WEBVTT - How important is cosmic dust? 0:00:08.480 --> 0:00:11.119 Hey, Daniel, you're kind of a neat freak, aren't you. 0:00:11.320 --> 0:00:14.360 I do like to keep my laptop nicely, well dusted. 0:00:15.040 --> 0:00:16.960 The weight dust it like you put dust in it, 0:00:17.160 --> 0:00:19.960 or you take out dust, or you wipe dust out 0:00:20.000 --> 0:00:20.159 of it. 0:00:20.520 --> 0:00:23.320 Good question. I mean, I like my cookies well dusted 0:00:23.360 --> 0:00:27.640 with sugar, but my laptop keyboard well dusted with zero dust. 0:00:28.280 --> 0:00:32.120 Yeah, household dust is less delicious, and powdered sugar is 0:00:32.159 --> 0:00:34.640 in regular dust, like fifty percent skin cells. 0:00:34.840 --> 0:00:36.519 That sounds like a pretty gross thing to put on 0:00:36.560 --> 0:00:38.960 your cookies. On the other hand, it would be pretty 0:00:38.960 --> 0:00:41.600 weird if powdered sugar just like accumulated in your. 0:00:41.440 --> 0:00:43.280 House, it'd be pretty sweet. 0:00:44.360 --> 0:00:46.400 We might call for some sweeping changes. 0:00:46.840 --> 0:00:49.960 Uh, I'm glad you got to dust off that old punt. 0:01:05.240 --> 0:01:05.319 Hi. 0:01:05.400 --> 0:01:08.000 I'm Poor hammy cartoonas and the author of Oliver's Great 0:01:08.000 --> 0:01:08.800 Big Universe. 0:01:08.920 --> 0:01:11.560 Hi. I'm Daniel. I'm a particle physicist and a professor 0:01:11.600 --> 0:01:14.400 at UC Irvine, and I don't like dust as much 0:01:14.440 --> 0:01:15.479 as astronomers do. 0:01:15.600 --> 0:01:16.880 But do you still like it a little bit? 0:01:17.000 --> 0:01:19.600 I like dust the way I like the sun. It's fascinating, 0:01:19.760 --> 0:01:23.399 it's interesting, it's useful, It tells us about the cosmos. 0:01:23.440 --> 0:01:26.000 But I don't really want it on my laptop or 0:01:26.040 --> 0:01:27.080 on my table. 0:01:27.440 --> 0:01:28.840 But everywhere else it's okay. 0:01:29.200 --> 0:01:32.000 Yeah, study it from a distance, you know, the way 0:01:32.080 --> 0:01:34.680 like I'm fascinated by cheetahs, but I don't really want 0:01:34.720 --> 0:01:35.800 to have a cheat on my lap. 0:01:37.240 --> 0:01:39.080 Do you carry a duster with you at all times? 0:01:39.080 --> 0:01:39.240 Then? 0:01:39.560 --> 0:01:42.000 I actually do have this very fancy little machine for 0:01:42.000 --> 0:01:43.800 removing dust from your keyboard. 0:01:44.000 --> 0:01:46.680 Is it called blowing on it? Or did you Did 0:01:46.680 --> 0:01:48.320 you actually pay for a machine to do that? 0:01:48.840 --> 0:01:51.400 I actually have a nice little machine. It's really quite good. Yeah, 0:01:51.440 --> 0:01:52.560 I should call it mini made. 0:01:52.600 --> 0:01:53.960 Wait, what is it like a vacuum? 0:01:54.000 --> 0:01:55.560 No, it's like a little blower, you know. It replaces 0:01:55.600 --> 0:01:58.960 those disposable cans that I thought were not very environmentally friendly, 0:01:59.120 --> 0:02:00.000 though I do love them. 0:02:00.080 --> 0:02:00.320 Mmm. 0:02:01.800 --> 0:02:04.000 Oh, I see you mean like the dust between the keys, 0:02:04.120 --> 0:02:06.280 like you want to get rid of it, like in 0:02:06.320 --> 0:02:07.240 the nooks and crannies. 0:02:07.480 --> 0:02:09.880 Yeah, exactly. I like a nice clean keyboard. 0:02:10.120 --> 0:02:10.280 Oh. 0:02:10.320 --> 0:02:12.079 I thought you meant like on your screen, because I 0:02:12.080 --> 0:02:13.320 think you can just wipe that off. 0:02:13.600 --> 0:02:16.720 I think you can. But probably that dust contains all 0:02:16.760 --> 0:02:19.679 sorts of fascinating stories where each of those bits has 0:02:19.760 --> 0:02:20.920 been But you. 0:02:20.960 --> 0:02:22.760 Know, if you just blow the dust, it's just getting 0:02:22.760 --> 0:02:24.200 in the air and then it's going to come back 0:02:24.240 --> 0:02:25.160 down on your keyboard. 0:02:25.280 --> 0:02:26.960 I know it's a cycle. Unless I'm willing to live 0:02:27.000 --> 0:02:29.359 in a clean room, I can never escape it. 0:02:29.400 --> 0:02:31.400 So you don't like living in clean rooms. 0:02:31.639 --> 0:02:33.720 I don't have to wear a hairnet and booties all 0:02:33.760 --> 0:02:34.120 the time. 0:02:34.240 --> 0:02:39.760 No, just some of the time. But anyways, welcome for 0:02:39.800 --> 0:02:42.760 a podcast Daniel and Jorge Explain the Universe, a production 0:02:42.880 --> 0:02:44.000 of our Heart Radio. 0:02:43.919 --> 0:02:47.240 In which we dive deep into the cycles of the universe, 0:02:47.320 --> 0:02:51.239 the ones that produce massive stars and tiny grains of dust. 0:02:51.600 --> 0:02:53.960 Everything out there in the universe has a history and 0:02:54.040 --> 0:02:57.359 tells a story, and if we can unpack it, unravel 0:02:57.360 --> 0:02:59.760 it and study it, you can reveal those stories and 0:02:59.800 --> 0:03:03.120 the history of our own cosmos. To learn about the 0:03:03.160 --> 0:03:07.320 formation of the planets and stars and the universe itself, 0:03:07.440 --> 0:03:09.840 from the biggest clues to the tiniest speck of dust. 0:03:10.080 --> 0:03:13.079 That's right, we blow the dust off of the universe, 0:03:13.240 --> 0:03:16.800 trying to uncover what's underneath, What shiny surface or interesting 0:03:16.840 --> 0:03:19.680 facts are there for us to understand and to learn about. 0:03:19.760 --> 0:03:21.760 I love in archaeology, how every time they're going to 0:03:21.760 --> 0:03:24.440 discover something amazing, they always have to blow dust off 0:03:24.440 --> 0:03:26.960 of it, pull cobwebs off of it. That's like your 0:03:27.040 --> 0:03:29.520 visual cue that you're about to learn something ancient. 0:03:29.760 --> 0:03:30.639 Wait, wait, what do you mean? 0:03:30.760 --> 0:03:32.920 I mean? I just watched a new Indian Jones. I guess. 0:03:33.240 --> 0:03:35.880 So you know anytime they unde earth something from the 0:03:35.920 --> 0:03:37.839 olden days, it's always covered in dust. 0:03:37.920 --> 0:03:40.920 Of course, mm to see they carry a dust with 0:03:40.960 --> 0:03:42.760 them at all times. Maybe you can buy one of 0:03:42.800 --> 0:03:45.840 those devices and you didn't have to waste electricity. 0:03:46.960 --> 0:03:49.200 I'd be that neat freak archaeologist. I don't think i'd 0:03:49.240 --> 0:03:50.280 get very far in the field. 0:03:50.640 --> 0:03:53.280 Yeah, it is a dusty universe full of amazing things, 0:03:53.600 --> 0:03:55.640 where even the dust is interesting. In the universe. 0:03:55.800 --> 0:03:57.920 Down here on Earth we see dust is sort of 0:03:57.960 --> 0:04:00.839 a nuisance, something to brush out of our But out 0:04:00.840 --> 0:04:03.640 in space dust plays a very important role in the 0:04:03.680 --> 0:04:08.040 formation of stars and planets, and it can reveal that history. 0:04:08.640 --> 0:04:11.600 Dust is not just a nuisance. It's a fascinating pile 0:04:11.640 --> 0:04:12.600 of tiny clues. 0:04:12.800 --> 0:04:20.279 So today end podcast, we'll be asking the question how 0:04:20.320 --> 0:04:24.560 important is cosmic dust? Now? Hopefully this episode won't be 0:04:24.600 --> 0:04:25.480 a bust. 0:04:27.360 --> 0:04:30.400 Should we just be sweeping cosmic dust under the cosmic 0:04:30.480 --> 0:04:33.360 rug or should we take it seriously and study it 0:04:33.440 --> 0:04:34.080 in detail. 0:04:34.680 --> 0:04:36.599 That's a bit of a dusty pun there, you used 0:04:36.600 --> 0:04:40.880 it already, But yeah, it's an interesting question here cosmic dust. 0:04:40.960 --> 0:04:42.559 I guess it's different than regular dust. 0:04:42.640 --> 0:04:45.279 Well, I think there's fewer dead skin cells and leftover 0:04:45.360 --> 0:04:47.960 bits of insects out there floating between the stars than 0:04:47.960 --> 0:04:50.520 there is here on Earth. But cosmic dust also falls 0:04:50.560 --> 0:04:51.039 to Earth. 0:04:51.120 --> 0:04:53.920 You mean it gets sprinkled from space like powdered sugar. 0:04:54.080 --> 0:04:56.440 Well, you know that space isn't empty, and there's dust 0:04:56.480 --> 0:04:59.040 out there between the stars but also between the planets, 0:04:59.160 --> 0:05:02.480 and as the Earth moves through these cosmic dust clouds, 0:05:02.640 --> 0:05:05.240 it accumulates some of them. Some tons of dust fall 0:05:05.320 --> 0:05:08.360 to Earth every year from interplanetary space out there in 0:05:08.400 --> 0:05:09.160 the Solar System. 0:05:09.400 --> 0:05:12.599 WHOA is it like dandruff space? Dandruff? Or is that 0:05:12.640 --> 0:05:13.279 too embarrassing? 0:05:15.200 --> 0:05:17.679 We had a whole fun episode about where this stuff 0:05:17.680 --> 0:05:19.640 comes from. It's a bit of a mystery. There's a 0:05:19.680 --> 0:05:22.560 recent experiment though, that tries to pin the blame on Mars. 0:05:22.960 --> 0:05:25.720 It might be that dust storms on Mars are blowing 0:05:25.720 --> 0:05:27.960 that stuff out into space and the Earth is flying 0:05:28.000 --> 0:05:31.000 through Mars's dust clouds. So yeah, I guess it's all 0:05:31.160 --> 0:05:32.120 Martian dandruff. 0:05:32.839 --> 0:05:35.400 Yeah, Mars needs some head and shoulders. 0:05:36.040 --> 0:05:38.799 Well first they need heads and shoulders. That'd be pretty 0:05:38.800 --> 0:05:39.599 awesome discovery. 0:05:39.680 --> 0:05:42.440 Yeah, or maybe just a hat that might help. But 0:05:42.520 --> 0:05:46.159 it is an interesting question. How important is cosmic dust? 0:05:46.200 --> 0:05:49.240 Which I guess means Daniel, that cosmic dust is important. 0:05:49.320 --> 0:05:51.800 Cosmic dust is more important than you might think. I mean, 0:05:51.800 --> 0:05:54.400 the word dust makes you think it's insignificant. It's just 0:05:54.440 --> 0:05:56.560 something to be blown off of. Something else. Man, it 0:05:56.560 --> 0:05:59.320 gets in your way, something, it messes things up, something 0:05:59.360 --> 0:06:02.120 to be gotten rid of. But dust has clues in it. 0:06:02.240 --> 0:06:03.680 This is like the dust here on Earth tells you 0:06:03.720 --> 0:06:06.080 who's been living there and the insects that have been around. 0:06:06.200 --> 0:06:07.960 Dust out in space tells you what's been happening in 0:06:08.000 --> 0:06:11.080 the universe, because there's dust makers and dust consumers, and 0:06:11.160 --> 0:06:15.000 dust also plays a big role in making stars and planets. 0:06:15.040 --> 0:06:18.599 Well, you just said dust consumers out in space like 0:06:18.680 --> 0:06:22.000 aliens who buy dust. That's what it sounds like. 0:06:22.720 --> 0:06:25.880 Not dust customers. You know, ways in which just is 0:06:25.920 --> 0:06:29.039 created and then dust is destroyed. I should say dust destroyers. 0:06:29.279 --> 0:06:31.080 Oh there you go. See that's a device. I would 0:06:31.080 --> 0:06:32.520 buy a dust destroyer. 0:06:33.720 --> 0:06:35.640 Wait till you learn how dust is destroyed. You don't 0:06:35.680 --> 0:06:36.520 want one of these things? 0:06:38.400 --> 0:06:40.640 Maybe I do. Let's find out. Well, as usual, we 0:06:40.680 --> 0:06:43.120 were wondering how many people had thought about the importance 0:06:43.320 --> 0:06:45.840 of cosmic does and what role it has in our 0:06:46.320 --> 0:06:48.839 search for the meaning of the universe and how it 0:06:48.880 --> 0:06:49.400 all works. 0:06:49.560 --> 0:06:52.000 Thanks to everybody who pitches in for this segment of 0:06:52.000 --> 0:06:54.800 the podcast. I hear from listeners that they really enjoy 0:06:55.160 --> 0:06:58.240 hearing your voices in your thoughts on the episode topic. 0:06:58.560 --> 0:07:00.559 If you would like to share your voice and thoughts, 0:07:00.600 --> 0:07:03.920 please don't be shy. Write me to Questions at Daniel 0:07:03.960 --> 0:07:05.240 Andandjorge dot com. 0:07:05.279 --> 0:07:07.400 So think about for a second, how important do you 0:07:07.440 --> 0:07:11.280 think cosmic dust is. Here's what people have to say. 0:07:11.480 --> 0:07:14.720 Stop waving from the universe. I would say that twenty 0:07:14.720 --> 0:07:20.200 percent is planet stars, black holes, sixty percent gus, and 0:07:20.280 --> 0:07:21.560 the rest twenty percent is dust. 0:07:21.920 --> 0:07:24.560 I think that this is the one of those questions 0:07:24.600 --> 0:07:27.520 that but you have to think about some things that 0:07:27.600 --> 0:07:31.880 you usually take for granted. So I would say that 0:07:32.560 --> 0:07:36.280 the QA is mostly composed by dust. 0:07:36.480 --> 0:07:40.720 All right, interesting, answers here, some people seem to interpret 0:07:40.760 --> 0:07:45.120 the questions like how significant is cosmic? Doest? 0:07:45.280 --> 0:07:45.520 Yeah? 0:07:45.680 --> 0:07:47.960 Like, or like how much how much of the universe 0:07:48.040 --> 0:07:48.720 is cosmic? Does? 0:07:49.280 --> 0:07:50.760 And they also seem to be taking it as a 0:07:50.840 --> 0:07:54.680 leading question, like because I'm asking it, they're figuring probably 0:07:54.720 --> 0:07:57.040 it's a big component of the universe and playing an 0:07:57.040 --> 0:07:57.760 important role. 0:07:58.640 --> 0:08:00.800 I see, it wouldn't be very interesting just the answer 0:08:00.920 --> 0:08:05.160 was just like not at all or nope, nobody cares. 0:08:05.240 --> 0:08:07.880 Yeah, Like how important are Daniel dirty socks? 0:08:08.040 --> 0:08:08.280 Yeah? 0:08:08.400 --> 0:08:11.120 Not interesting, not important? Move on, That wouldn't be a 0:08:11.200 --> 0:08:12.760 very fun episode. 0:08:13.680 --> 0:08:16.640 Let's not talk about your socks because I know you 0:08:16.680 --> 0:08:17.600 don't wear socks, so. 0:08:17.680 --> 0:08:20.000 Well, then it's a philosophy question, right can my socks 0:08:20.040 --> 0:08:22.040 be unimportant if they don't even exist? 0:08:22.280 --> 0:08:24.600 There you go, philosophy of footwear. 0:08:25.800 --> 0:08:28.400 Somebody out there is doing a whole PhD thesis on 0:08:28.440 --> 0:08:29.760 that topic, probably. 0:08:29.560 --> 0:08:31.760 On your socks. On socks, and Jackie, I know you're 0:08:31.760 --> 0:08:34.040 famous now, Daniel, but geez. 0:08:34.160 --> 0:08:37.640 No on socks? Why they disappear where they go? Why 0:08:37.720 --> 0:08:40.720 dryers consume them? See dryers are sock destroyers. 0:08:41.360 --> 0:08:42.560 Nay, it turns them into dust. 0:08:43.120 --> 0:08:45.720 Maybe it transports them to the hozone layer of the atmosphere. 0:08:45.880 --> 0:08:49.960 So let's dig into this topic, Daniel, what is cosmic dust? 0:08:50.120 --> 0:08:53.120 Cosmic dust is an important part of the Solar system, 0:08:53.400 --> 0:08:56.280 though it's not a big fraction of the Solar system. 0:08:56.440 --> 0:08:58.720 The answer from these listeners made me dig into the 0:08:58.800 --> 0:09:01.920 question of like, actually, but is the mass budget of 0:09:02.040 --> 0:09:04.960 the Solar system? How much of it is cosmic dust 0:09:04.960 --> 0:09:07.480 and how much of it is made of other stuff? 0:09:08.720 --> 0:09:09.640 So what's the breakdown? 0:09:09.679 --> 0:09:11.959 So the Milky Way weighs about one to one and 0:09:12.000 --> 0:09:15.800 a half trillion times the mass of the Sun. That's 0:09:15.920 --> 0:09:19.120 like our mass unit a solar mass, and the total 0:09:19.160 --> 0:09:21.480 Milky Way is about a trillion trillion and a half 0:09:21.559 --> 0:09:24.880 solar masses. Now, most of that, like ninety percent of 0:09:24.920 --> 0:09:27.800 that is dark matter. We know that the stuff that's 0:09:27.880 --> 0:09:30.160 visible in the universe, the stuff that glows, and even 0:09:30.160 --> 0:09:32.720 the stuff that doesn't glow that much, like rocks and 0:09:32.840 --> 0:09:36.000 dust and asteroids, that's only like ten percent of the 0:09:36.040 --> 0:09:38.840 mass of the Milky Way. Out there in the larger universe, 0:09:38.920 --> 0:09:40.920 dark matter is a little bit less common than it 0:09:40.960 --> 0:09:42.720 is here in the Milky Way. The Milky Way has 0:09:42.760 --> 0:09:45.160 more dark matter than an average galaxy. 0:09:44.800 --> 0:09:46.320 And I guess. How do we know these things? Like 0:09:46.320 --> 0:09:48.520 how do we know how much the Milky Way weighs? 0:09:48.640 --> 0:09:50.440 Do we put it on a scale or something. 0:09:50.480 --> 0:09:53.080 We can measure the component of the Milky Way independently 0:09:53.240 --> 0:09:56.880 and then add them up. The stars and the interstellar medium, 0:09:56.960 --> 0:09:59.880 the black hole, all that stuff we can measure independently, 0:10:00.320 --> 0:10:02.640 and then we can measure the total mass by looking 0:10:02.679 --> 0:10:05.520 at how fast the Milky Way is rotating. Because stars 0:10:05.559 --> 0:10:08.080 are like tracers, they move around the Milky Way, and 0:10:08.120 --> 0:10:12.000 their speed is determined by the gravitational traction of everything 0:10:12.160 --> 0:10:15.480 closer to the center than they are. Things further away 0:10:15.480 --> 0:10:17.960 from the center on the outer shell don't affect them 0:10:17.960 --> 0:10:20.400 at all, things on the inside do. So by reading 0:10:20.440 --> 0:10:23.160 the speed of these stars, we can tell how much 0:10:23.240 --> 0:10:26.960 mass they're radius encloses, and so that measures the total 0:10:26.960 --> 0:10:29.199 mass of the Solar system. And that's how we infer 0:10:29.320 --> 0:10:31.440 dark matter, sort of the left over bit that we 0:10:31.440 --> 0:10:34.439 can't account for with stars and planets and gas and dust. 0:10:34.920 --> 0:10:37.679 But we can't see all of the Milky Way right 0:10:37.720 --> 0:10:39.880 Like we're in the Milky Way, can we really see 0:10:40.080 --> 0:10:42.240 the full extent of it and have a good guess 0:10:42.280 --> 0:10:43.200 about its composition? 0:10:43.360 --> 0:10:45.160 There's a lot of uncertainty, which is why I said 0:10:45.360 --> 0:10:48.160 one to one and a half trillion solar masses. So 0:10:48.200 --> 0:10:51.679 that's like an uncertainty of five hundred billion solar masses. 0:10:52.160 --> 0:10:53.760 And yeah, part of that comes from the fact that 0:10:53.800 --> 0:10:55.800 we can't see the whole Milky Way because we're looking 0:10:55.840 --> 0:10:58.320 through it, we're inside of it, and the Milky Way 0:10:58.360 --> 0:10:59.880 has a good amount of dust in it, and that 0:11:00.160 --> 0:11:03.880 dust obscures our view. So there's a whole region of 0:11:03.880 --> 0:11:05.840 the Milky Way that we can't see very well in 0:11:05.920 --> 0:11:08.080 many frequencies of light, and that leads to a lot 0:11:08.120 --> 0:11:09.640 of this uncertainty. I see. 0:11:09.640 --> 0:11:11.959 So then how much of our Milky Way is dust? 0:11:12.080 --> 0:11:14.400 So it's like ninety percent dark matter, Then it's like 0:11:14.559 --> 0:11:17.360 three percent stars, it's like one hundred to two hundred 0:11:17.360 --> 0:11:20.800 billion stars. And then leftover is this stuff called the 0:11:20.840 --> 0:11:24.120 interstellar medium, which is maybe like half a percent or 0:11:24.200 --> 0:11:26.560 one percent of the mass of the Milky Way, and 0:11:26.679 --> 0:11:30.000 one percent of that is dust. The interstellar medium is 0:11:30.040 --> 0:11:33.440 mostly gas, it's like hydrogen and a little bit of helium. 0:11:33.559 --> 0:11:35.880 So one percent of the interstellar medium, which is one 0:11:35.920 --> 0:11:38.800 percent of the galaxy, is dust. So the dust is 0:11:38.880 --> 0:11:41.600 like point zho one percent or maybe half of that. 0:11:41.720 --> 0:11:43.960 It's a tiny fraction of the mass of the Milky Way. 0:11:44.920 --> 0:11:48.080 So I guess you don't count that gas is dust, right. 0:11:47.960 --> 0:11:50.680 That's right. And this is another example of humans putting 0:11:50.679 --> 0:11:54.400 categories on things where really there's a smooth spectrum. If 0:11:54.400 --> 0:11:56.280 we call it gas, it means it's like a molecule, 0:11:56.320 --> 0:11:59.199 there's like h two floating out there, we call that gas. 0:11:59.800 --> 0:12:02.320 If it's a larger clump of stuff, a bunch of 0:12:02.360 --> 0:12:06.280 molecules together, little grains down like one hundred nanometers or larger, 0:12:06.559 --> 0:12:09.320 we call that dust. Get much bigger, we start to 0:12:09.320 --> 0:12:12.560 call you like a meteor or an asteroid or even 0:12:12.559 --> 0:12:14.920 a planet. But in the end, there's a whole spectrum 0:12:14.960 --> 0:12:17.720 all the way down from individual molecules which we call gas, 0:12:18.040 --> 0:12:21.240 to larger clumps of stuff which we call dust, all 0:12:21.280 --> 0:12:24.000 the way up to much bigger objects stars and planets. 0:12:24.080 --> 0:12:26.520 I guess at some point you get to like pebbles, right, 0:12:27.520 --> 0:12:30.560 and little rocks. Is there such a thing as space sand? 0:12:32.240 --> 0:12:35.600 Well, you know this dust is made of carbon and silicates, right, 0:12:35.640 --> 0:12:38.080 and sand is mostly silicates. So in the end, like 0:12:38.160 --> 0:12:40.760 a lot of this space dust is kind of like 0:12:41.000 --> 0:12:42.800 super fine grains of sand. 0:12:43.000 --> 0:12:45.199 But then I also imagine there is sort of sand 0:12:45.320 --> 0:12:47.120 sized grains out there in space. 0:12:47.320 --> 0:12:49.959 There are larger pieces for sure, And so this intermedia 0:12:50.000 --> 0:12:52.880 category we call dust is not a very big fraction 0:12:53.200 --> 0:12:55.560 of the mass of the Milky Way. But to compare, 0:12:55.640 --> 0:12:58.440 it's about the same mass as the central black Hole. 0:12:58.559 --> 0:13:01.120 Point oh one percent of the Milky Way sounds like 0:13:01.160 --> 0:13:04.760 a tiny number. It's a tiny percentage of a huge number, right, 0:13:04.840 --> 0:13:07.480 one and a half trillion solar masses. So it comes 0:13:07.480 --> 0:13:09.800 out to be about the mass of the central black Hole. 0:13:11.480 --> 0:13:13.560 And so where did all this dust come from? Like 0:13:13.640 --> 0:13:16.920 are there giant space aliens shedding of their skin? 0:13:16.960 --> 0:13:18.559 To understand where the dust comes from, we need to 0:13:18.600 --> 0:13:20.400 dig into a little bit more about like what is 0:13:20.480 --> 0:13:23.319 this dust? And it's made of like a bunch of 0:13:23.320 --> 0:13:26.280 different stuff, some tiny little portion of it, this is 0:13:26.320 --> 0:13:30.760 really fascinating, comes from the atmospheres of stars. We know 0:13:30.800 --> 0:13:34.040 that stars their job is to take hydrogen and helium 0:13:34.120 --> 0:13:38.000 and lighter elements and fuse them into heavier elements, although 0:13:38.040 --> 0:13:39.680 I have to iron and even heavier in the case 0:13:39.720 --> 0:13:42.680 of supernova and in the atmospheres of these stars, especially 0:13:42.720 --> 0:13:45.120 when they get really really big and near the end 0:13:45.120 --> 0:13:48.720 of their life. Their atmospheres produce these little grains. They're 0:13:48.720 --> 0:13:51.480 like coalesce as they cool, and the outflow in the 0:13:51.520 --> 0:13:54.880 atmosphere of these stars. That's sort of like one source 0:13:54.960 --> 0:13:56.959 of this stuff. But if you look out into the 0:13:57.040 --> 0:13:59.800 universe and study this stuff, most of it is not 0:14:00.040 --> 0:14:03.320 these presolar grains, these like pristine little blobs made in 0:14:03.320 --> 0:14:06.359 the atmospheres of stars. Most of it's been like reprocessed, 0:14:06.400 --> 0:14:09.800 like shattered and ground up and reformed into new bits. 0:14:10.040 --> 0:14:12.959 Interesting just from like the churning of space, of stuff 0:14:13.040 --> 0:14:13.440 in space. 0:14:13.760 --> 0:14:15.640 Just from the churning of space. It turns out that 0:14:15.679 --> 0:14:18.040 you can't just hang out as a grain in the 0:14:18.080 --> 0:14:20.920 middle of space. There are processes happening out there. There 0:14:20.960 --> 0:14:24.640 are processes that destroy dust and processes that reform it. 0:14:24.720 --> 0:14:26.800 The dust destroyers that are out there. It sounds like, 0:14:26.840 --> 0:14:29.080 you know, some big alien ship coming along to clean 0:14:29.160 --> 0:14:32.880 up the universe, but actually it's shock waves from supernova. 0:14:33.040 --> 0:14:37.120 When supernova collapse and then explode, they produce these huge 0:14:37.160 --> 0:14:41.320 shock waves, massive amounts of energy, gamma, rays, neutrinos, all 0:14:41.360 --> 0:14:44.040 sorts of stuff, and that comes along and it shatters 0:14:44.120 --> 0:14:46.960 these grains, destroying the dust and breaking it like back 0:14:47.000 --> 0:14:47.880 down into gas. 0:14:48.480 --> 0:14:50.560 Well you know they say space is just a big vacuum, 0:14:50.640 --> 0:14:56.400 so those are just suckle. Anyways, So you were saying 0:14:56.440 --> 0:14:59.360 that dust is important in the universe. Is it important 0:14:59.400 --> 0:15:02.120 to the universe or just to our understanding or to 0:15:02.200 --> 0:15:04.080 our search for answers about the universe? 0:15:04.200 --> 0:15:06.840 Well both, Like the history of dust tells us what's 0:15:06.840 --> 0:15:09.320 happened out there in the universe. You can take each 0:15:09.400 --> 0:15:13.920 individual solar grain if it survived this like interstellar shattering process, 0:15:14.080 --> 0:15:16.280 and some of them have, and you can trace it 0:15:16.320 --> 0:15:19.360 back to an individual star. Like every star has a 0:15:19.400 --> 0:15:22.560 different mixture of elements and a different mixture of isotopes, 0:15:22.840 --> 0:15:26.600 so they leave special fingerprints in their solar grains, and 0:15:26.680 --> 0:15:29.040 so like ular grain can tell you, like what that 0:15:29.200 --> 0:15:32.040 star was. It's like a little sample from that star. 0:15:32.720 --> 0:15:35.880 And some of them are made during supernova and capture 0:15:35.920 --> 0:15:39.120 elements and isotopes that only exist, we think, in the 0:15:39.160 --> 0:15:42.760 atmospheres of supernova during those brief moments that are super 0:15:42.880 --> 0:15:45.840 energetic and can tell us about the formation of heavy 0:15:45.880 --> 0:15:48.640 elements and what's going on in supernova. So there are 0:15:48.680 --> 0:15:51.280 these amazing capsules that tell us about the history of 0:15:51.320 --> 0:15:51.880 the universe. 0:15:51.960 --> 0:15:54.320 But I think maybe you don't mean like each individual grain, 0:15:54.360 --> 0:15:57.320 do you look? You maybe need like a population or 0:15:57.360 --> 0:15:59.040 like a cloud of this dust to sort of know 0:15:59.640 --> 0:16:00.880 what the star was like. 0:16:01.120 --> 0:16:04.280 Well, each individual grain tells you something about that star. 0:16:04.440 --> 0:16:07.200 Not every grain produced by the star is identical, right, 0:16:07.240 --> 0:16:09.960 and the star has a variety of stuff in it, 0:16:10.320 --> 0:16:12.560 but each one traces back to an individual star. 0:16:12.800 --> 0:16:14.880 Just each grain would be made out of different things. 0:16:15.080 --> 0:16:17.640 Yeah, each star would make different kinds of grains. There's 0:16:17.640 --> 0:16:20.760 going to be some overlap. It's not completely unique, right, 0:16:20.840 --> 0:16:23.160 But each star is made out of different kinds of stuff, 0:16:23.200 --> 0:16:26.160 different elements, different mixtures. Each star is a slightly different 0:16:26.160 --> 0:16:29.480 mass and temperature and so produces different mixtures of stuff 0:16:29.520 --> 0:16:32.320 and different isotopes, and so the grains produced by each 0:16:32.360 --> 0:16:33.400 star are different. 0:16:33.680 --> 0:16:36.600 Like an individual grain would have different things in it 0:16:36.680 --> 0:16:37.960 and different signatures in it. 0:16:38.080 --> 0:16:42.040 Yeah, exactly. The isotopes found in an individual grain tell 0:16:42.080 --> 0:16:43.640 you about the star that it came from. 0:16:43.840 --> 0:16:47.360 Mmmm. Interesting, So how is it important to the universe itself? 0:16:47.400 --> 0:16:49.400 Because it doesn't seem like it weighs a lot in 0:16:49.440 --> 0:16:51.760 the Milca way, So maybe I wonder if it has 0:16:51.880 --> 0:16:54.000 a big role in you know, the dynamics of space. 0:16:54.120 --> 0:16:55.800 It does play a big role in the dynamics of 0:16:55.840 --> 0:16:58.960 space sort of for two reasons. One is that stuff 0:16:59.000 --> 0:17:02.080 heavier than gas is the reason that we have like 0:17:02.200 --> 0:17:05.359 planets and stars and stuff like that. Like the Earth 0:17:05.440 --> 0:17:08.119 is mostly made out of stuff that's not just hydrogen 0:17:08.160 --> 0:17:11.800 and helium, right, and that's cosmic dust gathered together to 0:17:11.960 --> 0:17:15.199 form planets. So most of the rocky stuff of the 0:17:15.240 --> 0:17:19.640 Solar system came originally from what we would call cosmic dust, right, 0:17:19.680 --> 0:17:23.080 those heavier elements that are created by stars and spewed 0:17:23.119 --> 0:17:26.080 out into space. And also we think that this cosmic 0:17:26.119 --> 0:17:28.600 dust plays a role in the formation of solar systems. 0:17:28.640 --> 0:17:31.320 You have a huge gas cloud that eventually collapses into 0:17:31.320 --> 0:17:34.800 a bunch of stars. Why does it collapse. It collapses 0:17:34.840 --> 0:17:37.520 because it's a little spot here that's denser, that's heavier, 0:17:37.920 --> 0:17:41.160 that's cosmic dust. Man, Those are like the iron grains 0:17:41.240 --> 0:17:44.240 and the little bits of heavy elements floating around that 0:17:44.440 --> 0:17:46.200 seed that gravitational collapse. 0:17:46.320 --> 0:17:48.080 Wait, are you saying the Bible was right? We all 0:17:48.080 --> 0:17:50.480 come from dust, from dust to dust. 0:17:50.400 --> 0:17:52.840 And even ashes, right, star ashes. 0:17:53.160 --> 0:17:55.800 Cool And so then how does it help us study 0:17:55.800 --> 0:17:58.159 the universe or how does it not help us study 0:17:58.160 --> 0:17:58.679 the universe. 0:17:58.840 --> 0:18:01.240 Yeah, it both hurts our ability to study the universe 0:18:01.280 --> 0:18:04.200 and helps us. Like it prevents us from seeing things 0:18:04.200 --> 0:18:06.960 in the universe because it absorbs light and it blocks 0:18:07.000 --> 0:18:09.240 our view. The center of the Milky Way, which is 0:18:09.440 --> 0:18:13.200 choked with dust, is famously called by astronomers the zone 0:18:13.280 --> 0:18:16.000 of avoidance because they have to look away from that region. 0:18:16.040 --> 0:18:18.320