WEBVTT - Black Hole Questions! 0:00:01.280 --> 0:00:03.320 Hey, it' Jorhan Daniel here, and we want to tell 0:00:03.360 --> 0:00:06.880 you about our new book. It's called Frequently Asked Questions 0:00:06.960 --> 0:00:09.719 about the Universe because you have questions about the universe, 0:00:09.800 --> 0:00:12.399 and so we decided to write a book all about them. 0:00:12.400 --> 0:00:14.800 We talk about your questions, we give some answers, we 0:00:14.880 --> 0:00:17.520 make a bunch of silly jokes as usual, and we 0:00:17.600 --> 0:00:20.159 tackle all kinds of questions, including what happens if I 0:00:20.200 --> 0:00:22.880 fall into a black hole? Or is there another version 0:00:22.920 --> 0:00:25.480 of you out there that's right? Like usual, we tackle 0:00:25.600 --> 0:00:29.960 the deepest, darkest, biggest, craziest questions about this incredible cosmos. 0:00:29.960 --> 0:00:31.800 If you want to support the podcast, please get the 0:00:31.800 --> 0:00:33.879 book and get a copy not just for yourself, but 0:00:34.120 --> 0:00:39.360 you know, for your nieces and nephews, cousins, friends, parents, dogs, hamsters, 0:00:39.400 --> 0:00:42.640 and for the aliens. So get your copy of Frequently 0:00:42.720 --> 0:00:46.440 Asked Questions about the Universe is available for pre order now, 0:00:46.520 --> 0:00:49.239 coming out November two. You can find more details at 0:00:49.240 --> 0:00:53.160 the book's website, Universe f a Q dot com. Thanks 0:00:53.159 --> 0:00:55.000 for your support, and if you have a hamster that 0:00:55.040 --> 0:00:57.240 can read, please let us know. We'd love to have 0:00:57.320 --> 0:01:10.119 them on the podcast. Hey, Jorge, why do you think 0:01:10.240 --> 0:01:14.560 we get so many questions about black holes. Well, you know, 0:01:14.640 --> 0:01:17.760 it's the mystery. You know, they're so inscrutable. They're like 0:01:18.000 --> 0:01:21.760 the reclusive celebrities of the universe exactly right, Like the 0:01:21.800 --> 0:01:24.160 more they avoid the paparazzi, the more people want to 0:01:24.160 --> 0:01:26.760 know about them. That could be true, but I was 0:01:26.800 --> 0:01:30.040 actually wondering if it might be the exact opposite. What 0:01:30.080 --> 0:01:31.960 do you mean, Well, what if black holes are like 0:01:32.000 --> 0:01:34.520 the car crash of the universe. They're like a cosmic 0:01:34.600 --> 0:01:37.600 disaster that you can't drive by without slowing down to 0:01:37.680 --> 0:01:41.080 check it out. Saying physicists are just rubber neckers, cosmic 0:01:41.120 --> 0:01:43.360 rubber neckers. That sounds kind of dangerous, like you might 0:01:43.400 --> 0:01:46.560 cause another accident by not watching where you were driving 0:01:46.560 --> 0:01:49.960 your spaceship. Exactly. That's the gravitational runaway effects of the 0:01:50.000 --> 0:01:52.440 black holes. Slow down to check it out, get sucked in, 0:01:52.680 --> 0:01:54.720 make a bigger black hole. That's how I feel about 0:01:54.760 --> 0:01:57.440 driving in Los Angeles. It's like an infinite black hole 0:01:57.560 --> 0:02:15.920 that you will never escape. I am Jorge made cartoonists 0:02:15.919 --> 0:02:18.600 and the creator of PhD comics. Hi, I'm Daniel. I'm 0:02:18.639 --> 0:02:21.519 a particle physicist and a professor at U C. Irvine, 0:02:21.600 --> 0:02:24.640 but I almost never go up to Los Angeles. Really 0:02:24.760 --> 0:02:28.440 do you avoid it like a black hole. If it 0:02:28.480 --> 0:02:30.600 was a black hole, it would suck me in. So yeah, 0:02:30.600 --> 0:02:33.080 I'm trying to stay in orbit around Los Angeles instead 0:02:33.080 --> 0:02:36.760 of falling into the singularity, yes, where time slows down 0:02:36.919 --> 0:02:39.880 through plastic surgery apparently. But yeah, I mean you're kind 0:02:39.880 --> 0:02:42.040 of famous now, Daniel. You don't get calls from Hollywood 0:02:42.080 --> 0:02:45.120 these days. I screened my calls, so if they're calling, 0:02:45.160 --> 0:02:46.840 I'm just not picking them up. You look for the 0:02:46.880 --> 0:02:49.440 aira code. If it's your local air code, it's ma'am. 0:02:49.480 --> 0:02:51.720 If it's three one oh, then it's someone from Hollywood, 0:02:51.880 --> 0:02:54.000 like Jorge, so you just hang up. Also, you know, 0:02:54.080 --> 0:02:56.480 there's famous and then there's Los Angeles famous. You can 0:02:56.560 --> 0:02:59.240 be like super famous in Orange County and be nobody 0:02:59.280 --> 0:03:02.040 in Los Angeles. But anyways, welcome to our podcast, Daniel 0:03:02.080 --> 0:03:04.960 and Jorge Explain the Universe, a production of I Heart Radio, 0:03:05.080 --> 0:03:07.920 in which we ask all the biggest and famous and 0:03:08.040 --> 0:03:12.000 most time dilated questions of the universe. We ask all 0:03:12.000 --> 0:03:14.320 of them about where it came from, where it's going, 0:03:14.440 --> 0:03:16.720 what it's made out of, and how it all works. 0:03:16.840 --> 0:03:19.480 We dive deep into the questions about black holes and 0:03:19.560 --> 0:03:23.640 neutron stars and galaxies and tiny particles and quaisars and 0:03:23.760 --> 0:03:26.760 everything in between, because we think it's possible to download 0:03:26.840 --> 0:03:29.920 all of that into your amazing brain and hold for 0:03:29.960 --> 0:03:33.959 a moment an understanding of the entire universe. Yeah, because 0:03:33.960 --> 0:03:36.720 it is a pretty famous universe. Everyone seems to know 0:03:36.800 --> 0:03:39.680 about it. Everyone's fan. I would hope, you know, it's 0:03:39.720 --> 0:03:42.320 everywhere he got. He can't get away from this universe, 0:03:42.400 --> 0:03:45.320 and it's pretty fascinating, even it's black sheep. You know, 0:03:45.360 --> 0:03:48.120 everyone wants to know about the black Sheep of the celebrities. Yes, 0:03:48.200 --> 0:03:51.200 have you been checking out the universe's reviews on yelp? Yes, 0:03:51.280 --> 0:03:54.280 I think it. It has about infinite stars and also 0:03:54.400 --> 0:03:57.760 infinite thumbs, but you know it's about fifty up and them. 0:03:57.920 --> 0:04:00.720 That's right, And you know nobody has any other are alternatives. 0:04:00.760 --> 0:04:02.360 It's not like people like, hey, I was in this 0:04:02.440 --> 0:04:05.040 other universe the other day and they have better chips. 0:04:05.360 --> 0:04:07.800 So you know, this is basically all we got learned 0:04:07.800 --> 0:04:09.320 to love at people. Maybe you just need to get 0:04:09.360 --> 0:04:11.800 out more than you You might find other universes if 0:04:11.840 --> 0:04:13.880 you just, you know, get out of your Orange County 0:04:13.880 --> 0:04:17.000 Bubble l A does seem like another universe sometimes, not 0:04:17.080 --> 0:04:19.320 just because it's weird, but because it takes forever to 0:04:19.400 --> 0:04:24.200 get there. Definitely an alternate reality for sure. But anyways, Yeah, 0:04:24.600 --> 0:04:27.080 people are curious not just about the universe but about 0:04:27.120 --> 0:04:30.680 the things in it, especially things that are extra mysterious, 0:04:30.680 --> 0:04:33.200 and those are the things that drive physics. We look 0:04:33.240 --> 0:04:35.200 around in the universe and we say, do we understand 0:04:35.200 --> 0:04:37.839 how this works? Does that bit over there makes sense? 0:04:38.040 --> 0:04:40.279 And if it doesn't, then we focus our brains on 0:04:40.320 --> 0:04:42.800 and try to understand how could that possibly work? How 0:04:42.839 --> 0:04:45.040 could that make sense? How could that be consistent with 0:04:45.120 --> 0:04:48.000 what we know about the nature of space and time 0:04:48.120 --> 0:04:51.440 and energy, And so the weirdest things are also the 0:04:51.480 --> 0:04:55.040 best opportunities to learn something about the universe. Yeah, because 0:04:55.040 --> 0:04:56.920 when you look around, I guess it's all pretty bright 0:04:56.960 --> 0:05:00.040 and beautiful and majestic and cosmic, but everyone's in a 0:05:00.120 --> 0:05:01.680 When you look at into the universe, there is a 0:05:02.279 --> 0:05:04.520 basically a big hole, like a big hole in our 0:05:04.560 --> 0:05:08.400 knowledge and also literally figuratively and in all the ways 0:05:08.520 --> 0:05:11.520 there there are actual holes in the universe. There are 0:05:11.640 --> 0:05:13.400 holes in the universe, and you know, to answer the 0:05:13.480 --> 0:05:15.640 question to our intro. I think one reason that they're 0:05:15.680 --> 0:05:19.800 fascinating is because they are so different from what we experience. 0:05:19.920 --> 0:05:22.120 You know, it's not just like, hey, there's a banana 0:05:22.160 --> 0:05:24.760 out there in space, like we know bananas, We bananas, 0:05:24.760 --> 0:05:27.320 were familiar with bananas. You know, it's something out there 0:05:27.320 --> 0:05:30.640 in space which is so different from our everyday experience, 0:05:30.720 --> 0:05:33.240 so bizarre that we just sort of like want to 0:05:33.240 --> 0:05:35.159 see it. Yeah, and so to be on the podcast, 0:05:35.240 --> 0:05:45.280 we'll be tackling unanswered questions about black holes. Now, Daniel, 0:05:45.320 --> 0:05:49.480 I assume it's not just bananas out there. We don't know, 0:05:49.520 --> 0:05:52.039 you know, maybe bananas are the fundamental element of the 0:05:52.120 --> 0:05:54.880 universe and it is just all bananas all the way down. 0:05:55.320 --> 0:05:58.800 That's a viable theory. It sounds like a slippery slope there. 0:06:00.760 --> 0:06:03.479 We just gotta peel back the layers of reality until 0:06:03.520 --> 0:06:07.920 we reveal the banana inside. But yeah, black holes. A 0:06:07.960 --> 0:06:10.200 lot of people have questions about black holes, and you're 0:06:10.240 --> 0:06:13.000 asking me earlier why they're so mysterious. Like everyone, you 0:06:13.040 --> 0:06:15.200 get a lot of questions about black holes, right, Yeah, 0:06:15.240 --> 0:06:17.080 I say like a third of all the questions we 0:06:17.160 --> 0:06:19.400 get are about black holes. What happens if you fall 0:06:19.480 --> 0:06:21.280 in them, What would they look like if you did this? 0:06:21.480 --> 0:06:23.320 What would happen if you shoot two black holes at 0:06:23.320 --> 0:06:25.760 each other? All sorts of questions people love to think 0:06:25.760 --> 0:06:30.160 about black holes. Interesting a third of the questions. That's amazing. 0:06:30.440 --> 0:06:33.520 It's like, it's some black hole in your It does 0:06:33.600 --> 0:06:36.359 make my inbox pretty dense. But I love it. I 0:06:36.400 --> 0:06:38.640 love thinking about black holes just as much as our 0:06:38.640 --> 0:06:41.080 listeners do for the same reasons, you know. And the 0:06:41.120 --> 0:06:44.080 cool thing about black holes is that we all understand 0:06:44.160 --> 0:06:46.440 them about as well, you know. I love that we 0:06:46.440 --> 0:06:48.880 can bring our listeners to the very forefront of knowledge, 0:06:48.920 --> 0:06:50.800 because in the case of black holes, it's not that 0:06:50.920 --> 0:06:53.880 far away. You know. We just don't understand very much 0:06:54.120 --> 0:06:57.159 about these weird, mysterious objects. I think that's why they're 0:06:57.160 --> 0:07:00.640 so fascinating to physicists, because they represent such a great 0:07:00.680 --> 0:07:04.280 opportunity to learn something new and shocking about the universe. Yeah, 0:07:04.320 --> 0:07:07.520 so today we're answering questions that we've gotten about black 0:07:07.520 --> 0:07:10.200 holes from listener. It's just like you, and we've got 0:07:10.240 --> 0:07:13.480 three pretty interesting questions, one of them about the mass 0:07:13.520 --> 0:07:17.440 of a black hole, about mini black holes, and also 0:07:17.600 --> 0:07:20.920 about whether or not black holes can explain dark matter. 0:07:21.520 --> 0:07:23.920 So let's jump into our first question right away here, 0:07:23.960 --> 0:07:27.800 and it comes from Levi from the Ukraine. I didn't 0:07:27.800 --> 0:07:31.880 know m Levi are Ukraine, and I had two questions 0:07:31.920 --> 0:07:36.239 about my favorite topic, which is black holes. First, how 0:07:36.560 --> 0:07:40.320 is the mass of a black hole calculated? And second? 0:07:41.120 --> 0:07:44.000 Is there anybody to know when an event horizon of 0:07:44.040 --> 0:07:46.720 a black hole begins? If I were to say, take 0:07:46.720 --> 0:07:48.440 a rocket ship to the black hole and this sene 0:07:48.520 --> 0:07:50.920 our galaxy, is there any way that I could know 0:07:51.120 --> 0:07:53.400 when I need to turn that thing around before I 0:07:53.520 --> 0:07:58.040 become spaghetti? Thank you? M M. Interesting question? Now? Was 0:07:58.080 --> 0:07:59.960 he allowed two questions? I feel like he's not good 0:08:00.080 --> 0:08:03.440 extra question in his question imploded into a black hole 0:08:03.480 --> 0:08:06.520 because of its density, he had it multiplied. It seems 0:08:07.160 --> 0:08:09.520 so you just can't stop asking questions. Once you start 0:08:09.520 --> 0:08:12.720 thinking about black holes, the questions just proliferate. What do 0:08:12.720 --> 0:08:15.400 you think it's captured the imagination of not just our listeners, 0:08:15.400 --> 0:08:18.080 but it seems like everyone out there has questions about 0:08:18.080 --> 0:08:21.040 black holes. I think it's just the opportunity to see 0:08:21.120 --> 0:08:23.880 something hidden, to learn something new. You know. The thing 0:08:23.920 --> 0:08:26.720 that captivates me about the black hole is knowing that 0:08:26.800 --> 0:08:29.920 one of the greatest mysteries in modern physics. How to 0:08:30.080 --> 0:08:35.080 reconcile crazy intense gravity and quantum little particles, how to 0:08:35.120 --> 0:08:37.880 bring those together into one idea is out there, and 0:08:37.920 --> 0:08:40.360 it's hidden inside a black hole. So if we could 0:08:40.360 --> 0:08:43.600 only peek inside, we could learn the very nature of 0:08:43.720 --> 0:08:46.679 space and time. There's so much we could know by 0:08:46.679 --> 0:08:49.280 the universe if only we could see inside a black hole. 0:08:49.320 --> 0:08:51.720 And yet he's hidden from us. So it's sort of 0:08:51.760 --> 0:08:54.520 like somebody saying, I have the secrets you want, and 0:08:54.520 --> 0:08:56.920 they're written on this envelope and I'm gonna burn it. 0:08:56.960 --> 0:08:58.880 I'm gonna throw in the fire instead of opening it 0:08:58.880 --> 0:09:01.319 to you. That would kill you. Oh man, if you's 0:09:01.360 --> 0:09:03.800 so frustrating to know the answers are out there and 0:09:03.960 --> 0:09:06.160 not be able to get them, that's very frustrating. These 0:09:06.160 --> 0:09:08.240 there a big red button into that envelope. That would 0:09:08.400 --> 0:09:11.480 drive doubly crazy. But all right, let's jump into Levi's 0:09:11.520 --> 0:09:13.880 questions here. The first one is how do you calculate 0:09:13.920 --> 0:09:16.920 the mass of a black hole? Now I'm guessing down 0:09:17.000 --> 0:09:20.679 or there are not gigantic scales we can use to 0:09:20.760 --> 0:09:23.400 measure the mass of a black hole, A sort of 0:09:23.400 --> 0:09:26.960 if we can Yeah, scales work by using gravity. Right, 0:09:27.080 --> 0:09:29.880 If you put something on a scale, you're measuring its weight, 0:09:30.120 --> 0:09:32.559 and its weight is the force of gravity on it, 0:09:32.760 --> 0:09:35.559 which is determined by its mass. And so to measure 0:09:35.600 --> 0:09:37.680 the mass of something you can use the strength of 0:09:37.679 --> 0:09:41.600 the gravitational pull on it, which depends on the object's mass. 0:09:41.600 --> 0:09:43.480 Now out there in space, You're right, there's not some 0:09:43.600 --> 0:09:45.960 like massive scale we can put it on. But we 0:09:46.040 --> 0:09:49.640 can see how the black hole tugs on things around 0:09:49.679 --> 0:09:52.000 it which are visible, and that's one way we can 0:09:52.040 --> 0:09:54.439 measure its mass, and so you can see the effects 0:09:54.440 --> 0:09:56.840 of its mass on the things around it. I guess 0:09:56.880 --> 0:09:58.720 kind of like our son, right, Like if our son 0:09:59.400 --> 0:10:01.720 with a different and mass, like if it was bigger 0:10:01.800 --> 0:10:05.040 or smaller than our orbit around it would be different. Right, 0:10:05.240 --> 0:10:07.280 Like you could tell what the mass of the Sun 0:10:07.360 --> 0:10:10.000 is maybe from our orbit. Yeah, if you measure just 0:10:10.080 --> 0:10:12.840 the velocity and location of the Earth as it moved 0:10:12.880 --> 0:10:15.440 around the Sun, you can deduce exactly the mass of 0:10:15.440 --> 0:10:18.200 the Sun because you can tell what gravitational force is 0:10:18.280 --> 0:10:21.560 necessary to move the Earth in that path, and that 0:10:21.559 --> 0:10:23.880 would tell you how much mass you need to provide 0:10:23.880 --> 0:10:26.680 that gravitational force. So, yeah, the Earth is like a 0:10:26.679 --> 0:10:29.320 little scale that's measuring the Sun all the time. But 0:10:29.360 --> 0:10:30.720 what do you need to know the mass of the 0:10:30.760 --> 0:10:33.720 Earth too, pretty accurately? Yes, absolutely, you need to know 0:10:33.760 --> 0:10:35.240 the mass of the Earth. And don't say you just 0:10:35.360 --> 0:10:39.280 use the sun, because then now we're in a circular argument. No, 0:10:39.440 --> 0:10:41.280 you need to use the mass of the Earth. Absolutely. 0:10:41.320 --> 0:10:43.080 The mass of the Earth you can get using like 0:10:43.400 --> 0:10:46.280 your knowledge of what it's made out of and it's volume. 0:10:46.360 --> 0:10:47.960 So if you know the radius of the Earth, like 0:10:48.000 --> 0:10:50.679 its size, and your understanding roughly what it's made out of, 0:10:50.840 --> 0:10:53.640 then you can tell its mass, or you can bootstrap. 0:10:53.679 --> 0:10:55.200 You can say, well, I'm gonna look at the moon 0:10:55.280 --> 0:10:57.040 and see how the moon moves around the Earth, and 0:10:57.040 --> 0:10:58.600 that's going to tell me the mass of the Earth 0:10:58.679 --> 0:11:02.079 if again you know the mass to the moon. Yeah, 0:11:02.120 --> 0:11:04.439 and so on and so on. I guess at some point, 0:11:04.480 --> 0:11:06.960 maybe the question is at some point when do you 0:11:06.960 --> 0:11:09.640 have to guess? Right, because something you have to guess 0:11:09.679 --> 0:11:11.800 what the moon is made out of, or even the 0:11:11.840 --> 0:11:13.679 Earth you cannot have to guess. I mean, we have 0:11:13.760 --> 0:11:17.000 some measurements, but we ultimately you're sort of guessing what's 0:11:17.000 --> 0:11:19.040 inside the Earth. Yeah, in the end, you do need 0:11:19.120 --> 0:11:20.760 to know the mass of one of the objects to 0:11:20.760 --> 0:11:23.079 measure the mass the other. But there's also some constraints. 0:11:23.080 --> 0:11:25.040 They're like, what you really need to know is the 0:11:25.080 --> 0:11:29.120 product of the two masses, right, mass one times mass too. 0:11:29.440 --> 0:11:32.320 So if you make enough measurements of pairs of objects 0:11:32.400 --> 0:11:34.560 and you can narrow that down, you get like enough 0:11:34.600 --> 0:11:37.640 systems of equations that you can constrain it. But yeah, 0:11:37.679 --> 0:11:39.720 you also do need to say something about what they 0:11:39.720 --> 0:11:41.800 are made out of to get some information about how 0:11:41.880 --> 0:11:43.800 much mass one of them has. You can also measure 0:11:43.800 --> 0:11:46.320 the mass of the Earth by flipping that around and saying, here, 0:11:46.360 --> 0:11:48.559 I have an object whose mass I know, and that 0:11:48.640 --> 0:11:51.400 can measure the gravitational effect on it, and from that 0:11:51.440 --> 0:11:53.360 I can measure the mass of the Earth. To build 0:11:53.400 --> 0:11:55.760 like a calibration object, like a test object, like a 0:11:55.800 --> 0:11:59.120 one kilogram pound of platinum or something. Yeah, you can 0:11:59.160 --> 0:12:02.160 see how much it pulls on like a known weight, 0:12:02.320 --> 0:12:04.280 and then that's how you would estimate the mass of 0:12:04.280 --> 0:12:06.560 the Earth. And that's just sort of definition. All you say, like, 0:12:06.800 --> 0:12:09.600 this is the definition of a kilogram this object, and 0:12:09.640 --> 0:12:12.480 from that you can measure essentially the ratio of its 0:12:12.559 --> 0:12:14.480 mass to the mass of the Earth. You can say 0:12:14.520 --> 0:12:17.400 how massive is the Earth in terms of this object 0:12:17.679 --> 0:12:19.800 I'm defining to be one kilogram, and then you can 0:12:19.840 --> 0:12:22.760 bootstrap your way up to the Sun and basically everything 0:12:22.760 --> 0:12:24.880 else in the universe. Right, you can strap your boot. 0:12:24.920 --> 0:12:27.240 You can boot your strap. But what about for like 0:12:27.280 --> 0:12:30.240 a black hole? I mean, they're so far away, we've 0:12:30.280 --> 0:12:33.000 barely seen one directly. You know, we can see the 0:12:33.120 --> 0:12:35.720 things flying around it, But how do we know what 0:12:35.840 --> 0:12:38.760 those things are? I mean, they're just like bright little pinpoints, right, yes, 0:12:38.800 --> 0:12:40.959 So one way we can see the black holes exist 0:12:41.200 --> 0:12:44.480 is by seeing their gravitational effect on stuff nearby. Because 0:12:44.520 --> 0:12:47.240 black holes, of course are black, they don't admit any 0:12:47.360 --> 0:12:50.520 radiation directly, or if they're emitting hawking radiation, then we 0:12:50.559 --> 0:12:52.560 can't see it. It's too faint. So you're right, we 0:12:52.600 --> 0:12:54.920 need to know the mass of the objects nearby. And so, 0:12:55.000 --> 0:12:58.520 for example, the black hole the center of our galaxy 0:12:58.640 --> 0:13:01.640 has some stars whizzing very close by to it, and 0:13:01.679 --> 0:13:04.360 we can measure the mass of those stars by looking 0:13:04.400 --> 0:13:06.480 at the light they emit, because we have a pretty 0:13:06.480 --> 0:13:08.960 good model for how the brightness of a star is 0:13:09.000 --> 0:13:11.840 related to its mass. So we did a whole episode 0:13:11.840 --> 0:13:14.160 on how you measure the mass of stars. And that's 0:13:14.200 --> 0:13:17.040 not perfect, it's not exact, but it's pretty good, right, 0:13:17.040 --> 0:13:20.200 it's based on like models and some observations, and so 0:13:20.400 --> 0:13:22.079 just from the light that you get from those stars 0:13:22.120 --> 0:13:24.440 around the black hole, you can say, well, that's a 0:13:24.440 --> 0:13:27.800 a stage so and so star weighs about they usually 0:13:27.960 --> 0:13:30.319 wait about this much and so there, and it's curving 0:13:30.360 --> 0:13:33.360 around the black hole this much. So therefore that black 0:13:33.360 --> 0:13:37.160 holes probably there's many kilograms exactly. And those models are 0:13:37.160 --> 0:13:40.000 pretty good, and we validate them using binary star systems 0:13:40.040 --> 0:13:42.480 where we can see two stars, we can measure their brightness, 0:13:42.520 --> 0:13:44.320 and we can see how they move around each other, 0:13:44.640 --> 0:13:47.120 and so we can really validate those models pretty well. 0:13:47.160 --> 0:13:49.199 I mean, there are uncertainties, but we can trust those 0:13:49.200 --> 0:13:51.640 because remember there are a lot of binary star systems 0:13:51.640 --> 0:13:54.040 out there in the universe, many more than you might expect. 0:13:54.120 --> 0:13:55.920 So that lets us measure the mass of the stars 0:13:55.960 --> 0:13:58.120 and from that deduced the mass of the black hole. 0:13:58.200 --> 0:14:01.320 Because remember, black holes don't emit any information from their 0:14:01.360 --> 0:14:05.280 inside except for the total mass of the black hole, 0:14:05.320 --> 0:14:08.680 which can be deduced by its gravitational effect. That's the 0:14:08.720 --> 0:14:11.280 only information that comes out other than the black holes 0:14:11.360 --> 0:14:13.959 spin and charge. And also do you have to account 0:14:13.960 --> 0:14:16.160 for like the camera adding ten pounds, like does the 0:14:16.240 --> 0:14:19.680 telescope at you know, ten million kims? No, the black 0:14:19.720 --> 0:14:22.240 holes agent is very particular by the cameras. We used 0:14:22.240 --> 0:14:25.160 to take their pictures nicely. These is doubles. When it's 0:14:25.200 --> 0:14:27.560 taking the naked pictures. I said, take a profile above 0:14:27.600 --> 0:14:29.800 the accretion disk. That's when it looks good, all right. 0:14:29.840 --> 0:14:31.720 And there's also sort of a different way to measure 0:14:31.760 --> 0:14:33.400 the mass of a black hole, which is by looking 0:14:33.440 --> 0:14:36.080 at its size. Like if we ever do get better 0:14:36.120 --> 0:14:38.240 pictures of a black hole, you might be able to 0:14:38.240 --> 0:14:41.120 tell how heavy it is by just seeing its size, right, 0:14:41.160 --> 0:14:44.000 Because the size of the event horizon depends on the 0:14:44.040 --> 0:14:46.360 mass of the black hole. Yeah, they're very closely connected. 0:14:46.440 --> 0:14:48.680 As the black hole eats more and gets more mass 0:14:49.000 --> 0:14:51.760 than it is gaining in size, the size the event 0:14:51.800 --> 0:14:55.160 horizon is growing, and so if you could measure the 0:14:55.200 --> 0:14:58.200 event horizon, then you could deduce its mass. Measuring the 0:14:58.200 --> 0:15:00.480 event horizon is tricky though, because you need to see 0:15:00.520 --> 0:15:03.560 photons like whizzing around it. So you need a direct 0:15:03.560 --> 0:15:06.120 picture and we've done that for one, maybe two black 0:15:06.120 --> 0:15:08.760 holes now. But it's much harder, obviously, And so that 0:15:08.760 --> 0:15:11.040 brings us to the second question leave I had, which 0:15:11.160 --> 0:15:13.880 is like, if I'm trying to check out a black hole, like, 0:15:13.960 --> 0:15:17.520 could I tell where the actual event horizon is? Like, 0:15:17.680 --> 0:15:19.560 at what point do you want to make sure you 0:15:19.960 --> 0:15:22.160 turn around before you get sucked in forever? Well, I 0:15:22.200 --> 0:15:24.360 would say turn around now, do not take that trip 0:15:24.400 --> 0:15:28.240 to the black hole. It's not a good idea. Don't 0:15:28.240 --> 0:15:30.600 even buy the ticket sets when you should turn around. Right, 0:15:30.640 --> 0:15:33.320 So it is a good idea to think about where 0:15:33.320 --> 0:15:36.480 a black hole begins, where it's event horizon is, so 0:15:36.520 --> 0:15:40.000 that if you are a billionaire scientist, entrepreneur and you 0:15:40.040 --> 0:15:42.320 do take that trip to the center of the Milky 0:15:42.360 --> 0:15:44.840 Way to study the black hole, you know when to 0:15:44.920 --> 0:15:47.560 turn around. And one thing you could do, if you 0:15:47.640 --> 0:15:49.560 know the mass of the black hole is, you could 0:15:49.600 --> 0:15:51.280 just calculate it. You could say, well, I know how 0:15:51.320 --> 0:15:53.960 massive it is, so I know the point of no return. 0:15:54.000 --> 0:15:57.120 I can calculate the event horizon. So, yeah, there's a 0:15:57.160 --> 0:15:59.240 point at a distance from the center of the black 0:15:59.240 --> 0:16:01.560 hole at which now even light can escape, right. I 0:16:01.560 --> 0:16:03.680 think maybe that's what LEVI is asking, Like, what's the 0:16:03.720 --> 0:16:06.840 point where not even light can escape. That's the event horizon, 0:16:07.320 --> 0:16:09.800 and from a distance you can sort of see it, right, Like, 0:16:09.960 --> 0:16:12.600 it's sort of where when you look at a black hole, 0:16:12.920 --> 0:16:15.240 and we've looked at one, it looks like a big 0:16:15.280 --> 0:16:18.880 black circle, and so that's generally where the event horizon is, 0:16:18.920 --> 0:16:21.400 although it's not exact right. That's right, the black circle 0:16:21.480 --> 0:16:23.560 you see when you look at a black hole is 0:16:23.600 --> 0:16:26.760 actually bigger than the event horizon because you can't see 0:16:26.800 --> 0:16:30.440 photons that like fly just above the event horizon from 0:16:30.440 --> 0:16:33.200 behind the black hole. Those we get curved and fall 0:16:33.280 --> 0:16:36.080 into the black hole. So there's the event horizon itself, 0:16:36.280 --> 0:16:38.400 and then there's like a shadow that the black hole 0:16:38.480 --> 0:16:41.280 makes that's even larger than the event horizon. You can 0:16:41.400 --> 0:16:43.880 get closer than the shadow, you see it looks bigger 0:16:43.920 --> 0:16:46.360 than it actually is. And as you get closer and 0:16:46.440 --> 0:16:49.720 closer to the black hole, that shadow grows and it 0:16:49.760 --> 0:16:52.240 grows to take over more and more of your view. 0:16:52.480 --> 0:16:54.680 So if you're very close to the black hole, for example, 0:16:54.720 --> 0:16:56.840 then it might appear to take up like half of 0:16:56.840 --> 0:16:59.960 your entire view. Right. That's kind of the tricky thing 0:17:00.000 --> 0:17:02.880 about black holes is that there's so much distortion around 0:17:02.920 --> 0:17:04.879 them that you know, from afar, they look like a 0:17:05.000 --> 0:17:08.720 nice clean circle, But as you get closer, everything gets 0:17:08.760 --> 0:17:11.560 distorted and kind of blown out of proportion, and so 0:17:11.600 --> 0:17:14.560 it's gonna be really hard to tell when you've reached 0:17:14.600 --> 0:17:17.320 the actual event horizon, right, because, like you're saying, the 0:17:17.359 --> 0:17:19.240 black hole is gonna start taking a bit more and 0:17:19.280 --> 0:17:21.520 more of your field of view, and you're gonna be 0:17:21.560 --> 0:17:23.080 like in my inn or am I out? I don't know, 0:17:23.240 --> 0:17:25.919 yeah exactly, And so this is very dangerous not to 0:17:25.920 --> 0:17:28.639 be recommended or endorsed. But as you get closer and 0:17:28.640 --> 0:17:30.840 closer to the black hole, the image of it grows 0:17:31.040 --> 0:17:33.640 larger and larger, and as you say, what you're seeing 0:17:33.840 --> 0:17:37.040 is not anymore a good representation of what's actually there. 0:17:37.320 --> 0:17:39.720 Like when you look around yourself in your room, the 0:17:39.760 --> 0:17:41.919 stuff you see is the stuff that's there, because the 0:17:41.960 --> 0:17:44.119 light is moving in a straight line from whatever it 0:17:44.240 --> 0:17:46.080 is to your eyes, and so you can look around 0:17:46.119 --> 0:17:48.320 and say, oh, that's over there and this is over here. 0:17:48.400 --> 0:17:50.920 But if there are like lenses around you that bend 0:17:50.960 --> 0:17:53.480 the light, then you get distorted images. Imagine you're in 0:17:53.480 --> 0:17:55.920 a fun house mirror. What you see is not what's 0:17:55.960 --> 0:17:58.200 actually there, and that's what's happening with the black hole. 0:17:58.320 --> 0:18:00.879 Light is no longer following straight lines, so what you 0:18:00.920 --> 0:18:03.480 see is a distortion. And it's really interesting. As you 0:18:03.520 --> 0:18:05.919 get closer and closer to the black hole than the 0:18:05.920 --> 0:18:08.919 shadow of the black hole, this big black image of 0:18:08.960 --> 0:18:12.720 the event horizon gets larger and larger eventually becomes more 0:18:12.760 --> 0:18:15.679 than just half of your view. It like takes up 0:18:15.800 --> 0:18:17.800 most of your view, and the rest of the universe 0:18:17.880 --> 0:18:20.919 is squeezed down into a smaller and smaller circle. And 0:18:20.960 --> 0:18:22.720 you can get a clue about when you're back to 0:18:22.760 --> 0:18:25.280 cross the event horizon, because when you cross the event horizon, 0:18:25.480 --> 0:18:28.080 that circle that there's the rest of the universe is 0:18:28.119 --> 0:18:31.000 now shrinking down to a tiny little dot. And once 0:18:31.000 --> 0:18:33.240 you fall inside the event horizon, then the rest of 0:18:33.240 --> 0:18:36.840 the universe is now exactly one tiny little point where 0:18:36.880 --> 0:18:39.360 light from the universe can still reach you. Yeah, it's 0:18:39.359 --> 0:18:42.639 a pretty trippy experience and pretty extreme and and actually, 0:18:42.680 --> 0:18:45.199 if you want to know more about this, it's conveniently 0:18:45.200 --> 0:18:47.879 a question we answer in our new book. Right Daniel 0:18:47.960 --> 0:18:50.760 frequently ask questions about the universe. That's right, This is 0:18:50.800 --> 0:18:53.320 a frequently asked question. What would it be like to 0:18:53.400 --> 0:18:55.639 fall into a black hole, and the book is a 0:18:55.640 --> 0:18:59.080 lot of fun. It's out on November two one. You 0:18:59.080 --> 0:19:00.840 can check it out at you reverse f a q 0:19:01.080 --> 0:19:03.639 dot com. It's filled with answers and a bunch of 0:19:03.680 --> 0:19:06.080 really awesome cartoons at or he drew. They give you 0:19:06.160 --> 0:19:08.000 a sense for what it would look like to fall 0:19:08.080 --> 0:19:10.560 into a black hole. Yeah, order a copy for yourself, 0:19:10.600 --> 0:19:14.040 for your nieces and nephews, uncles and best friends. But 0:19:14.200 --> 0:19:16.119 we do sort of go into a lot of details 0:19:16.160 --> 0:19:18.400 because there are a lot of details about going into 0:19:18.440 --> 0:19:20.240 the black hole, and I'm not sure we can cover 0:19:20.280 --> 0:19:22.080 all of them. So please check out the book if 0:19:22.080 --> 0:19:24.960 you are actually that curious, because there are a lot 0:19:24.960 --> 0:19:27.600 of complications, like not only does the black hole take 0:19:27.680 --> 0:19:29.680 up your whole field of view, but also like it's 0:19:29.720 --> 0:19:32.879 possible for you to get inside a black hole without 0:19:32.920 --> 0:19:36.439 getting stretched into spaghetti. It sort of all depends on 0:19:36.480 --> 0:19:39.040 these details about the mass of the black hole, right, 0:19:39.240 --> 0:19:41.879 And that's right. So if you're interested that, dig into 0:19:41.920 --> 0:19:43.760 that copy of that book and let us know if 0:19:43.800 --> 0:19:46.000 you have any follow up questions. All right, So, the 0:19:46.000 --> 0:19:49.440 basic answers for Levi is you can calculate the mess 0:19:49.440 --> 0:19:51.240 with a black hole by how the things around it 0:19:51.280 --> 0:19:53.720 are moving. And also when you need to turn around 0:19:53.760 --> 0:19:56.080 when you visit a black hole, before you visit a 0:19:56.080 --> 0:19:59.159 black hole, when you need to turn around right exactly 0:19:59.200 --> 0:20:03.160 before you start arching Airbnb for black hole opportunities. Yeah, 0:20:03.200 --> 0:20:07.800 don't believe those pictures. They distort the space inside of 0:20:07.840 --> 0:20:10.800 the airbnbs. All right, let's get into our two other 0:20:11.040 --> 0:20:13.800 listener questions about black holes. One of them is about 0:20:13.880 --> 0:20:17.160 mini black holes and the other one is about dark matter. 0:20:17.920 --> 0:20:32.840 But first, let's take a quick break. All right, we're 0:20:32.880 --> 0:20:37.560 answering questions about black holes from listeners, and you get 0:20:37.560 --> 0:20:39.760 a lot of questions about black holes. I do. I 0:20:39.840 --> 0:20:41.679 have a lot of questions for about black holes. I 0:20:41.760 --> 0:20:43.760 read a lot about black holes, and we get lots 0:20:43.760 --> 0:20:47.040 of questions from the listeners about black holes because everybody 0:20:47.080 --> 0:20:49.159 wants to know what's going on. I see, And what 0:20:49.240 --> 0:20:51.480 proportion of the questions you get do you actually know 0:20:51.560 --> 0:20:53.959 the answer? We'll have a wonderful backup, which is if 0:20:53.960 --> 0:20:55.600 I don't know the answer, I just send them a 0:20:55.640 --> 0:20:58.360 link to our book we have no idea and say 0:20:58.480 --> 0:21:00.520 that's the answer. Go buy a copy of the book. 0:21:01.240 --> 0:21:04.240 Oh boy, you're plugging away today. I'm plugging away. But 0:21:04.280 --> 0:21:07.159 also I think people like to hear that the question 0:21:07.200 --> 0:21:09.200 they've asked is not one that has an answer. Of 0:21:09.280 --> 0:21:11.440 course people would like to know the answer, but it's 0:21:11.440 --> 0:21:14.560 also satisfying to feel like, Oh, I'm at the forefront 0:21:14.600 --> 0:21:17.960 of human knowledge. I have questions, just like Kip Thorne 0:21:18.000 --> 0:21:20.840 has questions, or just like very Barish has questions. These 0:21:20.880 --> 0:21:24.159 Nobel Prize winners who also don't understand what's going on 0:21:24.200 --> 0:21:26.760 inside a black hole. Welcome to the club, the curious 0:21:26.760 --> 0:21:29.879 about black holes club. All right, so our second question 0:21:30.000 --> 0:21:32.160 is from Tim and he has a question about mini 0:21:32.200 --> 0:21:36.760 black holes. Hello, Daniel, Joaii, and Katie. I've got to 0:21:36.880 --> 0:21:39.520 question about many black holes. If you were to have 0:21:39.600 --> 0:21:43.200 some super large head dron collider and create miniature black 0:21:43.240 --> 0:21:47.639 holes that immediately disappear with Hawking radiation, how would you 0:21:47.640 --> 0:21:51.639 detect that Hawking radiation? And what would you learn since 0:21:51.800 --> 0:21:55.600 all the information other than the mass of the black 0:21:55.600 --> 0:22:01.280 hole is essentially destroyed? Curious about the answer? Shoots? Alright, 0:22:01.560 --> 0:22:04.760 awesome question here. There's a lot in this question. There's 0:22:04.960 --> 0:22:07.359 the idea of MENI black holes, there's the idea of 0:22:07.359 --> 0:22:11.679 Hawking radiation. And he asked about quantum information. I know 0:22:11.880 --> 0:22:15.040 so many good questions and so many fun opportunities to 0:22:15.119 --> 0:22:18.440 learn about black holes by creating them a particle colliders. 0:22:18.600 --> 0:22:20.600 All right, so let's dig into it, Daniel, What is 0:22:20.640 --> 0:22:22.680 a medi black hole? I guess it's just a small 0:22:22.720 --> 0:22:24.920 black hole. Are there's possible? How do you make them? Yeah? 0:22:24.920 --> 0:22:27.680 Black holes can come in almost any size. There is 0:22:27.720 --> 0:22:30.360 an absolute minimum size to a black hole, but it's 0:22:30.400 --> 0:22:32.919 pretty small. You can make a black hole that's the 0:22:32.960 --> 0:22:34.960 size of the galaxy. You can make a black hole 0:22:35.200 --> 0:22:37.800 that's like, you know, the size of a particle. Almost 0:22:37.920 --> 0:22:40.960 The crucial thing is not the mass, it's the density. 0:22:41.240 --> 0:22:44.200 If you compact enough stuff into a small enough space, 0:22:44.480 --> 0:22:47.280 then you can create a black hole. Is this combination 0:22:47.320 --> 0:22:49.760 of mass and radius. You know, for example, if you 0:22:49.800 --> 0:22:52.240 took the Earth, you could compact it into a peanut 0:22:52.320 --> 0:22:54.440 and that would be a black hole. So the mass 0:22:54.440 --> 0:22:56.400 of the Earth is enough to make a black hole, 0:22:56.520 --> 0:22:58.640 is just not dense enough. And so you can make 0:22:58.720 --> 0:23:01.879 many black holes by poor enough energy or enough mass 0:23:01.920 --> 0:23:04.280 into a small enough space. And that's what you do 0:23:04.320 --> 0:23:07.320 at the large Hadron collider. Right, you think you're making 0:23:07.320 --> 0:23:09.760 mini black holes, or you know you're making mini black holes. 0:23:09.920 --> 0:23:12.360 We hope we're making many black holes. We haven't yet 0:23:12.400 --> 0:23:14.720 seen any. But that is exactly what we do at 0:23:14.720 --> 0:23:17.359 the Hadron Collider and it Aeron Collider, is that we 0:23:17.400 --> 0:23:20.000 pour a lot of energy into a very small space 0:23:20.320 --> 0:23:22.679 and we let the universe decide what comes out. We 0:23:22.720 --> 0:23:26.119 take advantage of the quantum mechanical nature, the probabilistic nature 0:23:26.240 --> 0:23:28.359 of the rules of physics that say, if you have 0:23:28.440 --> 0:23:31.000 a little ball of energy there, it can basically turn 0:23:31.040 --> 0:23:33.480 into anything. It might turn into some new particle you 0:23:33.480 --> 0:23:36.560 haven't seen before, it might turn into a black hole, right, 0:23:36.600 --> 0:23:38.960 And so you sometimes you get enough energy pack into 0:23:39.000 --> 0:23:41.879 such a small space that you make a mini tiny 0:23:41.920 --> 0:23:44.719 black hole about the size of like a particle. And 0:23:44.760 --> 0:23:47.680 so those are actually black holes, just like the ones 0:23:47.720 --> 0:23:50.040 at the center of the galaxies. They're just really really small, 0:23:50.400 --> 0:23:52.720 and something special happens to them, right. They don't last 0:23:52.800 --> 0:23:54.560 very long, that's right. And so to be clear, we 0:23:54.640 --> 0:23:57.280 have not to our knowledge made any of these black holes. 0:23:57.320 --> 0:24:00.399 We have not seen any. It's hypothetical to fear radical 0:24:00.440 --> 0:24:03.840 idea that perhaps it's possible to make these black holes 0:24:04.040 --> 0:24:06.720 by colliding particles together. And so we are looking for them, 0:24:06.760 --> 0:24:08.639 and the thing you have to understand about many black 0:24:08.640 --> 0:24:11.000 holes is that they don't last very long. Like big 0:24:11.040 --> 0:24:13.439 black holes can last for billions of years as they 0:24:13.520 --> 0:24:16.719 keep eating stuff. But all black holes emit radiation. They 0:24:16.760 --> 0:24:20.160 don't actually keep all of their information is inside. They 0:24:20.240 --> 0:24:22.920 leak a little bit of mass all the time. It's 0:24:22.920 --> 0:24:26.359 called hawking radiation. And this happens faster if you're a 0:24:26.400 --> 0:24:29.240 small black hole. So a big black hole hardly emits 0:24:29.280 --> 0:24:31.680 any hawking radiation. It can last for a long time. 0:24:32.000 --> 0:24:35.880 A little black hole will very rapidly evaporate by giving 0:24:35.920 --> 0:24:38.120 away all of its mass in terms of hawking radiation. 0:24:38.200 --> 0:24:41.639 So the smaller the black hole is, the quicker it disappears, 0:24:41.680 --> 0:24:43.800 which is actually good because you want your black holes 0:24:43.840 --> 0:24:46.800 to evaporate rather than growing and gobbling up the earth. 0:24:46.920 --> 0:24:49.760 All right, So then the tiny black holes evaporate quickly. 0:24:49.800 --> 0:24:51.840 And the question I guess is can you detect that 0:24:51.880 --> 0:24:54.440 hawking radiation? And what would you learn from it? Yes, 0:24:54.480 --> 0:24:56.320 So these black holes, if you made them, they would 0:24:56.320 --> 0:25:00.159 basically explode almost instantaneously. The kind we're talking about making 0:25:00.200 --> 0:25:02.399 it the large Hadron collider would last like ten to 0:25:02.440 --> 0:25:05.480 the minus twenty seven seconds, and they would just admit 0:25:05.480 --> 0:25:08.240 a bunch of hawking radiation. But what is that hawking radiation? 0:25:08.320 --> 0:25:10.200 And how would you see it? The cool thing about 0:25:10.240 --> 0:25:13.560 black holes is that they couple gravitationally, right, They're connected 0:25:13.560 --> 0:25:15.920 to everything that has mass. They don't care about things 0:25:16.000 --> 0:25:19.040 electric charge or strong charge or weak charge, so there's 0:25:19.080 --> 0:25:21.879 sort of democratic. They turn into like all kinds of 0:25:21.920 --> 0:25:25.119 particles with basically equal probability, And so that means that 0:25:25.119 --> 0:25:27.760 what you would see is just a huge spray of 0:25:27.760 --> 0:25:30.720 a bunch of different particles, like a huge explosion at 0:25:30.720 --> 0:25:33.240 the center of your detector, with a lot more energy 0:25:33.280 --> 0:25:36.560 than you would typically seem I see, but you're eagually 0:25:36.600 --> 0:25:38.879 like to see like an electron or a proton or 0:25:39.320 --> 0:25:42.200 men kind of right. I mean, depending on how much 0:25:42.440 --> 0:25:45.000 energy they have, they might be more probable, but there's 0:25:45.000 --> 0:25:48.119 no constraint about what particular particles you'll see, that's what 0:25:48.160 --> 0:25:50.800 you're saying. Yeah, And because the particles that feel the 0:25:50.880 --> 0:25:54.880 strong force, like quarks and gluons, have so many more varieties, 0:25:54.880 --> 0:25:58.160 because for example, for the upcork, there's the red upcork, 0:25:58.240 --> 0:26:00.920 the green upcork, and the blue upcork, where the electron 0:26:01.119 --> 0:26:03.200 doesn't feel that, and so it only has one version. 0:26:03.400 --> 0:26:06.320 That means there are more versions of quirks and gluons, 0:26:06.359 --> 0:26:08.840 So you're more likely going to get quarks and gluons 0:26:08.880 --> 0:26:12.159 than electrons and muans, just because there are more of those, 0:26:12.480 --> 0:26:15.160 and black holes are democratic, So most likely what you're 0:26:15.160 --> 0:26:17.880 gonna see is a big spray of quarks and gluons 0:26:17.920 --> 0:26:20.000 that fly out, and quirks and gluons. We don't see 0:26:20.000 --> 0:26:23.480 those directly because quirks and gluons can't be by themselves, 0:26:23.520 --> 0:26:26.920 so instead each one turns into its own stream of particles. 0:26:26.920 --> 0:26:28.600 So what does a black hole look like? In our 0:26:28.640 --> 0:26:32.080 detector at CERN It looks like seven or ten streams 0:26:32.080 --> 0:26:34.800 of particles all coming out of the center of the collision. Well, 0:26:34.840 --> 0:26:37.400 I think the question that Tim had was like, could 0:26:37.480 --> 0:26:39.719 you learn or would you learn anything from that stream 0:26:39.800 --> 0:26:42.440 of particles? And it sort of seems like you wouldn't 0:26:42.440 --> 0:26:45.920 write because it just be a random spray of particles, right, Yeah, 0:26:45.920 --> 0:26:48.080 And this is a subtle point here, because you can't 0:26:48.080 --> 0:26:50.399 look at an individual collision that has like ten of 0:26:50.400 --> 0:26:52.880 these sprays of particles and say that's a smoking gun 0:26:52.920 --> 0:26:54.960 signature of a black hole, because there are other ways 0:26:55.000 --> 0:26:57.439 for that to happen. Sometimes two protons collide and you 0:26:57.520 --> 0:27:00.399 do get ten quarks flying out, which makes ten of 0:27:00.440 --> 0:27:02.840 these streams of particles. So that does happen. So we 0:27:02.880 --> 0:27:05.679 can't specifically say this was a black hole, that was 0:27:05.720 --> 0:27:07.200 a black hole. All we can do is say, look, 0:27:07.240 --> 0:27:09.800 we see more of these collisions that lead to ten 0:27:09.960 --> 0:27:13.320 or twelve sprays of particles than we expected from non 0:27:13.359 --> 0:27:16.800 black hole sources. So we can like statistically say we 0:27:16.840 --> 0:27:19.639 think we're making black holes because we see more of 0:27:19.680 --> 0:27:22.280 these weird kind of events than we can explain otherwise. 0:27:22.359 --> 0:27:24.600 And this weird kind of event is just what we 0:27:24.640 --> 0:27:27.480 expected to see from black holes. So we can't definitively 0:27:27.520 --> 0:27:30.520 say a black hole is created on Tuesday at four pm, 0:27:30.680 --> 0:27:32.920 but we can't say over the last year, we think 0:27:32.960 --> 0:27:34.520 we made ten of them. Well, I see, you can't 0:27:34.520 --> 0:27:37.000 study like a particular mini black hole. You can study 0:27:37.080 --> 0:27:39.960 kind of like a statistically what's going on in your collider. 0:27:40.080 --> 0:27:42.600 But I think Tim was sort of making the connection 0:27:42.840 --> 0:27:45.399 to this idea that we've talked about before, which is 0:27:45.400 --> 0:27:48.880 an inside of a black hole, quantum information is destroyed. 0:27:49.280 --> 0:27:52.480 So does that mean that when a mini black hole evaporates, 0:27:53.040 --> 0:27:56.439 there's no information in the Hawking radiation. Yeah, this is 0:27:56.440 --> 0:27:58.919 not something that we understand because we think that quantum 0:27:58.960 --> 0:28:02.080 information can't be stroids, and so we wonder if somehow 0:28:02.119 --> 0:28:05.600 that hockey information does have encoded in it the quantum 0:28:05.600 --> 0:28:08.119 information that went into the black hole. And we had 0:28:08.160 --> 0:28:10.640 recently a fun podcast episode where we talked about people 0:28:10.640 --> 0:28:13.160 who recently made a breakthrough about how this might work 0:28:13.359 --> 0:28:16.200 as super fascinating, but it's not something we understand very well. 0:28:16.240 --> 0:28:18.480 But the information is being destroyed in a black hole 0:28:18.760 --> 0:28:20.880 is just about the particles that went into it, which 0:28:20.880 --> 0:28:23.320 is like the two protons you smashed together. So you 0:28:23.359 --> 0:28:26.399 don't really care that much about that quantum information. It's 0:28:26.440 --> 0:28:28.640 not like useful or interesting. But if you do make 0:28:28.640 --> 0:28:31.359 black holes, you can learn something much more interesting about 0:28:31.359 --> 0:28:34.440 the universe. You can gain like contextual information because you 0:28:34.480 --> 0:28:37.480 can learn something about quantum gravity. If we make black 0:28:37.520 --> 0:28:40.400 holes with a large Hadron collider, it means that gravity 0:28:40.520 --> 0:28:43.800 is much stronger at very short distances than it is 0:28:43.840 --> 0:28:46.720 at long distances. Something weird and different is going on 0:28:47.000 --> 0:28:50.560 when two particles get really close together, their gravity gets different, 0:28:50.880 --> 0:28:53.760 and that's a clue about maybe the whole nature of space, 0:28:53.800 --> 0:28:57.200 about how many dimensions there are two space itself. Well, 0:28:57.320 --> 0:28:59.160 what do you mean, Like you would shoot things together, 0:28:59.320 --> 0:29:03.120 create many black goals, and then you would see how 0:29:03.200 --> 0:29:05.280 it interacts with the things around it. Like, can you 0:29:05.320 --> 0:29:08.000 actually get a sense of, you know, what happens as 0:29:08.000 --> 0:29:10.000 you get that close to mini black holes or is 0:29:10.040 --> 0:29:12.680 it maybe hidden in the fact that you do or 0:29:12.720 --> 0:29:14.720 do not get mini black holes. Yeah, it's the fact 0:29:14.720 --> 0:29:17.560 that you make black holes, and also their typical energy 0:29:17.800 --> 0:29:20.600 tells you something about how they are made. You can't 0:29:20.600 --> 0:29:23.160 study an individual black hole or like put things near 0:29:23.200 --> 0:29:25.120 it or anything like that. But one thing we are 0:29:25.160 --> 0:29:28.120 really curious about is why gravity seems to be so weak. 0:29:28.160 --> 0:29:30.400 You know, gravity is so much weaker than all of 0:29:30.400 --> 0:29:33.200 the other forces. Like we say, often you can defeat 0:29:33.240 --> 0:29:36.000 the entire gravity the Earth by using a simple kitchen 0:29:36.040 --> 0:29:38.640 magnet to pull on a screw, for example. So why 0:29:38.720 --> 0:29:42.040 is gravity so weak? It's not something we understand. One 0:29:42.120 --> 0:29:45.840 possible explanation is that maybe gravity is so weak because 0:29:45.960 --> 0:29:49.520 it's leaking out. It's like getting diluted. Because there are 0:29:49.640 --> 0:29:52.240 other ways that you can move through space other than 0:29:52.280 --> 0:29:55.719 the three were familiar with. So these are called extra dimensions, 0:29:55.760 --> 0:29:59.200 Like maybe space doesn't have just three dimensions, maybe it 0:29:59.240 --> 0:30:03.920 has eleven or twenty six, but only gravity can feel those, 0:30:04.000 --> 0:30:06.240 and so when you're far away from something, you're not 0:30:06.320 --> 0:30:09.200 really feeling it's true gravity because most of it's leaked 0:30:09.240 --> 0:30:11.840 out into these other dimensions. But these other dimensions might 0:30:11.840 --> 0:30:14.280 be really really small and compact, so if you get 0:30:14.320 --> 0:30:17.040 really close to something, you might feel it's like true 0:30:17.040 --> 0:30:19.440 strength of its gravity. So the idea is if you 0:30:19.480 --> 0:30:22.360 smash two protons together and you bring them really close 0:30:22.400 --> 0:30:25.080 together with enough energy, then they might feel that strong 0:30:25.120 --> 0:30:27.840 gravity enough to make a black hole. So the fact 0:30:27.880 --> 0:30:29.760 that you made the black hole would tap you off 0:30:30.000 --> 0:30:33.400 that gravity is getting strong at short distances and maybe 0:30:33.440 --> 0:30:36.840 reveal something about the existence of those other dimensions of 0:30:36.840 --> 0:30:38.920 space and time. So you're saying that if you do 0:30:38.960 --> 0:30:41.320 make black holes at the large Harding glider, then maybe 0:30:41.440 --> 0:30:45.000 that points to the existence of extra dimensions. Yes, exactly, 0:30:45.040 --> 0:30:47.360 so we can't learn that much from one black hole, 0:30:47.640 --> 0:30:49.920 but if we can prove that we have been making them, 0:30:50.000 --> 0:30:52.640 then that suggests that there must be extra dimensions space 0:30:52.640 --> 0:30:55.680 and time, and the pattern in which they appear, like 0:30:55.720 --> 0:30:58.640 the energy that they come with and how often we 0:30:58.720 --> 0:31:00.720 make them, can give us a clue to like how 0:31:00.760 --> 0:31:04.120 many dimensions are there and what radius do they have, 0:31:04.160 --> 0:31:06.640 because these aren't dimensions like the ones we're familiar with, 0:31:06.720 --> 0:31:08.719 like x, y, and z that we move around in. 0:31:08.840 --> 0:31:11.480 These are like a little looped dimensions. They're like moving 0:31:11.520 --> 0:31:14.520 a little circle, or they are only like a centimeter wide. 0:31:14.760 --> 0:31:17.560 They're really weird and strange dimensions. But lots of theories 0:31:17.560 --> 0:31:21.320 of physics actually insist on having more dimensions, like string theory. Yeah, 0:31:21.360 --> 0:31:23.840 and conveniently that's another topic we cover in our book. 0:31:24.600 --> 0:31:26.520 But it sort of sounds like the answer for tim 0:31:26.520 --> 0:31:29.760 here is that we haven't detected any mini black holes 0:31:29.840 --> 0:31:32.400 in you're in the colliders, but if you if you 0:31:32.440 --> 0:31:35.360 do create them, hey, you would see this big shower 0:31:35.360 --> 0:31:39.320 of sort of random particles, maybe mostly quirks, and be 0:31:39.520 --> 0:31:42.320 would point to the existence of extra dimensions. That's right, 0:31:42.360 --> 0:31:45.960 that's one explanation. There are other theories that also predict 0:31:45.960 --> 0:31:48.080 the creation of black holes, and so if we did 0:31:48.120 --> 0:31:50.560 see them, the theories would go crazy coming up with 0:31:50.600 --> 0:31:52.920 new ideas to explain our data. It would be very 0:31:53.040 --> 0:31:55.080 very exciting. And for those of you nervous about the 0:31:55.080 --> 0:31:57.520 safety aspect of this, don't worry. We've done all the 0:31:57.560 --> 0:32:00.200 calculations and we're confident we can't make black hole is 0:32:00.240 --> 0:32:05.080 big enough to eat. That's good to know, always reassuring 0:32:05.280 --> 0:32:08.239 that you've done the calculations and that you never make mistakes. Right, 0:32:08.280 --> 0:32:10.680 that's right. We've never ever made a mistake that destroyed 0:32:10.720 --> 0:32:13.440 the Earth. Right, that's a pretty good track record. Yeah, yeah, 0:32:13.440 --> 0:32:16.240 so far zero for zero. All right, well, let's get 0:32:16.240 --> 0:32:19.120 into our last question about black holes from a listener, 0:32:19.240 --> 0:32:22.000 and this one has to do with dark matter. But 0:32:22.040 --> 0:32:37.000 first let's take another quick break. All right, we're answering 0:32:37.080 --> 0:32:40.440 questions from listeners about black holes because they're so cool 0:32:40.520 --> 0:32:44.120 and mysterious and dark. And our last question comes from Jue, 0:32:44.280 --> 0:32:47.960 who has a question about whether black holes can explain 0:32:48.720 --> 0:32:51.680 a little bit of missing mass. If there's missing gravity 0:32:51.720 --> 0:32:54.840 in the galaxy, why can't we attribute it too the 0:32:55.080 --> 0:32:57.880 black hole in the center of it since we don't 0:32:57.880 --> 0:33:00.640 know it's mass. M interesting question, and first of all, 0:33:00.800 --> 0:33:03.400 we're missing mass, like did we misplace some mass in 0:33:03.400 --> 0:33:06.240 the galaxy? Oops? I thought you were going to bring 0:33:06.240 --> 0:33:08.480 it home? Where is it that the galaxy going a 0:33:08.560 --> 0:33:11.280 quick diet or something? In a go keto? You look 0:33:11.320 --> 0:33:13.720 in great these days, milky Way. Maybe it's like only 0:33:13.760 --> 0:33:16.520 two percent milky way or like low fat milky way 0:33:16.920 --> 0:33:20.000 skin milky way. All right, so there is some missing 0:33:20.040 --> 0:33:22.480 mass in the galaxy, right, I know this one. It's like, 0:33:22.520 --> 0:33:24.760 if you measure how the stars in the galaxy are 0:33:24.800 --> 0:33:29.240 spinning around, they are spinning around faster than they would 0:33:29.320 --> 0:33:32.560 be if there was only stars and planets in the galaxy. Right, 0:33:32.560 --> 0:33:36.400 there's something else missing from the mass of how we 0:33:36.440 --> 0:33:39.480 see the galaxy spinning exactly, just like we were talking about. 0:33:39.760 --> 0:33:42.040 You can deduce the mass that the Sun has to 0:33:42.120 --> 0:33:44.560 be to explain the Earth's motion. You can do the 0:33:44.600 --> 0:33:47.200 same thing with the whole galaxy. Measure the motion of 0:33:47.240 --> 0:33:50.240 the stars and from that deduce the mass of all 0:33:50.280 --> 0:33:52.440 the stuff that has to be pulling on those stars 0:33:52.480 --> 0:33:55.080 to keep them moving in a circle. It's exactly the 0:33:55.120 --> 0:33:58.200 same strategy, right, And this is kind of how people 0:33:58.200 --> 0:34:00.960 first started thinking about dark matter, which is that they 0:34:01.000 --> 0:34:04.320 saw that the galaxies were spinning faster than they would 0:34:04.560 --> 0:34:08.120 be if if the stars were to stay in the galaxy, 0:34:08.320 --> 0:34:11.920 and so they hypothesized like, hey, maybe there's some invisible mass. 0:34:12.160 --> 0:34:14.239 We'll call it dark matter, and that's what's keeping all 0:34:14.280 --> 0:34:16.680 the stars in the galaxy I usually think about it 0:34:16.760 --> 0:34:19.520 the other direction. They measure the velocity of the stars, 0:34:19.560 --> 0:34:21.560 and then they asked, how much gravity do you need 0:34:21.600 --> 0:34:24.239 to explain that motion to keep the stars from flying up? 0:34:24.640 --> 0:34:26.919 And then they couldn't find that much mass. They looked 0:34:26.960 --> 0:34:29.120 at all the stars and all the dust and all 0:34:29.120 --> 0:34:31.680 the things they could see, and it just didn't add up. 0:34:31.719 --> 0:34:34.920 It wasn't even close. So that was a big puzzle 0:34:34.960 --> 0:34:39.120 for decades, right, And so the idea of a lot 0:34:39.160 --> 0:34:42.359 of invisible mass out there in the universe is kind 0:34:42.360 --> 0:34:43.759 of crazy. So a lot of people are like, are 0:34:43.760 --> 0:34:46.200 you sure that sounds crazy? How do you know that 0:34:46.719 --> 0:34:49.320 maybe the black hole at the center of the galaxy 0:34:49.400 --> 0:34:51.640 isn't just heavier than you think it is. Maybe that 0:34:51.680 --> 0:34:54.680 would explain why the stars are not flying off into space. Yeah, 0:34:54.719 --> 0:34:57.799 it's a great question because it points to like our uncertainty, 0:34:57.880 --> 0:35:00.000 like how do you know how massive those stars are? 0:35:00.040 --> 0:35:01.840 And how do you know the other things in the galaxy? 0:35:01.920 --> 0:35:03.759 How well do you know their mass? And so it's 0:35:03.800 --> 0:35:06.160 just like pointing at you know, other places we could 0:35:06.200 --> 0:35:09.239 be making mistakes, which is a great scientific exercise, like 0:35:09.360 --> 0:35:11.520 to go back and think, maybe we just missestimated the 0:35:11.600 --> 0:35:14.359 number of stars, or maybe we missestimated their mass, or 0:35:14.480 --> 0:35:17.040 maybe it's all hiding at the center of the galaxy 0:35:17.120 --> 0:35:19.719 inside that black hole. Yeah, so the question is like, 0:35:19.800 --> 0:35:22.040 could a bigger black hole at the center of the 0:35:22.040 --> 0:35:26.080 galaxy explain how all the stars are moving around the 0:35:26.120 --> 0:35:28.800 galaxy or does it have to be something like dark matter. 0:35:28.960 --> 0:35:31.560 So there's sort of three answers, two knows, and then 0:35:31.760 --> 0:35:35.040 maybe yes. So the first know is that we actually 0:35:35.080 --> 0:35:37.319 kind of do know the mass of the black hole 0:35:37.360 --> 0:35:39.480 at the center of the galaxy. It's not just some 0:35:39.719 --> 0:35:42.359 huge cosmic noob that we can turn up and down 0:35:42.400 --> 0:35:44.480 and say nobody knows, So we can just set it 0:35:44.520 --> 0:35:47.080 to anything. As we talked about just a few minutes ago. 0:35:47.320 --> 0:35:49.520 We can measure the mass of black holes by looking 0:35:49.840 --> 0:35:52.120 at the movement of stars near it. And the one 0:35:52.239 --> 0:35:54.800 near the center of our Milky Way is actually super 0:35:54.840 --> 0:35:58.040 awesome because there's a star that gets really really close 0:35:58.080 --> 0:35:59.799 to it. It whizz is right by, It ends up 0:35:59.800 --> 0:36:02.640 going super fast and allows us to make a pretty 0:36:02.640 --> 0:36:04.960 precise measurement of the mass of the black hole at 0:36:04.960 --> 0:36:06.960 the center of the Milky Way. I see, so there 0:36:07.080 --> 0:36:09.759 isn't like a mysterious black hole at the center of 0:36:09.760 --> 0:36:12.399 the galaxy. There's one that we can measure. Yeah, we've 0:36:12.440 --> 0:36:14.640 measured its mass pretty well, and there's a bunch of 0:36:14.680 --> 0:36:17.680 stars moving around it. And this is this really awesome 0:36:17.800 --> 0:36:20.160 video you should watch. It took like decades to make 0:36:20.520 --> 0:36:23.120 of them observing the black hole and seeing the motion 0:36:23.160 --> 0:36:25.120 of the stars around it, and you can watch it 0:36:25.120 --> 0:36:26.879 in time lapse. You know, it took them twenty years, 0:36:26.920 --> 0:36:28.720 but you can watch the whole thing in twenty seconds, 0:36:28.760 --> 0:36:31.960 and you can see these stars moving around some obvious, 0:36:32.040 --> 0:36:35.960 invisible object, like they're bending their path around what seems 0:36:35.960 --> 0:36:38.880 to be nothing and therefore must be something. Right, And 0:36:38.920 --> 0:36:41.720 it's pretty massive, I imagine, right, it's a pretty massive 0:36:41.719 --> 0:36:43.879 black hole at the center of our galaxy. Yeah, it's 0:36:43.920 --> 0:36:47.520 pretty heavy. It has four point one million times the 0:36:47.560 --> 0:36:50.560 mass of our star, so it's pretty hefty. And I 0:36:50.640 --> 0:36:52.360 just want to make a plug for U. C. L 0:36:52.400 --> 0:36:56.400 a that won the Nobel Prize for these observations very recently. 0:36:56.600 --> 0:36:58.680 So go check out that video. It's pretty cool, but 0:36:58.719 --> 0:37:01.640 it's a pretty massive black hole hole, but it can't 0:37:01.680 --> 0:37:04.480 explain all of the dark matter. Number one, because we 0:37:04.600 --> 0:37:06.759 know it's mass, but number two also, it's in the 0:37:06.800 --> 0:37:10.040 wrong place to explain the dark matter, right, Like, even 0:37:10.080 --> 0:37:12.439 if we didn't know the mass of the black hole 0:37:12.480 --> 0:37:14.480 at the center of the galaxy, Like, even if we 0:37:14.520 --> 0:37:17.000 were wrong, one giant mass at the center of the 0:37:17.040 --> 0:37:19.800 galaxy wouldn't explain how the all the stars are moving. 0:37:19.880 --> 0:37:22.799 That's exactly right, because even if you increase the mass 0:37:22.800 --> 0:37:26.000 of the black hole to account for all the missing stuff, 0:37:26.040 --> 0:37:29.000 it wouldn't give you stars moving the way our stars 0:37:29.040 --> 0:37:30.880 are moving. And that's because we can look at the 0:37:30.920 --> 0:37:33.400 velocity of stars very close to the center of the 0:37:33.400 --> 0:37:36.560 galaxy and the velocity stars further away from the center 0:37:36.560 --> 0:37:38.600 of the galaxy. So what we need is dark matter 0:37:38.600 --> 0:37:41.840 to explain all of those different velocities stars closer to 0:37:41.880 --> 0:37:44.400 the center and stars further from the center, and every 0:37:44.400 --> 0:37:47.200 star it's motion tells you about how much mass is 0:37:47.239 --> 0:37:49.880 sort of in a sphere that's closer to the center 0:37:49.920 --> 0:37:52.400 of the galaxy. Event it like, stars are not affected 0:37:52.440 --> 0:37:55.080 by stuff that's further away from them, only by stuff 0:37:55.080 --> 0:37:57.680 that's closer to them. So as you look at stars 0:37:57.719 --> 0:38:00.400 as a function of their distance, you know is that 0:38:00.480 --> 0:38:02.880 you need a distribution of mass that's sort of spread 0:38:02.960 --> 0:38:05.560 out to the galaxy. If you only put a huge 0:38:05.560 --> 0:38:07.560 blob of mass at the very center. It would make 0:38:07.560 --> 0:38:10.319 the stars near the core of the galaxy move way 0:38:10.360 --> 0:38:13.719 too fast, for example, right, right, because that's kind of 0:38:13.760 --> 0:38:16.640 an interesting property of mass. It's like, you know, if 0:38:16.640 --> 0:38:18.799 you're really far away from it, you might as well 0:38:18.960 --> 0:38:21.120 treat it as a like a thought. But if you're 0:38:21.200 --> 0:38:23.759 really close to it, then it does matter whether or 0:38:23.800 --> 0:38:26.200 not it's like diffused in the little tiny ball in 0:38:26.200 --> 0:38:28.799 the middle or in a giant cloud that actually there 0:38:28.840 --> 0:38:31.600 is actually sort of engulfs you. Right, Yeah, if you're 0:38:31.680 --> 0:38:34.600 inside of it, then you're only sensitive to the parts 0:38:34.600 --> 0:38:36.839 of it that are closer to the center. Just like 0:38:36.880 --> 0:38:40.120 if you drill the whole inside the Earth and jumped inside, 0:38:40.440 --> 0:38:43.000 the force of gravity on you would decrease as you 0:38:43.000 --> 0:38:44.959 are closer and closer because a lot of the stuff 0:38:44.960 --> 0:38:48.040 would now be outside of your shell. You could ignore it, 0:38:48.200 --> 0:38:49.919 and when you get to the very center, there would 0:38:49.920 --> 0:38:51.960 be no force of gravity, so you can no longer 0:38:52.040 --> 0:38:54.240 treat and the Earth is like just a point particle. 0:38:54.320 --> 0:38:55.840 Was the mass of the Earth, and so it's the 0:38:55.880 --> 0:38:57.920 same thing with the galaxy. In order to explain the 0:38:58.000 --> 0:39:00.720 velocity of stars, we have to distribute be the mass 0:39:00.719 --> 0:39:03.000 in just the right way to make these stars go 0:39:03.080 --> 0:39:05.120 fast and these starts to go a little slower. So 0:39:05.160 --> 0:39:07.480 the cool thing about this velocity measurement is that we're 0:39:07.480 --> 0:39:10.640 not only sensitive to the overall amount of missing mass, 0:39:10.719 --> 0:39:14.319 but also how it's distributed through the galaxy. Right. I 0:39:14.400 --> 0:39:17.400 like that analogy about the Earth because like, if you 0:39:17.440 --> 0:39:19.160 fall to the center of the Earth, and you're at 0:39:19.200 --> 0:39:21.560 the center of the Earth, basically the Earth is all 0:39:21.600 --> 0:39:23.880 around you and it's pulling you in every direction, so 0:39:23.920 --> 0:39:26.359 you're basically weightless right in the middle of the Earth. Yeah, 0:39:26.360 --> 0:39:28.799 there's no force of gravity at the center of the Earth. Yeah, 0:39:28.840 --> 0:39:31.160 And so the same would be with a galaxy. Like 0:39:31.280 --> 0:39:34.120 if you're at the center of the galaxy and you 0:39:34.160 --> 0:39:36.600 would feel the dark matter pulling all around you, so 0:39:36.640 --> 0:39:39.439 you wouldn't feel this mass, but if you were out 0:39:39.440 --> 0:39:42.280 in the edge of the galaxy, you would feel the 0:39:42.320 --> 0:39:45.000 mass of the dark matter like it was a point 0:39:45.040 --> 0:39:47.879 in the middle. Yeah, exactly. So imagine now a star 0:39:48.000 --> 0:39:50.200 that's very close to the center of the galaxy. If 0:39:50.239 --> 0:39:52.239 you took all the dark matter and you put it 0:39:52.280 --> 0:39:54.839 inside the black hole, that would mean that that star 0:39:54.960 --> 0:39:57.520 is feeling all of that gravity, would be moving really 0:39:57.520 --> 0:40:00.239 really fast. If instead you took that dark matter, you 0:40:00.280 --> 0:40:02.320 spread it out through the galaxy, then most of it 0:40:02.360 --> 0:40:05.080 wouldn't affect that star near the core, because, as you say, 0:40:05.200 --> 0:40:06.840 it would all be balanced out, it will all be 0:40:06.840 --> 0:40:09.359 on the outside of it. It would be null. And 0:40:09.480 --> 0:40:12.239 so you can tell how it's distributed by looking at 0:40:12.239 --> 0:40:14.319 the velocity stars that are close to the center and 0:40:14.320 --> 0:40:16.240 then a little further away. In a little further away, 0:40:16.320 --> 0:40:18.680 a distributed mass of dark matter makes a very different 0:40:18.680 --> 0:40:21.920 prediction than dark matter concentrated all at the core of 0:40:21.960 --> 0:40:24.239 the galaxy. All right, So then that's the answer of 0:40:24.280 --> 0:40:27.480 the answer is that a black hole cannot explain the 0:40:27.480 --> 0:40:30.680 missing mass in the galaxies and the trajectory of stars. 0:40:30.880 --> 0:40:34.160 You kind of need something large and diffused like how 0:40:34.200 --> 0:40:37.279 we think dark matter is. But there's also a possible 0:40:37.360 --> 0:40:40.440 yes maybe to his answer, which is that we don't 0:40:40.560 --> 0:40:43.120 think that all of the dark matter is in the 0:40:43.120 --> 0:40:45.640 black hole the center of our galaxy. But remember that 0:40:45.680 --> 0:40:48.319 we don't know what dark matter is, and there's a 0:40:48.320 --> 0:40:51.320 possibility that dark matter, though it's spread out through the galaxy, 0:40:51.640 --> 0:40:54.759 might be a bunch of smaller black holes, right like 0:40:54.840 --> 0:40:57.920 primordial black holes. Right, Yes, black holes made in the 0:40:58.000 --> 0:41:00.759 very first few moments before there was and stuff and 0:41:00.840 --> 0:41:03.880 matter in the universe. They could still be around and 0:41:03.960 --> 0:41:06.200 they could account for the dark matter. It's one of 0:41:06.200 --> 0:41:08.560 the theories that are out there. It's maybe not the 0:41:08.600 --> 0:41:11.799 most common or highly voted theory of dark matter, but 0:41:11.840 --> 0:41:14.479 it's still possible. It's still plausible, and we haven't figured 0:41:14.520 --> 0:41:16.120 out what dark matter is, so it could just be 0:41:16.200 --> 0:41:18.960 a bunch of black holes spread out through the galaxy. Wow, 0:41:19.160 --> 0:41:21.839 that sounds a little horrifying to know then, Like if 0:41:21.840 --> 0:41:24.800 you were flying through space, it's like riddled with minds 0:41:24.880 --> 0:41:26.719 kind of right. You might be flying through space and 0:41:26.920 --> 0:41:29.360 there's a hole. You've flying through a cloud of little 0:41:29.440 --> 0:41:31.960 tiny black holes. That wouldn't be good for your spaceship, right, 0:41:32.000 --> 0:41:33.640 that would not be good for your spaceship. But you know, 0:41:33.800 --> 0:41:37.120 it's eaten zero earths so far, so it must be 0:41:37.160 --> 0:41:41.520 pretty safe so far. Zero. No, We've been flying through 0:41:41.520 --> 0:41:44.719 the galaxy for billions of years, right, and we have 0:41:44.760 --> 0:41:47.000 not yet run into a black hole. On the other hand, 0:41:47.280 --> 0:41:49.040 we don't know if there are other planets out there 0:41:49.080 --> 0:41:51.520 that have fallen into primordial black holes, because they've they 0:41:51.520 --> 0:41:53.520 had we wouldn't see them, so it's not really a 0:41:53.560 --> 0:41:56.479 great argument. All right. Well, then the answer is that 0:41:56.680 --> 0:41:58.560 a black hole at the center of the galaxy wouldn't 0:41:58.560 --> 0:42:02.120 explain dark matter. But maybe dark matter is explained by little, 0:42:02.160 --> 0:42:05.719 tiny black holes everywhere. But it's great thinking one to 0:42:05.840 --> 0:42:08.399 try to come up with some other explanation for dark 0:42:08.440 --> 0:42:10.400 matter in terms of like the things we do know 0:42:10.560 --> 0:42:13.160 and our uncertainties about them. It's a great way to 0:42:13.160 --> 0:42:17.000 exercise your brain and do physics and think about different hypotheses. 0:42:17.040 --> 0:42:20.320 So great idea. Cool. So those are three awesome questions 0:42:20.360 --> 0:42:23.040 about black holes than you do think. We've on our 0:42:23.120 --> 0:42:26.040 job here to fill the black hole of questions about 0:42:26.080 --> 0:42:28.520 black holes a little bit. Yeah. The problem is that 0:42:28.560 --> 0:42:31.200 the black hole questions just grow the more you feed them. 0:42:31.239 --> 0:42:33.799 The bigger gets, the stronger it's pulled, the more we 0:42:33.840 --> 0:42:36.120 want to know. It's just kind of like science that way. 0:42:36.160 --> 0:42:38.359 The more we ask questions and get answers, the more 0:42:38.440 --> 0:42:41.240 questions we have. Yeah, and hopefully we won't get stuck 0:42:41.239 --> 0:42:43.480 in them forever. At some point we'll get out of 0:42:43.520 --> 0:42:45.439 them or maybe Inside the black Hole is a really 0:42:45.480 --> 0:42:48.000 wonderful book, filled with the secrets of the universe and 0:42:48.040 --> 0:42:51.200 a cozy reading nook to enjoy it in Yeah, who 0:42:51.239 --> 0:42:54.120 doesn't love a good book about the universe? Titled Frequently 0:42:54.160 --> 0:42:57.800 Asked Questions about the un that's right Hypothetically at universe 0:42:57.880 --> 0:42:59.680 f a q dot com. You'll have to run an 0:42:59.680 --> 0:43:02.680 expair meant to see if it's a real website universe 0:43:02.760 --> 0:43:04.719 f a q dot com. You might find a black hole, 0:43:04.800 --> 0:43:07.000 or you might find a lot of interesting knowledge that's 0:43:07.080 --> 0:43:09.480 right and funny cartoon, and so go check it out, 0:43:09.520 --> 0:43:11.400 Go be a scientist. Those of you who write in 0:43:11.480 --> 0:43:14.200 asking how can we support the podcast, this is how 0:43:14.239 --> 0:43:16.440 you can support the podcast. Please go out there and 0:43:16.520 --> 0:43:18.440 check out our book. We put a lot of energy 0:43:18.480 --> 0:43:19.960 and a lot of fun and a lot of love 0:43:19.960 --> 0:43:22.359 into it, and we hope that you all enjoy it. Yeah. 0:43:22.360 --> 0:43:24.719 And more importantly, it's also those of you wondering, like 0:43:24.760 --> 0:43:27.640 how can I tell my friends or my cousin or 0:43:27.680 --> 0:43:30.080 my uncle or my mom, Like how cool all of 0:43:30.120 --> 0:43:32.080 this stuff is this book? I think it's a great 0:43:32.120 --> 0:43:34.280 way into these topics. You think it's going to convert 0:43:34.440 --> 0:43:37.600 the physics skeptics out there are an all physicists skeptics. 0:43:37.920 --> 0:43:41.239 I thought that was your thing, like that was your identifier. Yeah, 0:43:41.280 --> 0:43:45.600 but some people are skeptics about physicists, skeptic about skepticism, 0:43:45.920 --> 0:43:48.520 meta skeptics. All right, well, please go check it out 0:43:48.719 --> 0:43:51.520 and please send us more of your questions. Was really 0:43:51.520 --> 0:43:53.800 fun to get and really fun to answer on the podcast. 0:43:53.920 --> 0:43:56.680 That's right. Please don't hesitate right to us any questions 0:43:56.719 --> 0:43:59.560 you have about physics, except of course, homework problems to 0:44:00.040 --> 0:44:02.719 Westerns at Daniel and Jorge dot com. I hope you 0:44:02.800 --> 0:44:05.520 enjoyed that. Thanks for joining us, see you next time. 0:44:13.320 --> 0:44:16.200 Thanks for listening, and remember that Daniel and Jorge explained. 0:44:16.200 --> 0:44:19.120 The Universe is a production of I Heart Radio or 0:44:19.239 --> 0:44:22.160 more podcast for my heart Radio, visit the I Heart 0:44:22.239 --> 0:44:25.839 Radio app, Apple Podcasts, or wherever you listen to your 0:44:25.880 --> 0:44:26.640 favorite shows.