WEBVTT - Do things get more massive the faster they move? 0:00:08.480 --> 0:00:11.840 Hey, Daniel, has particle physics done anything useful lately? 0:00:12.039 --> 0:00:15.880 M you mean other than revealing the fundamental nature of reality? 0:00:16.040 --> 0:00:16.599 Have you done that? 0:00:17.760 --> 0:00:18.919 I mean it's a project. 0:00:21.400 --> 0:00:23.880 I mean that's all nice and cool, but it doesn't 0:00:23.920 --> 0:00:26.640 really help me, you know, with the dishes or you know, 0:00:26.880 --> 0:00:27.520 with my diet. 0:00:27.600 --> 0:00:29.840 I guess we did also invent the World Wide Web. 0:00:29.880 --> 0:00:30.720 That's pretty helpful. 0:00:31.000 --> 0:00:34.879 You mean web surfing. I would say that's not the 0:00:34.880 --> 0:00:36.479 most helpful thing in my life, but that was a 0:00:36.479 --> 0:00:39.040 long time ago. Anyways, what have you done for us recently? 0:00:39.159 --> 0:00:40.919 Yeah, maybe we should be coming up with like a 0:00:41.040 --> 0:00:42.720 fundamental physics diet plan. 0:00:43.680 --> 0:00:46.760 It's just coffee and doughnuts all. 0:00:46.680 --> 0:00:50.519 The time, existential angst about the nature of the universe. 0:00:50.600 --> 0:00:52.640 I guess the problem with physics is that it says 0:00:52.640 --> 0:00:55.279 that the faster you go, the more massive you get. Right, 0:00:55.360 --> 0:00:57.040 that's kind of an anti diet. 0:00:57.120 --> 0:00:59.320 I guess I was thinking, you know, black holes something 0:00:59.360 --> 0:01:01.960 something something liposuction, black holes. I don't know. I didn't 0:01:01.960 --> 0:01:02.760 really have it worked out. 0:01:03.520 --> 0:01:05.479 Quantum cosmetic surgery. 0:01:05.600 --> 0:01:08.399 Whoa, Orange County is definitely the place for. 0:01:08.360 --> 0:01:15.240 That, and you can get a ten to the color bage. 0:01:26.400 --> 0:01:29.360 Hi am jorhammy cartoonist and the creator of PhD comics. 0:01:29.640 --> 0:01:32.320 Hi. I'm Daniel. I'm a particle physicist and a professor 0:01:32.400 --> 0:01:36.000 at UC Irvine, and I was shocked when a pediatrician 0:01:36.120 --> 0:01:38.399 offered my one year old plastic surgery. 0:01:38.600 --> 0:01:41.520 Wait what they do that on one year. 0:01:41.400 --> 0:01:44.720 Old in Orange County? You're never too young for plastic surgery. 0:01:45.080 --> 0:01:48.160 Oh boy. I get to the offer like a subscription service, 0:01:49.520 --> 0:01:51.560 like a membership or something. 0:01:51.840 --> 0:01:54.240 It's a long term relationship. No. Our son had like 0:01:54.280 --> 0:01:56.680 a vein on his eyelid and the doctor was like, 0:01:56.680 --> 0:01:57.880 do you want me to remove that? 0:01:58.200 --> 0:02:02.840 And we were like, no, please, wait the eyelid or 0:02:02.880 --> 0:02:06.400 the vein. You're like, I think my son needs. It's 0:02:06.480 --> 0:02:07.640 his eyelid exactly. 0:02:08.760 --> 0:02:10.720 We were like, I'm pretty sure that's going to be fine, 0:02:11.000 --> 0:02:12.720 And newsflash, he's fine. 0:02:12.880 --> 0:02:14.680 Where You're like, I'm a real doctor, I don't think 0:02:14.680 --> 0:02:15.680 he meets any surgery. 0:02:17.520 --> 0:02:19.239 I'm not a real doctor, but I'm pretty sure he 0:02:19.320 --> 0:02:21.520 didn't need any surgery. 0:02:22.080 --> 0:02:23.840 Like, I'm not a real doctor, I just play one 0:02:23.880 --> 0:02:26.560 in the lab. But anyways, welcome to our podcast. Daniel 0:02:26.560 --> 0:02:30.200 and Jorge Explain the Universe, a production of iHeartRadio. 0:02:29.560 --> 0:02:31.600 In which we try to show you the nature of 0:02:31.639 --> 0:02:35.040 the universe in all of its unvarnished glory. We don't 0:02:35.040 --> 0:02:37.880 want to edit out the ugly bits and smooth over 0:02:37.919 --> 0:02:39.880 the bumps and wrinkles. We want to show you the 0:02:40.000 --> 0:02:43.240 universe the way it actually is, even when it conflicts 0:02:43.320 --> 0:02:46.680 with our intuition and runs aground for our preconceived ideas 0:02:46.720 --> 0:02:50.160 for how things move and flow and dance in the universe. 0:02:50.480 --> 0:02:52.520 That's right, that's because we love the universe just the 0:02:52.560 --> 0:02:55.760 way it is. We love the og universe, the original 0:02:55.919 --> 0:03:01.240 organic version of the universe, untreated, unvarnished, and pretty mysterious. 0:03:02.880 --> 0:03:05.960 That's right. We prefer the granola crunchy Berkeley version, with 0:03:06.120 --> 0:03:08.360 all of its hair and all the original places, even 0:03:08.360 --> 0:03:09.560 on all of its black holes. 0:03:09.880 --> 0:03:12.960 Well, let's not go too far there. I mean, I'm 0:03:12.960 --> 0:03:15.000 a big fan of socks and sandals, but you know, 0:03:15.200 --> 0:03:16.200 there's a time and a place. 0:03:16.280 --> 0:03:19.160 I'm all for accepting people and universes just the way 0:03:19.200 --> 0:03:19.600 they are. 0:03:19.720 --> 0:03:22.360 But it is a wonderful and beautiful universe. It doesn't 0:03:22.400 --> 0:03:24.520 need any cosmic surgery because when we look at it, 0:03:24.600 --> 0:03:28.040 we're just stricken with awe an amazement at how wonderfully 0:03:28.280 --> 0:03:30.760 complex and intriguing it all is. 0:03:30.919 --> 0:03:33.280 And one of my favorite things about the universe is 0:03:33.320 --> 0:03:36.400 that it's surprising. It's not like we look out into 0:03:36.440 --> 0:03:38.560 the universe and we're like, oh, yeah, that's pretty much 0:03:38.560 --> 0:03:40.960 how I expected, or oh yeah, there's nothing new out 0:03:41.000 --> 0:03:44.280 there to discover. Every time we dig deep into something, 0:03:44.560 --> 0:03:47.320 every time we scratch under the surface, we find out, Wow, 0:03:47.400 --> 0:03:49.840 the universe is quite different from the way that we 0:03:49.960 --> 0:03:52.720 imagined it, which is wonderful because it's an opportunity to 0:03:52.840 --> 0:03:56.120 learn to discover the truth instead of just coasting on 0:03:56.280 --> 0:03:57.040 our intuition. 0:03:57.440 --> 0:04:00.240 Yeah, the universe is very different out there in space, 0:04:00.480 --> 0:04:04.000 beyond our galaxy, beyond our cluster of galaxies, and it's 0:04:04.040 --> 0:04:07.960 also very different at the molecular and atomic and particle scills. 0:04:08.000 --> 0:04:11.640 Things are actually very different than our everyday experience. 0:04:11.840 --> 0:04:14.880 And we're tempted when we discover these new weird wrinkles 0:04:14.880 --> 0:04:17.359 in the universe to explain them in terms of things 0:04:17.360 --> 0:04:19.960 that we know, things we understand. It's a very natural 0:04:20.000 --> 0:04:22.240 a way to try to understand the universe, to describe 0:04:22.279 --> 0:04:25.800 it in terms of the language that you already have. Sometimes, though, 0:04:25.800 --> 0:04:29.120 that gets awkward. It's hard to understand how quantum particles 0:04:29.200 --> 0:04:31.719 dance around if you're thinking about them as little dots 0:04:31.720 --> 0:04:34.159 of stuff, And that's because they're not really little dots 0:04:34.160 --> 0:04:36.960 of stuff. And it's hard to think about velocity and 0:04:37.080 --> 0:04:39.400 energy and mass as things approach the speed of life 0:04:39.440 --> 0:04:42.400 because the definitions of those things have to change, and 0:04:42.440 --> 0:04:44.440 the way things move and bounce against each other and 0:04:44.480 --> 0:04:47.680 transfer energy and momentum is really very different at high 0:04:47.720 --> 0:04:50.800 speeds than it is down here in the slow motion 0:04:50.960 --> 0:04:51.719 life on Earth. 0:04:51.960 --> 0:04:54.600 Yeah, things are very weird and awkward in general when 0:04:54.600 --> 0:04:56.560 you talk to physicists, I feel, not just when you 0:04:56.680 --> 0:04:58.599 learn learn what they have to say. 0:04:58.680 --> 0:05:00.560 All right, this is not a therapy podcast. We're talking 0:05:00.600 --> 0:05:01.880 about the nature of the universe here. 0:05:02.040 --> 0:05:04.120 That's right. That's right. In the universe is not awkward 0:05:04.200 --> 0:05:05.599 or weird. It's just the way it is. And I 0:05:05.600 --> 0:05:08.080 guess it's us that are weird and awkward, right, because 0:05:08.160 --> 0:05:10.440 we have this picture of how the world works, but 0:05:10.480 --> 0:05:12.479 that may not be how the universe actually works. 0:05:12.640 --> 0:05:14.800 Yeah, And in physics, our project is to build a 0:05:14.800 --> 0:05:18.159 mathematical description of how things work in the universe, something 0:05:18.200 --> 0:05:20.480 that lets us make predictions and gives us a peek 0:05:20.480 --> 0:05:23.039 at the machinery behind the curtains that's deciding like what 0:05:23.160 --> 0:05:25.919 happens when two balls bounce against each other. But that 0:05:25.960 --> 0:05:29.919 doesn't always translate in an easy or simple way to English, 0:05:29.960 --> 0:05:33.080 the language that most humans speak. So when physicists are 0:05:33.120 --> 0:05:36.440 trying to explain how things work when the universe gets weird, 0:05:36.800 --> 0:05:40.080 they use the terms that we're familiar with, mass and energy, momentum, 0:05:40.080 --> 0:05:43.040 et cetera, and try to translate the weirdness in those terms. 0:05:43.160 --> 0:05:45.280 And so you hear a lot of explanations for what 0:05:45.360 --> 0:05:48.320 happens when things get fast. Some of those explanations are 0:05:48.360 --> 0:05:50.880 bang on, and some of them are a little bit misleading. 0:05:51.120 --> 0:05:53.880 Yeah, because I guess one of the biggest mind bending 0:05:53.920 --> 0:05:56.400 moments and autism and strangest moments in the history of 0:05:56.440 --> 0:05:58.600 science was when we found out that the universe is 0:05:58.680 --> 0:06:02.000 kind of difference once you start are moving really fast exactly. 0:06:02.000 --> 0:06:05.320 We've had Newtonian and Gallean mechanics for centuries, things that 0:06:05.360 --> 0:06:07.640 did a very good job of explaining what happens when 0:06:07.640 --> 0:06:10.839 two balls bounce against each other, and how momentum is transferred, 0:06:10.839 --> 0:06:13.520 and how things look when you're going fast. If you're 0:06:13.600 --> 0:06:15.479 driving in a car at thirty miles an hour, and 0:06:15.520 --> 0:06:17.440 you throw a ball at thirty miles an hour, then 0:06:17.480 --> 0:06:19.440 you know that ball should be moving at sixty miles 0:06:19.480 --> 0:06:21.760 an hour relative to the ground. All that stuff made 0:06:21.800 --> 0:06:24.200 sense for a long time until we started looking at 0:06:24.240 --> 0:06:26.920 things that weren't moving really really fast. We discovered there's 0:06:26.960 --> 0:06:29.360 a speed limit to the universe, and that really changed 0:06:29.440 --> 0:06:32.880 everything we thought about the nature of space and time 0:06:33.080 --> 0:06:35.520 and velocity and gives rise to all sorts of weird 0:06:35.520 --> 0:06:37.400 stuff that's very tricky to unpack. 0:06:37.520 --> 0:06:40.080 Yeah, it gets super tricky. Well, first of all, the 0:06:40.160 --> 0:06:42.120 idea that we have a speed limit in the universe 0:06:42.200 --> 0:06:44.159 is kind of wild. Like, you know, you sort of 0:06:44.160 --> 0:06:46.520 grew up thinking that disguise the limit. The more that 0:06:46.560 --> 0:06:48.560 you push something, the faster you go. But at some 0:06:48.600 --> 0:06:51.960 point the universe says, I think that's fast enough. It 0:06:51.960 --> 0:06:53.919 doesn't let you go faster than a certain speed. 0:06:54.160 --> 0:06:56.800 Yeah, it's a really bizarre feature of our universe, one 0:06:56.839 --> 0:07:00.680 that we've discovered experimentally at the Michaelson Morley. The experiments 0:07:00.720 --> 0:07:03.679 prove that light travels the same speed in every direction 0:07:04.040 --> 0:07:06.799 and effectively demonstrating that there is no absolute reference, framing 0:07:06.800 --> 0:07:10.120 that there is a maximum speed of information and transmission 0:07:10.280 --> 0:07:14.320 in the universe, which leads to all sorts of weird consequences, 0:07:14.600 --> 0:07:17.640 changes what we think about time and the nature of simultaneity. 0:07:18.200 --> 0:07:20.560 Things that happen at the same time for one person 0:07:20.760 --> 0:07:23.480 might happen in a different order for somebody else. The 0:07:23.480 --> 0:07:26.080 whole nature of reality becomes different when there is a 0:07:26.120 --> 0:07:28.120 maximum speed limit to the universe. 0:07:28.520 --> 0:07:30.680 Yeah, and I think it kind of makes people wonder 0:07:30.880 --> 0:07:32.840 what would happen if you try to go faster than 0:07:32.880 --> 0:07:34.920 the speed of light? Does the universe police come and 0:07:35.080 --> 0:07:38.040 flag you down and stop you? Or do you hit 0:07:38.080 --> 0:07:38.480 a wall? 0:07:38.760 --> 0:07:40.600 Or what are you considering trying to break some laws 0:07:40.640 --> 0:07:42.720 of the universe? Be asking for physics legal advice? 0:07:43.160 --> 0:07:44.960 Well, I'm trying to toe the line, you know. I'm 0:07:45.000 --> 0:07:47.560 kind of max out my life here. I need to 0:07:47.600 --> 0:07:48.480 know how far I can go. 0:07:50.200 --> 0:07:51.760 I just don't want to be held responsible if you 0:07:51.760 --> 0:07:52.760 get thrown in physics. 0:07:52.560 --> 0:07:54.120 Jail when I need a physics lawyer. 0:07:54.480 --> 0:07:56.480 I wonder if people who are lawyers are always on 0:07:56.560 --> 0:07:58.240 the look at for like, is this person asking me 0:07:58.320 --> 0:08:00.000 legal advice? I'm not going to get them in trouble 0:08:00.080 --> 0:08:01.720 if I say the wrong thing. I don't usually have 0:08:01.720 --> 0:08:03.920 to worry about that because most people aren't capable of 0:08:04.000 --> 0:08:05.320 trying to break the laws of the universe. 0:08:05.440 --> 0:08:08.400 I think most lawyers don't really care that much. 0:08:10.600 --> 0:08:12.520 But no, there is no physics police that are just 0:08:12.560 --> 0:08:15.080 going to pull you over. It's just that acceleration and 0:08:15.160 --> 0:08:18.600 momentums start working differently at high speeds. So you discover 0:08:18.840 --> 0:08:21.080 that you can pour energy into a particle, it just 0:08:21.160 --> 0:08:23.840 doesn't go much faster. So you can discover that as 0:08:23.880 --> 0:08:25.680 things approach the speed of light, you can keep pouring 0:08:25.840 --> 0:08:28.840 energy into something a rock, a particle of spaceship, whatever, 0:08:28.920 --> 0:08:31.840 it just doesn't go much faster. The same amount of 0:08:31.920 --> 0:08:35.320 energy doesn't get you increases in velocity the same rate. 0:08:35.559 --> 0:08:38.280 It's no longer linear. It becomes asymptotic. 0:08:38.480 --> 0:08:45.760 So today end podcast, we'll be tackling the question do 0:08:45.880 --> 0:08:49.640 things get more massive the faster they move? This is 0:08:49.720 --> 0:08:52.320 kind of like the anti diet, or at least I 0:08:52.320 --> 0:08:54.839 feel like it justifies maybe sitting down on your couch 0:08:55.000 --> 0:08:57.280 all the time, because if I get up up for 0:08:57.360 --> 0:08:58.880 my couch and I move, then I'm just going to 0:08:58.920 --> 0:09:01.200 gain more mass, Right, that's true. 0:09:01.280 --> 0:09:02.880 Well, what we're going to learn on the podcast today 0:09:02.920 --> 0:09:05.040 is that it's a little bit more complicated than that 0:09:05.160 --> 0:09:07.520 this is the kind of popular science thing you hear 0:09:07.640 --> 0:09:10.480 all the time and people write in and ask me about. 0:09:10.520 --> 0:09:12.319 And I think it was wide they taught in textbooks 0:09:12.360 --> 0:09:15.160 until about thirty forty years ago, the feeling that everything 0:09:15.160 --> 0:09:17.400 gets weird as you approach the speed of light, and 0:09:17.440 --> 0:09:20.080 then even your mass might change, things might get like 0:09:20.160 --> 0:09:23.280 infinitely heavy as you approach the speed of light. It's 0:09:23.280 --> 0:09:26.040 an attractive concept for people, I think, because it gives 0:09:26.080 --> 0:09:28.520 you a sense of the strange. But as we'll talk 0:09:28.559 --> 0:09:30.480 about today on the podcast, it's a little bit more 0:09:30.520 --> 0:09:33.280 complicated than that, and it's actually something of an outdated notion. 0:09:33.400 --> 0:09:37.480 Wait, wait, are you saying it's a massive lie. 0:09:38.520 --> 0:09:39.959 You know, there's a lot of different ways you can 0:09:39.960 --> 0:09:44.000 try to translate the crisp mathematics of relativity into English 0:09:44.040 --> 0:09:47.400 and into popular culture. This was one attempt early on 0:09:47.480 --> 0:09:49.080 that I don't think really works very well. 0:09:49.800 --> 0:09:52.720 I see it was just heavily exaggerated. Well, as usual, 0:09:52.760 --> 0:09:54.960 you were wondering how many people had wondered about this 0:09:55.120 --> 0:09:58.040 question at ask this about themselves, about the universe, about 0:09:58.080 --> 0:09:59.880 what happens when you try to go faster and faster, 0:10:00.080 --> 0:10:02.080 And so Daniel went out there into the Internet to 0:10:02.120 --> 0:10:05.400 ask people do you think things get more massive as 0:10:05.440 --> 0:10:06.960 you approach the speed of light? 0:10:07.320 --> 0:10:10.360 I am so grateful to everybody who answers these questions. 0:10:10.360 --> 0:10:12.560 They give me a sense for what people already know, 0:10:12.640 --> 0:10:15.280 and they give listeners a sense of what everybody else 0:10:15.400 --> 0:10:18.360 is thinking. If you would like to participate, please don't 0:10:18.400 --> 0:10:20.880 be shy. You're really very welcome to join the club. 0:10:21.360 --> 0:10:24.760 Just write to me two questions at Danielandjorge dot com. 0:10:24.840 --> 0:10:26.800 So think about it for a second. Do you think 0:10:27.120 --> 0:10:28.679 you should stay in your couch if you don't want 0:10:28.720 --> 0:10:31.200 to gain any mess? Here's what people had to say. 0:10:31.400 --> 0:10:35.080 This question just blows my mind. I'm just stumped. Do 0:10:35.200 --> 0:10:39.160 they get more massive? I guess maybe. I don't know how, 0:10:39.280 --> 0:10:41.760 but maybe something related to quantum mechanics. 0:10:41.760 --> 0:10:42.120 I don't know. 0:10:42.280 --> 0:10:44.880 As you approached the speed of light, I thought Einstein's 0:10:44.880 --> 0:10:48.840 equations told us that you would gain mess, But to 0:10:48.840 --> 0:10:51.880 an outside observer, I don't think you would actually look bigger. 0:10:52.040 --> 0:10:53.960 I mean, at the speed of lighte time was slower. 0:10:54.480 --> 0:10:57.720 Maybe space gets contracted. 0:10:57.880 --> 0:11:00.760 So I'm kind of stormy here. 0:11:01.240 --> 0:11:03.920 Maybe if that is true, then you will have a 0:11:04.000 --> 0:11:07.319 higher density and in that sense, wibly be more massive. 0:11:07.600 --> 0:11:08.079 Not sure. 0:11:08.280 --> 0:11:12.360 I think they do get more massive, but because it's 0:11:12.640 --> 0:11:16.520 it gets harder to move things at that speed, and 0:11:16.559 --> 0:11:18.840 not because they get more the feet. 0:11:18.960 --> 0:11:22.760 My understanding is mass and energy are interchangeable, so the 0:11:22.800 --> 0:11:26.800 more energy you have to pump into something to accelerate 0:11:26.840 --> 0:11:29.520 it closer and closer to the speed of light is 0:11:29.559 --> 0:11:32.920 really no different than making it more massive to begin with. 0:11:33.080 --> 0:11:36.880 So I think, yes, it gets more massive as you 0:11:36.920 --> 0:11:39.600 approach the speed of light, just because mass and energy 0:11:39.640 --> 0:11:41.439 are essentially the same thing. 0:11:41.920 --> 0:11:44.000 I think I remember hearing that they do get more 0:11:44.000 --> 0:11:47.280 massive as they approach the speed of light. I think 0:11:47.280 --> 0:11:50.560 it takes more energy to increase the speed, and like, yeah, 0:11:50.800 --> 0:11:53.280 they just can't really get to the speed of light 0:11:54.080 --> 0:11:55.640 unless it's like, you know, massless. 0:11:55.720 --> 0:11:58.360 I guess so based on the question. I'm not sure 0:11:58.400 --> 0:12:01.960 exactly why, but if has something to do with like 0:12:02.000 --> 0:12:08.120 the kinetic energy of something affecting its mass, then I 0:12:08.160 --> 0:12:08.920 would guess so. 0:12:09.120 --> 0:12:11.440 I think the answer is yes. First I was taught 0:12:11.480 --> 0:12:13.800 it that way. I've since heard that's an old school 0:12:13.800 --> 0:12:18.200 way of thinking about it. But definitely, if we consider 0:12:19.520 --> 0:12:25.600 energy as being mass, you know the way it works relativistically, 0:12:25.600 --> 0:12:28.920 you can concentrate energy as well as matter, and that 0:12:29.080 --> 0:12:32.319 is all mass energy. Then as you add velocity, you're 0:12:32.360 --> 0:12:34.480 adding energy and you become more massive. 0:12:35.280 --> 0:12:37.600 All right, a lot of great answers here. I feel 0:12:37.640 --> 0:12:40.280 like some people were blown away and some people were like, oh, 0:12:40.280 --> 0:12:43.080 I've heard of this. The answer is yes or no. 0:12:43.360 --> 0:12:45.520 Yeah, I thought this was really interesting. There's a lot 0:12:45.559 --> 0:12:48.360 of different ideas here about what energy is and what 0:12:48.480 --> 0:12:52.160 mass is. Very few people mentioned momentum even, but there's 0:12:52.160 --> 0:12:55.880 definitely this understanding that things change as you approach the 0:12:55.920 --> 0:12:59.480 speed of light, and that it's harder to go faster. Yeah. 0:12:59.559 --> 0:13:01.760 Somebody one of the listeners said that it's kind of 0:13:01.960 --> 0:13:05.000 strange that your mass would change, right, And that goes to. 0:13:04.920 --> 0:13:07.679 The heart of what we mean by mass. I think 0:13:07.720 --> 0:13:09.679 a lot of people think of mass is like the 0:13:09.720 --> 0:13:12.800 amount of stuff they have, and so it's really weird 0:13:12.840 --> 0:13:15.400 for them to imagine them getting like more stuff as 0:13:15.480 --> 0:13:17.640 they approach the speed of light. And that's one reason 0:13:17.679 --> 0:13:20.160 why I really don't like this concept of relativistic mass. 0:13:20.160 --> 0:13:23.480 It gives people the impression that something physical is happening, 0:13:23.480 --> 0:13:24.920 which isn't interesting. 0:13:24.960 --> 0:13:27.360 All right, Well, let's dig into it, and I guess 0:13:27.400 --> 0:13:29.640 let's start with the basics. As you said, let's start 0:13:29.679 --> 0:13:32.240 with the concept of mass. Now. I know mass is 0:13:32.320 --> 0:13:34.520 kind of a big mystery. We talked about it in 0:13:34.559 --> 0:13:36.679 our book, like what is mass? Anyways, we have a 0:13:36.720 --> 0:13:39.439 whole chapter about how we don't kind of know what 0:13:39.480 --> 0:13:41.360 mass is. But Daniel maybe step us through it. What 0:13:41.440 --> 0:13:43.360 do we know about what mass is? 0:13:43.679 --> 0:13:46.200 I think in the context of relativity and motion, the 0:13:46.200 --> 0:13:49.400 most important thing to think about is inertia, like the 0:13:49.480 --> 0:13:52.920 fact that it's not easy to change your velocity. You're 0:13:52.960 --> 0:13:55.920 flying through the universe at some speed. In order to 0:13:56.080 --> 0:13:58.960 change that speed, you need a push. Right. That's really 0:13:58.960 --> 0:14:03.040 what F equals is trying to say that to accelerate, 0:14:03.400 --> 0:14:05.360 you need to have a force applied to you, and 0:14:05.360 --> 0:14:08.280 that M in that equation, and F equals MA is 0:14:08.320 --> 0:14:11.240 the mass. It relates how much acceleration you get for 0:14:11.559 --> 0:14:13.800 how much force. We've all heard, for example, that the 0:14:13.840 --> 0:14:16.439 Earth's gravity on you is the same as your gravity 0:14:16.520 --> 0:14:19.400 on the Earth, Right, But we feel a much stronger 0:14:19.440 --> 0:14:21.440 force than the Earth does because the Earth has a 0:14:21.600 --> 0:14:24.760 huge mass. So we feel a much stronger acceleration than 0:14:24.760 --> 0:14:27.560 the Earth does because the Earth has a huge mass, 0:14:27.840 --> 0:14:30.560 and so its acceleration is tiny. Even though the force 0:14:30.720 --> 0:14:33.920 is the same. So really important concept in mass is inertia. 0:14:33.960 --> 0:14:36.520 That's really what mass is about when we're talking about motion, 0:14:36.720 --> 0:14:40.480 and that's connected to this idea of momentum. Right. Another 0:14:40.480 --> 0:14:43.200 way to think about F equals MA is that F 0:14:43.360 --> 0:14:46.080 is actually a change in momentum. When you're flying through 0:14:46.080 --> 0:14:49.200 the universe at a certain velocity, you have a certain momentum. 0:14:49.240 --> 0:14:51.480 In order to change your momentum, you need to have 0:14:51.600 --> 0:14:54.360 a force applied. So mass is this concept that tells 0:14:54.400 --> 0:14:58.360 us basically how hard it is to change your momentum. 0:14:58.360 --> 0:15:00.480 I feel like you're making us go that a rabbit 0:15:00.480 --> 0:15:02.880 hole a little bit, because then it makes me wonder, like, 0:15:02.960 --> 0:15:04.240 what is momentum anyways? 0:15:04.400 --> 0:15:07.000 Yeah, a momentum is something we know is important in 0:15:07.040 --> 0:15:09.680 the universe. It's a quantity that's conserved. Like we look 0:15:09.680 --> 0:15:12.480 at in the universe, we watch stuff, we see things happen, 0:15:12.680 --> 0:15:15.080 and we look for patterns, and a very important pattern 0:15:15.120 --> 0:15:18.760 are conservation laws. Things that don't change. So two balls 0:15:18.760 --> 0:15:21.200 bounce against each other, for example, you calculate all the 0:15:21.200 --> 0:15:23.800 momentum beforehand and all the momentum afterwards, and you notice 0:15:23.880 --> 0:15:26.320 it's the same. It is conserved. We actually know that 0:15:26.320 --> 0:15:28.880 there's a deep reason for why momentum is conserved. It's 0:15:28.920 --> 0:15:32.000 because space is the same everywhere. We did a whole 0:15:32.000 --> 0:15:34.680 fun podcast on Nother's theorem, which tells you that because 0:15:34.720 --> 0:15:37.359 space is the same everywhere, momentum has to be conserved. 0:15:37.600 --> 0:15:40.520 This is deep link there. So momentum is an important 0:15:40.520 --> 0:15:43.400 physical quantity in the universe. It's something that's really powerful 0:15:43.440 --> 0:15:45.480 and it really gives us insight into what's happened. And 0:15:45.560 --> 0:15:48.520 momentum is flowing through a system, right, but it's conserved 0:15:48.520 --> 0:15:51.720 in the universe. The universe at least thinks momentum is important, 0:15:51.760 --> 0:15:53.000 so maybe we should. 0:15:52.800 --> 0:15:56.040 Also well, how is it different from like energy? And 0:15:56.400 --> 0:15:59.240 is momentum the same as energy? Is the momentum of 0:15:59.280 --> 0:16:02.640 a particle or a baseball the same as its kinetic energy? 0:16:02.720 --> 0:16:03.640 How do the two connect? 0:16:03.760 --> 0:16:07.680 Yeah? Great question. First of all, momentum has directionality. You 0:16:07.680 --> 0:16:09.600 can have a momentum in one direction or momentum in 0:16:09.600 --> 0:16:12.400 another direction. It's a vector it points and for example, 0:16:12.520 --> 0:16:15.760 the Earth has a constant magnitude momentum, but the direction 0:16:15.880 --> 0:16:18.320 of its momentum is changing as it goes around the Sun. 0:16:18.440 --> 0:16:20.760 It's like an arrow that tells you which way the 0:16:20.800 --> 0:16:23.560 Earth is headed, and that's constantly changing. So the length 0:16:23.560 --> 0:16:26.440 of that vector isn't changing, but the direction of it is. 0:16:27.000 --> 0:16:29.800 And that's why it takes acceleration to move around the Sun, 0:16:29.880 --> 0:16:32.680 because you're changing the direction of that momentum vector. So 0:16:32.760 --> 0:16:35.880 momentum is a direction, right. Energy doesn't have a direction, 0:16:35.920 --> 0:16:38.760 it's just a number, right. And also, and energy includes 0:16:38.800 --> 0:16:42.000 something else. The energy of an object has two components. 0:16:42.040 --> 0:16:44.680 There's the internal energy what we call it's inertial mass, 0:16:45.040 --> 0:16:48.720 and the energy of its motion, it's kinetic energy. So 0:16:48.760 --> 0:16:51.640 there's two separate components there. So things could have energy 0:16:51.680 --> 0:16:54.320 when they're not moving, like an electron just sitting there 0:16:54.520 --> 0:16:57.240 has some mass, then that corresponds to some energy, and 0:16:57.280 --> 0:17:00.600 there's also energy of motion. Things can have only energy 0:17:00.600 --> 0:17:03.440 of motion, like a photon is just motion energy has 0:17:03.480 --> 0:17:06.120 no mass, or they can have both, like an electron 0:17:06.160 --> 0:17:09.159 flying through the universe has mass and that's energy and 0:17:09.320 --> 0:17:12.400 also has kinetic energy. So energy has two components. There's 0:17:12.440 --> 0:17:15.200 the mass and there's a contribution from the momentum, which 0:17:15.240 --> 0:17:16.639 we also call kinetic energy. 0:17:16.720 --> 0:17:19.879 And so the universe conserves both things, right, like it 0:17:19.960 --> 0:17:24.680 somehow conserves momentum, and it also conserves energy, but not 0:17:24.720 --> 0:17:26.640 necessarily the same way I think, right. 0:17:26.600 --> 0:17:29.720 So there's a little asterisk there in flat space. Yes, 0:17:29.840 --> 0:17:33.639 energy is conserved in the global universe. As space expands, 0:17:33.880 --> 0:17:37.560 actually energy increases, so energy is not strictly conserved in 0:17:37.600 --> 0:17:40.160 the universe. There's a whole podcast episode we did about 0:17:40.160 --> 0:17:41.880 that if you want to dig into it. But let's 0:17:41.920 --> 0:17:44.119 just assume we're like living in flat space and we're 0:17:44.160 --> 0:17:46.480 bouncing balls and particles off each other. We wouldn't notice 0:17:46.480 --> 0:17:48.359 the expansion of the universe. So let's just say for 0:17:48.400 --> 0:17:50.840 the sake of this discussion that, yes, energy is conserved. 0:17:50.880 --> 0:17:54.160 And so you're right, momentum is conserved and energy is conserved, 0:17:54.240 --> 0:17:57.480 and those are actually related. Those are four separate conservation 0:17:57.600 --> 0:18:01.080 laws because energy is one number and momentum is three numbers. 0:18:01.200 --> 0:18:04.080 Because we have three dimensions of space, and momentums can 0:18:04.119 --> 0:18:07.359 serve separately in each of those dimensions. So we have 0:18:07.440 --> 0:18:11.000 four conservation laws, three from momentum and one from energy. 0:18:11.119 --> 0:18:13.399 And in particle physics at least we group energy and 0:18:13.440 --> 0:18:16.000 momentum together into something we call four momentum, like the 0:18:16.000 --> 0:18:18.760 four dimensions of space time, and we say there's conservation 0:18:18.880 --> 0:18:22.280 of form momentum, which combines momentum and energy into one 0:18:22.359 --> 0:18:23.200 conservation law. 0:18:23.520 --> 0:18:27.320 So then mass is related to both things, like mass 0:18:27.480 --> 0:18:29.879 makes your momentum go higher and it makes your energy 0:18:29.880 --> 0:18:30.320 go higher. 0:18:30.400 --> 0:18:32.840 Yeah, that's right. So mass is like your internal stored energy. 0:18:33.080 --> 0:18:35.760 Take a proton, for example, it has a bunch of mass. 0:18:35.800 --> 0:18:37.320 Where does that mass come from. It comes from the 0:18:37.320 --> 0:18:40.119 internal energy of the proton, Like there's the mass of 0:18:40.119 --> 0:18:42.200 the quarks. They get their mass from the Higgs boson. 0:18:42.280 --> 0:18:44.800