StarTalk Radio - The Updated Physics of Black Holes with Steve Balbus & Andrew Mummery

Episode Date: August 13, 2024

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, magnetic fields, and the impact they have on the world around them with astrophysicist Steve Balbus and theoretical physicist Andy Mummery.NOTE: StarTalk+ Patrons can listen to this entire episode commercial-free here: https://startalkmedia.com/show/the-updated-physics-of-black-holes-with-steve-balbus-andrew-mummery/Thanks to our Patrons James Parrish, Sunny Thao, Elizabeth Terveer, Dawson Brandon, Bhanu, William Silverman, John Hutchison, Carl J. Patrizio, MariElsa, Aminah, and Anna Szamosi for supporting us this week. Subscribe to SiriusXM Podcasts+ on Apple Podcasts to listen to new episodes ad-free and a whole week early.

He's in a different gravitational field from the ones who went down to the planet, which was near the black hole. They lived 15 minutes or something, and the guy went 10 years or something. I think maybe even more. But yeah, crazy ratio of time. Time dilation. 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 going to wait until I get somebody else to do this. It sounds like you're the guy for that. Welcome to StarTalk. Your place in the universe where science and pop culture collide. StarTalk begins right now. Gary, we're in the UK now. Good.

This is your place. It is. I'm here as your interpreter. Oh. We're in the UK now. Good. This is your place. It is. I'm here as your interpreter. Oh. We're in the town of Oxford. Is it city or town? Oh, I don't know. But I...

We'll give it city status. All I care is that there's a university here, and I have colleagues. My people. You got peeps? I got people. All right. I got people.

Okay. All right. Very good. We're going to meet any? Yeah. And by the way, like, where's Chuck? Chuck is otherwise disposed. Okay. All right. Very good. We're going to meet any? Yeah. And by the way, like, where's Chuck? Chuck is otherwise disposed.

Okay. And I figure I'll settle for a Brit as my co-host. I am not the new Chuck. Okay.

I have a colleague who I met many, many years ago. All right. Like decades ago. All right. And he still

wants to know you? And I found him and I called him and said, I'm in town. And he invited me to come chill with him. Nice. He's sitting right here.

Is that who he is? 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. Does he? Yeah. Are we having a phenomenon envy? Are we? Are we having a little bit of phenomenon envy? Is that a thing? I didn't know.

It is now. The psychologists haven't gotten to that one yet. I see. If I've just invented it, I'm claiming it. So tell me about this thing that carries your name in our field. So it's based on work that I do. You're a theorist. Yeah, I do theory.

Yeah. Pencil, a lot of pencil and paper, and of course nowadays computational work. Yeah. And in particular, back in the 90s, I did some work with a colleague named John Hawley. Uh-huh. The late John Hawley. The late John Hawley. Recently.

So he passed away a few years ago, unfortunately. named John Hawley. The late John Hawley. The late John Hawley. Recently. So he passed away a few years ago, unfortunately. And at the time, we were trying to figure out how you make black holes. Oh. And the hard part of doing that, gravity is present, and of course, gravity ultimately is the reason that things make compact objects.

Wait, you go so far back to a time before we knew how to make black holes? That's how old you are? That's how old I am. I go back to a time when black holes were controversial. Polite astrophysicists. And since then, Nobel Prizes have been given for black holes. 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. If you read it, you put a fake cover on it. Oh, all right.

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. It's probably how the sun was made. But the planets in the solar system just go around in orbits. 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. 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. The powers of ten. Yeah, powers of ten. Yeah, yeah. Millions, it was millions of times too inefficient. Which is a fun state of mind, of research to be in, where you think you're on top

of the physics of something, you calculate it out, and you're off by factors of thousands. Yeah. And then, but you still go to work the next day. Exactly. You don't let that kind of thing bother you. Or you should find another line of work. It's a stimulation

to seek. You know that you're almost, that you're on to something, but there's an important piece that you're missing. Evidently. Yeah, okay. So what people suspected, and with good reason, is the reason that the disks work the way they do is it's not just friction, but the gas itself is turbulent. So it's a little bit like 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 and the flow can indeed be thousands or tens of thousands, millions of times higher and more efficient. So you say you can get like an eddy. You get lots of eddies. So that random thing spewing up. Exactly. They rub against each other. Turbulent eddies.

That's exactly what the professionals call them. I knew a turbulent eddy. I think we all do. Probably not the same guy, but there's always a turbulent Eddie. Actually, I got that from Al Roker. I mentioned the phrase turbulent Eddie, and he said, I knew a turbulent Eddie. And I felt, I walked right into it. I said, what's he doing now?

He said, five to ten. You're the straight man. I didn't know I walked into the straight man. That was with Al Rucker a few years ago. Al Rucker's turbulent eddies. That's what we're talking about. But you want to understand why they're there. 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. Interesting. 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. This is the accretion disk. This is the accretion disk around. It's circulating toilet bowl style. Exactly. Into the abyss. 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. 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. So you publish this, Balbus and Hawley, 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? No, I can't say that I had a conscious campaign. Yes, you did. Look at that face. And in fact, it's known by

a few names. It's not known, I should say, exclusively by Balbus. It's also called magneto-rotational 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 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. Was it able to predict emergence? 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. And without that, you're just pushing pencil. Yeah. Right, at that level. Yeah, but you're getting more clues. You said there was something missing in your puzzle, so now you're filling in that.

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 when a lot of people had a hard time getting their head around that something that seems so weak could have such an important effect. So this was an astrophysical instability, not an emotional instability. Well, I had those as well. But what I'm talking about, right, the astrophysical instability, not an emotional instability. Well, I had those as well. But what I'm talking about, right, the astrophysical side of things. So you mentioned like a whirlpool effect.

Yes. 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 from that? 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. But nevertheless... The sort of things you could see in nature.

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 and accretion. 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. Yes.

What is it you said to me earlier on today? I don't remember. That I'm going to get the T-shirt, physics is my god. Oh, physics. Okay. Are you going to get that T-shirt? No, I'm going to get it for StarTalk. We're going to have it made up.

We're going to have it murk and make money. Okay. So let's fast forward. And I understand recently that this year, 2024, you have a textbook coming out on Einstein's general theory of relativity. 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, to turn it 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.

That would have been 2016. 2016, that's exactly right. Is that the same as Hawking's radiation? No, that's a different kind of radiation. Then I won't blur the lines here, sorry. Get your radiation straight, dude. Sorry, dude. Last time I invited you on this program.

Yeah, no, this is the force of gravity itself being radiated in a way which is rather similar to the way that electromagnetic radiation is being radiated. An effect predicted by Einstein 100 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. So it's an update. It's very, a lot has been going on on the observational side. And so I'm fortunate because the textbook discusses that as well. All right, so it's a textbook. So is there like a general relativity for dummies that you can,

is there like the crib notes version of the textbook? Have you considered that? I haven't considered that, 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. So it would be General Relativity for Non-Oxford Physics Majors. Yeah.

You know what a very good book is? One that I love. I mean, you know, but it's meant for the layman because it's written very clearly. There's a book from the 1990s 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. That's Kip Thorne. And that's Kip Thorne. That's our book guy, Kip Thorne. That's your guy, Kiprageous Legacy. That's Kip Thorne.

And that's Kip Thorne. That's our book guy, Kip Thorne. That's your guy, Kip Thorne. We all love Kip Thorne. Kip Thorne is... Co-executive producer of the film Interstellar. Absolutely. Yes.

And he's the man who knows all there is to know about general relativity. He's one of the co-winners of the Nobel Prize for LIGO and the discovery of gravitational radiation. He did a lot of the heavy lifting on the theory side of that. Okay. And he writes brilliantly and very, very clearly. For the layman. Okay, good. 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. How did he do? He did okay. He predicted the traffic. You've just damned him by faint praise. Well, that's very hard. I'm just impressed that we live in a time where okay means not so well.

How'd you do? Okay. I mean, I can't throw shade on a Nobel Prize winner. I really just can't do it. And look, to give him credit, he was being optimistic. So at that point, gravitational radiation was still two decades in the future, 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. So you make me think, where are we now with what we don't know? Oh. And what is it we think we need to know? And sort of move on from... Yeah, let me add punctuation to that.

Einstein in 1915 or 16 publishes the general theory of relativity. Yes. Right. And we've been working with it for more than 100 years. That's right. And so what I ask of you, and I'm picking up his question. Yeah. 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? That's an interesting question. Because he laid it out more than 100 years ago. He gave us the equations for it. That's, of course, a very big step because you can't begin to do anything. 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. I think you just said you have to know the power of the equations. Is that another? Is that a translation of what you just said?

You said context. How powerful. Not context. Content. The content of the equation. That was definitely content. Content. The content of the equation.

Do you want to know what's sort of hidden in there? What do the solutions to the equations actually look like? For example, we now know that the most general kind of black… Wait, you're telling me he gave us equations but not solutions. That's not… that ain't right. Leave us hanging. Any great physicist will do that. They just left homework.

Right. Good homework. Isaac Newton didn't solve all the equations of gravity. Maxwell didn't solve all. There have been at least a half dozen Nobel Prizes given to people working on Einstein's equations. Absolutely. Very much on Einstein's equations. Absolutely. Very much. That's crazy. Crazy fact.

Yeah. Okay. 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.

And everything in Europe rotates. And everything rotates. So that's a very, very important solution. Just a Kerr black hole. It's its own kind of black hole. 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, 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. I'm from Bangladesh and I support StarTalk on Patreon. This is StarTalk with Neil deGrasse Tyson.

So today, what are some unsolved problems? Well, 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 that the black hole has on the surrounding gas. Or anything. Surrounding anything.

But gas is usually what you have at hand. And 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, 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.

So just to be clear, you know, black hole is not some giant sucking machine. That's 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 we're fine. Well, even more than that, there would be absolutely, if the sun were perfectly spherical as it is versus the sun, which was a black hole, there would be no difference whatsoever in terms of what it's doing to the entire space around it.

Right. That's right. You would get very cold. But other than that, and we freeze to death. In terms of the gravity, yeah. But ignoring that complication, we'd be fine. Right. Right.

Okay. Just the gravitational part. Do they rotate the same direction every single time? The splat calls? Yeah. No. Interesting. They can rotate however they like.

Alright. Like the 900 pound gorilla. Apparently so. It sits where it wants. Yep. These orbits, it seems to me they'd be easy to calculate. 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? Pull a Newton on a black hole. Pull a Newton on a black hole. And the answer is... Newton is your guy. I know. He's not from Oxford, he's from Cambridge.

Okay, well, that's okay. You'll take it. Oh, yeah, we're big fans of Newton. Okay. And so when you're dealing with orbits around Kerr black holes, the equations are so daunting. Just to write down the equation takes up a page of your notes. That's 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 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, you know, significantly. 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? I think that's a very fair statement. Okay. I think it's a very fair statement. Contrary to sort of 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… Muster the fortitude, what does that mean?

That sounds very British. No fun away to get it done. No fun away to get it done. Thank you. Thank you for the translation. Told you this one. Mustard the fortitude. Thank you, William Shakespeare.

But if they can find a simple way, 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 as well. With observational consequences. With observational consequences.

Okay. Very much so. Okay. So you have a student who did this. I do. So why am I still talking to you? Well, I don't know, Neil. I didn't arrange the schedule.

Okay. All right, Gary, let's get him out of here. Okay. Ready? On three. On three. One, two, three. There you go. There you go.

There you go. Hello. Hello. Your name? I'm Andy. Andy, pleased to meet you. Nice to meet you. Welcome.

You sound like this guy. Yes. How about that? Are you a Brit? I am a Brit. He's a Brit. What gave it away? Okay, you'll help me translate.

Of course. May not tell the truth, but I'll translate. So you're not literally a student. You're a postdoc. I'm a postdoc. So I was a student 2014 to 2018 to 2022. Okay. And then I've been a research fellow here since then.

Here at Oxford. In Oxford. Oxford. Yeah. So you picked up some of Einstein's mantle here. That's very generous. To the mantle of Einstein. Yeah, yeah, yeah.

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. I see. All right? And Kip Thorne 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.

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, and the guy up there went 10 years or something.

Yeah, I think maybe even more. But yeah, crazy ratio of time. Time dilation. 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 going to wait until I get somebody else to do this. It sounds like you're the guy for that. Yes, yeah, I'm all bits near to a black hole. That's the day job. He's the guy. That's the day job.

How many people do we bump into? How many of our audience this is not an accidental bump into 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 we have very curious people who watch this I'm sure they ask that question because you'll see it and they're not just going to receive it assuming it just can happen. Give me some answers there.

So you can get pretty close. So for your simplest Schwarzschild black hole. So that's the non-rotating black hole. Non-rotating. So let's make the event horizon one. Okay, we all know about the event horizon. The point of no return that we all know about. So the edge of the black hole, that's one. Then you can stably orbit on a circular orbit down to three.

But not less than three. Not less than three. So, yeah, I mean, it's the roundabout force. When you drive around a roundabout, you get pushed out. So that's what an orbit is. You balance that with gravity. A roundabout would be a traffic circle. Yes, sorry. It what an orbit is. You balance that with gravity. A roundabout would be a traffic circle. Yes, sorry.

It's a roundabout. When you're here, you're roundabout. When you're back home, traffic circle yourself silly. 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. Absolutely. Okay. So how close was the gargantuan planet? I don't remember them saying so. It would have to be really, I mean, fantastically

close. In fact, I'm not... Closer than three. I'm pretty sure it's gonna be closer than So this would mean Kip mm-hmm a boy You call in the mail we call that Kip Thorne Kip Thorne yeah, so then landing on the planet that would been unstable. That little kick would have sent it spiraling in. Wow. So what happens? Why can't you just orbit right above the event horizon? 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. So that keeps you at the same distance from the event. Absolutely. Your urge to fly off is a balance. Okay, so now what? And then you write down the same problem in Einstein's equation, and you find that there's a new force, effectively.

A new force? Well, no. So the force is gravity. That's the only force. But there's something, an effective force, which is gravity times rotation. So that's what the equation looks like. So this is a new term.

It's a new term in the energy equation. That operates on the stability of the system. And that points in. So the faster you go around... So that term is not there in Newton's equation. No, no, no. So as you get closer and closer to the black hole, this other term shows up that prevents you from sustaining a balance. 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. Yes. So you get closer, you have to go faster and faster and faster to stay in orbit. In order to stabilize that extra term. 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. Wow. So the faster you go, the worse it is. Yeah, exactly. And eventually... That ain't right. Diminishing returns.

Exactly. That ain't right. That's wrong. That's just wrong. Why did you come up with that? I mean, that's the universe. Are you telling me no one figured this out before you? So this was known.

We knew that the orbits became unstable. 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? 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. Yeah, exactly. So it's unstable in that you perturb it and you're gone. And it gets even more and you're in. Yeah, you're not. So you speed up to try and break the orbit and you just end up making it way worse. Worse, yeah. And you're gone. And you plunge across the event, and you just end up making it way worse.

And you plunge across the event horizon, and you're doomed. Say goodbye. Damn, dude. Yeah, and so, you know, this is a prediction. You're bumming us out. Yeah, yeah, I'm sorry. Well, it's the universe's fault. Oh, okay.

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. Yeah, so we knew this happened. Okay, so how did you contribute to that problem? So this guy, 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.

It's like a piece of paper that someone's ripped into tiny little bits and then scattered. Okay. And then you're now trying to bring it all back. Well, the paper is the pre-existing how the universe works. So they're trying to piece it back together to say, oh, no, that goes there, this goes here. Right. And then we're getting there. So this is what I think Andy's kind of…

Okay. So how did you come in on this? 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 that you...

You want to observe the unstable world. 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. So you've got to build a model of this plunging gas.

So build a model of this on a computer? Yeah, pen and paper, computer. What did you use? I used pen and paper. Oh! Oh, chalkboard! Oh! These are like the cheapest scientists to keep around. No, they're not. Yes, they are.

No, they're not. They're totally cheap. There's no computer. There's no telescope. There's no particle accelerator. Have you seen the price of graphite lately? Go through pencils. I need the best chalk.

Stick it in his office. I need the best chalk. And then he'll be busy and come out later. Okay, so go on. 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.

So you have to predict what unstable spiraling gas would look like. Exactly, yeah. So what does it look like? Well, it's hot and small. I could have said that. You didn't. But I said, stop it, Pat. You didn't, and you didn't go for swirling and unstable either.

But precisely how hot and precisely how small, that's where the money is. You got it. So we have these theories that Steve worked on since the 70s. Your advisor, Steve Vaubus, yes. Yeah, absolutely. Who we snapped him out of existence moments ago. Yeah, he did work on it. And they had these models, and they just stopped at this last stable orbit.

Then it plunges, it gets difficult, and we'll ignore it, basically. And so you stop there. That's what I would have done. And then eventually we started getting data that they couldn't explain if they just wanted. 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.

It's well inside. Inside you are unstable. Absolutely. Yeah. So that planet just would have not been hanging out. No. No. It would have been gone eons ago.

Eons. OK. 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.

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 there 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 the most famous relativity book there ever was.

Okay. It's called Gravitation. It has the proportions of a Manhattan Yellow Pages phone book. 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 that's what yeah yeah i get that yeah see what you did so it says three authors misner thorne and wheeler and kip thorne is the middle author there so we all have it in in my generation it's too old for you i don't know i've got it you do have

the book okay 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. I mean, the man's got a notable price. He's, you know... It might not have been him. He might have been overridden by producers and directors. Yeah, okay.

Because that does happen. Okay, I've got people slack. Yeah, okay. Because that does happen. Okay, I've had people slack in movies. If the idea is kind of right, even if in detail it's wrong. That orbit exists. That orbit exists that the plan's on. It's just unstable. So it just won't exist for long.

It wouldn't exist for long enough for them to do anything they were doing. Yeah, but it exists. It's a solution that's valid. It just won't hang around. We'll take the thorn out of your side for the moment. The kip thorn out of my side? 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 going to find what it'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... And what kind of telescopes... Coming to you as an astronomer, I want to know what I should point my telescope at.

So what are your data sources? Is it telescopes? Is it computational? So these are X-ray telescopes, so they're satellites in orbit. X-ray telescopes? And we're about to lose our last X-ray telescope, the Chandra Great Observatory. That's going to be a real... It's going to get de-orbited very soon, I think. Last I heard.

There will be others, but Chandra's a wonderful instrument. Yes, okay. So it's, you know... Name for? Chandra Sekhar. Chandra Sekhar. Very good.

He knows. I'm just checking in. He knows. He's still a student. Make him dance. I'm allowed to be like Professor Neil every now and then. Okay.

And as I remember, he was a great astrophysics theorist and good tradition in the steps you're following. If I have half the success of Chandrasekhar, I'll take that. So you published this? Yeah, yeah. So it's X-ray data. So these disks are super hot, incredibly hot, and they produce x-rays, and they are detected by satellites.

They're so hot, they radiate x-rays. Absolutely. As opposed to being so hot like your electric stove, it radiates infrared. Then you can radiate ultraviolet if you get hotter, and then x-rays. You keep radiating up the spectrum. How hot do you have to radiate ultraviolet if you get hotter, and then x-rays. You keep radiating up the spectrum. What goes hot? How hot do you have to radiate to get worse than x-rays?

Millions of degrees. So what happens if you get even hotter? And it's gamma rays. And then what's it going to say? Yeah, yeah, yeah. We're in Hulk territory. That's very hot. Whereas your stove is a thousand degrees.

Yeah. We're talking millions. We're talking millions 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 okay so you so you published did you publish your theoretical predictions and found some data that explained? Yeah, yeah. That's the best way to do that, right?

We did, exactly. Yeah, yeah. We had a bit of a heads up. We knew that there were mysteries out there, and we thought we had the answer. As they do us all, my friend. Yeah. And we were able to show, yes, you have this data, this beautiful data, and you just can't explain it without this plunge, this gas on the plunge.

And where did that appear? It was in the monthly notices of the Royal Astronomical Society, a very British journal. You kept it British. You know, we have journals, too, in America. Yeah, but they're not royal. They didn't have the king's approval. Okay, here we go.

Oh, I've got to get used to this. Not the queen's approval, the King's approval. King Charles, okay. So this is a leading journal in our field. Yes, so congratulations on that. Yeah, thank you. And if I understand correctly, that got some media attention. Yeah, it caused a bit of a stir.

Yeah, yeah, yeah, it was good fun. Classic British understatement. A bit of a stir. Which means people went apeshit. A couple of heads blew up. It was good fun. Classic British understatement. It was a bit of a stir. Which means people went apeshit. A couple of heads blew out. Before we let Andy go, what is your top unsolved problem? And at this point in your career, surely you have some ambitions.

So I want to know how fast black holes are rotating. The black holes we have out in the galaxy, I want to know how fast they're spinning. Dude, think bigger than that. Come on. Let's try again. This tells us how they're formed. So this tells us... There you go. That's why I want to...

Okay, the question you answer is how fast they're spinning. But the long term... But that's one question. But the real answer is how do they form and how do they evolve over the age of the universe? Okay, and this includes supermassive black holes?

Absolutely. Yeah, yeah, supermassive black holes. The big ones, isn't it? I got the hint. 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? That's the plan. So you're going to be the black hole guy?

Yeah, absolutely. 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, yeah, absolutely. I'm a black hole go-to guy. Go-to black hole guy. So good luck with that. Sometimes you need a little bit of that, of course. Yeah, yeah, yeah. My little island leading the way, Neil. How about that?

So tell me, why must everything circle a black hole to go in? Why can't it just fall straight in? It's got angular momentum. And angular momentum is hard to lose. Hard to lose? Yeah. Why? Stuff that's spinning.

Why can't I just... It's conserved. It's a conserved quantity. 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 going to have a little disky thing, somehow it has to have been exactly pointed at it. 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 outer edge. I learned what word that says that. The star is getting flayed. Is that a good word? Oh. That's a good word. The star gets skinned alive. It's to be flayed. Okay. Did I teach a Brit good word? That's a good word. It's skinned alive, is to be flayed. Okay.

Did I teach a Brit a word? I'm an American, we're not supposed to do that. I think we'd actually tell you. Okay, so you have these discs, but suppose other material comes the other way. Doesn't it all cancel out? We've got one source of amount, that's the problem. So it's all coming in from the same direction.

From one thing that's circulating that way. So you're peeling, so you inherit this angularity. It would be odd to have two things simultaneously doing that. So that's what gives you a job, thinking about the spiraling material. If everything just fell straight in, you'd be out of a job. Yeah, exactly. And what about really, really big black holes where they wouldn't necessarily have a disk?

Not always, no. Right. Ooh. Because it's just really, really big, and how are you going to coherently create a disk around it? You just fall in. Within a super massive black hole, does it not spawn its own little miniature? Sometimes there's you know gas in the middle of the galaxy it comes nearby switch on you switch on That's a supermassive black hole

Because the buckles is lurking yeah, right and only when it has something to dine upon Does the mechanism turn on. Very good. I like this book. Those are interesting ones. Yes, of course. Actually, physically. Well, this is great.

Well, thank you for sharing your expertise and for great things. And I still want you to be more ambitious. I just want to know how black holes form. Do it as a big universe, okay? Give him one thing to do at a time. One thing to do at a time. I learned to not, I'm kidding. Can I be wise here?

Go ahead. The wise elder? In my day, people said, I just want to know the value of the Hubble constant. I just want to know the rate that the universe is. 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 Whether you like it or not. Yeah, absolutely. All right, dude. Thanks for being on StarTalk. Thank you.

You got it. You have one last Brit thing you want to say before we sign off? Pop in the last thing, just ignore him. 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. But what does that mean? Those who have come before you, they've put together part of that cosmic puzzle. But no, it's not completely solved. 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. And I'm delighted to have brought you a slice of how science works. And that is a cosmic perspective. Till next time, as always, keep looking up.