WEBVTT - How do galaxies die? 0:00:08.400 --> 0:00:11.920 Hey, Daniel, how old are you? While I'm turning forty 0:00:12.000 --> 0:00:16.640 seven pretty soon? Does that feel old? Too? Well? Whenever 0:00:16.640 --> 0:00:20.160 I'm feeling old, I just decided to count my age differently. 0:00:20.280 --> 0:00:23.440 Oh yeah, like a different base number, you know, Like 0:00:23.480 --> 0:00:25.240 how old would I be if I lived in a 0:00:25.239 --> 0:00:29.080 different place, For example, because Mars is years longer, I'd 0:00:29.080 --> 0:00:31.000 be in my early twenties if I was a Martian. 0:00:31.880 --> 0:00:34.400 But you would die in like a few hours, would 0:00:34.400 --> 0:00:36.240 any or a few minutes if you lift the Mars 0:00:36.400 --> 0:00:39.080 right now, depending if Elon Musk has money left from 0:00:39.080 --> 0:00:42.559 his Twitter purchased to fund our oxygen on Mars. But 0:00:42.640 --> 0:00:45.080 I guess even if you're a Martian, you would still 0:00:45.120 --> 0:00:47.120 live the same amount of time, so you'd be just 0:00:47.159 --> 0:00:50.280 as old. It'd just be a different year unit, that's right. 0:00:50.280 --> 0:00:53.400 But it's all about how the number feels. Man. Yeah, 0:00:53.400 --> 0:00:55.360 but also you have to take it to account your 0:00:55.440 --> 0:00:59.240 life expectancy. That also gets changed on Mars, right yep. 0:00:59.640 --> 0:01:02.640 On my cars we all die young anyway, or maybe not. 0:01:02.760 --> 0:01:04.559 Maybe the air there is so much better that people 0:01:04.600 --> 0:01:22.040 would live longer, long enough to tweet forever. Hi, I'm 0:01:22.080 --> 0:01:24.559 Horrhand made cartoonists and the co author of frequently asked 0:01:24.640 --> 0:01:28.080 questions about the universe. Hi, I'm Daniel. I'm a particle 0:01:28.120 --> 0:01:31.600 physicist and a professor at U C Irvine, and I 0:01:31.720 --> 0:01:34.920 plan to teach until my old old age. Do you 0:01:34.920 --> 0:01:37.800 think you'll still have something to teach when you're that old? 0:01:37.920 --> 0:01:40.960 I often teach freshman physics, which hasn't changed since Newton, 0:01:41.440 --> 0:01:44.639 so I'm planning to teach it until I grade away. 0:01:46.440 --> 0:01:49.280 What if you start forgetting things, even Newtonian physics? I'm 0:01:49.280 --> 0:01:50.920 sorry would you ask? I forgot the first part of 0:01:50.920 --> 0:01:55.240 your question, but anyways, Welcome to our podcast, Daniel and 0:01:55.360 --> 0:01:58.320 Jorge Explain the Universe, a production of I Heart Radio, 0:01:58.440 --> 0:02:01.920 in which we explore this incre rereadibly old and incredibly 0:02:02.000 --> 0:02:05.680 young universe, which has lived for billions of years and 0:02:05.720 --> 0:02:09.359 may survive for trillions and trillions more. We explore all 0:02:09.360 --> 0:02:12.880 of the fast moving and slow paced processes that grow 0:02:13.040 --> 0:02:15.760 and shape and define our universe and make it the 0:02:15.800 --> 0:02:17.800 one that we love. Our goal is not to be 0:02:17.840 --> 0:02:20.800 intimidated by the age of the universe or the billions 0:02:20.800 --> 0:02:23.320 and trillions of years that are to come, but to 0:02:23.440 --> 0:02:26.280 try to understand the processes that shape it, and to 0:02:26.400 --> 0:02:28.960 explain all of them. To you, that's right, because we 0:02:29.000 --> 0:02:32.079 live in an amazing universe that's been around for fourteen 0:02:32.120 --> 0:02:35.720 billion years or maybe more, which sounds like a long time, 0:02:35.720 --> 0:02:38.519 but who knows. We could be maybe in the universe's 0:02:38.600 --> 0:02:41.560 infancy right now, and the universe might live on for 0:02:41.639 --> 0:02:44.320 a long time, maybe even forever. Imagine if you had 0:02:44.360 --> 0:02:47.120 lived in the universe in the first few hundred thousand years, 0:02:47.160 --> 0:02:49.960 you might think, oh, this is what the universe is like, 0:02:50.160 --> 0:02:52.480 not realizing that it was but the first flash of 0:02:52.520 --> 0:02:54.520 the universe and that it would live for billions of 0:02:54.600 --> 0:02:56.920 years with glowing stars. And now we live in the 0:02:56.960 --> 0:02:59.480 starfield era of the universe. But it might just be 0:02:59.639 --> 0:03:02.920 the first flash of a universe that lasts for trillions 0:03:02.919 --> 0:03:05.760 of years and is mostly filled with black holes. So 0:03:05.919 --> 0:03:08.560 this era of the universe could be very short lived 0:03:08.560 --> 0:03:11.960 and very weird, weird, but also pretty cool. I think 0:03:12.080 --> 0:03:14.600 you know right, Technically we are living in the cool 0:03:14.720 --> 0:03:17.919 years of the universe, not the hot, crazy, insane years, 0:03:18.120 --> 0:03:21.120 and also not the you know, super freezing years. Well, 0:03:21.160 --> 0:03:24.400 because the universe is expanding, it's cooling, and so technically 0:03:24.440 --> 0:03:27.720 it gets cooler every year, and not just because they 0:03:27.800 --> 0:03:31.320 keep releasing more Marvel movies about more multiverses. Yeah, but 0:03:31.320 --> 0:03:32.880 at some point you get it. I think it is 0:03:32.919 --> 0:03:35.480 possible to be too cool, you know, like if the 0:03:36.000 --> 0:03:38.080 entropy of the universe is set a maximum and the 0:03:38.120 --> 0:03:41.920 temperature is like zero out there, Kelvin, that's not cool, 0:03:42.040 --> 0:03:45.600 Doctor Strange, and the heat death of the universe coming soon. 0:03:47.000 --> 0:03:49.040 I hear the last one is pretty dark, right, Everything 0:03:49.160 --> 0:03:52.840 is getting darker. Everything in the Marvel universe is getting darker. 0:03:52.880 --> 0:03:55.920 But in our universe, things continue to glow and brighten 0:03:56.000 --> 0:03:58.440 and to fill the universe with photons that allow us 0:03:58.480 --> 0:04:01.760 to see the incredible view was across billions and billions 0:04:01.760 --> 0:04:05.000 of miles and allow our tiny human brains to grapple 0:04:05.120 --> 0:04:07.880 with questions about how everything came to look the way 0:04:07.880 --> 0:04:11.440 that it does and how long it will continue to shine. Yeah, 0:04:11.560 --> 0:04:14.760 because unless you're Elon Musk, I guess the universe will 0:04:14.800 --> 0:04:18.320 be bright and shiny and beautiful and amazing and an 0:04:18.360 --> 0:04:21.359 open mystery pretty much until your old age. Right, is 0:04:21.360 --> 0:04:22.840 Elon Musk going to figure it out? Is that what 0:04:22.880 --> 0:04:24.640 you're saying. I think he's going to figure out how 0:04:24.680 --> 0:04:28.680 to beat old age. He's going to download himself into 0:04:28.680 --> 0:04:31.119 a Tesla and launch himself into space and live there forever. 0:04:31.240 --> 0:04:35.040 That's right. With that, you know, special module for twittering, 0:04:36.200 --> 0:04:39.560 Maybe he should combine all of his companies, you know, twistler, 0:04:40.680 --> 0:04:43.640 put Twitter onto a Tesla in a boring tube and 0:04:43.720 --> 0:04:47.359 launch that whole thing into space. That's right, Yeah, be 0:04:47.400 --> 0:04:52.320 a Twistla X would be the company name, the Boring 0:04:52.440 --> 0:04:56.000 twistle X. But we are not funded by Elon Musk, 0:04:56.080 --> 0:04:58.000 although you know you know what to send your donations 0:04:58.000 --> 0:05:00.279 Elon if you're a listener. But we are motor vated 0:05:00.360 --> 0:05:03.200 by the desire to understand everything that's around us and 0:05:03.320 --> 0:05:06.040 figure out exactly how long this flash in the pan 0:05:06.240 --> 0:05:08.360 will last. Yeah, because as much as we know about 0:05:08.400 --> 0:05:11.200 how the universe works right now, there are still open 0:05:11.279 --> 0:05:14.440 questions about how the universe will keep on working and 0:05:14.440 --> 0:05:16.800 how it's gonna work up until the end of the universe. 0:05:16.880 --> 0:05:18.919 Remember that when you look up at the sky, it 0:05:19.040 --> 0:05:21.840 seems sort of static and frozen. You don't notice from 0:05:21.920 --> 0:05:25.840 day to day stars appearing or disappearing, or changing their location. 0:05:25.960 --> 0:05:28.479 But that's just because we live in a tiny little 0:05:28.520 --> 0:05:31.920 slice in the universe operates on much longer time scales. 0:05:32.360 --> 0:05:34.520 If you could see a movie of the universe sped 0:05:34.600 --> 0:05:37.200 up to see all fourteen billion years in just a minute, 0:05:37.320 --> 0:05:41.080 it would seem like a crazy, chaotic, dynamic place. Even 0:05:41.080 --> 0:05:44.400 our Solar System has had planets shift around in orbit. 0:05:44.440 --> 0:05:48.119 Our galaxy is spinning and swirling and colliding. All sorts 0:05:48.120 --> 0:05:50.360 of stuff is happening, and as we look out into 0:05:50.400 --> 0:05:53.479 the universe on those cosmic scales, we ask questions about 0:05:53.480 --> 0:05:55.760 how everything came to be and how long it will 0:05:55.800 --> 0:05:59.159 continue to swirl and glow. Yeah, so your planet to 0:05:59.160 --> 0:06:01.920 be a professor to you grow old or even die. 0:06:01.960 --> 0:06:03.960 Apparently they're going to have to drag me out of 0:06:03.960 --> 0:06:05.720 this office. I'm gonna be here until the Milky Way 0:06:05.800 --> 0:06:09.800 stops spinning. I have a similar plan and plans to 0:06:09.800 --> 0:06:13.719 be a cartoonis until rich I see, so another hundred 0:06:13.720 --> 0:06:18.359 billion years. Yeah, so basically the same thing as growing 0:06:18.400 --> 0:06:21.160 old till I die. Yeah. But anyways, it is an 0:06:21.200 --> 0:06:25.120 interesting and growing universe, which makes me sort of wondering 0:06:25.320 --> 0:06:27.440 how it's all going to end, If not the universe, 0:06:27.480 --> 0:06:30.240 at least maybe our galaxy. That's right. On the podcast, 0:06:30.279 --> 0:06:32.720 we have talked about the future of the Earth and 0:06:32.760 --> 0:06:36.080 our Solar System, how the Earth will get subsumed eventually, 0:06:36.080 --> 0:06:38.200 into the outer layers of the Sun. We've even talked 0:06:38.200 --> 0:06:40.880 about the lifetime of stars, how long they will burn, 0:06:40.960 --> 0:06:44.279 and how long our universe will keep making stars. But 0:06:44.320 --> 0:06:47.080 the universe is not made just of planets or solar 0:06:47.120 --> 0:06:49.560 systems or stars. One way to look at the universe 0:06:49.640 --> 0:06:53.039 is that the basic unit are galaxies, these big swirling 0:06:53.160 --> 0:06:56.719 swarms of billions of stars that flow through the universe. 0:06:56.839 --> 0:06:59.440 How do galaxies form and how long do they live? 0:07:00.040 --> 0:07:02.960 Do they just keep spinning until they become rich cartoonists? 0:07:03.240 --> 0:07:06.400 So today we have an amazing and galactic question. Today 0:07:06.440 --> 0:07:15.200 will be tackling how do galaxies die or how do 0:07:15.280 --> 0:07:17.520 they fade away? I guess maybe maybe that's a nicer 0:07:17.560 --> 0:07:20.360 way to say. How do they become emeritus galaxies? How 0:07:20.360 --> 0:07:22.400 do they move on? How do they join the farm? 0:07:23.720 --> 0:07:26.000 How do we make room for new galaxies because they're 0:07:26.040 --> 0:07:29.240 just taken up space these old folks, Oh right, well, 0:07:29.320 --> 0:07:31.800 well there's plenty of space and space right, that's true, 0:07:31.840 --> 0:07:34.120 there is plenty of room for galaxies. But you know, 0:07:34.240 --> 0:07:37.520 they are using the raw materials. They're occupying a whole 0:07:37.720 --> 0:07:40.320 lot of carbon and iron, all sorts of other stuff 0:07:40.360 --> 0:07:43.440 that could go to seed new stars and new galaxies 0:07:43.480 --> 0:07:46.880 and new forms of life and intelligence. Well, the first 0:07:46.880 --> 0:07:48.720 thing I thought when I saw this title was like, 0:07:48.760 --> 0:07:51.480 what galaxies can die? I didn't know that they do. 0:07:51.560 --> 0:07:54.800 They have like a beating heart. It depends a little 0:07:54.800 --> 0:07:58.600 bit how you define death, right. Galaxies don't live, of course, 0:07:58.640 --> 0:08:01.080 in the same sense that we're getic entities do the 0:08:01.080 --> 0:08:02.920 way you and I do. But they do have a 0:08:02.920 --> 0:08:05.880 really interesting life cycle, and at some point they stop 0:08:06.080 --> 0:08:09.640 making stars, and eventually those stars will burn out, and 0:08:09.680 --> 0:08:12.800 so the fate of galaxies is in fact to fade 0:08:12.800 --> 0:08:16.240 away into darkness, which some could describe as the death 0:08:16.280 --> 0:08:19.040 of a galaxy. I see you're defining the death of 0:08:19.040 --> 0:08:21.280 a galaxy as when it I guess when it goes dark? 0:08:21.440 --> 0:08:23.480 Is that what you're saying, Like when it stops shining 0:08:23.560 --> 0:08:25.320 or we can't see it, or do you define it 0:08:25.360 --> 0:08:28.600 there's like no activity, or when it breaks apart, or 0:08:28.720 --> 0:08:30.600 when it turns into a black hole. There are many 0:08:30.600 --> 0:08:33.080 possible ways to kill a galaxy. I guess there are 0:08:33.200 --> 0:08:36.360 lots of milestones in galaxy retirement. But scientists call this 0:08:36.480 --> 0:08:41.000 galaxy quenching. When it stops making stars, those stars burn 0:08:41.120 --> 0:08:43.800 for a while and then eventually they will all fade out, 0:08:44.080 --> 0:08:47.120 and you will indeed get just black holes with lumps 0:08:47.120 --> 0:08:50.079 of stuff swirling around it. I see, So you're really 0:08:50.160 --> 0:08:53.800 talking more about asking how do galaxies retire, like when 0:08:53.800 --> 0:08:56.199 they start producing light? Kind of. Yah, it's not a 0:08:56.240 --> 0:08:59.160 funeral home we're pushing these galaxies into. It's a nice 0:08:59.160 --> 0:09:03.040 senior living facility with all sorts of other active galaxies 0:09:03.080 --> 0:09:07.520 to hang out with. Interesting, there are cost bank retardant homes, 0:09:08.400 --> 0:09:10.559 so you have early bird specials too. Well. Once you 0:09:10.640 --> 0:09:12.800 no longer making stars, you're not really part of the 0:09:12.840 --> 0:09:18.400 game anymore. Uh yeah, yeah, I guess you're you're off 0:09:18.400 --> 0:09:21.400 the rat race kind of to see who's the Shinese galaxy. 0:09:21.720 --> 0:09:24.240 You're definitely onto a new era in your life because 0:09:24.240 --> 0:09:27.760 if you don't have stars, then you can't make new elements. 0:09:27.800 --> 0:09:30.320 You're stuck with the composition that you have. Remember that 0:09:30.360 --> 0:09:33.200 new elements are only born in the heart of stars 0:09:33.240 --> 0:09:36.720 and supernovas and then the collisions of neutron stars. But 0:09:36.760 --> 0:09:40.240 once you've stopped making stars, you're no longer initiating that 0:09:40.320 --> 0:09:43.480 process that ends up with new elements, and so eventually 0:09:43.520 --> 0:09:45.800 you're going to get stuck with whatever you have. You'd 0:09:45.800 --> 0:09:50.040 be sort of frozen with your mixture of stuff. All right, Well, 0:09:50.080 --> 0:09:54.680 we'll get into the details of galaxies retirement, both from 0:09:54.720 --> 0:09:57.160 its job and mainly from its life. But as usually, 0:09:57.240 --> 0:09:59.720 we were wondering how many people had had these dark 0:09:59.720 --> 0:10:03.160 thoughts about galaxies and what happens to them in the future. 0:10:03.240 --> 0:10:05.280 So it's usual Daniel went out there and ask people 0:10:05.280 --> 0:10:08.840 a question, how do galaxies die? So thanks everybody who 0:10:08.920 --> 0:10:11.880 participates in these one questions. If you'd like to hear 0:10:11.960 --> 0:10:15.400 your speculations here on the podcast for everybody else to enjoy, 0:10:15.520 --> 0:10:18.120 please don't be shy right to us two questions at 0:10:18.200 --> 0:10:20.640 Daniel and Jorge dot com. Think about it for a second, 0:10:20.679 --> 0:10:25.080 how do you think galaxies retired? Here's what people had 0:10:25.120 --> 0:10:27.520 to say. I think I have a decent guest for this. 0:10:27.960 --> 0:10:30.640 There are supermassive the black holes at the center of 0:10:30.800 --> 0:10:36.120 every galaxy, and at some point black holes do die 0:10:36.280 --> 0:10:41.280 or evaporate. Rather, it is possible. So maybe when that happens, 0:10:41.280 --> 0:10:44.720 when the black hole kind of doesn't exist anymore than 0:10:44.760 --> 0:10:49.439 the galaxies just disindigates. As far as I know, galaxies 0:10:49.480 --> 0:10:55.160 die when their stares start dying and stop making more 0:10:55.280 --> 0:10:58.840 stories and and it just becomes a cold cloud of 0:10:58.960 --> 0:11:04.520 sadness and you can't see it. So I guess that's 0:11:04.559 --> 0:11:08.520 a dead galaxy. I don't know how galaxies die. I 0:11:08.679 --> 0:11:12.839 would guess that either the if it's a black hole 0:11:12.920 --> 0:11:15.880 in the middle of the galaxy, that it as opposed 0:11:15.880 --> 0:11:19.120 to swallows large parts of the of the galaxy, or 0:11:19.600 --> 0:11:23.280 that stars either you should have died by not admitting 0:11:23.320 --> 0:11:25.640 as much light as they previously would have been, and 0:11:25.679 --> 0:11:28.600 so the galaxy becomes sort of darker and darker. So 0:11:28.640 --> 0:11:31.920 I think galaxies are so large and have so much 0:11:31.960 --> 0:11:35.880 angular momentum that all the stars within the galaxy will 0:11:35.920 --> 0:11:38.240 reach the end stages of their life and we will 0:11:38.360 --> 0:11:41.880 no longer have the starting conditions necessary to get new 0:11:42.000 --> 0:11:46.480 stars created before the entire galaxy will be eaten up 0:11:46.480 --> 0:11:50.720 by the supermassive black hole. Galaxies die in three ways, 0:11:51.280 --> 0:11:55.920 first when they crash in and merge with a larger galaxy, 0:11:56.280 --> 0:12:00.920 second when the stars fall in to the black hole 0:12:01.040 --> 0:12:05.680 at the center of the galaxy, and third when the 0:12:05.760 --> 0:12:11.240 galaxy creates no news stars and the stars and the 0:12:11.320 --> 0:12:18.839 galaxy die from old age. The galaxies die if eventually 0:12:18.920 --> 0:12:22.880 they lose the ability to make new stars. So this 0:12:23.160 --> 0:12:27.520 can come from a different reasons, but one of them 0:12:27.559 --> 0:12:30.720 that I know it might be that the black hole 0:12:31.600 --> 0:12:37.520 from the center of the galaxy starts this process by 0:12:37.760 --> 0:12:44.079 emitting probably powerful cluss or mm hmm, the supermassive black 0:12:44.080 --> 0:12:47.280 holes in the center suck them up or something. All right, 0:12:48.200 --> 0:12:50.400 dark answers for a dark question. I guess a lot 0:12:50.440 --> 0:12:53.240 of people went for the black hole scenario. Yeah, that's 0:12:53.280 --> 0:12:56.959 really interesting. People are aware that eventually everything will fall 0:12:57.040 --> 0:12:59.600 into the black hole and imagine that that's what's going 0:12:59.679 --> 0:13:01.880 to kill all the galaxy. But little do they know 0:13:04.120 --> 0:13:07.240 there's something worth around the corner or what. Yeah, there's 0:13:07.240 --> 0:13:09.760 sort of two competing timelines. They're like, will the stars 0:13:09.760 --> 0:13:13.400 burn out, will it stop making stars before it falls 0:13:13.440 --> 0:13:15.720 into the black hole? Or will the black hole like 0:13:15.800 --> 0:13:18.840 eat up a bunch of otherwise lively elements of the 0:13:18.880 --> 0:13:21.600 galaxy which could have made new stars if only they 0:13:21.640 --> 0:13:25.120 hadn't fallen into that gravitational Well, all right, Well, before 0:13:25.160 --> 0:13:28.120 we start to consider a galaxy's death, let's um, you know, 0:13:28.240 --> 0:13:31.000 let's do a little retrospective here, and let's consider the 0:13:31.000 --> 0:13:34.840 whole life of the galaxy. So let's start at getting Daniel, 0:13:34.920 --> 0:13:37.240 how did galaxies even get born? Yeah, I like that 0:13:37.320 --> 0:13:41.360 we begin with the nostalgic so like montage, musical mona, 0:13:42.080 --> 0:13:46.480 all the good moments, remember those with an old timey 0:13:46.559 --> 0:13:50.920 like film field, something soft focus, you know, fuzzy pictures 0:13:50.920 --> 0:13:53.120 of the galaxy playing in the kiddie pool, like the 0:13:53.160 --> 0:13:57.200 projector sounds quit, the galaxy being mean to the cat, 0:13:57.360 --> 0:14:00.840 you know, that kind of stuff, but looking so cute. 0:14:01.280 --> 0:14:06.199 No pictures of the galaxy crying or I think of 0:14:06.240 --> 0:14:08.920 galaxies is one of the most fundamental units of the 0:14:09.040 --> 0:14:12.560 universe because even though the stars are within them, it's 0:14:12.600 --> 0:14:17.079 the galaxies that are formed by like the initial fluctuations. 0:14:17.120 --> 0:14:19.240 So you know, you begin at the very very early 0:14:19.360 --> 0:14:22.800 stages of the universe, everything is smooth and filled with matter. 0:14:22.840 --> 0:14:25.520 There's no wiggles, there's no extra lumpy bits. And then 0:14:25.520 --> 0:14:27.960 you get quantum mechanics that fluctuates and gives you like 0:14:28.200 --> 0:14:31.440 a little bit more stuff here, maybe fewer particles over here. 0:14:31.760 --> 0:14:34.680 That's really tiny, that's super microscopic. That kind of quantum 0:14:34.680 --> 0:14:37.240 fluctuation is happening all the time, even today. But the 0:14:37.360 --> 0:14:40.800 very early universe, those fluctuations were blown up to a 0:14:40.960 --> 0:14:45.280 huge scale by early universe inflation. The way space itself 0:14:45.400 --> 0:14:47.400 was stretched by like a factor of ten to the 0:14:47.440 --> 0:14:51.320 thirty blew up these little tiny lumps, these little bits 0:14:51.320 --> 0:14:54.240 where something was heavier and something was lighter into actual 0:14:54.400 --> 0:14:57.920 macroscopic sizes. And then gravity took over and it said, 0:14:57.960 --> 0:15:00.560 all right, this spot is a little bit denser than 0:15:00.600 --> 0:15:02.800 that spot, so all the particles are going to get 0:15:02.840 --> 0:15:06.120 attracted over there. So you begin with these very shallow 0:15:06.200 --> 0:15:10.040 gravitational wells that slowly roll more particles into them, and 0:15:10.040 --> 0:15:12.840 then they get stronger and stronger and stronger. We're talking 0:15:12.840 --> 0:15:16.560 about it's mostly dark matter. It builds these gravitational wells 0:15:16.800 --> 0:15:19.280 that then normal matter falls into, and where you have 0:15:19.360 --> 0:15:22.040 these wells, you have big blobs of matter and that's 0:15:22.040 --> 0:15:25.520 what forms galaxies. Yeah, I think we start talk about 0:15:25.520 --> 0:15:29.200 it as the seeds of the galaxies, right, Like the seeds, 0:15:29.200 --> 0:15:31.760 like where the galaxies came from, was all sort of 0:15:31.840 --> 0:15:33.880 laid out in those first moments of the Big Bang, 0:15:34.080 --> 0:15:36.400 so kind of in a way like galaxies were maybe 0:15:36.440 --> 0:15:39.080 the first things that were defined in the universe, the 0:15:39.120 --> 0:15:41.360 first kind of organization, right, Yeah, you can think about 0:15:41.360 --> 0:15:43.920 it like that. We think that probably stars formed and 0:15:43.960 --> 0:15:46.440 then they formed into galaxies, but they all formed out 0:15:46.440 --> 0:15:50.640 of these big clouds of gas that were themselves formed 0:15:50.680 --> 0:15:54.720 by these dark matter halos, which were themselves formed by 0:15:54.760 --> 0:15:57.200 those initial seeds that we talked about. Something I think 0:15:57.320 --> 0:16:00.240 is really cool is that the pattern of dark matter, 0:16:00.280 --> 0:16:03.160 which controls the whole structure of the universe, is like 0:16:03.200 --> 0:16:06.200 these filaments, you know, these like lines of through a 0:16:06.280 --> 0:16:09.400 cosmic web, and where those filaments overlap with each other 0:16:09.680 --> 0:16:11.920 are the dark matter halos. You can think of it 0:16:12.000 --> 0:16:15.640 sort of like these filaments are funneling matter into these 0:16:15.720 --> 0:16:18.720 lakes which are where they intersect, and so gas is 0:16:18.800 --> 0:16:22.720 falling from these filaments into these halos and then swirling 0:16:22.800 --> 0:16:27.120 together to form stars which form galaxies. Interesting. I guess 0:16:27.120 --> 0:16:28.920 what I mean is like if you had been around 0:16:28.920 --> 0:16:31.240 at that time, that early in the universe, you could 0:16:31.240 --> 0:16:34.000 have been predicted maybe like, oh, there's gonna be a galaxy, 0:16:34.040 --> 0:16:35.960 and there's gonna be a galaxy, you know what I mean, 0:16:36.000 --> 0:16:39.280 Like the definition of a galaxy was sort of right 0:16:39.280 --> 0:16:41.360 there at the beginning of the universe. Yeah, you definitely 0:16:41.400 --> 0:16:43.800 would know that this is where complex structure is going 0:16:43.840 --> 0:16:46.520 to form. I think it's super fascinating what you end 0:16:46.600 --> 0:16:49.480 up getting. I mean, you start with just clouds of hydrogen, 0:16:49.880 --> 0:16:52.440 and then like you get stars and you get galaxies. 0:16:52.480 --> 0:16:55.520 It's really fascinating sort of the size and the scale 0:16:55.520 --> 0:16:57.720 and the shape of what forms out of that. It's 0:16:57.760 --> 0:17:00.440 one of the I think the deepest questions in modern physics. 0:17:00.760 --> 0:17:03.640 Why these objects emerge at these scales? You know, why 0:17:03.640 --> 0:17:05.840 do we get stars there about this size? Why do 0:17:05.920 --> 0:17:08.919 we galaxies about this size? Why don't we get just 0:17:09.000 --> 0:17:11.960 one humongous galaxy in the whole universe? Or why do 0:17:12.040 --> 0:17:14.080 galaxies form at all? Why don't we just have stars 0:17:14.119 --> 0:17:16.159 spread out everywhere? So I think it would have been 0:17:16.160 --> 0:17:19.320 pretty hard to predict computationally. I think it's really interesting 0:17:19.359 --> 0:17:22.520 to sort of see what emerges from structure in the universe. 0:17:22.520 --> 0:17:24.919 And that's just what we're doing now. We're still seeing 0:17:24.920 --> 0:17:28.720 structure emerged. Now we have clusters of galaxies and superclusters 0:17:28.720 --> 0:17:31.640 of galaxies, and that process is still happening because we're 0:17:31.640 --> 0:17:34.479 still fairly young in the universe. Yeah we are. Are 0:17:34.520 --> 0:17:36.400 we still in there like the teenage years? You think, 0:17:36.680 --> 0:17:39.720 the awkward teenage years full of pimples. Well, gravity is 0:17:39.760 --> 0:17:42.560 really slow, so it takes a long time to form structure, 0:17:42.760 --> 0:17:45.880 and so it's formed galaxies and galaxy clusters. But those 0:17:45.920 --> 0:17:49.600 galaxy clusters themselves are like very loosely grouped into superclusters. 0:17:49.640 --> 0:17:52.600 Gravity hasn't had time really to gather that together into 0:17:52.640 --> 0:17:55.280 something greater. In the meantime, dark energy is doing the 0:17:55.320 --> 0:18:00.119 opposite job. It's pushing everything apart, preventing gravity from making superstructures. 0:18:00.119 --> 0:18:02.080 So we might be living in the moment when the 0:18:02.160 --> 0:18:04.560 universe is the most organized. So I don't know if 0:18:04.600 --> 0:18:06.800 those are really the teenage years or that's like it's 0:18:06.840 --> 0:18:08.560 mid thirties. You know, it's really sort of on top 0:18:08.600 --> 0:18:11.120 of its stuff before it starts to get old, before 0:18:11.119 --> 0:18:15.920 it has its midlife crisis. We all do exactly all right, Well, 0:18:15.960 --> 0:18:18.080 I guess that's the birth of a galaxy and so 0:18:18.200 --> 0:18:21.920 and a surprising idea is that galaxies change and they 0:18:22.000 --> 0:18:24.679 might even die one day. So let's dive right into that. 0:18:24.760 --> 0:18:40.160 But first, let's take a quick break. All right, we're 0:18:40.160 --> 0:18:43.560 talking about the death of galaxies, Daniel, Does that mean 0:18:43.560 --> 0:18:46.520 our galaxy is gonna die? Scientists think that the Milky 0:18:46.520 --> 0:18:49.800 Way itself is beginning to quench. We're entering a period 0:18:49.840 --> 0:18:52.440 we're making fewer and fewer stars, and that's going to 0:18:52.520 --> 0:18:55.720 happen faster and faster, so sort of the milky ways 0:18:55.760 --> 0:18:59.160 peak might be behind us. Oh boy, well, for a second, 0:18:59.160 --> 0:19:00.600 I thought you were going to give it a super 0:19:00.600 --> 0:19:03.520 plot twist and say like, oh, our galaxy is already dead. 0:19:04.880 --> 0:19:07.840 It's been dead the whole time, where it's just ghosts. 0:19:08.000 --> 0:19:10.119 That's right, This whole galaxy is nothing but an m 0:19:10.240 --> 0:19:16.159 Night shun Land film. Yeah, spoiler alert. I talked to 0:19:16.240 --> 0:19:20.520 dead galaxies. I see that galaxies with my telescopes. Do 0:19:20.520 --> 0:19:22.440 you kind of do maybe? Right, Like if you look 0:19:22.440 --> 0:19:26.080 at into the far universe, you might be seeing galaxies 0:19:26.119 --> 0:19:28.280 that have died already. Right, We do see a lot 0:19:28.359 --> 0:19:31.200 of galaxies that aren't dead. And one of the surprising 0:19:31.240 --> 0:19:34.600 things with something we struggle to understand is what's killing 0:19:34.680 --> 0:19:37.560 all these galaxies? Why are there so many galaxies out 0:19:37.600 --> 0:19:41.720 there that are already quenched and have stopped making new stars. 0:19:42.320 --> 0:19:44.560 It just went from a thriller to a mystery. We 0:19:44.680 --> 0:19:47.600 just switched genres here. It's a combination because somebody is 0:19:47.640 --> 0:19:50.679 still out there killing galaxies. It's not over yet. We 0:19:50.720 --> 0:19:53.359 still have a chance to catch the killer and maybe 0:19:53.600 --> 0:19:58.159 save future galaxies and maybe do nothing about it because 0:19:59.520 --> 0:20:03.240 because just physics, physics, are you saying we can't learn 0:20:03.280 --> 0:20:05.679 things about the universe and intervene in its faith that 0:20:05.720 --> 0:20:08.720 we have no control, no power to change the future 0:20:08.720 --> 0:20:11.439 of humanity. That doesn't sound like an engineer, you tell me. 0:20:11.680 --> 0:20:14.040 I guess you know, the physicist has to tell us 0:20:14.080 --> 0:20:15.760 if it's possible. Well, the first thing to do is 0:20:15.800 --> 0:20:18.320 to understand what it is that's clean these galaxies, and 0:20:18.320 --> 0:20:20.840 then we can figure out if it's possible to intervene. 0:20:20.960 --> 0:20:23.920 Then we have to start training some galaxy engineers. That 0:20:24.040 --> 0:20:26.199 might be the sequel. I guess all right, Well, I 0:20:26.240 --> 0:20:28.800 think one interesting bit of news is that, you know, 0:20:28.840 --> 0:20:32.040 galaxies seem to change, and I guess they quention they 0:20:32.080 --> 0:20:35.440 maybe eventually die. And so is that something that we've 0:20:35.480 --> 0:20:38.199 always believed in, that galaxies can change or did we 0:20:38.280 --> 0:20:41.240 think that we just you know, swirl around forever. We've 0:20:41.240 --> 0:20:44.320 always thought that eventually galaxies would use up their raw 0:20:44.359 --> 0:20:47.080 materials in terms of making stars. You know, you have 0:20:47.119 --> 0:20:49.760 a certain amount of hydrogen in the universe, for example, 0:20:50.040 --> 0:20:53.000 that's primarily what's burned to make stars. Eventually you will 0:20:53.080 --> 0:20:55.320 run out of them. We have a podcast episode about 0:20:55.359 --> 0:20:58.280 how many generations of stars will there be? Because you know, 0:20:58.320 --> 0:21:00.879 stars don't live forever, and eventually they explode and spew 0:21:00.920 --> 0:21:03.560 their materials back out in the universe, which gets gathered 0:21:03.600 --> 0:21:06.199 back together. But we don't think that can happen forever. 0:21:06.640 --> 0:21:09.280 So we've always known that eventually waves of star formation 0:21:09.320 --> 0:21:11.239 will end. But we were surprised when we looked at 0:21:11.280 --> 0:21:14.159 the galaxies and discovered how many are already dead, how 0:21:14.200 --> 0:21:17.520 many have stopped making stars well before we expected them 0:21:17.560 --> 0:21:20.400 too interesting. Yeah, I guess you know, there's a limited 0:21:20.440 --> 0:21:23.280 supply of fuel in the universe, right, and at some 0:21:23.320 --> 0:21:25.000 point we run out, like we have a gas tank 0:21:25.080 --> 0:21:28.600 kind of and you know, hydrogen gets you stop, gets 0:21:28.600 --> 0:21:30.800 turned into heavier element, and then to break it apart, 0:21:30.920 --> 0:21:34.240 you need extra energy. Yeah, there's two things that drive this. 0:21:34.359 --> 0:21:36.159 One is you need to have the fuel, and the 0:21:36.200 --> 0:21:39.480 other is that the fuel has to have the right conditions. 0:21:39.480 --> 0:21:41.879 Like it's not just enough to have hydrogen. You have 0:21:41.920 --> 0:21:44.720