Why Black Holes are the most terrifying objects in the universe | Marcus Chown

There's something in our galaxy that shouldn't be there. It doesn't shine. It doesn't speak. But it warps time, bends space, and swallows light whole. Scientists once thought the very idea was too preposterous to be real. Now it might be the reason that you're here listening and watching this podcast. It's called a black hole. But what if black holes aren't just the universe's ultimate predators? What if they're also its midwives? What if every black hole is a kind of cosmic womb giving birth to a new universe with slightly different laws of physics in a process not unlike natural selection? Today's guest has spent years tracing the story of how we came to learn about black holes and not just the science, but the human struggle to comprehend these magnificent monsters of the cosmos.

From equations scribbled in the trenches of World War I to a vanishing dark star in the nineteen seventies that changed everything. Marcus Chan, today's guest, is one of the clearest voices in popular science writing that I know of in the known universe. And his latest book, A Crack in Everything, tells the astonishing story of how black holes went from absurd fantasy to the center of all we know. Marcus soon, I wanna ask you if black holes are actually creators, a type of force that acts as a womb perhaps for new universes, but certainly for solar systems like our own. But first, let's start where everyone starts, as black holes as destroyers of worlds. What makes black holes the most terrifying objects in the cosmos?

Well, the regions of space where, gravity is so strong that nothing, not even light, can escape. So they do have this reputation for sucking in material relentlessly. And this was, really a a big mistake that that physicists and astronomers made over the last century because they thought that they would just suck in material, They're black against the black of space, and they'd be actually impossible to see. But actually, one of the most striking features well, first of all, black holes the the black holes that we know of in the universe are are include some of the most luminous objects in creation so that they're far from being black. And although we can just about see material disappearing down the the whole of a black hole just about, the most striking feature is often of material coming out, you know, often along these titanic jets of material which stab out through galaxies for millions of light years. So really, you know, the idea of them sucking in material, is is kind of they do, but but actually they kind of defy that that picture. And that's basically because they're they're embedded in environment and physicists and astronomers assume that that that they would be black because they would be isolated. But in fact pretty much everything in the universe is embedded in environment.

Most stars are binary stars. You know, sun is quite unusual being a solitary star. It's quite unusual. And being embedded in an environment, having a companion, having gas or dust around you makes all the difference. And this leads to these objects being in fact incredibly luminous even though they're black holes.

One thing I really loved about your writing, I always love your writing, but, but about the book is that you kind of steer away from the kind of pop culture mythology of spaghettification. Yes, you mentioned it. Of course, you have to. It's a it's a law of nature. Right? But you really get into the hard facts and and physics of it and it's no surprise because of your scientific training and your your past books as well. And speaking of books, I like to do what you're never supposed to do on the show, which is a feature called judging books by their cover. So I actually bought the audiobook and rated it with an asterism of five stars. Nothing less would suffice.

It's got the encomium, that it well deserves from Richard Dawkins, a pretty wonderful book. And from my, one of my kids' favorite astrophysicist, also named Brian, Brian May. Oh my god. It says, Marcus Marcus Chung rocks. Wow. You can't ask for a better so so, please, that's the back cover. But judge the front cover, title, subtitle, and this mysterious monstrous cover art that's so beautiful.

Glad you like it. But I I should point out that there are two types of black holes. There are theoretical black holes, which you you talk about, which are fantastically important because, you know, major theories of physics collide in black holes. Our theory of the microscopic role, quantum theory, our theory of big things, general relativity, and thermodynamics, our theory of heat. They clash, and they're not melded. They they predict different things, in the same domain, which is gold dust for physicists because when when a a a theory is shown to to break down and Einstein's theory of gravity breaks down in the center of a black hole, then we we are encouraged to look for a deeper, better theory. So there's there's there's theoretical black holes, and, of course, Stephen Hawking's name is associated with those. And then there's the real black holes, which are the black holes we've actually found out in the universe.

And my book is essentially about the real black holes because incredibly, not only do they exist, but they're relatively common. And as you said in your intro, they they play a role in us us having this conversation today.

I need to really understand the nature of black holes. Are they really, you know, cosmic safes hiding away information forever? Are they cosmic shredders obliterating it beyond recovery? How do you as an as a, you know, as a popularizer and an explicator, exceptional explicator par excellence, How do you think of these things? How do you think of their paradoxical nature and Hawking radiation, information paradox, firewalls? Talk about how these objects are fascinating in their own right, but made even more so by the many paradoxes that they bring up.

They are paradoxical. As as I said, the the the real black holes in the universe are paradoxical because they aren't black. You know? They they are fantastically luminous because of the the material that falls into them and the friction because it turns out that the nothing everything in the universe is rotating, the earth is rotating, the galaxy is rotating, which means material, doesn't fall directly into a black hole. It kind of swirls down onto it like water down a black hole, and friction causes was it, the heat to millions of degrees, and this is what causes them to shine. But I ought to just point out that that black holes are the simplest objects in the whole of physics because there's nothing they're they're made of nothing more than space and time. As far as we know so I ought to tell you that stellar mass black holes, form when a star gets to the end of its life, runs out of fuel with no fuel to to to burn, to generate heat, to push outwards. Gravity crushes the star. And as far as we know, it crushes it down to to a point, what we call a singularity.

And really the star, as far as we know, actually vanishes. And all that's left is a bottomless pit in the fabric of space time. This is Einstein's picture. Einstein realized that gravity was actually the curvature of space time. You know, we can't visualize it because it's a four dimensional thing. That's why it took genius of Einstein to realize. So, you know, all there is left after the star has collapsed is this bottomless pit into from which nothing or even, like, can actually climb out. But you talked about Hawking radiation.

You you know, a lot of people get puzzled by this. Hawking in 1974 realized that actually black holes glow. They they have a temperature. They're all thermodynamic objects, and they they glow with this stuff called Hawking radiation that streams outwards. And people are often puzzled because they say, well, surely black holes are defined by by nothing ever getting out of them. Well, the Hawking radiation doesn't get out of them. It's created in the vacuum just outside the perimeter of the black hole. So we we define as kind of spherical membrane.

This is an imaginary membrane called the event horizon, and it's the point of no return for in falling light and matter, and the Hawking radiation is generated on the outside. But, I mean, I know the question you're asking me, and that is that as far as we know in physics, information is not is never destroyed. This is quite fundamental, to to our our laws of physics. And so the question then is, if the star, the massive star shrinks down to nothing and vanishes, leaving only a a kind of bottomless pit in space time, what happened to the information that described the star? Tremendous amount of information will be required to to, you know, tell you the the the type of atoms, their location, where their electrons are. You know, you can imagine this incredible amount of information. The actual event horizon is not a perfect sphere. That it's probably got a a microstructure. So if you were to zoom in on in on it on a very small scale, you would see it would it's kind of mountainous.

And this this actually impresses itself on the Hawking radiation. You know, just as your voice, or if you're on a on a radio impresses itself on the carrier wave, the radio wave that transmits the the your voice to the the listener, this kind of microscopic terrain, actually impresses itself on the Hawking radiation. And it's in this microscopic terrain that the information that describe the original star is recorded. So that's that's kind of one possible way. I think that's probably the consensus. You know, you're an astrophysicist, Brian. You must know.

There's so much to unpack in this lovely book. I I recommend the audio version because it's I always like to hear the author's voice. You didn't record the audiobook, but it's close enough to an American's ear that, it sounds like you, Marcus, I have to say. It's it's wonderfully done. Although and the printed book is as well.

So I've actually recorded audiobooks before, so I didn't get asked on it. Well, I really, really enjoyed it. I I mean, have you done it? I bet you have.

Yeah. I did it. Well, I did it for, seven or eight hours of the dialogue between, Galileo's, World Systems with my friend Carlo Rovelli and and others. So, yeah, we did it. We actually recorded the first ever audiobook of Galileo.

The last one I recorded, it was two days in a recording studio. And then the third day, we had one hour left. And when I got in the recording studio in the studio, they said, oh, yesterday when I recorded eight hours, we had an an unexplained hiss in the background. And and could you record it again? And, I mean, I was in the studio for ten hours, and I I was kind of speechless at the end. Because I thought it was all over. But obviously there are harder jobs like working down coal mines than recording your audio book.

Or, you know, writing equations in the trenches of World War I. And, you know, soon I want to ask you what the next great black hole discovery might be, whether it would be in theory, observation, experiment, you know, ranging from quantum gravity breakthroughs to so called multi messenger astronomy and observations that we haven't dreamed of yet. But first, to really understand where we're going, we have to look at how we got to our understanding of black holes from the first place because it's a it's a human story too, not just about, you know, cosmic monsters and and, ruptures in space time. And it involves people like Carl Schwartzchild and and Subramanian, Chandrasekhar and and many, many others. And I I wonder of all these, you know, kind of characters that you got to study, which is the most sympathetic or pathetic perhaps? There's a lot of sadness. There's a lot of debauchery or shall I say, you know, kind of skullduggery, by by some unsavory characters that goes along with it, including the ignorance of underrepresented groups in astronomy to get attention. So talk about the the history of of the discovery, the theoretical predictions, and the experimental triumphs that led us to the understanding that we have now before we pave paths forward to the future?

So the book begins with Karl Schwarzschild, who was, on the outbreak of the he was German. He was the director of the Berlin Observatory on the outbreak of the First World War. He joined the German army immediately. He had no need to. He was 40 years old, but antisemitism was on the rise in, Germany and he was Jewish. And he wanted to show you could be a patriotic German. He ended up running a weather station in Belgium, calculated in shell trajectories. He ended up at a place called Mollhaus, which was on the northern border of France between France and Germany.

The only bit of the Western Front that was mountainous. And in November 1915, he went on leave to see his family in Berlin. And on the 11/18/1915, he attended a lecture by Albert Einstein. And Einstein, in four lectures in November 1915, presented his revolutionary new theory of gravity. And and, Schwarzschild was completely captivated, went back to the front, and he did something that Einstein thought was impossible. And so what you have to realize is that Einstein had shown you know, Newton said there was a a a gravity was effectively an invisible tether that connected the Earth and the sun and kept the Earth orbiting forever. Einstein realized this is incorrect. What gravid what a mass like the sun actually does is it is it kinda walks the space time around into a valley.

I I said before, you can't actually see that valley. And the Earth kind of goes around the the the upper reaches of that valley rather like a roulette ball in a roulette wheel. So gravity is actually the curvature of space. Now the one thing you need to know is that, Newton used one formula to characterize gravity and Einstein used t. So actually finding a curvature of space for any useful body, like a star, was considered by Einstein to be impossible. But within about a couple of weeks, Schwarzschild, on the Western Front, found the solution, sent it to Einstein. Einstein was amazed to get a letter from the Western Front and then to find there was something in it that he he considered to be impossible. You know? And he presented this result at a Prussian Academy of Sciences.

But Schwarzschild had not finished and realized that if the basically, he found the curvature, sorry, around a spherical mass, which was the the shape of the valley of space time. And then he realized that if that mass were to become more and more compressed, the valley would become steeper. And so eventually it became a bottomless pit from which light could not escape. And therefore the object would be shut off from the universe. It would be black. He sent this to Einstein. Einstein presented it again at the Prussian Academy. Never believed in, black holes until he died.

And there's an obvious reason for that. It taken taken ten years of blood and sweat to come up with his news theory. And it's discovered within a few weeks of presenting it that there was actually a place where it broke down. I told you before that if a star shrinks, there's nothing to stop it shrinking down to a point. We call that a singularity. When everything skyrockets to infinity, the density or whatever, when you get that in a formula, when you get that in in a theory, it it tells you your theory has been stretched to a point beyond which is it's got anything sensible to say. So, Schwarzschild and then sadly, you know the story. Sadly, he had a disease called pemphigus vulgaris in late December.

In 1915, when he was writing to Einstein, he got these blisters in his mouth. They spread all over his body. Took a long time for them to for him to be diagnosed, but this is a disease in which the immune system attacks the skin. And the skin, of course, is your barrier against infection, against microorganisms. So he knew he was gonna die, and he actually went back to Berlin and died in May 1915. But his idea did not die with him. And I just I I there's a lot of things I could tell you, but you asked me about people who I I would like to, talk about. And one of them is Louise Webster, who has been entirely written out the history of science.

She was the current discoverer of black holes with Paul Mirden in, 1971. And, of course, as if you've read my book, you've read my book, of course. I was switched on to black holes at the age of 12 because I was a member of the Junior Astronomical Society, and my dad took me to a talk in London, by someone called Paul Murden, who hobbled towards the stage on crutches. He had had childhood, polio. And he proceeded to talk about this object called Cygnus X-one, which was the first black hole candidate. And, it blew my mind. It blew my 12 year old mind. You know? So, but it's only recently I discovered that he actually co discovered it with a woman called Louise Webster.

They were both 30 years old. She was Australian, and she went back to Australia. She had liver disease, and she had one of the very first successful liver transplants in Australia, but sadly got cancer, and she died at 49. And she's been completely forgotten. So if you remember anything about this podcast today, remember the name of the co discoverer of black holes, Louis Webster. And I think you also know that, you know, pulsars or or neutron stars, these are another collapsed form of stars. So if a star is not massive enough to collapse all the way down to singularity, it can form what we call a neutron star, which is a star basically, about the size of, I don't know. It's about half half the size of size of San Diego.

But but, but the mass of of the sun and, you know, sugar cube of material of a neutron star would weigh as much as the human race. So they're super dense objects. They were discovered by Jocelyn Bell, who was a graduate student at Cambridge in 1967, and there have been three Nobel Prizes for pulsars, and none have gone to her. So the two types of stars, what we call relativistic stars, the two types of stars or or endpoints of stellar evolution, that require relativity to understand, black holes and neutron stars were both discovered by women.

I had Dame Belle Murnau, on the podcast. I had her on, December 10 in 2023, which you'll recognize as the day the Nobel prizes are given away. So I wanted to make sure that at least, you know, we celebrated the proper way. There's one other object that plays, sort of it may might have been a red herring or it might have been kind of a a false start, but but is is integral to the story of black holes, and that's their, you know, kinda mirror image white dwarves, at least. The story that you weave so beautifully starts off with a young, Subramanian Chandra Sekhar, traveling and then ultimately getting undercut, and that delaying the progress of not only the discovery of black holes, but theoretical astrophysics for decades to come. He eventually did get recognition with a Nobel Prize, but not until he was quite old. So talk about him, his discoveries, why they're so important, and how they segue into the black hole narrative.

Well, of course, nobody who thought about it wanted to believe in black holes. I mean, this is the story of people over the last century being dragged kicking and screaming, having to consider these objects because no one wanted to think about the singularity at the center where everything breaks down. And certainly Einstein didn't want to believe it. So anyone after about 1915 who thought about it, which were which were very few people, thought there's got to be some other force that intervenes, that stops a massive star or it's the core of a massive star at the end of its life from shrinking down to an infinitely dense point to a singularity. There's gotta be something that stops it. And in the nineteen twenties, it that something turned up, which was, of course, what we call quantum theory. Quantum theory is our very best description of the microscopic world and their of atoms and their constituents. You know, it's given us lasers, nuclear reactors, iPhones, you know, basically created the the modern world.

There's a a principle called the Heisenberg uncertainty principle, and all we really need to know is that if you try and compress something like a a a proton or electron or whatever into a small volume, it resists. And this is not anything to do with its temperature. It's not the fact that it's flying around because it's moved because it's got temperature. This is a fundamental, this is a fundamental thing. And so anyone who thought about it thought, well, actually and there were people at Cambridge in in England, like Ralph Fowler, who thought about this thought, well, actually, this runaway catastrophic gravitational collapse will be stopped. And then a nine I should say a 19 year old Indian from Madras, which is now Chennai, I believe, in India, was on his way to Cambridge to to be to do a degree. And he was sitting on the deck of his ship as it went through the Suez Canal, and he was thinking about the death of stars. And he happened to know a better quantum theory, and he knew a bit about stars.

And he realized that everyone who thought about this problem had missed out one key element. And that was Einstein's theory of relativity, which basically gives an upper limit to the speed of anything. So if you compress, a star gets the end of its life and it and it shrinks and its electrons get pushed together, they can push back through the Heisenberg uncertainty principle. They push back, you know, rather like, you know, raindrops on a on a roof, you know, spattering on a roof. But there's a

Pushing New Yorkers.

Yeah. There's there's a limit. There's a limit to how fast fast they can push back because they cannot move faster than the speed of light. Henley realized that there was actually, if the star was more massive, what we called it what we his name was Supermanian Chandrasekhar. We now call it the Chandrasekhar limit. If a star is more than about one and a half times the mass of the sun, this Heisenberg uncertainty principle, what we call degeneracy pressure, could not prevent the star from collapsing. So if the star at the end of its life was more massive, a black hole would be the outcome. And as you say, probably the greatest one of the greatest astronomers of his day, Arthur Eddington, the the one of the two people who had understood Einstein's theory of gravity in 1915, and the other was Willem de Sitter, who was a a Dutch physicist.

But Eddington, understood it and and and presented it to the English speaking world. He was I mean, I remember there was a poll, I think it was in the twenties or thirties, in America of who was the, you know, the top 10 astronomers in the world. And he was ranked by American astronomers as the number one astronomer. And Eddington just did not believe in this limit, this this, Chandrasekhar limit. And and it's very hard to understand why he didn't because he just said the world does not work this way. Nature does not work this way, which is not really much of an argument. And he did his best to completely undermine Chandrasekhar. And in fact, humiliating, Chandrasekhar, gave a presentation at the Royal Astronomical Society in London, and he did not know that Eddington well, Eddington was gonna go to talk after him, and he did not know that Eddington's talk was to entirely undermine him.

And poor old Chandra Sekhar had to even move to another field of of astronomy because he knew he he could not compete with Eddington because Eddington was such a powerful figure. But as you just say, he in 1983, he was vindicated. He got the Nobel Prize. Eddington died, I think, in the second World War, never got the Nobel Prize, but but Charles de la Secard did. And he was very hurt all of his life, although he was always said that he admired Eddington. And I was there actually, on the spot at Caltech when Willie Fowler got the Nobel Prize in 1983 and Chandrasekhar shared the Physics Nobel Prize that year.

So given the fact that I see the black hole story as sort of a a relay race, not not a marathon, but bold ideas, you know, kind of first promulgated by theorists outpacing experimentalists and instrument builders. But that kind of, you know, trickles down when when we reach the limit of measuring, you know, massive and supermassive black holes. We but as I understand the the trajectory that this subject took, thanks to your book, white dwarves, then followed by neutron stars and then eventually pulsars and then black holes and and theory was always in front and even it was in front for a long time with gravitational waves. I've spoken to, you know, all three, Kip Thorne, Barry Barish, and Ray Weiss on this podcast, as well as people like Shep Doleman from the Event Horizon Telescope. What do you see as the future of this marriage between theory, phenomenology, observation, instrument builders of chasing down the impossible. What what's going to be the next frontier? Is it some new developments in theory, or have we reached the end of theory? Is it some new technological, device that we don't have yet, or is it some huge budget to build larger and larger instruments to the kind of which we do have? Where do you see the future of this field going?

Well, I mean, it's it's incredibly exciting. So first of all, you just mentioned gravitational waves, which are like ripples in the fabric of space time. I mean, basically, a tsunami in the fabric of space time. But, of course, by the time we we pick up these these signals, they filled a huge volume of space and become massively diluted. But they were detected in on the 09/14/2015 predicted by Einstein in 1916 because, you know, mass or energy can warp space. It can also ripple it. It can also jiggle it and and knows what gravitational waves are. The first discovery, was of two black holes which had merged and I think there were something like one was about 35 times the mass of the sun.

You have one about 50, something like that. This was much, much bigger than anyone had expected. And we're now seeing mergers. We've seen about a hundred now, including, neutron star mergers and black hole neutron star mergers. And we're seeing, black holes which are much more massive than actually could possibly exist. So there is actually a gap, a mass gap where we do not expect to see max black holes. And that is because when a star is massive enough, we get what was called a a pair instability supernova, and the star blows the solar completely apart. So there is no implosion at the center to form a black hole.

So we shouldn't see any black holes in a particular range, yet we do see them. So what we we're learning is that the black holes we're seeing merging, pairs that we're seeing merging, spiraling together and merging, individually had actually merged before. So this process of merging is quite common. That's gonna continue, and and we're going to be surprised by what we actually discover. I think probably one of the most amazing things is is the James Webb Space Telescope, which is, you know, showing us the pretty newborn universe when it was maybe two or 3% its current age. And we're beginning we're seeing these supermassive black holes or we're seeing evidence of these supermassive black holes very, very large, very early on. So we're seeing billion solar mass, supermassive black holes within, you know, three or four hundred million years of the Big Bang. And that's quite difficult to understand.

But I think there's some evidence. I mean, there are these things called red dots you've probably heard about which have been seen, and they may well be black holes enshrouded in a in a very, very dense shell of material. And so sucking in material at a rate greater than they ought to be able to do. So that we may get this pretty soon, I hope, the solution to where these supermassive black holes come from. Now I ought to just say what I haven't told you is there's probably a complete spectrum of of black holes from stellar mass up to really large ones. But but but we we we basically see two populations. One is stellar mass black holes which we believe form when in supernovae, a star blows itself apart. Paradoxically, the core implodes.

In fact, it's the implosion that drives the explosion. And then we see these supermassive black holes and and the biggest ones are something like 60,000,000,000 times the mass of the sun. And their origin is a complete mystery. We're seeing them very, very early on in the universe. So so we believe that black holes start off quite small. I mean, it could have been an early generation of stars, that formed very shortly after the Big Bang. There's a lot of evidence that they would have been more massive than stars today. So it's quite possible they would have gone through their livestock storage their their life histories quite quickly, exploded up for produced black hole.

Those black holes maybe would have merged, sucked in material. But it's quite difficult to see how a black hole could grow from stellar mass to a billion times the mass of the sun in the available time. So that's that's a really big mystery. I mean, it could be conceivably that they are spawned in some way in the in the Big Bang itself, in the, turbulent conditions in the Big Bang. That would be very interesting. So I think, you know, to answer your question, I think the origin of supermassive black holes would be that would be that's an incredibly important question to answer. So let's face it. There's one Hubble Space Telescope discovers in the nineteen nineties that there's actually a supermassive black hole in the heart of pretty much every galaxy.

In fact, essentially every galaxy. So we don't know what they're doing there. Did they come first? Were there supermassive black holes formed in the universe? And then maybe they gathered material around in which then collapsed to form stars. So were they the seeds around which galaxies formed? Or were the galaxies formed first and then maybe there were very dense clusters in the center that ended up forming a supermassive black hole? So we don't understand anything really about the origin of supermassive black holes. So the story of my book basically is how black holes have come in from the cold. So as you said in your introduction, Brian, at the very beginning, they were so ridiculous as to not not even be considered the preserve of science fiction. But gradually, last century, they've moved more and more into the center of of science. When, we realized that they had to exist because we discovered, Martin Schmidt at Caltech discovered quasars, which are often pump out 100 times the amount of light of a normal galaxy from a volume maybe the size of the solar system.

So that was 1963. Within a year, theorists had realized there was only one possible source of energy, and that was material swirling down like water down a black hole, you know, on onto a black hole being heated to millions of degrees and shining that way, but not a black hole of a few times the mass of the sun, a black hole of billions or or tens of billions times the

mass of

the sun. So supermassive black holes. But then we thought, well, quasars, they they they are what we call active galaxies. There's a there's a whole lot zoo of them. But basically, they're galaxies. We define them as galaxies that are, generating most of their light, not from stars, but from a accretion disk, what we call right behind a supermassive black hole. And at that point, you know, only 1% of of galaxies were active galaxies. So we could think, well, they're not really important.

We can sweep them on top of carpet. They're they're anomalies. And then we discover there's money in every single galaxy. And and the reason that we only see them in only 1% of galaxies are active is because in only 1% of galaxies are they being fed. So in 99% of galaxies, they've sucked in all the gas and Ritterbots Ritterbots stars, and and they're and they're slumbering. You know, they're slumbering. And and, of course, there's a supermassive black hole in the center of our own galaxy, although it's a titular.

That's right. Compared to our big brothers in m eighty seven. I wanna quote, a lyric, from the famous astrophysicist, not Brian May, but from Leonard Cohen. And it goes like this. Ring the bells that still can ring. Forget your perfect offering. There's a crack, a crack in everything. That's how the light gets in.

And I interpreted your title of your book along those lines and that you present black holes as this confluence between all the major ideas of of physics, modern physics, quantum mechanics, thermodynamics, information theory, general relativity, special relativity, they all sort of break down at one level or another. How important is that narrative, you know, where the cracks are what reveal the truth and and why and why we shouldn't as physicists be afraid of of flaws and cracks in our most cherished theories and ideas.

Well, you've put your finger on exactly what the title means, you know, because, you know, in in physics, places where our known laws of physics break down are are are gold mines. You know, they they're really what we look for. You know, we look for paradoxes. We look for places where there are certainly where there are two theories that predict for the in the same domain different things, then we know that one or both of those theories is wrong. And there is a great I saw this survey, a psychological survey, and it was about people who were willing to change their point of view. You know, it was talking about politics, but people were willing to change their point of view. And the people who scored highest, the people who were most likely to change their view were people of a scientific background. And that is because they actually enjoy seeing, you know, that they enjoy being proved wrong.

So really, you know, scientists get a lot of joy out of out of finding out that their theories don't work because they're constantly looking for the deeper, better theory. And really, our scientific theories are provisional. You know, they are they are the best description we have at this moment, but we know they break down. So, you know, to everyone but Einstein who was not happy with black holes, black holes are of gold dust, you know. I mean, there there if we get contradictions in physics and we are challenged by nature to come up with a better theory. And the better theory we expect, but we could be wrong, is what we call a quantum theory of gravity where we unite our our theory of the very small, which is quantum theory with our theory of the very big, which is general relativity. Because in a in a black hole, something very big becomes very small. You know, a star shrinks smaller than an atom.

So we we we need to unite these to understand what happens in the center of a black hole and coincidentally, where the universe came from because we believe that the universe also began in a singularity, although a singularity in time rather than a singularity in space, but similar kind of thing. So so yeah. And I was I was saying about how how how scientists actually revel in in having to change their mind, you know, because really, I mean, if you go back, fifty years, I mean, our picture of the of the universe is entirely different to the picture that we have now. I mean, imagine how many objects that we know of now in the universe that we didn't know about. I'm thinking of things like gamma ray bursters, which were actually they were known about, but the US military was keeping them a secret, discovered them because it was trying to find the gamma rays produced by clandestine Russian nuclear tests. It was it was using spice satellites to do that. And it discovered this, you know, a burst of gamma rays once a day from somewhere in the sky. Fortunately, those, satellites, they could tell where they were coming from.

Otherwise, it would've they would've triggered a nuclear war, and they knew that they were not coming from the Russians. They were coming from space. Black holes are just really challenging us.

Yeah. It's a unique, laboratory for understanding physics at the extremes. I wanna, mention something you hinted at before I get to the creation of the universe, from black holes. Maybe we can touch upon an interesting theory that you discuss in the book, which by the way, you don't discuss cosmic natural selection, which we're gonna get to in a minute, but you do discuss, how our existence might be owed in fact to black holes. Can you elaborate on that for listeners that might be shocked again to hear such a such a wild idea?

This is the greatest irony. So, you know, the the they start off, you know, as as really not even a preserve of science fiction, and they move so far in the to to the center of our picture that we actually think that, first of all, they they play some key and mysterious role, still mysterious role, in generating the universe we see around us. But specifically, in us having this conversation. It comes down to I told you every galaxy's got a supermassive black hole in its its core, and we've got one. It's called Sagittarius a star. It was discovered in 1974, so fifty one years ago. Two people in 2020, Andrea Ghez, a astronomer in California, and Reinhard Genzel in Germany won a Nobel Prize in 2024 working out its mass. And its mass is 4,200,000 times the mass of the sun.

Now this is this is a mystery because this is really, really tiny. This is thousands of times smaller than the supermassive black holes in active galaxies like quasars. And if we compare the Milky Way with Andromeda, Andromeda is the nearest big galaxy, a galaxy that's the spiral galaxy, and very, very similar to the Milky Way, its supermassive black hole is 50 times bigger. So why have we got such a tiny, tiny supermassive black hole connected to us being here? Because in I said in the beginning, in the guys with big black holes, they have these tremendous titanic jets that stab outwards from the north and south poles of the spinning black holes, stab outwards often not only millions of light years through space, but sometimes hundred billion light years through space. I mean, it's shockingly how they how they stay collimated, how they stay narrow for that long is is still a mystery. But what in in the galaxies with the big supermassive black holes, these jets can push away, drive away all the gas in the center of galaxies. Now that's the raw material of new stars. So in these galaxies, the star formation is is kind of snuffed out after one generation.

But it didn't happen in our galaxy because we've got a tiddler of a black hole. We've probably never had any powerful jets at all. And and so we've had multiple generations of stars, and our sun is a third generation star. And in each successive generation, which forms from the raw material, you know, of the exploding stars of the previous generation, in each successive generation, more heavy elements are forged. So more carbon, more oxygen, more iron, more calcium.

That brings up this this little, artifact that I give away to my listeners. If you go to brianking.com/list, this is a meteorite, which is a fragment probably of a population two star that eventually coalesced to be a part of our solar system as a bridge between the the earlier and later generations. So these stars give their give their lives to make our lives possible. Right?

And and I mean, in and out, because of our small black hole, it has been possible for there'd be multiple generations of stars. And and I I just listed those elements, and those elements that have been forged because we've had multiple generations, because we have a small supermassive black hole, those elements are precisely the ones needed to make your meteorite, to make a rocky planet like the Earth, and to make biological life like you and me. We could not be having this conversation in, for instance, M87. You mentioned M87. This is a nearby galaxy with a 6,500,000,000 solar mass black hole image was habilisized in 2019, the first ever image of a black hole, and we could not have arisen in that galaxy. So we believe that that galaxy is probably a biological desert. It's remarkable that we've come from thinking that these objects fine fiction to thinking that we're having this conversation because of a black hole, Sagittarius star.

And that brings me to this provocative question I've been teasing listeners about since the first few seconds. We we started off the conversation with a description of black holes as predators, as paradox machines, and I I promised I'd come back to this idea that the black hole might not be the end of the story when it comes to producing life on Earth. What about if it's, the the cause not only of our existence on this beautiful podcast, but of entire universes, like our own within the multiverse? And just for the readers and listeners that are not, familiar, rather, at least small and past guests on on the podcast, proposed that black holes might actually spawn new universes, each one with slightly mutated laws of physics, a kind of cosmic natural selection. He calls it that, in fact, CNS. Now I noticed in the book, I didn't see it, and that was a little bit surprising. I don't believe you mentioned cosmic natural. You mentioned Lee. Lee is in there, I think, one or two times, but I'm curious.

First of all, why didn't you mention it? Was it a little bit, of a bridge too far, or is there actually some justification for treating these black holes not only as, you know, fertile, fertilization within galaxies for life like us to exist, but also, for universes onto themselves to exist. In other words, within the multiverse to explain the peculiar qualities of our own. Is this a bridge too far or are

reason is that my book is principally about real black holes, you know, black holes that we've actually discovered. So it's it's the, you know, it culminates with you mentioned the event horizon telescope getting the first ever images of Sagittarius O star and m 87, the the black holes. My last chapter is about speculative ideas, but I didn't mention this one. And one of the reasons is that we really don't know what it's like inside a black hole. So I've got the the stories from people like Paul Mirding, who was the co discoverer of stellar mass black holes, and Roy Kerr, who was a really interesting character. He's he's now 91 years old. He basically came up with the first development in Einstein's theory of gravity for forty seven years, and he did something which people thought was impossible. He discovered the shape of the space time around a spinning black hole.

Now I told you everything in the universe is spinning. So actually, Schwarzschild had come up with the the shape around a static black hole, so that wasn't very realistic. So he came up with a a description which describes every single black hole in the universe. He was 29 at the time. He himself gave up on working out what the space time was like within inside a black hole because the problem was just too difficult to solve. So we really don't know what it's like inside a black hole. Not only can we not solve Einstein's equations to find out what the shape of the space time is inside a black hole, but we certainly don't know what it's like near the singularity. Because what the singularity is is doesn't exist, by the way.

I should tell you that. When a singularity appears in a in a theory, it tells you your theory is broken. You need a better theory. So we need a quantum theory of gravity to tell us what exactly is at the center of a black hole, and we don't know what that is. So saying that that, you know, it connects to another another region of space time, that it's a time machine, that generates another another black hole or another universe, this is so so far removed from what we can confidently talk about that I didn't really it's smoothie. There's loads of other books about black holes. Most books about black holes are about theoretical black holes, about Hawking radiation. I love Lee Smolin's idea.

I hope he's correct. But but again, it's not very well founded. And the problem is once you start admitting not very well founded ideas into this, you have a book which is a hundred times longer than the book that you were writing and people get lost. You know? What what do we know and what that we don't know? My thought is really that the things that we know are so fantastic and so amazing that we we don't need to really speak. Thank you more. Grain, you know, I mean, if if you tell me, you know, if I'm thinking of something else like dark matter. So with dark matter, which was this invisible stuff that that fills the union, outweighs the visible stars and galaxies by about a factor of six, we can speculate. And there's literally hundreds of speculations as to what that dark matter could be.

But it doesn't really get us anywhere, and the reader then gets confused by all these hundreds and hundreds of possible suggestions, none of which are constrained by physics because we've never detected any. So yeah. Now I I think Lee because Lee Smolin wrote a run wonderful book, didn't he? It was called, what was it called now?

In the life of the cosmos.

Cosmos. Yeah. About black holes. Yeah. So basically, he says that the conditions necessary to create black holes, the laws of physics necessary to create black holes, also the laws of physics necessary to create biological life. So the two are hand in hand. So so the universes that create the most born, the most black holes, I think that's correct, isn't it?

Produces constants of nature and and laws of physics that are compatible. It's an anthropic, what's called a weak anthropic.

Yeah. I mean, that is, you know, I mean, obviously, as Einstein said, the most incomprehensible thing about the universe is it's comprehensible, which is a fantastic remark, isn't it, really?

Oh, one thing I appreciated with bittersweetness was you're mentioning the BICEP two affair, which I played, not insignificant role in. And it made me think of some of the more again, there's a lot of, you know, pathos in these. Our mutual friend, Janet Levin, who you write about in the book, has written, you know, Black Hole Blues about the, you know, kind of stories of of the unsung heroes, the lovable losers, and so forth. And one of them, you know, which I resonate with, no pun intended, actually, pun intended. It was a good pun, is Joseph Webber. So, he, of course, was, you know, claiming that he had detected gravitational waves, you know, three or four decades before I go actually did it. And it was only because of a a slight amount of hubris, I think it's safe to say that on his part, that he never really gave up the belief that he had discovered these first. And it let me think about all the false starts and the and the curious characters in this book.

You know, you mentioned Louise and you mentioned, Johnson Bell and and others. But are there other stories maybe that didn't fit into the book or or perhaps would be in an additional book? Are there other, you know, sort of human stories, that that were neglected? You know, know, because we look at the black hole and it it's not unlike a black mirror. We we learn about the subterfuge and the chicanery and the stolen credit and the stolen valor, in this book very delightfully. Were there other characters that you didn't get a chance to disclose that maybe the public has, would have a desire in knowing more about?

Popular science writers tend to write science as if it's like, you know, one way street. Everything, you know, we we it's a logical timeline, but in fact, scientists are human beings. They propose the existence of things for the wrong reasons. Progress of science is like a drunkard's walk, you know, a few steps forward, a few a few backwards, you know. I mean, your subjects, I know, is the, is is the cosmic background radiation, which is after it's the afterglow of the Big Bang. My first popular science book was called Afterglow of Creation, and I went to interview lots of people who are unfortunately now dead. I I talked to Robert Wilson who discovered the microwave background, to people like Bob Dicke and David Wilkinson, all these kind of people. But I mean, interestingly, I mean, one of the one of the great, great figures was George Gamow.

He basically came up with the idea of the hot big bang. You know, I mean, I mean, common sense, I suppose, tells you that if the universe was was smaller, it would have been hotter because if you, you know, squeeze the air in a bicycle pump, it gets hotter. But but no one had really thought seriously about that. So Haidrin Hubble discovered the universe was expanding in 1929, which meant that if you ran the history of the universe back in your mind's eye, like the movie in reverse, you would come to a point when it was all compressed into a small space. You know, I call it a big bang. But no one really thought more about it. It was so ridiculous to think that they could think about physics then. But then then we get George Gamow, who was a Ukrainian American physicist, and he was very interested in when where the chemical elements had came from.

There there was a lot of evidence from the early twentieth century that the universe had begun with the simplest element and all the other elements, 92 naturally occurring ones, had been assembled by these these atoms or nuclei coming together. But that required a lot of heat. Turns out that the the nuclei, the cores of atoms are positively charged. And when you try and thrust together two positively charged nuclei, that they really repel ferociously. So you really have to smash them together at very high speed, and that means high temperature. We just mentioned, by the way, Arthur Eddington, and one of the greatest one of the greatest British astronomers, but he had made a mistake. And he thought that that well, he he had an idea that elements could not be built in inside stars. By this time, they knew in the by about the nineteen thirties that hydrogen nuclei, the the cause of hydrogen atoms, if they were glued together, in a multistep process to make the second heaviest element, helium, this would liberate enough energy to explain sunlight or starlight.

But he he thought, Eddington, that as the sun rotated, there would be currents, what we call meridional currents, which would kind of spread out that helium. So if you imagine the helium is the ash. So so basically, this this would actually cause stars to to fizzle out. He'd managed to rule out stars as the place where elements were built. So Gamow was thinking, where else? You know, and this is when he started thinking about the universe. When it was small, it would have been very hot. And he thought that's just it. That's the place, you know.

And he got his three students in Washington, Ralph Alfa and Robert Herman, to work out the details because Gamow was not a details man. He came up with a lot of brilliant ideas in his life that he was not a details man. And they worked it all out. And they realized that, incredibly, you could actually end up with 10% of the atoms in the universe as helium, 90% hydrogen, but you couldn't get really beyond that at all. So you could and it turns out that 10 of the atoms in the universe are hydrogen. So again so he comes up with the idea of the hot big bang for entirely the wrong reason, but he's correct. You know? And then again, when they when when people started searching for this, afterglow, there was a team, at Bell Labs in, Hongjo in New Jersey, and there was also a team, remarkably, only about 20 miles away in Princeton, and they had a little little, radio dish or radio, horn on their roof. The leader of their team was a guy called Bob Dicke, and he had the idea that the universe was, pulsating.

You know? It was what we so he

Cyclic.

Yeah. Like a like a cyclic universe, like a a giant beating heart. So it would there would be a big bang. It would expand. Gravity would eventually crack it down to a big crunch and expand again. And you realize that this this beating heart universe would have radiation over. You know, there'd be something like a billion 10,000,000,000 photons for every particle of matter or so. So his team was looking for this this afterglow for entirely the wrong reason because the universe we don't believe the universe is pulsated either.

This has happened with the discovery of planets. I mean, the first dots were found around a pulsar, weren't they? I can't remember.

Yeah. They were planted around a pulsar.

Yeah. Yeah. Obviously, it couldn't be there couldn't be any life on them because a pulsar is a super dense object with a lot of radiation around it. But this triggered people to actually look at real stars, you know, because they detected they detected it by the wobble of the star. So the star, the, pulsar was moving backwards and forwards because it was being periodically tugged from one side and the other side by a planet. And this got people looking at real stars. And sure enough, they began to find planets. And now we've probably got five or 6,000 extra solar planets that have been found.

So again, you know, there's all these accidental things that actually happen. I really love this, the way the way this work. One of my heroes is Fred Hoyle, who was at Caltech, but he he, in fact, quacked the problem of where all the all the elements in your body come come from. He found the about eight or nine processes, nuclear processes in stars that made all the elements. They put together some pieces of information. He was working on radar during the second World War. He came to America. In that time, he was supposed to be doing war work, but he meant went to California.

He met he met an astronomer for Walter Bader, who was at Caltech. Bader gave him some, papers on supernovae, stars that explode. And on his way back, he got delayed in Montreal because of bad weather. And he bumped into a lot of people that he knew from Cambridge. And he knew they'd been working on a project called Tube Alloys, which was the British project to build an atomic bomb. You know? So he he knew, and he he gathered from reeling between the lines that there was a problem. There was a problem that they they had a problem trying to build an atomic bomb and he couldn't think what the problem could be. He knew that one of the elements that were to be used was plutonium and he realized that plutonium as you push two bits together to to get a critical mass, would generate so much heat that it would push itself apart.

So the only way you could actually create the nuclear reactions of a of a nuclear bomb was to implode this stuff. In BARDA BARDA, it had realized that supernova were exploded by the implosion of stars. And he put the two ideas together, and he thought, is it the implosion of a star at the end of its life that creates the billions of degrees necessary heavy elements. So the idea had come from the atomic bomb. So so it's just weird the way all these ideas come together. And and he was able to show in about 1946 that you could, in what we we would get what's called nuclear thermodynamic equilibrium. Basically, the the the relative abundance of elements would freeze out. And he was able to show that the relative abundance of these elements like iron and nickel and, all these these was exactly what we'd observed.

And so that was is that information which came from the atomic is just being delayed in Montreal, that bit of information that gave him he was able to predict the relative abundances of some elements. And then he came to Caltech in 1953. And the reason he came to Caltech was because he was at a conference in Italy on galaxies. And Walter Bader had presented a result in which he realized that the distance indicators, there were two types of what we call Cepheid variables, and and we had not realized there were two types. And if you realize this, you realize that, in fact, the universe was twice as old as we had thought. And he had presented this in a paper, but there has been there were two people in the audience who then quickly published a paper with Barda's result as if it was theirs. And Hoyle had been sitting there because they didn't have a secretary to record the the results, and he was able to prove that Bader had had his ideas stolen. And Bader was so pleased that when he went back to Caltech, he wrote to Poyle and said, I've persuaded people here to to have you come over.

Would you like to come over? He went over. He met Willie Fowler, who was a nuclear physicist, and he had a prediction. You probably know this prediction that the problem in building up the elements is when you get helium, if you stick two helium nuclei together, you get beryllium eight and it's not stable. So how do you get to heavier elements? So he thought maybe occasionally three helium nuclei collide at the same moment. It's not like, you know, in a in a supermarket car park, three people with their shopping trolleys all collide at the same time. And if this reaction with what is called what we're gonna call resonant, then then you would get the formation of carbon and then you could build all the heavy elements. And he went to Willy Fowler, and Willy Fowler was a nuclear physicist. And I this this is something that physicists will never admit to you.

And that but they've only ever solved one problem exactly, and that's the two body problem. So they've only solved that problem of an electron going around a proton in a hydrogen atom, the moon going around the Earth. That's the only problem they can solve exactly. Once you get to three bodies or more, it's not possible to solve it exactly. It turns out that a nucleus of of carbon has 12 particles in it, six neutrons and six protons. This finding out anything about it, like its energy energy states was impossible. And this guy from England with round spectacles turned up in Willie Fowler's lab at Caltech, and he said something that no nuclear physicist or claimed something that no nuclear physicist would ever claim. He said it's got an energy state at this particular level because he knew it had to in order for three helium nuclei to come together and make carbon 12.

And, there was a discussion, and, and they realized that they had measured the properties of carbon 12, but if it had they might just have missed something. Three days later, they found the carbon 12. He's the only person to have made a prediction ahead of what you call an anthropic argument. So his only argument was we are here. We are made of carbon. Therefore, this state of carbon must exist. So I will use the problem.

A so called oil oil neuro And which

of these of course, he actually coined the term big bang and never believed in it.

And, he worked very closely with my late great colleagues, Jeff and Margaret Burbage.

Absolutely. He was considered to be a rather difficult character and a bit of a loner, but actually history shows that he had incredibly loyal colleagues that he worked with over long periods of time. You know, Margaret and Geoffrey Burbage and Willie Fowler. And then when we we mentioned earlier that the Nobel Prize Chandra Saikow getting in '83 and so did Willie Fowler. And that was very desperately sad for Fowler and Hoyle because they were such friends. And Fowler knew that Hoyle should have shared the prize with him because it had it not been for that visit to Caltech in 1953, Fowler said I would have been big I would have been a run of the mill nuclear physicist. In fact, he actually worked out the, he'd actually been able to prove the the the what we call the carbon, nitrogen, oxygen cycle, which generates heat in in massive stars. So he had done something.

But the actual discovery of of of where all the, you know, all the elements came from, that was due to Fred Hoyle in 1953. So, you know, that was so sad. Hoyle told me that he was very, very upset for three days. And then, like, Groffelin Bell, he said, well, I know the history books will remember that I did this. But it was it was very, very sad. Because, I mean, there's a man called Jacob Bronowski who did a big TV series in Britain, and he said a genius is someone with two good ideas. Oil had two good ideas. He he he turned out Definitely.

Steady state theory, which was wrong, but it was testable. It was testable. And it was it turned out that the universe was born in the Big Bang, and he was wrong. But it but it made testable predictions. And, of course, he figured out where all the heavy and all all the elements in our body come from. So he he certainly had two good ideas.

Marcus, this has been a delight. I I think of you whenever I think of a very clear, crisp, explications, that turn math and mystery into meaning for telling the human stories. And I think black holes are, in a sense, the universe's refusal to explain itself. You can, as as your late great friend at at Caltech, Richard Feynman said, you can, dance with nature, but she won't let you dip her and lift her veil, something like that. And I wanna just, thank you for the great work that you're doing. And where can people find out more about you?

Thank you very much. I really enjoyed our, conversation. Well, I've got a website called wwwmarcus.marcuschown. So it's marcusch0wn.com, c 0 n. And you can get my book if you want from Barnes and Noble or Amazon or or any of these places, hopefully in bookstores in America. We had a real problem recently. We had a cyber the the publisher had a cyber attack. So Oh, no.

They weren't able to reprint that. I think they reprinted by now.

Maybe it fell into a black hole. You know? The the the cyber attack. Marcus, thank you so much. I'll let you, get back to to your evening, and I just wanna thank you again for this wonderful book, A Crack in Everything, and that's how the light gets in. So now we'll ring the bells that still can ring. Thank you, Mark.

Thank you very much, Brian.