WEBVTT - How do particles carry forces? 0:00:08.360 --> 0:00:12.280 Hey, Jorge, I'm wondering how you feel about the Midi Chlorians, 0:00:12.360 --> 0:00:15.840 those little critters that give Jedi the ability to interact 0:00:15.840 --> 0:00:16.480 with the Force. 0:00:17.480 --> 0:00:21.400 You mean in Star Wars. I mostly try to ignore them. 0:00:21.920 --> 0:00:25.200 They're a bit of an awkward retroactive continuity or redcon 0:00:25.640 --> 0:00:26.960 of the original series. 0:00:27.320 --> 0:00:29.880 Mm so you prefer the original approach where it's like 0:00:29.880 --> 0:00:33.120 more democratic. Anybody can learn the force like yoga. 0:00:33.240 --> 0:00:34.640 You mean, like Yoda or yoga. 0:00:36.240 --> 0:00:37.760 I mean like Yoda doing. 0:00:37.680 --> 0:00:40.760 Yoga, and like downward facing Jedi. 0:00:40.760 --> 0:00:42.960 That conjured of a pretty awkward mental image. 0:00:43.120 --> 0:00:45.199 How flexible is Yoda? We may never know. 0:00:45.400 --> 0:00:47.159 Well, I'm a fan of the Midichlorians. I feel like 0:00:47.159 --> 0:00:48.280 they're more scientific. 0:00:48.479 --> 0:00:50.279 Oh are you a fan of jar Jar Binks too? 0:00:50.400 --> 0:00:53.080 Because I think most people who are in that camp 0:00:53.400 --> 0:00:55.360 are also in the jar Jar Binks camp. But you're 0:00:55.400 --> 0:00:57.480 not tall made up right? It's not real science. 0:00:57.800 --> 0:01:00.800 I know it's not real science, but it's science. You know. 0:01:00.840 --> 0:01:04.120 It's a better microscopic explanation than just like hand waving 0:01:04.240 --> 0:01:04.919 yoga magic. 0:01:05.520 --> 0:01:08.839 I think the magic in Star Wars is literally handwaving, 0:01:09.120 --> 0:01:10.959 like waving your hands in front of your face, going, 0:01:11.160 --> 0:01:12.720 does this not the signs you're looking for. 0:01:13.040 --> 0:01:15.040 I need the old physics mind trick instead. 0:01:15.280 --> 0:01:18.560 That's right, redcon our real universe, not my childhood fantasy. 0:01:18.920 --> 0:01:19.720 That's my job. 0:01:35.120 --> 0:01:37.920 Hi'm Jorhem, a cartoonist and the author of Oliver's Great 0:01:37.920 --> 0:01:38.680 Big Universe. 0:01:38.920 --> 0:01:39.080 Hi. 0:01:39.120 --> 0:01:41.640 I'm Daniel. I'm a particle physicist, and that means my 0:01:41.880 --> 0:01:45.039 job is to explain away all the apparent magic in 0:01:45.080 --> 0:01:45.679 the universe. 0:01:46.160 --> 0:01:48.120 You have to understand it first, though, don't you. Isn't 0:01:48.120 --> 0:01:51.120 that step one? Or are you just making stuff up? 0:01:51.160 --> 0:01:52.360 Are you? George Lucas seing it? 0:01:52.440 --> 0:01:55.680 I think explaining it away is understanding it. Describing how 0:01:55.720 --> 0:01:57.760 something works in terms of its like tiny little bits 0:01:57.760 --> 0:02:00.640 and how they bump and dance together. That's basically explanation. 0:02:00.920 --> 0:02:02.640 Or maybe I think you're maybe saying your job is 0:02:02.680 --> 0:02:04.720 to look for explanations. 0:02:04.160 --> 0:02:06.120 Yeah, and sometimes we actually find them. 0:02:06.120 --> 0:02:07.880 Yeah, and then explain it to other pe books like 0:02:07.880 --> 0:02:10.239 we do in this podcast. So welcome to Daniel and 0:02:10.320 --> 0:02:13.840 Jorge Explain the Universe, a production of iHeartRadio. 0:02:13.240 --> 0:02:15.679 In which we try to take everything in the universe 0:02:15.720 --> 0:02:19.440 that seems unexplainable, that seems magical, and figure out how 0:02:19.480 --> 0:02:22.480 it comes to be. Drill down into its tiny little 0:02:22.480 --> 0:02:25.200 bits and particles and explain how they bump and dance 0:02:25.240 --> 0:02:28.040 and push on each other to weave themselves together into 0:02:28.120 --> 0:02:31.440 our reality, to explain why yoga feels so good or 0:02:31.600 --> 0:02:32.120 so bad. 0:02:32.360 --> 0:02:34.840 That's right, because it is a marvelous universe out there, 0:02:34.880 --> 0:02:38.440 with giant gaxies moving across at cosmos and stars exploding 0:02:38.520 --> 0:02:40.720 and black holes sucking stuff in, and we're interested in 0:02:40.800 --> 0:02:42.920 knowing what are some of the forces that bind it 0:02:42.960 --> 0:02:45.639 all together, that flow through us and make it all 0:02:45.639 --> 0:02:46.120 make sense. 0:02:46.280 --> 0:02:49.799 And is it even possible to explain all of that craziness, 0:02:49.800 --> 0:02:52.480 all the amazing things we experience in the universe, from 0:02:52.560 --> 0:02:55.840 leaves swirling in the fall to black holes collapsing in 0:02:55.960 --> 0:02:58.959 terms of tiny particles. Is it really possible to break 0:02:58.960 --> 0:03:00.880 it all down and say it's just a bunch of 0:03:00.880 --> 0:03:03.280 electrons passing particles back and forth. 0:03:03.480 --> 0:03:06.040 I feel like you're minimizing electrons. You said, only a 0:03:06.040 --> 0:03:09.359 bunch of electrons. But electrons are pretty pretty special, aren't they. 0:03:09.400 --> 0:03:12.040 Each one is a tiny snowflake in the universe. 0:03:12.120 --> 0:03:15.160 They're all actually identical right in a way snowflakes aren't 0:03:15.160 --> 0:03:17.600 even But I think the job of particle physics is 0:03:17.800 --> 0:03:21.440 literally to minimize the universe, to say, everything that's big 0:03:21.480 --> 0:03:23.840 can be explained in terms of everything that's small. 0:03:24.120 --> 0:03:24.280 Yeah. 0:03:24.320 --> 0:03:26.520 I guess that's a job of physics to break things down. 0:03:26.880 --> 0:03:29.919 And I guess throughout the history of humans and signs, 0:03:30.160 --> 0:03:32.160 that's what you have been doing, right, first breaking things 0:03:32.200 --> 0:03:35.280 down into types of elements, and then atoms and then 0:03:35.320 --> 0:03:36.320 atomic particles. 0:03:36.400 --> 0:03:39.560 Yeah. We hope that breaking things down will give us explanations, 0:03:39.640 --> 0:03:42.440 will reveal the true nature of the universe, and that 0:03:42.480 --> 0:03:45.200 we could go the opposite direction also from the little 0:03:45.240 --> 0:03:47.800 bits tooing and frowing, that we can weave those little 0:03:47.800 --> 0:03:50.480 bits back together. All their tooing and frowing can be 0:03:50.600 --> 0:03:53.440 sewn together to explain everything that happens, the way like 0:03:53.520 --> 0:03:56.560 water droplets eventually could explain a hurricane, and the way 0:03:56.640 --> 0:03:59.960 quantum particles somehow make up your classical body. We hope 0:04:00.080 --> 0:04:02.920 that by drilling down we can expose the most fundamental 0:04:03.000 --> 0:04:05.000 layer of the universe and then build back up to 0:04:05.080 --> 0:04:05.960 explain everything. 0:04:06.120 --> 0:04:08.280 Yeah, and so, little by little, scientists have come up 0:04:08.280 --> 0:04:10.320 with a picture of the universe that can be broken 0:04:10.360 --> 0:04:14.200 down into subatomic particles called electrons and quarks, and also 0:04:14.360 --> 0:04:17.240 force particles. So the question is does it all make sense? 0:04:17.440 --> 0:04:18.200 Does it all stick? 0:04:18.760 --> 0:04:21.040 We have a mathematical description of how this all works, 0:04:21.080 --> 0:04:24.200 which is incredibly precise. We can predict the outcomes of 0:04:24.240 --> 0:04:27.560 experiments to ten or fifteen decimal places and mostly get 0:04:27.600 --> 0:04:30.240 it right. But is it possible to get an intuitive 0:04:30.360 --> 0:04:33.600 understanding to tell ourselves, like a little story about what's 0:04:33.640 --> 0:04:36.520 happening down there in the quantum realm in a way 0:04:36.520 --> 0:04:39.480 that gives us some insights, some understanding. Is it really 0:04:39.480 --> 0:04:42.560 true that particles are zipping around tossing force particles back 0:04:42.600 --> 0:04:44.760 and forth together or is something deeper happening? 0:04:45.080 --> 0:04:47.120 Yeah, so we're here to force out the truth. So 0:04:47.200 --> 0:04:54.080 today on the podcast, we'll be asking the question how 0:04:54.120 --> 0:04:59.520 do particles carry force? This is generic force, not the force, right. 0:04:59.360 --> 0:05:02.880 This is science force, not science fiction force or magical force. 0:05:03.040 --> 0:05:04.880 Who Science Force? I want to be part of that team. 0:05:05.000 --> 0:05:07.760 Do you wear uniforms? Do you have like a secret base? 0:05:08.520 --> 0:05:10.520 Absolutely, they're snappier than the Space Force. 0:05:10.560 --> 0:05:13.320 Also, yeah, well I'll join either one. To be honest, 0:05:13.520 --> 0:05:16.440 anything that has a base and involves space or science 0:05:17.480 --> 0:05:18.239 and laser guns. 0:05:18.240 --> 0:05:20.240 I mean, I think we settle this already. The Science 0:05:20.240 --> 0:05:21.839 Force is going to elect you to be part of 0:05:21.839 --> 0:05:24.080 the space Force and send you up to meet the aliens? 0:05:24.160 --> 0:05:24.320 Wait? 0:05:24.360 --> 0:05:26.320 Wait, when do we settle this? I didn't sign any 0:05:26.600 --> 0:05:27.719 agreements here. 0:05:27.920 --> 0:05:29.640 Oh sorry, we had a meeting of the Science Force. 0:05:29.640 --> 0:05:30.599 I guess you weren't there. 0:05:30.800 --> 0:05:32.720 Yeah, yeah, I guess it depends on how much you're 0:05:32.760 --> 0:05:34.839 paying me. How much are you paying me to do this? Daniel? 0:05:35.000 --> 0:05:37.360 And or am I surviving relatives? 0:05:37.480 --> 0:05:39.640 Yeah? You get paid on your return? Is that all right? 0:05:39.720 --> 0:05:42.040 What do you mean I pay or I get paid? 0:05:42.080 --> 0:05:43.520 You get paid if you survive. 0:05:43.800 --> 0:05:46.760 That sounds like a terrible deal. Do you get paid 0:05:46.839 --> 0:05:49.839 only if you discover something in physics Daniel? Or do 0:05:49.880 --> 0:05:50.839 you get paid either way? 0:05:50.920 --> 0:05:53.240 I'm getting paid and I never discovered anything? 0:05:54.480 --> 0:05:58.240 Then the answerds yes, so far, so far right. There's 0:05:58.240 --> 0:05:59.960 always an optimism. 0:05:59.440 --> 0:06:00.839 That's right and over yet. 0:06:00.960 --> 0:06:04.400 That's right, your careering over yet? But maybe have a 0:06:04.440 --> 0:06:07.560 podcast long enough and who knows what you'll say, day 0:06:07.560 --> 0:06:10.560 tuned folks. But anyways, it's an interesting question because we 0:06:10.920 --> 0:06:13.360 tend to think of matter and the things around us 0:06:13.440 --> 0:06:15.520 is being made out of particles. That kind of makes sense. 0:06:15.600 --> 0:06:18.520 But the idea that maybe the forces between those particles 0:06:18.520 --> 0:06:20.719 the things that make you stand here on Earth or 0:06:20.839 --> 0:06:23.680 that makes all your atoms stick together, or your hair 0:06:23.760 --> 0:06:27.520 stent when they're theirs static electricity, those things could be 0:06:27.560 --> 0:06:30.960 due to particles also is kind of confusing, right. 0:06:30.839 --> 0:06:33.080 It is confusing, and yet it's something you hear a 0:06:33.120 --> 0:06:36.120 lot in popular science without a sort of deeper explanation 0:06:36.240 --> 0:06:38.919 for what the limits are of that description. You know, 0:06:38.960 --> 0:06:41.040 everything in the end is an analogy, and those analogies 0:06:41.080 --> 0:06:43.400 always break down at some point. So which parts of 0:06:43.400 --> 0:06:45.640 that story are true and which parts of that story 0:06:45.680 --> 0:06:46.640 are just a cartoon? 0:06:46.880 --> 0:06:49.000 That's right. You don't want to force a force analogy 0:06:49.600 --> 0:06:51.720 that's too deep, all right? Well, as usual, we were 0:06:51.760 --> 0:06:53.880 wondering how many people out there I thought about the 0:06:53.920 --> 0:06:57.039 idea of particles caring force and how they might do that. 0:06:57.240 --> 0:07:00.600 So thanks to everybody who volunteers for this audience participation 0:07:00.720 --> 0:07:03.960 segment of the podcast. We'd love if you participated. Since 0:07:04.040 --> 0:07:06.360 you are part of the audience. Don't be shy write 0:07:06.360 --> 0:07:09.000 to me two questions at Daniel and Jorge dot com 0:07:09.000 --> 0:07:11.640 and in the future you'll hear your voice on the podcast. 0:07:11.760 --> 0:07:13.760 So think about it for a second. How do you 0:07:13.800 --> 0:07:17.000 think particles carry forth? Here's what I be glad to say. 0:07:17.120 --> 0:07:20.760 I think technically, they carry force by exchanging particles. I know, 0:07:20.840 --> 0:07:24.120 all the matter particles are called fermions, and they exchange 0:07:24.160 --> 0:07:28.480 force by passing around their boson counterparts. For example, the 0:07:28.840 --> 0:07:31.440 strong force I think passes around gluons, and so the 0:07:31.480 --> 0:07:35.160 mental model that I have is fermians passing their bosons around, 0:07:35.240 --> 0:07:37.480 sort of like playing catch. But I'm sure that's not 0:07:37.520 --> 0:07:39.960 even close to an accurate representation, but it's kind of 0:07:40.000 --> 0:07:40.640 what I've. 0:07:40.560 --> 0:07:43.320 Thought of boson's carry force, because there's a way paint 0:07:43.720 --> 0:07:50.520 qui fermions, just in the way light light steams up. 0:07:50.640 --> 0:07:56.040 I think particles carry forces by interacting with fields, or 0:07:56.080 --> 0:07:59.040 they might also carry a force by being like a 0:07:59.080 --> 0:08:02.720 part of them, like shaking in that dimension. Sort of. 0:08:03.080 --> 0:08:06.400 Particles carry force in their pockets, and when they want 0:08:06.440 --> 0:08:08.920 to transmit a force, they reach into their pocket and 0:08:08.920 --> 0:08:11.280 they pull out a boson and they lob it at 0:08:11.320 --> 0:08:13.040 another particle to push it out of the way. 0:08:13.360 --> 0:08:17.760 I assume particles carry force through velocity, mass, and spin, 0:08:18.360 --> 0:08:22.400 and they transfer force as they translate one of those 0:08:22.960 --> 0:08:25.239 upon interaction with something else. 0:08:25.600 --> 0:08:28.600 I thought that the forces were transmitted when the force 0:08:28.680 --> 0:08:31.800 particles were transferred from one particle to another, but Having 0:08:31.880 --> 0:08:35.200 just listened to your podcast on energy, I imagine the 0:08:35.240 --> 0:08:37.760 answer is probably just momentum. 0:08:37.840 --> 0:08:40.199 All right, a lot of pretty science the answers. Are 0:08:40.200 --> 0:08:42.560 you also recruiting them for the science force? Is there 0:08:42.559 --> 0:08:44.199 a pledge to be in the science force? 0:08:44.720 --> 0:08:46.439 Did you like the answer where the're pulling bosons out 0:08:46.440 --> 0:08:47.040 of their pockets? 0:08:47.920 --> 0:08:48.120 Yeah? 0:08:48.160 --> 0:08:49.959 What's it required? What kind of gadgets do you get? 0:08:50.280 --> 0:08:53.160 You get a pocket full of bosons and you set free, 0:08:53.600 --> 0:08:55.360 go go forth in science. 0:08:55.600 --> 0:08:58.439 Nice. Nice, that sounds like a ninety song pocket full 0:08:58.480 --> 0:09:01.480 of bosons. But anyways, interesting answers from our listeners here. 0:09:01.600 --> 0:09:06.959 None of them mentioned Yoda doing yoga or Medei Chlorians disappointed. Yeah, 0:09:07.120 --> 0:09:10.440 step it up, listeners. We have some interesting answers having 0:09:10.480 --> 0:09:14.160 to do with velocity and mass and colored matter and 0:09:14.200 --> 0:09:16.600 maybe extra dimensions. So I'll have to explore here. So 0:09:16.679 --> 0:09:19.400 let's break it down, Daniel, what is the technical definition 0:09:19.640 --> 0:09:21.360 of a force? Let's start with that. 0:09:21.440 --> 0:09:23.840 So all of these explanations in the end are trying 0:09:23.840 --> 0:09:27.280 to describe things we have experience with. That's what physics does, right, 0:09:27.360 --> 0:09:29.640 give labels to things and then try to explain them. 0:09:29.920 --> 0:09:32.440 And so a force is something we're familiar with. Right, 0:09:32.480 --> 0:09:35.040 somebody pushes you, or you press down the accelerator in 0:09:35.080 --> 0:09:38.520 your car. These are things that involve forces. Mathematically and 0:09:38.520 --> 0:09:41.320 in physics, we think about a force as anything that 0:09:41.440 --> 0:09:44.520 changes the momentum of an object. So a ball flying 0:09:44.520 --> 0:09:46.840 through space at the same velocity, there's no force on 0:09:46.920 --> 0:09:49.400 it. It just continues. If you want to change its velocity, 0:09:49.440 --> 0:09:52.120 its direction, or its overall momentum in any way, you 0:09:52.200 --> 0:09:53.680 have to apply a force. 0:09:54.160 --> 0:09:56.920 Right. It also goes back to basically f equals ma 0:09:56.960 --> 0:09:58.880 a right, like, if you have a mass, something with 0:09:59.000 --> 0:10:01.800 mass and it's change it's velocity, then there must be 0:10:02.000 --> 0:10:04.120 a force involved. And that's kind of maybe what you're 0:10:04.120 --> 0:10:05.160 saying is the definition of it. 0:10:05.280 --> 0:10:08.080 Yeah, you can actually even rewrite eth eqals ma as 0:10:08.160 --> 0:10:11.200 the change in momentum, and that really helps you understand 0:10:11.280 --> 0:10:14.679 the connection between forces and momentum because remember that in 0:10:14.720 --> 0:10:17.600 our universe, momentum is conserved, So if something has a 0:10:17.600 --> 0:10:20.000 certain momentum, it's just going to keep that momentum unless 0:10:20.000 --> 0:10:22.840 you add in momentum from somewhere else. That's what a 0:10:22.880 --> 0:10:25.400 force is. You have a particle flying through space, you 0:10:25.440 --> 0:10:27.960 want to change its direction, change its momentum, you have 0:10:28.040 --> 0:10:30.280 to bring in some external momentum, you have to have 0:10:30.280 --> 0:10:32.800 another particle come by and give it a push or pull. 0:10:32.960 --> 0:10:35.800 That's what the force is. It's the change of momentum 0:10:35.880 --> 0:10:36.600 of an object. 0:10:36.960 --> 0:10:39.959 But the objects ever really change mass, And if they 0:10:40.080 --> 0:10:42.120 never do, then what's the point of saying momentum? Why 0:10:42.160 --> 0:10:43.200 did you say ethicals? 0:10:43.600 --> 0:10:46.240 When things are moving slowly, you can think of momentum 0:10:46.240 --> 0:10:49.000 as just mass times velocity. But as things approach the 0:10:49.000 --> 0:10:51.680 speed of light, when they get relativistic, there's another term 0:10:51.760 --> 0:10:55.240 that creeps in there that changes the relationship between momentum 0:10:55.240 --> 0:10:58.160 and velocity. They're no longer just linear. We whole episode 0:10:58.200 --> 0:11:00.960 on the concept of like relativistic mass and whether that 0:11:01.040 --> 0:11:03.480 makes any sense, and you remember, we decided that the 0:11:03.520 --> 0:11:07.640 real concept is relativistic momentum. That momentum has a simple 0:11:07.679 --> 0:11:10.240 relationship with velocity when you're moving slowly, but when you 0:11:10.320 --> 0:11:13.199 move fast, it's much more complicated, And it's momentum that's 0:11:13.240 --> 0:11:15.720 really the more fundamental concept. That's the thing that the 0:11:15.840 --> 0:11:19.360 universe cares about, that's the thing the universe conserves. So 0:11:19.400 --> 0:11:22.599 it's really sort of the more pure idea is momentum. 0:11:22.679 --> 0:11:25.120 So when you say force is a change in momentum. 0:11:25.200 --> 0:11:28.800 Are you also talking about its relativistic momentum? 0:11:28.920 --> 0:11:29.120 Yeah? 0:11:29.120 --> 0:11:32.320 Absolutely. Relativistic momentum is the more general concept. You only 0:11:32.360 --> 0:11:34.200 really need it near the speed of light. Mostly you 0:11:34.200 --> 0:11:36.480 can use the old classical momentum, which is just mass 0:11:36.480 --> 0:11:39.679 times velocity, and it gets things mostly right. But it 0:11:39.760 --> 0:11:43.040 is the relativistic momentum that the universe conserves. And that's 0:11:43.040 --> 0:11:45.120 one way we know that relativity is right is that 0:11:45.160 --> 0:11:48.360 it's this relativistic momentum that the universe keeps track of. 0:11:49.160 --> 0:11:51.079 I see all right, So then to change your momentum, 0:11:51.120 --> 0:11:53.640 you can increase it or decrease it. So forces can 0:11:53.640 --> 0:11:54.719 push and pull. 0:11:54.640 --> 0:11:57.160 Right, yeah, exactly. The intuitive description of a force is 0:11:57.160 --> 0:11:59.040 a push or a pull. And what happens there is 0:11:59.040 --> 0:12:01.400 you're changing your momentum. When you hit the brakes on 0:12:01.440 --> 0:12:04.160 your car, you're changing your velocity. When you hit the accelerator, 0:12:04.200 --> 0:12:06.959 you're changing your velocity. A change in your velocity is 0:12:07.000 --> 0:12:10.000 an acceleration. It's a change in momentum, and there's always 0:12:10.000 --> 0:12:12.320 a force involved there. Like the fastest way to slow 0:12:12.360 --> 0:12:14.360 down is like hit a brick wall. There the wall 0:12:14.440 --> 0:12:17.320 is applying a force on you and your car changing 0:12:17.360 --> 0:12:18.760 your momentum. 0:12:18.800 --> 0:12:21.080 And it's kind of a weird feature of the universe 0:12:21.120 --> 0:12:23.560 that it has this conservation of momentum, right, or that 0:12:23.600 --> 0:12:25.280 you need a force to change momentum. It could have 0:12:25.280 --> 0:12:27.080 been that the universe was different, right. It could have 0:12:27.080 --> 0:12:30.440 been that the universe maybe preferred mass time's acceleration to 0:12:30.600 --> 0:12:31.240 be conserved. 0:12:32.200 --> 0:12:32.400 Right. 0:12:32.520 --> 0:12:35.040 Maybe yes, and no, it's not true that we have 0:12:35.080 --> 0:12:38.720 no idea why the universe conserves momentum. It comes from 0:12:38.720 --> 0:12:41.840 a deeper symmetry. We know because of Nuther's law, which 0:12:41.880 --> 0:12:44.400 tells us that every time the universe can serves something, 0:12:44.440 --> 0:12:47.240 it's because of a symmetry of the universe. In this case, 0:12:47.280 --> 0:12:50.280 the symmetry of the universe is a symmetry of space itself. 0:12:50.280 --> 0:12:52.760 The laws of physics are the same at every point 0:12:52.800 --> 0:12:56.040 in space, the momentum is conserved. That step there seems 0:12:56.080 --> 0:12:57.920 like a big leap, but that's exactly the leap from 0:12:57.960 --> 0:13:00.640 Nuther's law. I mean Nuther, this mathematics from about one 0:13:00.679 --> 0:13:03.400 hundred years ago made this deep realization that there's a 0:13:03.400 --> 0:13:07.160 connection between symmetry and conservation laws. So this law conservation 0:13:07.240 --> 0:13:10.640 momentum comes from the fact that space is the same everywhere, 0:13:10.679 --> 0:13:12.440 and so you're right, it doesn't have to be true 0:13:12.440 --> 0:13:14.679 that space is the same everywhere in our universe. It 0:13:14.760 --> 0:13:17.720 seems to be, and that's why we have conservation and momentum. 0:13:17.720 --> 0:13:20.040 But there could be other universes where the laws of 0:13:20.080 --> 0:13:23.120 physics change as you move through space and their momentum 0:13:23.160 --> 0:13:24.200 would not be conserved. 0:13:24.559 --> 0:13:26.400 I feel like you. You spend a minute agreeing with me. 0:13:26.640 --> 0:13:29.760 Awesome, can we agree? 0:13:30.120 --> 0:13:31.880 Well, this is the universe we live in, and it 0:13:31.880 --> 0:13:35.240 seems to conserve momentum. And there's several ways that you 0:13:35.280 --> 0:13:38.040 can do that, right, Several forces that will allow you 0:13:38.080 --> 0:13:41.480 to change particle's momentum, maybe depending on what kind of 0:13:41.520 --> 0:13:43.480 particle it is and what its properties are. 0:13:43.559 --> 0:13:45.440 Yeah, and so we can take the same concept of 0:13:45.480 --> 0:13:48.480 a force that applies to your car and applied also 0:13:48.480 --> 0:13:50.960 to particles. Particles have momentum, and if you want to 0:13:51.000 --> 0:13:53.000 change your momentum, you have to apply a force. And 0:13:53.000 --> 0:13:55.440 you're right, there's several ways to do that. We've observed 0:13:55.559 --> 0:13:58.320 several ways, and again this is just descriptive. We've noticed 0:13:58.360 --> 0:14:01.240 several things happened to particles, and we've categorized them as 0:14:01.320 --> 0:14:03.240 much as we can. We've tried to like weave them 0:14:03.280 --> 0:14:06.320 together into one concept, but haven't totally succeeded. We call 0:14:06.360 --> 0:14:10.120 these things the fundamental forces. So there's like electricity and magnetism. 0:14:10.440 --> 0:14:13.720 Charged particles will push or pull on each other. That's 0:14:13.760 --> 0:14:17.400 definitely a force. Electrons will change each other's momentum. They'll 0:14:17.480 --> 0:14:20.640 change their direction entirely, right, that's a change in momentum. 0:14:20.680 --> 0:14:23.320 Even if your velocity is the same but your direction 0:14:23.480 --> 0:14:26.520 is different, it's still a change in momentum. 0:14:25.840 --> 0:14:28.920 M So that's maybe the most familiar force to people, 0:14:28.960 --> 0:14:32.400 like your magnetism. That's basically what keeps our atoms together, right, 0:14:32.480 --> 0:14:35.960 and our molecules stuck together with the different atoms in it. Right. 0:14:36.000 --> 0:14:38.320 Without the electromagnetic force, it would be a big deal. 0:14:38.360 --> 0:14:41.400 We would all fall apart, exactly. We all need electromagnetism. 0:14:41.520 --> 0:14:44.160 So you truly acknowledge the electromagnetic force in like every 0:14:44.160 --> 0:14:46.520 book or paper you write, because you totally rely on it. 0:14:46.600 --> 0:14:49.920 That's right, every acceptance speech you give, every thank you 0:14:50.000 --> 0:14:51.400 card you write. 0:14:51.080 --> 0:14:53.240 There you go, yeah, you sent a holiday card to 0:14:53.280 --> 0:14:54.880 the electromagnetic force this year. 0:14:55.720 --> 0:14:58.280 Have put it on the holidays, and thanks again to 0:14:58.360 --> 0:14:59.400 the electromagnetic force. 0:14:59.560 --> 0:15:01.760 Thanks for all the photons but it's not the only 0:15:01.840 --> 0:15:04.880 force that's out there. There's another force called the weak force, 0:15:05.080 --> 0:15:08.280 which US physicists actually have managed to stitch together into 0:15:08.400 --> 0:15:11.640 one force we call the electro week. But traditionally people 0:15:11.640 --> 0:15:14.600 talk about the weak force as responsible for like radioactive 0:15:14.600 --> 0:15:18.240 decay and interactions of neutrinos and stuff like that. So 0:15:18.280 --> 0:15:19.600 it's sort of a shyer force. 0:15:20.400 --> 0:15:22.680 What does it mean that it's related to radioactive decay? 0:15:22.720 --> 0:15:26.360 Like when something decays radioactively, the weak force is there 0:15:26.400 --> 0:15:28.840 to split things apart or to hold things together. What 0:15:28.920 --> 0:15:29.520 is it doing there? 0:15:29.640 --> 0:15:32.160 Lots of radioactive decay can be explained by one kind 0:15:32.240 --> 0:15:35.160 of quark changing into another kind of quark, and it 0:15:35.160 --> 0:15:37.560 does so using the weak force. So the weak force 0:15:37.600 --> 0:15:39.840 can change, for example, like an upcork into a down 0:15:39.920 --> 0:15:42.240 cork if you emit a w boson, and the w 0:15:42.360 --> 0:15:44.760 boson is intimately connected to the weak force, as we'll 0:15:44.800 --> 0:15:47.640 talk about more later. Without the weak force, that can't happen. 0:15:47.720 --> 0:15:49.200 And so that's what we mean when we say the 0:15:49.200 --> 0:15:52.560 weak force is responsible for radioactive decay. It like opens 0:15:52.640 --> 0:15:53.880 up a channel for this to happen. 0:15:54.000 --> 0:15:55.640 But is it pushing or pulling on anything? 0:15:55.880 --> 0:15:58.360 That's a tricky question the weak force can push and 0:15:58.440 --> 0:16:01.200 it can pull. The whole podcast episode inspired by a 0:16:01.280 --> 0:16:04.320 question from an organic chemistry professor, but whether the weak 0:16:04.360 --> 0:16:06.800 force can push and can pull? The answer is that 0:16:06.840 --> 0:16:08.960 it can do both, but it's more complicated than the 0:16:09.000 --> 0:16:10.080 electromagnetic force. 0:16:10.480 --> 0:16:12.600 Well or right, what are some of the other forces 0:16:12.680 --> 0:16:13.160 in nature? 0:16:13.240 --> 0:16:15.440 So the last thing that's really a force is the 0:16:15.480 --> 0:16:17.560 strong force. This is the thing that quarks feel, but 0:16:17.640 --> 0:16:20.400 like electrons don't. Two electrons can pass near each other 0:16:20.480 --> 0:16:22.040 and not push or pull on each other with the 0:16:22.080 --> 0:16:25.880 strong force. But quarks or gluons, these things do feel 0:16:25.920 --> 0:16:28.680 the strong force. They have another kind of charge, the 0:16:28.720 --> 0:16:31.440 way an electron has an electric charge, which allows it 0:16:31.480 --> 0:16:35.360 to feel electric fields and electromagnetic force, but neutrinos don't. 0:16:35.640 --> 0:16:39.000 Quarks and gluons have a color charge, a strong force 0:16:39.160 --> 0:16:41.800 charge lets them interact using the strong force in a 0:16:41.840 --> 0:16:45.000 way that electrons just don't. And so that's the last force. 0:16:45.040 --> 0:16:47.240 And this is the one that holds quarks together into 0:16:47.280 --> 0:16:50.600 protons and neutrons, and the residual little forces bind those 0:16:50.640 --> 0:16:53.760 protons and neutrons together into nuclei. So we also rely 0:16:53.960 --> 0:16:56.080 on the strong force to build our world. 0:16:57.200 --> 0:16:58.800 So they're all pretty necessary. 0:16:58.840 --> 0:17:01.400 It seems they all have role to play exactly the 0:17:01.440 --> 0:17:03.160 top billing to the extras in the back. 0:17:03.320 --> 0:17:05.720 What about gravity? Is in gravity also a force. 0:17:05.560 --> 0:17:07.639 So we sometimes think of gravity as a force, and 0:17:07.640 --> 0:17:10.639 we talk about the force of gravity, and Newton describes 0:17:10.680 --> 0:17:13.199 his force law or gravity. But now we know that 0:17:13.240 --> 0:17:15.560 gravity isn't actually a force. Things move in a way 0:17:15.560 --> 0:17:17.639 that makes it look like there's a force there, but 0:17:17.680 --> 0:17:21.119 that's actually just because they are free falling in curved space. 0:17:21.280 --> 0:17:24.280 There's no actual change in momentum there. And you can 0:17:24.280 --> 0:17:27.080 tell the difference between gravity and these other forces because 0:17:27.080 --> 0:17:30.760 gravity doesn't cause a change in momentum. You can't measure 0:17:30.840 --> 0:17:32.520 acceleration due to gravity. 0:17:32.680 --> 0:17:34.439 Wait, what do you mean If I hold a bowling 0:17:34.440 --> 0:17:36.800 ball above you and I let it go, isn't it 0:17:36.800 --> 0:17:38.800 going to gain some dangerous momentum for you there? 0:17:38.840 --> 0:17:40.960 So if you're falling with the bowling ball and you 0:17:41.040 --> 0:17:43.760 have like an accelerometer, you're not going to measure any 0:17:43.800 --> 0:17:46.919 acceleration there. The bowling ball is in freefall, there are 0:17:46.920 --> 0:17:47.800 no forces on it. 0:17:47.840 --> 0:17:50.000 Right, But here it is going to measure a pretty 0:17:50.000 --> 0:17:51.280 big acceleration, isn't it. 0:17:51.359 --> 0:17:54.360