WEBVTT - Can Dark Matter feel itself 0:00:09.480 --> 0:00:12.680 Hey, Daniel, what's the best question anyone has ever asked 0:00:12.680 --> 0:00:15.480 you about dark matter? Well, it's tough to pick. There's 0:00:15.520 --> 0:00:17.960 so many good ones. But I remember a nine year 0:00:18.000 --> 0:00:19.959 old who read our book once and emailed me to 0:00:20.000 --> 0:00:24.200 ask is dark matter bad matter? It must be a 0:00:24.200 --> 0:00:27.200 Star Wars fan. You know the dark side doesn't sound 0:00:27.280 --> 0:00:31.080 very friendly. Yeah, dark matter sounds world of unfriendly and mean. 0:00:31.160 --> 0:00:33.680 It's doesn't never a really good pr team. Well, you know, 0:00:33.800 --> 0:00:36.440 if there are dark matter physicists out there that we 0:00:36.520 --> 0:00:39.120 can't see or touch, what do you think they would 0:00:39.120 --> 0:00:42.200 call us? M I guess they'll probably call us dork matter. 0:00:42.960 --> 0:00:46.280 We wouldn't seem dark to them and insidious. No, actually 0:00:46.320 --> 0:00:48.800 we would. I mean if they have their own dark photons, 0:00:48.840 --> 0:00:52.080 they wouldn't see ours, so we would be dark to them. Man, 0:00:52.320 --> 0:00:54.520 I can just imagine the conferences. You know, you just 0:00:54.560 --> 0:00:56.520 spent the whole day saying you're a dark matter. No, 0:00:56.640 --> 0:00:59.240 you're a dark matter. That's probably actually true. That's exactly 0:00:59.320 --> 0:01:17.320 what would happen. I am, forhand, a cartoonist and the 0:01:17.440 --> 0:01:20.560 creator of PhD comments. Hi, I'm Daniel Whitson, I'm a 0:01:20.560 --> 0:01:24.560 particle physicist, and I'm mostly made out of dork particles. Particles, 0:01:26.520 --> 0:01:30.399 dark dork particles. That's the worst. Well, mostly in the 0:01:30.400 --> 0:01:32.640 summer right now. I'm not going outside very much, so 0:01:33.400 --> 0:01:35.840 pale dark. My dork particles are not very dark. But 0:01:35.920 --> 0:01:38.680 welcome to our podcast Daniel and Jorge Explain the Universe, 0:01:38.720 --> 0:01:41.400 a production of I Heart Radio, in which we take 0:01:41.440 --> 0:01:44.280 you on a mental tour of the universe, zooming down 0:01:44.319 --> 0:01:46.120 to see what the universe is made out of, what 0:01:46.160 --> 0:01:49.800 it looks like at its largest scale, what crazy weird 0:01:49.840 --> 0:01:52.240 stuff we encounter in it, and how we can all 0:01:52.360 --> 0:01:55.440 understand it because humanity is on a journey, a journey 0:01:55.480 --> 0:01:59.040 to understand this universe. We started out really kind of 0:01:59.040 --> 0:02:01.560 clueless about the way things work, and we slowly put 0:02:01.600 --> 0:02:04.280 together little pieces of the picture. But we're here to 0:02:04.320 --> 0:02:06.080 give you a tour of what we have figured out 0:02:06.120 --> 0:02:08.880 and what still remains unknown. Yeah, and it turns out 0:02:08.919 --> 0:02:11.720 we haven't even left the garage, it seems, Daniel, in 0:02:11.720 --> 0:02:15.040 our journey of discovery, because a huge percentage of the 0:02:15.160 --> 0:02:17.440 universe is made out of stuff that we have no 0:02:17.520 --> 0:02:20.639 idea about. You know, twenty five percent of the universe 0:02:20.760 --> 0:02:23.680 is made out of something we call dark matter, which 0:02:24.320 --> 0:02:26.120 is a huge mystery. Right, that's right, And that might 0:02:26.160 --> 0:02:28.560 seem a bit deflating to you, like, wow, we haven't 0:02:28.560 --> 0:02:31.760 figured anything out, But to me that's exciting, Like, wow, 0:02:31.840 --> 0:02:35.839 we haven't figured anything out, which means more discoveries are 0:02:35.880 --> 0:02:39.000 to come, which means mind blowing revelations about the true 0:02:39.040 --> 0:02:41.720 nature of the universe are in our future. You know, 0:02:41.760 --> 0:02:43.400 if you haven't left the garage, that means you can 0:02:43.400 --> 0:02:46.520 still go back inside. If you forget something that's positive, 0:02:46.639 --> 0:02:48.720 that's right, Like you forgot to pack your banana. How 0:02:48.720 --> 0:02:51.400 can you even take a journey of discovery without banana? 0:02:52.200 --> 0:02:55.839 About these days, who can go anywhere? Yeah, we're talking 0:02:55.840 --> 0:02:58.280 about dark matter today and it's a huge mystery and 0:02:58.320 --> 0:03:00.840 it's out there. But a big question is what is 0:03:00.880 --> 0:03:03.359 it made out of? What is it? Is it a fluid, 0:03:03.600 --> 0:03:06.520 is it a an energy? Or is it made out 0:03:06.520 --> 0:03:09.959 of particles or something totally different. That's right, Everything we've 0:03:10.000 --> 0:03:13.280 ever experienced, everything you've ever eaten or touched or tasted, 0:03:13.360 --> 0:03:16.760 are made out of quarks and electrons and stuff like that, 0:03:17.040 --> 0:03:20.080 and so we wonder does the same thing hold for 0:03:20.200 --> 0:03:22.960 dark matter. But it's a pretty big extrapolation. I mean, 0:03:22.960 --> 0:03:24.919 the kind of matter that we're made out of that's 0:03:25.000 --> 0:03:28.320 very familiar, is unusual in the universe, and so it 0:03:28.320 --> 0:03:31.360 seems kind of odd to extrapolate from this tiny little 0:03:31.400 --> 0:03:35.080 corner to a huge fraction of the universe. And so 0:03:35.280 --> 0:03:37.760 particle physicists think maybe it's made of particles, but I 0:03:37.880 --> 0:03:40.640 like to think, hey, maybe it's made of something totally 0:03:40.680 --> 0:03:43.200 weird and new. Yeah, we really have no idea. And 0:03:43.240 --> 0:03:46.920 it's there's five times more dark matter in the universe 0:03:46.920 --> 0:03:49.640 than there is of the stuff that we are made 0:03:49.640 --> 0:03:51.560 out of. And it really could be anything like it 0:03:51.560 --> 0:03:54.000 could be something that's not even a particle. That's right, 0:03:54.000 --> 0:03:57.160 we've never seen matter that's not made of particles. Everything 0:03:57.200 --> 0:04:00.840 we've ever experienced can be broken down into these units. 0:04:00.880 --> 0:04:03.200 But that doesn't mean that everything is like that, Right. 0:04:03.520 --> 0:04:06.480 We have to be very careful about generalizing. We've seen 0:04:06.560 --> 0:04:10.000 so many times in physics when we've learned something we thought, oh, 0:04:10.000 --> 0:04:12.640 this must be the way everything works, and then we 0:04:12.720 --> 0:04:15.760 discover it's not. Actually and there are bigger stories, is 0:04:15.760 --> 0:04:18.640 a larger context, and that's the goal of science, is 0:04:18.720 --> 0:04:22.880 to reveal the actual truth, not just confirm our expectations. Yeah, 0:04:22.920 --> 0:04:25.320 and so one thing we know about dark matter is 0:04:25.360 --> 0:04:28.400 that we know that it feels gravity, because that's how 0:04:28.440 --> 0:04:30.560 we know that it's there. I mean, we can't see it, 0:04:30.560 --> 0:04:32.880 it's dark, but we know it's there because of gravity. 0:04:32.920 --> 0:04:36.440 It's keeping the gaxies together, it's pulling things together, and 0:04:36.440 --> 0:04:40.599 it's you know, affecting the trajectories of galaxies and stars. 0:04:41.520 --> 0:04:43.920 So we know it feels gravity. We certainly do. It's 0:04:43.960 --> 0:04:48.080 basically an invention to explain missing gravity. It's like a 0:04:48.120 --> 0:04:50.880 gravity fudge factor. Yeah. We see things in the universe 0:04:50.880 --> 0:04:53.480 that gravity has done, and we don't see the source 0:04:53.520 --> 0:04:56.920 of that gravity. We're like, what's this invisible thing that's 0:04:57.000 --> 0:05:00.160 making this gravity? And so dark matter is basically an 0:05:00.160 --> 0:05:03.960 explanation for this gravity that we do observe, and so 0:05:04.000 --> 0:05:06.279 it has to feel gravity otherwise it doesn't fit the 0:05:06.279 --> 0:05:09.200 bill at all. But then the question is what else 0:05:09.240 --> 0:05:11.479 does it do? Does it feel anything else? Does it 0:05:11.480 --> 0:05:14.479 feel lonely? Does it feel resentful that we call it 0:05:14.560 --> 0:05:18.160 dark matter? Yeah, we know that it feels gravity, and 0:05:18.200 --> 0:05:20.520 so the question is does it feel any other forces? 0:05:20.640 --> 0:05:24.160 And I think more interestingly about this question is does 0:05:24.200 --> 0:05:27.240 it feel itself like canna bump into itself? Yeah, And 0:05:27.240 --> 0:05:30.279 we got a really interesting question from a listener. Here's 0:05:30.279 --> 0:05:32.640 an email I god from Joe from China, who I 0:05:32.680 --> 0:05:35.679 think really put his finger on the question. He says, 0:05:35.960 --> 0:05:38.760 if you were to take two particles of dark matter 0:05:38.839 --> 0:05:41.360 and let them go in a vacuum, the gravity would 0:05:41.400 --> 0:05:44.640 attract the two particles together. But then would they pass 0:05:44.800 --> 0:05:47.680 right through each other and keep moving? Eventually would they 0:05:47.760 --> 0:05:50.000 settle down and be able to share the same point 0:05:50.040 --> 0:05:55.760 in space like overlapping? Can too dark matter particles? But 0:05:55.800 --> 0:05:59.119 I guess bump into each other or occupy the same space? Yeah? 0:05:59.240 --> 0:06:01.479 Do they not into each other and push back? Do 0:06:01.560 --> 0:06:03.520 they pass right through each other? Can they sit right 0:06:03.560 --> 0:06:06.279 on top of each other. It's a really fascinating question, 0:06:06.320 --> 0:06:07.640 and it goes right to the heart of the sort 0:06:07.680 --> 0:06:10.640 of the science matter of whether dark matter feels itself? 0:06:11.160 --> 0:06:13.120 This question blow your mind a little bit? Yeah, I 0:06:13.160 --> 0:06:14.800 did blow my mind a little bit. I just love 0:06:14.839 --> 0:06:17.280 when somebody asks a new question, a question I haven't 0:06:17.320 --> 0:06:20.120 heard before, or asks it in a new way. So 0:06:20.160 --> 0:06:23.839 I haven't really thought about whether dark matter feels itself? Okay, 0:06:23.880 --> 0:06:25.799 so it's kind of a funny question. Does dark matter 0:06:26.720 --> 0:06:30.680 feel itself? That means that you know it feels itself. Gravitationally, right, 0:06:31.080 --> 0:06:33.440 if you have one bit of dark matter here and 0:06:33.440 --> 0:06:35.120 a bit of dark matter, they're they're gonna be They're 0:06:35.120 --> 0:06:37.080 going to feel each other. They're gonna be attracted to 0:06:37.080 --> 0:06:39.960 each other by gravity. But the question is, you know 0:06:40.040 --> 0:06:43.400 what happens after they feel attracted by gravity. You know, 0:06:43.560 --> 0:06:46.520 they they're moving towards each other. Are they gonna bump 0:06:46.560 --> 0:06:49.240 against and and repel it themselves or are they going 0:06:49.279 --> 0:06:51.040 to pass through each other? Or are they going to 0:06:51.120 --> 0:06:53.560 stick together? Yeah, it's a great question. I mean, if 0:06:53.760 --> 0:06:55.960 you and I have gravitational attraction, if we were out 0:06:56.000 --> 0:06:58.640 in the middle of space, then gravity would very slowly 0:06:58.680 --> 0:07:00.640 pulls together and we would bump into each other. I 0:07:00.680 --> 0:07:04.000 wouldn't phase through each other. You woul get uncomfortable really fast. 0:07:04.120 --> 0:07:08.640 What you're saying more awkward than in space. No one 0:07:08.680 --> 0:07:11.280 can hear you say, hey, I need more space, Daniel, 0:07:11.320 --> 0:07:17.320 get off me. But you couldn't write. You'd be stuck together. 0:07:17.760 --> 0:07:20.000 That's right, we need some other kind of force. But 0:07:20.080 --> 0:07:21.960 you and I do have other kind of forces, right, 0:07:22.000 --> 0:07:24.520 the electromagnetic force who keep us from passing through each other. 0:07:24.760 --> 0:07:26.480 So it's a good way to ask the questions. Yeah, 0:07:26.680 --> 0:07:29.320 so the question is does dark matter feel itself? And so, 0:07:29.360 --> 0:07:31.960 as usual, we went out into the world, and in 0:07:31.960 --> 0:07:35.000 this case, the Internet, to see how many people felt 0:07:35.040 --> 0:07:37.400 that they knew the answer to this question. That's right, 0:07:37.440 --> 0:07:40.680 So thank you to everybody who volunteered to answer random 0:07:40.760 --> 0:07:44.400 Internet physics questions. If you'd like to volunteer right to 0:07:44.520 --> 0:07:47.600 us at questions at Daniel and Jorge dot com. Yeah, 0:07:47.640 --> 0:07:51.040 you can ask us questions or get questions from us. 0:07:51.760 --> 0:07:55.080 Questions in and questions out. It's an eternal flux of questions, right. 0:07:55.240 --> 0:07:56.720 But think about it for a second. If you were 0:07:56.760 --> 0:07:59.760 to try to answer the question does dark matter feel itself? 0:08:00.160 --> 0:08:03.160 What would you answer? And no googling, no googling? What? 0:08:03.200 --> 0:08:08.920 How about? Wikipedia? Also not allowed? About calling my physicist friend? 0:08:09.280 --> 0:08:12.920 Totally allowed, totally allowed. All right, Well, here's what people 0:08:13.000 --> 0:08:15.280 on the Internet had to say. I guess I'm really 0:08:15.320 --> 0:08:19.120 not sure. I know that some scientists hypothesize the dark 0:08:19.160 --> 0:08:22.080 matter is comprised of filaments, and if there were these 0:08:22.080 --> 0:08:24.640 filaments in the dark matter, one would think that they 0:08:24.960 --> 0:08:28.040 would interact in some way. I really don't think so. 0:08:28.400 --> 0:08:33.040 I remember it interacting with something visible. That's a good one. 0:08:33.160 --> 0:08:36.840 The interaction between light matter and dark matter is for 0:08:37.320 --> 0:08:39.600 obviously still figuring that out, but I would think that 0:08:39.640 --> 0:08:42.880 it does interact with itself. I don't think that turn 0:08:43.120 --> 0:08:47.359 dark matter interacts with itself. Um. I think whether discussed 0:08:47.360 --> 0:08:50.439 two galaxies colliding with each other, but there wasn't an 0:08:50.480 --> 0:08:56.240 evidence or the details, so not itself. I would guess 0:08:56.400 --> 0:09:00.320 that dark matter would interact with itself because I know 0:09:00.440 --> 0:09:04.160 that one guess of what dark matter is is the 0:09:04.600 --> 0:09:09.840 dark matter particle axion. And it's kind of hard to 0:09:10.040 --> 0:09:14.480 visualize how a particle can pass through another particle. I 0:09:14.520 --> 0:09:17.160 don't know. I've never thought about it. Okay, Um, dark 0:09:17.360 --> 0:09:20.680 matter and dark energy confuse me a little bit. I 0:09:20.760 --> 0:09:25.440 thought that dark matter was just a theory, and so 0:09:25.520 --> 0:09:28.800 it's like we've we've seen something out there, and the 0:09:28.800 --> 0:09:30.920 theory is that this dark matter, but we don't really know. 0:09:31.520 --> 0:09:34.680 I don't think it can interact with normal matter. I 0:09:35.440 --> 0:09:39.400 surely if it could pass through itself, we would be 0:09:39.440 --> 0:09:42.680 able to see it. It might be a dark force, 0:09:42.800 --> 0:09:45.720 which helps them incorrect. I know it doesn't interact with 0:09:45.880 --> 0:09:48.280 regular matter. I think we don't know whether how it 0:09:48.320 --> 0:09:51.040 interacts with itself. It is matter, so it has maths 0:09:51.080 --> 0:09:55.440 al must interact gravitationally. I don't know. Well, I think 0:09:55.440 --> 0:09:58.800 it does on some level. I don't know whether there 0:09:58.840 --> 0:10:02.480 would be quantum or molecular, but I think it's got 0:10:02.480 --> 0:10:06.720 to interact with itself enough to come together and blobs 0:10:06.760 --> 0:10:09.960 big enough to cause gravitational lensing that we can see 0:10:09.960 --> 0:10:13.000 here from Earth. I guess it's interact with yourself, since 0:10:13.040 --> 0:10:18.000 it's i've gravity. All right, pretty thoughtful answers, you know, 0:10:18.000 --> 0:10:19.920 people sort of thoughts through it. Yeah, there's some good 0:10:19.960 --> 0:10:21.760 stuff in here. People are really thinking about what it 0:10:21.840 --> 0:10:25.280 means to interact and whether gravity counts, and whether gravity 0:10:25.280 --> 0:10:31.400 would make something bump or not? Does gravity count? Does 0:10:31.440 --> 0:10:34.480 the Earth feel USh? Yeah? But also some people getting 0:10:34.480 --> 0:10:38.720 confused about dark energy versus dark matter. That's another rabbit 0:10:38.760 --> 0:10:43.040 hole there. Does dark energy feel? What is dark energy? Anyway? 0:10:43.120 --> 0:10:45.080 We have no idea, all right, So the question is 0:10:45.120 --> 0:10:48.280 that does dark matter feel? And so Daniel Um maybe 0:10:48.440 --> 0:10:50.760 step us through what we know about dark matter and 0:10:50.800 --> 0:10:54.880 it's it's not very sensitive. Unfortunately, you know, we wish 0:10:54.880 --> 0:10:57.559 you would react more. Oh good, that's a good thing, 0:10:57.640 --> 0:11:00.240 right as a thick skin. Well, perhaps know if you 0:11:00.240 --> 0:11:01.959 want to get along with your dark matter roommate. But 0:11:01.960 --> 0:11:04.079 if you want to do experiments to reveal the nature 0:11:04.080 --> 0:11:07.000 of dark matter, you'd like it to respond sometimes, and 0:11:07.080 --> 0:11:09.720 dark matter turns out to be very difficult to probe 0:11:09.920 --> 0:11:11.800 because the only way we've been able to interact with 0:11:11.880 --> 0:11:15.360 dark matter so far at all is with gravity. Like 0:11:15.400 --> 0:11:18.000 we said, we've discovered dark matter because we looked at 0:11:18.000 --> 0:11:21.360 how galaxies spin, and we notice that to spin as 0:11:21.400 --> 0:11:24.120 fast as they do and hold all the stars in place, 0:11:24.280 --> 0:11:27.120 you need a lot more gravity than is generated by 0:11:27.160 --> 0:11:30.040 the stars we see, which means there must be something 0:11:30.120 --> 0:11:34.200 else they're making that gravity. And we see blobs of 0:11:34.280 --> 0:11:36.520 dark matter in the sky. We don't see them. We 0:11:36.640 --> 0:11:39.720 deduce blobs of dark matter in the sky because they're 0:11:39.800 --> 0:11:43.160 bending the light that passes through them. That's a gravitational effect. 0:11:43.640 --> 0:11:47.400 So we have very concrete evidence that dark matter feels gravity. 0:11:47.440 --> 0:11:50.520 That's why we call it matter, not just like dark 0:11:50.600 --> 0:11:54.160 mysterious thing in the space right because it has gravity. 0:11:54.360 --> 0:11:56.960 I see. It's sort of like the probervial elephant in 0:11:57.000 --> 0:11:59.520 the room. You know it's there, everyone knows it's there, 0:12:00.080 --> 0:12:02.800 but it's, uh, it's nobody's talking about. Sort of. It's 0:12:02.840 --> 0:12:05.160 also sort of like the opposite of that, because the 0:12:05.240 --> 0:12:07.880 elf in the room. Everybody is ignoring it, right though 0:12:07.880 --> 0:12:09.800 you can all see it. In this case, we're all 0:12:09.880 --> 0:12:13.080 desperately searching for it, but nobody can find it. It's 0:12:13.080 --> 0:12:16.200 like you're right or right, except you're not. Well. You know, 0:12:16.360 --> 0:12:19.240 sometimes being exactly the opposite direction is also a way 0:12:19.240 --> 0:12:23.640 of being right. Yeah, yeah, you know up bean staff 0:12:24.000 --> 0:12:27.520 yes times minus one. Alright, So we know it feels gravity, 0:12:27.559 --> 0:12:29.600 but there are other forces that we know about in 0:12:29.640 --> 0:12:32.000 the universe, and as far as we know, the dark 0:12:32.000 --> 0:12:34.360 matter doesn't feel them. That's right. And so for example, 0:12:34.440 --> 0:12:37.200 electromagnetism is a very powerful force and when that we 0:12:37.280 --> 0:12:40.200 experience every day. The reason that your hand doesn't go 0:12:40.280 --> 0:12:42.320 through the wall when you're trying to touch it is 0:12:42.400 --> 0:12:45.000 that the wall has particles that are bound together with 0:12:45.040 --> 0:12:48.400 electromagnetic forces, and so it does your hand and so 0:12:48.440 --> 0:12:50.400 you think of them like a chain link fence trying 0:12:50.400 --> 0:12:53.040 to pass through another chain link fence. That's what prevents 0:12:53.080 --> 0:12:57.080 you from passing through another object. It's Electromagnetism is also 0:12:57.120 --> 0:13:00.280 responsible for why things glow right, why we can see things, 0:13:01.040 --> 0:13:03.440 or why they reflect light. To write like, it's light 0:13:03.559 --> 0:13:06.360 hits it and then it interacts and it comes back out. 0:13:06.400 --> 0:13:08.760 That's right. Even blobs of rock that don't glow on 0:13:08.800 --> 0:13:11.200 their own, we can see them in the sky because 0:13:11.200 --> 0:13:14.400 they reflect the sun's light, like the moon or like asteroids. 0:13:14.720 --> 0:13:17.160 And so we know dark matter isn't like that because 0:13:17.200 --> 0:13:20.200 it doesn't give off light, doesn't reflect light. Light passes 0:13:20.320 --> 0:13:24.880 right through it. So right through it, yeah, exactly. And 0:13:25.000 --> 0:13:27.920 I see this all the time in science fiction television, 0:13:28.320 --> 0:13:32.319 that they encounter dark matter and it obscures their view. Right. Oh, 0:13:32.360 --> 0:13:34.520 we can't get out of this cloud of dark matter 0:13:34.559 --> 0:13:36.959 and we can't see where we are. What show are 0:13:36.960 --> 0:13:40.319 you watching and seen that one? I don't remember the 0:13:40.400 --> 0:13:42.600 name of it right now. I watched too much science fiction, 0:13:42.880 --> 0:13:44.320 But you know that, to me, that sounds like a 0:13:44.320 --> 0:13:47.439 fantastic situation, like, oh my gosh, look we found dark matter. 0:13:47.880 --> 0:13:50.120 That's right home. We win the Nobel Prize. It's not like, 0:13:50.160 --> 0:13:52.640 get out of my picture, my photo. It's like I 0:13:52.679 --> 0:13:56.000 got a photo of dark matter. Exactly. We've been trying 0:13:56.040 --> 0:13:58.560 to spot dark matter forever and you just figured it 0:13:58.559 --> 0:14:00.600 out and now it seems like a hassled you. But 0:14:00.679 --> 0:14:02.320 if you were in a cloud of dark matter, you 0:14:02.320 --> 0:14:05.240 couldn't tell because it's invisible right. In fact, we think 0:14:05.280 --> 0:14:07.120 we are in a cloud of dark matter. We think 0:14:07.120 --> 0:14:10.000 the Earth is surrounded by dark matter, but we can't 0:14:10.040 --> 0:14:12.720 see it because it doesn't reflect light. It doesn't feel 0:14:12.720 --> 0:14:15.920 any electromagnetic forces at all. Yeah, we're swimming in dark 0:14:15.960 --> 0:14:19.160 matter right, Like everyone who's listening to this podcast right 0:14:19.200 --> 0:14:22.240 now is probably swimming in dark matter. Like right in 0:14:22.240 --> 0:14:25.160 front of their eyes, is dark matter passing through or 0:14:25.560 --> 0:14:28.080 sitting there? That's right. Dark matter, we think is spread 0:14:28.120 --> 0:14:31.440 out through the galaxy. It's fairly dilute, so it's there's 0:14:31.440 --> 0:14:33.320 a lot of it. There's a lot more dark matter 0:14:33.360 --> 0:14:35.480 than normal matter, but it's much more spread out we 0:14:35.520 --> 0:14:38.280 think the normal matter, which tends to cluster into planets 0:14:38.320 --> 0:14:40.920 and stars and stuff. So we think there's like one 0:14:41.040 --> 0:14:44.560 squirrel's worth of dark matter in the volume of the Earth. 0:14:44.640 --> 0:14:49.240 But it's there, it's out there. Wait, what one squirrels worth? 0:14:51.800 --> 0:14:55.160 One squirrel? Yeah, well it's a standard international unit of mass. 0:14:55.200 --> 0:14:59.520 One squirrel. Are you not familiar with squirrels? I don't. 0:14:59.560 --> 0:15:03.760 I didn't usually baked with squirrels. All my favorite recipes 0:15:03.800 --> 0:15:06.440 are in units of squirrels. You know, a third of 0:15:06.480 --> 0:15:08.840 a squirrel of oats and you know, half a squirrel 0:15:08.840 --> 0:15:12.680 of sugar man. That's that's the pandemic for you. It's 0:15:12.720 --> 0:15:15.760 forcing us into a more primitive Yeah, come over to 0:15:15.800 --> 0:15:18.080 my house sometime. We'll have a squirrel roast. So wait, 0:15:18.200 --> 0:15:20.480 the Earth you're saying is in a pool of dark 0:15:20.480 --> 0:15:23.080 matter that has the same amount of mass as a squirrel. 0:15:23.200 --> 0:15:25.560 That's what it means. That's right, And there's more dark 0:15:25.600 --> 0:15:27.800 matter than this normal matter, but the dark matter is 0:15:27.800 --> 0:15:30.360 more diffuse, it's more spread out, and so out there 0:15:30.400 --> 0:15:33.240 in empty space is about as much dark matter as 0:15:33.240 --> 0:15:35.520 there is here in our solar system. You just made 0:15:35.560 --> 0:15:37.920 me think of a giant squirrel the size of the 0:15:37.960 --> 0:15:41.720 Earth that a dark matter. You're a very visual person, 0:15:41.760 --> 0:15:43.160 so I'd love to see a drawing of that of 0:15:43.160 --> 0:15:47.680 a squirrel attacking the Earth and earth size squirrel attacking us. Finally, 0:15:47.680 --> 0:15:50.520 the aliens have come and they're just giants space squirrels. 0:15:51.280 --> 0:15:53.480 You did it again. Just because it's a dark matter squirrel, 0:15:53.480 --> 0:15:55.800 you assume it was bad, Daniel. Yeah, maybe it's a 0:15:55.840 --> 0:15:59.560 friendly planet sized space squirrel. Yeah, you're right. Now, so 0:15:59.640 --> 0:16:02.320 we we know that it doesn't feel electromagnetism, and that's 0:16:02.360 --> 0:16:05.000 principally because it's dark, we can't see it. But there 0:16:05.000 --> 0:16:07.280 are other forces out there, right, we talk about the 0:16:07.320 --> 0:16:11.800 weak nuclear force. That's a very very non powerful force. 0:16:11.840 --> 0:16:15.800 It's a weak force between particles. Neutrinos feel this force, 0:16:15.920 --> 0:16:18.400 Leptons feel this force. All the particles we know feel 0:16:18.440 --> 0:16:21.720 this force, but it's not very powerful. Like neutrinos pass 0:16:21.840 --> 0:16:25.040 through a light year of lead and have a fifty 0:16:25.040 --> 0:16:28.480 percent chance of feeling anything using the weak force. Our 0:16:28.560 --> 0:16:31.160 particles also feeling, like the particles in my body that 0:16:31.240 --> 0:16:33.280 they feel the weak force. Yeah, all the particles in 0:16:33.320 --> 0:16:35.800 your body, on the electrons and the corks, they all 0:16:35.880 --> 0:16:39.600 feel this force. It's responsible, for example, for a beta decay. 0:16:39.640 --> 0:16:42.640 So one of the corks in a neutron can turn 0:16:42.680 --> 0:16:45.240 into another kind of quirk which turns your neutron into 0:16:45.280 --> 0:16:48.440 a proton. That happens through the weak force, and that's 0:16:48.440 --> 0:16:52.240 why a little neutrinos emitted along with the electron that's created. 0:16:52.480 --> 0:16:55.000 So all the particles in your body are sensitive to 0:16:55.000 --> 0:16:58.400 the weak force. Neutrinos that pass through you can interact 0:16:58.400 --> 0:17:00.920 with you. It's just very very un likely, like there's 0:17:00.920 --> 0:17:05.440 a hundred billion newtrinos passing through your fingernail every second, 0:17:05.920 --> 0:17:07.920 and you don't feel them well, and we know that 0:17:07.960 --> 0:17:10.080 the dark matter doesn't feel it. We suspect that dark 0:17:10.080 --> 0:17:12.840 matter doesn't feel it because we've looked very very carefully. 0:17:13.080 --> 0:17:16.840 We've set up these big underground experiments filled with very quiet, 0:17:16.920 --> 0:17:20.080 heavy liquids, and we have a lot of those atoms 0:17:20.080 --> 0:17:21.919 in there, and we hope that a dark matter particle 0:17:21.960 --> 0:17:25.159 would come by and bump into one of those xenon atoms, 0:17:25.200 --> 0:17:27.240 for example, and we could spot it. And this is 0:17:27.440 --> 0:17:31.159 similar to how newtrinos were first discovered with vast tanks 0:17:31.160 --> 0:17:34.680 of underground liquid waiting for a little recoil from one 0:17:34.680 --> 0:17:37.280 of those atoms. So we have a similar in spirit 0:17:37.359 --> 0:17:41.440 kind of experiment done underground to look for passing dark 0:17:41.480 --> 0:17:44.200 matter particles. All right, So, and there's also the strong force, 0:17:44.320 --> 0:17:46.600 right which that one is pretty important, but dark matter 0:17:46.600 --> 0:17:48.560 doesn't feel that one either. That's right. The strong force 0:17:48.720 --> 0:17:51.600 is very powerful and so unlike the weak force, which 0:17:51.800 --> 0:17:53.520 you know, if dark matter felt it, it would be 0:17:53.600 --> 0:17:57.439 difficult but possible to detect in large underground experiments. If 0:17:57.520 --> 0:17:59.560 dark matter felt the strong force, we would notice that 0:17:59.680 --> 0:18:02.040 right way. I mean, it's very powerful. It wouldn't take 0:18:02.040 --> 0:18:04.760 a very big experiment. If dark matter felt the strong force, 0:18:04.920 --> 0:18:07.400 then it would react to almost every particle in your 0:18:07.440 --> 0:18:09.840 body and every particle in the Earth. It wouldn't be 0:18:09.840 --> 0:18:12.080 hard to notice. It would break up particles all the time. 0:18:12.119 --> 0:18:14.280 It would be a very powerful force. All right. So 0:18:14.320 --> 0:18:17.359 then those are the four main forces that we know about, 0:18:17.680 --> 0:18:20.560 and as far as we know, dark matter only feels gravity. 0:18:21.160 --> 0:18:24.719 And so the question is what what happens to dark matter? Then? 0:18:24.720 --> 0:18:27.680 Does it bump into itself or does it ignore it 0:18:27.760 --> 0:18:30.760 even itself? And so let's get into the question of 0:18:30.840 --> 0:18:33.600 does dark matter feel itself? But first let's take a 0:18:33.680 --> 0:18:49.480 quick break right there. We're talking about dark matter and 0:18:49.520 --> 0:18:52.760 whether it can feel itself, and so we know it 0:18:52.800 --> 0:18:56.280 feels gravity, and we know it doesn't feel the other forces. 0:18:56.320 --> 0:18:58.680 So I guess the question is, you know what happens 0:18:58.680 --> 0:19:00.959 when too dark matter? Part of goals if they are 0:19:01.040 --> 0:19:03.920 particles get attracted to each other, what's going to happen 0:19:03.960 --> 0:19:05.760 and are they gonna bump into each other or just 0:19:05.840 --> 0:19:07.960 totally ignore each other. It's a really fun sort of 0:19:07.960 --> 0:19:10.919 thought experiment. This is exactly what Joe is asking. And 0:19:11.000 --> 0:19:14.119 so you know, let's assume for the dark matter only 0:19:14.160 --> 0:19:17.479 feels gravity, that no other forces we don't know about 0:19:17.600 --> 0:19:20.280 that are involved, that it's just a gravitational thing. And 0:19:20.440 --> 0:19:23.359 you know, that is totally possible. It's possible for a 0:19:23.400 --> 0:19:26.399 particle to have mass and no other interactions. It's sort 0:19:26.440 --> 0:19:28.560 of incredible, but it would be something that we've never 0:19:28.600 --> 0:19:32.199 seen before. But hey, this physics is full of surprises. Well, 0:19:32.240 --> 0:19:35.320 because we know about neutrinos, right, Neutrinos are also sort 0:19:35.320 --> 0:19:37.880 of selective about which forces it feels. Yeah, we don't 0:19:37.960 --> 0:19:40.879 understand that at all, Like why do neutrinos only feel 0:19:40.960 --> 0:19:43.159 the weak force? You know, why don't they feel the 0:19:43.200 --> 0:19:46.160 strong force? Why don't electrons feel the strong force. It's 0:19:46.200 --> 0:19:48.680 just sort of like a thing we observe. We notice 0:19:48.720 --> 0:19:51.600 these things. All the corks feel the strong force. None 0:19:51.600 --> 0:19:54.160 of the electrons or neutrinos or muans or towels, those 0:19:54.160 --> 0:19:57.440 particles feel it. Why not? I mean, we don't know. 0:19:57.800 --> 0:20:01.399 We know that neutrinos don't feel elect a magnetism because 0:20:01.400 --> 0:20:03.840 they don't have a charge. Only things with electric charge 0:20:03.880 --> 0:20:06.679 can feel that. But we don't understand this. It's just 0:20:06.760 --> 0:20:09.120 it's something we observe, something that we hope one day 0:20:09.119 --> 0:20:12.199 to explain From the bottoms of principle. But at this 0:20:12.240 --> 0:20:15.760 point we're pretty clueless. All right, So then what happens, 0:20:15.920 --> 0:20:18.600 Like Joe put it, What if I take two particles 0:20:18.600 --> 0:20:21.399 of dark matter in an empty universe, said I'm a 0:20:21.440 --> 0:20:24.040 meter apart, and then I let go. Well, they attract 0:20:24.080 --> 0:20:26.840 each other, right, gravity pulls them together. But then now 0:20:26.880 --> 0:20:29.680 imagine what happens when sort of their edges meet, right, 0:20:29.680 --> 0:20:32.399 what happens that one blob versus the other blob. Now, 0:20:32.440 --> 0:20:35.719 if this was normal matter, when their edges meet, then 0:20:35.760 --> 0:20:38.440 they would repel each other. They would bump, literally, because 0:20:38.440 --> 0:20:41.520 they have forces to push against each other with. But 0:20:42.280 --> 0:20:46.320 if all you have is gravity, gravity can't push. Gravity 0:20:46.400 --> 0:20:50.480 only pulls. Right, you have two objects with positive mass, 0:20:50.520 --> 0:20:53.280 they only pull on each other unless you have negative 0:20:53.320 --> 0:20:56.040 mass particles. And we have a whole other podcast episode 0:20:56.080 --> 0:20:59.120 about that. Gravity can only attract. So there's no way 0:20:59.119 --> 0:21:02.040 for gravity to put ish, which means these particles just 0:21:02.080 --> 0:21:06.119 get closer and closer. There's no repelling force, and eventually 0:21:06.200 --> 0:21:08.919 they pass through each other. Right, Because there I guess 0:21:09.320 --> 0:21:11.840 point particles right, Well, we don't know if they're made 0:21:11.840 --> 0:21:14.480 of particles, right, but imagine they are mative particles. So 0:21:14.520 --> 0:21:16.399 I think these arguments hold even if they're made of 0:21:16.440 --> 0:21:19.120 some weird other kind of thing that you know isn't 0:21:19.119 --> 0:21:23.120 divided up into little particles. But they can basically cohabitate 0:21:23.200 --> 0:21:25.840 the same space. Right. The only thing that prevents things 0:21:25.840 --> 0:21:29.760 from overlapping are the forces. Right. The reason that one 0:21:29.800 --> 0:21:32.200 proton doesn't want to be next to another proton isn't 0:21:32.200 --> 0:21:35.679 because the stuff in them is like you're crowding me 0:21:35.800 --> 0:21:38.240 or something. It's all about the forces. As you said, 0:21:38.240 --> 0:21:40.920 if you imagined that their point particles, they have zero volume. 0:21:41.480 --> 0:21:44.000 So the only thing that gives distance to things are 0:21:44.040 --> 0:21:46.920 forces that repel, and gravity can't do that. Well. I 0:21:46.920 --> 0:21:49.480 think what's interesting to think about is that you know 0:21:49.480 --> 0:21:52.159 they wouldn't share the same space for very long, right, 0:21:52.359 --> 0:21:54.640 because if you set them a meter apart, they're gonna 0:21:54.640 --> 0:21:56.359 ask some velocity by the time that you get to 0:21:56.400 --> 0:21:58.240 the center, and so they'll just keep going. Yeah, they 0:21:58.280 --> 0:22:00.640 pass through each other, but then gravity will slow them down, 0:22:01.280 --> 0:22:03.239 stop them, turn them around, and they'll come through each 0:22:03.280 --> 0:22:06.320 other again. So like slash back and forth forever and 0:22:06.440 --> 0:22:10.320 right forever, right, because there's nothing, nothing would be making 0:22:10.320 --> 0:22:13.600 you lose energy. Yeah, in your hypothetical universe where there 0:22:13.760 --> 0:22:16.520 is nothing else, then they would slash back and forth forever. 0:22:17.080 --> 0:22:19.760 If they had some other way to lose energy. There's 0:22:19.800 --> 0:22:22.520 like larger blobs of dark matter that are sort of 0:22:22.720 --> 0:22:25.320 you know, equilibrating them or something. Then eventually they would 0:22:25.359 --> 0:22:27.679 slow down and then stop and sit right in the 0:22:27.720 --> 0:22:31.560 same place. But maybe not dark matter what you're saying. 0:22:31.560 --> 0:22:34.120 In in the real universe, that would it is possible 0:22:34.160 --> 0:22:36.880 out there that dark matter has settled. Yeah, it is possible. 0:22:36.960 --> 0:22:39.000 In fact, we think that dark matter is not moving 0:22:39.080 --> 0:22:41.680 very much. There's two theories of dark matter. There's warm 0:22:41.760 --> 0:22:44.880 dark matter and cold dark matter. And warm dark matter 0:22:44.960 --> 0:22:47.480 just means that the dark matter sort of zipping around everywhere. 0:22:47.520 --> 0:22:50.720 It's like has high velocity, and cold dark matter means 0:22:50.920 --> 0:22:54.040 it's mostly sitting around. It's like sluggist chilling and not 0:22:54.119 --> 0:22:58.240 moving very fast. It's chilling matter exactly, chill dark matter. 0:23:00.160 --> 0:23:03.159 That's for a statement of its feelings. Man. Yeah, so 0:23:03.200 --> 0:23:06.200 we think the dark matter is cold. It's cold dark matter, 0:23:06.200 --> 0:23:08.119 and so it's not moving very much. But yeah, if 0:23:08.119 --> 0:23:11.359 you imagine so, like a gravitational well constructed by something else, 0:23:11.400 --> 0:23:14.520 some larger object than two pieces of dark matter in 0:23:14.560 --> 0:23:17.000 that well would fall together to the bottom of it, 0:23:17.040 --> 0:23:18.879 and then they could just sit on top of each other. 0:23:19.280 --> 0:23:21.320 And I guess the same would happen with dark matter 0:23:21.400 --> 0:23:25.280 and regular matter, right, they would technically, like we only 0:23:25.320 --> 0:23:28.240 interact with gravity with dark matter, and so therefore we 0:23:28.480 --> 0:23:30.720 would just pass through us back and forth. Oh that's 0:23:30.720 --> 0:23:32.240 a good point. Yeah, And I think you're right, And 0:23:32.240 --> 0:23:34.800 I think dark matter is passing through us right now, 0:23:35.000 --> 0:23:37.720 or we're passing through dark matter in the same way 0:23:37.720 --> 0:23:40.440 that like neutrinos passed through us. But if there literally 0:23:40.640 --> 0:23:44.080 is no interaction other than gravity, then you're right. Dark 0:23:44.080 --> 0:23:46.080 matter can be in you and you can be in 0:23:46.200 --> 0:23:48.800 dark matter. Oh man, I feel like now we're getting 0:23:49.040 --> 0:23:52.919 ethereal here about dark matter and spiritual It's in you, 0:23:53.480 --> 0:23:56.480 in all of us, and it's not just a hypothetical question. 0:23:56.560 --> 0:23:59.880 We sort of did this experiment on a massive cause, 0:24:00.000 --> 0:24:02.159 a logical scale. Oh yeah, we did it. Oh we 0:24:02.280 --> 0:24:03.800 didn't sort of do what I mean, as much as 0:24:03.800 --> 0:24:06.800 astronomers do anything. They just sort of watched the universe 0:24:06.840 --> 0:24:10.600 do stuff. You say, astronomers don't do anything, Well, they 0:24:10.600 --> 0:24:13.679 don't construct experiments, right, They don't go like, let's build 0:24:13.680 --> 0:24:17.080 a sun that has these properties and distribute these planets 0:24:17.119 --> 0:24:18.760 around it and let it go. Right. They don't do 0:24:18.800 --> 0:24:22.160 that except in simulations, but they just look around and 0:24:22.320 --> 0:24:25.359 find that situation because the universe is so vast and 0:24:25.400 --> 0:24:28.359 so varied that they can usually find whatever they're looking for. 0:24:28.440 --> 0:24:33.160 The shoppers, not doers. I love astronomers. Nothing I say 0:24:33.200 --> 0:24:38.040 should be construed as negative towards astronomy or astronomers. But yeah, 0:24:38.200 --> 0:24:42.560 they're mostly observers, right, And what they found was these 0:24:42.640 --> 0:24:46.680 two clusters of galaxies that had slammed into each other. Yeah, 0:24:46.800 --> 0:24:49.879 it's called the Bullet cluster. Right, it's called the Bullet cluster. 0:24:50.160 --> 0:24:51.960 And this is a collision that happened a long long 0:24:52.000 --> 0:24:55.600 time ago. And by galaxy cluster, we just mean literally 0:24:55.640 --> 0:24:59.040 a group of galaxies, because galaxies orbit each other and 0:24:59.080 --> 0:25:00.879 are sort of grouped to either the same way that 0:25:01.000 --> 0:25:04.920 like stars are grouped together into a galaxy, galaxies themselves 0:25:04.920 --> 0:25:08.480 are grouped together into clusters of galaxies, and sometimes these 0:25:08.480 --> 0:25:12.359 things collide. Right. Dark energy is pushing the whole universe apart, 0:25:12.440 --> 0:25:15.800 creating spaces between things, but there are still forces and 0:25:15.840 --> 0:25:19.240 still directions that can pull things together. And so gravity 0:25:19.280 --> 0:25:22.920 pulled these two clusters together and they slammed into each other, 0:25:23.520 --> 0:25:26.320 and so we basically got to see this experiment happened. Yeah, 0:25:26.320 --> 0:25:28.840 you can look it up online if you google bullet cluster, 0:25:29.000 --> 0:25:32.320 and they're pretty spectacular images. Like, imagine a cluster of 0:25:32.320 --> 0:25:35.520 galaxies slamming into another cluster of galaxies. It's like a 0:25:35.560 --> 0:25:39.000 special effects bonanza. It's like a large hadron collider on 0:25:39.080 --> 0:25:45.440 the biggest scale possible, the largest, the large gaxy collider collider. Yeah, 0:25:45.520 --> 0:25:48.360 and of course you can't see it happen in real time. 0:25:48.400 --> 0:25:51.080 The whole collision took, you know, hundreds of millions of years. 0:25:51.320 --> 0:25:53.040 What we're looking at when we see it in the sky, 0:25:53.520 --> 0:25:56.040 it's just the after effects, and we can reconstruct what 0:25:56.080 --> 0:25:58.920 we think happened from what we're seeing now. And so, 0:25:59.240 --> 0:26:01.080 you know, the clusters are made of sort of three 0:26:01.119 --> 0:26:03.679 basic constituents. You have the stars, of course, so the 0:26:03.720 --> 0:26:06.359 things that are visible in the galaxy, and then between 0:26:06.400 --> 0:26:09.160 the stars you have gas, the things that make the stars. 0:26:09.400 --> 0:26:12.000 And then of course each one has dark matter, these 0:26:12.119 --> 0:26:15.040 huge blobs of dark matter. Remember that most of the 0:26:15.080 --> 0:26:17.480 things that are out there in the sky, the visible galaxies, 0:26:17.760 --> 0:26:21.320 have these halos of dark matter around them. So wherever 0:26:21.400 --> 0:26:23.760 you see stuff in the sky is probably where the 0:26:23.840 --> 0:26:26.360 dark matter is. They tend to follow each other. We've 0:26:26.359 --> 0:26:28.919 never seen or have we seen dark matter by itself. 0:26:29.119 --> 0:26:32.040 We have noticed some clumps, like that's what gravitational lensing is, 0:26:32.359 --> 0:26:35.080 so it is distributed. It goes out further past the 0:26:35.160 --> 0:26:37.639 edge of the galaxy, Like each galaxy has a halo 0:26:37.800 --> 0:26:40.960 that's longer and wider and larger than the galaxy itself. 0:26:41.200 --> 0:26:43.480 And we have seen blobs of dark matter in the 0:26:43.560 --> 0:26:46.919 universe by themselves. They do this gravitational lensing, but for 0:26:46.960 --> 0:26:49.680 the most part, the structure they follow each other. And 0:26:49.720 --> 0:26:52.560 that's not an accident. That's because of gravity. The structure 0:26:52.600 --> 0:26:55.679 of dark matter created the structure of normal matter, like 0:26:55.840 --> 0:26:59.200 created these gravitational wells for normal matter to fall into. 0:26:59.400 --> 0:27:03.040 That's why we have galaxies and stars and planets and squirrels. 0:27:03.160 --> 0:27:05.520 It's like, which came first, the dark matter or the galaxies, 0:27:05.560 --> 0:27:07.639 And the answer is the dark matter. Yeah, well, all 0:27:07.680 --> 0:27:09.520 the matter was created, i think at the same time, 0:27:09.560 --> 0:27:11.840 but dark matter there's more of it, and so it 0:27:11.880 --> 0:27:15.280 has a huge influence on the shape of the universe. 0:27:15.880 --> 0:27:18.359 So we saw this collision happen and we looked at it, 0:27:18.400 --> 0:27:21.560 and what we noticed is that when these two galaxy 0:27:21.720 --> 0:27:24.879 clusters passed through each other, the gas reacted like you 0:27:24.920 --> 0:27:28.000 would expect what to happen when two huge piles of 0:27:28.000 --> 0:27:30.800 stuff hit each other, right, big special effects, explosions, lots 0:27:30.800 --> 0:27:33.280 of friction and radiation at the edges and all that 0:27:33.320 --> 0:27:35.719 kind of stuff. And so you could see the gas 0:27:35.720 --> 0:27:37.959 not just kind of mixing with itself but actually like 0:27:38.119 --> 0:27:42.280 violently reacting. Oh yeah, these things are moving really fast. Absolutely, 0:27:42.320 --> 0:27:44.920 like if you shoot gas really fast and another cloud 0:27:44.960 --> 0:27:47.399 of gas, then things would happen. Things will happen, and 0:27:47.440 --> 0:27:49.359 they slow down, right, And so that energy had to 0:27:49.400 --> 0:27:51.879 go somewhere, and that energy went to heating up the 0:27:51.880 --> 0:27:53.560 gas and then it radiates, and you have all this 0:27:53.680 --> 0:27:57.280 friction between these two colliding clouds of gas. But the 0:27:57.359 --> 0:28:00.679 dark matter in these clusters got stripped way. It passed 0:28:00.800 --> 0:28:04.080 right through. It went right through the clouds of gas 0:28:04.280 --> 0:28:06.879 and right through the clouds of dark matter from the 0:28:06.920 --> 0:28:10.040 other galaxy and passed through to the other side like 0:28:10.080 --> 0:28:12.440 it went through the windshield or you know, thinking maybe 0:28:12.440 --> 0:28:14.760 like in the matrix, remember when they're fighting those ghosts 0:28:15.040 --> 0:28:17.080 and they're in the car and they slammed the brakes 0:28:17.119 --> 0:28:19.640 and the ghosts just keep going. Yeah, kind of like that, 0:28:19.920 --> 0:28:21.920 or like you're walking down the sidewalk with your kid 0:28:22.359 --> 0:28:24.480 and they notice something interesting and they stop and you 0:28:24.640 --> 0:28:26.520 just on your phone, and so you don't even pay 0:28:26.520 --> 0:28:28.359 attention to a block later, you're like, wait a second, 0:28:28.359 --> 0:28:32.600 where's my kid? I mean, that's never happened to me. 0:28:32.800 --> 0:28:35.359 They're reacting with some gas or is it running to 0:28:35.400 --> 0:28:38.719 another kid that you didn't spot? Right, there's the analogy, 0:28:38.800 --> 0:28:40.960 and the two parents just keep going looking at their phone. 0:28:41.880 --> 0:28:44.720 We're really modeling responsible parenting. I know, we're really talking 0:28:44.720 --> 0:28:47.400 about our feelings. And so we can see the dark 0:28:47.440 --> 0:28:50.360 matter came at the other side because we use gravitational lensing, 0:28:50.400 --> 0:28:53.600 we can see it distorting the light from background galaxies. 0:28:54.360 --> 0:28:58.200 So dark matter passed right through normal matter, gas, etcetera. 0:28:58.520 --> 0:29:01.880 Collided and so they got separated. So we really can't 0:29:01.880 --> 0:29:03.840 see in that case, this is a you know, collidab 0:29:03.920 --> 0:29:06.040 lab of dark matter with another lav of dark matter. 0:29:06.120 --> 0:29:10.320 What happens, Well, they massed right through nothing exactly, nothing happens. 0:29:10.320 --> 0:29:14.880 It just it just passes right through at least exciting collision. Ever, Well, 0:29:14.920 --> 0:29:16.800 I'm sure if it's exciting for them to lose their 0:29:16.880 --> 0:29:20.160 kids A few blocks back. All right. So we know 0:29:20.360 --> 0:29:24.360 then for sure through observational experiments that dark matter doesn't 0:29:24.400 --> 0:29:26.240 seem to feel itself, at least not in the way 0:29:26.280 --> 0:29:28.840 that we know about or with any forces that we 0:29:28.920 --> 0:29:31.440 know about. And so the question is, is there maybe 0:29:32.040 --> 0:29:34.440 another way that dark matter can feel itself that we 0:29:34.520 --> 0:29:36.760 don't know about? And so let's get into that. But 0:29:36.840 --> 0:29:51.960 first let's take a quick break. All right, Daniel, have 0:29:52.000 --> 0:29:54.719 you have you find your child yet? I've got your 0:29:54.800 --> 0:29:56.920 child and still looking for mine. Oh well no, wait, 0:29:56.960 --> 0:30:01.160 this one looks like, oh man, what take mishap here? Yeah, 0:30:01.240 --> 0:30:03.560 it's like parent trapped galaxy style. All right. So we're 0:30:03.600 --> 0:30:05.360 talking about dark matter and whether or not it can 0:30:05.480 --> 0:30:08.320 feel itself. And we know you can feel itself with gravity, 0:30:08.360 --> 0:30:12.120 but gravity doesn't help you really, you know, permanently feel 0:30:12.240 --> 0:30:14.760 or clump or things like that. And so the question 0:30:14.840 --> 0:30:16.760 is it could there be maybe another way that dark 0:30:16.800 --> 0:30:19.760 matter interacts with itself that we don't know? There absolutely 0:30:19.840 --> 0:30:22.240 could be, I mean, the existence of dark matter and 0:30:22.280 --> 0:30:26.000 the existence of dark energy, and our sheer ignorance about 0:30:26.000 --> 0:30:28.640 how the universe works, how it begins, and what controls 0:30:28.680 --> 0:30:31.200 its largest dynamics tells us that there's a lot to 0:30:31.280 --> 0:30:34.080 learn about the universe, and so there's certainly could be 0:30:34.120 --> 0:30:37.960 a whole other force out there, some force we've never discovered, 0:30:38.280 --> 0:30:41.040 some force that only dark matter feels and feels with 0:30:41.240 --> 0:30:43.880 other dark matter, and that might be the reason we've 0:30:43.920 --> 0:30:46.960 never seen it, the dark side of the force. Yeah, 0:30:47.000 --> 0:30:50.720 there's nothing preventing another kind of force from existing. It's 0:30:50.720 --> 0:30:53.440 not like we have any idea as to the number 0:30:53.480 --> 0:30:56.360 of forces that there could be, or is any limit 0:30:56.480 --> 0:30:58.120 to how many forces there are. It's just sort of 0:30:58.160 --> 0:31:01.160 like a list of stuff we've seen so far in 0:31:01.200 --> 0:31:04.959 our attempt to understand it. And so that's it. That 0:31:05.000 --> 0:31:08.160 list is almost certainly incomplete, the way our list of 0:31:08.280 --> 0:31:12.959 particles is incomplete, or the list of Beatles is incomplete. Right, 0:31:13.040 --> 0:31:15.320 Like every year he's scovered like a a thousand new kinds 0:31:15.320 --> 0:31:23.640 of Beatle. It's amazing. Yeah, Ringo, Paul Bob Robert And 0:31:23.720 --> 0:31:26.360 that was such a bad joke. I'm sorry. I did 0:31:26.440 --> 0:31:28.880 learn about a new Beatle last week. Actually, I discovered 0:31:28.920 --> 0:31:31.959 that they brought Ringo in, that they fired the original drummer, 0:31:31.960 --> 0:31:34.040 and he's still kind of better about the fifth One 0:31:34.040 --> 0:31:36.920 of the fifth Beatles is usually refers to their producer. 0:31:37.120 --> 0:31:39.560 But yeah, that the Ringo was not the original drummer. Yeah, 0:31:39.560 --> 0:31:42.160 not a music podcast, So let's stick to our strengths 0:31:42.160 --> 0:31:49.080 here matters. Yeah, well, this is a really interesting idea. 0:31:49.160 --> 0:31:51.240 I think that the you know, because it's it's like 0:31:51.320 --> 0:31:53.760 totally possible for there to be a whole another universe 0:31:53.800 --> 0:31:56.040 on top of us, right, Like there could be a 0:31:56.080 --> 0:31:59.120 whole set of other particles to feel, a whole other 0:31:59.200 --> 0:32:01.520 set of forces, but we just can't see them or 0:32:01.600 --> 0:32:04.000 feeling or touch them. Yeah, there's a whole party going on, 0:32:04.120 --> 0:32:06.680 and we weren't invited, and even if we had been invited, 0:32:06.720 --> 0:32:10.560 we couldn't even really attend because it just ignores us completely, right, 0:32:11.040 --> 0:32:13.080 And we know that there's a lot going out there 0:32:13.080 --> 0:32:15.360 that we can't see. Right, what we see in the 0:32:15.480 --> 0:32:19.040 universe is a tiny fraction what's actually happening, even just 0:32:19.160 --> 0:32:22.240 here on Earth with your eyeballs. Your eyeballs see a 0:32:22.440 --> 0:32:26.200 little sliver of all the electromagnetic radiation that's out there. 0:32:26.360 --> 0:32:28.200 There's a lot of stuff going on you can't see. 0:32:28.600 --> 0:32:31.280 And imagine if you could see, you know, cell phone 0:32:31.320 --> 0:32:35.200 signals and television signals and radio waves, the world would 0:32:35.200 --> 0:32:38.160 be a much different looking place. And so we see 0:32:38.200 --> 0:32:41.840 a little fraction of what's actually happening. Wow, and good 0:32:41.880 --> 0:32:45.400 thing to write like it be overwhelmed me. I mean, 0:32:45.440 --> 0:32:48.080 you can get Netflix in the Hulu for free, but 0:32:49.800 --> 0:32:52.200 you know, cloud based delivery would be a different kind 0:32:52.200 --> 0:32:54.120 of thing. All right, So there could be another force 0:32:54.160 --> 0:32:57.040 out there, and it's im possible the dark matter feels 0:32:57.080 --> 0:32:59.720 it then when we see it in these collisions, that 0:33:00.080 --> 0:33:02.440 was interacting with itself in another way. Yeah. So there's 0:33:02.440 --> 0:33:06.000 sort of two different categories of ideas. One is, could 0:33:06.040 --> 0:33:09.560 there be another force that dark matter feels and uses 0:33:09.640 --> 0:33:12.800 to interact with our kind of matter, some new kind 0:33:12.800 --> 0:33:15.840 of force we've never seen before that mediates the interaction 0:33:15.920 --> 0:33:18.800 between those two kinds of particles and that we're looking 0:33:18.840 --> 0:33:21.320 for and we haven't ever seen, and we're looking for 0:33:21.400 --> 0:33:23.640 that in the same way we're looking for like its 0:33:23.640 --> 0:33:26.280 interaction via the weak force. We have these big tanks 0:33:26.280 --> 0:33:29.200 of underground normal matter particles and we wait for dark 0:33:29.240 --> 0:33:31.880 matter to bump into It doesn't matter if it's the 0:33:31.920 --> 0:33:34.360 weak force or some other new kind of force. Like 0:33:34.440 --> 0:33:36.640 would it be really hard to, for example, to take 0:33:36.840 --> 0:33:40.760 one squirrel that's flying through the earth. Yes, And now 0:33:40.800 --> 0:33:44.400 you're talking about one squirrel particle and it's flying through 0:33:44.480 --> 0:33:48.680 like a ton of liquid zenon. These are very difficult experiments, 0:33:49.040 --> 0:33:52.440 and they're done underground, like a kilometer underground to keep 0:33:52.480 --> 0:33:55.880 them cold and isolated from all of the sources of background. 0:33:56.200 --> 0:33:59.360 They're very hard experiments, and they haven't seen anything so far. Right, 0:33:59.680 --> 0:34:02.240 But can you say it conclusively, like there's a pink 0:34:02.400 --> 0:34:05.280 squirrel out there with the purple polka dots, but we 0:34:05.320 --> 0:34:07.920 haven't found it on Earth, so therefore it must not exist. 0:34:07.960 --> 0:34:09.799 You're right. We can't say it does not exist. We 0:34:09.840 --> 0:34:14.320 can say it's less common than one squirrel per cubic 0:34:14.400 --> 0:34:17.720 volume per year. Right, We can just say how likely 0:34:17.719 --> 0:34:20.320 it is to exist at a certain level, and so 0:34:20.680 --> 0:34:22.520 it could still be there. And people are still running 0:34:22.560 --> 0:34:25.279 these experiments, and the longer we run them, the more 0:34:25.320 --> 0:34:27.719 we can push those limits. We can say, if this 0:34:27.760 --> 0:34:31.920 force does exist between standard model A matter and dark matter, 0:34:32.120 --> 0:34:35.239 that it must be even weaker than this limit, than 0:34:35.280 --> 0:34:37.320 this limit, than this lem We keep pushing that down. 0:34:37.840 --> 0:34:40.200 But there's a whole other category, which is like maybe 0:34:40.280 --> 0:34:43.759 dark matter just feel stuff with itself, not with our experiments, 0:34:43.760 --> 0:34:46.960 not with our bodies, but just between itself, like is 0:34:47.000 --> 0:34:49.720 it possible that dark matter bumps into itself and feels 0:34:49.719 --> 0:34:54.879 something right or repels each other with because you're telling 0:34:54.880 --> 0:34:57.880 me that this idea that it only feels gravity is 0:34:58.280 --> 0:35:02.520 sort of on thin nice like maybe there's evidence that 0:35:02.560 --> 0:35:04.440 maybe it does feel something else. Yeah, And this is 0:35:04.480 --> 0:35:07.800 really hard to probe because you can't do experiments using 0:35:08.280 --> 0:35:13.040 normal matter material to probe dark matters interactions with itself. 0:35:13.080 --> 0:35:15.799 You need to like build your experiment out of dark matter, right, 0:35:16.239 --> 0:35:18.400 So all we can do is look at how the 0:35:18.480 --> 0:35:20.799 dark matter is laid out in the universe, like where 0:35:20.840 --> 0:35:23.040 did it end up, and then try to see is 0:35:23.080 --> 0:35:26.120 that consistent with how it should end up if it 0:35:26.160 --> 0:35:29.200 only feels gravity, because if it is bumping into itself, 0:35:29.320 --> 0:35:31.719 that will change the way it's laid out, just like 0:35:32.040 --> 0:35:34.440 if it's hot or cold, if it's fast or slow, 0:35:34.640 --> 0:35:37.680 will also change the distribution of dark matter. So we 0:35:37.719 --> 0:35:39.840 look at the distribution and try to ask is it 0:35:39.880 --> 0:35:43.000 consistent with gravity only or do we need another piece 0:35:43.040 --> 0:35:44.840 of the puzzle aid And what do we see do 0:35:44.920 --> 0:35:47.800 we see out there in the universe that maybe it 0:35:47.800 --> 0:35:50.919 does feel another force? We see that mostly gets things 0:35:51.040 --> 0:35:54.040 right sort of on the scale of galaxies, and larger 0:35:54.560 --> 0:35:57.560 like the distribution of galaxies and how they cluster together 0:35:57.680 --> 0:36:00.400 and superclusters. That all seems right, and you run a 0:36:00.400 --> 0:36:03.319 simulation of the universe with dark matter and normal matter 0:36:03.560 --> 0:36:06.239 and dark matter is only gravity, it mostly gets that right. 0:36:06.560 --> 0:36:08.320 But then if you zoom in, like on the smaller 0:36:08.360 --> 0:36:12.000 scale here, smaller scales like less than a galaxy siza, 0:36:12.400 --> 0:36:16.400 then sub galaxy, then it's not quite right. It doesn't 0:36:16.400 --> 0:36:20.680 predict things the way we see them. For example, we 0:36:20.719 --> 0:36:22.760 know that we have a big blob of dark matter 0:36:22.800 --> 0:36:24.960 in our galaxy, and we know it's the densest at 0:36:24.960 --> 0:36:28.280 the center just because of gravity, But the exact shape 0:36:28.320 --> 0:36:31.200 of that blob is not something that we understand, like 0:36:31.680 --> 0:36:34.279 dark matter with only gravity predicts it sort of like 0:36:34.400 --> 0:36:36.520 peaked right at the center, that the center is like 0:36:36.640 --> 0:36:39.120 a hot spot for dark matter. But we go out 0:36:39.120 --> 0:36:40.960 and measure it, we see it's much more spread out 0:36:41.000 --> 0:36:43.520 than that. It's like much more of a rod core, 0:36:43.680 --> 0:36:46.600 not so much like peaked like a cusp, and so 0:36:47.080 --> 0:36:51.000 that's not something we understand. Fuzzier than what you would expect. 0:36:51.040 --> 0:36:54.040 You would expect it to sort of cluster more, but 0:36:54.440 --> 0:36:57.240 it's actually kind of fuzzy it's like a big fuzzy squirrel, 0:36:57.320 --> 0:37:01.440 not a little tiny intense squirrel. Yeah, it's a hedgehog 0:37:01.600 --> 0:37:04.400 or or something like that rather than a tiny little squirrel. 0:37:04.960 --> 0:37:07.919 And if you change your simulations and you add a 0:37:07.960 --> 0:37:09.960 little bit of bumping this like a little bit like 0:37:10.080 --> 0:37:13.600 maybe sometimes dark matter does bump into itself, that describes 0:37:13.600 --> 0:37:15.520 what we see better, meaning like a little bit of 0:37:15.560 --> 0:37:19.120 a repulsive force with itself. You just add in a 0:37:19.160 --> 0:37:21.440 made up force. You're like, we don't know, but let's 0:37:21.480 --> 0:37:24.279 see if it describes a situation, just like we made 0:37:24.360 --> 0:37:27.600 up dark matter to describe this gravity we were seeing. 0:37:27.880 --> 0:37:30.280 We're like, all right, well, now let's give another force 0:37:30.360 --> 0:37:32.880 to these particles that are creating the gravity, so that 0:37:32.960 --> 0:37:35.560 the distribution of gravity is the way we are seeing it. 0:37:35.640 --> 0:37:37.680 Let's make something up about something that we've made up. 0:37:39.600 --> 0:37:42.600 You're talking about all the physics, now, man, we'll come 0:37:42.600 --> 0:37:46.440 to science. What if that thing we made up for 0:37:46.520 --> 0:37:50.200 the thing we made up, that's something else we make up. Yeah, 0:37:50.239 --> 0:37:51.960 and so this is sort of the state of the art. 0:37:52.000 --> 0:37:55.280 Now we're like looking really carefully trying to understand where 0:37:55.440 --> 0:37:57.800 is the dark matter? Does it agree with what we 0:37:57.920 --> 0:38:00.839 predict and it turns out it doesn't quite agree, and 0:38:00.880 --> 0:38:04.720 there are other little details that the gravity only theory 0:38:05.280 --> 0:38:08.440 is getting wrong, so that they're sort of strong maybe 0:38:08.640 --> 0:38:11.600 or at least a hint of an indication that maybe 0:38:11.640 --> 0:38:14.759 dark matter does feel a whole new force or could 0:38:14.760 --> 0:38:16.279 it be one of the old force. It couldn't be 0:38:16.320 --> 0:38:17.799 one of the old forces. It would have to be 0:38:17.880 --> 0:38:20.840 some sort of self interaction. So this theory is called 0:38:21.120 --> 0:38:24.160 self interacting dark matter, and it solves some of these 0:38:24.440 --> 0:38:27.720 nagging problems that we've had in the gravity only theory 0:38:27.760 --> 0:38:30.120 of dark matter. So that makes it compelling. It's not 0:38:30.200 --> 0:38:33.560 proof at all that this is happening, but it's like, huh, 0:38:33.600 --> 0:38:36.120 we've had this problem. We add this new idea. It 0:38:36.160 --> 0:38:39.200 gives a better explanation. That's cool. And you always have 0:38:39.280 --> 0:38:42.359 to be careful when you're adding more stuff to your theory. Right, 0:38:42.400 --> 0:38:46.239 you'd like the simplest possible explanation, but if that doesn't work, 0:38:46.280 --> 0:38:48.360 then you have to add a little widget to your theory, 0:38:48.880 --> 0:38:52.120 like maybe what if there are two kinds of squirrels matter? Yeah, 0:38:52.160 --> 0:38:54.600 and and that's a whole other idea, right, Like if 0:38:54.680 --> 0:38:57.080 dark matter made of particles, is it one kind of particles? 0:38:57.160 --> 0:38:59.480 Is it two or is it ten? Didn't they decay 0:38:59.520 --> 0:39:01.920 from one kind particle to the other? Do only some 0:39:02.000 --> 0:39:04.200 of them have self interactions? I mean, look at the 0:39:04.200 --> 0:39:06.560 particles that make up our kind of matter. There's all 0:39:06.600 --> 0:39:10.200 sorts of complicated interactions with weird rules we don't understand. 0:39:10.560 --> 0:39:13.240 Why would we imagine dark matter would be like simpler. 0:39:13.280 --> 0:39:16.480 It could be different shades of dark matter, the darkest 0:39:16.520 --> 0:39:21.520 matters squirrels and cats. And and then then you wonder, like, 0:39:21.600 --> 0:39:24.520 all right, well, maybe dark matter could feel itself and 0:39:24.520 --> 0:39:27.239 that would explain like the weird distribution of gravity that 0:39:27.239 --> 0:39:30.240 we're seeing. But what about the bullet cluster? Right? Didn't 0:39:30.280 --> 0:39:34.080 we do this experiment because the two clouds of dark 0:39:34.120 --> 0:39:36.960 matter didn't repel each other. They didn't repel each other. 0:39:37.440 --> 0:39:39.880 But people went back and looked at that again, and 0:39:39.920 --> 0:39:42.879 they said, all right, well, can we explain this and 0:39:43.040 --> 0:39:46.520 have some amount of interaction in there, because it's not 0:39:46.600 --> 0:39:49.359 easy to tell exactly where all the dark matter is 0:39:49.680 --> 0:39:52.719 very precisely, like maybe some of it did interact and 0:39:52.760 --> 0:39:55.280 got sort of stuck in the middle. Most of it didn't, 0:39:55.520 --> 0:39:58.640 but maybe some of it did. You know. It's like 0:39:58.680 --> 0:40:00.320 we made it up in the first place when we 0:40:00.400 --> 0:40:03.160 just you know, it's like there's a first pass and 0:40:03.200 --> 0:40:05.960 there's a more precise test, right, you know, first you 0:40:06.000 --> 0:40:08.359 try to understand the broad strokes. Then you really dig 0:40:08.400 --> 0:40:10.640 in and see if it gets the details right. And 0:40:10.640 --> 0:40:12.239 the other thing is it turns out that this is 0:40:12.360 --> 0:40:17.000 not a great dark matter collider. It's too big dark matter. Well, 0:40:17.080 --> 0:40:19.800 dark matter is very dilute, and so if you throw 0:40:20.239 --> 0:40:23.680 a huge, very dilute cloud of dark matter at another one, 0:40:23.800 --> 0:40:26.200 most of it's just going to pass through anyway. Like, 0:40:26.280 --> 0:40:28.960 dark matter is not as dense as these gas clouds. 0:40:29.360 --> 0:40:31.759 It's sort of like like the stars. Like if you 0:40:31.840 --> 0:40:35.600 have two galaxies that pass through each other, mostly the 0:40:35.640 --> 0:40:39.320 stars don't collide because the stars are embedded in huge, 0:40:39.520 --> 0:40:43.360 vast empty spaces, and so they don't really collide with 0:40:43.360 --> 0:40:45.080 each other head to head. So you were saying, like, 0:40:45.120 --> 0:40:47.279 if I take two dark matter squirrels and I throw 0:40:47.320 --> 0:40:50.000 them at each other, they might repel one against the other. 0:40:50.040 --> 0:40:53.040 But if I take a whole cloud of squirrels that 0:40:53.120 --> 0:40:55.719 are really far apart, they might just pass through each 0:40:55.719 --> 0:40:58.160 other like we've seen in the cluster. Yeah, and they 0:40:58.200 --> 0:41:01.279 would mostly miss, just like the large Hadron collider what 0:41:01.320 --> 0:41:04.840 we do is we collide to clouds of protons against 0:41:04.880 --> 0:41:07.760 each other, because one proton will never hit another proton, 0:41:07.800 --> 0:41:10.000 they're too small. So we have like ten to the 0:41:10.040 --> 0:41:12.279 ten protons and one cloud and ten to the ten 0:41:12.360 --> 0:41:14.719 to the other, and we get you know, ten or 0:41:14.800 --> 0:41:18.560 twenty or fifty collisions. And so it's not that easy 0:41:18.680 --> 0:41:22.120 to make things collide. And so it turns out the 0:41:22.120 --> 0:41:25.760 bullet cluster is actually also consistent with dark matter feeling 0:41:25.800 --> 0:41:28.680 itself at sort of a low level of tweak how 0:41:28.719 --> 0:41:30.399 you look at it. Yeah, and so you know, the 0:41:30.440 --> 0:41:33.120 game here is come up with a theory um model 0:41:33.400 --> 0:41:36.920 that explains everything that we do see all the same time. 0:41:37.320 --> 0:41:40.000 And so you have to add some of this stuff 0:41:40.000 --> 0:41:43.120 to explain the distribution of dark matter and the core 0:41:43.400 --> 0:41:45.680 versus cup effect to the center of the galaxy, but 0:41:45.760 --> 0:41:47.840 not too much that you mess up the description of 0:41:47.840 --> 0:41:49.719 the bullet cluster. So you sort of hemmed in on 0:41:49.800 --> 0:41:53.480 both sides there. Interesting, But I guess maybe the takeaways 0:41:53.520 --> 0:41:57.520 that the answer is, yes, maybe dark matter does feel itself. 0:41:57.600 --> 0:42:00.560 It's totally possible, and there might be some indication out 0:42:00.560 --> 0:42:03.319 there that it does. Yeah, it's a new idea and 0:42:03.320 --> 0:42:06.840 it's gaining traction in the community self interacting dark matter. 0:42:07.280 --> 0:42:10.120 So it's possible that yes, dark matter could feel itself 0:42:10.160 --> 0:42:13.040 and there could be multiple forces that it feels all right, 0:42:13.160 --> 0:42:16.239 So maybe dark matter does have feelings, Daniel, It might 0:42:16.280 --> 0:42:18.719 have a lot more feelings than we could ever understand. 0:42:19.120 --> 0:42:22.280 Shades and shades of nuance. Well, I think it's all again, 0:42:22.320 --> 0:42:24.520 just all of this is just an interesting example of 0:42:24.560 --> 0:42:27.719 how there are things in the universe happening that we 0:42:27.960 --> 0:42:31.560 don't really know about or see or feel or effective. 0:42:31.680 --> 0:42:34.600 We're only seeing a tiny fraction of this grand play 0:42:34.600 --> 0:42:38.120 of the universe, and we're making huge, broad conclusions about 0:42:38.160 --> 0:42:40.880 how the universe works from this tiny little corner of 0:42:40.880 --> 0:42:43.200 the stage. And there's a lot going on that we 0:42:43.280 --> 0:42:46.480 haven't ever observed. And at least we know now. We 0:42:46.520 --> 0:42:49.280 know that we're ignorant, so we know to be humble 0:42:49.320 --> 0:42:52.799 and we know not to over generalize our ideas. But 0:42:52.880 --> 0:42:55.399 it also is tantalizing because you hope that one day 0:42:55.440 --> 0:42:57.160 we will see the rest of the action, We will 0:42:57.160 --> 0:42:59.719 get a glimpse for what's really happening. We might all 0:42:59.760 --> 0:43:04.920 be swimming in a giant squirrel up mr. I like 0:43:04.960 --> 0:43:08.160 to think of myself as a physics raccoon, because it's 0:43:08.160 --> 0:43:10.440 sneaking late at night to steal other people's garbage with 0:43:10.520 --> 0:43:14.000 dark circles on your eyes. That makes sense eating garbage. 0:43:16.080 --> 0:43:19.600 All right, Well that's pretty interesting and cool and or 0:43:19.680 --> 0:43:22.960 chill um, and so we hope you enjoyed that discussion. 0:43:23.040 --> 0:43:25.200 Thanks Joe for writing with your question. And if you 0:43:25.280 --> 0:43:27.719 have a question you'd like us to explore on the podcast, 0:43:27.960 --> 0:43:31.440 please write to us. We love your questions. Two questions 0:43:31.520 --> 0:43:35.239 at Daniel and Jorge dot com. A bit mysterious. See 0:43:35.280 --> 0:43:46.040 you next time. Thanks for listening, and remember that Daniel 0:43:46.040 --> 0:43:48.600 and Jorge Explain the Universe is a production of I 0:43:48.800 --> 0:43:52.239 Heart Radio. For more podcast from my Heart Radio, visit 0:43:52.280 --> 0:43:56.120 the I Heart Radio Apple Podcasts, or wherever you listen 0:43:56.239 --> 0:44:03.800 to your favorite shows.