WEBVTT - Why do some particles die? 0:00:08.480 --> 0:00:11.240 Or Hey, just starting a new decade? Make you feel 0:00:11.280 --> 0:00:14.640 young or old? What? It's a new decade. It's gonna 0:00:14.680 --> 0:00:18.919 be very soon when this podcast comes out, it will well, 0:00:18.960 --> 0:00:21.160 you know, it makes me feel a little bit of both. 0:00:21.200 --> 0:00:25.759 I guess I feel you old? You old? Is that 0:00:25.840 --> 0:00:28.639 a quantum superposition of young and old kids? It's both 0:00:28.640 --> 0:00:31.400 in neither. Well, here's something that might make you feel 0:00:31.480 --> 0:00:35.159 kind of young. Oh, this is this invent the Fountain 0:00:35.200 --> 0:00:37.960 of Youth. Still running a grand application for that project. 0:00:38.159 --> 0:00:41.599 But I know it's more a sense of perspective. All right, well, 0:00:41.720 --> 0:00:43.400 what is it? I'll take it. Well, did you know 0:00:43.440 --> 0:00:46.800 that the particles in your body are more than thirteen 0:00:46.840 --> 0:00:51.080 billion years old? Compared to that, you're like a baby. Wait, 0:00:51.120 --> 0:00:53.479 you're telling me that I'm a billion years old and 0:00:53.520 --> 0:00:55.720 that's supposed to make me feel young. Maybe it just 0:00:55.760 --> 0:01:15.800 means you need a n APP. Sounds good, calculatory. Hi. 0:01:15.840 --> 0:01:19.120 I'm Jorge. I'm a cartoonists and the creator of PhD Comics. 0:01:19.360 --> 0:01:22.440 Hi I'm Daniel. I'm a particle physicist and I've seen 0:01:22.640 --> 0:01:26.120 many many particles pass away. Welcome to a new decade 0:01:26.319 --> 0:01:29.880 of our podcast. Daniel and Jorge explain the Universe, a 0:01:30.000 --> 0:01:33.000 production of I Heart Radio, in which we venture forth 0:01:33.000 --> 0:01:36.000 into a whole new decade and try to understand the universe, 0:01:36.160 --> 0:01:39.360 a decade perhaps in which we will reveal new secrets 0:01:39.360 --> 0:01:43.240 about the universe that nobody in human history has ever understood. 0:01:43.360 --> 0:01:45.959 That's right. We like to talk about the planets and 0:01:46.000 --> 0:01:50.360 the stars and the cosmos, but also the little tiny 0:01:50.440 --> 0:01:53.520 things in the universe, the particles that we're all made 0:01:53.520 --> 0:01:57.600 out of and that are all around us all the time. 0:01:57.760 --> 0:01:59.600 I'm glad that you said we like to talk about 0:01:59.600 --> 0:02:04.760 a particle. Sometimes I think it's just me. Well, I'm 0:02:04.840 --> 0:02:12.200 using the Royal We, the Physicist podcast Arial We. But yeah, well, 0:02:12.240 --> 0:02:14.720 I do like to talk about particles because I feel like, 0:02:15.040 --> 0:02:17.120 in the end, we're all made of particles, and if 0:02:17.160 --> 0:02:19.560 we want to understand the universe, we got to start 0:02:19.560 --> 0:02:23.120 at the beginning, the smallest, the littlest nuggets. And if 0:02:23.160 --> 0:02:26.080 we understand the way the universe works at these smallest scales, 0:02:26.520 --> 0:02:29.000 then we have a chance to maybe understand the way 0:02:29.040 --> 0:02:31.480 things work at larger scales. Yeah, you know, I think 0:02:31.520 --> 0:02:33.760 that as human as we tend to kind of forget 0:02:33.800 --> 0:02:36.160 that fact. You know, we're made out of tiny, little 0:02:36.200 --> 0:02:39.840 molecules and atoms and tiny little particles. We I think 0:02:39.840 --> 0:02:42.200 we love to think of ourselves as as these sort 0:02:42.240 --> 0:02:45.800 of ethereal thinking beings, but really we're just like a 0:02:45.919 --> 0:02:49.200 giant lego set of particles, right, Yeah, And ever since 0:02:49.240 --> 0:02:52.320 I learned about quantum mechanics and the frothing vacuum and 0:02:52.560 --> 0:02:55.400 how particles are popping in out of existence at all times, 0:02:55.680 --> 0:02:58.320 it gives a different sense for what you are. You 0:02:58.360 --> 0:03:00.799 are a collection of particles, but that set of particles 0:03:00.919 --> 0:03:03.880 is changing, so you're more like a storm, like a cloud. 0:03:04.400 --> 0:03:07.280 You're like an excitation of the space in which you 0:03:07.320 --> 0:03:09.360 were living. He gives a different sense for what it 0:03:09.400 --> 0:03:11.280 means to be you. And that's why I want to 0:03:11.360 --> 0:03:14.200 understand the universe from the smallest scale, because it tells 0:03:14.280 --> 0:03:16.280 us what it's like to be us, what it means 0:03:16.480 --> 0:03:19.239 to be a thing. Well, I am definitely hopefully a thing, 0:03:19.320 --> 0:03:22.840 and I'm definitely in a state of excitation. And I 0:03:22.919 --> 0:03:25.640 have to say that I did get a fronting vacuum 0:03:25.720 --> 0:03:28.520 for Christmas, so I'm glad you. Does that mean that 0:03:28.560 --> 0:03:32.000 it makes phone for your coffee while it cleans the kitchen? Yeah, 0:03:32.880 --> 0:03:36.680 it's it's it's a multitasker's dream. I'll have the cappuccino 0:03:36.720 --> 0:03:40.360 vacuum please. Yeah. So, so today we'll be talking about 0:03:40.680 --> 0:03:44.119 the things that everyone is made out of. You, me, this, 0:03:44.120 --> 0:03:46.960 this um microphone that I'm speaking to, those speakers that 0:03:47.000 --> 0:03:51.960 are broadcasting our voices. Everything is made out of particles. 0:03:52.040 --> 0:03:55.360 And some people might be surprised, maybe or maybe not, 0:03:55.720 --> 0:03:59.840 that particles don't last forever. That's right, particles are not 0:04:00.040 --> 0:04:02.360 forever as far as we know. But there are kind 0:04:02.360 --> 0:04:05.600 of two different kinds of particles. There's the particles that 0:04:05.680 --> 0:04:08.080 make up me and you, and as we've talked about 0:04:08.080 --> 0:04:11.840 in the podcast, those are mostly three different particles up quarks, 0:04:12.240 --> 0:04:15.400 down quirks, and electrons. But then we talk about all 0:04:15.400 --> 0:04:20.200 these other particles higgs bosons, top quarks, w bosons, and 0:04:20.279 --> 0:04:23.080 those particles aren't around. You don't like find a pile 0:04:23.120 --> 0:04:26.240 of them under rock somewhere, and that's because they don't 0:04:26.320 --> 0:04:29.160 last very long. They flash into existence and then they 0:04:29.200 --> 0:04:31.560 die very quickly. Hey, can I choose what kind of 0:04:31.600 --> 0:04:33.159 quarks I'm made out of? Like? Can I be up 0:04:33.200 --> 0:04:35.359 corks all the time. I don't know what kind of 0:04:35.360 --> 0:04:38.120 special powers you have as a cartoonist, but if you're 0:04:38.120 --> 0:04:40.240 made of protons and neutrons, and there's not a whole 0:04:40.240 --> 0:04:44.080 lot of flexibility, so some of them disappear and some 0:04:44.160 --> 0:04:46.640 of them are born all the time. Um, And so 0:04:46.720 --> 0:04:48.680 to be on the podcast will be sort of tackling 0:04:48.720 --> 0:04:52.599 that crazy phenomenon of what makes particles come into and 0:04:52.680 --> 0:04:55.360 out of existence. Why is it that some particles were 0:04:55.400 --> 0:04:58.239 born in the Big Bang and are still around, whereas 0:04:58.240 --> 0:05:01.040 other particles only get to lie tend to the minus 0:05:01.120 --> 0:05:04.120 twenty three seconds in our universe. So to be on 0:05:04.160 --> 0:05:12.719 the podcast, we'll be talking about why do particles die? 0:05:13.560 --> 0:05:17.240 It make it sound so sad, you know, Oh, I see? 0:05:17.360 --> 0:05:21.920 Why do particles move on? We talk about why particles 0:05:21.920 --> 0:05:25.280 are born and what they've accomplished in their brief, beautiful lives. 0:05:25.720 --> 0:05:29.120 You know, why do particles go to Grandpa's farm where 0:05:29.120 --> 0:05:32.560 they're running happily and jumping over streams streams of particles? 0:05:33.279 --> 0:05:36.159 They go to the particle reserve where they're well taken 0:05:36.200 --> 0:05:39.320 care of. And here's another example of where we're sort 0:05:39.320 --> 0:05:43.440 of anthropomorphizing particles. Right, Particles definitely don't have feelings and 0:05:43.440 --> 0:05:46.520 emotions and families and Thanksgiving dinners, but we talk about 0:05:46.560 --> 0:05:48.679 them as if they are born and as if they die, 0:05:49.040 --> 0:05:50.920 and I think it just helps us connect to them, 0:05:50.920 --> 0:05:54.000 it helps us think about them. So some particles decay 0:05:54.040 --> 0:05:56.960 and others don't. So some particles die and some of 0:05:56.960 --> 0:06:00.240 them live forever? Is that true? Can some particles live 0:06:00.600 --> 0:06:02.480 from the beginning of time till the end of time? 0:06:02.600 --> 0:06:04.840 We can never say for sure. All we can say 0:06:05.000 --> 0:06:08.520 is what we've seen and were in. Some particles, like electrons, 0:06:08.720 --> 0:06:12.240 we have never seen them decay, so we can estimate 0:06:12.360 --> 0:06:15.520 how long the lifetime of an electron is based on 0:06:15.720 --> 0:06:17.920 never having seen any of them decay and having looked 0:06:17.920 --> 0:06:20.080 at a lot of them, And the current estimate is 0:06:20.120 --> 0:06:24.520 like seventeen ga jillion years. Now it might be is 0:06:24.520 --> 0:06:26.800 that is that? The is? What that in a paper? 0:06:26.880 --> 0:06:30.200 Actually I rounded up at six point nine gajillion years. 0:06:30.800 --> 0:06:33.200 But the point is we make some statistical statement and 0:06:33.240 --> 0:06:35.640 say it must be longer than this very very big number, 0:06:35.720 --> 0:06:37.920 much longer than the age of the universe, or we 0:06:37.920 --> 0:06:41.080 would have seen when decay. But we can never be sure. 0:06:41.400 --> 0:06:43.560 And it's the same with a proton. They're pretty stable. 0:06:43.600 --> 0:06:46.200 Like if you put an electron in a jar, it's 0:06:46.279 --> 0:06:49.239 just gonna sit there. It's never gonna turn into anything. 0:06:49.400 --> 0:06:53.279 It's never going to I guess collide with something and 0:06:53.279 --> 0:06:55.640 turn into something else. Is that possible? Oh, it certainly 0:06:55.680 --> 0:06:58.320 could actually could get absorbed and then disappeared. But an 0:06:58.360 --> 0:07:01.560 electron in isolation could you to sit there forever, the 0:07:01.600 --> 0:07:04.320 same way a photon can fly across the universe for 0:07:04.440 --> 0:07:08.280 billions of years and still be a photon. But other particles, 0:07:08.320 --> 0:07:10.200 you know, you put a neutron in a jar or 0:07:10.240 --> 0:07:13.440 a top cork in a jar, and it will spontaneously decay, 0:07:13.520 --> 0:07:16.000 will turn into other stuff. Some of the particles that 0:07:16.080 --> 0:07:19.320 I am made out of might be zillions of years old, 0:07:19.640 --> 0:07:24.480 and some of them could be, you know, three years old. Yeah, Unfortunately, 0:07:24.600 --> 0:07:28.640 most of them are billions of years old. If you 0:07:28.680 --> 0:07:30.280 were looking to feel young, that's not the way to 0:07:30.280 --> 0:07:32.440 do it. I'd like to focus on the young part 0:07:32.440 --> 0:07:36.720 of me, Daniel, I'm young inside. Yeah. And so in 0:07:36.760 --> 0:07:38.960 particle physics, the technical term we use is that some 0:07:39.040 --> 0:07:41.640 particles are stable. We think they just hang out forever, 0:07:41.680 --> 0:07:44.760 they don't do anything, and other particles are unstable because 0:07:44.800 --> 0:07:48.080 they decay into other particles. And so this is kind 0:07:48.080 --> 0:07:51.560 of an interesting word, decay and particle using them for particles, 0:07:52.000 --> 0:07:54.440 and so we were wondering, as usual, how many people 0:07:54.440 --> 0:07:57.960 out there associate the two works together and know about 0:07:58.000 --> 0:08:02.920 this process that all particles go through or don't go through. Yeah. 0:08:02.920 --> 0:08:05.320 So I walked around campus a UC Irvine and I 0:08:05.360 --> 0:08:09.280 asked people if they knew that heavier particles can decay 0:08:09.480 --> 0:08:12.679 into lighter particles and why it happens. So think about 0:08:12.680 --> 0:08:14.440 it for a second. How much do you know about 0:08:14.640 --> 0:08:17.240 particle decay? And what would you be able to answer 0:08:17.320 --> 0:08:20.720 if Daniel appros you on the street one day. Here's 0:08:20.720 --> 0:08:24.000 what people had to say. Do you know that particles decay? No? 0:08:24.120 --> 0:08:27.800 I didn't. Yes. Do you know why that happens? No? Yes? 0:08:28.080 --> 0:08:31.320 Do you know why that happens? I'm gonna say energy emissions? Yes? 0:08:31.480 --> 0:08:34.360 Do you know why that happens? A great active decay? 0:08:35.000 --> 0:08:37.400 You know what is it? I just know that if 0:08:37.440 --> 0:08:42.199 as too many neutrons and it's center, it's like unstable, 0:08:42.240 --> 0:08:47.160 so they can't I'll stay they shut off. No, I 0:08:47.200 --> 0:08:49.080 did not know that. I don't know because like there's 0:08:49.080 --> 0:08:51.920 some kind of potentials high for them. I'm actually not sure. 0:08:52.320 --> 0:08:55.480 Do you know why that happens? Uh? No, but I 0:08:55.520 --> 0:08:58.559 do know, like the half life of particles, and so 0:08:59.160 --> 0:09:02.480 all right, a couple of yes and no answers. None 0:09:02.480 --> 0:09:06.240 of the answers changed, none of the answers decayed. They're 0:09:06.280 --> 0:09:09.480 all stable in their ignorance of this question. You know, 0:09:09.600 --> 0:09:12.480 some people said yes, and are you saying they maybe 0:09:12.520 --> 0:09:14.560 they said yes, but they didn't really know. Some people 0:09:14.600 --> 0:09:16.960 said yes, they know that it does happen, but they 0:09:17.000 --> 0:09:19.760 weren't really clear on why. And when I pressed them, 0:09:19.840 --> 0:09:23.160 they just sort of described the process that happens, you know, 0:09:23.240 --> 0:09:26.000 like they have short lifetimes. That's like asking, you know, 0:09:26.240 --> 0:09:28.080 why does something I have a short lifetime? Because it 0:09:28.120 --> 0:09:30.679 has a short lifetime. There isn't really there wasn't really 0:09:30.760 --> 0:09:33.520 much understanding for why it happens, Like why can these 0:09:33.559 --> 0:09:36.520 heavy particles not just stick around forever? I see? Well, 0:09:36.559 --> 0:09:40.080 some people said radioactive decay, But that's that's a little 0:09:40.120 --> 0:09:43.199 bit different, right, that's when a whole atom sort of 0:09:43.240 --> 0:09:46.600 breaks down, not a particular particle. Yeah, it's a little 0:09:46.640 --> 0:09:48.800 bit different, but it's actually the same thing because what's 0:09:48.800 --> 0:09:52.839 going on inside radioactive decay is just a particle decay. 0:09:53.120 --> 0:09:55.400 It has an impact on the rest of the Atomate 0:09:55.520 --> 0:09:59.760 changes the automate changes a neutron into a proton and 0:10:00.000 --> 0:10:02.559 that changes what the atom is. But radioactive decay is 0:10:02.600 --> 0:10:05.280 actually just an example of one of the particles inside 0:10:05.320 --> 0:10:09.400 the atom decay. Oh wow, so it's like a Russian doll. Yeah, precisely. 0:10:09.480 --> 0:10:11.720 Well that's what reality is. It's like Russian dolls, right, 0:10:11.760 --> 0:10:14.640 you get these layers and layers of reality. Yeah, it 0:10:14.679 --> 0:10:18.240 all leads back to Russia. We were going to try 0:10:18.280 --> 0:10:21.160 to avoid politics on the show, but it's the new 0:10:21.480 --> 0:10:23.600 in the New decade. We're not doing politics, all right, 0:10:23.800 --> 0:10:25.880 So pretty good answers. And I have to admit I 0:10:25.920 --> 0:10:29.080 don't know why particle decay. I know that they decay, 0:10:29.200 --> 0:10:33.000 and they sometimes spontaneously trying to do other things, but 0:10:33.040 --> 0:10:35.559 I also don't know why some of them don't decay. 0:10:35.640 --> 0:10:38.760 That's kind of puzzling to me. So let's get into 0:10:38.800 --> 0:10:41.960 a Daniel. Well, let's maybe define for people first, what 0:10:42.200 --> 0:10:45.920 is particle decay. Yeah, decay is a funny word because 0:10:45.920 --> 0:10:48.720 it implies like you've died and your bits are sort 0:10:48.720 --> 0:10:52.240 of falling apart and blowing away in the winds really dramatically, right, 0:10:52.800 --> 0:10:55.439 But really, by decay, we just mean that a particle 0:10:55.480 --> 0:11:00.360 turns into other particles like it's it was kind of 0:11:00.360 --> 0:11:04.600 particle and then an instant later it's like it's broke apart. 0:11:04.800 --> 0:11:08.160 Did break apart or does it transform? Yeah, that's exactly it. 0:11:08.160 --> 0:11:11.480 It doesn't break apart. It transforms like when a higgs 0:11:11.480 --> 0:11:15.360 boson turns into a pair of bottom corks, which it 0:11:15.400 --> 0:11:18.120 likes to do. It's not like it was made out 0:11:18.120 --> 0:11:20.440 of a pair of bottom quarks and it broke up 0:11:20.480 --> 0:11:23.960 into those. This is not like you're taking a molecule 0:11:24.360 --> 0:11:26.760 of water and splitting it into the hydrogen and the 0:11:26.800 --> 0:11:29.959 oxygen that you can do. But when particles decay, they 0:11:30.040 --> 0:11:32.959 transform from one kind of matter to another. It's really 0:11:33.000 --> 0:11:36.040 it's alchemy. So the higgs boson was not made of 0:11:36.120 --> 0:11:40.000 bottom quarks. It transformed from higgs boson into a pair 0:11:40.000 --> 0:11:42.600 of bottom corks. It's kind of like when the Beatles 0:11:42.640 --> 0:11:50.080 broke up. It's not that they it's almost up. Good, 0:11:50.360 --> 0:11:55.040 I'm glad, I'm right, Okay. So it's not like a 0:11:55.320 --> 0:11:59.240 case like it breaks down, but it's more like, um, 0:11:59.280 --> 0:12:02.160 it just decide it to be something else totally. Yeah. 0:12:02.200 --> 0:12:03.839 And it's not like it's making a decision, right, It's 0:12:03.840 --> 0:12:06.360 like it's alive and his moods and it's like today 0:12:06.360 --> 0:12:08.000 I'm not feeling it. I just want to be be 0:12:08.120 --> 0:12:10.680 corks today. How do you know, Daniel, how do you 0:12:10.679 --> 0:12:14.360 know his bosons? I've interviewed them. They're not very insightful. 0:12:15.440 --> 0:12:17.360 You talk to them to find out that they don't talk. 0:12:17.760 --> 0:12:19.920 Is that what you're saying. I try to interview them. 0:12:19.960 --> 0:12:22.000 You know, their agent never calls me back, so you 0:12:22.040 --> 0:12:24.040 know they're super important or they have nothing to say. 0:12:25.400 --> 0:12:27.400 And we see the same process happened for lots of 0:12:27.480 --> 0:12:30.040 other particles and not to the Higgs boson. Right, Really, 0:12:30.080 --> 0:12:33.120 the neutron decays into a proton, and when it does so, 0:12:33.200 --> 0:12:36.839 it kicks out an electron and some neutrino um. The 0:12:36.880 --> 0:12:39.280 top cork decays into a W and a B corks. 0:12:39.360 --> 0:12:41.480 This kind of stuff happens all the time. Like, what 0:12:41.520 --> 0:12:43.640 do you mean It kicks out like it transformed into 0:12:43.720 --> 0:12:46.079 one thing and another thing, but one of the things 0:12:46.600 --> 0:12:50.079 flies away. Yeah, a particle can turns. We'll get into 0:12:50.120 --> 0:12:51.520 this a little bit later. There are a lot of 0:12:51.600 --> 0:12:53.440 rules for how particles decay, but one of the most 0:12:53.440 --> 0:12:56.080 important one is that a particle cannot decay into one 0:12:56.200 --> 0:12:59.720 other single particle. It can only decay into multiple particles. 0:13:00.200 --> 0:13:02.640 So when a neutron decase, It decays into a proton 0:13:02.960 --> 0:13:05.679 and an electron and an anti neutrino. And this is 0:13:05.720 --> 0:13:08.079 what we called beta decay. This is actually what happens 0:13:08.160 --> 0:13:11.880 inside the nucleus when an atom radioactively decays, is that 0:13:11.960 --> 0:13:14.240 one of the neutrons is turned into a proton. And 0:13:14.280 --> 0:13:17.920 this is all kind of that quantum mechanical magic. Don't 0:13:17.960 --> 0:13:24.360 say magic, not magic, quantum mechanical wizardry. Science. Man's you 0:13:24.480 --> 0:13:27.280 used to word alchemy? How is that any different? Alchemy 0:13:27.640 --> 0:13:30.880 is science. For a long time people thought it was nonsense, impossible, 0:13:31.200 --> 0:13:33.080 but then it turns out it's actually possible. We do 0:13:33.120 --> 0:13:35.880 it all the time, so it's been brought back into science. 0:13:36.280 --> 0:13:41.920 Well maybe he'll disabill happen for a wizardry. Okay, alright, alright, 0:13:41.960 --> 0:13:45.240 I'll compromise. We'll call it quantum witching about that in 0:13:45.360 --> 0:13:48.480 one way? Is that a compromise? I don't quite understand, 0:13:48.760 --> 0:13:52.080 But all right, it's quantum something. Yes, yeah, yeah, yeah, 0:13:52.080 --> 0:13:53.480 I guess what it's. What I mean is that it's 0:13:53.520 --> 0:13:56.440 not like things are like you said. They don't break 0:13:56.480 --> 0:13:59.040 apart into into the parts that they're made out of. 0:13:59.040 --> 0:14:02.720 They literally sort of like become a ball of for 0:14:02.880 --> 0:14:07.600 more deal energy, and then that energy transforms into other things. Yeah, precisely, 0:14:07.800 --> 0:14:11.360 you're converting one kind of matter into another kind of matter. 0:14:11.800 --> 0:14:14.120 And that seems really strange, right, like where did it go? 0:14:14.240 --> 0:14:17.000 But remember all of these things are particles, and particles 0:14:17.000 --> 0:14:20.640 are just excited states of the quantum fields. Space is 0:14:20.720 --> 0:14:23.720 filled with these fields, and sometimes they ripple, and those 0:14:23.800 --> 0:14:27.240 ripples are particles. So we're really talking about is moving 0:14:27.400 --> 0:14:30.280 energy from one quantum field, like the Higgs field, into 0:14:30.320 --> 0:14:33.360 another quantum field, like the field for bottom corks. It's 0:14:33.360 --> 0:14:37.640 like the excitation passes from one field to the other. Yeah, exactly, 0:14:38.000 --> 0:14:40.600 just like a wave can move from one kind of 0:14:40.600 --> 0:14:43.080 fluid into another kind of fluid. Or when you strum 0:14:43.120 --> 0:14:45.680 a guitar string, you're changing the shaking of the guitar 0:14:45.720 --> 0:14:49.920 string into the shaking of the air. Interesting, and so 0:14:49.960 --> 0:14:51.760 we go back to the Beatles because it's it is 0:14:51.760 --> 0:14:56.600 sort of like the loneliest guitar. All right, Yeah, go 0:14:56.720 --> 0:14:59.840 you win. You're right, it's just like the Beatles. But 0:15:00.000 --> 0:15:03.320 that's kind of what we call particle decay or particle death. 0:15:03.400 --> 0:15:05.040 I guess that. I mean, that's what we mean when 0:15:05.120 --> 0:15:08.720 when we asked the question why do some particles die 0:15:08.800 --> 0:15:12.720 because basically the elect the first particle that was there 0:15:12.720 --> 0:15:18.040 basically stops existing, stops existing, and something else exists. Yeah, 0:15:18.080 --> 0:15:20.120 and it's and it's bits are no longer there. We 0:15:20.160 --> 0:15:22.240 don't know if the Higgs boson is made of smaller 0:15:22.240 --> 0:15:24.040 bits right now we think of it. It's just fundamental. 0:15:24.480 --> 0:15:27.000 But whatever it is is no longer around. It's not 0:15:27.080 --> 0:15:31.040 just getting taken apart and rearranged like Jigsaw puscles into 0:15:31.080 --> 0:15:33.640 something else, like Lego pieces into something else. It's really 0:15:33.640 --> 0:15:36.880 getting transformed. And that's what we mean. You mean the 0:15:36.960 --> 0:15:41.080 Higgs is not made out of little Higgy's um. I 0:15:41.080 --> 0:15:43.000 think the Lego company has a copyrun on that name, 0:15:43.040 --> 0:15:44.720 so we should avoid using it, all right, So that 0:15:44.840 --> 0:15:47.480 and so it really dies, right, it's like it's no 0:15:47.600 --> 0:15:51.280 longer in the universe. Yeah, it's gone. And so we 0:15:51.320 --> 0:15:53.880 make particles like this in collisions all the time. We 0:15:53.920 --> 0:15:57.560 collide protons together, we make some heavy particle z W 0:15:57.800 --> 0:16:01.200 a top cork, Higgs boson, something else, and they live 0:16:01.280 --> 0:16:04.000 for like ten to the minus twenty three seconds before 0:16:04.040 --> 0:16:06.280 they turn into something else. And you know, that's what 0:16:06.360 --> 0:16:08.800 makes it so hard to study these particles that they're 0:16:08.800 --> 0:16:11.200 not around for very long, so it's hard to talk 0:16:11.200 --> 0:16:14.160 to them. Wow. Well, it seems like some particles are 0:16:14.280 --> 0:16:18.080 alive quote unquote for ten to the minus twenty three seconds, 0:16:18.080 --> 0:16:21.280 and some of them are live for seven bizillion years. 0:16:22.400 --> 0:16:24.560 It seems unfair, doesn't it. All right, so let's get 0:16:24.600 --> 0:16:28.360 into why that is and what causes a particle to 0:16:28.480 --> 0:16:31.360 decay or not. But first let's take a quick break, 0:16:44.280 --> 0:16:46.600 all right, Daniel, So why does it happen? Why the 0:16:46.680 --> 0:16:49.840 particles have to die? The key thing to understand is 0:16:49.880 --> 0:16:52.480 that there's a difference in the mass of these particles. 0:16:52.880 --> 0:16:56.520 So higher mass particles like the Higgs, like the top 0:16:56.760 --> 0:17:00.920 they decay into lower mass particles. And this makes simple 0:17:00.920 --> 0:17:03.520 sense because of conservation of energy. If you have a 0:17:03.600 --> 0:17:06.600 high mass particle just at rest all of its energies 0:17:06.600 --> 0:17:09.160 in its mass. If it turns into other particles, those 0:17:09.200 --> 0:17:12.360 particles have to have lower mass, otherwise you'd be violating 0:17:12.359 --> 0:17:15.640 conservation of energy. Oh, I see, And it's a it's 0:17:15.640 --> 0:17:19.840 a spontaneous event, right, Like nothing triggers it. It's not 0:17:19.880 --> 0:17:22.800 like it bumped into something and it broke up, or 0:17:23.119 --> 0:17:25.600 you shot you shot a particle at it and then 0:17:25.640 --> 0:17:27.760 that caused the transformation. It's like it was just sitting 0:17:27.800 --> 0:17:31.520 there and because it had too much, too much mass, 0:17:31.560 --> 0:17:35.160 it just suddenly breaks up. Yeah, it's spontaneous. It doesn't 0:17:35.200 --> 0:17:37.080 need to be triggered from anything from the outside. And 0:17:37.119 --> 0:17:39.600 it's also random. So if you have like a hundred 0:17:39.680 --> 0:17:42.920 Higgs bosons and you have them all in an array 0:17:42.960 --> 0:17:45.320 somewhere and you watch them, some of them would decay 0:17:45.400 --> 0:17:46.960 very quickly and some of them would live a little 0:17:46.960 --> 0:17:49.399 bit longer, and it's a distribution there. So we can 0:17:49.440 --> 0:17:52.639 predict the probability of the Higgs boson decaying after a 0:17:52.720 --> 0:17:55.320 certain time. You can't predict it for an individual one 0:17:55.400 --> 0:17:58.040 because it's quantum mechanical. But we know, like what the 0:17:58.440 --> 0:18:01.760 average lifespan is a Eiggs boson, where the average lifespan 0:18:01.880 --> 0:18:04.360 is of a top cork, and it's totally random, Like 0:18:04.440 --> 0:18:07.359 what what I guess? What triggers a death the death 0:18:07.400 --> 0:18:10.719 of a particle. That's the deepest question in quantum mechanics, right. 0:18:11.080 --> 0:18:14.800 We know that physics predicts the probability of things happening 0:18:14.800 --> 0:18:17.120 at various times, but we don't know how the universe 0:18:17.160 --> 0:18:19.600 makes a decision about what's going to happen when you 0:18:19.640 --> 0:18:22.760 know in which Shortinger's boxes the cat alive or dead. 0:18:22.960 --> 0:18:25.640 This is exactly that question, because the way the Shortinger's 0:18:25.680 --> 0:18:27.760 box works, if you have an atom inside the box 0:18:27.760 --> 0:18:30.199 that can decay or not decay, and it has a 0:18:30.240 --> 0:18:33.360 certain lifespan, and if it's already decayed, that's killed the cat. 0:18:33.400 --> 0:18:35.879 And if it hasn't decated, hasn't killed the cat. And 0:18:35.920 --> 0:18:38.600 what makes a decision for an individual box We don't know. 0:18:38.680 --> 0:18:43.680 The universe has some mysteriously not magical um which he 0:18:43.800 --> 0:18:49.119 dies somewhere that makes those decisions. I see, it's not magic, 0:18:49.160 --> 0:18:51.639 it's just mysterious. It is mysterious. Now. It's one of 0:18:51.720 --> 0:18:54.320 my deepest questions about the universe is how it picks 0:18:54.400 --> 0:18:58.480 random numbers. Where is the universe's random numbers generator? How's 0:18:58.560 --> 0:19:01.480 that work? Um and and way. That's a deep fascinating question. 0:19:01.680 --> 0:19:03.720 But the key thing to understand is that higher mass 0:19:03.760 --> 0:19:07.440 particles decay into lower mass particles. Right that that you're saying, 0:19:07.480 --> 0:19:11.080 that's like the Golden rule of particle decay. Yeah, there 0:19:11.160 --> 0:19:13.560 is actually something called the Golden rule, and it helps 0:19:13.560 --> 0:19:17.239 you sort of do that do onto other particles. As 0:19:17.320 --> 0:19:20.040 other particles we do onto you. Yeah, I don't know 0:19:20.119 --> 0:19:22.119 how particles behave and if they're nice to each other 0:19:22.200 --> 0:19:24.600 or not, but firm me. The golden rule helps you 0:19:24.680 --> 0:19:28.399 understand sort of why lower mass particles are more likely 0:19:28.440 --> 0:19:30.960 to exist in the universe than higher mass Like, why 0:19:31.040 --> 0:19:34.600 don't higher energy, lower mass particles turn into high mass 0:19:34.600 --> 0:19:36.560 particles all the time. Why does it mostly go the 0:19:36.560 --> 0:19:39.000 other way? Why do things sort of move down the 0:19:39.040 --> 0:19:41.840 mass ladder? Well, to to make something heavier rooting, you 0:19:41.880 --> 0:19:44.480 need to collide with something else and then from that 0:19:44.800 --> 0:19:47.639 you can like join together. Yeah, and that's exactly what 0:19:47.680 --> 0:19:50.160 we do in particle collisions. We make these heavy particles 0:19:50.240 --> 0:19:54.040 very briefly by smashing lower mass particles with a lot 0:19:54.040 --> 0:19:56.760 of energy together, So we have enough energy to create 0:19:56.800 --> 0:19:59.080 these high mass particles. But then you might wonder, like, 0:19:59.280 --> 0:20:01.640 why don't they just stick around? Why don't high mass 0:20:01.680 --> 0:20:06.040 particles just sit there being high mass particles forever? Right? 0:20:06.600 --> 0:20:08.919 And is that also a rule? I mean, so, the 0:20:08.920 --> 0:20:11.600 one rule is that you can only decay do things 0:20:11.680 --> 0:20:16.360 that are less massive than you, so kind of basically smaller, 0:20:16.560 --> 0:20:20.320 lighter things. That's one rule. The other rule seems to 0:20:20.359 --> 0:20:22.879 be that maybe the like the more mass you have, 0:20:23.200 --> 0:20:25.719 the more the quicker you are you're going to decay. 0:20:25.800 --> 0:20:28.919 Is there a correlation also in like if you have 0:20:29.000 --> 0:20:33.480 more mass, the less life you have. Yes, that's certainly true. 0:20:33.600 --> 0:20:36.199 The more mass you have, the more likely you are 0:20:36.280 --> 0:20:40.199 to decay quickly. Also, the more ways you have to decay, 0:20:40.280 --> 0:20:43.359 the more ways you're allowed to decay, the more rapidly 0:20:43.400 --> 0:20:44.880 you're going to decay. So if you have a really 0:20:44.880 --> 0:20:48.040 heavy particle but it can only decay via like the 0:20:48.119 --> 0:20:50.920 weak force, then it's gonna be around for longer because 0:20:50.920 --> 0:20:53.600 the weak force doesn't act for often. It's very weak. 0:20:54.119 --> 0:20:57.440 Where if you can decay via the strong force hydronically, 0:20:57.680 --> 0:20:59.960 then you can decay very very quickly because the strong 0:21:00.000 --> 0:21:03.119 force is very powerful. Oh so it's kind of like 0:21:03.600 --> 0:21:05.520 if it has a lot of options, then it's going 0:21:05.560 --> 0:21:08.080 to take one of those options sooner or later precisely. 0:21:08.240 --> 0:21:09.639 And the way I like to think about it is 0:21:09.680 --> 0:21:12.280 that these particles sort of like to relax. They start 0:21:12.280 --> 0:21:13.959 out in these very high mass states, and you think 0:21:13.960 --> 0:21:15.960 of it like having a lot of tension, and it 0:21:16.000 --> 0:21:18.320 wants to relax down to the lower mass the way 0:21:18.320 --> 0:21:20.719 it's sort of water likes to flow downhill, right, and 0:21:20.760 --> 0:21:23.679 everything in the universe likes to spread out and cool 0:21:23.760 --> 0:21:27.240 down and and sort of smooth out, and being in 0:21:27.359 --> 0:21:30.640 lower mass states is more smooth, has less energy sort 0:21:30.640 --> 0:21:33.359