Listener Questions 56: Neutron Stars, Dense matter and shared atmospheres!

00:00:08
Speaker 1: Hey, or hey, I got a question for you that connects our two favorite things.

00:00:13
Speaker 2: Ooh, is it about sleeping or taking a nap?

00:00:17
Speaker 1: No, it's about physics and food.

00:00:20
Speaker 2: H you mean are other two favorite things? All right? What's the question?

00:00:23
Speaker 1: Question? Is what astronomical object out there in the universe would you most want to taste like?

00:00:31
Speaker 2: Would I prefer to take a bite out of a black hole or a yellow star?

00:00:35
Speaker 1: Exactly? Chocolate versus banana?

00:00:37
Speaker 2: Wait? A black holes made out of chocolate? Is that what you're saying.

00:00:40
Speaker 1: That's what we're trying to find out.

00:00:42
Speaker 2: I see you're the mastermind in this evil scheme or tasty scheme, one of the two. I guess in either case, I'd rather just take a nap.

00:01:05
Speaker 3: Hi.

00:01:05
Speaker 2: I'm horim my cartoonists and the author of Oliver's Great Big Universe.

00:01:08
Speaker 1: Hi, I'm Daniel. I'm a particle physicist and a professor at UC Irvine, and I do want to know what a black hole tastes like?

00:01:15
Speaker 2: Isn't that sort of a strange question to ask what a whole tastes like? When did did you just leave you with an empty stomach?

00:01:20
Speaker 1: Maybe it actually be kind of a great diet you know, like, take a bite of a black hole. It's like negative bites.

00:01:26
Speaker 2: Oh, I see, we just suck out your ords and you would weigh less. Yeah that works. I mean I think that's all the rage in Hollywood.

00:01:33
Speaker 1: Now this is the physics ozembic exactly.

00:01:38
Speaker 2: Yeah. Well, I mean it's a philosophical question, like what does nothingness taste like?

00:01:42
Speaker 1: But a black hole isn't even nothing, right, it's super dense something.

00:01:45
Speaker 2: Well, there's things in the black hole, I guess, But is in most of a black hole nothingness or I guess? We don't know.

00:01:51
Speaker 1: We don't know.

00:01:52
Speaker 2: That's the point.

00:01:52
Speaker 1: That's the deepest question in modern physics, which I want you to take a bite out of.

00:01:56
Speaker 2: You mean, the biggest question in modern physics. This is what the black holes take?

00:02:00
Speaker 1: Yeah, exactly.

00:02:02
Speaker 2: But then here's the problem. If you do get this data, isn't it very subjective? Though? It's not really objective data, is it?

00:02:09
Speaker 1: It's still data?

00:02:09
Speaker 2: Like I might be like, hey, it's delicious, but then you know, other people might disagree.

00:02:14
Speaker 1: It's still data. We still want to know what's inside a black hole. It's like when you look at an amazing chocolate cake, it looks like chocolate on the outside, But what if it's secretly vanilla on the inside. The only way to know is to take a bite. So we want to learn about what's inside a black hole, maybe we just have to take a bite.

00:02:30
Speaker 2: But I guess what I'm saying is like having a person take a bite wouldn't really tell you what's inside. What if it's something I've never tasted.

00:02:36
Speaker 1: Before, But what if it's just vanilla?

00:02:38
Speaker 2: That would be the most boring result there, like literally, but anyways, welcome to our podcast, Daniel and Jorge Explain the Universe, a production of iHeartRadio.

00:02:48
Speaker 1: In which we encourage you to take a big, juicy bite out of the universe. We hope the universe tastes better than just vanilla. We hope that it's filled with all sorts of weird stuff we never anticipated, things we've never encountered before. That's just the way reality rolls. It's filled with all sorts of amazing things for us to discover, to understand, and to explain to you.

00:03:08
Speaker 2: That's right. It is a tasty universe, full of interesting and fascinating flavors and sometimes a lot of mysterious flavors. Flavors that make you want to go, Uh, what is this that I'm eating? What is it that I'm smelling? What is this made out of?

00:03:21
Speaker 1: And we know that listeners to the podcast are the ones who are curious about the nature of the universe. You listen because you have a deep itch to understand how the universe works, and we want to reach out and scratch that itch for you. And that same mitch will lead you to ask questions about how everything works. When ideas don't fit together in your mind, or when you read something that just doesn't make sense to you, you wonder, how does this all work? Is it possible to understand xyz? And we encourage you to reach out to us with your questions to questions At Danielandhorge dot com we write back to everybody that's ray.

00:03:53
Speaker 2: You can send in your questions and sometimes we'll pick those questions to answer on the podcast or at least talk about the question. Sometimes would you talk about the questions without getting to an answer.

00:04:02
Speaker 1: Well, sometimes we give an answer and you say that's not really an answer, that's just a description, and then we get into the philosophy.

00:04:10
Speaker 2: I guess in either case, it's an answer technically.

00:04:14
Speaker 1: Depends on what really is an answer anyway, man, there's a deep question in philosophy.

00:04:19
Speaker 2: But in either case, we talk about questions.

00:04:22
Speaker 1: We do. We play your questions, we talk about them. We hope to give you as much of an answer as we can. Not every question in science has an answer, but we want to take you at least to the forefront of human understanding and ignorance so you can share in our confusion.

00:04:36
Speaker 2: Yeah, and sometimes the answer is choco lily smooth, and sometimes the answer is a little spicy, little piquant.

00:04:43
Speaker 1: Either way, we love hearing your questions, we love answering them, we love talking about them. Please do keep sending them in.

00:04:49
Speaker 2: And also, I should say I'm a little offended at your negative comments about vanilla. It is one of my favorite flavor.

00:04:54
Speaker 1: You're the one who said that would be the most boring outcome to a black hole. I didn't say vanilla was boring.

00:05:01
Speaker 2: Well, what I mean is like, if the flavor of something as complex and mysterious as a black hole, it just came down to one flavor. I mean, I think vanilla would be the best case scenario, but it's not the most complex as so you could.

00:05:16
Speaker 1: Get it'd be pretty fascinating though. If black holes tasted familiar, you took a bite of a black hole, you're like, hmm, tastes like pineapple, that would be very surprising.

00:05:24
Speaker 2: Let's break this down, Daniel, how would you even taste a black hole because you can't take a scoop of it out of the black hole, right, it's the whole point of a black hole. Well, you'd have to go It's the only way to taste a black hole, is, Yeah, is to go inside of a black hole. That's the only way to sample what's inside of a black hole. Yeah, But then you could never get out. You can never even if you find out what it tastes like, you could never tell anyone unless the other person is there with you.

00:05:44
Speaker 1: You could take a bite of a cosmic pineapple. Maybe singularities taste like cherries, who knows, But yeah, you'd have to be inside the black hole to even take that bite, and.

00:05:54
Speaker 2: You could only tell people who are in the black hole with you.

00:05:56
Speaker 1: Right, the first real black hole club is you don't talk about black hole.

00:06:00
Speaker 2: No, you could, but then only people in the club can find out.

00:06:03
Speaker 1: Yeah, that's right, very secret.

00:06:05
Speaker 2: There's like a warmhole in the middle. I guess you could yes, transmit that information, or.

00:06:10
Speaker 1: If it's possible to encode the information in the pattern of hawking radiation, like some theories of quantum gravity suggest, then maybe you could tell everybody else what black holes taste like.

00:06:18
Speaker 2: Oh so wait, the first rule of a black hole is not that you can't ever get out of the black hole.

00:06:22
Speaker 1: You already broke the rules quantum mechanics. Less you break all sorts of rules. Man, it's wonderful. But anyway, we're here to answer other people's questions, not talk about the flavor of black holes.

00:06:32
Speaker 2: I don't know. I imagine this is a question for a lot of people. I mean, you brought it up.

00:06:35
Speaker 1: I did, Yes, I did bring it up.

00:06:37
Speaker 2: You're curious about it.

00:06:38
Speaker 1: But I'm still not taking about that black hole. I'm sending you up.

00:06:41
Speaker 2: Maybe I'll take more of it like a slurp. That's these more cautious.

00:06:44
Speaker 1: Well, I was inspired to think about tasting things by the phrasing of our first question.

00:06:49
Speaker 2: Yes, that's right, because today on the podcast we'll be tackling listener questions. Number fifty six Taste Edition. Is this the extra Spicy Edition, Extra Heavy Meal Edition? These are pretty heavy questions. We have a question here about a neutron star, about gravitational pressure, and about orbital dynamics. These are not light subjects you would have these appetizers.

00:07:16
Speaker 1: Know this is all heavy duty stuff.

00:07:19
Speaker 2: This is main course material here. Yeah, we like to answer questions here from our listeners, and so let's get down to our first question, and this one is from Drew Hi Daniel Jorge.

00:07:30
Speaker 3: I was listening to some of the older episodes and neutron stars kept coming up, and it seems like we always talk about a tablespoon or teaspoon of a neutron star material and how heavy and massive.

00:07:42
Speaker 2: That would be.

00:07:43
Speaker 4: And it got me to thinking, what would happen if we actually took that tablespoon or teaspoon of neutron star and dumped it into one of our oceans, And what would happen if we did it on land. I assume heat would be a major factor, but either way, that's my question.

00:08:02
Speaker 1: Let me know.

00:08:03
Speaker 2: Thanks. All right, this sounds like a terrible idea, which is why I'm glad you're asked us first. I'm glad he's not an experimental physicist who decided to try this out before asking anyone.

00:08:17
Speaker 1: And I love the impossible visual of this, you know, a teaspoon of neutron star dumping into the oceans. As if you could like hold a teaspoon of neutron star, like the spoon would be strong enough, or if you were holding it you might be like tempted to lick it or something.

00:08:31
Speaker 2: Well, I think that's what the question is all abouts. If you want to know what would happen could you take a teaspoon of a neutron star and what would happen if you brought it here to Earth.

00:08:39
Speaker 1: Yeah, it's a great question, and it really guessed at the heart of some mysteries of modern physics.

00:08:45
Speaker 2: All right, well break it down, Daniel. What is a neutron star?

00:08:48
Speaker 1: First of all, a neutron star is one of the possible end states of stars. Stars are big balls of gas that are compressed by gravity to a state where they can perform fusion at their core, creating heavier elements and also a lot of heat and radiation. But eventually that fusion runs out of fuel and gravity wins, collapsing the star. You can either get a white dwarf, which is like a really heavy lump of stuff, or you can get a neutron star if it's even heavier where it overcomes some of the degeneracy pressure and squeezes the electrons and protons down into neutrons, or if you have even more mass than gravity, totally wins and creates a black hole. So a neutron star is incredibly dense remnant of a star?

00:09:28
Speaker 2: Does it have to be the remnant of a star? You can make a neutron star potentially.

00:09:32
Speaker 1: Oh, yeah, you can make a neutron star. Step one is make a star.

00:09:35
Speaker 2: I mean, not necessarily star. I mean you could just take material and squeeze it down enough, and you potentially might make a neutron star.

00:09:41
Speaker 1: Right if you had like civilization HARDISHEV level three type abilities to do stellar engineering or something, then in principle, yeah, you can make one without making a star. But I think the recipe would be gather a star amount of material and let gravity squeeze it down into a neutron star. Maybe you could speed up the process by applying some external pressure.

00:10:00
Speaker 2: And why do we need the Kardashians for this, because they're so dense.

00:10:04
Speaker 1: So many jokes I'm not going to make there about the masses of various Kardashians. No Kardashev level of three. Oh Kardashev.

00:10:11
Speaker 2: Yes, I see, yes, you said that kind of fast, all right, So then a neutrons are is basically like kind of the heaviest or the densest thing you can have potentially in the universe before it turns into a black hole.

00:10:23
Speaker 1: Yeah, that's right. Remember that gravity is very powerful, but it's also super duper weak, so it's possible to overcome the effects of gravity, like you can overcome the effects of Earth's gravity is just by jumping. Your muscles are stronger than all the gravity on the Earth, And so the reason everything in the universe doesn't collapse into a black hole is because its structural strength can overcome gravity. So the Earth doesn't collapse into a black hole the size of a peanut because the strength of its material is more powerful than Earth's gravity.

00:10:50
Speaker 2: I mean, like the individual particles are repelling each other enough to fight the squeezing.

00:10:55
Speaker 1: Of gravity exactly. But as things get more mass, if you overcome the ability of those four resist So if you added enough mass to the Earth, for example, then it would overcome its structural strength and it would get squeeze down into something like a white dwarf. If you add even more mass than you overcome the next barrier and you get a neutron star. So each of these kinds of states represents overcoming one of these barriers in the battle against gravity, which it eventually will win and turn things into black holes.

00:11:23
Speaker 2: Now, wait, are you saying a neutron star is not stable, like it'll eventually collapse or can you have a neutron star lasting for a long time?

00:11:30
Speaker 1: Now, we think neutron stars are stable, but there are black holes out there, and eventually the black holes will just eat everything.

00:11:35
Speaker 2: Now, when you have a neutron star, did you just have the neutron star or is it like a giant cloud or blob of stuff with the neutron star in the center.

00:11:43
Speaker 1: Yeah, a lot of the material from the star is blown out. So often you have like a nebula with a neutron star at its heart, and.

00:11:49
Speaker 2: It's called a neutron star because basically all of the material in it has basically kind of degenerated to be neutrons.

00:11:57
Speaker 1: Yeah. You start out basically with protons and electrons and weaze them together and they do inverse beta decay into neutrons.

00:12:03
Speaker 2: You mean the electrons just disappear or they merge with protons.

00:12:07
Speaker 1: They merge with protons to make a neutron, So like a neutron will decay into a proton and an electron, and there's some neutrino accounting you've got to take care of also. But if you squeeze things down, the inverse can happen, and you can convert a proton and an electron into a neutron. But we don't actually know the state of matter inside a neutron star because it's so intense. The pressure is so great that gravity is powerful and the quantum forces are powerful, so both of those things are at play, and that's not something we know how to reconcile. So the heart of neutron stars really are getting at questions of like quantum gravity situations where you need to understand quantum mechanics and gravity.

00:12:40
Speaker 2: Wait, wait, are you saying that we don't know if neutron stars are made out of neutrons.

00:12:44
Speaker 1: We know there's a lot of neutrons in there, but as you get towards the center and the pressure gets really really high, we don't really know. If you can call them neutrons anymore because the neutrons get squeezed so closely together that like the difference between the quarks and one neutron and another neutron becomes artificial, and it might become like a cork gluon plasma. We talked about it in another episode. You might even get things like nuclear pasta weird new forms of matter that quarks and gluons can form under extreme pressure.

00:13:10
Speaker 2: And what would that pass the taste like very dense vanilla mint.

00:13:15
Speaker 1: Pineapple, I hope not squidd ink maybe.

00:13:18
Speaker 2: Or nothing or nothing because it's a neutron star.

00:13:20
Speaker 1: One of the fascinating things that matter can do is under high pressures, it can form new states. Like if you take carbon and you squeeze it with really high pressure, you get a diamond. But it doesn't always revert when you lower the pressure, Like you make a diamond, you bring it up to the surface of the Earth, it doesn't explode back into carbon. It retains that pressure. What we don't really know is what happens when you make neutron star stuff and then you take it out of the neutron star and put it somewhere else, like on Drew's teaspoon. Is it like a diamond of neutrons star material or does it explode back into a bunch of protons and electrons?

00:13:51
Speaker 2: Mmm, I feel like we skip the step there. So I guess first of all, the scenario drew withstinol was staying a teaspoon of a neutron star. So, since this is almost the densest stuff in the universe, how much does that teaspoon weight?

00:14:03
Speaker 1: So a teaspoon of neutron star material has the mass of like ten to the twelve kilograms. That's like a trillion kilograms. It's like a thousand times the mass of the Great Pyramid of Giza.

00:14:15
Speaker 2: Whoa, And this is like from the surface of the neutron star the center or is this just kind of like an average scoop.

00:14:22
Speaker 1: This is like an average scoop. It gets more dense at the core and less dense at the edge. But this is like roughly in the middle. But this stuff is like ten to the fifteen times denser than the Sun. It's really incredible. It's like ten to the seventeen kilograms per cubic meter.

00:14:37
Speaker 2: So the one teaspoon of neutron star you said weighs how many pyramids.

00:14:41
Speaker 1: Like about a thousand times the Great Pyramid of Giza.

00:14:44
Speaker 2: Wow, in one little tiny teaspoon. So first of all, I mean, let's forget the fact that it might be hard to take a scoop of a neutron star. But just bringing it to Earth, I mean you'd be carrying a huge amount of weight in this very small space, right, Like, it would probably be really hard to just like hold it.

00:14:59
Speaker 1: Up, very hard to accelerate it and to bring it to Earth and to gradually lower it down.

00:15:04
Speaker 2: Yeah, right, because it'd be sort of like balancing a thousand pyramids onto a little tiny point, right. It would probably break or crush anything you try to set it.

00:15:12
Speaker 1: On exactly, and if you accidentally dropped it while you were in orbit, it would plumb it towards the surface of the Earth and cause a lot of destruction.

00:15:20
Speaker 2: M because it has a lot of mass, right.

00:15:22
Speaker 1: It's very strong gravity.

00:15:24
Speaker 2: Okay, So let's say Drew brought a teaspoon of this stuff, brought it to Earth, and I think maybe the biggest question, as you said, is what would happen to that teaspoon when you first take it out of the nutron star? Because it was it's super dense because the forces in the neutron star are squeezing it together. When you take it out of the nutron star and nothing is squeezing that together, does it just explode or expand the.

00:15:45
Speaker 1: Short answer is that we don't know, because we don't understand the dynamics inside a neutron star. They are all sorts of theories for what's going on inside of it, nuclear pasta quarklow and plasma, other weird forms of matter. People are writing papers about this every day. Actually do a little bit of research on this topic myself, and there's just a lot of question marks because it's combining two of the hardest things in physics, general relativity, which is very difficult to do any calculations with, and the strong nuclear force, which is a huge headache to do any calculations with. So now you want to understand what's happening when these two things are both doing their thing, it's almost impossible. So we really just don't know. But I suspect that whatever is formed there is not stable, that if you suddenly transport it to Earth, you like build a wormhole between the center of the neutron star and Drew's kitchen and you got a tea spoons worth of material, they would not be stable that it would explode.

00:16:33
Speaker 2: Right, because there's all this stuff squeezing it together and suddenly nothing squeezing it together. So potentially it might explode. But as you said, it could also maybe be like a diamond, where it is super squeeze carbon, but it's somehow clicked into place, and diamonds don't explode.

00:16:47
Speaker 1: Diamonds do not explode.

00:16:48
Speaker 2: Yes, that's true, and so how bad would it be for this thing to explode here on Earth?

00:16:52
Speaker 1: It would be really really bad. Material with that density has really high kinetic energy, like the particles inside of it are whizzing around with incredible velocity kinetic energy.

00:17:03
Speaker 2: Why does it necessarily have kinetic energy?

00:17:05
Speaker 1: Well, think about how it was formed. You took a thousand pyramids of gizo's worth of hydrogen, for example, as a big diffuse gas, and you squeeze it down to a t spoon. To do that, you're pushing on it. If you have walls, for example, every time you're pushing those walls closer and closer, you're pushing on those particles. So applying that pressure to squeeze this down pushes on all the particles and now they have very very high energy.

00:17:27
Speaker 2: Right, that's find you maybe form a neutron star. But what if I take my a neutron star and I freeze it before taking a scoop out of it? Did I just blow your mind?

00:17:38
Speaker 1: Hm? I love the idea of like deep freezing a bit of neutron star, and then you could like deep fry it, and then you could take a bite out of.

00:17:44
Speaker 2: It, deep freeze the neutron star, yet the whole star, and then you take a scoop.

00:17:49
Speaker 1: I think it's impossible to cool down a neutron star because of the quantum mechanics of neutrons. The issue is that neutrons are fermions like electrons and other particles. You can't have two of them in the same state, and so that creates a minimum temperature for neutron stars because basically, if you have one neutron in like a really low energy state, then you can't have another one. The next one has to get into the next high energy state, so there's like a minimum energy.

00:18:13
Speaker 2: What would happen if you tried to freeze a neutron star.

00:18:15
Speaker 1: You just couldn't get that neutron into a lower state, like, they just don't go into that lower state if it's already occupied. It's like trying to get two electrons into the same state of hydrogen. No amount of cooling will get them that low. The electrons will just refuse to do that. They won't give up the energy.

00:18:30
Speaker 2: They can't sort of like maybe how you can't freeze an atom technically, right, at some point the electrons are still orbiting around the nucleus.

00:18:40
Speaker 1: And this actually touches on the topic of our next question.

00:18:42
Speaker 2: All right, So, continuing with the scoop of a neutron star, you're saying it would have a lot of compressed energy in there, and so when you take away the gravity, maybe all that energy would be released.

00:18:52
Speaker 1: Yeah, exactly. And the amount of energy is really incredible. It's a little bit of calculation. It's more energy than the sun emits of second. It's about equivalent to one billion atomic bombs.

00:19:05
Speaker 2: WHOA, that would be bad news for all of us.

00:19:09
Speaker 1: Yes, very very bad news for everybody. Neutrons are very dangerous. They are hadronic particles and if they go through you, they don't have electric charge. But they're basically just like tiny bullets and they can really do a lot of damage. And if you have a bunch of neutrons really high compressed and then they explode with high speed, you have like ten to the thirty eight neutrons traveling at some significant fraction of the speed of light. It's an enormous amount of energy deposited everywhere. And so you might wonder like, oh, is it going to drop through the Earth or whatever. No, it's just going to explode and basically vaporize a huge chunk of the Earth.

00:19:40
Speaker 2: Well, I guess you know, if you are able to get it front the neutron star to the Earth, it must be sort of stable though, right.

00:19:48
Speaker 1: It depends like maybe you used a wormhole. So you just like open up a wormhole between the center of the neutron star and Drew's kitchen and then a little bit leak through.

00:19:56
Speaker 2: Oh I see if you just use magic is what you're saying.

00:19:59
Speaker 1: Wormhold or not magic. I think it's probably impossible to take a spoonfull of neutron star and transport it through space to Drew's kitchen. I think that's probably impossible.

00:20:09
Speaker 2: Well, I guess either way, it's bad news.

00:20:11
Speaker 1: It's bad news and the rest of us. It would be like a huge asteroid hitting the Earth, something like several thousand times the devastation of the dinosaur killer that hit sixty five million years ago. So definitely bad news.

00:20:25
Speaker 2: Like maybe at the scale of the asteroid or rock that created the Moon perhaps.

00:20:29
Speaker 1: Or more maybe not that dramatic, but almost that scale. Yes, Like the Earth would look different. You could see it from space for sure, bad news for Drew and all of his neighbors and the rest of us on Earth.

00:20:41
Speaker 2: I see, all right, well, I guess the answer for drewis, Hey, Drew, maybe you should eat the teaspoon before you bring it to Earth.

00:20:48
Speaker 1: Don't order a teaspoon of neutron star on Instacart please.

00:20:52
Speaker 2: That's right on wormhold card. Exact age would not be good. All right, thanks Drew for that question. Let's get to our other questions here today. We have questions about gravity pressure and about orbital dynamics, say said heavy stuff. We'll get to that, but first let's take a quick break. We're taking listener questions here today, and our next question comes from Nol from Perth.

00:21:24
Speaker 5: Good day, Daniel, and Hi, this is Noel from Perth, Australia. I was sitting here thinking one day I wonder if matter under extreme pressure can ever be stopped. What I mean by that is, is there ever a point where we have so much gravitational pressure that all movement of matter can be frozen in time? Is that possible? Would love to hear your answer on this one. Thank you very much and love hearing your podcast. Cheers mate.

00:21:53
Speaker 2: See all right, gooday to two nol or good eight. I guess technically I'm not quite sure I understood this question. What do you think nol here is asking.

00:22:02
Speaker 1: I think Noel has heard that you can't cool matter down so that things actually stop forever, like absolute zero is impossible in quantum mechanics. But he's wondering if instead you can use pressure. You could just like squeeze stuff down so that it stops moving.

00:22:16
Speaker 3: Oh.

00:22:17
Speaker 2: I see, so we're talking kind of about the same question we talked about just now in the other question, Yeah, which is like, what's the coldest that you can get something, especially if it's super dense like a neutron star.

00:22:28
Speaker 1: Yeah, and he's probably also wondering, like is matter moving inside a singularity inside a black hole? Oh?

00:22:34
Speaker 2: Really? That's in here also it's a very dense question.

00:22:38
Speaker 1: He's wondering about the extremes of gravitational pressure, are you I.

00:22:42
Speaker 2: See, I see. Well, I guess I wouldn't necessarily associate extreme pressure with things stopping. In fact, I kind of associate, you know, the intense gravity inside of the sun to like fusion and things just getting hotter and hotter, or like we talked about the neutron star, just gets hotter the more you compress it.

00:22:57
Speaker 1: Yeah, exactly. It's like if your toddler is going crazy and you lock them in the room, They're not necessarily just going to calm down. They might just bounce off the walls. Same thing happens if you take an electron and try to squeeze it down to a smaller and smaller space.

00:23:10
Speaker 2: Well, let's maybe start with the concept that he talks about, which is getting things to stop. And I guess what he means is like cooling things down or squeezing them so much where they don't have any kinetic energy or they're not moving.

00:23:21
Speaker 1: Yeah, he talks about it being frozen in time, so no kinetic energy. So you want to simultaneously squeeze stuff down plus pull out that kinetic energy. Somehow cool it and squeeze it at the same time.

00:23:33
Speaker 2: What do you think frozen in time means doesn't change over time at all?

00:23:36
Speaker 1: Yeah exactly, that's just not moving. I think he's interested in absolute zero essentially, like finding a path to getting things completely frozen.

00:23:44
Speaker 3: Mmm.

00:23:45
Speaker 2: I see, But absolute zero does exist right in the universe.

00:23:49
Speaker 1: Absolute zero does exist, But quantum mechanics tells us it's impossible for anything to actually be stopped because that would violate some basic principles. There's a minimum amount of energy everything has to have in the universe according to quantum mechanics. So you can't actually ever get material to absolute zero.

00:24:04
Speaker 2: Like anything that has matter or substance to it, you can't freeze it down to zero. Is that things that are always going to be jiggling a little bit or moving or having some sort of minimum energy just from having the minimum quantum property.

00:24:18
Speaker 1: Yeah, exactly. And there's a few ways to think about that. One is in terms of the uncertainty principle, Like if something has zero energy, then you know its location and you know it's momentum both zero and you know both of those perfectly well, and that violates the uncertainty principle. So the uncertainty principle tells you if you locate something in one position, you squeeze it down super well, then the uncertainly on its momentum is infinite. Right, So essentially, squeezing something down to just one location you give it infinite temperature. So that tells you you can't. Another way to think about it is just in terms of the solutions of quantum fields, like what are quantum fields? These things that fill space and they vibrate, but if you look at the mathematics of them, they can vibrate in various ways, but they can never have zero energy. That configuration with the field has zero energy is not a solution to the wave equations. The wave equations require a minimum amount of buzzing in these fields at all times.

00:25:09
Speaker 2: But then no, I guess is imagining a scenario where maybe you squeeze things so much that they can't move anymore. Like, for example, if you take a gas and you squeeze it. As a gas, it's moving, all the particles in it are moving a lot, but as you squeeze it, maybe it turns first into I guess, liquid hydrogen, which makes the molecules there moveless, and then you keep squeezing it, you'll actually get like hydrogen ice, right, and then the atoms are almost not moving at all, maybe they're still vibrating. And so the question is, maybe if you keep squeezing beyond solid, can you actually make the molecules and the atoms in there stop?

00:25:42
Speaker 1: Yeah, exactly. It's sort of a fund mental question. And you know, if you put quantum mechanics aside and just think about like the classical universe, where everything has like a location and path through space and time, then there's no issue. You could take something, you could squeeze it down, you could give it zero energy, not a problem at all. If you think of tiny particles, is just like little grains of sand. Right. The issue really is with quantum mechanics that these particles are not little grains of sand. They follow different rules, so they do all have minimum energy, and they have uncertainty on them, and they also follow these other rules like the poly exclusion principle. If you have a big pile of electrons, you can't squeeze them all down to zero energy because they won't be in the same energy level. Fermions will not allow another fermion in the same energy level, the same quantum state. So there's a minimum energy to all those electrons. That's sometimes called electron degeneracy pressure. It's one of the things that keeps a white dwarf from collapsing, for example.

00:26:36
Speaker 2: But I guess maybe, just as a matter of exercise, let's maybe follow Knowle's reasoning here and let's just keep squeezing things, right, So if you squeeze things more, they'll get solid. Then eventually they'll turn into neutron stars, right, which is what we talked about in the previous question.

00:26:51
Speaker 1: Yeah, exactly, Then be neutron stars. And now we're already beyond level of knowledge because we don't know what's going on inside a neutron star. Maybe there's nuclear pasta, maybe there's weird new kinds of crystals, maybe weird neutron diamonds.

00:27:03
Speaker 2: We just don't know, right, So is it possible that inside of an entrance star things stop, like things click into place in such a way that they kind of have zero energy.

00:27:12
Speaker 1: I think the most correct answer is to just say we don't know, because it depends on the details of quantum gravity, like what happens to particles when you're under really intense pressure and really intense gravity. We just don't know the answer to that. We need a theory of quantum gravity that tells us how to do gravitational calculations for particles. So we're just speculating, and it might be that there are some theories of quantum gravity that reveal the universe is very different from the way that we expect. That we can't just extrapolate our quantum rules down to very very high pressures and very high densities.

00:27:41
Speaker 2: Any like, if we keep squeezing something, maybe at some point the Heisenberg uncertainty principle doesn't work. M m like extreme gravity is maybe Heisenberg takesification.

00:27:50
Speaker 1: Yeah, Like, let me say it this way. General relativity says, yes, that's no problem. You can squeeze things down to infinite density and zero velocity. That's the singularity at the heart of a black hole, for example. CIS says No, as you squeeze things down, they get higher and higher energy, and so it's impossible to get things down to zero velocity. But the crux is which wins at these very high I densities. What's actually going on inside a black hole? As you've pointed out, many times. I'm biased towards quantum mechanics, and I suspect that we can extrapolate from quantum mechanics and think that whatever is going on at the heart of black holes or in neutron stars or in Nole's kitchen is going to be more like quantum mechanics than like general relativity. But I could be wrong, and it could be very surprising, and it could be more gravitational, more classical than we expect.

00:28:31
Speaker 2: Yeah, yeah, no, I'm definitely in the vanilla camp. I think vanilla wins at the end, meaning like maybe general relativity wins at the end, and maybe things do freeze and then stop moving, right, yeah, or you know, at some point you make a black hole if you squeeze things enough, which technically does freeze time. Right, isn't time frozen on the surface of a black hole? And definitely just inside of a black hole, is in time technically frozen.

00:28:54
Speaker 1: M Yes. Absolutely. Then again, we have all sorts of reasons why we think general relativity must to be wrong and can't be an accurate description of what's going on in the universe. But again, it's a big open question. We don't know the answer to these things. And we could certainly be wrong. All we can do right now is extrapolate from quantum mechanics, or extrapolate from general relativity, or wait until some genius combines the two and gives us a picture of quantum gravity.

00:29:17
Speaker 2: Mmm, so somebody makes neopolitan ice cream out of a black hole? No, but with the black hole, don't we know they look like that. Time stops on the surface of a black hole, so it wouldn't that technically freeze things? As Noel suggests.

00:29:31
Speaker 1: Time stops at the event horizon for a distant observer. For somebody falling into a black hole, time doesn't stop, and you can continue to do your dance, or eat your ice cream, or take a bite out of whatever else you see inside the black hole.

00:29:42
Speaker 2: Yeah, but to us, they would appear frozen.

00:29:44
Speaker 1: To us, they would appear frozen. Yes, but again that violates quantum mechanics. So who knows if it's really true? But yes, general relativity allows things to freeze to zero velocity.

00:29:53
Speaker 2: All right, Well, no, I guess that's the answer for you. Daniel doesn't know. Nobody knows on that angel question of what's going on inside of a black hole, because that's the ultimate I guess a squeezing of things due to gravitational pressure.

00:30:08
Speaker 1: I feel like as this podcast goes along, more and more the questions have the same answer, which is, we don't know because we don't know quantum gravity.

00:30:15
Speaker 2: Gosh, why did you just fix that? Daniel, let's figure it out. What are you doing spending time on this podcast when you can be solving the biggest question we have?

00:30:24
Speaker 1: Yeah, well, just before we recorded this, I was eating some pineapple cake and trying to think deeply about the nature of condensed matter. But I didn't quite figure it out.

00:30:31
Speaker 2: It didn't work. Huh. Just gonna have to keep on trying. Yeah, I'm sure your doctor will have something to say about that. All right, well, thanks for that question. Now, now let's get to our last question. This one is about orbital dynamics and shared atmosphere, so let's explore that out there in space. But first let's take another quick break.

00:31:03
Speaker 5: All right.

00:31:04
Speaker 2: We're askering listener questions here today, and our last question here comes from Joe Hey.

00:31:08
Speaker 6: Daniel, and Jorge. I had a question about something I saw on the show Foundation, where a planet and its moon shared an atmosphere, and I was wondering if that's actually possible. I look forward to hearing what you guys have to say.

00:31:21
Speaker 2: All right, cool question. That's a fun show. Do you watch that show, Daniel?

00:31:24
Speaker 1: Yeah, I read all these books and I watched the show. It's a lot of fun and I love that scene that he's talking about.

00:31:30
Speaker 2: So I read all the books several times when I was younger, and I was very excited about the show. Loved the first season. Second season, I was like, I'm out. It just deviated a little bit too much from the books for my day. So I guess this is thank be a spoiler, but I'm probably not gonna watch it, so I guess we can talk about it.

00:31:47
Speaker 1: Yeah, this doesn't really spoil any of the plot. It's just a really cool, clever scene. One of the things I liked about the show is that it did dv from the books. It sort of lives in the same universe as the books, but doesn't just take those storylines, which I thought.

00:31:59
Speaker 2: Was creety, You mean it has the same foundation exactly.

00:32:04
Speaker 1: It's fundamentally the same universe.

00:32:06
Speaker 2: Except people have crazy superpowers.

00:32:07
Speaker 1: Right. Yeah, But here Joe's talking about a really striking scene where there's a herd of some kind of animal and they take a running leap off of a hill and they land on a moon that's orbiting very very close by. So there's like continuous atmosphere between the planet and its moon, so that you can jump from one to the other.

00:32:25
Speaker 2: What how big is this moon in this planet, like sort of Earth size or what.

00:32:29
Speaker 1: Yeah, that's a great question. I don't remember the details. It was definitely pretty big in the sky. So this is a real size planet and a real size moon, I mean big enough to have an atmosphere.

00:32:39
Speaker 2: So it's more like a dual planet, kind of like a twin planet sort of.

00:32:43
Speaker 1: One of them was definitely smaller than the other, so I'm sure astronomers would have a fun time arguing about whether one was the moon or they were binary planets.

00:32:50
Speaker 2: To be like, that's not a moon. So then in the show, there's a planet with a large sized moon that is orbiting around the planet, but it's so close that you can sort of jump between them.

00:33:02
Speaker 1: Yeah, exactly.

00:33:03
Speaker 2: Now there's two things here, like one is this technically possible? Like can you have a moon that big orbiting that close to a planet? And the other question, I guess is would they share an atmosphere.

00:33:14
Speaker 1: Yeah, exactly. So the first question has to do basically with gravitational tidal forces, because if you just think about the planets as points, there's no reason why they can't orbit super duper close to each other. Like gravity works really far away, gravity works really close together. You can get two things close together and orbiting. The reason it might not work is because of the tidal forces.

00:33:34
Speaker 2: Wait, wait, you're saying, technically it's possible, like our Moon could orbit really close to us enough for us to jump to it potentially.

00:33:41
Speaker 1: Potentially if you ignore the tidal forces. The tidal forces are the crux of the issue.

00:33:45
Speaker 2: But something that big orbiting wouldn't it have to be going super duper fast, Like what are the orbital dynamics there?

00:33:51
Speaker 1: Yes, absolutely, the closer you get, the smaller the radio is the higher of the velocity. So if you were like orbiting the Earth one meter above its surface, you'd have to go very very fast, where you could be moving more slowly if you were further away.

00:34:03
Speaker 2: I feel like I've seen a YouTube video about this, which I know is not the most reliable source, but I think at some point like you wouldn't get a stable orbit like at some point the Moon would start to spiral in and fall to the Earth. Maybe there's no actual orbit that could make that work.

00:34:18
Speaker 1: Well, the equations are pretty simple if you're talking about just two points, and if you're ignoring things like drag and tidle forces, then you can have orbits at any stage, Like you could have two grains of sand orbiting each other in deep space very close together.

00:34:31
Speaker 2: But wouldn't they be going super duper fast or wouldn't the orbits be like super stretched out.

00:34:37
Speaker 1: Yeah, they certainly could. But if again, if it's just two points with no drag, no friction, no tidle forces, then the math is pretty simple.

00:34:43
Speaker 2: All right, so it sounds like it's possible, but you're saying tidle forces would make this impossible exactly.

00:34:48
Speaker 1: You can calculate the gravity between two points. That's pretty simple. But now take one of those things and say what if it's not a point, what if it has real size to it? You know, inflate it from a point to like a basketball or a moon or whatever. Now, part of that thing is closer to the object that's orbiting, and part of it's further away. You have like the near side and the far side. Because gravity depends on distance, those two pieces are now feeling different amounts of gravity. The closer side of the Moon feels Earth's gravity more than the far side of the Moon, for example, and that's the tidal force. The difference between the strength of gravity on one side and the other is effectively a force pulling that object apart.

00:35:22
Speaker 2: So there would be a force on the Moon splitting it into two.

00:35:26
Speaker 1: Yeah exactly. And that's why as you approach a black hole, for example, the tidal forces can pull you apart because in really intense gravity, the difference between the force on your feet and the force on your head can be enough to overcome the structural integrity of your body. And this is why, for example, some planets have rings and some planets have moons, because if the stuff is too close to the planet, it's within some limit called the Roche limit, then the tidal forces of the planet would tear apart any moon and turn it into rings.

00:35:53
Speaker 2: M So I guess if this moon is not you know, stick enough or dense enough or strong enough, it would break apart.

00:35:59
Speaker 1: Yeah, exactly. And so it depends on the structural strength of the moon. Like if you have a moon made of water. It's much easier to tear apart than if you had a moon made of diamond, for example. So it's not just like a hard and fast limit around any object. You have to take intoccount lots of different things. It's a rough guide, so it depends on the masses of the planets and the rigidity the satellite. But I looked into a few calculations, and if you had two earths, for example, and estimating what their structural integrity are, the two earths could orbit each other as long as the surfaces were more than one thousand kilometers apart.

00:36:28
Speaker 2: What which is very little, right.

00:36:30
Speaker 1: Yeah, it's like a sixth of the radius of the Earth. Wow, so you couldn't jump a thousand kilometers, but a thousand kilometers is not that far. The Earth would be really big in the sky.

00:36:39
Speaker 2: Well, you would only need to jump five hundred kilometers because then you would get sucked into the gravity of the other planet.

00:36:46
Speaker 1: That's true. But if you jump five hundred kilometers and you got stuck there, you'd be like right between the gravity of the two I guess that would be kind of cool.

00:36:52
Speaker 2: Also, well, it would be kind of unstable, Like how fast would these two earths be orbiting around each other. Did you calculate that?

00:36:57
Speaker 1: I didn't calculate that, But it would be very very.

00:36:59
Speaker 2: Fast, super duper fast.

00:37:01
Speaker 1: Right, We're duper fast exactly because they have to avoid falling into each other.

00:37:05
Speaker 2: Right, That's what I was trying to say earlier, Like, at some point these orbits get unreasonably fast.

00:37:10
Speaker 1: I guess there could be a limit at the speed of light, right, So there might be some radius at which things need to go faster than the speed of light to avoid falling in and then there's no orbit. Maybe that's what you're referring to earlier.

00:37:21
Speaker 2: Or you know, at some point you're just spinning too fast, everything would fly off the surface of the Earth.

00:37:25
Speaker 1: Yeah, that's true.

00:37:26
Speaker 2: Or that you wouldn't be able to hold an atmosphere maybe, Yeah.

00:37:28
Speaker 1: The atmosphere is definitely an issue also because an atmosphere provides drag, right, And so if the Earth has an atmosphere and the other Earth has an atmosphere and they're that close together, then they're going to be dragging on each other. They're not just flying through empty space conserving their kinetic energy. They're losing energy the same way that like the Iss loses energy as it goes around the Earth because it's not in very high orbit, and so there's a little bit of drag there and has to constantly like bump itself up to avoid falling into the Earth. We have an atmosphere and the other Earth has an atmosphere. We're orbiting each other that close, we're going to be dragging on you each other a little bit.

00:38:01
Speaker 2: Okay, but it sounds like you're saying it is kind of possible if this Moon is made out of diamonds and it's okay that it's going so fast. Yeah, maybe we don't have such a need for an atmosphere between these two planets.

00:38:12
Speaker 1: But there's also maybe a solution there, like if you could end up in like a geosynchronous orbit and get tidal locking, like imagine the Moon is basically always above the same spot on the Earth, you're not actually dragging through the atmosphere. And if you get tidal locking, so they're not spinning a relative to each other, the two faces of the objects are facing each other constantly, then you could imagine having an atmosphere. You wouldn't be dragging through that atmosphere. The atmosphere would be spinning with the combined Earth Moon system.

00:38:39
Speaker 2: So if the Moon is made out of diamonds and we're tidally logged, meaning that the atmosphere is spinning around with the Moon, then you're saying it's possible. But even if you're going super super fast like I said earlier, wouldn't that blow away the atmosphere.

00:38:52
Speaker 1: If you want to be really close, then you can't be in geosynchronous orbit at the same time. But if you were willing to get a little bit further away, so the Moon was always above the same location in the atmosphere, then it wouldn't be moving through our atmosphere, so it wouldn't be blowing away all right.

00:39:08
Speaker 2: So it sounds like the answer is, yes, it's possible.

00:39:10
Speaker 1: I think it is possible. I think it's very unlikely for it to happen, though. I think this wouldn't form naturally. You'd have to like capture a moon that would have to come at exactly the right orbit because it need be perfectly circular. You know, if it goes like elliptical at all, then it's going like in and out of the atmosphere. It's going to be dragging. So this seems very very unlikely to ever see in the universe, even if you could make all the equations work.

00:39:33
Speaker 2: Oh, I see you were saying another possibilities that maybe this moon is more like a visitor every once in a while, Like it's in a very elliptical orbit, and sometimes it's really far away, and sometimes it comes really close enough for you to maybe jump from one to the other.

00:39:46
Speaker 1: Now I was actually saying the opposite. I was saying that in order for this to be stable, it have to be almost perfectly circular orbit, because if it's elliptical and it comes that close, then it's going to be dragging through the atmosphere. What you want is a really stable setup that never changes, and to get a the circular orbit is very challenging. You basically have to capture a moon in exactly the right situation.

00:40:06
Speaker 2: Well, I guess you mean by like having a constant bridge between the two planets, But maybe I mean I haven't seen the show, but maybe this only happened once in a while.

00:40:14
Speaker 1: Yeah, I think, Like again, if you had a Kardashev level three civilization, you might be able to engineer this, But I wouldn't expect to find this naturally happening in the universe.

00:40:21
Speaker 2: What if you're a Kardashian level seven planet.

00:40:25
Speaker 1: And your whole planet is made of chocolate cake.

00:40:28
Speaker 2: You can have a lot of hot air perhaps, all right, well, I guess he asked for Joe is Yeah, the show got something that is plausible, right, Yeah.

00:40:35
Speaker 1: If you are a Kardashian level seven civilization and you have moons made of diamonds, if you got that much bling, then yeah, you might be able to pull it off.

00:40:43
Speaker 2: And things are kind of perfectly locked in and spinning slow enough, and it's not spinning fast enough to blow away your atmosphere. It's potentially possible.

00:40:51
Speaker 1: It is potentially possible. Yeah, good luck, Joe.

00:40:54
Speaker 2: Well, I guess the problem is he would have to jump up a lot. All right, Well, that answers all of our questions here today. Thanks to everyone who asks questions.

00:41:01
Speaker 1: Thanks very much to everybody who shares your curiosity. It's the reason why we do this podcast, and it's the reason why science moves forward. It's our combined curiosity as a human species that lets us explore the universe. So thanks everyone for your support.

00:41:15
Speaker 2: We hope you enjoyed that. Thanks for joining us. See you next.

00:41:18
Speaker 1: Time for more science and curiosity. Come find us on social media, where we answer questions and post videos. We're on Twitter, Discorg, Insta, and now TikTok. Thanks for listening and remember that Daniel and Jorge Explain the Universe is a production of iHeartRadio. For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows.