Can you undress a black hole?

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Speaker 1: Hey, Jorgey, do you ever feel guilty when we send a probe to go poking around another planet? Guilty? What do you mean guilty? I think we're just being curious, right, I don't know. It's a bit presumptuous and forward, you know, like what if I sent a drone into your house to take pictures and samples? I see you mean, like for me, we're disregarding the planets privacy. Yeah, like maybe we should give them some morning so at least they can get dressed before we show up with our cameras, or maybe undressed, you know, maybe that's what they prefer. That makes me wonder what an embarrassed alien looks like anyway, and what account is not safe for work? I am R Handy cartoonists and the creator of pH D com Hi. I'm Daniel. I'm a particle physicist and I always get dressed for work. Oh nice, that's a good disclaimer to make in public. Even these days when everything is remote, you still got to put your pants on when you get started on your day, you know what I mean? Known as the naked physicists, I definitely do not want to be known for that. Absolutely not naked and Curious could be the name of the reality show Daniel Naked Curiosity. There you go, but welcome to our podcast. Daniel and Jorge explain the Universe Wearing Clothes, a production of I Heart Radio, in which we try to strip the mystery for everything in the universe. We try to find everything that makes you curious and peel back the layers, undressing the confusion and addressing your questions and trying to make sure that everything in the universe makes sense to you and give you the bare facts about the cosmos and everything in it, all the amazing things and all of the mysterious things, and also the things that we don't know if they exist. That's right, because we have two ways to get surprised in our universe. One is to go out there and see weird stuff that just doesn't make any sense to us until we can wrap our minds around it. And the other is to think of weird stuff, what if this kind of thing exists? What if that kind of thing exists? Is this even possible? And then to go out and look for it. Yeah, because a lot of times it seems like the math tells us what can exist, and oftentimes we actually go out there and find it. That's right. There's lots of times when we make a mathematical theory that describes something we see in the universe, and then we explore the corners of it. We say, well, if these rules are real, what else do they predict? What else should we be looking for? And you know, some people think that the universe is mathematical, that these rules are the ones that control the universe, and so if they have a wrinkle in them that predicts something weird, that might actually be real. So if you are not into math, we have news for you. You might be in math. As you might be math, math might be you. Yeah. And and I think a big example of that idea of thinking of something first and then discovering is black holes. Right. Black holes were first theorized by Einstein, and then people wondered about it for a long time, and then we started finding evidence for them, and then we actually just recently took a picture of a black hole. Yeah, And more than just wondered about them, people disregarded them for a long time. People figured like, well, that can't be real. That's evidence that there's something wrong with our theory. For our theory predicts something as absurd and as crazy as a black hole has got to be something wrong with it, But then of course they found it, and so the theory is not wrong, and that teaches you to follow the math. And this happens all the time, even in quantum mechanics, where we say, look, quantum mechanics predicts this totally absurd thing that could never really be real, and then you go out and you do the experiment and boom, it actually israel and the universe is as weird and as mathematical as we thought. Does that mean humans are not as weird as we should be? Do you think, like maybe we just to think weirder. Yeah, I think that's definitely true. I think of all the various layers of reality, the one we live in is the least weird. I mean, we live in this sort of large stuff that's not quantum mechanical and the slow stuff that's not relativistic, and so our corner of the universe is sort of very unweird, and if we were much much smaller or much much faster than physics would be much much weirder. Maybe that's just a perspective kind of thing, though, right, Maybe, like if we were smaller or bigger. We might think that's normal and our size is weird. Yeah, that's a difficult mental inversion, but you're right, it might be weird to think, Oh, my gosh, velocities add linearly in objects have like smooth trajectories. How bizarre is that? It's hard to put yourself in that frame of mind because this is the only one we've ever had. But that's exactly the point that physics tries to take us out of our familiar frame of mind and make us realize that the way we see the universe is limited, and the way the universe really is could be vastly to friends, And that's why we do these sort of mental and physical explorations. And black holes are weird, right, They are one of the weirdest things in the universe, and they are definitely very weird. They are little pockets of mystery, and one of the weirdest things about them is that we cannot see what's in them. We can't go inside a black hole or look inside a black hole, or get any information from what's going on inside the black hole to learn about these crazy corners of the universe. Yeah, because what's weird about them is what's inside the actual black hole? Right? What they call the singularity? That's right. General relativity at least predicts a singularity inside the black hole, although many other theories of physics, likede quantum mechanics objects to the existence of a singularity, and various mathematicians suggest the singularities are impossible in a physical universe. So then the question is what is inside the black hole? Yeah, there's a question of whether singularities can even exist, and unfortunately we can't see the ones inside of a black hole. So the question then is is it possible to see a singularity outside of a black hole or a singularity that's not a black hole? Yeah? Is it possible to uncloak the singularity, to strip away the event horizon so that as an observer you could directly see with your own eyes this bizarre thing, this singularity of space. Such a really fun, fascinating question. So to be on the podcast, we'll be asking the question what is a naked singularity and why doesn't it have any singular clothes? Even just one pair of pants? Right, if it's a singularity, should have one of everything, supposed to physicist who were three pants or four hats? At a time. That's right, And I love this name naked singularity. I mean, of course there's the slight blush factor, but also it invokes this sense that we could like really peel back the layers of the universe and see the truth, the bare naked truth of what's going on with space time. I guess the question is, we don't even know if a singularity is possible in our universe. I mean, it's theorized inside of a black hole, but you can't see inside of the black hole. Yeah, that's right, And so this is an experimental question and a theoretical question. It's an experimental question like could we see a singularity, what would it look like? Can we find one? If they do exist? And a theoretical question like what would it mean if they can exist? What would it actually be like? And then we'll get into this. But like, people don't even agree about what a singularity is, that there's no singular answer or a definition. There's a duopoly of singularities. Man. Well, as usually, we were wondering how many people had heard these two words together, naked and singularity at the same time, And so, as usual, Daniel went out there into the internet to ask people if they knew what a naked singularity was. So thank you to everybody who have volunteered to answer questions without any preparation. And if you would like to similarly give answers to tough physics questions without using any reference materials, please write to us two questions at Daniel and Jorge dot com. So think about it for a second. If someone as you on the street or on the internet what a naked singularity is, what would you answer. Here's what people had to say. I have never heard of naked singularity, but I definitely know what naked means, and I think I know what you mean by singularity, so I would imagine it has something to do with the very earliest of universe stripped of all forces. Singularity basically means when all the matter condenses down to one blob. For example, like all the gravitational force starts to attract all the matter and it just condenses down to one small blob, and that's you know how people say our universe is gonna end naked singularity? Um, I think might be when this blob doesn't feel any force, any other force from outside the singularity, so it might be naked to everything else in the universe. I'm not sure. Well, singularity is an intense amount of matter and energy in one point in space, so a naked singularity would be similarity that we could see like a center of a black hole if you if you took if you could just see into the center. I think it's something linked to a black hole. I think a naked singularity is something like a black hole without a short shirt radios, so a lot of mass on one point and it would not be heavy enough to keep light to itself. But I'm not sure if people agree upon if this can exist. Maybe this is a black hole without an event horizon, or maybe there's a start collapsing directly into a black hole without the supernova. Maybe there's something with other singularities, like technological singularity. All right, a lot of people linked it to black holes, which is what we were just talking about. And a lot of people had heard the to words separately, not together, naked and singularity, but maybe they had not heard of them together naked singularity. Yeah, but I think the name of this thing goes a long way to explaining it, as you can tell by people's answers that pretty quickly put together the idea that maybe a naked singularity is one that you could actually see, the one that isn't dressed by a black hole. All right, we'll step us through this, Daniel, First of all, what is a singularity? Because I think I know what naked means, and if you don't, I'm not going to be the one explaining it to you. I've known since I was born. I think, what's the definition of a singularity? And is there a singular definition of it? Yeah? So this is a fun question because you can have an idea about something before you have like a really precise, theoretical, crisp definition of what it is. And that's sort of the case here with singularity. That's sort of like the vague idea of a singularity, and then there's people trying to actually work out, well, what do we really mean, like mathematically when we talk about a singularity, And unfortunately there's not a whole lot of Chris definitions. It's sort of like two general ideas about what we mean about a singularity when we talk about in the theory, like in math. In the math and also in philosophy. Remember that almost every field of science in the end was born out of philosophy people thinking about tough questions and try to figure out, like how do we make progress on questions of like what is the universe? And eventually things get crisp enough and formed well enough and mathematical enough that like scientists can take over and actually make progress. So some of these things still are on the boundary between physics and philosophy because they're sort of like bubbling emerging questions. And that's the situation here with this question about what is a singularity? Yeah, so what are these two different ideas about what it is? You said, there's two, yeah, And so the first one is probably the one that comes to mind, and most people think about a singularity, and that's where the space sort of breaks down, where something in space becomes unphysical, it becomes like infinite, something that you figure like can't actually really happen. You know. For example, a black hole, we imagine might have a point at the center of it with an enormous amount of mass in a physical dot in a point with no volume, and that would be infinite density, and the curvature of space there is described by general relativity, would be infinite. And so we talk about that as a singularity because general relativity breaks down there where the curvature of space becomes infinite. Yeah. I think it's sort of related to infinity, right, because infinity is pretty much kind of the only thing that can break down math, right, Like we don't really understand it, or it's sort of like not defined in math, right. Yeah. In some cases though, it depends on the application, Like and sometimes when physics gives you an infinity, you say, well, that's wrong, that's nonsense, that can't happen. Although other times in physics you can have infinities, like the universe might be infinite in extent, it might go on forever in every direction, and that doesn't violate any principle of physics. It would mean the universe has an infinite amount of energy in it, right, Or the universe could have existed for an infinite amount of time or could exist for an infinite amount of times into the future. So sometimes infinity is allowed in physics, not a big deal. Other times it doesn't work, and it just depends on the theory. And in the case of a black hole. The reason that we don't like the infinity is that we describe what happens to space and things moving through space based on how space is curved, like how much is space bent by the presence of mass? And you know, for example that like space around the Sun is curved a little bit, which makes it natural for an object like the Earth to move in a circle around the Sun instead of what we would see as a straight line. So you can make predictions about what happens to something that moves through curved space. But you can't do that if the curvature is infinite, Like the equations just don't work. They give you nonsense answers. And so the theory general relativity breaks down when the curvature becomes infinite. So we call that a singularity of space time. Right, it seems like it it comes to singularity when something gets infinite in like a very short amount of space or a short amount of time. Maybe could that be sort of the one way to define it or to understand it. Yeah, And it really can be almost anything that can become infinite. You know, for example, you can have an electron. Electron is a point particle and it has a charge to it, and you can ask, for example, what is the electric field around an electron? Well, it depends on the distance you are from the electron. But if the electron is a point particle, then you can get as close as you want to it right that distance can basically go to zero, which means that the electric field or the force from the particle becomes infinite. And so you can find these singularities not just in sort of crazy exotic situations like the center of a black hole, but also in fairly simple, straightforward situations like an electron with all electrons are singularity. Is that what you're saying, or mathematically, that's what the math would tell you. So real electrons are not singularities, and that's because the simple mathematical description just gave you isn't the right one. What really happens when you get close to an electron is that it creates lots of other particles around its photons, which turned into quantum fluctuating positron electron pairs. We talked about this on another episode. Is called renormalization, where you redefine what it means to be the particle, and the particle becomes not just a point but a bunch of quantum mechanicals froth slashing around that point, and that becomes our definition of the particle, which in effect limits how close you can get to it. So quantum mechanics sort of covers up the singularity there prevents a singularity from happening. But in classical electromagnetism, if you just really did have an electron with a point particle, that would be a singularity. And so that's an example of how we don't think that singularity actually happens in the universe because electrons are not infinitely powerful points of charge. Okay, so that's one definition of a singularity. It's like when something goes infinite in a small amount of space or a short amount of time. So what's the other definition of a singularity. Well, there's this definition in philosophy of a singularity in space, which is a path that is not extendable. Like you can imagine moving through the universe and you can just keep going right in the path you're on, can just keep going, Well, what if you came to a spot where your path just couldn't go anymore? And this, for example, is what happens to a photon that falls into the singularity inside a black hole or right doesn't go anywhere anymore. It's not some other part of space. It goes to. So it's like another way to look at a singularity. It's like a weird deformation and sort of the arrangement of space itself. I mean like a like a stub in space, kind of like an abrupt end to space. That's also called a singularity. Yeah, an abrupt end to space. It's sort of like imagining that space has a boundary, but instead of that boundary being like on the edge of the universe, like we're all in some huge universe that has you know, a crust to it, this is like a boundary that's in a point, like a weird spot in the universe, where like there's a point of space there that's just not there, so you can't like go there. It's a really weird idea. It's sort of hard to get your mind around, but it's in some ways equivalent to the other way of looking at a singularity. You mean like it could exist in space, like a stub inside of space. Yeah, it could exist in space and like like a belly button or so many jokes to make their absolutely, yeah, it could be just like a weird feature of space where a particle that passes into it doesn't emerge and that's another way to think of a singularity. Right, just like belly bus, you know, link goes in. When does it ever come out? Nobody knows. Eventually it makes a black hole unless you're an audy I guess. All right, well, now that's a good definition of singularity. Now let's get into what a naked singularity is and whether or not they're real. But first let's take a quick break. All right, we're talking about naked singularities, Daniel, and this is a safer work, right, we can talk about naked singularities. Nobody's gonna get into trouble. That's right. I had the singularity sign a waiver also, so we're allowed to use the description of it as naked without paying it any royalty. It's comfortable with itself, the singularity. It's not self conscious singularity, alright. So singularity is either like a stubb in space, like a belly button in space, or just anything that kind of goes infinite in a short amount of space or time. That's a singularity. So then what is the naked singularity? Like something that is like that, but it's not close, like it's not covered. Yeah, exactly, it's just that simple. The idea is what a weird thing to have in space? What is this bizarre thing at the center of a black hole? What actually happens there? And it's frustrating because black holes are always cloaked, right, you can't see what's inside a black hole? Is there singularity in there? Is there not? Is there something else we're going on? We want to know? It? Frustrated and have this weirdest part of space be hidden from us by the event horizon. So then the question is it possible to have a singularity that's naked, that's revealed to us, a singularity that you could see from the outside, you know that you could visit and investigate and then report back to other people and maybe get some answers about the nature of the universe and what it can and can't do. Right, Well, the problem with the black hole singularity is that it bends space and time, and so it traps light, so we can't and everything else, and so therefore we can see it or get any information out of it. Right, Yeah, that's exactly right. The thing that creates the singularity is an extraordinary density of mass, and that mass also creates curvature of space around it, which creates an event horizon, right, it means that there's some point after which space has bent so much that every direction forward, every path forward, eventually leads to the center of the black hole. And you know, remember, the event horizon itself is not like a physical objects. It's just like a surface in space where once you pass it, there's just no way to ever avoid hitting the singularity. But it does mean that nothing that passes it can emit light out of it, which means we can get no information about what's going on beyond the event horizon. That's what's so frustrating, because of course all love to study the singularity, to see it, to row it, to shoot particles at it, to hit it with a tennis racket or whatever, but as long as it's behind an event horizon, we can't do that, right, And so a naked singularity then would be a singularity, but one that you can actually like walk up to and get right up next to it and look at it through a magnifying glass and coke at it. Right, Yeah, exactly, that's the idea. So if you have a picture in your mind of sort of like the rubber sheet of space where space gets bent by heavy mass, and the curvature grows very very rapidly as you get close to the black hole and then sort of goes to infinity at the center of the black hole. Then image you should have in your mind for naked singularity is more like just a pin prick, like a point, like space is mostly flat around the singularity, and then there's just this point where the curvature goes to infinity very very quickly, right, like a belly button, Just like a belly button. They should have called this a belly button of the universe. Yeah, bellybutton singularity. And in fact it works on multiple levels because the same way that a belly button tells you about like the origin of a person, it teaches you but like their origin story and how they were created through the placenta. Then a belly button singularity of the universe can tell you something about the origin of the universe because it teaches you about space, time and maybe even helps you understand the Big Bang. Right, And so I think belly button really is a great name for it. I think now you just tress it too far there. That was a little too much. But anyways, it is sort of like something in space. So I guess the question is, can you have a singularity without a black hole? Or maybe you can have other kinds of singularities that you could see, Yeah, exactly, And so that's the idea, and people are embarked on this sort of like theoretical exploration. They're like, can I make one in theory? Can I satisfy Einstein's equations of the universe and have a naked singularity? So it's like a way to explore the universe without ever leaving your living room, just like can I arrange this in reality? And you know, that's how black holes were discovered, basically, as people trying to figure out, like, well, we have these equations for how space and time bend in response to mass, would they allow the creation of this weird object. Let's see if the math says yes. And the math said yes, And so that's where we are with naked singularities, this sort of like exploring how you might be able to make one, to figure out is possible, is it allowed? What would it mean if it is allowed, what would it mean if it isn't allowed? All that sort of stuff, And so there's various ways people have thought of theoretically to try to manufacture a naked singularity in the equation right, Well, is it even possible to have like basically a black hole without the black hole? Can you have a singularity in space time just like a black hole, but not have the black you know, trap around it? Is that possible? The short answer is, we don't know. Some people think it's impossible, absolutely impossible. Some people think it might still be possible. And there's lots of areas of investigation and sort of a few paths people are going down and exploring the idea of a naked singularity, and one is to create a singularity using a black hole and then try to remove the event horizon. What do you mean, how can you remove the event horizon? Yeah, it's people actually writing about this all the time. They ask like, could you destroy a black hole? And we usually we say no, but we actually had a whole episode about how to destroy a black hole. And there is one possible way you could strip away the event horizon, and that's if you make the black hole spin really really fast. Because remember that black holes are not just heavy objects that curve space. The way that space gets curved is actually quite complicated and depends not just on like how much mass is there, but on its arrangement, and also on how fast it's spinning, because angular momentum contains energy, and space bends not just in response to mass, but also in response to energy. And there's one class of black holes. They're called curb black holes k E r R. And these black holes are spinning. Now, if you take that black hole and you convert a lot of its energy into spin, you like, drop something into it which has a lot of angle momentum but not a lot of mass, and you can bring the angular momentum up past a certain level, then the equations predict that the event horizon will shrink until eventually it hits the singularity and reveals the singularity. Wait, what too? More energy makes the black hole smaller? Isn't that weird? Doesn't usually more mass and energy make the black hole bigger? Yeah? Exactly? How to spinning it more? Make it small? What you need to do is somehow get it to convert its existing mass into spin. So it's not just about adding another object which is going to add overall mass. You need to somehow get it to convert its energy into spin. Because the location of this event horizon depends on the spin and on the mass, so you have to somehow do something, and nobody knows how to do this, which is like totally speculating. Somehow get this black hole to turn its mass into spin. And if you do that, they think the singularity will remain at the center, but the event horizon will essentially shrink because you're reducing the effective mass by just turning it into England momentum. Oh wow, but you would have to convert all of its mass into spin, right or just or some of it, just some of it. You need to cross some threshold. But if you read the papers about how to do this, they say, like, physically, we don't think bus is possible. So it's sort of like, well, the equations predict that if you violated this basic principle then the event horizon would disappear. That doesn't mean it's possible. It's just sort of like there's a region of theoretical space there where maybe if you could fix one problem, you might be able to get into this interesting region where the event horizon becomes part of the singularity. Can you maybe make a black hole and make it mostly out of spin, you know, like if you take a whole bunch of I don't know, fidget spinners and frisbees and tops, you know, and threw them out, spun them, throw them all together to make a black hole. Would that make a naked singularity that would still have more mass than angular momentum, and so it would be a spinning black hole and it would have a ring singularity at the heart of it, but it would still have an event horizon. So you need to somehow get a black hole that has like more angular momentum than mass itself, which is pretty hard to arrange and maybe impossible. All right, So that's one possibility, doesn't seem very likely. What are other ways we could maybe make a naked singularity. Another way to maybe make a naked singularity is to find a white hole. We talked about this also once on the podcast. A white hole might be like the opposite of a black hole. A black hole is a region in space where if something falls in, it can't ever leave, and a white hole is a region of space where things can only leave right they can't enter. And so a white hole in general relativity is sort of like the time reversal of a black hole. Like take a black hole as a star collapses and forms an event horizon and things get sucked into it. A white hole is like something that goes the opposite direction, like spews stuff out and then eventually boom, A star appears. Interesting. Now does it have a an event horizon like a black hole or is there such a thing as that the opposite of a event horizon. So it wouldn't have an event horizon. It would just be like a point in space where stuff is coming out of right, Like things are just flying out of this white hole the way like things fall into a black hole, things come out of a white hole. And we sometimes think of a white holes like the other end of a wormhole. You have a black hole connected through space somehow be a wormhole to a white hole and things that fall into the black hole and come out of the white hole. And so the white hole would be like a naked singularity, be at this weird point in space where you know, some of these metrics of spacetime become infinite, but not surrounded by an event horizon. I mean you can see it. Stuff is coming out of it at you. It's emitting light, or old socks or typewriters or whatever is coming out of this white hole. You can see those things, and so you can observe it. And so in that sense, it's a naked singularity because it's a singularity and it's something you can actually look at. Right, it would just look like a really bright pinpoint, right, like a star, but really really small. Yeah, And it might look like a bright pinpoint if it happens to be emitting gamma radiation or whatever, but it might also just look dark at some points if it's not giving off anything. You can't predict what a white hole is going to give out because it depends on what's inside the black hole it's linked to, and that's not something we can know. Okay, so that could also be a naked singularity. Are there any other possibilities can you have? I don't know, like an infinite charge somehow accumulated, or something else that doesn't bend spacetime. Well, really, the only kinds of singularities we can consider our gravitational ones, because everything else, like charge and particles, these are governed by quantum theory, and quantum theory prevents these kind of singularities by having uncertainty and by having fluctuations from random particles. The reason for example, an electron doesn't actually have negative infinite charge is because it creates this swarm of particles that surrounds it. And so quantum mechanics doesn't really allow for singularities in the same way. So they all have to be sort of gravitational or like geometric. Singularities of space time have to be about like the shape and structure of the universe. And so, for example, the Big Bang was a singularity, right, that's a timelike singularity. It is one that existed and no longer exists at the moment in time when the universe had essentially infinite density, and that was definitely naked because if you were around at the Big Bang you could have seen it. Yeah, I suppose. I don't know what it's like to observe if you're inside and infinite singularity of infinite density. I don't even know what that really means. It's like staring at your own belly Patty. It's like being inside an infinite belly button. And remember that general relativity doesn't tell us what happens during a singularity. General relativity tells us that, you know, space get denser and denser and denser, or a curvature gets infinite, but it breaks down at that point. You can't calculate with general relativity and say, what would happen if I did this, or if I had an eight ball flying through space and it hit a singularity, what would happen? It just cannot predict those things because general relativity breaks down when the curvature becomes infinite. So we need some new theory, something else to describe what would actually happen to physics of what would happen in a singularity. Alright, let's talk about whether or not naked singularities are real and if we could see one, what would they even look like? But first let's take another quick break. All right, we're talking about naked singularities being free, being visible, but also being almost infinite at the same time, and it sounds like there are a couple of possibilities. White holes or super spinning black holes are two possibilities. Daniel, you said there's another kind that could be out there, like a boundary point in space. Yeah. These are just points where a path of a particle ends. And this one, to me is like the most fun because I feel like we're sort of trapped in space like we're in this universe, we're in space. We're trying to understand what are the rules of this universe, but we're stuck sort of inside it, and it's hard to get your mind around the universe when you're looking at it from the inside. People are always asking us, like what is space expanding into or with outside of space? Because I think they're trying to grapple with the notion of the whole universe and its rules, and they want to do it by looking at it from the outside. And so if you can find like the edges of the universe, that gives you some sort of sense for like you know what the rules are, what the boundary conditions are. And so this this idea of a singularity is this like point in space. It's like a point that's an edge right where a particle flies in and just doesn't ever go anywhere else. It doesn't leave not there anymore. It's just there is no more space. So to me, this is one of the most fun ideas because it's hardest to think about, but also if you could actually see it, you'd be like, whoa, what is this? There's like a wrinkle in space is like a literal belly button in space? What is going on? Yeah, it'd be like a prinkle, like a pinch in space. Yeah, exactly, like a pinch in space. I would love to see a pinch. But would it become a black hole though, like when things get trapped inside of it? Well, it depends on what made it right, Like, first of all, there's nothing inside it. If we're talking about a boundary point in space, the inside of the singularity is not part of the universe, Like the particle just doesn't exist anymore, Like it's gone from our universe, like it's gone. The path just ends, right, Like you can think about particles as having worldlines, like they move through space and time. The singularity is a point where, like a worldline ends, it doesn't exist anymore. It's not like in there and you can't see it. It's just not anywhere anymore. Like, so what would happen to the particle? It would bounce back, like it would have to back out, or would it really disappear from our universe? It would disappear or from the universe. That's what it means for your world line to end. In that second definition of a singularity as a non extendable path, that's what a singularity is, a point where a particle, if it hits it just doesn't continue anymore in existing, which is really weird and hard to think about. What happens to its energy? It just it's energy disappears from the universe exactly. We talked about in another episode recently about how general relativity doesn't require that energy is conserved. It literally is like falling into a hole. Yeah, but the question is can that thing actually exist? And this is the kind of thing people are trying to figure out, like our naked singularity is real in the sense experimentally, like do they actually exist out there in reality? Could we see them and study them the way we can black holes? Or do they even exist theoretically? Like can you construct the equation in a way that predicts that they do exist? Whether or not they actually do in reality is one question. Whether we can make equations self consistent that describe them mathematically is a second question, Right, Well, it seemed to work for black hole holes, like general relativity predicted black holes and they're sort of consistent and we've seen them, so doesn't that answer the question? Doesn't that mean yes, that we can't theoretically make these, except that we know that general relatively breaks down at the singularity, so we don't actually know if this is singularity there. Like we know the black holes are real, yes, but you don't have to have a singularity inside a black hole to have a black hole, right, We don't know if there's actually a singularity in there or not, or something else weird is going on. We don't have a theory that describes correctly what happens at the center of a black hole. So another theory, some quantum gravity theory like glue quantum gravity might give us a different description of some very dense mass that's bending space in a weird way that's not a singularity. So we know that the Big Bang happened, but we don't really understand what it was. And in the same way, we know that black holes exist, but we don't know what's inside them. So we don't actually have hard proof that there are those gravitational singularities inside a black hole, or we also and that proof that they don't exist, right, because that's right. It could be that quantum physics is wrong in general relativity does maybe work at the center of a black hole. Well, it could be that there's some kind of singularity at the center of a black hole. But we know that general relativity as it stands can't describe them. You know, it just basically gives up. It fails there. And that's why they're so fascinating because we'd love to see general relativity fail because how it failed, what actually happens there could give us a clue about how to fix it. That's why seeing a naked singularity would be so much fun, because it would be clues to like ten Nobel Prizes in an afternoon in a singular place, like an infinite concentration of Nobel prices. Yeah, and one of the ways that people explore this theoretically is they say, well, here's a universe. Can I figure out how to make that universe? So, for example, we just talked about having a hole in space, a place where paths end, and general relativity tells us that any configuration to space that smooth can exist, though it's sometimes tricky to figure out, like how do you arrange the mass to get that bending of space? And so what people are doing now is trying to figure out, like wealthy ioretically, can I construct a universe in which I have a naked singularity. And they're doing all sorts of complex simulations, and they figured out ways to make singularities happen in simulated universes, but not simulated universes like ours. Simulated universes with like five dimensions instead of three dimensions, or different dimensions that like roll up and bend Weirdly, nobody succeeded in making a theoretical naked singularity in a universe that looks like ours. I see, you need more dimensions, You need like some extra juice, Yeah, exactly, because the rules are different in other dimensions. Right, if you have five dimensional space or nineteen dimensional space, and the way space bends and twists and wiggles is totally different than an our universe. And this has led people to wonder, like, if it's so hard to make a naked singularity, maybe they're just impossible. And so there was this idea in nineteen sixty nine by Roger Penrose. Recently when the Nobel Prize for thinking deeply about singularities and black holes. It's called the cosmic censorship conjecture, and it's the idea that the universe will always hide a singularity, so no naked singularities can exist because the universe will always find a way to block you from seeing. There's a certain prudishness to the universe, and that's because you know, anything that is singular would distort spacetime so much that you could never see it. Is that kind of the idea. There isn't really a firm idea. It's just like this idea makes people uncomfortable, so maybe there's something in the universe preventing it from happening. And it's very similar to the idea people had about black holes. Like when people heard about black holes originally they're like, that seems bonkers. I'm sure that that situation will never arise, or something about the universe will prevent it from happening, just the way that like, electrons are not singularities because quantum physics prevents it from happening. There's something inherent. It's not like an accident, and it's not like a conspiracy. There's just something about an electron and quantum physics that prevents that from happening. So the ideas maybe there's something going on, but it's really just a conjecture. It's not like there's a good reason. It's just like, boy, I kind of hope the universe prevents this from happening. That was penn Rose's original idea. Oh I see, it's like he didn't want there to be singularity. Yeah, you felt uncomfortable. He's like, this doesn't seem right, and so there must be some reason why they don't exist. And it sparked a lively debate in the field. Since then, other giants of black Hole thought, Stephen Hawking and Kip Thorne and John Preskill were having like a debate about whether naked singularities could exist, and they decided to make a bet. And so Hawking bet Preskill and Thorn that naked singularities are impossible. But then how would you settle the bet? You would have to see one or not see one, which is you know that could never happen. Yeah. Well, actually I think they were even just wondering, like, theoretically, could you find a solution to the Einstein equations? Could you describe a universe theoretically that had a naked singularity in it and didn't break any other rules? And a few years later some guy in Vancouver came up with like one very specific, crazy universe in which you could get a naked singularity, and so Hawking was forced to concede the bet because of this very specific exception that everybody agreed you could never have in reality, and so he lost the bet. But then they reformulated the bet, you know, removing this loophole. Oh, I see, so you could have a singularity, just maybe not in our universe. Yeah, exactly in our universe. It's maybe impossible. To help, it's maybe impossible. But you know, there's two ways to explore the universe. One is like have an idea theoretically proved that it's possible theoretically, and then go and look for it to see if your idea is correct. And the other is to actually just go out and look for the stuff. Like if we saw a naked singularity, that would sort of settle a question of whether they're possible theoretically, and then the theorists would have some work to do to figure out how to describe it and what does it mean. And so maybe the more interesting thing is, like, let's just go look for one. What would it look like? Right? Yeah, I guess that's the last question I have here is, you know, what would a naked s gularity look like? Would it look naked. Would it look shiny, you know, would it look like a black hole? Would it would it just you know, look like a weird pension space. What should we be looking for? Yeah, well, people don't really have a clear idea. There's lots of different ideas about what a naked singularity would look like, because there are different ideas for what a naked singularity would be. For some people, it would look like nothing. It would just look like a little hole in space, and the only way to see it would be like to observe particles disappearing as they pass into it, as for sort of the boundary condition, and that'd be pretty tough. It would be infinitely small too, write like, you know, it would be maybe hard to see an electron like fly right into it. Yeah, exactly, So that's pretty tough to ever spot. Then there's the other kind of singularity, you know, that one that's like maybe a white hole where things can come out of it. These could produce massive amounts of radiation. As you said earlier, a white hole could be very very bright. They could be glowing. And some people think that this could be the actual explanation for some weird stuff we see in our universe. We see things like gamma ray bursts and fast radio bursts, sources of really intense radiation that currently do not have any explanation in known astrophysics, and so it's always very tempting to say, ah ha, here's this new weird thing I'm thinking about. Maybe it explains this old weird thing we've been seeing. So, you know, it's not a great argument, but the idea is that a naked singularity might be like a very very bright point, you might explain some of the mysterious sources of energy, right that we see in the universe. Yeah, exactly. You know, if we did see one, to be an opportunity to study something new, something we haven't ever seen before, something that follows the rules of the universe, but maybe different rules than we're familiar with, or follows them in a new way that we weren't aware it was possible, And that's a great opportunity to figure out, like, what are the underlying rules? How does this universe actually work? Yeah, it'd be great to see one because it would tell us a lot about general relativity and quantum physics and help us kind of figure out what's going on with the tool yeah, And just like the belly button tells you about where you came from, it could tell us about the origins of the Big Bang. You know, one of the most famous singularities in history, of course, is the Big Bang. We think that the universe probably had this moment of infinite density, but it's not something that we understand even theoretically, like we can't calculate what caused it or calculate what happens during the singularity. So being able to see one and study it would really give us a handle on that, and it might also really help us think about future singularities. Future singularities might exist like the Big Crunch, you know, we could be heading for a new singular right yeah, but not for a while though, right not until after this podcast drops at the very least, so I have time to clean my belly button. Yes, you definitely do. The idea there is that the universe could slow down its acceleration and turn around and collapse back into a tiny point. So there might be a new singularity in our future. And you know, there are other kinds of singularities, you know, Singularities are cases where things go infinite. So another potential future for the universe is something we all the big Rip, where the acceleration of the universe doesn't slow down, but it continues and accelerates and eventually goes to infinity, and that would also be a singularity. Be the other kind of singularity with the universe is torn apart at infinite sping, and then the whole universe would be a singularity. And then the whole universe would be a singularity, just like if we had a big crunch, you would have the whole universe as a singularity. That would be infinite density. The big Rip would be a singularity of infinitely accelerating expansion. Man. That would be like the universe ripping out its clothes and saying I have my naked singularity exactly, And neither is one that we want to experience. But maybe to get a better handle on what that would be like and when it might happen, it would be great to spot the naked singularity floating out there in space so we could study it and get a handle on how this universe works. All right, well, we should all keep an eye out for naked singularity. Let us know if you see a belly button floating in space, shiny one you know, stay away from the dark ones. All right, Well that was pretty you staying. I feel like I learned a lot about nakedness and singular poison space. Yeah, alright, So maybe the next time you look out into space, think about what could be out there hiding, what could maybe be right in front of you. There could be singularities and singular things and events in space right in front of our noses. Thanks for joining us, see you next time. Thanks for listening, and remember that Daniel and Jorge explained. The Universe is a production at I Heart Radio. For more podcast from my Heart Radio, visit the I Heart Radio Apple Apple Podcasts, or wherever you listen to your favorite shows.