What's inside a neutron star?

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Speaker 1: Hey or hey, do you have strong opinions about pasta? I mean, like in my pro pasta or antipasta. Yeah, but I want to dig a little deeper, like, do you have opinions about all of the varieties? Yeah? No, I love that there are so many kinds of pasta, the more of the tastier. So then in the opinion of an artist, what is the prettiest pasta there is? M I try not to judge pasta bytes looks, you know, that seems kind of rude, So I just go by taste. Well, to me, it all tastes the same. I mean, fundamentally, it's all made of the same stuff. Though my kids insist that some of them are tastier than others. I think it's your kids. In an entire country called Italy would argue the same thing. I mean, it's all made of dough, right, which in the end just made of like protons, neutrons and electrons. How can it taste different? Can? We'll probably get a lot of hate mail from Italians because you know your physicist, right, Like, each pasta has a different cross section and a different ratio of volume to surface area. Right. Welcome to the physics of pasta podcasting. That's right, we're all postic. I am Jorge. I'm a cartoonists and the co author of Frequently Asked Questions about the Universe. Hi, I'm Daniel. I'm a particle physicist and a professor at u C Irvine. And I seriously can't taste the difference between different kinds of pasta. And I'm sure there are a lot of Italians right now feeling kind of sorry for you. You can't see. It's like nuts being able to see colors. I mean, I don't even understand the chemistry of it. Right once it gets into your mouth, it's just sauce and noodle. What does it matter what the shape of the noodle was when it was on your plate. Explain it to me. What's the science of it? Are you and those people that just blends all their food into smoothies, you know, salmon, steak, rice, whatever it just said, it's all going to get digested. It might as will blended together. No, I'm a big fan of texture. I get that absolutely, But you know, in the end, the noodles they don't taste different. They're not different texture when they go into your mouth. Maybe I'm overcooking them. I don't know. Yeah, I think if you overcook them, it's kind a big giant globe. But you know, it's like the ratio between the volume and the surface area, you know, makes the sauces kind of coat the pasta a little differently. Right, taste makes makes to taste different, I guess. So it definitely makes it look different, and it gives my kids an excuse to refuse to eat something like my son will not eat or Ka and my daughter will not eat Farfalla. And I'm like, look, it's just postable sauce on it. What's the big deal. Wow, your kids are pretty picky there. Maybe I should just blend it into a smoothie before I serve it to them. There you go. You could blend it and then make your own pasta. We do make our own pasta. Actually, sometimes we start from scratch, We make the dough, we roll it out. It's pretty fun. Yeah, it's kind of I guess. It's kind of like bread, right, Like all breads are basically flour and water. But you know you're gonna have a whole range of different breads and they all taste different. Oh my gosh, don't get into bread with me. Bread have very different mixtures of flower and water. You've got your moist breads, You've got your drier breads. You've got breads with more fat or less fat. It's totally different ingredients. That's what makes different kind of bread delicious. It's the same ingredients, isn't it. With different proportions? Oh, different proportions you mean, like different proportions of surface area volume. Alright, good point, but anyway, welcome to our I guess Culinary podcast. Daniel and Jorge Explain the Universe, a production of I Heart Radio in which to total lon experts argue about pasta when we really should be talking about the deepest questions in the universe. What shape do fundamental objects take? How do they come together to make this incredible universe with all of its amazing and different shapes. How do we get baseballs and fish and clouds and far falla and rikieta and spaghetti and cappellini and all the incredible shapes that we find here on our planet and the insane things going on inside our planet and inside stars and inside neutron stars and inside black hole. We dig into all of it for you. We codd with the delicious sauce of explanations and banana jokes and serve it up to you. That's right. It is a big, beautiful and delicious universe full of oodles and noodles of interesting things to learn and discover and to figure out how it works. Because somehow we are able to discover how things work in this universe using science. Absolutely, we think that it's possible to sit here on the crust of our planet and to just use our minds and our eyeballs to explore what's going on deep within our planet in conditions we could never replicate in our laboratories, and also what's going on inside crazy things out there in the universe. These our minds to try to extrapolate from the situations we can explore from the laws we have discovered, and wonder if those ideas and understandings hold up under very extreme conditions. Yeah, because that is one way to do science, is to observe things, and especially observe the crazy and the wild and the extreme situations out there in the universe, because they do teach us a lot about what can happen in the universe, even if you don't see it in an everyday basis, because one of our goals in physics is not to have a special set of rules for every situation. We don't want the physics of laundry and the physics of pasta, and the physics of air and the physics of water weight. That sounds like a great podcast. Actually, maybe we should do more of those rather than amplitus the physics of laundry. Yeah, I'll listen to that might give me some pointers, you know, like what are the physics of taking out post stains out of your white shirt? Wow? Crossover episode with our culinary podcast series. Yeah, well, that's fascinating. You know. All the different applications of physics in different conditions are interesting how these things emerge. But physics, you know, in the end, is reductionists. We want to go down to the lowest level. We want to understand a general theory about the universe that applies everywhere that you could take to your laundry or pasta or neutron star and say I can start from these rules and I can understand what's going on here, and the way to test that, the way to make sure that the ideas you have are not just specific to your pasta stains or to the experiments you do in your laboratory, but our general is to test them under extreme conditions, to say what happens if I make this really really dense or really really hot where we go really really fast. So that's why the extreme conditions are the best places to learn where your rules break down and to get clues about how to make new rules about the universe. Yeah, we like to look at extremes here on the podcast, and we have a whole series of extreme things that we've looked at in the universe, like the brightest things in the universe or the hottest things in the universe, and it usually comes down to only a couple of candidates. One of them are neutron stars. Neutron stars are one of the most amazing laboratories for physics in the universe because it's one of the few places where all of the forces are important. And we talk a lot in this podcast about quantum field theory and understanding three of the forces electromagnetism, the weak force, and the strong force. But we don't have many situations where we can put those three forces up against gravity because gravity is so weak. It's only really in the heart of black coals that gravity dominates and takes over. But in the inside of neutron stars, we think that gravity is just about as strong as these other forces. So it's a great laboratory for understanding how gravity and these other forces talk to each other and play together or don't play together. Yeah, we've talked about neutron stars before, but we've never sort of dug deeper into them to find out what it's all made out of on the inside. So to be on the program, we'll be asking the question what is inside a neutron star? And what would Italians call it? Neutrinos? No, that's taken. I think I know what the answer to this question is, though, Daniel, what's inside a neutron star? Isn't it just neutrons? Done? Thanks for joining us, see you next time. I thought you were gonna say what's inside a neutron star? One neutron star? I mean, that's like the ingredients, right, It's like what is pasta made out of pasta? Is that what you're saying? Is that what physics has come down to, giving up? Giving up? Yes, exactly. No, of course neutrons are inside a new tron star. But what are they doing. Man, what's the conditions? How dense are they? They form weird objects and shapes when they're in that crazy conditions. Are they even really still neutrons? Or they squeezed down into some other weird kind of matter, maybe even a quirk gluon plasma. Wait wait, neutron stars might not be made out of neutrons. I smell some misnaming here exactly. That is the question of the podcast, Our neutron stars fundamentally misnamed? That seems to be the mission of the entire program here. You're just trying to undermine people's confidence in physics, man or physicists. Is their confidence in physics? I mean, think about all the technology you're using to make this podcast and to listen to this podcast. All of that is based on fundamental physics that we understood through basic research. So I think, on one hand, we've been doing a pretty good job of exploring the universe and learning how to manipulate it for our benefit. On the other hand, we definitely don't understand a lot about the universe, so there's a huge amount left to discover. Yeah, I know, physics, it's just a big confident game, right, That's right. Keep paying us, and we'll keep teaching you the secrets of the universe. Except in this confidence game, the secrets are true, or at least as true as you think they can be. But I think maybe what you're saying that the question is in this episode is actually more like what's it like inside a neutron star? What's it like? You know, like, what's going on inside a neutron star? Yeah? Exactly. We did an episode on what's it like inside the Earth? What we dug into the crust and talked about, you know, the different layers. You could have answered that question what's inside the Earth by saying Earth, but that's not as satisfactory and answer. So, yeah, we want to understand like are there layers? There is it one big soup of neutrons? You know? Are there different phases of matter as you get crazy hot and dense? What is going on inside a neutron star? Can you find pasta inside? And apparently the answer is yes, there is pasta inside of neutron stars. If Michael Bay could film a movie about journey to the center of a neutron star, what would he show you on the screen? You would have to bring in some Italian consultants, because apparently the answer is pasta. Pasta is everywhere turns out to be the fundamental building block of the universe. Well, it's usually were wondering how many people out there had thought about this question, what's going on inside of a neutron star? So Daniel went out there to the wilds of the internet to get people's opinions. And I'm eternally grateful to our volunteers who answer these random questions and give us a sense for what people know and what they might be curious to learn about. Thank you very much. And if you are out there listening and they've never been on the podcast, we would love to have your voice to add it to our library. So please write to us two questions at Daniel and Jorge dot com. It's free, it's easy, it's fun. So think about it for a second. What kind of pasta would you like to see inside of a neutron star? And what do you think it's doing. Here's what people had to say. I've heard you guys talk about this in the past. Um, I know, like there is a crust and then as you go down deeper towards the core, there's like I think they call it quantum spaghetti. And then at the very center, I've heard you guys talk about luans, and the neutrons are no longer associated, so it's just like the soup of quarks and gluons floating around. Well, I would say it's pretty tight. I wouldn't want to be in there. Actually, in neutron stars are made out of nutrons, and the core I would think is the densest part of a star. So I would say there's a lot of nutrons, really really packed with nutrons. I would imagine it's hot and bright and chaotic, and if it had a high enough mass and you were actually inside it, then you might be able to find out what's in a black hole. Oh boy, very hot, very dense, very angry. I wouldn't want to be inside of a neutron star. A neutron star, other than a black hole, is the densest known object in the universe. It is so dense, in fact, that it has high enough pressure to merge to push all of the electrons and the protons together to form neutrons. Fusion is over, but it is very hot, and it is emanating very high frequency black body radiation, and I know it must be spinning very fast due to the laws of the conservation of angular momentum. Well, it's very compressed, extreme pressure, lots of heat, radiation, extreme electromagnetic fields, dizzy and spinning and death. I can only imagine that being inside a neutron star is like being inside of a bag of popcorn that is being cooked in the microwave. Um. There's a lot of pressure, a lot of build up, it's hot, and there's no escape. It seems like a prison. All right. People aren't painting a very pleasant picture here of neutron stars. Yeah, but they're reaching for a lot of food analogies. You know, we've got soup, We've got spaghetti, we even got popcorn. I guess did you pull people right before lunch or something. I think there's a deep and unexplored connection between physics and food, you know. I think that's what we're discovering here today because physicists like to eat a lot of or is that just your personal perspective, Daniel. You know I'm not a big eater. I don't eat anything actually during the day. I only eat at night, So you know, I can do physics all day long on an empty stomach. But I think that people reach for these analogies because they're trying to explain something weird and unfamiliar in terms of something that's familiar. And in the end, that's what physics is, right. We explain the unknown in terms of the known. So when you see something weird and new, you try to say that reminds me of and then you look for something familiar around you, like whatever you're having for lunch. Yeah, and most people here seem to have an idea that neutron stars are really hot and dance and compressed. A lot of the answers were sort of sort of people describing a pretty intense environment inside of a neutron star. Yes, exactly, And that's what get physicists excited, right, because we think it's a situation unlike any other in the universe, one that's very hard, if not impossible, to read create in our laboratory, and yet there it sits out there, actually doing its thing. And if we could know what was going on inside those neutron stars, we would have the answers to lots of questions about crazy conditions that we're curious about. You know, what happens when you squeeze these particles really close to each other, because remember that at the heart of a neutron star, these things are dominated by the strong force battling it out with gravity, and these are two forces that we do not understand very well. Of all of the fundamental forces in the universe. We understand the weak force and electromagnetism the best. We understand the strong force and gravity the worst. And so to get to see them fight it out helps us understand both of them. The strong mystery. Break it down for the audience here, what is exactly a neutron star. So a neutron star is one of the most amazing and weird objects in the universe, and it's also left over from one of the most dramatic kinds of events we have in the universe, which is a supernova. So you know, you start with a normal star which burns, and they have the typical battle between pressure from gravity squeezing in and fusion and radiation pushing out, and it burns for millions or billions of years, depending on its size, and at some point the core of it gets so heavy because it's fused all of these lighter elements and heavier elements carbon neon, oxygen. You work your way up the periodic table. At some point the core gets so heavy that gravity wins and the thing collapses. You get this shock wave that rushes in towards the heart of the star and then bounces back and comes out, and you get a supernova, and that blows out most of the stuff from the star. You know, huge amount of energy comes out in neutrinos and in photons and then just massive the stuff of the star. But it leaves behind this very very dense core. And so that's what the neutron star is. It's the remnant of a supernova from a super giant star. Yeah, that's something that I think, I know we've talked about before, but it's still pretty cool because I don't think a lot of people suld have realized that a supernova. You know, we think that maybe it's like an explosion or something reacts and explodes, but it's actually like what happens when stars and suns collapse. It's actually like the collapse of a star, and it's that collapse that kind of causes the big explosion. Yeah, you have the supersonic shock wave of traveling inwards and then traveling outwards, right it bounces back and explodes, and so it's a lot like you know, the way a fusion bomb works where we talked about laser fusion recently on the podcast, where you have this symmetric implosion which creates very fast runaway fusion which then triggers an explosion, right, and so it's really a dramatic end. It's incredible also the time scales, because these stars burned for millions or billions of years happily in almost a steady state, and then the end comes very quickly. You know, you think of cosmic objects having long time scales. You should do everything slowly, but when it dies, it dies very quickly, and it leaves behind these little remnants, these neutron stars, and they're super small, you know. These things have a radius of like ten to twenty kilometers, you know, so again we're talking about astrophysical objects. You used to thinking about like millions of kilometers. These things are billions of light years away, but we're talking about things like the size of Manhattan or Los Angeles, and yet they're super massive, like they still have the mass of an entire sun, like our sun. So these things of a mass of like one to maybe three masses of our Sun compressed into a tiny little space. Yeah, that's how That's exactly why I feel when I visit Manhattan actually super dance and compressing and hot as well. But what's interesting too is that, first of all, not every star goes supernova, and not every supernova turns into a neutron star. Right, that's right. The final fate of the star is determined almost entirely by how massive it was when it was born. If it has a mass between like ten and twenty or twenty five times the mass of our Sun, then it will go supernova and then go neutron star. If it has more mass than that, it'll go supernova, but it'll leave a black hole at the center instead of a neutron star. So if you have enough mass, then you can overcome even the strength of the neutron star and collapse it even further to a black hole. So gravity wins there if you add more mass. If you don't, if you had less mass, like less than ten times the mass of the Sun, then you don't get a supernova, and you get what's going to happen to our Sun, which is is just gonna leave behind the original core, which would be a white dwarf. So then for a neutron star, you start with a regular star that's about ten to twenty five times the mass of our sun. He's supernova that most of it I guess blows out in the supernova, but some of it, like one to three masses of our Sun, stays in the middle in this super duper dense state that I guess had its origin when the star collapse, right exactly, So you take the core of the star and you squeeze it down to this tiny little dot, this neutron star. So it's like a white dwarf that's been compressed by a supernova. And it's fascinating to me because it's like the last step before a black hole. You know, gravity is a runaway effect. If you only had gravity and no other forces in the universe, everything would eventually just collapse to a black hole to be nothing to stop it, because gravity just pull stuff in and it gets dense here and denser, and the denser gets the stronger it is, and then the stronger it is, the denser gets etcetera, etcetera. So the way to avoid becoming a black hole is to have something pushed back against gravity. So a star doesn't collapse into a black hole while it's burning because the fusion provides pressure outwards. The Earth doesn't collapse into a black hole right now because all that dirt has structural integrity. As the mass gets stronger and stronger, you need stronger forces to resist it, and eventually it just gives up and becomes a black hole. And a neutron star is like the last line of defense against gravity. It's like the densest thing in the universe that's not a black hole, right, Like, if you squeeze it a little bit more, you would get a black hole. But if you stop squeezing it or adding more mass right before it turns into black hole, then that's what you get. You get a neutron star exactly. And so it's this object which has enough strength to resist the incredible mass and the incredible gravity that it does have, but if you added a little bit more, yeah, it would collapse into a black hole. And so it's really the perfect way to understand this balance between the strong fo and the quantum mechanics that's resistant collapse and the gravitational pressure that's squeezing down on it. So like how many plates of pasta would you have to throw in to turn a neutron star into a black hole. It's a great question. We don't know actually, what is the maximum mass of a neutron star. Biggest ones we've seen are like two and a half up to maybe three times the mass of the sun. There's some speculative observations for larger ones, but we think it's probably impossible to have anything much more than three times the mass of the Sun. Well, that was kind of my next question, which is, you know, have we actually seen these things or are they like sort of like black holes that were sort of theoretical for a long time. We have seen these things, so they are not easy to see. These things don't have fusion inside of them, so they're not glowing very very brightly. Most neutron stars are kind of dim, right, They just sit there and they're cooling gradually, though you know, they can get bigger if something else comes behind, like dumps a huge load of pasta on them. So they're hard to see unless they're like in a binary system. So for example, there's another star nearby and they're strong gravity is affecting that star. So if you see like a normal star and then nothing nearby it, then you can say, oh, there must be something there because of its gravity. You can argue about whether it's a black hole or a neutron star based on its mass. So it's one way to know that they are there. You can also see them directly if they are pulsars. So a neutron stars is heavy, heavy object. It's also spinning really really fast, right because remember, angular momentum is conserved. If you take an object which was big and spinning and compress it, it's still gonna be spinning, and now it's going to spin much much faster in order to have the same angular momentum. So sometimes these neutron stars spin super fast, and they also sometimes shoot out energy from their polls, and if there's a misalignment between where they're shooting energy out and the spin axis, then this beam that they shoot out sort of sweeps across the universe, and if it passes Earth, then we see it. And that's what a pulsar is. So some action of neutron stars we can see because they are pulsars and they're pointed right in the exact direction where we can see them. But most neutron stars we cannot observe directly, right, because we call them stars, but they're really not sort of shining in the bright night sky unless, like you said, they somehow have this spin and the somehows shooting a beam in a particular direction, which is what pulsars are. Yeah, you can argue about exactly what is a star and whether these count. You know, there's sort of the endpoint of the life of a star. You definitely wouldn't call a black hole a star, right, even though it's also the endpoint of the life of a star. So these things do emit some light, and so the one way to see them is if there are pulsars. Another way to see them is to see X rays from their surface. So they don't glow in the visible light, but sometimes X rays leak out of their surface. If there's like a crack in the surface of the neutron star or like a hot spot, it can emit some X rays. And we have X ray telescopes that are able to see those X rays see of photons from these distant stars, and that can help us see that a neutron star is there. So we think there's like a billion of these things floating out there. In our galaxy, but most of them are basically invisible to us. Yeah. I was gonna ask next whether we have a picture of a neutron star, but actually then I realized we don't really have a picture of anything outside of the Solar system, right, Like, we don't really have a full on picture of any star out there in the universe. We just know them as pinpoints. That's interesting. I mean, we certainly have a picture of them, right Even a pin point is a picture. It's light from the star. So yeah, I guess we do have some, you know, pictures of these stars, but not in a lot of great resolution, certainly not the way we can look at our own son, for example. But yeah, we don't have pictures of these neutron stars at all. In most of the cases, all we have is like a stream of X rays, so like a time series when we say, oh, we saw some X rays, Oh we didn't see anymore. Now we saw some more, because the entire neutron star doesn't admit X rays, just little cracks and hot spots on the surface, and so sometimes the hot spot will be like around the back of the neutron star, and sometimes will be on the front of the neutron star. So you can learn a lot about the neutron star from these X rays. Yeah, and maybe it'll let you see inside of him like regular X rays. And so let's get into more amazing facts about neutron stars and also talk about what could be going on inside of him. But first let's take a quick break. We're talking about neutron stars and what's going on inside of them. I'm guessing it's non neutral things. If we have a whole episode about them, Well, there's definitely a lot of neutrons inside there. It's hard to imagine, like and to really conceptualize what this stuff is that's inside a neutron star because you've taken normal matter and you've squeezed it down to incredible densities. You know, this stuff, whatever it is, is a hundred trillion times denser than anything we have on Earth. You know, you think you ate a heavy lunch, that's nothing compared to like a spoonful of neutron star. Yeah, Like, how much is a spoonful of a neutron star weight? Well, here on Earth they would weigh three billion tons just one table spoon of neutron star material. Of course, if you had it here on Earth, it would explode because it's under great pressure. But you know, just to sort of like conceptualize how dense it is when it's in its location, it's a crazy amount of mass. It would explode in your mouth. I guess like a flavor explosion, like a flavor explosion exactly. They should have like a summer drink called Neutron Star, you know, added to our online store. I was thinking like a seven eleven crossover episode. You know, you mean like an icy kind of like a slushy. Yeah, a Neutron Star slurpy. You know. My daughter went in to get a slurpy recently and she came back with one. I said what flavor is it? And she said blue? And I was like, blue is not a flavor and she said, well, the guy asked me what flavor I wanted and I said blue, and this is what he gave me. That's thought. She was going to say, all of them, don't know what you're supposed to do mixing them all up. I don't know. Then we'll get gray, won't you. Nobody wants to get a gray slushy, and I think it comes out chocolate chocolate color. That sounds delicious. Maybe it's like neutron star chocolate. But anyways, back to neutron stars, I guess the question is what would it look like if I'm sitting in front of a neutron star. I know we want to get into it, but like if I was sitting outside of it and it's like, you know, a few light year or a half of a U from a neutron star, what would I be seen? So if you're close enough to you know, this thing is hot, so it's going to miss some light and you're also gonna see hot spots from its surface. But one thing about a neutron star is that the gravity is so strong and near the neutron star that it distorts the space around it, sort of the way a black hole does. We're used to thinking about this for black holes. You know that if you're in front of a black hole, you're looking at the event horizon. You're not only seeing the part of the event horizon that's on your side of it. You can also see around the back of the black hole because photons emitted near there would be bent by the curvature of ace and come to your eyeballs. The same thing is true around neutron stars because they are so incredibly dense. Right, the gravitational field at the surface of a neutron star is two hundred billion times stronger than the gravitational forces on the surface of the Earth. So if you're looking at a neutron star, you can not only see the front of it, you can also see the back of it at the same time. So if you're on a neutron star, you would wait two hundred billion times more than you do now. Yeah, so start working out so I can I can stand up, is that what you mean? Or so I can lose weight so you can survive. Man, that thing would tear you to shreds. Not only is the force of gravity very very strong, but it varies very quickly, you know, and so you get tidal forces. The difference between the gravitational force on your head and on your shoulders would be very strong enough to rip your head off of your shoulders. So I wouldn't recommend a trip to a neutron star. Would there be a spectification point like in a black hole? Yeah, well, before you got to the surface of the neutron star, you would be torn apart because the title forces would be very very strong. Remember, this thing only has the mass of the Sun right so far away. It has the same gravitational force as the Sun, but you can get much much closer to all of that mass because it's compressed down to just like you know, ten or twenty kilometers, whereas our Sun is huge. So if you're on the surface of our Sun, you're very far away from the gravitational center of mass, whereas if you're in the surface of the neutron star, you're only ten kilometers from an entire star's worth of mass. That's why the gravitational forces are so much stronger for the same amount of mass, because you can get closer to it. So you and the spaghetti head for lunch would turn into spaghetti exactly. You would be postified. Right. Well, I guess the big good question now is why is it even called the neutron star? Like is it full of neutrons basically? And how did a regular sun, which is what it was before it's supernova and collapse into a neutron star is made out of all kinds of stuff, right, like iron and all kinds of complex elements and electrons and protons, But now it seems to have collapsed into something that you now call a neutron star. So is that everything just turned into neutrons or what? Yeah, everything turns into neutrons. Right. You have your atom which has neutrons, protons, and electrons in it, right, Well, what happens if you squeeze that down really really far, if you really push a bunch of that stuff together, Well, if you get the electron and the proton close enough to each other, well, you know, they have opposite charges and so they actually kind of like to hang out together. So if you squeeze them down enough, the proton captures the electron, the electron gets like eaten by the proton, and that converts it into a neutron. It's exactly the opposite process of neutron decay that we talked about recently on the podcast, where a neutron turns into a proton and electron. This is the reverse process. So you put enough energy into it, you can reverse basically anything that happens in the universe. And so this is what happens. If you squeeze down matter, all the protons and electrons emerge and become neutrons. So usually electrons and protons are attracted to each other, but they don't get together and merge. Right, what's keeping them apart? Well, what's keeping them apart usually is that the electron is in a stable state, just the way, for example, the Earth is in a stable state around the Sun. The Earth and the Sun attract each other. There's gravity there. Right, Why doesn't the Earth collapse into the Sun. Because it has enough energy to resist that, right, it can stay in a stable orbit. And so you shouldn't be thinking about electrons as orbiting protons. But they have enough energy, they have a minimum energy in their stable solution to avoid collapsing into the proton. And so here you're overcoming that, right, you are like squeezing the electron down. You're applying external pressure. And so that's why an electron doesn't collapse into the proton, because it has enough energy to avoid it. But that's if it's by itself. If you squeeze on if you push on it from the outside, if you can find it to a location the size of the proton, then it gets captured by the proton. And then what happens The proton eats the electron. Right, Because the proton is made out of three quarks and a neutron is made out of three quarks. So then does the electron just sort of like flip one of the corks or or something. Yeah, that's exactly what happens. Remember, a proton is two up corks and a down and a neutron is two down corks and an up. So what happens when an electron is captured is that you're converting one of those up corks into a down cork, and so that converts the proton into a neutron. There's also one more step because you can't just delete electrons from the universe, so you also need to create an electron neutrino. Interesting, So it's like the proton eats the electrons and then then they become neutral. And then what happens to all of these neutrinos, It just gets spit out into space. Yeah, they get spit out into space because neutrinos mostly see stuff in the universe as transparent, right, they hardly interact with anything. They can go through a light year of lead without interacting, and so mostly they just get shot out while it's collapsing. Remember, supernova is the process that produces these neutron stars. Emit most of their energy via neutrinos, right, something like of the energy of a supernova is not emitted visually, not in the optical, not via photo tons at all, but via new trinos. And so this is part of the process that creates all of those neutrinos when the supernova happens. Yeah, supernovas are known to be silent, but deadly silent and invisible. Supernovas are incredible because you can see them in with a naked eye, right, that's how bright they are. All of a sudden, a star becomes as bright as the entire galaxy. And that's just the visible light we're talking about. It turns out there's a hundred times more energy in the new trinos. But a whole fun podcast episode about how supernovas can be seen first in new trinos with our new trino telescopes. And so this is part of the process. Creating those neutron stars means making neutrons, which also requires you to make the new trinos because you've got to balance the books of particle physics in the end. Right, So they're calling neutron stars, but actually not all of it inside our neutrons, and so maybe can maybe step us through a little bit, like asked, the supernova is collapsing, and as things are getting squeezed together, like what's happening to all those atoms of the bigger elements. They're just getting broken up and squeezed together or they just explode. What's going on? So some of them get broken up, and depends on where they end up. So we'll learn about it as we step through the layers of the neutron star. But near the outside of the neutron star, for example, the atoms don't get broken up. You get atomic nuclei still, for example, so the outer crust of a neutron star is atomic nuclei. You can have helium there, you can have carbon, you can have oxygen, this kind of stuff. It's only as you get deeper in that these nuclei get squished together so far that the separation between the nuclei breakdown, and then you just get like a sea of neutrons, or maybe a sea of corks, or maybe even weirder stuff. And so you can't really think about it as like lead or iron or carbon anymore because it's gotten broken up into its constituent bits that's at the very center. But you're saying that the crust of a neutron star you could get you just have regular stuff. Then, yeah, at the crust you just have regular stuff, like you might be able to like stand on it maybe or is it all sort of like in a liquid or gas form. So there is an atmosphere of a neutron star. Actually there's like a gaseous atmosphere, but it's micrometers thick, like micrometers. So this thing is like ten kilometers or fifteen kilometers wide, and it has an atmosphere and that's like micrometers of gas just above the surface. And then the surface itself is hard, it's like brittle, it's like a crunchy, right, and it's made of atomic nuclei. So these are things that used to be part of the star, carbon, oxygen, nitrogen, whatever, and now it's crystallized into this like lattice on the outside of the star, which is very very smooth because the gravity is so strong that you basically can't form any hills. So they think that like the maximum elevation on the surface of a neutron star might be like one millimeter, or gravity like pulls it back down. So if you're standing next to a neutron star. What you would see is a basically a big, shiny smooth ball, right, made out of some of these heavier elements, almost perfectly shiny smooth ball. Really incredible how spherical this thing will be, But there will be some exceptions because the crust is brittle. The crust can crack, right, it's under incredible pressure gravity squeezing it down, and sometimes you get like a little bit of a weakness, and so you can get like a star quake because you've got a crack in this crust and things like a just a little bit, and that's when, for example, X rays can leak out. So the reason you get X rays is from these hotspots, which can cause these little neutron star quakes on the surface. But what if it's spinning, wouldn't it also kind of give it a weird shape, right, It is spinning, and so that changes it from a spherical a little bit, right, But it's also very very compact gravitationally, how far something goes from sphericals a balance between how fast it's spinning and also how strong the gravity is. So we've never seen one of these things. But you're right, it wouldn't be perfectly spherical, though it still would be very very smooth. All right, So I'm standing on top of a neutron star. I wait, two hundred billion times more than I normally do. And so I take a pick ax and I cracked the surface. What do I see inside? So you gotta dig a little bit wet. So inside the neutron star is a little bit more crust. You've got to dig a little bit into it before you get to sort of like the next layer. And we're not sure, of course, about any of this. A lot of this is speculation. These are models that we've developed based on our calculations from our understanding of the strong force and gravity, etcetera. But we think that this outer crust is like three hundred to five hundred meters thick. Once you penetrate through the crust, then these elements are no longer able to hold onto themselves, right, They're squeezed together by pressure, and so you get this like soup of neutrons that we think are just sort of like floating around there where the atoms themselves are getting broken up, so they're no longer really like have their identity as an element. I see, so on the shell you still had the heavier elements like lead and carbon, but then now they're being squeezed together so much they what they like, they just break apart the nuclei or they merged together. They do both. They sort of varies. As you go in near the outer layers of this part. They first merged together because they're getting squeezed together, and so you have weird fusion happening. You have like weird heavy elements that couldn't exist in other situations, you know, that wouldn't be stable out there on their own in the universe. But under this crazy pressure, we think you can form like ridiculously heavy elements, you know, things with huge numbers of neutrons on them. As you go further and further in, things become more and more neutron e Right. It's not pure neutrons. You still have some protons and some electrons. Not every single proton and electron has been converted into a neutron. But as you go inwards you have like a higher and higher fraction of neutrons m Because I guess as you squeeze this stuff together, that's what it all ends up as, right, just play neutrons because all of the electrons, and the protons eat each other exactly, and we think that overall there's gonna be a charge balance. So there is a proton for every electron, and so you squeeze it hard enough and they'll find each other eventually. But so as you go deeper and deeper, and you get like a higher and higher fraction of neutrons, and then what happens as you go in deeper. As we go in deeper is where the real mystery is, right, and so you have this inner core where we don't really know what's going on, Like we think maybe there's some super fluid neutron matter there, Like we think that maybe under these conditions and neutrons just like slide around past each other and have all this weird chemistry. This is a lot of where the question marks are. You might wonder, like, well, why is it a question mark? Can't we just take the laws of physics that we have gravity and the strong force and do the calculations and say what does it predict? It's not always so easy, right to say I know what the laws are, what's going to happen. We can't even do that for lots of situations. You know, if you just gave me quantum mechanics and a baseball and said, here's ten to the twenty nine particles, what do they do next? It would be very very hard for me to come up with like parabolic motion. It's not easy always to go from the underlying laws to predicting what's going to happen on the macroscopic scale, and especially when things are very very strong, when the forces are very powerful. Here you have gravity, which is unusually powerful because it's so dense, and you have this strong force doing its thing with very short distances. These things are exchanging incredible numbers of gluons. So we just don't know how to do that calculation. Even if the laws that we have, the ideas that we have about what's fundamentally guiding it are true, we don't know how to take those and predict in great detail what's going on inside. It just gets too crazy. It just gets too crazy er. It's too many things to keep track of. So we've tried, and we have a few ideas. People make approximations this way or approximations that way to say maybe it's like this, or maybe this equation will work. But everybody's reaching past the edge of what they really know. So there's a bunch of speculative ideas and they're all really different, and they're all totally different from each other, and so we'd love to see it. We'd love to understand what's going on there, because it would tell us, oh, this idea is correct, or actually, none of your ideas are correct, and something totally weird and unexpected happens. So that's what we're trying to do. Unfortunately, of course, we can't see the inside of the neutron star. We have to just try to guess what's going on based on what we can see from outside. All right, well, let's get to the core of this mystery and think about what exciting and maybe delicious things could be inside at the core of neutron stars. But first let's take another quick break. All right, we're talking about neutron stars and what is inside of him, and I'm sort of getting the picture, Daniel, Dad, inside of a neutron star are not necessarily neutrons. There seems to be a lot of other stuff. They should be called mostly neutron stars. Neutron star, yeah, or neutrinas stars. Well, all the neutrinos have left the building. Right, they took their little weak forces and they ran away. I see there are no Italians in the room anymore. You're free to make whatever pasta you want. All the rules are out the window. How a d is the inside of a neutron star? So we correct the heart surface of a neutron star. We dug in a little bit. When you get this soup of electrons, the neutrons maybe like super deeper heavy atoms, but eventually those break down as you go deeper and deeper into the neutron start to you get basically just neutrons, right, like a sea of neutrons. But then what happens as you go even further in, So we don't know what those neutrons do, and that's fundamentally the question, Like if you have a bunch of neutrons and you squeeze them into these incredibly dense situations, what do they do? Do they form a super fluid or do they do something else? Something weird? But you're still calling them neutrons because like, inside of a neutrons are three quarks. But so you're saying at this point, like each triplet of quarks is still held together. They're just interacting with other triplets of neutrons, or have the corks sort of even broken out of that. That's one of the options, right, Do the neutrons stay together and form weird shapes, weird emergence structures, or do they break down? And really we should be talking about cork matter, you know, and cork gluon plasmas. That's one of the options that's on the table. But to me, it's a great example of some of the deepest mysteries at the heart of our understanding of the universe, you know, like what emerges. You can take the basic rules of physics, and incredible structures emerge, you know, atoms and ice cream and galaxies, all these things sort of emerge from the underlying complexity. And it's exciting to see a situation where we just don't know what will emerge. You put the neutrons in this situation, maybe they'll just be a crazy, chaotic soup, but maybe new structures will form, right, And so people have exciting ideas for what kind of weird structures might form from neutrons in these configurations, right, because, as you said, I think at this point it's so crazy and so dance. There's only two forces involved. The gravity that's keeping them all in and keeping them attracted to each other, and also the strong force, which is what bringing in the courts together, help holding the courts together, or what does this strong force do? Does a strong force repel? Also here it just attracts, right. The strong force is really really weird and has a very strange behavior with distance, but under short distance and will attract quarks and gluons to each other. And we think of protons and neutrons as sort of like balanced in the strong force, that all the quarks are bound together into this state that has overall no strong charge, no color. But that's not really true. If you get close up enough to a proton. If you get close up enough to a proton, then you'll be like closer to part of it then to the backside of it, and so you'll still feel a little bit of that effective color, right, And so if you get close up enough to a proton with your corks, then your corks will start talking to the quarks inside that proton. And that's for example, why a nucleus holds together. Remember a nucleus is filled with protons and neutrons, is only positive electric charges there, Why doesn't it blow apart Because the quarks inside the protons and neutrons are talking to each other. They're making it sticky. And so inside a neutron star, the strong forces pulling these things together the same way gravity is. Right, So you have all these neutrons, then these triplets of corks held together by gravity, and you're saying that they can sort of form matter like they can you know, arrange themselves in special, maybe delicious ways. Yeah, well, we don't know for sure, but we have done supercomputer studies where we simulate these things. We put in the laws of nature and we just see sort of what happens, and interesting stuff does seem to emerge. After like two hundred and fifty computer years of calculations, they see these weird blobs form, and so as things get denser, they form these sort of semi spherical blobs of matter where things sort of like clumped together into these huge blobs of neutrons with a few protons mixed in. And so they called these things Nioki might be Italian, you know, potato blobs that people enjoy eating for lunch. I guess it's sort of like if you take a whole bunch of carbon and atoms, loose atoms, and you squeeze them together enough at some point they'll sort of form into a diamond or some sort of shape. Right. That's kind of what's happening here, is that you're taking these neutrons and you're squeezing them so much they kind of lock into these shapes. Yeah, and so instead of having like a sleet ocean where everything is just mixed together, they form a blobs of a certain size. Right, They like distinguished themselves say, oh, we'd like to have this many neutrons into a blob with a few protons mixed in would have the same thing over there. So instead of being like totally indeterminate, they seem to want to form these structures. Right. And if you squeeze even further than these blobs form these long rods. They like come together to make these long rods, which looks sort of like spaghetti. Well, I mean, they could look like a lot of things, bread sticks, steel bars, but we're we're you're you're staying with the pasta analogy. They sort of look like spaghetti. I didn't name any of these things. I'm just enjoying saying them but yeah, they could have called them, you know, twizzlers or bread sticks or whatever. But they look sort of like spaghetti, and they form these long rods. They're parallel, right. Don't think of spaghetti like a big mess on your plate. Think of spaghetti sort of the way it comes in the package from the store. They're all these rods in parallel with each other. So they call this nuclear pasta, right, right, And so they kept going, and all the other shapes that neutrons can form have sort of a pasta analogy. Right. Yeah, you keep going, you keep squeezing this stuff down, and they think, or they predict from these calculations that the spaghetti will merge together to form sheets. So then you have nuclear lasagna, these like layers of this weird kind of matter that's mostly neutrons with a few protons in it. And it's very very strong stuff. In their calculations, this stuff has incredible strength. It's like very hard to break it apart. It might be some of the strongest stuff in the universe. You mean, these lasagna sheets of neutrons, and these Lasagna sheets of neutrons, they're not just like forming and then breaking up and then reforming it's not like a crazy gas or a plasma. Right. These things are like very very strong sheets of a weird kind of matter. Right. It's not like a solid or liquid or exactly like a crystal made out of almost all neutrons. Right, it's not like a regular lattice of atoms like the way we think of like a piece of steel. Right. And you're saying some of those strongest stuff in universe because it's it's basically surviving these intense and crazy pressures inside of the neutron star. But I guess if you took it out of the neutron star, which is blow up, Yeah, it would probably blow up. We don't know, right, Maybe it's strong enough it will hold itself together. Right, Because, for example, diamonds are formed under very crazy conditions, but then they're stable, so you pull them out from the heart of the Earth where they were made, they don't explode. So maybe nuclear pasta doesn't explode. We just don't know. But if you keep squeezing this stuff together, you squeeze the Lasagna sheets together, it forms this thing called anti spaghetti, which is like a blob of matter with holes in it, like long, thin spaghetti holes sort of like drilled through it. Wait, what kind of like pant pasta like Swiss cheese. More like Swiss cheese, Yeah, than penna pasta, right, more like parmiers Maybe should say parmesan or what's in the Italian cheese with holds in it. But those holes are bubbles right here. We're talking about holes that are like long tubes. So it's like wormholes through a block of parmesan. It's more like a clump of bucatinia then perhaps, yeah, like a clumb of bukatina. Any They called it anti spaghetti because it's like take the spaghetti state and flip it so that everything that was matter is now a hole and everything that was a whole is now matter. So if you add spaghetti and anti spaghetti together, you get, you know, like a complete block of matter. You get anti pasta. You annihilate your stomach, and that's not even like the core of the neutron star. Like if you go further in then things start to even this pasta can't survive. Yeah, so they think that this pasta is maybe like a layer that's like a hundred meters thick, and as you go even deeper, you know, we're in a huge question mark territory. But some people speculate that you might get a quark gluon plasma or something else, this stuff called cork matter, or as you suggested earlier, you no longer really can think about this stuff in terms of neutrons and protons anymore, because everything is just interacting with everything else. If it's a high enough energy, if the high enough temperature, that doesn't really matter that you used to call vs three quarks and neutron and those three quarks of proton. Now they're all talking to each other, so it's just like a big sea of quarks and gluons. I thought at the center you would find Daniel going, how this taste the same? That's all the same stuff. I bet a bite of nuclear lasagna and nuclear anti spaghetti tastes just about the same. The pats on how the I guess quark glulon sauce coats the shapes now. But I think what you're saying is that you get to a point where it doesn't make sense to call things uh neutron, because like the separation between a triple of quarks and a triple of corks here is sort of gone. Like you basically crack open those neutrons and it's just a soup of of the what's inside. Yeah, and that's the possibility, right. It might be that the conditions are intense enough to create that, but we're not sure, right, it might be that instead, other things happen. So there are other possibilities on the list. Some people think you might form weird, strange kinds of matter inside things like hyperon matter or kaon matter. These are other versions of nucleons. But instead of having just up quirks and down quirks, now you have strange quirks as well, just ing And then I guess you can break things down further because corks are fundamental particles in the universe, right, or could you maybe squeeze them down to like just pure energy. Well, we don't know the corks are fundamental, right, They are as fundamental as we have discovered. We don't know that there's anything inside of cork, but we have lots of hints that suggests that they shouldn't be fundamental. They are all these unexplained patterns among the corks, the kind of patterns you see when they're made out of something smaller, something more fundamental, like we saw patterns in the periodic table. Those were clues that atoms were actually made of smaller building blocks you could arrange in lots of different ways. We see similar patterns in the corks that suggests that they should probably be made of something smaller, but we've never seen it. So it's possible that the heart of neutron stars, you go beyond cork gluon plasma, and you can even go inside the corks, and maybe the things inside corks break open and talk to each other. We just don't know, all right, So then, uh, I guess what's inside when nintron star? The answer is we're not quite sure. I mean, defly you had neutrons there, but maybe at the core you get to something that is not even neutrons, or maybe even quarts, is what you're saying. Yeah, we just don't know. It's a big question mark, and lots of different calculations lead to different predictions, which is confusing and also exciting because it means that we can learn something about the universe. Unfortunately, we can't see the inside of neutron stars directly. Right Even if you were near a neutron star, how would you see what's going on inside it. We have the same question with our own star. We don't really understand all the plasmac currens inside the Sun and why it creates this magnetic field which flips every eleven years because we can't go inside it. We can only look at it from the outside. Well, these are even dimmer objects much further away, so they're even harder to study. But you know, we can use our X ray telescopes to look for these photons from these cracks on the surface of the neutron star, and those can give us a lot of clues. They tell us something about the mass and the radius of the neutron star, and we think that knowing the mass and radius the neutron star will help us try to figure out what's going on at the core of it. Because you're building this neutron star out of different kinds of stuff, So one idea for what's of the heart of a neutron star will give you different predictions for the masses and the radio you see than another idea. M I guess the problem is that, like in our son, the one we have here, we can sort of look in using our equations because things aren't that extreme yet, Like the regular laws of physics still work. But you know, with a neutron star, you start of getting up to that point where things start to get a little crazy, right, Like you're sort of starting to get into black hole territory where you don't even know if your loss of physics are the same. Yeah, we don't know if these hold. And you know, one of the guiding equations of these things is called the Tulman open hyber Molcov equation, which is the thing that constrains the structure of a spherically symmetric object that's homogeneous. It's all one kind of material which is in gravitational equilibrium. So that's like the simplest model we have for a neutron star, and it makes all sorts of predictions. And some of those predictions are, for example, that there's a connection between the mass and the radius of a neutron star that if you fix the mass of it, that also determines the radius. But when we look out into the universe, does neutron stars don't seem to be following that rule, Like we see some neutron stars that are twenty five kilometers hy that have the mass of one point four times the mass of the Sun and other ones that are the massive two point one times the mass of the Sun at the same radius, so they break these rules, which, as you say, suggest that these rules aren't complete, right, that something about what's going on inside the neutron star is different from what we imagine, from what our rules can currently predict, Which might mean that it's like a new complex way that these rules interact and new structures emerge. Or it might mean that there is some new physics, something else going on, a new force, something inside corks, something weird we haven't even imagined, but I guess on like a black hole, like it is maybe possible for us to one day get to a neutron star and maybe actually sort of like touch it and maybe even send probes into it. Do you think it certainly is possible? Right? We can't even land probes on the surface of Venus right now that lasts more than like nineties seconds without getting crushed, And Venus is the like, you know, a day on the beach compared to the surface of a neutron star. But yeah, you know, if you have a lot of faith in our engineers and our pasta engineers, our pasta engineers maybe they can imagine a way to drill into a neutron star and see it. Yeah, it's not technically forbidden, it's just very very difficult. Yeah, and they are out there, and neutron stars just like black holes, and they have lots of interesting secrets inside of them, right they do. If we could know today what's going on inside a neutron star, it would tell us so much about gravity and the strong force, and also just like what our universe can do. Remember that the part of the universe we experience, this liquid, the solid, the gases, is just a tiny, tiny slice of what the universe is capable of. We don't really observe most of what the universe can do. So I would love to let the universe show its colors, you know, like go crazy in the kitchen universe, make us some weird pasta. I want to see what you can cook up. Yeah, it's almost like they're kind of little lab experiments, right, or like they're like little labs, Like you want to know what happens when you crushed two quarts together. You know, that's what's happening inside of a neutron star. So if you want to know what happens go observe neutron stars. Yea, go observe neutron stars exactly. I wish we could. But it's wonderful that these experiments are happening, right Like, we can't create these things ourselves, but it's fantastic that the universe has arranged for them to happen so that we can study them. Unfortunately, they're very difficult to approach and very very far away, so there are some stumbling blocks there. But maybe one day we'll be able to visit them, or we'll just get more clever about observing them from the outside and using that information to infer what's going on inside. Maybe it will be the Italians to do it, since there are the experts that's right, Maybe to be so offended by these models of anti spaghetti that they will be motivated to figure this out. And then your kids will be like, no, I don't like that kind of pusta, not for me, thanks. I want blue pasta. I want all the pastas squished together. Next to you going to tell me that different colors of pasta change the flavor, Well, depen's how they get their color, but they do change. Do you really want to spend another hour talking about this. Have you never had squitting pasta or vegetable pasta? All right, that's a topic for our spinoff pasta podcast. Daniel and Jorge argue about food. Daniel and Jorge eat the Universe. Well, I hope you enjoyed that discussion, and it's certainly made me a little bit hungry. I need to go have lunch now, So thanks for joining us, see you next time. Thanks for listening, and remember that Daniel and Jorge explained. The Universe is a production of I Heart Radio. For more podcast from my heart Radio, visit the i heart Radio app, Apple Podcasts, or wherever you listen to your favorite shows. Yeah,