WEBVTT - Does the weak force attract or repel? 0:00:08.720 --> 0:00:12.400 Hey, Jorge, do the mysteries of physics pull you in 0:00:12.640 --> 0:00:17.239 or do they make you runaway screaming? You mean, does 0:00:17.320 --> 0:00:20.959 physics attract me or repel me? That's right, you know 0:00:21.000 --> 0:00:23.240 if you want to think about it physically. Now, are 0:00:23.239 --> 0:00:26.720 we talking about physics or physicists? No, the whole shebang. 0:00:26.800 --> 0:00:29.960 You can't separate the physics from the physicists. Well, you know, 0:00:30.000 --> 0:00:32.120 I kind of like the big questions that physics as 0:00:32.200 --> 0:00:35.000 they're pretty exciting, but you know, it's phys the math 0:00:35.120 --> 0:00:37.720 and all the jargon. It's kind of a little bit 0:00:37.720 --> 0:00:39.360 hard to put up with. So it's a little bit 0:00:39.400 --> 0:00:41.440 of a push an pole. That's right. Every time I 0:00:41.479 --> 0:00:44.040 think I'm free of physics, it just pulls me back in. 0:00:45.000 --> 0:00:48.040 We're like the mob. You're the al Pacina of physics, 0:00:49.159 --> 0:00:51.440 and you are the pun father. Now you're more like 0:00:51.479 --> 0:01:10.319 the dawn coreole is physics. Hi am Jorge, I'm your 0:01:10.360 --> 0:01:13.319 cartoonists and the creator of PhD comics. Hi, I'm Daniel. 0:01:13.360 --> 0:01:16.240 I'm a particle physicist and a professor U c Irvine. 0:01:16.319 --> 0:01:19.080 And I'm still laughing about that. Don coriole with joke. 0:01:20.400 --> 0:01:23.640 Do you need a break here? No? But I do 0:01:23.760 --> 0:01:27.679 love the idea of somebody who's like a master of physics, 0:01:28.200 --> 0:01:30.640 you know, like the godfather of physics. But you know, 0:01:30.720 --> 0:01:34.240 we just lost somebody who many people consider the godfather 0:01:34.400 --> 0:01:37.640 of the weak force and the standard model. Stephen Weinberg 0:01:37.720 --> 0:01:40.280 and Professor Ut Austin, who won the Nobel Prize forty 0:01:40.360 --> 0:01:43.399 years ago, just passed away last week. So rest in 0:01:43.440 --> 0:01:46.160 peace to one of the giants of the twentieth century. 0:01:46.360 --> 0:01:49.280 Oh man, rest in peace. Yeah. So who's gonna take 0:01:49.280 --> 0:01:53.280 the mantle of the godfather now of physics? I don't know, 0:01:53.320 --> 0:01:55.080 because the stakes are high, right, you gotta win the 0:01:55.120 --> 0:01:58.080 Oscar for the sequel also, and then not flubb it 0:01:58.160 --> 0:02:00.960 on the third moviee on the third a prize. You know, 0:02:01.320 --> 0:02:02.960 it's got to be as good as the rest. But 0:02:03.000 --> 0:02:05.680 welcome to our podcast Daniel and Jorge Explain the Universe, 0:02:05.760 --> 0:02:08.000 a production of Our Heart Radio in which we try 0:02:08.040 --> 0:02:11.640 to make you the godfather of everything in the universe. 0:02:11.919 --> 0:02:14.280 We try to give you an understanding of how things 0:02:14.320 --> 0:02:16.920 work at the very smallest scale. We share with you 0:02:17.040 --> 0:02:21.120 what humanity has accomplished in terms of understanding the true 0:02:21.240 --> 0:02:24.960 nature of reality around us, the context of our lives, 0:02:25.240 --> 0:02:30.079 the long cosmic stretch of history, the crazy, violent events 0:02:30.160 --> 0:02:33.600 that have led to our existence, and everything in between. 0:02:33.800 --> 0:02:37.120 We ask questions about the very nature of time and space, 0:02:37.400 --> 0:02:40.079 and we do our best to answer them. That's right, 0:02:40.120 --> 0:02:43.519 because it is a pretty wonderful universe, full of amazing 0:02:43.560 --> 0:02:48.800 and incredible forces and energies, and places to explore and 0:02:48.960 --> 0:02:53.919 particles to discover, full of intriguing mysteries and sometimes weak questions. 0:02:54.160 --> 0:02:57.520 That's right. It really is incredible to me how varied 0:02:57.720 --> 0:03:02.960 and complex and gorgeous and strange the university is. You know, 0:03:03.040 --> 0:03:06.040 it's filled with bananas and movies and all sorts of 0:03:06.080 --> 0:03:08.560 silly things. And then when you take it apart, you 0:03:08.560 --> 0:03:11.760 find that at its microscopic level, it's nature is fundamentally 0:03:11.800 --> 0:03:14.520 totally different, which means that everything we know about the 0:03:14.600 --> 0:03:18.120 universe is not fundamental. It's instead, it's emergent. It's just 0:03:18.240 --> 0:03:21.360 like an accident of how things come together. And so 0:03:21.440 --> 0:03:24.560 the real majesty of the universe, the real like nature 0:03:24.720 --> 0:03:27.640 of the reality around us, is embedded in how the 0:03:27.720 --> 0:03:30.720 basic bits are put together, and so the rules that 0:03:30.840 --> 0:03:33.840 govern how those bits come together and how they interact 0:03:33.919 --> 0:03:36.640 or how they don't interact, is really what leads to 0:03:36.720 --> 0:03:40.040 things like ice cream and movies and bananas, and so 0:03:40.120 --> 0:03:42.680 it's fascinating to me how the world exists at these 0:03:42.880 --> 0:03:45.320 different scales and we can somehow pull them apart and 0:03:45.400 --> 0:03:48.080 understand them at all different levels. Yeah, I guess that. 0:03:48.120 --> 0:03:50.160 You know, the universe is pretty majestic at like the 0:03:50.280 --> 0:03:53.560 gaxy level, at the nebula level, it's pretty amazing, And 0:03:53.600 --> 0:03:57.640 it's also pretty fascinating at like the smallest, tiniest levels 0:03:57.640 --> 0:04:00.880 that you can possibly get right at the quant level. Yeah, 0:04:00.920 --> 0:04:02.920 And that's sort of a philosophical question, like why do 0:04:03.040 --> 0:04:06.040 we find the universe majestic and beautiful? Could it have 0:04:06.120 --> 0:04:08.000 been that we like look at galaxies and we're like 0:04:08.720 --> 0:04:11.200 kind of an ugly smear. But instead, you know, we 0:04:11.200 --> 0:04:14.960 look at them, were like wow, maybe evolution filtered for 0:04:15.120 --> 0:04:19.880 optimists or our internal physicists, you know, somehow made to survive. Yeah, 0:04:19.960 --> 0:04:22.799 because we also find a lot of the Earth beautiful. 0:04:22.839 --> 0:04:24.920 You know, we see vistas, were like, wow, we're lucky 0:04:24.960 --> 0:04:27.320 you'll live here. Could we have evolved on a planet 0:04:27.360 --> 0:04:29.800 where we're like, man, this place is a dump. It 0:04:29.880 --> 0:04:32.240 makes me wonder sometimes, right, or maybe like there are 0:04:32.279 --> 0:04:34.680 aliens who grew up in a totally turned planet. Who think, 0:04:34.800 --> 0:04:38.520 are you know beautiful mountains and trees and rivers are 0:04:38.640 --> 0:04:42.200 are ugly or boring? Yeah? Exactly. The aliens who grew 0:04:42.279 --> 0:04:44.440 up in Irvine and they prefer Beiji. They don't like 0:04:44.520 --> 0:04:48.000 color or liveliness. Oh man, that would be terrible if 0:04:48.000 --> 0:04:51.080 we met aliens and they're like, Wow, your suburbs are nice, 0:04:51.160 --> 0:04:56.560 but these forests make it all like Irvine. Right where 0:04:56.560 --> 0:04:58.719 did the aliens come and they tear down everything beautiful 0:04:58.720 --> 0:05:00.840 and they just build subdivision. Well, then we should move 0:05:00.880 --> 0:05:03.480 to their planet because then their their planet must be gorgeous. 0:05:04.240 --> 0:05:06.440 That sounds good. But rolling back up to what we 0:05:06.440 --> 0:05:09.479 were talking about, I think it's amazing how many incredible 0:05:09.520 --> 0:05:11.320 things there are in our universe and how it all 0:05:11.400 --> 0:05:14.440 just comes out of how the little bits interact. You know, 0:05:14.480 --> 0:05:17.200 the nature of your body is mostly determined by the 0:05:17.240 --> 0:05:20.480 strength of the electromagnetic force. The structure of the atom 0:05:20.600 --> 0:05:23.400 is mostly due to a combination of the strong force 0:05:23.480 --> 0:05:27.039 and electromagnetism. The structure of the galaxy comes from the 0:05:27.120 --> 0:05:29.960 nature of gravity. It's really the forces that shape the 0:05:30.120 --> 0:05:33.359 very fabric of reality as we experience it. Yeah, the 0:05:33.440 --> 0:05:36.480 forces are pretty good, because without forces, the universe would 0:05:36.480 --> 0:05:38.520 be pretty boring, right, I mean, the forces in the 0:05:38.600 --> 0:05:41.680 universe are what makes things stick together and do things 0:05:41.839 --> 0:05:44.000 right and move, Otherwise it would be a pretty um 0:05:44.279 --> 0:05:46.599 static universe. Yeah, you could say they forced it to 0:05:46.640 --> 0:05:48.600 be interesting. It was a bit of a force joke there. 0:05:48.640 --> 0:05:51.880 Then don't force my hand or I'll make some more. Yeah. 0:05:51.880 --> 0:05:53.839 We like to talk about the giant things in the universe, 0:05:53.880 --> 0:05:55.840 but we also like to talk about the little things, 0:05:55.880 --> 0:05:58.839 like the forces that keep our particles together or repel 0:05:58.920 --> 0:06:01.880 them or or make them do interesting things. And so 0:06:01.960 --> 0:06:05.159 today we'll be talking about one specific question about one 0:06:05.160 --> 0:06:07.479 of the fundamental forces. That's right. And this is a 0:06:07.520 --> 0:06:09.840 super fun question for me because it came from a 0:06:09.839 --> 0:06:12.880 listener who attended one of my public office hours when 0:06:12.920 --> 0:06:15.160 I just hang out on Zoom and answer physics questions 0:06:15.160 --> 0:06:17.600 from all comers. And this one came from an organic 0:06:17.680 --> 0:06:20.960 chemistry professor who asked me a pretty tough question that 0:06:21.040 --> 0:06:24.400 I didn't know the answer to. Wow, was that scary? 0:06:24.480 --> 0:06:27.240 Did you freeze the panic? No, those public office hours 0:06:27.240 --> 0:06:29.560 are pretty low key, and I often get asked questions 0:06:29.600 --> 0:06:31.080 I don't know the answer to, and I just try 0:06:31.120 --> 0:06:33.440 to figure them out on the fly. Hoping that people 0:06:33.440 --> 0:06:36.920 appreciate seeing a physicist like make mistakes and back up 0:06:36.960 --> 0:06:39.440 and hopefully figure it out. All right, Well, let's get 0:06:39.440 --> 0:06:42.680 to the question that Daniel at his office hours. So 0:06:42.720 --> 0:06:50.039 today on the program, we'll be asking the question does 0:06:50.120 --> 0:06:55.120 the weak force attract or repel? Now, Daniel, is that 0:06:55.240 --> 0:06:58.320 repel or repel? How exciting is the week? The weak 0:06:58.360 --> 0:07:01.000 force likes to go climbing, elects to bouldering. I don't 0:07:01.080 --> 0:07:03.800 know if it likes to repel down cliffs. Also, it's 0:07:03.839 --> 0:07:07.039 too weak to do it. It just lays in bed 0:07:07.080 --> 0:07:09.760 and complains until somebody brings it lunch. Well, that's a 0:07:09.760 --> 0:07:12.720 pretty interesting question. Does the weak force attract or repel? 0:07:12.960 --> 0:07:15.200 I guess are there only two options? Can the force 0:07:15.280 --> 0:07:17.880 only attract or repel? Or can it do something else like, 0:07:18.240 --> 0:07:21.480 I don't know, push you sideways or this interest you? 0:07:21.720 --> 0:07:23.760 That's an awesome question, and no forces can do other 0:07:23.800 --> 0:07:26.680 things than just attract or repel. Will dig into it 0:07:26.720 --> 0:07:29.520 in the podcast. Some forces can do things like change 0:07:29.600 --> 0:07:31.840 the nature of a particle. You know, change you from 0:07:31.840 --> 0:07:34.160 an electron to a neutrino, for example, so you know 0:07:34.200 --> 0:07:36.200 you might end up in a different direction and be 0:07:36.280 --> 0:07:39.000 a different particle, so it's more complex than just getting 0:07:39.040 --> 0:07:41.960 pushed or pulled. And the force of magnetism can do 0:07:42.000 --> 0:07:45.400 things like turn you doesn't change your overall speed, but 0:07:45.480 --> 0:07:48.240 it bends your path. So there's all sorts of complicated, 0:07:48.280 --> 0:07:50.440 amazing things that forces can do. But I think the 0:07:50.480 --> 0:07:53.360 fundamental thing they do seems to be either pull things 0:07:53.360 --> 0:07:55.640 together and hold them tights so they can build up 0:07:55.640 --> 0:07:58.560 and make complex things like bananas and ice cream, or 0:07:58.880 --> 0:08:02.040 push things apart keep them from forming complex structure. And 0:08:02.080 --> 0:08:05.360 this is a pretty fundamental question because the weak force 0:08:05.560 --> 0:08:08.080 is one of the four fundamental forces. Like there are 0:08:08.120 --> 0:08:11.840 only four forces in the entire universe, right, that four 0:08:11.880 --> 0:08:14.400 forces that make everything work, and this is one of them. Yeah, 0:08:14.480 --> 0:08:17.120 although stein Weinbergley Nobel Prize Laurier we just talked about, 0:08:17.200 --> 0:08:20.840 he's the guy who brought together the weak force with electromagnetism. 0:08:21.160 --> 0:08:23.920 He showed that really it's one force, which we now 0:08:23.960 --> 0:08:27.040 call electro week. So depending on how you count, there 0:08:27.080 --> 0:08:30.640 either three fundamental forces or four fundamental forces. In the 0:08:30.640 --> 0:08:34.120 case where it's three, there's gravity, the strong force, and 0:08:34.160 --> 0:08:37.080 the electro weak force. In the case where there's four, 0:08:37.160 --> 0:08:40.040 you break up electro week into the weak force and 0:08:40.160 --> 0:08:43.559 electricity magnetism. All right, well, we'll get into that, but 0:08:43.720 --> 0:08:46.120 first we were wondering how many people out there knew 0:08:46.240 --> 0:08:48.920 whether the weak force attracts or repel or hadn't even 0:08:48.920 --> 0:08:51.360 thought about this question. So Daniel went out there into 0:08:51.400 --> 0:08:54.240 the internet to ask people does the weak force attract 0:08:54.559 --> 0:08:56.840 or repel? So thank you everybody out there in the 0:08:56.880 --> 0:08:59.320 Internet who was willing to play this simply physics game. 0:08:59.440 --> 0:09:01.160 And if you would like to be asked questions that 0:09:01.240 --> 0:09:04.079 stumped physics professor and hear your answers on the podcast, 0:09:04.160 --> 0:09:07.360 please write to us two questions at Daniel and Jorge 0:09:07.400 --> 0:09:09.520 dot com. Think about it for a second. What would 0:09:09.520 --> 0:09:12.160 you answer? Here's what people had to say. I can't 0:09:12.160 --> 0:09:15.240 remember exactly what the weak force is all about, so 0:09:15.320 --> 0:09:20.000 I'm going to say maybe neither or both. On this one. 0:09:20.000 --> 0:09:22.560 I'm gonna have to say, I'm gonna guess that the 0:09:22.640 --> 0:09:28.720 weak force repels. And I'm going to say that because 0:09:29.800 --> 0:09:32.200 things in the universe seemed to be, for the most 0:09:32.240 --> 0:09:36.360 part stuck together, and I have kind of thought that 0:09:36.400 --> 0:09:40.360 the weak force and the strong force are working against 0:09:40.360 --> 0:09:44.520 each other. So if everything is stuck together, I'm going 0:09:44.600 --> 0:09:47.760 to say that the strong force overpowers that weak force, 0:09:48.120 --> 0:09:52.520 and uh, that's why you know we are in clumps 0:09:52.559 --> 0:09:56.200 of atoms instead of just spread out everywhere as gas 0:09:56.280 --> 0:09:59.400 all the time. I guess I think the strong force 0:09:59.440 --> 0:10:04.640 attract so that maybe the weak force repels. I genuinely 0:10:04.679 --> 0:10:08.160 don't know that's the weak force repellent tract. I want 0:10:08.160 --> 0:10:11.920 to say maybe both. Although it holds party together, is 0:10:12.920 --> 0:10:15.920 what would the structures? I guess it would also have 0:10:16.080 --> 0:10:20.000 to retell stuff that it doesn't want to react with 0:10:20.920 --> 0:10:23.120 and allow in. I don't know. I feel like I 0:10:23.160 --> 0:10:26.720 should know, but I just don't know. I've actually never 0:10:26.800 --> 0:10:30.280 understood if the week fourth attractor repelled or they know? 0:10:30.480 --> 0:10:33.360 Is that the fourth profable for sometimes a productive the 0:10:33.440 --> 0:10:37.120 key like the bit of the kyform me from particles 0:10:37.400 --> 0:10:43.600 into order particles, So like electronics tretrino. If I remember, well, 0:10:44.120 --> 0:10:50.640 the gravitational force is the only one that attracts. Only 0:10:52.160 --> 0:10:57.040 the rest of them attract and repose. So the weak 0:10:57.080 --> 0:11:02.199 force attracts any repels. Not sure if it's the same 0:11:03.120 --> 0:11:07.840 like an electromagnetic force, but I know that it detracts 0:11:07.840 --> 0:11:11.120 any pills. I gotta say I was pretty relieved that 0:11:11.160 --> 0:11:14.240 these folks also didn't know the answer they had. Would 0:11:14.280 --> 0:11:17.280 you feel inadequate as a physicist? Yeah, I would have 0:11:17.360 --> 0:11:19.560 to give up my professorship. I would have lost it 0:11:19.600 --> 0:11:22.560 in physics combat. Oh man, I gotta get like a 0:11:22.600 --> 0:11:25.520 Nobel Price winner to be one of your respondents just 0:11:25.600 --> 0:11:28.640 to sabotage you. You gotta get a ringer in there, 0:11:28.679 --> 0:11:31.920 just to set me up. But so this surprising, and 0:11:31.920 --> 0:11:35.040 this question came from an organic chemistry professor. That's pretty cool. 0:11:35.240 --> 0:11:36.680 Are you going to take revenge now and go to 0:11:36.760 --> 0:11:39.280 his office hours and give him a really tough organic 0:11:39.320 --> 0:11:42.280 chemistry question. I don't even understand organic chemistry well enough 0:11:42.320 --> 0:11:45.040 to ask a question, not to mention find one that's tricky. 0:11:45.320 --> 0:11:48.600 But I totally respect this question because it's so simple. 0:11:48.679 --> 0:11:51.600 It's so basic. Right, It's like, well, we know forces 0:11:51.640 --> 0:11:54.600 push and pull, so what about the weak force? Where 0:11:54.600 --> 0:11:56.920 does it fit in? And it's such a simple and 0:11:56.920 --> 0:11:59.240 basic question, but one I had never thought of before 0:11:59.480 --> 0:12:01.679 because I did to think about the weak force only 0:12:01.720 --> 0:12:05.760 in terms of like particle interactions, like particles colliding and annihilating, 0:12:05.840 --> 0:12:08.920 because there doesn't really play a tactile role in our lives, right, 0:12:08.920 --> 0:12:11.679 you don't feel the weak force pushing against you or 0:12:11.880 --> 0:12:14.640 pulling things together, and so I never really thought about 0:12:14.640 --> 0:12:17.200 it in this context. It was really a fascinating question. 0:12:17.400 --> 0:12:19.440 You just like to break things. You don't worry about 0:12:19.520 --> 0:12:23.240 putting things together. It's kind of my job to break 0:12:23.280 --> 0:12:25.640 things at high speed. It's like the top gear of 0:12:25.679 --> 0:12:28.440 particle physics, and you get to survive most of the time. 0:12:28.520 --> 0:12:31.319 So that's good most of the time, exactly. Well, let's 0:12:31.360 --> 0:12:34.240 warm up to the answer here and maybe let's you know, 0:12:34.320 --> 0:12:36.800 start at the basics here, So let's talk about what 0:12:36.960 --> 0:12:39.200 is the weak force and what does it mean in 0:12:39.240 --> 0:12:43.480 general to attract or repel something to step us through. Then. Yeah, 0:12:43.520 --> 0:12:46.720 so we have a few ways that particles can interact 0:12:46.760 --> 0:12:49.040 with each other, and that's really what forces are. They 0:12:49.040 --> 0:12:52.920 are particles feeling each other. And when we first discovered 0:12:52.960 --> 0:12:54.920 that particles can do this, it was sort of a 0:12:55.000 --> 0:12:57.400 question of like, wait, how does this happen? How do 0:12:57.520 --> 0:13:00.280 particles like push and pull on each other with out 0:13:00.360 --> 0:13:04.439 actually touching, right? How they like feel each other? Two electrons, 0:13:04.440 --> 0:13:07.079 for example, can push against each other. It doesn't mean 0:13:07.080 --> 0:13:10.320 that the surfaces of the electrons have come into contact 0:13:10.600 --> 0:13:13.120 like little tiny balls, and the way they do this 0:13:13.240 --> 0:13:15.640 is with the forces between them, so that each one 0:13:15.640 --> 0:13:18.680 has a field, right, each electron has an electric field 0:13:18.679 --> 0:13:21.520 around it. Where the electric field really is is a 0:13:21.520 --> 0:13:24.800 way for the electron to apply a force to other things. 0:13:25.080 --> 0:13:27.520 And so that's for electricity, and this is a a similar 0:13:27.559 --> 0:13:31.320 field for magnetism. And electricity and magnetism were then shown 0:13:31.320 --> 0:13:33.800 to be actually two sides of the same coin. It 0:13:33.800 --> 0:13:36.680 made more sense to think about them together. Some phenomena 0:13:36.720 --> 0:13:39.440 seemed like electricity if you're at rest, and they seem 0:13:39.520 --> 0:13:42.600 like magnetism if you're moving, and so it's pretty clear 0:13:42.800 --> 0:13:45.160 that's really just sort of one thing that we were 0:13:45.160 --> 0:13:47.560 seeing two sides of. And the weak force is in 0:13:47.600 --> 0:13:51.240 the category of electromagnetism. It's a force that particles can 0:13:51.360 --> 0:13:54.480 use to operate on each other. And so it's a 0:13:54.480 --> 0:13:57.280 little weirder than the other forces because it's not something 0:13:57.320 --> 0:14:00.920 you experience day today because it's so weak. And the 0:14:01.000 --> 0:14:03.920 reason that it's so weak and so weird is that 0:14:03.960 --> 0:14:08.280 the particles that communicate those forces, the fields that it uses, 0:14:08.559 --> 0:14:11.640 have a lot of mass. They're very very heavy, and 0:14:11.679 --> 0:14:13.679 so they don't last for very long. They don't make 0:14:13.720 --> 0:14:17.040 it very far, and that mass really weakens their impact. 0:14:17.240 --> 0:14:20.320 So electromagnetism and the weak force are very closely related, 0:14:20.520 --> 0:14:23.320 but the big difference is that these particles that communicate 0:14:23.320 --> 0:14:26.200 the weak force are very heavy, and so they really 0:14:26.440 --> 0:14:29.560 weaken the force. So maybe let's step back a little 0:14:29.600 --> 0:14:31.480 bit here, because you just went through a lot there. 0:14:31.600 --> 0:14:34.200 So I think what most people are probably familiar with 0:14:34.280 --> 0:14:37.000 is the electromagnetic force. And we know that like you know, 0:14:37.000 --> 0:14:39.440 if I have two magnets, they repel, or two magnetic 0:14:39.480 --> 0:14:41.680 can attract each other and pushing pool and it's all 0:14:41.720 --> 0:14:44.720 because of the electromagnetic force, Right, That's the one that 0:14:44.920 --> 0:14:46.960 people are most familiar with. And people are i think 0:14:47.000 --> 0:14:50.120 also familiar with gravity, which kind of attracts things together. 0:14:50.440 --> 0:14:53.960 So that's where I think maybe people expect that all 0:14:54.000 --> 0:14:56.960 forces attract or repel. Yeah, and it's really interesting because 0:14:57.040 --> 0:15:02.320 electromagnetism can do both of those things. Electromagnetism can attract 0:15:02.480 --> 0:15:06.640 or repel with the same force. And that's because in electromagnetism, 0:15:06.800 --> 0:15:09.880 the force depends on the charge of the particle. Right, 0:15:09.920 --> 0:15:12.440 So every particle we add this label like a minus 0:15:12.560 --> 0:15:15.200 or a plus, right, and each one we call the 0:15:15.240 --> 0:15:18.120 electric charge, and there's two possible values. This plus and 0:15:18.120 --> 0:15:21.480 this minus. And if two particles have the same charge 0:15:21.600 --> 0:15:24.240 like plus plus, then they repel each other. They have 0:15:24.280 --> 0:15:27.560 opposite charges, they attract each other. It's important to understand though, 0:15:27.600 --> 0:15:30.280 that this charge we're talking about, what it means is 0:15:30.360 --> 0:15:33.440 that the particles feel the field like a particle that 0:15:33.480 --> 0:15:37.200 has no charge is a particle that ignores the electromagnetic field. 0:15:37.400 --> 0:15:40.200 A particle has a positive or negative charge is a 0:15:40.240 --> 0:15:43.720 particle that does feel the field. We discover that there 0:15:43.720 --> 0:15:46.520 are two these different kinds of charges, and if you 0:15:46.520 --> 0:15:48.560 combine them in one way, they repel, and if you 0:15:48.560 --> 0:15:51.120 combine them in another way, they attract. So that's a 0:15:51.160 --> 0:15:55.240 really fascinating thing about electromagnetism is that it can do both. Well, 0:15:55.280 --> 0:15:57.600 maybe us through through an example. So let's say have 0:15:57.600 --> 0:16:01.560 two electrons and they're like sitting close to each other, right, 0:16:01.760 --> 0:16:04.360 so they both have negative charge. And then you talked 0:16:04.360 --> 0:16:06.920 about there being a field and this force being going 0:16:06.960 --> 0:16:09.440 through the field. Can you step us through what's happening? 0:16:09.480 --> 0:16:11.400 Like if I have an electron here, an electron there, 0:16:11.440 --> 0:16:15.080 and then they're both the same charge, they're gonna push 0:16:15.080 --> 0:16:17.960 each other away, right, That's right, That's exactly what's gonna happen. 0:16:18.040 --> 0:16:20.040 So you have electron one and it's just hanging out, 0:16:20.280 --> 0:16:23.120 but it also fills the space around it with an 0:16:23.160 --> 0:16:26.600 electromagnetic field. And so now you put another particle in 0:16:26.640 --> 0:16:29.480 that field, a second electron, and it's going to feel 0:16:29.520 --> 0:16:33.880 that field. That field exists just to apply forces to 0:16:34.200 --> 0:16:37.880 other charged particles, and the direction of the force depends 0:16:38.160 --> 0:16:41.080 on the charge of the two particles, and why it happens, 0:16:41.120 --> 0:16:43.440 why there's a push or a pull depends on the 0:16:43.480 --> 0:16:47.120 potential energy of the field. Things like to basically roll 0:16:47.280 --> 0:16:50.840 downhill to low potential energy, and these fields, they have 0:16:50.960 --> 0:16:53.840 a potential energy which varies with distance, and the potential 0:16:53.920 --> 0:16:57.160 energy tends to be slanted, so the particles like roll 0:16:57.320 --> 0:16:59.920 down the potential towards each other. Then the force that 0:17:00.080 --> 0:17:02.880 tracks sort of like if you put two rocks in 0:17:02.920 --> 0:17:06.240 a valley, they would roll towards each other. The gravitational 0:17:06.240 --> 0:17:10.560 potential minimizes when they're closer, or if the shape of 0:17:10.560 --> 0:17:13.679 the potential energy is such that it minimizes when the 0:17:13.680 --> 0:17:16.080 particles are far apart, like you put two rocks on 0:17:16.080 --> 0:17:18.320 the top of a mountain that tend to roll away 0:17:18.320 --> 0:17:21.280 from each other, then the force will push the particles apart. 0:17:21.720 --> 0:17:25.359 And so when you have two charges, the shape of 0:17:25.400 --> 0:17:29.240 this potential, which determines whether it's pushing or pulling, depends 0:17:29.280 --> 0:17:32.040 on the charges of the particles. If the charges are 0:17:32.080 --> 0:17:35.240 the same, then they repel. The charges are opposite, then 0:17:35.280 --> 0:17:37.000 they attract. And it all has to do with the 0:17:37.040 --> 0:17:40.040 shape of this potential energy created by the field of 0:17:40.080 --> 0:17:42.359 one of the particles. Right. But maybe I think what 0:17:42.440 --> 0:17:45.080 might be confusing to some people is you mentioned it's 0:17:45.119 --> 0:17:47.199 like an electric field. Now is that the same as 0:17:47.240 --> 0:17:51.239 a quantum field? Right, because so the electrons are we 0:17:51.280 --> 0:17:53.920 know there's sort of like fluctuations in the quantum field 0:17:53.960 --> 0:17:56.719 of electrons. Are you saying there's like a separate field 0:17:57.119 --> 0:17:59.560 that's quantum or or is this more of a mathematical 0:18:00.119 --> 0:18:02.080 When you say field, that's the same field we've been 0:18:02.080 --> 0:18:05.360 talking about forever, the electromagnetic field. You can actually talk 0:18:05.359 --> 0:18:09.480 about electricity magnetism without quantum mechanics. It was developed before 0:18:09.560 --> 0:18:12.480 quantum mechanics. We have a classical theory of electricity and 0:18:12.520 --> 0:18:15.800 magnetism that explains how electrons pulling each other. That was 0:18:15.840 --> 0:18:19.280 just before we understood that this field was quantum. What 0:18:19.359 --> 0:18:22.320 that means is that it just can't have any arbitrary value, 0:18:22.480 --> 0:18:25.040 but it's like chopped up into discrete bits. It's like 0:18:25.080 --> 0:18:26.879 if you are eating a cake, it's like you have 0:18:26.920 --> 0:18:29.360 to have one piece, or two pieces, or three pieces. 0:18:29.520 --> 0:18:31.560 You can't just nable on the cake all day long. 0:18:31.680 --> 0:18:33.920 And so before quantum mechanics, we thought that these fields 0:18:33.960 --> 0:18:36.399 were classical fields. It could just have any value. And 0:18:36.440 --> 0:18:38.840 then we discovered that they have a minimum value and 0:18:38.880 --> 0:18:41.399 they have steps to them, So it is a quantum field. 0:18:41.400 --> 0:18:43.600 This is a quantum field we're talking about. And so 0:18:43.800 --> 0:18:47.480 ripples in this electromagnetic field are, for example, the photon, 0:18:47.520 --> 0:18:50.560 which is one quantum of the electromagnetic field. So that 0:18:50.640 --> 0:18:53.480 the electron is a ripple in the electromagnetic field, or 0:18:53.520 --> 0:18:56.320 it's a ripple in its own quantum field, but they're 0:18:56.320 --> 0:19:00.320 sitting in another field, which is the electromagnetic force field. Right. 0:19:00.400 --> 0:19:04.440 The electron is a ripple in the electron field, right, 0:19:04.840 --> 0:19:08.639 and it generates ripples in the electromagnetic field, which is 0:19:08.680 --> 0:19:11.640 the field of the photon. And that's because these two 0:19:11.640 --> 0:19:14.199 particles talk to each other, electrons and photons talk to 0:19:14.240 --> 0:19:16.160 each other. Or in the language of fields, you could 0:19:16.160 --> 0:19:19.080 say these two fields couple. You could have a universe 0:19:19.119 --> 0:19:22.240 in which you have a particle and then another field 0:19:22.240 --> 0:19:25.040 and they don't interact at all. Right, For example, like 0:19:25.119 --> 0:19:28.720 neutrinos are wiggles in the neutrino field, but they don't 0:19:28.760 --> 0:19:31.480 affect the electromagnetic field at all. They have no charge. 0:19:32.000 --> 0:19:35.239 And so electrons are wiggles in the electron field as 0:19:35.240 --> 0:19:37.760 a quantum field, but they also create wiggles in the 0:19:37.800 --> 0:19:41.840 electromagnetic field because they have charged as a charge that 0:19:41.920 --> 0:19:44.800 connects these two fields. Charges, Like how much these two 0:19:44.840 --> 0:19:48.359 fields are connected for that one particle. Yeah, And interestingly, 0:19:48.400 --> 0:19:51.520 for electromagnetism, there's assigned to it. There's two different kinds 0:19:51.520 --> 0:19:54.720 of charges, and that determines the shape of the potential 0:19:54.760 --> 0:19:57.560 from the field and whether they attract or repel. All right, 0:19:57.680 --> 0:20:01.560 let's field more questions about this main question of does 0:20:01.600 --> 0:20:03.800 the weak force attractor repel? And so let's get into 0:20:03.840 --> 0:20:06.080 the weak force itself when we come back from the break. 0:20:06.359 --> 0:20:21.480 But first let's take a quick break. All right, we're 0:20:21.520 --> 0:20:24.200 talking about the weak force and whether or not it's 0:20:24.240 --> 0:20:27.640 attractive or repulsive. I guess, Daniel, is that the same 0:20:27.680 --> 0:20:30.440 as asking whether it's hot or not? Is it appealing 0:20:30.640 --> 0:20:34.120 or not appealing? Well, I find it mysterious, which makes 0:20:34.119 --> 0:20:36.960 me want to know more. And so I think the 0:20:37.000 --> 0:20:40.240 weak force is definitely pretty hot, but it's pretty weak. 0:20:40.280 --> 0:20:43.080 It can't heat anything up, so it leaves the universe 0:20:43.160 --> 0:20:46.320 kind of cold. We were talking about the first electromagnetic 0:20:46.480 --> 0:20:49.840 force and how the force of it is actually the 0:20:49.920 --> 0:20:53.720 interaction of two particles in the electromagnetic field, and that 0:20:53.760 --> 0:20:56.720 happens when they exchange photons, and it's all because of 0:20:56.760 --> 0:20:58.680 the charge of the particles. But I guess you know, 0:20:59.600 --> 0:21:01.760 that's the way to look at things. But another way 0:21:01.760 --> 0:21:03.440 to look at it things might be the same way 0:21:03.480 --> 0:21:05.840 that we look at gravity, right Like gravity, we look 0:21:05.880 --> 0:21:08.760 at at it in a totally different way right now, Yeah, 0:21:08.960 --> 0:21:11.280 gravity actually is really interesting, and you can look at 0:21:11.280 --> 0:21:14.639 it using the same sort of set of concepts. You 0:21:14.680 --> 0:21:18.920 can say, like, well, what does gravity do? Gravity only attracts, 0:21:19.000 --> 0:21:21.560