WEBVTT - What is the axion? 0:00:08.720 --> 0:00:12.560 Hey, Daniel, if you ever discovered a particle, what would 0:00:12.600 --> 0:00:15.040 you name it? Oh? I feel a little bit put 0:00:15.120 --> 0:00:17.439 on the spot and no pressure. I mean, you wouldn't 0:00:17.480 --> 0:00:22.280 just name it the white sun or the white cuno, did, DANIELO. Well, 0:00:22.320 --> 0:00:24.760 you know, over the course of these podcasts, I've come 0:00:24.800 --> 0:00:27.480 to get a feeling of, I don't know, judgment from 0:00:27.480 --> 0:00:30.640 you by the quality of particle names. So I guess 0:00:30.680 --> 0:00:33.519 I feel some responsibility to like do it right and 0:00:33.600 --> 0:00:36.280 meet your high standards. Well, I'm glad I'm doing my 0:00:36.320 --> 0:00:39.080 bid to make physics better. You know. I just hope 0:00:39.120 --> 0:00:40.760 you don't give it a silly name, you know, like 0:00:40.800 --> 0:00:43.360 a random name, like a squiggly on or something. You know, 0:00:43.520 --> 0:00:46.479 those quiglyons. That would be a silly name. Well, I 0:00:46.520 --> 0:00:49.040 promised to do my best. I won't like name it 0:00:49.080 --> 0:00:52.199 after a random laundry detergent or something. All right, if 0:00:52.200 --> 0:01:10.480 you do that, this podcast is over. Hi am Orhammad, 0:01:10.520 --> 0:01:14.200 cartoonist and the creator of PhD comics. Hi. I'm Daniel. 0:01:14.280 --> 0:01:17.480 I'm a particle physicist who has never discovered a particle, 0:01:17.840 --> 0:01:20.200 at least one that nobody else has discovered. That's right. 0:01:20.520 --> 0:01:23.040 I found particles this morning when I had breakfast and 0:01:23.080 --> 0:01:25.400 I planned to find some more for lunch. But they're 0:01:25.440 --> 0:01:28.800 all your everyday running the mill quirks and electron Yeah, 0:01:28.800 --> 0:01:31.160 I find particles all the time in my belly button. 0:01:33.040 --> 0:01:35.240 That's probably not a picture we want to paint this 0:01:35.520 --> 0:01:38.119 really in the episode. That's probably what dark matter is. Jorge. 0:01:38.200 --> 0:01:40.720 It's just your belly button. Oh yeah, my billy win 0:01:40.840 --> 0:01:45.320 is full of dark matter and dark energy and physicists 0:01:45.319 --> 0:01:48.080 also can't explain it. But welcome to our podcast, Daniel 0:01:48.120 --> 0:01:51.040 and Jorge Explain the Universe, a production of I Heart 0:01:51.120 --> 0:01:53.960 Radio in which we try to tackle the biggest questions 0:01:54.000 --> 0:01:56.480 in the universe. What is dark matter, what is everything 0:01:56.520 --> 0:01:59.480 made out of? What is that weird thing in Jorge's 0:01:59.520 --> 0:02:01.400 belly button? And we try to do it in a 0:02:01.440 --> 0:02:04.720 way that educates you and entertains you along the way. 0:02:04.840 --> 0:02:06.840 And we like to talk about not just the science 0:02:06.840 --> 0:02:08.760 and what we know about the universe and what we 0:02:08.840 --> 0:02:11.120 don't know, but we also kind of like to talk 0:02:11.200 --> 0:02:13.840 sometimes about the process of science, like how are things 0:02:13.880 --> 0:02:17.000 discovered or what are scientists thinking about or what are 0:02:17.000 --> 0:02:19.840 they looking for. That's right, because the forefront of science, 0:02:19.880 --> 0:02:23.360 the edge of human curiosity, it belongs to everybody, and 0:02:23.400 --> 0:02:26.120 we want you to know what are scientists thinking about, 0:02:26.200 --> 0:02:28.359 what are they wondering about, what do they not know? 0:02:28.680 --> 0:02:30.799 And what are they doing to figure it out? How 0:02:30.840 --> 0:02:34.400 do we go from clueless too, slightly clued in, slightly 0:02:34.480 --> 0:02:39.919 less clueless, diminishing cluelessness. That'll be the title of my autobiography. Yeah, 0:02:39.919 --> 0:02:41.919 we would like to kind of stand at the precipice 0:02:42.000 --> 0:02:44.480 of ignorance. I'd like to call it like, we're right 0:02:44.520 --> 0:02:46.799 at the edge of what scientists know and don't know 0:02:47.320 --> 0:02:49.840 and what they're discovering right now at the moment. Do 0:02:49.880 --> 0:02:51.640 you think we are in danger of falling into that 0:02:51.680 --> 0:02:54.760 precipice or we're pushing it back. I think it's possible 0:02:54.800 --> 0:02:57.079 to go a little bit too deep into the rabid 0:02:57.120 --> 0:03:00.760 hole here of what we don't know in physics. Just 0:03:00.840 --> 0:03:02.680 following up on your metaphor there, does that make the 0:03:02.800 --> 0:03:07.480 rabbit is ignorance or rabbits are ignorant? Well, I don't 0:03:07.480 --> 0:03:10.880 want to insult any rabbits. We're definitely pro rabbit on 0:03:10.880 --> 0:03:14.320 this podcast. Were we are we like rabbits here? But 0:03:14.440 --> 0:03:16.239 you know, one question is that you know there are 0:03:16.400 --> 0:03:19.160 all these particles out there in the universe and there's 0:03:19.240 --> 0:03:22.320 a whole bunch of particles we've discovered in the universe, 0:03:22.600 --> 0:03:24.360 and and so the kind of the question is like, 0:03:24.400 --> 0:03:27.359 how do people find new particles? How do you physicists 0:03:27.360 --> 0:03:29.960 discover them? Yeah, there's sort of two big ways to 0:03:30.040 --> 0:03:31.840 do it. One is to look at the list of 0:03:31.880 --> 0:03:35.160 particles we have now and say it doesn't seem complete. 0:03:35.360 --> 0:03:38.080 We need another one. And this is the case when 0:03:38.120 --> 0:03:40.080 we talked about the top cork, for example, we had 0:03:40.120 --> 0:03:43.280 a nice little pattern of particles with a missing square 0:03:43.280 --> 0:03:45.480 in it. There was one particle that didn't have a 0:03:45.520 --> 0:03:47.880 partner and everything else was paired off, so we thought 0:03:48.040 --> 0:03:51.240 there must be one there. And sometimes, more abstractly, we 0:03:51.320 --> 0:03:54.160 say there's just a larger pattern that would make sense 0:03:54.440 --> 0:03:57.080 if we added one more particle. That's how the Higgs 0:03:57.120 --> 0:03:59.760 boson was discovered, for example. So you're saying particle physics, 0:03:59.760 --> 0:04:04.600 it's it's kind of like pokemon collecting or baseball card collecting. Yeah, 0:04:04.600 --> 0:04:07.120 except we can't trade. You know, if the aliens come, 0:04:07.160 --> 0:04:09.920 maybe we could trade our discoveries for their for theirs. Right, 0:04:10.120 --> 0:04:13.400 Oh my goodness, your nerve brain just exploded. I'll give 0:04:13.440 --> 0:04:15.680 you a Higgs boson for the dark matter. Please? Do 0:04:15.680 --> 0:04:20.440 you have dark matter? We want dark matter? Boy? That 0:04:20.440 --> 0:04:22.320 would be uh, that does sound kind of like fun. 0:04:22.400 --> 0:04:25.080 You know, you can get together the neighborhood and you 0:04:25.440 --> 0:04:28.120 exchange what do you know about the universe. I'm looking 0:04:28.160 --> 0:04:30.680 forward at that party. But there's a whole other way 0:04:30.720 --> 0:04:33.279 to discover particles, which is just to sort of stumble 0:04:33.360 --> 0:04:36.080 across them, to like find them in nature and see 0:04:36.080 --> 0:04:39.400 them and go what's that and then figure out how 0:04:39.440 --> 0:04:42.200 does it fit into the larger puzzle, where does this go? 0:04:42.360 --> 0:04:45.120 How do we connected? And we haven't done too much 0:04:45.120 --> 0:04:48.200 of that recently. Mostly we've been predicting particles and then 0:04:48.279 --> 0:04:50.560 find I see. So how would you stumble upon a 0:04:50.600 --> 0:04:53.520 particle like you're running the collider or any kind of 0:04:53.520 --> 0:04:56.960 collider and then suddenly you see something you weren't expecting. Yeah, precisely. 0:04:57.080 --> 0:04:59.760 This is how mu ones were discovered. For example, they 0:04:59.760 --> 0:05:03.239 had big blocks of photographic materials up on the tops 0:05:03.240 --> 0:05:05.520 of mountains and they saw these streaks of particles going 0:05:05.560 --> 0:05:08.560 through them, and the particles weren't consistent with electrons or 0:05:08.600 --> 0:05:10.640 anything else, and so they said, well, this must be 0:05:10.680 --> 0:05:14.040 some new particle we haven't seen before. And colliders are 0:05:14.040 --> 0:05:18.040 actually the best place to discover a new, unexpected particle 0:05:18.120 --> 0:05:20.719 because you smash the protons together and you get this 0:05:20.760 --> 0:05:24.640 little blob of energy which can turn into anything. Anything 0:05:24.720 --> 0:05:27.520 the universe is capable of making, and so you could 0:05:27.520 --> 0:05:30.600 just pop out some crazy new particle you've never seen 0:05:30.640 --> 0:05:33.520 before without you knowing that it exists. You don't have 0:05:33.600 --> 0:05:36.080 to know it's there in order to find it. That's 0:05:36.080 --> 0:05:39.160 the amazing thing about exploring the universe with colliders. You'd 0:05:39.160 --> 0:05:42.839 be like, who ordered that exactly where that? That's exactly 0:05:42.920 --> 0:05:45.520 literally what they said when they heard about the mule, 0:05:45.560 --> 0:05:47.839 and they said, what, we don't need that. That doesn't 0:05:47.839 --> 0:05:51.320 make any sense. Go take that somewhere else. Well, we've 0:05:51.320 --> 0:05:54.280 had several episodes where we talk about the discovery and 0:05:54.360 --> 0:05:56.599 the search for different particles. We had one about the 0:05:56.600 --> 0:06:00.240 top cork and the electron and all these other particles. 0:06:00.279 --> 0:06:03.080 And so today we'll tell the story of another particle, 0:06:03.160 --> 0:06:06.800 one that was proposed almost forty years ago and that 0:06:06.880 --> 0:06:09.520 we are still looking for. That's right, this is a 0:06:09.560 --> 0:06:13.200 particle which may or may not exist, and if it 0:06:13.240 --> 0:06:17.320 does exist, it may simultaneously solve two of the biggest 0:06:17.400 --> 0:06:21.920 problems in particle physics and weirdly, it's a particle almost 0:06:22.080 --> 0:06:25.360 nobody outside the field has even heard of. Wow, well, 0:06:25.400 --> 0:06:27.720 I guess we we don't know if it exists, and 0:06:27.800 --> 0:06:29.760 so if it doesn't exist, we have to erase this 0:06:29.800 --> 0:06:34.240 podcast episode. Daniel or no, we get paid Either way, 0:06:34.240 --> 0:06:39.040 it doesn't really matter. Okay, forget about that. Well apparently 0:06:39.040 --> 0:06:42.080 has the one of the citiest names in the history 0:06:42.080 --> 0:06:45.000 of particles. Yes, I'm looking forward to hearing your reaction 0:06:45.200 --> 0:06:47.640 to how this particle was named. It ends up with 0:06:47.720 --> 0:06:50.680 a really pretty cool name. But the reason for that 0:06:50.760 --> 0:06:54.440 name is really pretty ludicrous and whimsical. Oh man, I 0:06:54.440 --> 0:06:58.000 am not looking forward to that. But anyway, So today 0:06:58.000 --> 0:07:04.680 on the podcast, we'll be asking the question, what is 0:07:04.720 --> 0:07:08.520 the most important particle you've never heard of? It's just 0:07:08.600 --> 0:07:11.440 like a trendy band that everyone should listen to but 0:07:11.480 --> 0:07:13.960 nobody knows about. Yeah, this is the particle your teenager 0:07:14.040 --> 0:07:16.760 knows about, but you are clueless about it. It's super 0:07:16.760 --> 0:07:21.560 hot on TikTok You're like, what what is TikTok? That's 0:07:21.560 --> 0:07:24.080 precisely you don't even know the name of the social 0:07:24.120 --> 0:07:27.280 media app on which this particle is cool. That's how 0:07:27.360 --> 0:07:29.480 uncool you are. No, but it is. It is a 0:07:29.560 --> 0:07:32.440 really cool name. I like. I like the sound of 0:07:32.480 --> 0:07:35.120 the name of this particle. It's this particle is called 0:07:35.160 --> 0:07:38.960 the axion. That does sound pretty cool. It does sound 0:07:38.960 --> 0:07:41.160 pretty cool. What doesn't invoke in your mind or him 0:07:41.560 --> 0:07:45.240 like a robot or you know, like um like access 0:07:45.360 --> 0:07:49.280 maybe Unfortunately, the word for armpits in Spanish is kind 0:07:49.280 --> 0:07:51.320 of close to it, So it is making me think 0:07:51.320 --> 0:07:54.000 a little bit of art pits. But we won't go 0:07:54.080 --> 0:08:00.240 there is an unfortunate name. It makes me think of 0:08:00.280 --> 0:08:03.840 sort of like double edged axes being thrown in space 0:08:03.880 --> 0:08:06.760 along three different axes, you know, like X and y 0:08:06.800 --> 0:08:09.880 ax and your y ax and your zo throwing an 0:08:10.080 --> 0:08:13.480 X and X around. I don't know, I don't know, 0:08:13.840 --> 0:08:15.560 but it is a cool name. It's fun to say. 0:08:15.600 --> 0:08:18.800 It's got that same sound in their idea. I think 0:08:19.080 --> 0:08:21.440 as long as it sounds like a transformer, it sounds 0:08:21.720 --> 0:08:27.480 I think cool. In physics, you know, synchrotron, graviton megatron 0:08:27.600 --> 0:08:29.840 is not a particle, though the awesome there you go, 0:08:30.320 --> 0:08:32.160 that will be the name of a particle. Some of 0:08:32.200 --> 0:08:35.280 you may have heard about the new interesting axon result 0:08:35.360 --> 0:08:38.760 from the Zenon experiment. Now today we'll be talking about 0:08:38.760 --> 0:08:41.720 the axon more generally, but we're going to dig into 0:08:41.760 --> 0:08:46.160 the zenon solar axon question in a dedicated episode coming 0:08:46.280 --> 0:08:49.560 very soon. But as usual, I was curious, what did 0:08:49.600 --> 0:08:52.600 people know about the axon? Is this something people actually 0:08:52.600 --> 0:08:55.240 have heard of or is this something that only the 0:08:55.240 --> 0:08:58.319 cool kids on physics TikTok know about? And so is 0:08:58.480 --> 0:09:00.760 Daniel went out there into the files of the Internet 0:09:00.800 --> 0:09:04.520 to ask people what they know about the axion particle. 0:09:04.679 --> 0:09:07.720 So thank you to everybody who volunteered to answer random 0:09:07.840 --> 0:09:12.240 Internet questions and sending in your responses. If you'd like 0:09:12.280 --> 0:09:16.400 to participate in random person on the street internet questions, 0:09:16.600 --> 0:09:19.360 then please write to us at questions at Daniel and 0:09:19.440 --> 0:09:22.440 Jorge dot com. Before you hear these answers, think about 0:09:22.480 --> 0:09:24.520 it for a second and someone as you if you 0:09:24.600 --> 0:09:28.719 knew what the axion particle was, what would you say. 0:09:29.000 --> 0:09:31.200 Here's what people had to say. I think this is 0:09:31.440 --> 0:09:36.360 a way to classify particles. They like they can be axion, 0:09:36.559 --> 0:09:41.680 some boat songs and it has to do with them, 0:09:41.840 --> 0:09:45.079 for example, having mass or not. I don't know. I 0:09:45.760 --> 0:09:50.880 guess action access would perhaps be some sort of particle 0:09:50.960 --> 0:09:54.560 that other particles turn around. I have no idea but 0:09:54.640 --> 0:09:56.520 since it sounds like the word axel, I'm going to 0:09:56.600 --> 0:09:59.240 guess it has something to do with joining other particles together. 0:09:59.520 --> 0:10:03.000 I have no idea. I don't know. I think that's 0:10:03.040 --> 0:10:07.240 to do with what doll matter is might of I 0:10:07.360 --> 0:10:12.960 believe there are two options, are actions or whimps. Honestly, 0:10:12.960 --> 0:10:14.840 I have no idea. Because it has the word ion 0:10:14.840 --> 0:10:16.800 in it, maybe it's some kind of ion. It's got 0:10:17.240 --> 0:10:22.320 no idea. I never heard about something called axiom. Yeah, 0:10:22.360 --> 0:10:25.840 of course that's an elementary particle of an action figure 0:10:26.000 --> 0:10:30.760 the Caveman scientists in your book discussing what the most 0:10:30.800 --> 0:10:34.920 fundamental particle of a stone ax would be. I assume 0:10:36.000 --> 0:10:42.560 it's not a standard particle. Maybe it's more like strange matter. 0:10:43.040 --> 0:10:47.040 All right, not a lot of positive recognition there. I 0:10:47.080 --> 0:10:49.240 like the one that said it's it's an action figure, 0:10:49.360 --> 0:10:51.960 or it's related to an action figure, the fundamental element 0:10:52.000 --> 0:10:55.040 of an action figure. That makes a lot of sense. Well, 0:10:55.040 --> 0:10:57.080 if it does exist and it is part of nature, 0:10:57.120 --> 0:11:00.640 it could be part of all action figures. It could be. 0:11:00.880 --> 0:11:03.040 And the other great idea was the that maybe it's 0:11:03.040 --> 0:11:06.160 related to axles, so maybe like joins particles together at 0:11:06.200 --> 0:11:08.920 this some really creative responses here, I'm impressed, or maybe 0:11:08.960 --> 0:11:11.240 they were thinking like Axel Rose and like oh, I'm 0:11:11.240 --> 0:11:14.439 a gone some Roses fan, in which case the Axon's 0:11:14.480 --> 0:11:17.439 career has to also be in the dusk. Yeah, they 0:11:17.480 --> 0:11:20.840 better get on that physics TikTok right away. Some silly dances. 0:11:20.880 --> 0:11:22.679 But it did seem like none of these folks had 0:11:22.720 --> 0:11:25.240 heard of this particle or really had any clue about 0:11:25.240 --> 0:11:28.960 its incredibly important role in particle physics. Man, well, I 0:11:28.960 --> 0:11:32.400 would count myself among those numbers. I had no idea 0:11:32.480 --> 0:11:34.840 what this and have no idea of what this particle 0:11:35.480 --> 0:11:38.319 is before he sent me the outline for today's episode. 0:11:38.360 --> 0:11:40.960 But let's get into it, Daniel, what is the axion? 0:11:41.040 --> 0:11:45.200 It sounds kind of important but maybe not yet discovered. Yeah, 0:11:45.240 --> 0:11:48.800 the axion particle is totally theoretical, so we do not 0:11:49.000 --> 0:11:51.640 know if it's part of our universe at all. It 0:11:51.720 --> 0:11:54.679 may just be an idea in people's minds. And remember 0:11:54.920 --> 0:11:58.160 there's been a lot more ideas than actual particles. And 0:11:58.240 --> 0:12:01.640 sometimes these ideas are beautiful, they make perfect sense, and 0:12:01.679 --> 0:12:04.280 when the physicist has them, they go, Wow, everything is 0:12:04.320 --> 0:12:07.400 connected and this is the way the universe works. But 0:12:07.440 --> 0:12:09.600 then you go and you ask the universe like is 0:12:09.600 --> 0:12:12.880 it real? And Uver says, nice idea, but no, isn't 0:12:12.880 --> 0:12:14.960 that kind of strange? I feel like that's almost like 0:12:14.960 --> 0:12:18.160 trying to discover new animals by thinking of them before 0:12:18.200 --> 0:12:21.720 you actually find. It's like, oh, what if there's an 0:12:21.760 --> 0:12:24.760 animal with a duck bill, but then at a dinosaur 0:12:24.880 --> 0:12:27.480 nag and then butterfly wings, and then you go out 0:12:27.520 --> 0:12:30.040 looking for them. Wouldn't that be kind of not productive? Yeah? Well, 0:12:30.040 --> 0:12:32.280 but to stretch the you know, mixed metaphor of our 0:12:32.360 --> 0:12:35.360 rabbit holes here, it's more like that you see evidence 0:12:35.400 --> 0:12:38.440 for this animal. It's like what's eating all the deer? 0:12:38.880 --> 0:12:41.120 And you know, I see all these strange footprints, and 0:12:41.360 --> 0:12:43.800 maybe that would be explained if there was this new 0:12:43.880 --> 0:12:46.760 predator out there I've never seen before. And so you're 0:12:46.760 --> 0:12:49.520 trying to like tie up loose ends and complete the 0:12:49.559 --> 0:12:53.320 picture by suggesting an explanation. And that's exactly what the 0:12:53.360 --> 0:12:56.760 axion and a lot of other theoretically motivated particles do, 0:12:56.880 --> 0:12:58.840 is they sort of trying to tie together what we 0:12:58.920 --> 0:13:01.760 see in a small all are more compact explanation. It's 0:13:01.800 --> 0:13:04.280 just been a pretty horrible picture of this animal. Daniel 0:13:04.760 --> 0:13:08.000 because around eating deer. Oh my goodness, it's like a 0:13:08.040 --> 0:13:12.840 wolf man. You're trying to go for a cool animal wolf, 0:13:12.960 --> 0:13:15.400 the duck bill and butterfly wings. It does sound pretty cool. 0:13:15.400 --> 0:13:16.840 That does sound pretty cool. I want to see that 0:13:16.880 --> 0:13:19.079 animal if it exists, and you can name it. We 0:13:21.080 --> 0:13:23.360 already use that name for something else. That would be 0:13:23.440 --> 0:13:27.840 so confusing. But what if you find animal first, right, Like, 0:13:27.880 --> 0:13:29.840 what if you find animal and call it the axion 0:13:30.000 --> 0:13:32.560 before you discover this particle. I think we've already used 0:13:32.600 --> 0:13:34.760 up the name though. That's sort of like, you know 0:13:34.800 --> 0:13:38.959 how the Space Force television show on Netflix has trademarked 0:13:38.960 --> 0:13:42.080 the term Space Force before the actual US Space Force 0:13:42.120 --> 0:13:47.880 got around doing it. Oh that's a problem. That's a problem, yeah, exactly. Anyway, 0:13:47.920 --> 0:13:51.360 back to particle physics, the axion, if it exists, is 0:13:51.400 --> 0:13:55.679 a lot like a photon, but it doesn't have zero mass. 0:13:55.760 --> 0:14:01.440 It has a super tiny, little whispy mask really massive photon. Yeah, 0:14:01.480 --> 0:14:03.640 but it's not very massive. Like the mass if it 0:14:03.720 --> 0:14:07.840 has some is like two hundred billion of the mass 0:14:07.840 --> 0:14:11.480 of the electron, which is already one of the lightest particles. 0:14:12.679 --> 0:14:16.640 So it's like a light light particle. It's like light light. Exactly. 0:14:16.880 --> 0:14:19.640 It's very light light light, but not quite light, not 0:14:19.720 --> 0:14:23.880 quite light. It's not coke zero. It's like coke light, Yeah, exactly, 0:14:23.960 --> 0:14:25.520 it's that coke with a tiny little bit of real 0:14:25.560 --> 0:14:28.240 sugar in it, right, Um, And why did somebody come 0:14:28.320 --> 0:14:29.720 up with this, Well, they came up with it to 0:14:29.840 --> 0:14:33.000 sort of answer the biggest problem in physics that nobody 0:14:33.040 --> 0:14:35.800 ever heard of, which is, we're looking at the way 0:14:35.840 --> 0:14:39.440 that interactions happen in physics, and we noticed something weird, 0:14:39.480 --> 0:14:41.760 something that we cannot explain. And so it's sort of 0:14:41.960 --> 0:14:45.040 thought up to explain this other mystery the same way 0:14:45.120 --> 0:14:48.000 you know, you might hypothesize wolves if you see your 0:14:48.080 --> 0:14:51.240 dear missing. This is sort of like hypothesizing the axon 0:14:51.320 --> 0:14:54.240 to explain this other problem, which is called the strong 0:14:54.360 --> 0:14:57.880 CP problem. Interesting, and now is its official title, the 0:14:57.920 --> 0:15:00.920 biggest problem with notity has ever heard of? Like, do 0:15:00.960 --> 0:15:03.240 you guys talk about it that way? Yeah, it's sort 0:15:03.240 --> 0:15:05.880 of a famous problem that nobody really has any answer 0:15:05.920 --> 0:15:09.560 to except the axio. And so that's why people think 0:15:09.560 --> 0:15:12.240 the axon might really be real. And then we'll talk 0:15:12.320 --> 0:15:15.040 later in the program about how it could also simultaneously 0:15:15.120 --> 0:15:18.960 solve another huge problem, which makes the axon sort of 0:15:18.960 --> 0:15:22.160 a sexy particle right now. But it was originally dreamt 0:15:22.240 --> 0:15:25.479 up to solve this other problem called the strong CP problem. 0:15:25.520 --> 0:15:28.240 So what what's the strong CP problem? So this problem 0:15:28.320 --> 0:15:31.120 has to do with basically, why does the strong force 0:15:31.480 --> 0:15:34.560 not break some symmetries and particle physics, we have all 0:15:34.600 --> 0:15:39.400 these symmetries like charge symmetry and parity symmetry and time symmetry. 0:15:39.640 --> 0:15:43.360 These symmetries tell us whether something works the same when 0:15:43.400 --> 0:15:46.360 you flip it the other way. Like, if we say 0:15:46.440 --> 0:15:48.880 something could happen to an electron, we ask, well, can 0:15:48.920 --> 0:15:51.640 the same thing happen to a positron, which is the 0:15:51.680 --> 0:15:55.640 opposite charge version of it. Because we like symmetries in 0:15:55.680 --> 0:15:57.920 particle physics, we like the smallest set of rules, so 0:15:57.920 --> 0:16:00.000 we don't want a different set of rules for electron 0:16:00.040 --> 0:16:02.800 ones and for positrons for example. So it's kind of like, 0:16:02.840 --> 0:16:05.560 you know, like if two negative electrons propel each other, 0:16:06.120 --> 0:16:09.640 you can ask, like to positive electrons propel each other too, 0:16:09.720 --> 0:16:11.840 and if they do, then that means it's like symmetric. 0:16:11.960 --> 0:16:14.280 That's right, it's symmetric in charge. If you flip the 0:16:14.360 --> 0:16:16.120 charge and you get the same thing, and then it's 0:16:16.120 --> 0:16:18.680 symmetric in charge, and so we call that C for 0:16:19.160 --> 0:16:22.640 charge symmetry, and we ask that question about everything, and 0:16:22.760 --> 0:16:28.040 electromagnetism is charge symmetric. Everything that happens in electromagnetism would 0:16:28.040 --> 0:16:30.520 happen the same way if you flipped all of the charges, 0:16:30.600 --> 0:16:33.760 not just one, but all of the charges, okay. And 0:16:33.800 --> 0:16:37.400 then the second one is called P for parity violation, 0:16:37.520 --> 0:16:39.600 and that says, would the same thing happen if you 0:16:39.680 --> 0:16:42.400 did it in the mirror. So, if you like set 0:16:42.440 --> 0:16:46.320 up some particle experiment or particle decays to two other ones, 0:16:46.400 --> 0:16:49.480 or two particles collide into each other or whatever, and 0:16:49.520 --> 0:16:52.040 then you put that experiment in front of a mirror, 0:16:52.280 --> 0:16:54.360 the thing that happens in the mirror is not exactly 0:16:54.400 --> 0:16:56.600 the same as the thing that's happening in real life. 0:16:56.680 --> 0:16:59.960 It's flipped in one dimension. Yeah, a mirror will flip 0:17:00.160 --> 0:17:03.560 like the Z axis, for example, the axis perpendicular to 0:17:03.600 --> 0:17:06.160 the mirror, but not the other two. So, for example, 0:17:06.200 --> 0:17:08.720 if you hold up your left hand in front of 0:17:08.720 --> 0:17:10.760 a mirror, then it looks like your right hand doesn't 0:17:10.760 --> 0:17:14.440 look like your left hand, and so your hand has parody. 0:17:14.480 --> 0:17:17.639 It's not parody symmetric, right, because it doesn't look the 0:17:17.680 --> 0:17:20.160 same in the mirror. Doesn't look the same, but like 0:17:19.720 --> 0:17:21.879 a like a ball does sort of look like a 0:17:21.920 --> 0:17:25.600 perfectly round ball with no drawings or features on it 0:17:25.640 --> 0:17:28.119 does is parody symmetric because it looks the same in 0:17:28.160 --> 0:17:30.840 the mirror exactly. So for a long time, this is 0:17:30.840 --> 0:17:34.200 this thought that all of particle physics was charged symmetric 0:17:34.680 --> 0:17:37.800 and parody symmetric because it just sort of made sense, right, 0:17:38.080 --> 0:17:40.000 and this is like to do that. They say, the 0:17:40.160 --> 0:17:43.080 universe is beautiful and natural, and so it should follow 0:17:43.119 --> 0:17:45.600 this rule, Like it'd be weird if the electron looked 0:17:45.640 --> 0:17:47.680 like my right hand in front of the mirror, or 0:17:47.720 --> 0:17:49.960 if you had electrons for hands, that would also be weird, 0:17:50.240 --> 0:17:52.960 but for different reasons. And for a long time, everybody 0:17:52.960 --> 0:17:55.959 assumed that everything followed all these rules. And then in 0:17:56.000 --> 0:17:59.359 the fifties people realized, oh, nobody had ever actually checked this. 0:17:59.640 --> 0:18:02.080 For the weak force, we had a whole episode we 0:18:02.160 --> 0:18:06.160 dug into how the weak force actually violates parity. Interesting, Yeah, 0:18:06.200 --> 0:18:08.160 if you have a reaction in the mirror, it looks 0:18:08.359 --> 0:18:12.080 different than the reaction you're having like in your actual laboratory. 0:18:12.119 --> 0:18:14.880 And when we're talking about these These are particles, right, 0:18:14.920 --> 0:18:17.800 so they don't have features like hands, but they'll do 0:18:17.920 --> 0:18:20.560 things like they'll turn a certain way in a magnetic field, 0:18:20.680 --> 0:18:23.000 or they'll they'll react a certain way when they hit 0:18:23.080 --> 0:18:25.760 something else. Right. Yeah, the experiment that discovers the violation 0:18:25.800 --> 0:18:28.000 of parody did just that. It like takes a bunch 0:18:28.000 --> 0:18:31.360 of nuclei, aligns them in a magnetic field, and then 0:18:31.440 --> 0:18:34.480 watches the direction that they emit electrons. Is it like 0:18:34.520 --> 0:18:37.280 in the same direction as the magnetic field or backwards? 0:18:37.920 --> 0:18:40.760 And that's a fascinating experiment that if you're interested in 0:18:40.800 --> 0:18:43.320 you should dig into that whole podcast episode. But for 0:18:43.359 --> 0:18:45.760 a whild people thought, okay, parody is violated by the 0:18:45.800 --> 0:18:50.280 weak force. What about the combination of charge and parody? 0:18:50.359 --> 0:18:53.479 So put it in the mirror and flip the charge, 0:18:53.560 --> 0:18:56.359 so that says, will an electron look the same if 0:18:56.400 --> 0:18:58.200 you put it in the mirror and turn it into 0:18:58.240 --> 0:19:02.399 a positron? And then we discovered that that the weak 0:19:02.440 --> 0:19:06.000 force actually violates this also, so we call this c P. 0:19:06.800 --> 0:19:10.040 If an interaction or a particle physics thing that happens 0:19:10.480 --> 0:19:13.000 violates CP, it means that it doesn't look the same 0:19:13.160 --> 0:19:15.479 when you flip the charge and put it in the mirror. 0:19:15.520 --> 0:19:20.280 So and so the weak force violates parody, and it 0:19:20.320 --> 0:19:24.439 also violates charge and parody. That's right now violates parody 0:19:24.440 --> 0:19:27.520 big time. It's like a really big violation. And that 0:19:27.600 --> 0:19:30.320 was a Nobel prize. And then people thought, well, it 0:19:30.400 --> 0:19:33.760 must then preserve CP. It must be that parody is violated, 0:19:33.800 --> 0:19:36.440 but the combination of these two things is still preserved. 0:19:36.640 --> 0:19:39.760 And then they discovered that they violates CP, and that 0:19:39.880 --> 0:19:43.280 was another Nobel prize. So that's the weak force. A 0:19:43.320 --> 0:19:46.280 weak force violates CP, and that was sort of surprising. 0:19:46.280 --> 0:19:49.120 But then people realized, well why not, I mean, why 0:19:49.160 --> 0:19:52.560 shouldn't these things violate CP. They looked at the way 0:19:52.600 --> 0:19:54.439 that we write down these interactions and the way we 0:19:54.560 --> 0:19:57.119 understand these theories, and we say, well, it's actually totally 0:19:57.200 --> 0:20:00.000 natural for them to violate CP. So like the theorist 0:20:00.040 --> 0:20:03.760 went from that's impossible, that's absurd, to actually make a 0:20:03.800 --> 0:20:06.359 perfect sense. All right, Well, it sounds like there's a 0:20:06.400 --> 0:20:08.640 lot going on with the weak force here. It violates 0:20:08.640 --> 0:20:11.119 all kinds of symmetries, and so let's talk about some 0:20:11.160 --> 0:20:13.720 of the other forces and how that could maybe lead 0:20:13.760 --> 0:20:16.320 people to come up with a brand new particle called 0:20:16.359 --> 0:20:32.800 the axion. But first let's take a quick break. All right, Diane, 0:20:32.880 --> 0:20:36.840 we're we're talking about a potentially existing particle with a 0:20:36.840 --> 0:20:39.560 cool name called the axion, and you're telling me that 0:20:39.600 --> 0:20:43.080 it's definitely related to this idea of the CP problem, 0:20:43.080 --> 0:20:46.240 which is like a problem in theoretical physics about the 0:20:46.320 --> 0:20:50.359 symmetry of particles and whether or not they act the 0:20:50.400 --> 0:20:53.240 same way in all kinds of situations. And so we 0:20:53.359 --> 0:20:57.679 talked about how the weak force doesn't follows parody or 0:20:57.760 --> 0:21:01.480 charged parody symmetry, and so and and that's now become 0:21:01.480 --> 0:21:03.880 the normal. Before we gave them people a norval price. 0:21:03.920 --> 0:21:06.080 We're figuring that out. But now it's like, okay, that's 0:21:06.119 --> 0:21:09.120 the way, that's right. We realize that it's actually not 0:21:09.280 --> 0:21:12.719 outrageous for the weak force to violate CP. And then 0:21:12.720 --> 0:21:14.720 we looked at the other forces. We said, you know, 0:21:14.840 --> 0:21:18.359 the same thing that allows the weak force to violate CP, 0:21:18.960 --> 0:21:21.720 why doesn't it also allow the strong force to do it? Like, 0:21:21.760 --> 0:21:25.600 the strong force could also violate CP, No big deal, 0:21:25.760 --> 0:21:28.520