Can we put black holes to work for us?

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Speaker 1: Hey, Daniel, when is all this physics research going to pay off? Payoff? What do you mean did you invest in some exo planet startup kind of like with my taxes? Right? Isn't all of physics research funded by the public. I guess that's true. But isn't the sheer pleasure of learning about the universe enough for you? Like you want some cash out? Also, it's not enough for my bank account. That's fresh. But you know, I'd be nice to get at least some nice invengors out of it. You know, I think everyone is still waiting for the teleporting machine, or the backpacks or the warp drive. Well I might be able to offer you a pasta maker. Is it a warp pasta maker? No, but it's a black hole powered spaghettification machine. What what's the plane? Are were going to open an Italian restaurant next to a black hole? Yeah? Exactly, fresh black hole pasta delivered in a thousand years. You're getting not tipped from me if it takes a thousand years to get my dinner darker than a squid. Inc Is it fusion? For see or inguinilla physicists? It must be or zoes because their length contracted or is the little grain ones? Hi am more handmade cartoonists and the creator of PhD comics. Hi, I'm Daniel. I'm a particle physicist and a professor a UC Irvine and I do make homemade pasta. Oh you do? Do you make each noodle individually or do you have one of those machines? I sculpt them by hand. Each one is a work of art. I give them a name. I meant an n F T for each one I see. And then everyone just gets one piece of pasta for dinner, one big pasta, exactly pasta, and they're called one giant too. Do you just set it down in the middle of the dinner table? Sit here? That's right, exactly, Technically it's pasta. No, we use a pasta machine and so we slice it up into spaghetti or linguini or one of the other nies. Yeah, we have one of those in our house and we've used it a few times. But it's a lot of work. It absolutely is a lot of work, but there's also something fun about it. You get your kitchen all flowery and your pants all covering flower At the end, you get something which tastes a little bit better than something you can buy in the store, a little bit better. I guess it might be worth it that. But welcome to our podcast, Daniel and Jorge Explain the Universe, a production of I Heart Radio in which we turn your brain into spaghetti by exploring all of the mysteries of the universe, everything that's out there that makes sense to us, and everything that's out there that doesn't yet make sense. We talk about the tiniest little particles buzzing around in your toenail, all the way up to supermassive black holes anchoring enormous galaxies billions of years away. We don't shy away from the biggest, deepest, darkest, craziest, most bonker's question, because we want to introduce you to the craziness that is this universe. That's right. We take all of that amazing resource that physicists and scientists are doing at the edge of human knowledge. We take that and we boil it for a really long time until it's soft and soggy enough for people to consume. No, we stop at just the right moment so we can serve up the information all dente. We like it a little bit of crunch. Your kids like it with a little bit of crunch. Mine like it's super soggy. Yeah, no, mine like it overcooked. They even call it overcooked. They're like, make sure to make it overcooked. Make sure you overcook it. And then we sprinkle it with a little bit of olive oil, right, and that jokes exactly. Do you like your pasta with bananas? Well, that's how we're serving it today. Oh man, we just invented a new recipe, banana marinara. That's just fun to say a and b intriguingly tasty. Perhaps maybe, I don't know, maybe more controversial than pineapple on pizza is banana on pasta. It's a slippery slope once you start putting fruit into it telling food, especially if the banana peels are all over the floor, then it's definitely a slippery slope. Yeah. So we like to talk about science and all of the amazing things that people are out there discovering and all of the big mysteries, all the things we don't know about the universe, every thing that physicists are in their offices and labs thinking about and pondering about that maybe one day will be something that everybody knows. That's right, and there's a variety of motivations for digging into the mysteries of the universe. Some of us just want to know, are driven by the insatiable curiosity to understand the universe. See it as a giant puzzle, a mystery posed for humanity that we need to unravel, no matter how many millennia takes to gain that understanding of the universe. But others, the more practical minded folks among us, might be interested in figuring out how the universe works to better our lives, to figure out how to put it to work for us, to take advantage of that knowledge to deliver inventions to humanity. Yeah, because that's what the universe is there for. Right, It's there for us. It's the whole reason it's there, is just to make our lives easier and more exciting. I suppose. Maybe, I mean it could be there for the aliens, right, maybe we're just part of the aliens universe. Wait, what we're there for the aliens? Hopefully not for dinner. Maybe maybe we're just here to be a plot twist in some drama that's been going on for thousands of years over on Proximus Centauri. You know, well, I see, we're just like an adjacent to an event or Avengers movie or something exactly. You thought you were going to be part of the main cast. It turns out you only got a few lines. You won't get your own Marvel movie for another trillion years. Perhaps they'll eventually make a Marvel movie out of every single person in the Marvel University plant. It will be the ultimate crossover, you know, it will just be called not the Marvel Universe, just the universe. Well, regardless of why the universe exists, of question we may never know the answer to. It is interesting to think about how we can put the universe to work for us, because sometimes the knowledge of physics extracts does have practical value. Yeah, I mean, we have nuclear fission right, powering most of Europe, I think, and a lot of the United States and around the world. That was all physics, right, That was all physics, the good and the bad. We also have nuclear weapons into that civilian populations and used for political ends. But you know, there's two sides to every corn. Yeah, that's right, it's all your fault. But even our everyday sort of inventions that we use every day in our cell phones, have you know physics stuff in it that we learned, maybe not the cutting edge stuff now, but stuff that was cutting edge a long time ago. You know, all those tiny little circuits and how they work down at the atomic level. We needed to understand how to make those things. That's right. Essentially, the nature of your life today, the way you live your day is the way it is because we understood quantum mechanics that lead to revolutions in computing and therefore electronics and your life. And so it's true that basic research, digging into the nature of space and time and forces eventually gives us the power to change our lives. You know, it's a song I've lung many times on this podcast. I don't understand why politicians don't just invest more in basic research, because it pays itself back a hundredfold. Every dollar you spend today gives your children and your grandchildren improved quality of life. I don't get it. Why do we don't invest in that more? Actually, that's kind of an interesting philosophical question, like do you think we could have invented the cell phone without knowing physics? Right? Like could we just have been tinkered and then done engineering just to get it to work and eventually gone on the cell phone without understanding quantum mechanics or fusion. Absolutely, I think, as from a philosophical point of view, it is possible to make technological advancements without understanding what you're doing. We have sort of like the invention of modern science, at least in the Western world, only like five years ago. This question is like trying to develop models that explain what we're seeing. But we definitely had technological advancement well before then. People have been forging very impressive like samurai swords for thousands of years without understanding, like what's going on with the metallurgy they were doing. Why are you dipping the sword in water now? And then you dip it in this other thing and you wait this number of seconds. You can sort of random walk your way into technology without understanding what's going on. Could you get all the way to the cell phone? You know, you give yourself off another thousand years or million years? Yeah? Maybe? Wait, so are you saying that we don't need physics, then I think that's what you just concluded. I think technically you don't need physics, but definitely it helps. It's super charges your technological advancements because you understand what's going on, then you can come up with new ideas for how to use them. You're like the little sprinkle of parsley at the top of the pasta. Is that what physics has been reduced to in this episode? I'd say you're the reason you're getting your pasta in five minutes instead of in a million years. Oh, I see, I see, I see. That's you're the reason it's not stale and stiff. Right up, we're getting hot, fresh pasta because of physicists. That's right. I'll take credit for that hot fresh cell phones slurp it up. Would you like a little parsley on your cell phone? Having some bananas? Well, at least you can look at pictures of bananas and parsley in your cell phone now instead of in a thousand years, So that that's something. So that's something. Yeah, exactly, I'll put that on my CV. You can swipe left on a banana and do all kinds of things with it. But yeah, it is a pretty amazing universe, and sometimes we wonder if we can put more of it to work for us, especially the things out there that are amazing and seemingly super amazingly incredibly powerful exactly because we are struggling constantly as a species to extract enough energy for our survival. At the same time, we are surrounded by intensely powerful astrophysical objects. The Son, of course is a great example. We capture a tiny little bit of its energy, and they're even more powerful, incredibly vast things out there that are like huge engines pumping out energy. Could we take advantage of some of these incredible astrophysical machines to gather some energy we need, you know, to charge our cell phones. So today on the podcast, we'll be asking the question can we put black holes to work for us? WHOA Daniel? I feel like this is going to that idea of putting an Italian restaurant next to a black hole and maybe having a black hole watched the dishes for us. Is that what you mean? Yeah, I'm just wondering when the black holes are going to unionize, you know, when they're gonna rise up against us, their oppressors, and be like, hey, these conditions are terrible and stuck out here in the middle of nowhere and we're just eating gas and dust all day interesting, and then they're going to change their name to red holes. You know, solidarity of communism. That's right, black holes of the universe unite. You have nothing to lose but your event horizons. That is their ultimate plan, isn't it all black holes? They just want to unite and get basically create one giant union or one giant black hole, one socialist black hole exactly. That's the future of the universe. This is a question by tapping into the power of these crazy objects, I mean the amount of light radiated from black holes, amount of gravitational energy stored in black holes, we are like sitting on the edge of an incredible river of energy and we're just really bad at tapping into it. We're like burning coal that we dig up from underground to get tiny little slipper of energy out. It's ridiculous. Yeah, there's a lot of amazing things happening in the universe, but you know, I would think that black holes would be sort of like the last place you go to to get energy or to get anything useful out of it, because you know, they're kind of in the name their their holes. It's like, why would you go to a hole to get something out of it? Maybe we could throw a trash into the black hole, so we wouldn't have to think about it. But it's kind of weird, right, because black holes suck everything in and once he gets sucked in, you can't get out, So it's kind of weird to think that you could use them for anything useful. That's true, but they are also really vast stores of energy. I mean, the reason that they are black holes is because they have so much mass in them, and that mass reflects internal store and energy. So you can think of a black hole like a giant cosmic battery. So much energy has been poured into it. It's just sitting there, compressed and dense and bubbling up. So it's tempting to think, like, can we tap into that a tiny little bit? But it's weird because we know nothing can ever get out of a black hole. That's true, we can to take anything out of a black hole. But remember the black holes have influence far beyond their event horizon. If you're anywhere near a black hole, they will tug on you the same way the sun does. And so the mass of the black hole, even though it's contained within the event horizon, can influence things outside the event horizon, and you can use that gravity to maybe charge your cell phone. I see, you just want to mooch off of their influence, all of their hard earn, you know, connections and information. That's right. You go to the black holes Instagram page and you leave a comment and maybe you'll get it to followers. That's the plant. See there you go first to pose. But yeah, and and this has something to do with and the concept called the ergosphere, which is a sort of a weird, weird thing, right. Yeah, people are used to thinking about black holes is just having an event horizon, but black holes turn out to be much more complicated than that. They have various regions within and outside of the event horizon that might let you tap into it to use its energy. And so that's the central part of this concept. And then to buy Roger Penrose to tap into the energy of a black hole through its ergosphere. Right, So that's kind of a strange word. So as usual, we were wondering how many people out there had heard of this concept of the ergosphere or know that it's related to black holes. So Daniel went out there into the Internet to ask people the question, what do you think is an ergo sphere? And things very much to our volunteers. If you'd like to participate, please just email me. It's very easy. You can record your answers at home, in the leisure of your bathrobe or whatever you like. Please just email us two questions at Daniel and Jorge dot com. Right, but you don't have to wear a bathrobe to answer it to you? Or is that a weird little request just from you. You don't have to wear anything. You don't have to tell me what you're wearing. It's totally up to you. No dress code for these questions. Well, I feel like the more we talk about this, the creepier it gets. Anyways, here's what people have to say. People have some pretty interesting answers ergo the following. Well, that makes me think of two things. The exosphere, which is the sort of of um for this limitations I think of our planet, right, the exosphere is like the furthest layer out maybe before the magnetosphere you think of like atmo tripo sphere. So maybe ergosphere has something to do with that layering system of of different tiered spheres around the Earth. But it also makes me think of ergonomics, So maybe it has something to do with the most ergonomic the most efficient way to have a spear or um some sort of three dimensional object. I happen to know that ergo means work and sphere is a round object. If I had to guess, I would say it's some kind of moving or working around object, or surrounds something that's round that's moving. That's the best guess I got through. Sphere obviously makes me think of the term atmosphere, but it's nothing I ever heard in relation to Earth, So I would think maybe it has to do with the atmosphere of other planets, maybe even the atmosphere around stars. Well, it sounds like ergonomics, but I'm guessing it doesn't have anything to do with that, so maybe some sort of atmosphere. All right. People had some pretty good answers here. I mean people sort of related it to ergonomics, which is maybe sort of related, right because someone as someone pointed out the word ergo means work. Yeah. I like that when people have no idea what I'm talking about, they try to break down the linguistics and understand the origins of the word, because that assumes that somebody out there in the astronomy community has made a sensible choice of names. For this thing. Ha ha ha the fools, little did they know? You just picked names out of a hat. That's right. It is a bit of a leap of faith. So I appreciate that. Thank you. That's a vote of confidence right there for astronomical naming. But sort of is that true? Does ergo really mean work? Like that's where ergonomics come from. I just kind of got my mind blown a little bit. Yeah, ergonomics is like, how do you say comfortably while you do work? I see, it's not the economics of work, and there's the anomics of the ergo. But yeah, so it has something to do with black holes and also work, which is kind of what we're talking about, right, getting black holes to work for us exactly. The ergo sphere plays an important role in trying to extract work from a black hole, to get it to give you energy, and also to do it in a comfortable posture so that it doesn't get lower back paint. All right, well, Daniel, maybe let's start at the beginning here and maybe step us through what exactly is a black hole for those of us who had not heard about it before or heard our podcast. So black hole is the most dramatic feature of Einstein's general relativity, this concept that gravity is not just a force. It's not just the way two things tug at each other. But it's not really a force. It just comes out of the act that space itself is curved. So when you have a really massive object, it curves space time, meaning that it changes the relationship between points and makes some of them closer and some of them further, so that light, for example, appears to travel in a curve. It's very naturally moving through curved space. So matter bends space. It tells space how to curve, and then space tells matter how to move. And if you have enough matter somewhere, if you have enough density of stuff in a small enough area, then you curve space so much that it's distorted that every path now leads towards the center. And that's what a black hole is. It's a region of space where every path now leads towards the center of the black hole, making it impossible to exit. Some people think it's because gravity is so strong. It's like tugging on those photons and making it impossible for them to leave. That sort of a Newtonian view of a black hole A better way to think about it is that space is so distorted that every future you have ends in the singularity. Every path you could take always ends at the center of the black hole if you're inside the event horizon, right, because like even the Earth does that, right, Like the Earth technically sort of bend space time around it so that it to us, you know, it's kind of down is the only way to go, right, I mean the gravity we feel now sitting here, Like the reason I'm sitting in my ergonomic chair is that space time around me is bent in such a way that it makes my body go towards the center of the Earth. Yeah, precisely, every mass been space, not just black holes, not just the Sun, not just the Earth, but you and the banana you ate this morning also bend space. It's just that the amount of bending depends on the amount of mass, and so the more mass you have in a small amount of space, the more bending you get. Right. And so a black hole is is sort of like the Earth, but just super duper dense, right, like a lot more dancer and a lot more massive. Yeah, And you can make a black hole out of almost any mass. If you took the Earth for example, and compactified it down to the size of peanut. All that same matter, everything that's in and on the Earth, squeeze down to less than a centimeter, you would get a black hole, and it would have the same gravitational strength as the Earth does now, but you could get much closer to most of that mass. So if you got really close to that peanut, it would have a very very strong pull on you. Right. In fact, it's kind of mind blowing to think about it. Like if you took the Earth and you like only left like a mile of Earth at the surface, right, Like if you if you hallowed it out kind of like an eggshell, he took everything that was in the middle the yolk, and you squeeze it down to the size of a peanut. Then like we wouldn't tell the difference, right, Like life would just go on exactly the same way, you know, like the center of the return to a black hole, and we wouldn't maybe feel it, well, you wouldn't feel it gravitationally, that's for sure. You would have the same gravitational force on yourself, that's true. Of course, it would change, you know, tectonics and lava flow and all sorts of other stuff. And I don't think that a shell of the Earth that's a mile thick could hold itself up. But from a gravitational point of you absolutely you'd feel the same force. Because for gravity, you can always replace an object with a point particle at its center of mass with that same mass, and you'll feel the same gravity. You're not sensitive to the details of how the object is put together, right, And in fact, it would still kind of keep on spinning, right because black holes can spin, That's right. Black holes can spin. And if you make a black hole out of something that is spinning, then that black hole has to spin because spin is something that's conserved in this universe. Something that's spinning can't stop spinning unless you have some external torque on it. So in an isolated system like a star out in space, if it's spinning and then collapses into a black hole, that black hole has to have the same amount of spin as the original star. And one thing that's interesting about black holes is that you know, like if you made a black hole out of the Earth, you sort of know what was inside of that black hole, right, it would be the Earth just really squished together, but maybe not right, like maybe when things get squished down that much, things maybe change, and we have no idea what's going on when you squeeze it that small. We definitely have no idea what's going on inside the black hole. Like general relativity tells us, you don't have matter in the same way that we do. That it's all squeezed down into a singularity, a point of zero volume but non zero mass, and that's the sort of classical picture. That's what Einstein's prediction tells us. But we also know that that's wrong. That can't possibly be what's actually inside a black hole for a couple of reasons. One is that there's an infinity, there's an infinite density, so it's not as much a prediction of general relativity as a breakdown of general relativity is, like this is where general relativity doesn't work anymore. And the other is that we know it violates quantum mechanics. You can't have a point of zero size and know exactly where it is and have it have a zero velocity. It's just too much information. That amount of information doesn't exist in the universe. So we don't know what's going on with the matter that's inside a black hole. But we know it's definitely not a singularity. It's probably some other crazy froth and quantum stuff. And the closest analog we have our new tron stars, which are very very dense remnants from stars that are not dense enough to become a black hole. But close and inside the heart of a neutron star there are crazy things going on with very high temperatures and pressures and weird forms of matter that we've never seen before, all new kinds of pasta inside maybe turns into cuscous right, like a little tiny ball, a fuzzy infinite singularity cosmic cuscoose. That sounds like a nice name for a dish. All right, Well, black holes also have something pretty interesting called an ergosphere that may be able to do work for us and solve all of our energy needs. So let's get into what an ergosphere is. But first let's take a quick break. Alright, we're talking about black holes and their ergosphere. That's apparently a feature of black holes that we may be able to tap into for energy. I guess data would be to go to a black hole, Daniel and set up like an ergosphere energy sucking station. Next event, Yeah, precisely, and ergospheres are really cool because they're a feature of a more complicated black hole. Like typical black hole you imagine is what you just described. Take the Earth, compactify it down to a peanut, you get a black hole. But most actual black holes out there in the universe have more than just mass. They also have spin, like we talked about, and the reason is that basically everything out there in the universe that could make a black hole is spinning. It's very rare to find something out there in the universe that's not spinning in some way. The Sun is spinning, the Earth is spinning, or Solar system spinning, the galaxy is spinning. Everything is spinning. So if you're gonna make a black hole, then it's gonna end up spinning and spinning. Black Holes are more complicated than your normal, like vanilla short sized black hole, and they have more than just an event horizon. They have several regions both within and outside the event horizon, with really fascinating different effects on the spacetime. WHOA, and I guess you know, it's kind of weird to think of a whole spinning, right like a hole is the lack of something, you know, It's like if I dig a hole on the ground, that hole is not. It's weird to think that the whole will spin. It is weird to think about that, And there's sort of two things to grapple with their one is what's spinning on the inside of the hole, and the other is what's spinning on the outside. On the inside, it's hard to think about things spinning because we imagine a singularity at the heart of the black hole, at least in classical general relativity, and a singularity has no size as zero volume. So it's sort of like when we talk about a quantum particle, an electron that has spin, but we don't say it physically spin. This can't spin because there's no extent to it. It doesn't change by spinning. So black holes that spin don't have singularities in them. They have something else. They have a ring inside. It's like a ring ularity instead of a singularity. That's a nice pun, but I guess maybe one way to picture it is that if you like imagine a black hole forming, right, it's not every the stuff that makes that goes into the black hole is not going to go straight in and compact itself. It's usually like stuff that's swirling and because of gravity, it's swirling towards the middle, and then at some point it gets squished so much that it enters the event horizon. But maybe like the ideas that maybe as it goes in it preserves some of that spin, so that maybe inside of the black hole things are still spinning like the center. Maybe we don't know what's going on, but the stuff right outside the center up until the event horizon, maybe that stuff is still going around in circles. Definitely it is, and we see that right, that's what the accretion disk is. It's stuff that has so much spin that it hasn't yet fallen into the black hole. Like you might wonder, how does anything avoid falling into a black hole or the same way that the Earth avoids falling into the Sun, because we are spinning around that we have orbital velocity, and we can't just like lose that. It can't just go away. The Earth can't just stop spinning around the Sun and fall into the Sun. In the same way the stuff that on deck to go into the black hole but is spinning around it. You can't just like give up that spin and fall in the way things fall into the black holes, that they bump into each other and that slows them down or knocks one of them into the black hole and knocks one of them out. So you're write things that are about to go into a black hole mostly spin around it and then fall in. And if you think about it, if you're just like a random particle headed towards a black hole, unless you're headed exactly at the center of it, then you have some spin relative to the center of the black hole. Imagine just a spinning disk. For example, if you're a particle and you hit a spinning disk, unless you hit it at the very center, then you're gonna make that disc spin faster or slower. Right, But I guess I mean like, as I have this sort of spin relative to the black hole, and then as I enter the event horizon and before I fall to the very core of the black hole, maybe I'm still going around in circles or in a spiral. You are, yeah, and you still have that spin exactly. And so things are spinning on the outside of the black hole, and things are spinning on the inside of the black hole, and that's just because of conservation of angular momentum, right, It can't go away, and so if the black hole sort of isolated in space, then the stuff that started forming the black hole has to keep spinning. And what's fascinating is that, you know, maybe the insingularity, it's like a circle of zero volume that's spinning, so you can have angular momentum. But even more interesting is what's going on outside the event horizon, because outside the event horizon of a spinning black hole is not like a hole that you just sort of like slide into. It's more like a whirlpool, which I think you were like describing as you fall in, your spinning around it, and it's so strong that it's spinning space itself. It's like dragging space around with it as it spins. Well, what do you mean, like it's swirling spacetime itself. Yeah, I remember we had an episode about frame dragging. This incredible experiment, gravity Probe B that has the smoothest balls known demand spinning in these gyroscopes out in a satellite in space, and these gyroscopes can detect how the Earth spinning is dragging space with it, which makes those gyroscopes twist a tiny bit. So this has the effect of spinning things, not just pulling on them. So, because the Earth is spinning, it doesn't just tug on satellites out in space. It also gently spins them a little bit. And that's because it's dragging space with it. Sort of like imagine putting a fork into a big sheet of pasta and spinning it. The whole sheet of pasta then gets like twirled up around the fork. Whoa, And that's just sort of a consequence of the speed limit of the universe. Kind of like, why does that dragging occur? Why do things get spun around if they're not touching actually the center. It's just an extension of the question, you know, why does space get bent around masses? We don't know. It's just something we've observed. And the effect of space getting bent is the force of gravity. Now, the effect of space dragging around a spinning object is that it causes a spin on things. Remember, the curvature of space creates this fictitious force of gravity. Gravity is not just like pulling you towards the densest spot. It's also spinning you a little bit. So you're saying kind of like the Earth spinning right now is imparting a little bit of spin on the Moon for example. Yes, and it's a very very subtle effect compared to its tug, which is why it took a very sensitive experiment. We have a whole episode on gravity probe B and what is frame dragging people should dig into if they're interested in that. The effect of space being spun around on the outside past the event horizon of a spinning black hole creates this new region we call the ergosphere. Well wait, let me go back a little bit, Like in the example of the Earth and the Moon, like the Earth spinning is imparting some spin on the Moon, but in the sense that like it's making the Moon spin faster in place, or it's making it spin faster sort of around the Earth spin faster in place. Like if you put an object in orbit around the Earth that wasn't spinning the Earth but very gently started to spin around its own axis. Interesting, and that is that because of sort of like the difference in the distance from the end of the Moon that's furtherest from the Earth, and the difference to that from the point that's closer to the Earth. You know, do you know what I mean? Like, could that be a way to explain why the spinning happens. Yeah, Like, imagine what would happen if you put a ball into a whirlpool. It wouldn't just fall in towards the center. It would start to spin because the current on the inner side of it wouldn't be the same strength as the current on the outer side of it is. That would be an effective rotation on the Earth. I see, like the side of the Moon closer to the Earth is getting maybe pushed along a little bit faster, which is than making the Moon's kind of spin in place. Yeah, it's sort of like tidal forces where the Earth is pulling harder on the near side of the Moon, for example, than the far side because the difference in their distance from the center of the Earth, and that effectively elongates the Moon. In this case, it's the swirling of space time, which is faster closer to the spinning object. The Earth with a black hole, just like the near side of the Moon is being dragged faster than the far side, so it effectively spins the Moon as well as carrying it along in this swirling space time. Alright, So then you're saying that this is kind of what happens outside of a black hole, Like if I'm outside of a black hole, I'm gonna get spun in place because the part of me that's closer to the black hole sort of wants to spin faster around the black hole than the part of me that's furthest away from the black hole. And so now imagine a photon moving around a black hole. We're still outside the event horizon, right, All the same rules apply to a spinning black hole that you can't escape the event horizon. But now this is funny region outside the event horizon. Think about a photon moving around a black hole. A photon moving around a black hole is now moving through space itself that's being dragged. And so there's this region outside the event horizon where a photon moving as fast as it can at the speed of light through that space would appear to be stationary to you. It's sort of like swimming upstream. So say you're, for example, far away from the black hole, and you're watching this spinning black hole, and you see a photon enter this region outside the event horizon and move against the current of the black holes. The black hole spinning one way and the photons going in the other direction. It's sort of like swimming upstream, so like somebody in a whirlpool trying to escape. So you're saying, like the black hole is dragging space around sort of like you said, like the four you know, trailing on a Plato spaghetti, and so the spaghetti is all wanting to sort of troll in one direction. You're saying, what if I shoot a photon that's going in the opposite direction, You're saying, it's gonna seem like it's not moving exactly the same way. A photon inside the event horizon trying to escape the black hole in your sort of normal vanilla black hole would appear to stop right because it can't escape the event horizon. For an outside observer, that photon can appear to have zero velocity as it tries to climb out of the gravitational well of the black holes event horizon, but of course it can't make it out. The analogous behavior for a spinning black hole and a photon and its ergosphere is that the photon is trying to go around the black hole, moving opposite the direction of spin, but unable to overcome the swirling of space itself because it's limited to moving through space at the speed of light. It's like somebody trying to swim against a whirlpool and getting swept up along with it. Now, inside the ergosphere, it gets overcome by the swirling of space, so it actually moves backwards, the opposite direction you would expect. The edge of the ergosphere is defined as the points where the photon appears to be motionless, where its speed is exactly counteracted by the swirling of space, and outside the ergosphere further from the black hole. Of course, photon is going to overcome this swirling of space because it's not as strong whoa I see. So, because you know, the event horizon is where you might in a stationary black hole, that's where a photon that's trying to leave the black hole would seem like it's stuck in space right, not moving right. But you're saying that for a spinning black holes. Because of this dragging effect, there's some weird stuff that happens outside of the event horizon where you can actually maybe see a photon kind of stop in space that's right inside the ergosphere, which is this region outside the event horizon. In order to be like stationary relative to the black hole, you would have to be moving faster than light, and so at the ergosphere. Then what defines the edge of the ergosphere is where a photon which is moving at light speed can be stationary relative to the black hole, and so outside the ergosphere, of course, you can be stationary relative to the black hole without going faster than the speed of light. Inside the ergosphere, because the space is being spun so fast. To be stationary with respect to the black hole, you would have to go faster than the speed of light, which is impossible. So everything, even photons, are like pushed along in this whirlpool outside the event horizon, inside the ergosphere, I thought that was kind of like impossible to see a photon like stop. There's a really subtle and fascinating point here that we're going to dig into in a future episode. It's true that photons are always observed to be going at the speed of light. That's like a well known result of special relativity, But there are some qualifiers to that that are not usually explained. Those qualifiers are that the photon has to be near you is to be a local photon, and it has to be in flat space space without any curvature, So local observers people always see nearby photons moving at the speed of light, but things that are far away from you. General relativity says that if space is curved, you could see photons going at faster than the speed of light, or less than the speed of light, or even stopping, because in general relativity, it's very hard to even define what you mean by the velocity of objects that are far away from you in curved space, Like you wouldn't actually maybe see this photon stopping because you know, there's all kind of weird stuff going on, all sorts of weird stuff going on, and what you mean by velocity in that case is not even well defined. But we'll dig into that in an upcoming episode, right. Not to mention also the question of how do you even see a photon? Right, Like, the only way to see a photon is if it hits your eyeball, Like if it's if a photon it stuck outside of a black hole, how do you even see it? You can't see it, right, You can't even bounce a photon office, right. If you can't get to it, then you can't interact with it, and you can't observe it all. Right, So then an ergosphere is sort of the region of space around a black hole, of a spinning black hole, where space is being dragged so much it's like it can overpower a photon. Yeah. And there's one more really cool wrinkle about this, which is the shape of the ergosphere. You might think it would be a sphere, right, Well, wrong, It's more like a taurus or a donut. It's not spherically symmetric because there's a spin axis and the effect is due to spin, So the ergosphere is like a doughnut around that spin axis. There's actually no ergosphere past the event horizon along the north south spin axis because there's no spin in that direction. But on the plane where it's spinning perpendicular to the north south axis, the ergosphere can extend out like fifty percent further than the event horizon, depending of course, on how fast the black hole the spinning, And so there's no ergosphere sort of like on the north pole. In the south pole, it's sort of like a big fat blob around the event horizon along the equator. Oh, I see, But what is it a donut like a taurus or is it more like a you know, one of those jelly filled donuts, which is like just a flat block. It should have been called the ergo jelly filled donut. You're exactly right, no, but but seriously, like, what's the shape. Is it shaped like like a doughnut with a hole in the middle, or is it shape more like a blobby piece of bread. It's a blobby pizza dough that's spinning, right, and so it doesn't actually have a hole in the middle. At the very core. It's minimum size is the event horizon itself, and then it grows out to me to have a larger radius at the equator. So it's like a spinning piece of pizza dough. I feel like there's a mathematical name for that kind of shape, but we just don't can't come up with it right now. It's not jelly filled donut, is it. It's the jelly donut. It's it's totally the jelly filled donut. I hear geometrists talk about that all the time. All right, Well, apparently you can use this ergosphere, this jelly filled doughnut area around a spinning black hole to get some work out of the black hole. So let's get into how to do that. But first let's take a quick break, all right, Daniel, how do you put a giant jelly filled donut that bend space and time to work for you, instead of just adding some weight around your middle part. The idea invented by Roger Penrose is to throw something into the black hole's ergosphere and have a gravitationally slink shot out because of the swirling of space time, and have it come out with more speed more energy than it had going in. That you have, for example, a rock or a spaceship or something, and you let it come close to the black hole. You do not go inside the event horizon, or of course it's lost forever. You just go into the whirlpool near it, inside the ergosphere. And what happens there is your into this whirlpool, you pick up a bunch of energy because the black hole is pulling on you, so it's speeding you up. So now you have this energy. But of course you want to get out right. You don't want to just spend the rest of your life swirling around a black hole eventually to fall in. So what you have to do is somehow escape the vicinity of this black hole. But now you've picked up all of this energy which is pulling you in towards the center. So what you have to do is sacrifice something. You like chop off a piece of your block, or you use some fuel or something. You throw something into the event horizon. You sacrifice some part of your ship into the event horizon, which gives you momentum the other direction kicks you out and in the end you come out with more energy than you came in with. Wait what Okay, So I guess the idea is to throw something at a black hole but not and have it sort of like do a swing by of the black hole without going into the event horizon, because if it goes into the event horizon, then your toast. But you just go right outside of it and somehow you're able to escape that when of something escape anyways, like you know, we're swinging around the sun. You can swing a satellite towards the Sun, but it'll just come out the other way. Yeah, it's possible to whip around the Sun and come out the other side. It's harder to do that with a black hole because the angles of escape start to shrink down as you get close to the black hole, until you have to be going straight away perpendicular from the black hole in order to escape. We do something similar all the time. Change the direction of your space probe and give it a little bit of a speed boost. You can swing it around Jupiter, right, It doesn't have to fall into Jupiter. You can just go around Jupiter and it can pick up some energy. And we talked about that once on a previous episode. And what that does is steal a little bit of the energy from Jupiter and it gives it to the probe. This is an analogy to that, but it's more powerful because the ergosphere has a lot of energy in it, So it's like a supercharged version of this gravitational slingshot. I see. So then the idea is that I sling shot something into a black hole and somehow, actusly it comes out with more energy than it had when it went in. Yeah, and it's not a miracle, you know, it's physics. The reason it has more energy than when it came in is that it's stealing some of that energy from the black hole. The black hole is using its gravity, it's using the spinning mass to spin space time and you're getting carried along with it. So it's gusting up your kinetic energy. It's giving you more velocity. I see. So The idea would be, like I throw a rock at the black hole, it goes through the ergosphere, it picks up some spin like it's been some space, and then it shoots out the other end, or maybe it comes back around towards me. So now I have the same rock that I threw in, but now it's spinning, which has some extra energy to it. Not quite. You throw a rock near a black hole into the ergosphere, it wouldn't necessarily just come out right. So that comes that close to a black hole is very likely eventually going to fall into the black hole. So if you throw it that close to a black hole, it's probably doomed. It's technically possible for it to escape, but it's probably doomed, but it will pick up a bunch more energy before it falls into the black hole because spacetime is dragging it is pulling on it. Now, in order to get it out of the ergosphere, you're gonna have to either burn some fuel on your rocket or split that rock in half so that part of it falls into the center of the black hole and part of it gets a push out of the ergosphere. But you're saying, then what comes back is only half a rock. Yes, you get half a rock back, but it has more energy than the rock you threw in. What do you mean, like it's coming at me faster than the one I like, I drop it in, but it comes at me with a whole bunch of velocity. Yeah, exactly. And so you throw the rock in and you get a smaller rock out, but has overall more kinetic energy than the rock you threw in. Oh, I see. So it's like I'm feeding the black hole and in exchange, I'm getting shot at by little rocks. Yes, but it's not an even exchange, right. The black hole is getting some mass because it gets part of your rock, but it's giving you more energy than you're giving it. So you're extracting energy from the black hole. Wait what so the black hole loses in this little scheme of your The black hole slows down a tiny bit. If you do this, you're essentially stealing some of the energy from the black hole spin, which effectively slows it down a tiny bit, the same way hawking radiation shrinks the size of a black hole by stealing some of its energy, giving a little boost to a particle. This steals some of the energy of the black hole spin and slows down its spin. So does that mean that then you're sort of killing the black hole a little bit. You're slowing down the black hole stealing some of its energy, and so you can steal some like almost thirty percent of the energy of the black hole can be stored in its spin. So yeah, you can steal that much energy from a black hole using this idea. Oh I see, but you wouldn't kill the black hole because the only thing you can steal is a spin of it. You can't steal the actual black hole in the middle. Yeah, but remember that mass is just a reflection of energy that's stored inside, and so the spin of the black hole contributes to its mass. Right, a black hole that's spinning is more massive than a black hole with the same stuff in it that's not spinning because the whole gravitational energy reflects all the internal energy, even spin. So you are stealing some of its mass. You're right, But I guess what I mean is that you can steal energy from it. But at some point the black hole is gonna stop spinning. It's going to be game over for your little energy sucker. That's right, you'll suck all the rotational energy out of this giant cosmic battery, and then all you'll be left with is a short child black hole. You'll shrink the ergosphere gradually down to the event horizon, and it will disappear because short child black holes, normal ones that don't spin, don't have an ergosphere. Right, But it will be a bigger black hole, short child black hole, because you fed it all these little rocks. That's true, but you've stolen more energy than you've given so net it'll lose energy and therefore lose mass, but you lose a bunch of rocks of rock exactly. And you might remember this actually is a plot point in my favorite movie Interstellar. There's some moment when they realize they don't have enough fuel to get where they're going, and so they do a black hole gravitational slingshot where they dive into the ergosphere and take advantage of the penrose process. Wow, and then what did they sacrifice? They burned a bunch of fuel, right, And it's effectively the same thing. If you use fuel, you're giving yourself a momentum kick, and you're kicking something else out the other end. Interesting, all right, So then we could potentially get energy from this ergosphere, but you got to shoot a lot of rocks. Is there more sort of like practical scenario or some sort of like device that would do this automatically. You could do this also with photons, right, You can drop photons into the ergosphere and they would come out with more energy than they went in. They wouldn't be going faster, but it would change their frequency. And so if you build some device that like dropped photons into the ergosphere and they came out, and you could basically be harrasting the energy of the black hole by increasing the power of your light. All right, So then the scheme would be to gather a bunch of rocks, throw them at a black hole, and then have something that trends when when they come back faster at us, we somehow harness that energy. If you did this, for example, to the black hole at the center of our Milky Way, Sagittarius a star, you could steal as much energy as all the stars in the Milky Way are putting out in a billion years. So we're talking about like vast cosmic amounts of energy. It would just really dwarf you all of human energy production. Right, because I think what you mean is that the black hole at the center of our galaxy has all that energy stored in its spin. It has as much energy in its spin as the light that the Milky Way emits in a billion years. Yeah, there's a huge amount of energy stored in the spin of the black hole at the center of the galaxy. So that could potentially be stolen from us by some rocky scheme. Exactly. Maybe aliens are building pasta makers right next to the center of the galaxy. Yeah, thats right. Does it work with orzo pasta too, Like if I throw a bunch of little or zo collets, do they come out? You know? Like like Linquini on the other side, I suppose, So you know, for me, the question is is it theoretically possible to get energy out of a black hole? Once the answer is yes, the rest is up to the engineers. But I guess you know, to do this, you would need a lot of rocks, right, you would need a lot of You would need to build like giant rockets or something, or giant spaceships or giant like black hole the harvester devices or vehicles that you throw in and then they that know when to start coming out to on the other side, and that's your job. I guess to say, thanks for telling us that, but you're not telling us how to make it work. And our time is up. Thank you very much, Good luck. I'm gonna go make some homemade pasta lunch. No, but seriously, like, how practical is this idea? Right? Like you would need to come up with like some kind of spaceship that you throw into the black hole that then what then separates and then boost its way out and then you catch it on the other side. Yeah, so you need to develop some system, you know, where you have like explosive elements in rocks or rocks that split in half, or you know, somehow devise a way to do it with particle beams. But you know, in principle it is possible, all right. And so this idea is interesting because kind of where things are headed in the universe. We're heading towards sort of like an all black hole universe, right, Like eventually all of the black holes in the center of all those galaxies will eventually sort of consume all of those galaxies, and then they those clusters might also kind of crunched down to giant black holes. So We're going through a future where everything will be black holes, right, and so it might be good to know how to get energy out of the sons will continue to burn in this universe, and we do know that black holes will live on for billions and trillions of years, and so instead of just getting our energy from the nearest star, we might to learn how to get it from the nearest black hole. Right, But even then it's going to run out, right, Like, this is not a renewable resource, is it. Like once you take all the spin out of a black hole, it's kind of maybe useless to us, I suppose, But there are vast quantities of energy stored in these black holes, beyond even I think our capacity to charge our phones. I don't know. I wouldn't put it past humans to swipe their way into oblivion in the in trillions of years. All right, Well, an interesting idea and potentially maybe something that could propel humanity into the far far future. And just kind of another lesson about where the universe likes to hide energy, how it has all these crazy processes out there that are maybe storing vast amounts of potential energy. And we already know that the universe around us is very, very dense with energy. Every atom in your body contains an incredible amount of energy. Raisins worth of matter has more energy than a nuclear bomb. And so it's just a question of figuring out how to horror was that and how to do it safely? Yeah, I think I'll focus on the rhes fear first and the well, the more posture you eat, the larger the horhes fear gets. But then my head starts to spend and that creates these singularities or at least another jelly filled donut exactly the banana gularity. All right, well, we hope you enjoyed that. Thanks for joining us, see you next time. Thanks for listening, and remember that Daniel and Jorge Explain the Universe is a production of I Heart Radio or more podcast for my heart Radio, visit the I Heart Radio app, Apple Podcasts, or wherever you listen to your favorite shows. H