Pod Insights StarTalk Podcast The Updated Physics of Black Holes with Steve Balbus & Andrew Mummery About this episode What’s happening just outside a black hole? Neil deGrasse Tyson and co-host Gary O’Reilly travel to Oxford University to explore the mysterious universe of black holes, their accretion disks, and the impact they have on the world around them with astrophysicist Steve Balbus and theoretical physicist Andy Mummery.
Transcript Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.
0:00 Neil deGrasse Tyson? He's in a different gravitational field from the ones who went down to the planet, which was near the black hole. They'd lived fifteen minutes or something, and the guy up there went ten years or some.
0:10 Speaker 01 Yeah, I think they should have been more.
0:11 Neil deGrasse Tyson? But yeah, yeah, crazy ratio of time.
0:14 Speaker 01 Time dilation.
0:14 Neil deGrasse Tyson? Time dilation, crazy time dilation. So I was going to try to calculate how close that orbit had to be, and then I said, no, I'm not gonna, I will wait till I get somebody else to do this. It sounds like you're the guy for that.
0:28 Neil deGrasse Tyson? Welcome to StarTalk, your place in the universe where science and pop culture collide. StarTalk begins right now.
0:42 Neil deGrasse Tyson? Gary, we're in the UK now.
0:44 Speaker 01 Good.
0:44 Neil deGrasse Tyson? This is your place.
0:45 Speaker 01 It is. I'm here as your interpreter.
0:48 Neil deGrasse Tyson? We're in the town of Oxford.
0:50 Speaker 01 Is it city or town?
0:52 Neil deGrasse Tyson? Oh, I don't know, but I.
0:53 Speaker 01 We'll give it city sake.
0:54 Neil deGrasse Tyson? All I care is that there's a university here, and I have colleagues. My people.
0:58 Speaker 01 You've got peeps.
0:58 Neil deGrasse Tyson? I got people.
0:59 Speaker 01 All right.
0:59 Neil deGrasse Tyson? I got people.
1:00 Speaker 01 Okay.
1:00 Neil deGrasse Tyson? All right, very good.
1:02 Speaker 01 We're gonna meet any?
1:03 Neil deGrasse Tyson? Yeah, and, and by the way, like, where's Chuck?
1:05 Speaker 01 Chuck is otherwise disposed.
1:07 Neil deGrasse Tyson? Okay, and I figure I'll, I'll settle for a Brit.
1:10 Speaker 01 Okay.
1:10 Neil deGrasse Tyson? As my co-host.
1:11 Speaker 01 I am not the new Chuck.
1:13 Neil deGrasse Tyson? Episode, okay. I have a colleague who I met many, many years ago.
1:17 Speaker 01 All right.
1:17 Neil deGrasse Tyson? Like decades ago.
1:18 Speaker 01 All right, he still wants to know you?
1:22 Neil deGrasse Tyson? And I found him and I called him and said, I'm in town, and he like invited me to come chill with him.
1:27 Speaker 01 Nice.
1:27 Neil deGrasse Tyson? Sitting right here.
1:29 Speaker 01 Is that who he is?
1:31 Neil deGrasse Tyson? Steve Balbus, Steve. Hello, Neil, good to see you again. Welcome to StarTalk. Thank you, pleasure to be here. Dude, you're a fellow astrophysicist? Yes. And, you know, he has astrophysical phenomenon named after him.
1:45 Speaker 01 Did you know? Are we having a phenomenon envy?
1:50 Speaker 01 Are we, are we, are we having a little bit of phenomenon envy at all?
1:53 Neil deGrasse Tyson? Is that a thing? I didn't know.
1:54 Speaker 01 It is now.
1:54 Neil deGrasse Tyson? The psychologists haven't gotten to that one yet.
1:56 Speaker 01 I see, I see, if I've just invented it, I'm claiming it.
1:59 Neil deGrasse Tyson? No, so, uh, tell me about this thing that carries your name in our field.
2:05 Speaker 02 So, uh, it's work, based on work-
2:07 Neil deGrasse Tyson? You're a theorist.
2:09 Speaker 02 Yeah, well, I do theory.
2:10 Neil deGrasse Tyson? Yeah.
2:10 Speaker 02 A pencil, a lot of pencil and paper, and of course nowadays, computational work.
2:14 Neil deGrasse Tyson? Yeah.
2:15 Speaker 02 And in particular, back in the 90s, I did some work with a colleague named John Hawley.
2:21 Neil deGrasse Tyson? Uh huh.
2:22 Speaker 02 And-
2:22 Neil deGrasse Tyson? The late John Hawley.
2:23 Speaker 02 The late John Hawley. So he, yeah, he passed away a few years ago, unfortunately. And, um, at the time, we were trying to figure out how you make black holes.
2:36 Neil deGrasse Tyson? Oh.
2:36 Speaker 02 And the hard part of doing that, gravity is present, and of course, gravity ultimately is the reason that things make compact objects.
2:47 Neil deGrasse Tyson? Wait, wait, you're, you go so far back to a time before we knew how to make black holes? That's how old you were?
2:53 Speaker 02 That's how old I am.
2:54 Neil deGrasse Tyson? Okay.
2:54 Speaker 02 I would go back to a time when black holes were controversial.
2:58 Neil deGrasse Tyson? Oh, okay.
2:59 Speaker 02 You know, that polite astrophysicist-
3:01 Neil deGrasse Tyson? And since then, Nobel prizes have been given for black holes.
3:04 Speaker 02 We take pictures of them and put them on our iPhones. But there was a time when respectable astrophysicists didn't talk about it in mixed company.
3:13 Neil deGrasse Tyson? Okay.
3:14 Speaker 02 Yeah, you know, if you read it, you put a fake cover on it.
3:16 Neil deGrasse Tyson? Oh, alright.
3:18 Speaker 02 People wouldn't know. But the hard part was, if you have a black hole forming, the last stages, stuff is going around in a disk, a little bit like the planets go around the solar system. Our solar system was once a disk, that's probably how the sun was made. But the planets in the solar system just go around in orbits. Whereas, the gas in a disk around the black hole, or any other type of sort of compact object that's being made, has to get out of those orbits and down into the center. So how does it do that? And people talk about friction now.
4:02 Speaker 02 The gas rubs against itself, planets don't do that. But when you put in the numbers to see whether that would work or not, it would fail by orders of magnitude.
4:13 Neil deGrasse Tyson? The powers of 10.
4:14 Speaker 02 Yeah, powers of 10, yeah. Yeah, millions, it was millions of times too inefficient.
4:21 Neil deGrasse Tyson? Which is a fun state of mind of research to be in. Where you think you're on top of the physics or something. You calculate it out and you're off by factors of thousands.
4:31 Speaker 02 Yeah.
4:31 Neil deGrasse Tyson? And then, but you still go to work the next day.
4:36 Speaker 02 Exactly. You don't let that kind of thing bother you. Or, or you should find another line of work.
4:41 Speaker 01 It's a stimulation to seek.
4:43 Speaker 02 You know that you're almost, that you're on to something, but there's an important piece that you're missing.
4:48 Neil deGrasse Tyson? Evidently. Yeah, okay.
4:50 Speaker 02 So, what people suspected, and with good reason, is the reason that the discs work the way they do is it's not just friction, but the gas itself is turbulent. So it's a little bit like the, what you see in your sink when you turn on the faucet. There's a lot of, or in a river, there's a lot of churning and bubbling. And under those circumstances, the friction in the flow can indeed be thousands or tens of thousands, millions of times.
5:24 Neil deGrasse Tyson? Higher.
5:25 Speaker 02 Higher, more efficient.
5:26 Speaker 01 So you say you can get like an eddy?
5:29 Speaker 02 You get lots of eddies.
5:30 Speaker 01 So that random thing spinning and spearing up?
5:34 Speaker 02 Exactly. Exactly. They, they rub against each other. That's exactly what the professionals call them.
5:41 Neil deGrasse Tyson? I knew a turbulent eddy.
5:42 Speaker 01 I think we all do. Probably, probably not the same guy, but there's always a turbulent eddy.
5:47 Neil deGrasse Tyson? Actually, I got that from Al Roker. I, I mentioned the phrase turbulent eddy. And, and he said, I knew a turbulent eddy. And I, I felt, I walked right into it. I said, what's he doing now? He said, five to 10.
6:01 Speaker 02 You're the straight man.
6:02 Neil deGrasse Tyson? I didn't know I walked into the straight man.
6:05 Speaker 01 Torneville, we're here all week.
6:06 Neil deGrasse Tyson? That was with Al Roker a few years ago.
6:08 Speaker 02 Al Roker's turbulent eddies, that's what we're talking about. So the, but you want to understand why they're there. Um, because when you actually write down the mathematical equations for the flow and you analyze whether it should break down into this kind of structure, the answer is no.
6:26 Speaker 01 Interesting.
6:27 Speaker 02 There just wasn't any way that you could do that. So it occurred to me that there was one thing that people were leaving out, which seemed kind of inconsequential. But because of other work I had done, I wondered whether it might be a good idea to put it back in. And that is that every magnet, every disk in astrophysics.
6:48 Neil deGrasse Tyson? This is the accretion disk.
6:50 Speaker 02 This is the accretion disk around.
6:52 Neil deGrasse Tyson? Circulating toilet bowl style.
6:54 Speaker 02 Exactly, the whirlpool. Any kind of a disk or even any astrophysical gas, wherever it might be, has some kind of a magnetic field in it. There's magnetic field in this room.
7:08 Neil deGrasse Tyson? Yep.
7:09 Speaker 02 And if there are enough charged particles to make a current, then the magnetic field can affect the way that that gas flows. And you don't need very much. Even a very little bit will work quite well for that gas to act as though it's magnetized.
7:29 Neil deGrasse Tyson? So you published this, Balbus and Hawley.
7:31 Speaker 02 Mm-hmm.
7:32 Neil deGrasse Tyson? And then, the polite way is you just publish it and let other people say, "The Balbus and Hawley paper talked about this instability." "Oh, the Balbus and Hawley instability." And then it just becomes part of our lexicon. Is that how that happened? Or did you have a campaign?
7:49 Speaker 02 No, I can't say that I had a conscious campaign. Yes, he did. Look at that face. Yeah. And in fact, it's known by a few names. It's not known, I should say, exclusively by Balbus. It's also called magnetorotational instability. Because that describes why, what breaks, what it actually, it's a combination of the magnetic field and the rotation that renders the gas unstable and makes it break down into these kind of turbulent eddies. And what John was able to do, John Hawley, my colleague, at the time, which nobody, very few people in the world could do, was to set up a computer program.
8:33 Speaker 02 Which could actually follow the equations at a level of detail that we could actually see not just the breakdown of the circular orbits, but the emergence of turbulence itself and actually visualize that.
8:48 Speaker 01 Was it able to predict emergence?
8:51 Speaker 02 So that's an interesting question. So yes, it was able to predict if you put a magnetic field which is this strong in this kind of a disk, then there won't be a breakdown. If you put a magnetic field which is this strong, then there will be, and that could be tested.
9:09 Neil deGrasse Tyson? And without that, you're just pushing pencil, right, at that level.
9:13 Speaker 01 Yeah, but you're getting more clues. You said there was something missing in your puzzle.
9:17 Speaker 02 So it was clear that that was what was missing. And the amazing thing is, is that even a very weak magnetic field would be enough to completely disrupt the stability properties of the gas. And that's what a lot of people had a hard time getting their head around. That something that seems so weak could have such an important effect.
9:40 Neil deGrasse Tyson? So this was an astrophysical instability, not an emotional instability?
9:44 Speaker 02 Well, I had those as well, but what I'm talking about, right, the astrophysical side of things.
9:49 Speaker 01 So you mentioned like a whirlpool effect?
9:53 Speaker 02 Yes.
9:54 Speaker 01 Would it have been any use to study whirlpools and maybe construct the computational element of that to see if there was anything that you could learn?
10:03 Speaker 02 Well, yes and no, in the sense that the whirlpools in your kitchen sink or something like that won't be sort of run by a magnetic field.
10:11 Speaker 01 No, I was just thinking, the sort of things you could see in nature.
10:14 Speaker 02 Absolutely. In terms of what people, people can do rather detailed studies now of turbulence, its statistical properties and so forth, and absolutely those kinds of studies would be of interest and are of interest to the people who do this kind of turbulence in accretion disks.
10:32 Neil deGrasse Tyson? So I think what's fun about this is, the great thing about physics, when you break it down, is physical principles are transplantable to multiple different questions in search of various answers. So the power of physics, it knows no bounds.
10:49 Speaker 01 Yes. What is it you said to me earlier on today?
10:52 Neil deGrasse Tyson? I don't remember.
10:53 Speaker 01 That I'm gonna get the T-shirt, "Physics is my god."
10:57 Neil deGrasse Tyson? Okay, you're gonna get that T-shirt?
10:59 Speaker 01 No, I'm gonna get it for start off. We're gonna have it made up, we're gonna murk and make money.
11:03 Neil deGrasse Tyson? Okay, alright. So let's fast forward, and I understand, uh, recently that, uh, this year, uh, twenty twenty-four, uh, you have a textbook coming out on Einstein's general theory of relativity.
11:16 Speaker 02 That's right, I've taught a course here at Oxford for several years, and had a set of notes, and then I've been encouraged, because people liked it, to turn it on to, into a textbook on general relativity. And the timing was very good, because the very first year that I taught the course was the year that gravitational radiation was discovered.
11:40 Neil deGrasse Tyson? That would have been two thousand sixteen.
11:42 Speaker 02 Two thousand sixteen, that's exactly right.
11:44 Speaker 01 Is that the same as Hawking's?
11:45 Speaker 02 No, that's a different kind of radiation.
11:47 Neil deGrasse Tyson? This one was like a-
11:48 Speaker 01 Then I won't blur the lines here, sorry.
11:51 Speaker 02 Yeah.
11:51 Neil deGrasse Tyson? Get your radiation straight, dude.
11:53 Speaker 01 Sorry, dude.
11:54 Neil deGrasse Tyson? Last time I bite you on this program.
11:56 Speaker 02 Yeah, no, this is, this is the force of gravity itself being radiated, in a way which is some rather similar to the way that electromagnetic radiation is being radiated. An effect predicted by Einstein a hundred years ago, but so small and so difficult to measure. It was only in the last few years that the technology was there to do that. And so, the book covers that.
12:22 Neil deGrasse Tyson? It's an update.
12:24 Speaker 02 It's very, there are a lot has been going on on the observational side. And so I'm fortunate, because the textbook can, discusses that as well.
12:32 Neil deGrasse Tyson? Alright, so it's a textbook, so is there like a general relativity for dummies that you can, uh, is there like the, the crib, crib notes version of the textbook? Have you considered that?
12:45 Speaker 02 I haven't considered it, but talking to you now makes me think perhaps I should consider that a little bit more, that's a thought. There are good, very good books.
12:53 Neil deGrasse Tyson? So it'll be general relativity for non-Oxford physics majors?
12:56 Speaker 02 Yeah, you know what a very good book is? One that I love, and, I mean, you know, but, but it's meant for, you know, the layman, because it's written very clearly. There's a book from the nineteen nineties by Kip Thorne. Probably the most famous relativist in the world, but also very gifted for writing and for making things very, very clear. So yeah, the book is called Black Holes and Time Warps: Einstein's Outrageous Legacy.
13:24 Neil deGrasse Tyson? That's Kip Thorne.
13:25 Speaker 02 And that's Kip Thorne.
13:26 Neil deGrasse Tyson? That's our book guy, Kip Thorne.
13:27 Speaker 02 That's your guy?
13:28 Neil deGrasse Tyson? We all live love Kip Thorne.
13:29 Speaker 02 Kip Thorne is-
13:30 Neil deGrasse Tyson? Co-executive producer of the film Interstellar.
13:34 Speaker 02 Absolutely.
13:35 Neil deGrasse Tyson? Yes.
13:36 Speaker 02 And he's the man who knows all there is to know about general relativity.
13:41 Neil deGrasse Tyson? He's one of the co-winners of the Nobel Prize for LIGO and the discovery of gravitational radiation.
13:46 Speaker 02 He did a lot of the heavy lifting on the theory side of that.
13:49 Speaker 01 Okay.
13:50 Speaker 02 Yeah, yeah. And he writes brilliantly and very, very clearly.
13:53 Neil deGrasse Tyson? For The Laman, okay, good.
13:54 Speaker 02 Yes, and so that's an excellent book. And he makes predictions about what he thought was going to happen in the years after 1992.
14:03 Speaker 01 How'd he do?
14:05 Speaker 02 He did okay. He predicted-
14:09 Speaker 01 You're just damned if by faint praise.
14:12 Speaker 02 Well, that's very hard.
14:14 Neil deGrasse Tyson? I'm just impressed that we live in a time where okay means not so well.
14:20 Neil deGrasse Tyson? How'd he do? Okay.
14:22 Speaker 01 I mean, I can't, I can't throw shade on a Nobel Prize winner. Really, just can't do it.
14:26 Speaker 02 And look, to give him credit, he was being optimistic. So at that point, gravitational radiation was still two decades in the future. Um, and, or more, and he predicted that. That that would happen. And at about roughly the right time scale. On the more theoretical side of things, theories that would combine quantum mechanics with general relativity, he was much too optimistic. So he didn't get quite those right.
14:56 Speaker 01 So you made me think, where are we now with what we don't know? And, and what is it we think we need to know? And sort of move on from-
15:05 Neil deGrasse Tyson? Yeah, let me, let me add punctuation to that. Einstein in 1915 or 16 publishes The General Theory of Relativity.
15:14 Speaker 02 Yes.
15:14 Neil deGrasse Tyson? Right, and, um, we've been working with it for more than 100 years.
15:19 Speaker 02 That's right.
15:20 Neil deGrasse Tyson? And so what I ask of you, and I'm picking up his question.
15:24 Speaker 02 Yeah.
15:25 Neil deGrasse Tyson? Are there still loose ends today? We're a quarter of the way into the 21st century. Are there still loose ends, not only in general relativity, but in those fields? Are there still parts of black holes we don't know or understand?
15:41 Speaker 02 That's an interesting question, so...
15:44 Neil deGrasse Tyson? Because he laid it out
15:45 Speaker 02 Yeah.
15:45 Neil deGrasse Tyson? More than 100 years ago.
15:46 Speaker 02 Well, he gave us the equations for it. And that's, of course, a very big step because you can't begin to do anything.
15:53 Neil deGrasse Tyson? Right.
15:54 Speaker 02 But it's only the beginning step because unless you know the content of the equations and are able to understand their implications, you only know relatively little.
16:06 Neil deGrasse Tyson? I think he just said you have to know the power of the equations. Is that another?
16:11 Speaker 02 Well, I would say...
16:13 Neil deGrasse Tyson? You said context, that how powerful...
16:16 Speaker 02 Not context, content.
16:18 Neil deGrasse Tyson? The content of the equation.
16:20 Speaker 01 I'm here to translate, that was definitely content.
16:22 Speaker 02 Content.
16:22 Neil deGrasse Tyson? The content of the equation. You want to know what's sort of hidden in there?
16:27 Speaker 02 What do the solutions to the equations actually look like? For example, we now know that the most general kind of black...
16:37 Neil deGrasse Tyson? Wait, you're telling me he gave us equations but not solutions? That's not, that ain't right.
16:45 Neil deGrasse Tyson? Leave us hanging?
16:47 Speaker 02 Any great physicist will do that.
16:50 Speaker 01 They just left homework.
16:51 Speaker 02 Right.
16:52 Neil deGrasse Tyson? Homework.
16:52 Speaker 02 Isaac Newton didn't solve all the equations of gravity.
16:57 Neil deGrasse Tyson? Okay.
16:57 Speaker 02 Maxwell didn't solve all...
16:59 Neil deGrasse Tyson? There have been at least a half dozen Nobel Prizes given to people working on Einstein's equations.
17:05 Speaker 02 Absolutely, very much.
17:06 Neil deGrasse Tyson? That's crazy, crazy fact.
17:08 Speaker 02 Yeah.
17:09 Neil deGrasse Tyson? Okay.
17:09 Speaker 02 And in fact, we didn't even really know what a black hole was in terms of solving Einstein's equations in a relatively simple context. Just what they call the vacuum solutions. The solutions to Einstein's equations when there's nothing there but some kind of a little point mass, the black hole. So the solution to that really didn't come until the 1960s, when the mathematician Roy Kerr... Published his solution to what a rotating black hole looks like.
17:46 Neil deGrasse Tyson? And everything of yours rotates.
17:47 Speaker 02 And everything rotates. So that's a very, very important solution.
17:50 Neil deGrasse Tyson? That's the care black hole. That's its own kind of black hole.
17:52 Speaker 02 That's right. It has his name. There's a Schwarzschild black hole. That came pretty quickly. That came within a month of when Einstein published his theory. But that's no rotating at all. And that's a little too simple for nature. That's an important solution and we learn a lot from it. Yeah. But it's not really a practical solution as we learn later. Because most black holes have a lot of rotation. And that makes a big difference in terms of how they behave.
18:39 Speaker 03 I'm Kais from Bangladesh and I support StarTalk on Patreon. This is StarTalk with Neil deGrasse Tyson.
18:56 Neil deGrasse Tyson? All right, so today, what are some unsolved problems?
19:00 Speaker 02 Well, so there are different kinds of unsolved problems. So one problem which is still not really well understood is what happens? How do you see a black hole? Because the black hole itself is just empty space. You see a black hole because of the effect of the, that the black hole has on the surrounding gas.
19:26 Neil deGrasse Tyson? Or anything surrounding it.
19:27 Speaker 02 Surrounding anything. But this gas is usually what you have at hand.
19:31 Neil deGrasse Tyson? Mm-hmm.
19:33 Speaker 02 And yeah, under some circumstances, if there are a lot of stars, you can see how the stars are concentrated near the black hole and learn something from that. But most of the time, you get most of your information from the gas, which is around the black hole. So it was important to learn, for example, in my earlier work, that the gas is turbulent and to make use of that. But there was still things to learn about the orbits that are very, very close to the, what they call the singularity, to the real point mass, which is the black hole. That's where the effects of relativity become very important.
20:13 Neil deGrasse Tyson? So just to be clear, you know, a black hole is not some giant sucking machine, right? So if you have a stable orbit around a black hole, you're cool. The sun could become a black hole today, we'll get very cold, but we'll just keep orbiting it like it was not, like, we're fine.
20:29 Speaker 02 Well, even more than that, there would be absolutely, if the sun were perfectly spherical as it is, versus a sun which was a black hole, there would be no difference whatsoever in terms of what it's doing to the, to the, to the entire space around it.
20:46 Neil deGrasse Tyson? Right.
20:46 Speaker 02 That's right.
20:47 Neil deGrasse Tyson? You would get very cold, but other than that, and we free suggest, but otherwise, but ignoring that complication, we'd be fine.
20:54 Speaker 02 Right.
20:54 Neil deGrasse Tyson? Right, okay.
20:55 Speaker 02 Just the gravitational part.
20:56 Speaker 01 Do they rotate the same direction every single time?
21:01 Speaker 02 The black holes?
21:02 Speaker 01 Yeah.
21:02 Neil deGrasse Tyson? No.
21:03 Speaker 01 Interesting.
21:04 Speaker 02 They can rotate however they like.
21:06 Speaker 01 All right.
21:07 Neil deGrasse Tyson? Like the 900-pound gorilla.
21:08 Speaker 01 I don't think so.
21:10 Neil deGrasse Tyson? It sits where it wants.
21:11 Speaker 02 Yep.
21:12 Neil deGrasse Tyson? These orbits, it seems to me they'd be easy to calculate.
21:17 Speaker 02 Well, no, because the equations themselves, I mean, they are easy to calculate in some sense, if you put it all on a computer, but it's often very hard to understand what the results mean. The hard part is to be able to calculate orbits, say, the same way that Isaac Newton was able to prove that the orbits in his theory of gravity would be exactly ellipses. So that's very useful to know. So can you do the same thing around black holes?
21:51 Neil deGrasse Tyson? Pull a Newton on a black hole.
21:53 Speaker 02 Pull a Newton on a black hole. And the answer is...
21:57 Neil deGrasse Tyson? Newton is your guy.
21:58 Speaker 01 I know.
21:59 Neil deGrasse Tyson? But he's not, he's not from Oxford, he's from Cambridge.
22:01 Speaker 01 Okay, well, that's okay, yeah.
22:03 Neil deGrasse Tyson? You'll take it, you'll take it.
22:04 Speaker 01 Oh, yeah, we're big fans of Newton.
22:06 Neil deGrasse Tyson? Okay.
22:07 Speaker 02 And so, when you're dealing with orbits around Kerr black holes, the equations are so daunting. They, just to write down the equation takes up a page of your notes. Not just to write it, let alone find a solution, that most people were put off by that task. But it turns out, when you study black holes, there are some simplifications that you can bring to bear that people were not really aware of, that people didn't fully appreciate. And you can exploit those, and then it turns out, you can kind of pull a Newton
22:51 Speaker 02 for some of the orbits which are not just, you know, kind of mathematical curiosities, but which actually have some practical interest as well. And so, I have a student who is actually able to do precisely that. And so, that, I think, has been able to advance the field significantly.
23:14 Neil deGrasse Tyson? Interesting. So this would be a fresh advance on our understanding of black holes' effect on their environment that we haven't really had in a while. Is that a fair statement?
23:24 Speaker 02 I think that's a very fair statement.
23:26 Neil deGrasse Tyson? Okay.
23:26 Speaker 02 I think it's a very fair statement. Contrary to sort of, you know, popular impressions, physicists don't really love complexity. If they have to deal with it, they'll muster the fortitude, and they will do so. But if they can find something...
23:44 Neil deGrasse Tyson? Muster the fortitude, what does that mean? That sounds very British. No fun to wait to get it done.
23:50 Speaker 02 Thank you.
23:51 Neil deGrasse Tyson? Thank you for the translation. Told you, that's why I'm here. Muster the fortitude. Thank you, William Shakespeare.
23:59 Speaker 02 But if they can find a simple way to, that is really the holy grail. That's really what they're after. And so that, I think, is where we're heading with that. We really do have a much simpler way of understanding what is going on with the orbits which are quite close to the black hole. And those are the ones of also not just kind of mathematical interest, but astronomical interest, observational interest.
24:26 Neil deGrasse Tyson? Observational consequences.
24:28 Speaker 02 With observational consequences, very much so.
24:30 Neil deGrasse Tyson? Okay, so you have a student who did this?
24:32 Speaker 02 I do.
24:33 Neil deGrasse Tyson? So why am I still talking to you?
24:35 Speaker 02 Well, I don't know, Neil. I didn't arrange the schedule.
24:37 Neil deGrasse Tyson? Okay, all right, Gary, let's get him out of here. Okay, ready, on three, on three. One, two, three. There you go.
24:45 Speaker 04 There you go.
24:45 Neil deGrasse Tyson? Hello.
24:46 Speaker 04 Hello.
24:46 Neil deGrasse Tyson? Your name?
24:47 Speaker 04 I'm Andy.
24:48 Neil deGrasse Tyson? Andy, pleased to meet you.
24:49 Speaker 04 Nice to meet you.
24:50 Neil deGrasse Tyson? Welcome. You sound like this guy. Yes, how about that? You're a Brit.
24:54 Speaker 04 I am a Brit.
24:55 Neil deGrasse Tyson? What gave it away?
24:58 Neil deGrasse Tyson? Okay, you'll help me translate. Of course, yeah. May not tell the truth, but I'll translate. So you're not literally a student, you're a postdoc.
25:07 Speaker 04 I'm a postdoc.
25:08 Neil deGrasse Tyson? Postdoc.
25:08 Speaker 04 So I was Steve's student 2014 to 20, no, 2018 to 2022.
25:15 Neil deGrasse Tyson? Okay.
25:16 Speaker 04 And then I've been a research fellow here since then.
25:18 Neil deGrasse Tyson? Here at Oxford.
25:20 Speaker 04 In Oxford.
25:20 Neil deGrasse Tyson? Oxford.
25:21 Speaker 04 Oxford.
25:24 Neil deGrasse Tyson? So you picked up some of Einstein's mantle here.
25:29 Speaker 04 That's very generous.
25:31 Neil deGrasse Tyson? To the mantle of Einstein.
25:32 Speaker 04 Yeah, yeah, yeah.
25:33 Neil deGrasse Tyson? So what exactly did you do? And let me tell you our angle into this, all right? The public's, the public's angle is everyone has seen the movie Interstellar. All right, and Kip Thorne. Yes. Had a hand in that, helped write a lot of the physics that was in it. And one of the more intriguing scenes was This visit to this black hole planet, the gargantuan, I think, was the name of it. And it left one of their astronauts up in the orbiting spacecraft. And so he's in a different gravitational field from the ones who went down to the planet, which was near the black hole. And I forgot what the ratio was, but they lived 15 minutes or something,
26:18 Neil deGrasse Tyson? and the guy up there went 10 years or some...
26:21 Speaker 04 Yeah, I think they even more.
26:22 Neil deGrasse Tyson? But yeah, crazy ratio of time.
26:25 Speaker 04 Time dilation.
26:25 Neil deGrasse Tyson? Time dilation, crazy time dilation. So I was going to try to calculate how close that orbit had to be. And then I said, "No, I'm not gonna, I will wait till I get somebody else to do this." It sounds like you're the guy for that.
26:37 Speaker 04 Yes, that's, yeah, I'm orbiting near to a black hole, that's my, that's the danger.
26:41 Neil deGrasse Tyson? He's the guy.
26:42 Speaker 04 That's the danger.
26:42 Speaker 01 How many people do we bump into? How many of our audience...
26:46 Neil deGrasse Tyson? This was not an accidental bump into the...
26:47 Speaker 01 No, no, no, I'm not bumping into Andy, but how many people in our StarTalk realm and universe want to know, "How close can I orbit to a black hole?" Because that's what they do. Before I get or...
27:00 Neil deGrasse Tyson? We have very curious people who watch this.
27:02 Speaker 04 Yeah, I'm sure they ask that question frequently.
27:04 Neil deGrasse Tyson? Because you'll see it, and they're not just gonna receive it, assuming it just can happen. Give me some answers there.
27:09 Speaker 04 So you can get pretty close. So for your simplest Schwarzschild black hole?
27:14 Neil deGrasse Tyson? Schwarzschild, so that's the non-rotating black hole.
27:16 Speaker 04 Non-rotating, so let's make the event horizon one.
27:19 Neil deGrasse Tyson? Okay, we all know what the event horizon is. The point of no return that we all know about.
27:24 Speaker 04 So the edge of the black hole, that's one. Then you can stably orbit on a circular orbit down to three.
27:31 Neil deGrasse Tyson? But not less than three?
27:33 Speaker 04 Not less than three. So, yeah, I mean, it's, you know, it's the roundabout force. When you drive around a roundabout, you get pushed out. Okay, so that's what an orbit is, you balance that with gravity.
27:42 Neil deGrasse Tyson? A roundabout would be a traffic circle.
27:44 Speaker 04 Yes, sorry.
27:46 Speaker 01 It's a roundabout.
27:48 Speaker 04 Yeah.
27:48 Speaker 01 When you're here, you're roundabout. When you're back home, traffic circle yourself silly.
27:54 Neil deGrasse Tyson? This, so the planet Gargantuan, to have that much time dilation difference, because, I think most of our audience knows, as you get to a stronger and stronger gravitational field, your time slows down relative to others.
28:10 Speaker 04 Absolutely.
28:11 Neil deGrasse Tyson? So, so how close was the Gargantuan planet? I don't remember them saying so. Do you?
28:18 Speaker 04 It has to be really, I mean fantastically close. In fact, I'm not-
28:21 Neil deGrasse Tyson? Closer than three?
28:23 Speaker 04 I'm pretty sure it's gonna be closer than three.
28:25 Neil deGrasse Tyson? Uh-oh. Uh-oh. Uh-oh.
28:31 Neil deGrasse Tyson? Okay, so this would mean Kip? Kip, oh boy. Kip Thorne. You're calling him out. We're calling out Kip Thorne. Kip Thorne.
28:40 Speaker 04 Yeah, so them landing on the planet, that would have been unstable. That little kick would have sent it spiraling in.
28:45 Neil deGrasse Tyson? Wow. So, so what happens? Why can't you just orbit right above the event horizon?
28:52 Speaker 04 In Newtonian gravity, so the Earth going around the Sun, you have to balance two forces. You've got gravity coming in and revolution pushing you out.
29:00 Neil deGrasse Tyson? So that keeps you at the same distance from the big red?
29:03 Speaker 04 Absolutely.
29:04 Neil deGrasse Tyson? Your urge to fly off is a balance. Okay, so now what?
29:08 Speaker 04 And then you write down the same problem in Einstein's equation, and you find that there's a new force effectively. Or there's a new-
29:15 Neil deGrasse Tyson? A new force?
29:15 Speaker 04 Well, no. Okay, so the force is gravity. That's the only force. But there's something, an effective force effectively, which is gravity times rotation. So that's what the equation looks like.
29:25 Neil deGrasse Tyson? So this is a new term?
29:27 Speaker 04 It's a new term in the energy equation.
29:29 Neil deGrasse Tyson? That operates on the stability of the system.
29:32 Speaker 04 Yeah, and that points in. Okay? So the faster you go around-
29:36 Neil deGrasse Tyson? So that term is not there in Newton's equations?
29:38 Speaker 04 No, no, no.
29:39 Neil deGrasse Tyson? So as you get closer and closer to a black hole, this other term shows up that prevents you from sustaining a balance.
29:45 Speaker 04 So this is one of the things that we didn't know, that we need to know, because this is helping solve why this happens the way it does.
29:53 Neil deGrasse Tyson? Yes.
29:54 Speaker 04 So you get closer, you have to go faster and faster and faster-
29:57 Neil deGrasse Tyson? In order to stabilize that extra term.
29:59 Speaker 04 To stay in orbit, but that just makes this third term even bigger. Because it's gravity times rotation. And that eventually destabilizes the orbit.
30:08 Speaker 01 So the faster you go.
30:09 Speaker 04 Yeah.
30:10 Speaker 01 It starts to work against you.
30:11 Speaker 04 Yeah, exactly. And eventually.
30:12 Neil deGrasse Tyson? That ain't right.
30:13 Speaker 01 Diminishing returns.
30:14 Speaker 04 Exactly.
30:15 Neil deGrasse Tyson? That ain't right. That's wrong. That's just wrong. Why did you come up with that?
30:20 Speaker 04 I mean, that's the universe.
30:21 Neil deGrasse Tyson? Are you telling me no one figured this out before you?
30:24 Speaker 04 So this was known. We knew the orbits became unstable. Okay, but the point was, how simply can you describe the plunge effectively? So you get flicked off the circular orbit and you dive in towards the black hole. And the question is, how do you describe that?
30:40 Neil deGrasse Tyson? And by the way, as I understand it, if you dive into the black hole, your orbital speed increases, which would further increase the term. Is that correct? So it's catastrophically unstable.
30:52 Speaker 04 Yeah, exactly. So it's unstable in that you perturb it and you're gone.
30:56 Neil deGrasse Tyson? And it gets even more and you're in.
30:59 Speaker 04 Yeah, you're not.
31:00 Speaker 01 So you speed up to try and break the orbit and you just end up making it way worse.
31:05 Neil deGrasse Tyson? Worse, okay.
31:05 Speaker 04 And you're gone. And you plunge into across the event horizon and you're doomed. Yeah, absolutely.
31:09 Speaker 01 Say goodbye.
31:10 Neil deGrasse Tyson? Damn, dude.
31:12 Speaker 04 Yeah, and so, you know, this is a prediction.
31:14 Neil deGrasse Tyson? You're bumming us out here.
31:15 Speaker 04 Yeah, yeah, I'm sorry. It's the universe's fault.
31:19 Neil deGrasse Tyson? Yeah, it's not your fault. The universe revealed it. Right, so let's get the understanding, just so we learn how science works. Some of this was known before your work.
31:27 Speaker 04 Yes, we knew this happened.
31:29 Neil deGrasse Tyson? Okay, but so how did you contribute to that problem? So just to make it clear, so much of what's out there, people have little bits of solutions to it. Right? And we're all sort of touching the elephant, trying to understand it.
31:43 Speaker 04 Well, it's like a piece of paper that someone's ripped into tiny little bits and then scattered.
31:47 Neil deGrasse Tyson? Okay.
31:48 Speaker 04 And then you're now trying to bring it all back.
31:49 Neil deGrasse Tyson? Well, the papers, it's a pre-existing how the universe works.
31:52 Speaker 04 So then trying to piece it back together to say, oh, no, that goes there, this goes here.
31:57 Neil deGrasse Tyson? Right.
31:57 Speaker 04 And then we're getting there. So this is what I think Andy's kind of.
32:00 Neil deGrasse Tyson? Okay, so how did you come in on this?
32:02 Speaker 04 So we knew this should happen. Okay? And I mean, you know something should happen, you want to go see it effectively. Okay, so you want to go see it out in nature. You want to observe it in a real physical system. Now, to know.
32:14 Neil deGrasse Tyson? You want to observe the unstable world.
32:17 Speaker 04 Yeah, the plunge. You want to see this gas that's plunging. That's what you want to do. Because then you know it's there, you know. And so before you can tell. That you've seen this, you need to know what to look for. Okay, so you've got to build a model of this plunging gas.
32:30 Neil deGrasse Tyson? So build a model, this on a computer.
32:32 Speaker 04 Yeah, pen and paper, computer.
32:33 Neil deGrasse Tyson? What did you use?
32:34 Speaker 04 I used pen and paper.
32:35 Neil deGrasse Tyson? Old school. Oh, oh chalkboard. Oh, oh. These are like the cheapest scientists to keep around.
32:45 Speaker 04 No, they're not.
32:46 Neil deGrasse Tyson? Yes, they are.
32:47 Speaker 04 No, they're not.
32:47 Neil deGrasse Tyson? They're totally cheap. There's no computer, there's no telescope, there's no particle accelerator.
32:51 Speaker 04 Have you seen the price of graphite lately? Go through pencils. I need the best chalk.
32:57 Neil deGrasse Tyson? And then he'll be busy and come out later. Okay, so go on.
33:01 Speaker 04 So you want to simplify these equations down to make them useful? So that you can make predictions and then you can go and look in the data and see if there's any black hole sources out there that we just can't understand without this plunging gas.
33:13 Neil deGrasse Tyson? So you have to predict what unstable spiraling gas would look like?
33:20 Speaker 04 Exactly, yeah.
33:21 Neil deGrasse Tyson? So what does it look like?
33:22 Speaker 04 Well, essentially, it's hot and small is the...
33:25 Neil deGrasse Tyson? I just said that.
33:26 Speaker 04 Yeah.
33:27 Speaker 01 You didn't.
33:27 Neil deGrasse Tyson? But I said stop.
33:29 Speaker 01 You didn't, and you didn't go for swirling and unstable either.
33:33 Neil deGrasse Tyson? Okay.
33:34 Speaker 04 Precisely how hot, precisely how small, that's for the money.
33:37 Neil deGrasse Tyson? You got it, you got it.
33:39 Speaker 04 So, yeah, so we have these theories that Steve worked on, you know, since the 70s.
33:45 Neil deGrasse Tyson? Your advisor, Steve Bobbys?
33:46 Speaker 04 Yeah, absolutely.
33:47 Neil deGrasse Tyson? Who snapped him out of existence.
33:48 Speaker 04 Yeah, he did work on it. And, you know, they had these models and they just stopped at this stable, last stable orbit because then it plunges, it gets difficult and we'll just, we'll ignore it, basically. And so you stop there, that's what I would have done, okay, you know? And then eventually we started getting data that they couldn't explain with these models.
34:25 Neil deGrasse Tyson? Okay, so now that you have insights, right down to the orbits at the event horizon, non-orbits at the event horizon, tell me now where you think Gargantuan had to have been to give you that stark difference in time dilation? I think it's well inside. Inside your unstable orbit. Absolutely, yeah. So that planet just would have not been hanging out? No, absolutely not. It would have been gone eons ago? Gone, eons. Okay, why didn't Kip Thorne know this? I'm sure Kip Thorne did know this. I'm sure it was just very inconvenient for the plot. That may well have more than a grain of truth in it. Oh, okay, so you're being very kind here.
35:08 Neil deGrasse Tyson? What you're saying, let me reword what you're saying. Okay, you're saying, apart from the extra detail that you have provided, all of us inside those unstable orbits, we knew they were unstable orbits. He certainly would have known there's unstable orbits, because his middle name is General Relativity. Okay. He's co-author of like the most famous relativity book there ever was. Okay. It's called Gravitation. It has the proportions of a Manhattan Yellow Pages phone book, okay? Well, he certainly simplified the title, didn't he? Well, it's the only book you learn all about just by carrying it around, right? Yeah, I get that, yeah, see what you did. So it says three authors, Misner, Thorne, and Wheeler, and Kip Thorne is the middle
35:53 Neil deGrasse Tyson? author there. So we all have it in my generation. It's too old for you. No, I've got it on. You do have the book, okay? It's a pencil and paper, he'll have a book. All right, so what you're suggesting is that he wanted that degree of time dilation difference. And took some cinematic liberties to get it.
36:15 Speaker 04 I mean, the man's got an overall prize, he's, you know.
36:18 Speaker 01 It might not have been him, he might have been overridden by producers and directors.
36:22 Neil deGrasse Tyson? Yeah, okay.
36:23 Speaker 01 Because that does, that does happen.
36:25 Neil deGrasse Tyson? Okay, I cut people's slack in movies.
36:27 Speaker 01 I know.
36:28 Neil deGrasse Tyson? If the idea is kind of right.
36:30 Speaker 01 Okay.
36:31 Neil deGrasse Tyson? Even if in detail is wrong.
36:32 Speaker 04 That, that orbit exists. That orbit exists that the planet's on, it's just unstable. So it just won't exist for long, but, but, but it.
36:38 Neil deGrasse Tyson? It wouldn't exist for long enough for them to do anything they were doing.
36:40 Speaker 04 But it exists, it's a solution that's, that's valid, it just won't, just won't.
36:44 Speaker 01 All right, we'll, we'll take the thorn out of your side for the moment.
36:46 Neil deGrasse Tyson? The kit thorn out of my side?
36:48 Speaker 01 Yes, thank you. You talked about we're finding new data coming in. Now, if you're a forensic accountant, follow the money, stupid, you're gonna find what's all about. This, for me, is you being forensic for the data. So what kind of data is coming in and what are you able to kind of?
37:08 Neil deGrasse Tyson? And what kind of telescopes? Yeah, coming to you as an astronomer, I want to know what I should point my telescope.
37:14 Speaker 01 So what are your data sources? Is it telescopes? Is it computational? Where are we headed?
37:18 Speaker 04 So these are, these are X-ray telescopes, so, so they're satellites in orbit?
37:21 Neil deGrasse Tyson? X-ray telescopes.
37:22 Speaker 04 Yeah, yeah, yeah.
37:23 Neil deGrasse Tyson? And we're about to lose our last X-ray telescope, the Chandra Great Observatory.
37:27 Speaker 04 That's, that's gonna be a real, a real.
37:29 Neil deGrasse Tyson? It's gonna get de-orbited very soon, I think, last I heard.
37:32 Speaker 04 There will be, there will be others, but, but Chandra is a wonderful instrument.
37:35 Neil deGrasse Tyson? Yes.
37:35 Speaker 04 So it's, you know, it.
37:36 Neil deGrasse Tyson? Named for?
37:37 Speaker 04 Chandra Seharkar.
37:38 Neil deGrasse Tyson? Chandra Seharkar, very good.
37:40 Speaker 01 He knows.
37:40 Neil deGrasse Tyson? I'm just checking, he knows. I'm still a student.
37:43 Speaker 01 Make him dance.
37:43 Neil deGrasse Tyson? I'm allowed to be my professor Neo every now and then, okay?
37:49 Neil deGrasse Tyson? Uh, and, uh, as I remember, he was a great astrophysics theorist and good tradition in the steps you're following.
37:57 Speaker 04 If I have half the success of Chandra Seharkar, I'd take that, yeah.
38:01 Neil deGrasse Tyson? So you publish this.
38:02 Speaker 04 Yeah, yeah, so, so it's X-ray data, so these, these discs are super hot. They're incredibly hot and they produce X-rays and they, they, you know, they, they are detected by satellites.
38:11 Neil deGrasse Tyson? They're so hot, they radiate X-rays.
38:13 Speaker 04 Absolutely.
38:13 Neil deGrasse Tyson? As opposed to being so hot like your electric stove, it radiates infrared.
38:19 Speaker 04 Yeah.
38:20 Neil deGrasse Tyson? Then you can radiate like ultraviolet if you get like hotter and then. And then X-rays, you keep radiating up the spectrum.
38:26 Speaker 01 What goes hot, what, how hot do you have to radiate to get worse than X-rays?
38:30 Speaker 04 Millions of, millions of degrees.
38:32 Speaker 01 So why would it get even hotter?
38:33 Speaker 04 And it's gamma rays.
38:34 Speaker 01 And then what's gonna say like, we're in Hulk territory.
38:37 Neil deGrasse Tyson? That's very hot, whereas your stove is a thousand degrees, you know? Yeah.
38:42 Speaker 01 We're talking millions.
38:44 Speaker 04 We're talking millions of degrees and, and, and so we, yeah, yeah. And it's, and it's, and it's, you know, tens of kilometers from the edge of a black hole, millions of degrees, X-ray photons are coming across the galaxy, 10,000 light years.
38:58 Neil deGrasse Tyson? Okay, so you, so you published, did you publish your theoretical predictions and found some data that explained?
39:06 Speaker 04 So, yeah, yeah, so we, we did.
39:07 Neil deGrasse Tyson? That's the best way to do that, right?
39:08 Speaker 04 We, we did, exactly, yeah, yeah. We, we had a bit of a, we had a bit of a heads up. We knew that there were mysteries out there and, and we thought we had the answer.
39:17 Speaker 01 As they do us all, my friend.
39:19 Speaker 04 Yeah, and, and we were able to show, yes, you have this, this data, it's beautiful data, and you just can't explain it without this, this plunge, this gas on the planet.
39:26 Neil deGrasse Tyson? And where did that appear?
39:27 Speaker 04 It was in the monthly notices of the Royal Astronomical Society, a very, a very British journal, yeah.
39:33 Neil deGrasse Tyson? Kept it bred. You know, we have journals too in America.
39:36 Speaker 01 Yeah, but they're not royal.
39:37 Speaker 04 Yeah, they don't have the king's approval.
39:40 Speaker 01 Okay, here we go.
39:41 Neil deGrasse Tyson? I gotta get used to this, not the queen's approval, the king's approval, King Charles, okay. So this is, this is a leading journal in our field, yes, so congratulations on that.
39:51 Speaker 04 Yeah, thank you.
39:52 Neil deGrasse Tyson? And if I understand correctly, that, that got some media attention.
39:57 Speaker 04 Yeah, it caused a bit of a stir, yeah, yeah, it was, it was good fun.
40:00 Speaker 01 Classic British understatement.
40:04 Neil deGrasse Tyson? Which means people went ape shit.
40:07 Speaker 01 A couple of heads blew out.
40:10 Speaker 01 So. Before we let Andy go, what is your top unsolved problem?
40:15 Neil deGrasse Tyson? And at this point in your career, surely you have some ambitions.
40:18 Speaker 04 So I, I wanna know how fast black holes are rotating, the black holes we have out in the galaxy, I wanna know how fast they're spinning.
40:24 Neil deGrasse Tyson? Dude, think bigger than that, come on.
40:26 Speaker 04 Oh, no, this, this tells us, this tells us how they're formed, so this tells us.
40:30 Speaker 01 There you go, that's why I want.
40:31 Speaker 04 So, okay, the, the question you answer is how fast they're spinning, but the, the long term, but that, you know, that's, that's one question, but the real, the real answer is how, how do they form and how do they evolve over the age of the universe?
40:42 Neil deGrasse Tyson? Okay, and, and this includes supermassive black holes?
40:45 Speaker 04 Absolutely, yeah, yeah, supermassive.
40:46 Neil deGrasse Tyson? The big ones, isn't it?
40:47 Speaker 01 I got the hint.
40:50 Neil deGrasse Tyson? Supermassive, the big ones, yeah. So, you think you can have a general understanding that can apply to all the regimes of black holes that we know?
40:57 Speaker 04 That's the plan.
40:58 Neil deGrasse Tyson? So you're gonna be the black hole guy?
40:59 Speaker 04 Yeah, absolutely.
41:00 Neil deGrasse Tyson? I'm a black hole go-to guy. Go-to black hole guy. Well, so, good luck with that. Sometimes you need a little bit of that, of course. Yeah. My little island leading the way now, how about that? So, so tell me, why must everything circle a black hole to go in? Why can't it just fall straight in?
41:19 Speaker 04 It's got angular momentum, basically, and angular momentum's hard to lose.
41:23 Neil deGrasse Tyson? Hard to lose?
41:23 Speaker 04 Yeah.
41:25 Neil deGrasse Tyson? Why?
41:26 Speaker 04 Stuff that's spinning.
41:27 Neil deGrasse Tyson? Why can't I just?
41:29 Speaker 04 It's conserved, it's conserved quantity.
41:32 Neil deGrasse Tyson? What about a black hole that doesn't spin? What do you call those? That's a Schwarzschild black hole. How about that one? No, but we're talking about stuff that falls in. Yeah, that's what I'm thinking. If it's not rotating, is it? If you're not gonna have a little disky thing, somehow it has to have been exactly pointed at it.
41:49 Speaker 04 And in these systems, we're peeling off the outer edge of a star. That's where this gas is coming from. So you've got a star in an orbit around a black hole, and you're peeling off the outside.
41:56 Neil deGrasse Tyson? I learned what word that says that. The star's getting flayed. Is that a good word? Oh. That's a good word. It's skinned alive, it's to be flayed. Okay. Did I teach a Brit a word? That's not, I'm an American, we're not supposed to. I think we'd actually tell you.
42:17 Neil deGrasse Tyson? So, but okay, so we have these discs, but suppose other material comes the other way? Doesn't it all cancel out?
42:23 Speaker 04 We've got one source of matter, that's the problem.
42:26 Neil deGrasse Tyson? Oh.
42:27 Speaker 04 So you've got, it's all coming in from the same direction.
42:29 Neil deGrasse Tyson? From one thing that's circulating that way.
42:31 Speaker 04 So you're peeling, so you inherit this angular momentum.
42:34 Neil deGrasse Tyson? It would be odd to have two things simultaneously.
42:36 Speaker 04 Absolutely.
42:37 Neil deGrasse Tyson? Doing that, okay. So that, that's what gives you a job, thinking about the spiraling material.
42:43 Speaker 04 Yeah, yeah.
42:43 Neil deGrasse Tyson? If everything just fell straight in, you'd be out of job.
42:45 Speaker 04 Yeah, exactly.
42:47 Neil deGrasse Tyson? And what about really, really big black holes? Where? They wouldn't necessarily have a disk.
42:54 Speaker 01 Not always, no.
42:55 Speaker 04 Oh.
42:56 Neil deGrasse Tyson? Because it's just really, really big. And how are you going to coherently create a disk around it? You just fall in.
43:02 Speaker 01 Within a supermassive black hole, does it not spawn its own little miniature?
43:07 Speaker 04 Sometimes there's, you know, gas in the middle of the galaxy. It comes nearby. You switch on, you switch on the effect of a supermassive black hole.
43:15 Neil deGrasse Tyson? I like that phrase. Because the black hole is lurking.
43:19 Speaker 01 Yep.
43:20 Neil deGrasse Tyson? Right? And only when it has something to dine upon, does the mechanism turn on. Very good. I like this.
43:28 Speaker 04 Those are the interesting ones.
43:29 Neil deGrasse Tyson? Yes, of course. Actually, physically. Well, this is great. Well, thank you.
43:33 Speaker 01 Yeah.
43:33 Neil deGrasse Tyson? For sharing us your expertise. And we'll look for great things. And I still want you to be more ambitious. I just want to know how black holes form. Dude, it's a big universe. Okay?
43:44 Speaker 01 Give him one thing to do at a time.
43:46 Neil deGrasse Tyson? No, no.
43:47 Speaker 01 One thing to do at a time.
43:49 Neil deGrasse Tyson? I learned to not, I'm pick, I'm.
43:51 Speaker 01 All right, okay.
43:52 Neil deGrasse Tyson? Can I be wise here?
43:53 Speaker 01 Go ahead.
43:54 Neil deGrasse Tyson? The wise elder?
43:54 Speaker 01 Mm-hmm.
43:55 Neil deGrasse Tyson? In my day, people said, I just want to know the value of the Hubble constant. I just want to know the rate of the universe. I just want to know. And then we discover that and we're on to other questions. Because it's not so much, I want to know the answer to these questions I posed. I want to know the answers to questions I have yet to think of. And that's your future.
44:24 Neil deGrasse Tyson? Whether you like it or not.
44:25 Speaker 04 Absolutely.
44:26 Neil deGrasse Tyson? All right, dude. Thanks for being on StarTalk.
44:28 Speaker 04 Thank you.
44:29 Neil deGrasse Tyson? You got it.
44:29 Speaker 04 Cheers.
44:30 Neil deGrasse Tyson? You have one last Brit thing you want to say before we sign off?
44:33 Speaker 01 Hop on the last thing, just ignore him.
44:37 Neil deGrasse Tyson? What is science if not this eternal quest to decode the operations of nature? Isaac Newton once said, if I can see farther than others, it's because I've stood on the shoulders of giants that have come before me. Now, I don't really believe him because he was completely brilliant. But for most of us, that's true. And, but what does that mean? Those who come before you, they put together part of that cosmic puzzle. But no, it's not completely solved.
45:09 Neil deGrasse Tyson? And there are parts of the puzzle we don't even know exist yet that will need to be assembled. And this, the act of asking questions, probing the universe and finding answers, is the passing of a torch. I think of like the Olympic torch. It goes from one group to another, from one generation to the next. And is the sum of all of this that is responsible for our understanding of the world as we know it. And in this little slice of theoretical physics, in the Beecroft Building on the campus of Oxford University, we got a little taste of that.
45:52 Neil deGrasse Tyson? And I'm delighted to have brought you a slice of how science works. And that is a cosmic perspective. Until next time, as always, keep looking up.
Previous Planetary Defense with Bill Nye Next Engineering Humans for Deep Space with Ronke Olabisi Page updated October 26, 2026 · transcript and summary are machine-generated
