WEBVTT - Classic episode - Why is gravity so weird? 0:00:07.240 --> 0:00:10.440 I just think it's fascinating that it's such a fundamental 0:00:10.840 --> 0:00:14.720 force in the universe, right, Like, it's basically the thing 0:00:14.800 --> 0:00:20.000 that builds galaxies and keeps planets moving right, and gives 0:00:20.000 --> 0:00:21.880 structure to the entire cosmos. 0:00:22.239 --> 0:00:25.079 That's right. On the largest scale, it's actually the most 0:00:25.200 --> 0:00:28.360 important force. It's the reason why things look the way 0:00:28.360 --> 0:00:31.080 they do. It's the reason why our planet is round, 0:00:31.120 --> 0:00:33.200 it's the reason why we're on the planet. 0:00:33.479 --> 0:00:37.120 It's pretty important, and yet we don't know a lot 0:00:37.159 --> 0:00:40.560 about it, right Like, there's some really deep and strange 0:00:40.880 --> 0:00:41.800 mysteries about it. 0:00:41.960 --> 0:00:44.200 On one hand, we have a theory which works really 0:00:44.200 --> 0:00:46.360 really well. On the other hand, we have questions about 0:00:46.360 --> 0:00:48.120 it which seems really really basic. 0:00:48.560 --> 0:00:51.040 And not only that, it's very different than all the 0:00:51.040 --> 0:00:52.600 other forces of nature. 0:00:53.159 --> 0:00:55.840 That's right, one of these things is not like the 0:00:55.920 --> 0:00:56.440 other ones. 0:01:15.080 --> 0:01:17.160 Hi, I'm Hohe, I'm a cartoonist. 0:01:16.880 --> 0:01:19.000 And I'm Daniel. I'm a particle physicist. 0:01:19.240 --> 0:01:22.920 And this is our podcast Daniel and Jorge explain the universe. 0:01:22.680 --> 0:01:25.199 In which a cartoonist and a physicists try to figure 0:01:25.200 --> 0:01:28.600 out how to make the universe understandable to anybody. 0:01:28.880 --> 0:01:32.560 Yeah, and today on the podcast we are examining a 0:01:32.680 --> 0:01:43.640 very heavy topic, gravity and specifically why is gravity so. 0:01:43.840 --> 0:01:48.800 Weak and strange. Gravity, as we said earlier, is something 0:01:48.800 --> 0:01:51.400 which controls the structure of the universe. I mean, the 0:01:51.480 --> 0:01:53.720 reason the Solar system looks the way it does is 0:01:53.760 --> 0:01:56.560 because of gravity. The reason the Earth is round is 0:01:56.560 --> 0:01:59.440 because of gravity. The reason we have galaxies is because 0:01:59.440 --> 0:02:00.000 of gravity. 0:02:00.280 --> 0:02:02.960 The reason we weigh so much, it is because of gravity. Right, 0:02:03.000 --> 0:02:04.920 it's not my belt. 0:02:06.520 --> 0:02:08.320 No, that's because of late night cake eating. 0:02:10.080 --> 0:02:13.320 But it's such a fundamental force of nature, right, Like 0:02:13.360 --> 0:02:16.519 it's present in our everyday life. We spend a lot 0:02:16.560 --> 0:02:20.560 of time thinking about gravity, right, how not to fall down, 0:02:20.840 --> 0:02:23.560 how not to drop things, how to go up buildings, 0:02:23.600 --> 0:02:24.639 how to go down buildings. 0:02:24.720 --> 0:02:26.760 Right, that's right. It seems like one of the most 0:02:26.760 --> 0:02:29.320 important forces. I mean, if you ask people, you know, 0:02:29.480 --> 0:02:31.680 to name a force or what kind of forces they 0:02:31.760 --> 0:02:34.040 experience in their life, gravity is the one that's present 0:02:34.080 --> 0:02:36.880 in their lives. Right, you're climbing upstairs, you're fighting gravity, 0:02:36.880 --> 0:02:39.560 your trip, you fall down, you're feeling gravity. You look 0:02:39.600 --> 0:02:42.440 around you. The shape of things is controlled by gravity, 0:02:42.760 --> 0:02:46.440 and that's why it's particularly strange that gravity is the 0:02:46.480 --> 0:02:50.320 weakest force of all the forces we've discovered, it's by 0:02:50.440 --> 0:02:51.280 far the weakest. 0:02:51.480 --> 0:02:54.360 Yeah, it's really strange to hear you say that, Like, 0:02:54.440 --> 0:02:56.880 how can gravity be weak? Like you know, like it's 0:02:57.200 --> 0:02:59.960 it's keeping the whole Earth together, it's making the entire 0:03:00.080 --> 0:03:04.440 higher planet swing around going a circle basically, right. Without gravity, 0:03:04.480 --> 0:03:05.959 we would just shoot off into space. 0:03:06.280 --> 0:03:09.280 That's right. It's a really strange situation. And there's other 0:03:09.320 --> 0:03:12.520 things about gravity we don't understand as well. It's really strange. 0:03:12.520 --> 0:03:15.119 It doesn't play well with the other forces. It's very, 0:03:15.200 --> 0:03:18.080 very weak. It's a total mystery to science, except that 0:03:18.120 --> 0:03:20.560 we have a theory which works beautifully right. We can 0:03:20.600 --> 0:03:24.080 calculate exactly how mercury orbits the Sun. We can send 0:03:24.080 --> 0:03:26.920 things into outer space and know with to millimeter precision 0:03:26.960 --> 0:03:29.079 exactly where they're going to land. We have a working 0:03:29.120 --> 0:03:32.320 theory that we can use, right, but we don't understand 0:03:32.360 --> 0:03:34.840 it on a conceptual level. We have these basic, deep 0:03:34.920 --> 0:03:38.040 questions about what gravity is and how the universe works 0:03:38.080 --> 0:03:38.600 because of it. 0:03:38.800 --> 0:03:41.160 So it's a weird question, and maybe one of the 0:03:41.160 --> 0:03:44.080 people hadn't thought about before. So Daniel went out as 0:03:44.160 --> 0:03:46.760 usual and asked people on the street, why do you 0:03:46.800 --> 0:03:48.040 think gravity is so weak. 0:03:48.320 --> 0:03:50.520 Here's what a random selection of folks who were willing 0:03:50.560 --> 0:03:52.560 to talk to me on a Tuesday morning had to 0:03:52.560 --> 0:03:55.640 say about gravity. I don't know. I should don't know 0:03:55.760 --> 0:03:58.320 about that, all right. I thought it was a pretty 0:03:58.320 --> 0:03:59.280 strong force, so I don't know. 0:04:00.080 --> 0:04:05.520 But yeah, because it depends on the distance, and it's 0:04:05.560 --> 0:04:08.040 a long range one, so that's why we feel it 0:04:08.240 --> 0:04:12.120 very weak most of the time. Cool, No, okay, I 0:04:12.120 --> 0:04:14.400 have no I'm sorry, it's not very fruitful. 0:04:14.960 --> 0:04:18.599 Hmmm, I have no idea, but I'd be interested in 0:04:18.640 --> 0:04:19.880 finding out why. 0:04:20.320 --> 0:04:23.520 All right, that that was pretty good. Most people weren't 0:04:23.600 --> 0:04:25.320 surprised when you said gravity's weak. 0:04:26.200 --> 0:04:28.360 I don't know. I feel like, of all the questions 0:04:28.360 --> 0:04:30.680 I've asked people, this is the one that flumms them 0:04:30.680 --> 0:04:33.159 the most. You know. People were like, what, I have 0:04:33.279 --> 0:04:37.200 no idea, or they had crazy ideas why gravity must 0:04:37.240 --> 0:04:40.000 be weak. I feel like usually we get one person 0:04:40.040 --> 0:04:41.880 who knows what the answer is or has a good 0:04:41.920 --> 0:04:44.520 clue about what's going on. This time, I feel like 0:04:44.600 --> 0:04:47.040 almost everybody was pretty clueless. I mean, one person said 0:04:47.120 --> 0:04:49.760 I always thought gravity was pretty strong, right, which kind 0:04:49.800 --> 0:04:53.800 of sums up the situation. Right, Gravity's omnipresent in our lives. 0:04:53.800 --> 0:04:57.440 It dominates our experience, and yet it's so weak compared 0:04:57.480 --> 0:04:59.640 to the other really powerful forces we've discovered. 0:04:59.800 --> 0:05:02.160 Well, some people a couple of answers were that it 0:05:02.200 --> 0:05:05.719 had to do with distance, Like gravity gets really weak 0:05:05.760 --> 0:05:06.400 with distance. 0:05:06.680 --> 0:05:08.400 That's right. And the problem there is that all the 0:05:08.400 --> 0:05:13.159 forces get weak with distance, like electromagnetism also falls as 0:05:13.520 --> 0:05:16.920 a distance grows. Right, So all of these forces follow 0:05:16.960 --> 0:05:19.280 this one over R squared rule or are as your 0:05:19.320 --> 0:05:21.840 distance from the things that's giving. 0:05:21.640 --> 0:05:23.919 You the force, right, maybe maybe right. 0:05:24.240 --> 0:05:28.000 Maybe, yeah, mostly we think, And so that can't be 0:05:28.040 --> 0:05:29.919 the answer, right, because all the other forces have that 0:05:29.960 --> 0:05:30.520 same feature. 0:05:30.640 --> 0:05:32.080 So when you say it's the weak is it's not 0:05:32.160 --> 0:05:35.719 that it changes over distances differently than the other forces. 0:05:35.839 --> 0:05:38.040 That's right. So maybe we should talk about what the 0:05:38.040 --> 0:05:41.480 forces are and compare them to each other so folks 0:05:41.520 --> 0:05:44.839 can get understanding of how crazy weak gravity is. Right. 0:05:44.880 --> 0:05:48.400 So, Daniel, what are the forces of nature besides a 0:05:48.440 --> 0:05:50.720 bad movie with Ben Affleck than center bullet. 0:05:52.240 --> 0:05:55.240 Well, I think comedy. Comedy is definitely a force of nature. 0:05:55.960 --> 0:05:58.720 You know, it solves big problems around the world. Now, 0:05:59.240 --> 0:06:02.880 the fundamental force are electromagnetism, right, that's the one that 0:06:02.960 --> 0:06:06.640 controls electricity and magnetism obviously, and is responsible for the 0:06:06.680 --> 0:06:11.040 cool things like light and lightning and all that cool stuff. 0:06:11.960 --> 0:06:15.040 And then there's the weak nuclear force, which is a 0:06:15.120 --> 0:06:18.560 force which is responsible for radioactive decay of a nuclei. Right. 0:06:18.600 --> 0:06:21.359 And the cool thing about electricity and magnetism and the 0:06:21.400 --> 0:06:24.080 weak nuclear force is that we actually have shown that 0:06:24.080 --> 0:06:26.880 there are two sides of the same coin. As a 0:06:26.920 --> 0:06:29.359 particle physicist, we refer to them as one force. We 0:06:29.400 --> 0:06:33.159 call it the electro week. So sort of magnetism lost 0:06:33.160 --> 0:06:35.479 out there in the name merger, right, it should be 0:06:35.520 --> 0:06:39.160 electromagnetic week. But nobody voted to keep magnetism in the 0:06:39.279 --> 0:06:41.160 sort of the name of the partners in the law firm. 0:06:41.440 --> 0:06:44.200 Nobody lobbied for weak electro. 0:06:44.320 --> 0:06:50.719 Or magneto weak force. Yeah. Yeah, again, we are suffering 0:06:50.760 --> 0:06:53.520 the fate of some anonymous committee of scientists that get 0:06:53.520 --> 0:06:55.480 to name these things. Right, Who are these people? 0:06:55.680 --> 0:06:58.919 Probably some grad student, right or some you know, like 0:06:59.000 --> 0:07:01.320 this is really weird, we'll call it this. 0:07:01.839 --> 0:07:04.760 Yeah. So we have electricity and magnetism, which is a 0:07:04.800 --> 0:07:06.919 single force. We have the weak nuclear force, which is 0:07:06.960 --> 0:07:09.800 really should be combined with electricity and magnetism. And then 0:07:09.800 --> 0:07:12.040 there's the strong nuclear force, and this is the one 0:07:12.040 --> 0:07:14.640 that holds the nucleus together. You know, the nucleus is 0:07:14.680 --> 0:07:18.760 of just a bunch of positively charged protons and neutral neutrons. Right, 0:07:19.000 --> 0:07:22.080 it says only positively charged particles in the nucleus. So 0:07:22.120 --> 0:07:24.800 you might think, what it even holds the nucleus together? Right, 0:07:24.800 --> 0:07:28.280 you have all this positively charged stuff should be repelling themselves. Well, 0:07:28.320 --> 0:07:31.000 it's the strong nuclear force, and it does so by 0:07:31.000 --> 0:07:34.760 exchanging these crazy little particles we call gluons, and that 0:07:34.880 --> 0:07:37.480 holds the nucleus together, and it's pretty strong. It's even 0:07:37.520 --> 0:07:38.960 stronger than electromagnetism. 0:07:39.080 --> 0:07:41.560 Well, let's take a step back. So in the universe 0:07:41.600 --> 0:07:42.239 there's stuff. 0:07:43.000 --> 0:07:47.240 There's like, yes, firm that there is stuff in the university. Yes, 0:07:47.720 --> 0:07:49.280 without reservation, there is stuff. 0:07:49.320 --> 0:07:52.480 I'm glad we saw that question. But I mean it's 0:07:52.480 --> 0:07:55.480 like there's stuff that has substance to it, that has 0:07:55.720 --> 0:07:58.280 mass to it, or you know that it sort of exists. 0:07:58.320 --> 0:08:01.360 And then there's also besides the at how these things 0:08:01.680 --> 0:08:03.960 interact with each other, like how they affect each other. 0:08:04.120 --> 0:08:07.080 That's right, there's the matter and then there's the forces, right, 0:08:07.080 --> 0:08:09.240 and the forces affect how they interact with each other. 0:08:09.120 --> 0:08:11.760 And that's pretty much the universe. That's like, it's matter 0:08:11.800 --> 0:08:12.360 and forces. 0:08:13.360 --> 0:08:15.040 Yeah. One way to look at the universe is that 0:08:15.080 --> 0:08:18.240 it's particles, right, or you would say matter and their forces. 0:08:18.680 --> 0:08:21.360 In modern particle physics, we think about one level deeper, 0:08:21.400 --> 0:08:24.520 which is we think of quantum fields, and quantum fields 0:08:24.520 --> 0:08:27.600 are responsible both for matter and for forces. So we 0:08:27.600 --> 0:08:30.000 can talk about that maybe in another podcast. What is 0:08:30.040 --> 0:08:32.400 a quantum field? And how can I get one? You know, 0:08:32.440 --> 0:08:35.040 for lease or rent? What can they do for me? 0:08:35.320 --> 0:08:37.319 But yeah, I think it's fair still to think about 0:08:37.600 --> 0:08:39.880 the universe in terms of particles and forces. 0:08:40.679 --> 0:08:56.160 On that note, let's take a quick break. There are 0:08:56.160 --> 0:08:57.720 only four kinds of forces. 0:08:58.040 --> 0:09:01.400 Yeah, there are four kinds of forces, so electromagnetism, weak 0:09:01.480 --> 0:09:05.320 nuclear force, strong nuclear force, and then of course gravity. Right, 0:09:05.320 --> 0:09:07.079 that's the fourth force that we've discovered. 0:09:07.320 --> 0:09:07.600 Okay. 0:09:07.920 --> 0:09:12.520 The fascinating thing is that different particles feel different forces, right, Like, 0:09:12.559 --> 0:09:15.080 some particles feel this set of forces, some particles feel 0:09:15.120 --> 0:09:18.880 those set of forces. For example, right, particles with electric 0:09:19.000 --> 0:09:23.920 charge feel electromagnetism. Right. The electron, for example, is negatively charged. 0:09:24.160 --> 0:09:27.440 The proton is positively charged. You bring them close together, 0:09:27.679 --> 0:09:29.920 they're gonna pull on each other, They're gonna suck each 0:09:29.960 --> 0:09:32.439 other together, right, because they have opposite charges. We all 0:09:32.480 --> 0:09:36.240 know that. But you bring a neutral particle nearby, it 0:09:36.320 --> 0:09:39.360 just totally ignores it, right, It doesn't feel it at all. Right, Right, 0:09:39.440 --> 0:09:42.240 It's like it's like somebody's walking through a crowd of 0:09:42.280 --> 0:09:44.600 people shouting, but they have headphones on, so they can't 0:09:44.600 --> 0:09:46.960 hear anything, and they're totally oblivious to it. 0:09:46.960 --> 0:09:48.440 It's kind of like how we talked about in a 0:09:48.440 --> 0:09:53.200 previous podcast. They're almost like languages or like social media platforms. 0:09:53.240 --> 0:09:55.880 Like some people are on Twitter, some people are on Facebook, 0:09:55.880 --> 0:09:58.000 but some people are not on this. And so if somebody, 0:09:58.200 --> 0:09:59.960 if you're not on Twitter and somebody sends you a tweet, 0:10:00.080 --> 0:10:02.280 you're not gonna get it. And so it's just different 0:10:02.320 --> 0:10:04.200 ways that particles interact. 0:10:03.880 --> 0:10:07.240 That's right. Gravity is the Google plus of social media, 0:10:07.360 --> 0:10:14.560 right because nobody uses the trends. It's ancient but powerless. Yeah, 0:10:14.600 --> 0:10:17.360 And so different particles feel different forces. And for example, 0:10:17.360 --> 0:10:20.800 an electron, while it feels electromagnetism because it has a 0:10:20.840 --> 0:10:23.880 negative charge, it doesn't feel the strong force at all. 0:10:24.200 --> 0:10:26.400 It will pass right by a bunch of particles that 0:10:26.440 --> 0:10:28.600 are really tugging on each other with a strong force 0:10:28.800 --> 0:10:32.319 and not be affected at all. Whereas quarks, quarks feel 0:10:32.440 --> 0:10:35.560 all the forces. They feel a strong force, which is 0:10:35.559 --> 0:10:37.920 how they get pulled together in the nucleus. Remember, protons 0:10:37.960 --> 0:10:41.320 and neutrons are made of quarks. Quarks feel electromagnetism because 0:10:41.360 --> 0:10:44.160 they have electric charge. They feel the weak force. They 0:10:44.200 --> 0:10:46.360 also feel gravity, of course, because they have masks. So 0:10:46.720 --> 0:10:49.840 quarks get their fingers in everything feel. 0:10:49.960 --> 0:10:51.400 They get the feels for everything. 0:10:51.640 --> 0:10:54.319 They feel everything that's right, They got the strong feels. 0:10:55.840 --> 0:10:57.480 They're really deeply emotional. 0:10:57.480 --> 0:10:57.880 Part of the. 0:11:00.000 --> 0:11:01.439 And the other side of the spectrum you got things 0:11:01.480 --> 0:11:04.719 like neutrinos. The trinos don't have electric charge, so they 0:11:04.760 --> 0:11:08.360 ignore all electricity and magnetism. Right, They don't interact with light. 0:11:08.640 --> 0:11:12.960 They're invisible. They pass right through anything that They ignore 0:11:13.000 --> 0:11:16.800 electromagnetic bonds, so they pass through most materials. They don't 0:11:16.800 --> 0:11:19.360 feel the strong force. The only way they interact is 0:11:19.400 --> 0:11:21.840 with the weak force, and the weak force is pretty weak, 0:11:22.000 --> 0:11:24.959 which is why neutrinos can mostly just pass through matter unaffected. 0:11:29.320 --> 0:11:32.080 So we have four fundamental forces right, And gravity is 0:11:32.120 --> 0:11:33.880 one of these forces, and so when you say that 0:11:33.960 --> 0:11:37.640 gravity is weak, you actually mean it's weak compared to 0:11:37.720 --> 0:11:39.520 these other three forces. 0:11:39.280 --> 0:11:42.160 That's right. And so the ranking is the strong force 0:11:42.440 --> 0:11:45.439 is the strongest, so that one is actually well named. 0:11:45.480 --> 0:11:50.120 Congratulations anonymous group of scientists. Yeah, we should be called 0:11:50.120 --> 0:11:52.400 the as of twenty eighteen, currently known to be the 0:11:52.440 --> 0:11:58.320 strongest force force. After that comes electromagnetism. And you know, 0:11:58.400 --> 0:12:00.560 we know that force is pretty powerful. Stick your finger 0:12:00.559 --> 0:12:03.520 in a socket, you're gonna feel the wrath of electromagnetism. Right, 0:12:03.559 --> 0:12:05.640 It's not an unfamiliar feeling, right. 0:12:05.559 --> 0:12:07.680 Try to stick your finger in anything. You feel it, right, 0:12:07.720 --> 0:12:11.440 because it's Electromagnetism is the force that keeps you from 0:12:11.800 --> 0:12:16.760 basically passing through the table or passing through your car. 0:12:16.920 --> 0:12:20.920 Right, that's right. Because electromagnetism is the basis of chemical bonds, right, 0:12:20.960 --> 0:12:22.960 And chemical bonds are really the thing that form the 0:12:23.000 --> 0:12:25.480 structure of your body. Right. You think of your body 0:12:25.520 --> 0:12:27.720 is like a bunch of particles, but it's held together 0:12:27.760 --> 0:12:30.320 by all these forces. It's like a chain link fence 0:12:30.640 --> 0:12:33.439 binding together these little particles that prevents you from passing 0:12:33.520 --> 0:12:36.800 through something else. Yeah, So we got the strong force, 0:12:36.880 --> 0:12:40.640 and then electromagnetism, and then actually the weak nuclear force. Right, 0:12:40.679 --> 0:12:43.560 this is the force that like powers neutrinos and radioactive decay. 0:12:43.800 --> 0:12:48.079 It's much weaker than electromagnetism and much weaker than the 0:12:48.120 --> 0:12:48.760 strong force. 0:12:49.120 --> 0:12:51.280 Even weaker than the weak is gravity. 0:12:51.440 --> 0:12:55.000 That's right. If you make a list like strong force, electromagnetism, 0:12:55.040 --> 0:12:57.040 in the weak force, then you should leave like one 0:12:57.120 --> 0:13:00.840 hundred blank pages and then you get to grab because 0:13:00.840 --> 0:13:03.199 when we compare these forces, we put things like an 0:13:03.200 --> 0:13:06.280 equal distance apart, and we compare the strength of the forces. 0:13:06.520 --> 0:13:11.040 Gravity is ten to the thirty six times weaker than 0:13:11.040 --> 0:13:15.000 the weak force. That's ten with thirty six zeros in 0:13:15.040 --> 0:13:15.520 front of it. 0:13:15.720 --> 0:13:19.360 But isn't that sort of a matter of units or scale? 0:13:19.440 --> 0:13:21.840 Do you know what I mean? Like, it's much weaker, 0:13:21.880 --> 0:13:26.120 but only if you compare apples to apples, right, orange oranges? 0:13:26.200 --> 0:13:28.480 That's right. But put two protons next to each other, right, 0:13:28.760 --> 0:13:31.400 h two protons have a certain amount of mass and 0:13:31.440 --> 0:13:34.000 a certain amount of electric charge, and the force of 0:13:34.040 --> 0:13:36.640 their charges is going to be much much stronger than 0:13:36.640 --> 0:13:38.640 the force from their masses. Oh I see, So yeah, 0:13:38.679 --> 0:13:41.520 if everything was much much more massive, then there would 0:13:41.520 --> 0:13:44.200 be stronger gravity. But you can compare these things apples 0:13:44.200 --> 0:13:46.040 to apples by comparing them at you know, the same 0:13:46.080 --> 0:13:48.560 distance and the same basic unit of interaction. 0:13:48.840 --> 0:13:50.319 Right, But what if you take an apple put it 0:13:50.400 --> 0:13:51.280 next to another apple? 0:13:52.280 --> 0:13:54.360 Well, I think you can do that experiment. Nothing's going 0:13:54.400 --> 0:13:56.719 to happen because gravity is so weak. Right. You don't 0:13:56.760 --> 0:13:59.360 see two apples like pulling themselves together on the counter, right, 0:14:00.040 --> 0:14:02.960 built in apple collider. You know, the apples are not 0:14:03.040 --> 0:14:05.800 drawn to each other. Gravity is a super weak force, 0:14:05.800 --> 0:14:08.200 and you can see this yourself. Right, you can do 0:14:08.240 --> 0:14:12.240 an experiment where you counter the entire gravitational force of 0:14:12.280 --> 0:14:15.720 an enormous celestial body like the Earth. Right, take a 0:14:15.960 --> 0:14:18.880 small kitchen magnet and use it to hold up a nail, 0:14:19.160 --> 0:14:21.600 and think about what's happening there. Right, you have the 0:14:21.680 --> 0:14:25.120 nail is being pulled down by every single rock in 0:14:25.160 --> 0:14:27.760 the Earth. It's pulling with all of its gravity. But 0:14:27.840 --> 0:14:30.600 a tiny little kitchen magnet totally overcomes that. 0:14:31.840 --> 0:14:34.400 It can lift a nail even though it's pulling. It's 0:14:34.440 --> 0:14:37.200 being pulled down by the whole entire planet Earth. 0:14:37.080 --> 0:14:39.480 Right exactly. And now imagine a magnet the size of 0:14:39.520 --> 0:14:42.320 the Earth, right, I mean that would be that would 0:14:42.320 --> 0:14:46.080 be extraordinarily powerful. And so you have basically like a 0:14:46.120 --> 0:14:49.600 gravitational blob the size of the Earth. Still pretty ineffective 0:14:49.680 --> 0:14:51.240 compared to electromagnetism. 0:14:51.400 --> 0:14:56.720 Mmmm, so it's weak if you sort of compare it 0:14:56.760 --> 0:14:59.400 by object, Like you said, if you take a proton 0:14:59.440 --> 0:15:02.600 and put a nice proton, the force are going to 0:15:02.640 --> 0:15:06.200 feel from electromagnetism is so much bigger than the force 0:15:06.200 --> 0:15:08.520 of gravity. They're going to feel towards each other, the 0:15:08.560 --> 0:15:12.440 same with like two electrons or two quarks and things. 0:15:12.680 --> 0:15:14.720 So in the scale of like the particles that we know, 0:15:15.120 --> 0:15:16.359 it's a really weak. 0:15:16.160 --> 0:15:20.320 Force, that's right, exactly, And yet and yet it seems 0:15:20.360 --> 0:15:22.320 to dominate, right. That's a bit of a puzzle, Like, 0:15:22.800 --> 0:15:25.080 on one hand, it's super duper weak, and we're telling 0:15:25.080 --> 0:15:27.200 you that it hardly counts for anything. On the other hand, 0:15:27.520 --> 0:15:29.960 it's responsible for the structure of the Solar System, man 0:15:30.000 --> 0:15:32.360 for the galaxy, and it's the reason the universe looks 0:15:32.360 --> 0:15:34.240 the way it is, right, right, And so that can 0:15:34.280 --> 0:15:36.400 be confusing to people, Like how do you reconcile those 0:15:36.400 --> 0:15:37.400 two things in your head? 0:15:37.560 --> 0:15:40.520 Yeah, Like, why doesn't the Earth feel an electromagnetic force 0:15:40.600 --> 0:15:43.280 with the Sun, which it would be so much bigger 0:15:43.320 --> 0:15:44.960 than the force of gravity. 0:15:45.080 --> 0:15:48.000 Yeah, well it would be pretty shocking. And that's actually 0:15:48.080 --> 0:15:51.360 the reason is gravity is different from the other forces 0:15:51.400 --> 0:15:53.960 and that it can't be canceled out right, If there 0:15:53.960 --> 0:15:57.240 was some huge electrostatic difference between the Sun and the Earth, 0:15:57.360 --> 0:15:59.080 like a bunch of positive charges there and a bunch 0:15:59.120 --> 0:16:02.800 of negative charges, it would create such an enormous force 0:16:03.200 --> 0:16:06.400 that it would be very quickly balanced. Like that's what 0:16:06.560 --> 0:16:10.320 lightning is. Right. When there's a charge differential between clouds 0:16:10.320 --> 0:16:13.720 and the grounds, it doesn't take that much before those 0:16:13.800 --> 0:16:16.880 charges want to rearrange themselves to a lower energy configuration. 0:16:16.960 --> 0:16:18.960 They rush down to the ground, or they rush up 0:16:18.960 --> 0:16:21.080 to the clouds, or they jump from clouded cloud to 0:16:21.120 --> 0:16:24.040 balance themselves out. Because you have two kinds of charges, 0:16:24.040 --> 0:16:26.680 you have positive and you have negative, so you can 0:16:26.840 --> 0:16:30.520 find an arrangement where basically everybody's happy. It's an equilibrium, right, 0:16:30.720 --> 0:16:32.720 But that's not true for gravity. 0:16:32.520 --> 0:16:34.400 Okay, I get it. So for example, if the Earth 0:16:34.640 --> 0:16:38.840 was every particle on Earth had a positive electromagnetic charge, 0:16:39.240 --> 0:16:42.640 and every particle in the Sun had a negative electromagnetic charge, 0:16:43.120 --> 0:16:48.200 there would be a humongous pull from electromagnetism pulling the 0:16:48.240 --> 0:16:49.120 Earth into the Sun. 0:16:49.320 --> 0:16:53.280 Yeah, we'd be toast pretty quick. Yeah, very long lived experment. 0:16:53.400 --> 0:16:56.000 Yeah, it would be huge. Even the opposite, if we 0:16:56.040 --> 0:16:58.240 were all positive and the Sun was all positive, we 0:16:58.240 --> 0:17:01.360 would get shot out of the sort of system very quickly. 0:17:01.440 --> 0:17:03.920 That's right. And that's why you know, early days of 0:17:03.960 --> 0:17:07.359 the Solar system being formed, you have these gases and 0:17:07.400 --> 0:17:11.840 the gas and dust coalescing, and very rapidly things neutralize, right, 0:17:11.840 --> 0:17:15.560 because anything that feels an electrostatic force to something else 0:17:15.800 --> 0:17:18.119 is going to find the opposite charge and they're going 0:17:18.119 --> 0:17:20.080 to coalesce and they're going to make something neutral. Right. 0:17:20.400 --> 0:17:22.840 That's why most of the things around you are neutral, right, 0:17:22.880 --> 0:17:26.560 Most of the elements are neutral because any deviation from 0:17:26.600 --> 0:17:29.600 neutral results in a powerful force to neutralize it. 0:17:29.800 --> 0:17:32.679 So, thankfully the Earth is made out of both like 0:17:32.800 --> 0:17:36.720 equal amounts of positive and negative particles, right, that's right. 0:17:36.960 --> 0:17:40.679 Thankfully we're sort of balanced electromagnetically, and so even if 0:17:40.720 --> 0:17:44.080 the Sun was all positive, we would look like neutral, 0:17:44.200 --> 0:17:45.880 like a neutral ball to the Sun. 0:17:46.160 --> 0:17:49.199 Yeah, that's right. Where on large scales the Earth is neutral, right, 0:17:49.240 --> 0:17:52.000 I mean there might be some residual positive or negative 0:17:52.040 --> 0:17:55.240 charge depending on the solar wind, et cetera. But basically 0:17:55.320 --> 0:17:58.040 the Earth is neutral, and so the largest force of 0:17:58.119 --> 0:18:00.840 the Earth feels is the gravity from the Sun. Even 0:18:00.840 --> 0:18:03.639 though gravity is super duper weak, right, it doesn't take 0:18:03.680 --> 0:18:05.879 a lot to counteract gravity. But it's the only player 0:18:06.000 --> 0:18:08.400 left because everybody else is sort of pair it up 0:18:08.760 --> 0:18:11.600 and danced off for the night, and gravity's just there left, 0:18:11.600 --> 0:18:14.680 hold in the bag. And gravity can't be balanced, right. 0:18:14.800 --> 0:18:17.720 You feel gravity if you have any mass, right, there's 0:18:17.760 --> 0:18:20.679 only positive masses. There's no such thing as a negative 0:18:20.760 --> 0:18:22.560 mass to give anti gravity. 0:18:22.960 --> 0:18:26.320 Wow, well, let's keep going, but first let's take a 0:18:26.400 --> 0:18:42.720 quick break. Okay, So that's how gravity is so much 0:18:42.760 --> 0:18:46.359 weaker than the other forces. So how's it different than 0:18:46.359 --> 0:18:48.160 the other three forces of nature? 0:18:48.320 --> 0:18:51.639 There's like no end to waste. The gravity is weird, 0:18:51.720 --> 0:18:53.639 you know, there's no end to like the puzzles of 0:18:53.680 --> 0:18:55.280 gravity is fascinating. 0:18:54.800 --> 0:18:55.520 Bottomless pit. 0:18:56.560 --> 0:19:00.600 That's right, it's a black hole of questions. And one 0:19:00.680 --> 0:19:03.080 of my favorites is just that we have no way 0:19:03.160 --> 0:19:06.000 to sort of fit gravity in with the way the 0:19:06.080 --> 0:19:08.960 universe works according to everything else. You know, we talked 0:19:08.960 --> 0:19:11.560 earlier about how we have particles and we have forces 0:19:11.640 --> 0:19:15.880 or quantum fields equivalently, and that's a really successful way 0:19:15.880 --> 0:19:17.800 to describe the universe. You know, we have the Large 0:19:17.840 --> 0:19:20.639 Hadron Collider to explore these things really high energies, and 0:19:20.680 --> 0:19:24.199 we've understood all sorts of things using this theory. But 0:19:24.280 --> 0:19:27.520 that theory is used as quantum mechanics. So the way 0:19:27.520 --> 0:19:30.480 we describe interactions, you know, the way we talk about 0:19:30.480 --> 0:19:34.000 two electrons repelling each other, or the way lightning is 0:19:34.040 --> 0:19:37.919 formed or anything, involves passing quantum particles back and forth. 0:19:38.200 --> 0:19:39.720 And that's just not true for gravity. 0:19:40.359 --> 0:19:42.960 What does that mean? Passing particles back and forth? Like 0:19:43.000 --> 0:19:46.920 when like if I have two magnets and they're attracted 0:19:46.960 --> 0:19:49.119 to each other, they're not. They're not It's not like 0:19:49.119 --> 0:19:52.679 an invisible telekinesis pulling on each other. They're actually swapping 0:19:52.720 --> 0:19:54.760 particles and I can't see that is that kind of 0:19:54.800 --> 0:19:55.200 what do you mean? 0:19:55.359 --> 0:19:58.639 That's exactly what I mean. That the way two things 0:19:58.680 --> 0:20:02.280 interact via some four is by exchanging particles. And so 0:20:02.359 --> 0:20:06.360 for example, electromagnetism, right, is the force behind a magnet, 0:20:06.720 --> 0:20:09.240 and the way electromagnetism works, we think at a sort 0:20:09.240 --> 0:20:12.600 of microscopic particle level is that there's a particle that 0:20:12.680 --> 0:20:15.840 transmits that force, that sends sort of the information back 0:20:15.880 --> 0:20:18.560 and forth between two things that are feeling it. And 0:20:18.600 --> 0:20:21.840 in the case of electromagnetism, that particle is the photon. 0:20:22.560 --> 0:20:25.560 The particle is also a packet of light. So each 0:20:25.600 --> 0:20:29.120