Daniel and Kelly’s Extraordinary Universe - Listener Questions 60,491: Mini solar systems, greek physics and black holes!

Episode Date: June 20, 2024

Daniel and Jorge answer questions from listeners like you! Send your questions to [e-mail] omnystudio.com/listener for privacy information.

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A message from NHTSA and the ad council. Hey, Daniel, so we're answering more listener questions today? Oh, yes, we are. What number is it today? You know, I sort of gave up on giving them numbers in order. What? I figured, you know, we just go on vibes rather than being limited by the traditional numbering system. Hmm.

So we're just doing random numbers now, or are there secret codes embedded in the numbers? I'm not just going to give that answer away right now. Hmm. I see. So you were just picking numbers out of the air. Just the same way we answer questions, picking answers out of the air. And sometimes it aligns with reality. You're just a physicist typing on a typewriter.

One of many. And statistically, eventually, one of you will type out the answers to the universe. Maybe it'll be the number of this episode. Hi, I'm Jorge, a cartoonist, and the author of Oliver's Great Big Universe. Hi, I'm Daniel. I'm a particle physicist, a professor of Oliver's great big universe. Hi, I'm Daniel. I'm a particle physicist, a professor at UC Irvine, and I hope to one day type in the true explanation for the universe. Like you come up with it yourself or are you just taking notes? Well, you know, Mozart said he was basically taking dictation from God. So maybe I can just be a

vessel for the truth. I see you're born again. Is that what's going on? If I could one day be the Mozart of physics, I feel like that would be pretty good. Maybe they'll call Mozart the white sin of music. Oh, man, that's so ridiculous. I can't even laugh about it. I just blew your mind. But you've got to dream big, Daniel. That's like at my university, Rice, they got tired of people calling them the Harvard of the South.

So they printed up a bunch shirts saying Harvard is the Rice of the North. Yeah, aspirational T-shirts. Yeah, it's a clever joke. Not really, folks. So if you're the Mozart of physics, would that make me the Solieri of physics? Or am I the Mozart of podcast hosting? No, man, you're the Beethoven of cartooning. Oh, there you go.

I think maybe we should get Bach to physics, though. Or maybe there's a bag of basket weaving already. But anyways, welcome to our podcast, Daniel and Jorge, Explain the Universe, a production of IHeartRadio. in which we do our best to compose a symphony of understanding to bring into harmony your brain with the universe we think that everything that's out there is somehow following physical laws laws that are rational that are mathematical that makes sense to our tiny little human brains our goal is to bring you up to speed with a current effort to write down the opera of the universe and perform it for you that's right we try to belt out the melody of the loss of physics and also sing the praises of the amazing scientists that are out there trying to discover what is the song of the universe and in what key is it in? Do you think when we have the final melodic understanding of the universe, we'll find it beautiful and harmonious?

What if it's like Philip Glass, just like a bunch of random notes? You mean like, are we going to like the music of the universe? Yeah. Or is it not going to be of our taste? Yeah, exactly. For the same reason that I wonder why we often find the earth beautiful, you know, random landscapes we're like oh wow look how pretty why do we find it pretty does that mean we're likely to find the explanations for the universe also to be pretty or beautiful or just sort of

subjectively appealing you mean to give it a thumbs down if you didn't like it you're like oh that's the universe swipe left no thanks yeah i wonder if there are aliens out there that have evolved on their planet and they're like man this place is kind of a dump and they would also think the universe is just kind of blah, whereas it's sort of human to find our surroundings beautiful, or maybe it's not, maybe that's universal, who knows? Well, don't I say that beauty and our appreciation of what we find beautiful is maybe genetic? Like we've evolved to like certain colors and certain landscapes just because maybe it helps us survive, maybe only the physicists who find the universe beautiful are the ones who are going

to survive. How does it help us survive to like trees and hills? and waterfalls and that kind of stuff. Well, all of those things are signs of life, right? Like, it's helpful to like water and green, right? So what does it say about me that I like desert scenes? It means maybe you were born in Israel. Or have very dry tastes.

All of your ancestors that didn't like deserts probably didn't quite make it, maybe. Yeah, but none of my ancestors were born in the desert. So that doesn't really work. Anyway, it's not a time to dig into Daniel's evolutionary history. Yeah, the whites in line. It's not our topic here today. Our topic here today is questions, questions that scientists ask about the universe, that they ask about how things work,

and that trickle down to what everyday people are asking about their everyday lives. That's right. We are all curious about the music of the universe. Is it possible to make sense of it? Can we boil down everything that's out there into ideas that fit into our heads? and we encourage you to also ask questions about the nature of the universe and we want to hear your questions

we want to hear from you when things don't make sense when you need a little bit of help sticking ideas together and explaining everything that you see out there in the universe that's right sometimes people send those questions and sometimes we answer them here on the podcast

and so to the end the program we'll be tackling listener questions Now, Daniel, you gave this one an odd number. What was the number you gave it? 672,491. And that number was that random or is this your go-to random number? That's not my go-to random number.

Last time you were making fun of me for keeping track of these episodes since they've gotten to such a large number. So I decided, let's just go with vibes. And I felt like, what number does this episode want to be? And that's the number I typed out. Interesting. So this episode talked to you, even though we haven't recorded it yet. That's right. We hadn't yet recorded it, but of course I thought about it in advance.

And I thought, what number does this map to? If I had to pick a number for this episode, what would it be? And that's what came out. I see. So basically it means nothing. It's a one-dimensional representation of the high-dimensional complexity of the ideas in this episode. So, yeah, nothing. That's right, because we have no big ideas here on the program.

Only tiny ideas. Our big idea is to stimulate crazy questions and ideas in your mind out there. So thanks very much to everybody who sends in your questions. Don't Be Shy. Write to us to Questions at Danielanhorpe.com. We will answer everybody's questions and we might even pick yours to talk about here on the podcast. Yeah, like we're doing here today. And so today we have three great questions from listeners.

We have a question about microsolar systems, about whether the universe really is all Greek to physicists. And also a question about whether a black hole could destroy our planet. So cheerful topics. Cosmic importance. I am getting a 600,000, 472, 491 vibe here. Yeah, right. You're feeling it, aren't you?

You're feeling it. Mm-hmm. No, I was being totally. Totally fake there. So let's jump into our first question, and it comes from Tim. Hey, Daniel. I'm curious if there is such a question. a thing as a small solar system out there somewhere, maybe a place where the planets are the size

of marbles or something. I don't think so. I would imagine for this to happen, the star would have to form, which would require a lot of material. But I was just wondering if physics supported this. Thanks. All right. I think it's kind of ironic that Tim is asking about tiny solar systems, you know, tiny Tim. Tiny Tim is an ironic nickname, and Tim is like a very large dude. Huge dude. Like you to John from Rubbing Hood. Exactly.

But I love that Tim's question is about scales because I often wonder about that in the universe. Like why do things form in the universe at certain sizes and not other sizes? What does that reveal about the fundamental workings of the universe? Can you have solar systems that are super duper tiny and super duper huge? or is there a reason why galaxies tend to be a certain size and stars tend to be a certain size and planets a certain size?

What does that teach us about the fundamental rules of the universe and how they come into balance? Yeah, pretty interesting question about scales out there and I think we've tackled like what's the largest planet but this question is interesting because it talks about, you know, what is the smallest solar system you could have? Yeah, and there's a couple of different angles here

like, can you have a miniature sun? What is the smallest possible star you could form? And also how small can you make a planet? So I think both of these are really interesting questions. Yeah, pretty cool. So maybe let's tackle them one at a time. I mean, to have a solar system, you need a soul, a sun. So what's the smallest sun that you could make or have?

So if you want your solar system to have a sun in the middle of it, and by sun you mean something that's giving off energy, that's fusing, that's creating light and heavier elements at its core, then there is a minimum size there. Because you need enough stuff for gravity to have enough power to compress the core of this object to be high pressure and high temperature and for fusion to start. There's a reason, for example, why the sun is glowing and Jupiter is not, even though Jupiter is an enormous ball of hydrogen and other stuff, which could fuse. There isn't enough gravity in Jupiter to kick star fusion. At its core, there's not enough pressure and temperature to get that going.

So there is a threshold there. There is a minimum size you can have for a star to begin fusion. To begin, could there be one that has already started or what if you kickstarted one? Would it just blow everything away? Yeah, that's a cool question. Essentially, you're asking, could you ignite a star by injecting fusion into it and then let it go? The way you can, for example, have a piece of wood sitting in front of you. It's not burning.

But if you heat it up, then it will actually ignite and the rest of the fuel will burn. That, I don't think, will happen with fusion. because fusion needs a certain temperature and a certain pressure in order to be sustained. Like it'll just fizzle out if you don't maintain those conditions. You need a certain amount of density too, right? Yeah. Yeah, because fusion is hard to accomplish. You know, protons don't like to stick together with other protons.

They're both positively charged. They push against each other pretty hard. And so you've got to really squeeze them together. You've got to make sure it's enough density that have nowhere else to go in order for some fusion to happen. And even if you do that, mostly the protons are not fusion. fusing. That's why stars can burn for so long because there's comparatively little fusion happening. Most of the protons in the center of the sun are not fusing with other protons. It's a tiny fraction where that's actually accomplished. And that only happens when you have

an object like 80 times the mass of Jupiter. So you take Jupiter and you add like 79 more Jupiters, then you'd have enough mass to create the conditions at the core to make a star. like it'll start burning on its own for sure or do you still need something to kind of trigger it it'll start burning on its own and that's how all stars have started you know enough mass has coalesced together to create the conditions and then fusion is inevitable because there's enough protons banging against other protons and they fuse and they create energy and that sustains itself don't you need sometimes like a supernova to go off somewhere for you to start burning a star? You don't need a supernova for the star to start burning. You do need something to

trigger the gravitational runaway effect to form the star. Like you might have a huge cloud of gas and dust, you know, just like a big molecular cloud. What makes it actually collapse into a star is a little bit of a question. You might just have like a seed of a slightly heavier element from something else or you could have a shockwave from a supernova that just like triggers the collapse. That collapse still takes millions and millions of years. And then once the star forms, fusion starts at the core. Could a supernova trigger a tiny star to start burning or not? Or as he said, it just wouldn't sustain itself.

Yeah, it just wouldn't sustain itself because it's not hot enough and there's not enough pressure. So even if you, like, created your own fusion at the heart of a star, that heat would then just dissipate and wouldn't ignite more fusion. You need that temperature and that pressure. Like we do that here on Earth and magnetized fusion. and we can get a few fusion reactions to go, but unless you have enough temperature and pressure and density,

it doesn't ignite so that it's self-sustaining. So then what's the smallest star we could get or have in nature? So in order to have our kind of fusion, like the kind of fusion in our star, you need 80 times the mass of Jupiter. 80 times the mass, but then how big would that sun be? It wouldn't be 80 times bigger than Jupiter necessarily. It might be more compact.

Oh, that's right. It wouldn't be 80 times the volume of Jupiter because it'd be much more dense. But we have lots of small stars in the galaxy. In fact, our star is quite heavy and quite big compared to the average star, which is a red dwarf. So red dwarfs go down to like 10% of the mass of the sun. I'm asking like, how big is it? Is it bigger than Jupiter?

Is it smaller than Jupiter? What's the diameter of this smallest sun? So these things are not actually much bigger than Jupiter because as you add more mass to them, they just get denser and denser. In the same way that like a rocky planet can't get much bigger than Earth. that just gets denser and denser. There are stars out there whose radius is not much bigger than Jupiter, but they are burning.

There are red dwarfs and they have fusion at their core. So there wouldn't be much larger than Jupiter. They're just a lot more massive. Interesting. So the lower limit for the size of a star is about the size of Jupiter then. Yeah, order in magnitude, Jupiter.

So you couldn't have a solar system the size of marbles, but you could have a Jupiter-sized star at the heart of a solar system. But then what is a broad? round dwarf. Yeah. So if you require the kind of fusion that happens at the heart of our star, like true fusion, then you need that much mass. But it is possible to have a different kind of fusion happening at the heart of a star called deuterium fusion. And this happens sometimes in

objects we call brown dwarfs, which are just like big Jupiters. You have like 10 times the mass of Jupiter. Then you can get this other kind of nuclear fusion going where deuterium and protons combined to make helium three. And it like releases a little bit of huge. heat, but it's not as hot and not as productive as the kind of fusion that happens at the heart of our star. So brown dwarfs are called brown because they don't like glow. They don't give off photons the same way that red dwarfs and like yellow stars like our sun do. So they're more like simmering, but they're still burning inside. So what do they look like from the outside of you were standing next to one? Like a glowy Jupiter or what? There's a whole range of course

of brown dwarfs from low temperature to higher temperatures. Some of them do glow. They don't glow as bright as a sun, but they do glow brighter than Jupiter, of course. And of course, Jupiter gives off a lot of radiation on its own, but not like a brown dwarf. So yeah, it'd be sort of like intermediate between Jupiter and an actual sun. And how big would those be? Those are again, not much bigger than Jupiter, right? Because as you keep adding mass, it doesn't get larger, it just gets denser. But it would maybe only be like 10 times more massive than Jupiter, in which case, like a solar system with a star like that would maybe look a lot like Jupiter with its moons? Yeah, exactly. like that. So definitely not marble-sized, but smaller than our solar system for sure.

And would that sun give enough light to maybe sustain life? Or I guess it depends on what kind of life. There's a lot of debate about whether you can have life around a brown dwarf, whether there is sort of a habitable zone around there. I don't think we know enough about brown dwarfs to say for sure. I guess it maybe depends on the size of the planet, which is sort of Tim's other part of the question, which is maybe what's the smallest planet you could have? Yeah, this is a really interesting question. And it sort of comes down to the nature of like how you define a planet and also like how things get round. Because there's a lot of stuff out there in the solar system. You know, there's rocks like the earth, but there's also tiny little rocks just floating out there all the way

down from asteroids to meteorids to just like grains of dust. You might ask like, could you consider all those things planets? Well, we have requirements for. what a planet is. Planets have to orbit the sun, not some other object, which is like why the moon is not a planet. They also have to have enough gravity to make themselves round. Like if you're long in cigar shape, you're not a planet. This is a way to like avoid calling every tiny piece of dust that's orbiting the solar system a planet. And then the last requirement is that it has to clear its neighborhood. It has to be like the dominant gravitational thing in its neighborhood. And so that sort of sets an effective minimum size for a planet.

What would be that size? How many kilometers? Yeah, it's interesting. It depends a little bit on what it's made out of. Like, first of all, like, why does gravity make things round? Well, gravity makes things round because it likes to pull stuff down, you know? Imagine a spherical planet. Then you put a really tall mountain on it.

Eventually, gravity is going to pull that mountain down, especially if there's weathering effects on the planet that shake things or tectonics, et cetera. And by down, you mean like the center of whatever it is, right? Yeah. And so a sphere is like the gravitationally most stable object. If something is a perfect sphere, there's nowhere for anything to fall further down. So gravity likes to make things round, but it can't always do that, right? Like you take a pencil, a pencil has its own gravity, but not enough for gravity to make it into like a round ball, right?

So the amount of stuff you need in order to become round also depends a little bit on your mass. So as things get bigger, they have more gravity. and then gravity can, like, overcome the internal strength of an object and make it round. And so there's this size called, like, the potato radius around which gravity starts to round things out. I feel, though, that maybe that's a, like, a very human-centric definition of a planet. Like, we just want our planets to be round. But I wonder if there could be, you know, some body out there, some oddly shaped asteroid or

giant rock that maybe has evolved life. And then those aliens would call their little rock a planet, right? Or at least they would call it home. For sure, our definition of planet is human-centric. We made this thing up. And you're right. We're interested in planets because that's the first thing we noticed. We live on one.

To us, it's the most important part of the solar system. In reality, the solar system is filled with a huge, beautiful spectrum of different shaped objects. And this is just like people drawing dotted lines around certain kinds of them and then trying to defend those dotted lines, even though they're ridiculous and arbitrary. Yeah, you could probably have life form on not around objects. And then those aliens might think that our distinction is arbitrary. But, you know, Tim is a human. He's asking questions from a human perspective.

Is he now? I'm not vetting, but I'm guessing. I mean, if he's so tiny, then maybe he's. But the minimum size to make something round if you're like made of ice or water is like 400 kilometers. That's when things tend to form like potato shapes. If you're made of rock, it's about twice that big. And so you need like 800 kilometer wide stuff, tend to be pretty round.

So that's like the minimum size for an object for gravity to make it roundish. Oh. Well, I feel like maybe also your definition of a sun is also human-centric because that's what happens in our sun is the regular kind of fusion. But aren't some stars out there that astronomers call stars? Aren't they just like really hot rocks? Well, there are objects out there called white dwarfs, which are the remnants of stars. They're not burning anymore. There's no fusion happening at their core.

They're left over bits of stars that have ended their life. And those are called like white dwarfs. And you can see them in the night sky sometimes, right? I don't know that you can see them with a naked eye. We have detected a few of them, but they're pretty hard because they don't glow the same way that other stars do. But you still call them stars, though, right? Because they're emitting a lot of radiation. They do emit a lot of radiation.

I don't know if astronomers would call them stars or stellar remnants, but yeah, they're definitely related to stars. Because I wonder if you can just have maybe like a super duper hot marvel out there in space. And they have really, really tiny marvels orbiting around that hot marble. And then maybe you can call that a solar system. And maybe things have evolved in those teeny tiny marble planets and they're living in their little marble existence. Marveling at how small they are. Yeah, that's certainly possible. You could take a scoop of neutron star material, right?

That'd be a hot blob of stuff and you could put a few rocks in orbit around it. And you could call that a solar system, sure. Right. And then the thing in the middle, the hot stuff in the middle would be emitting light and that might sustain life in those little tiny rocks orbiting around it. Yeah, absolutely. I don't know how long that would last because you don't have that much stuff. And so it's going to radiate its heat out pretty fast. So I don't know if there's really time for life to evolve under those circumstances.

But, you know, if you're setting up a little vivarium in space, you could put some microbes on there. And then you could say, hey, look, I have a solar system with life on it. Yeah, yeah. It'd be like instead of sea monkeys, the space monkeys. Exactly. Space monkeys. Well, it sounds like the answer for Tim is that you could have a teeny tiny marble-sized solar system. Like, that's technically possible if you make it.

But maybe naturally occurring, it'd be kind of hard to. find something like that. Yeah, the universe has certain scales because of the forces of gravity and the strength of other materials gives us a minimum size for stars and a minimum size for planets. I think that's really interesting and it really does reveal something about the balance of the various forces in our universe. Yeah, because in the end, everything's limited by physics, right? Not our imagination. I'm certainly limited by physics, yeah. All right, well, thanks, Tim, for that question. Let's get to our next question. And this one is about the Greeks and what they knew about the universe. So we'll dig into that. But first, let's take a quick break.

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I thought about an offhand comment you made many episodes ago about things we still don't understand that the ancient Greeks didn't understand. So my question tonight is, what are the three most opaque things we still don't have a good answer for since the Greeks? And what is our best understanding of them now? And what was the most common ancient understanding of them? All right. Awesome question from Michael. He's basically asking, what is still all Greek to us? Yeah, apparently I made some comment about how there are still questions we haven't answered that the Greeks puzzled about, which is super awesome because it just means that some of these questions are timeless.

It also excites me to imagine that one day we might know the answers that in the future physicists and philosophers could look back at us and lump us in with like Aristotle as the clueless pre-knowledge kind of human, you know, before we really understood how things were. I see. Well, in that case, would being called the Aristotle of the 21st century be a good thing or a bad thing? Oh, yeah. Being the Aristotle of anything would be awesome. Wow, that deal is super smart. Yeah. Yeah. I wouldn't mind being the Aristotle of baking. I could be the Aristotle of Naps. That sounds wonderful. You do it in a toga. Anyways, right? All right. Well, I guess Michael's question is kind of a little bit straightforward. He's saying, what did we not know back then when the Greeks were? we're hanging on and thinking about the universe that we still don't know today. Yeah, great question, Michael. And the answer is pretty basic stuff, you know, questions that like your kids might ask you.

So question number one is like, how did the universe come to be? Did it come to be, right? Really, what is the age of the universe? What is its origin? This is not something we know the answer to and definitely something the Greeks didn't understand. Is there a record of the Greeks asking this question or wondering about? it? Oh, absolutely. And a lot of Greek mythology tries to explain how they thought the universe came to be. But their answers were not at all scientific. You know, as much as the Greeks made

progress in trying to understand the nature of the universe around them, the answers to the question of the origin of the universe really read like pure mythology. You know, they talk about gods that created the air, a god named chaos, and then another god that created the earth. And, you know, created Mount Olympus and then battles between these gods that formed the earth that they know about and then came forth darkness and then came forth the night.

The whole thing just reads like pure mythology. But I guess that's mythology and religion in Greek times, but I wonder if everyone back then believed these things, or did maybe like Aristotle think have other questions or maybe other theories about the beginning of the universe?

It's certainly not possible to know for sure what all the Greeks thought about these things because remember we have a tiny fragment of all the Greek writing. The Greeks were very prolific, thought about lots of things, wrote about a lot of things. And when we talk about our knowledge of the Greeks, we talk about what has survived. And that's really a tiny fraction of everything that was written. And in many cases, we have only like references to discussions about other topics that Aristotle mentioned. I'm sure that there are people thinking about the origin of the universe in Greek times that we have not captured. And actually, we live right now at a very exciting moment because we're using new technology to read ancient

scroll that have never been read before, ones that were burned in fire and in volcanic destructions where we have like the charred scroll, but we never have read it before because if you try to open it up, it just falls apart. And then they have new scanning technology that can read the scrolls without unrolling them. And so for the first time, we're discovering huge numbers. of new Greek writings, which is going to change completely our understanding of what the Greeks thought. But that said, even Aristotle and these other guys, they're basically philosophers. And at the time, these were the cutting edge ideas for how the universe came to be. Right, right.

Well, I wonder if he had asked Aristotle how he thought the universe began, what do you think he would say? Would he say Zeus? Or would he say, beats me. I suspect that Aristotle would say that he didn't know. I mean, Aristotle and the Greeks had trouble even conceiving. of the cosmos, like this question we're asking, where did the universe come from? They didn't even really understand the universe the same way that we do. They mostly thought about the earth and the solar system and a few stars.

They had no concept for even like how big the universe was, which we'll talk about in a minute. So it's sort of like asking him a question. He wouldn't even understand the question. Right, because they just didn't know as much as we do now. Yeah, exactly. And yet even today, we still don't have an answer to this question. we have a few ideas for where the universe came from we know at least how old it is like we can date the evolution of the universe back almost 14 billion years that's often quoted as the age of the

universe but we really don't know what came before that we don't know if there was a singularity and the universe was birthed somehow just before that as general relativity says or if there was some other weird state that predated that early hot moment that we can describe and the universe was like infinitely old before that in just some other form that's now beyond our understanding and capacity to describe. So we still don't have any idea really how the universe came to be, how long it's been around. We do have some concept for at least how old it must be. So that's something, but we're still struggling to answer this very basic question that the Greeks wondered about. Wait, wait, are you saying that maybe the Greeks could still be right?

He said that maybe it's all chaos before the Big Bang that might make them correct. I mean, in principle, it could all just be some simulation run by external super intelligent beings. And you could call those the Greek gods. So yeah, I guess in that sense, the Greeks could still be right. All right. Well, what's another question that we know that they were asking that we're still asking today? Another question is how much of the universe is there, right? How big is the universe?

And it's really fun to dig into like what they're. the Greeks thought about the universe because the Greeks were really careful and trying to understand the nature of the solar system, you know, the Earth and the planets and the sun, they're very geometrical, very mathematical about what they saw happening in the night sky. But then it's very difficult for them to think much beyond that, for them to cast their minds and understand how big the universe really was. Right. Well, back then, did they believe that the Earth was the center of the universe and that the Sun went around the Earth? Yeah, absolutely. They thought the Earth was the center of the solar system and everything went around the Earth.

And the reason they thought this is not because they were stupid. It's actually because they had a misunderstanding of how big the universe was. Like they considered the idea that maybe the Earth and all the other planets went around the sun. Absolutely. And their thinking was, well, if that's true, then we should see the stars move in the sky. And they were right because as the Earth moves around the sun, we do see the stars wiggle in the sky. It's called the parallax effect. Like we have a different perspective on the stars from

one side of the sun and the other. They looked up with the stars and they didn't see any wiggling because they didn't yet have the capacity to see the tiny wiggles of the star. Parallax effect was too small for humans to detect until like the 18th century. So they concluded from that that the earth was not moving around the sun. Wow. They actually had like data to back this up. Yeah, exactly. Their mistake was they thought the stars were super duper close and so the parallax should be pretty obvious. Actually, the stars are much, much further away than they could even conceive of. And so while the parallax effect is there, the stars are wiggling in the sky, they just couldn't see it.

So their mistake in thinking that the stars were much closer than they were is actually what led them to misunderstand the structure of our solar system. But it was very logical and very reasonable. Like just one tiny assumption, right? Like one assumption in their thinking and can really throw you off. Mm-hmm. And yet they also knew. that the Earth was tiny. We have evidence in their writing, like Marcus Aurelius said, quote, the whole Earth is a point

in space. And Aristotle described the Earth as, quote, no great size relative to the cosmos. So they knew that the Earth was a tiny dot in space. They just couldn't even conceive of how big that space actually was. They knew it was a dot, but actually, it's like a super duper tiny microdot. Exactly. It's like a dot of a dot. And today we know that the universe is much vaster than they could conceive of at least 92 billion light years across.

And yet we don't know if that entire observable universe is just a dot in some much vaster universe, potentially even infinite. So we basically have no clue as to the absolute answer to this question of how big is the universe. I see. So like proportionally, like if the size of the possible universe is from zero to infinity, we're still pretty clueless. Because infinity is infinity, so we have no idea, right? It could be that we have as much of an idea plus or minus a few percent than the Greeks. Well, you know, in the same way that we've made progress in understanding the age of the universe, we know at least how old it is, we know at least how big the universe is.

So we've made some measurable progress. But you're right, that could be a zero percent fraction of the actual size of the universe. All right, great question from Michael. It sounds like we still have a lot that we haven't figured out since the Greeks. Yeah, if we had Aristotle over for dinner, we could teach him a bunch of stuff, but I think in the end, he would still be unsatisfied because his fundamental questions have not yet been answered. Well, I feel like he would just spend the whole night playing with your iPhone. He'd be like, what is this magic? This eye? What? No, he'd probably follow

for a fishing scheme immediately and send all of our money to Nigeria or something. He'd be watching YouTube all night, probably. It makes me wonder if I had dinner with physicists from a thousand or 2,000 years in the future, would they have answers to these questions, would they have made measurable progress, but still have no real fundamental answers? That's exhilarating, but also potentially frustrating. Nice. And that's why you want to freeze yourself, right? Oh, yeah, absolutely.

Let's do it. Just for that dinner date in the future. Multiple dinner dates. Do you have to book it now? I'm going to leave it in my will. I'm going to have dinner with your great, great, great, great, great, great, great, great, great, great, great, great grandkids. It's on the calendar. Don't forget.

I sent them a count. A calendar invite, absolutely. Don't forget to defrost me, please. My daughter sends me calendar invites for like 10 years in the future or 30 years in the future. Oh, yeah? For like asking you for money. Yeah, like, buy Hazel a car. Say, okay, dad, buy me a car in five years.

Yeah, exactly. All right. Well, thank you, Michael. Now let's get to our last question, which is about whether a tiny black hole could still destroy the earth. And so let's get to do that question. But first, let's take another quick break. Hey, sis, what if I could promise you you never had to listen to a condescending finance, bro, tell you how to manage your money again? Welcome to Brown ambition.

This is the hard part when you pay down those credit cards. If you haven't gotten to the bottom of why you were racking up credit or turning to credit cards, you may just recreate the same problem a year from now. When you do feel like you are bleeding from these high interest rates, I would start shopping for a debt consolidation loan, starting with your local credit union, shopping around online, looking for some online lenders because they tend to have fewer fees and be more affordable. Listen, I am not here to judge. It is so expensive in these streets. I 100% can see how in just a few months you can have this much credit card debt when it weighs on you. It's really easy to just like stick your head in the sand. It's nice and dark in the sand.

Even if it's scary, it's not going to go away just because you're avoiding it. And in fact, it may get even worse. For more judgment-free money advice, listen to Brown Ambition on the IHeart Radio app, Apple Podcast, or wherever you get your podcast. Your entire identity has been fabricated. Your beloved brother goes missing without a trace. You discover the depths of your mother's illness, the way it has echoed and reverberated throughout your life, impacting your very legacy. Hi, I'm Danny Shapiro. And these are just a few of the profound and powerful stories I'll be mining on our 12th season of Family Secrets. With over 37 million downloads,

we continue to be moved and inspired by our guests and their courageously told stories. I can't wait to share 10 powerful new episodes with you, stories of tangled up identities, concealed truths, and the way in which family secrets almost always need to be told. I hope you'll join me and my extraordinary guests for this new season of Family Secrets. Family Secrets. Listen to Family Secrets Season 12 on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts.

I had this, like, overwhelming sensation that I had to call her right then. And I just hit call. I said, you know, hey, I'm Jacob Schick. I'm the CEO of One Tribe Foundation. And I just wanted to call on and let her know there's a lot of people battling some of the very same things you're battling. And there is help out there. The Good Stuff Podcast Season 2 takes a deep look into One Tribe Foundation, a non-profit fighting suicide in the veteran community. September is National Suicide Prevention Month, so join host Jacob and Ashley Schick as they bring you to the front lines of One Tribe's mission. I was married to a combat army veteran, and he actually took his own life to suicide.

One Tribe saved my life twice. There's a lot of love that flows through this place, and it's sincere. Now it's a personal mission. Don't have to go to any more funerals, you know. I got blown up on a React mission. I ended up having amputation below the knee of my right leg and a traumatic brain injury because I landed on my head. Welcome to Season 2 of The Good Stuff. Listen to the Good Stuff podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast.

Hola, it's Honey German and my podcast, Grasias Come Again, is back. This season, we're going even deeper into the world of music and entertainment with raw and honest conversations with some of your favorite Latin artists and celebrities. You didn't have to audition? No, I didn't audition. I haven't auditioned in like over 25 years. Oh, wow. That's a real G-talk right there. Oh, yeah.

We've got some of the biggest actors, musicians, content creators, and culture shifters, sharing their real stories of failure and success. You were destined to be a start. We talk all about what's viral and trending with a little bit of chisement, a lot of laughs, and those amazing vibras you've come to expect. And of course, we'll explore deeper topics dealing with identity, struggles, and all the issues affecting our Latin community. You feel like you get a little whitewash because you have to do the code switching?

I won't say whitewash because at the end of the day, you know, I'm me. But the whole pretending and code, you know, it takes a toll on you. Listen to the new season of Grasas Has Come Again as part of My Cultura Podcast Network on the IHart Radio app, Apple Podcasts, or wherever you get your podcast. All right. We're answering listener questions here today. And our last question is about the destruction of our planet by a small black hole. The question that comes from Scott. My name is Scott and I'm from Medical Lake Washington. And my question is, if a black hole were to suddenly pop into existence about the size of a pea in the middle of the earth, would it eat the planet? And if so, about how long would it take? Thank you. All right. Another tiny question I feel like. A cosmic question about tiny things.

And big destruction here. Because Scott's question is that if you suddenly made a pea-sized black hole appear in the middle of the planet, would it eat up the planet and swallow us all into this black hole or would we survive? Yeah. Great question. And how long would we be alive if it ends up killing us? How much time do you have to pack and board a ship off the planet? Right. How long can you take a nap before?

waking up to meet your doom in your toga. Well, Daniel, what's the answer for this question? What are some of the basics of black holes we need to know? So remember that black holes

are like a deformation in space and time. They're a place where there's so much energy concentrated in a tiny little spot that space is curved so much that you formed an event horizon, which means nothing can ever escape.

And the important thing to understand is black holes can basically eat anything you throw anything into a black hole it just adds to its energy you drop in a shark it gets more massive and it gets bigger right exactly there's a close relationship between the mass of the black hole and its radius and so as you add stuff to the black hole it tends to grow the only exception to this is if you had a black hole isolated in space it would emit hawking radiation and gradually disappear so if you don't feed a black hole it will eventually fade out of existence but any black hole that's near stuff is going to grab that stuff, pull it in and grow.

There's no way for the earth to hang out with like a black hole inside of it without that black hole eventually eating the planet. So Scott's question number one is like, is it going to eat the planet? And the answer is yes. So you have a black hole at the heart of the planet. That black hole already has a lot of gravity. He's talking about a black hole the size of a pea. Well, a black hole that size of p doesn't sound very large. Like a p doesn't have much gravity. but to make a black hole of that size would require about as much mass as the Earth. So now you're talking about about as much mass of the Earth,

concentrated down to a P, that's going to have a very strong gravitational effect. Put it anywhere inside the Earth, it's going to pull that part of the Earth apart, and it's going to feed itself on the Earth. And then it's going to grow and get more gravity and you have a very rapid runaway effect there where everything eventually falls into this new black hole.

Right, because I guess if you plop it in the middle of the Earth, it has material to eat right away, right? Like, what would happen if you plop a pea-sized black hole in the middle space with nothing around it? Would it just evaporate or would it stick around for a long time? Yeah, absolutely. If you don't feed a black hole, it will evaporate. How long it takes to evaporate depends on its size because the hawking radiation depends on the temperature and the temperature is connected to the size.

And actually bigger black holes are colder, tend to radiate more slowly. So the smaller the black hole, the more the radiation. So really big black holes very gently radiate and shrink very slowly. As they get smaller and smaller, they radiate faster and faster until eventually they disappear in quite a bright flash of light, which would make evaporating black holes from hooking radiation something we might be able to see out in the night sky. We've never actually seen one before, but people are looking for it.

But yeah, you put it in the center of the earth, it's going to gobble it up. Right, it's going to start eating the earth and then it's going to grow. But then I wonder if it would eat all of the earth. Like I wonder if at some point you'll eat the inside of the earth but maybe it'll leave a space between it and the outer shell of the earth. Yeah, it actually gets a little bit

complicated. What we often do in physics is just start with like the simplest scenario. Imagine all the mass of the earth is just like a bunch of balls on the surface of the earth and they all fall into the black hole and you can ask like how long does it take all of that mass to fall into the black hole. And so that would take about 10ish minutes

for all the mass of the earth. to fall into this central black hole. That's like the fastest it could possibly happen. You know, like around 10 minutes before everything actually reaches the black hole. Like if it just goes straight in. Yeah, if it just goes straight in. And that's the most efficient, the fastest way. And then you made this calculation how just by like measuring how long a ball

on the surface of Earth would take to fall into the center of a black hole in the middle of Earth? Yeah, essentially. Simple gravity for a simple object, not interacting with anything else. And that's the fastest possible thing. Nothing is interfering with these objects. But that ignores a lot of important physics, like the Earth is spinning. And what would happen if the black hole actually did start to eat the center of the Earth

is black holes have tremendous tidal forces. And those tidal forces would heat up the stuff near the black hole. Like surrounding every black hole we actually see out there in the universe is an accretion disk of stuff that's swirling around it and hasn't yet fallen in. So this new black hole of the center of the Earth would compresses, and heat up the stuff around the earth and it would create a lot of radiation which would push stuff out away from the black hole so what we see in reality out there in the universe is that there's a maximum rate at which black holes can grow because they have very strong gravity to pull stuff in but they also tend to create accretion disks which create radiation to push stuff away so black holes cannot form super duper quickly because of this effect because if things fall into quickly then they tend to explode as they go in which would push the stuff that's in line to fall in away. Exactly.

And stuff is also rotating, right? So it doesn't fall in immediately. It tends to swirl around the black hole before it falls in. It gets heated up and it radiates and it pushes out on other stuff. And so while the minimum time for this to happen is like 10-ish minutes, in reality, it would probably take much, much longer because it would form an accretion disk. And it would take a long time for that accretion disk to all fall into the black hole. Eventually, it still would, but it would take much, much longer.

Like how much? Because I think that's the question. Yeah, I don't have a solid answer for that because that requires calculations that are very complicated and require like really intense gravity and multi-body simulations. I'd estimate thousands of years or maybe even millions of years before the last bits of the earth actually do fall into this new black hole. But the earth would very rapidly be uninhabitable. Like this is answering the question of when the last tiny bit of earth dust falls into the black hole, that might take thousands or millions of years

but still you would not want to be on the surface of the earth for more than a few minutes after that black hole is created because it's going to get very unpleasant very quickly like it's going to basically break up to earth right shatter it yeah exactly they can collapse under its own sort of weight 10 minutes is the fastest possible time

for the earth to disappear which tells you that like the time scale for effects to appear on the surface of the earth is minutes so the earth is going to get pulled apart and distorted and all sorts of craziness is going to happen within minutes even if the complete hoovering up all the last bit of the earth

might take much longer because of the feedback effect from black hole radiation. So all bad news. You want to get on that spaceship ASAP. That's the answer. Isn't there some science fiction story where some aliens have created a planet

with a black hole in the middle that's powering it or something? I haven't read a book like that. In principle, it's possible to have a stable structure around a black hole, like if it's strong enough and far enough away and thin enough to avoid tidal forces, then yeah, you could build a big spherical structure, kind of like a Dyson sphere around a black hole. Like a giant shell, right?

Yeah, like a giant shell. And if you pour stuff into the black hole, you could use the hawking radiation from the black hole as an energy source. We even talked about using black holes to power a spaceship. We have a whole episode about that. So yeah, all these things, are potentially possible. But it depends a lot of the details. And you don't build that kind of thing by just plopping a black hole at the center of an existing planet.

And it's also unstable as I remember about it. But I guess maybe then an extension of Scott's question is what's the smallest black hole we could survive? Or is that any size black hole that is plopped in the middle of Earth would eventually swallow us up? Yeah, any size black hole that's plopped in the center of the Earth gets bigger.

And so there is no minimum size we could survive because every black hole just grows to be a larger black hole. But don't you talk about in the Large Hadron Collider? Sometimes you make black holes or you might be making black holes, but they disappear very quickly? Yeah. If you made a super tiny microscopic black hole in a vacuum like we might do with the Large Hadron Collider, then it could evaporate too quickly to absorb any other material. If you put it in the center of the Earth, then you have no chance. Even a microscopic black hole will eventually get bigger.

But if you make a microscopic black hole in a vacuum, it'll evaporate before it's dangerous. Unless you created a knocks on the wall of the Large Hadron Collider, would that be bad news? Black hole we make at the LHC will actually have a lot of velocity. So it's not just going to stay there inside the LHC and actually fly off and just go through the Earth or into outer space before it has a chance to eat anything. They've done all these calculations and they're pretty convinced that it's not dangerous. So, you know. Dot, dot, dot. I mean, fundamentally, we do not understand microscopic black holes because it requires a theory of quantum gravity to predict what would happen.

Because now you're talking about the gravity of quantum objects, which are uncertain. And so it's not something we really know how to calculate. And all the calculations is done for like black holes with a large Hedron Collider. They use a semi-classical approximation of quantum gravity, which nobody really believes anyway. You're not really making me feel more comfortable here, Daniel. No, that wasn't the goal. Your assurance is only getting worse. I'm telling you we don't really understand super microscopic black holes anyway.

I see. And so therefore we should believe you when you say not to worry about it? I didn't say not to worry about it. I said they've done the calculations and they tell us not to worry about it. Uh-huh. And now you're telling us. I'm saying I'm not worried about it. Oh, well, in that case.

But remember, you can always check the website. Has the Large Hadron Collider Destroyed the World Yet. which we always keep up to date. Right, right. Although there would be a delay technically, right? So it could be wrong for about five minutes. I don't know about five minutes. I think it would be updated faster than that.

I hear a lot of nervous laughter here, Daniel. If you're destroyed by a black hole and you have complaints about that website, feel free to email me. Yeah. Well, you get it in time, though. I've promised to answer all emails, and so I'm going to do my best. Yeah, yeah. You might have to break that promise.

All right. Well, I think that's the answer for Scott, which is, yes, if you put a piece-sized black hole, which would be the equivalent of a black hole with a mass of the earth, in the middle of the earth, next to all of the material inside the earth. And, yeah, it would quickly grow and swallow us all up. Or at least destroy the earth and then eventually swallow our remnants up. Don't do it, Scott. Bad idea.

Don't do it, Scott. Don't do it, Daniel. We're not creating pea-sized black holes, man. Oh, right. Although you said any size is dangerous, so you're not helping me sleep well at night. Not my job. All right. Well, thanks to everyone who sent in their questions.

We always appreciate it. And thanks everybody who's curious about the universe and shares their curiosity with us. This whole podcast project is just us marinating in the joy of your curiosity. Thanks very much everybody. You hope you enjoyed that. Thanks for joining us. See you next time. For more science and curiosity, come find us on social media where we answer questions and post videos. We're on Twitter, Discord, Insta, and now TikTok. Thanks for listening and remember that Daniel and Jorge Explain the Universe is a production of iHeartRadio. For more podcast from

My Heart Radio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows. I'm Dr. Scott Barry Kaufman, host of the Psychology Podcast. Here's a clip from an upcoming conversation about how to be a better you. When you think about emotion regulation, you're not going to choose an adaptive strategy which is more effortful to use unless you think there's a good outcome avoidance is easier ignoring is easier denials easier complex problem solving takes effort listen to the psychology podcast on the iHeart radio app apple podcasts or wherever you get your podcasts every case that is a cold case that has DNA right now in a backlog will be identified in our lifetime on the new podcast america's crime lab every case has a story to tell and the DNA holds the truth he never thought he was

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