WEBVTT - Who ordered the muon? 0:00:09.440 --> 0:00:11.400 Hey, Orne, Hey, do you have a lot of cousins 0:00:11.400 --> 0:00:14.200 in your family? Yeah, I've got a few. I have 0:00:14.400 --> 0:00:18.439 maybe over thirty six cousins, maybeing around the number. Wow, 0:00:18.480 --> 0:00:21.560 that's a big family. Well, would you be surprised to discover, 0:00:21.640 --> 0:00:24.599 sort of late in life, a brand new cousin you'd 0:00:24.760 --> 0:00:27.840 never even heard of before? That would be pretty amazing, 0:00:27.920 --> 0:00:30.840 kind of weird, I guess, but maybe yeah, I would 0:00:30.880 --> 0:00:33.160 be surprised, all right. And then what if that cousin 0:00:33.240 --> 0:00:36.199 turns out to be exactly like you, like, look like 0:00:36.240 --> 0:00:39.160 you in every single way. Okay, Yeah, that's that's getting 0:00:39.200 --> 0:00:41.760 kind of weird, all right. And then what if this 0:00:41.840 --> 0:00:46.000 cousin looks exactly like you? Accept there are two hundred 0:00:46.080 --> 0:01:07.399 times more massive Dan, Hi, I'm Poor. Hey, I'm a 0:01:07.480 --> 0:01:11.240 cartoonist and the creator of PhD comics. Hi I'm Daniel. 0:01:11.319 --> 0:01:14.279 I'm a particle physicist, and I do not have thirty 0:01:14.319 --> 0:01:18.200 six cousins. Welcome to our podcast, Daniel and Jorge Explore 0:01:18.240 --> 0:01:21.760 your Family Tree, in which we examine all the amazing 0:01:21.800 --> 0:01:25.280 and fascinating things about the universe, about the big things, 0:01:25.360 --> 0:01:28.080 the small things, and about how things are related to 0:01:28.120 --> 0:01:30.840 each other. Yeah. So, um no, that's not the name 0:01:30.840 --> 0:01:34.000 of our podcast. It's actually Daniel and Jorge explain the 0:01:34.080 --> 0:01:37.319 university production of My Heart Radio, in which we do 0:01:37.520 --> 0:01:40.319 examine crazy things about the universe and we try to 0:01:40.360 --> 0:01:42.480 make them relatable. We try to present them in a 0:01:42.480 --> 0:01:44.680 way that you can understand them, so they connect to 0:01:44.680 --> 0:01:46.840 topics that matter to you. Yeah, in a way, we 0:01:46.880 --> 0:01:49.800 do sort of explore the family tree of the universe. 0:01:49.880 --> 0:01:51.960 You know, how you came to be here, what what 0:01:52.160 --> 0:01:55.720 sort of pairings and fusions occurred for you to be 0:01:55.800 --> 0:01:59.840 here in this universe appreciating it and listening to funny podcasts. 0:02:00.160 --> 0:02:02.560 H I think one of the reasons people are interested 0:02:02.680 --> 0:02:05.560 in the origins of the universe and the creations of 0:02:05.560 --> 0:02:07.680 our cosmos is because they want to understand how we 0:02:07.720 --> 0:02:09.959 got here and what it means in the same way 0:02:10.000 --> 0:02:12.680 people explore their family tree. They want to know where 0:02:12.680 --> 0:02:15.560 did my family come from, what stories are in our past, 0:02:15.840 --> 0:02:19.040 what is my personal context? And also I think it's 0:02:19.040 --> 0:02:21.440 a useful way for us to sort of organize our thoughts. 0:02:21.480 --> 0:02:24.000 You know, when we think about the the universe in 0:02:24.080 --> 0:02:26.560 terms of particles, we sometimes think about how those particles 0:02:26.600 --> 0:02:30.519 are related to each other, Like, do particles have families. Yeah, 0:02:30.600 --> 0:02:33.679 and I think you know, every part of anyone's family 0:02:33.720 --> 0:02:36.880 tree or origin tree kind of tells you a little 0:02:36.919 --> 0:02:39.239 bit of the story of the of the whole thing, right, 0:02:39.280 --> 0:02:42.200 like how you came to be, how things work, and 0:02:42.280 --> 0:02:45.440 how things move about in life, and other ways your 0:02:45.480 --> 0:02:47.480 life could have gone. Like if you have a very 0:02:47.560 --> 0:02:50.560 successful cousin that's a gazillionaire, then you know, you wonder 0:02:51.240 --> 0:02:53.919 could I have made different choices and been a gazillionaire? 0:02:54.360 --> 0:02:57.359 Or if be people's paths in life diverge. Yeah, or 0:02:57.400 --> 0:02:59.919 if you are that busile in our cousin, then good 0:03:00.040 --> 0:03:03.679 for you. Please please contact us. We would love to 0:03:03.720 --> 0:03:06.280 take your donations. That's right. It would be awesome to 0:03:06.280 --> 0:03:10.040 have at least one gazillionaire listener. Who is our richest listener? 0:03:10.080 --> 0:03:12.640 That's a good question. Pod. You have to send us 0:03:12.639 --> 0:03:16.680 a check. Whoever sends it is the biggest check that 0:03:16.760 --> 0:03:21.120 doesn't bounce. When's this little plaque here that I am 0:03:21.160 --> 0:03:25.880 just now putting together. It's made of platinum? Right, Yeah, 0:03:25.880 --> 0:03:27.919 well it's going to be once we get those checks. Yes, 0:03:28.040 --> 0:03:31.360 you'll get a drawing of a plaque that's made of platinum. 0:03:31.400 --> 0:03:35.360 Oh my gosh. Even more valuable from a well known 0:03:35.400 --> 0:03:41.080 internet cartoonist exactly. But we do try to understand the 0:03:41.120 --> 0:03:43.680 world around us, and sometimes that means putting things in 0:03:43.800 --> 0:03:47.280 context and understanding what are the patterns, what are the 0:03:47.440 --> 0:03:50.720 structures there, and what clues do those patterns give us 0:03:50.720 --> 0:03:53.480 about that sort of fundamental nature of the universe. Yeah, 0:03:53.480 --> 0:03:55.440 so to be on the podcast, we'll be talking about 0:03:56.200 --> 0:03:58.840 a particle in nature that is maybe not the most 0:03:58.960 --> 0:04:03.680 famous one um and maybe not the most well known 0:04:03.720 --> 0:04:07.080 one or consequential in your existence, but which does I 0:04:07.120 --> 0:04:10.400 think tell you a little bit about and told humanity 0:04:10.440 --> 0:04:13.320 a little bit about how the universe works. Yeah, this 0:04:13.400 --> 0:04:16.520 is the non gazillionaire cousin. This is the cousin that 0:04:16.600 --> 0:04:19.599 ended up maybe sleeping under the overpast and wearing funny 0:04:19.640 --> 0:04:22.640 clothes to the family reunion. I feel bad for this particle. Now, 0:04:24.440 --> 0:04:27.160 this particle doesn't need your help. It's very massive. Yes, 0:04:27.200 --> 0:04:36.760 So in today's episode, we'll be talking about the muan electrons, mysterious, 0:04:36.839 --> 0:04:40.640 lesser known, much more massive cousin. And I'm biased, of 0:04:40.680 --> 0:04:43.159 course because I'm a particle physicist, but I think it's 0:04:43.200 --> 0:04:46.920 really fascinating to think about how we know each particle 0:04:47.080 --> 0:04:49.880 is there. We talk about the standard model of particle 0:04:49.880 --> 0:04:53.240 physics sometimes, but that's a theoretical construct. It's like our 0:04:53.640 --> 0:04:56.560 idea for how these particles might relate to each other. 0:04:56.600 --> 0:04:58.760 And that's fascinating. We'll dig into all that, but I 0:04:58.800 --> 0:05:02.240 think it's also really important. Remember each of these were discovered. 0:05:02.279 --> 0:05:05.760 There's a story behind each particle. Humanity didn't know it 0:05:05.839 --> 0:05:09.880 existed and then boom, some experiment revealed it. And on 0:05:09.920 --> 0:05:12.880 the podcast, we've talked about the first discovery of the particle, 0:05:12.920 --> 0:05:16.080 how the whole concept of a particle was created, the electron. 0:05:16.360 --> 0:05:18.200 Then we talked about how we know the photon is 0:05:18.240 --> 0:05:20.240 a thing, how we know it's really a particle, the 0:05:20.240 --> 0:05:22.479 photo electric effect, And so now we're gonna take the 0:05:22.520 --> 0:05:25.040 next step and talk about the discovery of the muan. Yeah, 0:05:25.120 --> 0:05:27.680 because you know, I think that every particle tells a story, 0:05:27.880 --> 0:05:31.200 you know, and also every story is made out of particle. 0:05:31.279 --> 0:05:33.960 So there's kind of this really weird, confusing loop there 0:05:34.520 --> 0:05:38.000 that honestly, Yeah, this is like the Superhero Origin story 0:05:38.279 --> 0:05:43.200 particle version. Yeah. So the muan is not a name 0:05:43.240 --> 0:05:46.560 that rolls off the tongue. Makes me think of maybe cows, 0:05:46.800 --> 0:05:54.280 mu muans, maybe uan Muan, Muan mu Off, muanmu Off. 0:05:54.560 --> 0:05:58.120 I was thinking sort about karate kid thing there, but 0:05:58.279 --> 0:06:01.120 it's back to the eighties reference. Yeah, back to the 0:06:01.120 --> 0:06:03.920 age differences. And it's it's funny actually because the name 0:06:04.040 --> 0:06:06.719 Uan is totally inappropriate. We'll dig into it later. But 0:06:07.040 --> 0:06:09.600 they named it before they discovered it because they thought 0:06:09.640 --> 0:06:12.120 it was going to be a different particle, and then 0:06:12.160 --> 0:06:15.040 they sort of changed the name later. Um, it's not 0:06:15.080 --> 0:06:18.360 a great history for naming particles. Boy, my favorite topic 0:06:18.600 --> 0:06:23.880 in science. Yeah, and so I was wondering, how much 0:06:23.920 --> 0:06:26.200 do people know about me once? Is it a famous 0:06:26.240 --> 0:06:29.240 particle or is it sort of the darker cousin of 0:06:29.279 --> 0:06:31.599 the electron that nobody really knows about, hasn't gotten the 0:06:31.640 --> 0:06:36.760 same Instagram attention the black Sheep, the gotee wearing particle 0:06:38.120 --> 0:06:40.719 of the family tree. Now you're setting enough to be 0:06:40.760 --> 0:06:42.599 like the grumpy particle. It's going to come in with 0:06:42.640 --> 0:06:45.520 some evil plan to finally get It's it's revenge, and 0:06:45.520 --> 0:06:47.640 it's you already made this particle, the homeless particle that 0:06:47.720 --> 0:06:51.359 lives under a bridge. So yeah, that was the sad 0:06:51.560 --> 0:06:54.840 particle that deserves our love and compassion, not the one 0:06:54.839 --> 0:06:58.479 that's been plotting its victorious return to the center of attention. Well, 0:06:58.520 --> 0:07:04.520 you never know what these particles, you know, physics, there's 0:07:04.560 --> 0:07:07.240 a lot of drama. But as usual, I walked around 0:07:07.279 --> 0:07:10.119 and I asked people if they knew what the muan 0:07:10.360 --> 0:07:12.280 was and how we knew it was a thing. Yeah, 0:07:12.280 --> 0:07:14.200 So before you listen to these answers, think about it 0:07:14.200 --> 0:07:16.280 for a second. If someone asked you what a mu 0:07:16.360 --> 0:07:18.160 on is, would you know what it is? Have you 0:07:18.200 --> 0:07:21.360 heard it before? Here's what people had to say. I'd 0:07:21.400 --> 0:07:23.440 say it's a unit of measure. It's like one of 0:07:23.440 --> 0:07:27.240 the fundamental elements or particle of what makes up everything. 0:07:27.800 --> 0:07:31.520 Mu one. I believe this to be the name of 0:07:31.560 --> 0:07:39.040 a sub atomic particle uh luans luans uh. I don't 0:07:39.040 --> 0:07:43.080 remember what classification they follow under as far as the 0:07:43.440 --> 0:07:50.040 naming conventions. Fundamental particle, some sort. It's real small subotomic particles. 0:07:51.240 --> 0:07:53.000 I kind of represented what it does. How do we 0:07:53.040 --> 0:07:58.800 know nuance exist um particle starts. So what's your opinion 0:07:58.840 --> 0:08:01.440 of these answers today? Good? It sounds like most people 0:08:01.480 --> 0:08:04.560 have heard of it or I heard of the word before. 0:08:05.360 --> 0:08:07.640 You know, very only a few people said never heard 0:08:07.640 --> 0:08:11.120 of it or think it was a unit of measure, 0:08:11.360 --> 0:08:13.280 like a you know how much water? Would you like, 0:08:13.320 --> 0:08:16.360 I'll have seven muans of water. I wonder that if 0:08:16.360 --> 0:08:19.080 you pronounced it correctly, maybe they knew about it, but 0:08:19.200 --> 0:08:22.920 just under a different pronunciation. Do you think I'm mispronouncing 0:08:22.960 --> 0:08:24.920 the name of mu. I don't know. I mean, what's 0:08:24.920 --> 0:08:30.400 the correct way? Is it muan or muan? Like you're 0:08:30.400 --> 0:08:33.000 making it sound like a Disney movie, like, oh, my 0:08:33.080 --> 0:08:40.520 favorite Disney princess is mulan. My favorite Disney princess muan muan. Oh. 0:08:40.559 --> 0:08:43.240 That is a great way, though, to get more attention 0:08:43.280 --> 0:08:45.480 for particles in the mainstream. We should get Disney to 0:08:45.600 --> 0:08:49.920 name the next Disney Princess after a particle. Why not that? 0:08:50.080 --> 0:08:52.160 Why it could be the next Pixure movie. What it's like? 0:08:52.240 --> 0:08:56.040 What's the emotional roller coaster right of being a fundamental 0:08:56.160 --> 0:08:59.160 particle of nature? Yeah? So much to explore there, and 0:08:59.240 --> 0:09:01.560 I expect that will be getting checks from Pixar when 0:09:01.600 --> 0:09:03.680 they make a billion dollar movie out of it. But 0:09:04.000 --> 0:09:05.840 I was impressed with these answers, though, I want to 0:09:05.840 --> 0:09:09.480 pick a bone about one thing. People say, yes, it's 0:09:09.480 --> 0:09:13.000 a fundamental particle, totally cool. People also say it's a 0:09:13.040 --> 0:09:15.960 sub atomic particle or it's one of the fundamental particles 0:09:16.000 --> 0:09:19.600 that make up everything. And that's really a key idea 0:09:19.679 --> 0:09:22.199 that I think people have not understood about muans, that 0:09:22.240 --> 0:09:25.119 you can be a tiny particle and not be sub atomic, 0:09:25.240 --> 0:09:28.240 not be part of the atom. Oh, I see, subotomic 0:09:28.280 --> 0:09:31.800 doesn't just mean it's smaller than atom. You're saying that, 0:09:32.440 --> 0:09:36.120 it means that you're part of the atom. Remember, fundamental 0:09:36.160 --> 0:09:40.000 particles have no size, their dots, they're zero volumes, so 0:09:40.160 --> 0:09:43.200 they're all smaller than the atom. In that sense of 0:09:43.240 --> 0:09:46.520 being fundamental guarantees you'd be smaller than the atom. I 0:09:46.559 --> 0:09:48.679 think to me, sub atomic means it's part of the atom, 0:09:48.720 --> 0:09:50.800 like you break it up and you find it inside 0:09:50.840 --> 0:09:53.920 the atom. Okay, so we'll get into that, but let's 0:09:53.920 --> 0:09:55.880 bring it down for people. For us, what is a 0:09:56.000 --> 0:09:59.880 muan and why does it sound like an electron? You 0:10:00.120 --> 0:10:02.679 it ends with O N, but maybe, but it's not 0:10:02.720 --> 0:10:06.000 the electron. Yeah, but it really is related to the electron. 0:10:06.000 --> 0:10:08.880 It's sort of like the electrons cousin. And by that 0:10:08.960 --> 0:10:11.959 I mean that it's identical to the electron in so 0:10:11.960 --> 0:10:15.560 many ways. It has the same electric charge, it has 0:10:15.640 --> 0:10:19.360 the same interactions with matter like it interacts via the 0:10:19.400 --> 0:10:23.000 weak force and via the electromagnetic force, but it doesn't 0:10:23.080 --> 0:10:26.880 feel the strong force, just like the electron. It has 0:10:26.880 --> 0:10:30.080 a neutrino, just like the electron has its neutrino. So 0:10:30.120 --> 0:10:32.960 in so many ways, it's exactly the same as the electron. 0:10:33.000 --> 0:10:34.760 Sound like when you discover a new particle and it's 0:10:34.800 --> 0:10:37.440 totally different, like a cork or a gluon, it's just 0:10:37.880 --> 0:10:40.960 completely different from the electron. This one is very very 0:10:40.960 --> 0:10:43.839 similar to the electron. It's like weirdly similar, but then 0:10:43.880 --> 0:10:51.160 with one important difference. Okay, so it's a particles. It's 0:10:51.200 --> 0:10:54.360 not a cow, it's not a Disney princess. So it's 0:10:54.360 --> 0:10:56.839 a particle, meaning like it's a it's one of these 0:10:56.840 --> 0:10:59.200 things that you see nature in the universe, like things 0:10:59.240 --> 0:11:02.720 that pop up and you can touch them and and 0:11:02.960 --> 0:11:05.640 there it's a thing. Yes, muans are a thing. There 0:11:05.640 --> 0:11:08.840 are a little thing. There are particles, and there are 0:11:08.960 --> 0:11:11.640 little dots of matter. They have mass and they have 0:11:11.840 --> 0:11:14.880 charge and they interact. Okay, so it's it's a particle 0:11:15.040 --> 0:11:17.600 like the electron. But you're saying and you say it's 0:11:17.600 --> 0:11:20.160 a cousin of the electron, not that they share like 0:11:21.160 --> 0:11:23.240 not that their parents were siblings, but just like in 0:11:23.280 --> 0:11:27.400 the sense that it's very similar to the electron. Yeah, 0:11:27.520 --> 0:11:30.640 when we organize our knowledge, we look for patterns. We 0:11:30.640 --> 0:11:33.040 look for similarities. Right like when we were a hundred 0:11:33.120 --> 0:11:35.160 years ago, when the state of knowledge about the universe 0:11:35.240 --> 0:11:37.360 was the periodic table. We didn't just have like a 0:11:37.400 --> 0:11:39.880 pile of different elements and say here's an element. There's 0:11:39.880 --> 0:11:42.320 an element. We said, oh, look, this one is similar 0:11:42.360 --> 0:11:44.959 to that one. They're both really active, or these are 0:11:45.200 --> 0:11:47.880 really similar because they're both really inactive, or this one 0:11:47.920 --> 0:11:50.400 weighs a tiny bit more than that one. We notice patterns. 0:11:50.400 --> 0:11:53.000 We put those patterns together in the same way we're 0:11:53.040 --> 0:11:56.480 looking for patterns in the fundamental particles. So we try 0:11:56.520 --> 0:11:58.520 to figure out which ones are related to each other. 0:11:58.920 --> 0:12:01.440 And we have only a few handles on each particle. 0:12:01.520 --> 0:12:03.160 Is only like a few things we can know about 0:12:03.200 --> 0:12:06.240 a particle, right, And so is this a particle that 0:12:06.280 --> 0:12:08.520 we can see in our everyday lives, like is it 0:12:08.640 --> 0:12:14.120 floating around? Does it move around wires and electricity like 0:12:14.559 --> 0:12:18.080 the electron, or is this kind of a weird one 0:12:18.120 --> 0:12:20.640 of those weird particles And you know you don't ever 0:12:20.960 --> 0:12:23.720 actually see Yeah, you don't see the muan because it 0:12:23.760 --> 0:12:26.679 doesn't last for very long. It lives for two point 0:12:26.720 --> 0:12:29.760 two microseconds and then it turns into an electron and 0:12:29.800 --> 0:12:33.360 some neutrinos. But they are actually everywhere. There's ten thousand 0:12:33.480 --> 0:12:36.840 muons going through a square meter of Earth every minute, 0:12:37.080 --> 0:12:39.560 so there's a lots of muans everywhere, but you just 0:12:39.600 --> 0:12:42.040 can't really see them very easily because they don't last 0:12:42.160 --> 0:12:43.760 very long. Wait, what I mean? How can they be 0:12:43.840 --> 0:12:47.840 everywhere but also only last two point to microseconds? Does 0:12:47.880 --> 0:12:51.640 that mean that they're they're constantly coming into existence, lasting 0:12:51.640 --> 0:12:55.560 for two point two microseconds and then disappearing and breaking up, 0:12:55.679 --> 0:12:58.080 or what does that mean? How can they be all 0:12:58.120 --> 0:13:00.800 around is but also evaporating at the same time. Well, 0:13:00.800 --> 0:13:02.559 there's two things going on there. One is your right, 0:13:02.640 --> 0:13:06.120 they're being created um when particles hit the atmosphere. So 0:13:06.120 --> 0:13:08.840 protons hit the atmosphere and they create a shower of particles, 0:13:08.840 --> 0:13:11.719 some which include muans, and those muans fly along a 0:13:11.760 --> 0:13:13.840 little bit, but they don't last very long, just two 0:13:13.840 --> 0:13:17.000 point two microseconds, and then they turn into electrons. But 0:13:17.840 --> 0:13:20.800 they last for two point two microseconds according to their 0:13:20.840 --> 0:13:25.240 clocks because they move really fast. There's a relativistic time dilation. 0:13:25.559 --> 0:13:28.439 So the according to us that two point two microseconds 0:13:28.480 --> 0:13:31.880 takes longer to click, and so for us it can 0:13:31.920 --> 0:13:35.680 take like seconds or minutes from muans to decay. But 0:13:35.880 --> 0:13:39.120 for them, if you're sitting on top of the muan, 0:13:40.440 --> 0:13:42.240 it would only last You would only be alive for 0:13:42.320 --> 0:13:44.920 two point two microseconds. Yeah, that's the half life of 0:13:44.920 --> 0:13:47.000 a muan. So muon is not stable. It's not like 0:13:47.000 --> 0:13:49.040 an electron you can just sit there for eons and 0:13:49.080 --> 0:13:52.080 eons and just be itself. A muon is a heavy particle, 0:13:52.080 --> 0:13:55.040 and heavy particles like to decay into lighter particles. In 0:13:55.080 --> 0:13:58.160 this case, the muon turns into an electron very quickly 0:13:58.160 --> 0:14:00.320 according to its clock. Oh, I see the ones that 0:14:00.400 --> 0:14:03.360 we see. The ones coming from the atmosphere are moving fast, 0:14:03.400 --> 0:14:05.920 so they last longer. But if I just created a 0:14:06.000 --> 0:14:07.640 mew on here in front of me, it would last 0:14:07.679 --> 0:14:09.880 only for two point two micro seconds, and it's not 0:14:09.920 --> 0:14:12.800 going anywhere. If you could bake muans in your oven 0:14:13.000 --> 0:14:14.439 and you take them out of the oven two point 0:14:14.480 --> 0:14:17.120 two microseconds later, boom, they turn into a electro. Yeah, 0:14:17.120 --> 0:14:20.120 you gotta eat them up real quick. Exactly. They're like 0:14:20.200 --> 0:14:22.840 making fortune cookies or toss them really fast, have him 0:14:22.880 --> 0:14:25.000 pop out of the toaster really fast, in which case 0:14:25.040 --> 0:14:29.040 they would last longer technically, right, that's true. Yeah, exactly. 0:14:29.160 --> 0:14:31.760 Somebody could shoot muans into your mouth and it would 0:14:31.800 --> 0:14:33.880 last long enough to get there. I wouldn't recommend that. 0:14:33.640 --> 0:14:36.560 That's that's not a suggestion for something somebody should do. 0:14:36.800 --> 0:14:38.680 And actually, two point two microseconds it is kind of 0:14:38.720 --> 0:14:41.960 a long time for a particle that's this massive to last. 0:14:42.880 --> 0:14:44.760 And so what does it mean that it disappears or 0:14:44.760 --> 0:14:47.000 breaks up like it? It's just unstable like it, just 0:14:48.920 --> 0:14:51.080 it's made out of other things and it breaks up 0:14:51.400 --> 0:14:54.720 or literally just kind of evaporates into energy and that 0:14:54.840 --> 0:14:57.640 energy turns into something else. Yeah, that's a great question. 0:14:57.760 --> 0:15:00.160 These are fundamental particles, so they're not made up of 0:15:00.200 --> 0:15:03.440 anything else. As far as we know. The muon turns 0:15:03.480 --> 0:15:05.880 into the electron. It's not like it has an electron 0:15:05.920 --> 0:15:08.560 inside of it, and it breaks up into an electron 0:15:08.600 --> 0:15:11.880 and other stuff it converts. It goes from a muan, 0:15:12.280 --> 0:15:15.160 it turns via the weak force into a W particle 0:15:15.480 --> 0:15:18.520 and a neutrino, and then the W particle turns into 0:15:18.520 --> 0:15:22.480 an electron and another neutrino. So the muon turns into 0:15:22.560 --> 0:15:26.040 an electron and two different neutrinos, but it didn't have 0:15:26.080 --> 0:15:29.080 those bits inside of it. Remember, particle physics is like alchemy. 0:15:29.080 --> 0:15:31.800 We can convert one kind of matter into another kind 0:15:31.800 --> 0:15:35.720 of matter. Okay, so it's um. It doesn't break apart, 0:15:35.960 --> 0:15:39.640 it's just somehow. It's it's very existence. The universe sort 0:15:39.640 --> 0:15:43.120 of doesn't like it. Like it. It can just seesis 0:15:43.160 --> 0:15:47.000 to exist and in favor of other things existing instead 0:15:47.040 --> 0:15:49.280 of it. Yeah, and this is true for every particle 0:15:49.600 --> 0:15:53.200 that is pretty massive. The universe doesn't like massive particles. 0:15:53.240 --> 0:15:55.400 It's like putting a particle on the top of a hill. 0:15:55.440 --> 0:15:58.240 Eventually it's going to roll down. And so the muon 0:15:58.400 --> 0:16:00.240 is like the at the top of the on. The 0:16:00.240 --> 0:16:02.520 electron is rolling down to the bottom of the hill. 0:16:02.520 --> 0:16:05.000 Eventually the muon is going to turn into the electron. 0:16:05.640 --> 0:16:08.480 And every particle in nature that that can do this 0:16:08.520 --> 0:16:10.520 does this. The only reason the electron doesn't is that 0:16:10.520 --> 0:16:14.040 there's no lighter particle for it to turn into. Oh, 0:16:14.560 --> 0:16:18.720 and that's why we are able to exist, because the 0:16:18.800 --> 0:16:23.560 universe does seem to like electrons and quarks which make 0:16:23.800 --> 0:16:26.040 us up. And so that's why we were stable. But 0:16:26.080 --> 0:16:27.800 if we were made out of me as, we would 0:16:27.920 --> 0:16:30.880 disappear pretty quickly. Yes, exactly. We are made up of 0:16:30.920 --> 0:16:33.560 the lightest particles out there, up corks and down corks. 0:16:33.560 --> 0:16:36.680 Of the lightest corks. Electrons are the lightest version of 0:16:36.680 --> 0:16:39.240 that kind of particle called a lepton. So the matter 0:16:39.280 --> 0:16:41.360 that makes us up that's stable is made out of 0:16:41.400 --> 0:16:44.120 stuff that can't turn into lighter stuff because there is 0:16:44.160 --> 0:16:47.280 no lighter stuff for it to turn into. Right, Yeah, 0:16:47.600 --> 0:16:49.640 there's nothing for it to turn into, so we we 0:16:50.000 --> 0:16:52.960 stay where we are. But the muon is heavy and 0:16:53.080 --> 0:16:55.760 could turn into something else. So it does precisely. And 0:16:55.800 --> 0:16:57.760 for those of you wondering, like, well, what about a photon? 0:16:57.800 --> 0:17:00.240 Why can't an electron turn into a photon? Of photon 0:17:00.360 --> 0:17:03.040 is mass lists Remember that there are rules about how 0:17:03.080 --> 0:17:05.760 these things happen, and one of those rules is conservation 0:17:05.800 --> 0:17:09.280 of electric charge. An electron has a minus one charge, 0:17:09.320 --> 0:17:11.800 so it can't turn into a photon which has zero charge, 0:17:11.920 --> 0:17:14.560 because you have to somehow disappear that charge. The only 0:17:14.600 --> 0:17:16.879 way for that to happen is for an electron to 0:17:17.000 --> 0:17:19.800 hit a plus one positron, and then they can turn 0:17:19.800 --> 0:17:22.119 into a photon together, but for a particle to just 0:17:22.240 --> 0:17:26.000 spontaneously decay, it has to convert to another particle that 0:17:26.080 --> 0:17:29.520 has all the same sort of quantum mechanical numbers. Okay, 0:17:29.520 --> 0:17:34.160 so the muon is the electrons massive cousin or massive 0:17:34.320 --> 0:17:37.600 sort of like alternate universe version of the electron. Right, Yeah, 0:17:37.600 --> 0:17:40.400 it's two hundred times the mass of the electron. It's 0:17:40.520 --> 0:17:43.840 really really massive. That's a lot. It's like crunched into 0:17:43.880 --> 0:17:46.240 the same meat. Yes, exactly. It's like if you met 0:17:46.520 --> 0:17:48.679 another version of you, but you weren't bigger, you were 0:17:48.840 --> 0:17:51.960 denser or something. You're two hundred times as much mass, 0:17:52.040 --> 0:17:56.199 but still fundamental. And it doesn't hang around existence very long, 0:17:56.240 --> 0:17:59.560 and it usually breaks up into or not breaks up 0:17:59.680 --> 0:18:03.480 into runs into lighter particles, so we don't really seed 0:18:03.520 --> 0:18:05.920 around that much. But still it's sort of an important 0:18:05.960 --> 0:18:08.840 part of the universe, and it seems that it's important 0:18:08.840 --> 0:18:10.760 part of the universe and also tells us a lot 0:18:10.800 --> 0:18:14.240 about the mysteries of how everything is put together. Yeah, 0:18:14.280 --> 0:18:17.320 and it actually lasts a long time for a heavy particle. 0:18:17.600 --> 0:18:20.160 Other particles that are heavy, like the Higgs boson, they 0:18:20.200 --> 0:18:23.399 decay much more quickly. They decayed in like ten to 0:18:23.440 --> 0:18:27.520 the minus twenty seconds, whereas this one decays very slowly, 0:18:27.520 --> 0:18:30.320 it's just two point two microseconds. And the reason is 0:18:30.359 --> 0:18:32.720 that it decays via the weak force, which is very weak. 0:18:33.080 --> 0:18:35.199 To the weaker the force, the longer takes for that 0:18:35.240 --> 0:18:37.720 decay to happen. M hmm. All right, let's get into 0:18:37.760 --> 0:18:39.480 that a little bit more, and also how it was 0:18:39.560 --> 0:18:43.520 discovered and why it is such an important particle. But 0:18:43.600 --> 0:18:58.280 first let's take a quick break. All right, So the 0:18:58.359 --> 0:19:01.000 meuan decays by the weak force. What does that mean? 0:19:01.080 --> 0:19:04.919 How can something decay via a force like the force 0:19:05.000 --> 0:19:07.359 makes a decay? Yeah, the fource sort of provides the 0:19:07.400 --> 0:19:10.080 avenue for the decay to happen. Like, how does a 0:19:10.160 --> 0:19:12.600 muon turn into an electron just just roll down a 0:19:12.680 --> 0:19:15.200 hill and say, hey, now I'm an electron. It has 0:19:15.240 --> 0:19:17.840 to has to be an interaction there. And so what 0:19:17.920 --> 0:19:21.320 happens is the muon turns into a W particle and 0:19:21.400 --> 0:19:24.280 a neutrino. And the W particle, remember, is the particle 0:19:24.440 --> 0:19:27.000 of the weak force. It's like the weak force version 0:19:27.200 --> 0:19:29.520 of the photon. And so that's what we mean when 0:19:29.560 --> 0:19:32.200 we say uses the weak force to decay. It doesn't 0:19:32.240 --> 0:19:35.600 just spontaneously happen. Something has to sort of carry that information, 0:19:35.680 --> 0:19:38.000 so it has to make it happen. It's like a reaction, 0:19:38.440 --> 0:19:41.000 and that reaction always includes one of the forces, and 0:19:41.000 --> 0:19:43.399 in this case it uses the weak force, right, and 0:19:43.440 --> 0:19:46.200 that weak force came out of just its own energy. 0:19:46.359 --> 0:19:48.320 It uses the mass. Right. The muon is a huge 0:19:48.359 --> 0:19:50.720 amount of energy in it because it has so much mass, 0:19:50.800 --> 0:19:53.080 and that mass is turned into the energy of the 0:19:53.119 --> 0:19:56.320 electron and the neutrinos that come out of it. So yeah, 0:19:56.320 --> 0:19:59.159 the weak force turns the mass of the muan into 0:19:59.520 --> 0:20:02.160 very small masses of these other particles and gives them 0:20:02.160 --> 0:20:04.240 a lot of energy, right, and it ends up as 0:20:04.280 --> 0:20:08.520 an electron and to neutrinos precisely. All right, Well, to 0:20:08.600 --> 0:20:10.919 tell us Daniel, how was it discovered and why is 0:20:10.920 --> 0:20:13.600 this an important particle? Well, it was discovered initially in 0:20:13.880 --> 0:20:17.439 cosmic rays. Um. People saw these particles just sort of 0:20:17.480 --> 0:20:20.359 shooting from the sky and they didn't understand what was 0:20:20.400 --> 0:20:22.639 making them, and they thought, oh, well, you know, we 0:20:22.720 --> 0:20:25.520 found a few particles, so these are probably electrons. This 0:20:25.600 --> 0:20:27.880 is you know, in the early nineteen hundreds, we didn't 0:20:27.880 --> 0:20:31.200 have a really deep understanding of how particles work. We 0:20:31.240 --> 0:20:34.960 didn't have a good bench of particles, and so people thought, 0:20:34.960 --> 0:20:37.200 you know, everything they saw they thought in terms of 0:20:37.200 --> 0:20:38.680 the particles at the time. So you have to sort 0:20:38.720 --> 0:20:41.239 of wind your mind back to what we knew at 0:20:41.240 --> 0:20:44.240 the time. Back then, we knew about protons, we knew 0:20:44.240 --> 0:20:47.240 about neutrons, we knew about electrons, and so people saw 0:20:47.280 --> 0:20:49.720 these particles shooting from the sky. They didn't know what 0:20:49.800 --> 0:20:52.320 made them, but what they saw was that they penetrated 0:20:52.400 --> 0:20:56.359 really far into matter, much more than electrons could. We 0:20:56.640 --> 0:20:59.439 saw the actual nuance and not the not what it 0:20:59.480 --> 0:21:03.200 looks like after it decays or turns into something else. 0:21:03.359 --> 0:21:06.240 Like we actually you can actually see and feel the muants. 0:21:06.440 --> 0:21:08.399 You can't really feel them, but you can make particle 0:21:08.440 --> 0:21:10.840 detectors that can detect them. You can actually do this 0:21:10.880 --> 0:21:13.800 in your garage using something called the cloud chamber. They 0:21:13.800 --> 0:21:16.200 were able to see them using detectors that they put together. 0:21:16.200 --> 0:21:18.919 And these detectors were like a cubic piece of film, 0:21:19.160 --> 0:21:21.920