1 00:00:08,720 --> 00:00:12,240 Speaker 1: Hey, Dannie, I'm curious how does a physicist make mental 2 00:00:12,240 --> 00:00:14,640 Speaker 1: images of some of the tricky things you do research on. 3 00:00:14,840 --> 00:00:16,880 Speaker 2: You know, I'm not sure you really want to see 4 00:00:16,920 --> 00:00:20,080 Speaker 2: inside the brain of physicists. It's a bit of a mess. 5 00:00:20,280 --> 00:00:23,320 Speaker 1: Well, let's find out what's your mental image of dark matter? 6 00:00:23,440 --> 00:00:27,080 Speaker 2: Okay, that's a really tough one because it's invisible. I 7 00:00:27,120 --> 00:00:29,920 Speaker 2: guess I sort of imagine it like water, which is, 8 00:00:29,960 --> 00:00:32,960 Speaker 2: you know, mostly transparent, but you can definitely tell it's there. 9 00:00:33,159 --> 00:00:35,480 Speaker 1: So we're all swimming in a bath of dark matter. 10 00:00:36,640 --> 00:00:38,960 Speaker 2: I hope there's some dark matter rubber duckies out. 11 00:00:38,800 --> 00:00:41,080 Speaker 1: There, some dark duckies. I wonder if they have a 12 00:00:41,159 --> 00:00:42,920 Speaker 1: cute song for that on Sesame Street. 13 00:00:42,960 --> 00:00:45,280 Speaker 2: That would make dark matter bath time lots of fun. 14 00:00:45,440 --> 00:00:49,200 Speaker 1: It's a special episode on the Letter D for dark Matter. 15 00:01:04,520 --> 00:01:04,640 Speaker 3: Hi. 16 00:01:04,640 --> 00:01:07,240 Speaker 1: I am Horam mccartoonist and the author of Oliver's Great 17 00:01:07,280 --> 00:01:08,360 Speaker 1: Big Universe. Hi. 18 00:01:08,520 --> 00:01:11,200 Speaker 2: I'm Daniel. I'm a particle physicist and a professor you 19 00:01:11,240 --> 00:01:14,080 Speaker 2: see Irvine. And this episode is brought to you by 20 00:01:14,080 --> 00:01:15,640 Speaker 2: the taxpayers of California. 21 00:01:15,800 --> 00:01:16,880 Speaker 1: Is it They're not paying me? 22 00:01:18,680 --> 00:01:21,360 Speaker 2: This professor is brought to you by the taxpayers of California. 23 00:01:21,360 --> 00:01:24,720 Speaker 1: I should say I thought our heart worth paying you. 24 00:01:25,000 --> 00:01:28,080 Speaker 1: Are you double dipping here, Daniel? Sounds like it. I 25 00:01:28,160 --> 00:01:32,520 Speaker 1: am multifaceted, your multi paid? Is that what you're saying 26 00:01:33,240 --> 00:01:37,320 Speaker 1: by multiple people? Sounds like a good setup there. 27 00:01:37,400 --> 00:01:38,720 Speaker 2: I got no complaints, but. 28 00:01:38,680 --> 00:01:41,680 Speaker 1: Anyways, welcome to our podcast, Daniel and Jorge Explain the Universe, 29 00:01:41,760 --> 00:01:43,920 Speaker 1: a production of iHeartRadio. 30 00:01:43,400 --> 00:01:46,680 Speaker 2: In which we try to bring multiple streams of understanding 31 00:01:46,760 --> 00:01:50,640 Speaker 2: together into your brain. There's so many ways to understand 32 00:01:50,640 --> 00:01:53,040 Speaker 2: the universe, so many questions to ask about it, so 33 00:01:53,080 --> 00:01:56,680 Speaker 2: many things to understand, and the challenge of physics is 34 00:01:56,760 --> 00:02:00,240 Speaker 2: to weave all those together into one coherent, comprehend of 35 00:02:00,360 --> 00:02:03,640 Speaker 2: story that explains the universe to us and to you 36 00:02:04,000 --> 00:02:06,280 Speaker 2: and to our kids. And that is the goal of 37 00:02:06,320 --> 00:02:07,200 Speaker 2: this podcast. 38 00:02:07,680 --> 00:02:09,880 Speaker 1: That's right, because it is a vast universe full of 39 00:02:10,000 --> 00:02:12,440 Speaker 1: all kinds of things that start with all kinds of letters, 40 00:02:12,480 --> 00:02:14,639 Speaker 1: the letter A, the letter B, the letter C, all 41 00:02:14,680 --> 00:02:16,920 Speaker 1: of the letters in the universe, even the ones we 42 00:02:17,000 --> 00:02:18,160 Speaker 1: haven't discovered. 43 00:02:17,800 --> 00:02:21,280 Speaker 2: Yet, even letters in other alphabets. In particle physics, we 44 00:02:21,320 --> 00:02:24,080 Speaker 2: often reach to the Greek alphabet to name our particles. 45 00:02:24,280 --> 00:02:25,520 Speaker 1: Is that why it's all Greek? To me. 46 00:02:27,880 --> 00:02:29,920 Speaker 2: That's exactly right. And sometimes when we run out of 47 00:02:29,919 --> 00:02:31,959 Speaker 2: Greek letters, we dip into the Hebrew alphabet. 48 00:02:32,040 --> 00:02:33,720 Speaker 1: Mmm. I thought you were going to say, we're gonna 49 00:02:33,840 --> 00:02:36,280 Speaker 1: you're gonna dip into alien alphabets, or one day we 50 00:02:36,400 --> 00:02:39,880 Speaker 1: might have variables that are only defined in an alien language. 51 00:02:40,160 --> 00:02:43,679 Speaker 2: That sounds wonderful. I look forward to figuring out how 52 00:02:43,680 --> 00:02:45,680 Speaker 2: to write alien letters in word. 53 00:02:45,840 --> 00:02:48,120 Speaker 1: You're going to need like another app like trio Linguo 54 00:02:48,320 --> 00:02:48,720 Speaker 1: or something. 55 00:02:50,520 --> 00:02:53,560 Speaker 2: I'm sure this's gonna be a Unicode symbol for alien languages. 56 00:02:53,800 --> 00:02:56,400 Speaker 1: Oh so, I mean they'll be alien emojis. 57 00:02:57,200 --> 00:02:59,600 Speaker 2: What if the first message we get from aliens is 58 00:02:59,760 --> 00:03:02,600 Speaker 2: just in emojis that we need our kids to help. 59 00:03:02,520 --> 00:03:05,440 Speaker 1: Us interpret it. Yeah, let's hope it's not like food 60 00:03:05,639 --> 00:03:11,120 Speaker 1: icons like hey, hey dinner, Hey hot dog, hamburger, pizza. 61 00:03:11,520 --> 00:03:14,200 Speaker 2: I think the food emojis have other meanings sometimes, you know, 62 00:03:14,280 --> 00:03:15,480 Speaker 2: the eggplant for example. 63 00:03:15,720 --> 00:03:18,320 Speaker 1: I don't know what you're talking about, Daniel. What kinds 64 00:03:18,320 --> 00:03:19,800 Speaker 1: of websites have you been surfing? 65 00:03:19,960 --> 00:03:21,160 Speaker 2: Ask your kids about it later. 66 00:03:24,440 --> 00:03:28,519 Speaker 1: I doubt it. But anyways, it is a big universe 67 00:03:28,520 --> 00:03:31,800 Speaker 1: full of amazing things to study and observe. If we 68 00:03:31,919 --> 00:03:33,399 Speaker 1: can actually see them. 69 00:03:33,480 --> 00:03:36,040 Speaker 2: One of the challenges of understanding the universe is first 70 00:03:36,320 --> 00:03:39,360 Speaker 2: figuring out what's out there. We begin by using the 71 00:03:39,440 --> 00:03:42,520 Speaker 2: natural senses. We're all familiar with our eyes, our ears, 72 00:03:42,600 --> 00:03:45,280 Speaker 2: our noses, et cetera. But there's so much more out 73 00:03:45,320 --> 00:03:48,080 Speaker 2: there that we can detect with more subtle methods. 74 00:03:48,400 --> 00:03:49,960 Speaker 1: Yeah, because there's a lot of stuff out there that 75 00:03:50,000 --> 00:03:51,840 Speaker 1: we can see, but also a lot of stuff we 76 00:03:51,960 --> 00:03:56,200 Speaker 1: can't see. The most amazing discoveries in recent decades has 77 00:03:56,240 --> 00:03:59,160 Speaker 1: been the idea that most of the universe is out there, 78 00:03:59,200 --> 00:04:02,040 Speaker 1: but we can't see it, or touch it or feel it. 79 00:04:02,200 --> 00:04:06,120 Speaker 2: As we progress scientifically and technologically, we build new kinds 80 00:04:06,120 --> 00:04:09,200 Speaker 2: of eyeballs, new kinds of sensors, new kinds of ears 81 00:04:09,560 --> 00:04:12,200 Speaker 2: that let us detect things happening in the universe that 82 00:04:12,240 --> 00:04:16,400 Speaker 2: were otherwise invisible and impossible for us to notice. Sometimes 83 00:04:16,440 --> 00:04:19,520 Speaker 2: that means seeing entirely new signals like photons of very 84 00:04:19,560 --> 00:04:23,280 Speaker 2: high energy or low energy. Sometimes that means noticing patterns 85 00:04:23,279 --> 00:04:26,640 Speaker 2: in other signals, like the rotations of galaxies and gravitational 86 00:04:26,720 --> 00:04:29,560 Speaker 2: hints in the motions of other objects that tell us 87 00:04:29,640 --> 00:04:32,080 Speaker 2: there's so much more going on out there than we 88 00:04:32,120 --> 00:04:33,159 Speaker 2: could immediately see. 89 00:04:33,400 --> 00:04:36,200 Speaker 1: Yep, and one of the biggest pieces of stuff out 90 00:04:36,240 --> 00:04:38,960 Speaker 1: there that we can see is called dark matter. It 91 00:04:39,040 --> 00:04:42,400 Speaker 1: accounts for about twenty seven percent of the universe, right, Daniel. 92 00:04:42,120 --> 00:04:44,359 Speaker 2: That's right. In any given chunk of the universe, just 93 00:04:44,440 --> 00:04:48,040 Speaker 2: over a quarridor of the energy is devoted to dark matter, 94 00:04:48,440 --> 00:04:50,320 Speaker 2: and only five percent of it is made of the 95 00:04:50,400 --> 00:04:54,240 Speaker 2: kind of stuff that you and I are made out of, baryons, quarks, leptons, 96 00:04:54,240 --> 00:04:56,600 Speaker 2: this kind of stuff, which means that there's a lot 97 00:04:56,760 --> 00:05:00,240 Speaker 2: more of the invisible stuff out there than the visible stuf. 98 00:05:00,320 --> 00:05:02,400 Speaker 1: Yeah, which can I make you wonder if maybe we're 99 00:05:02,400 --> 00:05:03,480 Speaker 1: the ones that are invisible. 100 00:05:03,600 --> 00:05:06,839 Speaker 2: Maybe we needs learn those dark matter emojis pretty quickly, 101 00:05:07,240 --> 00:05:07,880 Speaker 2: but could. 102 00:05:07,640 --> 00:05:10,279 Speaker 1: We see them? Maybe you are receiving dark matter emojis, 103 00:05:10,279 --> 00:05:10,880 Speaker 1: you just don't know it. 104 00:05:10,920 --> 00:05:12,880 Speaker 2: I've kind of an outdated operating system, so a lot 105 00:05:12,880 --> 00:05:15,599 Speaker 2: of the emojis I get are question marks anyway. Maybe 106 00:05:15,640 --> 00:05:17,400 Speaker 2: those are the aliens trying to talk to me. 107 00:05:17,680 --> 00:05:21,320 Speaker 1: Mmm, maybe they're actually sending you question marks. They're like, Daniel, 108 00:05:21,360 --> 00:05:23,000 Speaker 1: why are you getting paid so many ways for the 109 00:05:23,040 --> 00:05:23,440 Speaker 1: same thing? 110 00:05:25,320 --> 00:05:27,520 Speaker 2: You know, I do get lots of questions from listeners, 111 00:05:27,680 --> 00:05:29,960 Speaker 2: so maybe some of those are actually coming from the aliens. 112 00:05:30,240 --> 00:05:32,520 Speaker 1: Interesting, are you calling our listeners aliens? 113 00:05:33,760 --> 00:05:36,880 Speaker 2: I'm saying we're inclusive, right, everybody is welcome. We try 114 00:05:36,880 --> 00:05:38,799 Speaker 2: to reach everybody, not just humans. 115 00:05:38,839 --> 00:05:40,760 Speaker 1: Well, there you go. If you want to stump a physicists, 116 00:05:40,880 --> 00:05:43,240 Speaker 1: just send them a question in the form of emojis. 117 00:05:43,680 --> 00:05:46,440 Speaker 1: You know how they summarize movies sometimes with just emojis. 118 00:05:46,440 --> 00:05:48,279 Speaker 1: I wonder if you could do that with physics theory. 119 00:05:48,400 --> 00:05:52,560 Speaker 2: What they summarize movies with just emojis? 120 00:05:52,760 --> 00:05:55,600 Speaker 1: Yeah? Or books or stories or news items. 121 00:05:55,720 --> 00:05:56,960 Speaker 2: Oh, I feel really out of touch. 122 00:05:57,120 --> 00:06:00,000 Speaker 1: Speaking of out of touch, that's what dark matter is. 123 00:06:00,120 --> 00:06:02,400 Speaker 1: Stuff that's out there that you can't see and you 124 00:06:02,440 --> 00:06:06,119 Speaker 1: can't even touch, right, because it doesn't feel the electromagnetic force, 125 00:06:06,200 --> 00:06:08,200 Speaker 1: so you can feel it with your fingers. 126 00:06:08,080 --> 00:06:10,880 Speaker 2: That's right. It doesn't emit light, give off light, reflect light, 127 00:06:11,000 --> 00:06:14,560 Speaker 2: or interact with light at all, which makes it pretty dark. 128 00:06:15,040 --> 00:06:17,440 Speaker 2: And if a huge chunk of the universe is so 129 00:06:17,640 --> 00:06:21,400 Speaker 2: dark but so important, then scientists really have to figure 130 00:06:21,440 --> 00:06:24,600 Speaker 2: out how to study, how to understand what it is. 131 00:06:24,920 --> 00:06:27,080 Speaker 2: So we're doing our best to be creative to find 132 00:06:27,320 --> 00:06:28,400 Speaker 2: new ways. 133 00:06:28,120 --> 00:06:30,400 Speaker 1: To look for it so that we can study it 134 00:06:30,520 --> 00:06:32,479 Speaker 1: and kind of figure out what it's made out of. 135 00:06:33,240 --> 00:06:36,320 Speaker 1: So there are maybe new ideas out there about how 136 00:06:36,400 --> 00:06:38,320 Speaker 1: to do this. So today on the podcast, we'll be 137 00:06:38,320 --> 00:06:47,400 Speaker 1: tackling the question good dark matter be making flashes of light? 138 00:06:48,080 --> 00:06:50,279 Speaker 1: I always figured dark matter was pretty flashy. 139 00:06:52,440 --> 00:06:54,520 Speaker 2: Well, I don't know. The name dark matter is more 140 00:06:54,560 --> 00:06:56,560 Speaker 2: mysterious than flashy, isn't it. 141 00:06:56,600 --> 00:06:59,520 Speaker 1: Well, that's just what we'll call it. Maybe it's something 142 00:06:59,600 --> 00:07:03,040 Speaker 1: we can but really inside it's fancy and flashy. 143 00:07:03,279 --> 00:07:05,800 Speaker 2: Maybe when we finally meet the beings made of dark matter, 144 00:07:05,880 --> 00:07:08,839 Speaker 2: they'll be like annoyed or offended or disappointed that we 145 00:07:08,880 --> 00:07:09,920 Speaker 2: call them dark matter. 146 00:07:10,600 --> 00:07:12,160 Speaker 1: Hopefully they won't flash us. 147 00:07:12,360 --> 00:07:14,040 Speaker 2: You mean like zap us with a laser being from 148 00:07:14,080 --> 00:07:16,240 Speaker 2: orbit or open the trench code. 149 00:07:15,960 --> 00:07:20,480 Speaker 1: I mean like send this fruit emojis. So, as usually, 150 00:07:20,480 --> 00:07:22,600 Speaker 1: we were wondering how many people out there had thought 151 00:07:22,600 --> 00:07:26,080 Speaker 1: about the idea of seeing dark matter through flashes of light. 152 00:07:26,280 --> 00:07:28,520 Speaker 2: Thank you very much to our group of volunteers who 153 00:07:28,560 --> 00:07:31,800 Speaker 2: answers these questions. We'd love hearing your thoughts on the 154 00:07:31,840 --> 00:07:34,520 Speaker 2: topic of the day. If you would like to contribute, 155 00:07:34,520 --> 00:07:36,960 Speaker 2: please don't be shy. Everybody is welcome, whether you've been 156 00:07:37,000 --> 00:07:39,680 Speaker 2: listening for years or weeks or days or this is 157 00:07:39,720 --> 00:07:42,760 Speaker 2: your first episode, just write to me too, questions at 158 00:07:42,880 --> 00:07:44,560 Speaker 2: Danielandjorge dot com. 159 00:07:44,600 --> 00:07:46,320 Speaker 1: So think about it for a second. Do you think 160 00:07:46,440 --> 00:07:49,440 Speaker 1: dark matter could be making flashes of light that we 161 00:07:49,440 --> 00:07:51,520 Speaker 1: could see? Here's what people had to say. 162 00:07:51,680 --> 00:07:53,239 Speaker 2: I don't know, but that'd be cool. 163 00:07:53,680 --> 00:07:58,120 Speaker 3: The concept of dark matter making flashes of light is 164 00:07:58,320 --> 00:08:01,760 Speaker 3: quite interesting since dark matter seems to make up a 165 00:08:01,840 --> 00:08:04,560 Speaker 3: large part of the universe. I don't see why it 166 00:08:04,560 --> 00:08:09,280 Speaker 3: could be giving off light pulses given the right circumstances. 167 00:08:09,560 --> 00:08:13,280 Speaker 3: I think that only directly by making stuff made of 168 00:08:13,360 --> 00:08:16,560 Speaker 3: regular matter to behave in a certain way due to 169 00:08:16,840 --> 00:08:21,120 Speaker 3: gravitational effects, since it doesn't interact with the electra week force, I. 170 00:08:21,040 --> 00:08:23,600 Speaker 1: Think not all right. I think that pretty much summarizes 171 00:08:23,640 --> 00:08:25,800 Speaker 1: the episode here. I don't know, but that would be cool. 172 00:08:26,880 --> 00:08:29,040 Speaker 1: I feel like that's al those every episode. 173 00:08:29,280 --> 00:08:31,640 Speaker 2: That's the emoji version of the episode. Yeah, if you 174 00:08:31,680 --> 00:08:34,120 Speaker 2: have to summarize it, so that would be what shrug 175 00:08:34,400 --> 00:08:38,080 Speaker 2: question mark check mark is how you summarize the emojis. 176 00:08:37,720 --> 00:08:41,160 Speaker 1: Yeah, or like a black square for dark matter question 177 00:08:41,280 --> 00:08:45,360 Speaker 1: mark trump, and then the emoji with the sunglasses. 178 00:08:44,720 --> 00:08:47,360 Speaker 2: For cool yeah or sparkles. Isn't there a sparkles emoji. 179 00:08:47,400 --> 00:08:49,200 Speaker 1: Well, depends how flashy you want to get. 180 00:08:49,280 --> 00:08:51,880 Speaker 2: Daniel, let's go all out. We got multiple funding sources here. 181 00:08:52,000 --> 00:08:54,080 Speaker 1: There you go. Let's go out with a flash of 182 00:08:54,280 --> 00:08:59,120 Speaker 1: jail time. But anyways, let's get down to it, Daniel, 183 00:08:59,200 --> 00:09:02,280 Speaker 1: let's recap for listeners. What is dark matter in the 184 00:09:02,280 --> 00:09:02,800 Speaker 1: first place. 185 00:09:02,880 --> 00:09:04,880 Speaker 2: It's important that we explain what we mean when we 186 00:09:04,920 --> 00:09:07,320 Speaker 2: say dark matter, because I noticed there's lots of different 187 00:09:07,360 --> 00:09:10,560 Speaker 2: ideas out there about what dark matter is. Online you 188 00:09:10,559 --> 00:09:12,400 Speaker 2: see a lot of people saying dark matter is just 189 00:09:12,400 --> 00:09:14,840 Speaker 2: a placeholder. Is just a way to say we don't know. 190 00:09:15,480 --> 00:09:17,400 Speaker 2: Other people talk about dark matter as if it was 191 00:09:17,440 --> 00:09:21,280 Speaker 2: a very specific theory of a very specific particle. There's 192 00:09:21,280 --> 00:09:22,640 Speaker 2: a whole bunch of people in the middle to talk 193 00:09:22,640 --> 00:09:26,240 Speaker 2: about dark matter as a sort of general catalog of ideas. 194 00:09:26,480 --> 00:09:29,360 Speaker 2: But all of these things are there to explain something 195 00:09:29,360 --> 00:09:32,280 Speaker 2: that we don't understand, which is that there's a lot 196 00:09:32,360 --> 00:09:35,880 Speaker 2: of gravity happening in the universe that we cannot explain, 197 00:09:36,320 --> 00:09:38,520 Speaker 2: Like when you look at how galaxies spin, and when 198 00:09:38,520 --> 00:09:40,480 Speaker 2: you look at how the universe formed, and all the 199 00:09:40,520 --> 00:09:45,040 Speaker 2: gravity necessary to pull the stars together into galaxies. We 200 00:09:45,200 --> 00:09:48,679 Speaker 2: just cannot explain all that galaxy using the stuff that 201 00:09:48,800 --> 00:09:51,080 Speaker 2: lights up, using the stuff made of quarks. It either 202 00:09:51,160 --> 00:09:54,120 Speaker 2: glows or reflects light or gives off light. We just 203 00:09:54,200 --> 00:09:57,000 Speaker 2: cannot tell the story of the universe and have it 204 00:09:57,080 --> 00:10:00,720 Speaker 2: make sense without something else out there provid a bunch 205 00:10:00,760 --> 00:10:03,079 Speaker 2: of gravity. So much gravity is missing that you need 206 00:10:03,200 --> 00:10:06,199 Speaker 2: five times as much of this mysterious stuff we call 207 00:10:06,320 --> 00:10:09,440 Speaker 2: dark matter as there is normal matter. So very briefly, 208 00:10:09,520 --> 00:10:11,520 Speaker 2: dark matter is just an idea to explain all this 209 00:10:11,760 --> 00:10:13,800 Speaker 2: unexplained gravity in the universe. 210 00:10:14,080 --> 00:10:16,760 Speaker 1: Yeah, and there are different ways that scientists have sort 211 00:10:16,800 --> 00:10:19,560 Speaker 1: of found or think that dark matter is there and there. 212 00:10:19,600 --> 00:10:21,599 Speaker 1: As you said, they all relate to gravity. But I 213 00:10:21,640 --> 00:10:24,200 Speaker 1: think basically the main idea is that what we see 214 00:10:24,200 --> 00:10:26,280 Speaker 1: of the universe tells us that there's more matter out 215 00:10:26,320 --> 00:10:28,199 Speaker 1: there than the stuff that glows or that we can 216 00:10:28,240 --> 00:10:29,840 Speaker 1: see and feel right exactly. 217 00:10:29,880 --> 00:10:32,679 Speaker 2: And the story started with the galaxy rotation curves. We 218 00:10:32,720 --> 00:10:35,080 Speaker 2: looked at galaxies and measured how fast they spin, and 219 00:10:35,120 --> 00:10:38,520 Speaker 2: we notice that they spin really really fast, and that 220 00:10:38,600 --> 00:10:40,640 Speaker 2: if you add up all of the stars and the 221 00:10:40,640 --> 00:10:43,200 Speaker 2: gas and the dust in those galaxies, they don't provide 222 00:10:43,280 --> 00:10:46,560 Speaker 2: enough gravity to hold that galaxy together as it spins. 223 00:10:47,000 --> 00:10:49,599 Speaker 2: So that was evidence number one, and for decades we 224 00:10:49,679 --> 00:10:51,680 Speaker 2: knew about that, but it was sort of hard to 225 00:10:51,760 --> 00:10:54,680 Speaker 2: accept the idea that there could be so much more 226 00:10:54,760 --> 00:10:58,199 Speaker 2: missing matter out there. It was just one piece of evidence. 227 00:10:58,600 --> 00:11:01,320 Speaker 2: But slowly, over the decades we've pieced together lots of 228 00:11:01,360 --> 00:11:05,040 Speaker 2: totally independent measurements that tell us that there is missing 229 00:11:05,080 --> 00:11:08,079 Speaker 2: stuff out there, that there's matter out there providing gravity 230 00:11:08,440 --> 00:11:09,840 Speaker 2: that we cannot see. 231 00:11:10,040 --> 00:11:12,160 Speaker 1: Like initially, for example, it could have just been that 232 00:11:12,520 --> 00:11:14,880 Speaker 1: galaxies out there had a lot of like dark rocks, 233 00:11:14,960 --> 00:11:18,920 Speaker 1: right or gas that you couldn't see through the telescope exactly. 234 00:11:19,320 --> 00:11:22,080 Speaker 2: Or it could have been that gravity work differently over 235 00:11:22,200 --> 00:11:25,760 Speaker 2: really really long distances, like we've measured gravity in the 236 00:11:25,800 --> 00:11:28,880 Speaker 2: Solar System and on Earth, but maybe over hundreds of 237 00:11:28,920 --> 00:11:32,680 Speaker 2: thousands of light years gravity operates differently than Newton and 238 00:11:32,800 --> 00:11:36,080 Speaker 2: even Einstein suggested that could have been the explanation when 239 00:11:36,120 --> 00:11:39,480 Speaker 2: you were just looking at, one example, just at galaxy 240 00:11:39,559 --> 00:11:42,000 Speaker 2: rotation curves. But now we have lots of other ways 241 00:11:42,000 --> 00:11:44,000 Speaker 2: to probe this, you know, we look for example, at 242 00:11:44,000 --> 00:11:46,680 Speaker 2: the structure of the universe. How did it come together? 243 00:11:46,720 --> 00:11:50,240 Speaker 2: How did you go from blobs of gas mostly dispersed 244 00:11:50,280 --> 00:11:53,880 Speaker 2: through the universe clumping together into stars and galaxies, and 245 00:11:53,960 --> 00:11:57,320 Speaker 2: that requires gravity. And if you run the universe without 246 00:11:57,360 --> 00:11:59,400 Speaker 2: any dark matter, just with the kind of matter we 247 00:11:59,440 --> 00:12:02,400 Speaker 2: can see, you don't get stars and galaxies after fourteen 248 00:12:02,400 --> 00:12:05,480 Speaker 2: billion years. There isn't enough gravity to do it. You've 249 00:12:05,480 --> 00:12:07,880 Speaker 2: got to add in the dark matter and boom, then 250 00:12:07,920 --> 00:12:11,160 Speaker 2: you get a universe that looks just like ours. So 251 00:12:11,200 --> 00:12:13,720 Speaker 2: it's another very convincing piece of evidence that there is 252 00:12:13,880 --> 00:12:16,520 Speaker 2: matter out there. It's not just like gravity operates differently 253 00:12:16,679 --> 00:12:19,240 Speaker 2: that those distance scales. There really is missing matter. 254 00:12:19,480 --> 00:12:21,760 Speaker 1: But could you ask the same question about these large 255 00:12:21,760 --> 00:12:24,920 Speaker 1: scale structure theories. Could it be just that gravity works 256 00:12:24,920 --> 00:12:27,120 Speaker 1: differently though we thought at different scales, and that might 257 00:12:27,200 --> 00:12:29,480 Speaker 1: explain why galaxies form the way they are. 258 00:12:29,600 --> 00:12:32,000 Speaker 2: It is possible, and people who work on these theories 259 00:12:32,000 --> 00:12:36,360 Speaker 2: they're called like mond modified Newtonian dynamics, have tried to 260 00:12:36,400 --> 00:12:39,480 Speaker 2: tweak them. I've not seen one that can successfully explain 261 00:12:39,640 --> 00:12:43,760 Speaker 2: both the galaxy rotation curves and the large scale structure 262 00:12:43,800 --> 00:12:47,080 Speaker 2: of the universe. Mostly these theories are tuned to explain 263 00:12:47,080 --> 00:12:50,160 Speaker 2: the galaxy rotations, and they don't even try to explain 264 00:12:50,200 --> 00:12:51,839 Speaker 2: the other evidence for dark matter. 265 00:12:52,400 --> 00:12:54,280 Speaker 1: What's this other evidence. 266 00:12:53,880 --> 00:12:56,120 Speaker 2: Maybe one of the most compelling and precise piece of 267 00:12:56,160 --> 00:12:58,880 Speaker 2: evidence for dark matter is seeing its effect on the 268 00:12:59,000 --> 00:13:02,520 Speaker 2: very very early universe plasma. Before stars were formed, we 269 00:13:02,600 --> 00:13:05,000 Speaker 2: really had any structure in the universe at all. It 270 00:13:05,040 --> 00:13:07,960 Speaker 2: was just huge blobs of hot gas everywhere in the universe. 271 00:13:08,040 --> 00:13:10,040 Speaker 2: And we see the glow from that gas in the 272 00:13:10,080 --> 00:13:13,960 Speaker 2: cosmic microwave background radiation. When that gas cooled enough to 273 00:13:14,000 --> 00:13:17,800 Speaker 2: become transparent, when it formed neutral atoms, so photons mostly 274 00:13:17,800 --> 00:13:20,600 Speaker 2: could fly through it. Those photons are still around and 275 00:13:20,640 --> 00:13:22,920 Speaker 2: we see them, so they're like the last glow of 276 00:13:22,920 --> 00:13:25,400 Speaker 2: this plasma from the very early universe, and we see 277 00:13:25,480 --> 00:13:28,679 Speaker 2: ripples in that plasma, ripples that show us how the 278 00:13:28,720 --> 00:13:31,280 Speaker 2: normal matter and the dark matter and the photons were 279 00:13:31,280 --> 00:13:35,000 Speaker 2: all sloshing around. And it's a very very precise measurement, 280 00:13:35,400 --> 00:13:37,319 Speaker 2: and it tells us how much normal matter there is 281 00:13:37,360 --> 00:13:39,880 Speaker 2: in the universe, how much radiation there was in the universe, 282 00:13:39,960 --> 00:13:42,160 Speaker 2: how much dark matter there was in the universe back then. 283 00:13:42,679 --> 00:13:45,680 Speaker 2: It's very very precise because we've taken these very very 284 00:13:45,679 --> 00:13:48,880 Speaker 2: detailed maps of this early universe plasma, and that tells 285 00:13:48,960 --> 00:13:51,520 Speaker 2: us that there is a component of that plasma that 286 00:13:51,600 --> 00:13:54,959 Speaker 2: doesn't interact with photons, it's not buryonic, it's not our 287 00:13:55,080 --> 00:13:58,679 Speaker 2: kind of matter at all. So it's another completely independent 288 00:13:58,760 --> 00:14:02,280 Speaker 2: measurement that tells us there's a dark but gravitationally active 289 00:14:02,320 --> 00:14:03,640 Speaker 2: component to the universe. 290 00:14:03,880 --> 00:14:07,520 Speaker 1: Now, is that also due to gravity? Does that evidence 291 00:14:07,520 --> 00:14:09,920 Speaker 1: also depend on our current model of gravity? 292 00:14:10,040 --> 00:14:13,640 Speaker 2: It does, but those are much shorter distances. Those oscillations 293 00:14:13,720 --> 00:14:16,240 Speaker 2: ended up seeding the larger scale structure of the universe, 294 00:14:16,280 --> 00:14:18,199 Speaker 2: but it was before a lot of the expansion. So 295 00:14:18,240 --> 00:14:20,840 Speaker 2: we're talking about things that happened over short distance scales. 296 00:14:21,080 --> 00:14:24,000 Speaker 1: There were a short distance but there are large distance now. 297 00:14:23,880 --> 00:14:26,400 Speaker 2: That's right, But the CMB comes from when it was 298 00:14:26,520 --> 00:14:29,680 Speaker 2: short distance. Earlier, you were asking if this could all 299 00:14:29,720 --> 00:14:32,680 Speaker 2: just be due to like long distance gravitational effects, and 300 00:14:32,760 --> 00:14:36,200 Speaker 2: the CMB proves shorter distance scales gravity because the picture 301 00:14:36,200 --> 00:14:38,000 Speaker 2: we have of it comes from back when things were 302 00:14:38,080 --> 00:14:39,480 Speaker 2: much more cozy and compact. 303 00:14:39,800 --> 00:14:42,200 Speaker 1: All right, So then the prevailing picture is that there's 304 00:14:42,320 --> 00:14:45,120 Speaker 1: a lot of stuff out there, stuff that creates gravity 305 00:14:45,120 --> 00:14:48,360 Speaker 1: and feels gravity, but we just can't see it. So 306 00:14:48,440 --> 00:14:50,680 Speaker 1: let's get into what it could be, how we might 307 00:14:50,760 --> 00:14:53,640 Speaker 1: see it, and what might be new ways to figure 308 00:14:53,640 --> 00:14:56,440 Speaker 1: out where it is and what it's doing. So we'll 309 00:14:56,440 --> 00:14:58,520 Speaker 1: dig into that, but first let's take a quick break. 310 00:15:11,000 --> 00:15:13,440 Speaker 1: All right, we're talking about dark matter now, Daniel. How 311 00:15:13,440 --> 00:15:15,520 Speaker 1: many episodes now have we talked about dark matter? 312 00:15:15,680 --> 00:15:19,400 Speaker 2: Oh? Man, so many episodes. But it's still a thing 313 00:15:19,520 --> 00:15:22,800 Speaker 2: people are most confused and most interested about. In the 314 00:15:22,840 --> 00:15:25,320 Speaker 2: emails we get from people, people are still in the 315 00:15:25,360 --> 00:15:27,760 Speaker 2: dark about it. Yeah, And it's a really active area 316 00:15:27,800 --> 00:15:30,520 Speaker 2: of research, obviously, because it's one of the biggest open 317 00:15:30,640 --> 00:15:34,120 Speaker 2: questions in modern physics. So people are constantly trying to 318 00:15:34,160 --> 00:15:36,600 Speaker 2: come up with new theories for what dark matter might be. 319 00:15:36,960 --> 00:15:38,960 Speaker 2: Is it this particle, is it that particle, Is it 320 00:15:39,040 --> 00:15:41,680 Speaker 2: not a particle at all? Is it something else entirely? 321 00:15:42,200 --> 00:15:45,000 Speaker 2: And new ways to spot dark matter. If it's this 322 00:15:45,080 --> 00:15:46,880 Speaker 2: kind of particle, how could we see it? Could we 323 00:15:46,920 --> 00:15:50,000 Speaker 2: build a detector to observe it. So it's a huge 324 00:15:50,080 --> 00:15:51,200 Speaker 2: area of active research. 325 00:15:51,520 --> 00:15:51,680 Speaker 3: Mm. 326 00:15:51,960 --> 00:15:53,600 Speaker 1: Yeah, I guess we can't just wait for the Sesame 327 00:15:53,720 --> 00:15:54,760 Speaker 1: Street episode on it. 328 00:15:55,880 --> 00:15:57,520 Speaker 2: We could just sit back and wait for the aliens 329 00:15:57,520 --> 00:15:59,400 Speaker 2: to show up and tell us the answers to the universe, 330 00:15:59,440 --> 00:16:01,720 Speaker 2: But that kind of embarrassing if they showed up and 331 00:16:01,760 --> 00:16:03,040 Speaker 2: we had nothing to contribute. 332 00:16:03,120 --> 00:16:04,800 Speaker 1: Yeah, it'd be more embassing if they have to do 333 00:16:04,840 --> 00:16:07,920 Speaker 1: it over dinner while they eat us. I wonder if 334 00:16:07,960 --> 00:16:10,720 Speaker 1: they would feel less bad about eating us if they 335 00:16:10,800 --> 00:16:14,800 Speaker 1: knew we weren't. You know, dark matter intelligence, All right, Well, 336 00:16:14,840 --> 00:16:17,000 Speaker 1: we just kind of define what dark matter is. It's 337 00:16:17,040 --> 00:16:19,280 Speaker 1: the stuff we think that's out there to explain a 338 00:16:19,280 --> 00:16:21,920 Speaker 1: lot of the gravitational effects we see in how the 339 00:16:22,040 --> 00:16:25,640 Speaker 1: universe form and also in the microwave background radiation. Now 340 00:16:25,680 --> 00:16:28,360 Speaker 1: there are candidates where what we think this stuff might. 341 00:16:28,240 --> 00:16:30,680 Speaker 2: Be, right Daniel, There are lots of ideas for what 342 00:16:30,800 --> 00:16:33,840 Speaker 2: dark matter might be, and people initially thought, well, maybe 343 00:16:33,960 --> 00:16:37,040 Speaker 2: dark matter isn't some new, weird kind of stuff. It's 344 00:16:37,120 --> 00:16:39,440 Speaker 2: just more of the kind of stuff we already know about. 345 00:16:39,560 --> 00:16:42,240 Speaker 2: But you know, it's just hiding or something. People thought, 346 00:16:42,280 --> 00:16:46,240 Speaker 2: maybe dark matter is like neutrinos, because neutrinos are tiny 347 00:16:46,280 --> 00:16:49,480 Speaker 2: little particles that don't interact with photons, they don't give 348 00:16:49,480 --> 00:16:52,760 Speaker 2: off light, they don't reflect light, they pass right through 349 00:16:52,800 --> 00:16:55,240 Speaker 2: a lot of stuff. So they seemed initially like a 350 00:16:55,280 --> 00:16:57,960 Speaker 2: really good candidate maybe for dark matter, Like maybe the 351 00:16:58,040 --> 00:17:03,160 Speaker 2: universe is just filled with accountable numbers of neutrinos that 352 00:17:03,200 --> 00:17:05,800 Speaker 2: would have been amazing. But neutrinos don't have a lot 353 00:17:05,840 --> 00:17:09,040 Speaker 2: of mass. They're very very low mass particles, which means 354 00:17:09,080 --> 00:17:11,760 Speaker 2: they almost always move nearly the speed of light. And 355 00:17:11,840 --> 00:17:13,960 Speaker 2: one thing we do know about dark matter is that 356 00:17:14,000 --> 00:17:17,520 Speaker 2: it's kind of slow moving. It's not a fast particle. 357 00:17:17,600 --> 00:17:20,080 Speaker 1: Well, I guess that's Those are two questions. First of all, 358 00:17:20,119 --> 00:17:22,680 Speaker 1: why can't theatrinos go slow? Even if they're light? Can't 359 00:17:22,720 --> 00:17:24,080 Speaker 1: you still stop them from moving? 360 00:17:24,400 --> 00:17:26,959 Speaker 2: You can stop a neutrino because they have very low mass, 361 00:17:27,040 --> 00:17:29,359 Speaker 2: but their mass is so low it's like thousands of 362 00:17:29,400 --> 00:17:33,359 Speaker 2: times lower than even an electron. That essentially any energy 363 00:17:33,359 --> 00:17:35,920 Speaker 2: in putrino has means it's moving at almost the speed 364 00:17:36,000 --> 00:17:37,960 Speaker 2: of light. So it's almost impossible to have a natural 365 00:17:38,000 --> 00:17:40,919 Speaker 2: process that produces a huge number of neutrinos and have 366 00:17:41,040 --> 00:17:42,000 Speaker 2: them be slow moving. 367 00:17:42,280 --> 00:17:44,280 Speaker 1: And you also say dark matter is cold. How do 368 00:17:44,280 --> 00:17:45,720 Speaker 1: we know it is cold if we can't feel it. 369 00:17:45,840 --> 00:17:48,160 Speaker 2: Yeah, we know that dark matter can be moving very 370 00:17:48,160 --> 00:17:51,159 Speaker 2: fast because of the way it's influenced the structure of 371 00:17:51,200 --> 00:17:54,199 Speaker 2: the universe, like, dark matter is mostly responsible for what 372 00:17:54,240 --> 00:17:56,400 Speaker 2: we see out there. The reason you have a galaxy 373 00:17:56,440 --> 00:17:58,919 Speaker 2: here or a galaxy there is because there's a huge 374 00:17:58,960 --> 00:18:02,840 Speaker 2: blob of dark matter that created gravitational attraction that pulled 375 00:18:02,840 --> 00:18:05,760 Speaker 2: all that gas in to form the stars and the galaxy. Now, 376 00:18:05,840 --> 00:18:08,199 Speaker 2: if dark matter was moving really really fast, if it 377 00:18:08,280 --> 00:18:10,240 Speaker 2: was hot, then it wouldn't clump the same way. It 378 00:18:10,240 --> 00:18:13,040 Speaker 2: would spread itself out much more. So, we know that 379 00:18:13,119 --> 00:18:16,120 Speaker 2: dark matter has to be below a certain speed basically, 380 00:18:16,440 --> 00:18:19,280 Speaker 2: or it wouldn't have clumped into these blobs, which then 381 00:18:19,359 --> 00:18:22,560 Speaker 2: formed the structure of the universe. Like you run simulations 382 00:18:22,560 --> 00:18:25,160 Speaker 2: where dark matter is a fast moving particle, you don't 383 00:18:25,160 --> 00:18:27,439 Speaker 2: get the same kind of structure that we see in 384 00:18:27,480 --> 00:18:29,680 Speaker 2: our universe. That means dark matter has to be slow 385 00:18:29,760 --> 00:18:32,240 Speaker 2: moving or cold, as physicists say, and that means that 386 00:18:32,280 --> 00:18:33,399 Speaker 2: it can't be neutrinos. 387 00:18:33,600 --> 00:18:36,320 Speaker 1: Couldn't it be like super massive but hot too? 388 00:18:36,480 --> 00:18:39,960 Speaker 2: Well, hot essentially refers to its velocity regardless of its mass. 389 00:18:40,080 --> 00:18:42,440 Speaker 2: The issue is the velocity, and the problem is neutrinos 390 00:18:42,440 --> 00:18:45,200 Speaker 2: basically can't have low velocity. We know that dark matter 391 00:18:45,440 --> 00:18:48,000 Speaker 2: can't be moving very fast, otherwise it would spread itself 392 00:18:48,040 --> 00:18:50,320 Speaker 2: out and wash out the structure of the universe. 393 00:18:50,560 --> 00:18:52,840 Speaker 1: All right, well, then how is it that we can 394 00:18:52,920 --> 00:18:54,280 Speaker 1: see it? How can we hope to see it and 395 00:18:54,320 --> 00:18:54,720 Speaker 1: study it. 396 00:18:54,720 --> 00:18:56,960 Speaker 2: Then yeah, it's tricky. You know. The one thing that 397 00:18:57,000 --> 00:19:00,440 Speaker 2: we do know is that dark matter feels gravity. Vitational 398 00:19:00,480 --> 00:19:04,280 Speaker 2: studies are surefire way to detect dark matter. The problem 399 00:19:04,359 --> 00:19:06,679 Speaker 2: is that gravity is super duper weak. It's like the 400 00:19:06,720 --> 00:19:09,480 Speaker 2: weakest of the fundamental forces. If it even is a 401 00:19:09,600 --> 00:19:12,679 Speaker 2: fundamental force, it's weaker than the weak force by like 402 00:19:12,880 --> 00:19:16,360 Speaker 2: ten to the thirty, which means that it's basically impossible 403 00:19:16,440 --> 00:19:20,159 Speaker 2: to use gravity to detect tiny bits of dark matter, 404 00:19:20,680 --> 00:19:22,920 Speaker 2: like we can see like Solar System sized chunks of 405 00:19:23,000 --> 00:19:26,600 Speaker 2: dark matter maybe, but anything smaller than that, the gravity 406 00:19:26,640 --> 00:19:28,840 Speaker 2: from it is too weak for us to even detect it. 407 00:19:28,880 --> 00:19:31,159 Speaker 2: And that means that you couldn't really use gravity to 408 00:19:31,240 --> 00:19:34,520 Speaker 2: detect the particle nature of dark matter. Like one of 409 00:19:34,560 --> 00:19:37,679 Speaker 2: the deepest questions is what is dark matter made out of? 410 00:19:37,760 --> 00:19:39,640 Speaker 2: Is that this kind of particle? Is that kind of particle? 411 00:19:39,720 --> 00:19:42,040 Speaker 2: But gravity is really too weak to tell us anything 412 00:19:42,240 --> 00:19:44,320 Speaker 2: about the particle nature of dark. 413 00:19:44,080 --> 00:19:46,720 Speaker 1: Matter, and we don't even know if it is a particle, right, 414 00:19:46,760 --> 00:19:49,439 Speaker 1: it could be that dark matter is something that doesn't 415 00:19:49,560 --> 00:19:51,440 Speaker 1: form into particles. Is that possible. 416 00:19:51,520 --> 00:19:55,320 Speaker 2: It's totally possible. It's not a mainstream idea, like most 417 00:19:55,320 --> 00:19:57,600 Speaker 2: of modern physics right now, is focused on the idea 418 00:19:57,640 --> 00:20:00,040 Speaker 2: of particle dark matter, because the kind of matter we 419 00:20:00,200 --> 00:20:02,480 Speaker 2: know is all made of particles, and so we extrapolate 420 00:20:02,440 --> 00:20:04,840 Speaker 2: and we say, well, probably this other kind of matter 421 00:20:04,880 --> 00:20:07,080 Speaker 2: is made out of particles. And you might think that 422 00:20:07,119 --> 00:20:10,120 Speaker 2: sounds reasonable. It's a pretty basic assumption, but it's also 423 00:20:10,200 --> 00:20:13,520 Speaker 2: extrapolating from five percent of the universe to like twenty 424 00:20:13,520 --> 00:20:16,600 Speaker 2: five percent of the universe. It's entirely possible that the 425 00:20:16,600 --> 00:20:19,720 Speaker 2: physics of this other huge section of the universe is 426 00:20:19,880 --> 00:20:22,600 Speaker 2: very different from anything we've imagined. We've talked in the 427 00:20:22,600 --> 00:20:26,400 Speaker 2: podcast before about unparticles or other weird kind of theories 428 00:20:26,520 --> 00:20:28,919 Speaker 2: that describe it as not made of particles. So like 429 00:20:28,960 --> 00:20:31,679 Speaker 2: as you zoom in, it doesn't ever change. It's not 430 00:20:31,720 --> 00:20:33,840 Speaker 2: like there's a basic unit of it. You can just 431 00:20:33,920 --> 00:20:36,399 Speaker 2: keep zooming in forever and it always looks the same. 432 00:20:36,920 --> 00:20:39,439 Speaker 2: That would be really weird but super awesome. But the 433 00:20:39,480 --> 00:20:42,639 Speaker 2: mainstream theories are mostly particle dark matter because that's what 434 00:20:42,720 --> 00:20:43,280 Speaker 2: we know how to. 435 00:20:43,280 --> 00:20:46,320 Speaker 1: Think about, because that's kind of the only way to 436 00:20:46,359 --> 00:20:47,320 Speaker 1: think about things right. 437 00:20:47,280 --> 00:20:49,320 Speaker 2: Well, you know, there are people trying to think outside 438 00:20:49,359 --> 00:20:52,360 Speaker 2: the box. That requires a lot more creativity and flashes 439 00:20:52,400 --> 00:20:54,639 Speaker 2: of insight. But there definitely are people out there working 440 00:20:54,680 --> 00:20:57,600 Speaker 2: on sort of crazier theories of what dark matter is. 441 00:20:57,800 --> 00:21:00,640 Speaker 2: But I think most people are working on article dark 442 00:21:00,680 --> 00:21:03,080 Speaker 2: matter because yeah, that's what we're good at thinking about. 443 00:21:03,359 --> 00:21:05,119 Speaker 2: I mean, you talk to a particle physicist, you're going 444 00:21:05,119 --> 00:21:07,040 Speaker 2: to get a particle explanation for everything. 445 00:21:07,680 --> 00:21:10,199 Speaker 1: I guess. I mean, like, we haven't seen anything that 446 00:21:10,480 --> 00:21:14,720 Speaker 1: isn't explained by particle theory, right, and we wouldn't even 447 00:21:14,760 --> 00:21:16,800 Speaker 1: know what that math would look like. 448 00:21:16,960 --> 00:21:19,479 Speaker 2: Yes and no, we've never seen anything that we've been 449 00:21:19,480 --> 00:21:22,600 Speaker 2: able to explain with a non particle based theory. But 450 00:21:22,760 --> 00:21:25,480 Speaker 2: remember there's ninety five percent of the universe dark matter 451 00:21:25,520 --> 00:21:28,080 Speaker 2: and dark energy that we still can't really explain. So 452 00:21:28,160 --> 00:21:30,000 Speaker 2: particle based theories are the only ones that have ever 453 00:21:30,000 --> 00:21:32,639 Speaker 2: been successful, but they've only been successful in five percent 454 00:21:32,720 --> 00:21:33,560 Speaker 2: of the universe. 455 00:21:34,280 --> 00:21:36,399 Speaker 1: So yes and no, I guess there's a lot out 456 00:21:36,440 --> 00:21:39,840 Speaker 1: there that we can't still explain. So maybe our current 457 00:21:39,880 --> 00:21:42,000 Speaker 1: theory only covers five percent of the universe. 458 00:21:42,160 --> 00:21:44,520 Speaker 2: Yeah, that's exactly right. So we should definitely keep an 459 00:21:44,520 --> 00:21:47,800 Speaker 2: open mind to other crazy theories of what dark matter 460 00:21:47,880 --> 00:21:51,400 Speaker 2: might be. But currently we're mostly working on. Is dark 461 00:21:51,440 --> 00:21:53,880 Speaker 2: matter a particle? Is it a new kind of particle? 462 00:21:54,160 --> 00:21:56,600 Speaker 2: What does it do? How could we possibly spot it 463 00:21:56,760 --> 00:21:57,800 Speaker 2: if it is a particle? 464 00:21:57,920 --> 00:21:59,840 Speaker 1: All right, So if it is a particle, how do 465 00:21:59,880 --> 00:22:01,679 Speaker 1: we see it? How do we study it? We know 466 00:22:01,720 --> 00:22:04,040 Speaker 1: that it feels gravity, what else does it feel or 467 00:22:04,080 --> 00:22:04,480 Speaker 1: not feel? 468 00:22:04,560 --> 00:22:06,600 Speaker 2: So the short answer is we have no idea. Like, 469 00:22:06,680 --> 00:22:08,800 Speaker 2: it could be that dark matter feels some new kind 470 00:22:08,800 --> 00:22:11,200 Speaker 2: of force with itself. It could be the dark matter 471 00:22:11,200 --> 00:22:14,320 Speaker 2: feels no forces other than gravity, and like that could 472 00:22:14,400 --> 00:22:18,120 Speaker 2: totally be our universe, in which case it's almost impossible 473 00:22:18,160 --> 00:22:21,280 Speaker 2: to ever discover the particle nature of dark matter. It 474 00:22:21,280 --> 00:22:24,320 Speaker 2: could just be a mystery forever because gravity is just 475 00:22:24,400 --> 00:22:27,080 Speaker 2: so weak. There's another possibility that dark matter is kind 476 00:22:27,119 --> 00:22:31,520 Speaker 2: of misnamed, that dark matter does actually interact with our 477 00:22:31,680 --> 00:22:35,119 Speaker 2: kind of matter through some mechanism we haven't discovered yet 478 00:22:35,280 --> 00:22:37,760 Speaker 2: that's not really truly one hundred percent. 479 00:22:37,560 --> 00:22:41,760 Speaker 1: Dark, But I guess you mean using electromagnetic forces or 480 00:22:41,800 --> 00:22:44,119 Speaker 1: other kinds of forces, like it dark in terms of 481 00:22:44,240 --> 00:22:47,119 Speaker 1: light or dark in terms of all the forces in nature. 482 00:22:47,240 --> 00:22:50,000 Speaker 2: We're imagining maybe there's a new force out there also, 483 00:22:50,280 --> 00:22:52,600 Speaker 2: So we're suggesting maybe dark matter is some new kind 484 00:22:52,600 --> 00:22:55,840 Speaker 2: of particle, right, And in addition, maybe there's a new 485 00:22:55,880 --> 00:22:59,200 Speaker 2: force out there, a force that helps dark matter particles 486 00:22:59,240 --> 00:23:02,199 Speaker 2: interact with our kind of particles. So call this a 487 00:23:02,240 --> 00:23:04,840 Speaker 2: new dark force or a portal to the dark sector 488 00:23:04,960 --> 00:23:08,000 Speaker 2: or whatever. If there is this new kind of force, 489 00:23:08,280 --> 00:23:11,400 Speaker 2: then maybe it helps dark matter particles bump into our 490 00:23:11,480 --> 00:23:14,000 Speaker 2: kind of particles, or turn into our kind of particles, 491 00:23:14,080 --> 00:23:17,480 Speaker 2: or somehow interact with our kind of particles, which would 492 00:23:17,520 --> 00:23:18,960 Speaker 2: make them effectively visible. 493 00:23:20,040 --> 00:23:22,480 Speaker 1: But would you need to come up with a new 494 00:23:22,640 --> 00:23:25,359 Speaker 1: kind of force. Couldn't interact with us through the weak 495 00:23:25,400 --> 00:23:26,879 Speaker 1: force or the strong force somehow? 496 00:23:27,040 --> 00:23:29,720 Speaker 2: It's totally possible that dark matter could have interacted with 497 00:23:29,800 --> 00:23:32,600 Speaker 2: us via one of the forces we know already, but 498 00:23:32,640 --> 00:23:34,960 Speaker 2: we've basically ruled that out with our experiments. 499 00:23:35,119 --> 00:23:36,600 Speaker 1: Have we really is that official? 500 00:23:36,680 --> 00:23:38,960 Speaker 2: If dark matter interacted with a strong force, it would 501 00:23:39,000 --> 00:23:41,800 Speaker 2: be a very powerful interaction because the strong force is 502 00:23:41,920 --> 00:23:45,000 Speaker 2: super duper strong, and that would actually be pretty easy 503 00:23:45,040 --> 00:23:47,440 Speaker 2: to find. We look for dark matter giving off photons. 504 00:23:47,480 --> 00:23:49,840 Speaker 2: We've never seen that, so we don't think that dark 505 00:23:49,880 --> 00:23:53,919 Speaker 2: matter actually directly interacts with photons. We've also looked for 506 00:23:54,040 --> 00:23:56,480 Speaker 2: dark matter interacting via the weak force. And this is 507 00:23:56,520 --> 00:23:59,760 Speaker 2: probably the biggest area of experimental dark matter particle physics 508 00:23:59,840 --> 00:24:04,159 Speaker 2: right now, with these huge tanks underground very quiet liquid 509 00:24:04,240 --> 00:24:07,560 Speaker 2: like xenon, and we wait for dark matter to pass 510 00:24:07,640 --> 00:24:10,359 Speaker 2: through the Earth and interact with one of these xenon 511 00:24:10,440 --> 00:24:12,960 Speaker 2: molecules and give it a little kick. So these huge 512 00:24:13,040 --> 00:24:16,320 Speaker 2: tanks of underground liquid xenon are just waiting for a 513 00:24:16,359 --> 00:24:19,040 Speaker 2: dark matter particle to bump into it via the weak force. 514 00:24:19,160 --> 00:24:20,919 Speaker 2: And if it does interact via the weak force, we 515 00:24:20,920 --> 00:24:23,520 Speaker 2: can calculate how often that should happen. And we've been 516 00:24:23,600 --> 00:24:26,359 Speaker 2: running these experiments for years and years and years, and 517 00:24:26,400 --> 00:24:29,560 Speaker 2: we've never seen a blip that looks like dark matter 518 00:24:29,960 --> 00:24:32,840 Speaker 2: kicking one of these xenon molecules via the weak force. 519 00:24:33,280 --> 00:24:35,520 Speaker 2: So now we can pretty definitely rule it out. 520 00:24:36,400 --> 00:24:38,959 Speaker 1: I see, we've been putting stuff out there to hopefully 521 00:24:39,000 --> 00:24:41,280 Speaker 1: interact with dark matter through the weak force, but so 522 00:24:41,359 --> 00:24:44,320 Speaker 1: far nothing has been bumped that way. So now you're 523 00:24:44,400 --> 00:24:48,359 Speaker 1: saying the dark matter probably doesn't interact with the weak force. 524 00:24:48,520 --> 00:24:50,359 Speaker 2: As time goes on and we don't see any of 525 00:24:50,359 --> 00:24:53,359 Speaker 2: those interactions, we more confidently say that they never happen. 526 00:24:53,520 --> 00:24:55,040 Speaker 2: If you only listen for a day. It might be 527 00:24:55,080 --> 00:24:56,679 Speaker 2: that they only happen once a year and you just 528 00:24:56,720 --> 00:24:59,480 Speaker 2: haven't seen one yet. But after you've listened for five years, 529 00:24:59,520 --> 00:25:03,040 Speaker 2: ten years, twenty years, either you're getting very very unlucky 530 00:25:03,280 --> 00:25:05,560 Speaker 2: or it just doesn't happen. And so now we've had 531 00:25:05,600 --> 00:25:08,439 Speaker 2: big enough detectors running for enough years that were pretty 532 00:25:08,440 --> 00:25:11,159 Speaker 2: confident in ruling that out. But it doesn't mean that 533 00:25:11,200 --> 00:25:14,040 Speaker 2: there isn't a new kind of force, like an even 534 00:25:14,160 --> 00:25:17,199 Speaker 2: weaker force, that would allow dark matter to interact with 535 00:25:17,200 --> 00:25:19,600 Speaker 2: our detectors. So that's what they're looking for now. Like 536 00:25:19,880 --> 00:25:21,359 Speaker 2: they call it the feeble force. 537 00:25:21,600 --> 00:25:25,040 Speaker 1: It's weaker than weak. That's the idea, exactly weaker than weak. 538 00:25:25,119 --> 00:25:28,119 Speaker 1: We only we have seen that already with our detectors, 539 00:25:28,200 --> 00:25:30,800 Speaker 1: with the tanks of Xenon they're sitting there waiting. 540 00:25:31,080 --> 00:25:33,719 Speaker 2: Depends on how weak it is. If it's super duper 541 00:25:33,800 --> 00:25:36,480 Speaker 2: extra week, if it's the feeblest force, you can imagine 542 00:25:36,560 --> 00:25:38,720 Speaker 2: it might take a very very long time. It might 543 00:25:38,760 --> 00:25:41,760 Speaker 2: be so unlikely they have to run for ten years 544 00:25:41,880 --> 00:25:44,280 Speaker 2: or one hundred years in order to see it. And 545 00:25:44,320 --> 00:25:46,480 Speaker 2: that's why we're also at the same time using other 546 00:25:46,560 --> 00:25:49,080 Speaker 2: methods to try to look for these kinds of interactions, 547 00:25:49,200 --> 00:25:51,679 Speaker 2: like we're hoping to use this new feeble force to 548 00:25:51,800 --> 00:25:54,280 Speaker 2: create dark matter at particle colliders. 549 00:25:54,520 --> 00:25:56,840 Speaker 1: What do you mean, like when you collide protons or 550 00:25:57,000 --> 00:25:59,720 Speaker 1: quarks like that, it might make dark matter. 551 00:25:59,760 --> 00:26:04,040 Speaker 2: Yeah, if this feeble force exists that allows dark matter 552 00:26:04,080 --> 00:26:07,520 Speaker 2: to bump into protons and neutrons inside a xenon atom, 553 00:26:07,960 --> 00:26:11,240 Speaker 2: then in principle you can reverse that. You can say, well, 554 00:26:11,240 --> 00:26:14,000 Speaker 2: what if we smash protons together, maybe sometimes they can 555 00:26:14,119 --> 00:26:16,719 Speaker 2: use the feeble force to create dark matter. Because that's 556 00:26:16,760 --> 00:26:19,440 Speaker 2: what we do with the particle collider. We annihilate protons 557 00:26:19,480 --> 00:26:22,760 Speaker 2: together and create new kinds of stuff. And the cool 558 00:26:22,760 --> 00:26:24,840 Speaker 2: thing about a collider is that anything that's out there, 559 00:26:24,920 --> 00:26:27,080 Speaker 2: you can make it as long as your protons can 560 00:26:27,119 --> 00:26:30,119 Speaker 2: interact with it. So anything that protons interact with we 561 00:26:30,200 --> 00:26:32,960 Speaker 2: produce at the collider eventually. Things that interact with protons 562 00:26:32,960 --> 00:26:35,119 Speaker 2: a lot, we produce them all the time. Things that 563 00:26:35,119 --> 00:26:37,919 Speaker 2: don't interact with protons very often, we produce them more rarely, 564 00:26:38,000 --> 00:26:40,439 Speaker 2: So higgs bosons are pretty rare, for example. But we 565 00:26:40,560 --> 00:26:43,159 Speaker 2: comb through all of those collisions looking for evidence of 566 00:26:43,200 --> 00:26:44,520 Speaker 2: the production of dark matter. 567 00:26:44,640 --> 00:26:47,400 Speaker 1: Wouldn't we have seen evidence of that already? I mean, 568 00:26:47,400 --> 00:26:49,560 Speaker 1: you've been running the LHC for a long time and 569 00:26:49,960 --> 00:26:53,040 Speaker 1: particle colliders for decades. You know, if there was some 570 00:26:53,080 --> 00:26:56,119 Speaker 1: sort of unaccounted for force, wouldn't we have seen it 571 00:26:56,119 --> 00:26:56,480 Speaker 1: by now? 572 00:26:56,680 --> 00:26:59,200 Speaker 2: We haven't seen anything. You're right, And again it's a 573 00:26:59,280 --> 00:27:02,200 Speaker 2: question to the of that force. If that force was 574 00:27:02,240 --> 00:27:04,240 Speaker 2: as strong as the weak force, yeah, we probably would 575 00:27:04,240 --> 00:27:06,760 Speaker 2: have seen it. And the longer we run our colliders 576 00:27:06,760 --> 00:27:09,320 Speaker 2: and don't see it, the weaker that force has to 577 00:27:09,359 --> 00:27:11,600 Speaker 2: be to still be consistent with our data, to still 578 00:27:11,600 --> 00:27:14,640 Speaker 2: be hiding from all of these experiments. But we don't 579 00:27:14,640 --> 00:27:17,720 Speaker 2: know how weak that force is. Maybe it's really ridiculously weak, 580 00:27:18,000 --> 00:27:20,119 Speaker 2: so weak that we haven't seen it underground and we 581 00:27:20,200 --> 00:27:22,480 Speaker 2: haven't seen it in our colliders. So we actually turn 582 00:27:22,560 --> 00:27:25,919 Speaker 2: to another mechanism to try to see this super duper 583 00:27:25,960 --> 00:27:28,040 Speaker 2: weak force in action, which is to look at the 584 00:27:28,040 --> 00:27:30,399 Speaker 2: center of the galaxy to see if dark matter is 585 00:27:30,440 --> 00:27:31,720 Speaker 2: smashing into itself. 586 00:27:32,200 --> 00:27:34,760 Speaker 1: I see use the center of the galaxy as a 587 00:27:34,920 --> 00:27:36,720 Speaker 1: particle collider. 588 00:27:36,440 --> 00:27:39,320 Speaker 2: Exactly because one problem with the particle collider is that 589 00:27:39,359 --> 00:27:42,720 Speaker 2: it's not very dense. Right. We have protons smashing into protons, 590 00:27:42,760 --> 00:27:45,399 Speaker 2: but it's like very few protons and we try to 591 00:27:45,480 --> 00:27:48,080 Speaker 2: run it as often as we can, and it adds 592 00:27:48,200 --> 00:27:50,960 Speaker 2: up to zillions of collisions, but it just might not 593 00:27:51,040 --> 00:27:53,399 Speaker 2: be enough. But we think that the center of the 594 00:27:53,480 --> 00:27:56,680 Speaker 2: galaxy is very very dense with dark matter. We can 595 00:27:56,720 --> 00:27:58,840 Speaker 2: map out where the dark matter is in the galaxy 596 00:27:58,880 --> 00:28:01,560 Speaker 2: by looking at how things rouse and how fast things 597 00:28:01,600 --> 00:28:03,679 Speaker 2: are moving, and we suspect that the center of the 598 00:28:03,720 --> 00:28:06,960 Speaker 2: galaxy is very dense with dark matter. And so if 599 00:28:07,040 --> 00:28:10,080 Speaker 2: dark matter has this feeble force, this super weak force, 600 00:28:10,440 --> 00:28:13,560 Speaker 2: then occasionally two dark matter particles should bump into each 601 00:28:13,560 --> 00:28:17,040 Speaker 2: other and produce normal matter particles, like the opposite of 602 00:28:17,040 --> 00:28:19,160 Speaker 2: what we think might happen in the collider, which two 603 00:28:19,200 --> 00:28:22,320 Speaker 2: protons smash together to make dark matter run that backwards 604 00:28:22,359 --> 00:28:25,439 Speaker 2: in time. We hope that's the operation happening in the 605 00:28:25,480 --> 00:28:28,880 Speaker 2: center of the galaxy. So we turn these special telescopes 606 00:28:28,920 --> 00:28:30,560 Speaker 2: to the wards the center of the galaxy and look 607 00:28:30,640 --> 00:28:34,119 Speaker 2: for these characteristic flashes of light that might come from 608 00:28:34,200 --> 00:28:34,960 Speaker 2: those collisions. 609 00:28:35,440 --> 00:28:37,840 Speaker 1: Interesting, that sounds a little cheaper than building a thirty 610 00:28:37,880 --> 00:28:39,160 Speaker 1: billion dollar collider here. 611 00:28:40,240 --> 00:28:42,560 Speaker 2: Well, it was only ten billion dollars, right, so we 612 00:28:42,600 --> 00:28:44,960 Speaker 2: can save you twenty billion off the top right there, 613 00:28:45,040 --> 00:28:47,040 Speaker 2: and it wasn't that cheap because you're building a particle 614 00:28:47,080 --> 00:28:51,000 Speaker 2: detector and launching it into space, which is never simple. 615 00:28:51,080 --> 00:28:53,200 Speaker 1: All right, Well, let's get into the details of how 616 00:28:53,240 --> 00:28:55,480 Speaker 1: we're using the center of the galaxy as a collider 617 00:28:55,560 --> 00:28:57,840 Speaker 1: to look for dark matter. Let's dig into that, but 618 00:28:57,880 --> 00:29:13,280 Speaker 1: first let's take another quick break. All right, we're looking 619 00:29:13,320 --> 00:29:15,640 Speaker 1: for dark matter. I had some right here, Daniel. You 620 00:29:15,640 --> 00:29:16,760 Speaker 1: don't know where I put it. 621 00:29:16,880 --> 00:29:19,320 Speaker 2: I can give you emoji based directions to it, Derry, 622 00:29:19,760 --> 00:29:21,240 Speaker 2: I'll send you some arrows. 623 00:29:21,080 --> 00:29:24,000 Speaker 1: That might not be helpful there. But yeah, there's a 624 00:29:24,000 --> 00:29:27,320 Speaker 1: lot of matter missing in the universe. All twenty seven 625 00:29:27,360 --> 00:29:30,240 Speaker 1: percent of the universe is out there, but it's invisible. 626 00:29:30,280 --> 00:29:32,360 Speaker 1: We can't see it or touch it called dark matter, 627 00:29:32,920 --> 00:29:36,680 Speaker 1: and our only hope for ever studying its particle nature 628 00:29:36,800 --> 00:29:39,160 Speaker 1: is that there's some sort of new force that we 629 00:29:39,240 --> 00:29:42,600 Speaker 1: haven't discovered yet, some super weak force that you're calling 630 00:29:42,640 --> 00:29:45,240 Speaker 1: the feeble force. Although Daniel, I'm kind of disappointing you 631 00:29:45,400 --> 00:29:47,000 Speaker 1: didn't call it the dark force. 632 00:29:48,880 --> 00:29:51,960 Speaker 2: Because then forever it would dominate my destiny exactly right. 633 00:29:52,520 --> 00:29:55,560 Speaker 1: Then you get the cool red lightsabers or the cool 634 00:29:55,600 --> 00:29:57,200 Speaker 1: laser pointers when you give your lectures. 635 00:29:57,320 --> 00:29:58,840 Speaker 2: Yeah, that's true, but I didn't want to have to 636 00:29:58,840 --> 00:29:59,600 Speaker 2: grow those horns. 637 00:30:00,240 --> 00:30:01,280 Speaker 1: Sith have horns. 638 00:30:01,480 --> 00:30:02,160 Speaker 2: That's relief. 639 00:30:03,040 --> 00:30:05,480 Speaker 1: You need to brush up on your Star Wars there apparently. Yeah, 640 00:30:05,720 --> 00:30:08,520 Speaker 1: but yeah. Our only hope forever studying the particle nature 641 00:30:08,520 --> 00:30:10,400 Speaker 1: of dark matter is that it feels a new kind 642 00:30:10,400 --> 00:30:13,240 Speaker 1: of force we haven't seen before, and we can't generate 643 00:30:13,280 --> 00:30:16,000 Speaker 1: that force apparently here in our colliders. But there's hope 644 00:30:16,040 --> 00:30:18,080 Speaker 1: that maybe you can use the center of the galaxy 645 00:30:18,280 --> 00:30:22,920 Speaker 1: as a collider to maybe study this part of this 646 00:30:23,000 --> 00:30:26,440 Speaker 1: aspect of dark matter we think we're hoping is there. 647 00:30:26,320 --> 00:30:29,600 Speaker 2: Exactly, And the idea is dark matter smashes into itself 648 00:30:29,840 --> 00:30:33,760 Speaker 2: and then via this new feeble force, turns into standard 649 00:30:33,760 --> 00:30:37,520 Speaker 2: model particles, maybe tau leptons or be quarks or something, 650 00:30:38,000 --> 00:30:40,840 Speaker 2: and those particles can then give you flashes of light 651 00:30:40,920 --> 00:30:44,200 Speaker 2: because those particles do interact with light. So what we 652 00:30:44,240 --> 00:30:46,160 Speaker 2: do is we turn this telescope to the center of 653 00:30:46,200 --> 00:30:48,920 Speaker 2: the galaxy and we look for these flashes of light 654 00:30:48,960 --> 00:30:52,200 Speaker 2: that we can't otherwise explain. If you see flashes of 655 00:30:52,240 --> 00:30:54,600 Speaker 2: light that look like they come from dark matter turning 656 00:30:54,640 --> 00:30:57,120 Speaker 2: into particles, we know, then you can say, oh, there's 657 00:30:57,160 --> 00:30:58,800 Speaker 2: evidence for dark matter. There. 658 00:30:58,920 --> 00:31:02,680 Speaker 1: Wait, the idea is that dark matter smashes into itself. 659 00:31:02,880 --> 00:31:04,720 Speaker 1: Why does it have to smash into itself. 660 00:31:05,040 --> 00:31:07,240 Speaker 2: It doesn't have to. It's possible for dark matter also 661 00:31:07,360 --> 00:31:10,400 Speaker 2: interact with normal matter particles in the sension of the galaxy, 662 00:31:10,520 --> 00:31:12,720 Speaker 2: the way it might interact, for example, with our tanks 663 00:31:12,760 --> 00:31:15,960 Speaker 2: of Xenon underground. But the signature we're looking for would 664 00:31:16,040 --> 00:31:19,880 Speaker 2: come from two dark matter particles smashing into itself, producing 665 00:31:20,000 --> 00:31:21,840 Speaker 2: like a pair of bottom quarks or a pair of 666 00:31:21,880 --> 00:31:25,760 Speaker 2: tau leptons, which then give off some photons which travel 667 00:31:25,840 --> 00:31:27,840 Speaker 2: to our telescope and we observe them. 668 00:31:27,960 --> 00:31:31,160 Speaker 1: Wait, so two dark matter particles can interact with each 669 00:31:31,200 --> 00:31:35,120 Speaker 1: other and generate regular kind of matter? Yeah, exactly does 670 00:31:35,120 --> 00:31:37,320 Speaker 1: that work the other way too? Like, can regular matter 671 00:31:37,520 --> 00:31:39,360 Speaker 1: interact and come up with dark matter? 672 00:31:39,400 --> 00:31:40,760 Speaker 2: That's what we're trying to do with the Large Hadron 673 00:31:40,840 --> 00:31:44,160 Speaker 2: collider is smash regular matter together two protons and turn 674 00:31:44,240 --> 00:31:46,720 Speaker 2: it into dark matter. We haven't seen that yet, so 675 00:31:46,720 --> 00:31:49,400 Speaker 2: we're trying to do the opposite, smash dark matter together 676 00:31:49,480 --> 00:31:52,160 Speaker 2: and turn it into regular matter. It's like the inverse collider. 677 00:31:52,360 --> 00:31:56,040 Speaker 1: What's the inverse of a collider? An expander as a separator. 678 00:31:56,120 --> 00:31:58,720 Speaker 2: It just runs it the other direction, you know, instead 679 00:31:58,720 --> 00:32:00,880 Speaker 2: of colliding normal matter to make dark matter, and we 680 00:32:00,920 --> 00:32:02,800 Speaker 2: collide dark matter to make normal matter. 681 00:32:02,920 --> 00:32:05,560 Speaker 1: So the picture is that in the center of the galaxy, 682 00:32:05,640 --> 00:32:08,040 Speaker 1: you're saying, there's a high density of dark matter, and 683 00:32:08,200 --> 00:32:11,400 Speaker 1: some dark matter particle just happens to smash head on 684 00:32:11,480 --> 00:32:14,720 Speaker 1: with another dark matter particle. Hopefully they're going fast enough 685 00:32:14,720 --> 00:32:18,160 Speaker 1: to actually sort of interact and create a lot of energy. 686 00:32:18,520 --> 00:32:21,240 Speaker 1: And then out of that comes a regular matter particle 687 00:32:22,240 --> 00:32:24,680 Speaker 1: from the center of the galaxy that then we see 688 00:32:24,720 --> 00:32:27,120 Speaker 1: here on Earth and go, yep, that came from two 689 00:32:27,200 --> 00:32:28,120 Speaker 1: dark matter particles. 690 00:32:28,160 --> 00:32:31,360 Speaker 2: Yeah, And if you want the microparticle physics explanation, two 691 00:32:31,480 --> 00:32:34,920 Speaker 2: dark matter particles smashed together form some new kind of 692 00:32:34,960 --> 00:32:38,160 Speaker 2: particle that mediates this feeble force, call it a dark 693 00:32:38,200 --> 00:32:41,880 Speaker 2: photon or something. And then that dark photon turns into 694 00:32:42,000 --> 00:32:45,400 Speaker 2: a pair of normal particles like two bottom corks or 695 00:32:45,440 --> 00:32:48,840 Speaker 2: two tau leptons or two muons or something, and then 696 00:32:49,040 --> 00:32:51,640 Speaker 2: those produce photons which then we see here. 697 00:32:51,760 --> 00:32:54,640 Speaker 1: But then how can we hope to like discern that 698 00:32:54,720 --> 00:32:57,440 Speaker 1: from all the way here the center of the galaxy is, 699 00:32:57,760 --> 00:32:59,560 Speaker 1: you know, fifty thousand light years away. 700 00:32:59,600 --> 00:33:02,320 Speaker 2: It's very very tricky, and that's exactly the difficulty of 701 00:33:02,360 --> 00:33:05,560 Speaker 2: this method. Number one. It's far away. We think that 702 00:33:05,600 --> 00:33:08,760 Speaker 2: these photons would be very high energy, so we think 703 00:33:08,800 --> 00:33:11,720 Speaker 2: that gamma rays would survive travel from the center of 704 00:33:11,760 --> 00:33:14,160 Speaker 2: the galaxy. But the real problem is that we don't 705 00:33:14,200 --> 00:33:16,200 Speaker 2: understand the center of the galaxy. So a lot of 706 00:33:16,240 --> 00:33:19,479 Speaker 2: stuff going on there, making flashes of light anyway that 707 00:33:19,560 --> 00:33:22,640 Speaker 2: we can't really understand. And so actually we have seen 708 00:33:23,000 --> 00:33:25,400 Speaker 2: flashes of light from the center of the galaxy that 709 00:33:25,480 --> 00:33:29,360 Speaker 2: we cannot explain that No astrophysical explanation has been provided 710 00:33:29,400 --> 00:33:31,560 Speaker 2: to explain these flashes of light, and so some people 711 00:33:31,560 --> 00:33:34,200 Speaker 2: are actually pretty excited about that. They say, whoa, maybe 712 00:33:34,240 --> 00:33:36,880 Speaker 2: this is dark matter. But you know, the problem is, 713 00:33:36,920 --> 00:33:39,240 Speaker 2: we don't really know what's in there in the center 714 00:33:39,280 --> 00:33:41,680 Speaker 2: of the galaxy. It's a very weird, dense region. We 715 00:33:41,800 --> 00:33:44,000 Speaker 2: just did a whole episode about how weird it is 716 00:33:44,040 --> 00:33:46,840 Speaker 2: and how little we understand about what's there. So it 717 00:33:46,920 --> 00:33:49,640 Speaker 2: could just be new, weird stuff made of normal matter 718 00:33:49,680 --> 00:33:52,120 Speaker 2: in the center of the galaxy flashing lights and ways 719 00:33:52,160 --> 00:33:55,440 Speaker 2: we don't understand, or it could be dark matter creating 720 00:33:55,440 --> 00:33:56,440 Speaker 2: these flashes of light. 721 00:33:56,560 --> 00:33:59,200 Speaker 1: Wait, wait, wait, what do these flashes look like? Like 722 00:33:59,280 --> 00:34:01,120 Speaker 1: You're just looking at at the galaxy center of the 723 00:34:01,120 --> 00:34:05,080 Speaker 1: galaxy and suddenly there's like a spike or a pulse 724 00:34:05,280 --> 00:34:08,799 Speaker 1: or a train of pulses. What do these flashes look like? 725 00:34:08,880 --> 00:34:12,719 Speaker 2: So these flashes come as individual photons. So this telescope, 726 00:34:12,719 --> 00:34:15,799 Speaker 2: a Fermila telescope, can see gamma ray photons, which are 727 00:34:15,840 --> 00:34:18,600 Speaker 2: just photons in a certain energy range in this case 728 00:34:18,600 --> 00:34:22,440 Speaker 2: from fifty million electron volts up to a trillion electron volts. 729 00:34:22,480 --> 00:34:25,080 Speaker 2: And they see a bunch of these gamma ray photons 730 00:34:25,120 --> 00:34:28,319 Speaker 2: from the center of the galaxy, and we cannot explain. 731 00:34:27,960 --> 00:34:30,040 Speaker 1: Them otherwise, like one at a time, Well, the. 732 00:34:29,960 --> 00:34:32,080 Speaker 2: Detector can only see one photon at a time. 733 00:34:32,160 --> 00:34:33,840 Speaker 1: Yeah, I guess. I mean, like you see one and 734 00:34:33,840 --> 00:34:36,000 Speaker 1: then you don't see one for another year. Or is 735 00:34:36,040 --> 00:34:37,359 Speaker 1: it do you see like a whole bunch of them 736 00:34:37,360 --> 00:34:38,640 Speaker 1: in a cluster or something. 737 00:34:38,760 --> 00:34:40,880 Speaker 2: So the higher energies are definitely more rare than they 738 00:34:40,920 --> 00:34:42,920 Speaker 2: are at the lower energies, but there's a lot of them. 739 00:34:42,960 --> 00:34:45,239 Speaker 2: It's not just like one or two or seven photons. 740 00:34:45,440 --> 00:34:48,080 Speaker 2: You know, we're talking about thousands of photons here, accumulated 741 00:34:48,120 --> 00:34:51,000 Speaker 2: over many, many years and so people are trying to 742 00:34:51,080 --> 00:34:54,080 Speaker 2: understand where are these photons coming from. Is there something 743 00:34:54,120 --> 00:34:55,840 Speaker 2: going on with normal matter at the center of the 744 00:34:55,840 --> 00:34:58,240 Speaker 2: galaxy or is this actually dark matter? 745 00:34:58,360 --> 00:35:00,920 Speaker 1: But I guess, why are they eplainable or why are 746 00:35:00,960 --> 00:35:03,279 Speaker 1: they so mysterious. Isn't it just like, oh, here's a 747 00:35:03,320 --> 00:35:05,080 Speaker 1: photo with a lot of energy. 748 00:35:05,880 --> 00:35:07,680 Speaker 2: Well, we have an idea for what's in the center 749 00:35:07,680 --> 00:35:10,080 Speaker 2: of the galaxy. We think that there's a black hole there, 750 00:35:10,080 --> 00:35:11,920 Speaker 2: and we think there's a swirl of stuff around the 751 00:35:11,920 --> 00:35:14,320 Speaker 2: black hole, and we think there's a certain density of stars. 752 00:35:14,360 --> 00:35:16,560 Speaker 2: We think there's gas and dust and all sorts of stuff, 753 00:35:17,040 --> 00:35:19,320 Speaker 2: and we use that model to predict what we should 754 00:35:19,360 --> 00:35:21,799 Speaker 2: see from the center of the galaxy, and we see 755 00:35:21,840 --> 00:35:24,080 Speaker 2: all that stuff, plus we see more. We see another 756 00:35:24,160 --> 00:35:27,400 Speaker 2: spectrum of photons that have sort of like a different shape, 757 00:35:27,560 --> 00:35:31,200 Speaker 2: like they emit light in different patterns. They're distributed around 758 00:35:31,239 --> 00:35:33,200 Speaker 2: the center of the galaxy, and their brightness and their 759 00:35:33,200 --> 00:35:36,440 Speaker 2: wavelengths can't be explained by any of the components that 760 00:35:36,480 --> 00:35:38,680 Speaker 2: we do know about in the center of the galaxy. 761 00:35:38,920 --> 00:35:41,239 Speaker 2: So it's definitely something new happening in the center of 762 00:35:41,280 --> 00:35:43,960 Speaker 2: the galaxy emitting photons in a way that we can't 763 00:35:43,960 --> 00:35:48,400 Speaker 2: otherwise explain, and it's consistent with some theories of dark matter. 764 00:35:48,800 --> 00:35:51,200 Speaker 1: All right, so well, let's dig into that part of it. Then, 765 00:35:51,360 --> 00:35:54,360 Speaker 1: what's the connection between gravity and or what might be 766 00:35:54,360 --> 00:35:56,600 Speaker 1: the connection between gravity and these flashes of light. 767 00:35:56,760 --> 00:35:58,720 Speaker 2: Yes, so we've been seeing these flashes for a while, 768 00:35:58,920 --> 00:36:01,399 Speaker 2: and there's been theories of dark matter for decades from 769 00:36:01,400 --> 00:36:04,280 Speaker 2: the center of the galaxy, but people have been unsure 770 00:36:04,320 --> 00:36:06,759 Speaker 2: about what it means because we don't understand what's going 771 00:36:06,760 --> 00:36:08,799 Speaker 2: on at the center of the galaxy very well. So 772 00:36:08,920 --> 00:36:11,960 Speaker 2: recently people came up with a really cool clever idea 773 00:36:12,080 --> 00:36:17,760 Speaker 2: to combine gravitational information with these flashes of light. They say, look, 774 00:36:17,920 --> 00:36:20,719 Speaker 2: if there is dark matter creating these flashes of light, 775 00:36:20,800 --> 00:36:22,600 Speaker 2: we should be able to zero in on where these 776 00:36:22,600 --> 00:36:25,279 Speaker 2: flashes come from and see if there's dark matter there. 777 00:36:25,360 --> 00:36:28,760 Speaker 2: By seeing if there's a gravitational effect from that dark matter, 778 00:36:28,840 --> 00:36:30,680 Speaker 2: Like if there's a blob of dark matter there that's 779 00:36:30,760 --> 00:36:33,399 Speaker 2: extra dense and making these flashes, we should be able 780 00:36:33,440 --> 00:36:37,239 Speaker 2: to see gravitational lensing from that dark matter blob to 781 00:36:37,320 --> 00:36:39,759 Speaker 2: tell us, oh, that really is dark matter and not 782 00:36:39,880 --> 00:36:41,400 Speaker 2: just some star going crazy. 783 00:36:41,560 --> 00:36:43,960 Speaker 1: Couldn't it just be a star going crazy or maybe 784 00:36:43,960 --> 00:36:46,840 Speaker 1: like a quasar or something like that. Doesn't that seem 785 00:36:46,840 --> 00:36:48,640 Speaker 1: more likely? But like, how do you know which is 786 00:36:48,680 --> 00:36:49,120 Speaker 1: more likely? 787 00:36:49,280 --> 00:36:51,960 Speaker 2: Exactly? We don't really understand what's there, so it is tricky. 788 00:36:52,000 --> 00:36:54,080 Speaker 2: But the first thing they did is they tried to 789 00:36:54,080 --> 00:36:56,960 Speaker 2: map all the gravitational lensing near the center of the 790 00:36:57,000 --> 00:36:59,839 Speaker 2: galaxy and measure that by seeing like how that does 791 00:37:00,080 --> 00:37:02,520 Speaker 2: or it's light from behind the galaxy, Like galaxies in 792 00:37:02,520 --> 00:37:05,080 Speaker 2: the background far away, how is their light being distorted 793 00:37:05,160 --> 00:37:08,440 Speaker 2: as it passes through the center of the galaxy. So 794 00:37:08,440 --> 00:37:11,400 Speaker 2: that's the gravitational lensing measurement. They use that as a 795 00:37:11,400 --> 00:37:13,640 Speaker 2: way to just see like are there pockets of extra 796 00:37:13,680 --> 00:37:16,560 Speaker 2: gravity in the center of the galaxy. So they make 797 00:37:16,600 --> 00:37:19,480 Speaker 2: a map of all this gravitational lensing and then they 798 00:37:19,640 --> 00:37:22,239 Speaker 2: line that up with the map of these extra flashes 799 00:37:22,280 --> 00:37:24,840 Speaker 2: from the center of the galaxy, and boom, boom, boom, 800 00:37:24,960 --> 00:37:28,480 Speaker 2: they do line up. They line up very nicely. So 801 00:37:28,520 --> 00:37:32,040 Speaker 2: there seems to be this correlation between where there's extra 802 00:37:32,040 --> 00:37:35,360 Speaker 2: gravitational lensing and where there's more gamma ray flashes. 803 00:37:36,280 --> 00:37:39,520 Speaker 1: That's pretty interesting, although it could just be something else. 804 00:37:39,600 --> 00:37:41,920 Speaker 1: I wonder, like, you know where maybe where there's a 805 00:37:41,960 --> 00:37:43,839 Speaker 1: lot of dark matter. There are also a lot of 806 00:37:44,480 --> 00:37:45,560 Speaker 1: black holes. 807 00:37:45,400 --> 00:37:47,759 Speaker 2: Exactly, and everybody's very skeptical at first, right, you don't 808 00:37:47,760 --> 00:37:49,279 Speaker 2: want to just like jump up and down and claim 809 00:37:49,320 --> 00:37:51,960 Speaker 2: you discover dark matter. So then they try to explain 810 00:37:52,040 --> 00:37:54,520 Speaker 2: this with other sources, you know, And one idea they 811 00:37:54,560 --> 00:37:58,320 Speaker 2: have in this paper is that maybe it's blazars. Blazars 812 00:37:58,320 --> 00:38:01,000 Speaker 2: are these super awesome galaxies that are generating a really 813 00:38:01,080 --> 00:38:03,680 Speaker 2: powerful beam of light from the center of the galaxy. 814 00:38:03,920 --> 00:38:06,279 Speaker 2: If you have a super massive black hole the core 815 00:38:06,320 --> 00:38:10,360 Speaker 2: of a galaxy, then its magnetic field can funnel radiation 816 00:38:10,640 --> 00:38:13,160 Speaker 2: up and down the north and south pole of that 817 00:38:13,200 --> 00:38:16,080 Speaker 2: galaxy and produce a very powerful beam of light. And 818 00:38:16,200 --> 00:38:19,080 Speaker 2: if that beam of light is pointed right at the Earth, 819 00:38:19,360 --> 00:38:22,520 Speaker 2: the relativistic effects effectively make the Earth a little shorter 820 00:38:22,680 --> 00:38:24,680 Speaker 2: and pile up the light beams a little bit to 821 00:38:24,680 --> 00:38:27,839 Speaker 2: make it extra bright. So these things are called blazars, 822 00:38:27,960 --> 00:38:30,840 Speaker 2: and blazars could also explain these effects that we're seeing. 823 00:38:31,480 --> 00:38:33,680 Speaker 2: And so in the paper they analyze like, well, is 824 00:38:33,719 --> 00:38:36,560 Speaker 2: this just more blazars than we anticipated, or is it 825 00:38:36,680 --> 00:38:39,760 Speaker 2: dark matter? And they can explain part of this effect 826 00:38:39,800 --> 00:38:42,120 Speaker 2: with blazars, but there's a part of it that blazars 827 00:38:42,160 --> 00:38:46,400 Speaker 2: cannot explain, and that is very nicely explained by dark matter. 828 00:38:46,480 --> 00:38:48,600 Speaker 2: And so this is the challenge with studying dark matter. 829 00:38:49,000 --> 00:38:51,319 Speaker 2: It's like, is what we're seeing dark matter or is 830 00:38:51,360 --> 00:38:54,080 Speaker 2: it something else we don't understand because dark matter is 831 00:38:54,080 --> 00:38:55,960 Speaker 2: still kind of a fuzzy idea. 832 00:38:56,560 --> 00:38:59,840 Speaker 1: M yeah, I mean we don't really know or have 833 00:39:00,000 --> 00:39:02,719 Speaker 1: a clear idea what it's nature is. I feel like 834 00:39:02,760 --> 00:39:05,800 Speaker 1: we're sort of like putting assumptions on top of assumptions 835 00:39:05,800 --> 00:39:07,640 Speaker 1: on top of assumptions and then checking that. 836 00:39:07,840 --> 00:39:10,000 Speaker 2: That is what we're doing. We're making hypotheses and we're 837 00:39:10,040 --> 00:39:12,640 Speaker 2: checking them, and we're coming up with alternatives, like is 838 00:39:12,680 --> 00:39:15,080 Speaker 2: this dark matter? Is this something else? What we know 839 00:39:15,200 --> 00:39:17,319 Speaker 2: is that there is something new happening at the center 840 00:39:17,320 --> 00:39:20,120 Speaker 2: of the galaxy. Something is generating these flashes of light 841 00:39:20,320 --> 00:39:22,879 Speaker 2: that we do not understand. Maybe it's dark matter, maybe 842 00:39:22,880 --> 00:39:26,200 Speaker 2: it's some other new astrophysical source. Maybe it's some new 843 00:39:26,200 --> 00:39:29,120 Speaker 2: process that's distorting light from behind the galaxy. We don't know. 844 00:39:29,160 --> 00:39:31,520 Speaker 2: There's something new to be discovered there. We don't know 845 00:39:31,520 --> 00:39:33,680 Speaker 2: if that lines up with these other mysteries we're seeing, 846 00:39:33,719 --> 00:39:36,440 Speaker 2: like galactic rotation, curves and the structure of the galaxy. 847 00:39:36,680 --> 00:39:39,000 Speaker 2: So maybe this reveals something about dark matter, but maybe 848 00:39:39,040 --> 00:39:41,880 Speaker 2: it reveals something about something else. Right, we're so clueless 849 00:39:41,920 --> 00:39:44,040 Speaker 2: about the nature of the universe that we're trying to 850 00:39:44,040 --> 00:39:46,560 Speaker 2: put these puzzle pieces together. But maybe they don't click. 851 00:39:46,600 --> 00:39:49,600 Speaker 2: Maybe they're parts of different puzzles. It's just because we're 852 00:39:49,640 --> 00:39:52,360 Speaker 2: at the beginning of understanding the universe that we're so 853 00:39:52,480 --> 00:39:54,320 Speaker 2: clueless about how to put this all together. 854 00:39:54,960 --> 00:39:57,200 Speaker 1: Yeah, I guess it could be anything. Could be alien 855 00:39:57,239 --> 00:40:00,560 Speaker 1: sending us emojis. Maybe those high speed photons are there 856 00:40:00,640 --> 00:40:01,200 Speaker 1: version of. 857 00:40:01,239 --> 00:40:06,480 Speaker 2: Emojis exactly, Maybe there are express emojis, hopefully they're safer work. 858 00:40:07,600 --> 00:40:09,759 Speaker 2: This is a very difficult kind of science because the 859 00:40:09,840 --> 00:40:12,000 Speaker 2: data is sparse. You just have like these flashes of 860 00:40:12,040 --> 00:40:14,279 Speaker 2: life from the center of the galaxy, and we're very 861 00:40:14,280 --> 00:40:16,640 Speaker 2: far away from the center, as you said. So I've 862 00:40:16,680 --> 00:40:19,840 Speaker 2: been to like whole conferences dedicated just to this signal 863 00:40:19,880 --> 00:40:23,920 Speaker 2: and understanding it, and people show completely different interpretations. They say, oh, 864 00:40:23,960 --> 00:40:27,000 Speaker 2: I can explain all of it using some astrophysical source, 865 00:40:27,280 --> 00:40:29,880 Speaker 2: and other people say, no, that's impossible, it can't describe it. 866 00:40:29,920 --> 00:40:32,160 Speaker 2: And other people say, well, you forgot to account for 867 00:40:32,200 --> 00:40:34,680 Speaker 2: all these uncertainties in that and if you let these 868 00:40:34,719 --> 00:40:37,359 Speaker 2: things float and consider other possible ways that these things 869 00:40:37,360 --> 00:40:39,479 Speaker 2: get interact, then maybe it explains it. So we really 870 00:40:39,480 --> 00:40:41,600 Speaker 2: are at the beginning days of understanding what it is 871 00:40:41,600 --> 00:40:43,480 Speaker 2: we're seeing. But it's cool to see people try to 872 00:40:43,520 --> 00:40:45,920 Speaker 2: line these things up, you know, gravity and flashes of 873 00:40:45,960 --> 00:40:48,120 Speaker 2: light and other ways to try to get ideas for 874 00:40:48,200 --> 00:40:49,200 Speaker 2: what dark matter might be. 875 00:40:49,520 --> 00:40:52,200 Speaker 1: All right, well, it sounds like it's still kind of 876 00:40:52,280 --> 00:40:53,960 Speaker 1: an open question and a big mystery, but it is 877 00:40:54,000 --> 00:40:56,680 Speaker 1: a pretty exciting idea to kind of like use one 878 00:40:56,719 --> 00:40:59,640 Speaker 1: mystery to try to explain another mystery. It's like you're 879 00:40:59,680 --> 00:41:00,800 Speaker 1: piling on the mysteries. 880 00:41:00,880 --> 00:41:02,600 Speaker 2: We are piling on the mysteries, and we're trying to 881 00:41:02,680 --> 00:41:05,000 Speaker 2: line things up. You know, we're trying to come up 882 00:41:05,040 --> 00:41:07,879 Speaker 2: with a coherent explanation for everything we see out there 883 00:41:07,880 --> 00:41:09,800 Speaker 2: in the universe. It's not fair to have one story 884 00:41:09,840 --> 00:41:12,000 Speaker 2: you tell in one case and a completely different story 885 00:41:12,040 --> 00:41:14,320 Speaker 2: you tell in another case. Right, you need a single 886 00:41:14,400 --> 00:41:18,400 Speaker 2: theory that explains everything we see. And that's really a challenge, 887 00:41:18,560 --> 00:41:20,399 Speaker 2: especially because the data is not as good as we'd 888 00:41:20,440 --> 00:41:22,040 Speaker 2: like it to be. You know, we'd like to have 889 00:41:22,080 --> 00:41:24,719 Speaker 2: these sensors at the center of the galaxy probing these 890 00:41:24,760 --> 00:41:28,320 Speaker 2: things in detail with very fine spatial resolution. But instead 891 00:41:28,320 --> 00:41:31,399 Speaker 2: we're limited to these like tiny cameras orbiting very far 892 00:41:31,440 --> 00:41:34,000 Speaker 2: from the center of the galaxy trying to get a glimpse. 893 00:41:34,080 --> 00:41:36,080 Speaker 2: Like imagine you were trying to understand what was happening 894 00:41:36,120 --> 00:41:38,240 Speaker 2: in Manhattan and all you had was like a camera 895 00:41:38,320 --> 00:41:40,280 Speaker 2: in Indiana. It'd be pretty tricky. 896 00:41:40,480 --> 00:41:42,719 Speaker 1: Yeah, especially with all those buildings, be hard to kind 897 00:41:42,760 --> 00:41:45,880 Speaker 1: of see what's going on between there. So it sounds 898 00:41:45,880 --> 00:41:47,640 Speaker 1: like maybe we just need to send a pro to 899 00:41:47,680 --> 00:41:50,360 Speaker 1: the center of the galaxy right figure out what's there, 900 00:41:50,920 --> 00:41:53,000 Speaker 1: you know, and just wait fifty thousand years or so. 901 00:41:53,760 --> 00:41:56,120 Speaker 2: Yeah, some poor graduate student is going to wait fifty 902 00:41:56,200 --> 00:41:57,880 Speaker 2: thousand years to defend their thesis. 903 00:41:58,000 --> 00:41:59,840 Speaker 1: I'll get paid for that. I could get paid for 904 00:41:59,840 --> 00:42:01,280 Speaker 1: that while I'm doing this podcast. 905 00:42:02,080 --> 00:42:02,720 Speaker 2: Sounds good. 906 00:42:02,880 --> 00:42:04,640 Speaker 1: I mean, as long as we're double dipping. 907 00:42:04,520 --> 00:42:06,160 Speaker 2: Are your checks going to come from the sense of 908 00:42:06,160 --> 00:42:08,000 Speaker 2: the galaxy because you might be waiting a while? 909 00:42:08,600 --> 00:42:11,600 Speaker 1: Yeah, no, no, no, they're going to come in a dollar bill. 910 00:42:11,640 --> 00:42:16,120 Speaker 1: Emojis the magically transform into cash into my Venmo or the. 911 00:42:16,120 --> 00:42:18,240 Speaker 2: New x app quantum Cash entanglement. 912 00:42:18,440 --> 00:42:20,560 Speaker 1: There you go. I'll be rich and not rich at 913 00:42:20,600 --> 00:42:21,320 Speaker 1: the same time. 914 00:42:22,400 --> 00:42:24,000 Speaker 2: I hope your finances don't collapse. 915 00:42:24,520 --> 00:42:28,040 Speaker 1: All right, Well, another reminder that there are still humongous 916 00:42:28,080 --> 00:42:30,680 Speaker 1: mysteries out there in the universe, and that there are 917 00:42:30,760 --> 00:42:33,920 Speaker 1: scientists out there actively searching for the answers and searching 918 00:42:33,960 --> 00:42:35,920 Speaker 1: for it, trying to find ways to study it and 919 00:42:36,640 --> 00:42:39,680 Speaker 1: reveal to the rest of us what its true nature is. 920 00:42:39,880 --> 00:42:42,720 Speaker 2: So remember that dark matter is really a whole suite 921 00:42:42,760 --> 00:42:46,000 Speaker 2: of ideas. It's not just like a blank check placeholder 922 00:42:46,040 --> 00:42:48,600 Speaker 2: for things we don't understand. It's an empty chalkboard for 923 00:42:48,680 --> 00:42:51,600 Speaker 2: us to fill in with details, and scientists are constantly 924 00:42:51,600 --> 00:42:53,839 Speaker 2: coming up with ideas for what dark matter might be 925 00:42:54,080 --> 00:42:56,759 Speaker 2: and then being creative about how we might discover it 926 00:42:57,120 --> 00:42:59,560 Speaker 2: because we hope one day to fill that chalkboard in 927 00:42:59,600 --> 00:43:01,600 Speaker 2: with some thing we really do understand. 928 00:43:01,920 --> 00:43:03,480 Speaker 1: Does that mean you have to call it dark matters 929 00:43:03,960 --> 00:43:07,319 Speaker 1: or dark's matter? These are the types of questions that 930 00:43:07,360 --> 00:43:10,920 Speaker 1: I get paid to the thing about from multiple people. 931 00:43:11,239 --> 00:43:14,080 Speaker 2: That sounds good. Sounds like you are qualified to answer. 932 00:43:13,760 --> 00:43:16,600 Speaker 1: That question, as are we all all right, well, we 933 00:43:16,680 --> 00:43:19,799 Speaker 1: hope you enjoyed that. Thanks for joining us. See you 934 00:43:19,800 --> 00:43:20,239 Speaker 1: next time. 935 00:43:28,040 --> 00:43:30,840 Speaker 2: Thanks for listening, and remember that Daniel and Jorge Explain 936 00:43:30,880 --> 00:43:34,879 Speaker 2: the Universe is a production of iHeartRadio. For more podcasts 937 00:43:34,880 --> 00:43:39,560 Speaker 2: from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever 938 00:43:39,640 --> 00:43:41,360 Speaker 2: you listen to your favorite shows.