Daniel and Jorge answer questions from kids about black holes, diamond planets and faster-than-light travel!
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Any Daniel, Do you think kids think about the world differently?
Oh, I'm sure they do, because they aren't tied down by all of our crazy misconceptions.
Actually, I meant because they have smaller brains. But I think you're right about the misconceptions. Do you think that makes them smarter than us?
I don't know, but I think there's a reason that it's rare to have like a brilliant inside or crazy new idea after you're thirty.
Hmmmm. So just because I'm older than thirty, that means I'm never going to win the Nobel Prize in physics.
Oh no, No, you might still, but it would be for an idea you had when you were twenty nine.
I mean, like when I decided to leave academia and become a cartoonist.
Yeah, maybe the best idea you ever had.
Do they give Nobel Prizes in bad career choices? Hi am more handmade cartoonist and the creator of PhD comics.
Hi.
I'm Daniel. I'm a particle physicist and a professor at UC Irvine. And I was once stumped by a question from a six year old.
Really, huh Was it a question about physics or just about life?
It sort of was. I was doing demonstrations at the elementary school about how cool liquid nitrogen is, and some kid asked me if lightsabers were real, would they be made of liquid nitrogen.
H interesting question. It's like it's blending fiction and reality and some imagination there.
Yeah. I was literally stumped. I had no idea how to answer that question in the universe in which lightsabers.
Like, is a kyber crystal made out of liquid nitigen? Really? It could be, right?
Yeah?
Yeah, I suppose it could.
Can you make a crystal out of liquid nitgrogen? Somehow?
I guess that would be crystal nitrogen?
Yeah, But welcome to our podcast Daniel and Jorge Explain the Universe, a production of iHeartRadio.
In which we try to summon that curiosity we all had when we were children about the way the world worked and extend that to everything in the universe and wonder about the nature of the universe, the origin of the universe, explanations for how everything works, and dig into the mysteries for the things that we still don't understand. We apply our innate curiosity to everything in the universe because we think that everything is understandable and that if we bang away at it long enough, we eventually we will figure things out.
Yeah, because it is a big universe and there are enough questions in it for all kinds of people young and old. You might be eight years old and still have questions about the universe, or you might be ninety nine and also have questions about the universe. The universe seems to never run out of questions.
That's right, And some of the questions that we are asking suggest that we as a species are quite young, you know, the way the kids ask very basic questions, you know, like where does the sun go at night? Stuff like that. We are still asking really basic questions. How old is the universe, what happened before it? How big is it? What's past? What we can see? Really, just like novice initial questions you ask as a species coming into these universe and wondering about our place in it.
Are you saying our species is like in its teenage years you think, or are we tweens?
No? I think we're basically six year olds intellectually as a species. I think we're six years old. We're asking really basic questions. We're still in the kindergarten of the galaxy exactly. We're asking questions that reveal the way we think about the universe, rather than the way the universe works. You know, we're asking the questions we think are important, and that reveal our misunderstandings about how the universe works.
Well, we definitely don't have our wisdom teeth yet. As a species, we're definitely lacking any wisdom, it seems these days. But there is a lot that you can ask about the universe, and it's for all kinds of ages.
Yeah, and sometimes it's fun to dig back into that. You know, as a researcher, I'm working at like the very edge of knowledge, asking very specific questions what's inside a quark? Or are electrons made of something smaller? But it's fun to go back to the questions that five year old, six year old ten year olds ask and remember that we still don't have answers to those big questions. And like the whole context of our exploration is that we're trying to answer these really big, basic, deep questions, and that all the specific work we're doing at the edge of knowledge in the end is motivated by trying to get back to those basic questions.
I think trying to make a lightsaber is at the edge of knowledge, you think, I mean, have you seen those YouTube videos where people try to recreate lightsabers. It's hard, It's really impossible. Almost what motivated you to walk to those for Hey, when you trying to build on yourself house, I was curious as a kid, Yes, to watch YouTube videos.
You're going to slice your way out of your childhood situation. No, I've not gone down that particular rabbit hole. But yeah, there's a lot of really fun questions we asked there.
Yeah, and sometimes we get those questions here in our inbox, and specifically we get questions from little kids, not just adults or young people like the people listening to this podcast right now, but we get questions from little little kids.
That's right. Sometimes folks have their seven year olds or their ten year olds listening with them, have been a podcast will inspire a question, and then they'll write to us and say, Hey, my kid asked me this question. I don't know the answer. Maybe you guys can help out.
Which makes me glad about all the jokes we don't see in this podcast, all those jokes about dark matter, and.
That's right, all those racy browser histories if we don't like to talk about, but exactly because we hope that you are out there listening with your kids and that inspires conversations. I'm always really happy to hear when somebody writes it and says, I was listening to your podcast with my eleven year old and then we spent an hour talking about what's inside a black hole or just on the way to school, wondering about the nature of the universe. Our whole goal here is to share our joy of our ignorance and wondering about what's in the universe and helping you talk to everybody in your life about it.
Yeah, so, if you're a kid listening to this podcast right now, we want to thank you for listening. We're glad that you're here, and I'm sure you have a lot of questions as well, as well as a lot of other kids. And we have a whole inbox full of questions from kids.
That's right, So don't be shy to ask your parents questions or to send your questions to us. We'd love to tackle them.
So to the on the podcast, we'll be tackling kid questions about the universe. At least are questions about kids or by kids.
These are the biggest questions from the littlest people. These are questions about the whole universe, about black holes, and about how things work. You know, the kind of things that go through the minds of an eight year old.
And these are all spontaneously generated, right, Like kids just sent this question in with their parents.
That's right. I don't know if the parents put the kids up to it, or if these are actually child's actors. I can't vouch for the veracity of these, but they are good questions, and so I thought they'd be fun to talk about on the podcast.
Yes, honest, you didn't go around soliciting little kids or things on the internet. I think we're safe.
No.
I try to stay ways I can from the child acting industry down here in southern California.
Yeah, so we have all kinds of awesome questions here from kids about black holes, about diamond cores, about the expanding universe. And we have a whole bunch of them. So let's dig into him, Daniel, what's our first question?
Our first question comes from Joey. He's seven years old.
What are the newest and the oldest black holes in the universe? Hmm? Interesting, appropriately a question about youngest and oldest something in the universe.
I wonder if there's a relationship there with like Grandpa black holes and grand kid black holes.
Yeah, like maybe the younger black holes and more attitude, maybe they think they know everything in the universe.
I was thinking the other direction, like maybe the little black holes look up to the super massive black holes and they're like, that's gonna be me.
One day.
I'm gonna have my own galaxy of stars swirling around me.
I'm gonna devour millions of stars and planets and potentially is civilizations and then get bigger something.
I'm gonna be huge and round.
One day, I'm going to have a whole galaxy re balling around me, just me.
Yeah.
So it's a great question because black holes weren't all made at the same time. I guess it is one thing that people may not know that black holes are not all the same age.
That's right, And part of the reason is that we have several different categories of black holes. We have different ways that black holes could be made, so different processes that are capable of creating this crazy density that you need to create this craziest and most mysterious of universal objects.
Yeah, so there are black holes being born right now, and there were maybe black holes that were made in the Big Bang. So let's get into what we know, Daniel, what is the youngest black hole that we know about.
So we think, as you say, that black holes are being made all the time, right, because black holes come from collapsing stars, at least one category do so the end of the life of a star, we think that they collapse and they form a black hole if they have enough mass, And that should be happening basically all the time around the universe. I mean, not like thousand every second per qbic light year, but at a certain rate all over the universe. So there should be a black hole being made right now, and another one right now, another one right now.
Every ten seconds a black hole is born.
Yeah, it's like asking who is the youngest person on Earth. It's a constantly changing answer because new babies are constantly being born. But as you say, we can ask the question, what is the youngest black hole that we have seen?
Right?
And then there's another twist there because you know, the things that are further away from us are a little older, So we're naturally going to have seen things that are younger that are closer to us, just because the light has had a chance to reach us.
Oh I see, So there's kind of a delay between when something happens and when we find out about it. So what we think might be the youngest might not be the youngest. It's just the youngest that we know about that the news of which has gone into us.
Yeah, precisely. And so the youngest black hole that we know about is about twenty six thousand light years from Earth. It's called W forty nine B because astronomers are so creative with names, and we think it's about one thousand years old. We think that it was formed in a supernova that happened about a thousand years ago.
Mmmm, a supernova black hole. Now, not all stars go super nova and become black holes, right, Like, there's lots of stars that never become a black hole. Like our star is not going to become a black hole.
That's right. And our star won't even go supernova. And the whole thing is determined just by how much stuff there is in the original star. The more stuff there is, the more likely that it's going to have a supernova collapse. And then only the heaviest of stars have enough mass to create a black hole. Because remember, to create a black hole, you have to have gravity overcome all of the things that are pushing back against gravity's pressure. Gravity is trying to push everything into the smallest space possible because it's just attracting mass to other masks. But things prevent that, like our star is burning and shooting out radiation, which prevents it from collapse. When that burning stops, then there are other things that will prevent it from collapsing, like just the atoms pushing against each other, or eventually just like quantum chamic effects. But if you have enough stuff, you have a big enough scoop of original hydrogen serving, then you can overcome that if you're above a minimum threshold. So you're right, not every supernova becomes a black hole.
And so the youngest supernova and that became a black hole that we know about happened we think one thousand years ago, twenty six light years from.
Earth, twenty six thousand light years from.
Earth, twenty six thousands already light years from Earth. What did I say, thirty six thousand miles.
Twenty six light years? But hey, what's three over some magnitude between friends?
Yeah, it's right here, But really it must have been then that it was maybe born twenty five thousand light years or something like that, years ago, like it can't be one thousand years old, but then it's twenty six thousand light years away, because it would take twenty six thousand years for the light to get to us.
That's right. What we mean by that is the supernova should have been visible here on Earth a thousand years ago, right, So a thousand years ago we should have seen a supernova indicating the formation of the black hole. But of course that would have happened twenty seven thousand years ago.
I guess, how do we know that it's there or how do we know it's age? Like black holes are black, so they're kind of hard to see in space. How do we know it's there? And how do we know how old it is?
So these are tricky to identify, right, every time you see a supernova, you don't necessarily get a black hole, and so you can't actually see these black holes directly. You always have to infer it indirectly, and so you see, for example, in accretion disk forming, but you don't see any object there at the core. Or perhaps you can measure the mass because there's something else nearby, and you can measure the radius because things are passing near it, and so you can tell what the density of the object is and it's denser than a neutron star could be. And so, as we talked about on a recent episode about black holes, we're never one hundred percent sure about a black hole. We're always inferring it. The argument is usually something like, this is denser than a neutron star could be or anything we know, therefore it must be a black hole. There's always a bit of a leap there, like we don't know anything other than a black hole that could be this small and this dense, So therefore we think it's a black hole. And that's sort of the art we make when we look at these nebula.
Right, you sort of look at it black spot in the in space and you see things moving around it in an orbit, and so you must infer that there's something like a black hole there. But I guess, how do you know it's a thousand years old? Like, how do you know when it happened? Like we weren't looking a thousand years ago?
That's right, But these things have clouds, right. The supernova is an active process, and so there's a big explosion and a lot of the stuff gets thrown out to form this nebula and some of it collapses into the black hole. But we can watch the process of this nebula and it's going to like create new planets and have all sorts of dynamics, and so that's sort of a thing that we can watch and we can look at it and we can say, well, this nebula looks like it's about a thousand years old, because we think it looks like about a thousand years worth of like gravitational reformation has happened.
You can see the wrinkles. You don't have to check the ID, you can just guess by looking at them.
You can measure the velocity of things in the nebula by seeing the red shift, and so you can sort of tell where it is in this process of having exploded and then reforming something. Sometimes you'll get like new planets forming around the neutron star or the black.
Hole at the core. Well that's cool. So then that's the youngest black hole we've ever seen, Like we haven't seen one in the last thousand years, or we don't think one has come into existence in the last thousand years. Isn't that weird? Given how many stars there are in the galaxy and in the universe.
It is kind of weird, and there's a couple of things going on there. One is that there aren't that many supernova in our galaxy, Like there's a lot of stars in our galaxy, and we expect only like a few supernova per century because not many stars actually end up turning into supernova. And one of the weird things is that we haven't seen a supernova in more than four hundred years, like the last supernova in the Milky Way that we saw. We see lots of them in other galaxies constantly, hundreds every year, but the last one that we saw in our galaxy was in sixteen oh four. Kepler saw the last supernova any human has ever observed in our galaxy.
WHOA really, how do you know we didn't miss it? And like in the eighteen hundreds, for everyone looking, was everyone looking diligently, Like what if we kind of like one happened and we were looking the other way, or you know, the French Revolution was happening, so people were a little busy, or World War two was happening, and so there are other things we were attending to do.
Yeah, there are a couple of candidates where we see in nebulation We're like, Hm, this looks like it should have been a supernova about one hundred years ago. We should have seen it. Why didn't anybody notice it? There are a couple of candidates, but even still, it's kind of weird because we expect a few per century and we haven't seen a single one in four hundred years. We're actually going to dig into that in a whole podcast episode about the formation of supernova and why we haven't seen any in the Milky Way pretty soon. But basically, we haven't seen a lot of supernova in the Milky Way recently, and you need a supernova to form these black.
Holes, all right, So then the answer is stay tuned. But that is the youngest black hole we've seen. It's one thousand years old, twenty six thousand light years from Earth, and so what's the oldest black hole we know about?
The oldest black holes we know about are ones that formed at the hearts of galaxies in the very beginning of the universe. Remember that, after the Big Bang, stuff flew out, and then gravity started doing its job and made stars and galaxies, and that took about a billion years for the universe to look familiar, you know, eight hundred million, maybe a billion years before we had the first galaxies. And the interesting thing is that we already have super massive black holes at the hearts of those galaxies. Now, those galaxies are billions of years old, which means we can only see them if they're very very far away, because the light from those faraway galaxies is just now hitting Earth. So you look deep out into space, you're looking back in time and you're looking at the very very early galaxies. And the crazy thing is at the heart of those galaxies there are these very bright emissions, these things we called quasars, which are light from the gas that's surrounding those huge black holes in the very early universe. So we think that black holes were formed at the heart of these early galaxies, you know, just a few hundred million years after the Big Bang.
Mmmmm. Interesting. So we can see these black holes because they're actually really shiny. What's around them is really shiny, in fact, super shiny. Right, It's like it's brighter than the whole galaxy that it's in.
That's right, They are crazy shiny. These things are called quasars, and when they were first discovered, people didn't really understand. They didn't believe them there must be something wrong because you're looking at something super distant and yet super bright, which means that at it source it must be like ridoculously bright. And people thought that just must be wrong. What could power that? Then they discover that, oh, it's the energy from these black holes that's like squeezing and pushing on all this gas around it that creates this very intense radiation. Again not from the black hole, as you say, but from the gas that's around it.
And so you're saying that we see these quasars, these super bright black holes in galaxies that are really really far away, which means that they're really really old, which puts their age at around thirteen billion years old. We think the black hole is thirteen billion years old. Yeah, we think the black hole is thirteen billion years old. Now we haven't seen them recently, right, we are looking at very outdated information. So we're looking at a black hole which is fairly young, maybe a few hundred million years, but thirteen billion years ago. So now we're assuming that those black holes are still around because we don't know of any mechanism for super massive black holes to disappear. The only way a black hole can shrink is through hawking radiation, but that happens very very gradually for very large black holes, and these things are probably still eating, so they're probably even bigger now than we are seeing them from thirteen billion years ago. Well, it's like getting a photograph of someone from the nineteen twenties, and you know, assuming they're still alive, that would make them really old, just because we have a photo of them when they were young, but the photo is really old.
Yeah, exactly. So these things have been around basically the entire history of the universe.
Right, almost though almost by like what one hundred thousand years you said, one hundred billion, A few hundred million years, Yeah, I want to order of magnitude between a podcast hook code.
That's right, exactly, So.
Those are pretty old. Thirteen billion years old is pretty old. But there might be even older black holes.
That's right. We don't know, but it's possible that there were black holes made before there was even matter, before the universe cooled down, so that the energy in the quantum fields could even be described as like particles as you know, like quarks and electrons flying around when the universe is still so crazy dense and intense that you couldn't even describe things as particles. We think there might have been black holes made in that state of matter, and those we call primordial black holes.
I see, because you don't necessarily need matter to make a black hole, right, you could also make one out of pure energy.
That's right, because general relativity treats matter as just another form of energy, and it's really energy density that curves space, and so you can accomplish that with matter, of course, but you could also accomplish that with energy. Like if you take powerful enough lasers and overlap them, you can create a black hole out of light.
How about liquid nitrogen lightsabers? What if you cross those beams?
Can you cut a black hole in half with a lightsaber? It's a physics question. I don't have the answer to.
Only hear Yoda.
Only after nine hundred years of training.
Yeah, so these primordial black holes would be the oldest black holes in the universe. But we don't really know if they exist, right.
We definitely do not know if they exist. If they did exist, we should be seeing them because they should have been created all sorts of different sizes, really large ones, really small ones. It's nice to imagine that they might exist because they might explain how super massive black holes got so massive so young, Like you might ask, how do you get such a big black hole after only a few hundred million years, Well, they could have been seated by primordial black holes. They could also explain what the dark matter is. Maybe dark matter is just a bunch of these primordial black holes floating around in the universe. But if they were created in all sorts of different sizes, then some of them should be just the right size to live around fourteen billion years and then evaporate to disappear. And when black holes evaporate, they're giving off their light. It happens more rapidly. They get brighter and brighter as they're about to disappear, so we should be able to see them sort of like flashing out of existence. But we've never seen that happen, and so it's sort of hard to understand how you can have primordial black holes.
M Maybe they feel all out, you know, kind of silently. Maybe they don't fill all out with a bang. Is that possible.
It's possible, But our current theory of black hole evaporation suggests that when they evaporate, they turn into photons. And all sorts of other crazy particles, and we should definitely be seeing those, like at the edges of the galaxy or something. But we've been looking and we haven't seen a single one. We've never seen a black hole of aporation, and so that's suggests that probably they're either just not formed in the right sizes, like maybe they're only formed really really small and really really big. That's possible, or they just weren't made. But if they were made, then they'd be essentially as old as the universe. They would be made like less than a second after the Big Bang.
Interesting, But isn't it a theory that some of those super massive black holes in the middle of galaxies maybe were made by primordial black holes.
It could be, yeah, because as we said, we don't understand how those black holes got so big so fast. If you try to model the formation of galaxies in the early universe, stars coming together forming a black hole, et cetera, you can't get black holes that are like billions of solar masses so quickly. So we just don't understand how that happened. And as you say, one idea is maybe they got a jumpstart because they were seated by a really big primordial black hole, so that's a possibility.
So it sounds like the oldest black holes in the universe are thirteen billion years old at least at least they might be older. All right, Well, thank you Joy for a great question. I think that's your answer. The youngest and the oldest black holes in the universe are both still older than your parents, apparently, but maybe billions of year or at least one thousand years and maybe billions of years.
That's right. These black holes make your parents seem like children.
All right, Thank you, Joey. And so let's get into more questions from kids. But first let's take a quick break.
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All right, we are answering kid questions about the universe on today's episode, and we have some pretty cool questions here, Daniel, or any of these questions from your own kids.
None of these questions are from my kids. These are questions that people didn't have answers too, so they wanted me to answer them. If my kids asked me questions, I just answered them. Or if I don't know the answer, I try to look it up, but I don't send them to the podcast.
I see, you're like a pinch hit hitter parents when it couts to physics questions.
Yeah, I try to be. I think that's a lot of fun. I just love hearing the kinds of questions that other kids are asking because they tell you something about how they see the universe. And you know, I feel like my brain is sort of like stuck in the modern physics view of how things work. And I'm sure they have all sorts of like misconceptions that have sort of fallen into and been thinking about for twenty years. So a kid's question can really stop you in your tracks and ask you like, how do we know this? Or Why do we think about it this way? It's really refreshing, all right.
Our next question comes from Anthony, who has a question about diamond core.
Hi, Daniel and Jory.
My name is Anthony.
I am eight years old, and why does fifty five King crying e have a diamond core?
Looking forward to hear your answer. Please and thank you. Hey, thanks Anthony. What a polite little young person. I know they said please and thank you.
Some of our listeners apparently are teaching their kids manner in addition to science.
Can Anthony talk to my kids please and run a little etiquette class?
That's right, and we'll trade you some physics answers for some manners lessons.
Now, this is an interesting question because, to be honest, I didn't quite understand it. It almost sounded like a Star Wars reference, like does this kind of lightsaber model have a crystal core?
It's a great question. It's about an exo planet. This is the planet around another star that we are trying to understand because you know, we are looking at our own solar system and wondering are these the only kinds of planets you can have? Or are there other weird kinds of planets out there. As always when we venture out from our little corner of the universe, we expect to be shocked. We look forward to seeing things that we couldn't have imagined. And so this is a planet around another star, and we're trying to understand what it's made out of and you know, like what it's like to walk on its surface. And so there was a recent paper suggesting that maybe the entire core of this planet could be one huge diamond. And that's what Anthony's asking about.
WHOA, yeah, because we've seen now thousands and thousands of planets in other solar systems, right like, we've detected them, we've even sort of sort of had pictures of them. We can tell what's in their atmosphere. Are we down to the point where we can tell what's inside these planets out there in space?
We sort of can. And you know, we have very limited information about each one of these things, and so we're trying to do as much science as we can with a very basic information. And here, for example, we have like some knowledge about the mass of the planet and then some knowledge of the radius of the planet, and that lets you do really basic stuff like ask what's the density of the planet, and if you know what the density is, then you can ask questions like, well, what could make a planet of that density? What materials are consistent with that? So now we can't like go and drill into the planet and say, oh, look we found diamond, but we can ask questions about what it might be meant out of based on what we do know.
Interesting and Anthony was asking about a specific planet that has been found out there and he had a name for it. It was fifty five something.
Yeah, the official name of the planet is fifty five can create E and so sometimes abbreviated fifty five CE.
Can create E. That does sound like a star trick name.
Yeah, it's a planet that's orbiting the star. Fifty five can crete A and so can create E. Is you know, like one of the things around can create A.
I see there's a BCD and a D but we're talking about the E thing around that star.
That's right. This is the one that's most interesting, and it's got a really interesting history to it because it was first discovered in two thousand and four using the Wiggle method. The Wiggle method says that a planet moving around a star should tug on the star it's not just that the star is pulling on the planet. The planet is pulling on the star. And so if you have a planet moving around the star, you should see the star moving also, and you can measure that by measuring the velocity of the star by seeing how much it changes the light that's coming to us from the star. So these doppler shifts.
Right, just like the Earth is making the Sun wiggle a little tiny bit. And if you were you know, smart enough and had pretty good tusks in another galaxy or another planet, you could tell that we were here.
And so you can tell if there's a planet there because it's pulling on the star. And you can tell something about the mass of the planet because you can tell how much it's pulling on the star, and you can tell something about its period because you can tell, like how when the star wiggles one way and the other way. But this wiggle method doesn't tell you anything about the size of the planet, because you know, you don't know if it's like a big fluffy pile of styrofoam or a tiny little black hole. They would have the same gravitational effect on the star.
Right, they would wiggle the star in the same way.
And so that was two thousand and four. All we knew about this thing was how long it took to go around its Sun and how massive it was. But then like seven years later, we got better telescopes and we trained them on the star, and we were able to measure the size of this planet by seeing it eclipsing its star. Like you know, if you go out and you watch an eclipse, you see the Moon passing in front of the Sun and it blocks it out. It's very dramatic. This is very different because the planet is much much smaller than the star, and so it's sort of like watching a moth walk in front of a light bulb from like thousands of miles away and then measuring how much the light bulb dims because of the moth. And you can use that to measure the size of the planet, because the larger planet would dim the star more than a smaller planet.
Right.
Or if you were like looking at the Moon at night, for example, and a little fly flu between you and the Moon, you would sort of see the light from the Moon, you know, get a little bit dimmer, but it's just a little tiny bit.
Just a little tiny bit. But if you watch, you can see it, and you can see it happened periodically also, which really helps. It's not just like one blip and you can say, oh, with that noise or mistake in my data. If it happens periodically regularly and it matches up with the velocity measurements you're making of the star, then you can be pretty confident that that's what you're seeing. So then you know the size of the planet also, and from that you can make measurements of its density, and you can know like something about what it's made out of.
So you can tell the mass from the wiggle, and you can tell the size from the shadow it makes in front that star. And so we have a measure of its density and I'm guessing it must be pretty dense if we're thinking it might be made out of diamond core.
Yeah, this thing is like nine times the mass of the Earth, but its diameter is only twice the Earth, right, and so it's definitely denser than the Earth is by how much like three or four times? Yeah? Well, the diameter of twice the Earth means that its volume is eight times the Earth, right, And it's got a mass of nine times the Earth. So it's actually only a little bit denser than the Earth.
Is, so it must be like a rocky planet or something. But it's just a little bit more dense than the Earth, and the Earth is pretty dense, right, Like the Earth is a rocky planet with lava and rock, right, it's not We're not made out of a con candy exactly.
But this planet is very different from the Earth because it's so close to its Sun and it has an eighteen hour orbit, like it takes eighteen hours for a year to pass on this planet, like it goes around its Sun every eighteen hours.
Every eighteen hours. There's a birthday part.
It's spent basically all of your time shopping for present.
Yeah, an opening presence, half the time dropping the other have opening there.
That's right, an eating cake. And that makes the surface of this planet very very hot, like three nine hundred degrees fahrenheit or twenty one hundred c.
That's hot.
That's pretty hot.
You don't need to light your birthday candles exactly, they're already on fire.
So I recommend a pool party. And that's important to understand because when you're building models of these planets, you have to understand, like what state the materials that you're putting into your model of the planet are. So, for example, they started off by assuming that this planet, like Earth, has a lot of oxygen in it. Like Earth is a lot of oxygen, it doesn't have a whole lot of carbon in it. And if you're going to have a planet this size and with a lot of oxygen in it, it should have a lot of water on it. But it's sort of weird to have all that water on the surface, Like this planet would be like ten percent water. Ten percent of the mass of this planet would be water to get the right size and the right density. But if you have that much water, you're basically talking an ocean planet. But that much radiation on the surface would split all the water and put it in a super critical state. So sort of a weird idea to begin.
With, right, It's not a good assumption to think it's just like the Earth.
Yeah, So then what happened to convince them that maybe this planet was different was that they learned something about the star. They looked in more depth at what the star was made out of, and they noticed that it had a lot of carbon in it, a lot more carbon than our star. For example, remember that these solar systems are formed from leftover materials from other generations of solar systems. So you have still mostly hydrogen, but like, some of them have more oxygen, some of them more carbon, some of them have more of this, some of them have more of that. This solar system seemed to have been formed out of materials that were richer in carbon than our solar system. So they think, Okay, that star has a lot of carbon in it. Maybe the planet has a lot of carbon. Also, maybe our assumption that this planet was oxygen rich like the Earth was wrong. And they said, well, what model could you build if you started from carbon instead of from oxygen?
I see, to get the right sort of like size and maps, and to make a sort of carbon ridge, you would have to make the planet have a lot of carbon.
Yeah, so they say, well, maybe the planet's like one third carbon. And then they started playing with models like what would happen if you had a planet that was one third carbon and this big right at this certain density. They realized that would create an incredible pressure at its core and that in some circumstances you would get an enormous diamond, you know, like we're talking at a diamond that's like thousands of kilometers.
Across, because I guess you're assuming all the carbon would sort of fall to the middle or like it would push all the other stuff out as it forms the diamond.
Mm hmm. And this incredible pressure, you know, would essentially turn all of this carbon at the core into a diamond. And obviously there would be impurities, right, You'd have heavier metals like iron also, so it wouldn't be just like one pure perfect diamond gray triple A or anything, but it would be like mostly diamond.
Wow.
And so we're talking how big do you think this diamond is? Like the size of Manhattan or the size of Australia. How big do you think is diamond? Choris?
You know, this thing would be a third of the planet, So it's huge. Yeah, I mean we're talking thousands of kilometers across.
Wow, Like bigger than the moon. Bigger than the moon, yes, much bigger, like almost the size of Earth exactly.
So what the kind of ring would you need for a diamond bigger than the moon?
Yeah, so I guess if you like it, you better put a ring on it, right.
Exactly, there you go. Fifty five can create a better step up.
All right, well, thank you, Anthony. I that's a great question, and I think that's the answer. We think that this planet that's out there orbiting another star has a lot of carbon in it, and if you have that much carbon in a planet under that much pressure inside it might form into a diamond. And so yes, there might be a giant diamond inside of that planet.
That's right. But this, of course is all hypothetical. We have a very few pieces of information. We're playing a lot of games about what might be possible, and in coming years we'll be able to image these planets and see more about the light that's reflected from the surface off of their stars and learning more about their atmospheres. We'll get a lot more information about these planets, and then we'll figure out what's out there, and probably what we learn will be even more shocking than anything we hypothesized.
I guess the hard part would be mining this giant diamond, Like, first of all, how do you break it apart? And the other part is how do you get it out of the core of a giant planet?
How do you polish it?
Right?
You need to shine this thing up if you're going to sell it at market value.
All right, well, let's get into our last question from kids today, and it's about the expanding universe. But first, let's take another quick break.
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Right we are taking questions from kids today and our last question comes from Addi, who is eight years old.
Hi, Daniel, and.
My name is Adi.
And I am eight years old.
My question is, since in the universe is expanding faster than the speed of why can it go back in time? Thank you? Whoa This question just blew my mind. Can the universe itself be traveling back in time? That's crazy? But first of all, I have a question for you, Daniel, why do kids always identify their age? Like, at what point do we as adults stop saying how old we are?
I think the point where we stop remembering how old we are. I introduced myself and I'm like, I'm forty four. My kids are like, no, you're forty six, dude.
Yeah.
Yeah, but it's great to know. Thank you, Audi. This is a great question. I think Audi is putting a couple of ideas here together, right, Like we know and we've talked about the idea that the universe is expanding, and it's expanding at its edges, or at least as far as the furthest from us as you can faster than the speed of light. And we've also talked about how like, nothing can move this faster than the speed of light, but if it does, it would mean it would sort of go back in time or break the rules of time.
Yeah, these are two really fun ideas, and I love hearing kids put these ideas together and your first you're like, no, that's crazy, and then you hold on a second, maybe that's a good point. Maybe he's right, maybe he.
Is going back right, not your kids. I'm like, yeah, yeah, what's the answer here is the edge of the universe going back in time.
It's a great question. And you know, he's right that the universe is expanding faster than the speed of light. But there's some important subtleties there, right, like what is happening. It's not that things are flying out through the universe and that they are traveling relative to each other faster than the speed of light. You know, like no object is looking at another object and saying, oh, your velocity is greater than the speed of light. However, that doesn't mean that distances can't increase faster than the speed of light. Right, It all depends on sort of who's asking the question.
It's like, nobody's moving faster than the speed of light, but things are. The space itself is growing faster than the speed of light. Overall.
That's right, because new space is being created between galaxies. New space is being created, and there's no limit to how fast space can be created. And you might ask, like, well, hold on a second, who's creating new space and how does it work? And certainly there's somebody in charge of it, and there's limits, right. We don't know the answer to any of those questions. We just see that space is expanding. This is what we call dark energy, and so we know that something out there is capable of expanding the universe itself, of stretching space or making new space, and that's happening everywhere isotropically. The whole universe is expanding, but it only happens a little bit over a short distance. So between me and you, for example, wherever you are in the Earth, space is expanding a very very tiny bit every year, but you know, the Earth holds us together. Between us and the Sun, space is expanding a little bit more every year, but the Sun holds us together. But between us and other galaxies there's a lot of space there. So all the new little bits of space add up and it becomes pretty significant. And across the whole universe there's huge amounts of space. So you add up all of those expansions and you actually do get speeds that exceed the speed of light.
It's kind of like maybe for audi here, it's almost like you can't run faster than the speed of light in your house, but your house is sort of growing a little bit. So you stand on one end of the house and you look at the other end of the house, at the on the other side, you would see it sort of growing faster than light could move.
That's exactly right, And so we can measure the distances to things we see that those velocities do seem to add up to be greater than the speed of light. But you know, if you looked at any one thing and you asked, how fast is this one thing moving relative to me, you would never measure a velocity greater than the speed of light, because remember, you can't measure velocity relative to space. Space doesn't have like a reference frame. There's no absolute frame there. You can only measure velocities relative to an object.
All right. So then the universe is expanding faster than light can travel, but nothing's actually moving faster than light. And so the other idea they put together is this idea that going faster than light somehow breaks time or makes it go backwards in time.
Yeah, that's a really fun conclusion, and it's sort of meant to tell you that you can't go faster than the speed of light. You know, we have these ideas of how the universe works, of how information can propagate, and how there's a maximum speed of information, that no information can move faster than the speed of light. No object, and no information, no particle, no wave can ripple faster than the speed of light. And what happens if you ask, like, well, what happens if an object does move faster than the speed of light, Well, then you get a paradox, You get contradictions. You get things like, well, if it could move fast than the speed of light, that would be equivalent to it moving backwards in time, which we know to be impossible. And so it's sort of just like another way of saying that you can't move faster than the speed of light. Sometimes people interpret this saying like, oh, if you want to go backwards in time, all you got to do is go fast than the speed of light. But it's sort of like saying, no, that's impossible.
Right, like Superman and Superman the movie. But I guess maybe I'm wondering if it's maybe a little bit of a circular argument, like you're sort of assuming you can go it faster than the speed of light, and then you say, but if you can, then it would break the rules. It's almost like you make an assumption and then you say, if you break the assumption, then it doesn't work.
Yeah. Absolutely, And you're right, And we don't understand this limit at all. You know, we observe this limit. We say the speed of light is constant. It doesn't depend on who is sending the message or their velocity. It's always the same speed. And if you start from that, then you get to consequences like you can't move faster than the speed of light, and all sorts of things about how time varies, all of special relativity is based on that one observation. We don't know why that thing is true, but everything flows from that thing that the speed of light is constant for all observers, and so that's what limits you to going faster than the speed of light. And so you're right. If we observe the scenario in which that wasn't true anymore, then maybe you would, you know, change all these other rules, or maybe that's wrong and we just don't understand. So if you see somebody going faster than the speed of light or going backwards in time, that suggests that the speed of light is not constant for all observers.
Hmm. Interesting. I see. It's like, from what we can see about the universe, we came up with this speed limit of the universe, and then breaking that speed limit suddenly breaks everything we know about time and everything else. But it is, I guess, technically possible that you could, we'd like, go faster than light.
It's technically possible in the sense that you know, we've never observed it, and everything we have observed suggests that it is impossible. But you know, that's just physics. These are theories. We make an observation here, we infer about the universe. From it, we draw conclusions. If those conclusions are wrong, then either our inference was wrong or the observations we made were wrong. And hey, that would be awesome because that would be, you know, a childlike dream to overthrow something so basic as like the fact that the speed of light is the same is measured by everybody, but you know, it's something it's experiments we've been doing for more than one hundred years, and we've seen it very concretely and very stably for a long time. So we're pretty confident in this observation that the speed of light is always the same no matter who measures it. And the implication of that that it means you can't go faster than the speed of light is also pretty solid. So I think it's pretty airtight. But yeah, we haven't made mistakes.
Before, right, And so where does this idea that going faster than the speed of light would make time go backwards somehow?
Well, it comes from the idea that time is sort of fungible, that like the order of events that happen depends on your speed. Like if you're watching two things happen, like Alice eats a pie and then Bob eats a pie, and you're sitting there with them and you're watching, maybe you think Alice finishes first. But if I'm going at really high speed, I can find some scenario in which I see the order of events happening differently. Right, So, like Alice finishing before Bob is not like a universal truth. It depends on who's asking and how fast they're going. And so this idea that you know you can change the order of events depends on your velocity tells you that you can sort of play with time, and that velocity and time are connected.
But it's not necessarily the case that if you are going faster than the speed of light. Let's say, what was possible that somehow time would flow backwards, or like your clocks would suddenly start going the other way, or you know, you would travel to a different time, And that's sort of so far kind of not really establishing the math.
Well, what the math suggests is that if you go faster than the speed of light, then you can invert the order of things that you otherwise shouldn't be able to, Like you can switch who wins the pie eating contest Alice or Bob by going faster or slower going in some direction. Because those things aren't like causally connected, it doesn't really matter which one happens first. But if you go faster than the speed of light, then you might see weird things like Alice arrives at the piloting contest before she leaves her house, and you can switch the order of things, so they're like reversed in time. So in that sense, you're sort of like going backwards.
You would maybe experience things backwards, is what you're saying, which is sort of like and if the whole universe is going backwards, and it's sort of like you're going back in time, is what you're saying.
And we have a whole interesting episode about this theoretical particle called a tachion, which in principle, who's faster than the speed of light. But you know, if it exists, it would break all sorts of special relativity but has really weird properties, like you see it as if it's leaving, even if it's arriving because the later light arrives first because it's moving faster than light.
I see. So if if this particle's real, it would be very tacky, right, it would be breaking everything in the universe, and that's just not.
Cool, That's right. You'd invite it to your birthday party and would look like it's leaving your birthday party, and you're like, hey.
Man, yeah, hey man. All right. Well, it's a great question from Audi, is if the universe is expanding faster than light, can it go back in time? And the answer is kind of yes and no, Like, yes, the universe is expanding faster than light, but for you to sort of break the laws of time, you kind of have to travel faster than light, which is not what the universe is doing. The universe is expanding faster than light, but it's not traveling faster than light.
That's right. Nothing is moving faster than light relative to any other thing, and so that doesn't break the laws of special relativity.
Well, things are growing in distance from one edge of the universe to the other's faster than light, but nothing's actually, you could say, is traveling through that space faster than light.
Yeah, that's right, all right.
Well those were three awesome questions from kids. Thank you kids for sending in your questions.
And thank you parents for encouraging your kids to think about the universe and ask deep questions, because it's those kids that we hope are going to one day figure out the answers to these questions. They're not so entrenched in today's ideas about how the universe work, and they might have crazy new ideas about how to use lightsabers to cut open black holes and solve the mysteries of quantum gravity.
I don't think we need to think the parents, Daniel. Everyone knows it's a thankless job. You don't really get credit. But thank you to all of our listeners, young and old for having questions about the universe. I'm being curious for wandering about this amazing and mysterious cosmos that we live in, and if you have questions, please feel free to send them to us. We hope you enjoyed that. Thanks for listening, See you next time.
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. When you pop a piece of cheese into your mouth, you're probably not thinking about the environmental impact. But the people in the dairy industry are. That's why they're working hard every day to find new ways to reduce waste, conserve natural resources, and drive down greenhouse gas emissions. House US dairy tackling greenhouse gases. Many farms use anaerobic digestors to turn the methane from manure into renewable energy that can power farms, towns, and electric cars. Visit you as dairy dot COM's Last Sustainability to learn more.
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