WEBVTT - Why is there quantum uncertainty? 0:00:00.080 --> 0:00:03.160 Hey, quick announcement everyone, we have just joined TikTok, So 0:00:03.240 --> 0:00:05.240 head over there and follow us to see videos of 0:00:05.320 --> 0:00:09.800 Daniel asking and answering science questions. All right, enjoy the pod. 0:00:18.320 --> 0:00:21.840 Hey Daniel, does quantum mechanics really explain reality? 0:00:22.200 --> 0:00:24.800 I mean I think so, even though it's pretty weird. 0:00:25.200 --> 0:00:28.760 Are you sure? Well? Lots of experiments we've done over 0:00:28.760 --> 0:00:29.400 the last century. 0:00:29.520 --> 0:00:32.080 See yes, Yeah, But like, how can you be certain? 0:00:32.159 --> 0:00:32.320 You know? 0:00:32.360 --> 0:00:34.640 I thought quantum mechanics is everything is uncertain. 0:00:35.960 --> 0:00:39.199 Well, we're very certain that quantum mechanics is uncertain, but 0:00:39.520 --> 0:00:40.920 only about certain things. 0:00:41.120 --> 0:00:42.720 I'm pretty certain that makes no sense. 0:00:43.840 --> 0:00:45.360 I think it's curtains for certainty. 0:00:45.440 --> 0:00:46.199 Are you sure about that? 0:00:47.960 --> 0:00:49.159 Now? I'm not sure about anything. 0:00:49.400 --> 0:00:51.280 I'm welcome to being a non physicist. 0:01:06.560 --> 0:01:06.720 Hi. 0:01:06.760 --> 0:01:09.479 I'm poor Hendrick Cartoonis and the author of Oliver's Great 0:01:09.520 --> 0:01:10.280 Big Universe. 0:01:10.560 --> 0:01:10.680 Hi. 0:01:10.800 --> 0:01:13.480 I'm Daniel. I'm a particle physicist and a professor at 0:01:13.560 --> 0:01:15.760 UC Irvine. Or at least I was certain of that 0:01:15.840 --> 0:01:16.400 a moment ago. 0:01:16.800 --> 0:01:19.000 Yeah, Now you're not sure that you have a job, 0:01:19.240 --> 0:01:23.320 so he might have said something to get you fired here. 0:01:23.400 --> 0:01:25.280 Yeah, that's one of those questions you shouldn't ask because 0:01:25.319 --> 0:01:26.280 it might change the answer. 0:01:27.000 --> 0:01:30.200 I thought ye had tenure that prevented them from firing you. 0:01:31.040 --> 0:01:33.440 There are still limits to what we can do even 0:01:33.480 --> 0:01:34.319 if we have tenure. 0:01:34.520 --> 0:01:37.240 But anyways, welcome to our podcast Daniel and Jorge Explain 0:01:37.319 --> 0:01:40.039 the Universe, a production of iHeartRadio. 0:01:39.600 --> 0:01:42.640 In which we test the limits of our understanding of 0:01:42.800 --> 0:01:46.000 the universe. How certain are we that the universe works 0:01:46.040 --> 0:01:48.560 in a different way on a tiny scale, that there 0:01:48.600 --> 0:01:52.440 are tiny quantum particles fluctuating in and out of existence, 0:01:52.600 --> 0:01:54.400 that when we zoom down to the universe at its 0:01:54.520 --> 0:01:58.400 smallest scale, different rules apply. On this podcast, we pushed 0:01:58.440 --> 0:02:00.560 all those limits and we try to answer all of 0:02:00.600 --> 0:02:01.280 your questions. 0:02:01.480 --> 0:02:03.920 That's right, because it is a wonderful and amazing but 0:02:04.120 --> 0:02:06.800 yet also a very mysterious universe that seems kind of 0:02:06.880 --> 0:02:09.640 random at times, but also seems like a giant clock 0:02:09.720 --> 0:02:12.760 that seems to be working precisely as it's supposed to be. 0:02:14.040 --> 0:02:16.519 And the big goal of physics is not just to 0:02:16.840 --> 0:02:20.600 reassure us that the universe works the way our intuition suggests, 0:02:21.000 --> 0:02:25.280 but to discover the truth. Science is a knowledge building mechanism, right, 0:02:25.360 --> 0:02:28.560 It's a way to figure out how the universe actually works, 0:02:28.639 --> 0:02:30.959 even if it's deeply in contradiction with the way we 0:02:31.120 --> 0:02:31.800 thought it worked. 0:02:31.919 --> 0:02:34.400 Wait, I thought philosophers thought that you can never uncover 0:02:34.520 --> 0:02:37.840 the real truth of things. It's impossible to be completely 0:02:37.919 --> 0:02:38.679 certain about the truth. 0:02:38.720 --> 0:02:41.000 Philosophers don't even agree about what you mean by the 0:02:41.160 --> 0:02:41.840 real truth. 0:02:42.000 --> 0:02:44.239 Well, I see, it's about I guess vocabulary. 0:02:44.400 --> 0:02:44.520 Man. 0:02:44.639 --> 0:02:47.760 Every philosophy argument in the end comes down to vocabulary. Like, 0:02:48.040 --> 0:02:50.400 what do you mean when you say vocabulary? Anyway? 0:02:50.760 --> 0:02:54.280 Oh, you can get a few inception levels deep into 0:02:54.360 --> 0:02:55.400 this discussion. 0:02:55.560 --> 0:02:57.640 What do you mean by what do you mean exactly? 0:02:58.120 --> 0:02:58.919 What do you mean? 0:02:59.040 --> 0:02:59.680 What is meaning? 0:03:00.160 --> 0:03:02.040 Yes? What is meaning? What is a question? 0:03:02.160 --> 0:03:03.480 Anyway? What is a what? 0:03:05.560 --> 0:03:07.720 And I'd laugh at all these jokes, not to laugh 0:03:07.800 --> 0:03:10.120 at philosophy, but out of deep respect for the way 0:03:10.120 --> 0:03:12.320 philosophy forces us to figure out what we mean by 0:03:12.400 --> 0:03:14.640 our questions? What is it? In the end, we're asking 0:03:14.720 --> 0:03:16.840 what kind of answers do we expect? All this kind 0:03:16.880 --> 0:03:18.520 of stuff? These are hard questions. 0:03:18.760 --> 0:03:20.919 Wait, does that mean that philosophers don't think you actually 0:03:21.040 --> 0:03:22.359 have a job as a physicist? 0:03:22.440 --> 0:03:25.440 I mean, philosophers definitely recognize the physics is building a 0:03:25.480 --> 0:03:27.760 set of facts, and those facts like power the world. 0:03:28.160 --> 0:03:31.040 There is a reason that technology works, for example, But 0:03:31.240 --> 0:03:33.480 exactly what it means about the universe, what is the 0:03:33.600 --> 0:03:36.440 real story? What is real depends a little bit on 0:03:36.480 --> 0:03:39.200 the questions we're asking, and it's not even clear that 0:03:39.280 --> 0:03:41.600 there is an objective truth about it. It might just 0:03:41.720 --> 0:03:44.040 be our perception of it answers to the kind of 0:03:44.120 --> 0:03:45.240 questions we would ask. 0:03:45.800 --> 0:03:48.800 Well, I guess the elusive quests for the real truth 0:03:48.880 --> 0:03:50.720 of the universe is kind of what signs. It's all about, 0:03:50.920 --> 0:03:52.560 you know, even if we don't get there, it's all 0:03:52.600 --> 0:03:53.920 about trying to get there. 0:03:54.000 --> 0:03:56.080 Exactly, and we can all work together to get there, 0:03:56.160 --> 0:03:58.200 even if we're not in agreement about what there is. 0:03:58.920 --> 0:04:01.720 Some of us think we are revealing the true underlying 0:04:01.880 --> 0:04:05.880 mechanism of reality, something that like alien scientists would also 0:04:05.960 --> 0:04:08.800 be revealing. Other folks don't care about that. They say, hey, look, 0:04:08.840 --> 0:04:11.280 we're just getting something that works, something that predicts the 0:04:11.360 --> 0:04:14.440 outcomes of experiments and lets us build technology. Who even 0:04:14.520 --> 0:04:16.880 cares if it's real or what aliens would think about it. 0:04:16.960 --> 0:04:19.640 You can totally disagree with the lofty philosophical goals of 0:04:19.720 --> 0:04:22.839 science and still work hand in hand and get concrete results. 0:04:23.200 --> 0:04:25.360 I feel like maybe that'sis's favorite part of the job. 0:04:25.480 --> 0:04:28.680 It's arguing about the job, you know. 0:04:28.800 --> 0:04:30.880 I think that there's a division early on, and people 0:04:30.880 --> 0:04:32.839 who like to argue about it more end up in philosophy, 0:04:33.040 --> 0:04:34.360 and the people who just want to like get in 0:04:34.400 --> 0:04:36.800 the lab and learn stuff about the world end up 0:04:36.839 --> 0:04:37.359 in physics. 0:04:37.960 --> 0:04:39.400 You just want to get in there and blow stuff. 0:04:40.200 --> 0:04:43.200 But there's always this tension, right. The juiciest questions in 0:04:43.279 --> 0:04:45.479 physics are the ones that when we get the answer, 0:04:45.560 --> 0:04:47.840 we go, hmmm, well, but why is it like that? 0:04:48.040 --> 0:04:51.080 What does that mean about the world. The best physics 0:04:51.200 --> 0:04:53.600 questions have philosophical implications. 0:04:54.120 --> 0:04:56.440 Yeah, and so there's a lot of uncertainty about what 0:04:56.560 --> 0:04:58.400 we do know or what we don't know, or what 0:04:58.520 --> 0:05:01.000 we can know about the universe. But even deeper than that, 0:05:01.160 --> 0:05:04.920 there seems to be a uncertainty about the universe itself. 0:05:05.320 --> 0:05:08.960 Something shocking, something very difficult to understand about the quantum 0:05:09.040 --> 0:05:11.480 picture of the world is that the world itself might 0:05:11.520 --> 0:05:14.480 be limited in its precision, not just in our ability 0:05:14.600 --> 0:05:17.440 to measure it or to extract that knowledge, but there 0:05:17.440 --> 0:05:21.080 could be a fundamental fuzziness to the universe, a lack 0:05:21.200 --> 0:05:23.479 of determination about reality. 0:05:23.800 --> 0:05:26.560 It's not just me getting older and needing reading glasses. 0:05:26.400 --> 0:05:29.120 It's that also. Yes, those two effects are combining. 0:05:30.000 --> 0:05:31.200 I mean, have quantum vision. 0:05:31.279 --> 0:05:31.400 Now. 0:05:33.040 --> 0:05:35.960 I think we should start that company. Quantum laser surgery. Yeah, 0:05:36.080 --> 0:05:38.800 quantum reading glasses. Yeah, I'm parably the only coast of dollars, 0:05:38.880 --> 0:05:40.239 so we make a killer profit. 0:05:40.400 --> 0:05:41.960 You can only read one word at a time. 0:05:42.240 --> 0:05:45.560 But anyways, Yeah, there seems to be this interesting nugget 0:05:45.839 --> 0:05:50.360 of strangeness to quantum mechanics which tries to explain the 0:05:50.520 --> 0:05:52.680 entire universe. And so today on the podcast, we'll be 0:05:52.760 --> 0:06:02.160 asking the question why is there quantum uncertainty? I feel 0:06:02.160 --> 0:06:05.200 like we're asking a question about uncertainty. 0:06:06.440 --> 0:06:08.680 We are uncertain about why there's uncertainty. 0:06:09.440 --> 0:06:10.120 That's what I mean. 0:06:10.800 --> 0:06:12.000 It's meta uncertainty. 0:06:12.279 --> 0:06:14.440 We get very meta here. Well, if it helps, I'm 0:06:14.440 --> 0:06:16.560 pretty sure. I'm a cartoonist, that's one thing I know. 0:06:16.800 --> 0:06:19.360 Yeah, Well, this is exactly the kind of difficult philosophical 0:06:19.480 --> 0:06:21.640 question because you know, I even sure like what kind 0:06:21.680 --> 0:06:24.800 of answer we're looking for, Like, are we hoping to 0:06:25.000 --> 0:06:28.200 reveal that the universe could have only ever been this way? 0:06:28.600 --> 0:06:30.480 Or to argue that look, we could be in lots 0:06:30.520 --> 0:06:33.600 of different universes. This one happens to have this quantum uncertainty. 0:06:34.440 --> 0:06:36.200 You know, there's lots of different ways to attack this 0:06:36.279 --> 0:06:37.720 sort of philosophical problem. 0:06:38.960 --> 0:06:42.520 Well, hopefully it's more than just a philosophical problem, right, Eventually, 0:06:42.720 --> 0:06:45.919 the hope, the goal is to find kind of physics, 0:06:46.000 --> 0:06:48.880 math based answers to these questions, isn't it to me? 0:06:49.000 --> 0:06:51.160 I think the sort of highest level process would be 0:06:51.440 --> 0:06:53.240 go out and look at the universe, see what it's like, 0:06:53.400 --> 0:06:56.679 boiling that down to like a few essential facts, build 0:06:56.760 --> 0:07:00.239 a theory that describes how that works, why that works, 0:07:00.279 --> 0:07:02.840 the mathematics to describe it, and then look at that 0:07:02.960 --> 0:07:05.760 theory and ask philosophical questions like did it have to 0:07:05.839 --> 0:07:08.400 be this way? Could you have a universe that was different? 0:07:08.520 --> 0:07:10.800 Could we have built a different theory of the universe 0:07:10.840 --> 0:07:13.560 that didn't have this feature or that feature about it? 0:07:14.160 --> 0:07:16.559 So in the end, it's mathematical, but it's really rooted 0:07:16.600 --> 0:07:19.160 in explaining what we see out there in the universe. 0:07:19.760 --> 0:07:22.360 But couldn't you answer those questions you just asked in 0:07:22.440 --> 0:07:25.240 a mathematical way. Maybe in the future. We don't know 0:07:25.320 --> 0:07:26.880 for certain they can't be answered, right. 0:07:26.920 --> 0:07:28.720 We don't know for certain they can't be answered. I 0:07:28.760 --> 0:07:31.440 think a great analog that's going to help us understand 0:07:31.520 --> 0:07:33.800 this question today is the question of like the speed 0:07:33.840 --> 0:07:36.240 of light. You know, we live in a universe where 0:07:36.360 --> 0:07:38.920 the speed of light is constant for all observers, and 0:07:39.000 --> 0:07:41.360 if you start from that, you can build special relativity 0:07:41.400 --> 0:07:43.560 and you can explain the whole universe. But you have 0:07:43.680 --> 0:07:45.840 to start from that assumption. That's something we've seen in 0:07:45.960 --> 0:07:48.320 the universe, something we know is true, we've measured it, 0:07:48.360 --> 0:07:51.119 we've done the experiments, we've now coded it into our theory, 0:07:51.440 --> 0:07:54.119 but we don't have an answer for why that is true. 0:07:54.400 --> 0:07:57.520 And one day maybe people will have a deeper understanding 0:07:57.560 --> 0:07:59.880 of the nature of space from which that bubbles up. 0:08:00.080 --> 0:08:03.000 You might be able to explain that someday, but currently 0:08:03.080 --> 0:08:05.160 we don't have an answer to why. It's just sort 0:08:05.160 --> 0:08:07.560 of like the foundational assumption that we need to explain 0:08:07.640 --> 0:08:09.040 everything we see in the universe. 0:08:09.360 --> 0:08:09.480 Right. 0:08:09.560 --> 0:08:12.760 Well, as you said, hopefully maybe someday somebody will answer 0:08:12.880 --> 0:08:15.720 this deep question, but that person doesn't seem to be 0:08:15.720 --> 0:08:17.600 out there, because Daniel went out there and asked this 0:08:17.720 --> 0:08:20.800 question of folks and we got some pretty interesting answers back. 0:08:21.000 --> 0:08:24.080 Yeah. Thanks, everybody who answers these questions as wacky and 0:08:24.160 --> 0:08:27.160 as crazy as they are, without having any chance to 0:08:27.320 --> 0:08:30.400 prepare yourself. Really appreciate your participation, and I'd love to 0:08:30.480 --> 0:08:33.000 hear your voice on the podcast. That's right, I'm talking 0:08:33.080 --> 0:08:35.240 to you. We haven't heard from you yet, and we 0:08:35.360 --> 0:08:37.000 want your voice on the air. 0:08:37.280 --> 0:08:39.439 Well, there's a bunch of people who have heard we 0:08:39.559 --> 0:08:42.560 have heard from BOM. Right, you just totally snubbed them, 0:08:42.640 --> 0:08:43.240 I feel. 0:08:43.240 --> 0:08:44.520 I said, thanks to all those folks. 0:08:44.559 --> 0:08:48.040 Also, Oh, you meant the other people. 0:08:48.160 --> 0:08:50.280 It's a shockingly small group of people who volunteer for 0:08:50.320 --> 0:08:52.439 these which is why you hear the same voices over 0:08:52.480 --> 0:08:53.120 and over again. 0:08:53.400 --> 0:08:55.800 Oh, I never noticed. You didn't have to tell me. 0:08:56.880 --> 0:08:58.679 I should have maintained your quantumuncertainty. 0:08:58.960 --> 0:09:01.680 She'd kept that a mystery of the universe. But anyways, 0:09:01.679 --> 0:09:03.559 think about it for a second. Why do you think 0:09:03.800 --> 0:09:07.480 there is quantum uncertainty in the universe. Here's what people 0:09:07.520 --> 0:09:07.920 had to say. 0:09:08.160 --> 0:09:11.920 I guess that both because we can't really have an 0:09:12.000 --> 0:09:17.600 accurate measurement on that very timey scale, and because measuring 0:09:17.760 --> 0:09:20.680 a quantum process interferes on that process. 0:09:21.080 --> 0:09:25.120 There's quantum uncertainty because when we measure a particle, it 0:09:25.280 --> 0:09:27.320 changes what the particle's doing, and when we're not looking 0:09:27.320 --> 0:09:29.360 at the particle, we never quite know what it's doing 0:09:29.400 --> 0:09:31.720 without measuring it, which changes the state and the particle. 0:09:32.080 --> 0:09:34.360 So we can never quite know exactly what a particle's 0:09:34.400 --> 0:09:35.560 doing without changing the state. 0:09:35.920 --> 0:09:41.040 I know that if you measure something, it falls into 0:09:41.400 --> 0:09:45.120 the wave function collapses, and you fall into one of 0:09:45.200 --> 0:09:49.920 the states. I guess is uncertainty, because there's a wave function. 0:09:50.000 --> 0:09:52.480 All right, and pretty deep answers here, I'm pretty certain 0:09:52.480 --> 0:09:52.640 of that. 0:09:52.760 --> 0:09:54.439 Yeah, a lot of these folks are developing like a 0:09:54.559 --> 0:09:58.560 microphysical picture, like what's happening when you make a measurement? 0:09:59.120 --> 0:10:01.280 What prevents you for being able to measure things super 0:10:01.320 --> 0:10:04.080 duper precisely? And that's helpful, but I think it's only 0:10:04.160 --> 0:10:05.480 really part of the story. 0:10:05.600 --> 0:10:07.760 All right, Well, let's dig into this topic, and let's 0:10:07.760 --> 0:10:11.199 start with the basic question, Daniel, what is quantum uncertainty? 0:10:11.440 --> 0:10:14.160 There's so many weird things about quantum mechanics that we 0:10:14.200 --> 0:10:16.120 could dig into for hours and hours, but I just 0:10:16.160 --> 0:10:18.839 want to zoom in on this one thing, this quantum uncertainty, 0:10:19.200 --> 0:10:22.440 which is different from other weird aspects of quantum mechanics, 0:10:22.520 --> 0:10:25.160 and quantum uncertainty is a very specific thing. But let's 0:10:25.160 --> 0:10:28.160 start off by talking about classical physics, because quantum uncertainty 0:10:28.200 --> 0:10:30.760 is basically a rejection of that. So classical physics, the 0:10:30.840 --> 0:10:34.240 physics of Newton, and even the physics of Einstein, says 0:10:34.320 --> 0:10:36.679 that we live in a universe where you can know 0:10:36.960 --> 0:10:39.839 everything about an object, like take a particle or a 0:10:39.920 --> 0:10:43.240 banana or whatever. You can know everything about its location, 0:10:43.520 --> 0:10:45.319 you can know everything about its velocity, you can know 0:10:45.360 --> 0:10:48.720 its entire history that it moves in these smooth paths. 0:10:48.840 --> 0:10:51.439 It always has a position, always has a velocity that 0:10:51.600 --> 0:10:54.560 to reality, there is no fuzziness that there's an exactness 0:10:54.600 --> 0:10:56.760 to this information, and you can know all of it 0:10:56.920 --> 0:11:01.000 simultaneously because it's well defined. That's the classic physics picture 0:11:01.440 --> 0:11:03.800 of like how things move in the universe. Right. 0:11:03.840 --> 0:11:05.360 That's sort of like maybe a good way to explain 0:11:05.400 --> 0:11:08.160 it is basically like up to high school physics, right, 0:11:08.600 --> 0:11:11.439 like you know, predicting where the baseball that you throw 0:11:11.520 --> 0:11:14.079 is going to land, or you know how things move 0:11:14.240 --> 0:11:17.120 you shake him orver you swing them. That's classical physics, right, 0:11:17.160 --> 0:11:19.800 Like you can predict where the things are, what things 0:11:19.840 --> 0:11:22.640 are going to do. Like you in those exams in 0:11:22.720 --> 0:11:25.400 high school, there's no room for uncertainty, Like there's a 0:11:25.480 --> 0:11:27.000 right answer, there's a wrong answer. 0:11:26.960 --> 0:11:29.520 That's right, and there's an exactness to the answer, and 0:11:29.640 --> 0:11:32.280 even well past high school physics, I guess, depending on 0:11:32.360 --> 0:11:35.920 your high school you know, Einstein's physics is also classical 0:11:36.000 --> 0:11:38.040 in that sense. I mean, Einstein was a huge revolution 0:11:38.200 --> 0:11:41.319 compared to Newtonian physics. Relativity is a whole other brain twister. 0:11:41.880 --> 0:11:44.560 But Einstein's picture of the universe fundamentally is the same 0:11:45.040 --> 0:11:47.640 in that there's no uncertainty. He imagined you could know 0:11:47.720 --> 0:11:50.160 where a particle is that had an exact position, and 0:11:50.240 --> 0:11:52.760 you could simultaneously know its position and its momentum and 0:11:52.760 --> 0:11:54.280 all sorts of other things about. 0:11:54.040 --> 0:11:54.920 It, even like light. 0:11:55.240 --> 0:11:58.240 Yeah, the classical theory of electrodynamics, you know, which comes 0:11:58.280 --> 0:12:02.199 from Maxwell and inspired Stein to develop relativity, didn't have 0:12:02.400 --> 0:12:05.440 any sort of quantum uncertainty to it. Photons had an 0:12:05.480 --> 0:12:07.480 exact position, all. 0:12:07.440 --> 0:12:10.840 Right, So then that's Einstein and newtune. But then around 0:12:11.000 --> 0:12:13.760 the beginning of the nineteen hundreds they figured out that 0:12:13.840 --> 0:12:15.800 things are kind of strange and weird. 0:12:15.880 --> 0:12:18.640 Yeah, basically, quantum mechanics looks at that and says, yeah, no, 0:12:19.679 --> 0:12:22.719 you can't know all of these things simultaneously. And the 0:12:22.800 --> 0:12:24.839 history of it's really fascinating. It comes around in the 0:12:24.920 --> 0:12:28.160 nineteen twenties when people were trying to understand how the 0:12:28.200 --> 0:12:30.240 atom worked and what was the picture of microscopically of 0:12:30.280 --> 0:12:32.199 the electron and the nucleus. Was this sort of like 0:12:32.200 --> 0:12:34.840 an orbital picture like bor was suggesting, or was there 0:12:34.920 --> 0:12:37.439 something funnier and more complicated going on? And it was 0:12:37.480 --> 0:12:41.800 really Heisenberg of the famous Heisenberg uncertainty principle, who developed 0:12:41.840 --> 0:12:44.520 the sort of first theory of quantum mechanics that describe 0:12:44.559 --> 0:12:46.720 how the atom worked in a way different from boor 0:12:47.080 --> 0:12:49.800 that had like a fundamental different mathematics underneath it. 0:12:50.600 --> 0:12:52.800 I feel like, or I seem to recall that initially 0:12:52.880 --> 0:12:55.840 quantum mechanics didn't have this idea of uncertainty to it, right, 0:12:55.920 --> 0:12:59.360 Like didn't it start with people just noticing that like 0:12:59.559 --> 0:13:02.360 light case and packets, or that electrons wouldn't you know, 0:13:02.600 --> 0:13:05.839 fly off unless you met certain minimum energy requirements and 0:13:05.920 --> 0:13:08.079 things like that. There's no uncertain to your fuzziness to 0:13:08.160 --> 0:13:08.960 it at the beginning. 0:13:09.120 --> 0:13:11.360 Was there the roots of quantum mechanics are exactly as 0:13:11.360 --> 0:13:14.040 you described. You know, there's like the black body radiation problem, 0:13:14.440 --> 0:13:16.520 and there's the photoelectric effect that we dug into on 0:13:16.600 --> 0:13:18.920 the podcast several times, and you're right, it was actually 0:13:18.960 --> 0:13:20.640 Einstein who figured that out. 0:13:20.760 --> 0:13:20.840 Right. 0:13:20.920 --> 0:13:23.880 You connected the ideas of Plank with the experiments that 0:13:23.960 --> 0:13:25.679 we were seeing and saw that light had to come 0:13:25.720 --> 0:13:28.960 and packet, so it can only interact with a single electron. Absolutely. 0:13:29.040 --> 0:13:31.480 So those really those core ideas which then led to 0:13:31.559 --> 0:13:34.920 the formulation of quantum mechanics. Those didn't have uncertainty in them. 0:13:35.000 --> 0:13:36.520 That wasn't an essential ingredient. 0:13:36.760 --> 0:13:39.600 Right, That's where the word quantum comes from, right, like quanta, 0:13:39.760 --> 0:13:43.040 like little quantity, little countable things. 0:13:43.120 --> 0:13:45.040 Right, you can have one electron or two electrons or 0:13:45.080 --> 0:13:48.280 nine electrons, but you can't have one point seven photons, 0:13:48.320 --> 0:13:50.400 for example. But then as people were trying to apply 0:13:50.559 --> 0:13:53.960 these theories and these ideas to describing the atom, they 0:13:54.040 --> 0:13:56.959 need to develop mathematics that work, mathematics that explained what 0:13:57.080 --> 0:14:01.360 we saw. And Heisenberg developed this theory of quantum mechanics 0:14:01.679 --> 0:14:04.199 that he used to make calculations and to understand like 0:14:04.440 --> 0:14:06.760 why did the electron have this energy level? Around the 0:14:06.800 --> 0:14:08.840 atom and not that energy level. Why did we get 0:14:08.880 --> 0:14:11.680 this atomic spectrum from the atom? He developed this whole 0:14:11.720 --> 0:14:14.400 theory of quantum mechanics, and you can see inherent in 0:14:14.520 --> 0:14:18.520 the mathematics of his theory comes out this basic idea 0:14:18.559 --> 0:14:21.480 of the quantum uncertainty sort of falls out of the mathematics. 0:14:21.760 --> 0:14:24.160 He needed to describe the world as he saw it. 0:14:24.400 --> 0:14:26.120 Can you describe that a little bit more? 0:14:26.240 --> 0:14:26.280 Like? 0:14:26.400 --> 0:14:29.560 Why did it need to include that uncertainty into these 0:14:29.640 --> 0:14:33.000 formulations in order to explain things like the little packets 0:14:33.040 --> 0:14:33.320 of light? 0:14:33.520 --> 0:14:36.560 Well, Heisenberg developed his theory of quant mechanics, and it 0:14:36.680 --> 0:14:39.320 was based on a certain kind of mathematical object called 0:14:39.400 --> 0:14:41.640 matrix's that we don't have to dig into. But what 0:14:41.760 --> 0:14:43.560 he noticed about the structure of his theory was that 0:14:43.640 --> 0:14:46.840 it seemed to matter the order in which you make measurements. 0:14:47.360 --> 0:14:49.760 Like if you measure one thing, it changes the state 0:14:49.800 --> 0:14:51.600 of the system, and then if you measure something else 0:14:51.880 --> 0:14:54.840 you'll get a different answer. And so quantu uncertainty is 0:14:54.880 --> 0:14:57.480 all about this. It's about recognizing that the order of 0:14:57.560 --> 0:15:01.120 the measurements you makes matter for some pairs of quantities, 0:15:01.240 --> 0:15:03.640 measuring one thing can change something else. 0:15:03.920 --> 0:15:06.720 I feel like maybe that's at the root of quantum uncertainty, 0:15:06.760 --> 0:15:09.840 which is like, it's really only uncertainly with regards to 0:15:10.000 --> 0:15:12.840 two things at the same time, right, Like, it's not 0:15:13.000 --> 0:15:15.760 like something has an inherent fuzziness, but its location you 0:15:15.800 --> 0:15:18.480 can know its location sort of very precisely, but then 0:15:18.520 --> 0:15:21.240 you lose out in some other quantities, right Exactly. 0:15:21.320 --> 0:15:26.600 It's about simultaneous knowledge of specific pairs of quantities, right, 0:15:26.680 --> 0:15:28.920 And it's really very specific. It's not like general and 0:15:29.000 --> 0:15:31.400 broad and say you can't ever know the position very well, 0:15:31.520 --> 0:15:33.680 or you can't ever know the momentum very well. You 0:15:33.760 --> 0:15:36.320 can know the position as well as you like, but 0:15:36.440 --> 0:15:39.680 it comes at a cost for one specific other quantity, 0:15:39.840 --> 0:15:41.760 the momentum. And there are other things that are paired 0:15:41.880 --> 0:15:44.200 in this way. If you dig deeper into this in physics, 0:15:44.360 --> 0:15:47.400 you discover that these things are called conjugate variables. And 0:15:47.520 --> 0:15:50.320 this came out of the mathematics that Heisenberg was using 0:15:50.440 --> 0:15:53.000 to describe his theory of quantum mechanics. 0:15:53.600 --> 0:15:55.760 Well, I'm pretty certain that we're going to get into 0:15:55.800 --> 0:15:59.520 this uncertainty and this idea of conjugate pairs, and how 0:15:59.560 --> 0:16:02.240 that figures into the uncertainty that we see in quantum 0:16:02.240 --> 0:16:05.120 mechanics that tries to explain the universe, and so let's 0:16:05.200 --> 0:16:08.720 dig into those details. But first let's take a quick break. 0:16:21.400 --> 0:16:26.200 All right, we are uncertainly talking about uncertainty today, specifically 0:16:26.360 --> 0:16:29.600 quantum uncertainty, or at least we're trying to understand here 0:16:29.640 --> 0:16:31.880 where it comes from and how it manifests itself in 0:16:32.000 --> 0:16:36.280 our everyday lives. And so we talked about how quantum 0:16:36.320 --> 0:16:39.120 mechanics kind of change things, and there's a certain uncertainty 0:16:39.200 --> 0:16:42.400 about it that has to do with two things being 0:16:42.480 --> 0:16:44.440 measured at the same time. That's kind of a key 0:16:44.600 --> 0:16:46.880 to the concept of quantum uncertainty, right, first of all 0:16:46.920 --> 0:16:49.720 measurements and second of all two things at the same 0:16:49.800 --> 0:16:50.560 time exactly. 0:16:50.960 --> 0:16:53.160 And there's lots of fuzziness about quantum mechanics, but this 0:16:53.320 --> 0:16:55.320 is what we're talking about right now, is this uncertainly 0:16:55.360 --> 0:16:59.040 about simultaneous knowledge. There's a whole other issue in quantum 0:16:59.040 --> 0:17:02.920 mechanics about indeterminism, you know, laws of quantum mechanics determining 0:17:03.000 --> 0:17:06.920 probabilities rather than outcomes. That's a whole separate issue, super fascinating, 0:17:07.240 --> 0:17:11.040 but different from quantum uncertainty. Right, So quantum indeterminism is 0:17:11.119 --> 0:17:13.800 different from quantum uncertainty, which tells us about like how 0:17:13.880 --> 0:17:17.840 much we can know simultaneously about a particle or an object. 0:17:18.240 --> 0:17:21.560 Wait, what that's different. There's two kinds of uncertainties. 0:17:21.800 --> 0:17:24.359 Well, one of them is uncertainty. The other one is indeterminism. 0:17:24.520 --> 0:17:27.320 Well, that's what you call it, but it's basically another 0:17:27.359 --> 0:17:29.480 word for uncertainty, Isn't it Like you're not certain of 0:17:29.680 --> 0:17:32.240 what the outcome is going to be. So today we're 0:17:32.280 --> 0:17:34.719 not talking about like if I throw an electron at 0:17:34.760 --> 0:17:36.359 a magnetic field, I don't know if it's going to 0:17:36.440 --> 0:17:38.520 be your rider left. That's a different kind of uncertainty. 0:17:38.560 --> 0:17:39.000 What are you saying? 0:17:39.160 --> 0:17:42.479 So in quantum mechanics, we talk about randomness to describe 0:17:42.600 --> 0:17:45.920 predictions that are probabilistic. If you put a particle in 0:17:46.000 --> 0:17:48.120 a box and you ask where is it, you don't 0:17:48.160 --> 0:17:51.360 get a specific prediction the way you do for classical mechanics. 0:17:51.400 --> 0:17:54.000 You get predictions for where it's likely to be. You 0:17:54.080 --> 0:17:56.920 get predictions for the probability distribution, so that if you 0:17:57.000 --> 0:17:59.520 do it like a thousand times and measure its location, 0:18:00.040 --> 0:18:02.920 you then get a distribution of measurements that follow the 0:18:03.040 --> 0:18:06.800 predicted probability distribution. That's inherent in most of the quantum 0:18:06.800 --> 0:18:08.960 mechanics we're used to thinking about due to the story 0:18:09.040 --> 0:18:12.240 it tells us about how the universe works. It's not 0:18:12.320 --> 0:18:15.440 a particle that's following equations of motion that are fundamental. 0:18:15.640 --> 0:18:18.040 It's the wave function or the quantum field, which is 0:18:18.119 --> 0:18:21.439 inherently probabilistic about the measurements you'll make of it. Now, 0:18:21.520 --> 0:18:25.600 quantum uncertainty is related but actually quite distinct. You can 0:18:25.720 --> 0:18:28.720 think of it as another source of randomness, but it 0:18:28.840 --> 0:18:32.719