1 00:00:07,840 --> 00:00:11,880 Speaker 1: Think about where you are right now. Maybe you're in 2 00:00:11,920 --> 00:00:14,800 Speaker 1: your car commuting, or you're out walking the dogs or 3 00:00:14,920 --> 00:00:19,120 Speaker 1: at home doing the dishes. But where are you relative 4 00:00:19,239 --> 00:00:22,319 Speaker 1: to everyone else? How do you define it? Probably you 5 00:00:22,520 --> 00:00:25,880 Speaker 1: zoom out and put yourself in a wider context, your town, 6 00:00:26,040 --> 00:00:29,920 Speaker 1: your region, your whole country. Listeners to this pod will 7 00:00:30,000 --> 00:00:33,280 Speaker 1: likely be inclined to zoom out even further to all 8 00:00:33,320 --> 00:00:36,959 Speaker 1: of Earth and then the whole Solar System. From there, 9 00:00:37,000 --> 00:00:39,880 Speaker 1: it's very tempting to skip forward and put our solar 10 00:00:39,880 --> 00:00:43,120 Speaker 1: system into its place in the galaxy, than the galaxy 11 00:00:43,280 --> 00:00:47,800 Speaker 1: into its cluster, and then that cluster within the supercluster foam. 12 00:00:48,800 --> 00:00:52,040 Speaker 1: But have we been too hasty? Is our galaxy so simple, 13 00:00:52,200 --> 00:00:55,520 Speaker 1: just a collection of stars floating around a central black hole? 14 00:00:56,240 --> 00:01:00,480 Speaker 1: Or is there more nuance to our galactic context? We 15 00:01:00,520 --> 00:01:03,480 Speaker 1: think of the galaxy as mostly stars, but they're formed, 16 00:01:03,640 --> 00:01:06,959 Speaker 1: they burn, and they die. There's a constant slashing of 17 00:01:07,120 --> 00:01:11,360 Speaker 1: energy back and forth between those stars and vast clouds 18 00:01:11,360 --> 00:01:15,360 Speaker 1: of raw material. Where is our Solar system relative to 19 00:01:15,440 --> 00:01:18,839 Speaker 1: those clouds? Are we in the midst of a galactic fog? 20 00:01:19,240 --> 00:01:22,319 Speaker 1: Or are we floating through an open bubble? Today on 21 00:01:22,360 --> 00:01:25,399 Speaker 1: the pod will zoom out to this fascinating scene, understand 22 00:01:25,440 --> 00:01:28,440 Speaker 1: the dynamics of star formation and destruction, and let you 23 00:01:28,600 --> 00:01:33,840 Speaker 1: know exactly where you we all of us stand galactically speaking. 24 00:01:34,720 --> 00:01:38,000 Speaker 1: Welcome to Daniel and Kelly's Extraordinary Galaxy. 25 00:01:51,280 --> 00:01:54,240 Speaker 2: Hello, I'm Kelly Winer Smith. I study parasites and space 26 00:01:54,280 --> 00:01:55,440 Speaker 2: and I love bubbles. 27 00:02:04,920 --> 00:02:09,120 Speaker 1: Well, Hi, I'm Daniel. I'm a particle physicist. I love bubbles, 28 00:02:09,120 --> 00:02:10,880 Speaker 1: and I have all of my organs. 29 00:02:11,240 --> 00:02:13,800 Speaker 2: Okay, yeah, right, So that I was gonna ask you 30 00:02:14,360 --> 00:02:17,520 Speaker 2: about the most painful thing you ever experienced in your 31 00:02:17,560 --> 00:02:19,600 Speaker 2: life as a lead into why my laugh is going 32 00:02:19,639 --> 00:02:23,040 Speaker 2: to be a little off today, folks. 33 00:02:23,120 --> 00:02:25,640 Speaker 1: I'm going to try to restrain myself from being funny 34 00:02:25,680 --> 00:02:28,320 Speaker 1: today because if I make a joke that makes Kelly 35 00:02:28,360 --> 00:02:30,240 Speaker 1: crack up, she could literally crack up. 36 00:02:30,840 --> 00:02:36,239 Speaker 2: Oh I could, Yes, I could split a stitch. So 37 00:02:36,919 --> 00:02:40,720 Speaker 2: what aside from labor, The most painful thing that ever 38 00:02:40,720 --> 00:02:45,320 Speaker 2: happens to me was the gallstones that tried to pass 39 00:02:45,400 --> 00:02:48,200 Speaker 2: their way out of my body on Friday, but ended 40 00:02:48,240 --> 00:02:51,600 Speaker 2: up getting removed surgically. The whole thing, the whole gallbladder 41 00:02:51,639 --> 00:02:55,520 Speaker 2: was removed, and so I am still working on resolving 42 00:02:55,560 --> 00:02:58,520 Speaker 2: my stitches. And so it hurts to laugh. So I 43 00:02:58,560 --> 00:02:59,880 Speaker 2: think I've come up with the way to laugh that 44 00:03:00,000 --> 00:03:02,240 Speaker 2: it hurts less, and so my my laugh will sound 45 00:03:02,320 --> 00:03:04,440 Speaker 2: a little I don't know, maybe even less annoying. I 46 00:03:04,480 --> 00:03:06,800 Speaker 2: have seen there's a couple complaints about the way I laugh. 47 00:03:07,200 --> 00:03:10,120 Speaker 2: You'all can just kiss my rear ends. But anyway, Daniel, 48 00:03:10,160 --> 00:03:11,960 Speaker 2: what is the most painful thing that's ever happened to you? 49 00:03:13,520 --> 00:03:16,480 Speaker 1: Oh? Most painful thing that's ever happened to me? I 50 00:03:16,560 --> 00:03:19,280 Speaker 1: broken my wrist, but weirdly that didn't hurt that much. 51 00:03:20,400 --> 00:03:22,720 Speaker 1: I think maybe the most painful thing is when I 52 00:03:22,720 --> 00:03:27,360 Speaker 1: broke my little toe. I like massively stubbed it on 53 00:03:27,440 --> 00:03:31,720 Speaker 1: a little concrete outpost and cracked it and wow, yeah, 54 00:03:31,760 --> 00:03:32,920 Speaker 1: I thought I was gonna die. 55 00:03:33,400 --> 00:03:35,520 Speaker 2: Ouch. Yeah, And how long did it take to heal? 56 00:03:35,920 --> 00:03:37,600 Speaker 2: What do you do? Just put like a nothing. 57 00:03:37,600 --> 00:03:39,880 Speaker 1: You just tape it to the next toe, and like 58 00:03:40,400 --> 00:03:43,920 Speaker 1: whatever happens inside of it happens. Like there's no surgery 59 00:03:44,000 --> 00:03:46,280 Speaker 1: to correct, like the little bones inside your little toe, 60 00:03:46,320 --> 00:03:48,960 Speaker 1: nobody needs it. I was like, just cut that bugger off, 61 00:03:49,000 --> 00:03:51,000 Speaker 1: but I was like, no, you just tape it to 62 00:03:51,000 --> 00:03:53,920 Speaker 1: the next one. That's it. 63 00:03:55,120 --> 00:03:57,200 Speaker 2: Well, you know, Daniel, it sounds like if you lived 64 00:03:57,200 --> 00:03:59,119 Speaker 2: in a bubble, you would have been safe. But if 65 00:03:59,160 --> 00:04:01,520 Speaker 2: I lived in a bubble, well, that wouldn't have saved me. 66 00:04:02,560 --> 00:04:04,640 Speaker 2: And so well, you know, maybe if the whole universe 67 00:04:04,680 --> 00:04:06,360 Speaker 2: was in a bubble, that would save us from some 68 00:04:06,400 --> 00:04:09,760 Speaker 2: of the bumps and bruises of existence. But do we 69 00:04:09,840 --> 00:04:11,000 Speaker 2: live in a bubble? Daniel? 70 00:04:13,440 --> 00:04:15,760 Speaker 1: Well, we are trying to pop the bubble of ignorance 71 00:04:15,800 --> 00:04:20,240 Speaker 1: out there and help everybody understand their cosmic context, where 72 00:04:20,279 --> 00:04:22,840 Speaker 1: we are situated in our solar system, where our solar 73 00:04:22,839 --> 00:04:25,960 Speaker 1: system is situated in the galaxy, and the whole context 74 00:04:26,240 --> 00:04:29,680 Speaker 1: for our existence. I love filling in all those details 75 00:04:29,680 --> 00:04:33,000 Speaker 1: and helping people understand really where they live. And today 76 00:04:33,000 --> 00:04:35,920 Speaker 1: we're going to dive into that topic essentially, where our 77 00:04:36,040 --> 00:04:39,240 Speaker 1: sun is in the galaxy? Is there structure out there? 78 00:04:39,240 --> 00:04:40,080 Speaker 1: How does it all work? 79 00:04:40,200 --> 00:04:42,480 Speaker 2: And I think all of our inner kids are excited 80 00:04:42,520 --> 00:04:45,240 Speaker 2: today to find out whether or not we live in 81 00:04:45,279 --> 00:04:46,040 Speaker 2: a super bubble. 82 00:04:47,520 --> 00:04:49,719 Speaker 1: So before we dive into it, I was wondering what 83 00:04:49,800 --> 00:04:52,400 Speaker 1: people out there knew on the topic. So I went 84 00:04:52,440 --> 00:04:55,040 Speaker 1: to our group of volunteers, I asked them, do we 85 00:04:55,120 --> 00:04:59,920 Speaker 1: live in a super bubble? Here's what folks had to say, 86 00:05:00,080 --> 00:05:02,080 Speaker 1: I don't even really know what a super bubble is, 87 00:05:02,839 --> 00:05:06,520 Speaker 1: so maybe what do you think, Glen. I have no 88 00:05:06,600 --> 00:05:08,800 Speaker 1: idea what a super bubble is. I have not heard 89 00:05:08,800 --> 00:05:11,720 Speaker 1: the term super bubble. It makes me think about some 90 00:05:11,760 --> 00:05:15,000 Speaker 1: conceptualizations of fourth dimensionality. 91 00:05:14,640 --> 00:05:17,280 Speaker 3: Considering I couldn't tell you what a super bubble is. 92 00:05:18,200 --> 00:05:20,919 Speaker 3: I can't really say if we live in one, but 93 00:05:21,320 --> 00:05:26,360 Speaker 3: it sounds like one of these really exciting astrophysical maybe 94 00:05:26,400 --> 00:05:29,960 Speaker 3: who knows cool universe things, so I'm eager to learn 95 00:05:29,960 --> 00:05:32,839 Speaker 3: about it. I have never heard of the term super bubble, 96 00:05:33,360 --> 00:05:35,200 Speaker 3: but we probably live in one. 97 00:05:35,640 --> 00:05:37,839 Speaker 2: I like the I've never heard of it, so yes, 98 00:05:41,080 --> 00:05:41,400 Speaker 2: this is. 99 00:05:41,360 --> 00:05:42,919 Speaker 1: Really exciting to me that nobody had heard of it, 100 00:05:42,960 --> 00:05:45,240 Speaker 1: because it means we get to share this really cool 101 00:05:45,279 --> 00:05:48,679 Speaker 1: thing about the universe with everybody. Yay. 102 00:05:49,080 --> 00:05:49,919 Speaker 2: We love doing that. 103 00:05:51,320 --> 00:05:53,960 Speaker 1: You know that great XKCD comic. I mean they're all great, 104 00:05:54,200 --> 00:05:57,440 Speaker 1: but the one about the moment you discover somebody doesn't 105 00:05:57,480 --> 00:05:59,919 Speaker 1: know something really cool about the universe and how you 106 00:06:00,000 --> 00:06:02,279 Speaker 1: should treat that with reverence and respect because it's a 107 00:06:02,320 --> 00:06:05,560 Speaker 1: wonderful teaching moment. That's where we are today about super bubbles. 108 00:06:06,279 --> 00:06:07,799 Speaker 2: I mean, I think we can all agree that Randall 109 00:06:07,839 --> 00:06:10,159 Speaker 2: Monroe is the greatest web cartoonist to have ever lived. 110 00:06:10,200 --> 00:06:25,719 Speaker 1: Right, Wow, that's instant karma right there. Wow. I hope 111 00:06:25,800 --> 00:06:27,280 Speaker 1: Zach is listening and laughing at that. 112 00:06:31,440 --> 00:06:32,840 Speaker 2: All right, all right, bubbles, all. 113 00:06:32,839 --> 00:06:35,200 Speaker 1: Right, bubbles. So we're talking about the Sun and the 114 00:06:35,200 --> 00:06:38,840 Speaker 1: Solar System's context in the galaxy. But before we get there, 115 00:06:38,920 --> 00:06:42,040 Speaker 1: let's do like an overview of like what's out there 116 00:06:42,080 --> 00:06:45,760 Speaker 1: in space? How empty is it? Anyway? So to get oriented, 117 00:06:45,800 --> 00:06:49,039 Speaker 1: remember that our situation here on Earth is very unusual. 118 00:06:49,760 --> 00:06:52,839 Speaker 1: Like the density of stuff around you is very rare 119 00:06:52,920 --> 00:06:56,200 Speaker 1: in the universe. The universe is mostly very very low density, 120 00:06:56,200 --> 00:06:58,839 Speaker 1: and we live in a very very high density situation. 121 00:06:59,240 --> 00:07:02,920 Speaker 1: The Earth, of course, is wonderful and cozy, and in 122 00:07:03,000 --> 00:07:06,680 Speaker 1: like a normal atmosphere, you'll find a huge number of 123 00:07:06,720 --> 00:07:09,159 Speaker 1: molecules per cubic meter, like ten to the twenty five 124 00:07:09,200 --> 00:07:12,440 Speaker 1: molecules per cubic meter. It's a big number. And that's 125 00:07:12,480 --> 00:07:15,680 Speaker 1: just because like Avagadro's number is pretty big, and gravity 126 00:07:15,720 --> 00:07:18,000 Speaker 1: has gathered the Earth and the stars and all that 127 00:07:18,000 --> 00:07:20,240 Speaker 1: stuff together into little dense clumps. 128 00:07:20,360 --> 00:07:23,360 Speaker 2: I thought Avagadro's number was ten to the twenty three. 129 00:07:23,160 --> 00:07:24,640 Speaker 1: It is, yeah, exactly. 130 00:07:24,800 --> 00:07:26,679 Speaker 2: Oh but this is ten to the twenty fifth. 131 00:07:26,840 --> 00:07:29,160 Speaker 1: Yeah, because a mole is less than a cubic meter. 132 00:07:29,400 --> 00:07:31,560 Speaker 2: Got it, got it. I'm with you now, Okay, these 133 00:07:31,560 --> 00:07:33,320 Speaker 2: are big numbers, Daniel, big numbers. 134 00:07:33,400 --> 00:07:36,119 Speaker 1: These are big numbers. And you know, sometimes on Earth 135 00:07:36,120 --> 00:07:39,480 Speaker 1: we want to do experiments in low density situations, like 136 00:07:39,520 --> 00:07:41,920 Speaker 1: when we collide particles together, we don't want a whole 137 00:07:41,920 --> 00:07:44,400 Speaker 1: bunch of other particles around, Or when you build a 138 00:07:44,440 --> 00:07:48,840 Speaker 1: plasma inside eater to diffusion, you want mostly a vacuum 139 00:07:48,880 --> 00:07:51,560 Speaker 1: before you start. And so we have all these vacuums 140 00:07:51,560 --> 00:07:54,240 Speaker 1: in labs. We've created these situations you pump out all 141 00:07:54,280 --> 00:07:56,880 Speaker 1: the air, and you might be surprised to learn that 142 00:07:56,960 --> 00:08:00,560 Speaker 1: even in those highly specialized vacuums on Earth, we still 143 00:08:00,560 --> 00:08:02,920 Speaker 1: have something like ten to the twelve or ten to 144 00:08:02,960 --> 00:08:06,760 Speaker 1: the fifteen molecules per cubic meter. Like that's down ten 145 00:08:07,080 --> 00:08:11,120 Speaker 1: or thirteen orders of magnitude from your general atmosphere. So like, 146 00:08:11,360 --> 00:08:14,160 Speaker 1: really good work, and this is not easy, but still 147 00:08:14,200 --> 00:08:15,560 Speaker 1: it's a lot of molecules. 148 00:08:15,760 --> 00:08:18,880 Speaker 2: When somebody says the vacuum of space, are we doing 149 00:08:19,040 --> 00:08:21,920 Speaker 2: better than the vacuum of space? When we make a 150 00:08:22,000 --> 00:08:24,440 Speaker 2: vacuum in the lab or are we doing about the 151 00:08:24,480 --> 00:08:27,240 Speaker 2: same as the quote unquote vacuum of space. 152 00:08:27,680 --> 00:08:31,000 Speaker 1: Neither. We're not doing anywhere close to the vacuum of space. 153 00:08:31,360 --> 00:08:34,520 Speaker 1: The density of vacuums in labs here on Earth is 154 00:08:35,000 --> 00:08:38,240 Speaker 1: much higher, is much much more stuff in our lab 155 00:08:38,320 --> 00:08:41,840 Speaker 1: quote unquote vacuums than there is out there in space. Okay, 156 00:08:41,960 --> 00:08:44,840 Speaker 1: but let's stick into that and zoom our mental picture 157 00:08:44,960 --> 00:08:48,000 Speaker 1: out from the surface of the Earth. Obviously, the atmosphere 158 00:08:48,080 --> 00:08:51,880 Speaker 1: drops gradually, right, There's no like huge wall or gait 159 00:08:52,000 --> 00:08:54,319 Speaker 1: or anything. This is not space balls, where atmosphere is 160 00:08:54,320 --> 00:08:57,640 Speaker 1: that contained by a huge bubble right where the code 161 00:08:57,640 --> 00:09:00,200 Speaker 1: is one two three four. But in a funny way, 162 00:09:00,240 --> 00:09:02,880 Speaker 1: there is because space officially starts at like one hundred 163 00:09:02,920 --> 00:09:05,760 Speaker 1: kilometers above the surface of the Earth, which I always 164 00:09:05,760 --> 00:09:06,400 Speaker 1: thought was weird. 165 00:09:06,760 --> 00:09:08,880 Speaker 2: There's some debate about that though, isn't there. 166 00:09:09,000 --> 00:09:11,240 Speaker 1: Yes, absolutely there is, and like you can be an 167 00:09:11,280 --> 00:09:15,679 Speaker 1: astronaut if you've gone eighty kilometers above. There's definitely a debate. 168 00:09:15,720 --> 00:09:18,120 Speaker 1: It's something about astronomy, so it's not just it depends. 169 00:09:18,200 --> 00:09:19,839 Speaker 1: It's a bunch of nerds arguing about it. 170 00:09:20,000 --> 00:09:23,560 Speaker 2: I thought one hundred kilometers was something like at that point, 171 00:09:23,640 --> 00:09:27,119 Speaker 2: there aren't enough molecules to hold up your airplane anymore, 172 00:09:27,240 --> 00:09:28,880 Speaker 2: and so that's where space starts. 173 00:09:29,200 --> 00:09:30,680 Speaker 1: Oh that's cool, isn't it. 174 00:09:30,679 --> 00:09:31,640 Speaker 2: The Von Carmon line. 175 00:09:31,960 --> 00:09:35,320 Speaker 1: That's the Von Carmen line. Yeah, And the ISS is 176 00:09:35,440 --> 00:09:37,760 Speaker 1: like three hundred or four hundred kilometers above the surface 177 00:09:37,800 --> 00:09:40,720 Speaker 1: of the Earth, so definitely in space. And so if 178 00:09:40,720 --> 00:09:44,439 Speaker 1: you're inside our Solar system but outside Earth and its atmosphere, 179 00:09:44,840 --> 00:09:47,640 Speaker 1: then there's still stuff out there. The vacuum of space 180 00:09:47,720 --> 00:09:51,000 Speaker 1: inside the Solar System is not a perfect vacuum. There's 181 00:09:51,000 --> 00:09:53,120 Speaker 1: a bunch of particles. Most of it comes from the 182 00:09:53,160 --> 00:09:55,520 Speaker 1: Sun because the Sun, as we say often is producing 183 00:09:55,559 --> 00:09:58,360 Speaker 1: a lot of stuff, not just photons but also matter. 184 00:09:58,640 --> 00:10:01,800 Speaker 1: The solar wind is electronic and protons and alpha particles. 185 00:10:02,280 --> 00:10:04,280 Speaker 1: These things are zooming around with a lot of energy. 186 00:10:04,720 --> 00:10:08,520 Speaker 1: And so there's something like ten million protons per cubic 187 00:10:08,640 --> 00:10:12,680 Speaker 1: meter between planets. So remember on Earth it's ten to 188 00:10:12,679 --> 00:10:16,400 Speaker 1: the twenty five molecules per cubic meter, labs on Earth 189 00:10:16,480 --> 00:10:18,280 Speaker 1: is ten to the twelve. Now we're down to like 190 00:10:18,320 --> 00:10:21,760 Speaker 1: ten to the seven protons per cubic meter, so that's 191 00:10:21,800 --> 00:10:24,760 Speaker 1: down like five or six orders of magnitude compared to 192 00:10:24,800 --> 00:10:25,640 Speaker 1: vacuums on Earth. 193 00:10:26,080 --> 00:10:29,959 Speaker 2: Wow, you wouldn't want to go out there, people, but. 194 00:10:29,920 --> 00:10:32,200 Speaker 1: It would be a good place to do vacuum based experiments. 195 00:10:32,559 --> 00:10:33,000 Speaker 2: Sure. 196 00:10:33,200 --> 00:10:36,800 Speaker 1: Yeah, but it's still not that empty, right, Like millions 197 00:10:36,840 --> 00:10:39,160 Speaker 1: and millions of protons are out there. It's not something 198 00:10:39,200 --> 00:10:40,679 Speaker 1: you could say is empty. And when we talk about 199 00:10:40,760 --> 00:10:45,280 Speaker 1: vacuum in physics and theoretical physics, we mean space with 200 00:10:45,480 --> 00:10:48,439 Speaker 1: no extra energy, and it's a minimum energy state of space. 201 00:10:48,480 --> 00:10:52,480 Speaker 1: And so this interplanetary space is not approaching the theoretical 202 00:10:52,520 --> 00:10:55,839 Speaker 1: physics vacuum at all. Okay, And then take your mental 203 00:10:55,840 --> 00:10:58,319 Speaker 1: picture and zoom out from the Solar System and now 204 00:10:58,320 --> 00:11:02,120 Speaker 1: we're between stars. Were between our star and Alpha Centauri 205 00:11:02,200 --> 00:11:05,760 Speaker 1: for example. Now we're in what we call the interstellar medium, 206 00:11:05,800 --> 00:11:08,840 Speaker 1: the stuff between the stars. And even this is not 207 00:11:09,080 --> 00:11:11,720 Speaker 1: that empty, right. It turns out there's a big range 208 00:11:11,720 --> 00:11:14,960 Speaker 1: of densities of stuff from ten to the six molecule 209 00:11:15,040 --> 00:11:18,920 Speaker 1: percubic meter, which is like the density in our Solar system, 210 00:11:19,120 --> 00:11:21,280 Speaker 1: all the way down to ten to the four molecules 211 00:11:21,280 --> 00:11:22,000 Speaker 1: per cubic meter. 212 00:11:22,240 --> 00:11:24,080 Speaker 2: Isn't this where we thought the Ork cloud would be? 213 00:11:24,200 --> 00:11:26,160 Speaker 2: Or this is like when we get past the Ork Cloud. 214 00:11:26,320 --> 00:11:28,680 Speaker 1: Yeah, so there's a couple of different boundaries here. You 215 00:11:28,720 --> 00:11:30,640 Speaker 1: go out past the planets, you get to like the 216 00:11:30,720 --> 00:11:34,320 Speaker 1: dwarf planets, and then the Kuiper Belt objects. Beyond that, 217 00:11:34,800 --> 00:11:38,719 Speaker 1: there's the boundary of the heliosphere where the Sun dominates 218 00:11:38,760 --> 00:11:42,880 Speaker 1: and it meets the interstellar wind, the galactic wind. That's 219 00:11:42,920 --> 00:11:45,480 Speaker 1: a region where you're exiting the Solar System. But you're 220 00:11:45,559 --> 00:11:49,520 Speaker 1: right beyond that is more stuff. So the Orc Cloud 221 00:11:49,600 --> 00:11:53,360 Speaker 1: technically is part of the interstellar medium because it's past 222 00:11:53,440 --> 00:11:56,880 Speaker 1: that boundary. It's in a region where the interstellar wind 223 00:11:57,040 --> 00:12:01,640 Speaker 1: dominates over the Sun's wind, but it is gravitationally bound 224 00:12:01,640 --> 00:12:03,840 Speaker 1: to the Sun, so it's sort of like playing both 225 00:12:03,880 --> 00:12:04,880 Speaker 1: sides of the equation off. 226 00:12:04,880 --> 00:12:10,439 Speaker 2: That makes sense, it does, but it's still so overwhelmed 227 00:12:10,480 --> 00:12:12,920 Speaker 2: by the gas in that area that the interstellar medium 228 00:12:12,960 --> 00:12:15,000 Speaker 2: is ninety nine percent gas and all the rocks out 229 00:12:15,000 --> 00:12:17,880 Speaker 2: there are just make up one percent dust. Would that 230 00:12:17,880 --> 00:12:18,520 Speaker 2: be fair to say? 231 00:12:18,720 --> 00:12:20,360 Speaker 1: Yes, that's right, and we're going to come back to 232 00:12:20,400 --> 00:12:22,440 Speaker 1: the interstellar medium and do a deep dive into it. 233 00:12:22,440 --> 00:12:25,800 Speaker 1: Has a lot of really interesting structure, but yeah, most 234 00:12:25,800 --> 00:12:28,600 Speaker 1: of it is gas. It's ninety nine percent gas, and 235 00:12:28,640 --> 00:12:31,520 Speaker 1: then a little bit of it is rocks or comets, 236 00:12:31,559 --> 00:12:34,160 Speaker 1: like in the oricloud and dust. There's a few cosmic 237 00:12:34,240 --> 00:12:37,840 Speaker 1: rays out there, but mostly it's just gas and has 238 00:12:37,880 --> 00:12:40,400 Speaker 1: all sorts of interesting turbulence and structure that we're going 239 00:12:40,480 --> 00:12:43,320 Speaker 1: to talk about and don't forget out there. Also in 240 00:12:43,360 --> 00:12:46,720 Speaker 1: the galaxy is dark matter. We're only talking right now 241 00:12:46,760 --> 00:12:49,000 Speaker 1: about the luminous matter, the kind of stuff that's made 242 00:12:49,040 --> 00:12:52,120 Speaker 1: up of atoms, but we know that the universe is 243 00:12:52,160 --> 00:12:55,080 Speaker 1: dominated by dark matter. We know that it's spread out 244 00:12:55,120 --> 00:12:57,760 Speaker 1: throughout the galaxy, but it there's five times as much 245 00:12:57,800 --> 00:13:00,959 Speaker 1: of it as there is luminous matter, so you can't 246 00:13:01,000 --> 00:13:03,120 Speaker 1: interact with it, but it is there. And so if 247 00:13:03,160 --> 00:13:05,960 Speaker 1: you're just thinking about like the density of matter overall, 248 00:13:06,200 --> 00:13:08,079 Speaker 1: you have to also account for that dark matter. 249 00:13:08,520 --> 00:13:12,080 Speaker 2: Okay, so in the interstellar space mostly gas, little bit 250 00:13:12,120 --> 00:13:15,400 Speaker 2: of dust, you're not likely to stub your toe. But 251 00:13:15,559 --> 00:13:18,880 Speaker 2: so now we're talking about what's between the stars, But 252 00:13:18,920 --> 00:13:22,680 Speaker 2: what about what's between the galaxies and the intergalactic space. 253 00:13:23,120 --> 00:13:26,000 Speaker 1: Yeah, so now we're leaving the region we've ever probed directly, 254 00:13:26,080 --> 00:13:28,600 Speaker 1: Like we've sent probes that have left the Solar System 255 00:13:28,880 --> 00:13:32,120 Speaker 1: just barely like Voyager one reached the interstellar medium in 256 00:13:32,160 --> 00:13:35,960 Speaker 1: twenty twelve, Voyager two and twenty eighteen. But now we're 257 00:13:36,040 --> 00:13:39,000 Speaker 1: going well beyond where we've ever probed directly, and we're 258 00:13:39,040 --> 00:13:42,480 Speaker 1: relying just on observations and theory and stimulation. So now 259 00:13:42,520 --> 00:13:45,400 Speaker 1: between the galaxies, what is there, Well, this is something 260 00:13:45,400 --> 00:13:49,200 Speaker 1: we call very creatively the intergalactic medium, and this is 261 00:13:49,320 --> 00:13:53,800 Speaker 1: mostly rarefied plasma, so that means essentially ionized hydrogen is 262 00:13:53,880 --> 00:13:57,560 Speaker 1: just protons and out there. On average it's like one 263 00:13:57,640 --> 00:14:01,400 Speaker 1: to ten atoms per cubic meter, so a pretty small number, 264 00:14:01,600 --> 00:14:05,200 Speaker 1: but still not that small. I mean, intergalactic space is 265 00:14:05,559 --> 00:14:09,560 Speaker 1: unimaginably vast. There's just so much of it. Even if 266 00:14:09,600 --> 00:14:12,240 Speaker 1: you think about space between the planets as being big, 267 00:14:12,520 --> 00:14:14,760 Speaker 1: and most of the space and the Solar System is 268 00:14:14,800 --> 00:14:17,920 Speaker 1: the space between the planets, right, planets and the Sun 269 00:14:18,040 --> 00:14:21,040 Speaker 1: are rare, like you're randomly sampled inside the Solar System. 270 00:14:21,080 --> 00:14:22,960 Speaker 1: You would very rarely touch a planet or a star 271 00:14:23,640 --> 00:14:27,080 Speaker 1: inside the galaxy. Right structure is also very rare. But 272 00:14:27,120 --> 00:14:29,960 Speaker 1: between the galaxies, it's even hard to comprehend because we 273 00:14:30,000 --> 00:14:33,360 Speaker 1: have like millions of light years between these galaxies, and 274 00:14:33,480 --> 00:14:36,280 Speaker 1: yet it's still filled with stuff. There's one to ten 275 00:14:36,320 --> 00:14:40,760 Speaker 1: atoms out there, and actually these tendrils of plasma there's 276 00:14:40,800 --> 00:14:43,800 Speaker 1: also structure to it. It's not just randomly distributed. All 277 00:14:43,840 --> 00:14:47,360 Speaker 1: the galaxies are connected by these tendrils of plasma, these filaments, 278 00:14:47,920 --> 00:14:50,480 Speaker 1: and something like half of all the atoms in the 279 00:14:50,560 --> 00:14:54,720 Speaker 1: universe are outside of galaxies and are inside these tendrils 280 00:14:54,800 --> 00:14:55,960 Speaker 1: between galaxies. 281 00:14:56,000 --> 00:14:58,120 Speaker 2: It's incredible, wow, And how do they get there? Do 282 00:14:58,320 --> 00:15:00,400 Speaker 2: they get like shot out by suns? They were just 283 00:15:00,440 --> 00:15:02,800 Speaker 2: there from the beginning of the creation of the universe 284 00:15:02,840 --> 00:15:03,840 Speaker 2: and they just stayed. 285 00:15:03,520 --> 00:15:07,080 Speaker 1: There both and all of those like there's a feedback 286 00:15:07,120 --> 00:15:12,040 Speaker 1: loop where galaxies are emitting particles right, supernovas and shockwaves 287 00:15:12,080 --> 00:15:15,640 Speaker 1: and all sorts of stuff. But mostly this structure represents 288 00:15:15,840 --> 00:15:19,480 Speaker 1: the dark matter structure of the universe. Galaxies form in 289 00:15:19,480 --> 00:15:22,000 Speaker 1: the deepest wells and then there are tendrils of dark 290 00:15:22,040 --> 00:15:24,960 Speaker 1: matter between these wells, and that's where you find these 291 00:15:24,960 --> 00:15:27,760 Speaker 1: tendrils of plasma. So the plasma is like a tracer 292 00:15:27,800 --> 00:15:30,760 Speaker 1: that tells you where the dark matter is. And also 293 00:15:30,880 --> 00:15:33,440 Speaker 1: between these galaxies, of course, is a significant amount of 294 00:15:33,520 --> 00:15:36,200 Speaker 1: dark energy. Dark energy is everywhere in space. It's just 295 00:15:36,240 --> 00:15:39,640 Speaker 1: a really, really tiny amount, but because it doesn't get diluted, 296 00:15:39,640 --> 00:15:43,320 Speaker 1: as the universe expands over vast spaces, it really starts 297 00:15:43,320 --> 00:15:45,840 Speaker 1: to add up. Between the galaxies, you have to start 298 00:15:45,880 --> 00:15:48,840 Speaker 1: accounting for the dark energy. And then as you zoom out, 299 00:15:48,960 --> 00:15:53,160 Speaker 1: galaxies form clusters, and between those clusters most of the 300 00:15:53,280 --> 00:15:56,120 Speaker 1: energy density between those clusters. It's not matter at all. 301 00:15:56,360 --> 00:15:59,440 Speaker 1: It's dark energy, all right. 302 00:15:59,560 --> 00:16:02,920 Speaker 2: So at the big scale, we're mostly thinking about dark energy, 303 00:16:03,080 --> 00:16:06,200 Speaker 2: and as we zoom in, we're starting to think about gas. 304 00:16:07,920 --> 00:16:10,200 Speaker 2: Let's take a break, and when we come back, I 305 00:16:10,240 --> 00:16:13,600 Speaker 2: want to go back to the interstellar medium and go 306 00:16:13,640 --> 00:16:36,320 Speaker 2: into more detail about what's there. Yeah, and we're back, 307 00:16:36,360 --> 00:16:38,440 Speaker 2: and Daniel is going to be telling us more about 308 00:16:38,440 --> 00:16:40,800 Speaker 2: what is in the interstellar medium. 309 00:16:40,840 --> 00:16:43,200 Speaker 1: That's right. Today we're talking about the context of our 310 00:16:43,240 --> 00:16:45,320 Speaker 1: solar system where it is and how much stuff there 311 00:16:45,400 --> 00:16:48,800 Speaker 1: is around us, and whether our solar system is jumping 312 00:16:48,920 --> 00:16:52,840 Speaker 1: into a huge bubble in the galaxy. Sounds fun, and 313 00:16:52,880 --> 00:16:55,320 Speaker 1: so the important thing is to understand this bit between 314 00:16:55,400 --> 00:16:57,680 Speaker 1: the stars. And the thing I love doing is going 315 00:16:57,720 --> 00:17:01,080 Speaker 1: back in history and understanding when we understood something and 316 00:17:01,080 --> 00:17:04,680 Speaker 1: what our early silly ideas were, you know, because it's 317 00:17:04,680 --> 00:17:07,000 Speaker 1: easy to just like, download all of human knowledge into 318 00:17:07,040 --> 00:17:10,320 Speaker 1: your brain right now. But remember that people like struggled 319 00:17:10,359 --> 00:17:12,439 Speaker 1: and puzzled to figure this out, and there were many 320 00:17:12,520 --> 00:17:16,320 Speaker 1: wrong paths and silly ideas entertained for hundreds of years 321 00:17:16,359 --> 00:17:17,120 Speaker 1: along the way. 322 00:17:17,480 --> 00:17:19,639 Speaker 2: It's kind of cute to imagine that nobody in like 323 00:17:19,680 --> 00:17:21,320 Speaker 2: fifty years is going to look back at us and 324 00:17:21,359 --> 00:17:24,639 Speaker 2: be like, oh, remember that cute thing that the physicists 325 00:17:24,640 --> 00:17:28,320 Speaker 2: thought in twenty twenty six about anyway, they could be 326 00:17:28,400 --> 00:17:30,840 Speaker 2: laughing at us eventually, but let's go ahead and laugh 327 00:17:30,880 --> 00:17:31,200 Speaker 2: at them. 328 00:17:33,040 --> 00:17:37,160 Speaker 1: So first, remember, in the broader context, we didn't know 329 00:17:37,240 --> 00:17:41,199 Speaker 1: that our galaxy was one of many galaxies until like 330 00:17:41,240 --> 00:17:44,200 Speaker 1: the early nineteen hundreds, right, we thought we had a galaxy. 331 00:17:44,400 --> 00:17:46,359 Speaker 1: It was a bunch of stars and that was it. 332 00:17:46,359 --> 00:17:48,800 Speaker 1: It was just our galaxy, and that was everything. The 333 00:17:48,840 --> 00:17:52,280 Speaker 1: galaxy was basically the universe and everything that was out 334 00:17:52,320 --> 00:17:54,840 Speaker 1: there that wasn't actually in our galaxy, but we didn't 335 00:17:54,840 --> 00:17:56,760 Speaker 1: know it yet. We called like a nebula because it 336 00:17:56,840 --> 00:17:59,440 Speaker 1: was like a smeary blob in the sky we couldn't resolve. 337 00:18:00,160 --> 00:18:02,160 Speaker 1: So that's sort of like the bigger picture. But then 338 00:18:02,200 --> 00:18:04,560 Speaker 1: what about inside the galaxy, Well, people try to make 339 00:18:04,640 --> 00:18:07,119 Speaker 1: like maps of the galaxy early on to try to 340 00:18:07,200 --> 00:18:10,240 Speaker 1: understand the structure. But we're interested in like the bit 341 00:18:10,359 --> 00:18:13,280 Speaker 1: between the stars. And it was like the late seventeen 342 00:18:13,320 --> 00:18:16,280 Speaker 1: hundreds people started to wonder, like, hmm, is the space 343 00:18:16,359 --> 00:18:20,440 Speaker 1: between the stars really a vacuum or is there something there? 344 00:18:21,119 --> 00:18:24,200 Speaker 1: You know? And how would we know? And this coincides 345 00:18:24,200 --> 00:18:27,960 Speaker 1: a little bit later with Maxwell's development of electromagnetism, the 346 00:18:28,040 --> 00:18:32,200 Speaker 1: idea that light is a balance between electricity and magnetism. 347 00:18:32,400 --> 00:18:35,160 Speaker 1: The energy slashes back and forth between the two fields, 348 00:18:35,400 --> 00:18:38,440 Speaker 1: but then it moves as a wave in these fields 349 00:18:38,800 --> 00:18:41,080 Speaker 1: at the speed of light. And this is Maxwell's great 350 00:18:41,080 --> 00:18:44,280 Speaker 1: discovery that light is a wave, which of course begged 351 00:18:44,280 --> 00:18:47,879 Speaker 1: the question of a wave in what right, And so 352 00:18:48,119 --> 00:18:52,040 Speaker 1: we saw the rise of the theory of the luminiferous ether. Right. 353 00:18:52,160 --> 00:18:55,000 Speaker 1: This is a famous theory which was invented to explain 354 00:18:55,800 --> 00:18:59,080 Speaker 1: what light is wiggling? Right, Maybe there's something out there, 355 00:18:59,119 --> 00:19:02,600 Speaker 1: like if waves are wiggles and water, and sounds wiggles 356 00:19:02,600 --> 00:19:05,200 Speaker 1: and air, maybe light is a wiggle in this luminiferous 357 00:19:05,200 --> 00:19:08,560 Speaker 1: ether that we hadn't ever discovered before it fills the universe. 358 00:19:09,040 --> 00:19:12,879 Speaker 1: So this would be an early theory of the interstellar medium. 359 00:19:12,920 --> 00:19:15,240 Speaker 1: What is out there between the stars, what allows the 360 00:19:15,320 --> 00:19:18,080 Speaker 1: light to go from Alpha Centauri to us here? 361 00:19:18,600 --> 00:19:21,600 Speaker 2: And so the luminiferous ether. I thought I was going 362 00:19:21,680 --> 00:19:24,320 Speaker 2: to get it on the first shot. Totally did I 363 00:19:24,400 --> 00:19:28,320 Speaker 2: stumbled a little. Would you find that between like Earth 364 00:19:28,520 --> 00:19:31,800 Speaker 2: and Mars or that was just between the end of 365 00:19:31,840 --> 00:19:34,640 Speaker 2: our solar system and the start of the next solar system? 366 00:19:35,000 --> 00:19:37,760 Speaker 1: Great question. No, is should be everywhere. If it exists, 367 00:19:37,800 --> 00:19:40,720 Speaker 1: it should be everywhere. And that was key because people 368 00:19:40,760 --> 00:19:42,159 Speaker 1: looked for it and they said, well, let's try to 369 00:19:42,200 --> 00:19:46,160 Speaker 1: measure our velocity through this ether. If it's out there 370 00:19:46,200 --> 00:19:48,680 Speaker 1: and it's a medium for light, light is wiggling through 371 00:19:48,680 --> 00:19:52,080 Speaker 1: this ether, then Earth moving around the Sun should be 372 00:19:52,200 --> 00:19:56,000 Speaker 1: moving zigzagging basically back and forth through this ether. And 373 00:19:56,080 --> 00:19:58,720 Speaker 1: if light has a constant velocity relative to the ether, 374 00:19:59,240 --> 00:20:01,200 Speaker 1: then we should be able to measure light moving in 375 00:20:01,280 --> 00:20:05,080 Speaker 1: different velocities as we move in different velocities through the ether. Okay, right, 376 00:20:05,119 --> 00:20:07,399 Speaker 1: the same way that like you can catch up to 377 00:20:07,520 --> 00:20:10,040 Speaker 1: sound waves and air because they have a constant velocity 378 00:20:10,119 --> 00:20:12,399 Speaker 1: relative to the air, so you can catch up to 379 00:20:12,440 --> 00:20:14,800 Speaker 1: them and even pass them. Right, just like when you're 380 00:20:14,800 --> 00:20:16,840 Speaker 1: on a boat in a lake, you're making ripples. If 381 00:20:16,880 --> 00:20:18,719 Speaker 1: you go fast enough, you can catch up to them, 382 00:20:18,760 --> 00:20:22,320 Speaker 1: which it gives you awake, right, And so if light 383 00:20:22,400 --> 00:20:24,160 Speaker 1: is moving through this ether, and then as the Earth 384 00:20:24,200 --> 00:20:26,320 Speaker 1: moves around the Sun, we should see a change in 385 00:20:26,359 --> 00:20:29,520 Speaker 1: the velocity of light famous Michaelson. More the experiment of 386 00:20:29,520 --> 00:20:32,639 Speaker 1: course proved that light is the same speed year round, 387 00:20:32,720 --> 00:20:36,119 Speaker 1: regardless of the direction, and so apparently there is no 388 00:20:36,280 --> 00:20:39,320 Speaker 1: luminiferous ether. So then people are like, oh, wow, maybe 389 00:20:39,440 --> 00:20:41,880 Speaker 1: there really is a vacuum in between the stars. 390 00:20:42,119 --> 00:20:44,240 Speaker 2: And you all didn't find another use for the word 391 00:20:44,480 --> 00:20:47,440 Speaker 2: luminiferous ether. That's a total bummer because it just sounds 392 00:20:47,520 --> 00:20:49,920 Speaker 2: so nice. 393 00:20:50,400 --> 00:20:53,760 Speaker 1: Well, these days is actually a proliferation of ether theories, 394 00:20:54,000 --> 00:20:57,280 Speaker 1: which is very confusing because ether most generally just refers 395 00:20:57,320 --> 00:21:00,520 Speaker 1: to like a theory of the substrate of space, and 396 00:21:00,600 --> 00:21:03,480 Speaker 1: our current theory that quantum field theory, where space is 397 00:21:03,480 --> 00:21:07,080 Speaker 1: filled with these fields and these fields exist in space. 398 00:21:07,400 --> 00:21:10,560 Speaker 1: Then that's sort of the modern ether, and that's totally 399 00:21:10,600 --> 00:21:13,560 Speaker 1: cool and nobody objects to that. But that's an ether 400 00:21:13,640 --> 00:21:17,399 Speaker 1: where you can't measure your velocity relative to it, like 401 00:21:17,520 --> 00:21:20,320 Speaker 1: the luminiferous ether has a frame it's at rest in 402 00:21:20,359 --> 00:21:23,399 Speaker 1: some frame, and light moves at a constant speed only 403 00:21:23,440 --> 00:21:27,600 Speaker 1: in that frame. The modern ether quantum field theory vacuum 404 00:21:28,000 --> 00:21:31,160 Speaker 1: has no frame. And so there's a big distinction between 405 00:21:31,200 --> 00:21:35,080 Speaker 1: the luminiferous ether of two centuries ago and today's concepts 406 00:21:35,080 --> 00:21:37,840 Speaker 1: of the ether. And in lots of pop side descriptions 407 00:21:37,880 --> 00:21:41,920 Speaker 1: you see this important distinction sort of ignored or fuzzed over. 408 00:21:42,440 --> 00:21:45,040 Speaker 2: Okay, all right, and I could use a quick step 409 00:21:45,080 --> 00:21:46,920 Speaker 2: back and a reminder about where we are. So we've 410 00:21:46,960 --> 00:21:51,320 Speaker 2: been talking about what is in space between things. Yeah, 411 00:21:51,359 --> 00:21:53,920 Speaker 2: and we've just established that we used to think there 412 00:21:54,000 --> 00:21:57,119 Speaker 2: was ether between stuff, but there's not. But there's not, 413 00:21:57,280 --> 00:22:00,160 Speaker 2: but there's not. And so now, okay, so we're going 414 00:22:00,160 --> 00:22:02,560 Speaker 2: through the history of our understanding of what was in 415 00:22:02,600 --> 00:22:04,000 Speaker 2: the interstellar medium. 416 00:22:04,480 --> 00:22:07,760 Speaker 1: That's right. And then in eighteen ninety nine people discovered, oh, 417 00:22:07,760 --> 00:22:10,400 Speaker 1: there is some actual stuff out there between the stars, 418 00:22:10,760 --> 00:22:13,919 Speaker 1: not ether, but like actual matter. There were these things 419 00:22:13,960 --> 00:22:17,680 Speaker 1: called dark nebulae, essentially these dusty clouds you could see 420 00:22:17,720 --> 00:22:21,760 Speaker 1: out there that passed between the stars, right between us 421 00:22:21,800 --> 00:22:24,240 Speaker 1: and other stars. There were like these clouds of stuff 422 00:22:24,640 --> 00:22:28,439 Speaker 1: which were sometimes silhouetted against this background starfield. This is 423 00:22:28,520 --> 00:22:32,680 Speaker 1: essentially the first discovery of interstellar gas. It's just blobs 424 00:22:32,680 --> 00:22:35,280 Speaker 1: of gas that are out there between the stars. And 425 00:22:35,320 --> 00:22:38,520 Speaker 1: so as you make more and more accurate observations of 426 00:22:38,560 --> 00:22:41,120 Speaker 1: these stars and understand like why they dim or what 427 00:22:41,160 --> 00:22:43,520 Speaker 1: you can see and what's between you and those stars, 428 00:22:43,560 --> 00:22:46,040 Speaker 1: you start to build a map of the galaxy and 429 00:22:46,119 --> 00:22:49,480 Speaker 1: understand like where there's dust and where there's gas. And 430 00:22:49,520 --> 00:22:52,800 Speaker 1: this is our first like understanding really of the context 431 00:22:52,840 --> 00:22:53,720 Speaker 1: of our Solar. 432 00:22:53,400 --> 00:22:56,960 Speaker 2: System, understanding that there's gas out there. That gas isn't 433 00:22:58,000 --> 00:23:01,600 Speaker 2: like the ort cloud. That's just under standing where other 434 00:23:02,400 --> 00:23:04,560 Speaker 2: galaxies are out there and you're just kind of seeing 435 00:23:04,560 --> 00:23:06,800 Speaker 2: them as gas or what is that gas exactly? 436 00:23:07,119 --> 00:23:09,720 Speaker 1: Yeah, this is gas within our galaxy, okay, right, not 437 00:23:09,800 --> 00:23:13,560 Speaker 1: between galaxies. This is just understanding like what's between the stars. 438 00:23:13,640 --> 00:23:16,639 Speaker 1: Are the stars dots in a true vacuum or is 439 00:23:16,680 --> 00:23:18,800 Speaker 1: there like a soup out there? And it turns out 440 00:23:18,840 --> 00:23:22,480 Speaker 1: it's pretty soupy. We discovered these dark clouds of gas 441 00:23:22,520 --> 00:23:25,399 Speaker 1: between the stars, and then in the early nineteen hundreds 442 00:23:25,400 --> 00:23:29,159 Speaker 1: we discovered cosmic rays, which are just particles from space 443 00:23:29,240 --> 00:23:31,679 Speaker 1: that are zipping towards the Earth. And if there are 444 00:23:31,680 --> 00:23:34,439 Speaker 1: particles zpping towards the Earth. There's zipping from somewhere right, 445 00:23:34,440 --> 00:23:36,840 Speaker 1: which means that like space out there is filled with 446 00:23:36,880 --> 00:23:39,879 Speaker 1: all of these particles. So we had this growing awareness 447 00:23:39,880 --> 00:23:42,160 Speaker 1: that the space between the stars is filled with gas 448 00:23:42,280 --> 00:23:45,720 Speaker 1: and with ions and with electrons, just like in the 449 00:23:45,720 --> 00:23:47,800 Speaker 1: Solar System. And so instead of thinking of it like 450 00:23:48,240 --> 00:23:50,879 Speaker 1: here's a pocket of stuff the star and the planets, 451 00:23:51,720 --> 00:23:53,720 Speaker 1: you know how, now we think about like a spectrum 452 00:23:53,760 --> 00:23:56,480 Speaker 1: of stuff inside the Solar System, little bits of dust 453 00:23:56,560 --> 00:23:58,359 Speaker 1: all the way up to Jupiter and then the Sun. 454 00:23:58,800 --> 00:24:00,680 Speaker 1: In the same way, you should think about a smooth 455 00:24:00,840 --> 00:24:04,960 Speaker 1: transition between the Solar System and the interstellar medium that 456 00:24:05,040 --> 00:24:07,840 Speaker 1: between the stars there is still stuff. Yes, there is 457 00:24:07,880 --> 00:24:10,919 Speaker 1: a boundary where the solar wind stops dominating and the 458 00:24:11,000 --> 00:24:14,320 Speaker 1: interstellar wind starts dominating, But in terms of the distribution 459 00:24:14,359 --> 00:24:17,520 Speaker 1: of stuff, it's pretty smooth, and so you should expect 460 00:24:17,520 --> 00:24:19,840 Speaker 1: there to be stuff out there in the interstellar medium, 461 00:24:19,880 --> 00:24:22,160 Speaker 1: and it actually makes up like between ten and fifteen 462 00:24:22,200 --> 00:24:25,040 Speaker 1: percent of the mass of the galaxy is not inside 463 00:24:25,040 --> 00:24:28,760 Speaker 1: the stars. Yeah, it's between the stars, and it's going 464 00:24:28,840 --> 00:24:31,320 Speaker 1: to play an important role in how those stars are 465 00:24:31,359 --> 00:24:34,639 Speaker 1: formed and the health of our galaxy in forming stars, 466 00:24:34,680 --> 00:24:37,160 Speaker 1: whether our galaxy keeps making stars or whether it gets 467 00:24:37,280 --> 00:24:42,840 Speaker 1: quenched as they say, don't get quenched. So let's dig 468 00:24:43,000 --> 00:24:45,800 Speaker 1: a little bit more deeply into what's in the interstellar medium. 469 00:24:46,160 --> 00:24:48,080 Speaker 1: We said before the break that it's mostly gas, which 470 00:24:48,119 --> 00:24:51,040 Speaker 1: means that it's mostly hydrogen. It's like ninety percent hydrogen 471 00:24:51,520 --> 00:24:55,000 Speaker 1: ten percent helium, and the universe is mostly hydrogen, so 472 00:24:55,080 --> 00:24:58,280 Speaker 1: that makes sense. Something that's interesting, though, is that even 473 00:24:58,320 --> 00:25:00,760 Speaker 1: though there's a lot of space out there, it's super dense, 474 00:25:00,800 --> 00:25:03,919 Speaker 1: this stuff still behaves like a gas, like it interacts 475 00:25:03,920 --> 00:25:07,640 Speaker 1: with itself. It's not like non interacting, like the way 476 00:25:07,680 --> 00:25:09,800 Speaker 1: the exosphere of the Moon is just a bunch of 477 00:25:09,800 --> 00:25:13,040 Speaker 1: particles that ignore each other. Out there, these particles are 478 00:25:13,119 --> 00:25:16,360 Speaker 1: moving so fast the mean free path is pretty short, 479 00:25:16,680 --> 00:25:19,000 Speaker 1: Like they don't go very far before they run into 480 00:25:19,000 --> 00:25:21,520 Speaker 1: another one or interact with another one. They don't have 481 00:25:21,520 --> 00:25:24,439 Speaker 1: to actually touch because they have charges. They can interact 482 00:25:24,480 --> 00:25:26,879 Speaker 1: without touching each other. So that's really fast and that 483 00:25:26,960 --> 00:25:28,159 Speaker 1: was a little bit of a surprise to me when 484 00:25:28,200 --> 00:25:28,919 Speaker 1: I learned about that. 485 00:25:29,280 --> 00:25:32,200 Speaker 2: So if somebody were living out there, could they be 486 00:25:32,359 --> 00:25:35,360 Speaker 2: getting power from that, They. 487 00:25:35,320 --> 00:25:38,200 Speaker 1: Could be getting killed from that. I mean, this is radiation, right, 488 00:25:38,600 --> 00:25:41,480 Speaker 1: These particles are moving at high speeds even though it's 489 00:25:41,480 --> 00:25:44,600 Speaker 1: fairly low density. These things are moving pretty fast, like 490 00:25:44,920 --> 00:25:47,760 Speaker 1: inside the solar system, the solar wind is moving at 491 00:25:47,800 --> 00:25:51,359 Speaker 1: four hundred kilometers per second. Sometimes these particles of energy 492 00:25:51,400 --> 00:25:54,880 Speaker 1: up to ten keV, And in the interstellar medium, these 493 00:25:54,880 --> 00:25:58,119 Speaker 1: things are even higher speeds. So technically the temperature can 494 00:25:58,160 --> 00:26:01,080 Speaker 1: sometimes be like up in the millions of even though 495 00:26:01,080 --> 00:26:03,760 Speaker 1: the density is very very low, So you would like 496 00:26:03,880 --> 00:26:06,119 Speaker 1: freeze because there's not a lot of heat being deposited, 497 00:26:06,320 --> 00:26:08,720 Speaker 1: but also you'd be riddled with all of these tiny, 498 00:26:08,800 --> 00:26:09,800 Speaker 1: little high speed bullets. 499 00:26:09,960 --> 00:26:11,600 Speaker 2: That's definitely worse than New Jersey. 500 00:26:13,160 --> 00:26:14,639 Speaker 1: It's a close call, but I agree with you. 501 00:26:14,800 --> 00:26:17,119 Speaker 2: Ah, I do like New Jersey though I was born there. 502 00:26:17,440 --> 00:26:20,520 Speaker 1: The others fascinating bit about the interstellar medium is what's 503 00:26:20,560 --> 00:26:23,639 Speaker 1: not gas, which is the dust. And dust sounds like, 504 00:26:23,720 --> 00:26:26,040 Speaker 1: you know, stuff you'd sweep up and throw away, but 505 00:26:26,119 --> 00:26:30,080 Speaker 1: dust is actually super fascinating from a cosmic sense because 506 00:26:30,200 --> 00:26:32,800 Speaker 1: dust comes from dead stars. Right, Like, how do you 507 00:26:32,920 --> 00:26:35,919 Speaker 1: make dust? You need heavier elements. You need those elements 508 00:26:35,960 --> 00:26:38,679 Speaker 1: to stick together, You need them to form these little 509 00:26:38,720 --> 00:26:42,040 Speaker 1: crystals and to gather more bits to themselves, and dust 510 00:26:42,119 --> 00:26:46,240 Speaker 1: is like the seed for new solar systems and new planets. Right, 511 00:26:46,520 --> 00:26:49,119 Speaker 1: our Earth formed by a bunch of dust which bounced 512 00:26:49,119 --> 00:26:51,560 Speaker 1: into itself and stuck together and formed a bigger piece 513 00:26:51,560 --> 00:26:54,280 Speaker 1: of dust and gathered more together. So these are really 514 00:26:54,280 --> 00:26:56,679 Speaker 1: the seeds of future solar systems as well as the 515 00:26:56,720 --> 00:26:58,080 Speaker 1: ashes of previous ones. 516 00:26:58,480 --> 00:27:00,280 Speaker 2: Oh man, at first I thought you were talking about 517 00:27:00,280 --> 00:27:03,320 Speaker 2: gallstone formation, and then it sounded much more beautiful, and 518 00:27:03,359 --> 00:27:05,960 Speaker 2: I'm glad my gallstones, you know, stopped getting bigger before 519 00:27:06,000 --> 00:27:07,840 Speaker 2: they formed planets and universes. 520 00:27:10,440 --> 00:27:13,600 Speaker 1: But these huge amounts of like iron in silicon, magnesium, 521 00:27:14,119 --> 00:27:17,040 Speaker 1: a bunch of oxygen and carbon. This even like nano 522 00:27:17,119 --> 00:27:21,800 Speaker 1: diamonds and fullerines out there. They're really fascinating. And some 523 00:27:21,880 --> 00:27:26,000 Speaker 1: of these things are presolar grains, which are preserved from 524 00:27:26,040 --> 00:27:29,520 Speaker 1: the original star. So things formed like in the atmosphere 525 00:27:29,560 --> 00:27:31,920 Speaker 1: of the star, and then there's a supernova that blasts 526 00:27:31,920 --> 00:27:34,480 Speaker 1: out and spreads all these dust grains, and some of 527 00:27:34,520 --> 00:27:37,440 Speaker 1: them survive, right, They're not shattered. A lot of this 528 00:27:37,480 --> 00:27:41,159 Speaker 1: stuff is smashed into itself and shattered and reprocessed, but 529 00:27:41,280 --> 00:27:44,040 Speaker 1: some of these presolar grains survive and we actually find them, 530 00:27:44,080 --> 00:27:47,560 Speaker 1: like on the ocean floor, we can find little grains 531 00:27:47,560 --> 00:27:51,159 Speaker 1: of dust that survived a supernova and zoomed across the 532 00:27:51,240 --> 00:27:54,240 Speaker 1: universe and gathered together to help form the Earth. 533 00:27:54,600 --> 00:27:56,760 Speaker 2: How could you know? How could you find a grain 534 00:27:56,840 --> 00:28:01,200 Speaker 2: of sand and be like, I know where you came from. 535 00:28:01,400 --> 00:28:04,800 Speaker 1: Yeah, they have really unusual isotope mixtures which you only 536 00:28:04,880 --> 00:28:07,679 Speaker 1: find like in those conditions that are formed, like in 537 00:28:07,720 --> 00:28:09,960 Speaker 1: the atmospheres of supernovas. It's really incredible. 538 00:28:10,080 --> 00:28:11,600 Speaker 2: Wow, that is incredible. 539 00:28:12,119 --> 00:28:14,840 Speaker 1: And so the interstellar medium, it's mostly gas. There's a 540 00:28:14,880 --> 00:28:16,600 Speaker 1: little bit of dust out there, it's like one percent, 541 00:28:16,640 --> 00:28:18,600 Speaker 1: but I think that's the most interesting part. And then 542 00:28:18,640 --> 00:28:21,200 Speaker 1: of course some of it is very very high energy 543 00:28:21,200 --> 00:28:24,880 Speaker 1: particles zooming through space cosmic rays, and so you mix 544 00:28:24,920 --> 00:28:28,160 Speaker 1: all this together and that's what interstellar medium is made 545 00:28:28,160 --> 00:28:32,600 Speaker 1: out of. Mostly gas, which is actually mostly molecular not ionized, 546 00:28:32,960 --> 00:28:35,200 Speaker 1: and then one percent dust and then a few very 547 00:28:35,280 --> 00:28:36,440 Speaker 1: high energy ions. 548 00:28:36,840 --> 00:28:39,160 Speaker 2: All Right, we are getting closer to talking about the 549 00:28:39,240 --> 00:28:42,360 Speaker 2: amazing and exciting superbubble. So we're going to take a break, 550 00:28:42,480 --> 00:28:44,160 Speaker 2: and when we get back, we're going to talk about 551 00:28:44,240 --> 00:28:47,160 Speaker 2: how the gas and the dust are structured inside of 552 00:28:47,200 --> 00:29:09,720 Speaker 2: the interstellar medium. We are back and we're talking about 553 00:29:09,720 --> 00:29:12,880 Speaker 2: the interstellar medium, the space between the stars, and we've 554 00:29:13,080 --> 00:29:17,960 Speaker 2: established that it's mostly gas some dust in there. How 555 00:29:18,040 --> 00:29:20,400 Speaker 2: is all of that stuff structured in this space? 556 00:29:20,520 --> 00:29:23,160 Speaker 1: Daniel, Yeah, So you might imagine, oh, it's just smooth, 557 00:29:23,280 --> 00:29:26,280 Speaker 1: it's just spread out out there. But it's like a 558 00:29:26,360 --> 00:29:29,400 Speaker 1: vast fluid, which means that it has all sorts of stuff 559 00:29:29,440 --> 00:29:32,320 Speaker 1: going on. It's like our atmosphere, right, which we model 560 00:29:32,360 --> 00:29:35,760 Speaker 1: and has currents and winds and high density regions and 561 00:29:35,760 --> 00:29:38,960 Speaker 1: low density regions, and so you can think about the 562 00:29:39,000 --> 00:29:42,160 Speaker 1: interstellar medium as a vast fluid because it is interacting. Right, 563 00:29:42,200 --> 00:29:45,080 Speaker 1: The meanfree path of these particles is pretty short, but 564 00:29:45,120 --> 00:29:48,520 Speaker 1: it's also more complex than a simple fluid because often 565 00:29:48,520 --> 00:29:51,120 Speaker 1: these particles are moving really really fast. Our whole regions 566 00:29:51,160 --> 00:29:53,800 Speaker 1: of particles are moving super duper fast. So you can 567 00:29:53,880 --> 00:29:59,160 Speaker 1: have supersonic regions of this interstellar medium right places where 568 00:29:59,160 --> 00:30:01,480 Speaker 1: the gas is moved being faster than the speed of 569 00:30:01,560 --> 00:30:04,440 Speaker 1: sound in that medium. Remember, you can define the speed 570 00:30:04,480 --> 00:30:08,080 Speaker 1: of sound in anything, in water and air and steel, 571 00:30:08,400 --> 00:30:10,280 Speaker 1: and it depends like on the density of the thing. 572 00:30:10,680 --> 00:30:13,520 Speaker 1: Things that are denser, the bonds are tighter, and if 573 00:30:13,520 --> 00:30:16,880 Speaker 1: you push on one, then the pressure wave propagates more quickly, 574 00:30:17,200 --> 00:30:19,720 Speaker 1: and then it would if something was really low density, 575 00:30:19,840 --> 00:30:21,920 Speaker 1: because then the particles have to drift longer before they 576 00:30:21,920 --> 00:30:24,880 Speaker 1: bump into each other. Okay, And so what happens in 577 00:30:24,920 --> 00:30:28,880 Speaker 1: the interstellar medium is you have these shockwaves, these supersonic 578 00:30:28,920 --> 00:30:32,760 Speaker 1: shockwaves which smash into something else, and so you get 579 00:30:32,800 --> 00:30:35,959 Speaker 1: this supersonic shockwave, but that compresses the gas, makes it 580 00:30:36,040 --> 00:30:39,800 Speaker 1: more dense, and that actually raises the speed of sound. 581 00:30:40,080 --> 00:30:43,080 Speaker 1: So then the local flow becomes subsonic. So you get 582 00:30:43,200 --> 00:30:46,960 Speaker 1: supersonic shockwaves, which then actually becomes subsonic, and so it 583 00:30:47,000 --> 00:30:51,200 Speaker 1: creates this really complex structure and these really interesting patterns 584 00:30:51,200 --> 00:30:54,480 Speaker 1: of density. It's really hard to model because it's so chaotic. 585 00:30:54,960 --> 00:30:58,800 Speaker 2: So in order to hear sound, you need like molecules 586 00:30:58,840 --> 00:31:00,800 Speaker 2: to transmit it. So like if you were out there, 587 00:31:00,840 --> 00:31:05,120 Speaker 2: would you be hearing these particles or or not? 588 00:31:05,160 --> 00:31:09,479 Speaker 1: Really you can technically scream and be heard in the 589 00:31:09,480 --> 00:31:13,720 Speaker 1: interstellar medium, it would be very faint and very very slow. Right, Okay, 590 00:31:13,840 --> 00:31:15,600 Speaker 1: you could hear these things, I can tell you what 591 00:31:15,640 --> 00:31:20,080 Speaker 1: they would sound like. You know, probably like shh cool. 592 00:31:20,160 --> 00:31:23,000 Speaker 2: Okay, interesting, I don't know why, But in my mind, 593 00:31:23,000 --> 00:31:26,040 Speaker 2: I'd imagine the interstellar space is being like a quiet, calm, 594 00:31:26,120 --> 00:31:28,800 Speaker 2: still place, which is probably silly because you know, like 595 00:31:28,840 --> 00:31:31,080 Speaker 2: solar winds keep things moving. There's probably nowhere that in 596 00:31:31,080 --> 00:31:34,080 Speaker 2: space that's actually super still, But I hadn't imagined it 597 00:31:34,120 --> 00:31:36,000 Speaker 2: being super turbulent like this. 598 00:31:36,120 --> 00:31:39,400 Speaker 1: So yeah, it's really turbulent. And you know, on time 599 00:31:39,440 --> 00:31:41,320 Speaker 1: scales that we don't usually think about, but if you 600 00:31:41,640 --> 00:31:44,320 Speaker 1: played a movie, you know, where a million years passes 601 00:31:44,360 --> 00:31:47,720 Speaker 1: in a second, it would look like bubbling, frothing tea 602 00:31:47,880 --> 00:31:50,440 Speaker 1: or something. You know, it's a lot of stuff going on. 603 00:31:51,200 --> 00:31:53,200 Speaker 1: And the most interesting stuff that goes on is that 604 00:31:53,240 --> 00:31:56,320 Speaker 1: when you get dense regions, you get star formation. Right, 605 00:31:56,840 --> 00:31:59,400 Speaker 1: if you have a clump of gas and it cools 606 00:31:59,480 --> 00:32:02,440 Speaker 1: down and then one of those grains of dust can 607 00:32:02,480 --> 00:32:06,040 Speaker 1: start to gather other stuff near it. It's important that's cool, remember, 608 00:32:06,320 --> 00:32:08,560 Speaker 1: because if things are really really hot, and that means 609 00:32:08,600 --> 00:32:11,520 Speaker 1: they're moving fast and then gravity has no chance to 610 00:32:11,520 --> 00:32:13,800 Speaker 1: pull them together. But if things are cool, that means 611 00:32:13,840 --> 00:32:17,080 Speaker 1: they're slow moving and gravity can gather dust grains together 612 00:32:17,200 --> 00:32:20,080 Speaker 1: little bits at a time. They stick together, they start 613 00:32:20,120 --> 00:32:22,600 Speaker 1: forming bigger and bigger stuff and that's when you get 614 00:32:22,600 --> 00:32:25,840 Speaker 1: gravitational collapse leads to a runaway effect. You get more gravity, 615 00:32:26,200 --> 00:32:28,400 Speaker 1: and then you get a star forming and there stuff 616 00:32:28,440 --> 00:32:31,800 Speaker 1: around it starts to swirl around it to a protoplanetary disc. 617 00:32:32,160 --> 00:32:34,600 Speaker 1: And that's how a star is born. It's born from 618 00:32:34,800 --> 00:32:38,200 Speaker 1: denser regions in the interstellar medium, and those regions come 619 00:32:38,240 --> 00:32:41,520 Speaker 1: from the turbulence. So the structure in the interstellar medium 620 00:32:41,680 --> 00:32:43,200 Speaker 1: is the reason we have stars. 621 00:32:43,840 --> 00:32:46,880 Speaker 2: The structure in the interstellar medium. But don't you only 622 00:32:46,920 --> 00:32:51,480 Speaker 2: have interstellar medium because it's the region between pre existing stars. 623 00:32:52,000 --> 00:32:56,040 Speaker 1: Yeah, there's sort of a circular definition there, but yeah, 624 00:32:56,080 --> 00:32:59,040 Speaker 1: the interstellar medium can make new stars and then it's 625 00:32:59,040 --> 00:33:00,480 Speaker 1: no longer the interstellar medium. 626 00:33:00,600 --> 00:33:04,560 Speaker 2: Okay, So you can imagine this process going on infinitely 627 00:33:04,560 --> 00:33:06,640 Speaker 2: many times, and then you just have an infinite number 628 00:33:06,640 --> 00:33:09,120 Speaker 2: of suns. So how often does this process happen? 629 00:33:09,320 --> 00:33:12,120 Speaker 1: So it depends a lot on the details of the 630 00:33:12,160 --> 00:33:15,600 Speaker 1: temperature of the cloud and the composition. But when it happens, 631 00:33:15,600 --> 00:33:17,479 Speaker 1: it happens a lot. Like you get a lot of 632 00:33:17,520 --> 00:33:20,520 Speaker 1: stars all born in one of the neighborhood together. And 633 00:33:20,560 --> 00:33:23,680 Speaker 1: this is why, for example, stars are very often found 634 00:33:23,680 --> 00:33:27,240 Speaker 1: in binary systems like pairs of stars gravitationally bound to 635 00:33:27,280 --> 00:33:31,040 Speaker 1: each other, or even briefly trinary systems or more long 636 00:33:31,080 --> 00:33:33,240 Speaker 1: lived systems where you have like a binary star and 637 00:33:33,320 --> 00:33:36,360 Speaker 1: another one that's more distant, so that it's like effectively 638 00:33:36,360 --> 00:33:39,120 Speaker 1: a binary system. So you have these regions of star 639 00:33:39,160 --> 00:33:42,480 Speaker 1: formation where a huge cloud meets these requirements where you 640 00:33:42,480 --> 00:33:45,000 Speaker 1: have like little dense grains and the whole thing is 641 00:33:45,040 --> 00:33:48,400 Speaker 1: cold enough, and how often it happens depends a lot 642 00:33:48,480 --> 00:33:51,720 Speaker 1: on the history of your galaxy. There's actually an interplay 643 00:33:51,760 --> 00:33:54,160 Speaker 1: between the stars and the interstelling medium, which we're going 644 00:33:54,240 --> 00:33:56,840 Speaker 1: to talk about, because the stars push back and form 645 00:33:56,920 --> 00:34:00,480 Speaker 1: these bubbles, and so it's a whole complex of all thing. 646 00:34:00,560 --> 00:34:03,520 Speaker 1: And the rate at which stars form changes a lot 647 00:34:03,640 --> 00:34:06,120 Speaker 1: where you are in the galaxy and over time, and 648 00:34:06,160 --> 00:34:09,719 Speaker 1: it's not something we fully understand. Like some galaxies out 649 00:34:09,760 --> 00:34:12,719 Speaker 1: there have stopped forming stars at all, and some of 650 00:34:12,760 --> 00:34:15,480 Speaker 1: them are still making stars and this is called quenching, 651 00:34:15,960 --> 00:34:17,840 Speaker 1: and it's not something that's fully understood. 652 00:34:18,160 --> 00:34:20,080 Speaker 2: All right, well, we still haven't gotten to the bubbles. 653 00:34:20,120 --> 00:34:21,440 Speaker 2: How do we get closer to bubbles? 654 00:34:21,760 --> 00:34:24,120 Speaker 1: Yeah, so you have the interstellar medium. You got these 655 00:34:24,160 --> 00:34:26,560 Speaker 1: clouds of gas. Sometimes they collapse and form a star. 656 00:34:27,000 --> 00:34:29,080 Speaker 1: What happens when you make a star is that it 657 00:34:29,120 --> 00:34:33,000 Speaker 1: pushes back against the interstellar medium, right, Like our Sun 658 00:34:33,080 --> 00:34:35,800 Speaker 1: has a solar wind, and that's pushing back. The reason 659 00:34:35,840 --> 00:34:38,000 Speaker 1: we call it a solar system is it's the region 660 00:34:38,040 --> 00:34:40,920 Speaker 1: where our solar wind dominates. So now you have this 661 00:34:41,040 --> 00:34:44,799 Speaker 1: cavity inside the interstellar medium, right, And so the Sun 662 00:34:44,880 --> 00:34:47,239 Speaker 1: basically makes like a little bubble, which we call the 663 00:34:47,239 --> 00:34:51,279 Speaker 1: heliosphere by pushing back against the interstellar medium. So now 664 00:34:51,360 --> 00:34:53,520 Speaker 1: imagine you have a bunch of stars, each with their 665 00:34:53,560 --> 00:34:56,640 Speaker 1: little bubbles, and one of them goes supernova, right, So 666 00:34:56,719 --> 00:34:59,800 Speaker 1: this blows out a huge region inside the ism, and 667 00:34:59,840 --> 00:35:03,279 Speaker 1: this can create a superbubble that's like hundreds of light 668 00:35:03,360 --> 00:35:07,320 Speaker 1: years across. Because remember a supernova is the collapse of 669 00:35:07,320 --> 00:35:10,319 Speaker 1: a star of gravitationally, which then bounces back out and 670 00:35:10,400 --> 00:35:13,440 Speaker 1: dumps an enormous amount of energy. A single supernova can 671 00:35:13,480 --> 00:35:16,440 Speaker 1: be brighter than the entire galaxy and it doesn't just 672 00:35:16,440 --> 00:35:18,800 Speaker 1: put out photons. That also shoots out a huge number 673 00:35:18,840 --> 00:35:19,520 Speaker 1: of particles. 674 00:35:19,760 --> 00:35:24,040 Speaker 2: How many light years across is our solar system? 675 00:35:24,239 --> 00:35:26,919 Speaker 1: So our solar system is like one or two light 676 00:35:27,000 --> 00:35:30,440 Speaker 1: years in radius, okay, right, So it's pretty small. But 677 00:35:30,480 --> 00:35:33,120 Speaker 1: then a supernova can make a bubble that's like hundreds 678 00:35:33,120 --> 00:35:36,439 Speaker 1: of light years across. And if there's multiple supernova, because 679 00:35:36,440 --> 00:35:39,040 Speaker 1: remember stars are formed in bunches, and that means they 680 00:35:39,040 --> 00:35:41,600 Speaker 1: can also go supernova in bunches they have like their 681 00:35:41,600 --> 00:35:44,239 Speaker 1: cycles all synchronized. Oh boy, then you can get a 682 00:35:44,360 --> 00:35:47,480 Speaker 1: really big bubble that lasts for like tens of millions 683 00:35:47,480 --> 00:35:48,000 Speaker 1: of years. 684 00:35:48,600 --> 00:35:51,399 Speaker 2: Okay, so the bubbles that we're talking about then are 685 00:35:52,360 --> 00:35:56,799 Speaker 2: solar winds of some sort blowing interstellar medium out, and 686 00:35:56,840 --> 00:35:58,960 Speaker 2: that is the bubble. These are not the fun bubbles 687 00:35:58,960 --> 00:36:00,800 Speaker 2: that I was imagining, Daniel. 688 00:36:02,120 --> 00:36:04,160 Speaker 1: So you get little bubbles from solar winds, but you 689 00:36:04,200 --> 00:36:07,080 Speaker 1: really get the super bubbles from a bunch of supernova's 690 00:36:07,120 --> 00:36:10,880 Speaker 1: all going off at once and making these really vast bubbles. 691 00:36:11,200 --> 00:36:14,160 Speaker 1: It's super cool. Also, if one happens near the edge 692 00:36:14,200 --> 00:36:17,840 Speaker 1: of the galaxy, Like the galaxy is a big disc, right, 693 00:36:18,080 --> 00:36:21,239 Speaker 1: it's like much broader than it is thick. So if 694 00:36:21,280 --> 00:36:23,680 Speaker 1: it occurs like near the top of the disk, then 695 00:36:23,760 --> 00:36:27,040 Speaker 1: essentially it creates like a hole in the galaxy. And 696 00:36:27,120 --> 00:36:29,960 Speaker 1: they call it a galactic chimney because in hot gas 697 00:36:30,000 --> 00:36:33,520 Speaker 1: from inside the galaxy basically vents out from the galaxy, 698 00:36:34,040 --> 00:36:35,520 Speaker 1: so you have like a little spurt. 699 00:36:35,800 --> 00:36:38,440 Speaker 2: So the question that we're answering today is do we 700 00:36:38,480 --> 00:36:41,000 Speaker 2: live in a super bubble? But timing's got to matter too, 701 00:36:41,080 --> 00:36:43,000 Speaker 2: right now, if you get a bunch of stars going 702 00:36:43,040 --> 00:36:46,680 Speaker 2: supernova all at once to make your super bubble, you 703 00:36:46,719 --> 00:36:48,480 Speaker 2: would be dead if you were inside of the super 704 00:36:48,480 --> 00:36:51,200 Speaker 2: bubble region, right, So it's got to go super bubble, 705 00:36:51,360 --> 00:36:53,759 Speaker 2: make a bubble exact, and then a planet needs to 706 00:36:53,840 --> 00:36:57,120 Speaker 2: like wander in or get captured and then become habitable, 707 00:36:57,800 --> 00:37:00,360 Speaker 2: and then you find yourself inside the super bubble. That 708 00:37:00,360 --> 00:37:01,759 Speaker 2: would have to work, right, okay. 709 00:37:01,520 --> 00:37:03,719 Speaker 1: Right, And remember, our Solar system has existed for like 710 00:37:03,880 --> 00:37:06,640 Speaker 1: almost five billion years, but these super bubbles last for 711 00:37:06,760 --> 00:37:10,200 Speaker 1: tens of millions of years. They're very transient, and our 712 00:37:10,280 --> 00:37:13,719 Speaker 1: star is moving through the galaxy, right, and its orbit 713 00:37:13,760 --> 00:37:17,640 Speaker 1: takes hundreds of millions of years, and so they're created 714 00:37:17,640 --> 00:37:19,480 Speaker 1: by supernova. But you don't want to be there when 715 00:37:19,480 --> 00:37:24,000 Speaker 1: they're made, you're right, And so coincidentally, there is a bubble. 716 00:37:24,000 --> 00:37:26,799 Speaker 1: It's called the local bubble. It's three hundred to one 717 00:37:26,920 --> 00:37:30,280 Speaker 1: thousand light year wide. It has a much lower gas 718 00:37:30,320 --> 00:37:33,120 Speaker 1: density than the rest of the interstellar medium by like 719 00:37:33,280 --> 00:37:36,840 Speaker 1: down by ten, and it's surrounded by denser walls of 720 00:37:36,880 --> 00:37:40,080 Speaker 1: neutral gas and dust. Probably it was formed by like 721 00:37:40,120 --> 00:37:42,680 Speaker 1: maybe ten to twenty supernovas that happened over the last 722 00:37:42,680 --> 00:37:46,160 Speaker 1: ten to fifteen million years, so sort of recently on 723 00:37:46,239 --> 00:37:50,920 Speaker 1: cosmic history scales. We can't pinpoint exactly which stars they are. 724 00:37:50,960 --> 00:37:55,960 Speaker 1: Probably their stars related to the Scorpius Centaurus association of stars. 725 00:37:56,440 --> 00:37:58,440 Speaker 1: And the shape of it is kind of weird. It's 726 00:37:58,520 --> 00:38:01,880 Speaker 1: not spherical, and there's other like nearby bubbles that it 727 00:38:01,920 --> 00:38:06,240 Speaker 1: connects to called loop one, and so fortunately it formed 728 00:38:06,320 --> 00:38:09,439 Speaker 1: before we got here. Right, the Sun orbits the center 729 00:38:09,440 --> 00:38:12,439 Speaker 1: of the galaxy at like two hundred and twenty kilometers 730 00:38:12,440 --> 00:38:15,640 Speaker 1: per second and moves it like twenty five kilometers per 731 00:38:15,680 --> 00:38:19,720 Speaker 1: second relative to the interstellar medium, and so that means 732 00:38:19,719 --> 00:38:23,560 Speaker 1: that we go like twenty to thirty parsecs every million 733 00:38:23,640 --> 00:38:28,120 Speaker 1: years or so. This bubble is a few hundred parsecs across, 734 00:38:28,680 --> 00:38:32,520 Speaker 1: so seems like about fifteen million years ago the first 735 00:38:32,560 --> 00:38:37,000 Speaker 1: supernova started inflating this bubble. Five or ten million years 736 00:38:37,040 --> 00:38:40,440 Speaker 1: ago we entered the cavity, and now we're in this superbubble. 737 00:38:40,680 --> 00:38:44,120 Speaker 1: We're drifting through a little warm cloud of gas inside 738 00:38:44,160 --> 00:38:47,240 Speaker 1: this bubble, and in a couple million years we're probably 739 00:38:47,239 --> 00:38:50,440 Speaker 1: going to exit it back into the interstellar medium, which 740 00:38:50,480 --> 00:38:51,360 Speaker 1: is a little bit denser. 741 00:38:52,080 --> 00:38:55,440 Speaker 2: So when we enter the interstellar medium where there's all 742 00:38:55,440 --> 00:38:58,480 Speaker 2: of that turbulence and it's crazy, is that going to 743 00:38:58,520 --> 00:38:59,560 Speaker 2: be a bad time for us? 744 00:39:00,320 --> 00:39:03,399 Speaker 1: No, probably not, because we have the solar wind which 745 00:39:03,400 --> 00:39:06,960 Speaker 1: protects us. Were moving within our own little bubble anyway, 746 00:39:07,480 --> 00:39:09,840 Speaker 1: So it doesn't really matter that much. It's just a 747 00:39:09,840 --> 00:39:12,120 Speaker 1: way to highlight that there's a lot of stuff happening 748 00:39:12,160 --> 00:39:16,160 Speaker 1: out there, right there's turbulence and chaos and all that stuff, 749 00:39:16,160 --> 00:39:18,800 Speaker 1: and star formation and start dying and all that happens 750 00:39:18,920 --> 00:39:22,560 Speaker 1: because of this structure. Like you get stars because you 751 00:39:22,640 --> 00:39:26,120 Speaker 1: have denser regions, and then those stars blow out make 752 00:39:26,200 --> 00:39:29,120 Speaker 1: superbubbles when they die to make less dense regions. But 753 00:39:29,160 --> 00:39:32,720 Speaker 1: then those superbubbles collapse because the interior is lower density 754 00:39:32,719 --> 00:39:36,080 Speaker 1: but higher temperature, and that hot gas leaks out and 755 00:39:36,160 --> 00:39:39,480 Speaker 1: ruptures the shell, and so you get this cycle of stuff. 756 00:39:39,840 --> 00:39:42,120 Speaker 1: And so you know, you shouldn't think of the galaxy 757 00:39:42,160 --> 00:39:44,719 Speaker 1: out there between the stars is empty. In fact, it's 758 00:39:44,719 --> 00:39:48,880 Speaker 1: filled with stuff, and it's really dynamic, and the structure 759 00:39:49,000 --> 00:39:52,160 Speaker 1: out there is what determines like where stars are made 760 00:39:52,560 --> 00:39:56,400 Speaker 1: and then stars explode and replenish the interstellar medium, and 761 00:39:56,440 --> 00:39:59,320 Speaker 1: so the interplay between the stars and the interstellar medium 762 00:39:59,400 --> 00:40:03,279 Speaker 1: really determined, like, hey, is your galaxy making stars or not? 763 00:40:03,440 --> 00:40:05,920 Speaker 1: Is it to pleasing all of its gas? All this 764 00:40:06,000 --> 00:40:09,040 Speaker 1: kind of stuff is determined by this interaction between the 765 00:40:09,080 --> 00:40:10,760 Speaker 1: stars and the interstellar medium. 766 00:40:10,920 --> 00:40:14,239 Speaker 2: Huh. So we live inside of a bubble made by 767 00:40:14,280 --> 00:40:18,160 Speaker 2: our son, which is currently inside of the local super bubble. 768 00:40:18,239 --> 00:40:21,560 Speaker 1: That's right, that was made by supernovas of other stars, 769 00:40:21,719 --> 00:40:23,720 Speaker 1: fortunately before we entered this region. 770 00:40:24,600 --> 00:40:27,719 Speaker 2: Amazing exactly, And. 771 00:40:27,719 --> 00:40:30,560 Speaker 1: So that's the broader context of your life. We happen 772 00:40:30,600 --> 00:40:32,920 Speaker 1: to be living inside this bubble, and now you. 773 00:40:32,960 --> 00:40:35,400 Speaker 2: Know all about it, that's right. And we hope that 774 00:40:35,440 --> 00:40:38,360 Speaker 2: you don't stub your toes on any galactic dust or 775 00:40:38,440 --> 00:40:41,200 Speaker 2: happen to get dust of any sort inside of your 776 00:40:41,239 --> 00:40:44,360 Speaker 2: gallbladder or kidneys or anything else. We wish you health. 777 00:40:44,360 --> 00:40:47,520 Speaker 2: And this is not a great transition. But man, it 778 00:40:47,640 --> 00:40:49,400 Speaker 2: hurt to laugh at Daniel's jokes today. 779 00:40:50,160 --> 00:40:51,879 Speaker 1: I try to hold back. I really really did. 780 00:40:52,280 --> 00:40:54,600 Speaker 2: I appreciate it. Daniel. You can't help yourself. You're just 781 00:40:54,640 --> 00:40:55,200 Speaker 2: a funny guy. 782 00:40:57,160 --> 00:41:00,920 Speaker 1: Looks, Aren't everything right ready? 783 00:41:09,040 --> 00:41:12,880 Speaker 2: Daniel and Kelly's Extraordinary Universe is produced by iHeartRadio. We 784 00:41:12,920 --> 00:41:14,319 Speaker 2: would love to hear from you. 785 00:41:14,440 --> 00:41:17,360 Speaker 1: We really would. We want to know what questions you 786 00:41:17,600 --> 00:41:20,200 Speaker 1: have about this Extraordinary Universe. 787 00:41:20,320 --> 00:41:23,239 Speaker 2: We want to know your thoughts on recent shows, suggestions 788 00:41:23,280 --> 00:41:26,279 Speaker 2: for future shows. If you contact us, we will get 789 00:41:26,320 --> 00:41:26,719 Speaker 2: back to you. 790 00:41:26,960 --> 00:41:30,520 Speaker 1: We really mean it. We answer every message. Email us 791 00:41:30,560 --> 00:41:33,759 Speaker 1: at Questions at Danielankelly. 792 00:41:32,800 --> 00:41:34,880 Speaker 2: Dot org, or you can find us on social media. 793 00:41:35,000 --> 00:41:38,799 Speaker 2: We have accounts on x, Instagram, Blue Sky and on 794 00:41:38,880 --> 00:41:40,840 Speaker 2: all of those platforms. You can find us at d 795 00:41:41,280 --> 00:41:42,800 Speaker 2: and kuniverse. 796 00:41:43,000 --> 00:41:44,560 Speaker 1: Don't be shy, write to us