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If I was Dark Matter, I would 0:02:08.200 --> 0:02:11.120 totally parade myself in front of all the scientists in 0:02:11.160 --> 0:02:11.800 the galaxy. 0:02:12.160 --> 0:02:14.160 Ooh, a parade You mean like a pageant queen? 0:02:16.360 --> 0:02:18.919 Yeah, something like that. You know, just don't be so shy. 0:02:20.120 --> 0:02:21.919 Well, if it turns out you are dark matter, we'll 0:02:22.000 --> 0:02:25.000 definitely throw you a parade. But so far, it seems 0:02:25.000 --> 0:02:27.480 like dark matter is kind of reclusive, right, it's kind 0:02:27.480 --> 0:02:30.560 of shy, so maybe it is hiding. What would be 0:02:30.600 --> 0:02:31.840 some good spots for it to hide it? 0:02:32.080 --> 0:02:34.960 Well, if dark matter doesn't want a tiara and it's 0:02:35.040 --> 0:02:37.639 hiding somewhere, then I don't know where it would hide. 0:02:37.680 --> 0:02:39.440 I mean, if I knew, I would go and look 0:02:39.480 --> 0:02:39.959 for it there. 0:02:40.160 --> 0:02:42.919 What if it's somewhere kind of obvious. 0:02:42.720 --> 0:02:44.120 Like what like right behind me? 0:02:44.440 --> 0:02:47.640 Yeah, or right in front of you or right on 0:02:47.680 --> 0:02:50.240 TV and the Matter universe contest. 0:02:50.080 --> 0:02:52.280 That would be a great twist ending for the m 0:02:52.360 --> 0:02:54.680 Knight Shamanlan version of this story. 0:02:54.840 --> 0:02:58.280 Well, man, do you think he knows I see dark matter? 0:03:13.680 --> 0:03:13.840 Hi? 0:03:13.840 --> 0:03:17.120 I'm Jorge Mack, cartoonist and author of Allor's Great Big Universe. 0:03:17.200 --> 0:03:20.000 Hi, I'm Daniel. I'm a particle physicist, and I wish 0:03:20.040 --> 0:03:21.760 I had a dark matter tiara. 0:03:22.080 --> 0:03:24.560 Oh, but it wouldn't be very shiny or bright. It 0:03:24.600 --> 0:03:27.239 would be dark, So what's the point. Also, when it 0:03:27.360 --> 0:03:28.520 it just fall through your head. 0:03:30.440 --> 0:03:32.520 It would be hard to wear, but it'd be like 0:03:32.560 --> 0:03:35.040 the greatest, most amazing piece of jewelry. 0:03:35.160 --> 0:03:39.160 Ever, how would you even keep it in your house? 0:03:39.720 --> 0:03:41.640 These are just like engineering details. 0:03:41.640 --> 0:03:41.840 You know. 0:03:41.960 --> 0:03:44.200 Once I've solved the physics of a dark matter Tiara, 0:03:44.640 --> 0:03:46.320 I'll just pass that off to the engineers. 0:03:46.520 --> 0:03:48.200 This is just all part of your dream to be 0:03:48.280 --> 0:03:50.560 the universe's darktor universe. 0:03:53.240 --> 0:03:55.080 I would like a little bit of bling. Yeah, you know, 0:03:55.160 --> 0:03:57.200 physics bling would be nice. I'm not gonna win a 0:03:57.200 --> 0:04:00.520 Nobel Prize anytime soon, So dark matter Tirres sounds good. 0:04:00.640 --> 0:04:01.040 I see. 0:04:01.080 --> 0:04:02.600 I see. You could just say you have a dark 0:04:02.640 --> 0:04:05.440 matter Tierra, and they know nobody would be able to 0:04:05.440 --> 0:04:08.080 see it, or feel it or detect it. They would 0:04:08.120 --> 0:04:08.800 just have to believe you. 0:04:09.080 --> 0:04:11.440 I need evidence, man, That's what science is all about. 0:04:11.760 --> 0:04:12.680 You got to have data. 0:04:14.160 --> 0:04:16.840 I don't think those beauty contests depend on data very much. 0:04:16.640 --> 0:04:18.400 But I'm trying to win a science contest. 0:04:18.480 --> 0:04:21.960 But anyway's welcome. Podcast Daniel and Jorge Explain the Universe, 0:04:22.080 --> 0:04:25.320 a production of iHeartRadio in which we enter you in. 0:04:25.360 --> 0:04:29.320 The greatest science contest of all time, the quest to 0:04:29.520 --> 0:04:33.039 understand the nature of the universe. What is it, what's 0:04:33.200 --> 0:04:35.400 in it? What's it made out? Of how does it 0:04:35.440 --> 0:04:38.560 all work. We think these questions are deep and fundamental 0:04:38.600 --> 0:04:41.719 parts of being a human being in this cosmos, and 0:04:41.920 --> 0:04:45.480 unraveling these questions is a joy that everybody should share. 0:04:45.960 --> 0:04:48.479 So on this podcast we take those questions apart and 0:04:48.520 --> 0:04:51.480 try to share our answers and our ignorance with you. 0:04:51.880 --> 0:04:54.760 That's right, because science is the greatest beauty contest in 0:04:54.800 --> 0:04:57.080 the universe. We're the goal is to discover the beauty 0:04:57.080 --> 0:04:59.680 of how this universe is put together, how it works, 0:04:59.760 --> 0:05:01.320 and what is our place in it. 0:05:01.400 --> 0:05:03.640 Over the last fifty one hundred years, we've developed a 0:05:03.680 --> 0:05:06.599 pretty good sense for what's in the universe. We know 0:05:06.680 --> 0:05:10.400 about stars and galaxies and all the bright and shiny 0:05:10.440 --> 0:05:13.000 stuff that's out there in the universe. And we've also 0:05:13.080 --> 0:05:15.000 figured out that there's a lot of the universe that 0:05:15.080 --> 0:05:18.160 we can't see directly using our senses or any of 0:05:18.200 --> 0:05:22.599 the forces that we've discovered except for gravity. We know 0:05:22.680 --> 0:05:24.960 that a huge chunk of the stuff that's out there 0:05:25.000 --> 0:05:29.200 in the universe is invisible. It's intangible, which makes it 0:05:29.400 --> 0:05:31.960 very hard to discover and to figure out how to 0:05:32.000 --> 0:05:33.039 make it into a tiara. 0:05:33.160 --> 0:05:35.440 Yeah, because it turns out that a pretty good understanding 0:05:35.520 --> 0:05:39.200 of the universe only covers about uh five percent of 0:05:39.240 --> 0:05:41.040 what we know is out there. The rest, the ninety 0:05:41.040 --> 0:05:43.400 five percent of the universe that we know is there, 0:05:43.520 --> 0:05:47.919 we have no idea what it is or how it works. 0:05:48.040 --> 0:05:49.799 That sounds like a good title for a book. 0:05:49.920 --> 0:05:53.080 Yeah, I think we wrote one, Daniel, which is available 0:05:53.160 --> 0:05:54.400 for us sale everywhere. 0:05:54.640 --> 0:05:56.960 That's right. The kind of stuff that you and I 0:05:57.200 --> 0:06:01.080 are made out of, atoms specifically, or what physicists called baryons, 0:06:01.760 --> 0:06:05.040 only makes up five percent of the energy budget in 0:06:05.120 --> 0:06:09.440 the universe. There's another twenty five twenty seven percent that's 0:06:09.560 --> 0:06:12.480 dark matter, some kind of stuff that we know is matter. 0:06:12.680 --> 0:06:14.640 We know it's out there, but we don't know what 0:06:14.760 --> 0:06:17.159 it is, and we only have a very rough sense 0:06:17.200 --> 0:06:20.360 of even where it is around us. The rest of 0:06:20.360 --> 0:06:22.640 the universe is something we call dark energy, which is 0:06:22.640 --> 0:06:25.560 contributing to the accelerating expansion of the universe, and we 0:06:25.600 --> 0:06:28.760 have even less clue about what makes that up. 0:06:29.040 --> 0:06:31.440 Yeah, there's a lot we don't know, and it seems 0:06:31.520 --> 0:06:35.120 like these are maybe the defining mysteries of our times 0:06:35.600 --> 0:06:37.839 is to figure out what the universe is actually made 0:06:37.839 --> 0:06:41.160 out of. Given that what we're made out of counts 0:06:41.200 --> 0:06:42.240 is so little of it. 0:06:42.360 --> 0:06:44.440 Yeah, you're right, And in the last few decades there's 0:06:44.480 --> 0:06:47.599 been a huge program of people looking for dark matter. 0:06:47.920 --> 0:06:50.800 We've talked on the podcast about trying to make dark 0:06:50.839 --> 0:06:54.279 matter in the laboratory by smashing particles together. We're searching 0:06:54.320 --> 0:06:56.919 for the dark matter wind. We might be floating through 0:06:57.160 --> 0:07:01.599 with very sensitive underground facilities looking for an individual piece 0:07:01.640 --> 0:07:05.000 of dark matter to bump into liquid xenon, for example, 0:07:05.560 --> 0:07:08.240 or maybe evidence of dark matter annihilating itself in the 0:07:08.279 --> 0:07:10.600 center of the galaxy. But so far, none of these 0:07:10.640 --> 0:07:13.480 experiments have found dark matter, which means we've got to 0:07:13.520 --> 0:07:17.240 get creative about other ways to maybe detect this most 0:07:17.320 --> 0:07:20.440 important or at least most common kind of matter in 0:07:20.480 --> 0:07:21.120 the universe. 0:07:21.280 --> 0:07:23.080 So to be On the podcast, we'll be tackling the 0:07:23.160 --> 0:07:33.600 question could quantum clocks detect dark matter? And how many 0:07:34.080 --> 0:07:36.880 jargon words can we fit into one podcast title? 0:07:38.520 --> 0:07:41.400 I know it does sound like buzzword sound, you know, 0:07:41.960 --> 0:07:45.440 like could we use AI generated crypto bitcoin to detect 0:07:45.520 --> 0:07:46.040 dark matter? 0:07:46.280 --> 0:07:50.440 You mean quantum nano matter, Yes, exactly, quantum nano matter. 0:07:50.640 --> 0:07:54.000 Tiras Wow, I like quantum nanomatter. I'm going to use 0:07:54.040 --> 0:07:54.679 that in a proposal. 0:07:54.800 --> 0:08:00.240 That's good, that's said Daniel. Also, it's probably our on 0:08:00.320 --> 0:08:02.920 sale on Amazon. There's probably some product out there with 0:08:03.000 --> 0:08:03.440 that name. 0:08:03.560 --> 0:08:06.680 So yeah, but you didn't say ching tm after it, 0:08:06.800 --> 0:08:07.600 so I can use it. 0:08:07.760 --> 0:08:08.400 No, you don't have to. 0:08:09.320 --> 0:08:13.360 What I gotta brush up on my podcast property law. 0:08:13.520 --> 0:08:16.560 Yeah, you better or else I'm gonna see you for 0:08:16.680 --> 0:08:20.320 nano dollars for nano bitcoins, you know what? 0:08:20.440 --> 0:08:22.440 Or hey, you can have all of my nano bitcoins. 0:08:25.000 --> 0:08:26.560 What's the price of bitcoin these days? 0:08:26.800 --> 0:08:29.920 Nano bitcoins zero? Yeah, doesn't exist. 0:08:31.040 --> 0:08:33.760 But anyways, it's kind of an intriguing title. Could quantum 0:08:33.840 --> 0:08:37.880 clocks detect dark matter and quantum clocks sounds like it 0:08:37.880 --> 0:08:39.920 does sound like something you could buy an off of Amazon. 0:08:40.920 --> 0:08:43.120 Did you check to see if it's something you can 0:08:43.240 --> 0:08:44.319 just get next day? 0:08:44.559 --> 0:08:44.719 Oh? 0:08:44.800 --> 0:08:47.320 Yeah, it turns out Amazon will sell you something it 0:08:47.440 --> 0:08:52.480 calls a quantum clock, like a quantum entanglement led wall clock. 0:08:53.040 --> 0:08:56.520 But none of these things are actually quantum clocks the 0:08:56.559 --> 0:08:57.760 way that we understand them. 0:08:57.880 --> 0:09:01.679 Well, technically, isn't everything a quantum something? Well, I mean 0:09:01.720 --> 0:09:03.640 not everything, but you know the five percent that we 0:09:03.679 --> 0:09:07.480 know about in the universe, it's in it all quantum technically, 0:09:08.080 --> 0:09:09.520 like this is a quantum podcast. 0:09:11.200 --> 0:09:13.800 I mean, that's a really interesting philosophical question and not 0:09:13.880 --> 0:09:16.120 one that we really have an answer to, because on 0:09:16.120 --> 0:09:18.240 one hand, you're right that everything is made out of 0:09:18.280 --> 0:09:21.440 quantum particle, so isn't the whole universe quantum. On the 0:09:21.440 --> 0:09:24.000 other hand, we know that when you zoom out things 0:09:24.040 --> 0:09:26.480 behave by different rules. We call that classical. We don't 0:09:26.480 --> 0:09:29.560 really understand why there is that transition, but there definitely 0:09:29.679 --> 0:09:32.720 is a transition. So to call everything quantum is either 0:09:32.760 --> 0:09:36.320 to say that look classical is just big zoomed out quantum, 0:09:36.760 --> 0:09:39.040 or is to say that clackical doesn't really matter, which 0:09:39.120 --> 0:09:40.880 doesn't really sit well with me. Or what if I 0:09:40.880 --> 0:09:44.959 have no class, then you probably have a lot of 0:09:45.000 --> 0:09:45.360 big coin. 0:09:47.480 --> 0:09:50.880 Then I'm not gonna win any beauty contest. I have poise, 0:09:51.160 --> 0:09:52.080 but just no class. 0:09:52.360 --> 0:09:55.600 Yeah, exactly. But you know, for example, a clock that 0:09:55.800 --> 0:09:58.880 just works on mechanical parts would also work in the 0:09:58.960 --> 0:10:02.280 universe where QUANTUMU didn't rule the microscopic because it's not 0:10:02.360 --> 0:10:06.360 sensitive to those microscopic details, and so that wouldn't be 0:10:06.360 --> 0:10:09.200 a quantum clock. For example, like a pendulum clock or 0:10:09.200 --> 0:10:12.320 an old fashioned Swiss gear based. 0:10:11.960 --> 0:10:15.840 Clock a discussion about now mankla Sure that's my favorite. 0:10:16.000 --> 0:10:17.160 Hey you brought it up. 0:10:17.240 --> 0:10:19.320 But anyways, it's a kind of an interesting question and 0:10:19.360 --> 0:10:21.520 so we'll dig into it. But as usual, we were 0:10:21.520 --> 0:10:24.160 wondering how many people out there have thought about putting 0:10:24.280 --> 0:10:27.840 the concepts of dark matter and quantum and clocks all 0:10:27.880 --> 0:10:29.320 together in one sentence. 0:10:29.640 --> 0:10:31.920 So thanks very much to everybody who participates in this 0:10:32.000 --> 0:10:34.640 segment of the podcast. We love that you volunteer, We 0:10:34.679 --> 0:10:37.640 love hearing your thoughts, and we love sharing your voice 0:10:37.679 --> 0:10:40.719 with all of the other listeners. Please chime in if 0:10:40.720 --> 0:10:43.680 you'd like, write to me two questions at Danielanjorge dot 0:10:43.679 --> 0:10:45.960 com and you can't participate. 0:10:45.559 --> 0:10:47.319 So think about it for a second. Do you think 0:10:47.760 --> 0:10:52.080 quantum clocks can be used to detect dark matter? Here's 0:10:52.080 --> 0:10:53.040 what people had to say. 0:10:53.400 --> 0:10:55.679 I've never heard of a quantum clock, but I'm not 0:10:55.720 --> 0:10:57.920 sure how it would be able to detect dark matter 0:10:57.960 --> 0:11:01.760 anymore than a regular clock could. I guess maybe even 0:11:01.760 --> 0:11:04.199 with a regular clock, you could send it out into space, 0:11:04.240 --> 0:11:06.400 and if it hits a huge clump of dark matter 0:11:06.640 --> 0:11:09.559 and therefore gravity, maybe we could learn that there's a 0:11:09.559 --> 0:11:12.240 big well of gravity out in some location that we 0:11:12.360 --> 0:11:13.560 otherwise couldn't detect. 0:11:13.880 --> 0:11:14.480 Not so sure. 0:11:14.480 --> 0:11:16.679 I suppose it's possible, but I have no clue how 0:11:16.720 --> 0:11:19.880 it would Maybe something to do with entanglement. 0:11:20.240 --> 0:11:23.160 Since you're asking, the answer is probably yes, but maybe 0:11:23.200 --> 0:11:27.000 still theoretical. I would think you'd have to use the 0:11:27.120 --> 0:11:32.199 idea of measuring light passing through an area of more density, 0:11:32.320 --> 0:11:36.200 thus possibly dark matter that causes curvature of space and 0:11:36.240 --> 0:11:39.560 also time dilation. How to do that, I'm not sure. 0:11:39.800 --> 0:11:42.640 Since we don't possess a quantum clock, it doesn't seem 0:11:42.720 --> 0:11:46.160 unreasonable to suggest that a non existent clock cannot detect 0:11:46.280 --> 0:11:46.800 dark matter. 0:11:47.120 --> 0:11:51.040 All right, it's pretty uh intense answers here. I feel 0:11:51.080 --> 0:11:54.720 like it's something that some of the listeners had heard 0:11:54.760 --> 0:11:58.280 about before. Did you pull your professor colleagues this time? 0:11:59.000 --> 0:12:02.360 No, these are our listeners online. You know. There's some 0:12:02.400 --> 0:12:07.920 good answers here about entanglement and light passing through areas 0:12:07.960 --> 0:12:10.520 with dark matter density in them, and just in general 0:12:10.640 --> 0:12:12.160 sense that this is a hard problem. 0:12:12.280 --> 0:12:14.960 Maybe you should ask a bunch of beauty queens next time, 0:12:15.760 --> 0:12:17.439 or make it one of the standard questions in a 0:12:17.480 --> 0:12:21.120 beauty pageant. Forget howdy, how would you save the world? 0:12:21.240 --> 0:12:24.040 Or how would you know make things better? What do 0:12:24.040 --> 0:12:25.439 you think about quantum clocks? 0:12:27.040 --> 0:12:29.040 Well, where is the dark matter? Yeah, I'd love to 0:12:29.040 --> 0:12:30.439 hear that answer in the beauty pageant. 0:12:32.080 --> 0:12:35.200 Not that it couldn't happen, of course, no, absolutely. All right, Well, 0:12:35.280 --> 0:12:39.200 let's dig into this intriguing question of whether dark matter 0:12:39.240 --> 0:12:42.440 can be detected by quantum clocks, and let's start with 0:12:42.480 --> 0:12:45.560 the basics. Daniel, what do we know about dark matter? 0:12:45.640 --> 0:12:47.480 So there's a lot that we do and do not 0:12:47.679 --> 0:12:50.679 know about dark matter. So let's start with what we 0:12:50.760 --> 0:12:53.360 do know. We know that it's out there, and we 0:12:53.400 --> 0:12:56.360 know that it's here as well. We know that dark 0:12:56.400 --> 0:12:58.760 matter is something that exists in the universe. And then 0:12:58.800 --> 0:13:01.520 it's matter. We know that because we see its gravity. 0:13:02.000 --> 0:13:05.440 We see it holding galaxies together as they spin. There 0:13:05.520 --> 0:13:07.880 isn't enough gravity from the stars and the gas and 0:13:08.000 --> 0:13:10.960 dust that make up those galaxies to keep the stars 0:13:11.000 --> 0:13:13.320 in place as they swirl around the center of the 0:13:13.320 --> 0:13:16.959 galaxy at very high speeds, and yet they do stay 0:13:16.960 --> 0:13:20.680 in place. Galaxies are mostly not throwing stars out into 0:13:20.720 --> 0:13:23.560 intergalactic space, and so we infer that there must be 0:13:23.600 --> 0:13:27.360 some matter there to hold that galaxy together. But it's 0:13:27.400 --> 0:13:30.200 more than just that one inference, that one fudge factor 0:13:30.240 --> 0:13:33.360 to make that particular equation work. We see evidence for 0:13:33.440 --> 0:13:36.000 dark matter all over the history of the universe, from 0:13:36.000 --> 0:13:39.000 the very first few moments when the early universe plasma 0:13:39.080 --> 0:13:42.360 is slashing around and you have dark matter and normal 0:13:42.400 --> 0:13:45.920 matter and photons all acting very differently and creating different 0:13:45.960 --> 0:13:49.720 slashing patterns. From looking at that slashing in the cosmic 0:13:49.760 --> 0:13:53.040 microwave background radiation, we can figure out that there was 0:13:53.160 --> 0:13:55.560 dark matter and even measure how much of it there is, 0:13:55.920 --> 0:13:58.520 and we can trace the history of dark matter's gravity 0:13:58.559 --> 0:14:01.240 as it shapes the structure formation of the whole universe 0:14:01.559 --> 0:14:04.160 why we have galaxies at all this early in the 0:14:04.240 --> 0:14:06.880 history of the universe, And so dark matter is definitely 0:14:06.880 --> 0:14:08.840 out there as a kind of matter, but we don't 0:14:08.840 --> 0:14:12.719 know really what it is or very specifically where it is, 0:14:12.840 --> 0:14:16.680 because it's so hard to see since it only feels gravity. 0:14:16.679 --> 0:14:19.360 It doesn't feel any of the other forces that we've discovered. 0:14:19.720 --> 0:14:22.360 And we can also sort of see dark matter right like, 0:14:22.400 --> 0:14:23.840 we can see it in the same way that you 0:14:23.840 --> 0:14:26.280 can see a lens or glass lens or example. You 0:14:26.280 --> 0:14:29.360 can see how it distorts the light behind it, right. 0:14:29.280 --> 0:14:32.440 Yeah, exactly. We can see dark matter through gravity, and 0:14:32.480 --> 0:14:35.720 so that means we can see stuff bending around dark matter. 0:14:35.960 --> 0:14:38.680 We can see it holding galaxies together, and that even 0:14:38.760 --> 0:14:41.880 impacts how light moves in the vicinity of dark matter. 0:14:42.000 --> 0:14:44.880 If you have a big blob of dark matter between 0:14:44.880 --> 0:14:48.160 you and some distant galaxy, for example, the photons from 0:14:48.200 --> 0:14:50.880 that distant galaxy will bend as they move through that 0:14:51.040 --> 0:14:54.480 dark matter, creating apparent distortions in your image. You can 0:14:54.520 --> 0:14:57.680 even sometimes see the same galaxy twice in the sky 0:14:57.920 --> 0:15:01.240 because of this gravitational lensing. And so we know that 0:15:01.280 --> 0:15:03.160 it's out there, and we can use some techniques like 0:15:03.200 --> 0:15:06.760 that to sometimes tell roughly where it is. But because 0:15:06.880 --> 0:15:10.520 dark matter is so weak it's particles only feel gravity, 0:15:10.560 --> 0:15:13.440 we think it's very difficult to figure out what exactly 0:15:13.560 --> 0:15:16.440 is made out of to isolate one piece of dark matter, 0:15:16.680 --> 0:15:20.040 because gravity is so weak that essentially a particle's gravity 0:15:20.320 --> 0:15:21.960 is almost impossible to measure. 0:15:22.160 --> 0:15:24.560 Yeah, and dark matter is also something that's not just 0:15:24.720 --> 0:15:27.920 out there in space. It's sort of like all around us, 0:15:28.000 --> 0:15:30.440 right like it's floating through us right now, sort of 0:15:30.480 --> 0:15:32.880 like the fourth you know, it flows through us, binds 0:15:32.920 --> 0:15:36.440 us all together. It's made out of medtichlorians. 0:15:36.480 --> 0:15:40.600 Perhaps perhaps, yeah, exactly, you'll only really understand it after 0:15:40.720 --> 0:15:43.440 nine hundred years of study. That's a really good question, 0:15:43.520 --> 0:15:46.200 and that's sort of the central question of this episode 0:15:46.320 --> 0:15:49.760 is exactly where is the dark matter? And can we 0:15:49.800 --> 0:15:53.000 find like concentrations of it? Can we map it out? 0:15:53.760 --> 0:15:57.640 Because dark matter is so weakly interacting like only gravity, 0:15:57.680 --> 0:16:00.360 it takes huge amounts of it to feel anything, and 0:16:00.440 --> 0:16:02.880 so that makes it very hard to tell exactly where 0:16:02.920 --> 0:16:05.400 the dark matter is. It might be that it's mostly 0:16:05.480 --> 0:16:08.240 spread out evenly through the galaxy. It might be more 0:16:08.320 --> 0:16:11.480 clumpy than that depends a lot on your particular theory 0:16:11.640 --> 0:16:14.800 of dark matter. Where it exactly is. So it could 0:16:14.800 --> 0:16:16.840 be that we are in a dark matter wind as 0:16:16.880 --> 0:16:19.120 the Earth orbits the Sun and the Sun moves through 0:16:19.120 --> 0:16:22.080 the galaxy. We could also be in a dark matter 0:16:22.200 --> 0:16:25.560 liss bubble, a bubble of space in which there's comparatively 0:16:25.680 --> 0:16:27.960 little dark matter. Or it could be that dark matter 0:16:28.000 --> 0:16:29.560 is fairly dense in our area. 0:16:29.720 --> 0:16:31.000 You know, I have to say, every time you say 0:16:31.080 --> 0:16:34.640 dark matter wind, it makes me think of dark parts. 0:16:37.280 --> 0:16:39.320 Elevating the discourse every week. 0:16:41.760 --> 0:16:43.120 That's my job. That's why I'm here. 0:16:43.320 --> 0:16:43.960 Smells. 0:16:43.680 --> 0:16:48.080 It's all grounded or grounded or you know, flat as 0:16:48.120 --> 0:16:51.600 in fletch wents. But anyways, so it's sort of all 0:16:51.640 --> 0:16:53.440 around this, and I guess I'm wondering, like, if it 0:16:53.480 --> 0:16:56.440 is all around us, would we be able to tell, Like, 0:16:56.600 --> 0:16:58.600 you know, if let's say dark matter is flowing through 0:16:58.640 --> 0:17:01.080 the Earth right now, or say it wasn't, would you 0:17:01.120 --> 0:17:02.200 be able to tell the difference. 0:17:02.440 --> 0:17:05.359 That's exactly what these experiments are trying to measure. And 0:17:05.440 --> 0:17:08.240 to give you a sense of the difficulty the challenge 0:17:08.240 --> 0:17:11.280 of this, think about like why we didn't discover dark 0:17:11.320 --> 0:17:14.760 matter earlier, just in studying how our Solar system moves. 0:17:15.119 --> 0:17:18.080 We have now very precise measurements of the orbit of 0:17:18.160 --> 0:17:20.679 Jupiter and Mars and all the planets and all the 0:17:20.720 --> 0:17:23.960 little pieces of the Solar System as they orbit the Sun. 0:17:24.320 --> 0:17:26.080 You might think, hey, if dark matter is here in 0:17:26.080 --> 0:17:28.960 our Solar system and it has gravity, wouldn't it change 0:17:29.000 --> 0:17:31.399 the way those things orbit? Shouldn't we be able to 0:17:31.480 --> 0:17:33.720 detect it? But because we think dark matter might be 0:17:33.920 --> 0:17:37.800 spread very thin, probably there isn't that much dark matter 0:17:37.880 --> 0:17:40.520 in the vicinity of our Solar system. So even those 0:17:40.640 --> 0:17:43.639 very very precise measurements you know, like knowing the motion 0:17:43.760 --> 0:17:47.639 of Jupiter to meters or centimeters, can't detect dark matter 0:17:47.960 --> 0:17:50.200 because it would be very thin and very spread out 0:17:50.240 --> 0:17:53.399 and mostly we think homogeneous, which in the end doesn't 0:17:53.440 --> 0:17:56.680 give much gravitational pull on the objects in the Solar System. 0:17:57.040 --> 0:18:00.399 So it takes a very specialized, highly sensitive device to 0:18:00.400 --> 0:18:02.200 be able to detect this dark matter. 0:18:02.400 --> 0:18:04.199 Yeah, and then don't we say once like, if you 0:18:04.240 --> 0:18:07.000 take all the dark matter that is potentially floating through 0:18:07.040 --> 0:18:09.439 the Earth right now, it would only weigh about as 0:18:09.520 --> 0:18:11.680 much as a squirrel or something like that. 0:18:11.880 --> 0:18:14.879 Yeah, exactly, though that's very speculative, right. That assumes that 0:18:15.000 --> 0:18:18.520 dark matter is essentially equally spread out in our galaxy, 0:18:18.600 --> 0:18:21.520 which we don't believe is true. But if you assume 0:18:21.640 --> 0:18:24.880 that there is, then we know our galaxy, for example, 0:18:25.080 --> 0:18:28.640 is ninety five percent dark matter. That means for every 0:18:28.720 --> 0:18:31.720 kilogram of matter made out of atoms like hydrogen and 0:18:31.720 --> 0:18:35.400 helium or whatever, there's nineteen kilograms of matter made out 0:18:35.400 --> 0:18:38.320 of whatever dark matter is made out of. And so 0:18:38.440 --> 0:18:41.679 it's like nineteen to one in our galaxy. 0:18:41.280 --> 0:18:44.119 Which sounds like a lot, but I guess also galaxies 0:18:44.240 --> 0:18:47.600 kind of very empty mostly right, like it's probably like 0:18:47.680 --> 0:18:48.840 ninety nine percent empty. 0:18:48.960 --> 0:18:51.960 Yeah exactly. Now, normal matter clumps up a lot, right, 0:18:52.400 --> 0:18:56.080 Like the Sun is an extraordinarily dense collection of normal matter. 0:18:56.160 --> 0:18:59.119 Normal matter is not spread evenly through the galaxy. But 0:18:59.160 --> 0:19:01.640 if you take dark man and spread it evenly through 0:19:01.640 --> 0:19:05.040 the galaxy, you get a pretty small density. It's like 0:19:05.240 --> 0:19:08.680 ten to the twenty six kilograms per cubic light year, 0:19:08.880 --> 0:19:12.240 which is a huge volume, which means it's like ten 0:19:12.280 --> 0:19:16.280 to the negative twenty two kilograms per cubic meter. So 0:19:16.320 --> 0:19:18.119 then if you add up all the cubic meters in 0:19:18.160 --> 0:19:20.840 the Earth, that adds up to about two thirds of 0:19:20.880 --> 0:19:24.480 a kilogram of dark matter inside the volume of the Earth. Again, 0:19:24.560 --> 0:19:28.160 assuming that dark matter is evenly spread throughout the galaxy, 0:19:28.160 --> 0:19:30.280 which it probably isn't, but it might be. 0:19:30.320 --> 0:19:33.920 Roughly, which is about the size or mass of a squirrel. 0:19:34.080 --> 0:19:37.240 Yeah exactly, So one squirrel of dark matter inside the 0:19:37.280 --> 0:19:39.560 volume of the Earth compared to you know, the many, 0:19:39.600 --> 0:19:42.679 many millions and billions of kilograms of normal matter inside 0:19:42.680 --> 0:19:45.680 the volume of the Earth. That sounds the importance of clumping, right, 0:19:45.680 --> 0:19:49.040 Because normal matter clumps together, it's gravity is much more powerful. 0:19:49.200 --> 0:19:52.080 In our local neighborhood, than dark matter. Even though dark 0:19:52.119 --> 0:19:55.480 matter outweighs normal matter by nineteen to one, if it's 0:19:55.560 --> 0:19:58.160 much more thinly spread out, the local effects of its 0:19:58.200 --> 0:19:59.880 gravity are much harder to detect. 0:20:00.000 --> 0:20:02.240 I think maybe what you're saying is that dark matter, 0:20:02.840 --> 0:20:06.160 in terms of the universe scale, it mostly hangs out 0:20:06.200 --> 0:20:08.120 in galaxies. Like you don't see a lot of dark 0:20:08.160 --> 0:20:10.680 matter floating out there on its own between galaxies. 0:20:10.760 --> 0:20:12.720 Yeah, we can do really precise measurements of where dark 0:20:12.720 --> 0:20:15.400 matter is on the galaxy scale, because galaxies are really 0:20:15.440 --> 0:20:18.359 really big. If we can tell how galaxies are orbiting 0:20:18.400 --> 0:20:20.600 around each other, just the way we can tell how 0:20:20.680 --> 0:20:23.879 stars are moving through the galaxy, so enormous clumps of 0:20:23.960 --> 0:20:26.840 dark matter, absolutely, we can measure their gravity. But when 0:20:26.840 --> 0:20:29.040 you zoom in in a really fine grained way and 0:20:29.080 --> 0:20:31.639 want to say, hey, is there a moon sized blob 0:20:31.680 --> 0:20:34.000 of dark matter anywhere in our solar system, that's a 0:20:34.000 --> 0:20:35.080 tough question to answer. 0:20:35.160 --> 0:20:37.840 So then within the galaxy, you're saying, like, there's a 0:20:37.880 --> 0:20:39.880 lot of dark matter within our galaxy. Ninety five percent 0:20:39.920 --> 0:20:42.199 of the mass of our galaxy is dark matter, And 0:20:42.240 --> 0:20:44.320 what does it look like. Does it look like, you know, 0:20:44.600 --> 0:20:47.439 an intense dense ball of dark matter in the middle, 0:20:48.000 --> 0:20:51.000 is it evenly distributed? And also, like our galaxy looks 0:20:51.040 --> 0:20:53.119 like a disc sort of like a flat disk, is 0:20:53.240 --> 0:20:55.040 dark matter also shaped like a flat disk. 0:20:55.280 --> 0:20:57.560 So we have the best answers the more we zoom out, 0:20:57.600 --> 0:21:00.000 and then as we zoom in things get literally funny. 0:21:00.280 --> 0:21:02.560 But on the scale of the galaxy we have some ideas. 0:21:02.920 --> 0:21:05.040 We think that dark matter is like a big halo. 0:21:05.400 --> 0:21:08.680 So imagine the visible galaxy right the edge of the stars. 0:21:09.160 --> 0:21:11.920 Dark matter is a big halo that goes out beyond 0:21:12.040 --> 0:21:15.440 the visible stars, and it's bigger and fuzzier. It hasn't 0:21:15.440 --> 0:21:17.919 collapsed the way normal matter has because it just doesn't 0:21:17.920 --> 0:21:20.520 clump right. In order to clump, things need other kinds 0:21:20.520 --> 0:21:23.119 of interaction other than gravity. Like if you have two 0:21:23.200 --> 0:21:25.919 dark matter particles they attract each other gravitationally and then 0:21:26.000 --> 0:21:28.240 just passed right through each other. They're just gonna zig 0:21:28.280 --> 0:21:30.919 and zag back and forth oscillate forever. They're not going 0:21:31.000 --> 0:21:34.000 to clump together. To do that, you need like electromagnetism 0:21:34.080 --> 0:21:36.240 or the strong force or something that wants to grab 0:21:36.280 --> 0:21:39.600 onto each other. So dark matter stays a big puffy 0:21:39.640 --> 0:21:42.800 halo and the galaxy is sort of embedded in that halo, 0:21:43.200 --> 0:21:45.800 and that's not a coincidence. Right. The reason the galaxy 0:21:45.840 --> 0:21:49.080 exists is because of a big dark matter blob there 0:21:49.280 --> 0:21:53.800 that's gathered together all the hydrogen helium gravitationally and made 0:21:53.800 --> 0:21:56.720 it into a galaxy. It's the reason we have stars, etc. 0:21:57.240 --> 0:21:59.960 Now, when you say halo, you don't actually mean like 0:22:00.040 --> 0:22:02.520 an angel's halo that looks like a ring. You actually 0:22:02.600 --> 0:22:04.000 mean just like a blob, right. 0:22:03.960 --> 0:22:07.159 Yeah, exactly, like a big fuzzy blob that extends out 0:22:07.200 --> 0:22:10.119 further along the disc and then further above and below 0:22:10.200 --> 0:22:13.080 the disc. But even that we know already is not 0:22:13.160 --> 0:22:14.080 evenly distributed. 0:22:14.160 --> 0:22:16.800 Is it like football shaped? Is it kind of flat? 0:22:16.960 --> 0:22:18.040 Or is it a perfect sphere. 0:22:18.320 --> 0:22:20.840 It's more like a hockey puck, right, It's flat, but 0:22:20.920 --> 0:22:22.920 not as flat as the galaxy itself. 0:22:23.040 --> 0:22:23.879 What made it flat? 0:22:24.000 --> 0:22:26.120 Yeah, maybe a hockey puck is the wrong analogy. It's 0:22:26.119 --> 0:22:29.360 not quite that flat. It's more like a big ellipsoid. 0:22:29.560 --> 0:22:31.280 You mean like a slightly squished ball. 0:22:31.600 --> 0:22:35.800 Yeah exactly. It's like a big basketball that somebody's sitting 0:22:35.840 --> 0:22:36.440 on or something. 0:22:36.600 --> 0:22:38.960 All right, Well, let's get a little bit more into 0:22:39.160 --> 0:22:41.600 the details of what we know about dark matter, how 0:22:41.680 --> 0:22:43.600 much of it can we see, how much can we 0:22:43.720 --> 0:22:47.720 discern about what it's doing in our universe? 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We have this sense of a big, 0:27:38.200 --> 0:27:42.919 fuzzy halo that surrounds the galaxy, and we can also 0:27:43.000 --> 0:27:46.200 measure the density as a function of distance from the center. 0:27:46.359 --> 0:27:48.800 So if you're a star, for example, orbiting the center 0:27:48.840 --> 0:27:52.119 of the galaxy, the speed at which you orbit depends 0:27:52.240 --> 0:27:55.600 on the force that's holding you in that orbit. So 0:27:55.640 --> 0:27:58.639 the stronger the force, the faster you can go, or 0:27:58.720 --> 0:28:00.520 the faster you can go, the stronger the force that's 0:28:00.600 --> 0:28:03.240 needed to hold you in that orbit. So by measuring 0:28:03.240 --> 0:28:06.159 the speed of a given star, we can essentially measure 0:28:06.160 --> 0:28:08.720 the mass of all that stuff that's holding on to 0:28:08.840 --> 0:28:10.800 that star. So then if you look at stars at 0:28:10.800 --> 0:28:14.280 different distances from the center, you can basically map out 0:28:14.359 --> 0:28:17.320 the density of stuff in the galaxy as you go 0:28:17.560 --> 0:28:20.080 further and closer to the center of the galaxy. 0:28:20.400 --> 0:28:23.359 Like, if dark matter was super condensed in the middle 0:28:23.359 --> 0:28:26.400 of the galaxy, then the stars in the galaxy we'd 0:28:26.440 --> 0:28:29.400 be rotating a certain way. Or if the dark matter 0:28:29.520 --> 0:28:32.080 was more spread out then the stars in the galaxy 0:28:32.080 --> 0:28:33.760 we'd be rotating in a different way. 0:28:33.920 --> 0:28:36.720 Yeah, exactly, if all the dark matter in the galaxy 0:28:36.880 --> 0:28:39.040 was at the center, then everything would act in a 0:28:39.040 --> 0:28:41.000 certain way, would just go like one over are squared. 0:28:41.000 --> 0:28:42.880 It's sort of like the way the Solar system orbits 0:28:42.920 --> 0:28:44.960 the Sun. But if you take some of that mass 0:28:44.960 --> 0:28:47.800 and you spread it out through the galaxy instead, then 0:28:47.800 --> 0:28:50.160 the dark matter that's further out than a given star 0:28:50.240 --> 0:28:53.440 doesn't affect its orbit because it's gravity all cancels out. 0:28:53.680 --> 0:28:56.880 So that changes the rotation speed of those stars, and 0:28:56.920 --> 0:28:59.720 that's in fact how we first discover dark matter. Was 0:28:59.720 --> 0:29:02.600 by looking at these rotation speeds of stars around the 0:29:02.600 --> 0:29:05.320 center of the galaxy and seeing that we couldn't explain 0:29:05.360 --> 0:29:07.640 it by mapping all the mass from the stars and 0:29:07.680 --> 0:29:09.560 the gas and the dust. And that's exactly how you 0:29:09.560 --> 0:29:12.120 can tell where you need to add more mass to 0:29:12.200 --> 0:29:14.960 explain these rotation speeds. It's not just like, hey, add 0:29:14.960 --> 0:29:16.840 a big blob of the center. You need to add 0:29:16.840 --> 0:29:18.920 some of the center and also some further out and 0:29:19.000 --> 0:29:22.720 some further out, and so precise measurements of those velocities 0:29:22.880 --> 0:29:25.160 give you a fairly accurate picture of where the dark 0:29:25.200 --> 0:29:28.160 matter is in the galaxy. And it's not evenly spread out. 0:29:28.320 --> 0:29:31.280 It's more densely clumped at the center, which is something you'd. 0:29:31.080 --> 0:29:34.360 Expect because it is affected by gravity, right. 0:29:34.200 --> 0:29:36.440 It is, in the end affected by gravity, and so 0:29:36.560 --> 0:29:39.520 it's pulled itself together. And the whole reason that this 0:29:39.680 --> 0:29:44.440 exists is because of some like early universe perturbation where 0:29:44.440 --> 0:29:47.360 you had a denser blob of dark matter that created 0:29:47.400 --> 0:29:50.240 this whole well, gathered together the other dark matter and 0:29:50.280 --> 0:29:53.320 created this over density which then pulled in hydrogen, helium 0:29:53.320 --> 0:29:56.440 and whatever was around to make a galaxy. So it's 0:29:56.440 --> 0:29:58.600 a little bit denser at the center, though it's not 0:29:58.840 --> 0:30:02.560 very well understood, like if we do calculations simulations to 0:30:02.640 --> 0:30:05.160 describe what we think should happen. If you have a 0:30:05.160 --> 0:30:06.920 bunch of dark matter and you give it a few 0:30:06.960 --> 0:30:09.720 billion years to fall together and to form some structure, 0:30:09.800 --> 0:30:12.880 it describes what astronomers call a cusp, which means like 0:30:13.120 --> 0:30:14.959 a point of high density of the center and then 0:30:15.080 --> 0:30:17.680 very steeply falling should like drop off quickly. But if 0:30:17.680 --> 0:30:21.680 you go out and measure the actual distributions of stars velocities, 0:30:21.960 --> 0:30:24.320 you see something that looks like a bigger core. It's 0:30:24.320 --> 0:30:27.040 not like it's pointing near the center. It's more spread 0:30:27.040 --> 0:30:30.600 out in the inner galaxy. It's like flatter, and so 0:30:30.720 --> 0:30:32.760 this is not something we understand very well. And it 0:30:32.760 --> 0:30:34.760 also gives you a sense of like the scale of 0:30:34.840 --> 0:30:36.880 which we can figure this stuff out. We're talking about 0:30:36.920 --> 0:30:40.000 over light years distances, right, We're not resolving dark matter 0:30:40.080 --> 0:30:44.240 in meters or even in aus with very very coarse 0:30:44.280 --> 0:30:47.120 ways to measure where the dark matter is again, because 0:30:47.160 --> 0:30:48.360 its gravity is so weak. 0:30:48.480 --> 0:30:51.000 Are you saying like the beginning of the universe, dark 0:30:51.040 --> 0:30:53.760 matter was more evenly spread out, like you know, all 0:30:53.800 --> 0:30:56.560 those light years of empty space between US and Andromeda 0:30:56.600 --> 0:30:59.080 and other galaxies was all filled with dark matter, and 0:30:59.120 --> 0:31:01.600 then it all colleutes through certain clusters. 0:31:01.760 --> 0:31:04.600 Yeah, it definitely gathered itself together. The early universe had 0:31:04.640 --> 0:31:08.360 initial density fluctuations, and that's a whole big question about 0:31:08.400 --> 0:31:11.920 where exactly that came from. And then those seated gravity 0:31:11.960 --> 0:31:15.360 to pull things together. So gravity does form structure, but 0:31:15.440 --> 0:31:17.960 it takes time. And so yeah, dark matter was more 0:31:18.000 --> 0:31:19.920 spread out and now it's less spread out. 0:31:19.960 --> 0:31:21.880 Why would dark matter stay stuck together? 0:31:22.080 --> 0:31:24.400 Well, it's not that dark matter is sticking together. It's 0:31:24.440 --> 0:31:26.480 not like it's bonded to itself. And again we don't 0:31:26.480 --> 0:31:29.080 really know because we don't have a microscopic picture of 0:31:29.160 --> 0:31:31.800 the dark matter. But I think you're asking, like, why 0:31:31.880 --> 0:31:34.880 does dark matter form even gravitational structures? Like why does 0:31:34.920 --> 0:31:37.400 it get more dense in some places and then in others? 0:31:37.520 --> 0:31:38.280 Is that what you're asking? 0:31:38.480 --> 0:31:40.600 Yeah, Like I'm imagining at the beginning of the universe 0:31:40.600 --> 0:31:43.440 there's a bit of dark matter that was, you know, 0:31:43.560 --> 0:31:45.640 let's say, ten light years away, and then it got 0:31:45.640 --> 0:31:48.760 attracted to our galaxy, so it flew over here. But 0:31:48.840 --> 0:31:51.200 then why didn't just keep flying to the other side. 0:31:51.360 --> 0:31:53.800 Yeah, So as that distant piece of dark matter approaches 0:31:53.840 --> 0:31:58.040 the galaxy, it gains velocity. Right, it's exchanging gravitational potential 0:31:58.120 --> 0:32:01.120 energy for kinetic energy. And then you're imagining like the 0:32:01.120 --> 0:32:03.040 way a ball rolls down a valley, why doesn't it 0:32:03.120 --> 0:32:05.800 roll back up the other side? And it will, yes, 0:32:05.880 --> 0:32:08.760 but then it comes back right, And so gravity in 0:32:08.800 --> 0:32:12.320 the end is organizing something. There's the second piece to that, 0:32:12.440 --> 0:32:15.640 which is that it doesn't completely roll back up the 0:32:15.640 --> 0:32:19.480 other side. You know, anything that's accelerating is emitting gravitational 0:32:19.560 --> 0:32:22.960 radiation for example. So the reason, for example, two black 0:32:23.000 --> 0:32:26.680 holes orbiting each other will eventually spiral in and collapse 0:32:27.000 --> 0:32:29.960 is that they're emitting gravitational energy. So none of these 0:32:30.000 --> 0:32:32.880 things are really stable. So over long periods of time, 0:32:33.120 --> 0:32:37.320 even without inelastic interactions like electromagnetism or whatever, these things 0:32:37.360 --> 0:32:41.680 will form very large structures and they will gradually collapse 0:32:41.760 --> 0:32:43.200 due to gravitational radiation. 0:32:43.560 --> 0:32:45.800 All right, so we kind of have a fuzzy picture 0:32:45.840 --> 0:32:48.480 of where it is in the universe. So now the 0:32:48.520 --> 0:32:51.280 question of the episode is can we use quantum clocks 0:32:51.600 --> 0:32:55.000 to detect dark matter? How do quantum clocks fit into this? 0:32:55.280 --> 0:32:57.920 So quantum clocks might give us a sense for where 0:32:57.920 --> 0:33:00.560 the dark matter is if we can find a place 0:33:00.640 --> 0:33:03.360 where it's like clumpy, if we can find a place 0:33:03.520 --> 0:33:06.840 in our solar system where it's like gathered together for 0:33:06.880 --> 0:33:09.440 some reason. And that would be really cool, because not 0:33:09.480 --> 0:33:11.960 only would it help us detect what dark matter is, 0:33:12.160 --> 0:33:14.880 but it would help us understand where it is. It's 0:33:14.880 --> 0:33:16.960 a really deep mystery. I think, not just because we 0:33:16.960 --> 0:33:18.960 want to understand dark matter, but because we want like 0:33:18.960 --> 0:33:22.000 a map. You know, humans are visual creatures. We want 0:33:22.040 --> 0:33:24.080 to know like where the stuff is, and just not 0:33:24.320 --> 0:33:27.600 knowing where dark matter is in the universe really bugs me. 0:33:27.680 --> 0:33:29.720 So I would love to know where it is, and 0:33:30.200 --> 0:33:33.880 understanding its map on a finer scale would be really helpful. 0:33:33.920 --> 0:33:36.400 And quantum clocks might be able to help us map 0:33:36.600 --> 0:33:38.760 where dark matter is if we can send them out 0:33:38.840 --> 0:33:42.640 into space and if they're sensitive to dark matter, if 0:33:42.680 --> 0:33:45.680 their operation changes as they pass through dark matter. 0:33:45.800 --> 0:33:47.280 Okay, I think you're saying that you know, at the 0:33:47.320 --> 0:33:50.280 galaxy level, we know that it looks like a big blob. 0:33:50.320 --> 0:33:52.360 It's sort of like a switch ball. It's sort of 0:33:52.560 --> 0:33:55.120 more intense or more dense in the center of the galaxy. 0:33:55.320 --> 0:33:57.440 But I think maybe you're saying, can we know in 0:33:57.560 --> 0:34:02.360 finer detail what it looks like between stars within the galaxy, 0:34:02.440 --> 0:34:05.200 like is it clumpy, is it chunky, or is it 0:34:05.240 --> 0:34:06.040 like peanut butter. 0:34:06.000 --> 0:34:10.480 Smooth exactly, And people have tackled this problem in the past, 0:34:10.680 --> 0:34:13.600 Like people use the technique you mentioned gravitation lensing to 0:34:13.640 --> 0:34:16.520 look for blobs of dark matter, and that works, and 0:34:16.560 --> 0:34:19.400 it's powerful, but only if you have like a really 0:34:19.480 --> 0:34:22.799 nice galaxy behind the blob of dark matter that can 0:34:22.840 --> 0:34:25.040 show you that it's there, so that tells us a 0:34:25.080 --> 0:34:27.200 little bit about the dark matter density. But there aren't 0:34:27.239 --> 0:34:29.400 like galaxies in all the right places to like X 0:34:29.520 --> 0:34:31.920 ray the whole Solar system and figure out where it is. 0:34:32.000 --> 0:34:34.000 And that technique isn't always powerful enough. You need like 0:34:34.040 --> 0:34:36.759 a really big blob of dark matter. Another technique people 0:34:36.760 --> 0:34:40.000 have used is to look for dwarf galaxies. Essentially, our 0:34:40.040 --> 0:34:43.560 galaxy is formed by the combination of lots of galaxies, right, 0:34:43.760 --> 0:34:46.160 we think galaxies formed kind of small and then grew 0:34:46.200 --> 0:34:49.480 together with all sorts of absorptions and collisions. That means 0:34:49.520 --> 0:34:53.279 that our galaxy has other like mini galaxies embedded within it. 0:34:53.680 --> 0:34:56.360 Some of these we call dwarf galaxies because they're small, 0:34:56.560 --> 0:34:59.800 and we think they're like very high dark matter density 0:34:59.400 --> 0:35:02.759 therew stars, and so we can look at the motion 0:35:02.800 --> 0:35:05.480 of the stars inside those little galaxies to get sensors 0:35:05.560 --> 0:35:08.080 for like where those blobs are. But we don't have 0:35:08.120 --> 0:35:10.480 a great way to like X ray the Solar System 0:35:10.520 --> 0:35:12.640 and figure out, like where is the dark matter in 0:35:12.640 --> 0:35:15.239 our Solar system? Is it hanging out by Jupiter? Is 0:35:15.239 --> 0:35:18.000 it spread evenly like peanut butter? What's going on? 0:35:18.480 --> 0:35:21.120 You want to know it's distribution at the Solar system 0:35:21.120 --> 0:35:21.880 scale exactly. 0:35:21.960 --> 0:35:23.600 That's what I want to do. And I read a 0:35:23.640 --> 0:35:26.239 recent paper which was very clever, which is looking at 0:35:26.280 --> 0:35:29.520 asteroids and trying to track asteroid trajectories and see if 0:35:29.560 --> 0:35:33.120 like tiny little deviations in the trajectory of asteroids or 0:35:33.160 --> 0:35:36.480 comets as they move through the Solar System could reveal 0:35:36.520 --> 0:35:38.960 the presence of dark matter. It's very difficult to do 0:35:39.000 --> 0:35:41.640 because if dark matter is evenly spread out or only 0:35:41.680 --> 0:35:44.560 a little bit clumpy, that'd be basically no effect on 0:35:44.640 --> 0:35:47.080 those asteroids. But it's the kind of thing that we're 0:35:47.160 --> 0:35:49.359 just on the verge of being able to potentially do 0:35:49.480 --> 0:35:52.680 now that we have better measurements and better computational tools 0:35:52.719 --> 0:35:56.640 to try to like infer this information from really specific measurements. 0:35:56.719 --> 0:35:58.800 All right, So then how would you use a quantum 0:35:58.800 --> 0:36:00.520 clock to deteg dark matter? 0:36:00.640 --> 0:36:02.799 So when we talk about a quantum clock, really what 0:36:02.840 --> 0:36:06.000 we mean is something which is based on fundamental quantum 0:36:06.000 --> 0:36:08.719 mechanical principles. And you know it sounds fancy, but even 0:36:08.800 --> 0:36:11.799 just like an atomic clock, is a quantum clock. An 0:36:11.840 --> 0:36:14.440 atomic clock is something that looks at like the oscillation 0:36:14.520 --> 0:36:17.480 of electron between two energy levels and a caesium atom, 0:36:17.760 --> 0:36:21.840 which is a very precise, very very regular process that 0:36:21.920 --> 0:36:25.160 we can use essentially to tell how time has passed, 0:36:25.760 --> 0:36:29.320 and so on Earth, we have extraordinarily precise atomic clocks 0:36:29.360 --> 0:36:31.960 which now set the standard and in fact define what 0:36:32.000 --> 0:36:34.120 we mean by a second. A second used to have 0:36:34.200 --> 0:36:36.960 a different definition, but now a second is defined as 0:36:37.040 --> 0:36:39.800 like a certain number of cycle of a specific kind 0:36:39.840 --> 0:36:44.200 of atom. That's literally how we measure time now, and 0:36:44.280 --> 0:36:45.640 so it's the standard. 0:36:46.120 --> 0:36:48.120 It's like the minute, like it used to be like 0:36:48.160 --> 0:36:50.600 a minute with sixty seconds, but now people say, oh, 0:36:50.640 --> 0:36:53.560 it's been a minute to really mean something totally different. 0:36:57.560 --> 0:37:02.360 Yes, it's just like that exactly, and we call it 0:37:02.360 --> 0:37:05.120 a quantum clock because this really is a quantum process 0:37:05.120 --> 0:37:08.400 we're talking about quantum particles. There's an electron, there's an atom. 0:37:08.600 --> 0:37:11.640 The electron is moving in the potential well of the atom, 0:37:11.719 --> 0:37:15.120 so it's interacting electromagnetically with the nucleus. And the way 0:37:15.120 --> 0:37:17.720 that it's moving, the way it oscillates between energy levels, 0:37:17.920 --> 0:37:21.120 is completely controlled by quantum processes. This is not a 0:37:21.120 --> 0:37:23.680 clock that you could have in a perfectly classical universe. 0:37:23.920 --> 0:37:26.320 You know, if we lived in a universe where electrons 0:37:26.320 --> 0:37:28.799 really were tiny little balls that went to orbits and 0:37:28.840 --> 0:37:31.960 had smooth classical paths the way planets do, then this 0:37:32.000 --> 0:37:34.680 clock could not exist. And so that's when we meet 0:37:34.719 --> 0:37:35.800 by quantum clock. 0:37:36.040 --> 0:37:38.160 But I guess, if it's a quantum clock, doesn't it 0:37:38.239 --> 0:37:41.560 have a certain amount of uncertainty to it or unknowability? 0:37:41.840 --> 0:37:45.280 How can it be precise if there's the Heisenberg uncertainty principle. 0:37:46.560 --> 0:37:49.920 Yeah, you're right, there's no absolutely precise quantum clock. But 0:37:50.080 --> 0:37:52.520 this is about as regular as it gets. And amazingly, 0:37:52.640 --> 0:37:56.120 these quantum clocks are more precise than mechanical clocks, which 0:37:56.120 --> 0:37:58.880 of course also have uncertainty in them, because no mechanical 0:37:58.920 --> 0:38:02.040 device is perfect created, right, And so this is as 0:38:02.080 --> 0:38:04.520 accurate as they've been able to make them, and recently 0:38:04.520 --> 0:38:07.920 they've been even able to make them small and transportable. 0:38:08.160 --> 0:38:10.279 You might think of an atomic clock as like some 0:38:10.480 --> 0:38:13.839 huge device in the basement of a laboratory in Colorado 0:38:14.080 --> 0:38:16.520 that weighs like ten tons and fills a room. But 0:38:16.640 --> 0:38:18.840 actually these things can be made quite small. 0:38:19.120 --> 0:38:21.680 So a quantum clock is really just an atomic clock 0:38:21.800 --> 0:38:24.160 or is there another kind that doesn't use atoms? 0:38:24.239 --> 0:38:26.480 There's no atomic clock that's not a quantum clock. So 0:38:26.560 --> 0:38:29.280 quantum clock is just a fancier sounding name for atomic clock. 0:38:29.360 --> 0:38:31.800 Yes, can you have a quantum clock that maybe doesn't 0:38:31.880 --> 0:38:34.799 use an atom, that maybe just relies on electrons or 0:38:34.960 --> 0:38:35.800 quarks or something. 0:38:35.960 --> 0:38:38.840 Yeah, sure, you're not limited to atoms. You can imagine 0:38:38.920 --> 0:38:42.280 quantum clocks made out of like photons interacting or splitting 0:38:42.360 --> 0:38:45.760 or bouncing or something like that. In some sense, lego 0:38:46.000 --> 0:38:49.320 is a clock because it's measuring the time for photons 0:38:49.360 --> 0:38:52.680 to travel along its legs, right, it's just converting that 0:38:52.760 --> 0:38:55.440 to a distance measurement. And so you could have other 0:38:55.520 --> 0:38:58.000 quantum clocks that are not based on atoms. Yes, And 0:38:58.040 --> 0:39:00.000 one day, when we discover dark matter, maybe we could 0:39:00.080 --> 0:39:01.640 build a clock out of dark. 0:39:01.440 --> 0:39:04.759 Matter, which may or may not tell you the time. 0:39:05.120 --> 0:39:07.120 And may or may not smell like flatulence. 0:39:07.320 --> 0:39:09.000 Well, I guess maybe give us an example of, like 0:39:09.040 --> 0:39:12.800 what's a typical or popular or a commonly used quantum 0:39:12.800 --> 0:39:13.879 clock and how does it work. 0:39:14.160 --> 0:39:16.920 Well, the most precise quantum clock is based on the 0:39:16.920 --> 0:39:20.080 caesium one thirty three atom. That's the one that's actually 0:39:20.120 --> 0:39:23.360 used to define what a second is. And so here 0:39:23.400 --> 0:39:26.400 we have two states of electrons. There's a small splitting 0:39:26.440 --> 0:39:28.840 in an energy in state here. It's called a hyper 0:39:28.880 --> 0:39:31.640 fine splitting because the difference is very very small, and 0:39:31.680 --> 0:39:33.439 when the electron sits in there, it sort of goes 0:39:33.480 --> 0:39:36.320 back and forth between the two different states. 0:39:36.120 --> 0:39:39.400 Meaning like, this is an electron that's orbiting around the 0:39:39.440 --> 0:39:40.240 caesium atom. 0:39:40.480 --> 0:39:42.520 Yeah, I wouldn't say orbiting if we want to be 0:39:42.560 --> 0:39:45.360 really really technical, But it's captured by the caesium atom. 0:39:45.560 --> 0:39:47.840 And you're saying it's switching energy levels. Why would it 0:39:47.840 --> 0:39:48.880 switch energy levels? 0:39:49.080 --> 0:39:51.279 So you have this caesium atom and you embed the 0:39:51.280 --> 0:39:53.839 whole thing in some microwave radiation that can lift those 0:39:53.880 --> 0:39:56.799 electrons up from the lower state to the higher. 0:39:56.480 --> 0:39:58.600 State, meaning you like put it in a microwave or 0:39:58.680 --> 0:40:00.600 you shoot it with it like a light gun. 0:40:01.560 --> 0:40:03.799 There's not a difference, right, that's what a microwave is. 0:40:03.840 --> 0:40:06.960 A microwave is shooting microwave radiation at your food, and 0:40:07.080 --> 0:40:10.640 microwaves are lights. Though basically a microwave is a light gun. 0:40:10.880 --> 0:40:13.240 Sounds hot. So then you have this atom and you 0:40:13.239 --> 0:40:14.280 you stick it in the microwave. 0:40:14.320 --> 0:40:16.640 Uh huh, yeah, So you stick in the microwave and 0:40:16.719 --> 0:40:18.839 you measure how often it jumps up and then down 0:40:18.920 --> 0:40:19.840 and then up and then. 0:40:19.719 --> 0:40:23.000 Down because the light, as the light passes through it, 0:40:23.000 --> 0:40:25.319 it knocks the electron up and down or what. 0:40:25.560 --> 0:40:28.319 Yeah, the light is tuned to exactly the frequency for 0:40:28.360 --> 0:40:31.680 the electron to jump up into the higher energy level. Remember, 0:40:31.719 --> 0:40:33.920 electrons can go from a lower to a higher energy 0:40:33.960 --> 0:40:36.520 level if a photon of the right energy comes along. 0:40:36.880 --> 0:40:40.320 So they've tuned this microwave to exactly that energy level. 0:40:40.520 --> 0:40:43.320 So electrons and the lower level can absorb these photons 0:40:43.400 --> 0:40:45.640 jump up to the higher level. But then they'll naturally 0:40:45.680 --> 0:40:49.120 decay down because the universe likes to spread energy out 0:40:49.320 --> 0:40:51.880 and so the time of these oscillations turns out to 0:40:51.920 --> 0:40:55.000 be very very regular, Like an electron will do this 0:40:55.239 --> 0:40:58.840 nine point one nine two billion times per second. 0:40:59.000 --> 0:41:01.359 And it doesn't depend on the frequency of the light, 0:41:01.480 --> 0:41:01.879 or it does. 0:41:02.000 --> 0:41:03.920 It definitely depends on the frequency of the light. If 0:41:03.920 --> 0:41:06.239 the frequency of the light is not correct, then it 0:41:06.239 --> 0:41:08.080 won't even absorb it, right, it won't happen. 0:41:08.360 --> 0:41:11.080 Oh, but then don't you need to make that frequency 0:41:11.239 --> 0:41:11.960 super precise? 0:41:12.120 --> 0:41:14.600 Yeah, exactly, And this is one source of uncertainty in 0:41:14.640 --> 0:41:18.000 these clocks, right, making those accurate. And you can measure 0:41:18.000 --> 0:41:20.200 these things, like you build two independent ones, you can 0:41:20.239 --> 0:41:23.279 see how their counts drift relative to each other. And 0:41:23.680 --> 0:41:26.000 that's how you measure the accuracy of clocks. In general. 0:41:26.040 --> 0:41:28.279 There's no absolute standard by which you can tell like, oh, 0:41:28.280 --> 0:41:30.120 this clock is off or that clock is off. You 0:41:30.239 --> 0:41:31.719 just build a few of them and you measure them 0:41:31.760 --> 0:41:34.160 relative to each other. And this is something that we 0:41:34.280 --> 0:41:36.520 know well enough. We know how to design the mean 0:41:36.640 --> 0:41:39.120 of the physics and the engineering that you can build 0:41:39.120 --> 0:41:43.160 these things so that atomic clocks in independent locations agree 0:41:43.520 --> 0:41:46.879 to zero point three nanoseconds per day. It's really very 0:41:46.880 --> 0:41:47.880 incredibly precise. 0:41:48.320 --> 0:41:51.000 WHOA, so what are you measuring? How are you measuring 0:41:51.040 --> 0:41:53.000 whether these electrons are going up and down? 0:41:53.080 --> 0:41:55.919 When the electron goes back down. It emits radiation, right, 0:41:55.960 --> 0:41:57.920 and so you can gather that as well. 0:41:57.880 --> 0:41:59.960 Like it shoots off light like an a blink. 0:41:59.680 --> 0:42:01.800 Basically exactly little flash. 0:42:01.920 --> 0:42:04.040 All right. So then, and you're saying you can build 0:42:04.160 --> 0:42:06.520 these things now to be the size of a toaster 0:42:07.080 --> 0:42:09.160 or a microwave oven. 0:42:09.760 --> 0:42:12.760 A quantum toaster. They have them now and they've deployed 0:42:12.800 --> 0:42:15.480 them out in space. They actually built the Deep Space 0:42:15.560 --> 0:42:18.359 Atomic Clock Mission and they sent an atomic clock out 0:42:18.400 --> 0:42:20.759 into space to see, like, hey, can we operate one 0:42:20.840 --> 0:42:23.080 of these things out in space? And you might wonder 0:42:23.120 --> 0:42:25.319 like is this just a bunch of nerds trying to 0:42:25.360 --> 0:42:29.160 do something that seems cool? Yes, is always the answer. 0:42:28.920 --> 0:42:31.879 Like can we shoot a microwave into space and will 0:42:31.880 --> 0:42:35.319 it still heat up my burrito? My season Burritoah? Is 0:42:35.320 --> 0:42:35.960 that the challenge? 0:42:35.960 --> 0:42:38.160 That's the challenge. But also if we want to do 0:42:38.280 --> 0:42:42.120 things like navigate in space, navigation needs timing. You need 0:42:42.160 --> 0:42:44.480 to know like how long you're going in one direction. 0:42:44.719 --> 0:42:46.319 If you want to do dead reckoning, you want to 0:42:46.360 --> 0:42:49.480 know where you are. Timing is absolutely crucial. Or if 0:42:49.480 --> 0:42:53.200 you want to use like nearby pulsars to triangulate your position, 0:42:53.440 --> 0:42:55.799 I have whole episode about how that works. You also 0:42:55.880 --> 0:42:58.319 need very accurate timing so you can measure the time 0:42:58.360 --> 0:43:01.400 between the pulses. So this was like a technological challenge 0:43:01.440 --> 0:43:03.840 that's going to lay the groundwork for all sorts of 0:43:03.840 --> 0:43:06.919 cool innovations, and this was totally successful in this deep 0:43:06.960 --> 0:43:08.360 space atomic clock mission. 0:43:08.560 --> 0:43:11.000 Well, let's get into how you would actually use these 0:43:11.239 --> 0:43:14.759 and how the timing might tell you where dark matter 0:43:14.880 --> 0:43:18.760 is within our Solar system and maybe even within the Earth. 0:43:18.880 --> 0:43:21.320 So let's dig into that. But first, let's take another 0:43:21.360 --> 0:43:22.160 quick break. 0:43:26.200 --> 0:43:29.880 With the United Explorer Card. Earn fifty thousand bonus miles, 0:43:30.040 --> 0:43:33.440 then head for places unseen and destinations unknown. 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We're talking about using a microwave stuck inside 0:46:53.400 --> 0:46:55.920 of a microwave to the tech dark matter so you 0:46:55.960 --> 0:46:59.120 can win a Tierra for being the prettiest scientist. 0:47:00.080 --> 0:47:02.600 Exactly does it take longer to heat up your burrito 0:47:02.680 --> 0:47:04.120 when there's dark matter around? 0:47:04.400 --> 0:47:06.799 So the idea is that you take these atomic or 0:47:07.080 --> 0:47:09.759 basically an atomic clock, which is a quantum clock. But 0:47:10.640 --> 0:47:13.480 it seems like the most popular ones use atoms, and 0:47:13.520 --> 0:47:15.560 so you shrink them down to the size of a 0:47:15.600 --> 0:47:17.560 toaster or microwave, and then you shoot them in space. 0:47:17.600 --> 0:47:19.680 And then how does that help you measure dark matter? 0:47:20.440 --> 0:47:22.400 Well, there were a bunch of physicists who thought, Okay, 0:47:22.440 --> 0:47:25.040 this is cool because now we not only have all 0:47:25.120 --> 0:47:28.319 some super precise atomic clocks, but now we have them 0:47:28.320 --> 0:47:30.960 spread out through the Solar system, like in principle the 0:47:30.960 --> 0:47:32.880 way we like scent devices near the Sun with a 0:47:32.920 --> 0:47:35.439 Parker solar probe. People are like, what if we built 0:47:35.480 --> 0:47:37.319 a bunch of these things and we spread them out 0:47:37.360 --> 0:47:39.640 in the Solar system? Could they give us a picture 0:47:39.680 --> 0:47:42.320 of where the dark matter is in the Solar system? 0:47:42.760 --> 0:47:46.040 If they operate differently when there's dark matter around, like 0:47:46.040 --> 0:47:48.880 if they're sensitive to the dark matter density, Like if 0:47:48.920 --> 0:47:52.319 your atomic clock gets off if it drifts when there's 0:47:52.360 --> 0:47:54.960 more or less dark matter around, than having a bunch 0:47:55.000 --> 0:47:57.760 of these atomic clocks spread out through the Solar system 0:47:57.880 --> 0:48:00.000 could give you a picture for where in the Solar 0:48:00.080 --> 0:48:01.359 System the dark matter is. 0:48:02.040 --> 0:48:05.160 But I guess what's the mechanism by which dark matter 0:48:05.200 --> 0:48:07.520 would affect the timing of these clocks. 0:48:07.719 --> 0:48:10.600 Yeah, so mostly it wouldn't For many theories of dark matter. 0:48:10.680 --> 0:48:13.880 Dark matter is just some whimp. It's a massive particle 0:48:13.920 --> 0:48:17.120 that only interacts gravitationally, and so it has essentially no 0:48:17.239 --> 0:48:20.960 effect on these clocks except for gravitational time dilation. We 0:48:21.040 --> 0:48:23.759 know the areas with greater mass have more curvature, and 0:48:23.840 --> 0:48:26.440 a curvature causes time dilation, but that would be very, 0:48:26.520 --> 0:48:29.200 very difficult to measure even with these quantum clocks. 0:48:29.239 --> 0:48:30.800 But wait, why would it be difficult. 0:48:30.880 --> 0:48:33.880 You can measure gravitational time dilation with quantum clocks, and 0:48:33.880 --> 0:48:36.040 we've done that. You can do it on the surface 0:48:36.040 --> 0:48:37.960 of the Earth, for example, and you can put a 0:48:38.040 --> 0:48:41.040 quantum clock one meter above another one and you can 0:48:41.120 --> 0:48:43.680 see the difference between them because one of them is 0:48:43.760 --> 0:48:46.840 deeper in the curvature than the other. Super duper awesome, 0:48:47.080 --> 0:48:49.120 but that's because the Earth has a huge amount of 0:48:49.120 --> 0:48:52.880 gravity and this significant curvature. Here. Dark matter doesn't contribute 0:48:52.880 --> 0:48:56.600 significantly to the curvature because it's pretty spread out. And 0:48:56.719 --> 0:48:59.560 we would already know if dark matter wasn't pretty spread out, 0:48:59.680 --> 0:49:02.239 because we would have seen deviations and like Jupiter's orbit 0:49:02.320 --> 0:49:05.000 and whatever. So in principle you can, but we don't 0:49:05.040 --> 0:49:06.719 think it's going to be very sensitive. If you had 0:49:06.760 --> 0:49:09.160 a lot of quantum clocks and there were much more sensitive, 0:49:09.320 --> 0:49:12.879 then you could probably detect dark matter local density variations 0:49:13.160 --> 0:49:14.120 using that principle. 0:49:14.320 --> 0:49:18.520 Meaning these clocks would tick at a different frequency depending 0:49:18.680 --> 0:49:21.920 on how close it was to big sources of mass 0:49:22.040 --> 0:49:24.640 or even light sources of mass, because that's just how 0:49:24.719 --> 0:49:25.560 relativity works. 0:49:25.680 --> 0:49:27.920 Yeah, that's how relativity works. Remember, in relativity, it is 0:49:27.960 --> 0:49:30.840 two kinds of time dilation. One is based on speed. 0:49:30.840 --> 0:49:33.279 If you see a clock moving quickly, then you see 0:49:33.280 --> 0:49:36.719 it ticking slowly, and that's very confusing because it's relative, 0:49:36.760 --> 0:49:39.160 and so it depends on two observers. But there's another 0:49:39.280 --> 0:49:42.759 kind of time dilation, gravitational, which is absolute. It just 0:49:42.800 --> 0:49:46.280 says anybody in curature their clock is going to tick slowly, 0:49:46.480 --> 0:49:48.360 no matter who's looking at it, and everybody's going to 0:49:48.440 --> 0:49:51.359 agree about whose clock is ticking slowly. So that's very 0:49:51.400 --> 0:49:54.520 powerful and that's something you can use to measure just 0:49:54.600 --> 0:49:57.680 like how much stuff is there in general, because clocks 0:49:57.680 --> 0:50:01.080 tick slower near stuff. Really kind of awesome feature of. 0:50:01.040 --> 0:50:03.120 The universe, meaning like if I had two of these 0:50:03.120 --> 0:50:05.000 atomic clocks and one of them is out there in 0:50:05.000 --> 0:50:07.400 the middle of empty space, and the other one is 0:50:07.480 --> 0:50:09.520 near a big blob of dark matter. The one near 0:50:09.560 --> 0:50:13.080 the blob of dark matter would take slower. 0:50:12.800 --> 0:50:14.560 Right, Yeah, that's exactly right. 0:50:14.600 --> 0:50:16.719 And so you might like start them out in the 0:50:16.760 --> 0:50:20.480 same spot. But then after being for a while and 0:50:20.480 --> 0:50:22.360 two different spots, one near the dark matter, and you 0:50:22.400 --> 0:50:24.080 brun them back, you would see that one of them 0:50:24.600 --> 0:50:26.040 take more ticks than the other. 0:50:26.239 --> 0:50:28.719 Yeah. And so now imagine like a grid, you have 0:50:28.760 --> 0:50:32.239 a quantum clock every ten meters in the solar system, right, 0:50:32.320 --> 0:50:34.000 you start them all out at the same time, and 0:50:34.000 --> 0:50:36.200 then you monitor it, and by measuring the difference in 0:50:36.239 --> 0:50:39.160 that number of ticks after a year on your reference clock, 0:50:39.200 --> 0:50:41.399 the one that's hanging out with you, you can tell 0:50:41.440 --> 0:50:43.799 where stuff is in the solar system. 0:50:43.680 --> 0:50:47.440 Like which spots in the solar system have slower time. 0:50:47.280 --> 0:50:51.120 Yes, exactly, because slower time means more matter, more curvature, 0:50:51.239 --> 0:50:52.200 more energy density. 0:50:52.239 --> 0:50:54.600 Really, I guess, on top of what you already know 0:50:54.719 --> 0:50:57.839 about the Solar system right like right now, even if 0:50:57.880 --> 0:51:01.000 we didn't have dark matter, a clock near the Sun 0:51:01.040 --> 0:51:03.120 would takes lower than a clock here exactly. 0:51:03.320 --> 0:51:05.640 And we've done some basic version of this, as I 0:51:05.680 --> 0:51:08.919 said earlier, if a few clocks on Earth at different altitudes. 0:51:09.360 --> 0:51:11.560 Those are different distances from the matter of the Earth, 0:51:11.600 --> 0:51:14.840 and the ones closer do ticks more slowly, And satellites 0:51:14.960 --> 0:51:18.440 up in space their clocks tick faster than atomic clocks 0:51:18.440 --> 0:51:19.680 here on the surface of the Earth, And you've got 0:51:19.719 --> 0:51:22.560 to take that new account famously when you're doing GPS, 0:51:22.600 --> 0:51:23.040 et cetera. 0:51:23.239 --> 0:51:26.360 But you're saying, we're not going to be using this effect, 0:51:26.560 --> 0:51:29.799 this time dilation from relativity to measure dark matter. Dark 0:51:29.840 --> 0:51:30.960 matter is just too weak. 0:51:31.120 --> 0:51:32.759 Dark matter is too weak, and we think it's not 0:51:32.880 --> 0:51:34.960 cluppy enough to really detect that, though it would be 0:51:35.000 --> 0:51:38.320 super awesome. There's a special kind of dark matter which 0:51:38.520 --> 0:51:41.480 might give much larger effects, which would be much easier 0:51:41.520 --> 0:51:44.880 to discover. And this is a theory called fuzzy dark matter. 0:51:45.280 --> 0:51:50.080 Sounds fuzzy. But wait, so you're saying, like this idea 0:51:50.080 --> 0:51:53.120 of using atomic clocks to measure dark matter would only 0:51:53.160 --> 0:51:59.800 work for a certain theoretical meaning guessie type of dark matter, 0:52:00.000 --> 0:52:01.880 which we don't know whether it's true or not, or 0:52:01.920 --> 0:52:02.440 exist or not. 0:52:02.560 --> 0:52:03.000 Mm hmmm. 0:52:03.239 --> 0:52:06.600 So this is a huge sources in white scheme that 0:52:07.480 --> 0:52:08.879 you don't really know if it's going to work. 0:52:08.960 --> 0:52:10.879 You know, you were talking about nomenclature and now you're 0:52:10.920 --> 0:52:13.680 using the words guess and scheme, you know, really kind 0:52:13.680 --> 0:52:15.920 of undermine the credibility of science. But you know, this 0:52:16.120 --> 0:52:18.359 is good faith stuff. This is like, hey, what if 0:52:18.400 --> 0:52:21.319 dark matter is this other weird particular thing, how could 0:52:21.320 --> 0:52:23.239 we see that? And yet it'd be best if we 0:52:23.280 --> 0:52:25.960 had experiments which could detect any kind of dark matter, 0:52:26.080 --> 0:52:27.839 But you know, there might be kinds of dark matter 0:52:27.880 --> 0:52:30.400 which we could only detect in certain ways or easier 0:52:30.440 --> 0:52:32.239 to spot in some ways. And so it's good to 0:52:32.239 --> 0:52:35.200 be creative and think about how we could detect specific 0:52:35.360 --> 0:52:37.640 kinds of dark matter as well, even though we don't 0:52:37.680 --> 0:52:40.160 know what dark matter is. And if this theory is at. 0:52:40.040 --> 0:52:42.880 All correct, well, I'm just trying to understand the scheme. 0:52:45.080 --> 0:52:47.279 So are you saying there's a theoretical kind of dark 0:52:47.320 --> 0:52:49.359 matter called fuzzy dark matter? So what is it? 0:52:49.400 --> 0:52:49.520 So? 0:52:49.640 --> 0:52:53.400 Fuzzy dark matter suggests that maybe dark matter isn't very massive, 0:52:53.800 --> 0:52:56.279 like some people suggest that dark matter could be like 0:52:56.320 --> 0:52:58.920 one hundred GeV like the mass of a w or 0:52:58.960 --> 0:53:01.640 a z boson, like one hundred times the mass of 0:53:01.640 --> 0:53:05.040 a proton, a pretty hefty particle, almost as massive as 0:53:05.040 --> 0:53:08.040 a Higgs. That's sort of the classic strategy, and there's 0:53:08.080 --> 0:53:10.960 reasons for that. There's something called the Wimp miracle. Check 0:53:11.000 --> 0:53:14.239 on our podcast about that, which argues strongly that dark 0:53:14.280 --> 0:53:16.839 matter should be around one hundred gv based on how 0:53:16.920 --> 0:53:19.200 much of it there is in the universe. But people 0:53:19.200 --> 0:53:20.719 are like, well, maybe that's all wrong, and there's an 0:53:20.760 --> 0:53:23.240 assumption there that's wrong. What if dark matter is super 0:53:23.360 --> 0:53:26.759 duper light, like a trilliance the mass of an electron. 0:53:26.960 --> 0:53:30.320 So now there's an enormous number of these dark matter particles, 0:53:30.360 --> 0:53:33.000 so many more than you could even imagine, because you 0:53:33.040 --> 0:53:35.799 have to somehow make like a big fraction of the 0:53:35.800 --> 0:53:38.600 mass of the universe out of particles that are a 0:53:38.640 --> 0:53:41.319 tiny fraction in the mass of the electron, which is 0:53:41.360 --> 0:53:42.680 already very very light. 0:53:42.880 --> 0:53:45.040 Well, first of all, I think this whole podcast is 0:53:45.080 --> 0:53:49.000 a Wimp miracle, Daniel. But I think you're saying, like 0:53:49.239 --> 0:53:52.360 this version of dark matter, instead of being maybe marble 0:53:52.440 --> 0:53:56.160 sized particles, they're like super tiny BB sized particles, And 0:53:56.239 --> 0:53:57.480 some of that makes it fuzzier. 0:53:57.600 --> 0:53:59.759 Yeah, it makes it fuzzier because if they're very very 0:53:59.760 --> 0:54:03.480 low mass, then their wavelengths are more spread out. Some 0:54:03.520 --> 0:54:05.720 of these things can have a wavelength like the size 0:54:05.760 --> 0:54:06.480 of the galaxy. 0:54:06.760 --> 0:54:07.759 What do you mean a wavelength. 0:54:07.960 --> 0:54:10.400 The wavelength of a particle is like the distance on 0:54:10.440 --> 0:54:14.239 which these quantum interference effects appear, and so you can 0:54:14.280 --> 0:54:17.520 calculate this quantity. It's called the Debrogely wavelength. You'll see 0:54:17.560 --> 0:54:21.160 wave like effects for a particle when you interact over 0:54:21.200 --> 0:54:24.320 these kinds of distances, and that's the wavelength of a particle. 0:54:24.120 --> 0:54:25.560 Meaning sort of like the size of it. 0:54:25.680 --> 0:54:27.880 Kind of right, sort of, Yeah, it's when it stops 0:54:27.880 --> 0:54:30.560 acting like a blob like a particle and starts acting 0:54:30.600 --> 0:54:34.080 more like a wave. Things that have wavelike behaviors. Really 0:54:34.120 --> 0:54:36.120 it's always acting like a wave. It's just that when 0:54:36.120 --> 0:54:38.880 you zoom out you can approximate it as a particle. 0:54:38.560 --> 0:54:41.359 Because they have low mass. What's the relationship between having 0:54:41.360 --> 0:54:43.960 low mass and being having big wavelengths. 0:54:44.200 --> 0:54:46.800 Well, the wavelength depends on your momentum and your mass. 0:54:47.000 --> 0:54:50.719 So lower mass just means a larger wavelength because it's 0:54:50.760 --> 0:54:53.600 really like a ratio between the momentum and the mass. 0:54:53.640 --> 0:54:55.759 When things have a lot of kinetic energy relative to 0:54:55.760 --> 0:54:58.480 their mass, they act more like light because light is 0:54:58.560 --> 0:55:01.960 pure kinetic energy. Have very small amounts of energy relative 0:55:02.000 --> 0:55:04.600 to their mass their stationary so they act more like 0:55:04.760 --> 0:55:07.600 bits of sand like particles. And so it's just sort 0:55:07.640 --> 0:55:10.760 of a rough way to understand where that transition happens. 0:55:11.040 --> 0:55:13.040 Okay, so then if dark matter is this kind of 0:55:13.040 --> 0:55:15.920 fuzzy kind of dark matter, you're saying that each particle 0:55:15.920 --> 0:55:18.839 would be super super light, and it would also have 0:55:19.080 --> 0:55:22.560 huge variations in their size. That's what you mean by fuzzy. 0:55:22.600 --> 0:55:24.520 It's like they might be some of them might be 0:55:24.600 --> 0:55:26.240 super big and somewhere might be super small. 0:55:26.520 --> 0:55:29.000 Yeah, well, the wavelengths could be very very large, which 0:55:29.040 --> 0:55:31.879 means they can interact over long distances. The fascinating thing 0:55:32.000 --> 0:55:34.800 is that in simulations of this dark matter, it predicts 0:55:35.080 --> 0:55:37.880 like a mini halo of dark matter in our Solar system, 0:55:37.960 --> 0:55:40.719 essentially that this stuff would be clumped up in and 0:55:41.040 --> 0:55:43.520 near the Sun. That most of the dark matter in 0:55:43.560 --> 0:55:46.839 the Solar System might be like clumped up near the Sun. 0:55:46.920 --> 0:55:48.720 It might be like hiding in the Sun. 0:55:49.320 --> 0:55:51.359 And if it wasn't this kind of fuzzy dark matter, 0:55:51.400 --> 0:55:51.960 it wouldn't. 0:55:52.200 --> 0:55:54.479 Now, this kind of fuzzy dark matter is the kind 0:55:54.520 --> 0:55:57.280 we think would clump up like a halo near the Sun. 0:55:57.400 --> 0:55:58.480 And the other kinds wouldn't. 0:55:58.520 --> 0:56:01.000 Yeah, the other kinds wouldn't. As I mean, I've heard 0:56:01.040 --> 0:56:03.560 of other theories of dark matter clumping in the Sun. 0:56:03.600 --> 0:56:06.840 There's all sorts of theories, but this particular one tends 0:56:06.840 --> 0:56:09.680 to make a halo near the Sun and would affect 0:56:09.719 --> 0:56:13.080 the operation of quantum clocks because of its special fuzziness. 0:56:13.200 --> 0:56:16.600 It can also slightly interact with electrons through sort of 0:56:16.600 --> 0:56:19.200 like a back door in quantum mechanics, which would change 0:56:19.200 --> 0:56:21.760 the way a quantum clock operates. It's like it changes 0:56:21.800 --> 0:56:25.320 the electrons' mass and how it responds to photons because 0:56:25.320 --> 0:56:29.160 of oscillations in this fuzzy dark matter field, and so 0:56:29.280 --> 0:56:32.839 effectively it changes the frequency of these clocks. And so 0:56:32.920 --> 0:56:35.960 you can detect in principle whether you're near a dense 0:56:36.040 --> 0:56:39.239 blob of this ultra light dark matter by looking at 0:56:39.280 --> 0:56:42.160 a quantum clock and counting its ticks very carefully. And 0:56:42.200 --> 0:56:44.120 this would be a bigger effect than the effect we 0:56:44.400 --> 0:56:46.600 talked about earlier, the gravitational curvature. 0:56:46.719 --> 0:56:49.320 But I thought that dark matter couldn't interact with regular 0:56:49.360 --> 0:56:51.920 matter only through it could only do it through gravity. 0:56:52.000 --> 0:56:54.400 Yeah, it could only do it through gravity in general, 0:56:54.440 --> 0:56:56.680 But this one takes a back door through the Higgs field. 0:56:57.000 --> 0:56:59.200 It like interacts with the Higgs field and it changes 0:56:59.239 --> 0:57:01.880 how the Higgs field works. And so near the presence 0:57:01.920 --> 0:57:04.600 of this ultra light dark matter, electrons effectively have a 0:57:04.600 --> 0:57:05.440 different mass. 0:57:06.440 --> 0:57:08.680 But I guess if that was true, wouldn't we see 0:57:08.920 --> 0:57:11.840 it affect regular matter on a larger scale. 0:57:11.880 --> 0:57:13.760 You would see it happen, but it's a subtle effect, 0:57:13.960 --> 0:57:16.000 and so you need to be near a dense clump 0:57:16.080 --> 0:57:18.920 of it. So the idea is, take something that's very 0:57:19.000 --> 0:57:21.560 very sensitive to the electron mass, like a quantum clock, 0:57:21.720 --> 0:57:23.760 and try to put it near a dense clump of 0:57:23.800 --> 0:57:26.800 this special ultra light dark matter, maybe near the Sun. 0:57:27.400 --> 0:57:29.240 So that's the idea is, like launch a bunch of 0:57:29.320 --> 0:57:31.919 quantum clocks, have them orbit near the Sun, and look 0:57:31.960 --> 0:57:35.160 for deviations in their timekeeping and see if that's evidence 0:57:35.280 --> 0:57:38.560 for ultra light dark matter interfering with the masses of 0:57:38.560 --> 0:57:40.520 the electrons in these quantum clocks. 0:57:40.640 --> 0:57:42.520 We mean that you would maybe like throw a bunch 0:57:42.600 --> 0:57:45.360 of the sun, have them kind of form a half 0:57:45.480 --> 0:57:48.320 ring around the Sun to see if time changes there, 0:57:48.520 --> 0:57:50.640 sort of like a giant tirra. 0:57:50.880 --> 0:57:53.960 Like a giant tr a quantum cosmic tiara. 0:57:54.160 --> 0:57:56.200 All right, but I guess which one would you be proving. 0:57:56.240 --> 0:57:59.240 Would you be proving that dark matter is fuzzy or 0:57:59.320 --> 0:58:02.320 would you be proved that it's there? Or are they 0:58:02.320 --> 0:58:02.960 both related? 0:58:03.160 --> 0:58:04.000 They're both related. 0:58:04.040 --> 0:58:04.200 Though. 0:58:04.280 --> 0:58:06.560 You know, if we saw this thing, there would instantly 0:58:06.600 --> 0:58:09.360 be like fifty other theories to explain it as well. 0:58:09.640 --> 0:58:12.320 It probably wouldn't be a unique prediction of this kind 0:58:12.360 --> 0:58:14.960 of dark matter. Theories are very very clever people, and 0:58:14.960 --> 0:58:17.240 they'll always come up with another way to explain the 0:58:17.320 --> 0:58:20.120 data that we're seeing. But it's cool because it's a 0:58:20.120 --> 0:58:22.480 prediction that this theory makes and we go out and 0:58:22.520 --> 0:58:24.920 we see it. That's really fascinating, and then we can 0:58:24.960 --> 0:58:27.440 think about ways to distinguish all the different ideas that 0:58:27.520 --> 0:58:30.880 might also explain this kind of observation. It would just 0:58:30.880 --> 0:58:33.360 be cool to see something different. Currently, all of our 0:58:33.440 --> 0:58:37.120 dark matter experiments basically see nothing. It would be cool 0:58:37.160 --> 0:58:38.400 to have a signal somewhere. 0:58:39.280 --> 0:58:41.040 So you're thinking, hey, let's put up a bunch of 0:58:41.040 --> 0:58:43.880 microways in space and see if at sticks exactly. 0:58:43.960 --> 0:58:45.880 Let's see if one burrito is a little bit colder 0:58:45.880 --> 0:58:46.360 than another. 0:58:46.680 --> 0:58:49.360 All right, Well, an interesting idea for how we could 0:58:49.360 --> 0:58:54.200 maybe possibly crack sort of a theoretical version of one 0:58:54.240 --> 0:58:55.960 of the biggest mysteries in the universe. 0:58:56.160 --> 0:58:58.480 That's right. Physicists are being very creative and trying to 0:58:58.480 --> 0:59:00.840 come up with new theories of dark matter and new 0:59:00.880 --> 0:59:04.680 ways to discover them, including using super duper sets in 0:59:04.680 --> 0:59:08.240 and quantum clocks distributed through the solar system, which also 0:59:08.400 --> 0:59:09.400 would just be fun to do. 0:59:09.720 --> 0:59:11.520 You just want to parade, Daniel, I. 0:59:11.480 --> 0:59:14.200 Just want a tiara? Is that too much to ask? 0:59:16.200 --> 0:59:17.760 How about we just buy you a tiara? 0:59:18.200 --> 0:59:20.040 Is it made of dark matter? Are you using your bitcoin? 0:59:20.200 --> 0:59:22.120 It can be, but in any way that you want. 0:59:23.120 --> 0:59:26.360 But if it saves tax dollars billions of dollars, you know, 0:59:26.400 --> 0:59:27.600 it would be a pretty good investment. 0:59:27.680 --> 0:59:29.840 Yeah, there we go. That was my scheme the whole time. 0:59:30.000 --> 0:59:33.280 Yeah, to get us to buy you a tiara without 0:59:33.280 --> 0:59:35.080 actually having to run in a beauty contest. 0:59:36.520 --> 0:59:37.160 I'm busted. 0:59:38.240 --> 0:59:42.120 Well, you are the most beautiful podcaster with a show 0:59:42.160 --> 0:59:44.960 called Daniel Jorge is playing the universe. So whose name 0:59:45.000 --> 0:59:45.600 is Daniels? 0:59:45.760 --> 0:59:47.920 I'll take very highly qualified compliments, thank you. 0:59:49.280 --> 0:59:53.320 It's a very specific tiara based on a very theoretical 0:59:54.040 --> 0:59:55.320 model of the. 0:59:55.320 --> 0:59:57.040 Universe fuzzy compliments from Warhead. 0:59:57.240 --> 0:59:59.320 All right, well, we hope you enjoyed that. Thanks for 0:59:59.400 --> 1:00:01.400 joining us. 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