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Marcus Chown, "A Crack in Everything: How Black Holes Came in from the Cold and Took Cosmic Centre Stage" (Apollo, 2025)
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Go beyond the verses and achieve a deeper understanding of Scripture with the Rebind Study Bible App. An audio experience of the Bible interwoven with expert commentary. The Rebind Study Bible App reads Scripture to you, enriching your comprehension with insights from the world renowned New International commentary on the Old and the New Testament in an accessible podcast episode format.
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Be not therefore anxious for the morrow. Matthew chapter 6. Each day will have its troubles, but by God's grace they can be survived.
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Use the Rebind Study Bible App's chat function to ask questions and get answers in real time. That's thought provoking discussion and analysis rooted in decades of research and wisdom from more than 40 scholars at your fingertips. The Rebind Study Bible App is a new way to experience the Bible with enhanced depth, at your own pace in the moments you have. Search the Apple App Store for Rebind Study Bible or go to rebind app.com newbooks network for a free seven day trial. 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 Production. Click that, fill out the form and we can talk. Welcome to the New Books Network.
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B
Welcome to the New Books Network. I'm your host, Gregory McNiff and I'm excited to be joined by Marcus Challen, the author of A Crack in Everything How Black Holes Came in from the Cold and Took Cosmic Center. The book was published by Apollo in the United States in January of 2025. Marcus was formerly a radio astronomer at California Institute of Technology and is now a cosmology consultant for new scientists and the author of many books on science, including the Matchbox that ate a 40 ton truck. I selected A Crack in Everything because it traces how both black holes went from being dismissed as theoretical oddities to becoming the very engines of cosmic structure as reflected in the subtitle. They have come in from the Cold. Marcus writes with the clarity of a teacher and the curiosity of someone still amazed by the universe. I should also say his personal interviews are fantastic. He captures the individuals and their contributions in such a way that it makes you feel like you're right there with all the messiness, brilliance, and wonder at the same time. Essentially, he makes science both approachable and brings it alive. On a personal note, I love the quotes that open each chapter. They're beautifully chosen and set the tone for the mix of reflection and discovery that runs through the whole book. Hello, Marcus. Thank you for joining me today to discuss your book.
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C
Hello. Great to be here.
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B
Thank you, Marcus. I'll start with a question I ask all authors. Why did you write A Crack in Everything? And who is the target reader?
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C
Yeah. Well, when I was 12, my dad took me to a meeting in London of the Junior Astronomical Society. I was a member and a man spoke. He was actually on crutches. I didn't realize that he'd had polio as a child. His name was Paul Murdin. And he proceeded to describe the discovery of the very first black hole, which was in the constellation of cygnus, called Cygnus X1. And it literally blew my mind, you know, that things were real and they've been discovered. So that was how it all started. Then I became a researcher and I worked on quasars, which are powered by black holes. And recently, of course, the topic has exploded with gravitational wave detectors, allowing us to see black holes and the detection of ever more supermassive black holes in the center of galaxies. So my target readership is basically anybody you know, I write for anybody. People without any scientific background, people with a science background. I try and write the books that are accessible to my wife. My wife is a nurse in England. She doesn't have any scientific background. Obviously, she has a bit of medical background. So if she. If her eyes glaze over, I have to start again and try and write more clearly.
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B
Oh, that's excellent. No, no eye glazing over on this end. Like I said, you really do bring these. I don't know how else to describe them, but wonderful Cosmic events alive. Marcus, before we dig into the book, what is really unique about your book is you've spoken firsthand with a number of these individuals. Again, we're really only talking about the last hundred or so years with the advent of cosmology. But could you briefly describe your, I guess, your unique process with this book? I mean, it's anything but a textbook. Like I said, I feel like we're really hearing from the individuals firsthand.
- [05:24]
C
Yeah, I think you've really understood my book because it's really about people and it's about their stories of discovery. Apart from a few people in the book who obviously are long, you know, dead, anyone who is alive, I. I tried to. To telephone them and talk to them, you know, and try and get their stories. And that's a real joy because you, you know, you get off the phone after about two hours and you've got a notebook full of all these stories that nobody else knows. You know, it's incredible that so many books are written about black holes, but nobody appears to go back to the actual discoveries and talk to them. So it's wonderful to get their stories.
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B
Yeah, fantastic. And let's jump right in there. Marcus, I think the public consciousness, certainly familiar with the term black hole, but could you tell us specifically what it is and why you think they've come in from the cold?
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C
Yeah, well, a black hole is a region of space where gravity is so strong that nothing, not even light, can escape, which is, of course, why they're actually black. They commonly form when a massive star gets to the end of its life. It runs out of fuel because it hasn't got any fuel to burn. It cannot generate any heat to push outwards against gravity, and gravity crushes the whole star down to form a black hole. What was the best of your question?
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B
Why do you think it's, quote, coming from the cold? I mean, it seems like that's really my story.
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C
You see, because just over 100 years ago, Black holes were considered so ridiculous as to not even be the preserve of science fiction. But gradually, over the last hundred years, they've moved more and more into the center of science. Until today we realize that they play some key but ultimately mysterious role in creating the universe that we see around us today. And even in you and me having this conversation today, that, you know, they are, they. They have some mysterious role. And, and it's incredible, really, because it's taken that, that, that all that time for. I mean, they were the most ridiculous things. Even Einstein, whose theory predicted their existence, didn't believe in them.
- [07:31]
B
Yeah, no, I. I found that amazing. I absolutely want to get into that. Just a little background. John Wheeler coined the term. I think he had a student saying, like, why don't you call these things you're talking about black holes? Is that, is that accurate?
- [07:45]
C
So John Wheeler was an American scientist, physicist, had a very famous student that people may have heard of, Richard Feynman, although they were quite close in age. And he didn't actually coin the term black hole, but he, I think a student, he was talking about these, you know, regions of intense gravity. And some students said, well, why didn't you call him a black hole? So he basically took the phrase and ran with it. And the interesting thing is that before the coining of the term black hole, there was very little research on black holes. And afterwards, research kind of mushroomed. And it just goes to show how important in science it is to coin a term that paints a vivid picture in people's minds. So. But it paints so vivid a picture that there's hardly anyone on the planet who doesn't know the term black hole. And we commonly talk about, you know, losing our passport down a black hole or a pain or something like that. But I think one of the incredible things is that in many ways, the picture that's painted is completely wrong. Because the black holes we see out in the universe include some of the most phenomenally luminous objects in the entire universe. And far from seeing stuff being sucked into them, we do see stuff being sucked into them. But their most prominent features is often of stuff coming out, often in titanic jets that can stab for millions or even tens of millions of light years across space.
- [09:15]
B
Absolutely. And Marcus, as you say in the introduction, you effectively say they're neither black nor holes, and we'll talk about this.
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C
Yeah, it's very interesting because there's another term, Big Bang, which was coined by the British cosmologist Spritz Hoyle in a radio program in 1949. And of course, that paints. It stuck. You know, the titanic explosion that gave birth to the universe. Big Bang really stuck. But in no way was that an explosion like a conventional explosion. There was no point where that explosion occurred. It occurred everywhere at once. And there was no pre existing air or void for that explosion to explode into. So in many ways, that is another term that stuck. That paints a picture which is completely at odds with the reality.
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B
That's fascinating. And I should just say for our viewers, you paint a great picture right out of the gate describing black holes sitting in the eye of Quote, an irresistible tornado of swirling space time. And I want to get into that and laugh. Sort of initial question is, why do you describe black holes as called the stuff of physicists nightmares?
- [10:30]
C
Yeah. Well, this is of course what upset Einstein, because he presented his theory in a series of four lectures in November 1915 in Berlin at the height of the First World War. And one of those lectures, Carl Schwarzschild, who was a soldier on the Western Front, attended one of those lectures and he went back to the front and he was completely captivated by this theory. Now, the theory replaced the one formula described that Newton used to describe gravity with 10. And the theory showed that gravity is in fact the curvature or warpage of invisible space time. So actually something like the, the sun. You know, Newton would have thought that there's an invisible tether that connects the Earth to the sun and keeps the Earth going around the sun. But in fact, Einstein realized that what actually happens to the mass, like the sun creates a kind of valley in the space time around it. We can't see that valley because it's a curvature of four dimensional space time. That's why it took the genius of Einstein to realize. But the Earth goes around the upper reaches of that valley like a roulette ball in a roulette wheel. And gravity is the curvature of this spacetime. Now, given that there were 10 formulas to describe gravity, Einstein himself thought it would be impossible to figure out the curvature of space time for any given object. And then within a couple of weeks of getting back to the front, Schwarzschild had actually done the impossible. And al, he found out a description of the value of spacetime around a compact mass, like a, a star. And he sent it to Einstein in Berlin. And he was completely shocked that this had happened. But of course, it turned out that Schwarzschild had not finished. If the mass became more compressed, the valley would become steeper and steeper and steeper until it became a bottomless pit from which nothing, not even light, could escape. But what Einstein realized is that any mass that was shrinking would shrink forever. There wouldn't be anything to stop its shrinkage, and the density would eventually become infinite. We call that a singularity. So at the center of the black hole, everything would explode to infinity. And when you get that in a mathematical theory, it's telling you the theory has been stretched to a place where it no longer applies. Now, Einstein has spent 10 years of blood and sweat trying to get this new theory of gravity. The last thing he wanted was, was within a few weeks of actually presenting it, that someone had actually found a flaw in it. So that's probably why he never believed in black holes.
- [13:18]
B
No, that's fantastic. And I should say you end that first chapter with this idea. Quote, the years of searching in the dark for the truth that one feels but cannot express. Contained within it the seeds of its own destruction. Could you just briefly. I think you vamped.
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C
Yeah. So yeah, that is interesting that Einstein's theory of gravity, which is also called the general theory of relativity, does contain within the seeds of its own destruction. So at two points in this theory, the theory breaks down. One is that the point of infinite density, or we call it a singularity in the center of a black hole. And there was also a singularity at the beginning of time. So if we were to. The universe is expanding at the moment. It's galaxies which are its constituents are flying apart like pieces of, you know, cosmic shrapnel. If you ran that expansion backwards, like a movie in reverse, everything would be concentrated at a single point. A singularity that was about 13.8 billion years ago. So at these two points, the theory actually breaks down. So we know that the theory is not the final word, that there is a better, deeper theory. We think it's what we call a quantum theory of gravity. There is a deeper theory, but unfortunately, after 100 years, no one's been able to find it. But that will tell us what there really is at the center of a black hole. Because we do not believe there really is a singularity at the center of a black hole because that's not a physical thing. So we need a better theory to know what's actually at the center of a black hole.
- [14:47]
B
Nope. Fascinating. I want to get there because as we talked about earlier, it feels like our understanding is evolving almost weekly, if not daily. Moving on. Schwarzschild, very sympathetic, very somewhat tragic figure, dying young. The next individual you profile, and please correct someone whose name certainly should be pronounced properly is Chandraskar. And his idea of the Chandraskar limit. Could you briefly talk about his contributions, particularly as it concerns.
- [15:19]
C
So, yes, Supermanian Chandrasekhar was a 19 year old Indian and he was on a ship going from Bombay, which is present day Mumbai to Britain to go to Cambridge. And he just had a few textbooks on the deck and he was thinking about the death of stars. Now people like Einstein, if they or anybody who thought about what Schwarzschild had predicted, thought that this can't possibly ever happen. We can't possibly have a black hole. It's ridiculous. Physics breaks down, you get a singularity. This is just nonsensical. You can't possibly have them. There must be some force in nature that we don't know about that intervenes and stops the shrinkage of a mass down to form a singularity. And in the 1920s, it looked as if there was such a force because that was when quantum theory was developed, which is our very best theory of the microscopic world of atoms and their constituents. And there's a thing called the. Well, it turns out that the particles, the building blocks of everything, the electrons and quarks, they have this strange dual nature. They behave like waves, which is rather like ripples on a pond. And obviously a ripple on a pond occupies some space. You can't squeeze it smaller than the, the ripple. So it looked as if matter was compressed. This wave like character would actually prevent the collapse. It would stop the collapse. And this was believed in the 1920s. But then in 1930, as I say, John Prosecco was on this ship, sitting on deck, and he began thinking about the future of dying stars. And he realized that people had thought about quantum theory and this wave like property which would stop matter being compressed, but they'd forgotten one thing, relativity, Einstein's theory of relativity. And Einstein's theory says that nothing can travel faster than light. So of course, when you squeeze something, it turns out that the particles of matter fly around faster and faster and faster. And it's kind of that drumming, you know, rather like raindrops on a corrugated iron roof, that creates the outward pressure. But it turned out that those particles could not move faster than the speed of light, so they couldn't move as fast as they needed to to stop the collapse. So he realized that actually quantum theory with relativity, did not stop the shrinkage of a dying star if it was above a certain mass. Now we know that mass today is about one and a half times the mass of the. Called the Chandrasekhar limit. And if a star at the end of its life, generally they explode. They blow away their outer layers and the core implodes. If that core is more than about 1.5 times the mass of the sun, then a black hole is unavoidable. So that was the key thing. There was no escape.
- [18:33]
B
Yeah, fascinating. I should say they were both to some extent outsiders, obviously. Schwarz challenging Einstein and Chandrasekhar, candidly being challenged by Eddington in a very bizarre manner. And so it was interesting to read. You know, these two individuals sort of came outside the establishment at that time. I know Chandrasekhar, I think Ended up at Cambridge at one point, but. And mentioned. Went on winning the Nobel, I believe.
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C
But, well, Schwarzschild. Yeah, I mean, oddly enough, I was there when he. Because I was at Caltech in 1983 and that was the year Chandrasekhar got the Nobel Prize. He shared it with Willie Fowler at Caltech. And yeah, I mean, it was vindication, really. Eddington, as you say, Arthur Eddington, was one of the towering figures of astrophysics in the early 20th century. And if Eddington said you were wrong, you pretty much had to move to another field of science, which is what Chandrasekhar did. He was vindicated all those years later when he got the Nobel Prize and Eddington was wrong. And yeah, you're right. Ellington humiliated young Chandrasekhar at the Royal Astronomical Society in London, I think it was about 1932. Completely humiliated him. And it's really hard to understand why he did it. Was he racist? Was he. I mean, it's just really. Oddly enough, another person that I'm interested in is Cecilia Payne, who wrote the most important astrophysics PhD of the 20th century. She figured out. She was from England, but she went to Harvard. She figured out what the universe is made of. And Eddington was incredibly supportive of her. And yet he wasn't supportive of trying to say car. So he didn't seem to be sexist, but maybe he was racist. I don't know. It's very hard to understand these people, but like all human being, they're pretty inconsistent. You know, they have good, good. They have good points and bad points. You know, nobody's universally good, apart from Jesus Christ, of course.
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B
That. On that note, Marcus, we'll move on to somebody else who. I don't know if you say it was inconsistent, but I found him the most mesmerizing character in your book. A book full of great characters, namely Roy Kerr, talked about Schwarzschild solving the issue for a static black hole. But Roy Kerr really addressed this issue and please describe it of the rotation problem. Could you talk about his contribution?
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C
Yeah, yeah. So basically, Schwarzschild's black hole was an unrealistic black hole because it wasn't actually rotating. And one thing we know about the universe is everything is rotating. The Earth is rotating. The. The Earth is moving around the sun, the sun's going around the center of the galaxy, the galaxies are turning. Everything in the universe is rotating. So it was always, it was always possible to believe that Schwarzschild's description of the space time around a body was not realistic because it wasn't a rotating body. And then 47 years later, I think Roy Kerr, a young New Zealand of 30 or 29 year old New Zealander working in Texas, does what nobody thought was possible. And he finds the shape of the space time around a spinning object and that proves that in fact they do exist. And his description, his equation or his formula that describes this, describes every single black hole in the whole universe. And he has a, you know, as you say, he's a really interesting character because he grew up in poverty in the south island of New Zealand. And to make the Ken's meat, he worked in a factory counting rubber bands. I think it was a factory that made jam for jam jars. And they were sealed with rubber bands, elastic bands. And he got paid on how many rubber bands he could count. And he realized that if he threw them up in the air they would fall down in specific patterns. And those patterns were related to the number of plastic bands or rubber bands. So he was able to earn more than everyone else, you know, but, but then, then of course he went to the University of Christchurch, which is in New Zealand and they were so backward there that they. He only used like 19th century physics books. So he certainly. And then he, then he got a place at Cambridge in England. But he thought that he was too young. He was only 16, he'd have to wait until he was 18. In fact he could have gone and he could have sat in on, you know, audited lectures anyway, but he didn't know this. So he took up pool, he took up boxing, he took up all these, all these weird sports bridge and finally went to Cambridge. And because he had this incredibly different background from everyone else, you know, he just thought differently to everyone else. He was a real maverick.
- [23:33]
B
Yeah, you really bring him to life. We don't have time obviously to focus on him, but you've got some great quotes. My favorite is my advantage over the others was that I was not stupid. And also the interactions with Penrose at that conference in Texas was amazing. You really bring the life. And his contribution is just awesome. I do want to ask two follow ups that are related. A, could you describe what the ergosphere was? And then B, going back to the distinction between Kerr and Schwarzschild's insight, you note that singularity was a ring. And I think this has to do with the rotation versus being a point of infinite density. Could you just.
- [24:16]
C
Yeah, so. So yeah, so the Schwarzschild metric or the Schwarzschild black hole has a point at the center which is, which is the singularity. But the rotation, as Kerr discovered it, creates a circular singularity. Not, not, not. Yeah, so the difference basically, is that you. The. We think of the Schwarzschild black hole as having an event horizon around it, right? So the black hole. Actually, black holes are the simplest things in the whole of science, right? They're made of nothing but space and time. As far as we know, the mass that actually shrunk under its own gravity catastrophically to make the black hole has vanished. And all that's been left is this bottomless pit in space time. So they're not actually. They're not actually physical things. They're just these warpages of space time. So we invent this thing called the event horizon, which is the kind of the imaginary membrane, which is the last, you know, is the point of no return for infalling stuff. You know, once you get to this surface, spherical surface, and you pass into the black hole, you can never get out again. So to give you some idea, the sun could never become a black hole, but if you wanted to compress it to make a black hole, it would be 6km across. So that would be the diameter of the event horizon. The Earth would be the size of a peanut. That would be the size of the event horizon, okay? But what actually happens with rotation is things get slightly more complicated. You don't just have an event horizon. You have a second surface further out and between the. It's called the static limit. Between the event horizon. The static limit is this thing called the ergosphere. So basically, as you said when we began this interview, a black hole, a spinning black hole, spins at the center of a irresistible tornado of space time. So the tornado is felt within the ergosphere, okay? So if you were to cross what's called the static link into the ergosphere, so you've gone quite close to the black hole. Nothing you could do could prevent yourself from whirling around with it. It wouldn't matter if you had the most powerful rocket imaginable. It wouldn't matter if you had access to all the energy in the universe, you would be swept around within this ergosphere. So to some extent, the black hole is kind of like a flywheel spinning in space, but it's not just a hole. It's this space around it, this ergosphere around it. So you could tap the energy of a flywheel and you can tap the energy of a spinning black hole. And pen. Roger Penrose, who you mentioned, who got the Nobel Prize recently, Actually, in the last few years, British mathematician who worked with Kerr in Texas. He found a way that you could extract energy from this ergosphere. And it involves injecting particles into the ergosphere. And there's a clever way of doing it. But we're pretty certain that nature has already achieved this, because when we see supermassive black holes spinning, we see these titanic jets which, where matter stabs outwards at almost the speed of light. If you think the Large Hadron Collider in Geneva, the particle accelerator, we can accelerate nanograms, you know, to almost the speed of light. Nature can accelerate 10 times the mass of the sun to almost the speed of light along these jets. So in some way the energy of the ergosphere is being capped by these objects. Yeah, yeah.
- [27:54]
B
No, that's a fascinating discovery and description. I want to move on. To date, black holes are conceptual, you know, even through Kerr. And then along comes the discovery of Sigma X1. Could you talk about why that was so important? It almost confirms the, the concept they believe.
- [28:15]
C
Yeah, so, I mean, so I should just quickly say that, that one of the. I'll tell you who discovered them. But one of the discoverers, Paul Murdin, that was his thought when he discovered it. My God, these things actually exist. You know, he couldn't quite believe that. No one could quite believe these things existed. You know, this is another thing. Steven Weinberg, the American physicist, he famously said that physicists do not take their theories too seriously. They don't take them seriously enough. So it's very, very difficult. You've got this mathematical formula. Basically the universe has a twin, right? So there's the real universe and there's the mathematical universe that you can write down on a blackboard, on a whiteboard, and it completely mimics the real universe. And that is just a mind boggling fact. So, for instance, you know, you can predict that the mathematical formally on a blackboard. Say there are these things out there called black holes. But it's very, very hard to think that those marks on a blackboard can really tell you about the real world. But in many, many instances, think things of the Higgs particle. You know that Peter Higgs was hiking in the mountains of northern Scotland in 1964, 65, and he predicts that there should be this subatomic particle called the Higgs particle. 45 years later, at cost of 5 billion euros, it pops up at the Large Hadron Collider. So it's very difficult. I mean, this happens time and time again. Paul Dirac, the British physicist, predicted existence of antimatter in the 1930s. So, again, getting back to this. Yes, they couldn't rule out the existence of black holes, but the fact that they would actually exist. And Paul, that was a shock when Paul Murdin actually found the first Black Hole, Cygnus X1. Paul Murdin and someone called Louise Webster.
- [30:15]
A
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- [31:17]
B
Absolutely. And quick aside, Marcus, because you seem like the person to ask. We in the public think of the scientific theory of gathering data, doing experiments, collecting data, and slowly constructing a theory. What was unique about your book and overall, our understanding of black holes is sort of, as you said, the theory almost preceded the discovery or the data. How common is that? I mean, how do you think about the scientific.
- [31:44]
C
I wrote an entire book on that. It's called the Magicians. And then it got in paperback, it got another name. It was called Breakthrough. But I thought, this is the central magic of science, this central magic that you can write down these formulae and they can tell you something about the real world, things that are out there that nobody ever suspected. So this begins in the late 19th century with the discovery of Neptune. So Neptune was discovered at a desk in Paris by a man with a quill pen. Okay? Because the planet Uranus, or Uranus, however you pronounce it, was not. Whenever they calculated the orbit for never turned up where it was supposed to be. And so there was a suspicion there has to be another planet. And it was possible to use Newton's law of gravity to infer where the missing planet was. So this was the first time Uranus itself had been discovered in England in 1781 by a German musician. But he just found it by accident. But this discovery by Urban Le Verrier of Neptune was a discovery of a completely different order because it had been discovered by mathematics. And then as we went going to the 20th century, we see this happening more and more. So James Clerk Maxwell in the late 19th century had predicted that the light was a wave of electricity and magnetism. No one had ever guessed that there was any connection between electricity, magnetism and light. But the theory said that there was no constraint on how fast or how slow an electromagnetic wave could wiggle. So I should tell you that the difference between colors is the difference in the rate of vibration. So something like a red light is vibrating twice as sluggishly as blue light. Okay. But the theory said there was no constraint. And so there should exist millions of other invisible colors beyond the red end of the spectrum and beyond the blue end. And of course, in the 20th century, we discovered radio waves. And then later we discovered a huge spectrum. There are millions of invisible colors. We've discovered X rays, infrared, all this kind of stuff. Once again, a prediction of a mathematical theory. So this happens time and time again, and nobody knows why the universe has a mathematical twin. You know, Dirac said, God must be a mathematician.
- [34:28]
B
Oh, you stole my quote. I was going to come at you.
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C
So that kind of fascinates me. And then, of course, knowing this, every physicist knows this. Eugene Wigner, the Austrian physicist, wrote a famous paper in 1960 called the Unreasonable Effectiveness of Mathematics in the Natural Sciences. So no one knows why, but we know that mathematics is. Can describe the universe. And yet you write down an equation, as a physicist, you still think it's just symbols, arcane symbols on a piece of paper. You can't quite get your head around that this is actually going to be real. And time and time again, we're caught out.
- [35:10]
B
You know, Marcus, you are hitting on something that I've been thinking about, and I want to get back to your book. But is there an underlying language of the universe, of mathematics, that we discover or does this is a symbolic representation of what we're discovering? I mean, my background's classics and Plato and the idea of the.
- [35:26]
C
Well, an interesting and interesting. I mean, you probably heard of Stephen Wolfram Who? Yeah, yeah, yeah, yeah. He's a Londoner and he's a billionaire and he invented a computer language called Mathematica and whatever, you know. But he, he, he, he has a different take on this. You know, why, why is mathematics so good at describing the universe? And he just uses this old example of somebody looking for their car keys at night, at midnight. They look under a street lamp. They look under a street lamp because the only place they can look. And he thinks that mathematics only illuminates a part of the universe. And what most of the universe is doing is not mathematical. Okay. So he believes that obviously there's some regularity to the universe, but it isn't mathematical. Equations don't describe most of the universe, they only describe part of it. And he believes that what the most of the universe is doing is computing. Okay? So when it, so he, when it compute and it's a computation where you have to do the whole computation to get the end result. There's no shortcut. But as humans, we have found some of this computation where you can actually know the end point without doing a calculation. And that's mathematical physics. So he thinks that that's just this is tiny little portion of reality that we're explaining. So that's an interesting take on it. So that most of what the university is not doing is not mathematical, but it's what we see. It's our streetlight.
- [36:59]
B
Yeah, that's funny. I mean, yes, maybe his approach is more like a quantum computer, I'm not sure, but that is interesting. But I have to say the broad. The power is amazing. I do want to.
- [37:12]
C
It is amazing. It is amazing and it is mind blowing. I mean, you know, and the question is, is mathematics a human invention or is it out there? We don't know. I mean, these very important philosophical questions.
- [37:27]
B
No, I mean that Dirac. I mean, it seems like it is the language of the universe. And I realize this, I should say you touch on this in your book and hopefully you've got another one coming on this topic, but fascinating. Marcus, could we briefly touch about how we detect black holes? You talk about the electromagnetic spectrum. There's obviously optical telescopes, radio waves. You talk about infrared telescopes as well. Could you briefly talk about how our, the technology in advance allow us to detect.
- [37:58]
C
Yeah, so if we Talk about Cygnus X1, this was basically a NASA satellite, Uhura went up in 1970, found lots of X ray sources in the sky. We didn't know what they were. X rays are produced by matter at millions of Degrees. So that tells you there's something interesting going on. And Murdin had been in New York doing a PhD, came back to England, came back to the Royal Observatory, Royal Greenwich Observatory, which happened to be in a 15th century castle surrounded by a moat. So it was a pretty idyllic place. And he desperately needed to make his name because he had a wife and two young boys, and he only had a temporary job. And when he'd been in New York, he used to talk with the other graduate students about how you actually make your name as astronomer. How do you discover something interesting? And the basic problem in astronomy is that there are more stars in the universe than there are sand grains on all the beaches in the world. How do you find an interesting sand grain? How do you find an interesting star? And he realized that if it was emitting X rays, it would be interesting. So he got hold of the catalog from Uhuru in 1971, and he found that, you know, he looked at this object called Cygnus X1. It was somewhere in the constellation Cygnus. The box. There was a box around it, its location. He looked on star maps, and there was a very big star, what we call a blue supergiant, very unusual star, pumping out hundreds of thousands as much light as a normal star. You know, very hot, very massive star. That couldn't be the source of the X rays. It wasn't hot enough. Their surface temperature is about 50,000 degrees. But he wondered, did it have a companion? Because if it had a companion that it was orbiting, it could be that matter was sucked off it swirled down onto the companion, and friction within the gas could heat it to millions of degrees. And he was sharing a room that was actually an octagonal turret room at this castle. He looked out through the window and he could see the moats and geese grazing in the distance. It was quite idyllic. He was sharing this. This office with an Australian that's about the same age. She was 30. She'd been working in America as well, and she was working on a project to measure the speed of stars. And you're probably aware that when a police siren comes towards you, it's a higher pitch when it goes away. Lower pitch. There's the same effect with light. The light pitch. Light is, yeah, become blue and red, become, you know, lower pitch is red. So. So, yeah, so. So the question was if this blue supergiant star was orbiting something, it would periodically be coming towards us and periodically be going away from us. We see a blue and a red shift. She went away she found it. This blue supergiant star was orbiting something else every 5.2 days. So something was swinging this enormously massive star about 50 times the mass of around every 5.2 days. They sat down, did a calculation. It had to be something at least four times the mass of the sun, maybe even six times the mass of the sun. We now know it's 15 times the mass of the sun. But there was nothing visible on the, you know, on the, on the photographs. So what could be invisible and that massive? It could only be a black hole. They found the first black hole. So that was a long winded excellent.
- [41:19]
B
And I think it goes back to as we were discussing earlier, just your, the, the what you're able to bring out to the in person interviews and the, the unique behind the scenes insight there.
- [41:30]
C
Another, although that's indirect observation, that's only indirect. We only really the, the actual definitive evidence of the existence of black holes. This comes into how we detect them came on 14th September 2015 with the gravitational waves. These are ripples in the fabric of space time. They were picked up by two basically giant rulers in the states, one in Washington state, one in Louisiana, two 4 kilometer rulers made of laser light. And basically one, one shuddered and about a hundredth of a second later the other one shuddered. And those shutters were identical. And that was the unmistakable imprint of gravitational waves which are ripples in the fabric of spacetime predicted by Einstein in 1916, coming from the merger between two black holes. So that was the definitive evidence that they actually existed.
- [42:24]
B
You know, you're jumping ahead, but I'll ask you about the gravitational waves now. Why do you call them the voice of space?
- [42:30]
C
Yeah, well, for all of human history we've been able to see the universe, you know, with our eyes and then later with, with telescopes. And even though we can actually pick up stuff with light that's invisible to the naked eye, it's still light, it's still electromagnetic waves. But gravitational waves are basically vibrations of space time, of the fabric of space. And they are very similar to the vibrations of a drum skin. The big difference. So they are sound waves. So we've actually gained a new sense. So often you hear a lot of hype from science journalists about discoveries, but actually this discovery really was the most important discovery since Galileo turned his telescope on, you know, on the sky in Padua in, I don't know, 1610, something like that. It really, really was because we gained an entirely new sense and we were actually hearing the universe for the first time. Interestingly, that analogy I gave you about a drum skin, it turns out that space time is very stiff. So it'd be like having a drum skin which was about a billion, billion, billion times stiffer than a normal drum skin. And that's why it takes these incredibly violent objects, events like the merger of two black holes, to shake spacetime enough to create gravitational waves that we can detect.
- [44:01]
B
Yeah, Marcus, one thing I found really interesting is these mergers are happening almost constantly, frequently. They're not one off events, is that correct? They're happening much more so than we can capture. But we believe it's an ongoing dynamic.
- [44:15]
C
Well, when these two gravitational wave detectors, they're known as ligo, the Laser Interferometric Gravitational Wave Observatory, when they were. They weren't even operating. This was in, in 2015. Do I say, yeah, 2015, they weren't even operating. They were. It was an engineering phase where they were just checking it out and they suddenly got this, this signal and nobody believed it because it was so big. And, you know, you have to rule out lots of things. I mean, somebody riding on a bicycle past one of these sites can create a vibration bigger than what we're looking for. You know, someone driving by on a, in a, On a car 20 miles away, you know, it can pick up. It can pick up vibrations of, of the surf, you know, pounding on the beach in Santa Monica. You know, it's that. It's like a. Basically a seismometer, you know, so it was very, very. But anyway, this signal was much bigger than anyone expected, and they got it almost immediately. So really, physicists don't believe in coincidences. If they picked up something immediately, then they must be common. And we've actually found hundreds now. I think we're going to find thousands of these events. And interestingly, they're not at all what we expected. So the black holes we were expecting to see were black holes that were going to be, I don't know, could be a couple of solar masses, maybe up to 10, something like that. Cygnus X1 was 15, by the way. The first two were each more than 30 times the mass of the sun. And we've now found mergers where the individual black holes are impossible. They're impossibly big because there's actually a region. I think it's. I can't remember off the top of my head, but it's probably between about 70 and 120 times the mass of Sun. We shouldn't see a black hole because black holes form when a star goes supernova, so it explodes and Paradoxically, it's the implosion of its core that generates the energy for the explosion. And if the core is in that range that I just mentioned, the core just disintegrates. It just blows itself apart. It's called a pair instability supernova. So we should not see any black holes, but we have. And that's telling us to get back to your original question. These are much more common than we expected, because the only way that we could see mergers between black holes that shouldn't exist is if they individually are the result of earlier mergers. So they're much more common than we expected, and they're much bigger than we expected as well. But that's why you do science. You do science to. To surprise yourself, really. I mean, one of the sad things about a large hadron collider is about for the first time in the history of science, there's an experiment that only found what it was looking for and nothing else. That's really unprecedented. Normally, when you probe a different size scale, a different energy scale, you always find unexpected things. And this is what's happening with gravitational wave astronomy.
- [47:36]
B
Yeah, no, I've always heard one of the best expressions in science is that's a funny thing, because it produces that. Understand what's going on.
- [47:46]
C
We want to be surprised. You know, we don't want to. I mean, that's the reason we do it. If we knew it all, there'd be no point in actually doing science. But we're constantly surprised by what we find. And astrophysics is going through a golden era. I mean, obviously we know biology is. Because of all the techniques in biology. We know that that's going through a golden age, but so is cosmology and astrophysics. Particle physics is unfortunately having a really bad time, but these other sciences is doing very well at the moment.
- [48:15]
B
No, I will leave that. I'll leave the. The particle physicists and the cosmologists to sort that out. I have enormous respect for both on that topic of wonder. I mean, could we briefly talk about supermassive black holes? You characterize them as one of the great mysteries of cosmology. Why?
- [48:33]
C
Yeah, well, you know, surprisingly. Okay, so the first stellar mass black hole was found in 1971 by Paul Murdin and Louise Webster. By the way, just before I go on. Louise Webster has been written out the history of science. She's an Australian. Sadly, she went to Australia. She had one of the first successful liver transplants in Australia. Then she had liver cancer and she died at age of 49 in Sydney. And she's been completely forgotten. So if you don't remember anything at all from this interview today, please remember the name of the co discoverer of black holes, Louise Webster. Forgotten even in Australia. But yeah. So actually it turns out that black holes had been discovered about eight years before they'd been discovered, but no one had actually realized. And these were supermassive black holes and they'd been discovered by Martin Schmidt, who was Dutch American astronomer, who was actually at Caltech when I was there. I didn't take any lectures from him, but I passed him in the corridor and he discovered basically that quasars. He discovered quasars. I mean, what to go back after the Second World War, radar engineers who had, some of them had decided to become astronomers, which was a very risky thing because basically there was no expectation that anything in the universe was going to produce appreciable radio waves. But then in the 1950s, John Bolton, who was British, but he was Australia, and in fact, actually he also set up the radio dishes at Caltech. He's the only person to have set up major observatories in the Southern and Northern hemisphere. Yeah. So he discovered extragalactic radio sources. You know, there were these sources out in the sky. What the hell were they? The problem was that radio waves have a wavelength about a million times that of optical light, which means that radio images are a million times blurrier. So if you have a telescope of the comparable radio telescope with a comparable size to an optical one, its images are a million times blurrier. So you could only say, well, there's something in a particular constellation. But in the end of 1962, an opportunity arose because an object called 3C273, it was in the third Cambridge catalog, was going to be occulted by the Moon. So the Moon was going to go across it. Now, if there's one thing we know about the Moon, we know exactly where it is. Okay? So if you could observe when it disappeared, 3C273, and when it came out, you could find its location. And this was done by John Bolton in, in Australia. And he sent the coordinates to Martin Schmidt. And Martin Schmidt found on a photographic plate that there was just a star. And that was puzzling. But just after Christmas 1962, he went to Mount Palomar, which was at the time the biggest telescope in the world, 5 meter optical telescope in the mountains north of San Diego. And he basically took its spectrum. What astronomers do is they span out the light into its constituent rainbow colors. And it turns out that nature has been unbelievably kind to us because it's created these missing colors. So a spectrum looks like a supermarket barcode. Every element has its own fingerprint of these lines. And so we can tell what stars are made of. We can see the fingerprint of calcium, of carbon or whatever. Anyway, when you took the spectrum of 3c273, nothing made any sense. There wasn't a single black line, a single spectral line that, corresponding to any. Any element. He took it back to Caltech. None of his colleagues knew what it was. And it lay on his desk for about three months. And then Bolton wrote from Australia, and he said, we're going to publish. We're going to send an article to the international journal Nature about the location of 3C273. Could you write an accompanying paper? And Schmidt was panicked because there was nothing he could write. So he was sitting, looking at a microscope on his desk at this spectrum, and he thought, well, there seemed to be a bit of a pattern. And he. To cut a long story short, he realized that what he was seeing was the fingerprint of hydrogen, the most common element in the universe, but shifted by 16% to the red end of the spectrum. That meant that this object was moving away from us at 16% of the speed of light. No one had ever even observed the star going at 1% of speed of light. However, in 1929, Edwin Hubble, the American astronomer, had found the universe was expanding its galaxies, 2 trillion of them, you know, of which the Milky Ways one, were flying apart like bits of cosmic shrapnel. And the further away a galaxy was, the faster it was moving. So Schmidt was able to find from its speed it had to be a thousand times further away than Andromeda, which is the nearest galaxy. But this star was very bright. It was almost visible to the naked eye. So when he works out, how could it be that bright and that far away? You realize it was pumping out about 100 times the light of a normal galaxy. And we knew that it fluctuated very quickly on timescales of a day or so. That tells astronomers that it's very small. So this object pumping out 100 times the energy of a galaxy was smaller than the solar system. And within a year, theorists realized there could only be one possible source, and it was matter swirling down onto a black hole heating to millions of degrees. But not a black hole of a few times the mass of the Sun, a black hole of millions or even billions of times the mass of the Sun. A supermassive black hole.
- [54:20]
B
Yeah, Marcus, you Have a great chapter and you reference Hubble, but the Hubble Space Telescope really dramatically increased our awareness of black holes. I think you say previously to the Hubble, they were thought only to be 1%. And then it basically confirmed Donald Lyndon Bell's prediction that every galaxy contained a supermassive black hole. And I think wonderful description there. For me, the book is great. The book is wonderful. Where the book really is worth purchasing alone for one chapter is the Big Black Hole Bonanza. And that talks about, as you know, the relationship between supermassive black holes and galaxy formation. And I, I really just, this is like mind blowing in every sense of the word. I'm not going to read the entire chapter, but I do want to quote here. Galaxies and supermassive black holes are two sides of the same coin. You cannot have one without the other. The key to understanding the link between the two is that as far as Einstein's monsters are concerned, size does not matter. What matters is energy. I realize that is a PhD thesis, but for my wife. What does that mean?
- [55:32]
C
Yeah, well, just to quickly tell you that, yeah, only 1%, we thought only 1% of galaxies are like quasars, what we call active galaxies that appear to have powered by supermassive black holes. An active galaxy is one whose light comes not from stars principally, but from a supermassive black hole. Black hole. And as you just said, Hubble discovered that in fact there's a supermassive black hole in essentially every galaxy nearby. So the reason we only see 1% active is that 99% are basically eaten all the material in their neighborhood and they are basically dormant. But yeah, to get back to what you're saying, they are very small. I mean, they're very massive, but they're very, very tiny. So if you imagine a bacterium compared to say New York City, that's the size of a supermassive black hole compared to its parent galaxy, you wouldn't think that a bacterium could orchestrate the street pan or create the street pan of New York, would you? But these supermassive black holes control their galaxies, and that was a bit of a mystery because their reach, their gravitational reach is only a few tens of light years, Whereas the centers of galaxies are like 10, 20,000 light years across. But as you just said, you, size doesn't matter. Energy, that matters. So if I were to walk past a house and a slate were to fall on my head, what would be happening is that the gravitational potential energy, the energy that slate had by virtue of being high in the gravitational field as it Fell to a lower point, would be converted into other forms of energy, energy of its motion. So it speeds up the energy of my headache as it hit my head. Okay, so we don't know how supermassive black holes form, But a lot of matter has got to come together, and that's like countless quadrillion slates all falling together. And when you do the calculation, you find that the amount of energy liberated in that process, that formation process, is 1,000 times bigger than is necessary to, will be necessary to actually blast the galaxy apart. So in other words, to blow all of its stars to infinity. So then you realize that only 0.1% of that available energy, if that's transferred to the gas in the galaxy, which is the raw material of stars, this tiny black hole can leave its imprint. And that's what we see. So we see in every one of the galaxies nearby. The supermassive black hole is about 1000th the mass of the central bulge of stars. So somehow it leaves its imprint. We don't quite know how they do it, but they leave their imprint. These tiny little supermassive, supermassive black holes.
- [58:10]
B
And let's just to follow up on that, at one point you quote a researcher, Philip Penko, saying supermassive black holes are precisely 0.5% of the mass of their bulges hardness of the galaxy. It's like a consistent or universal rule.
- [58:27]
C
Yeah, I think probably I was probably a bit closer to 0.1% now. I think I would have changed it. But yeah, yeah, there is this ratio everywhere, and that's telling you that there is some intimate connection between these tiny, tiny supermassive black holes and their parent galaxies. So we think it's the supermassive black hole that's imprinting itself on it, that's controlling the galaxy. And it can do this in multiple ways. But I mean, they can actually blow away the gas in the senses of galaxies and snuff out star formation. But interestingly, the James Webb Space Telescope, which was launched a few Christmases ago, is looking back in the early universe and it's finding this ratio was different in the early universe. So it just seems to be the ratio at the moment, on that note.
- [59:17]
B
Of looking back to the early part of the universe. You know, we have detected so many supermassive black holes when the universe was relatively young, call it 700 million years, which is virtually impossible or seems to challenge our understanding or thesis that these existed so early, so large, so many. How do you account for that?
- [59:38]
C
Yeah, I mean, obviously it's still Possible, just about to explain them. But it becomes increasingly difficult because the universe starts off completely uniform, pretty much uniform. You know, after the Big Bang, the fireball is pretty uniform. There were some very gradual variations in density. One part in a hundred thousand, which we've actually seen. When we look back to what we look at what we call the cosmic background radiation, which. Which takes us is a snapshot of the universe when it was about 380,000 years old. So those tiny little density enhancements, they became bigger as the universe aged. It's just like a process, like the rich growing ever richer. So the areas that were slightly denser had slightly stronger gravity, so they dragged in material faster and faster. So you've got to create galaxies and black holes, great concentrations of matter, and it is difficult to see how you could do it in that short amount of time. But it's still maybe possible because some of the processes by which galaxies, so by which black holes form may have been different in the early universe than they are today. Remember, this was an environment that if we go back to when the universe was a tenth of its current size, everything was hugely closer together, obviously. And, you know, processes that could create black holes more quickly may have occurred. But it could be that we will find it is a problem. And if it is a problem, we may have to be thinking about black holes being seeded in the Big Bang itself, you know, in some form. So actual, they may have been the seeds, you know, that gave black holes, you know, a head start in the Big Bang itself.
- [61:28]
B
Yeah. That's amazing. I mean, they really are. It's almost like the. They play a role, obviously, in galaxy formation, but even maybe in the creation of the universe. I want to ask you. We've talked about the micro and the macro relativity and quantum mechanics, and you have a very nice chapter on Hawking radiation and the information paradox. I don't think we have time to go through all that here. But do you think in terms of us looking for a final theory that quantizes gravity or unites the quantum and the relativity, do you think black holes could play a part there, sort of be the lab or the test bed for final theory?
- [62:05]
C
Definitely. I mean, you know, so there's two. There's. There are two things that are interesting here about black holes. There's real black holes and theoretical black holes. And most of the books you're likely to read, popular books, will be about theoretical black holes. They'll be about Hawking radiation, Steve. You know, and can you go through a black hole and travel in Time, you know, all these kind of speculative things which are really pretty out there and not backed up by science. And then they're real black holes, which are the. Which is what my book is about, which is the things that are really out there. But the theoretical black holes are very, very interesting because three of the most important theories in physics collide in black holes. So quantum theory, which is our theory of the microscopic world of atoms and their constituents, that is essentially a theory of the very small. But when you compress something down, something big, which is described by Einstein theory of gravity, until it's really, really tiny, it becomes a quantum object. So you need an explanation in terms of these two theories united. And then, of course, the third theory is thermodynamics, which is our theory of heat, heat and motion. And this comes back to Hawking radiation. Because black holes have a temperature. This is an astonishing fact. They are nothing but space and time. So they're not like a bit of matter that you've heated up. They're not like, you know, your dinner that you've heated up in the oven. They are just space and time, but they actually have a temperature. This was discovered by an Israeli physicist called Jakob Bekenstein, before Hawking. But then when Hawking discovered that they actually radiate heat, it explained why they had a temp, you know, why they had a temperature. So this radiation, the interesting thing is that the Hawking radiation was predicted by Hawking, even though we don't have a quantum theory of gravity. And you would have thought that quantum theory, this theory of the microscopic world, would only play a role when you got down to this mass being compressed smaller than an atom. But it was Hawking's genius to realize that he actually plays a role outside the event horizon. And this is because quantum theory does predict that empty space is not empty. It's full of quantum particles popping in and out of existence. We call them virtual particles, for instance, like an electron, and it's antiparticle, positron. These things are happening throughout space all the time. So when we look at a hydrogen atom and we look at the outer electrons, these particles, which are antiparticles, which are popping in and out of existence all the time, have an effect. They buffet the outer electrons, and they cause a thing called a lamb shift. And Willis Lamb won the Nobel Prize, I think it was about 1948, for predicting this lamb shift. So it's a real effect. But what actually happens around the event horizon of a supermassive black hole, of a black hole, the Point of no return is that a positron and an electron can suddenly pop into existence, but they can't pop out of existence again because one of them will fall into the black hole and the other one won't. And if it hasn't got its partner to basically annihilate with, it becomes real. And so streaming away from the horizon of the black hole is this Hawking radiation. Now, I might have told you that nothing can come out of a black hole. The Hawking radiation does not come out of the black hole. It comes from just beyond the edge of the black hole. And as I say, the shocking thing is that this is not necessarily an extreme region. So if we, it turns out that you may have heard about the tidal forces of black holes. People talk about spaghettification. If you were, if you were an astronaut falling into a black hole, a stellar mass black hole, the gravity on your feet would be so much stronger than on your head that you'd be pulled apart. Okay, well, this tidal effect becomes less and less for bigger and bigger black holes. So these supermassive black holes, this effect is negligible. You could walk across the event horizon of a supermassive black hole with no ill effect at all. So it's bizarre that this Hawking radiation would be produced around a horizon which isn't an extreme thing at all. But anyway, as far as Hawking radiation is concerned, one of the reasons that Hawking never got the Nobel Prize is because it's essentially unpredictable. Sorry, it's undetectable. It's a very. For a normal sized black hole, it's really undetectable. You would need a mini black hole to see Hawking radio. But yeah, so there is this collision between these three theories. Basically what you want in science is you want some domain where you have two theories that you, you know, that are really, really accepted. And they predict different things because that tells you that one or both of those theories is wrong. And that is a gold mine for physicists because that's, that's what they're looking for. So they do know that one or more of those theories is wrong. It could be all three. It could be thermodynamics, Einstein, theory of gravity, and quantum theory. But that's what we're looking for. So theorists have found a domain where current physics does not explain what's going on. And so that's why we're looking for what we call a theory of everything, which is a deeper theory. We know, for instance, we have this General relativity is a very good theory. The theory of gravity, of Einstein. But arguably, a better theory is our theory of particle physics, which is known as the Standard Model. It's incredible that the High point of 350 years of physics is a theory called the Standard Model. You would have thought someone would have come up with a bit more of an impressive title for this fantastic theory, but it basically predicts the fundamental building blocks of the universe, which are quarks and electrons are glued together by three fundamental forces. The electric force, which is holding together the particles in your body, and two nuclear forces, which don't really appear in the everyday world. And it's fantastically successful, this theory, and it predicts what we see in experiments to obscene numbers of decimal places. We've never had a theory this good, and yet it does not predict the masses of the particles, the fundamental particles, the masses of the quarks and electrons. It doesn't predict the strength of the forces. You know why? Why one force is stronger than the other. And it does not predict why nature has triplicated its basic building blocks. So if you imagine, I mean, is Lego, is Lego a toy in America?
- [68:50]
B
It is a very, well, very popular toy in America, as evidenced by my nephew's basement.
- [68:57]
C
Yeah, well, say, say, say LEGO decided next year that it's going to come up with a new type of Lego where all of the bricks are hundreds of times bigger than the current bricks. And what happens the year after it suddenly decides it's going to come up with a third type of Lego and all the bricks are thousands of times bigger? Well, that's what nature has done, because it turns out that most of the universe is basically that we see, that we know of, that science has given us access to, is basically made of just three building blocks. The up and down quark and the electron, three particles. That's all it is. But nature has triplicated this, so it's created a heavy electron, two versions of those heavy quarks, and it's created a super heavy electron and two super heavy quarks. Now, none of these heavier particles, like the heavier LEGO bricks, play any role in today's universe because they require a lot of energy to create. So they obviously played some roles in the first split second of the universe's existence when there was a lot of energy around. But apart from that, they don't. So the theory, this wonderful theory, the best theory we've ever devised, you know, predict the existence of the Higgs particle, predicted the existence of the top quark before we found it, does not tell us why nature has Triplicated its basic building blocks.
- [70:17]
B
Yeah, yeah. I mean, like we were saying earlier, it feels like we're on the. The precipice. I mean, it's amazing. The more we learn, the more we realize how little we don't know. But.
- [70:26]
C
Well, I think Sagan. Yeah, I remember Carl Sagan saying it was a fantastic time to be alive. You know, it really was. I mean, because, you know, when we look at cost the universe, we can see the age of the observable universe. We can actually see age, and we can count up all the basic building blocks, which are galaxies. There's 2 trillion of them. So we can. We know the extent and content of the universe. Not only that, we know that it all began in this Titanic explosion 13.8 billion years ago. And out of the cooling debris there congealed these galaxies. So we have this fantastic picture that previous generations would have killed for. I mean, they had to say things like, oh, the universe is on the back of a turtle, or something like that. We actually have this amazing picture. But it does then allow us to ask questions, really serious questions, about what was the Big Bang? What drove the Big Bang? What happened before the Big Bang? Is that, you know, is that a meaningful question? What is space? What is time? These really fundamental questions, and they're no longer philosophical questions. They are questions that we may get the answer to in the next couple of decades. So I think there's a really, really exciting time to be alive. And just to mention one other thing, it's a shocking time in the history of science to discover that all that science has been looking at over the last 400 years is only 5% of what there is. So we know that 95% of the universe is not made of atoms. It's invisible. We can sense it there because of its gravitational pull on the visible stars and galaxies. There is stuff called dark matter, which outweighs the visible stuff by a factor of six. And dark energy, the dominant component of the universe, accounts for two thirds of the mass of the universe. Didn't even know of its existence before 1998. So these are huge, huge mysteries. And, you know, it's a great time to be interested in science. So when I was at school, I definitely got switched off science and teachers really implied that science was sewn up and done, but it is so not sewn up. And there are just so many really important questions that are occurring to us that need answers. So it's a really important time to be alive.
- [72:45]
B
No, absolutely. And you do a wonderful job of articulating those questions as we end the interview, I want to bring it back to Earth and our own little supermassive black hole at the center of the Milky Way, namely Sagittarius a star. Why do we owe our existence to its, quote, unquote, diminutive status? Diminutive statute, as you.
- [73:10]
C
Well, that's a really. So basically. So Sagittarius A is the supermassive black hole in our galaxy. Because I said there's one in every galaxy, that means there's one in ours. It was actually discovered 51 years ago, 1974. And we've actually taken a picture of it, the second picture ever of a black hole taken by the Event Horizon telescope in 2022, a global array of radio dishes. We got a photograph. But two astronomers, an American in California and a German, shared the Nobel Prize for actually determining the mass of this supermassive black hole. They were able to observe the motion of stars in a very dense cluster of stars called the S cluster, because it's in Sagittarius going around this black hole. And they were able to be looking at the speed at which they were orbiting. They were able to determine the mass, and it's 4.2 million times the mass of the Sun. And for that, it got the Nobel Prize. But this is a real mystery, because in the quasars in the active galaxies, we're looking at supermassive black holes that are tens of billions of times the mass of the Sun. So we're talking about thousands of times bigger. And even more puzzlingly, our galaxy in the Milky Way has a neighbor, its nearest neighbor, called Andromeda, which is very, very similar to the Milky Way, a spiral galaxy, yet its supermassive black hole is 50 times bigger than ours. So we have to ask the question, why are we living in this galaxy with this ridiculously, inexplicably small supermassive black hole? And it may be it's why we're here. So if you imagine the galaxies with the big supermassive black holes, they tend to have these powerful jets that come out that stab outwards from the poles of the spinning black holes. And these jets can push away all the gas in the centers of galaxies. So remember, that gas is the raw material from which stars are made. So in these galaxies with the big supermassive black holes, star formation tends to be snuffed out after one generation. But this never happened in our Milky Way because the jets and the supermassive black hole were too small. So we've had multiple generations, and you probably know that our sun is a third generation star. That means that two generations of stars have gone through their life cycle, blown up, and then the next generation has formed, congealed out of the debris. And in each generation, more heavy elements have been forged in those stars. So more carbon, more oxygen, more calcium, more iron, precisely the elements needed to make a rocky planet like the Earth. Precisely the elements needed for us to exist. So it looks as if our existence is connected to the supermassive black hole at the center of our galaxy.
- [76:01]
B
Yeah, Absolutely amazing. You start the book by saying we owe our existence and our origins to it, or we could potentially. And you end it by as you just described now, sort of exactly explaining why. And it's unbelievable. That concludes our interview. Again, the book is A Crack in Everything. How Black Holes Came in from the Cold into a Cosmic center by Marcus Chown. I should know, we really just scratched the surface here. Marcus, thank you so much for your time and writing such a thoughtful and illuminating book. I hope you've got the next one in the works.
- [76:36]
C
Oh, well, thanks very much, Greg. I really enjoyed it and it's wonderful to have somebody who really, really got my book and really enjoyed it and actually read it because I often get by people, I even read my book. But that's very good. Thank you.
- [76:50]
B
It is, it is. I highly recommend it. Like I said at the beginning, you just do a wonderful job of tying the individuals, the science, the people and presenting the larger picture all around. Fantastic book and great interview, Markus. Thank you so much.
- [77:04]
C
Thanks very much, Greg.