WEBVTT - Can quantum gravity save physics? 0:00:08.480 --> 0:00:11.240 Hey, Daniel, do you think physics is in a rut? 0:00:11.440 --> 0:00:14.840 A rut like we've been solving deep problems and delivering 0:00:14.840 --> 0:00:19.040 amazing technology for too long. You're getting tired of it? Yeah, 0:00:19.079 --> 0:00:23.200 I mean it's getting a little repetitive, all these discoveries. No, No, 0:00:23.320 --> 0:00:25.439 I mean, like, is it on the right track? You know? 0:00:25.560 --> 0:00:27.600 Do you think it will it get to the final 0:00:27.800 --> 0:00:30.520 deep questions about the universe? I don't know. Sometimes I 0:00:30.520 --> 0:00:33.640 wonder if we need like a revolution in physics. Does 0:00:33.680 --> 0:00:36.680 physics need to be disrupted? Somebody out there should start 0:00:36.800 --> 0:00:40.680 uber for physics. I'm more of a lift person, to 0:00:40.720 --> 0:00:43.239 be honest, I think they have a better outlook in 0:00:43.280 --> 0:00:45.479 the world. But yes, that's what I mean. You know, 0:00:45.520 --> 0:00:48.800 I want to be able to call a physicist anytime 0:00:48.840 --> 0:00:51.440 in my with my phone. Um, well you already have that. 0:00:51.440 --> 0:00:55.200 That's this podcast. Nice, I'll give you four stars. Daniel here. 0:01:12.080 --> 0:01:16.000 Hi am Rhema cartoonist and the creator of PhD comics. Hi. 0:01:16.120 --> 0:01:19.240 I'm Daniel Whitson. I'm a particle physicist, and I'm here 0:01:19.280 --> 0:01:22.080 to answer any question of physics on your app anytime. 0:01:22.240 --> 0:01:26.000 Welcome to our podcast. Daniel and Jorge invent new physics apps. 0:01:26.240 --> 0:01:30.280 For people who need physics on demand. Daniel and Jorge 0:01:30.520 --> 0:01:35.240 make up terrible business ideas and pretending they're awesome. Now 0:01:35.319 --> 0:01:38.000 it's Daniel and Jorge Explained the Universe, a production of 0:01:38.040 --> 0:01:40.200 Our Heart Radio, in which we talk about all the 0:01:40.240 --> 0:01:44.360 things amazing and beautiful but crazy and bonkers about our 0:01:44.560 --> 0:01:47.400 universe because the more we learn, the more it makes sense, 0:01:47.600 --> 0:01:50.520 the more it seems surprising and amazing. You know, within 0:01:50.640 --> 0:01:52.000 we joke about it. But I think it would be 0:01:52.040 --> 0:01:54.320 kind of a useful app. Don't you think, like anytime 0:01:54.320 --> 0:01:58.160 anyone has a question about anything, you could just request 0:01:58.240 --> 0:02:01.880 a physicist on your phone own and the nearest or 0:02:02.000 --> 0:02:05.560 the most available physicists would answer and then answer your question. 0:02:05.640 --> 0:02:06.960 Do you think that would be used a lot? Like 0:02:07.000 --> 0:02:09.360 what kind of questions would people ask? How do we 0:02:09.480 --> 0:02:15.359 reconcile the different theories about quantum physics? Sure? I think 0:02:15.400 --> 0:02:17.720 it's more prosaic. It's like can I build a force 0:02:17.760 --> 0:02:22.000 field to keep my teenager in his bedroom all night long? Also? 0:02:22.080 --> 0:02:26.079 How does my toaster work? Why doesn't my toaster work? 0:02:26.120 --> 0:02:28.440 That's probably be the number one question again? Can you 0:02:28.440 --> 0:02:31.079 come fix my toaster? No, we're not engineers. You need 0:02:31.080 --> 0:02:33.080 a different Uber for that. Yeah, but think about all 0:02:33.120 --> 0:02:35.560 those grad students and post talcs and physics who are 0:02:35.639 --> 0:02:38.600 looking for a little extra money. You know, they would, 0:02:38.639 --> 0:02:41.239 I'm sure they would sign up to answer people's questions. Yeah, 0:02:41.280 --> 0:02:44.560 you know, there actually is a physics consulting service where 0:02:44.600 --> 0:02:47.960 if you think you have the great next theory of 0:02:48.000 --> 0:02:52.160 physics but you're not being taken seriously by the mainstream establishment, 0:02:52.600 --> 0:02:55.560 there is a service where expert physicists will read your 0:02:55.639 --> 0:02:58.480 theory and give you like top level criticism of it. 0:02:58.520 --> 0:03:01.480 Why it's probably not the winner of the next year's 0:03:01.520 --> 0:03:07.400 Nobel Prize. Yeah, it's called Daniel at Daniel and Jorge 0:03:07.440 --> 0:03:11.040 dot com. It's true. There are people who send me 0:03:11.120 --> 0:03:14.440 their theories two questions at Daniel and Jorge dot com, 0:03:14.760 --> 0:03:16.480 and I try to take a look at them. But 0:03:16.680 --> 0:03:18.560 there is a service which will spend you know, half 0:03:18.600 --> 0:03:21.680 an hour or an hour actually digging into your theory. Yeah, 0:03:22.240 --> 0:03:24.120 but they charge a lot, don't they don't They charge 0:03:24.120 --> 0:03:27.519 you like fifty or something. You think that's a lot. 0:03:27.560 --> 0:03:30.840 You think, like, you know, deep deep expertise of the 0:03:30.919 --> 0:03:34.080 universe should coming like seven. Sure, I mean, you know, 0:03:34.160 --> 0:03:37.040 I want to know how my toaster works. But not 0:03:37.240 --> 0:03:40.720 for fifty dollars, buy any toaster Roman for fifty dollars. Well, 0:03:40.720 --> 0:03:42.480 then I guess you don't really want to know how 0:03:42.520 --> 0:03:45.360 it works. You just want to buy a new one. 0:03:46.120 --> 0:03:47.960 I want to buy a transparent toaster so I can 0:03:47.960 --> 0:03:50.280 see how it works. Well, that's the difference between the 0:03:50.280 --> 0:03:52.840 scientists and the engineer. The engineer just wants to make 0:03:52.840 --> 0:03:54.920 it work, and the scientist wants to know why it 0:03:55.040 --> 0:03:57.280 doesn't work. Yeah, we we just want to eat toast. 0:03:57.480 --> 0:04:01.360 That's the basic difference. But sometimes scientists also want a 0:04:01.400 --> 0:04:05.480 theory that just works. And in physics we were making 0:04:05.480 --> 0:04:08.320 progress towards sort of like answering those deep questions of 0:04:08.360 --> 0:04:11.320 the universe, but we're not quite there yet. Yeah, you 0:04:11.320 --> 0:04:14.080 guys have been pretty successful. You have a standard model 0:04:14.120 --> 0:04:17.039 of the universe and some pretty good theories. You know, 0:04:17.120 --> 0:04:19.440 you have the standard model, not the not the non 0:04:19.480 --> 0:04:21.720 standard model. We should have called it something else, right, 0:04:21.760 --> 0:04:24.479 Standard models just so boring. It's like the Beije model 0:04:24.520 --> 0:04:27.840 of the universe. We should have called it the amazing model. Yeah, 0:04:28.320 --> 0:04:31.280 but you have pretty much everything answered right, kind of, 0:04:31.320 --> 0:04:35.360 except for some basic things about the universe. Yeah, we've 0:04:35.360 --> 0:04:40.159 made a lot of progress, which is incredible. We've explained electromagnetism, 0:04:40.279 --> 0:04:42.479 we've explained the weak foce, we've made a lot of 0:04:42.520 --> 0:04:46.479 progress and understanding the strong nuclear force. And then, in 0:04:46.520 --> 0:04:50.280 a totally different camp, with totally different people, using completely 0:04:50.360 --> 0:04:53.320 different mathematics and ways of thinking, we've made some in 0:04:53.440 --> 0:04:57.599 rows into understanding gravity. Yeah, but there are some You 0:04:57.600 --> 0:05:00.360 have all these great theories, but there's something not wide 0:05:00.760 --> 0:05:04.159 right right, Like it works, it's pretty successful for a 0:05:04.160 --> 0:05:07.679 lot of things, but there's something kind of fundamentally almost 0:05:07.720 --> 0:05:10.520 wrong with all of your theories. What did you say, Yeah, 0:05:10.680 --> 0:05:12.880 the problem is we have no theory that describes sort 0:05:12.880 --> 0:05:14.840 of all of it. We have people who started from 0:05:14.839 --> 0:05:17.600 the quantum mechanical side of things understanding that building an 0:05:17.600 --> 0:05:21.400 incredible mind bending theory of the universe that seems to 0:05:21.440 --> 0:05:24.440 be like an accurate description of the way things actually are. 0:05:25.000 --> 0:05:27.000 And then we have people working from the other side, 0:05:27.040 --> 0:05:30.320 starting from gravity and saying like, let's understand gravity is 0:05:30.360 --> 0:05:33.880 a bending of space man, and they're actually making progress. Also, 0:05:33.960 --> 0:05:37.280 the problem is these two theories don't agree with each other. 0:05:37.320 --> 0:05:40.960 They don't play well, they don't have completely different views 0:05:41.040 --> 0:05:44.680 of how the universe actually is. They're sort of incompatible. 0:05:44.800 --> 0:05:46.920 It's kind of like if you're building a bridge across 0:05:46.960 --> 0:05:50.880 the Atlantic, and you know, you build one side starts 0:05:50.880 --> 0:05:52.640 building a bridge, and the other side starts building a 0:05:52.640 --> 0:05:54.920 bridge from their side, and you find out that you're 0:05:54.960 --> 0:05:57.600 nowhere near each other in the middle. Yeah, exactly. Or 0:05:57.640 --> 0:06:00.640 you're using technologies which just cannot fit to other and 0:06:00.720 --> 0:06:03.320 that's the problem. Right. You're hoping that there is one 0:06:03.360 --> 0:06:06.240 truth that you can start in different places in your 0:06:06.279 --> 0:06:09.560 investigation and sort of work together to find the central truth. 0:06:10.040 --> 0:06:12.240 But sometimes we wonder if these models just depend on 0:06:12.279 --> 0:06:15.159 your perspective. There's different ways to look at the universe, 0:06:15.200 --> 0:06:18.080 and some are successful and some are limited, and so 0:06:18.160 --> 0:06:19.880 we don't know like which is the right way to 0:06:19.880 --> 0:06:22.200 look at the universe, if if either of them are 0:06:22.240 --> 0:06:25.360 even right, or we need something totally new, right, if 0:06:25.400 --> 0:06:27.960 either of them right, because it almost sounds like maybe 0:06:28.120 --> 0:06:31.520 both of them are not looking at the world, at 0:06:31.560 --> 0:06:34.200 the universe and quite the right way, you know, if 0:06:34.200 --> 0:06:36.400 you can't make them work together. Yeah, And there's a 0:06:36.440 --> 0:06:38.880 lot of examples in history where physics has been like 0:06:39.279 --> 0:06:42.800 very confidently almost wrapped everything up except for a couple 0:06:42.800 --> 0:06:45.599 of little details which turn out when you pull on them, 0:06:45.720 --> 0:06:50.000 unravel everything and reveal like a completely different view of 0:06:50.040 --> 0:06:52.520 the universe that was quantum mechanics. You know, in the 0:06:52.600 --> 0:06:55.359 late eighteen hundreds, people felt like we've almost got this 0:06:55.440 --> 0:06:58.120 thing wrapped up except for like, you know, the photoelectric 0:06:58.120 --> 0:07:01.039 effect and the black body radiation, which revealed, of course 0:07:01.080 --> 0:07:03.800 that the universe is quantized on a fundamental scale, which 0:07:03.920 --> 0:07:07.159 blew everybody's minds. Kind of makes you wonder if maybe 0:07:07.200 --> 0:07:10.440 physics needs to be shaken up a little bit, you know, 0:07:10.600 --> 0:07:14.200 kind of reset or you know, disrupted, or you know, 0:07:14.320 --> 0:07:18.200 start from a totally needed perspective. Yeah, I think it's 0:07:18.240 --> 0:07:22.600 possible physics today has all those elements of needing a 0:07:22.640 --> 0:07:25.080 new idea, of needing a new perspective, of discovering, of 0:07:25.120 --> 0:07:28.360 stumbling over something which shows us that we've just been 0:07:28.400 --> 0:07:31.440 asking the wrong questions or starting our solutions from the 0:07:31.440 --> 0:07:34.440 wrong point of view. And that's not embarrassing, you know. 0:07:34.520 --> 0:07:36.680 That's the way we explore the world. We start from 0:07:36.680 --> 0:07:39.160 our current understanding. We see how long it works, and 0:07:39.200 --> 0:07:41.920 when it breaks, we think, can we just add another 0:07:41.960 --> 0:07:43.800 little widget to it, or do we have to toss 0:07:43.840 --> 0:07:46.280 everything out and build it from a different kind of 0:07:46.280 --> 0:07:49.440 bit In today's episode, we'll be talking about one such 0:07:49.480 --> 0:07:54.400 idea that might help bridge this connector gap between quantum 0:07:54.400 --> 0:07:58.800 mechanics and gravity. And it's a pretty new theory when 0:07:58.920 --> 0:08:00.680 you say, it's sort of it's come out in the 0:08:00.760 --> 0:08:03.240 last maybe what ten years, twenty years. I think it 0:08:03.240 --> 0:08:06.240 has its history in the eighties, but it's been picking 0:08:06.320 --> 0:08:09.040 up steam in the last ten or fifteen years, and 0:08:09.040 --> 0:08:11.160 it's sort of emerging as a dark horse. It was 0:08:11.200 --> 0:08:14.160 like first was sort of laughed off as a fringe 0:08:14.200 --> 0:08:17.960 theory and you know, not nearly this popular other theories 0:08:17.960 --> 0:08:20.760 of everything in quantum gravity, and so I think it's 0:08:21.000 --> 0:08:24.320 recently gaining some sort of respectability. It's like millennials, you know, 0:08:24.400 --> 0:08:27.280 born in the eighties but kind of easily discounted, but 0:08:27.280 --> 0:08:30.040 now they're taking over the world. Are millennials getting respectable? 0:08:30.040 --> 0:08:35.480 When did that happen? When we died? There? I'm working 0:08:35.480 --> 0:08:38.200 on my theory of quantum respectability and currently I have 0:08:38.360 --> 0:08:40.680 zero there you go. So today we'll be talking about 0:08:40.720 --> 0:08:50.600 what about that theory. And the theory is loop quantum gravity. 0:08:51.200 --> 0:08:53.679 What is it? Why is it in a loop? And 0:08:53.960 --> 0:08:56.360 will it solve all the problems in physics? And here 0:08:56.360 --> 0:08:57.680 I have to make a shout out to one of 0:08:57.679 --> 0:09:01.000 our listeners, Jim Milco. Jim has been sending me questions 0:09:01.040 --> 0:09:03.400 for about as long as we've been doing this podcast, 0:09:03.559 --> 0:09:07.200 and he has been consistently asking for a podcast episode 0:09:07.200 --> 0:09:10.880 about loop quantum gravity. So thanks for your patients, Jim, 0:09:10.920 --> 0:09:13.280 here's your episode. Awesome as he sent you, any idea 0:09:13.320 --> 0:09:15.640 is worthy of a Nobel price yet, Jim has sent 0:09:15.760 --> 0:09:18.040 a lot of ideas and they're always fun to read. 0:09:18.360 --> 0:09:21.200 So if you have ideas about the universe, or just questions, 0:09:21.360 --> 0:09:23.720 or there's something you really want to understand more deeply 0:09:23.760 --> 0:09:25.840 and you think we might be able to break it down, 0:09:25.920 --> 0:09:30.440 please send your questions, your suggestions, your fundamental new theories 0:09:30.480 --> 0:09:34.360 of the universe to questions at Daniel and Jore dot com. Yeah, 0:09:34.440 --> 0:09:36.920 thanks to Jim for listening and to everyone out there listening. 0:09:37.240 --> 0:09:39.720 And so as usual, we were wondering how many people 0:09:39.760 --> 0:09:44.240 out there know or have heard of loop quantum gravity. 0:09:44.280 --> 0:09:46.640 It's sort of a it's sort of a it has 0:09:46.679 --> 0:09:49.679 two sort of technical familiar words, but then a pretty 0:09:49.679 --> 0:09:52.680 common word, which is loop. I was very curious in 0:09:52.720 --> 0:09:54.760 these interviews to see if anybody had heard of this 0:09:54.800 --> 0:09:57.559 thing and had any ideas. So I went in with 0:09:57.600 --> 0:10:01.240 a completely open mind. So before you hear these answers, 0:10:01.480 --> 0:10:04.440 think to yourself, do you know what Luke quantum gravity is? 0:10:04.440 --> 0:10:07.640 Could you describe it? What would you answer? Here's what 0:10:07.679 --> 0:10:09.960 people had to say. I mean, I would assume it 0:10:10.000 --> 0:10:14.360 has something to do with gravity, nothing at all, nothing 0:10:14.400 --> 0:10:17.120 at all. So I heard of quantum mechanics and read 0:10:17.960 --> 0:10:21.000 like brief history of time. Okay, but I don't don't 0:10:21.000 --> 0:10:25.320 know what loup quantum gravity could be. What came to 0:10:25.360 --> 0:10:28.920 mind first was entanglement. But I don't think that necessarily 0:10:28.960 --> 0:10:31.600 has anything to do with that. So it's just as 0:10:31.600 --> 0:10:33.600 opposed to just making up something that I think it 0:10:33.679 --> 0:10:36.560 might be. I don't know. I have not no no 0:10:36.600 --> 0:10:41.160 idea that I'm not No, I have it nothing. I 0:10:41.200 --> 0:10:44.840 don't know, all right, not a lot of penetration in 0:10:44.920 --> 0:10:48.360 the public market. No, these folks have to work on 0:10:48.440 --> 0:10:52.120 their pr for sure. String theory has them beat, for sure. 0:10:53.920 --> 0:10:55.560 Maybe they need to get it mentioned in the next 0:10:55.600 --> 0:10:58.600 Big Bang Theory episode. Oh maybe we should create a 0:10:58.600 --> 0:11:02.680 setim called loop quantum gravity. I want to see you 0:11:02.760 --> 0:11:08.040 pitching that, like, Hey, it worked for the Big Bang theory. 0:11:08.240 --> 0:11:12.599 We just need another physics theory named titled sitcom that 0:11:12.760 --> 0:11:15.079 makes fun of nerds. Yeah, well I'm in as long 0:11:15.160 --> 0:11:19.480 as we have characters that both are smart and can 0:11:19.520 --> 0:11:29.160 talk to human beings. Oh really yeah? Any Oh that hurts, man, 0:11:29.320 --> 0:11:32.200 That hurts. So not. Not only a lot of people 0:11:32.200 --> 0:11:34.120 seem to have heard of it. I mean I imagine 0:11:34.160 --> 0:11:37.360 they most of them have heard of quantum mechanics or 0:11:37.360 --> 0:11:40.920 have heard the word quantum if anything, from the Marvel movies, 0:11:41.080 --> 0:11:44.240 and they surely have heard of gravity, but loop quantum 0:11:44.240 --> 0:11:48.319 gravity is pretty pretty unknown. Yeah, it's a little bit esoteric, 0:11:48.760 --> 0:11:52.120 but it's fascinating and it has really interesting ideas, and 0:11:52.160 --> 0:11:55.360 those ideas could have really deep implications. It's the kind 0:11:55.400 --> 0:11:59.120 of theory which, if it's correct, really changes the way 0:11:59.160 --> 0:12:02.560 we think about the entire universe and the fundamental nature 0:12:02.960 --> 0:12:05.760 of our relationship with it. So it's super fun to 0:12:05.800 --> 0:12:10.040 think about. And it's also really complicated and very technical, 0:12:10.200 --> 0:12:14.040 and there's a humongous amount of complicated math involved, none 0:12:14.080 --> 0:12:16.640 of which none of which you will have to understand 0:12:17.120 --> 0:12:19.960 to get the basic ideas today, which is why Daniel, 0:12:20.000 --> 0:12:21.840 you went out there and found an expert to talk 0:12:21.920 --> 0:12:24.520 to about this topic. Right, that's right, because I'm a 0:12:24.559 --> 0:12:28.559 particle physicist and my expertise doesn't extend to theories of 0:12:28.679 --> 0:12:32.200 quantum gravity. So I went and I talked to Bianca Dittrich. 0:12:32.679 --> 0:12:35.960 She's a professor at the Perimeter Institute in Canada, and 0:12:36.040 --> 0:12:39.800 she's an active researcher on the forefront of quantum gravity. 0:12:39.960 --> 0:12:43.000 So here is Bianca. So my name is Bianca Ditwich, 0:12:43.400 --> 0:12:49.160 originately from Germany. Also studied in Germany and then oscillated 0:12:49.480 --> 0:12:53.920 between the Canada and Europe a number of times and 0:12:54.120 --> 0:12:58.840 ended up at in Canada. It's a parameter institute, a faculty. 0:13:00.000 --> 0:13:03.040 All right, cool, So Bianca explained to you what loop 0:13:03.160 --> 0:13:06.480 quantum gravity is. Yeah. I had a long conversation with 0:13:06.520 --> 0:13:09.560 Bianca about why we need loop quantum gravity, how it 0:13:09.640 --> 0:13:12.600 solves the problems in physics, where the current criticisms of 0:13:12.640 --> 0:13:15.480 it are, how we could test it, and of course 0:13:15.520 --> 0:13:17.400 then I had to ask her at the end about 0:13:17.480 --> 0:13:22.400 black holes. Of course, because every good conversation ends in 0:13:22.440 --> 0:13:25.480 a black hole literally, right, maybe at the end of 0:13:25.480 --> 0:13:28.920 the universe, all that every conversation, everyone will ever have, 0:13:29.040 --> 0:13:32.439 all that information will end up maybe in a black hole. Well, 0:13:32.440 --> 0:13:33.960 what happens if you take a black hole and you 0:13:34.040 --> 0:13:37.640 put it in a toaster oven. There's a question nobody's 0:13:37.640 --> 0:13:41.320 ever asked, if I need to ask that a crunchy 0:13:41.320 --> 0:13:46.640 outside of the inside will still be cold black hole temperature. Yes, 0:13:46.720 --> 0:13:48.720 So what if I put a black hole in a microwave? 0:13:48.720 --> 0:13:51.000 Then do I heat up the inside of the black hole. 0:13:51.760 --> 0:13:53.679 That's a question I've never thought of. That's really a 0:13:53.720 --> 0:13:56.000 fun question. All right, Well, that step us through what 0:13:56.040 --> 0:13:58.920 Bianca explained to you, Daniel was so first of all, 0:13:58.960 --> 0:14:01.719 I guess what is the big problem in physics? Did 0:14:01.920 --> 0:14:04.079 that needs to be fixing? The big problem is that, 0:14:04.160 --> 0:14:07.400 as we said earlier, we have two different basic ideas 0:14:07.440 --> 0:14:10.880 about sort of how the universe works at the smallest scale, 0:14:10.920 --> 0:14:13.880 and they start from very different places, and as you 0:14:13.920 --> 0:14:16.480 said that they when they come together across the Atlantic, 0:14:16.679 --> 0:14:19.680 they just don't meet. And those two ideas are quantum 0:14:19.720 --> 0:14:23.760 mechanics and general relativity of theory Einstein's theory of gravity. 0:14:23.880 --> 0:14:26.240 It's weird to me that there would be too so 0:14:26.320 --> 0:14:29.400 many so different theories about the universe. You know, wouldn't 0:14:29.440 --> 0:14:31.560 they all sort of meet at the at the you know, 0:14:31.640 --> 0:14:34.640 plus and minus mathematical level. Well, you'd hope so. And 0:14:34.640 --> 0:14:36.360 this is sort of the way physics starts. You know, 0:14:36.480 --> 0:14:39.640 if your caveman cave woman physicist, you begin building your 0:14:39.640 --> 0:14:41.840 model of the universe by sort of looking at all 0:14:41.840 --> 0:14:45.400 this stuff around you, cataloging what it can do, and 0:14:45.440 --> 0:14:48.320 then saying, can I understand all of this stuff in 0:14:48.360 --> 0:14:51.040 as simple as possible terms? And so you're like, all right, 0:14:51.080 --> 0:14:53.280 there's the thing where things fall down, there's the thing 0:14:53.360 --> 0:14:56.040 where lightning comes from the sky. You know, there's a 0:14:56.080 --> 0:14:58.640 thing where there's wind. And then you have a very 0:14:58.680 --> 0:15:00.600 long list of stuff and try to boil it down 0:15:00.600 --> 0:15:02.760 and say, oh, you know, this lightning thing is the 0:15:02.800 --> 0:15:04.800 same as this other thing where I get zapped, and 0:15:05.240 --> 0:15:07.760 things falling down is actually the same thing as stars 0:15:07.800 --> 0:15:10.160 moving through the sky. There's all these moments when we 0:15:10.200 --> 0:15:12.640 sort of shrunk the list of ideas we need to 0:15:12.640 --> 0:15:15.760 explain the universe. And so you hope that as this 0:15:15.800 --> 0:15:17.960 list gets shorter and shorter, they fit together nicely. And 0:15:18.000 --> 0:15:20.520 that's happened a lot of time so far. Electricity is 0:15:20.560 --> 0:15:22.960 the same thing as magnetism, and it's all part of 0:15:22.960 --> 0:15:25.840 this other thing called the electroweak force that has happened. 0:15:26.080 --> 0:15:28.640 But sometimes you get, you know, you get two puzzle 0:15:28.640 --> 0:15:31.280 pieces and they just don't fit together, all right. So 0:15:31.360 --> 0:15:35.440 maybe step remind us Daniel, what each of these theories are, Like, 0:15:35.520 --> 0:15:38.600 what's the what's the easy way to describe what general 0:15:38.680 --> 0:15:41.840 relativity is, And what's the easy way to describe what 0:15:42.000 --> 0:15:44.720 quantum mechanics is. So general relativity is a way to 0:15:44.760 --> 0:15:47.960 try to understand what is gravity. And remember that Newton 0:15:48.040 --> 0:15:51.200 said gravity is things pulling on each other, things that 0:15:51.240 --> 0:15:54.560 have mass pull on each other. So take a force, yeah, Newton, 0:15:54.760 --> 0:15:56.760 that was the old thinking. That was the old thinking. 0:15:56.840 --> 0:15:59.640 Newton thought gravity is a force, and it seems kind 0:15:59.640 --> 0:16:01.320 of like a force. It acts like a force, like 0:16:01.400 --> 0:16:04.360 electricity and magnetism, and he was able to write down 0:16:04.360 --> 0:16:07.880 an equation that described how the Earth moved around the 0:16:07.920 --> 0:16:10.440 Sun and how to move the Moon moved around the Earth, 0:16:10.480 --> 0:16:13.240 and it works pretty well. Now, Einstein came along and 0:16:13.280 --> 0:16:16.600 he gave us general relativity, which is a complete reconception 0:16:16.640 --> 0:16:19.520 of how gravity works. He said, no, no, gravity is 0:16:19.560 --> 0:16:23.160 not a force. Gravity is a change in the shape 0:16:23.200 --> 0:16:27.160 of space and time itself. Like you have a blob 0:16:27.200 --> 0:16:29.480 of mass or blob of any kind of energy density, 0:16:29.720 --> 0:16:32.560 it changes the shape of space and that's what makes 0:16:32.720 --> 0:16:36.160 things move in curves. Rather than moving and what feels 0:16:36.200 --> 0:16:39.040 like a straight line to us, things moved through bent space. 0:16:39.280 --> 0:16:43.120 It's not like a mysterious invisible force that pulls things together. 0:16:43.240 --> 0:16:46.880 It's more like when things exist, they distort, they bend 0:16:46.920 --> 0:16:49.440 the space around them, and that's why they come together. Yeah. 0:16:49.440 --> 0:16:52.520 And it's a beautiful idea and it's been tested exilient 0:16:52.600 --> 0:16:57.880 ways and it works. It describes very tiny deviations in 0:16:58.440 --> 0:17:01.840 Mercury's orbit. It describes how light bends around the Moon 0:17:02.000 --> 0:17:06.240 during an eclipse. Big stuff, big stuff, Yeah, really thoroughly 0:17:06.280 --> 0:17:10.240 extensively tested. It predicted gravitational waves, which we've actually seen 0:17:10.840 --> 0:17:13.960 black holes to right and black holes. Yeah. And and 0:17:14.080 --> 0:17:16.119 the thing to understand the things that that's going to 0:17:16.200 --> 0:17:19.240 be make it in conflict with quantum mechanics is that 0:17:19.280 --> 0:17:22.840 it's a classical theory meeting that it assumes that, like 0:17:22.880 --> 0:17:26.320 you can describe everything perfectly, that everything has a position 0:17:26.480 --> 0:17:29.679 and a direction and a location, right, and that the 0:17:29.720 --> 0:17:33.640 space is operating in is smooth, Like you can subdivide 0:17:33.640 --> 0:17:37.320 space as many times as you want between me and you. 0:17:37.720 --> 0:17:41.119 There's an infinite possible locations for like a ball that 0:17:41.160 --> 0:17:45.400 we're throwing back and forth. That's Einstein's vision of space. Right, 0:17:45.760 --> 0:17:49.200 it assumes that everything is kind of smooth and continuous, 0:17:49.200 --> 0:17:51.840 and there there are no bumps in the universe at 0:17:51.840 --> 0:17:54.719 the microscopic level. That's right. You can zoom in forever 0:17:55.040 --> 0:17:58.399 according to Einstein and general relativity, and things still stay 0:17:58.480 --> 0:18:01.280 smooth and and everything has a fixed location. Right, the 0:18:01.280 --> 0:18:04.840 ball is somewhere and space and time makes some sense. 0:18:05.040 --> 0:18:09.120 There's no uncertainty or or weird or weirdness. That's right. 0:18:09.160 --> 0:18:12.760 The world can be known, everything can be determined according 0:18:12.800 --> 0:18:15.760 to general relativity. But then you have quantum mechanics, that's right. 0:18:15.800 --> 0:18:18.000 And then on the other hand, building from the other 0:18:18.119 --> 0:18:20.200 side of the ocean, you know, the toaster side of 0:18:20.200 --> 0:18:22.159 the ocean instead of the microwave side of the ocean. 0:18:22.640 --> 0:18:26.560 Um completely mixing metaphors, there is quantum mechanics. And quantum mechanics, 0:18:26.600 --> 0:18:29.200 of course developed in the early part of this century 0:18:29.240 --> 0:18:32.840 to explain some things that didn't make sense, some experiments 0:18:32.880 --> 0:18:36.520 we saw which just could not be described using a 0:18:36.560 --> 0:18:40.520 classical understanding of electromagnetism. It was really what was light 0:18:40.640 --> 0:18:42.960 that gave us the first clues. We did a whole 0:18:42.960 --> 0:18:46.359 podcast episode about the photoelectric effect and how we know, 0:18:46.400 --> 0:18:49.600 the photon is a thing, and they did these experiments 0:18:49.840 --> 0:18:52.280 that just didn't make sense unless you thought of light 0:18:52.359 --> 0:18:55.360 as being made of tiny little packets of energy rather 0:18:55.359 --> 0:18:58.399 than a smooth, continuous beam. You had to think about 0:18:58.400 --> 0:19:01.200 it as these tiny packets. When you zoom in, things 0:19:01.320 --> 0:19:04.280 don't behave nice and smooth and continuous there are sort 0:19:04.280 --> 0:19:08.359 of lumpy and clumpy. Yeah, And there were also just 0:19:08.400 --> 0:19:11.119 some problems with the theory, like there's a kind of 0:19:11.200 --> 0:19:13.840 radiation in the universe called black body radiation, which is 0:19:13.880 --> 0:19:16.959 just how things glow, Like everything in the universe has 0:19:16.960 --> 0:19:20.040 a temperature and it glows with that temperature, and quantum 0:19:20.040 --> 0:19:25.200 mechanics predicted that well. Classical theory electromagnetism predicted a certain spectrum, 0:19:25.240 --> 0:19:27.919 like if you're this temperature, you should glow with this color. 0:19:28.000 --> 0:19:30.160 If you're that temperature, you should glow with that other color. 0:19:30.520 --> 0:19:34.919 The problem was that it predicted that for certain temperatures 0:19:34.960 --> 0:19:37.720 you should glow at a crazy nonsensical color, like if 0:19:37.720 --> 0:19:40.760 you get an infinite amount of radiation. The original theory, 0:19:40.800 --> 0:19:44.800 the one before quantum mechanics, said that things that certain 0:19:44.840 --> 0:19:48.520 temperatures should have an infinite amount of light at very 0:19:48.600 --> 0:19:52.200 very low wavelengths, right, it really really sort of it's 0:19:52.200 --> 0:19:54.520 called ultra violet light, and that they should have like 0:19:54.560 --> 0:19:57.400 a ridiculous amount of infinite amount of ultra violet light, 0:19:57.440 --> 0:20:00.359 which is nonsensical. So you can do an ex perament 0:20:00.440 --> 0:20:05.320 basically that proves that general relativity doesn't work for all cases. Well, 0:20:05.359 --> 0:20:08.040 you can do an experiment that proves that the old 0:20:08.080 --> 0:20:11.320 theory of electricity and magnetism doesn't work. And we knew 0:20:11.320 --> 0:20:13.280 that didn't work. We're like, okay, this theory is making 0:20:13.280 --> 0:20:15.879 a prediction that just doesn't make sense. But if you 0:20:15.880 --> 0:20:18.840 add quantum mechanics to it, quantum mechanics says, oh, that's 0:20:18.880 --> 0:20:22.440 just because light is not continuous. If you make light 0:20:22.440 --> 0:20:25.080 into chunks, then if you predict that, you don't see 0:20:25.080 --> 0:20:27.240 this crazy behavior. And that's in fact what we saw 0:20:27.320 --> 0:20:29.760 in nature. And so we needed to sort of change 0:20:29.760 --> 0:20:32.760 the theory. The theory gave nonsensical results. I mean, I 0:20:32.800 --> 0:20:34.640 have to add this bit to it to say bit 0:20:34.720 --> 0:20:37.920 that says, okay, well there's a minimum size to a photon, 0:20:38.320 --> 0:20:40.919 and that solved that problem. It said, okay, now you 0:20:40.960 --> 0:20:44.359 can make realistic predictions. And so but the thing to 0:20:44.440 --> 0:20:47.680 understand is that like quantum mechanics changes also the way 0:20:47.720 --> 0:20:51.080 we think about the universe, right, it says things are uncertain, 0:20:51.119 --> 0:20:54.480 things are fluctuating. This is like crazy randomness the heart 0:20:54.520 --> 0:20:56.720 of the universe. All right. So those are the two 0:20:57.240 --> 0:21:00.679 two big titans in physics theories, right, general activity and 0:21:00.760 --> 0:21:03.560 quantum mechanics to try to explain the universe. And the 0:21:03.640 --> 0:21:06.480 problem is that they don't play well together. So let's 0:21:06.560 --> 0:21:08.320 get into a little bit of why they don't play 0:21:08.400 --> 0:21:12.160 well together and whether this idea of loop quantum gravity 0:21:12.320 --> 0:21:15.280 can help solve that. But first let's take a quick break, 0:21:28.040 --> 0:21:31.600 all right, Daniel, So general relativity and quantum mechanics don't 0:21:31.600 --> 0:21:33.439 play well together. Is it fair to say? Is it? 0:21:33.520 --> 0:21:34.800 Is it kind of like I'm trying to think of 0:21:34.840 --> 0:21:38.840 an analogy. Is it kind of like microeconomics and macro economics, Like, 0:21:38.880 --> 0:21:42.520 you know, macro economics is good for you know, big 0:21:42.960 --> 0:21:46.439 economies and countries and and micro economics is good for 0:21:46.520 --> 0:21:50.280 like how people make decisions, but like somehow they don't always. 0:21:50.440 --> 0:21:53.640