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- [00:00]
A
Hello, everybody. This is Marshall Po. I'm the founder and editor of the New Books Network. And if you're listening to this, you know that the NBN is the largest academic podcast network in the world. We reach a worldwide audience of 2 million people. You may have a podcast or you may be thinking about starting a podcast. As you probably know, there are challenges basically of two kinds. One is technical. There are things you have to know in order to get your podcast produced and distributed. And the second is, and this is the biggest problem, you need to get an audience. Building an audience in podcasting is the hardest thing to do today. With this in mind, we at the NBM have started a service called NBN Productions. What we do is help you create a podcast, produce your podcast, distribute your podcast, and we host your podcast. Most importantly, what we do is we distribute your podcast to the NBN audience. We've done this many times with many academic podcasts and we would like to help you. If you would be interested in talking to us about how we can help you with your podcast, please contact us. Just go to the front page of the New Books Network and you will see a link to NBN Productions. Click that, fill out the form, and we can talk. Welcome to the New Books Network.
- [01:07]
B
Hello, everyone, and welcome to academic life. This is a podcast for your academic journey and beyond. I'm the producer and your host, Dr. Christina Gessler. And today I am so pleased to be joined by Dr. Jonas Anander, who is the author of Facing Black Holes and Our Place on Earth. Welcome to the show, Dr. Anander.
- [01:31]
C
Thank you, Christina. It's a pleasure to be here.
- [01:33]
B
I am so glad that you're here and that we get to learn about black holes and your book from you. Before we do that, will you please tell us a bit about yourself?
- [01:42]
C
Yeah, sure. So I'm from Sweden. I was born in Stockholm, and today I live up in northern Sweden, close to the Polar circle. And I have a background as a researcher in physics. I did a PhD in physics at Stockholm University, and I've been doing research about a little bit different topics, but most mostly in cosmology and astrophysics, like studying Einstein's theory of general relativity and investigating dark matter and dark energy. But then I have switched careers, so nowadays I work as science journalist, a science writer, and a science communicator. So I spend most of my time talking with other scientists about their research and then promoting that research to the world. Like in this book, for example, when.
- [02:37]
B
You were young, did you know this is the path that you Wanted to take what sparked your love of science?
- [02:43]
C
Not at all, actually. I wasn't very interested in physics or mathematics when I was young and. And it's. So sometimes I get a bit envious about people who say that. Ever since I was 5 years old and looked at the stars, I knew I wanted to be an astronomer. And for me, it was definitely not like that. It was a little bit later, when I was a few years after 20, and I didn't really know what to do in life, to be honest. And then around that time, I was watching a lot of science documentaries, so it was very popular. For example, the question about astrobiology, can there be life in the universe, life on other planets? And somehow I just became very, very interested in that. And then I decided, like, why don't I give that a shot to try to study math and maybe go to the university. So I read up on some mathematics courses and just fell in love with it somehow and became quite obsessed about studying mathematics and physics primarily. So, yeah, I guess sometimes you don't know in advance where your life is going to take you.
- [03:59]
B
The book, in some ways, is life taking you places. In some ways, it almost reads like a travel journal. You go to so many different places to do your research and you very generously describe what it's like in each of those places, who you meet, the questions that you're there to po. But my first question is, what inspired you to write this book?
- [04:18]
C
Yeah, so that was an image that came in 2019. So at the time I was at a cinema in Stockholm and I was going to watch a Swedish science fiction movie that was just coming out. And then I looked at my phone just before the movie started, and there was this new image, the first ever image of a black hole created by the Event Horizon Telescope collaboration. And I knew that they had something going on, that they wanted to try to create an image like that, to really show what it looks like near a black hole. But I didn't know if they were going to succeed or not. And when I saw that image, I felt that this is something I want to learn more about. I really want to write about this and talk with the scientists who have produced this image, but also with other black hole researchers and really understand what is our current knowledge about black holes and also what do black holes mean for us as humans here on Earth. So that was the original inspiration.
- [05:24]
B
And as we dig into the book, we encounter quite a bit that scientists know about black holes. And you bring us into maybe some of the limits of what we can know about black holes before we dig deeper, though. Can you explain for listeners who, like me, may not be scientists or what we mean when we say black hole?
- [05:44]
C
Yeah, absolutely. So the kind of formal definition of a black hole is that it's a place in the universe. So I say place, not an object, but really like a place in the universe where gravity is so strong that nothing, not even light, can escape it. But. But what does that mean, actually? So the first thing is to think about here is the word gravity, because that's something that we all have experience of here on Earth. Like, we feel gravity every day from the moment we wake up to when we go to bed. And while we sleep, gravity is always there. So we so kind of used it that sometimes maybe we don't think that much about it, or we just take it for granted that it's always there. But a black hole is what is what happens when you let gravity go to its most extreme. So gravity gone wild. And that can happen, for example, when you take very, very heavy stars, and at the end of their lifetime, when they have burned all the nuclear fuel they can explode, and the stellar matter gets compressed into a very, very dense small volume. And if that happens at enough compression, at enough strength, if you can compress enough volume matter inside a small enough volume, then gravity becomes so strong that light can't escape there. And then you have a black hole. So that's the rough idea of what a black hole is.
- [07:21]
B
And as we go further into the book, you tell us also what a black hole is not. On page 88, you say definitively, black holes are not cosmic vacuum cleaners. Cleaners. So while we're imagining this profound gravity so strong that nothing can escape it, we are not to imagine a profound vacuum cleaner.
- [07:42]
C
Yeah, exactly. That's correct. That's one of the most common myths about black holes, that they kind of roam around the cosmos and they suck everything in and grow as the do so, and eventually they will swallow everything around them. And there's also this kind of idea. It appears a lot in popular culture. There's a Simpsons episode, for example, when a black hole is created and sucks the entire village or city that Simpsons live in inside of it. But that's not really correct. And if we take, for example, the sun. The sun cannot become a black hole. It doesn't have enough mass so that by the end of its life, in 4 or 5 billion years from now, it would become a black hole. That's not going to happen. But we can still imagine what would Happen if the sun turned into a black hole. So you would take all the stellar matter that we see in the sky and you would compress it down into a volume that's not bigger than some 6km across. So about the size of a small city, a very small city, or the center of a city center. And when that happens, the sun would become completely black and turn into a black hole. But we further away, we would still continue on our orbit around the sun. So the Earth would continue around there, Jupiter would continue around there, the planets would go around there. Everyone would be happy. Besides the fact that there's not any light anymore, there's no light anymore. And the reason for that is it's only very, very close to the black hole where you start to feel these new strong gravitational effects. Further away from it, it's still the same amount of mass as before, and it still gives the same kind of gravitational effect as before. And furthermore, if you would like to go into the black hole, it's kind of hard to pinpoint it because it's only 6km across, right? So the sun that has turned into a black hole is a very small object in the solar system, Even if it sits there dead center in the middle of it. So you have to navigate quite efficiently to target that black hole. So it's. Yeah, and there's more to say about that. Maybe we'll talk about that a bit later. That they also produce these kind of jets and can transform into quasars. But I end there for now.
- [10:06]
B
Early on in the book, in the epilogue, you invite us to imagine a black hole. Speaking of using your imagination and what we would experience if we fell into the black hole. I started reading this book as bedtime reading. I don't recommend chapter as bedtime reading, but chapter one takes us into the priest who wanted to weigh the stars. And you open it by saying that you're not sure an author wants to begin a book by taking their reader's life as they fall into this black hole. But you, you assure us that we are never going to have that dramatic journey. No one has even come close to that. But you also invite us into how long people have been thinking about, about black holes and taking us into the wondering that was happening before the term was defined, before the full concept came together. And so chapter one, we meet who might in some ways be an unlikely scientist as we meet him in the story. He's a minister, but he started out when you first introduced him. He's a professor. And for many of us, particularly here in the States, he has what we imagine is the dream job. He's at a revered university. He has a job that he's in no danger of losing, but he leaves it. And yet he doesn't actually leave the study of science. Can you take us into his story, please?
- [11:28]
C
Yeah, thanks for summarizing that. The man in question is John Mitchell. He's a really fascinating researcher and cleric at the end of the 18th century, and he lived in England, and as I say, he was a very prolific, extremely skilled in many areas, researcher at Cambridge. But he wanted to get married, and apparently he was supposed to live in celibacy if he was to continue to be at Cambridge. And he didn't really like that. And he had some misfortune in his life, and he has decided that he wanted to start afresh and to go into the world of religion instead. So he became cleric, a priest at the city of Thornhill in England. And that didn't stop him from continuing to think about the universe and the natural world. And he still did a lot of astronomical and geological research. And one of the things he thought quite deeply about was how stars behave. How many stars are there when you look up in the sky? How are they distributed? But also, how massive are there? Are they people? At the time, they didn't know a lot about this. And through a series of arguments based on Newton's theory of gravity, he came to realize that maybe they could be out there in space, certain stars that have so much mass that nothing can leave them. At the time, they knew that the speed of light was finite. It's not an infinite quantity. So it always takes some time for light to go from one place to another. And they also knew about the concept of escape velocity. So that's the velocity that you need to throw something away from a celestial body, like the Earth or the Moon or the Sun. So on Earth, it's 11 kilometers per second. You have to throw a rock that fast to overcome Earth's gravity and make the rock continue out into space. On the Moon, it's much less. It has a much lesser gravity, whereas on the sun, it's a much higher quantity. But from there, it's quite easy to ask the question, okay, but can something have such a strong gravity that its escape velocity equals the speed of light? And in that case, light couldn't leave it? And John Mitchell did that calculation. He saw that if you take something like the sun and have its chemical composition the same, but you increase its volume, its radius by a factor of 500, so you make it really, really big. Then its gravity would be as strong so that no light could leave it. And this was later called dark stars. And this idea about dark stars, it spread to France and Germany. So in France, there was another physicist and mathematician called Piercemon de Laplace, who speculated widely that maybe the most common object in the universe are not the luminous stars. Maybe it's these dark objects. And then in Berlin at the time, there was another astronomer a few years later who thought, but maybe these dark objects is actually at the center of the Milky Way. But could that really be? Could there be stars moving around it? And he even tried to look at that with a telescope. And he writes that not even with the best telescopes, we can see a sign of, for example, other stars moving around such a dark object. So people really speculated a lot about these dark stars and that they could be very common in the universe and that you could even try to observe them by looking at how other stars are moving around them. But nothing was found. And at the beginning of the 19th century, there also emerged a new theory of light, where light was not made of small particles, maybe it was a wave structure in light. So it was a bit confusing. Was this calculation really correct about the relationship between light and gravity? So pretty quickly, the idea disappeared kind of from the imagination of the scientists. So it appeared very quickly, and it also disappeared very quickly, which is quite fascinating. But it was the first idea that maybe there can be this kind of completely dark objects out there in space. And I'll stop there. Yeah.
- [16:27]
B
In the book, you explain science to us in a highly accessible way, but you also explain scientists to us. As we meet Mitchell in this chapter, we also see his concerns about if he does his research, will other scientists take credit for it? It's something that scholars do worry about, and you don't shy away from bringing that up. You also talk about how he can read ancient Greek and hebr. He's a member of the prestigious Royal Society. He was liked by his colleagues. You open by telling us how he left his. His job really for love. He wanted to get married, and yet his. His wife dies in childbirth. He ends up at Thornhill Rectory, which was not a large town. He wasn't in London, he wasn't near Cambridge, and yet thinkers come to see him. At one point, I believe you introduced a story of Ben Franklin. In that chapter, we also see him growing a botanic garden. He remarries, and yet you point out that the Seven Years War happens. One of the things I appreciate about this book is science and Philosophy and research are happening not in times of ease, but it's still happening in difficult times, during obstacles. And I think that piece of the story as well, in many ways serves as an encouragement for people everywhere who are trying to work on knowledge production.
- [17:54]
C
Yeah, thanks, Kristina, for bringing that perspective up. It's very true. And I do try to situate all the research that happens in some kind of historical context and to see all the influences that also affect the scientists and their possibility to do research. And as we move on in the historical development of the black hole idea, we see that it's actually very, very closely related to war. Later on, we have Carl Schwarzschild, who during the First World War, really discovered the modern theory of black holes with aid of a formula. And we can get deeper into that that requires some explanation. But also later on, we have someone like Robert Oppenheimer, who showed us how black holes can form and really strengthen this idea that they can exist in nature. And he was, as everyone knows, of course, responsible for the Manhattan Project, the development of the atomic bomb. And a lot of the physics that they learned from these atomic bomb explosions was later applied also to understand how stars develop. So. So it's not possible really to isolate the mind of the scientist from the rest of the society and the life of the scientist from the rest of the society. Definitely.
- [19:18]
B
We also see the long view. There's so much thinking, there's so much building upon each other's theories. These aren't quick discoveries often. Once it makes the news, people think of it as a sudden thing. But you point out on page 24 that in October 2020, more than 200 years after the speculations of Mitchell that he's proven right. When the Nobel Prize in Physics is given in 2020, it's long after his death, it's 200 years later. But there's work that takes such amount of time to prove. And it starts with sometimes in unlikely places. Here he was in the rectory, continuing to do his work. The story picks up with Einstein in another chapter. And again we see him as a human being living his life. He's at school, but he's really not in his classes. He's off discussing philosophy, he's failing tests, he's reading Hume. Basically, his teachers didn't like him. I think that's also heartening for many listeners and readers. He can't get an academic job because nobody wants to give him a reference. And he ends up at the patent office, which is a story I think we do tend to know about Einstein and yet the default when we even mention Einstein's name is this unquestioned genius who was always a genius and he had an interesting zigzaggy pathway. And we see that while he's doing his government day job, he names his desk drawer the Institute for Physics. So here's yet another person who's not doing work where we would expect him to. And yet he's still a scientist through and through, and we see his contribution again to this understanding of what a black hole is or could be. Can you take us into Einstein's story, please?
- [21:10]
C
Yeah, absolutely, yeah. Einstein is, for me, when I think of Einstein, I think of someone, a quite funny character. We often have this view of Einstein as this kind of old genius with whirly white hair and who sticks out his tongue in front of the camera and cracks lines of wisdom and so on. But when he did some of his main discoveries, he was first of all, not an academic, as you said. He worked in the patent office and he was quite young and to a certain extent, bohemian. And he has a very witty style of writing and his humor and so on. And yeah, I really liked the character of Einstein the more I read about him. And what he primarily had was a very, very deep curiosity about the world. So he's really driven to understand how the world works. And that's why he continues to do research while he is not employed as an academic, while he has a day job investigating patent applications. And he was very perplexed about the question, what is actually time and what is actually space? So time is something we also kind of. We take for granted that it exists. We always want more of it. Like, we always feel like we have too little time. Like that's the constant stress in life. And we always, when we go about our daily business, we. We have this continuous array of clocks everywhere that signals us to us, what the time is. But Einstein really wanted to know, but what's beneath that? What's beneath the superficial phenomena of clocks and so on? And the same with space. And when he was thinking about that, he came to this really huge realization that I think we are still grappling with the consequences of. And that is the famous statement that time and space are relative. So it doesn't exist like a universal clock in the entire universe that ticks at the same rate for everyone everywhere. And there's no universal ruler that shows the same length distance measurements for everyone everywhere. On the contrary, time and space change their properties depending on how fast you move and also where you are in a gravitational field. And it's a bit tricky to explain exactly what that means because that's usually what you read about towards the final year, if you study physics at an undergraduate level and then maybe you take a course in general relativity and so on, but to make it very concrete, this is something we measure today. We have such a good clocks today, atomic clocks. And you can place one of them on the ground and you can take another one and place it on a table one meter higher up. And researchers can see that after a while these clocks start to drift away from one another. So even though they are completely synchronized when you start the experiment, after a while they start to drift a little bit and the clock that's closer to the ground ticks slower compared to the clock that's higher up. And what Einstein said was that's actually why objects fall to the ground. They follow a curved trajectory in space time. So if you drop an object and it falls towards the ground, and it sounds so weird to say it, but what Einstein said was it goes to the ground because time flows slower at the ground. So different bodies, celestial bodies, massive bodies in the universe, Earth and the moon and the sun and other stars and entire galaxies, but also asteroids and smaller bodies because of the mass and energy they contain. They will warp space and time around them and surround the sun. This warping is much of a much higher degree than around the Earth, but it's still kind of hard to twist and bend space and time. It requires a lot of mass to do that. And that then turns us into the question of how does this relate to black hole? And it turns out that black hole is the most extreme example of this bending of space and time that you can have so close to the black hole. Time can become infinitely slow compared to much further away. So that happens at the surface of the black hole, the so called event horizon. So that was the kind of world and the vision about the universe and how space and time work that Einstein opened up just by the first investigations, thought experiments that he did while still being a clerk at the patent office and then later on becoming a full time academic and continuing his research. But it all started there at his, what you mentioned, the desk that he jokingly referred to as the Institute of Physics.
- [26:45]
B
And you point out in the sections on Einstein that while he has this job, he has already written several scientific papers, one of which you point out, is the basis for a major award he will win more than a decade later. And again highlights the length of time that it takes not only for science to be done, but for it to be tested and retested, for it to be accepted by its field, and for the field to grow because of it. In chapter five, you bring us into the story of someone that you've mentioned earlier. I'm going to try to pronounce his name. Carl Schwarzschild. He's on the Western front of World War I. He's picking up on Einstein's work, and he hits upon the formula for a black hole. Can you tell us about that, please?
- [27:32]
C
Yeah, Exactly. So in 1915, so during the First World War and during all the conflicts and problems and death that happened at that time, Einstein succeeded in formulating his general theory of relativity, which is our modern theory of how gravity works. And in it, he says that gravity is actually just space and time getting warped and distorted and changed because of mass and energy. And he also gives us a recipe for how different objects, such as planets, will move in this curved space time. And that explains, for example, why the Earth moves around the Sun. It moves in this curved space time on a specific trajectory, which for us looks like an ellipse around the sun. But this theory of general relativity by itself, it says this is kind of like a law of nature. This is how nature functions on a very abstract general way. And just because you have a theory, that doesn't mean that you know everything that it will predict. That takes time to understand. And the mathematics is actually very, very difficult of general relativity. It's. I did my PhD on that. It was very difficult, I can promise you. So it takes a lot of time to solve the equations of general relativity. But there was a guy in Germany at the time, he was one of the best astronomers in Germany. And during First World War, he did serve as a lieutenant in an artillery unit to do calculations, ballistic calculations, for the army. For the German army. And he was stationed at the Western Front. And he knew that Einstein had hit up on this new formula, and he was very curious. Okay, so what does it say then about the motion of the Earth around the sun and the structure of the stars? Like, what does it predict? And he really wanted to know that. So when he had a break from his military work called Schwarzschild, he sat down, did the calculations, and he was very good at math, so he managed to solve that. And he hit upon this formula. Today, it's known as Schwarzschild's formula, which describes how black holes work. And it's really the foundation of our modern understanding of black holes. And late, of course, there has been a lot more development afterwards, but that's the starting point. But intriguingly enough, Karl Schwarzschild himself, he didn't understand the consequences of this formula. The mathematics was so new and so weird. And unfortunately, he was also struck by a disease, a skin disease at the time. So he has died a few months later in 1916, May. So it's a very. Historically, it's such a weird situation, like it's a war time. Someone who takes a break from his military work finds this formula and then dies very soon afterwards. And it's left for other people to figure out the full consequences of the very weird mathematics that is found. And I would like to add that what I found also to be one of the most intriguing things about black holes is this thing that we discover them mathematically first. So it's not like the sun and the stars. First we see them empirically, we do observations, and then we also question, oh, so how do they work? Why do they shine? How long are they shining for? But with black holes, it's the opposite. First we have encountered the mathematics and trying to grasp that mathematics and work out the consequences of that. And people doubted for a long time, can this really exist in nature? And it took much longer for the observations to come. So for me, that shows how far our mathematical thinking can reach when it comes to understanding objects that lies millions of light years away from us. So we can still use our mathematical power in our brains to understand that. For me, that's really, really amazing.
- [31:55]
B
And the book in many ways highlights how far away from the black holes the scientists are when they're doing this research. You mentioned the time period when he's doing the work, but you also give us a picture of his military ID car, and later there's a picture of one of the letters that he wrote. We see him so very much here on Earth while he's contemplating things that are so, so many miles away from him. And you bring us into you as a researcher trying to read his handwriting. There's more about him in both chapters three and five in the book. And again, the humanity of the scientists that you're introducing us to, as you pointed out, his health concerns. You also keep bringing us back into the science. And in the chapter called beyond the Event Horizon, you're explaining to us about how the event horizon gets longer and longer. And you want us to understand a key concept called the light's redshift. What is the redshift?
- [33:08]
C
So redshift is something we are acquainted with when it comes to sound. We know that for Example, if you stand on the street and you hear an ambulance passing the pitch. So the frequency of the sound of the ambulance will go up a bit, and then it will go down when the ambulance moves away from us. And something similar can happen to light. For example, if I take a laser, if someone shoots a laser towards me and I'm moving towards the laser, then I will actually detect, if I measure it carefully, that the light of the laser, the frequency is a little bit higher. So the color has changed a little bit in this case to the bluer part compared to if I would have been stationary. So light can. We can observe light in a bit different way depending on how we move relative to light source. And that's called redshifting. So redshift is like a generic name for just how the frequency of light changes depending on how you move relative to it. But there's also another effect to it, and that's that light can become redshifted when it has to move in a gravitational field. So if it has to, for example, leave the very strong gravitational field around the black hole, of course, if it's inside the black hole, the light ray, it can't leave the black hole. And if the light is emitted exactly on the event horizon, it can't leave the black hole either. But it could be emitted a bit further out. So, for example, maybe an astronaut is there with a flashlight and turns on the flashlight. Or maybe this, like a gas, some matter moving around the black hole, which we know it can do. And that could also emit a light. And then that light can become redshifted. So in this case, it means that it will get a lower and lower frequency because it costs energy kind of to move away from the black hole. And the closer the light is emitted to the black hole, the more it is redshifted. So the more, the less energy it also has. And if the light is emitted right outside of the event horizon, then this redshift will be almost infinitely large. So that means that the energy it contains will also be almost infinitely weak. And that's one of the reasons why black holes are black. It's not only that light can't escape them, it's also that the light escapes them that manages to live very close outside of them and leave further out into space that that light also becomes so extremely weak. And therefore it becomes almost impossible to see what happens very, very close to a black hole.
- [36:02]
B
There is so much to understand about black holes. On page 84. You offer a great deal of compassion to the reader. You say if you're feeling uncertain about how a black hole works, you're in good company. Most physicists studying them have felt this way at some point or another. On page 308, you say, it's as though the universe will not allow us to know everything that is happening inside it. The dream of science is to understand and explain the entire cosmos. But you go on to explain that because of the nature of event horizons and black holes, that there's right now at least an absolute limit placed on our access to knowledge. That. And that brings me back to the opening story of the image that was released in 2019 about the importance of telescopes in modern research, and to a story that you bring us in early on. In a chapter called the Dark Heart of the Milky Way. You're in a jeep and you're headed up Mauna Kea. Can you tell us about the importance of telescopes and what we're learning?
- [37:08]
C
Yeah, absolutely. So we talked a bit about what is a black hole? And this theory going back to Einstein and Schwarzschild, about the modern mathematical formulation of black holes. But then, of course, you're left to wonder, so sounds great, everything. But how do you actually observe them? And the key to observing black holes is really to try to understand and observe what happens around them. So you want to see how things move and change around them, and then from that, you want to deduce the existence of a black hole, because the black hole itself is completely black and impossible to see. But in a way, that situation is similar to if you go into a dark room, it's dark, you can't see anything, although obviously it's dark. So you need a flashlight. You need something to kind of see what goes on there, and something that traces what exists in that room. Exist in that room. And in the case of Mauna Kea and Observatory Stair, one of the main discoveries was to see how stars move around a black hole. And it's not just any black hole. It's the black hole at the center of the Milky Way. And this is what we call a super massive black holes hole. So black holes really come in two types. There are smaller black holes created when stars die, certain very heavy stars, and there are these supermassive black holes that live at the center of many, almost every galaxy. And these supermassive black holes, they can have a mass of millions, up to several billions of suns, and their size can be on the order a little bit smaller, a little bit bigger than our solar system. So what two teams of astronomers did, one based in The US with Andrea Ghez, and one based in Germany with Reinhard Genzel. I should say based is a bit fluffy world here because science is a very international endeavor and there's a lot of mixing between different countries and so on, and international collaboration. But if we take Andrea Ghez, who I interviewed for the book, she at length and described more in depth of the visiting Mauna Kea. She used the telescopes there to really painstakingly follow the stars over several years, and she could show how they move around the Milky Way, a black hole at the center of the Milky Way. Whereas Reinhard Genzel, the German astronomer, he used a set of telescopes, primarily in Chile, in the Atacama Desert, to also study the same stars. And the question of the telescopes is really important here that you had two teams that did this, because in science you always need a verification. You always need someone else to check your result and also criticize result and question it, even so that you really know that your measurements are correct. And in this case, we had two independent teams that did this study of the Milky Way black hole, and they were also awarded the Nobel Prize in 2020 for this research. But the funny thing is that this idea goes back to John Mitchell, who proposed that, okay, if this kind of dark object exists, then we can at least see that they exist by looking at how other stars move around them. So it's one of the most common techniques to deduce the existence of black holes today in the book.
- [40:46]
B
You do go in depth in that story and in your interview with her. And one of the things that stood out for me was her story of how many times she had to apply to be able to go use that telescope to do her study. You point out that there's still a scarcity of resources as we develop more and more advanced technology. There's maybe a handful of places where that's even available and the bar to get access is quite high. And again, she's another story of not giving up, that her application was rejected and she had to keep at it. And to get there to do the work, to spend the years concluding her study. You also address kind of the so what? Question. Sometimes when things are so far away, as space is, as black holes are, there can be a question of, well, what does this have to do with things here? And in chapter 11, you bring it very dramatically to what it means for life on Earth. Chapter 11 is Black Holes and Climate Change. And in this, you talk about about how there's quite a lot we can learn about the Health of the planet and how to take care of it and what climate change means if we continue to learn about black holes. The chapter opens with a rather bleak setting. Much of the world is underwater. The islands, nations in the Pacific Ocean have drowned. Sea levels are changing the world as we knew it. And you're also talking about how these changes to the sea temperature and to the. To the sea rise are actually really small measurements. And it's partly grasping what these mean and what they can do that makes it so difficult to really predict about climate change. And yet, at the same time, we know climate change is happening, and we know that the danger is real. Can. Can you take us into chapter 11 and why black holes are so important?
- [42:40]
C
Yeah. So when I tell people that black holes are important to study climate change, I get a very skeptical look on their faces, like, what's that? How can that possibly be true? And I share that skepticism because when I started doing research for this book, I had no idea that black holes actually help us to understand how our Earth changes. And that's possible thanks to one of the great cosmic ironies of black holes, that although black holes themselves are completely dark, the matter that moves around them can start to shine very brightly because of the strong gravitational field and other effects. And when it shines so brightly, you can see that all across the universe. You can see that from very, very far away. And these objects are called quasars. So black holes actually create some of the most bright phenomena in the universe thanks to their intense gravity. And that light that we can see across the universe appears as kind of point sources, small points of light in the sky. And sometimes that's confused with stars, ordinary stars, which also looks like a point source in the sky. And here's where how we can use them here on Earth, because ordinary stars we have used forever when it comes to navigation. If you want to cross a desert, if you want to cross an ocean, if you want to get from one point to another point on the Earth, you need to know how to get there. You need to navigate. And in order to navigate, you need something that looks fixed in the sky. And that has been stars traditionally. So you learn how to do star navigation techniques, and that can take you across the ocean. But there's a problem with stars when it comes to navigation today, and that stars also move in the Milky Way. They are not stationary completely. When you have really sensitive measurement instruments, you can clearly see that the stars are moving in the sky, too. So in order to have a fixed point of reference in the sky, you need something that's more stable than the stars, something that's even further away than the stars. And what's further away, furthest away that you really can see at a long distance? Well, that's the black holes, that's the quasars, the light from emitted from the surroundings of black holes. So rather remarkably, they actually can be used to create what's called a international cosmic reference frame. So what researchers do is that they link up a series of telescopes all around the globe, and they look at the same quasars, and then they compare their observations. And by doing that, they can see how the telescopes are moving relative to each other on the order of a few centimeters every year. So they get an extremely precise measurement of how the mass, land mass of the Earth is changing. So they can use that to see things like continental plate motion, for example, so how the tectonic plates are moving with respect to each other. And that can also be used to study things like how is the relationship between the sea and the land changing at different places. How can we use that to calibrate also our navigation satellites? It's also used to very carefully monitor how the rotation of the Earth is changing in time, because that's not completely static. There are very, very tiny changes to that. And one of our most fundamental time measurement systems we use today is the rotation of the Earth. And these black holes help us calibrate that. So we actually use these quasars to not only study the surface of the Earth, but also to calibrate our navigation satellites and also to calibrate our timekeeping system. And that's amazing for me. And that really shows how weird humans are. Like, of all the animals on the planet, which one of them actually used distant quasars to better understand their surroundings? So for me, that was quite remarkable. So that became one of the main themes of my book, how black holes impact our understanding of both the Earth and ourselves.
- [47:14]
B
And on page 241, you take us there to a very vivid moment. You're standing there at the ANSALA telescopes and you said, you stand by this enormous machine and look out across the rocks and you say, I think about how humans are capable of measuring a centimeter shift in a continental plate, or a few nanoseconds reduction per day in the time it takes the Earth to spin on its axis. I'm struck by how, despite this detailed understanding of our planet, we're unable to take care of it. What's the point of all this knowledge and technology if we can't look after our world, our only home in the universe.
- [47:56]
C
Yeah, I remember when I wrote that. Yeah, there are several people who picked up on exactly that formulation. And when I wrote that, I just felt it was a very honest feeling when I wrote that sentence that we have such an enormous technological capacity and we understand so many things, but still we're not capable of drawing the right conclusions from that and making the right adjustments to take care of our world. So in a sense, it felt so paradoxical that we have these enormous capabilities, but at the same time, we unleashed this enormous destruction on our planet. So it was a very strong feeling I had there. Yeah. And many people have reacted to that, that sentence.
- [48:43]
B
As we get towards the end of the book, you're inspired by a newly released article that's asking, are we living in a black hole? And you begin to tackle that question. And on page 297, you say, in our observable universe, every second sees the explosion of roughly 100 stars that could lead to the formation of a black hole. And you bring us into the work of a US physicist named Lee Smolin, and you start to consider what it would mean if there was the creation of new universes every second. Did you feel you could answer the question, if we are living in a black hole?
- [49:24]
C
Yeah, I think the answer is no, we're not living in a black hole. And I think the reason why that question gets so much attention is that it's something that really sparks the imagination of people over living inside a black hole. But when you look deeply at the math and observations that we have and how black holes actually work on the inside, I don't think our universe actually resembles the inside of a black hole. And I felt that I wanted to write that chapter and do that investigation because I think it can give the wrong impression to people in the general public that we quite often have this kind of headlines about some kind of new idea or maybe there's some minor investigation that maybe points in that direction. But if you look closely at it, it doesn't quite hold up the results. So I felt that it's a little bit like clickbaity, and there's a little bit too many media headlines that exclaim that we might be living inside a black hole. So I wanted to write a critical chapter about that and answer that question. And for me, the answer is no. But at the same time, who knows? We don't understand black holes completely. We don't understand the universe completely. Maybe at the largest cosmic scales, something very weird happens that we still don't understand fully, so you should never say never. But from what we can say till today, I don't think the universe is a black hole. No.
- [51:00]
B
You go on to say that we do not know how big the universe is right now. And you tell us that the realization that the universe is expanding made humanity reconsider once again its place in the cosmos. You take us all the way back to Copernicus in considering that question. And you take us all the way in this chapter into a popular article that came out in 2025. We're starting to come to the close of our time together. There's so much more I could have asked you, including questions that you raised about wormholes and comparing and contrasting what a black hole is with that. There's so much more for listeners and readers to dive into in this book. But my final question is, what do you hope this episode sparks for listeners?
- [51:46]
C
Yeah, of course, A curiosity to read the book and learn more about black holes. But also curiosity. Yeah. To look at science from the human perspective. I mean, we are fragile, vain human beings that often fight not only for knowledge, but also prestige. And we are affected by our surroundings. So. And everyone has their moral problems and everything. So science is a human endeavor. And. But what's so amazing about it is that out of this struggle of scientists comes what you could call objective knowledge about the universe and nature and about how black holes work and about how the universe expands and everything. And for me, that's the greatest story of all this scientific knowledge that we reach. So just an inspiration for science in general. It's a great knowledge adventure. Yeah. Yeah, something like that.
- [52:49]
B
Thank you so much for being here and sharing from your book, Facing Infinity, Black Holes, and Our Place on Earth. You've been listening to the academic life. Please join us again.