New discoveries in our cosmic neighborhood

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Speaker 1: Hey, or hey, do you know what our cosmic addresses? Yeah, it's a one universe lane, isn't it. Well, that's where you can send us all your gifts of presence and bananas. I mean, that's how the aliens know where to find, is right, that's true. But I actually don't need a lot of bananas delivered in the mail, So let's not encourage people to send us any fresh fruit. No, no, I think you know what you mean, Like our address like in the universe, Like if we're here on Earth around our star about halfway down the Milky Way. Yeah, that's enough to get your mail delivered to your house. But like, what about the rest of our cosmic context? I mean, like what's the equivalent of our city or zip code? Yeah, And it turns out that we're part of a cluster called the Local Group sounds local, and then zooming out a little bit where the suburbs of an even bigger cluster called Virga, and then part of a super cluster of a hundred thousand galaxies called Lena Kia. And then you know, that's actually about as far as we've mapped. Wait, we don't know where we live exactly in the universe. We don't know, So if you want to order alien bananas, you just gotta put a question mark. Gonna throw up a flare. I am more handy cartoonists and the creator of PhD comics. Hi, I'm Daniel. I'm a particle physicist, and I don't like Earth bananas, but I'd be willing to try alien bananas. Really, how do you know they're not going to be worse? You don't know. But that's the joy of exploration. I want to land on a new planet, to see the new kinds of life, the new kinds of animals and critters, and taste any new potentially delicious fruits. Well, you're welcome to be humanity's taste. I guess to make sure it's all right, somebody's gotta do it. I'll probably come down with the alien banana flu. But welcome to our podcast Daniel and Jorge Explain the Universe, a production of My Heart Radio in which we don't take any actual trips out into the universe, but a mental journey through all the amazing questions and discoveries, all the things science has figured out and the things that science is still working on. We think that curiosity belongs to everybody, and that you are questions are as fascinating and as important as those that scientists are working on right now. Yeah, because it is a huge universe out there, with a lot of places to explore and a lot of things to discover, and a big question is how do we fit into all of this? What is our place in the universe? And how do we fit into this giant cosmic ballet of stars and galaxies and dust. And it's sort of an extension of exploration that humans have been doing basically forever, since we wondered what was over that hill, what's past that mountain, what's over that ocean? And modern day explorers might wonder like, well, is there anything left for me to look for? Thanks to Google Earth and satellite technology, we basically know where all the mountains are and all the little islands you can name after your chihuahua. But it turns out there's a lot of exploration left to do. Yeah, is there an equivalent of Google Universe? Google? Get on it now. Yet it's mostly a big question mark. But you can look at maps of our cosmic neighborhood to see what's around us, what's nearby? If you just google large scale structures of the universe. Wow, does it tell you how much each galaxy is worth? Can you figure out the perse square light here value? You know, even just our solar system is worth like a gazillion dollars because of all the platinum and gold and stuff that you can find in aster. So it's basically just infinite. Well, we are still learning about the basics of where we are in the universe and what's kind of around is and so a big question is, you know, what can we find? What interesting things are there in our very own neighborhood here in the universe, And it's not something that we can easily explore in person. In the old days of exploration, you would hop in a ship and you would land on foreign shores and you would wonder who else was living there and what kind of fruits did they enjoy. But these days it's not so easy. The distances are vast, the technology is still so primitive. But we have other ways of exploring the universe. You mean, we don't have those warp drives and teleportation devices yet. Well, you know, I sent them to the Daniel and Jorge Engineering department. So I'm just waiting for the prototype to come back last engineer in our team here. But yeah, you're right, it is kind of interesting that we have to explore the universe from here. From Earth using telescopes, we can actually like go out that far because some of the things that we can see are hundreds or millions of light years away, like the pretty much we might never see them in person. That's right, most of these things we will never see in person. And most of these things that we're looking at, they don't exist right now on the way that we are seeing them, right, we are seeing old light that comes to us from them. So what's actually happening now out there is not what we are seeing. Yeah, So astronomers are out there looking and exploring and checking out what's around us, and recently there's been an incredible discovery. Just this past summer, astronomers discovered a whole new thing pretty close to our corner of the universe here, and it's huge. It's basically the biggest thing anybody has ever found, and it's shockingly large and shockingly close. It's basically a literal mind exploder. So today on the podcast, we'll be asking the question what is the South Pole Wall and why did they give it such a ridiculous name south? But yeah, it's a little confusing because is it a pole or is it a wall? Is it a wall of poles? Is it a wall around the South Pole? I guess it's south, but south relative to who, Well, you have a very northern bias, right, You tend to view the earth is up, north is up, and so you know, maybe that gives you a clue. I was born in the equator, so, Daniel, I'm pretty agnasting. I think maybe this time you can rag on after physicists and how they name things, and as particle physicists can get a break for a weekend for once. Yeah, and also, who's paying for this wallt Daniel? The Aliens are definitely paying for the wall, yeah, with the tariffs. But yeah, so they discovered something huge and enormous. I mean, it's like you said, it's the biggest thing pretty much ever discovered. Is that true. Yeah, it's in the top five biggest things we know about in the universe, and of the top five, it's the closest one. So it's really kind of amazing that we haven't seen this before, that we didn't even know about it before. It really it makes me feel like, you know, cartographers in the fifteen hundreds drawing maps to the Earth and like leaving out America. You know, like how could to be so ignorant of like an enormous continent that's honestly not that far away. It'd be like discovering a whole wall of poles in your backyard and you're like, where did that come from? That's right, I didn't order this online. Yeah, so it's a new discovery. It's huge, it's very close. But we're wondering how many people out there know about this south Pole Wall and whether it was discovered recently. So, as usual, Daniel went out there and ask people on the internet if they knew what is the south Pole Wall? So thanks to everybody who volunteered to share their baseless and uninformed speculation with us for our podcast. And if you would like to be a victim War Future podcast to share your unprepared thoughts on difficult questions in physics, please write to us two questions at Daniel and Jorge dot com. Think about it for a second. Do you know what the south Pole Wall is? Here's what people had to say. Does that have something to do with flat earther theory, it's all a man made will but around South Pole to stop animals or in shooters from coming in as a way to preserve this out pole. Maybe it's some sort of electromagnetic barrier, not just an obvious structure, something to do with like a magnetic like the Earth's magnetic field, some sort of barrier for particles in the sun from the sun. Maybe it's related somehow to the like Aurora borealis and southern lights. The South Pole Wall is a ice fault formation that is incredibly difficult to traverse on foot or sled or with dogs. I have no idea. I am guessing that it is a wall, either physical or metaphorical, located in the South Pole. The first thing that comes into mind is a big rule of ice in the South Pole, like the one phone Game of Thrones. I'm not sure, but I believe there are some I don't know if they're called caverns or cliffs or something like that, but I believe there's some impediment in our way to get to the uh, to travel freely to the South Pole where the ice is all right. It sounds like nobody knew well. I think this is a real commentary on the name of this thing, right, because everybody keyed in on south Pole and wall, right, And I like how somebody said it was like Game of Thrones, although that wall wasn't the North. That's right, Maybe it's the equivalent. Maybe it's for like the penguin zombie. Well, we physicists, we do like having symmetry in the universe. So if there's going to be a wall in the north, there should be a wall in the south, because otherwise you gotta ask why what's special about North? Right? Yeah, winter is coming? Is there another version of our universe out there in the multiverse in which summer is coming? Well, technically, if it's a south Pole wall, it would come in our summer, which is winter for them. The beauty and power of symmetry once again displayed. But I guess maybe the takeaway here is that not a lot of people had heard of it, which means it didn't make the news that much. Maybe that's right. Most of our listeners are pretty up on the cosmic news here. Yeah, I think it just didn't fall into people's brains. It's an incredible discovery. It's something that's fascinating and something it tells us about where we live in the universe, but it doesn't really actually change your day to day life. So maybe people just heard about it and filed it away. But honestly, I think we should pin most of the blame on the name of this thing. Wow, I can't disagree with you more, Daniel about the naming of things. Finally we're agreeing about how the name. All right, let's let's not keep people in suspense here. So what is the South Pole Wall, Daniel? And when was it discovered? So? The South Pole Wall is an incredibly huge and immensely vast, gargantuan wall of galaxies. I remember that galaxies are not just sprinkled everywhere through space. Our Earth goes around our Sun, which is the core of our solar system, which is one of many solar systems in our galaxy. But those galaxies are not just everywhere in space, sprinkled randomly. They tend to clump together into clusters of galaxies, and those clusters of galaxies form structures we call superclusters. And then those superclusters are not just sprinkled everywhere. They tend to form these enormous structures, these walls, these filaments, these sheets that surround incredible voids in which there are no stars, no galaxies, no planets, no people, no podcasts. Yeah, it's weird to think of space being not random, you know what I mean, Like we're just still looking at the nights guy and seeing stars kind of sprinkled kind of randomly and evenly. But actually the universe has a lot of structure, like, it has a lot of things in it, Like everything's kind of organized in the way. That's right, Things are organized, and it's gravity that's doing the organizing. Gravity is very gently but very gradually pulling things together and clumping them. And it's kind of incredible that gravity is the thing doing this job. Because of all the forces we are aware of, the strong force, the weak force, electromagnetism, gravity, Gravity is the weakest, and not by a little bit, but like by tens of orders of magnitude. But it's also the only one that can't be like balanced out. Electromagnetism can be neutralized with positive and negative forces, but gravity always pulls. It can't push, so eventually everything else gets balanced out. Is just gravity left over to sweep stuff together into stars and planets and galaxies and superclusters. And then these incredibly immense voids and walls and filaments. And that's essentially where the exploration is today, is figuring out like where is our cluster and our supercluster in this larger structure, what's around us? Right? Yeah, And what's kind of cool too is that these giants, you know, super ginormous structures, they're all kind of evidence of the quantum fluctuations right at the very beginning of the universe. Right, there's sort of like the wrinkles or the fingerprints of quantum randomness and structure that was in the early universe. That's exactly right. Gravity has essentially just exaggerated initial little over densities. If you had only gravity in the universe was totally smooth, you wouldn't get any sort of structure at all, because gravity would pull equally on everything in all directions, and you wouldn't get any clumping. You need some sort of initial clumping to get things started and form this runaway effect where gravity makes things heavier and then pulls harder, and then makes things heavier which pulls harder. And you're right in the very beginning what this comes from, our little tiny quantum fluctuations in the very first moments of the universe, and basically everything's been derivative from that. It's like we had one idea very early on sketch the doodle, and everything else is just derived from that. And it's amazing. Do you think that you can go from like a quantum fluctuation is something that huge sort of like you know, like a little baby scar that you had as a baby, you still have it as an adult. And let's give people a sense for like how big we're talking about. These structures are like billions of light years wide. These are not little things. There's not like one galaxy, two galaxies. Remember each galaxy already is an incredibly enormous thing. But we're talking about bubbles and sheets that are billions of light years on a side, and that all comes from tiny quantum fluctuations expanded rapidly during inflation. Yeah, because you know, I guess like one galzi is a hundred thousand light years, and so if you put like thousands of them together, then it's literally billions of light years. It's billions of light years, meaning if you're going at the speed of light, it still takes you a billion years to go from one side to the other. And so you can imagine the whole universe is sort of like a big pile of bubbles, like a big quantum foam that was inflated from the early universe to this incredibly vast quantum foam. And we've recently discovered that we're essentially living on the edge of one of those bubbles. And we're now looking around us. We're like, oh, look, there's a bubble over there. There's a bubble over there. But we're really just beginning to map the universe to understand what is our cosmic neighborhood. We're seeing edges of bubbles here and bubbles merging over there, and so it's like it's early days, you know, we have only just begun to explore. Yeah, and so tell me about this wall that we just found. This wall, the South Pole wall. You said it's a ginormous. When you say ginormous, is that the technical term or is there a number associated? The technical term actually is huge jungis. But this one is a billion and a half light years wide. Right, So you shoot a photon, you press the button on your laser on one side of the thing. You wait a billion and a half years before across it to the other side. And that's only the part of it that we've seen so far. It could go on more. Yeah, astronomers are not even sure that we've seen all of it. So it's a structure of galaxies basically. Right, it's not like a row of stars. It's like a row of galaxies and they're all sort of like sprinkled in a wall or or what's going on. That's right, it's actually a row of clusters of galaxies. Clusters of galaxies are grouped together. They're gravitationally bound. There there's enough gravity between galaxies to sort of hold them together into objects. That's why we call them a cluster. We don't just like artificially draw a line and say this is a cluster, that's a cluster. We look for things that are holding themselves together gravitationally. So this is a wall of clusters of galaxies, and we call it a wall because it's much wider and longer than it is thick, sort of like our galaxy. Right, our galaxy is flat, it's like a hundred thousand light years across and a thousand light years thick, and these things have sort of similar dimensions. There are much much wider and longer than they are thick. So we called them a wall. Now do you call them Do you group them together because they're close to each other, or because they're actually kind of gravitationally affecting each other, or bound together they are gravitationally holding themselves together. Remember that the whole universe is expanding. Everything is moving away from everything else. That's because space between objects is getting bigger. We don't understand it. It's this thing called dark energy that's just inflating all of space and increasing the distances between everything. But if stuff is near enough to each other and has enough mass, it can resist that. It can be gravitationally bound. Like our solar system. Dark energy is increasing the space between the Earth and the Sun, but gravity of the Sun holds the Earth in place so that distance doesn't change. So our solar system is gravitationally bound. Our galaxy is gravitationally bound. It's small enough and compact enough that on that scale, gravity wins. And that's true also on the scale of clusters, and it's sort of true on the scale of super clusters. Clusters of clusters, people argue about whether they're actually gravitationally bound. Are they going to hold together in the long term future of the universe, or is dark energy gonna win and tear on them apartment. That's sort of on the edge, right, because I guess if expansion is fascin enough or big enough, it would even rip our solar system. But I guess we're we're lucky that it's not. That's right, We're lucky that it's not. But we're living in a fascinating moment in the universe where gravity has had time to build galaxies and clusters, and now superclusters have sort of formed and maybe gravitationally bound, but it's not clear if gravity will have time to build those together and really hold them together and then build super duper clusters, or whether dark energy will tear them apart. So we're living at this fascinating moment in the history of the universe. That's why there is a maximum size to an object in the universe, because any bigger than that, gravity hasn't had time to sort of pull it together. And so we're really looking at the biggest things in the universe. It's sort of incredible, right. So we found this giant wall, and so a big question I have is how did we find it and why didn't we see this earlier? If it's so big? So let's get into that. But first let's take a quick break. All right, Daniel, we're talking about the South Pole Wall, which is I guess, is that where the anti Santa Claus lives? Is that defense that it put around into health village? That's right, it's his first line of defense against folks coming to trying to steal their Christmas presents earlier. He's not as or she's not as jolly as the North Pole Santa Claus. No, there's South Pole boiling oil, and there's archery, and it's all sorts of stuff. Just just leave them alone. But anyways, they found this summer a giant wall of galaxies called the South Pole Wall, and it's huge. It's one and have billion light years wide. And Daniel, this seems like a big thing that we should have seen earlier, but we didn't. So I guess what's the history of finding this? How do we find it? And why didn't we see it before? We didn't see it before because it's not easy to spot. We can't actually see it very well because there's something in the way and that's the rest of our galaxy. If you look out into the sky, mostly you're seeing stars, and those stars are other stars in our galaxy. But remember the galaxy is much wider than it is thick, So in most directions you're looking out through a little bit of our galaxy and then out into deep space where you can see other galaxies and stuff. But if you look in just the right direction, then you're looking through the galaxy. And on a really dark night you can see this. You can see the Milky Way, which is the plane of the rest of the galaxy, and it looks much brighter and sort of more smeared out than individual stars because it's a huge number of stars that are further away there on the other side of the Milky Way, and so they sort of add up to this milky spread. And it's hard to see things on the other side of this plane of the Milky Way because there are so many stars and gas and dust in our way. Yeah, we're in the way of our view, kind of kind of like the back of your head. Yeah, the rest of the galaxy. And so they called it the South Pole Wall because if you're standing on Earth, it's sort of in the direction that the South Pole points. That is, the south pole of Earth sort of points towards the center of the galaxy. Not exactly, but you know, close enough, close enough for astronomical naming committees apparently. Yeah. Yeah, it is pretty amazing to think that we can see the Milky Way, right. I mean, it looks like a fuzzy cloud, but it really it's like millions of stars kind of all kind of joining their light together and causing this glow. Yeah, it's billions of stars. Right. The Milky Way has more than a hundred billion stars in it, and the center of the Milky Ways, where most of them are. There's also a lot of gas and dust, so it's just very difficult to see through the center of the Milky Way. Astronomers called this whole region of the sky the Zone of Avoidance. It sounds like something from a video game, but it basically means look somewhere else because this part is hard. Don't look here, you're not gonna be able to see much. Yeah, and so we can't actually see most of the South Pole wall in the visible light. We can't just like look at and say, oh, there's a galaxy. There's a galaxy. There's a galaxy, otherwise we would have spotted it earlier. You know. It was like in the nineteen eighties people started to understand that we could make a huge three D map of our universe and that it had interesting things to look at, and that's when we discovered the first of these voids and walls, and so now it's you know, forty years later, we're finally figuring out one of the biggest structures was hiding right behind the bulge of the Milky Way. It is sort of fascinating that, you know, from our little point on Earth, just sitting in the spherical ball and looking out at the stars, we can get a three D D view of things, right, because when you look at the night sky it looks kind of like two D, like all the stars are painted on the ceiling. But somehow we're able to get a three D view of what's going on out there, to the point where you know, we can make out these super cluster structures. Yeah, it's incredible, because of course you're right, we do see it two D image, right, We can't resolve distance. We don't know necessarily how far a star is, and this ambiguity there when you look at one individual star, you don't know is it's super bright but very far away, or not that bright and kind of close up. So for a long time, that was a big puzzle in astronomy, is how to measure the distance two stars. We had a whole fun podcast episode just on that topic, and it turns out that it depends on how far away it is. If it's really close by, you can use the equivalent of sort of like opening one eye and closing the other one and seeing how the image changes to see how far away it is. As the Earth goes around the Sun, you get two images of the star, and if it's further away, you have to rely on these super clever little stars, these variable stars, whose brightness is connected to how fast they pulse. And then if they're really far away, then you have to use type one a supernova, which is sort of a standard candle. We know how bright they are because the physics constrains them to only be a certain brightness, and so we can tell how far away they are. So we have this sort of cosmic distance ladder, but that only works for things we can see. Yeah, so the Milky Way is kind of standing in the way of a huge part of our field of view. It's blocking it, but somehow we were able to see through it is to find this South Pole wall. So how do we look through the Milky Way? Well, again, the answer is gravity. Gravity is like the most important thing astronomically. It basically controls the whole universe. And in this case, what we did is we measured how fast some galaxies were moving and in what direction to make a sort of cosmic map of the flow of galaxies, and then we use that to figure out, like, well, where is there stuff? Because gravity affects how things move. So we started from understanding how galaxies are flowing, and then we look for sort of like blobs, like discontinuities, like oh, everything is clustering over here, there must be something there, or these guys are flowing fast, and then we expected so they must be pulled on by something. From the velocity of galaxies, you can infer where the mass is. But wait, our galaxies moving that fast, and we as humans and in such a short period of time, can tell they're moving because like, if I look at the stars, they don't look like they're moving. That's right. We are not watching galaxies move and like clocking them. It's not like Usain Bolt, where we measure a distance and measure of time and then use that to measure the velocity. Instead, we're looking at the light from those stars and we're seeing how the light from the stars is shifted in frequency because like the Doppler effect, if something is moving away from you, then light from it will get shifted to longer wavelengths so gets stretched out. And something is moving towards you, light from it will get shifted to shorter wavelengths to get blue shifted. And so we can measure the light from these stars and we can see hasn't been shifted away from what we expect because we we know what the light from these stars, from these galaxies should look like. Because stars around the universe are all the same, they admit from hydrogen and from sodium in various lines. We can see those lines get shifted, so we can measure the velocity of all of these galaxies. So we have this huge catalog of thousands of thousands of galaxies and we know in which direction they're moving. But wait, I thought the shifting of light only works if it's moving away or towards you. How do you tell if it's moving to the right or to the left, or up or down. That's true. The red shift and blue shift measures the velocity along a line from us to them, and sort of the radial velocity, and so you have to use other tricks to try to sort of guess and construct from the motion of all the galaxies nearby what these sort of three D map is. But you're right, we don't really know a lot about this sort of transverse motion of these galaxies. So everything we know is is just from that velocity towards or away from us, that's right, and we're we're sort of guessing about everything else guessing. You can see these things moving over short periods of time, so you have some idea, but they are really far away, so it's very difficult to measure those distances. And also how do we know where they are how far away they are? Don't we need like a supernova to happen in them before we know, or do we have supernova from each of those thousands of galaxies, we have supernova that go out really, really far. That's the nice thing about type one A supernova is they're they're super bright and they're basically in every galaxy, but we don't have one. We haven't seen one necessarily in every galaxy. But we have ideas for where other things are, so we can place them sort of in a ladder, and we have the most information about the closest things. And so that's why we're starting to map the structure of the universe. And we're beginning from the nearby neighborhood. That's where we can see for examples, to sephids in some of these galaxies and type of a supernova. We definitely have the most information about the local neighborhood. All right, So then step us through, how do we find the South Pole Wall. Did we, you know, gain some sort of new trick to look through the milky way or we just got better at it and suddenly it popped up. It's just sort of like being careful and finally analyzing the hard bit of the data. You know, if you're doing science, you get a bunch of data and the first thing you do is you eat the ice cream off the top, right, And I said, well, here's the easy question to answer, the most exciting one. You do that, and people have found cool stuff. They found the Sloane Great Wall, which is as big as the South Pole Wall, but it's further away and it's easier to spot. So they found other structures. But then people started to get more comprehensive about their search, and so they looked through sort of some gaps, and they noticed there was a gap in our cosmic neighborhood where we didn't understand what was going on. That's because it was behind this zone of avoidance. So they decided to look like, well, what is there, and they combined data from a bunch of different surveys slowing Digital Sky Survey and lots of other surveys to make one sort of mega database of all the galaxies called cosmic flows. And so they analyzed this hard bit and they noticed that galaxies between us and this region, we're moving away from us faster than you would expect from just dark energy, and the galaxies past this region we're moving away from us more slowly than you would expect. And so that's suggest right there that there's some like big blob of some moving together. There's some gravity. They're holding it together, pulling on galaxies between us and this blob and slowing down galaxies that are past the blob. We saw like this giant, like if you're looking at it on a on a radar, you would see like a like a flock of birds kind of all moving together away from us. Yeah, exactly. So you put together where all these galaxies are and how fast they're moving away from us, and the only way to explore in the velocities of these galaxies. They call this peculiar velocity, velocity other than the velocity of the expansion of the universe. The only way to explain this peculiar velocity, such a quaint term peculiar, is in like local, you know, like as in our velocity and not somebody else's. They didn't want to go with weird or or local velocity or something anyway. The only way to explain this peculiar velocity is to say, well, there must be something big there, some new source of gravity. And this is not the first time that we've used gravity to deduce the presence of something. Remember our podcast episode about the Great Attractiveate. That's some other like incredible source of gravity that's similarly tugging on stuff and changing the peculiar velocities. So we know that there must be something there, all right, So we saw something big out there but we can we see it directly, like can we see the glow from it, or we can only see the gravity of it. We can only see the gravity from most bit little bits of it sort of peek out the sides of the zone of avoidance. Then you can't spot it. And then they actually went back through old surveys to say, shouldn't we have seen this before? And it turns out that you can see sort of edges of it in previous astronomical surveys, and so people have been sort of like known to look for it and and have been paying more attention. They could have discovered this like ten twenty years ago. They saw like the edges of it, the edges of it sort of peek out past the zone of avoidance. The bulk of it, though, is basically invisible to us in terms of electromagnetic radiation that we can't see it via radio waves, are infrared or anything because it has to pass through the galaxy. So it's only gravitational information that we have about most of it. But that's pretty good, Like if you look up this paper, they're pretty good three D map of the density of this thing that shows you like where the galaxies are and where they aren't. It's a fascinating structure. All right, Let's get into the shape of this South Pole Wall and why it's important that we found it. But first let's take another quick break. All right, Daniel, we're talking about the wall south, the Southern Wall that the first man built, or the first Aliens built, I guess to keep out the alien zombies. You know, I'm just kidding. We found a giant galactic structure, or a structure of galaxies kind of pointing if you look south of the Earth towards the South Pole and keep going past the Milky Way out there in space, and it's huge. It's one and a half billion light years wide. And what does it look like, Daniel? Is it like literally a wall, or like a sheet or just like a giant lump. This looks like a giant cosmic banana. You're just saying that, Daniel, just saying that. It really does look like a huge banana. What do you mean, like like it's curved. If you look at this thing from the paper, it's sort of long and narrow, and it even has like a little thing sticking up at the top that could be like you know, where it's peeled off the giant cosmic banana tree man. So are you saying it looks delicious, is what you're saying. I'm saying you've got to be hungry to eat this thing as well. It's huge and it has a lot of potassium, a lot. I'm not joking that it looks like a banana. But you know, it's sort of like staring at clouds. You can see whatever shape you want, and so I guess I just had bananas on the brain in my mind. It's not as much of a wall as is sort of like a vast tube, but it's definitely big, and it's incredible because it's it's also telling us not just where the stuff is that we can see where the galaxies and the stars and maybe the aliens and their bananas are. It's also a map of the dark matter. What what do you mean? Well, remember that stuff in the universe is not sprinkled at randomly, right, It's clumped together based on the gravitational over densities from the early universe. But most of the stuff in the universe is not the kind of stuff that we can see. It's dark matter. There's five times as much invisible mysterious matter that's affected by gravity. As the kind of matter that we're familiar with and the kinds of matter that we can see tend to line up with the dark matter. Both of them are affected by gravity and they pull on each other. So actually, when you look at stars in the sky, they're telling you where the dark matter is, because dark matter has created these like gravitational wells for stars and galaxies to fall into into form. So the light matter, the normal matter, is sort of like lights showing you where the dark matter is. I mean, but we think right like, you're assuming that where there are stars, there is dark matter. I mean you're assuming like it's the same kind of concentration or ratio between dark matter and regular matter as we have. Yes, and that's something that we've seen. We've measured in lots of different galaxies and we see some variation there. There are some galaxies with more dark matter or less dark matter, and we don't full understand that at all, but roughly we can say that there's a five to one relationship between dark matter and normal matter, and certainly on distances this large enormous supercluster sized structures, we expect the dark matter to have formed these structures like they just would not have formed without the dark matter. You run a simulation the universe without the dark matter, you just don't get structures like this this early in the universe. I feel like you're almost telling me that the you know, basically most of the universe is dark matter, and it's clumping and doing its own thing, and really the stars the bright stuff. Us, we're really just kind of like the bling, you know, like we're just here to tell everyone where the dark matter is. Yeah, we're like those birds that ride on the back of rhinoceroses and sort of like pick the worms off of them. That's us. Yeah, I mean, call us the bling, call us the worm eating birds. Whatever you like. Where the frosting on the cupcake. Yeah, kind of right. I mean when you when you talk about the structure of the universe, it's really the dark matter structure we're just hanging on. Yeah, we call it normal matter because we're used to it, but it's actually pretty unusual in the universe. It's just five percent of the energy in the universe is devoted to making me and you and cosmic bananas. So that's why it's fascinating to sort of use this light matter, this luminous matter to tell us what's actually going on in the universe, and gravity is really the key there. It tells us where the dark matter is. It's also telling us about the balance between the dark matter holding stuff together and dark energy trying to tear it apart. Except that here we can't actually see the galaxies in the stars in the light right like we can only see the gravity, which means maybe this whole wall is just a giant wall of dark matter. We don't really know, right, that's true, We don't really know. Although on the bits of it that we do see, the edges of the banana that stick out past the zone of avoidance, we can't see luminous stars there. So it would be pretty weird to find a massive dark matter wall, But that would be pretty awesome and gives a sense of how big this thing is, Like how any galaxies are in this giant wall? Or like how many stars? Do you have a sense? It's trillions and trillions of stars, you know, it's thousands and thousands of galaxies, and each galaxy has billions of stars, and we don't know how big this thing is. The thing that's incredible to me is that before we discovered this, we had sort of a gap in our understanding of the cosmic neighborhood right around this spot, right, and people like, well, we don't know what's there, probably nothing interesting. And then they found this great wall and it's basically completely fills that gap. You know, it's like it couldn't have been any bigger. You know, there's like a little spot you haven't checked and you open up the door and it turns out it's totally full of stuff. We have this giant gap that looks like a banana, but we don't know what's inside. Oh wait, it is a giant banana. The giant banana. And you know, it's really important that we understand the shape of the universe around us. It really is telling us about how the universe was formed, because it tells us about how this structure has made and it's telling us about the future of the universe. Is telling us, is dark matter gonna win and hold this stuff together? Is dark energy gonna win and tear this stuff apart? You know, we think about this stuff on really long time scales, billions of years, but it's really sort of frothing and dynamical. This is sort of like if you watch froth forming or water boiling, but you just watch the first like two milliseconds of the movie. We're basically two milliseconds into the movie of the universe, of this frothing, bubbling boiler, trying to understand the forces at play. Wow, you mean, like we don't know who's gonna win at the end, but we're still figuring that out looking at the things around us. Yeah, well, we know that dark energy, if it continues as it has been, is gonna eventually tear things apart, but we don't know where those fractures are going to happen exactly. Like how much will gravity get to clump together to form structures that will be impervious to dark energy, and then dark energy will just increase the distance between them. How big will those objects be? We don't really know. It depends sort of delicately on how much dark matter and how much dark energy there is. I mean, like, well, the universe is expanding, but the stuff in it could hold together. Potentially, the stuff and it probably will hold together. Our galaxy will hold together, Our cluster of galaxies probably will hold together. Will our superclusters survive or be torn apart? By dark energy. We don't really know will these walls and filaments be pulled apart. Are they even gravitationally held together today? Or are they just sort of near each other. These are the questions we don't know the answer to. It's like a cosmic battle between the two greatest forces in the universe, and we're basically right in the middle of We're just here on the back of the rhinoceros picking worms, looking at it like eating popcorn, but instead of popcorn, it's it's worm. That's right. Hey, look this worm looks like a banana. Al right, Well, it's pretty amazing that we are still discovering things that are that big. Like you know, if I look at into the sky, how big is this giant wall, Daniel? Is it like like an inch or like a centimeter, or like a whole foot as a fracture of the night sky? If you held, I think a banana at arms length. It's about that big. No, that's too much of a coinci is, Danny. It goes from the constellation Perseus in the northern hemisphere to the constellation APUs. I can't pronounce this one in the far south, so it is really pretty big. And the incredible thing is that it's twice as close as the Sloan Great Wall, right, this long great Wall, just as big discovered decades ago. This thing is twice is close, which should make it more obvious. But you know, there's just so much we still don't know about, the pretty local, large scale structure and sort of the grand scheme of things in our neighborhood. It's amazing. It's amazing. It's almost like we're, you know, explorers. Only a thousand years ago. We didn't know that America was there, or you know, Australia was there. Probably I know how many incredible opportunities were there to discover things, you just have to hop in a boat and sail for a few days. If you had known where to look, discovery is easy. And that's the situation we're in today. We're looking around us and we just don't know what's out there. There could be incredible, mind blowing surprises if we just look a little further or look in the places that have been hard to look at so far. Are definitely surprises out there. And then remember we've only mapped a tiny little dot of the universe. When we talked about like our Solar System being a tiny fraction of the Milky Way, which is a tiny fraction of our cluster. If you look out even further, it just goes on and on and on, and what we've mapped is a tiny fraction of just the observable universe. So most of it is a huge cosmic question. It could be maybe an infinite question mark. It could be an infinite question mark, And it could be that we just have sort of bubbles and walls and voids that go on forever. But it could also be that once you get a sense of those bubbles and voids, that you see a larger pattern and that could tell you something about the early universe and this quantum foam that generated all of this structure. Or it could be that at that level it's mostly random. We just don't know the answer. Like that's a pretty big question to not know the answer to. And maybe once we figure out our address, we can finally get those deliveries from the Amazon aliens. That's right, and I want them in thirty minutes by drone from across the universe, same century delivery. I'll pay extra for that, all right, Well, we hope you enjoyed that and you've got a little bit of a better sense of where we are in the universe and what's out there for us to discover. Thanks for listening, See you next time. Thanks for listening, and remember that Daniel and Jorge Explain the Universe is a production of I Heart Radio. For more podcast from My Heart Radio, visit the I Heart Radio Apple Apple Podcasts, or wherever you listen to your favorite shows. M