It’s time for school! The Astro101 series will cover some of the most important questions in astronomy. In today’s lesson, we’ll have: How did the universe begin? How will it end? What’s going on in here and how did we learn all this? I discuss these questions and more in today’s Ask a Spaceman!
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Now this is a Dunkin run, a $3 sausage, egg and cheese with a medium or larger coffee. I'm going on a Dunkin run. You want anything? Oh, a sausage, egg and cheese croissant and a hot coffee. You got it. Wait. 00, actually, a sausage, egg and cheese and an iced coffee. Time for a Dunkin run. Add a $3 sausage, egg and cheese to a medium or larger coffee. America runs on Dunkin Offer valid with the purchase of a medium or larger coffee price, and participation may vary. Limited time offer terms apply. Class is in session, and today's topic is a big one and not big, as in an exceedingly long episode. But big as in large, very large, the largest of the largest, the biggest of the bigs, the grandest of the grounds, the whole entire universe. In this Astro 101 series, we've gone from the basics like pointing at stuff on the sky to exploring planets and stars and Galaxies. And now we are going extreme.
We're going to talk about cosmology now. As you might have guessed from the number of episodes of this podcast devoted to this subject. Cosmology is near and dear to my heart because I consider myself when, When I do think about myself and try to categorize myself as a cosmologist, cosmologist, cosmologist Cosmo Loi The study of the cosmos of the heavens of the Universe Cosmology is the branch of astrophysics, which is the branch of physics, which is the branch of science, which is the branch of philosophy that studies all of it on big scales. We're talking about the history of the universe, the origins of the universe, if if that even has meaning. But we'll get to that. The contents of the universe, the evolution of your the fate of the universe. It's about the universe in general, and this is the most general of generals. It's a story of cosmology, and not just any cosmology, which has been done for millennia by all sorts of people, for all sorts of reasons but physical cosmology, physical cosmology, as you've probably guessed, the story of the universe based on science.
But cosmologists are attempting to answer all the same questions that everyone has been trying to answer since the beginning of being able to ask questions. Why are we here what's our place in the universe by my? How does it all fit together? These are questions that people have been asking forever and have been providing answers for in all sorts of different contexts, usually religious ones. And so cosmology is one of the fields of science, one of the few fields of science that comes into direct, apparent conflict and contradiction with religious teachings. You know, like if you're studying like etymology there, there probably aren't a lot of religions that have a lot of specific things to say about insects and have their own views of insects that they ask their followers to believe in.
And so when you study insects and you learn something new, it comes into conflict with, you know, this passage or this saying or this teaching Oh, OK, like you're pretty safe cosmology, though the stories that we tell in cosmology based on evidence based on rationality based on mathematics, all the usual science ways that we tell stories do come into direct conflict with the stories told by religions both present and all the multitude of religions that have come in the past. This has caused quite a lot of headaches I to this day will give public presentations about the Big Bang and have people challenge the existence of the Big Bang based on what they believe. When people challenge me and they and they say though they might raise their hand during the presentation, they might come up after me. It still happens. They they come up and say, like, I don't think the big Bang happened. I don't believe in the Big Bang.
You know, my answer is always the same. OK, it's not my job to make you believe things. It's not my job to make you believe a physical Cosmo. I can't make one person believe something else. All I can do is explain, and that's what I'm gonna do in the episode today is I'm gonna explain physical cosmology. I'm going to explain this story of the universe as we currently understand it through the lens of science. It's up to you to believe it or not, and it's also up to you to reconcile it with your religious beliefs or not. That's not my job. That's not why I'm here, not just cosmologists, but all scientists. They're atheist scientists. They're Christian scientists. They're Buddhist scientists. You know every religion has a representative in the scientist club and they all sleep at night. They all do their work. They all understand what they're doing. I don't know their particular answer. How they've reconciled the story of physical cosmology with other stories of cosmology that they may have heard or that they believe.
I just know that they do it. And so if you are facing a conflict or if you know of someone who has a conflict, an internal struggle with physical cosmology, because some of the things that I'm about to say may like, make people feel not all that great and not want to believe it. That's OK. It's not my job to make people believe it's my job to explain. So I'm gonna tell you a story. The story is based on the evidence, and I'll tell you the evidence and we'll get there. That's that. It's part of the science story that's fun. Part of the fun of the science story is we don't just say what we believe. We say why we believe in it always ends up being evidence, and then we get to talk about the evidence and how we know that. And that's super fun. If you find any of this, a possible source of contention, I don't know what to tell you. Except, uh I'm sorry to make you feel bad, but I like telling stories and I'm gonna tell a story about cosmology. And before I dig in more deeply, I just want us to all to take a pause here and reflect on a tremendous thought that personally, when I contemplate, it makes me mentally shrink down into a tiny little ball.
This is the thought Patreon can support this show. That's patreon dot com slash PM Sutter. But this one was earlier than you were expecting. It is your contributions that keep this show going. And also also, if you sign up for patreon, you do get access to an advertiser free stream of the show. If that is important to you. If not, you can still go to patreon dot com slash BM to keep this show going. I really do appreciate The advertisers are nice. Uh, but patreon is much nicer, if you know what I mean. Anyway, let's take a moment here. I don't care what you're doing. Put down and close your eyes. I suppose you can get a pass if you're currently operating heavy machinery it in this episode. I'm going to close your eyes. Think about this. We're going to explore the entire universe. We're going to study it. We're going to analyze it. We're going to measure it. We're going to summarize it in the form of neat little equations. We're going to mentally grapple with it with success. We are going to treat the whole entire universe as a single physical object.
We can use physics to study a ball rolling down an inclined plane. We can use the exact same physics to study the evolution of the entire universe. That blows me away every single time. And that's the exact reason that got me so interested in cosmology in graduate school that I can write down an equation on a chalkboard. And yes, some physicists don't prefer using real chalkboards that represents, I don't know, a structure billions of light years across and 10 billion years old and composed of I don't even know how many tons of material, just the enormity in both time and space with what we're dealing with. And yet we can write down equations. We can make predictions just as easily as we do with a ball rolling down an inclined plane. It is almost real and and almost like magical to me. It's part of the beauty and wonder of physics. And before I get carried away, waxing romantically about a field of science, how about we just talk about the universe?
Here's the thing. When it comes to the universe, we've got two main questions that we want to answer, and each question contains lots of sub questions, because that's how science rolls in the two kinds of questions. The two categories of questions that you can ask in cosmology are What is the universe made of? And how has the universe evolved? That's our two categories, like if, like, think of like any not just physical cosmology, but any story from any religion, any belief system. When they start addressing the universe and our place in it, there are two central themes. One. What is the universe made of? What are all the characters in the universe, and then how has it evolved or not like just how What's what's the time? Evolution of the universe and there could be all sorts of answers. You might answer that the universe doesn't evolve, and it's just made of a bunch of stars. In fact, this is what we believed a century ago. Based on the evidence, you know, AAA little over 100 years ago, we just had observations of stars and locations of stars, and that was it.
And, yes, there were these weird fuzzy spiral nebulae that we didn't really understand. But other than that, it was just stars. It was just stars doing their stellar thing. And like we understood finally that, like the planets move around the sun. And that was a big deal 400 years ago. And then we realized that the stars themselves were moving. We realized that a couple 100 years ago, and then we figured out that the stars evolved that they are born and they live, and then they die and they turned into Nebula. And then they turn back into stars and like, OK, that's fine. But the whole entire universe, we assume, to just be static. You'll remember in I believe it was our last episode when we talked about Galaxies and the Curtis Shapeley debates about the size of the universe, the contents of the universe. That was a big deal. But these two questions, What is the universe made of? And how is the universe evolved to have lots of sub questions associated with them in these subcategories. How is the stuff in the universe organized? So it's like, OK, now that you know what that stuff is, where is it?
How much of it is there all that kind of stuff? What are the different kinds of stuff? How do they interact? What does it smell like? Like all these sub questions And then with the main question of how is the universe evolved? Like, what was the universe like in the past? How old is it? Does even have a beginning. What's gonna happen tomorrow? Are we all gonna die? Et cetera, et cetera, et cetera. So you can see all the particular questions of cosmology flowing down from these two main questions of what is the universe made of? And how has it evolved? And guess what? This is one of the coolest things. Just absolutely coolest thing in cosmology. These two categories of questions are actually just different ways. of asking the exact same question. I know it's wild because these two questions, what are the different kinds of stuff and how has the universe evolved? Sound like completely different questions? But in cosmology they are actually very connected, and they are actually two sides of the same coin. And why? How? How do we know this? Because Einstein said so. Dang it. When Einstein says something, you really need to listen.
He said that through the magic of general relativity, remember, general relativity is our theory of gravity. General relativity connects matter and energy to the dynamics of spacetime and the, you know, the bending and warping of spacetime and then bending of war warping in spacetime tells matter and energy how to act. So there's this intimate connection in general relativity between the actors on the stage, the matter and energy in the stage itself, which is space time. The stage itself gets to become its own character, and it gets to talk to the other characters and interacts with them. And so we can apply. We're gonna use general relativity to understand the evolution of the universe. Why? Well, the universe is made of stuff, General relativity is our theory of stuff and how it evolves gravitationally. And when you look at big, big, big, big scales and weak nuclear force isn't doing anything strong nuclear force is way too short range. Electromagnetic is important, but not not really. Overall, the universe is neutral, so that just leaves the force of gravity.
So once you understand the force of gravity, you understand the universe. And our theory of the force of gravity is general relativity. And it tells us that there is an intimate, intimate connection between matter and energy and space time itself. So that is how we are going to operate in the universe, what we end up with when we apply general relativity to the universe, the universe is made of stuff. So once we know what the stuff is, we know how it evolves. And once we know how it evolves, we know what the stuff is because the two are connected, they're on opposite sides of an equation. We end up with a set of equations that directly connect the contents of the universe to the evolution of the universe. Answering one tells us about the other and vice versa. That's why cosmologists get so worked up about the ingredients of the universe is like taking the DNA samples of people today and working out the history of human migration, which is something we do. I mean, not me personally, I biologists and ethnographers and that, but But generally we we take DNA samples and we can reconstruct past history of human migration.
We can take a DNA sample of the universe by measuring its contents and then work out its history and vice versa. If you know the history, you know the contents. This is just absolutely cool and needs to be appreciated because it's the fundamental conceit of physical cosmology so fundamental that even Einstein missed it. When Einstein first came up with general relativity, one of the first things he did was apply to the universe because, of course he did. It was obvious, like, Hey, if I've got this really awesome theory, I wonder if it can describe the whole entire universe. Just because I'm Einstein is super cool. So he did that. He did that, and his equations predicted a dynamic universe. It predicted that the universe would be in either a state of expansion or contraction. But all the observations we had made to that point so far had said the universe was stacked. The assumption was that the universe was stag. What do you mean? The universe is expanding or contracting like it's just is.
And Einstein looked at that and he said, You know what? One of the like The only time Einstein had great guts and great physical insight and mathematical intuition, and he would go out on a limb and he would say, No, it's right because my math says it's right. Go out and do another observation. They do another observation, another test. And they're like, Wow, Einstein, you really are right. And he's like, Told you so. But this time was different. His equations when he he was the first one to do like physical cosmology, as we currently understand, because he invented general relativity and he did it in general relativity. The math came back, Crystal Clear said, Hey, dude, the universe is either expanding or contracting. Its natural state is to be dynamic, but our observations until then it's that the universe is static, so we had to add in some fudge numbers to fix it, he could have been famous. Think about think of he If Einstein had predicted an expanding years, man, think of how popular he would be instead of just some you know, random name dropped on a podcast.
But I digress. Before I continue, though I did want to geek out over something, and that is the great courses. Plus, yes, the great Courses Plus are proudly sponsoring the ask of Space Man podcast. And there's one course in particular. I mean, there's so many courses you have no idea, folks, what you're in for if you sign up. But one course in particular that I'd love for you to check out is how science shapes science fiction like the physics of space flight, the creation of alien languages like how real world science goes into creating these fantastic worlds that we can all enjoy. I mean great courses. Plus, beyond that, you get unlimited streaming access. You have something for every everyone. It's all vetted. In fact, it based and and and just it's real science, which is surprisingly hard to come by. So in order to get into this, you need to sign up. But check this out. You can get an entire month of of unlimited access for free. That's if you go to the great courses plus dot com slash spaceman.
That's the great courses, plus dot com slash spaceman for your unlimited access for free for one month. That's awesome. That's awesome. That's awesome. Now back to the show about that whole dynamic universe thing that Einstein predicted but then backed away from. I can't emphasize it enough. If I could put one sentence on a t-shirt that summarizes all of modern cosmology, it would not be an equation. It wouldn't be a quote from Einstein or Hubble or whatever. It would be three simple words. The universe changes, the universe changes. We live in a dynamic, evolving universe. That was Hubble's major breakthrough in Einstein's biggest mess. Einstein predicted a dynamic, evolving universe, but the observations to that date had showed it was static. And then Hubble came along the same guy who figured out that the Andromeda Galaxy was really, really far away.
He then looked at a bunch of other Galaxies and measured their distances and measured their speeds, and he found that on average, all the Galaxies were moving away from us and that the farther away they were, the faster they were moving away from us. There was a relationship between the distance of a galaxy and its speed away from us. The only conclusion you can make if if if you have this kind of set up, either there's some sort of crazy conspiracy where all the Galaxies in the universe know where the Milky Way is and measure their distance and then react to that which doesn't make any sense at all, or something funky is happening to light and causing it to distort on its path through interstellar space. But you can test for that. You can measure that, and that doesn't come out right. The only explanation left is that the universe is expanding. Edwin Hubble discovered that in 1924 he discovered that we live in a dynamic, evolving universe.
The universe of the past is different than the universe of today, and the universe of today is different than the universe of the future. This changes everything, and I'm going to make a bold statement here, feel free to challenge me on it. Nobody had ever thought of this before. Nobody had thought about a dynamic, evolving universe in this way, Before nobody we had to wait for nature to tell us. I mean, yes, like there are like the Judeo Christian cosmology is the universe started and then hangs out for a while, and then it's gonna end, or they're like the Hindu cosmology of like, we got a universe and then it's gonna reset, and it'll be a little a little different next time. And then it'll reset again, et cetera, et cetera. But in each of those cosmologies, once you get the universe as we know it, it stays as the universe as we know it, until some outside event changes things like, OK, guys, you had a good run, but it's all over now. Or like you know what?
I'm gonna hit that big red reset button. But once you get the universe, it just stays as the universe in this new cosmology. In this physical cosmology, the universe is constantly and naturally, changing and evolving. Every second, the universe is a little bit different than the way it was before. That's a new thing. That's a new thought that is a radical thought. It's a crazy thought that the universe has an age that the universe goes through epoch, that we live in a particular slice of time that is different than any other slice of time. This concept, I believe, and not just because I'm a cosmologist is one of the most important revelations that science has ever produced. It's up there with evolution and cave cheese. It it's big. Just the insight for this observation of Edwin Hubble and then eventually the mathematics of general relativity.
To back it up to give us an understanding of it is huge. The universe changes. So what did the universe look like back in the day? Well, I want you to think of a kid. No, seriously, this is going to be an extended and horrible analogy, and you're going to like it. We know the age of the universe. Uh, currently, it's 13.77 billion years old, plus or minus around, uh, 10 to 100 million years, depending on your uncertainty level, Uh, from your observation. And yes, we know it to that level of precision. We're very proud of it. Our universe is changing with time. It's getting bigger. A general relativity said that our universe can either get smaller or bigger with time. Its natural state is to be dynamic. A static universe is actually very unnatural. It's like balancing a pencil on its tip. Yes, you can do it, but as soon as you like, even look at it, it's gonna fall over. The universe does not like to be static. It likes to be moving, but it couldn't tell us. General relativity by itself couldn't tell us if it's contracting or expanding. Turns out it's expanding.
Galaxies are moving away from each other with time. And if you're having a hard time understanding what that means, don't worry. Everyone does even cosmologists, because then people start asking like, Well, where is it expanding from? Where is the center of the universe? What's outside the universe? What are we expanding into? I get it. Those are natural questions to ask. I want you to stop asking those questions. When I say that the universe is expanding. I just want you to mentally replace, cut and paste the phrase over time. On average, the distance between Galaxies grows. That's it. When I say the universe is spending, that just means that tomorrow the average distances between Galaxies will be larger than the average distance is today. That's it. And, yes, there can still be little collisions like Galaxy mergers here and there. But like we're on the way to Andromeda, we're gonna crash in them. But on the large scale, things are just the distances are growing bigger. That's it. Just forget all the other stuff because it's nonsense.
I. I mean, it's not nonsense. It's like nonsensical when we say expanding universe, we mean the distances between Galaxies are I. I can't say this enough. Don't worry about it. There's no such thing as the outside of the universe. There's no such thing as the center of the universe. There's no such thing as What is the universe expanding into? It's just Galaxies are getting farther away from each other anyway. This means if we're expanding, it means in the past, the universe was smaller. Galaxies were closer together. The same amount of stuff was crammed into a smaller volume, which means that it was denser and hotter, and then the way distant past, it was way smaller and way smaller volume and way higher density and way hotter and one of the most amazing statements you could possibly say. And if you really want to impress your first day, you blurt this out in the first five minutes, you say, Did you know that 13.77 billion years ago, the entire universe was the size of a peach and at a temperature of over a quadrillion degrees, you don't have to choose a peach.
You can choose any fruit you want that is roughly peach sized and peach shaped. I would not go with pineapples. Pomegranates are OK. Bananas are right out. Apples. Acceptable grapes. Too small. 13.77 billion years ago, the entire universe was the size of a peach and had a temperature of over a quadrillion degrees. If that doesn't land you a second date, I don't know what will. But then again, I'm a cosmologist and not a relationship expert. So I don't know why you're taking advice from me. Let that sink in. Look around you Look at the night sky. Look at those stars. Look at the Hubble deep field in all those Galaxies. Think about all that stuff. The sheer amount of stuff crammed into that tiny volume, something you could hold in your hand. The early universe was a lot like childbirth. It was loud. It was messy, sweaty. They were screaming involved. And it was a very sharp pointed event. Like my like child. Birth is a very, very focused event before there is no child born.
And then after there is a child born. So there's an event like that. We don't understand the extremely early universe. We just don't, uh when the universe was less than a millionth of a billionth of a billionth of a second old, we just flat out don't understand it. That's another show. Feel free to ask. But there was an important event in the history of the universe, just like, you know, imagine like premodern medicine where we don't know about, uh, like development of fetuses. And it's just like something funky is happening. And man, her belly is getting bigger and that wow, there's a baby. Well, that worked, but who cares? But now there's a baby. So, like the event I'm talking about is inflation before inflation. We don't really understand it because we're in that premodern medicine era trying to understand pregnancy. Uh, and then there's a very significant event that is also very messy, and we poorly understood. But then there's a baby after and you can kind of understand babies because you can poke at them and stuff. I told you this was a horrible analogy.
Uh, so inflation was an event that happened when our universe was incredibly young, a tiny, tiny fraction of a second old and where our universe underwent a dramatic phase transition and became really, really big by really, really big. It stretched from like the size of an electron to the size of an atom or something like that, to give you some perspective. And it did so in a tiny fraction, a billionth of a billionth of a billionth of a second. But that event was incredibly important for our universe. It's so important. I did a couple episodes on it way back in the day. But that event was important that that event of inflation talk microscopic variations in the quantum fields of nature themselves and inflated them, made them big, made them important, drew them out to that quantum foam that's baked into the nature of reality itself and made them bigger, made them macroscopic.
It sent the seeds of tiny little density differences that would eventually accumulate matter slowly over the course of billions of years and then eventually grew up to become stars and Galaxies. In the largest structures we see today, that event of inflation set the seeds for all future structures. That was in the newborn baby universe shortly after inflation. As the seconds and minutes rolled on, we had a nuclear inferno that forged the elements. The first hydrogen, the first helium, appeared in the first dozen minutes or so, and we can actually understand that epoch that era relatively well, because we know nuclear physics. We have nuclear bombs and nuclear power plants and nuclear reactions like we understand nuclear physics. So when the universe is five minutes old, it's in a regime of physics that we can directly probe in the laboratory.
Think about that. He set off a nuclear bomb. The conditions inside that bomb are what the entire universe was going through when it was five minutes old. And so we can understand the production of hydrogen and the production of helium, but a lot like babies. There's still a lot of mysteries, like OK, you know, the baby is crying. Is it crying because it has to poop because it has to eat? Because it has to do both because it wants cuddled because it wants to put down because it wants both. Like you. You, you you have a hard time. You can generally understand and grapple with the baby. But there's still a lot of mysteries. There are a lot of mysteries about this epoch. How did matter went out over antimatter? What was the role of neutrinos? A bunch of questions here. But then the baby gets older. It starts crawling and walking and talking. It becomes a little more recognizable. As our university expanded, it got bigger and cooler and more sorted out. The force is separated into the four that we know today. Matter and antimatter diverge somehow. The first atoms formed when our universe was 380,000 years old. Our universe was expanding and cooling all the while, and there was a plasma where all these protons wanted electrons.
They wanted to turn into full fledged atoms, but the energies were too high, the radiation was too much and the electrons would just get knocked off. But by the time our universe was 380,000 years old, which its size. Back then it was about one millionth. The volume that it has today. The universe cooled down enough that it could stop being a plasma, where electrons could finally attach themselves to protons, become little atoms, and a high energy bit of radiation would not knock it away. This released light our universe up until this point was opaque. It was a hot ball of plasma, and then it stopped being a hot ball of plasma, and it let go of a bunch of light. At that time, it was around a temperature of 10,000 degrees, which is white hot, literally white hot radiation. Over time, as the universe has expanded, that radiation has cooled off and stretched out. Nowadays, that radiation has a temperature of around three degrees above absolute zero, and it's in the microwaves, and we call that life that remains today the cosmic microwave background, and we can see it all around us, and that's really cool.
It's light. It's a baby picture of you. The equivalent is if we had a picture of you when you were seven seconds old, we have a picture of the universe when it was only 380,000 years old when it was just a baby. After that critical event, the universe became a preteen, which are pretty much delightful and horrifying in equal amounts largely kept to itself. This is what we call the dark Ages. After the first atoms form and this light was released, it cooled off pretty quickly. And then that's it. There's just cast floating around, not doing anything for hundreds of millions of years in those little seeds that were laid in. The first PICO, second of the history of the universe became big enough for gas to start accumulating in those dense pockets to start flowing inwards. And then puberty hits. It's awkward, It's messy. It's sweaty. Screaming is involved our universe of puberty. Somewhere within the first billion years of its existence.
We call it the Cosmic Dawn. The cosmic Don is when the first stars formed. When the first stars ignited, they released radiation. They released light for the first time in hundreds of millions of years, but it was a pretty messy thing, just like pure like, Yeah, you're becoming an adult at first, you gotta go through a a couple awkward years And the universe had some really awkward years because the first stars to come online were giant. They were hot. They were throwing out ionizing radiation like high intensity radiation. Up until this point, the gas in the universe was neutral. It was just atoms, protons and electrons. Neutrons, you know, hanging out one little happy family. And then the cosmic dawn happens. And there are all these stars and it just rips apart the neutral gas and ionizes. It turns it back into a plasma, which is the way has remained ever since. And like after puberty, you you're pretty much like a mini adult. You're like a grown up.
You just don't know as much. But you can mostly function in the real world and pass yourself off in civilized society. After the cosmic dawn, After this event of re ionization, you have evolution. The stars start to group themselves together into clusters. The clusters group themselves into Galaxies. Galaxies group themselves into groups. We're starting to run out of names. The groups start to group themselves together into larger clusters. You get the cosmic web, you get giant clusters of Galaxies. You know, millions of light years across home to thousands of Galaxies. You get these long filaments, highways of Galaxies headed towards the clusters. You get these broad walls of Galaxies millions of light years wide. And then you get the voids, these vast deserts, these vast expanses of almost nothing. You get the universe that we see today, and since then the universe has pretty much just been evolving.
This is a wonderful story, but how do we know? Well, that's what makes physical cosmology different than any other cosmology is that it's based on evidence. And when it comes to this story, which we call the Big Bang, that's generally the name for this history of the universe. We only got to this story very begrudgingly, like nobody wanted this story. Nobody wanted the universe to evolve. It was too complicated. But the evidence pushed us in this direction. The first piece of evidence was that General Relativity said so and general relativity was like, really successful. And then it's also saying some whack a doodle things about the dynamics of the universe, and everyone's like, Oh, shoot! So we tried to ignore it But then Hubble made his observations, saw that the Galaxies were expanding away from each other. That's really what got the Big Bang story going, but it was still debated for a couple decades. Like these observations happened in the 19 twenties. It's not really until you get into the forties and fifties, where big bang cosmology really gets cemented in place.
One thing that we saw was that quasars are thing you know. Quasars is these super bright radio sources. We found that quasars only happened in the very distant universe and they weren't in the nearby universe. And we know that the farther out you look in astronomy, the deeper in the past. You look so this means that quasars were a thing in the past and they're not a thing today right there. That is a sign that the universe changes with time because quasars were around billions of years ago and now they're not so right there. That points to a dynamic, evolving cosmos. And then really, really, what locked it in was the cosmic microwave background, the discovery of that which it was discovered on accident by two radio engineers who were just trying to build a radio telescope, and they had this constant source of noise in the background that they couldn't get rid of. Turns out they made a Nobel Prize winning discovery. And no, I'm not bitter about the fact that the Nobel Prize did not go to the theorist who predicted the existence of the CMB, just two radio jokers who accent, I'm OK, I'm I'm moving past it.
And then there's also like nucleosynthesis. I talked about nuclear reactions in the first dozen minutes of the history of the universe and how we can calculate their reactions. We can calculate how much hydrogen and helium and lithium and all these other elements that the universe produced in its first few minutes, and then it matches up with observations. So Big bang theory is capable of making predictions and matching it with observations. And that's just the start. You want your own model of cosmology. You don't think Big Bang is up to stuff. That's fine. But if you want, scientists believe that you have to address all these observational realities and then some and you know what? Once you include all these observations, like Galaxies receding away from each other like the existence of quasars only in the past, like the cosmic microwave background like nucleosynthesis formation of the elements like the appearance and structure of the cosmic Web. Like the effects of realization on, you know, et cetera, et cetera.
Once you add up all of these, the story I'm betting, I'm betting that the story you would end up telling would look a lot like this one because there's only so many ways to tell a story with these kinds of constraints. But remember what I said earlier about how the history of the universe is tied to its ingredients? We desperately want to know what the universe is made of, and this has presented some challenges. And these ingredients have altered our story of the history of the universe, and they will definitely alter our story of the future of the universe. In the 19 seventies, we discovered dark matter. We discovered that most of the mass of the universe is non luminous, which means it doesn't interact with light. A better name for dark matter is invisible matter. But again, I am not in charge of naming things. I'm very sorry. So it gets something confusing it's dark matter. It's just it turns out you look at a galaxy, and most of the mass of that galaxy is made of something that is not glowing or capable of glowing or even interacting with lights.
It's invisible, but it takes up about 80% of the mass of the universe. So if you look at a galaxy, you're looking at no more than 20% of it. 80% of it is of a form of matter unknown to the standard model of physics. We don't know what dark matter is made of it. We suspect by now that it's some new particle. We suspect that it's like flowing through us right now, like your room is swamped with dark matter. But because it doesn't interact with light because it doesn't interact with normal matter like you don't see it. The only way to see it is by looking at it gravitationally at big scales like the motion of stars and Galaxies, the motion of Galaxies inside of clusters, the evolution of the cosmic web, the bending of light around massive structures. You know things like this. The only way we can tell that dark matter is real. And in the 19 nineties we noticed that the expansion of the universe is accelerating. It's not just getting bigger and bigger every day. It's getting bigger and bigger, faster and faster every day. We have no idea what's going on here. We call it dark energy and we are lost.
It's been over 20 years since the discovery of dark energy, and we know all we've accomplished in the past two decades is that dark energy really does exist. But we are not any closer to understanding it. All we know is that it's making the expansion of the universe accelerate. We don't know why and we don't know how nobody asks for dark matter or dark energy. But we must confront the observational reality. The observations are demanding that they exist. We can't get around it now. We know things like, you know, these do impact the story of our universe that we now we know we need dark matter to even form Galaxies because for the 1st 380,000 years of the history of the universe, regular matter was getting all tangled up with radiation. Having this big plasma party, it couldn't form dense structures. It couldn't form like balls, but dark matter could have just slipped on by and that provided the bigger seeds needed to form Galaxies.
If you don't have dark matter in the story, you can't form a galaxy in time. We know that dark energy did not play a major role in the early universe, but it switched on about 5 billion years ago. It was always lurking in the shadows until it could come out and play. And now it's playing, and we don't know exactly what its end game is. What will the future hold? Well, it depends on what the universe is made of. Best guess story is that our current era is known as the Deli Ferous era or the star forming era. It's definitely the most fun, but it's on the decline. Star formation peaked about 10 billion years ago. Our universe is getting too big for clumps of gas to glue themselves together to make stars. It's just getting harder and harder as the day goes. Go by. In the far future, we predicted that the cosmic web will evaporate because dark energy will tear everything apart. It's doing it right now, structure formation in our universe that started with that event of inflation has led to the grand cosmic Web, this giant filament structure that is the biggest pattern found in nature that is getting ripped apart as we speak.
Because of dark energy, Galaxies will either merge together. If they're close enough already, or they'll get flung apart. The stars will burn out. The black holes will dominate in an era we call the degenerate era. Everything will dissolve through various quantum mechanical processes, and then the far, far, far, far, far, far future. We're talking like 10 to 100 years from now. You'll just have a thing called super particles light years apart, slowly cooling off to absolute zero. That doesn't sound like so much fun. But right now that's our best guess for the deep history, future history of the universe or not. It's like predicting the weather next month. It's based on current conditions. We don't know enough about dark matter and dark energy to really say something inclusive. Could new physics kick in? After all, the early universe was a very strange place, and the late universe might be just as strange. What we're trying to do in cosmology is measure dark energy capture, Dark matter probe, The Dark Ages. Lots of dark stuff going on here in cosmology. We learned a lot, but we're still in the dark. I can't resist the pun.
I mean, can you blame me? Why do we do it? Well, it's fun. And, well, that will be the subject of the next and final lesson class dismissed. Thank you to my top Patreon supporters this month. Matthew K, Justin Z, Justin G, Kevin O, Duncan M, Corey D, Barbara Kay, Robert M, Nate H and F Chris Cameron, NAIA, Aaron S, Tom B, Scott M, Rob H and Scott M. That's patreon dot com to keep this show going, and you can also leave a review on iTunes. Go to PM suter dot com slash store to check out autograph copies of my books or merchandise. It's so funny. I have mugs and t-shirts that say, if it's interesting, is probably wrong and you can always please. The biggest thing you can do to support the show is send me questions hashtag ask the spaceman email. Ask a spaceman on at gmail dot com. That is what keeps the show going and what I'm always grateful for every single month. And I will see you next time for more complete knowledge of time and space.