WEBVTT - Can we see inside things using muons? 0:00:08.560 --> 0:00:12.320 Hey, Daniel, is particle physics actually useful for anything? 0:00:12.520 --> 0:00:15.480 I mean it's good for like understanding the universe for sure. 0:00:15.680 --> 0:00:18.040 Yeah, But what can I use particles for? Can I 0:00:18.160 --> 0:00:23.200 use a charm quark charm my way into a better life? 0:00:23.960 --> 0:00:26.760 I think you're plenty charming already without any charm quarks. 0:00:27.240 --> 0:00:29.680 But we might be able to, like use muons to 0:00:29.720 --> 0:00:30.760 help us get to the moon. 0:00:31.400 --> 0:00:34.320 What just because they start with an M, because there 0:00:34.320 --> 0:00:36.640 are one letter off from moon and muon? 0:00:37.080 --> 0:00:38.560 I'm just reaching here. Man. 0:00:41.240 --> 0:00:42.960 Do you use a muans to feed cows? 0:00:43.000 --> 0:00:43.199 You know? 0:00:43.920 --> 0:00:45.080 Or grow more corn? 0:00:46.440 --> 0:00:46.599 More? 0:00:46.720 --> 0:00:50.000 Meuse less corn? I mean, nothing is certain in science, 0:00:50.080 --> 0:00:51.400 but that's probably a no. 0:00:51.760 --> 0:00:56.680 Why not? Don't cows eat muans? Don't they eat muuons? 0:00:56.760 --> 0:01:00.920 I think muons actually cause cows to mutate and make 0:01:01.000 --> 0:01:01.920 new kinds of cows. 0:01:03.760 --> 0:01:07.039 Oh well, maybe we'll get a taste of cout of it, 0:01:07.200 --> 0:01:08.800 In which case particles would be useful. 0:01:09.280 --> 0:01:11.279 Better steaks through physics, that's. 0:01:11.200 --> 0:01:29.080 Right, better particle burgers. Hi am jorg Im, cartoonist and 0:01:29.080 --> 0:01:31.240 the author of Oliver's Great Big Universe. 0:01:31.480 --> 0:01:31.640 Hi. 0:01:31.800 --> 0:01:34.800 I'm Daniel. I'm a particle physicist and a professor at 0:01:34.920 --> 0:01:39.199 UC Irvine, and I like believing that physics raises the steaks. 0:01:39.480 --> 0:01:43.200 The steaks like the cow steaks. Yeah, we've got to 0:01:43.280 --> 0:01:46.600 raise some steaks or the burgers maybe. 0:01:46.760 --> 0:01:49.640 I mean you're always talking about setting the steaks and stories. 0:01:49.320 --> 0:01:53.880 Right, Yeah, that's always important, but usually makes the emotional steaks, 0:01:53.960 --> 0:01:56.040 not the raw or well done kind. 0:01:58.360 --> 0:02:00.000 Well, I like to get my stakes at the restaurant 0:02:00.080 --> 0:02:00.960 called mcguffins. 0:02:01.000 --> 0:02:05.160 So do you like them rare or well done? 0:02:05.240 --> 0:02:07.720 I rarely eat steaks. Actually, it's the truth. 0:02:08.400 --> 0:02:12.080 He eats steaks rarely or rarely eat steaks. 0:02:12.440 --> 0:02:14.280 Yeah, I almost never eat steaks. My son is a 0:02:14.280 --> 0:02:17.400 big fan of protein, but he prefers chicken and turkey. 0:02:17.600 --> 0:02:18.600 He's the poultry man. 0:02:18.960 --> 0:02:21.119 Oh I see, he likes it lean. 0:02:22.240 --> 0:02:23.399 He likes it with wings. 0:02:23.800 --> 0:02:28.520 Nice's nice to stay lean and flighty as well. But anyways, 0:02:28.520 --> 0:02:31.120 welcome to our podcast Daniel and Jorge Explain the Universe, 0:02:31.120 --> 0:02:33.160 a production of our Heart Radio in. 0:02:33.080 --> 0:02:34.959 Which we help your brain to take flight and trim 0:02:35.040 --> 0:02:38.120 all the fat from your understanding of the universe. We 0:02:38.160 --> 0:02:41.040 think it's possible to zoom out there with our minds 0:02:41.120 --> 0:02:44.359 and understand everything that happens in the universe from the 0:02:44.400 --> 0:02:47.840 tiniest little particles to the biggest, most massive black holes, 0:02:48.000 --> 0:02:49.800 and our goal is to break it all down and 0:02:49.880 --> 0:02:50.880 explain it to you. 0:02:51.080 --> 0:02:53.160 That's right. We try to prevent your brain from having 0:02:53.240 --> 0:02:56.360 a cow thinking about the amazing and vast universe we 0:02:56.400 --> 0:02:59.480 live in, with all the complete physics and mechanics that 0:02:59.520 --> 0:03:02.080 are happening. We try to boil it all down to 0:03:02.160 --> 0:03:05.640 make it digestible and lean. We trim all the fat 0:03:05.760 --> 0:03:09.919 out of science communication while trying to keep it still 0:03:10.080 --> 0:03:13.560 plenty juice. And it's all one hundred percent organic, right, 0:03:14.919 --> 0:03:16.799 These no chemicals in this podcast. 0:03:18.360 --> 0:03:20.160 I mean, I guess everything's a chemical. 0:03:20.400 --> 0:03:24.120 So yeah, I mean I did use growth horribones to 0:03:25.480 --> 0:03:28.320 inflate my intelligence a little bit. 0:03:28.360 --> 0:03:30.760 But one of the reasons we're talking about such practical 0:03:30.800 --> 0:03:33.959 matters is because one of the criticisms of particle physics 0:03:34.080 --> 0:03:36.480 is that it can be kind of abstract, Like, are 0:03:36.520 --> 0:03:39.440 the questions of particle physics really useful to you on 0:03:39.480 --> 0:03:42.520 an everyday basis or is it more of a philosophical 0:03:42.560 --> 0:03:45.400 search for understanding of the nature of the universe. 0:03:45.840 --> 0:03:47.680 Yeah, you got to kind of wonder what is smashing 0:03:47.720 --> 0:03:50.520 all those particles together, spending billions of dollars. What it 0:03:50.560 --> 0:03:53.400 is that all useful for? How is that helping humanity 0:03:53.920 --> 0:03:56.920 move forward and maybe eat better as well? 0:03:56.960 --> 0:03:59.520 And of course there are lots of indirect benefits, just 0:03:59.640 --> 0:04:01.960 understan in the nature of the universe is its own 0:04:02.040 --> 0:04:05.360 prize and is priceless. But every dollar we invest in 0:04:05.440 --> 0:04:08.320 basic research comes back to us in terms of technological 0:04:08.360 --> 0:04:13.280 advancements and economic output and education and employment. So it's 0:04:13.400 --> 0:04:16.040 definitely a worthy way to spend money, I say, with 0:04:16.120 --> 0:04:18.400 absolutely no conflict of interest whatsoever. 0:04:19.240 --> 0:04:22.560 I was gonna say it definitely means employment for certain 0:04:22.600 --> 0:04:24.800 people like physicists. 0:04:24.800 --> 0:04:28.159 Perhaps it certainly does, but it benefits everybody because investment 0:04:28.200 --> 0:04:31.840 in basic research always leads to revolutions and our understanding 0:04:31.920 --> 0:04:34.720 and in technology and all sorts of stuff. 0:04:34.800 --> 0:04:37.360 Yeah. I guess without physics there wouldn't be this podcast, 0:04:37.680 --> 0:04:39.640 which sort of employs us right. 0:04:40.400 --> 0:04:42.440 And improves the lives of everybody on Earth. 0:04:42.600 --> 0:04:44.600 I guess if physics wasn't around, we'd have to talk 0:04:44.600 --> 0:04:47.920 about something else or explain the universe using other things. 0:04:48.240 --> 0:04:51.839 Absolutely, but sometimes particle physics can be more directly useful. 0:04:52.120 --> 0:04:55.719 Things we learned about weird particles exotic matter can actually 0:04:55.720 --> 0:04:59.440 be put to use to help us solve everyday earthly mysteries. 0:05:00.040 --> 0:05:03.239 It might actually also help us have X ray vision 0:05:03.360 --> 0:05:05.680 in a way. So today on the podcast, we'll be 0:05:05.720 --> 0:05:14.600 taxing the question can we use muons to see inside 0:05:14.640 --> 0:05:17.800 of things? What kinds of things are we talking about? 0:05:17.839 --> 0:05:20.400 Daniel m all kinds of boxes? 0:05:20.480 --> 0:05:26.000 Yes, absolutely, escape rooms, people's pockets, safes and banks. 0:05:26.279 --> 0:05:29.320 Yeah, oh boy? What's inside the burgers at McDonald's. 0:05:29.360 --> 0:05:34.120 Perhaps nobody wants to know that for real, that's not 0:05:34.160 --> 0:05:35.520 why you go to McDonald's. 0:05:35.880 --> 0:05:37.839 I don't think we'll get grand funding for that question. 0:05:38.000 --> 0:05:40.480 Now that's a situation where knowledge can ruin something. 0:05:40.920 --> 0:05:43.520 Yeah, yeah, but it is an interesting question whether we 0:05:43.560 --> 0:05:45.880 can use meons to see inside of things? You mean, 0:05:45.960 --> 0:05:48.119 is this sort of like using muons as X rays? 0:05:48.200 --> 0:05:50.640 Kind of Yeah, it's a similar idea. Can we use 0:05:50.680 --> 0:05:55.120 penetrating radiation to reveal something that is hidden from us? 0:05:55.440 --> 0:05:58.320 Can we look inside something without opening it up? 0:05:58.960 --> 0:06:03.560 Can we just use X ray? I thought that was 0:06:03.600 --> 0:06:04.360 already invented. 0:06:05.839 --> 0:06:08.039 We can use X rays, but X rays also have 0:06:08.120 --> 0:06:11.360 their limits, and some muons might open up the possibility 0:06:11.400 --> 0:06:14.520 to see inside things that are otherwise still close to us. 0:06:14.600 --> 0:06:16.080 Even with X rays hmm. 0:06:16.200 --> 0:06:18.480 Interesting. All right, we'll dig into it, but first, as usual, 0:06:18.560 --> 0:06:20.520 we were wondering how many people out there had thought 0:06:20.560 --> 0:06:23.920 about using muons to see inside of things and how 0:06:23.960 --> 0:06:25.120 we might be able to do that. 0:06:25.200 --> 0:06:27.560 Thanks very much to everybody who plays the game for 0:06:27.640 --> 0:06:30.279 this section of the podcast. We love hearing your voice, 0:06:30.320 --> 0:06:32.400 and if you would like to participate, it's very easy. 0:06:32.400 --> 0:06:35.040 It all happens over email. Just write to me too 0:06:35.160 --> 0:06:37.400 questions at Danielandjorge dot com. 0:06:37.400 --> 0:06:39.599 So think about it for a second. Do you think 0:06:39.720 --> 0:06:43.160 we can use muons to see inside of things? Here's 0:06:43.160 --> 0:06:44.000 what people had to say. 0:06:44.680 --> 0:06:48.039 No idea, absolutely, But I know that there's some talk 0:06:48.120 --> 0:06:51.440 of making a Muon's collider or something like that. I 0:06:51.440 --> 0:06:55.920 read about that in some news reports. So I'm gonna say, yeah, ah, 0:06:55.960 --> 0:06:58.800 why not. You know, if you can accelerate them enough 0:06:58.800 --> 0:07:02.560 and they don't dissipate energy like electrons, there should be 0:07:02.600 --> 0:07:05.800 a way to create collisions. 0:07:06.200 --> 0:07:08.320 I'm going to say, yes, I listened to your whole 0:07:08.320 --> 0:07:12.760 podcast about muons, but I've completely forgotten what they are. 0:07:13.040 --> 0:07:16.840 So I am going to take a kiss and say, yes, 0:07:17.000 --> 0:07:19.120 you can use mulons to see inside something. 0:07:19.560 --> 0:07:24.440 I would imagine using muons to look inside things would 0:07:24.480 --> 0:07:27.320 be what the same principle is using an electron microscope. 0:07:27.560 --> 0:07:32.960 I suspect muons are smaller than electrons, so for them 0:07:33.000 --> 0:07:35.600 to bounce off something and give an image to be 0:07:35.640 --> 0:07:39.480 bouncing off very small sub atomic particles. 0:07:39.560 --> 0:07:40.640 I don't know what a mion is. 0:07:40.600 --> 0:07:43.600 So I don't know, all right. I imagine a lot of 0:07:43.600 --> 0:07:45.800 people are like that person who said they don't know 0:07:45.840 --> 0:07:49.160 what a muon is. They don't know, but it sounds 0:07:49.160 --> 0:07:51.119 like a reasonable question. A lot of people will seem 0:07:51.160 --> 0:07:52.200 pretty optimistic about this. 0:07:52.280 --> 0:07:54.160 Yeah, if a muone is some new kind of particle, 0:07:54.200 --> 0:07:56.680 maybe it's got some new kind of powers or abilities 0:07:56.760 --> 0:07:59.400 or properties that lets you do new kinds of stuff. 0:08:00.200 --> 0:08:01.200 That's the optimism. 0:08:01.240 --> 0:08:05.000 All right, Well, let's put a steak through this question, 0:08:05.320 --> 0:08:09.040 and they started the basics, Daniel, What is exactly a muon? 0:08:09.160 --> 0:08:10.800 A lot of people seem to have heard us talk 0:08:10.800 --> 0:08:12.920 about it, but maybe forgotten. What it is. 0:08:13.200 --> 0:08:16.160 A muon can best be understood is like a heavier version, 0:08:16.160 --> 0:08:19.680 a more massive version of the electron. It's very very 0:08:19.720 --> 0:08:22.560 similar to the electron, has a lot of the same properties, 0:08:22.840 --> 0:08:27.160 same kinds of relationships as the electron, but it's more massive. 0:08:27.920 --> 0:08:30.160 I see, So it's a particle, And I guess maybe 0:08:30.200 --> 0:08:33.160 we should mention that the universe has particles, or at 0:08:33.240 --> 0:08:36.720 least the potential to create particles or further to exist particles, 0:08:36.920 --> 0:08:39.280 and a muon is one of these particles. 0:08:39.440 --> 0:08:41.600 Yeah, there are lots of particles that make up me 0:08:41.800 --> 0:08:44.560 and you and all the normal matter that's out there. 0:08:44.679 --> 0:08:47.439 If you drill inside of us, you find molecules and atoms, 0:08:47.480 --> 0:08:50.680 and those atoms are made of protons and neutrons and electrons. 0:08:51.000 --> 0:08:53.560 The protons and neutrons are made out of quarks. So 0:08:53.600 --> 0:08:55.760 at the most fundamental level, everything that you and I 0:08:55.800 --> 0:08:58.080 are made out of, and everything that you and I eat, 0:08:58.320 --> 0:09:02.080 including steaks and cows, are made up of upquarks and 0:09:02.200 --> 0:09:05.440 down quarks and electrons. So those are the three basic 0:09:05.520 --> 0:09:09.320 building blocks of normal matter. But there are other kinds 0:09:09.360 --> 0:09:12.120 of particles out there that the universe can make. They're 0:09:12.120 --> 0:09:14.200 sort of on the menu, but they're not stable and 0:09:14.240 --> 0:09:18.240 they're not involved in building normal, everyday atomic matter. So 0:09:18.280 --> 0:09:20.960 there's sort of various categories of particles out there. Ones 0:09:21.000 --> 0:09:23.600 it can be made and exist all over the universe, 0:09:23.880 --> 0:09:26.640 and ones it can be made but only exist briefly. 0:09:27.520 --> 0:09:30.120 Or at least in the current universe that we have, right, 0:09:30.160 --> 0:09:32.080 I think we talked about maybe before, Like maybe in 0:09:32.080 --> 0:09:35.160 the early universe, the particles like nuons were common and 0:09:35.200 --> 0:09:35.960 they would hang out. 0:09:36.160 --> 0:09:38.520 Yeah, the frequency of which you find these particles definitely 0:09:38.559 --> 0:09:42.360 depends on the temperature of the universe because the unstable 0:09:42.400 --> 0:09:45.720 particles muons, charm corks, top quarks are a lot more 0:09:45.760 --> 0:09:48.800 massive than the other particles that take more energy. These days, 0:09:48.800 --> 0:09:50.960 it's rarer to create that kind of energy because the 0:09:51.000 --> 0:09:53.599 universe is more spread out and colder. Back in the 0:09:53.679 --> 0:09:55.680 early days of the universe, it wasn't as hard to 0:09:55.679 --> 0:09:57.880 get enough energy together to make a muon or a 0:09:57.880 --> 0:10:00.439 top quark. They always have a short lifetime, though they 0:10:00.480 --> 0:10:03.320 still don't last very long, but they're made much more 0:10:03.320 --> 0:10:05.719 often in the early universe. These days, it takes more 0:10:05.760 --> 0:10:10.160 specialized conditions like humans smashing particles together or cosmic rays 0:10:10.240 --> 0:10:13.280 hitting the atmosphere to create the conditions to make these 0:10:13.320 --> 0:10:15.880 weird particles. They still don't last for very long. 0:10:16.840 --> 0:10:19.080 So like the meon you said only lives for a 0:10:19.120 --> 0:10:20.640 few microseconds, right. 0:10:20.679 --> 0:10:24.040 Yeah, the muon lives for two point two microseconds before 0:10:24.080 --> 0:10:27.640 it decays into an electron and a couple of neutrinos, 0:10:27.760 --> 0:10:29.720 and we call the muon like a cousin of the 0:10:29.800 --> 0:10:32.880 electron because it has a lot of the similar properties. 0:10:33.040 --> 0:10:36.280 It's negatively charged like the electron is. It's paired with 0:10:36.360 --> 0:10:39.240 the neutrino the way an electron is. So in our 0:10:39.280 --> 0:10:41.760 sort of table of particles, we put the quarks in 0:10:41.800 --> 0:10:44.760 one category and these other particles we call leptons in 0:10:44.800 --> 0:10:48.360 another category because the muon, and like the electron, also 0:10:48.400 --> 0:10:51.440 doesn't feel the strong nuclear force that the quarks do. 0:10:52.720 --> 0:10:55.760 I see. So it's basically an electron, but somehow it 0:10:55.880 --> 0:10:58.560 just has a more mass to it. Like the label 0:10:59.000 --> 0:11:01.079 that says this is this is how much an electronic way, 0:11:01.120 --> 0:11:03.560 it just happens to be more for the muon, But 0:11:03.600 --> 0:11:06.080 other than that, it's almost exactly the same, Like it 0:11:06.160 --> 0:11:10.520 has the same electrical charge and all the other quantum values. 0:11:10.600 --> 0:11:13.679 Right, Yeah, it's about two hundred times more massive than 0:11:13.720 --> 0:11:16.600 the electron. And nobody knows why that is, Like why 0:11:16.600 --> 0:11:18.440 does the electron have this mass and the muon have 0:11:18.520 --> 0:11:21.160 that mass? These are just numbers that we've discovered in 0:11:21.200 --> 0:11:24.560 the universe without any explanation. You might think that the 0:11:24.640 --> 0:11:27.559 Higgs gives an explanation for why some particles have more 0:11:27.600 --> 0:11:30.719 mass than some have less. And it's true that the 0:11:30.840 --> 0:11:34.200 muon has more mass than the electron because the Higgs 0:11:34.200 --> 0:11:37.440 interacts with it more, giving it more mass, but that 0:11:37.480 --> 0:11:40.400 doesn't explain why there's a difference. It just kicks the 0:11:40.400 --> 0:11:43.120 can down the road. Instead of asking why does the 0:11:43.200 --> 0:11:46.120 muon have more mass than the electron, we now ask 0:11:46.600 --> 0:11:48.960 why does the muon interact with the Higgs more than 0:11:49.000 --> 0:11:52.880 the electron does. The Higgs explains what mass is, but 0:11:53.120 --> 0:11:56.319 not why some particles have more or less of it. 0:11:56.320 --> 0:11:59.600 It's still just two numbers without an explanation. Now there's 0:11:59.640 --> 0:12:02.760 two are interaction strength instead of mass. And there's a 0:12:02.760 --> 0:12:05.160 third version of the electron called the tao, which is 0:12:05.200 --> 0:12:08.120 even more massive. And this is the general pattern of 0:12:08.160 --> 0:12:11.040 the particles. Each of the particles we talked about, the electron, 0:12:11.080 --> 0:12:13.719 the upcork, the down cork has two copies of it 0:12:13.800 --> 0:12:16.960 which are more massive. So this is some deep symmetry, 0:12:17.000 --> 0:12:20.079 some structure to the universe that we've observed. We've organized, 0:12:20.120 --> 0:12:22.200 we've seen the pattern, we've laid it out of the table, 0:12:22.440 --> 0:12:24.520 but we've not understood it. And the mew one was 0:12:24.520 --> 0:12:26.559 like one of the first clues we had that there 0:12:26.600 --> 0:12:28.800 was more out there to the universe than just the 0:12:28.840 --> 0:12:30.360 particles that made up our matter. 0:12:31.320 --> 0:12:32.880 But I guess, you know, what does it mean that 0:12:32.880 --> 0:12:35.600 it only lists for two point two microseconds? Like does 0:12:35.640 --> 0:12:38.880 that even count as existing? You know, like why I 0:12:38.960 --> 0:12:41.160 didn't call it a thing if it's only around for 0:12:41.200 --> 0:12:44.240 two point two microseconds? You know, like can it move 0:12:44.280 --> 0:12:46.760 around that much? Or or is this one of these 0:12:46.760 --> 0:12:49.760 like relativistic things where to us it lists or two 0:12:49.760 --> 0:12:52.240 point two microseconds, but maybe it's going really fast it 0:12:52.280 --> 0:12:53.800 lives for a really really long time. 0:12:54.000 --> 0:12:56.400 I think yes to all of that, although you know, 0:12:56.440 --> 0:12:58.760 the timescale is always relative, like we only live for 0:12:58.760 --> 0:13:01.080 one hundred years on the time scale the universe, that's 0:13:01.120 --> 0:13:03.920 basically nothing. Do we even count as existing? I would 0:13:03.960 --> 0:13:08.040 say yes, right, because time scales are relative relative to 0:13:08.120 --> 0:13:10.760 some other particles, like the top quark lives for ten 0:13:10.800 --> 0:13:13.880 to the money twenty three seconds, But we still think 0:13:13.920 --> 0:13:16.320 that it's a thing. Like the neutron lasts for I 0:13:16.320 --> 0:13:19.800 think eleven minutes before it decays, So these timescales are 0:13:19.840 --> 0:13:22.400 all relative. What we actually mean by two point two 0:13:22.480 --> 0:13:25.160 microseconds is in the muon's rest frame, like if you 0:13:25.160 --> 0:13:27.480 had a muon in front of you at rest, and 0:13:27.520 --> 0:13:29.640 you started a clock when it was created, and you 0:13:29.720 --> 0:13:32.600 waited until a decayed, that would be two point two microseconds. 0:13:32.679 --> 0:13:35.920 But you're right, relativity plays a big role. Muons are 0:13:35.960 --> 0:13:38.800 often moving really really fast, especially when they're created in 0:13:38.840 --> 0:13:41.600 the atmosphere, So if they're moving near the speed of light, 0:13:41.880 --> 0:13:44.679 then a clock that's moving with them is slowed down. 0:13:44.880 --> 0:13:47.280 And so the reason muons can actually survive from the 0:13:47.320 --> 0:13:49.760 top of the atmosphere where they're made to hit us 0:13:49.760 --> 0:13:53.080 on the ground is because their time is slowed. So 0:13:53.120 --> 0:13:55.560 from our perspective, they can last for much much longer 0:13:55.600 --> 0:13:58.280 than two point two microseconds, long enough to make it 0:13:58.280 --> 0:13:59.360 to the surface of the Earth. 0:13:59.520 --> 0:14:02.760 And what is it mean that it decays or does 0:14:02.760 --> 0:14:06.000 it disintegrade? Does it like the energy just diffuses or 0:14:06.040 --> 0:14:08.360 transforms it through something else? What does that actually mean? 0:14:08.480 --> 0:14:11.000 Yeah, sometimes we think about decay as like something breaks 0:14:11.120 --> 0:14:14.480 up and you get the component bits. It's like cracking 0:14:14.480 --> 0:14:17.280 something open, breaking it into its basic legos, like an 0:14:17.320 --> 0:14:20.200 atom broken up into its protons and neutrons. That's not 0:14:20.240 --> 0:14:23.320 what's happening here, because when a muon decays, it turns 0:14:23.360 --> 0:14:26.400 into an electron and two neutrinos. But it's not like 0:14:26.440 --> 0:14:29.560 the electron and those neutrinos were inside the muon. It's 0:14:29.560 --> 0:14:31.960 not like the muon is made of the electron and 0:14:32.000 --> 0:14:34.920 the two neutrinos. Instead, think of that energy as passing 0:14:34.960 --> 0:14:38.040 from the muon field to the electron field and the 0:14:38.080 --> 0:14:41.240 neutrino fields. Remember that all these particles are really just 0:14:41.640 --> 0:14:45.160 ripples in universe spanning fields that feel all of space. 0:14:45.520 --> 0:14:48.600 Every part of space has a muon field, an electron field, 0:14:48.720 --> 0:14:52.120 and the three different neutrino fields. So it's happening here 0:14:52.200 --> 0:14:54.840 is that those fields are coming into contact, they're interacting, 0:14:54.960 --> 0:14:57.520 and the muon field oscillations in that field are not stable. 0:14:57.680 --> 0:15:00.280 They like to decay down into the electron field and 0:15:00.280 --> 0:15:02.760 the neutrino fields. So that's what's happening here. 0:15:03.040 --> 0:15:05.840 But maybe a question is like why is it so unstable, 0:15:06.120 --> 0:15:09.960 Like what makes the muon field which makes muons prone 0:15:10.000 --> 0:15:14.640 to be to basically dissipating or disappearing, and not, for example, 0:15:14.640 --> 0:15:17.040 the electron field, which seems super duper stable. 0:15:17.160 --> 0:15:19.400 The electron would like to decay, but there's nothing for 0:15:19.480 --> 0:15:21.960 it to decay into because it's the lowest mass particle 0:15:22.000 --> 0:15:25.040 in this chain, it's the lightest charged particle, and so 0:15:25.080 --> 0:15:27.200 the muon can decay to an electron, which is a 0:15:27.240 --> 0:15:30.400 lower mass particle, and so it does because in doing so, 0:15:30.480 --> 0:15:33.040 it spreads out the energy. The universe doesn't like to 0:15:33.080 --> 0:15:35.840 have a lot of energy concentrated in one place, likes 0:15:35.840 --> 0:15:37.840 to spread it out. It's like entropy at a most 0:15:37.840 --> 0:15:40.200 basic level. And so a high mass particle will tend 0:15:40.240 --> 0:15:43.200 to decay into lower mass particles if it can, because 0:15:43.200 --> 0:15:46.480 that provides more arrangements of that energy. Instead of having 0:15:46.520 --> 0:15:48.360 all of it just in mass, now you have it 0:15:48.400 --> 0:15:51.280 in a lower mass particle, plus lots of different possible 0:15:51.360 --> 0:15:55.600 momentum states. So the quantum mechanical probabilities are just much 0:15:55.680 --> 0:15:58.560 more for lower mass particles, and so they're more likely 0:15:58.640 --> 0:15:59.160 to happen. 0:16:00.280 --> 0:16:02.800 But I guess, maybe why doesn't Why can't the electron 0:16:02.840 --> 0:16:05.400 break into something smaller? Is it just like we just 0:16:05.440 --> 0:16:08.960 haven't seen it do that, or maybe it's impossible. 0:16:08.400 --> 0:16:11.200 Well, we haven't seen an electron decay. We think electrons 0:16:11.200 --> 0:16:14.000 are stable. Though it's possible that electrons live for like 0:16:14.040 --> 0:16:16.720 a trillion years, we just never seen one decay because 0:16:16.720 --> 0:16:19.240 they just last for a long, long time, right, it's 0:16:19.240 --> 0:16:21.440 the same with the proton. We think the proton is stable, 0:16:21.520 --> 0:16:24.280 but we don't know. We've never seen one decay, so 0:16:24.360 --> 0:16:26.680 we think it might be stable or very very very 0:16:26.720 --> 0:16:29.560 long lived. But for the electron to decay, there would 0:16:29.600 --> 0:16:32.200 have to be something for it to decay into that 0:16:32.320 --> 0:16:35.440 also has electric charge. Because electric charge is conserved, it 0:16:35.440 --> 0:16:38.400 can't just go away. We don't know if any lower 0:16:38.520 --> 0:16:41.520 mass charged particle than the electron, So it's sort of 0:16:41.520 --> 0:16:43.600 like the bottom rung of the ladder, which is why 0:16:43.720 --> 0:16:45.080 energy sort of gets stuck there. 0:16:45.640 --> 0:16:48.400 I see, okay, so well, then the muon decays because 0:16:48.400 --> 0:16:50.920 it can decay to other particles. Does it get triggered 0:16:51.000 --> 0:16:52.880 by something, or if you just leave a meuon there, 0:16:52.920 --> 0:16:55.560 it'll be like okay, I'm done, and then it breaks apart. 0:16:57.280 --> 0:16:59.000 If you just leave a muon in the vacuum, it 0:16:59.040 --> 0:17:02.600 will decay. Mwan flying through space will decay on their own. 0:17:02.840 --> 0:17:05.760 They can also interact with stuff because they have charge. 0:17:05.840 --> 0:17:08.840 They can interact with electrons, and they can interact with 0:17:08.920 --> 0:17:11.200 protons and all sorts of stuff. So if you slam 0:17:11.280 --> 0:17:13.440 them into a block of lead, for example, they will 0:17:13.480 --> 0:17:16.000 interact and that can also trigger the decay, but muons 0:17:16.040 --> 0:17:17.520 on their own will also just decay. 0:17:18.320 --> 0:17:20.600 Can they appear out of nowhere? Like, what does it 0:17:20.600 --> 0:17:22.880 take to make a muon? Or how are they made 0:17:22.880 --> 0:17:25.320 if they're a thing in the universe. Is it just 0:17:25.320 --> 0:17:28.959 whenever you have enough energy concentrated into one spot or 0:17:29.320 --> 0:17:31.000 what's the origin story of a muon? 0:17:32.480 --> 0:17:35.040 So the origin stories that you get enough energy into 0:17:35.080 --> 0:17:37.680 sort of a higher mass field to feel that can 0:17:37.800 --> 0:17:41.480 decay into muons. Energy likes to flow down the lower 0:17:41.520 --> 0:17:44.480 mass fields like rungs down the ladder, So you got 0:17:44.520 --> 0:17:46.760 to get enough energy into a higher mass field and 0:17:46.800 --> 0:17:49.600 then it can decay into muons. So the typical way 0:17:49.640 --> 0:17:52.840 that muons are made naturally in our environment is they 0:17:52.880 --> 0:17:55.280 have a cosmic ray, which is like a proton slimming 0:17:55.280 --> 0:17:57.960 into some particle in the atmosphere, which creates a lot 0:17:58.000 --> 0:18:00.800 of energy density in one space, and then you create 0:18:00.880 --> 0:18:04.240 some very massive, unstable particle, and a lot of particles 0:18:04.280 --> 0:18:07.320 decay into muons, So you might create like a pion 0:18:07.520 --> 0:18:10.359 or a chaon. These are more massive particles that like 0:18:10.440 --> 0:18:13.320 to decay into muons, and then those decay in the atmosphere, 0:18:13.359 --> 0:18:15.679 giving you a muon which flies down to the surface. 0:18:15.720 --> 0:18:16.200 Of the Earth. 0:18:16.320 --> 0:18:18.160 But don't you need where does the charge come from? 0:18:18.280 --> 0:18:20.879 Protons are charged, right, so the charge comes from the 0:18:20.920 --> 0:18:23.240 cosmic ray, and also there's loss of charge in the 0:18:23.280 --> 0:18:25.800 upper atmosphere. Even a neutron slamming into a particle in 0:18:25.800 --> 0:18:29.320 the upper atmosphere, and like disintegrating an oxygen molecule can 0:18:29.400 --> 0:18:31.200 create showers of charged particles. 0:18:31.480 --> 0:18:35.399 M where does the negative charge come from? Isn't a 0:18:35.400 --> 0:18:36.480 photon neutral? 0:18:36.600 --> 0:18:38.439 Well, first of all, we have two flavors of muons. 0:18:38.480 --> 0:18:40.399 We have negative muons, which are the normal ones, and 0:18:40.440 --> 0:18:43.520 then anti muons, which are positively charged. In particle physics 0:18:43.520 --> 0:18:45.720 we don't really care so much about it, and both 0:18:45.760 --> 0:18:47.879 of them are created in the upper atmospherees, So we 0:18:47.920 --> 0:18:51.399 have anti muons and muons created in the upper atmosphere. 0:18:51.440 --> 0:18:52.880 But your question is a good one. If you start 0:18:52.880 --> 0:18:55.600 from a positively charged proton, how you end up making 0:18:55.680 --> 0:18:58.600 like a negatively charged muon. The answer is that there's 0:18:58.680 --> 0:19:01.679 just a lot more stuff in in this interaction then 0:19:01.720 --> 0:19:04.760 we're describing, Because a proton is a big complicated bag 0:19:04.800 --> 0:19:07.520 of quarks and it slams into something else in the atmosphere, 0:19:07.520 --> 0:19:10.679 which is a big complicated bag of other protons and neutrons, 0:19:10.920 --> 0:19:13.640 so there's plenty of charges around to create something which 0:19:13.680 --> 0:19:16.880 decays into a negatively charged particle and balance it out 0:19:16.920 --> 0:19:19.000 with all the rest of the stuff. So a proton 0:19:19.080 --> 0:19:22.160 can turn into a huge shower of negative and positive 0:19:22.200 --> 0:19:25.439 particles with a total charge of plus one. So you 0:19:25.480 --> 0:19:28.439 can have lots of muons and anti muons created in 0:19:28.480 --> 0:19:29.160 these showers. 0:19:29.880 --> 0:19:33.720 All right, Well, whether you're pro or anti muon maybe 0:19:33.840 --> 0:19:35.680 is the question of the episodes. Can we use a 0:19:35.760 --> 0:19:38.760 muon to see inside of things and maybe put these 0:19:39.000 --> 0:19:43.199