What's the Oldest Thing in the Universe?

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Speaker 1: Hey, Jorge, who is the oldest person you know? I have a couple of uncles that are in their late eighties. I think that's about as old as it gets in my family. That's pretty good. They must have eaten a lot of bananas or zero bananas, whichever is best. I can't keep trying. May either been at a neutral What about you? My grandmother, my mom's mom is a hundred and five years old and she still beats me at scrabble. Wow, what's her secret? I think she just likes beating people at scrabble, and that's what keeps her alive. I guess what age comes wisdom and a very large vocabulary. Hi am orgem a cartoonists and the creator of PhD Comics. Hi. I'm Daniel. I'm a particle physicist and my kids think I'm pretty old, but I feel young at heart. Welcome to our podcast, Daniel and Jorge Explain the Universe, a production of I Heart Radio in which we talk about all the amazing things in the universe, the new stuff, the old stuff, the close stuff, the far away stuff. We talk about everything you want to hear about. We break it down, we explain it to you in a way that we hope also makes you laugh. It's right, we talk about the boring stuff in the universe, but we also like to talk about the extreme stuff in the universe, the things that are pushing the boundaries of what is possible in this crazy cosmos. That's right because the extremes tell us about what the rules are. How hot can something possibly get, how cold can something be, how fast can it's been? What is the brightest possible thing? Because usually when we look at the extremes is when we learned about something new in the universe, we say, wow, we didn't realize it was possible to shoot particles at that high energy the Earth. What could be doing that? So that's why it's a lot of fun to look at the most extreme stuff in the universe. And so we have a series of episodes dealing with the most of a lot of things in the universe. If you look back to our archive, you can listen to episodes about the biggest thing in the universe, the brightest things in the universe, the darkest things in the universe. And so today we'll have an episode about one such extremes. Are are are we giving out awards? Should we be like making trophies and handing them out to astrophysical objects, and we we can send them as certificate, like an email certificate. Maybe just being the subject of a whole podcast episode is enough reward for them. Yeah, they can listen under CV, or they can put a little like logo next to their cover or something that says they were featured in our podcast. That's right. I'm sure the supercluster we're in is always emailing at CV around the universe. And by the way, did you know I was the subject of a podcast? What do you think the email addresses everywhere everywhere at everything dot com. That's right. But even if nobody is interested in winning these prizes, we are interested in exploring them and talking about them because they're super fun. Not only because it teaches us something about the universe, but because these are the wow factors. These are the reasons why the universe is amazing, because things are super big and super hot and super fast and super spinny and super everything. And so today on the program, we'll be asking the question, what is the oldest thing in the universe? The oldest thing, not the oldest person. We already determined that's her grandmother. No, she's she's like twenty something years away from being the oldest person. The oldest person is like almost a hundred and thirty. It's ridiculous. For real, Yeah, for real, Yeah, I think it was like some old French lady. Don't you remember? There was a guy when she was in her eighties. He bought her apartment for some really low price under the deal that she could live in it until she died. He figured she was going to expire in a few years, but then she outlived him, and she lived to one twenty something and he died in his eighties, never having moved into the apartment that he purchased. It's amazing. I'd love to see that person plays grapple with your grandmother. What do you think would win? I don't know. I think there'd be a lot of cheating. I guess who's going to call them out right? Exactly exactly. But I think this is a really fun question because it makes you think about the early days of the universe and like what God formed first and then what's still around. And it's also makes you understand like the grand sweep of time. You know, a hundred deers seems like a long time for us humans. But it's the blink of an eye. Cosmologically, our universe has been around for billions of years, and so it's it's fun to think about those things that just exist on a completely different scale. And I guess we need to get a little bit philosophical here, because you know, this sort of opens up a couple of questions. First of all, what do you mean by the oldest thing in the universe? And I guess do you mean the oldest surviving thing in the universe. You know, there's a whole branch of philosophy, you know, thing is um what is a thing? What defines a thing? What isn't the thing? What makes something two things? Is that a thing? Really? In philosophy? No, I just made that up. We just founded a whole new branch of philosophy right here on the podcast. It's the newest thing in the universe, the latest thing. We should put a sticker in ourselves saying, I philosophies. Yeah, it is an interesting question. What do you call a thing? You have to go through several categories and talk about what is the oldest for various answers of the question what do you mean by a thing? All? Right, well as usual, we were wondering how many people out there thought they knew what is the oldest thing in the universe? So I solicited volunteers to answer questions without doing any research, off the top of your head, answer a hard physics question from a dude on the Internet, and of course people were happy to oblige. So thank you to everybody who participated, And if you would like to answer random future physics questions, please write to me at questions at Daniel and Jorge dot com. Before you listen to these answers, think about it for a second. If someone ask you what is the oldest thing in the universe, what would you answer. Here's what people had to say. Maybe as some proton it is a fortune thing. The oldest thing in the universe, from what I understanding, would be the leftover resident cosmic microwave radiation after the initial Big Bang. But if you're looking for an actual object or a thing, I believe primordial black holes, I'm thinking cosmic background radiation. I think the oldest thing in the universe um is CMD. That's what we can observe at least after that. I think it is cluster of Alexi cluster, which is about twelve and a half million years old. I'm gonna go with space. How about that? Wow, tough question. Maybe black holes. So I would say the oldest thing in the universe would be quirks. But if you mean by something that actually gets assembled, then I would say hydrogen. If you don't mean an object, then I would say a primordial black hole. I'm not entirely sure what the oldest thing in the universe is. I know that after the Big bag Um, as far as we know, that was just plasma and quantum fluctuations. There weren't particles at that point um. These quantum fluctuations we think may have caused primordial black holes. So perhaps that's the oldest thing in the universe. Man, there are some good answers there. Huh yeah, Wow, it's been impressed. Some of these made me think, like, a proton is a protonon of thing? I'm like, huh is it a thing? If you asked the protein, it would say it's definitely a thing, or it's like space. Somebody said space like a space the thing? And could that be all their than anything else. Yeah, that's a really good question because you might then think, well, is the universe a thing? Right, what's the oldest thing in the universe. It's the universe Boom podcast over everything whatever, everything is that that was there from the beginning of everything. Yeah, and you might say everything is definitely a thing because it has the word thing in it, But then nothing is not a thing and it has the word thing in it. So now I'm overthinking it or overthinking it. I think you're trying to win a scrabble here. It sounds like trying to argue what a word is. But yeah, it's it's it's interesting to think about what is the oldest thing because there is sort of an age to the universe. That's right. When we look out to the universe, we see that everything is rushing away from us, that the universe is getting less and less dense. It's spreading out, and when you run the clock backwards, everything compresses and get back to some like original really high dense point. And we have an age for that. We can project that backwards in time, and it's about fourteen billion years ago when everything was really hot and dense. Of course, we don't really know what happens then our theories breakdown at that moment. We don't know if there was a singularity or something came before it or whatever. But that's generally considered roughly to be the approximate age of the whole universe just under fourteen billion years, fourteen billion years young, and you could be fourteen billion years young. This could be like the first moments of the universe on the trillions or quadrillion years life cycle of the universe. Right, we don't know how far down the road we've walked. It seems like a long time, but then again, after ten million years it might have seemed like a long time. And we know now that that's only just the first blip, So we don't really know if we're like looking at most of the iceberg or just the tip of it. Right, it's like a teenager. They feel like they've lived a whole life and everything there's to know about everything. Everything the universe knows nothing man, wait till it grows up. But yeah, how sure are we that's the age of the universe? I know we can we get it from, you know, rewinding the trajectory of space and the expansion of the universe, But is there any ambiguity about that? Like, how sure we couldn't be that the universe didn't do what we think it did, you know what I mean, like, maybe it didn't compress smoothly from what we've see right now, Well, we can see pretty well back in the history of the universe. We don't just project, we can actually see the history of the universe as we look out into space. Remember that it takes light a long time to get here from other places, so things that happened a long time ago really far away, that light is just now arriving at Earth. So we can literally see the history of the universe and we can record its expansion, and so we're pretty sure about the history of the expansion of the universe. What we're not sure about is what that represents. That moment fourteen billion years ago. Was it really a beginning? Was it just like the start of cycle number four and fifty two? Is there an infinite number of cycles before that? Did the universe space assemble from something else, some deeper quantum foam. We don't really understand and whether we can call that a beginning, But we know there was a special moment about fourteen billion years ago. And how certain are we We haven't nailed down to within about a hundred million years. Wow, that is very specific. It's pretty specific, but it's also a big range. You know, like if somebody said to you, hey, I'll meet you tomorrow at three pm plus or mind is a hundred million years, that wouldn't feel very specific, but that would be hard to sing happy birthday about. But if someone said, you know, you're a hundred years old plus or mine is a couple of days, Yeah, yeah, that's true. But I guess my question is how far back can we see, Like can we actually see things back that long? Or is this is it all sort of based on a projection? Now we can see that far back in time. If you look at stuff near our galaxy, you know, we're in the Milky Way, and the neighboring galaxy, Andromeda, is like millions of light years away. So when you're looking at Andromeda, you're seeing what happened, what it looked like millions of years ago. That's the closest galaxy, that's like our immediate neighbor, and that's millions of light years away. Then if you look further out, like billions of light years, you get to these big structures. Because galaxies form themselves into superclusters, and those superclusters are organized into sheets that encompass these vast voids, these bubbles, and one of them, for example, is called the Sloane Great Wall, one of the first of these really big structures to be discovered, and it's about a billion light years away. A great wall of stars or galaxies, a great wall of galaxy superclusters, right, So stars are formed into galaxies, galaxies are formed into clusters, Galaxy clusters are formed into superclusters, and then those are organized into these walls, these sheets that wrap around these bubbles. I wonder who paid for that, Danny. It's a lot of dry wall and a lot of paint. Who picked those colors? Right? With their galactic arguments about which shade of green or which shade of red to burn, which spectrum of the electromagnetic radiation it's going to give off, So that that's a billion light years away. That's billion light years away, and then we can look further out, and it becomes hard earned harder to look further out because these things are more distant, and so you need more powerful telescopes, or you need to focus those telescopes for a longer time. And that's like the reason we don't have a great map of the entire universe so far is just that that light is distant and dim, and so you need a lot of telescopes looking at it. But we do see some individual galaxies, like the hubble points itself in one direction of space and just sort of like accumulates photons for days and days and days. Then you can see the dimmest galaxies, the ones where photons are arriving most rarely because they've spread out through the whole universe. And there we can see galaxies that are like more than thirteen billion light years away. Wow, that's almost the age of the universe. It's almost the age of the universe, which means something amazing and fascinating, right. It means that galaxies formed very early on in the universe. For example, the oldest known galaxy is one called g n Z eleven. It's thirteen point four billion light years away. That means that it's formed just a few hundred million years after the start of the whole universe. Well, and the images we're seeing of that galaxy, it looks like it did thirteen billion years ago, right, Yes, we're seeing baby pictures of that galaxy, Like we don't know what's going on with that galaxy today. Does it even still exist, did it leave home, did it get a job, did it have a big argument with his parents? We don't know, But the baby pictures are what are arriving now at Earth. And if we waited another ten billion years or so, we would see the future of that galaxy, what happened to it, and everything that subsequently occurred. But right now we're only seeing the original light that left thirteen billion years and when it was and it looks like a fully formed galaxy, like you can see the structure in it. And even though it's that young, what I mean is it doesn't look lumpy and wrinkled like a baby. It doesn't look lumpy and wrinkled like galaxy in the very early universe do look different than galaxies today. A lot of galaxies we have today are really big because they're the product of galaxy mergers. Many galaxies come together in a lot out of the spiral galaxies are the product of the mergers of several galaxies. So this looks like a younger galaxy and it's a great way to study the very early universe. Like these infrared telescopes that we have and that we're sending up soon are going to be great at looking at this light from the really really oldest galaxies, the ones that don't glow as much. So, yeah, we can use this to study galaxies at the very early age. And they do look a little different, like galaxies looked different in the very beginning of the universe than they do today. You see. I guess the question is, and have we seen any stars that old or I guess I mean, if you look at the galaxy, you're looking at the stars in it, so you're sort of looking at really old stars too. Yeah, we are looking at old stars. But there's sort of three populations of stars. There's the stars that are around today, and most of these have formed from the collapse of the previous generation of stars, and those stars formed from the collapse of the previous generation of stars. Remember, stars happen when you have a bunch of gas and stuff gathered together by gravity enough so that they burn. And we think that the first generation of stars formed fairly early in the universe, but they were really big, and really big stars burn really really hot, and so they don't last for very long. And so that population of stars we haven't ever seen. We haven't seen any stars from that time. But if we're seeing a galaxy from that time, aren't we seeing the stars from that time too, Or are you saying we haven't seen like an individual pinpoint of light that is one of the oldest stars. We haven't seen an individual pin point of light. But also we think that this galaxy has stars from the second population. We think that first population didn't live long enough in this galaxy. It lived less than a billion years, less than a billion years. Those stars did not last for a billion years. They were really big and hot and burned very quickly, so we haven't seen any direct evidence of those stars yet. Those are called population three stars. Wow, they burned out in less than a billion years, less than a billion years, absolutely just out of hydrogen, just out of hygen and the keys that they're really big and really big stars burned really hot and really fast, and so those are all gone. And that's an interesting point because those stars were created a long time ago, but they're no longer around. So they were created in the early universe, but they don't exist anymore, so they're not really old because they're gone. I see. So galaxy g n Z eleven is thirteen point four billion light years away, which means it's thirteen point four billion years old. So is that the oldest thing in the universe? We don't know if it's thirteen point four billion years old. We know it existed thirteen point four billion years ago, we don't know what it's doing today. Right. It's like if you look at a baby picture from somebody from a hundred years ago, you don't know if they lived till two or five or a hundred. So they could be the oldest person alive if they were still around today, but you don't know, you're just looking at the baby picture. I see a lot of people when they think about, you know, what is the oldest thing in the universe, they are tempted to think really far away, really distant in time. But we don't know if those things are still around. I see, we're asking what's the oldest thing that is still around? Yeah, because you're not old if you didn't live very long. Right, somebody was born two hundred years ago and died ten minutes later, isn't the oldest person in the world? Right? Oh? Interesting, I guess I guess what would happen? What could have happened? To that galaxy. Like galaxies just don't disappear. Galaxies don't disappear, that's true. They get absorbed into other galaxies sometimes or they get torn apart by other galaxies that come near them. You know, there can be a lot of gravitational turbulence, so that galaxy may not exist on its own anymore and may have been absorbed by collisions into other galaxies, or it could have gone shredded, yeah, by other galaxies coming nearby and the gravitational tidal forces. It's a dangerous universe. When you send your galaxies out there into the wild, you don't know what's going to happen. And make sure they look both ways before crossing the universal streets. All right, let's talk about what is still around and what might be the oldest thing in the universe still alive today. But first it's take a quick break. All right, we're talking about what is the oldest thing in the universe, and so Daniel, we were talking about a galaxy that was around thirteen point four billion light years away, But you're saying that's not necessarily something that is still around today, meaning that like what we're looking at is stuff that was in the past, but we can't tell if it's still around today. Yeah exactly. We don't know what's going on really far away right now because it's going to take that light another thirteen billion years to get here. So if we want to talk about what the oldest thing in the universe is, we need to look at stuff that's kind of nearby to us, that's kind of close so it doesn't take the light so long to get here, so we can see it that it's still around. But it feels like a you know, like a loophole or like a paradox almost, like you know, we can only tell if it's old by looking at it, but we can only confirm how old it is if the light is old that we're seeing of it. Do you know what I mean? Well, if there was something that was created in the very early universe nearby and still around, and we could somehow measure its age, then that could be crowned as the oldest thing in the universe. It wouldn't take light very long to get here from it because it'd be nearby. I see. We have to see something old, is what you're saying, Yes, exactly, and not just a really old picture of it. Yeah, we want something around now that's old, not just old information about something that existed a long time ago, which might not be around anymore. You see. It's not like you're trying to ask, what is the oldest baby picture of a person you can find. You're trying to ask like, who is the oldest French lady living in an apartment that we can talk to today? Exactly? And both are fascinating questions. And I want to see the oldest baby picture ever. That's actually a really cool question. What is the oldest baby picture? Who was the first baby to ever be photographed? I don't even know the answer to that. And that's why we do look really far away to look back in time, because we want to know the original history of the universe. But that doesn't tell us who's still around today. So yeah, I want to see the astrophysical equivalent of the oldest French lady. All right, So let's start in our neighborhood. I guess in our galaxy, what's the oldest I don't know, star or cloud that we can see. Yeah, things get pretty old right around in our neighborhood. Now, our star is only about five billion years old. It's formed just under five billion years ago from collapse of a big cloud of gas and dust and bits of other stars. Right, that's about five billion years ago, But the Milky Way itself is much older, and there are older stars right here in our Milky Way, much much older. How old are we to, Well, what's the oldest star we can see here in our galaxy? Yeah, there's a star here that goes by the awesome aime of h D one zero to eight three, and at least it's you know, that's a big plus twenty years ago. We're trying to upgrade it to four K but it costs a lot of money and it has a really weird age. So, you know, the universe is just under fourteen billion years old, this star is fourteen and a half billion years old, which is weird, Like, what, yeah, how can the star be older than the universe. Well, it turns out there's a big uncertainty on that measurement. It's fourteen and a half plus or minus point eight billion years, so it's almost a billion years of uncertainty. But it's super wow. Wait, and it's right here in our backyard. Yeah, it's only two hundred light years away. It's like pretty close by. It's one of the closer stars in our galaxy, and it's the oldest star we've seen in the galaxy. Wow, or maybe ever? Is it possible? Ever? Yes, absolutely, it's one of the oldest stars known in the universe. Of course, it's much easier to measure the age of stars in our galaxy than in other galaxies. But yeah, it's one of the oldest stars in our galaxy and in the universe it's crazy old. Yeah, because we we can't really see stars in other galaxies, right, I mean, unless it's like a supernova or something super duper bright. But generally speaking, you know, most of the stars that you've seen in the night sky are in the galaxy. Yeah, exactly. You can if you have a very powerful telescope sometimes resolve stars and other galaxies, as you say, if they're very very bright. But most of the stars we're looking at the constellations, for example, this is just the rest of the Milky Way. We're embedded in it, and as we look out into the night sky, those are the stars we see. And this star here is really old and it's lasted a long time because it's pretty small, like these stars don't burn very quickly. A really big star burns really fast, and a really small star burns much slower, and so it can sort of like stretch its fuel out much longer. It just sits there, simmering, simmering and anger and being small. Exactly, it's grumpy and even it literally comes from a previous generation of stars, Like our sun is made out of the destroyed bits of this second generation stars. So there was the first generation that burned really quickly, then the second generation that had a little bit of heavier metals in them from the remnants of that first generation, and then our star is born in the third generation of stars, the remnants of the second generation. This one h D whatever is actually still from that second generation of stars. It's still around, and so it's it's pretty old. It's I feel like it's a fourteen point five billion years old. It's almost as old as the universe itself. Is it older than the Milky Way, Then it's almost as old as the universe itself. You're exactly right. We don't know if it's older than the Milky Way. We know the Milky Way is about thirteen and a half billion years old. It's almost as old as the universe. It's a galaxy that formed very very early on, so like it's as old as that galaxy we talked about g n Z eleven that's thirteen and a half billion light years away. We have pictures of that one from when it was forming the thirteen and a half billion years ago. But our galaxy was also forming thirteen and a half billion years ago, so we live in an ancient neighborhood. It's almost like the star was around when the galaxy was formed, when the Milky Way was being born. Yeah, and you know, there's a bit of a definitional question there because galaxies are formed from stars as they come together. And we talked to the podcast once about how the structure of the universe formed and how it's influenced by dark matter, and we're pretty sure that the structure forms bottom up, that you know, stars collapse and then are gathered together into galaxies rather than like huge sheets of matter breaking off into chunks which then separate into galaxies and separate into stars. So we think it's stars before galaxies that like galaxies are formed out of stars that have coalesced from early blobs of gas and dust. All right, So this planet may have been around when all that was happening in our galaxy. But I guess the question is, how do we know how old this star is? Mean, it's just a big ball of simmering resentment or fire. How can you tell how old it is? I mean, does it look different than it did billion years ago? You can tell by how well it plays scrabble. Actually that's pretty good predictor. You know, it's really hard to measure the age of one star. It's very difficult because stars, when they burn, like our sun, look mostly the same from most of their lifetime. Like our son. We expect to have about a ten billion year lifetime. We're about halfway through it, and it's not going to look very different now and in a billion years and in four billion years. It looks pretty different at the very beginning as it's forming, and it's pretty exciting stuff happens at the end when it's fizzling out. But in that intermediate time, it's really hard to nail down the age of a star just by looking at it. But wait, how so then, how can we tell how old our star is? Yeah? So, mostly the way we tell the age of stars is not by telling the age of individual stars. But by looking at star clusters groups of stars, because we think that they are formed together, that like these big clouds of gas and dust smashed together or something happens to trigger star formation, and you get these clusters of stars that are all the same age. Now, you can't tell the individual age of a starter easily, so how could you tell the age of a whole cluster. Well, the cool thing about a cluster is that it has stars of different sizes, as bigger ones and smaller ones. So if it gets old enough, then you start to see a few of those stars burn out. They go from like being a normal star to being like a red giant in the last phases of their life. And when that happens, you can measure the age of a star. You can measure it when it's starting to fizzle out. Oh, I see, but you don't actually see it fizzle out. You just see like if you see a red giant. You know that red giants don't last very long, so it must have happened recently. Yeah, exactly. So you look at a whole group of stars and you look at this population, you say, oh, some of them have started to fall off onto this red giant track, and once you look at that star, you can see how big it is, and then you can tell how bright it's burning, like how fast it was using its fuel, And now that you know it's turned off on the Red Giant track, give an idea of how long it took to burn that fuel, so you can figure out like, okay, it must be seven billion years old or something, and then you can look at the whole cluster and say, oh, the whole cluster is about seven billion years old. Even though most of the stars individually you can't really tell anything about them because they're just burning happily. Still. Clusters do have signs of aging, but stars don't. So then how do we know that this particular star HD one four oh to eight three is fourteen and a half billion years old? Well, we don't know it very well. And the reason is that it's not part of a cluster. It's just like out there on its own, called these field stars. They're just like loners, you know, and a loner star it's really hard to tell its age. We have some ways of doing it, like we have models for how stars age as they get older. You know, they change their spin rate for example, or the color changes a little bit. But these methods are much less reliable, much less precise than looking at a whole star cluster. And that's why there's so much uncertainty, Like fourteen and a half plus or minus point eight is a big uncertainty, And the reason is that it's by itself. We have to use these models and make a lot of theoretical assumptions about how stars look. So that's why we're not so sure. I see, I see. We just think it's fourteen and a halfpenion years old from what we can tell of it. Yeah, you know, we see a bunch of wrinkles and we think, wow, that looks like an old star. If it was hanging out with all of its friends and half of them had died already, would be more confident that it was really old. But we can't really pin it down as well. Maybe that's a secret to old age. Daniel don't don't have any friends. That's a secret to looking old. Maybe that's the track I'm on. All right, Well, let's get into bigger things and maybe older things in our galaxy. But first let's take another quick break. All right, we're talking about the old thing in the universe, and Daniel. Why I think we mean like an organization of matter, because there is matter in the universe that is still around from the Big Bang, right, Like, like protons and electrons were all sort of born in the Big Bang. Yeah, there's a lot of stuff left over from the Big Bang. And so if you call protons a thing or electrons a thing, then some of those could be almost as old as the universe. Remember the very first moments of the universe, there weren't protons and electrons and particles, and the way we think about them, things were so hot and so dense and so crazy. There was so much energy slashing around in the field that didn't really like get discretized and localized into what we think of now as particles. It's like you had an ocean. You don't think about any individual marine drops, right. And for the most part, electrons and protons, which are made out of orcs, they don't really disappear or appear all of a sudden, right Like. They hang around. They might change from being a star to being dust to being people. But pretty much the things were made out of have been around maybe since the Big Bang, Yeah, exactly. Now you can annihilate a proton or an electron. We smash a lot of protons every day at the Large Adron Collider, and electrons. If they hit a positron, they can turn into a photon, so it's possible to kill them. They're not immortal in that way, but on their own they are a stable. You have an electron just sitting in space, it will stay there as an electron forever, and the same we think for a proton. So you're right that some of the protons and electrons in us may be as old as any particle in the universe. That could be the first generation of particles ever made. Can you imagine me in a proton that old, like you've survived fifteen billion years and then only to be sucked into a particle collider by some physicists and then be killed that way. I don't know. I'd rather be in an excitement of a particle collider than like end up as somebody's tone nail or both. I mean, if you get to do both, that might be better. Well, we are working on a tonail collider, so yeah, you could be both. That would be quite a feat. Oh, I don't know what to say to that. You just put your foot in my mouth. All right, So that star might be the oldest thing that we know about, or it may not, because there's a big uncertainty about it. But what else we think is maybe as old or older than this star in our galaxy? Well, there are black holes, right. Black holes are fascinating mysterious objects we'd like to understand better. There are ones at the centers of our galaxy. There are individuals stellar black holes floating around. And then there's the possibility that there are primordial black holes. Black holes formed in the first moments of the Big Bang, maybe even before protons were made. Wow, wait, what black hole? That's that are older than particles, older than particles. We had a whole fun episode about primordial black holes. And remember that the very early universe things were hot and dense, and we talked about why there wasn't just like a whole universe size black hole in the very big ending, because you need like localized pockets of over density for stuff to gather together to make a black hole. You can't just have the whole universe be a black hole. But after things spread out a little bit, that's exactly what you had. You had pockets of very dense matter that were more dense than the neighboring stuff, and so it's possible that some of those formed black holes, which could still be around today. Nobody's ever seen one of these black holes, these primordial ones, but we can't prove that they don't exist, and some people think they might even be a good candidate for dark matter. Wait, meaning that the black hole is made out of dark matter. That dark matter is made out of black holes, right right, like little tiny black holes floating around in space. Yeah, because we know there's more stuff out there that has gravity that we can't explain, and black holes fit the bill because they are massive and they are dark, and they would have been created before the quarks, and so they would explain why these things can't be made out of quarks. So it's a really fun idea that primordial black holes could be out there. In fact, there's even this idea that there's another planet in our Solar system because people have seen weird tugs on Neptune and Uranus that they can't explain without some kind of dark, massive object out there tugging on them gravitationally, and some folks think it might be a primordial black hole. And remember these things are small, Like a black hole with the mass of a planet would be about the size of a tennis ball, so it would be pretty easy to miss. You don't want to play tennis with that unless you have a pretty good racket. You can really hit a planet mass ball very hard. Anyway, just like smashing your tennis racket on the ground, it doesn't really do anything to the trajectory of the planet. And so this primordial black hole could be in our in our own solar system, so like maybe the oldest thing in our universe, we could be really nearby. It could be pulling on us right now. It could be in fact. But one of the really interesting things about black holes is that you cannot tell their age. Remember, black holes hide information that give out nothing about what's inside them. The only thing you can know about a black hole is it's mas us, it's spin, and its electric charge. And that means that it's impossible to know the age of a black hole, the same way you can't know the age of a proton. Black Holes are like quantum mechanically indistinguishable from each other. If they have the same mass, charge and spin. They're like the canoes of the universe can't tell how old they are. That's right, yeah, exactly, though his career is not exactly a black hole. But you know, if you form a black hole yesterday and you form a black hole a billion years ago with the same amount of mass, they will look totally identical. There's no way to get any information but when that stuff went into the black hole, which is pretty fascinating. But it also means that even if we saw a primordial black hole, we wouldn't know how old it was. And but and again these are theoretical. We haven't seen any of these. But what about the ones like at the center of galaxies, like at the center of our galaxies? Are those made out of primordial black holes or do we know for sure they were formed more recently. We don't know. And one of the mysteries of those black holes is that they're really, really big. We can't explain how they got so big so fast. Our models of galaxy formation suggests that those black holes should be smaller. One way to make them bigger. To explain the mystery of super massive black holes is if they were actually seated with pretty big primordial black holes from the Big Bang. But that's just an idea we don't understand. But if they were formed just from like stars and gas and dust collapsing into a black hole, which is possible, then there would be as old as our galaxy and probably less old than the stars in our galaxy. Yeah, like, we know how old our galaxy is, but do we know of other galaxies out there that might be older than ours? Well, we do live in one of the oldest galaxies, one of the oldest neighborhoods in the universe, and as we look at the galaxies around us, we see that they're all pretty old. The galaxies nearby seem to be about ten billion to thirteen and a half billion years old, so there're no like new, fresh galaxies in the neighborhood. But wait, how do we know how old they are? It is pretty rude. We have two ways to measure the age of galaxies. One is just to look at the stuff inside of it and say, like, can we see old populations of stars? And this works for nearby galaxies where we can actually resolve a few of the stars and the star clusters and play the same trick where we try to see some of those clusters having stars that die off, but it's pretty hard because those galaxies are pretty far away. Another way to do it is to look at the like the overall light from the galaxy, and look at the ratio of various heavy elements, because as the galaxy gets older, the stars have burned more of the light elements and turned them into heavier stuff. Remember that's what happens at the heart of stars. You turn light elements like hydrogen and helium or whatever into heavier stuff like magnesium and eventually iron. So if you look at the ratio of magnesium to iron, you can start to see this change as the galaxy gets older. And so this works mostly for younger galaxies that are far away, and this sort of number is rapidly changing as the stars collapse. For older galaxies, it's not as effective because it ends up pretty stable. You end up with a lot of stars like our sun, and the amount of iron is not changing quickly. And we can tell these proportions from the light right like the light these galaxies give off sort of tell us what kind of stuff is in it. Yeah, exactly. We can't go out and scoop up a chunk of that galaxy and then measure it, though we'd love to and you know, NASA comes up with an idea for building wormholes to do it. I would definitely pay more in taxes to make that happen. But you're right. The only way to probe those galaxies to look at the light that comes from them, and the light is like a fingerprint that tells you what's in a galaxy because different kinds of stuff glow at different frequencies. You know, every kind of element has a different arrangement of electrons, and it's the wiggling and jumping of those electrons that give off the light. So there's like a fingerprint for every element. You can tell what contributions there are from every element just by looking at the spectrum of the light, which frequently sees have a lot of light in which frequencies don't have a lot of light. All right, So that's galaxies. They are maybe about thirteen point six billion years old, but they're kind of far away, so we also have to kind of account for the fact that they may not still be around today. Yeah, we're pretty sure Andromeda is there, for example, but yeah, you never really know because you're looking at stuff that's millions or billions of years old. Yeah, it could have been crossing the universe street and who knows. All right, so is that then the oldest large scale structure in the universe or can we see older, bigger things. There are things probably older than galaxies that probably formed before galaxies. So we talked about how in the early universe you had stars, and the stars gathered together to make galaxies, but not every club of stars was destined to make like a full on galaxy. Sometimes they make something smaller called a globular cluster. These things are really amazing and we're gonna have to do a whole podcast episode just about globular clusters and you know who give them that name. But these are like non ga see blobs of stars usually orbiting a galaxy. Interesting and what makes them a blob and not a galaxy? I guess is it just like um, it doesn't form need swirls or is there something more fundamental about them? It's their fundamental blobbiness. Yeah, absolutely, that's a That's a thing that visits now is that they're smaller than galaxies. There's like a hundred thousand stars and so there's just not big enough to form the interesting structures. And there's also just like a naming convention. You know, things that are smaller that are orbiting actual galaxies, You call them a globular cluster, all right, And so those we can tell are older than the galaxies. How can we tell their age. We can tell their age by looking at the stars inside them and playing the same game. And the interesting thing is that a lot of these clusters seem to have stars all the same age, like they all formed at once and then just sort of like gathered together to make this cluster. And there's one that's pretty nearby. It's like eight thousand light years away, and it looks like it's really really old. Well, it's super close, I mean speaking in the skill of the universe, eight thousand nine years away, eight thousand light years away. It's like a satellite to our galaxy. It's orbiting the Milky Way. It's like a little blob that's like moving around the Milky Way. And when we look at this thing, it looks like it's about thirteen and a half billion years old. It's got the sexy name of n g C sixty nineties. I love how ustromers go for sexy names. If you if you like numbers, if you like numbers. Well, they just see so many things, right, how can they give them all individual names? It's like if you had a billion children, would you come up with creative, beautiful names for each of them where you start numbering them. I think I would probably be dead if I don't have any children. You would definitely be broke. All right, So, um, it sounds like there's a galaxy globular cluster that's thirteen point four billion years old. There's our galaxy is also kind of that old. About that old? Um, there's a star in our galaxy that we can tell is maybe about that old, And there are far away galaxies we think might be that old, or at least we're alive back then. I guess the question then, is, Daniel, who do we give the award to? Who? What is the oldest thing in the universe? Whoever is willing to come and be a guest on the podcast? That's we could the award to have to break the tie somehow. I see, whoever comes into tux and stays within the acceptance speech limit. Yeah no, but you're right, we don't exactly know what is the oldest thing in the universe. It could be one of these stars which came together to form some of these galaxies and globular clusters, but we're not sure. It could be one of the black holes that's floating around I think. I think to take away is that there's a lot of really old stuff nearby. You don't have to look into the depths of the universe to see stuff that was created a long time ago, and this stuff is still around. So there's a lot of like awesome archaeology about the early days of the universe. What was it like to be around a few hundred million years after the Big Bang? Is evidence for that right here in our backyard, because I guess we are like still in the middle of the universe, right, Like we're not out far away from where the action is. You can still see things today around this that we're around maybe around the time of the Big Bang. Yeah, there's not really any middle of the universe, but yeah, we're in the center of the action, that's for sure. There's plenty of good stuff all around here to tell us about what happened in the very early days of the universe, and we get to watch it age. We get to see, like when many stuff going to burn out, what is the lifespan of a star cann go for twenty thirty billion years. Well, my money is still on that French old lady. I think she's going to outlive us all and the rest of the universe. That's right, and she'd probably still beat us all at scrabble. All right. Well, we hope you enjoyed that and maybe think a little bit about the age of the universe and maybe makes you appreciate a little bit of our time in it, because it is a pretty short clip in such an old universe. Thanks for joining us, 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 for my Heart Radio, visit the I Heart Radio Apple Apple Podcasts, or wherever you listen to your favorite shows. Yea