WEBVTT - What is Relational Quantum Mechanics? 0:00:01.280 --> 0:00:03.320 Hey, it' Jorhan Daniel here, and we want to tell 0:00:03.360 --> 0:00:06.840 you about our new book. It's called Frequently Asked Questions 0:00:06.960 --> 0:00:09.719 about the Universe because you have questions about the universe, 0:00:09.760 --> 0:00:12.360 and so we decided to write a book all about them. 0:00:12.440 --> 0:00:14.800 We talk about your questions, we give some answers, we 0:00:14.880 --> 0:00:17.560 make a bunch of silly jokes as usual, and we 0:00:17.600 --> 0:00:20.159 tackle all kinds of questions, including what happens if I 0:00:20.200 --> 0:00:22.880 fall into a black hole? Or is there another version 0:00:22.920 --> 0:00:25.480 of you out there that's right? 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We all know that quantum mechanics 0:01:10.560 --> 0:01:14.920 can't be quite right. I'm not talking about the counter intuitive, 0:01:15.160 --> 0:01:18.440 probabilistic aspects of it that it forced us to accept 0:01:18.520 --> 0:01:22.240 that the world we live in is fundamentally weirder than 0:01:22.319 --> 0:01:27.080 we have ever imagined. Probabilities and correlations and uncertainty is no. 0:01:27.480 --> 0:01:30.800 Those bits are probably right, But there's a problem at 0:01:30.840 --> 0:01:34.720 the heart of quantum mechanics, one that has baffled physicists 0:01:34.720 --> 0:01:38.320 and philosophers for nearly a hundred years, and that may 0:01:38.360 --> 0:01:42.840 take another hundred years to solve. But some recent ideas 0:01:43.120 --> 0:01:46.240 maybe showing us a path forward, even if it's a 0:01:46.360 --> 0:02:05.000 stranger path. Then we imagine, Hi, I'm Daniel. I'm a 0:02:05.000 --> 0:02:08.280 particle physicist and a professor at u C Irvine, and 0:02:08.400 --> 0:02:13.560 I'm still confused by quantum mechanics. Confused but not frustrated, 0:02:13.919 --> 0:02:17.200 You might say, I'm deliciously confused. What could be more 0:02:17.240 --> 0:02:20.639 delightful than grappling with the deep mysteries of the nature 0:02:20.680 --> 0:02:24.080 of reality, seeing the truth written down in cold black 0:02:24.120 --> 0:02:27.440 and white and mathematical equations, and struggling to gain an 0:02:27.440 --> 0:02:32.520 intuition to incorporate those alien concepts into our human brains. 0:02:32.600 --> 0:02:36.720 After all, that is the deepest goal of physics, and 0:02:36.760 --> 0:02:39.960 that's the goal of our podcast. Daniel and Jorgey explain 0:02:40.040 --> 0:02:42.960 the university production of My Heart Radio, in which we 0:02:43.040 --> 0:02:46.760 tackled the biggest and hardest and nastiest and funnest of 0:02:46.880 --> 0:02:50.600 questions of the universe, the ones that make your brains twist, 0:02:50.639 --> 0:02:53.080 the ones that slip away from you just as you 0:02:53.160 --> 0:02:55.440 thought you had figured them out, the ones that might 0:02:55.480 --> 0:03:00.240 elude humanity for centuries or forever. We don't show away 0:03:00.280 --> 0:03:02.800 from any questions on the podcast, but we seek to 0:03:02.840 --> 0:03:06.880 approach them and explain our knowledge and our ignorance to you. 0:03:07.200 --> 0:03:09.440 My friend and co host Jorge is on a break, 0:03:09.440 --> 0:03:12.040 but I have a special treat for you. We are 0:03:12.200 --> 0:03:14.480 very lucky to have as a guest one of my 0:03:14.639 --> 0:03:18.600 favorite physicists, one of my favorite writers, and one of 0:03:18.639 --> 0:03:23.120 my favorite writers about physics, truly a poet of science communication. 0:03:23.200 --> 0:03:26.680 Today we'll be talking to Carlo Rovelli about some of 0:03:26.720 --> 0:03:29.919 the problems at the heart of quantum mechanics and explaining 0:03:30.000 --> 0:03:35.600 a lesser known but absolutely fascinating alternative version of quantum mechanics. 0:03:35.640 --> 0:03:38.240 So today on the podcast, we'll be answering the question 0:03:43.240 --> 0:03:47.840 what is relational quantum mechanics? So it's my great pleasure 0:03:47.840 --> 0:03:51.080 today to introduce Professor Carlo Rovelli. He's a professor of 0:03:51.080 --> 0:03:53.440 physics in Marseille, and he cut his teeth and made 0:03:53.440 --> 0:03:56.720 his name for himself developing theories of quantum gravity, mostly 0:03:56.800 --> 0:03:59.840 loop quantum gravity. If I understand correctly, he also became 0:03:59.880 --> 0:04:02.000 a household name. Is the author of the book Seven 0:04:02.040 --> 0:04:04.440 Brief Lessons on Physics, which sold more than a million 0:04:04.480 --> 0:04:07.920 copies and was translated into forty one languages. I've read 0:04:07.920 --> 0:04:10.680 it and enjoyed it immensely and heartily recommended to you. Today, 0:04:10.680 --> 0:04:12.600 Professor Rivelli is here to talk to us about his 0:04:12.640 --> 0:04:16.240 new book, Hell Go Land and a fascinating alternative take 0:04:16.400 --> 0:04:19.920 on the measurement problem in quantum mechanics. Professor Velli, welcome 0:04:19.960 --> 0:04:22.200 to the podcast, and thank you for joining us. Thank 0:04:22.240 --> 0:04:24.440 you question that it's a pleasure in the honor of 0:04:24.480 --> 0:04:28.240 being here, wonderful. Well. I always love talking about quantum 0:04:28.240 --> 0:04:31.080 mechanics and puzzling over it with other people. I feel 0:04:31.120 --> 0:04:33.440 like every time I talk about quantum mechanics with somebody else, 0:04:33.720 --> 0:04:36.240 I think of a new question I've never thought of before, 0:04:36.680 --> 0:04:38.760 or a new angle on it, or a new mystery 0:04:38.800 --> 0:04:41.320 frankly like a new corner of my mind that I 0:04:41.360 --> 0:04:44.040 haven't ever really examined, and I get confused, and so 0:04:44.080 --> 0:04:46.120 it's always fun to figure things outside of on the fly. 0:04:46.520 --> 0:04:48.719 So today we wanted to talk about your new book 0:04:48.880 --> 0:04:51.640 and Hell Go Land, And the book essentially lays out 0:04:51.720 --> 0:04:56.240 for lay audience this idea of relational quantum mechanics, sort 0:04:56.279 --> 0:04:59.040 of a new interpretation on quantum mechanics. And the first 0:04:59.080 --> 0:05:01.719 question for you I have is if you could describe 0:05:01.720 --> 0:05:06.040 for us what is the problem that relational quantum mechanics solves, Like, 0:05:06.160 --> 0:05:09.920 why do we need another quantum mechanics interpretation? What is it? 0:05:09.960 --> 0:05:12.880 At the heart of relational quantum mechanics is trying to 0:05:12.960 --> 0:05:16.479 do One of the difficulties the problem of quantum mechanics 0:05:16.720 --> 0:05:21.080 is to say exactly what the problem is. So quass mechanics, 0:05:21.080 --> 0:05:24.960 on the one hand, it's extraordinary successful, is used in 0:05:25.440 --> 0:05:28.400 a lot of our technology, is used a lot of 0:05:28.440 --> 0:05:31.719 our understanding of the world world. We explain with quantum 0:05:31.720 --> 0:05:37.800 mechanics the basics of chemistry, basic apastrophysics, all sorts of stuff, 0:05:37.839 --> 0:05:40.440 and it works. It works fantastically. On the other hand, 0:05:40.680 --> 0:05:45.200 there is a persisting, mysterious aspect about this theory. It's 0:05:45.200 --> 0:05:47.799 a theory that it's a it's sort of formulity differently 0:05:48.080 --> 0:05:53.720 than previous basic physical theories. This difference puzzles everybody, and 0:05:54.120 --> 0:05:57.600 this is where the problems can in because the scientists 0:05:57.680 --> 0:06:01.479 disagree about how to think abou quantum mechanics. If you 0:06:01.640 --> 0:06:03.839 if you want to, if you go to a physicist 0:06:03.920 --> 0:06:07.760 conference and you want to really start a furious discussion, 0:06:08.279 --> 0:06:11.120 just like drop the question at the banquets, say oh, 0:06:11.160 --> 0:06:14.120 by the way, what do you think going to mechanics, 0:06:14.200 --> 0:06:16.960 And ten minutes later everyone's screaming against everybody. But is 0:06:17.000 --> 0:06:20.320 this a conference of philosophers or physicists in your mind? No, 0:06:20.440 --> 0:06:23.520 No physicist physicist physicism, including the one to say there's 0:06:23.560 --> 0:06:25.640 no problem at all, what are you talking about? And 0:06:25.680 --> 0:06:29.240 that they say, of course there's a problem. You know, 0:06:29.320 --> 0:06:31.039 where is the problem? I mean, how how can we 0:06:31.120 --> 0:06:35.119 characterize the problem? Well? Sort of all physical theories from 0:06:35.560 --> 0:06:38.560 saying Newton or maybe even before from the card or 0:06:38.560 --> 0:06:42.479 even from Aristotle all the way to Maxwell and Twinstein, 0:06:43.520 --> 0:06:48.680 special activity, general activity, electro dynamics. The theories describes the 0:06:48.839 --> 0:06:52.280 systems and just the sens the system with some variables. 0:06:52.560 --> 0:06:55.200 I don't know a pendulum. It's a physical object and 0:06:55.279 --> 0:06:58.360 the variable is the angle with the vertical and tell 0:06:58.400 --> 0:07:03.600 you how this variable ease and evolves. Given something that 0:07:03.640 --> 0:07:05.520 you know at the beginning and you know where it is, 0:07:05.600 --> 0:07:07.320 you know the velocity, and then you have you have 0:07:07.360 --> 0:07:10.200 any questions that tell you how the variable changes continuously 0:07:10.200 --> 0:07:13.680 in time. So of course this allows assume ex predictions 0:07:13.680 --> 0:07:17.000 because we can measure the position. The velocity doesn't close 0:07:17.000 --> 0:07:20.960 our eyes with two seconds, open again and the new position. 0:07:21.000 --> 0:07:24.480 New velocity can be predicted by the theory because they 0:07:24.560 --> 0:07:27.400 tell us exactly how it moves in time. So that's 0:07:27.440 --> 0:07:31.400 how Newton physics works, or Maxwell theory works of ice. 0:07:31.440 --> 0:07:34.200 Since theory works well probamical, it does not work this way. 0:07:34.440 --> 0:07:37.640 That's the point. It works in a completely different manner. 0:07:38.560 --> 0:07:41.840 It does not tell us what happens at the pendulum 0:07:42.160 --> 0:07:47.880 while he's moving. It only tells us the prediction without 0:07:47.880 --> 0:07:50.920 saying what is in between. And if you try to reconstruct, 0:07:50.960 --> 0:07:53.960 what is this in between? So the data that you 0:07:54.040 --> 0:07:57.600 know and the prediction that you make, all devils go loose, 0:07:58.040 --> 0:08:02.280 namely every stray. Things happen, and people disagree about what 0:08:02.400 --> 0:08:05.560 happened in between in between, you mean that moment when 0:08:05.600 --> 0:08:07.600 you close your eyes and you're trying to use physics 0:08:07.640 --> 0:08:11.720 to predict the future exactly. So typically think about quantum 0:08:11.720 --> 0:08:13.680 mechanics in this way. I mean, you make a measurement, 0:08:13.800 --> 0:08:17.760 that's the language which is used. They'll certainly makes a measurement, 0:08:18.000 --> 0:08:20.160 and you make a prediction of what's going to happen 0:08:20.520 --> 0:08:24.840 at the next measurement sometime later, and the prediction is binger. 0:08:25.120 --> 0:08:28.160 It works. I mean, it tell us exactly what we see, 0:08:28.280 --> 0:08:31.680 but if you ask what happened in between, it's confusing. 0:08:31.680 --> 0:08:34.680 And the reason it's confusing one way of presenting it, 0:08:34.840 --> 0:08:37.040 one of the many ways of presenting it is the following. 0:08:37.480 --> 0:08:40.000 If you have a particle, an electron, or a little 0:08:40.040 --> 0:08:42.840 mole for that, or an atom remocal, and you throw 0:08:42.920 --> 0:08:45.840 it in some way, then going to mechanics tell you 0:08:45.960 --> 0:08:48.600 where it's going to be, or at least probility distribution 0:08:48.600 --> 0:08:50.360 of what's going to be. Because the prediction about the 0:08:50.360 --> 0:08:53.400 mechanics and probabilistics are not not exactly that's one of 0:08:53.400 --> 0:08:55.920 the corrector is still going to mechanics, but it's telling 0:08:55.960 --> 0:08:58.360 me the sort of probility going to be here that 0:08:58.360 --> 0:09:00.280 you're probably going to be here, to be going to 0:09:00.360 --> 0:09:04.679 be here. Then in between, what happens to the mathematics 0:09:04.840 --> 0:09:09.040 is the particle opens up in a wave. It's it's everywhere, 0:09:09.520 --> 0:09:13.120 and with this way you compute the different probabilities, so 0:09:13.640 --> 0:09:17.640 the particles at the same time many positions in the mathematics. 0:09:18.080 --> 0:09:21.199 So some people say, okay, so the particle isn't many, 0:09:21.320 --> 0:09:23.840 it's a wave, it's all over. But then when you 0:09:23.880 --> 0:09:25.840 look at the particle is not a way. It's in 0:09:25.880 --> 0:09:28.680 a single position. So other people say, no, come on, 0:09:28.880 --> 0:09:30.880 I mean, we look at the particle is always a particle. 0:09:30.920 --> 0:09:33.000 When we look where it is, it is always in 0:09:33.120 --> 0:09:37.040 one point. But when you compute how it goes from 0:09:37.040 --> 0:09:40.240 from here to here, it's not in one point. And 0:09:40.280 --> 0:09:43.000 if you assume that it is in one point, you're 0:09:43.080 --> 0:09:45.560 led to make some kind of mistakes and things like that. 0:09:45.840 --> 0:09:49.760 So it's capable of making predictions, concrete predictions, or be 0:09:49.800 --> 0:09:52.680 can compared to measurements. But to make those predictions you 0:09:52.720 --> 0:09:56.600 need this intermediate step, which seems sort of nonsensical and 0:09:56.920 --> 0:09:59.040 conflicts with our sense of like what is real in 0:09:59.080 --> 0:10:02.840 the universe around exactly. So, but the real problem, it's 0:10:03.679 --> 0:10:06.000 the thing people are debating with is what does it 0:10:06.040 --> 0:10:11.079 mean that the theory describe what we measure. That's why 0:10:11.120 --> 0:10:14.000 it's called the measurement problem. In a sense, it's like 0:10:14.120 --> 0:10:18.640 when we measure something special happened, But we are not special, right, 0:10:18.720 --> 0:10:21.200 We are just you know, piece of the universe like 0:10:21.240 --> 0:10:25.040 any others. So the standard formulation of quantum mechanics, the 0:10:25.080 --> 0:10:28.920 one reading textbooks, it's only in terms of the observer 0:10:29.120 --> 0:10:31.320 and the measurement, which is fine as long as you 0:10:31.360 --> 0:10:34.640 don't ask, what about the physics of the observer? What 0:10:34.720 --> 0:10:39.199 about the observer itself isn't to observe itself a quantum system, 0:10:39.400 --> 0:10:42.000 so it should be described the quantum mechanics as well, 0:10:42.280 --> 0:10:44.160 so it should also open up on it like a wave. 0:10:44.920 --> 0:10:47.959 But that's it, and that's where people start disagree. And 0:10:48.360 --> 0:10:51.200 some physicists thinkly, yes, we do. We do our waves 0:10:51.679 --> 0:10:55.320 the multiple copies of Daniel and me and Carolo and 0:10:55.440 --> 0:10:58.520 some versions of us, some some some answers are given, 0:10:58.520 --> 0:11:01.280 is some other versions of different. It is given because 0:11:01.320 --> 0:11:05.640 we're a wave of different configurations of ourselves. Other people think, no, 0:11:05.760 --> 0:11:07.880 come on, that's not a good way of thinking about reality. 0:11:07.960 --> 0:11:12.120 And that's where the the disagreement start. So the disagreement 0:11:12.600 --> 0:11:15.400 is realized in the number of so called interpretations of 0:11:15.440 --> 0:11:18.680 quanto methadnics ways to make sense about this funny story 0:11:18.720 --> 0:11:22.120 about the observer and the measurement and on the market 0:11:22.240 --> 0:11:26.079 that there are many but maybe three or four or 0:11:26.120 --> 0:11:29.480 four or five which are dominant, and many variants of 0:11:29.559 --> 0:11:32.040 these which is pretty different from one another, and give 0:11:32.080 --> 0:11:34.959 a profoundly different picture of reality. And that's the beauty 0:11:34.960 --> 0:11:37.559 of the story. It's not just a technical thing about 0:11:37.640 --> 0:11:39.320 using the theory. In fact, it's not the technical thing 0:11:39.360 --> 0:11:41.880 about using Everybody agrees on using the theory, but everybody 0:11:41.920 --> 0:11:45.439 disagrees on if you want on what happens between the measurements, 0:11:45.480 --> 0:11:47.280 that's what way you're putting it. So I think it's 0:11:47.280 --> 0:11:50.679 really fascinating that it's so important to us to understand 0:11:51.080 --> 0:11:55.040 what happens when we're not looking. Right. Clearly, physics takes 0:11:55.080 --> 0:11:57.440 it very important to predict what happens when we look, 0:11:57.520 --> 0:11:59.800 because it's very practical. We need to know how trans 0:12:00.000 --> 0:12:02.959 star's working, whether our airplanes will fly. But when we're 0:12:02.960 --> 0:12:04.960 not making measurements, where we're not looking, when we're not 0:12:05.000 --> 0:12:08.040 watching the universe, we still want to know what is real, 0:12:08.120 --> 0:12:09.760 what is going on? We want to have like a 0:12:09.800 --> 0:12:13.199 model in our minds of how the universe works. Are 0:12:13.240 --> 0:12:15.439 we still doing physics in that case there's that philosophy 0:12:15.520 --> 0:12:17.559 or do you think they're you know, forever intertwined. I 0:12:17.600 --> 0:12:20.480 think they're forever intertwined, and I think they should be 0:12:20.520 --> 0:12:24.719 forever intertwined, because it's precisely by asking those kinds of 0:12:24.800 --> 0:12:31.920 questions that in the past physics has made the big jumps. Um, 0:12:32.040 --> 0:12:34.480 let me make an example of maybe two. What example 0:12:34.600 --> 0:12:38.440 is is the Earth the center of the universe. This 0:12:38.600 --> 0:12:41.959 was a huge debate at the time of between Copernicus 0:12:42.040 --> 0:12:45.360 and Newton. It's it's it's a center of debate, and 0:12:46.040 --> 0:12:48.600 nobody could say that this was not a scientific debate, 0:12:48.880 --> 0:12:52.560 because that's the debate that started that allowed Newton to 0:12:52.559 --> 0:12:56.439 do new to mechanics and allowed Galileo to understand the 0:12:56.480 --> 0:13:00.720 Gali little relativity, and this debate on on which Kepler BILLT. 0:13:00.840 --> 0:13:05.240 Kepler was a strenuous defender of the idea that there 0:13:05.400 --> 0:13:07.320 is not the center the universe. The universe is not 0:13:07.400 --> 0:13:09.679 the center. Going around the said, but if you think 0:13:09.720 --> 0:13:12.840 for a moment, is this Earth as the central universe? 0:13:13.200 --> 0:13:16.840 A scientific question in the sense of something we can 0:13:16.880 --> 0:13:20.320 test them, of course not. There's no way of testing. 0:13:20.360 --> 0:13:23.920 There's no there's no operational meaning, there's no measurement that 0:13:23.920 --> 0:13:27.480 I can make that can distinguish if there Earth is 0:13:27.520 --> 0:13:30.000 the central universe. So it is not because you know, 0:13:30.040 --> 0:13:32.440 I mean it can stay somewhere and see moving. But 0:13:32.559 --> 0:13:34.560 what does it mean if I am moving, I see 0:13:34.600 --> 0:13:38.360 I I see the center moving. So it's really a 0:13:38.559 --> 0:13:43.920 non empirical question. And yet it's a profound way scientific question. 0:13:44.400 --> 0:13:48.320 Why because it gives a different way depending if you 0:13:48.360 --> 0:13:50.880 answer one way or the other. If you start by 0:13:50.920 --> 0:13:53.319 thinking there Earth is the center, everything goes around that all. 0:13:53.360 --> 0:13:55.200 If you start by allowing there is to be one 0:13:55.280 --> 0:13:57.280 of the things moves, so you go to a completely 0:13:57.320 --> 0:14:02.120 different way for conceptualizing reality, and one which worked very well. 0:14:02.600 --> 0:14:04.520 The other was bad. It was not the good one. 0:14:04.720 --> 0:14:07.920 So I think this is one of the aspect of 0:14:07.960 --> 0:14:11.560 science which I think is often misunderstood. They would say, 0:14:11.760 --> 0:14:15.080 sciences is not just about you know, close your eye, 0:14:15.160 --> 0:14:18.520 make make a model, make mathematics, make a measurement, make 0:14:18.559 --> 0:14:22.560 a prediction, and that's it. Science is about understanding reality, 0:14:22.600 --> 0:14:27.200 meaning building up a conceptual structure, the way you're thinking reality, 0:14:27.600 --> 0:14:30.760 how to put things in cases. One way of putting 0:14:30.760 --> 0:14:32.840 things in cases is in one case there's the Earth 0:14:33.640 --> 0:14:36.840 and in the other the celestial bodies, the sound, the wound, 0:14:37.160 --> 0:14:40.120 the planets, the stars, and then you throw that away. 0:14:40.280 --> 0:14:42.920 That's that's that. That's not the right characterizasue. The right 0:14:42.920 --> 0:14:46.040 way is there are stars, the planets, and then there 0:14:46.040 --> 0:14:49.800 are satellites. Do something different and that's works really different, 0:14:50.040 --> 0:14:53.200 and boom, we understand the universe better. So I think 0:14:53.280 --> 0:14:58.400 there are questions which are not directly empirical but are scientific, 0:14:58.400 --> 0:15:01.280 and I think the interpetitional quantum mechanics turn out something 0:15:01.360 --> 0:15:04.200 like that, Namely, one way you're thinking about the story 0:15:04.280 --> 0:15:07.560 will turn out to be useful on the long run. 0:15:20.320 --> 0:15:23.680 So then let's dig into the details of the different interpretations, 0:15:24.000 --> 0:15:26.320 just to recap for our listeners, what exactly is the 0:15:26.320 --> 0:15:28.200 problem that we're trying to solve here. The way I 0:15:28.240 --> 0:15:30.920 think about it sometimes is that we have these particles, 0:15:30.920 --> 0:15:33.720 and our mathematical model of them is that they are probabilistic. 0:15:33.800 --> 0:15:35.800 They can have the probability to be doing one thing 0:15:35.960 --> 0:15:38.120 or another thing. But of course that's not what we 0:15:38.160 --> 0:15:40.680 measure when we measure something, it does either one thing 0:15:41.120 --> 0:15:43.160 or the other. And the question is, how do you 0:15:43.200 --> 0:15:46.760 go from being probabilistic to being sort of classical. And 0:15:46.840 --> 0:15:49.680 you know, it seems arbitrary to say I'm making a 0:15:49.720 --> 0:15:52.400 measurement now or I'm not making a measurement, And you 0:15:52.400 --> 0:15:55.400 can ask questions like, well, when it interacts with other particles, 0:15:55.440 --> 0:15:58.080 why isn't that a measurement? Or if I'm making a 0:15:58.120 --> 0:16:00.480 measurement and I'm using a stick, and you know the 0:16:00.520 --> 0:16:03.440 tip of that stick is made of quantum mechanical particles, 0:16:03.440 --> 0:16:05.520 So why doesn't it just interact with my stick the 0:16:05.520 --> 0:16:08.240 way it interacts with other quantum mechanical particles and maintain 0:16:08.320 --> 0:16:11.000 it's probabilistic nature. And you know, people think about like 0:16:11.320 --> 0:16:13.880 do you have to have a conscious observer involved? But 0:16:13.920 --> 0:16:15.880 there's all sorts of fun things that you can dig 0:16:15.920 --> 0:16:18.560 into there. And had a fun conversation with the author 0:16:18.600 --> 0:16:21.160 of What is Real, which people can also dig into 0:16:21.280 --> 0:16:23.320 if they're interested in more details on what the measurement 0:16:23.320 --> 0:16:26.520 problem is. And the classical approach to people take this 0:16:26.600 --> 0:16:30.680 Copenhagen interpretation seems sort of arbitrary. It says that you know, 0:16:30.760 --> 0:16:33.320 the wave function moves by the shorting air equation, and 0:16:33.320 --> 0:16:36.120 it's smooth and continuous, and then boom, all of a sudden, 0:16:36.240 --> 0:16:38.920 when there's a measurement, everything collapses. But it doesn't tell 0:16:38.960 --> 0:16:41.640 you what a measurement is, right, And so there's this 0:16:41.760 --> 0:16:45.040 deep question still the heart of the most common interpretation. 0:16:45.200 --> 0:16:47.480 And let's listener as the podcast can also check out 0:16:47.480 --> 0:16:50.080 our episodes on the Many World's interpretation. But today I 0:16:50.160 --> 0:16:52.800 want to talk about your idea or this concept of 0:16:52.840 --> 0:16:56.400 relational quantum mechanics. So how does relational quantum mechanics deal 0:16:56.480 --> 0:16:59.080 with the measurement problem in a way that's different from 0:16:59.080 --> 0:17:03.600 this our try obviously unworkable approach of the Copenhagen interpretation. 0:17:03.760 --> 0:17:06.400 Yea very good and I think this is a nice 0:17:06.440 --> 0:17:10.120 way of putting the question. Let's take a let's take 0:17:10.119 --> 0:17:13.960 a concrete case. Was simplest the quantum mechanical experiment and 0:17:14.000 --> 0:17:16.159 measurement that we can make. We can take an atom, 0:17:16.440 --> 0:17:19.879 radioactive atom, right, just a piece of a block of 0:17:21.160 --> 0:17:25.479 radius radius uranium. They waited there and you put around 0:17:25.520 --> 0:17:29.679 it some detectors of radiation, you know, the guide detector, 0:17:29.680 --> 0:17:32.840 the click when when a radiation arrives to wait for 0:17:32.880 --> 0:17:35.159 a while and after a while, one of these clicks 0:17:35.280 --> 0:17:38.399 flink okay, and then you say, okay, the atom has 0:17:38.400 --> 0:17:42.240 emitted a radiation and it has been detected by these detectives. 0:17:42.280 --> 0:17:44.920 This is the fact. Now, how do we describe this 0:17:45.600 --> 0:17:48.920 in the equations? What we do when we do want 0:17:48.960 --> 0:17:52.400 to mechanics, we pretend that this radiation is some particles 0:17:52.480 --> 0:17:56.080 that are inside trapped inside the atoms, and they have 0:17:56.080 --> 0:17:58.800 a wave that describe them is a wave the way 0:17:58.800 --> 0:18:02.359 functions describes them and never automatics. These waves leaks out 0:18:03.400 --> 0:18:07.480 from the atom or from the nucleus of the atom 0:18:07.640 --> 0:18:11.520 slowly and continuously, and it's all over so and slowly. 0:18:11.720 --> 0:18:15.600 The imagine that this this wave continuously leaking out. So 0:18:15.640 --> 0:18:19.840 there's this continuously wave that around spherical and go out. 0:18:20.080 --> 0:18:23.440 So each one of the detectors is touched by these waves. 0:18:23.480 --> 0:18:27.160 Goes on. Then at some point the measurement happened. As 0:18:27.200 --> 0:18:32.119 you say, something happens. We go from this quantum wave 0:18:32.320 --> 0:18:35.600 to a classical factor, which is one single detector that happened, 0:18:36.240 --> 0:18:40.040 and this is a measurement. Now, different interpretation try to 0:18:40.080 --> 0:18:42.320 fill up the story in different way. Let me just 0:18:42.600 --> 0:18:46.960 compare to one or two interpretation. What is the many 0:18:47.000 --> 0:18:49.040 world interpretation that you mentioned, and the other is the 0:18:49.080 --> 0:18:52.880 Copenagen interpretation that dimension the many world, in a sense 0:18:52.960 --> 0:18:55.840 is the most radical idea of taking away very seriously, 0:18:56.000 --> 0:18:58.479 the Copenaga interpetition is the one we study at school, 0:18:58.680 --> 0:19:00.800 the one the teacher tell you tell you how to use. 0:19:01.000 --> 0:19:04.359 So the many one interpretation says that there's this wave 0:19:04.400 --> 0:19:08.640 that come out and you see only one detector clicking. 0:19:08.800 --> 0:19:11.080 But why do you see one the technical clicking, Because 0:19:11.080 --> 0:19:16.080 in reality, you yourself are a wave. Okay, So you, 0:19:16.080 --> 0:19:20.400 yourself are a superposition of different you like the particle 0:19:20.440 --> 0:19:23.640 and different positions in a superposition different positions. So it's 0:19:23.680 --> 0:19:26.000 not true that there is one detector that clicks. All 0:19:26.000 --> 0:19:30.200 the detectors clicks, but you yourself interacting with these detectors 0:19:30.320 --> 0:19:35.160 split up in one you that sees this the technical clicking. 0:19:35.240 --> 0:19:38.119 One UITs is that the tector clicking. One U that 0:19:38.440 --> 0:19:41.199 is that the technical clipping, and so on. Okay, So 0:19:41.280 --> 0:19:45.960 now you would imagine that the wave contains copies of you, 0:19:46.960 --> 0:19:48.800 and the reason you've seen one and not the others 0:19:48.920 --> 0:19:51.639 is only because you happen to be one copy of 0:19:51.640 --> 0:19:53.439 you and not the other copies of the other. Now 0:19:53.480 --> 0:19:56.639 does this work. Yes, it works. Is it plausible, Well, 0:19:57.160 --> 0:20:01.320 it sounds very implausible, extremely implosed. Well, the problem is 0:20:01.359 --> 0:20:03.720 everything you do with pant the mechanics sounds implausible. So 0:20:03.760 --> 0:20:06.199 many people say, Okay, we have to accept this, that 0:20:06.600 --> 0:20:09.199 in reality we live in immense waves, that the copies 0:20:09.240 --> 0:20:12.600 and copies of ourselves, and that's the many world interpetation. 0:20:12.720 --> 0:20:14.640 Can I ask you a question actually about that many 0:20:14.640 --> 0:20:17.000 world interpretation? There is something about that that's never set 0:20:17.080 --> 0:20:19.679 right with me. But maybe it's very naive and and 0:20:19.760 --> 0:20:21.920 that's this you say that there are many, many copies 0:20:22.040 --> 0:20:25.120 of me, And so it breaks the problem of why 0:20:25.200 --> 0:20:27.760 is this one detector clicked by saying it's not just 0:20:27.840 --> 0:20:29.800 that one detector clicked, all of them have clicked, just 0:20:29.880 --> 0:20:33.440 in other versions of the universe. But that doesn't make 0:20:33.560 --> 0:20:35.679 all the versions of the universe equal or on the 0:20:35.720 --> 0:20:38.840 same footing. Because I'm in this one, you know, this 0:20:38.960 --> 0:20:41.159 is the one that I feel is the truth that 0:20:41.280 --> 0:20:44.000 I'm making the measurement in. And that's different from the 0:20:44.000 --> 0:20:46.159 other ones because I'm not in those other ones. And 0:20:46.160 --> 0:20:48.439 maybe there are other means in the other ones. And 0:20:48.560 --> 0:20:51.320 let's say that they're you know who I actually am. 0:20:51.400 --> 0:20:53.199 But this is the one that I'm experiencing, and so 0:20:53.240 --> 0:20:56.160 it still feels to me like it has a special place. 0:20:56.400 --> 0:20:58.600 Is that a naive concern or is that something that 0:20:58.640 --> 0:21:01.760 you think many worlds can address. It is a concern 0:21:02.359 --> 0:21:05.680 because about many words plays exactly on the fact that 0:21:06.480 --> 0:21:09.639 there is a contingency in who you are, which is 0:21:09.720 --> 0:21:14.840 hard to making, not either informals or in words, and 0:21:15.240 --> 0:21:18.760 it is left a little bit vague into that. So 0:21:19.600 --> 0:21:23.080 it is a concern that some philosophers have raised about 0:21:24.200 --> 0:21:26.800 about many worlds. All right, Well, as long as philosophers 0:21:26.840 --> 0:21:31.760 agree with me, then i'm solid. Okay, Yeah, but you know, 0:21:31.960 --> 0:21:35.840 you can always find a philosopher that has a low 0:21:35.880 --> 0:21:39.560 bar apparently. All right, so that's the many worlds interpretation. 0:21:39.840 --> 0:21:41.720 Let's go to the cobanagen which is what you said 0:21:41.760 --> 0:21:44.760 at school, okay, The communities says, well, there are special 0:21:44.760 --> 0:21:50.440 things which observers, okay, which are classical, namely a big, 0:21:50.840 --> 0:21:54.960 big compared to to the quantum phenomena. It's when you 0:21:55.000 --> 0:21:58.359 don't see quantum phenomena because they're too subtle for you. 0:21:58.440 --> 0:22:00.800 They are not visible to you there because you're too 0:22:00.840 --> 0:22:03.760 heavy to see quant phenomena. To isolate things, you go 0:22:03.880 --> 0:22:06.600 to small things, so they are classical ob genia many 0:22:06.880 --> 0:22:09.120 all the ones around us, and there is a classical 0:22:09.160 --> 0:22:12.359 So forget quantum mechanics. About this. When a quantum system 0:22:12.440 --> 0:22:17.400 interacts with the classical world, bingo, that's a measurement. And 0:22:17.760 --> 0:22:22.199 this works in practice very well. That's what we do 0:22:22.240 --> 0:22:25.560 in the laboratory. But in theory it obviously does not 0:22:25.680 --> 0:22:28.960 work because what is a classical system? But we I 0:22:29.080 --> 0:22:32.440 am many electrons and protons, and each one of them 0:22:32.600 --> 0:22:35.240 it's a quantum particle, so each one has a wave, 0:22:35.400 --> 0:22:37.800 so I have a big wave. I am a quantum 0:22:37.840 --> 0:22:43.479