WEBVTT - Why Is Gravity So Weird? 0:00:07.160 --> 0:00:10.200 I just think it's fascinating that it's such a fundamental 0:00:10.720 --> 0:00:14.440 force in the universe, right Like, it's it's basically the 0:00:14.480 --> 0:00:19.520 thing that builds galaxies and keeps planets moving right and 0:00:19.640 --> 0:00:23.000 gets structured to the entire cosmos. That's right on the 0:00:23.079 --> 0:00:26.880 largest scales, actually the most important force. It's the reason 0:00:26.960 --> 0:00:29.520 why things look the way they do, the reason why 0:00:29.800 --> 0:00:32.559 our planet is around, it's the reason why we're on 0:00:32.640 --> 0:00:36.239 the planet. It's pretty important, and yet we don't know 0:00:36.760 --> 0:00:39.240 a lot about it, right, Like, there's some really deep 0:00:39.560 --> 0:00:42.760 and strange mysteries about it. On one hand, we have 0:00:42.840 --> 0:00:45.360 a theory which works really really well. On the other hand, 0:00:45.400 --> 0:00:48.040 we have questions about it, but to seem really really basic. 0:00:48.520 --> 0:00:50.879 And not only that, it's it's very different than all 0:00:50.880 --> 0:00:54.240 the other forces of nature. That's right, one of these 0:00:54.280 --> 0:01:15.520 things is not like the other ones. Ye hi am more. 0:01:15.640 --> 0:01:18.920 I'm a cartoonist and I'm Daniel, I'm a particle physicist. 0:01:19.160 --> 0:01:22.440 And this is our podcast Daniel and Joe explained the universe, 0:01:22.600 --> 0:01:25.320 in which our cartoonist and physicists try to figure out 0:01:25.360 --> 0:01:29.960 how to make the universe understandable to anybody. Yeah, and 0:01:30.000 --> 0:01:34.360 today on the podcast we are examining a very heavy topic, 0:01:39.440 --> 0:01:46.959 gravity and specifically why is gravity so weak and strange. Gravity, 0:01:47.120 --> 0:01:50.200 as we said earlier, is something which controls the structure 0:01:50.280 --> 0:01:52.520 of the universe. I mean, the reason the Solar system 0:01:52.560 --> 0:01:54.920 looks the way it does is because of gravity. The 0:01:54.960 --> 0:01:57.560 reason the Earth is round is because of gravity. The 0:01:57.600 --> 0:02:00.600 reason we have galaxies is because of gravity. The reason 0:02:00.640 --> 0:02:02.920 we weighed so much, it's it's because of gravity. Right, 0:02:02.960 --> 0:02:07.640 it's not my belt, No, that's because of late night 0:02:07.720 --> 0:02:13.200 cake eating. Um. But it's such a fundamental force of nature. Rights, Like, 0:02:13.280 --> 0:02:16.440 it's present in our everyday live We spend a lot 0:02:16.480 --> 0:02:20.480 of time thinking about gravity, right, how not to fall down, 0:02:20.760 --> 0:02:23.639 how not drop things, how to go up buildings, how 0:02:23.680 --> 0:02:26.120 to go down buildings? Right, that's right. It seems like 0:02:26.200 --> 0:02:27.799 one of the most important forces. I mean, if you 0:02:27.880 --> 0:02:30.840 ask people, you know, to name a force or what 0:02:30.919 --> 0:02:33.200 kind of forces the experience in their life, gravity is 0:02:33.200 --> 0:02:35.919 the one that's present in their lives. Right, you're climbing upstairs, 0:02:35.919 --> 0:02:38.960 you're fighting gravity. Trip, you fall down, you're feeling gravity. 0:02:39.160 --> 0:02:41.720 You look around you. The shape of things is controlled 0:02:41.720 --> 0:02:46.000 by gravity, and that's why it's particularly strange that gravity 0:02:46.120 --> 0:02:49.200 is the weakest force of all the forces we've discovered, 0:02:49.440 --> 0:02:52.760 it's by far the weakest. Yeah, it's really strange to 0:02:53.120 --> 0:02:55.680 hear you say that, Like, how can gravity be weak? 0:02:56.000 --> 0:02:58.600 Like you know, like it's it's keeping the whole Earth together, 0:02:58.680 --> 0:03:02.200 it's making the entire higher planet swing around, going to 0:03:02.240 --> 0:03:05.359 circle basically, right. Without gravity, we would just shoot off 0:03:05.360 --> 0:03:08.760 into space. That's right. It's a really strange situation. And 0:03:08.800 --> 0:03:11.160 there's other things about gravity we don't understand as well. 0:03:11.520 --> 0:03:14.040 It's really strange. It doesn't play well with the other forces. 0:03:14.400 --> 0:03:17.400 It's very, very weak. It's a total mystery to science, 0:03:17.480 --> 0:03:20.160 except that we have a theory which works beautifully. Right. 0:03:20.200 --> 0:03:23.200 We can calculate exactly how mercury orbits the Sun. We 0:03:23.200 --> 0:03:25.880 can send things into outer space and note with two 0:03:25.919 --> 0:03:28.400 millimeter precision exactly where they're going to land. We have 0:03:28.520 --> 0:03:31.360 a working theory that we can use, right, but we 0:03:31.440 --> 0:03:34.400 don't understand it on a conceptual level. We have these basic, 0:03:34.520 --> 0:03:37.240 deep questions about about what gravity is and how the 0:03:37.320 --> 0:03:39.840 universe works because of it. So it's a weird question, 0:03:40.160 --> 0:03:42.560 and maybe one of the people hadn't thought about before. 0:03:43.000 --> 0:03:45.240 So Daniel went out as usual and ask people on 0:03:45.280 --> 0:03:47.960 the street, why do you think gravity is so weak. 0:03:48.240 --> 0:03:50.440 Here's what a random selection of folks who are willing 0:03:50.440 --> 0:03:52.480 to talk to me on a Tuesday morning had to 0:03:52.480 --> 0:03:55.600 say about gravity. I don't know. I should don't know 0:03:55.680 --> 0:03:57.880 about that, all right, I was. I was thought it 0:03:57.880 --> 0:04:03.720 was a pretty strong force. So I don't know. But yeah, because, um, 0:04:03.760 --> 0:04:06.480 it depends on the distance and it's long range one, 0:04:06.880 --> 0:04:08.880 so that's why we feel it's very weak most of 0:04:08.920 --> 0:04:13.200 the time. Cool. No, okay, I have no I'm sorry, 0:04:13.280 --> 0:04:18.000 it's not very fruitful. I have no idea, but I'd 0:04:18.000 --> 0:04:21.240 be interested in finding out why. All right, that wasn't 0:04:21.279 --> 0:04:24.240 that was pretty good. Most people weren't surprised when you 0:04:24.279 --> 0:04:27.520 said gravity is weak. I don't know. I feel like 0:04:27.520 --> 0:04:29.320 of all the questions I've asked people, this is the 0:04:29.360 --> 0:04:32.720 one that flams them the most. You know. People were like, what, 0:04:32.880 --> 0:04:36.040 I have no idea, or um, they had crazy ideas 0:04:36.040 --> 0:04:39.000 why gravity must must be weak. I feel like, usually 0:04:39.040 --> 0:04:41.200 we get one person who knows what the answer is 0:04:41.279 --> 0:04:43.440 or has a good clue about what what's going on. 0:04:43.640 --> 0:04:46.080 This time, I feel like almost everybody was pretty clueless. 0:04:46.120 --> 0:04:48.120 I mean, one person said I always thought gravity was 0:04:48.120 --> 0:04:51.680 pretty strong, right, which kind of sums up the situation. Right. 0:04:51.720 --> 0:04:55.040 Gravity is omnipresent in our lives. It dominates our experience, 0:04:55.320 --> 0:04:58.039 and yet it's so weak compared to the other really 0:04:58.080 --> 0:05:00.800 powerful forces we've discovered. Well of people, A couple of 0:05:00.880 --> 0:05:04.440 answers were that had to do with distance, Like, gravity 0:05:04.800 --> 0:05:07.560 gets really weak with distance, that's right. And the problem 0:05:07.600 --> 0:05:09.640 there is that all the forces get weak with distance, 0:05:09.800 --> 0:05:15.120 like electromagnetism also falls as a as a distance grows. Right, 0:05:15.160 --> 0:05:17.760 So all of these forces followed this one over our 0:05:17.839 --> 0:05:20.600 squared rule or are as your distance from the thing 0:05:20.680 --> 0:05:24.839 that's that's giving you the force, right, maybe maybe right? Maybe? Yeah, 0:05:24.920 --> 0:05:27.919 mostly we think and uh, and so that can't be 0:05:27.960 --> 0:05:29.880 the answer, right, because all the other forces have that 0:05:29.920 --> 0:05:31.640 same feature. So when you say it's the weak is 0:05:31.720 --> 0:05:34.960 it's not that it changes over distances differently than the 0:05:35.000 --> 0:05:37.320 other forces. That's right. So maybe we should talk about 0:05:37.680 --> 0:05:40.640 what the forces are and compare them to each other. 0:05:40.680 --> 0:05:45.320 So focus and get understanding of how crazy weak gravity is. Right. So, Daniel, 0:05:45.320 --> 0:05:48.960 what are the forces of nature besides a bad movie 0:05:49.000 --> 0:05:53.320 with Ben Affleck in center Bullock? Well, I think comedy. 0:05:53.520 --> 0:05:57.279 Comedy is definitely force of nature. You know, it solves 0:05:57.279 --> 0:06:00.240 big problems around the world. You know. The fundamental forces 0:06:00.360 --> 0:06:04.400 are electromagnetism, right, that's the one that controls electricity and 0:06:04.520 --> 0:06:07.240 magnetism obviously and is responsible for the cool things like 0:06:07.640 --> 0:06:11.839 light and lightning and all that all that cool stuff. Um. 0:06:11.880 --> 0:06:14.960 And then there's the weak nuclear force, which is a 0:06:15.040 --> 0:06:18.440 force which is responsible for radioactive decay of a nuclei. Right. 0:06:18.520 --> 0:06:21.279 And the cool thing about electricity and magnetism and the 0:06:21.320 --> 0:06:24.000 weak nuclear force is that we actually have shown that 0:06:24.040 --> 0:06:27.760 there are two sides of the same coin as a particle. Physicists, 0:06:27.760 --> 0:06:29.599 we refer to them as one force. We call it 0:06:29.640 --> 0:06:33.440 the electro week. So sort of magnetism lost out there 0:06:33.440 --> 0:06:36.800 in the name merger, right, it should be electro magnetic week. 0:06:36.839 --> 0:06:39.680 But nobody voted to keep magnetism in the the name 0:06:39.720 --> 0:06:42.520 of the partners on the law firm. Nobody, nobody lobbied 0:06:42.560 --> 0:06:49.599 for weak electro or magneto weak force. Yeah. Yeah, again, 0:06:49.880 --> 0:06:52.720 we are suffering the fate of some anonymous committee of 0:06:52.760 --> 0:06:54.839 scientists that get to name these things. Right, who are 0:06:54.920 --> 0:06:57.360 these people? It's probably some grad student, right or some 0:06:58.120 --> 0:07:02.240 you know, like this is really weird call it this. Yeah. 0:07:02.320 --> 0:07:05.280 So we have electricity and magnetism, which is a single force. 0:07:05.320 --> 0:07:07.520 We have the weak nuclear force, which is really should 0:07:07.520 --> 0:07:10.560 be combined with electricity magnetism. And then there's the strong 0:07:10.720 --> 0:07:12.520 nuclear force, and this is the one that holds the 0:07:12.600 --> 0:07:15.160 nucleus together. You know, the nucleus is just a bunch 0:07:15.200 --> 0:07:19.320 of positively charged protons and neutral neutrons, right, so it's 0:07:19.400 --> 0:07:22.520 only positively charged particles in the nucleus. So you might think, 0:07:22.560 --> 0:07:24.920 what it even holds the nucleus together, right, you have 0:07:24.960 --> 0:07:28.200 all this positively charged stuff should be repelling themselves. Well, 0:07:28.240 --> 0:07:30.920 it's the strong nuclear force, and it does so by 0:07:30.920 --> 0:07:34.720 exchanging these crazy little particles we call gluons, and that 0:07:34.800 --> 0:07:37.360 holds the nucleus together, and it's pretty strong. It's even 0:07:37.440 --> 0:07:40.680 stronger than electromagnetism. Well, let's take a step back. So 0:07:40.760 --> 0:07:45.400 in the universe there's stuff. There's like, yes, affirm that 0:07:45.440 --> 0:07:49.400 there is stuff in without reservation, there is stuff. I'm 0:07:49.400 --> 0:07:52.480 glad we saw that question. But I mean it's like 0:07:52.520 --> 0:07:56.000 there's stuff that has substance to it, that has masked 0:07:56.000 --> 0:07:58.240 to it, or you know that it sort of exists. 0:07:58.240 --> 0:08:01.240 And then there's also besides the at how these things 0:08:01.600 --> 0:08:03.920 interact with each other, like how they affect each other 0:08:04.080 --> 0:08:07.040 that's right. There's the matter and then there's the forces. Right. 0:08:07.120 --> 0:08:09.120 The forces affect how they interact with each other, and 0:08:09.160 --> 0:08:11.640 that's pretty much the universe. That's that's like, it's matter 0:08:11.720 --> 0:08:14.679 and forces. Yeah. One way to look at the universe 0:08:14.760 --> 0:08:17.320 is that it's particles, right, or you would say matter 0:08:17.360 --> 0:08:20.440 and their forces. In modern particle physics we think about 0:08:20.560 --> 0:08:23.120 one level deeper, which if we think of quantum fields, 0:08:23.520 --> 0:08:26.840 and quantum fields are responsible both for matter and for forces. 0:08:27.320 --> 0:08:29.560 So we can talk about that maybe in another podcast. 0:08:29.600 --> 0:08:32.040 What is a quantum field and how can I get one? 0:08:32.120 --> 0:08:34.600 You know for leaser rent um? What can they do 0:08:34.679 --> 0:08:36.600 for me? But yeah, I think it's it's fair still 0:08:36.720 --> 0:08:40.480 to think about the universe in terms of particles and forces. 0:08:40.640 --> 0:08:56.080 On that note, let's take a quick break. There are 0:08:56.120 --> 0:08:58.880 only four kinds of forces. Yeah, there are four kinds 0:08:58.880 --> 0:09:03.360 of forces. So after magnetism, weak nuclear force, strong nuclear force, 0:09:03.440 --> 0:09:06.120 and then of course gravity, right, that's the fourth force 0:09:06.120 --> 0:09:10.360 that we've discovered. The fascinating thing is that different particles 0:09:10.440 --> 0:09:13.840 feel different forces, right, Like, some particles feel this set 0:09:13.840 --> 0:09:17.160 of forces, some particles feel those set of forces. For example, right, 0:09:17.559 --> 0:09:22.800 particles with electric charge feel electromagnetism. Right. The electron, for example, 0:09:22.880 --> 0:09:26.600 is negatively charged, the proton is positively charged. You bring 0:09:26.640 --> 0:09:28.920 them close together, they're gonna pull on each other. They're 0:09:28.920 --> 0:09:32.040 gonna suck each other together, right, because they have opposite charges. 0:09:32.080 --> 0:09:34.920 We all know that, um. But you bring a neutral 0:09:34.960 --> 0:09:37.680 particle nearby, it just totally ignores it. Right, It doesn't 0:09:37.760 --> 0:09:41.120 feel it at all. Right, It's like it's like somebody's 0:09:41.160 --> 0:09:43.360 walking through a crowd of people shouting, but they have 0:09:43.400 --> 0:09:45.880 headphones on so they can't hear anything, and they're totally 0:09:45.960 --> 0:09:47.920 oblivious to it. It's kind of like how we talked 0:09:47.920 --> 0:09:51.320 about in a previous podcast. They're almost like languages or 0:09:51.400 --> 0:09:54.320 like social media platforms. Like some people are on Twitter, 0:09:54.559 --> 0:09:56.720 some people are on Facebook, but some people are not 0:09:56.800 --> 0:09:58.640 on this. And so if somebody if you're not on 0:09:58.640 --> 0:10:00.320 Twitter and so many sense to your tweet, you're not 0:10:00.320 --> 0:10:02.560 going to get it. And so it's just different ways 0:10:02.640 --> 0:10:05.240 the particles in right, that's right. Gravity is the Google 0:10:05.280 --> 0:10:12.240 plus social media right because nobody uses the trendstor it's 0:10:12.320 --> 0:10:16.640 ancient but powerless. Yeah, And so different particles feel different forces. 0:10:16.640 --> 0:10:20.120 And for example, an electron, while it feels electromagnetism. Because 0:10:20.120 --> 0:10:22.880 it has a negative charge, it doesn't feel a strong 0:10:22.920 --> 0:10:25.720 force at all. It will pass right by a bunch 0:10:25.720 --> 0:10:27.840 of particles that are really tugging on each other with 0:10:27.880 --> 0:10:31.160 a strong force and not be affected at all. Whereas corks. 0:10:31.559 --> 0:10:34.760 Corks feel all the forces. They feel a strong force, 0:10:35.160 --> 0:10:37.440 which is how they get pulled together in the nucleus. Remember, 0:10:37.440 --> 0:10:41.040 protons and neutrons are made of quarks. Quarks feel electromagnetism 0:10:41.040 --> 0:10:43.760 because they have electric charge. They feel the weak force. 0:10:43.960 --> 0:10:46.160 They also feel gravity, of course, because they have mass. 0:10:46.160 --> 0:10:50.040 So quarks get their fingers in everything they feel. They 0:10:50.080 --> 0:10:53.160 get the feels for everything. They feel everything's right, They 0:10:53.200 --> 0:10:57.640 got the strong feels. Course, they're really deeply emotional part 0:10:57.640 --> 0:11:00.960 of um. And on the other side of the spectrum, 0:11:00.960 --> 0:11:04.080 you've got things like neutrinos. Patrinos don't have electric charge, 0:11:04.360 --> 0:11:07.880 so they ignore all electricity magnetism, right, They don't interact 0:11:07.920 --> 0:11:11.319 with light. They're invisible. They pass right through anything that that. 0:11:12.360 --> 0:11:16.000 They ignore electro magnetic bonds, so they pass through most materials. 0:11:16.360 --> 0:11:18.760 They don't feel the strong force. The only way they 0:11:18.760 --> 0:11:20.880 interact is with the weak force, and the weak force 0:11:20.960 --> 0:11:23.480 is pretty weak, which is why neutrinos can mostly just 0:11:23.520 --> 0:11:31.160 pass through matter unaffected. So we have four fundamental forces, right, 0:11:31.200 --> 0:11:33.439 and gravity is one of these forces. And so when 0:11:33.440 --> 0:11:36.480 you say that antravity is weak, you actually mean it's 0:11:36.559 --> 0:11:39.960 weak compared to these other three forces, that's right. And 0:11:40.000 --> 0:11:43.160 so the ranking is the strong force is the strongest, 0:11:43.720 --> 0:11:46.800 so that one is actually well named. Congratulations, you know, 0:11:46.840 --> 0:11:50.040 anonymous group of scientists. Yeah, yeah, we should be called 0:11:50.040 --> 0:11:55.120 the as currently known to be the strongest force force. Um. 0:11:55.360 --> 0:11:58.600 Right after that comes electromagnetism, and you know, we know 0:11:58.679 --> 0:12:00.559 that force is pretty powerful. You stick your finger in 0:12:00.559 --> 0:12:03.480 a socket, you're going to feel the wrath of electromagnetism, right. 0:12:03.520 --> 0:12:05.920 It's it's not an unfamiliar feeling, right, right to think 0:12:05.960 --> 0:12:08.480 your finger in anything? You feel it, right, because it's 0:12:08.640 --> 0:12:13.000 electromagnetism is the force that keeps you from basically passing 0:12:13.040 --> 0:12:17.640 through the table or passing through your car. Right, that's right. 0:12:17.679 --> 0:12:20.960 Because electromagnetism is the basis of chemical bonds, right. And 0:12:21.080 --> 0:12:23.400 chemical bonds are really the thing that form the structure 0:12:23.440 --> 0:12:25.520 of your body. Right. You think if your body is 0:12:25.520 --> 0:12:27.839 like a bunch of particles, but it's held together by 0:12:27.840 --> 0:12:30.920 all these forces, it's like a chain link fence binding 0:12:30.960 --> 0:12:33.640 together these little particles and prevents you from passing through 0:12:33.679 --> 0:12:36.880 something else. Yeah, so we got the strong force, and 0:12:36.920 --> 0:12:40.560 then electromagnetism, and then actually the weak nuclear force. Right, 0:12:40.600 --> 0:12:43.480 this is the force that like powers neutrinos and radioactive decay. 0:12:43.760 --> 0:12:47.920 It's much weaker than electromagnetism um and much weaker than 0:12:47.960 --> 0:12:51.360 the strong force. Even weaker than the weak is gravity. 0:12:51.400 --> 0:12:54.920 That's right. If you make a list like strong force, electromagnetism, 0:12:55.000 --> 0:12:57.480 the weak force, then you should leave like a hundred 0:12:57.480 --> 0:13:00.920 blank pages and then you get to grab because when 0:13:00.920 --> 0:13:03.480 we compare these forces, we put things like an equal 0:13:03.520 --> 0:13:07.040 distance apart and compare the strength of the forces. Gravity 0:13:07.080 --> 0:13:11.080 is ten to the thirty six times weaker than the 0:13:11.080 --> 0:13:14.920 weak force. But that's ten with thirty six zeros in 0:13:14.960 --> 0:13:16.920 front of it. But it isn't that sort of a 0:13:16.920 --> 0:13:20.280 matter of units or scale, do you know what I mean? Like, 0:13:20.640 --> 0:13:24.839 it's much weaker, but only if you compare apples to apples, right, 0:13:25.160 --> 0:13:27.480 or orange to oranges. That's right. But put two protons 0:13:27.559 --> 0:13:30.559 next to each other, right, Two protons have a certain 0:13:30.600 --> 0:13:32.760 amount of mass and a certain amount of electric charge, 0:13:33.200 --> 0:13:35.360 and the force of their charges is going to be 0:13:35.480 --> 0:13:38.560 much much stronger than the force from their masses. So yeah, 0:13:38.600 --> 0:13:41.440 if everything was much much more massive, then there would 0:13:41.480 --> 0:13:44.120 be stronger gravity. But you can compare these things apples 0:13:44.120 --> 0:13:46.400 to apples by comparing them, you know, the same distance 0:13:46.440 --> 0:13:49.120 and the same basic unit of interaction. Right, But what 0:13:49.160 --> 0:13:52.400 if you take an apple put it next to another apple? Well, 0:13:52.440 --> 0:13:54.319 I think you can do that experiment. Nothing's going to 0:13:54.400 --> 0:13:56.839 happen because gravity is so weak. Right. You don't see 0:13:56.840 --> 0:13:59.280 two apples like pulling themselves together on the counter, right, 0:13:59.320 --> 0:14:02.680 then they'll alden apple collider um. You know, the apples 0:14:02.679 --> 0:14:05.200 are not drawn to each other. Gravity is a super 0:14:05.240 --> 0:14:07.319 weak force, and you can see this yourself. Right, you 0:14:07.840 --> 0:14:11.520 can do an experiment where you counter the entire gravitational 0:14:11.559 --> 0:14:14.640 force of an enormous celestial body like the Earth. Right, 0:14:15.200 --> 0:14:18.199 take a small kitchen magnet and use it to hold 0:14:18.280 --> 0:14:20.520 up a nail and think about what's happening there. Right, 0:14:20.560 --> 0:14:23.960 you have the nail is being pulled down by every 0:14:24.080 --> 0:14:26.560 single rock in the Earth. It's pulling with all of 0:14:26.600 --> 0:14:30.480 its gravity. But a tiny little kitchen magnet totally overcomes that. 0:14:31.760 --> 0:14:34.320 It can lift the nail even though it's pulling. It's 0:14:34.360 --> 0:14:37.760 being pulled down by the whole entire planet Earth, right exactly. Now, 0:14:37.800 --> 0:14:41.120 imagine a magnet the size of the Earth, right, I 0:14:41.120 --> 0:14:44.440 mean that would be that would be extraordinarily powerful. And 0:14:44.480 --> 0:14:47.400 so you have basically like a gravitational blob the size 0:14:47.440 --> 0:14:53.320 of the Earth. Still pretty ineffective compared to electromagnetism. So 0:14:53.320 --> 0:14:57.520 so it's weak if you sort of compare it by object, 0:14:58.080 --> 0:14:59.600 Like you said, if you take a proton and put 0:14:59.600 --> 0:15:02.480 it next to proton, the the force are going to 0:15:02.560 --> 0:15:05.680 feel from electro magnetism is so much bigger than the 0:15:05.840 --> 0:15:07.960 force of gravity. They're going to feel towards each other 0:15:08.400 --> 0:15:12.360 the same with like two electrons or two cords and things. 0:15:12.560 --> 0:15:14.640 So in the scale of like the particles that we know, 0:15:15.080 --> 0:15:18.920 it's a really weak force, that's right, exactly. And yet 0:15:19.280 --> 0:15:21.480 and yet it seems to dominate. Right. That's a bit 0:15:21.520 --> 0:15:24.440 of a puzzle. Like, on one hand, it's super duper weak, 0:15:24.520 --> 0:15:26.360 and we're telling you that it hardly counts for anything. 0:15:26.400 --> 0:15:28.880 On the other hand, it's responsible for the structure of 0:15:28.880 --> 0:15:31.160 the Solar System, man for the galaxy, and it's the 0:15:31.160 --> 0:15:33.720 reason the universe looks the way it is, right, And 0:15:33.760 --> 0:15:35.520 so that can be confusing to people, Like how do 0:15:35.560 --> 0:15:38.040 you reconcile those two things in your head? Yeah, Like 0:15:38.080 --> 0:15:41.040 why doesn't the Earth feel an electromagnetic force with the Sun, 0:15:41.360 --> 0:15:44.320 which it would be so much bigger than the force 0:15:44.360 --> 0:15:47.200 of gravity. Yeah, what, it would be pretty shocking. And 0:15:47.320 --> 0:15:50.440 and that's actually the reason is um gravity is different 0:15:50.480 --> 0:15:53.280 from the other forces and that it can't be canceled out. Right, 0:15:53.560 --> 0:15:56.680 if there was some huge electrostatic difference between the Sun 0:15:56.720 --> 0:15:58.680 and the Earth, like a bunch of positive charges there 0:15:58.720 --> 0:16:01.280 and a bunch of negative charges year, it would create 0:16:01.400 --> 0:16:05.560 such an enormous force that it would be very quickly balanced. 0:16:05.800 --> 0:16:08.360 Like that's what lightning is, right, When there's a charge 0:16:08.400 --> 0:16:12.520 differential between clouds and the ground, it's it doesn't take 0:16:12.560 --> 0:16:15.360 that much before those charges want to rearrange themselves to 0:16:15.400 --> 0:16:18.160 a lower energy configuration. They rushed down to the ground, 0:16:18.240 --> 0:16:19.800 or they rushed up to the clouds and they jump 0:16:20.880 --> 0:16:23.960 to balance themselves up. Because you have two kinds of charges, 0:16:23.960 --> 0:16:26.600 you have positive and you have negative, so you can 0:16:26.760 --> 0:16:30.440 find an arrangement where basically everybody is happy. It's an equilibrium, right, 0:16:30.640 --> 0:16:33.120 But that's not true for gravity, Okay, I get it. 0:16:33.160 --> 0:16:36.080 So for example, if the Earth was every particle on 0:16:36.120 --> 0:16:40.080 Earth had a positive electromagnetic charge and every particle in 0:16:40.120 --> 0:16:43.440 the Sun had a negative electromagnetic charge, there would be 0:16:43.480 --> 0:16:49.440 a humongous pool from electromagnetism pulling the Earth into the Sun. Yeah, 0:16:49.480 --> 0:16:54.480 we'd be toasted pretty quick. Yeah, I would be huge. 0:16:54.840 --> 0:16:57.040 Even the opposite if we were all positive and the 0:16:57.080 --> 0:16:59.400 Sun was all positive, we would get shot out of 0:16:59.400 --> 0:17:02.600 the solar stem very quickly, that's right. And that's why 0:17:02.680 --> 0:17:05.280 you know, early days of the Solar system being formed, 0:17:05.280 --> 0:17:08.840 you have these gases and the gas and dust coalescing, 0:17:09.080 --> 0:17:13.119 and very rapidly things neutralize, right, because anything that feels 0:17:13.160 --> 0:17:16.439 an electrostatic force to something else is going to find 0:17:16.480 --> 0:17:18.760 the opposite charge and they're going to coalesce and they're 0:17:18.760 --> 0:17:21.119 gonna make something neutral. Right. That's why most of the 0:17:21.200 --> 0:17:23.680 things around you are neutral, Right, Most of the elements 0:17:23.880 --> 0:17:27.679 are neutral, because any deviation from neutral results in a 0:17:27.680 --> 0:17:31.440 powerful force to neutralize it. So, thankfully the Earth is 0:17:31.480 --> 0:17:34.359 made out of both like equal amounts of positive and 0:17:34.359 --> 0:17:39.439 negative particles, right, that's right. Thankfully we're sort of balanced electromagnetically, 0:17:39.720 --> 0:17:42.439 and so even if the Sun was all positive, we 0:17:42.480 --> 0:17:45.359 would look like neutral, like a neutral ball to to 0:17:45.440 --> 0:17:48.119 the sun. Yeah, that's right, we're on large scales. The 0:17:48.160 --> 0:17:49.960 Earth is neutral, right, I mean there might be some 0:17:50.520 --> 0:17:53.879 residual positive or negative charge depending on the solar wind, etcetera. 0:17:54.119 --> 0:17:57.600 But basically the Earth is neutral, and so the largest 0:17:57.640 --> 0:18:00.440 force of the Earth feels is the gravity in the sun, 0:18:00.520 --> 0:18:03.440 even though gravity is super duper weak. Right, it doesn't 0:18:03.440 --> 0:18:05.440 take a lot to counteract gravity. But it's the only 0:18:05.480 --> 0:18:08.080 player left because everybody else is sort of pair it 0:18:08.200 --> 0:18:10.760 up and danced off for the night, and gravity is 0:18:10.800 --> 0:18:14.560 just there left holding the bag. And gravity can't be balanced, right. 0:18:14.760 --> 0:18:17.320 You feel gravity if you have any mass, right, But 0:18:17.359 --> 0:18:19.879 there's only positive masses and no such thing as a 0:18:20.040 --> 0:18:24.480 negative mass to give anti gravity. Well, let's keep going, 0:18:24.600 --> 0:18:40.760 but first let's take a quick break. Okay, So that's 0:18:40.760 --> 0:18:45.280 how gravity is so much weaker than the other forces. Um, 0:18:45.320 --> 0:18:48.080 so how's it different than the other three forces of nature? 0:18:48.280 --> 0:18:51.560 There's like no end to to weys, the gravity is weird, 0:18:51.640 --> 0:18:53.560 you know, there's no end to like the puzzles of 0:18:53.600 --> 0:18:57.720 Gravity's fascinating bottomless pit. That's right, it's a black hole 0:18:58.080 --> 0:19:01.520 of questions. Um. And one of my favorites is just 0:19:01.600 --> 0:19:05.000 that we have no way to sort of fit gravity 0:19:05.040 --> 0:19:07.960 in with the way the universe works according to everything else. 0:19:08.320 --> 0:19:10.679 You know, we talked earlier about how we have particles 0:19:10.720 --> 0:19:14.560 and we have forces or quantum fields equivalently, and that's 0:19:14.600 --> 0:19:17.040 a really successful way to describe the universe. You know, 0:19:17.119 --> 0:19:19.520 we have the Large Hadron Collider to explore these things, 0:19:19.560 --> 0:19:22.520 really high energies, and we've understood all sorts of things 0:19:22.600 --> 0:19:26.560 using this theory. But that theory is used as quantum mechanics. 0:19:26.920 --> 0:19:29.800 So the way we describe interactions, you know, the way 0:19:29.840 --> 0:19:33.159 we talk about two electrons um repelling each other, or 0:19:33.160 --> 0:19:36.520 the way lightning is formed or anything involves passing quantum 0:19:36.560 --> 0:19:39.640 particles back and forth. And that's just not true for gravity. 0:19:40.119 --> 0:19:42.879 What does that mean? Passing particles back and forth? Like 0:19:42.920 --> 0:19:46.840 when like if I have two magnets and they're attracted 0:19:46.880 --> 0:19:49.040 to each other, they're not. They're not It's not like 0:19:49.040 --> 0:19:52.600 an invisible telekinesis pulling on each other. They're actually swapping 0:19:52.640 --> 0:19:54.720 particles and I can't see that. Is that kind of 0:19:54.720 --> 0:19:57.280 what you mean? That's exactly what I mean. Um that 0:19:57.520 --> 0:20:00.440 the way two things interact via some four is by 0:20:00.480 --> 0:20:04.679 exchanging particles. And so for example, electromagnetism, right, is the 0:20:04.720 --> 0:20:08.480 force behind a magnet, And the way electromagnetism works, we 0:20:08.520 --> 0:20:11.359 think at a sort of microscopic particle level, is that 0:20:11.400 --> 0:20:14.640 there's a particle that transmits that force, that sends sort 0:20:14.640 --> 0:20:17.199 of the information back and forth between two things that 0:20:17.240 --> 0:20:20.399 are feeling it. And in the case of electromagnetism, that 0:20:20.480 --> 0:20:23.720 particle is the photon. Right. The particle is also a 0:20:23.760 --> 0:20:26.760 packet of light. So each of the quantum forces that 0:20:26.760 --> 0:20:30.240 we talked about before, electromagnetism, the weak force and the 0:20:30.280 --> 0:20:33.240 strong force, each of them have a particle we associate 0:20:33.320 --> 0:20:36.160 with it. And that's not just like some name tag 0:20:36.200 --> 0:20:37.880 we put on and say, hey, you get this one, 0:20:37.920 --> 0:20:40.120 you get this one. We think that that's the particle 0:20:40.160 --> 0:20:43.560 that's responsible for making the force work. So when two 0:20:43.560 --> 0:20:46.720 electrons come near each other, how do they repel each other? 0:20:46.720 --> 0:20:49.560 How does that actually happen? But we think that they 0:20:49.600 --> 0:20:54.320 send photons out right, The electric field of a moving electron, right, 0:20:54.359 --> 0:20:59.320 and accelerating electron generates photons, and those photons um interact 0:20:59.320 --> 0:21:02.640 with the other chron's and so basically the passing messages 0:21:02.680 --> 0:21:06.359 back and forth using these quantum particles. So gravity is 0:21:06.400 --> 0:21:10.040 weird because we don't know that there is an quantum 0:21:10.080 --> 0:21:14.440 particle being exchanged when two things get attracted gravitationally. That's right. 0:21:14.440 --> 0:21:16.960 So we have this great framework. We say, oh, maybe 0:21:17.000 --> 0:21:21.840 all forces are quantum mechanical fields interacting with each other. Right, 0:21:22.000 --> 0:21:24.560 Let's apply that to the electromagnetic field. Yeah it works. 0:21:24.680 --> 0:21:26.639 Let's apply that to the weak force. Yeah it works. 0:21:26.800 --> 0:21:29.080 Let's applies to the strong force. Oh cool, it works. 0:21:29.280 --> 0:21:31.560 Maybe this is something deep about the way the universe works. 0:21:31.720 --> 0:21:37.000 Let's apply to gravity. Oh it doesn't work, right, So 0:21:37.040 --> 0:21:38.399 what does that mean? What does it mean when I 0:21:38.400 --> 0:21:40.879 say it doesn't work? Well? For a theory to work, 0:21:41.240 --> 0:21:44.600 it has to provide predictions for experiments. You have to 0:21:44.640 --> 0:21:47.320 be able to say, okay, theory, what would happen in 0:21:47.359 --> 0:21:50.920 this configuration if I shot a proton and another particle. 0:21:51.359 --> 0:21:53.280 Predict what would happen, and then you can go off 0:21:53.280 --> 0:21:56.200 and do the experiments and compare it. Right. Well, when 0:21:56.200 --> 0:21:57.760 you do that for gravity, you try to form a 0:21:57.880 --> 0:22:02.120 quantum theory of gravity, it doesn't work. You get nonsense answers. 0:22:02.400 --> 0:22:05.760 You can answers like infinity right, or things disappear, or 0:22:06.000 --> 0:22:09.480 it just it doesn't mathematically function like there's no way 0:22:09.520 --> 0:22:12.600