here, which that may somewhat explain why they're
• 44:48
  Speaker 1: getting different results. So first let's go over like Team Bottle.
• 44:52
  Speaker 1: What is Team Bottle doing just you know, shaking up
• 44:55
  Speaker 1: some neutrons and a bottle, seeing what happens to them.
• 44:57
  Speaker 1: That's basically, yeah, they have a new tron source. This
• 45:00
  Speaker 1: is actually at Los Alumos, New Mexico, where I grew up.
• 45:03
  Speaker 1: I was wasn't involved in this experiment. It's a huge
• 45:05
  Speaker 1: facility there. As far as you know. Anyways, go on,
• 45:10
  Speaker 1: I may have been unwittingly roped into this experiment. They
• 45:14
  Speaker 1: have a bunch of neutrons there and basically they put
• 45:16
  Speaker 1: them in a bottle. They get them ultra cold, so
• 45:19
  Speaker 1: they're not moving very fast, and neutrons are a bit
• 45:21
  Speaker 1: hard to store because they don't have electric charts, so
• 45:23
  Speaker 1: you can't use magnetic fields or electric fields to control them.
• 45:26
  Speaker 1: You have to use gravity to get them cold. So
• 45:29
  Speaker 1: they slow down and let them just like fall into
• 45:31
  Speaker 1: this container. They call it the bathtub, And basically they
• 45:35
  Speaker 1: just collect a bunch of neutrons. They very carefully count
• 45:37
  Speaker 1: how many introns they start with, and then they measure
• 45:39
  Speaker 1: the number of neutrons in their bottle, and then they
• 45:41
  Speaker 1: come back ten minutes later, measured again. And they come
• 45:43
  Speaker 1: back ten minutes later and they measure it again. And
• 45:45
  Speaker 1: that's the essence of the experiment, is like, if you
• 45:48
  Speaker 1: think something doesn't last very long, put a bunch of
• 45:50
  Speaker 1: them in a bottle. Count how many you have come
• 45:52
  Speaker 1: back later and count them again. So it's very simple
• 45:55
  Speaker 1: experiment in that way. So you've got this this ice
• 45:57
  Speaker 1: cold bottle of delicious new atron's man that makes me thirsty.
• 46:02
  Speaker 1: And so they would measure these and they would find
• 46:04
  Speaker 1: that they are sort of disappearing at a certain rate,
• 46:07
  Speaker 1: and that is how they got at fourteen minutes and
• 46:10
  Speaker 1: thirty nine seconds exactly. The important thing to understand is
• 46:13
  Speaker 1: that the neutron lifetime doesn't mean that every neutron has
• 46:16
  Speaker 1: a clock in it and it expires exactly after fourteen
• 46:19
  Speaker 1: minutes and thirty nine seconds. It's an exponential decay. Every
• 46:23
  Speaker 1: neutron has a probability to decay in any moment. And
• 46:26
  Speaker 1: if some fraction of your neutrons will decay in shorter time,
• 46:29
  Speaker 1: and a fraction of the neutrons will last longer, just
• 46:31
  Speaker 1: like radioactive decay, it's the same fundamental process. In fact,
• 46:35
  Speaker 1: it is that process protons turning into neutrons, which drives
• 46:38
  Speaker 1: also radioactive decay. So you don't like watch one neutron,
• 46:41
  Speaker 1: just ask how long did it live. Have a whole
• 46:43
  Speaker 1: population of neutrons, and you count how many you have
• 46:46
  Speaker 1: over time, and you fit that to a function and
• 46:49
  Speaker 1: exponential decay, and you measure sort of the parameter the
• 46:52
  Speaker 1: slope of that function. So it's a bit more than
• 46:54
  Speaker 1: just watching one neutron decay. That's why you have a
• 46:56
  Speaker 1: population of them. So they have these in a little
• 46:59
  Speaker 1: bathtub and then every once in a while they're trying
• 47:01
  Speaker 1: to count all of them. They pushed them against this
• 47:03
  Speaker 1: counter which is covered in boron and zinc, and that
• 47:06
  Speaker 1: makes the neutrons give off a little flash of light,
• 47:08
  Speaker 1: and they count how many flashes of light they saw,
• 47:11
  Speaker 1: and that tells them how many neutrons they have left
• 47:13
  Speaker 1: I see. So these two experiments would be like two
• 47:16
  Speaker 1: groups of alien scientists measuring the average lifespan of a human. Like, sure,
• 47:22
  Speaker 1: our lifespans are going to differ, but they're not going
• 47:24
  Speaker 1: to differ by like hundreds of years. They're going to
• 47:27
  Speaker 1: differ by a matter of a few years. And so
• 47:30
  Speaker 1: you should in theory, even if these two alien scientists
• 47:34
  Speaker 1: groups have different methods of measuring our lifespan, they should
• 47:37
  Speaker 1: in theory be able to both come up with the
• 47:40
  Speaker 1: same average lifespan. But in this case they're not. So
• 47:43
  Speaker 1: then what is what is Team Beam doing? The Team
• 47:46
  Speaker 1: Beam is taking the opposite approach, where his team Bottle
• 47:48
  Speaker 1: is saying, let's count how many neutrons we still have left,
• 47:51
  Speaker 1: Team Beam is asking how many neutrons disappear. So they
• 47:54
  Speaker 1: have a beam of neutrons that they create, and they
• 47:57
  Speaker 1: count how many protons are created within these beams, because
• 48:01
  Speaker 1: remember a neutron decays and it decays into a proton,
• 48:04
  Speaker 1: So to count how many neutrons have disappeared, they count
• 48:07
  Speaker 1: how many protons are created. And so instead of counting
• 48:10
  Speaker 1: how many neutrons they still have, like the Bottle guys
• 48:13
  Speaker 1: are doing, they're counting how many neutrons have left the room.
• 48:16
  Speaker 1: So in the analogy you were talking about with human lifetime,
• 48:19
  Speaker 1: instead of counting how many humans do we still have left,
• 48:22
  Speaker 1: they're counting graves. I see. I mean it makes me wonder.
• 48:26
  Speaker 1: And again this is probably you know, me strolling in
• 48:30
  Speaker 1: without having done the rigorous testing that Team Beam has done.
• 48:34
  Speaker 1: But like, could there be like some infiltration of protons,
• 48:38
  Speaker 1: like protons coming from some other source that is messing
• 48:41
  Speaker 1: with their results. Absolutely, that's the kind of thing that
• 48:44
  Speaker 1: they've been thinking about for like the last twenty years.
• 48:47
  Speaker 1: So you're right, it's something to be worried about, but
• 48:49
  Speaker 1: they're very careful. They shield their experiments that magnetic fields
• 48:52
  Speaker 1: to prevent anything from creeping in, and they filter these
• 48:55
  Speaker 1: protons out using magnetic fields and very careful to only
• 48:58
  Speaker 1: count the protons that they think come from their beam.
• 49:02
  Speaker 1: So each experiment has like a long list of ways
• 49:04
  Speaker 1: that they can get it wrong. And over the last
• 49:06
  Speaker 1: ten years they've been like going down that list and thinking,
• 49:09
  Speaker 1: how can we check this, How do we really know
• 49:12
  Speaker 1: this is true? Can we do this another way just
• 49:14
  Speaker 1: to verify, just like as a sanity check, maybe there's
• 49:17
  Speaker 1: something going wrong here. And they've gone down that list
• 49:19
  Speaker 1: and nobody's found any basic mistakes, and as a result,
• 49:22
  Speaker 1: they've been able to shave down their uncertainty because now
• 49:25
  Speaker 1: they have like multiple ways of doing every step of
• 49:28
  Speaker 1: their experiment to convinced themselves that their number is correct.
• 49:32
  Speaker 1: So we still have Team Bottle and Team Beam doing
• 49:34
  Speaker 1: very careful work. Nobody has an idea for what might
• 49:37
  Speaker 1: be different where the mistake could be, but they're still
• 49:40
  Speaker 1: getting different answers. Also, bringing it back to the aliens
• 49:44
  Speaker 1: observing Earth analogy, I mean, I wonder if maybe there
• 49:48
  Speaker 1: could like these teams could be doing everything perfectly and
• 49:52
  Speaker 1: executing the experiments perfectly, still getting the different results, but
• 49:56
  Speaker 1: not because they made an error, but because there's something
• 49:59
  Speaker 1: else going on. So, for instance, maybe if the Team
• 50:02
  Speaker 1: Alien one is just counting the number of humans left
• 50:06
  Speaker 1: after a certain amount of time and average getting the
• 50:08
  Speaker 1: lifespan average from that, they may not be taking into
• 50:13
  Speaker 1: account like a new births or something. And then for
• 50:17
  Speaker 1: Team Alien just measuring the graves. You know, what if
• 50:20
  Speaker 1: you have a grave that has like more than one
• 50:23
  Speaker 1: person in it, So could there be something going on
• 50:26
  Speaker 1: where these these two you know, let's not blame the
• 50:29
  Speaker 1: groups of scientists or the intern or the janitor. Nobody's
• 50:33
  Speaker 1: doing anything wrong. But they are actually correct. But just
• 50:37
  Speaker 1: because their method of measurement is different, there is some
• 50:40
  Speaker 1: some mysterious mechanism going on that is creating that difference. Yes, absolutely,
• 50:45
  Speaker 1: that is sort of the hope, right. The boring answer
• 50:48
  Speaker 1: is like, oh, it turns out the cable wasn't plugged
• 50:50
  Speaker 1: in right, or this temperature was set to the wrong number,
• 50:52
  Speaker 1: and like you know, from an experimental point of view,
• 50:55
  Speaker 1: that would be satisfied to figure it out. More exciting
• 50:57
  Speaker 1: would be is if it reveals that one of the
• 50:59
  Speaker 1: assumptions that are made that suggests that these two experiments
• 51:02
  Speaker 1: should be getting the same answer are fundamentally wrong. So
• 51:05
  Speaker 1: people have been very creative about this, and there is
• 51:08
  Speaker 1: one cool idea floating out there that maybe when the
• 51:11
  Speaker 1: neutron decays, it doesn't always decay into a proton. Maybe
• 51:15
  Speaker 1: sometimes it decays into something else like dark matter. Some
• 51:19
  Speaker 1: tiny fraction of time, the neutron turns into dark matter,
• 51:23
  Speaker 1: and that would explain this difference because remember that the
• 51:26
  Speaker 1: beam folks, they won't see it if the neutron decays
• 51:29
  Speaker 1: into something else. They only count the number of times
• 51:32
  Speaker 1: the neutron decays into a proton because they assume it
• 51:34
  Speaker 1: always decays into a proton. Now the bottle folks, they
• 51:37
  Speaker 1: will see that neutron disappear because they're counting the neutrons themselves.
• 51:41
  Speaker 1: So if the neutrons sometimes decay into something which is
• 51:44
  Speaker 1: not a proton, then these two groups will get different numbers.
• 51:48
  Speaker 1: So this is fun idea out there about how maybe
• 51:50
  Speaker 1: neutrons will sometimes decay into dark matter instead of into protons.
• 51:54
  Speaker 1: That is really cool. I love that when in science,
• 51:57
  Speaker 1: like if you get an unexpected result bolt or something
• 52:01
  Speaker 1: that seems like a mistake, it could actually lead you
• 52:03
  Speaker 1: to an even bigger, even more interesting discovery. And there's
• 52:07
  Speaker 1: so many times in the history of science when you
• 52:09
  Speaker 1: do that, When people do experiments, they think just like
• 52:11
  Speaker 1: wrapping up everything, tying up the loose ends. We're pretty
• 52:14
  Speaker 1: sure we understand what we're gonna see. And then there's
• 52:16
  Speaker 1: a discrepancy and it's persistent and it won't go away,
• 52:19
  Speaker 1: and sometimes you tug on that thread and it unravels
• 52:22
  Speaker 1: like everything we thought we knew about the universe. You know,
• 52:25
  Speaker 1: the whole discovery of quantum mechanics was from people like
• 52:28
  Speaker 1: m that's weird. You don't really understand what's going on
• 52:30
  Speaker 1: with the photoelectric effect. So these little discrepancies are very important.
• 52:34
  Speaker 1: They're very powerful ways to test your assumptions and to
• 52:37
  Speaker 1: maybe get a clue that there's something new going on
• 52:40
  Speaker 1: in the universe we don't know. And the dark matter
• 52:43
  Speaker 1: idea is just sort of like a category of possibilities.
• 52:46
  Speaker 1: The specific theory that was bounced around for a few
• 52:49
  Speaker 1: years about the neutrons decay in the dark matter doesn't
• 52:51
  Speaker 1: look like it works. They made this very specific prediction
• 52:54
  Speaker 1: that it would decay into a new state, and in
• 52:56
  Speaker 1: that state, we decay into dark matter, and along the
• 52:58
  Speaker 1: way it would make a tiny little lash, a very
• 53:00
  Speaker 1: specific light. And so the bottle folks looked for this
• 53:03
  Speaker 1: flash of light, but they didn't see it. But that
• 53:05
  Speaker 1: doesn't mean that it's wrong. There might be some other
• 53:07
  Speaker 1: explanation in the same vein the neutrons could be turning
• 53:10
  Speaker 1: into something else. We don't expect a new kind of
• 53:12
  Speaker 1: dark matter or even something else weirder, So, are are
• 53:16
  Speaker 1: they looking into new experiments that they could potentially do
• 53:19
  Speaker 1: to sort of find out what's going on here exactly?
• 53:22
  Speaker 1: They're trying to develop like a third way to measure
• 53:24
  Speaker 1: the neutron lifetime, because that will give us a handle.
• 53:26
  Speaker 1: It's like a vote, right, we develop a third, totally
• 53:29
  Speaker 1: independent way with different assumptions than either the first two.
• 53:32
  Speaker 1: It will tell us which of those first two is
• 53:34
  Speaker 1: correct and which one is not. Actually measuring the neutron
• 53:37
  Speaker 1: lifetime the way we thought it was. A third way
• 53:39
  Speaker 1: to measure this is actually in space because one way
• 53:42
  Speaker 1: to make neutrons is to smash protons against the Earth's atmosphere,
• 53:47
  Speaker 1: which happens all the time out there in space because
• 53:49
  Speaker 1: space is filled with high energy cosmic rays. Protons from
• 53:53
  Speaker 1: the center of the galaxy or from other solar systems
• 53:55
  Speaker 1: smashing into Earth's atmosphere, creating these showers of particles, including
• 53:59
  Speaker 1: neutron on. Now, most of these neutrons then like rain
• 54:02
  Speaker 1: down on the Earth's surface, and as they do, because
• 54:05
  Speaker 1: they're by themselves, they're not inside atomic nuclei, they turn
• 54:08
  Speaker 1: into protons. So if you can count like the number
• 54:11
  Speaker 1: of neutrons created at the edge of the atmosphere with
• 54:14
  Speaker 1: a number of protons you then see raining down, you
• 54:17
  Speaker 1: can get a sense for how many of those neutrons
• 54:19
  Speaker 1: have converted from neutrons into protons. And that's a way
• 54:23
  Speaker 1: to measure the neutron lifetime. It's a bit tricky and
• 54:25
  Speaker 1: it's more complicated, which is why it wasn't like the
• 54:27
  Speaker 1: first option or the second option. But now we need
• 54:30
  Speaker 1: a third option and we need to figure this out.
• 54:32
  Speaker 1: And so people are even talking about like building probes
• 54:34
  Speaker 1: that an orbit Venus, because Venus might have the perfect
• 54:38
  Speaker 1: atmosphere to do this kind of experiment, because it's got
• 54:41
  Speaker 1: so much C O two in it, So it's using
• 54:43
  Speaker 1: a whole planet as a test tube exactly. Particle physicists
• 54:48
  Speaker 1: are not content to just do experiments in one tiny
• 54:51
  Speaker 1: little lab. We want to use the whole universe as
• 54:54
  Speaker 1: our experiment. I see you're just trying to use your
• 54:57
  Speaker 1: research budget for travel. I get it, exactly. What's this
• 55:02
  Speaker 1: first class ticket to Venus? Daniel? Can you explain this charge?
• 55:07
  Speaker 1: But this is something that's really important, you know, not
• 55:09
  Speaker 1: just because we want to understand what's inside the neutron
• 55:12
  Speaker 1: and how does it work and is the neutron turning
• 55:14
  Speaker 1: into something else? The neutron lifetime is a really important
• 55:17
  Speaker 1: component of our universe. You know, in the early universe,
• 55:21
  Speaker 1: neutrons were made, as we talked about, but if they
• 55:23
  Speaker 1: didn't last for long enough, they couldn't get served up
• 55:26
  Speaker 1: into atomic nuclei. So the length of the neutron lifetime
• 55:29
  Speaker 1: sort of determines how many isotopes are made, how much
• 55:33
  Speaker 1: helium is made, and so it's important to get this
• 55:35
  Speaker 1: number right. You know. They determines like the hydrogen to
• 55:38
  Speaker 1: helium ratio that's made during the Big Bang, but also
• 55:42
  Speaker 1: determines like how long stars will live, because the more
• 55:45
  Speaker 1: helium you get, the smaller and heavier the stars are
• 55:49
  Speaker 1: that are made, which don't burn as long. So this
• 55:51
  Speaker 1: is like a fundamental ingredient to the early universe calculations.
• 55:54
  Speaker 1: It's something we really need to understand. So even a
• 55:57
  Speaker 1: discrepancy of a few seconds is very important to determine
• 56:01
  Speaker 1: what is causing that and what the answer is to
• 56:04
  Speaker 1: this right, and it goes to really deep questions in
• 56:06
  Speaker 1: particle physics about the strong force. You know, this is
• 56:09
  Speaker 1: something that we can't sit down and predict very confidently.
• 56:12
  Speaker 1: It takes massive calculation to try to get a sense
• 56:15
  Speaker 1: for how corks talk to each other because the forces
• 56:17
  Speaker 1: are so strong and so difficult to calculate with. It's
• 56:20
  Speaker 1: something physicists called non perturbative, which means that we can't
• 56:23
  Speaker 1: make many of our typical assumptions and simplifications when we
• 56:26
  Speaker 1: do these calculations. So this is a great laboratory to
• 56:30
  Speaker 1: force the universe to teach us something about how the
• 56:32
  Speaker 1: strong force actually works, to force it to like tell us,
• 56:35
  Speaker 1: here's how this happens. Here's the result of this calculation.
• 56:38
  Speaker 1: So it's a really powerful way to try to get
• 56:40
  Speaker 1: some inside how these little particles are talking to each other.
• 56:43
  Speaker 1: And in the end, I got neutrons and you got neutrons.
• 56:46
  Speaker 1: So this should be important to all of us. Yeah,
• 56:48
  Speaker 1: it is interesting. It's such a humble particle that you
• 56:51
  Speaker 1: think of this like neutral doesn't seem to have such
• 56:55
  Speaker 1: a big role to play, But really it's so important
• 56:58
  Speaker 1: to not only to keep us together apparently, like I
• 57:01
  Speaker 1: don't want to fall apart into a bunch of protons
• 57:03
  Speaker 1: and w minuses and then which turns into ghost particles
• 57:07
  Speaker 1: and electrons. I want to stay me for as long
• 57:10
  Speaker 1: as possible, but also just it seems like it's really
• 57:12
  Speaker 1: important to understand them, to understand the universe. Yeah, and
• 57:16
  Speaker 1: it's an enduring mystery. We're gonna stay tuned to figure
• 57:19
  Speaker 1: out what's going on with these neutrons, how long they live,
• 57:21
  Speaker 1: and whether Team Bottle or Team Beam got it right.
• 57:24
  Speaker 1: This is exciting. I want to print shirts Team Bottle,
• 57:27
  Speaker 1: Team Beam and see we're the dialay. Thank you everybody
• 57:31
  Speaker 1: for joining us on this journey, the journey inside our
• 57:34
  Speaker 1: atoms and your atoms and the universe's atoms, where tiny
• 57:38
  Speaker 1: little clocks determine the fate of neutrons and the fate
• 57:40
  Speaker 1: of stars. And thanks very much Katie for joining us
• 57:43
  Speaker 1: on this very particular podcast. Thanks for having me, and
• 57:47
  Speaker 1: good luck with your neutron soup. Flay tune in next time. Everybody,
• 57:59
  Speaker 1: thanks for listening, and remember that Daniel and Jorge Explain
• 58:01
  Speaker 1: the Universe is a production of I heart Radio. For
• 58:04
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• 58:07
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• 58:11
  Speaker 1: favorite shows. Ye