WEBVTT - What is a symmetron? 0:00:08.560 --> 0:00:10.360 Hey, Jorge, are you a collector? 0:00:10.600 --> 0:00:12.039 What do you mean like a debt collector? 0:00:13.920 --> 0:00:15.400 I mean, like, do you have a room in your 0:00:15.400 --> 0:00:18.800 house full of original Transformers still in the packages? 0:00:19.000 --> 0:00:21.680 I wish, but no. Those might be worth a lot 0:00:21.680 --> 0:00:23.800 of money now, but no, I actually took them out 0:00:23.840 --> 0:00:26.279 and played with them, although I wish you had those also. 0:00:27.400 --> 0:00:30.120 So is that the source of your encyclopedic knowledge of 0:00:30.120 --> 0:00:31.440 Pokemon and Transformers? 0:00:31.520 --> 0:00:31.960 What do you mean? 0:00:32.120 --> 0:00:35.199 Well, you know, every time I describe some new hypothetical particle, 0:00:35.320 --> 0:00:37.839 you tell me that's actually the name of a Transformer. 0:00:39.120 --> 0:00:40.879 I don't think that's because I'm an expert. I think 0:00:40.880 --> 0:00:44.120 that's just because all physics names sound like Transformers. 0:00:44.400 --> 0:00:47.199 Or maybe because we actually stole them from Transformers. 0:00:47.440 --> 0:00:50.440 What do you have to give credit then, to Hasbro 0:00:50.760 --> 0:00:51.440 in your papers? 0:00:51.640 --> 0:00:53.760 Yeah, we give them a share of the zero dollars 0:00:53.800 --> 0:00:55.000 we make off of each particle. 0:00:55.480 --> 0:00:56.920 What do you mean you don't work for free? 0:00:57.000 --> 0:00:59.240 Do you the particles? 0:00:59.320 --> 0:00:59.360 Do? 0:00:59.560 --> 0:01:01.000 Did you tax dollars? 0:01:16.280 --> 0:01:16.440 Hi? 0:01:16.440 --> 0:01:19.160 I'm Hori mccartoonist and the author of All Our's Great 0:01:19.160 --> 0:01:19.920 Big Universe. 0:01:20.200 --> 0:01:23.200 Hi I'm Daniel. I'm a particle physicist and a professor 0:01:23.319 --> 0:01:26.080 at UC Irvine. And I hope you never have to 0:01:26.160 --> 0:01:28.480 name a particle. Wait, why not, doesn't it mean you 0:01:28.560 --> 0:01:31.240 discovered it. Oh I'd love to discover a particle. But 0:01:31.280 --> 0:01:34.080 then I'm given that huge responsibility of choosing a name. 0:01:34.400 --> 0:01:36.960 And frankly, after all our conversations, I'm terrified. 0:01:38.400 --> 0:01:42.959 You're terrified of cartoonis criticizing your name choices. 0:01:44.160 --> 0:01:46.120 I'm terrified of legacy history. 0:01:46.200 --> 0:01:46.400 Man. 0:01:46.480 --> 0:01:49.160 People who have given particles silly names. History doesn't look 0:01:49.240 --> 0:01:50.120 kindly on them. Oh. 0:01:50.160 --> 0:01:52.400 I see, so that's your excuse for not having discovered 0:01:52.400 --> 0:01:52.880 a particle. 0:01:53.760 --> 0:01:55.560 That's one of my many excuses. 0:01:55.680 --> 0:01:58.440 Yes, that sounds a little convenient. 0:01:58.560 --> 0:02:01.120 Know the truth is, I would love to discover particle. 0:02:01.240 --> 0:02:03.400 And in that case, you know, I just crowdsourced the 0:02:03.480 --> 0:02:07.040 name hmmm, to your kids, maybe to the internet. So 0:02:07.040 --> 0:02:08.400 it ended up with like particle face. 0:02:09.080 --> 0:02:10.919 Is it a website? Like? Is there a website for 0:02:11.440 --> 0:02:12.760 coming up with particle names? 0:02:13.880 --> 0:02:15.480 Not yet, but what a great idea. 0:02:15.600 --> 0:02:17.960 You can find anything on the Internet. I wonder what 0:02:18.040 --> 0:02:20.200 happened if you ask Chad Gpt to come up with 0:02:20.200 --> 0:02:21.320 a name for a new particle. 0:02:21.639 --> 0:02:25.079 Let's do it. Naming a new particle is a significant responsibility. 0:02:25.400 --> 0:02:28.440 It suggests we avoid personal or self referential names. We 0:02:28.440 --> 0:02:32.400 should consider its properties, we should go after historical figure, 0:02:32.600 --> 0:02:35.320 we should consult with the scientific community. See, this is 0:02:35.440 --> 0:02:36.200 serious stuff. 0:02:36.600 --> 0:02:40.040 I feel like maybe that chat GPT's trained on your neuroses. 0:02:40.800 --> 0:02:43.560 It seems to know your anxieties. Maybe maybe it's been 0:02:43.680 --> 0:02:45.640 learning all this time that you've been talking to it. 0:02:45.800 --> 0:02:48.520 No, I think chat GPT and I are both trained 0:02:48.520 --> 0:02:49.960 on the neurosis of the internet. 0:02:50.200 --> 0:02:53.160 Hmmm, well, now you have chat GPT, so you have 0:02:53.160 --> 0:02:55.120 no excuse for not discovering a new particle. 0:02:55.480 --> 0:02:56.520 All right, I'll get to work. 0:02:56.600 --> 0:02:59.200 But anyways, welcome to our podcast. Daniel and Jorge explain 0:02:59.280 --> 0:03:02.240 the universe production of iHeartRadio. 0:03:01.680 --> 0:03:05.800 In which we are absolutely desperate to understand the nature 0:03:05.840 --> 0:03:09.760 of the universe, to uncover new particles and forces, to 0:03:09.800 --> 0:03:13.520 reveal the fundamental nature of space and time, and to 0:03:13.600 --> 0:03:16.840 put it all together, to explain our experience in this 0:03:17.000 --> 0:03:18.080 crazy cosmos. 0:03:18.400 --> 0:03:20.520 WHOA, WHOA desperate. I don't know if we could go 0:03:20.639 --> 0:03:23.519 that far. It make us sound kind of thirsty. 0:03:24.000 --> 0:03:28.440 I am thirsty for knowledge. Absolutely, Yes, you're thirsty to 0:03:28.480 --> 0:03:31.280 get it on with the particles of the universe. I mean, 0:03:31.320 --> 0:03:33.920 I've said it before. I would invite aliens to Earth, 0:03:34.000 --> 0:03:35.640 even if I knew they were going to zap Us 0:03:35.680 --> 0:03:37.960 from orbit, if they would only tell us the truth 0:03:38.000 --> 0:03:39.120 of the universe. 0:03:38.920 --> 0:03:41.680 Boy, you would make that choice for the entire human race. 0:03:41.920 --> 0:03:45.000 I'm thirsty, man, I got a thirst, and it's got 0:03:45.000 --> 0:03:45.560 to be quenched. 0:03:45.640 --> 0:03:47.080 It sounds like a good excuse to put you in 0:03:47.160 --> 0:03:50.400 a rocket ship and shoot you out of here. You're 0:03:50.400 --> 0:03:51.880 clearly not on our side. 0:03:51.960 --> 0:03:53.400 I'm on the side of knowledge, man. 0:03:55.360 --> 0:03:58.200 You're on the side of dinner apparently. But yeah, it 0:03:58.240 --> 0:04:00.800 is an interesting universe and we are are really at 0:04:00.840 --> 0:04:03.160 a loss for understanding how it all works, what it's 0:04:03.200 --> 0:04:05.760 all made out of, and what are the rules that 0:04:05.840 --> 0:04:08.840 govern what can happen and what cannot happen in the universe. 0:04:08.920 --> 0:04:11.520 Though you might feel like the universe is pretty well 0:04:11.600 --> 0:04:16.640 understood scientifically speaking, and historically, we're just beginning our journey 0:04:16.680 --> 0:04:18.880 of understanding it. In one hundred years or in five 0:04:18.960 --> 0:04:21.520 hundred years, people will look back on this era of 0:04:21.560 --> 0:04:24.800 science and say, Wow, they were very clueless about how 0:04:24.839 --> 0:04:25.960 the universe worked. 0:04:26.040 --> 0:04:28.760 Do you think that's a very optimistic view of humanity. 0:04:28.480 --> 0:04:30.680 That will be around in five hundred years To look back. 0:04:30.720 --> 0:04:32.920 You mean, yeah, that we're not going to go into 0:04:32.960 --> 0:04:37.520 the post apocalyptic healthscape of humanity, and we'll look back 0:04:37.560 --> 0:04:39.960 at this time as maybe the peak of humanity. 0:04:41.120 --> 0:04:43.760 In our caves in a few hundred years, scratching out 0:04:43.839 --> 0:04:47.520 podcasts for our few listeners. We will look back to 0:04:47.560 --> 0:04:50.520 the golden age of science when Daniel didn't discover anything. 0:04:50.600 --> 0:04:52.760 We're going to look back and be like, what's a podcast? 0:04:54.160 --> 0:04:54.960 Was that a particle? 0:04:55.000 --> 0:04:55.919 Who had time for that? 0:04:57.680 --> 0:05:01.920 You're right, I'm implicitly being optimistic, assuming that scientific knowledge 0:05:01.920 --> 0:05:04.839 will continue to accumulate and the pace will continue to 0:05:04.920 --> 0:05:07.920 accelerate the way it has over the last decade, fifty years, 0:05:07.960 --> 0:05:10.880 even one hundred years. I'm hopeful. But that requires us 0:05:10.880 --> 0:05:14.839 to survive and maintain society and to make science a priority. 0:05:15.120 --> 0:05:17.800 Yeah, and not to sell us out to the hungry aliens. 0:05:18.160 --> 0:05:20.960 Hmm though that would fast forward us into the future 0:05:21.120 --> 0:05:25.719 of knowledge and dinner. But what if the aliens don't 0:05:25.760 --> 0:05:27.760 have all the answers? Well, what if they have the 0:05:27.800 --> 0:05:31.000 answers and we just can't grock them? Oof? So frustrating. 0:05:31.040 --> 0:05:32.520 I just sold the human race for nothing. 0:05:32.640 --> 0:05:34.560 Yeah, you might want to look at the menu first, 0:05:37.360 --> 0:05:40.240 figure it out. Before they sell us all out. 0:05:40.440 --> 0:05:42.360 But we can't rely on those aliens or even those 0:05:42.360 --> 0:05:44.480 future humans. We got to figure it out. We are 0:05:44.520 --> 0:05:47.480 working hard today to try to understand the nature of 0:05:47.520 --> 0:05:50.080 the universe on the largest scales, how big is it, 0:05:50.120 --> 0:05:52.520 how much bigger is it getting? And how quickly is 0:05:52.560 --> 0:05:53.400 it getting bigger. 0:05:53.520 --> 0:05:55.280 That's right. We're on our own trying to figure out 0:05:55.279 --> 0:05:57.200 the mysteries of the universe, and it all starts with 0:05:57.360 --> 0:06:01.560 asking questions and coming up with maybe sometimes crazy ideas 0:06:01.600 --> 0:06:03.240 to try to explain how it all works. 0:06:03.440 --> 0:06:06.240 We're pretty sure that most of our ideas about how 0:06:06.279 --> 0:06:09.000 the universe works and the largest scale, the size of it, 0:06:09.120 --> 0:06:11.840 the shape of it, the rate of its expansion, why 0:06:11.880 --> 0:06:15.279 it's expanding, why that expansion is accelerating, We're pretty sure 0:06:15.279 --> 0:06:17.919 those ideas are wrong. And what we looked back on 0:06:18.080 --> 0:06:20.960 is just sort of like initial explorations. But that's crucial. 0:06:21.400 --> 0:06:24.400 Science is not a straight line. It's a zigzag wandering 0:06:24.400 --> 0:06:27.200 through a dark forest hoping to find the clearing and. 0:06:27.160 --> 0:06:29.440 So sometimes you have to get creative about it and 0:06:29.520 --> 0:06:33.120 even come up with things that sound like transformers or pokemons, 0:06:33.920 --> 0:06:36.400 or maybe come up with transformers that would be pretty cool. 0:06:37.080 --> 0:06:39.560 They could help us find the answers to the universe. 0:06:39.760 --> 0:06:41.520 You think they'll be mad when they discovered to've been 0:06:41.520 --> 0:06:44.160 stealing their names for particles for a few decades. 0:06:44.040 --> 0:06:47.120 Or maybe they'd be honored to be named after certain particles. 0:06:47.200 --> 0:06:48.600 Now you're the one being optimistic. 0:06:48.880 --> 0:06:53.560 Yeah, I am an optimist prime And so today on 0:06:53.560 --> 0:07:04.560 the podcast, we'll be tackling the question what is a symtron. 0:07:03.520 --> 0:07:05.040 And what does it transform into? 0:07:05.279 --> 0:07:06.719 What does it not transform into? 0:07:08.320 --> 0:07:13.080 Maybe it transforms us into aliens that do understand the universe. 0:07:13.720 --> 0:07:15.800 What is a symmetron? I don't think I've heard that 0:07:15.840 --> 0:07:18.080 word before, but it sounds a little bit like symmetry 0:07:18.320 --> 0:07:21.040 and tron, so something electronic. 0:07:21.400 --> 0:07:23.840 You're not far from the truth. Yeah, boom podcast over. 0:07:24.000 --> 0:07:26.240 Do you know why the word tron or ending a 0:07:26.280 --> 0:07:31.040 word with tron somehow implies electricity or technology or particles. 0:07:31.600 --> 0:07:33.520 Do you know the origin of that? I'm asking if 0:07:33.520 --> 0:07:34.320 you know, because I don't know. 0:07:34.760 --> 0:07:37.679 I think the word ion comes from some Greek word, 0:07:38.400 --> 0:07:41.560 but I'm not an expert in the etymology of particles. 0:07:41.960 --> 0:07:44.960 Oh, you're saying like, maybe that's where the word electron 0:07:45.120 --> 0:07:45.880 comes from. 0:07:46.120 --> 0:07:49.080 Yeah, although you know the electron originally was named something else. 0:07:49.120 --> 0:07:52.480 The discoverer of it, JJ. Thompson called it a corpuscule, 0:07:52.880 --> 0:07:56.400 and then later it was renamed electron. But my guess 0:07:56.520 --> 0:07:59.400 is that all these ons come from ion, which is 0:07:59.400 --> 0:07:59.960 a Greek word. 0:08:00.320 --> 0:08:02.200 Well, I guess that was a good thing, because otherwise 0:08:02.240 --> 0:08:05.520 we'd be associating technology. But the word puscal with the 0:08:05.640 --> 0:08:11.080 ending puscol, and everything would be named pusicle. The bad 0:08:11.080 --> 0:08:14.760 guy in Transformers would be called megapuscal. But I'm guessing 0:08:14.760 --> 0:08:16.800 this is maybe one of those creative ideas that a 0:08:16.920 --> 0:08:19.240 scientists have come up with to try to explain some 0:08:19.880 --> 0:08:21.120 deep mystery of the universe. 0:08:21.480 --> 0:08:23.400 It is indeed well as usually. 0:08:23.480 --> 0:08:25.600 We were wondering how many people out there had heard 0:08:25.640 --> 0:08:28.600 of a symmetron or could guess what it is or 0:08:28.800 --> 0:08:32.480 what it transforms into. So Daniel went out there into 0:08:32.520 --> 0:08:36.719 the internet again to ask people what is a symmetron. 0:08:37.000 --> 0:08:40.679 Because this podcast is all about audience participation, you guys 0:08:40.679 --> 0:08:43.040 can write us questions and we'll answer. You can hear 0:08:43.080 --> 0:08:46.160 your voice on the podcast speculating about the topic of 0:08:46.200 --> 0:08:48.679 the day. If you'd like to join this group, please 0:08:48.720 --> 0:08:51.680 write to me two questions at Danielandhorge dot com. 0:08:51.760 --> 0:08:53.280 So think about it for a second. Is it a 0:08:53.280 --> 0:08:56.800 pokemon or is it a robot? Here's what people had 0:08:56.840 --> 0:08:57.160 to say. 0:08:57.520 --> 0:09:04.880 Well, it's either a transformer or a quantum particle or both. Symmetron, 0:09:05.000 --> 0:09:08.040 it obviously has something to do with symmetry. Other than that, 0:09:08.120 --> 0:09:10.119 I can't really hazard a guess. 0:09:10.040 --> 0:09:12.360 Guessing based on the on at the end of it 0:09:12.600 --> 0:09:15.800 that like a photon or a beryon, that it's some 0:09:15.880 --> 0:09:20.120 kind of particle that conveys a type of symmetry. 0:09:20.360 --> 0:09:25.160 Well, symmetron makes me think of cyclotron, and a cycloton 0:09:25.240 --> 0:09:28.160 I think is the old term for a well another 0:09:28.240 --> 0:09:34.000 term for a particle collider and symmetron symmetrical would be 0:09:34.280 --> 0:09:38.000 sort of means that it's the same in some way. 0:09:38.120 --> 0:09:41.160 Maybe is it a strait as opposed to a ring 0:09:41.480 --> 0:09:43.160 format particle collider? 0:09:43.320 --> 0:09:45.360 Well, I've never heard of a symotron. It sounds like 0:09:45.400 --> 0:09:48.480 a particle that exhibits some special symmetry, But lots of 0:09:48.480 --> 0:09:51.600 particles exhibit symmetry, which makes me think it's probably some 0:09:51.720 --> 0:09:55.040 theoretical symmetry we haven't seen yet that defines what this 0:09:55.080 --> 0:09:55.679 particle is. 0:09:55.920 --> 0:09:57.960 A symmetron, is a device that you can set on 0:09:58.040 --> 0:10:00.880 top of your piano to the pace it goes. 0:10:02.400 --> 0:10:03.800 No, I guess it's a. 0:10:03.520 --> 0:10:09.880 Particle and it communicates symmetry between other particles. I have 0:10:10.280 --> 0:10:10.760 no idea. 0:10:11.000 --> 0:10:18.800 Is that a particle wave it's identical to another particle? 0:10:20.679 --> 0:10:21.480 Cancels it out? 0:10:21.559 --> 0:10:21.839 Maybe? 0:10:22.080 --> 0:10:25.800 Or all right? Some creative answers here. 0:10:26.920 --> 0:10:28.719 Well, I mean you put this name on anything. You 0:10:28.720 --> 0:10:30.400 could name it your cat, right, The answer to the 0:10:30.400 --> 0:10:32.400 podcast could be like, Symmetron is my cat? 0:10:33.000 --> 0:10:36.439 Oh, there you go. You could name your cat Symmetron. Yes, 0:10:37.040 --> 0:10:40.400 but isn't that a big responsibility also to name your cat? 0:10:40.520 --> 0:10:43.600 Hmmm? That's true, although I don't think history will judge 0:10:43.640 --> 0:10:45.800 you as much because it's probably just between you and 0:10:45.840 --> 0:10:48.880 the cat, mostly unless the cat becomes famous. 0:10:49.160 --> 0:10:51.640 Yeah. Well, also, you don't mind your cat unhappy with you? 0:10:51.720 --> 0:10:54.040 I hear that's a bad thing. It would be a 0:10:54.040 --> 0:10:55.320 catastrophe in IIan. 0:10:55.480 --> 0:10:56.720 It's the cats who are in charge. 0:10:56.800 --> 0:10:59.120 But yeah, it's an interesting idea, and so let's dig 0:10:59.200 --> 0:11:02.439 into this, Uh, Daniel, what is a symotron? 0:11:02.679 --> 0:11:06.760 So, a symotron is a hypothetical new particle that of 0:11:06.760 --> 0:11:11.120 course also comes with a field that has really unusual properties, 0:11:11.880 --> 0:11:15.160 and physicists invent a new field and particles sometimes not 0:11:15.280 --> 0:11:16.840 just for fun. We don't just like line in the 0:11:16.840 --> 0:11:18.719 grass and be like, h what if there's this kind 0:11:18.720 --> 0:11:21.839 of particle. We do it to explain something we've seen 0:11:21.920 --> 0:11:24.800 in the universe. The whole process of physics is like 0:11:24.920 --> 0:11:27.600 go out there, see stuff that's happens, and then try 0:11:27.640 --> 0:11:30.200 to build a model that explains it. And when the 0:11:30.240 --> 0:11:32.800 model fails, we add new who's it's and what's it's 0:11:33.040 --> 0:11:35.800 to try to get it to describe the universe. So 0:11:35.880 --> 0:11:38.280 the symmetron is a new thing people are trying to 0:11:38.320 --> 0:11:41.160 add into our model of physics to explain some stuff 0:11:41.200 --> 0:11:42.880 that we otherwise can't explain. 0:11:43.720 --> 0:11:46.679 Although sometimes in the history of physics it has been 0:11:46.720 --> 0:11:48.640 the case that you just kind of like tool around 0:11:48.640 --> 0:11:50.040 in the lab and you discover stuff. 0:11:50.080 --> 0:11:52.600 Right. Oh, there was a golden era the particle Zoo, 0:11:52.840 --> 0:11:55.000 when every time you turned on the accelerator you saw 0:11:55.040 --> 0:11:56.480 a new particle and you could give it. 0:11:56.480 --> 0:11:57.880 A name every time. 0:11:58.320 --> 0:12:01.520 It was incredible, and they cranked up the energy boom 0:12:01.600 --> 0:12:05.559 new particles made. It was amazing. I missed those days, hmmm. 0:12:06.360 --> 0:12:08.440 They were decades before I was born, but I still 0:12:08.440 --> 0:12:08.880 miss them. 0:12:08.960 --> 0:12:11.800 But I think we're talking about a theoretical particle here, 0:12:12.120 --> 0:12:15.199 not one that we have discovered or seen or explored experimentally, 0:12:15.280 --> 0:12:18.720 just one that we have dreamed of to try to 0:12:18.720 --> 0:12:22.000 explain something that is happening that we can't explain. 0:12:22.160 --> 0:12:24.280 Yeah, and the same spirit that, like the Higgs boson, 0:12:24.440 --> 0:12:28.360 was conceived of theoretically. Peter Higgs saw this pattern in 0:12:28.440 --> 0:12:31.160 nature and he thought, hmm, this would be so much prettier. 0:12:31.200 --> 0:12:33.200 It would make much more sense if we added a 0:12:33.200 --> 0:12:35.560 new particle and feel to the story. And it all 0:12:35.600 --> 0:12:37.760 worked out mathematically and beautifully, and then we went out 0:12:37.840 --> 0:12:40.760 and looked for it. So you can add things theoretically, 0:12:40.840 --> 0:12:43.559 but if they don't actually describe what's happening in the universe, 0:12:43.600 --> 0:12:46.240 it's not very useful. So in this case, people are 0:12:46.280 --> 0:12:49.720 again adding a new theoretical particle to try to explain 0:12:49.800 --> 0:12:51.800 some stuff that otherwise doesn't make sense. 0:12:52.520 --> 0:12:54.840 Okay, So then what is the mystery that the symotron 0:12:55.120 --> 0:12:56.400 hopes to resolve? 0:12:56.559 --> 0:12:59.040 So the simitron is here to do battle with a 0:12:59.240 --> 0:13:02.680 really big question in physics, which is why is the 0:13:02.800 --> 0:13:06.800 universe expanding faster and faster every year? Like we know 0:13:06.880 --> 0:13:09.280 the universe is really big. We can look out there 0:13:09.360 --> 0:13:11.480 and see stuff that's really far away. We've known for 0:13:11.520 --> 0:13:14.280 like one hundred years that the universe is expanding. You 0:13:14.320 --> 0:13:17.079 look out in every direction and you see galaxies moving 0:13:17.080 --> 0:13:19.480 away from us. But a couple of decades ago we 0:13:19.559 --> 0:13:23.480 got precise enough measurements about how that expansion is changing 0:13:23.520 --> 0:13:26.760 over time that we learned something kind of shocking that 0:13:26.840 --> 0:13:30.360 the expansion is not slowing down like Einstein thought, but 0:13:30.440 --> 0:13:34.000 that it's actually speeding up. There's something out there accelerating 0:13:34.240 --> 0:13:36.240 the expansion of space. 0:13:36.200 --> 0:13:39.120 Meaning it's getting bigger, faster and faster each time. 0:13:39.520 --> 0:13:43.320 Yeah, space between galaxy clusters is getting bigger, and every 0:13:43.440 --> 0:13:46.480 year it's getting bigger at a higher rate. So we 0:13:46.559 --> 0:13:49.000 new space is being created faster. 0:13:48.800 --> 0:13:52.200 And faster, and they're not just running away from alias 0:13:52.240 --> 0:13:52.960 that want to eat them. 0:13:54.559 --> 0:13:56.720 They may be accomplishing that, but it's sort of the 0:13:56.760 --> 0:13:59.360 secondary thing. And in physics we give this a name 0:13:59.679 --> 0:14:01.959 dark energy, But just because we give it a name 0:14:02.080 --> 0:14:04.959 doesn't mean we understand what's going on or we can 0:14:05.040 --> 0:14:08.960 explain what's happening. So far, this is just observational. We've 0:14:09.000 --> 0:14:11.720 seen this in our telescopes and in our measurements and 0:14:11.760 --> 0:14:14.720 we've tried to grapple with it. We've like, what could 0:14:14.760 --> 0:14:18.360 explain this, What possible mechanism could we have that could 0:14:18.440 --> 0:14:21.640 generate this kind of crazy accelerating expansion. 0:14:21.920 --> 0:14:26.480 Because I guess the idea that it's accelerating is weird, right, Like, 0:14:26.560 --> 0:14:28.840 if it was expanding at a constant rate, then you 0:14:28.920 --> 0:14:32.960 might assume that, well, maybe you had some initial velocity 0:14:33.040 --> 0:14:35.000 from the beginning of the universe and so it's just 0:14:35.040 --> 0:14:37.479 coasting and getting bigger. But the idea that it's accelerating 0:14:37.520 --> 0:14:40.480 means there's something going on, right, something must be powering 0:14:40.800 --> 0:14:41.640 this acceleration. 0:14:42.040 --> 0:14:44.360 Yeah, exactly. It was really shocking in the context of 0:14:44.400 --> 0:14:48.160 Einstein's general relativity because in his model, if you have 0:14:48.200 --> 0:14:52.240 a universe with mass in it, that causes negative acceleration 0:14:52.360 --> 0:14:56.280 of the expansion basically pulls everything together. It curves the universe, 0:14:56.280 --> 0:14:59.200 and it pulls everything together. Basically just gravity should pull 0:14:59.240 --> 0:15:02.120 the whole universe together. But when Hubble and others discovered 0:15:02.160 --> 0:15:04.600 that the universe is expanding, then people thought, all right, 0:15:04.680 --> 0:15:07.800 so we have an expanding universe as you say, initial velocity, 0:15:08.040 --> 0:15:11.120 but still should be negative acceleration because all the gravity 0:15:11.120 --> 0:15:13.880 should be pulling everything together, and we didn't know if 0:15:13.880 --> 0:15:16.840 there's gonna be enough gravity to pull everything back together 0:15:16.920 --> 0:15:19.840 to like squeeze it down into a big crunch, or 0:15:19.920 --> 0:15:22.200 if there's gonna be so much velocity that it coast forever, 0:15:22.320 --> 0:15:25.640 slowing down but never actually come back. Then we discovered 0:15:25.640 --> 0:15:27.720 that neither of those are the case, and what actually 0:15:27.760 --> 0:15:31.680 happening is something else is giving us positive acceleration, is 0:15:31.720 --> 0:15:34.480 increasing the rate of expansion every year. 0:15:34.720 --> 0:15:36.480 Now, back then, do we know that it was space 0:15:36.560 --> 0:15:39.280 itself that was expanding or did we maybe think that 0:15:39.360 --> 0:15:42.040 all the galaxies were just moving through space and getting 0:15:42.080 --> 0:15:43.240 further apart from each other. 0:15:43.760 --> 0:15:46.640 How far back then are you talking Einstein and Hubble? 0:15:46.680 --> 0:15:49.640 Are you talking discovery dark energy twenty years ago? 0:15:50.280 --> 0:15:57.000 I mean before an hour ago before. I'm becoming familiar 0:15:57.000 --> 0:15:57.600 with this topic. 0:15:57.760 --> 0:16:01.960 Well, ever since we've had general relativity, we've understood that 0:16:02.120 --> 0:16:05.480 to describe the expanding universe is to describe the expansion 0:16:05.560 --> 0:16:08.520 of space itself, because general relativity tells us that the 0:16:08.600 --> 0:16:10.920 universe has a shape and it has curvature, and so 0:16:10.960 --> 0:16:13.080 you can't have like a single reference frame for the 0:16:13.120 --> 0:16:15.800 whole universe. Instead, you should think about it as like 0:16:16.080 --> 0:16:18.920 a reference frame for each galaxy, and then those reference 0:16:18.920 --> 0:16:21.240 frames are moving relative to each other in space is 0:16:21.280 --> 0:16:24.960 expanding between them, So you can't really answer the question 0:16:25.080 --> 0:16:28.720 like what is the velocity of that galaxy and measured 0:16:28.760 --> 0:16:31.200 in our frame? You really just have to say, they 0:16:31.240 --> 0:16:33.640 have a frame, we have a frame, and the space 0:16:33.680 --> 0:16:35.040 between them is expanding. 0:16:35.440 --> 0:16:38.520 But back then, did we know that, Like when we 0:16:38.560 --> 0:16:41.040 first noticed that the galaxies were moving away from us, 0:16:41.360 --> 0:16:43.600 did we know that it was space it's expanding, or 0:16:43.640 --> 0:16:45.720 did we maybe at first thought, oh, they're just moving 0:16:45.720 --> 0:16:46.960 away from us through space. 0:16:47.160 --> 0:16:49.880 Well, all this requires is general relativity, which we've had 0:16:49.920 --> 0:16:52.920 well before we knew the universe was expanding. So the 0:16:52.960 --> 0:16:55.520 answer is yes, we've described in terms of expanding space 0:16:55.640 --> 0:16:57.800 since the beginning. This might sound a little confusing to 0:16:57.840 --> 0:17:00.880 listeners because we often talk about the receipt eschen velocity 0:17:00.880 --> 0:17:03.560 of galaxies, and when you hear about the expansion of 0:17:03.600 --> 0:17:06.200 the universe, we talk about these velocities, and for stuff 0:17:06.240 --> 0:17:08.359 that's really really far away, you could even say that 0:17:08.400 --> 0:17:11.160 recession velocity is faster than the speed of light. That's 0:17:11.200 --> 0:17:13.480 just sort of a sloppy shorthand that's saying, well, look, 0:17:13.520 --> 0:17:16.320 we know it's space expanding but that's hard to think about. 0:17:16.400 --> 0:17:19.040 So let's just pretend we could measure the velocities of 0:17:19.040 --> 0:17:21.439 those galaxies. If we could do that, what would that 0:17:21.520 --> 0:17:25.040 velocity be? But those velocities aren't meaningful. We can't actually 0:17:25.040 --> 0:17:27.280 measure those things because we don't have a single frame 0:17:27.280 --> 0:17:30.000 that puts both galaxies in it. So the technical way 0:17:30.000 --> 0:17:32.479 to think about it accurately is to think about separate 0:17:32.520 --> 0:17:35.719 frames with space expanding between them. 0:17:35.720 --> 0:17:39.040 You're saying, like, these velocities are really just the expansion 0:17:39.080 --> 0:17:40.800 of space getting bigger. 0:17:40.880 --> 0:17:43.320 Yeah, exactly, And you know that because you can't measure 0:17:43.320 --> 0:17:45.960 that acceleration. Like, if you wanted to think about it 0:17:45.960 --> 0:17:48.800 in terms of acceleration, then all those galaxies should be 0:17:48.880 --> 0:17:50.919 accelerating away from us. You should be able to measure 0:17:50.960 --> 0:17:54.000 that acceleration. You like, have an accelerometer in that galaxy. 0:17:54.000 --> 0:17:55.960 You should be able to measure it. But you can't 0:17:56.000 --> 0:17:58.359 because there is no real acceleration there. It's just the 0:17:58.400 --> 0:18:00.440 expansion of space. If you put a ball in the 0:18:00.480 --> 0:18:03.280 back of a pickup truck, doesn't slant one side because 0:18:03.400 --> 0:18:06.840 space is expanding in some direction, right, it stays flat. 0:18:06.840 --> 0:18:09.359 Because we don't measure any local acceleration. Because we're not 0:18:09.440 --> 0:18:13.119 accelerating in our frame, even though the expansion of space 0:18:13.160 --> 0:18:16.320 between us and other galaxies is accelerating. And all of 0:18:16.320 --> 0:18:19.560 this happily lives within general relativity, but it requires an 0:18:19.560 --> 0:18:22.919 explanation the same way like you need mass to bend space, 0:18:23.000 --> 0:18:27.040 you need something to provide this negative pressure to expand space. 0:18:27.400 --> 0:18:29.880 And the big question about dark energy is what is that? 0:18:30.080 --> 0:18:33.200 What is doing this thing? What is providing the energy 0:18:33.240 --> 0:18:35.040 to accelerate the expansion of space. 0:18:35.880 --> 0:18:38.680 Okay, I think you're saying that space it's growing. It's 0:18:38.720 --> 0:18:41.480 not just growing, it's growing faster and faster so that 0:18:41.520 --> 0:18:44.399 the galaxies look like they're accelerating away from us. But 0:18:44.440 --> 0:18:47.359 really it's just the expansion of space that's like going 0:18:47.400 --> 0:18:50.639 a double time. And so the question now is what's 0:18:50.960 --> 0:18:54.520 powering all that creation of new space? And so that's 0:18:54.600 --> 0:18:57.080 kind of what dark energy is a placeholder for. 0:18:57.720 --> 0:19:01.040 Yeah, dark energy says something's doing it, we don't know what. 0:19:01.359 --> 0:19:02.840 And the cool thing is you don't have to throw 0:19:02.880 --> 0:19:05.600 away general relativity. General relativity has a knob in it. 0:19:05.760 --> 0:19:08.920 This is called Einstein's cosmological constant. You could just crank 0:19:08.960 --> 0:19:11.440 this knob up and say, what if there's energy in 0:19:11.520 --> 0:19:14.280