WEBVTT - Black Holes, Part 2: Detection 0:00:00.160 --> 0:00:05.520 My welcome to Stuff to Blow Your Mind from how 0:00:05.559 --> 0:00:14.000 Stuff Works dot com. Hey you welcome to Stuff to 0:00:14.000 --> 0:00:16.120 Blow your Mind. My name is Robert Lamb and I'm 0:00:16.200 --> 0:00:19.240 Joe McCormick, and we're back. It's part two of our 0:00:19.320 --> 0:00:22.360 multi part exploration of black holes. Because you know what, 0:00:22.440 --> 0:00:25.239 this year Robert went to the World Science Festival in 0:00:25.239 --> 0:00:27.520 New York and came back with black Hole Fever. Yeah. 0:00:27.560 --> 0:00:28.880 It was a great It was a great talk that 0:00:28.920 --> 0:00:30.680 really opened my eyes a little more to some of 0:00:30.760 --> 0:00:33.720 the finer details of of black holes. And you mean 0:00:33.760 --> 0:00:36.800 that Brian Green talk with the guests. Yeah, Darkness made visible, 0:00:37.159 --> 0:00:40.040 wonderful talk. It's available online. Will include a link to 0:00:40.040 --> 0:00:42.760 that in the landing page for this episode. Certainly inspired 0:00:42.840 --> 0:00:45.760 us to to really give black holes a proper shake 0:00:45.840 --> 0:00:47.640 on Stuff to Blow your Mind. Yeah, I mean, there's 0:00:47.680 --> 0:00:49.840 so much interesting stuff to talk about, and the fact 0:00:49.840 --> 0:00:52.120 that they're just one of the most interesting objects in 0:00:52.159 --> 0:00:55.520 the entire universe. It's not that they're probably I would say, 0:00:55.560 --> 0:00:59.080 maybe the most interesting non living thing in the universe. 0:00:59.360 --> 0:01:01.640 What do you think about that? Yeah, yeah, I would 0:01:01.680 --> 0:01:05.200 say that because we're pretty interesting ultimately humans are. Um. 0:01:05.240 --> 0:01:07.200 I do want to remind everyone. If you did not 0:01:07.360 --> 0:01:09.880 listen to the previous episode on black holes, you do 0:01:09.959 --> 0:01:11.760 want to go back and listen to it, because this 0:01:11.840 --> 0:01:13.200 is this is not one of those where you can 0:01:13.240 --> 0:01:15.119 kind of take part one and part two in any order. 0:01:15.319 --> 0:01:17.240 You really need to hit the first episode. I mean, 0:01:17.280 --> 0:01:19.080 you could if you really wanted, But we're going to 0:01:19.160 --> 0:01:21.440 be referring back to the groundwork we laid in the 0:01:21.440 --> 0:01:23.840 previous episode. And the previous episode we talked a lot 0:01:23.880 --> 0:01:27.200 about the development of black holes. Uh, sort of as 0:01:27.240 --> 0:01:30.520 the history of an idea, something that was unlike the 0:01:30.600 --> 0:01:32.920 stars in the sky. You know, the stars in the sky, 0:01:33.040 --> 0:01:36.119 we first observed and we could see them, and then 0:01:36.480 --> 0:01:39.080 by making observations about them, we were able to come 0:01:39.160 --> 0:01:42.319 up with theories to explain them. Black holes weren't like that. 0:01:42.360 --> 0:01:45.120 It went the other way around. Black Holes existed in 0:01:45.280 --> 0:01:49.080 theory long before anybody accepted that they existed in reality, 0:01:49.120 --> 0:01:53.560 and long after they existed in theory, many scientists ardently 0:01:53.600 --> 0:01:57.000 opposed the idea that black holes could exist in nature. Yeah, 0:01:57.000 --> 0:02:00.560 it's the idea that that these various individuals said, well, X, Y, 0:02:00.600 --> 0:02:05.520 and Z are true, then this thing might exist and uh, 0:02:05.640 --> 0:02:08.960 and and that thing is the black hole. But of course, 0:02:09.080 --> 0:02:12.320 you know, lots of people when a thing sounds outlandish, 0:02:12.520 --> 0:02:15.560 even if your best theories tell you it might be possible, 0:02:15.919 --> 0:02:17.760 people want to find a way to say, no, that 0:02:17.880 --> 0:02:20.800 just sounds unintuitive. It couldn't be real. It doesn't fit 0:02:20.919 --> 0:02:24.560 my picture of how the universe works. It doesn't feel right. Yeah, 0:02:25.000 --> 0:02:28.079 maybe that's a thought experiment, but I doubt will actually 0:02:28.120 --> 0:02:31.320 find something like this when we start looking out into 0:02:31.320 --> 0:02:34.800 the cosmos with better observational technology. You know, it's often 0:02:34.840 --> 0:02:38.120 said that Albert Einstein did some of his worst work ever, 0:02:38.240 --> 0:02:41.200 Like the worst science of his entire career was him 0:02:41.240 --> 0:02:44.480 trying to write papers to prove that black holes didn't 0:02:44.520 --> 0:02:48.080 exist in reality. It just didn't seem right to him, 0:02:48.120 --> 0:02:51.280 even though his general relativity became the basis of our 0:02:51.320 --> 0:02:54.920 modern theory of black holes. But so anyway, yeah, so 0:02:54.960 --> 0:02:59.120 how did today? We want to explore making the darkness flesh, 0:02:59.320 --> 0:03:02.400 making the black hole into a thing that is real 0:03:02.760 --> 0:03:05.480 in existence in the universe and we can detect it. 0:03:05.800 --> 0:03:07.600 So I think first we want to tell the story 0:03:07.639 --> 0:03:09.760 of sort of like a bridging the gap between the 0:03:10.120 --> 0:03:14.840 black holes of general relativity theory and the actual observations 0:03:14.880 --> 0:03:16.720 of them and then talk a little bit about what's 0:03:16.760 --> 0:03:18.960 it like to detect black holes and how we might 0:03:19.000 --> 0:03:21.880 do it. And we do have to distress that in 0:03:21.960 --> 0:03:25.880 today's world, black holes are pretty much an established reality. 0:03:26.040 --> 0:03:28.679 You talk to experts and they say yes, without a 0:03:28.680 --> 0:03:30.839 shadow of a doubt. Yeah. I don't know if it's 0:03:30.880 --> 0:03:33.639 the case that every single expert would say without a 0:03:33.639 --> 0:03:36.240 shadow of a doubt, but yeah, they're They're generally accepted 0:03:36.280 --> 0:03:38.680 as a fact of reality. You know, we've reached the 0:03:38.680 --> 0:03:42.720 point where black holes exist and they're completely non politicized. 0:03:43.120 --> 0:03:46.240 That's the other great Yeah, oh man, I love a 0:03:46.240 --> 0:03:49.880 scientific controversy that doesn't never have a political angle. Yeah, 0:03:50.000 --> 0:03:53.280 it's the black holes are are. Thus far, they've remained 0:03:53.280 --> 0:03:55.400 pretty safe. Well, maybe we can muck it up today. 0:03:55.840 --> 0:03:59.320 Let's let's get people taking tribal sides on it. Okay, 0:03:59.320 --> 0:04:02.160 So the story of how black holes went from this 0:04:02.320 --> 0:04:05.840 theoretical anomaly to a thing known to exist in the world, 0:04:06.280 --> 0:04:09.760 it's a long, complicated story, so we definitely can't explore 0:04:09.800 --> 0:04:11.040 all of it, but I just want to mention a 0:04:11.040 --> 0:04:14.800 few highlights, and one of the first ones is serious 0:04:14.840 --> 0:04:18.880 b Now, Serious is the brightest star in the night. 0:04:18.920 --> 0:04:22.000 Sky from Earth, often known as the Dog Star because 0:04:22.040 --> 0:04:26.120 it's part of the Cannus Major constellation, the Great Dog constellation. 0:04:26.520 --> 0:04:28.839 Side note, I didn't know this until I was reading 0:04:28.839 --> 0:04:31.000 this the other day. Do you know the origin of 0:04:31.040 --> 0:04:35.240 the term dog days of summer doesn't actually have anything 0:04:35.279 --> 0:04:37.599 to do with the behavior of dogs. Really. I always 0:04:37.600 --> 0:04:40.360 thought it came from a Don Henley song. Wait, one 0:04:40.360 --> 0:04:43.360 of the Boys of Summer. Sorry, after the dog Days 0:04:43.400 --> 0:04:46.680 of Summer have gone. Yeah, man, I grew so hard 0:04:46.720 --> 0:04:48.800 whenever that song comes on the radios. It's a great 0:04:49.000 --> 0:04:50.720 it's a great track. I love it. It's yacht rock 0:04:50.880 --> 0:04:54.120 that touches my heart. Yeah. So the term dog days 0:04:54.120 --> 0:04:58.160 of Summer actually refers to the period of Serious, the 0:04:58.839 --> 0:05:03.120 star in the Cannus Major constellation, rising roughly in conjunction 0:05:03.200 --> 0:05:06.039 with the Sun, which happens in July through August in 0:05:06.040 --> 0:05:08.800 the Northern Hemisphere, and so this is also the hottest 0:05:08.800 --> 0:05:10.960 time of the summer, and so it came to be 0:05:11.000 --> 0:05:14.120 associated with Okay, so Serious is coming up with the 0:05:14.160 --> 0:05:16.640 sun in the morning, and that means it's going to 0:05:16.680 --> 0:05:19.640 be real hot out. But back in the eighteen hundreds, 0:05:20.680 --> 0:05:23.600 it had been observed that the extremely bright star we 0:05:23.680 --> 0:05:29.280 now call Serious A behaved oddly. Its motion was not 0:05:29.480 --> 0:05:32.120 it was it was not smooth. It was kind of wobbly, 0:05:32.680 --> 0:05:36.160 as if it were being destabilized and tugged on by 0:05:36.160 --> 0:05:40.359 an invisible hand. And it turned out that Serious A 0:05:40.360 --> 0:05:44.159 actually had a very dim companion star. It was a 0:05:44.160 --> 0:05:47.560 binary star system, and the companion was what we now 0:05:47.600 --> 0:05:50.640 call Serious B. But it was a very strange type 0:05:50.680 --> 0:05:53.799 of companion because based on the motion of the two 0:05:53.839 --> 0:05:58.640 bodies and the light they produced, astrophysicists could calculate that 0:05:58.839 --> 0:06:02.600 the companion of Sirius at the same time was somewhere 0:06:02.600 --> 0:06:05.320 around the mass of our Sun, and yet was barely 0:06:05.400 --> 0:06:10.240 larger than the size of planet Earth and burning extremely hot, 0:06:10.400 --> 0:06:14.160 much hotter than the Sun. So Serious Be turned out 0:06:14.240 --> 0:06:16.320 to be an early example of what would later be 0:06:16.360 --> 0:06:20.720 called a white dwarf, a tiny, hot, massive star that 0:06:20.800 --> 0:06:25.719 proved matter could be compressed to pressures previously thought absolutely impossible. 0:06:26.320 --> 0:06:29.440 In the words of Arthur Eddington, quote a ton, and 0:06:29.480 --> 0:06:32.200 he's talking about the the material making up the star. 0:06:32.320 --> 0:06:35.200 A ton of this material would be a little nugget 0:06:35.240 --> 0:06:38.200 that you could put in a matchbox. So imagine something 0:06:38.240 --> 0:06:41.600 matchbox size. But that weighs a ton, and so for many, 0:06:41.680 --> 0:06:45.800 including Eddington, the very concept of this density was so 0:06:45.880 --> 0:06:48.640 absurd that it should just basically cause us to dismiss 0:06:48.680 --> 0:06:51.279 the observations out of hand, dismiss the idea of a 0:06:51.279 --> 0:06:56.120 white dwarf. It's absurd, but reality is stranger than our imagination. 0:06:56.200 --> 0:06:58.640 White dwarves came to be accepted as a feature of 0:06:58.640 --> 0:07:02.000 the universe and a part of ller revolution, especially after 0:07:02.120 --> 0:07:06.279 quantum mechanics eventually came along. To explain how matter could 0:07:06.320 --> 0:07:10.200 be compressed to such an unbelievable density. Basically has to 0:07:10.240 --> 0:07:13.440 do with packing atomic nuclei tighter and tighter, and you 0:07:13.480 --> 0:07:15.760 can actually do this to some extent because most of 0:07:15.760 --> 0:07:18.480 an adam is empty space. There's a good explanation of 0:07:18.480 --> 0:07:20.640 this actually in a book that's one of our sources 0:07:20.680 --> 0:07:24.120 on this episode, Black Hole, by Marcia Bartousciak, which I 0:07:24.160 --> 0:07:27.720 thought I should mention again, which is a good good 0:07:27.720 --> 0:07:29.320 book if you want to go in more depth than 0:07:29.320 --> 0:07:32.040 we're going into here. But so with serious b you've 0:07:32.080 --> 0:07:35.200 got these white dwarves, You've got these objects that are 0:07:35.280 --> 0:07:39.400 observed to be tiny and very hot and very bright 0:07:39.560 --> 0:07:43.000 and very massive, and so what would be the limits 0:07:43.040 --> 0:07:46.200 on what a star like that could be like uh 0:07:46.280 --> 0:07:50.720 In nineteen thirty, the young Indian astrophysicist Supermania and Chandra 0:07:50.800 --> 0:07:54.880 Sheker calculated that there was an upper limit to the 0:07:54.920 --> 0:07:58.280 mass of a white dwarf. White dwarves could vary in size, 0:07:58.320 --> 0:08:02.880 but somewhere around one point four solar masses. If a 0:08:02.880 --> 0:08:06.000 white dwarf is about one point four times the mass 0:08:06.080 --> 0:08:09.640 of our Sun, something happens. This is now known as 0:08:09.720 --> 0:08:12.720 the chander Shaker limit, and it around this mass, the 0:08:12.800 --> 0:08:17.440 force of gravity chander Shaker calculated appears to become more 0:08:17.480 --> 0:08:22.680 powerful than the force that's known as the electron degeneracy pressure. 0:08:22.960 --> 0:08:25.160 And what that is is it just causes atoms to 0:08:25.240 --> 0:08:28.560 push against one another and resist compression. So why can't 0:08:28.640 --> 0:08:31.360 you keep compressing it down more and more? There's this 0:08:31.440 --> 0:08:36.880 electron degeneracy pressure pushing back, but at a certain point, gravity, 0:08:36.920 --> 0:08:40.800 at least on paper, appears to completely overwhelm this degeneracy 0:08:40.840 --> 0:08:45.000 pressure and just crush everything down. So any clump of 0:08:45.040 --> 0:08:49.040 white dwarf stellar matter more massive than this could not 0:08:49.360 --> 0:08:53.120 maintain the white dwarf density at a stable pressure given 0:08:53.160 --> 0:08:55.800 the laws of general relativity. Past this point of star's 0:08:55.800 --> 0:08:59.679 density would just not scale up regularly, but would collapse, 0:09:00.000 --> 0:09:04.319 and it would collapse toward infinity. But when you think 0:09:04.320 --> 0:09:07.400 about that, like try to imagine your in Chonder Shaker's 0:09:07.640 --> 0:09:10.880 position infinite density, what does it mean to collapse to 0:09:11.040 --> 0:09:14.280 infinite density? You'd almost be tempted to think, Okay, well 0:09:14.320 --> 0:09:17.480 I made a mistake. Yeah. It's like it's like suddenly 0:09:17.520 --> 0:09:19.640 everything is reduced to zero and you know that the 0:09:19.679 --> 0:09:21.840 equation must be flowed. Yeah, it's like you've you've hit 0:09:21.920 --> 0:09:24.760 a divide by zero area or something. You you know 0:09:24.960 --> 0:09:28.199 that you must have done something wrong. It was difficult 0:09:28.240 --> 0:09:31.120 to believe that something like this could be possible in reality. 0:09:31.120 --> 0:09:34.480 How could a real physical object collapse toward a point 0:09:34.480 --> 0:09:37.959 of infinite density? Though this is what the math appeared 0:09:37.960 --> 0:09:41.600 to show. But Chonder Shaker did not actually argue about 0:09:41.640 --> 0:09:44.959 what physically happened to the white dwarf past the limit 0:09:45.040 --> 0:09:48.160 that he had established, only that the limit of stability 0:09:48.240 --> 0:09:51.920 at about one point four solar masses existed, and Chandra 0:09:52.000 --> 0:09:55.000 Shaker spent years arguing against the grain of scholarship on 0:09:55.080 --> 0:09:57.520 this point. There's a famous story about how when he 0:09:57.559 --> 0:09:59.960 presented his findings at a meeting of the Royal last 0:10:00.000 --> 0:10:03.280 Atronomical Society of London and nineteen thirty five our old 0:10:03.280 --> 0:10:07.000 friend Arthur Eddington's uh. He supposedly exclaimed there should be 0:10:07.040 --> 0:10:09.480 a law of nature to prevent a star from behaving 0:10:09.480 --> 0:10:15.080 in this absurd way. That's some wicked cantankerousness, just like 0:10:15.240 --> 0:10:20.840 yelling at the laws of physics. But but no, I 0:10:20.840 --> 0:10:23.920 mean so, that kind of attitude from Eddington actually kept 0:10:24.000 --> 0:10:26.520 this idea down for a long time, even though we 0:10:26.520 --> 0:10:28.640 would eventually find out that chander Shaker was on the 0:10:28.720 --> 0:10:32.000 right side of this argument, and the prolific Soviet physicist 0:10:32.120 --> 0:10:34.960 live Landau also made a similar calculation around this point, 0:10:35.040 --> 0:10:37.800 and he also arrived at the conclusion that a heavy 0:10:37.920 --> 0:10:40.680 enough star could collapse to what appears to be a point. 0:10:41.080 --> 0:10:43.440 But he said, that can't be quite right, so he 0:10:43.480 --> 0:10:46.840 ignored this result and instead concluded that the core of 0:10:46.880 --> 0:10:49.280 a star like this that at the core of a 0:10:49.280 --> 0:10:51.920 star like this, matter sort of begins to ignore the 0:10:51.960 --> 0:10:55.839 laws of physics and becomes quote, one gigantic nucleus. Now, 0:10:55.920 --> 0:10:58.839 chander Shaker was eventually recognized for being in the right 0:10:58.880 --> 0:11:01.720 on this question. He see the Nobel Prize in Physics 0:11:01.720 --> 0:11:04.360 for his work on stellar evolution, and he got that 0:11:04.400 --> 0:11:07.720 in nineteen eighty three. Now, also in the nineteen thirties, 0:11:07.720 --> 0:11:10.960 a parallel idea to the idea of the black hole emerges, 0:11:11.120 --> 0:11:14.839 and that is the idea of a neutron star. Now, 0:11:14.840 --> 0:11:19.079 a neutron star is another form that stellar collapse can take, 0:11:19.120 --> 0:11:22.440 in which you've got protons and electrons that form the 0:11:22.440 --> 0:11:24.920 core of a star and they compressed together with such 0:11:25.000 --> 0:11:28.520 force that they combine and form neutrons, which have mass 0:11:28.920 --> 0:11:32.280 but no electric charge. And a neutron star is not 0:11:32.440 --> 0:11:35.280 as a reality warping as a black hole, but it 0:11:35.400 --> 0:11:39.480 is an unbelievably exotic type of object composed matter so 0:11:39.559 --> 0:11:42.760 dense that it's been compared to an atomic nucleus the 0:11:42.800 --> 0:11:46.080 size of a city. If you can picture that, Uh, 0:11:46.400 --> 0:11:49.040 can you picture that? Of course you can't, nobody can, 0:11:49.400 --> 0:11:53.120 but just just try. I can picture an illustration that 0:11:53.200 --> 0:11:57.040 was presented of this. That's that's the best I can do. Well. 0:11:57.080 --> 0:11:59.319 I mean, part of the problem is that matter already 0:11:59.360 --> 0:12:01.760 looks solid enough to us, right, I mean, you take 0:12:01.800 --> 0:12:04.199 a rock or something like that, You're like, this looks 0:12:04.280 --> 0:12:07.240 really really solid, but most of it is empty space. 0:12:07.960 --> 0:12:10.600 Most of it is just the space between the atomic 0:12:10.679 --> 0:12:14.240 nuclei and the electrons orbiting them, and the other atomic 0:12:14.320 --> 0:12:18.160 nuclei that they're bonded with. Um. I mean, the molecules 0:12:18.320 --> 0:12:22.120 that make that very solid seeming object are mostly empty space, 0:12:22.400 --> 0:12:24.920 and there's a lot of space you can press things 0:12:25.040 --> 0:12:28.719 further and further into if you really must. You may 0:12:28.720 --> 0:12:30.360 not be able to get blood from a stone, but 0:12:30.440 --> 0:12:32.920 there's a lot of empty space there. If empty space 0:12:32.960 --> 0:12:34.920 is when you're after, it's there, you can get space 0:12:34.960 --> 0:12:38.120 from a stone. So, just to show how much things 0:12:38.160 --> 0:12:40.480 can be compressed, it's often said that, like a square 0:12:40.600 --> 0:12:44.120 centimeter of a neutron star, material might weigh more than 0:12:44.160 --> 0:12:48.680 a billion tons. Uh So. In the late nineteen thirties, J. 0:12:48.840 --> 0:12:52.959 Robert Oppenheimer, who's famous for working on the Manhattan Project, 0:12:53.000 --> 0:12:56.760 among many things. Oppenheimer and some students of his published 0:12:56.800 --> 0:13:00.160 work tending in the same direction as Chandra shako Are. 0:13:00.160 --> 0:13:03.520 Oppenheimer and George Volkoff did work on the emerging idea 0:13:03.520 --> 0:13:05.960 of neutron stars, which we were just talking about, and 0:13:05.960 --> 0:13:09.319 found that neutron stars, like white dwarves, had an upper 0:13:09.440 --> 0:13:13.040 limit of mass, after which something very strange seems to 0:13:13.120 --> 0:13:15.679 happen to them. You've got this upper limit, and if 0:13:15.720 --> 0:13:18.920 they have more mass than this limit, there's some kind 0:13:18.920 --> 0:13:23.599 of collapse, something, something goes wrong with the physics. Oppenheimer 0:13:23.640 --> 0:13:26.960 also published a paper on stellar evolution with Heartland Snyder 0:13:27.320 --> 0:13:30.640 in which they determined that late stage stellar remnants of 0:13:30.679 --> 0:13:33.920 stars passed a certain mass would seem to enter this 0:13:34.000 --> 0:13:37.960 state of permanent infinite collapse. The matter within them would 0:13:37.960 --> 0:13:40.880 exist in this perpetual free fall towards a point of 0:13:40.960 --> 0:13:44.520 infinite density, the singularity. And that is a that is 0:13:44.559 --> 0:13:48.840 a mind boggling concept to toy around with, falling forever. 0:13:49.880 --> 0:13:53.240 The never ending pit essentially, which was it was something 0:13:53.240 --> 0:13:54.960 like as a kid, you, or at least when I 0:13:55.000 --> 0:13:56.800 was a kid, that's what we played instead of the 0:13:56.800 --> 0:13:58.520 floor is lava. Always said the floor is an never 0:13:58.640 --> 0:14:01.439 ending pit. That's more than lava. Yeah. I think it's 0:14:01.440 --> 0:14:04.400 because we saw it on like key Man cartoons or something. 0:14:04.440 --> 0:14:07.319 I feel like it isn't that what's underneath Castle Gray 0:14:07.320 --> 0:14:09.839 Skull and never ending pit? I don't remember it is 0:14:09.880 --> 0:14:12.440 in my mind. Well, then what's Castle gray Skull built on. 0:14:13.280 --> 0:14:15.360 It's built over and never ending. I see it's called 0:14:15.360 --> 0:14:17.360 a strut since yeah, yeah, I guess they had to 0:14:17.400 --> 0:14:20.120 cap that thing, you know up, They're like, don't people 0:14:20.160 --> 0:14:21.920 gonna fall into that, Let's put a castle on top 0:14:21.960 --> 0:14:25.000 of it. So it's playing fast and loose with masters 0:14:25.000 --> 0:14:27.720 of the universe. Um myth those here. By the way, 0:14:27.760 --> 0:14:29.960 I apologize for just trying to move us along. I 0:14:29.960 --> 0:14:34.479 think we should dwell. No, no, I'm good, I'm good. Okay, 0:14:34.720 --> 0:14:38.480 don't ever let me be too square. Okay. Uh So, 0:14:38.680 --> 0:14:42.240 starting in the nineteen fifties and sixties, both experimental and 0:14:42.320 --> 0:14:45.400 theoretical work really seems to accelerate in the direction of 0:14:45.440 --> 0:14:48.920 indicating the reality of neutron stars and black holes. These 0:14:49.040 --> 0:14:54.480 these really exotic collapsed star remnant objects and theoretical models 0:14:55.040 --> 0:14:58.720 are affirmed over and over and they appear increasingly sound. 0:14:58.800 --> 0:15:04.480 While new astro comical observations really seem to make us think, wow, yeah, 0:15:04.480 --> 0:15:06.760 there could be black holes out there. I think some 0:15:06.840 --> 0:15:09.920 of the skepticism could be unfounded. Like in the nineteen 0:15:10.000 --> 0:15:14.360 sixties you had scientists identifying quasars, which are these distant 0:15:14.400 --> 0:15:17.960 high energy objects, possibly young galaxies, with black holes at 0:15:17.960 --> 0:15:21.120 the center of them, emitting trillions of times the energy 0:15:21.120 --> 0:15:24.080 of a sun. And you had pulsars, which are spinning 0:15:24.120 --> 0:15:27.640 objects emitting a repeating pattern of radio bursts. And around 0:15:27.640 --> 0:15:31.120 the same time, astronomers identified sources of X rays and 0:15:31.160 --> 0:15:34.360 gamma rays from all over the celestial map. And these 0:15:34.400 --> 0:15:38.160 signals really strongly pointed to the physical reality of collapse 0:15:38.200 --> 0:15:41.920 stars like neutron stars and black holes. And now we 0:15:42.000 --> 0:15:45.280 know that actually pretty much every mature galaxy in the 0:15:45.360 --> 0:15:48.640 universe that we know of seems to have a supermassive 0:15:48.680 --> 0:15:51.200 black hole at its center. It may be the black 0:15:51.200 --> 0:15:55.000 holes are necessary for the formation of galaxies, and galaxies 0:15:55.080 --> 0:15:57.440 are where things like us live. The black hole the 0:15:57.520 --> 0:16:03.080 life giver. Yeah, we were rebrand rebranding the black hole today. So, 0:16:03.120 --> 0:16:06.240 speaking of supermassive black holes, I I do want to 0:16:06.280 --> 0:16:09.920 just touch in once more on the three forms of 0:16:09.960 --> 0:16:12.720 black holes that we tend to discuss. Okay, so we've 0:16:12.760 --> 0:16:16.000 mainly been talking about stellar black holes, right right. The 0:16:16.000 --> 0:16:17.960 idea of a collapse star. Yeah, these would be as 0:16:18.040 --> 0:16:21.760 massive as as twenty of our sons uh fit inside 0:16:21.760 --> 0:16:24.680 a one mile radius sphere. Uh. These are the would 0:16:24.680 --> 0:16:27.080 be the remnants of very massive stars that have run 0:16:27.120 --> 0:16:29.760 through their innergy energy reserves. They go supernova and then 0:16:29.760 --> 0:16:32.360 they collapse upon themselves and they're thought to be the 0:16:32.360 --> 0:16:35.920 most common type of black holes, and there are likely 0:16:36.080 --> 0:16:39.320 dozens within our own Milky Way galaxy. And then they're 0:16:39.320 --> 0:16:42.000 the primordial black holes. These tho I touched on the 0:16:42.040 --> 0:16:44.560 first episode that the size of an atom. They have 0:16:44.560 --> 0:16:47.080 the massive a mountain, So these are hypothetical, and they 0:16:47.080 --> 0:16:50.520 probably formed soon after the Big Bang. And then of 0:16:50.560 --> 0:16:54.600 course they're the big ones, the supermassive black holes. They 0:16:54.640 --> 0:16:57.160 likely exist at the center of most galaxies. Our own 0:16:57.400 --> 0:17:01.240 galaxy boast Sagittarius A, and it has a mass equal 0:17:01.280 --> 0:17:05.639 to about four million sons. And uh, these black holes 0:17:05.680 --> 0:17:09.760 formed with their respective galaxies and are proportional in size. 0:17:10.119 --> 0:17:13.679 And again these these are these are a part of 0:17:13.720 --> 0:17:16.560 our universe. You know, as much as we we tend 0:17:16.560 --> 0:17:17.960 to sort of fall into the trap of thinking of 0:17:18.000 --> 0:17:22.720 black holes as you know, cosmic love crafty and evil consumers, 0:17:23.200 --> 0:17:26.520 they're they're just a part of the life cycle of stars. 0:17:26.560 --> 0:17:30.280 They are part of the general physical reality of the universe. Yeah, 0:17:30.320 --> 0:17:34.520 they're not reapers from another dimension. They're the life givers. 0:17:36.520 --> 0:17:40.040 Let's not go too far alright. Well, on that note, 0:17:40.480 --> 0:17:42.480 we're gonna take a quick break and when we come back, 0:17:42.600 --> 0:17:47.399 we will get into the science detecting black holes. Thank you, 0:17:47.600 --> 0:17:50.760 thank you. All Right, we're back. So I want to 0:17:50.760 --> 0:17:54.840 tell you a story about signas X one. Okay, let's 0:17:54.840 --> 0:17:56.840 have it. So. Way back in the nineteen sixties and 0:17:56.880 --> 0:18:00.920 the Swinging sixties, the astronomers out there, we're making use 0:18:00.960 --> 0:18:04.120 of a new class of tools to study distant regions 0:18:04.119 --> 0:18:08.040 of the sky, and these were space based X ray detectors. 0:18:08.480 --> 0:18:12.720 They were attached to orbital rockets and artificial satellites, and 0:18:12.840 --> 0:18:16.159 these instruments looked for X ray signals the astronomers and 0:18:16.200 --> 0:18:20.840 astrophysicists thought they might find emanating from all kinds of 0:18:20.840 --> 0:18:24.000 celestial sources, from say, the surface of the Moon. You know, 0:18:24.040 --> 0:18:27.560 it's the moon shooting X rays. Two distant star systems 0:18:27.560 --> 0:18:31.960 and nebulae, and one strong source of X ray radiation 0:18:32.040 --> 0:18:35.480 detected by rockets in the nineteen sixties was a point 0:18:35.520 --> 0:18:39.040 in the constellation Scorpius, and the source of the radiation 0:18:39.119 --> 0:18:41.560 came to be known as s c O X one 0:18:41.680 --> 0:18:43.400 or SCO X one. I don't know if you say 0:18:43.440 --> 0:18:45.720 it like SCO that makes it sound kind of scummy, 0:18:46.640 --> 0:18:50.120 but it was a truly remarkable fine because this radiation 0:18:50.200 --> 0:18:53.560 source was about nine thousand light years from our solar system, 0:18:53.640 --> 0:18:57.280 and it's X ray output was millions of times stronger 0:18:57.320 --> 0:19:01.000 than that of normal sun like stars. And this massive 0:19:01.080 --> 0:19:04.960 energy output came we discovered from a neutron star in 0:19:05.000 --> 0:19:08.919 a binary system, and since then other similar sources have 0:19:09.040 --> 0:19:12.760 been discovered. These X rays are generated when matter from 0:19:12.960 --> 0:19:14.600 so you've got a binary system, you've got like a 0:19:14.640 --> 0:19:17.200 neutron star or a black hole, and then some other 0:19:17.280 --> 0:19:21.160 kind of object like a star. They're dancing, Yeah, they're 0:19:21.200 --> 0:19:24.720 they're they're doing the polka out there in space. And 0:19:25.119 --> 0:19:28.280 the X rays are generated when matter from the surface 0:19:28.320 --> 0:19:32.159 of the more normal star gets sucked violently into the 0:19:32.200 --> 0:19:35.800 gravitational field and onto the surface of the neutron star. 0:19:35.960 --> 0:19:38.159 That's what's going on in the case of s c 0:19:38.320 --> 0:19:42.200 O X one. And during so so this this gets 0:19:42.240 --> 0:19:44.560 sucked in, the matter gets heated up a lot, and 0:19:44.840 --> 0:19:47.840 X rays get blasted out into space. But during these 0:19:47.840 --> 0:19:50.439 surveys of the nineteen sixties, one X ray source in 0:19:50.440 --> 0:19:53.840 the sky was not like the others. In nineteen sixty 0:19:53.920 --> 0:19:55.840 four we started to get a clear picture of the 0:19:55.960 --> 0:20:00.119 radiation output of one source in the Sickness constellation, and 0:20:00.160 --> 0:20:02.919 this source came to be known as signus X one, 0:20:03.200 --> 0:20:06.720 and unlike the X ray sources that emitted like regular 0:20:06.840 --> 0:20:10.440 pulses you know sometimes that would happen be be beep, 0:20:10.760 --> 0:20:15.159 Signus X one seemed to be releasing unbelievably powerful, irregular 0:20:15.240 --> 0:20:19.640 bursts of this deadly high frequency radiation, and sometimes these 0:20:19.680 --> 0:20:22.560 irregular bursts were incredibly short, like on the scale of 0:20:22.680 --> 0:20:26.040 millionths of a second, and so at a meeting in 0:20:26.200 --> 0:20:31.919 March ninety one, the Italian astrophysicist Ricardi Giaconi speculated that 0:20:31.960 --> 0:20:34.840 the source of the X one signal might be a 0:20:34.960 --> 0:20:39.720 real black hole, the first black hole apparently observed in space, 0:20:40.200 --> 0:20:43.720 and later analysis did seem to bear out this hypothesis. 0:20:43.760 --> 0:20:46.919 The signus X one system seems to consist of a 0:20:47.000 --> 0:20:51.000 blue giant star orbiting with a much smaller object that 0:20:51.119 --> 0:20:54.040 we can't see. And by observing the size of the 0:20:54.040 --> 0:20:56.840 companion star, the blue giant known as h d E 0:20:56.920 --> 0:20:59.960 two to six six eight, and the rate of its 0:21:00.200 --> 0:21:03.040 orbit it completes an orbit in less than six earth 0:21:03.160 --> 0:21:06.919 days and the size of that orbit, astronomers began to 0:21:06.960 --> 0:21:11.080 get a picture of this unseen orbital center. It appears 0:21:11.080 --> 0:21:14.800 to be invisible, tiny and heavy. Current estimates of its 0:21:14.840 --> 0:21:18.520 mass are at about fourteen point eight of our sons, 0:21:18.560 --> 0:21:21.600 and the radiation coming from this source is emitted as 0:21:21.640 --> 0:21:25.639 this apparent black hole sucks matter off of the orbiting 0:21:25.680 --> 0:21:27.720 star like we were just talking about with the neutron star. 0:21:27.760 --> 0:21:30.760 It sucks gas or matter off of that star, and 0:21:30.800 --> 0:21:34.560 the matter swirls down into the gravity pit of this object, 0:21:34.920 --> 0:21:37.359 heating up as it does, and eventually it heats to 0:21:37.400 --> 0:21:40.080 the point that it gives off X rays, and of course, 0:21:40.160 --> 0:21:43.679 once that gas falls past the event horizon, presumably nothing 0:21:43.720 --> 0:21:46.919 more is emitted. It's stuck inside. But you've got so 0:21:46.960 --> 0:21:51.360 you've got these observations. It's massive, it's tiny, it's invisible, 0:21:51.640 --> 0:21:54.560 and it shoots radiation out into space as it appears 0:21:54.600 --> 0:21:58.320 to suck matter from neighboring bodies. Really really seems like 0:21:58.320 --> 0:22:02.000 a black hole. But was it proof? This was actually 0:22:02.160 --> 0:22:05.600 famously the subject of a bet between physicist Stephen Hawking, 0:22:06.280 --> 0:22:08.600 who did plenty of his own important work on black 0:22:08.640 --> 0:22:11.480