What processes create all the elements? Why are some elements more common than others? How does fusion happen inside and outside of a star? I discuss these questions and more in today’s Ask a Spaceman!

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EPISODE TRANSCRIPT (AUTO-GENERATED)

I'm a big fan of creation stories. Myths, legends, the works. I remember this distinct phase in late middle school, early high school, so we're talking early teenage years, when I became obsessed with mythology. I would check out every single book in my school library and when that wasn't enough, I went to my local library. Now considering that I was growing up in a small town in Ohio, I wasn't exactly exposed to the wide variety of humanity's various creation stories.

So I had my pick from Greek mythology to, some more Greek mythology and that was about it. But since then, if you've got a creation story for me, I'm all ears. And so perhaps upon reflection, I shouldn't be so surprised that I became a cosmologist. And, yes, I do believe that physical cosmology, especially the big bang theory, is a creation story. Yeah.

I believe that. It's one rooted in evidence and rationality and skepticism AKA the scientific method, but all that doesn't make it not a story. It's just a different kind of story. And dang it. It's a good one.

And let me show you an example of how the big bang is a creation story and can work as a creation story because your typical creation story has a few major components. The first component is well, the creation. How things started. How what is came to be. Some stories lean on this part pretty hard like the opening pages of Genesis while other stories breeze by this on their way to more interesting bits, especially cosmological stories and mythologies where the universe has always existed.

And you just say, oh, yeah. Yeah. The universe exists. And and now we're gonna get to the interesting parts. You know, not all creation stories address it in-depth, but they always discuss the beginning or the creation or the bare fact of the existence of the universe itself.

Now in today's story, the story of the big bang, we're going to take this first part and just skip it. Why? Well, the beginning of the big bang, the beginning of the universe is the cosmological singularity, which makes things difficult to interpret physically what exactly is going on. The physics gets so complex. It breaks down, so our story gets a little bit muddled there.

And, b, that's a great topic for another episode. So just go ahead and ask. I dare you. Why is there something rather than nothing? That would be a very fun question to tackle on this show.

Now, the second part of a typical run of the mill creation story is a little meatier. The second part isn't about the fact of existence itself, which again is sometimes taken for granted, but concerns itself with the origins of specific objects or materials. We're talking about the part in the stories that concerns themselves with not the creation of the universe, but with the creation of parts of the universe. So the creation of the sky or the stars or the oceans or that important mountain over there or fire or that one delicious food we can only have on feast days or the color magenta or tax returns. The bits and pieces that make up creation and how they got their start.

And that that is something we're definitely going to talk about today. By the way, there are usually a few other parts to a complete creation story like the ordering of the cosmos and the definition of our relationship to it. But again, those are stories for a different day. In the big bang framework, it is a scientific theory. We do know it is accurate and and true as far as the evidence can tell us.

And it's still a story. That's one of the cool parts about it. Because it fills the same niches that mythical stories do, that religious or theological based stories do. And today, we're talking about the creation story of the big bang and how it led to the formation of mountains and skies and magentas and tax returns. But, of course, the big bang theory is a different kind of creation story.

I would argue it's very unique in the history of creation stories, but that is a topic for another day. So in our big bang creation story, we're not going to talk directly about the story of the how the mountains and oceans and stars came to be because this is physics. And in physics, we're not so concerned with the creation of mountains and oceans and stars. We're more concerned with the fundamental units of reality that build up to become mountains and oceans and stars. We're talking about the elements.

For millennia, philosophers across the world worked to discover the fundamental constituents of matter. The basic building blocks or if you don't believe in atoms, a fluids or substance, just stuff, substances, whatever you wanna call it, fundamental things that combine in various interesting ways to explain the variety of material existence. When we look around in the world we have dirt which is very different than water, which is very different than a knife, which is very different than a chair, which is very different than the sun. So we see substances that are very different from each other, but sometimes the substances are rather similar. I can fill a jug with air or water.

I can combine dirt and water to make mud that has properties of both. And so not everything we see in the universe, dirt, water, chairs, knives, are are entirely different things. Surely, they're not different things in their own right, but merely different combinations of some more other more fundamental things. And we call those fundamental things the elements. If we can make a short list of elements, then everything in existence exists as a combination of those elements.

And we see this system crop up in European philosophy, Middle Eastern philosophy, Indian philosophy, Chinese philosophical systems. They they all seem to come to the same conclusion that there are a handful of elements. The numbers or labels change, but they were usually something like earth, fire, water, maybe wood if you felt like it, maybe metal, maybe not air if that gets too complex for you, but there's a list a small list of elements. And in the cosmological systems that these philosophies worked with, you had to create these elements. So there are various deities involved or supernatural events that trigger the formation of these elements, and then the elements go on to create everything around us and also us.

Fast forward a couple 1000 years, and while the basic ideas hold up that there are things called elements that combine in interesting ways to make up material existence. The names and numbers of the elements have changed. We begin to develop chemistry. We isolate various compounds, discover the existence of atoms, begin to separate matter from reactions involving matter. So sorry, fire.

Hate to break it to you. You're not an element anymore. But, hey, water turns out you are kind of an element. You're made of 2 other elements. You're not as fundamental as you thought you were, but, you know, you're still you're doing better than fire is.

That's for sure. And we eventually arrive at the periodic table, a list of elements neatly and orderly arranged and categorized, and these elements combine together in interesting and fascinating ways to give rise to, let me see here, just about everything. And we are able to dig further because we realize that the elements themselves are not so, well, elemental, that the atoms are not fundamental. They are made of smaller units of subatomic units like protons and neutrons and electrons. But this is really powerful because it helps us explain why the elements are different.

And it all comes down to how many protons and neutrons you pack into a nucleus. That's it. And that's a really, really cool thought and a fundamental thought and one that is going to be key to our big bang creation story is that you just take protons and neutrons. They like to buddy up together, and they like to pack together into really tight tiny nuclei. And the number of protons dictates the properties of what that grouping will do, and then we call that grouping a particular element.

This is why helium with 2 protons, the physics of those protons and the neutrons with them and the electrons around them dictate how that grouping behaves and is very different than oxygen or carbon, which have different numbers of protons. And it's this, like, magical thing that we discovered through fundamental physics that we can not only arrive at the conclusion that elements exist, but figure out why the elements behave the way they do, and it all comes down to the number of protons and neutrons in the nuclei. That's it. That's what makes one element different than the other. So we can start with incredibly basic building blocks, the subatomic particles themselves, specifically protons and neutrons, and from there we can build these elements.

And seemingly simple everyday items are astoundingly complex in the variety and combination of elements. Take for example, a piece of cheese. Cheese is roughly 1 third water, 1 third protein, a small percentage of carbohydrates, a small percentage of patreon. That's patreon.com/pmsutter so that I can afford more cheese and provide more cheese based metaphors. It is through your generous contributions that I am able to make that possible.

That's patreon.com/pmsutter. And another small percentage of minerals. The water itself, we can break this down, is made of hydrogen and oxygen. The proteins are casein and whey, which add carbon, nitrogen, sulfur, ammonia. Common metals in cheese include zinc, phosphorus, sodium, magnesium, potassium.

Don't forget the calcium. A dozen elements combined together in different arrangements to make cheese. And what it all boils down to when you look at something deliciously complex like cheese, you see a dozen different elements. The oxygen plays a different role than the hydrogen, which plays a different role than the ammonia or the sulfur or the calcium. They behave that way because oxygen has a different number of protons and neutrons than ammonia does.

That's what makes oxygen oxygen. We label this grouping of protons and neutrons oxygen. We label that grouping of protons and neutrons calcium, and we're done. And the question we must answer in this creation story, a physical story of the creation of the universe around us through the big bang is how did we get those elements? So the same question faced by every philosophical system ever.

Now we get a little advantage here because we get to look at evidence to decide what our story is. There is a side debate that, mythologies, might be a proto form of science. That's also a very interesting topic to explore in a future episode. I'll leave that to the side. How do we get these elements?

Once the elements are in place, we can just let chemistry do the work. You know? Then it's then it's our, you know, another building. It's another department on the university campus. It's chemistry, it's not physics anymore, then we can build mountains and stars and whatnot.

But how do we get the elements themselves? We need to explain the existence of these elements in these abundances and not other ones in order to build the universe that we recognize, and it is this crucial idea that unlocks this part of the creation story in the big bang that the fundamental elements are not immutable. The fundamental elements are themselves not as fundamental as they seem. They are just made of protons and neutrons, so that makes it possible to change one element into another. All you have to do is add or subtract protons or neutrons and voila.

You've got different elements. I take an element. I yank a proton out of it. Now it's a different element. I add a couple protons back in.

Now it's a completely different element. Add some neutrons, subtract some neutrons. Same element, different isotope. Now maybe it's radioactive. Now it behaves differently.

There are many processes, nuclear processes that can do just that. This is yet another episode. This episode has a lot of pointers to other cool potential topics as the the history of alchemy and how it was finally realized in the splitting of the atom. That's a fun topic to explore. Please ask so I have an excuse to talk about it.

But the fact that the fundamental elements like, what if you went to the ancient philosophers and said, okay, you figured out this system of fundamental elements, earth, water, fire. What if I told you that you can transform fire into water, or water into air, or air into dirt? That is what we're talking about. And it is the ability to transform the fundamental elements of nature that gives us the ability to build the elements. In the early 20th century, we realized 2 things.

1, we realized the subatomic nature of atoms. We discovered the existence of protons and neutrons. We realized that we could explain the existence of the periodic table of the elements. We could explain the existence of elements themselves through the arrangement, the counting of protons and neutrons in atomic nuclei. We discovered that we could split these, combine these, that we could transform elements to each other.

It just takes, a little bit of energy, and simultaneously, we discovered the big bang. We discovered that the universe is expanding. As soon as we conceived of the big bang theory, we saw golden opportunity. Remember, we're trying to craft a story of creation and and the big bang theory gives us the start, which is a long time ago the universe was very small and very hot and very dense, and it has expanded since then. Now it's old and cold.

That's the start of a pretty interesting creation story, but we need to fill in the gaps. We need to build the universe out of that, the material existence out of that. So we saw this golden opportunity because at one point, if the universe used to be small and hot and dense, then at one point, it had to be really small and really hot and really dense, like over a 1000000000 degrees hot. Hot enough for nuclear reactions to take place all willy nilly, for elements to to transmute and change, for this is the alchemist like philosopher stone existing in the earliest few moments of the big bang where we can transform any element into any other element. We can create elements.

I love reading early papers on this subject, because they called this epoch of the universe the fireball, and we don't use that term anymore. I don't know why because it's a really really cool term, And in this fireball, there was a dedicated research program for many, many cosmologists attempting to build all the elements. Like, if you have the universe in such a state that nuclear reactions can take place throughout the entire volume of that universe, then maybe you can just craft all the elements and be done with it. It didn't work out so well because it turns out it's very difficult to fashion most of the elements. This was a kind of a failure of a research program.

This story didn't didn't end well. It didn't build the universe that we see, but it did get the ball rolling and it did generate one very fruitful idea. Instead of trying to create all the elements in the nuclear fireball of the early universe, what if we just built the smallest ones? What if we just seeded the universe with light elements? They're much easier to build, they last a lot longer, and then maybe later there can be some other process that turns these light elements into heavier ones.

The key idea here is nuclear fusion. This is what powers our story of the big bang creation. And the story of the big bang creation when it comes to the elements is the story of what we call nucleosynthesis. The synthesis of nuclear material, the creation of atoms, the creation of nuclei, and specifically, a very specific ordering of that building where it starts with the smallest, lightest elements, and then steadily builds from there as the universe expands. This is a different kind of cosmological story where we're not creating the mountains and the air in the sea kinda all at once.

No. No. No. No. We're gonna take our time.

1st, we're just going to build the light elements. There isn't enough, gas, so to speak, in the early universe to build the heavier one, so we need some other process later. We'll get to that other process, but let me start with the lightest elements to get the game started perhaps the most amazing part of this big bang creation story the most surprising is how simple this part is how straightforward folks it is easy stupid easy for the universe to build light elements, and it's easy for us to understand it and predict it. It's almost like once you get the gist of the big bang theory, once you realize that the universe was smaller and hotter in the past, you can't not build the light elements. You can't not fill that universe with hydrogen, helium, the light elements.

The prediction just falls right out of the basic idea, And it's a very generic robust prediction. The exact details of what went down in the very early universe don't really matter. You don't need to know the precise temperature ranges or the precise expansion rates. You don't need to know about dark matter or dark energy. The the physics of of nuclear cross sections and interactions and all that mess don't really matter.

You just need to know that at one time, the universe had a temperature of over a 1000000000 degrees, and it cooled and expanded from that. And boom, you get the light elements. This is a prediction. This is bonafide genuine scientific theory prediction generated by the idea of the big bang. You come up with the idea of a big bang immediately.

You can take textbook nuclear physics calculations. I'm serious. This is undergraduate level stuff, the stuff that's even too basic to run a nuclear reactor, let alone detonating an atom bomb. This is undergraduate level calculations. You can say, okay.

If the universe was small and hot and dense in the past, and if at one time it had a temperature of over a 1000000000 degrees, what would the nuclear reactions look like? Junior level college physicists do this for homework, and it just falls out. The answers just fall out. What pops out is the big bang nucleosynthesis, the part of the nucleosynthesis story that starts at the big bang itself. And the story goes like this.

In the first few minutes of the big bang, you know, the details don't matter. It could be the first few seconds all the way out to somewhere around the first, 20 minutes or so. The temperature of the universe was over a 1000000000 degrees. At that temperature, protons and neutrons are not stable. As soon as one forms, it gets blasted apart by all the collisions with all of its neighbors.

And so what you have is just a soup, a plasma of even more fundamental particles called quarks and gluons. Eventually, the universe cools off. Protons and neutrons begin to condense. They can form. They can, solidify, so to speak, without being blasted apart by their neighbors because it's colder now.

It's less dense. Things are a little bit more chill. So they form, and then the protons and neutrons start combining into deuterium. The deuterium combines into helium. You add a little bit more to make lithium.

And then by that point, the universe gets too big and too cold where nuclear reactions can't happen anymore, and it all freezes out and you're done. Like I said, the real magic here is just how robust and generic the predictions are. I like to think of it, like a traffic jam. When there is a traffic jam, it doesn't matter what kind of car you're driving. You can be in a motorcycle.

You could be in in an electric car. You could be in an 18 wheeler. You can be in a broken down minivan. It doesn't matter. You're still gonna get stuck in the traffic jam.

As soon as you hit the traffic jam, you're stuck in there for a while. And then when the traffic jam is over, you're free to drive. The traffic jam just exists. The details of the cars don't matter for how long you're going to be stuck in the traffic jam. The era of big bang nucleosynthesis, which occurred starting roughly anywhere from 30 seconds to a few minutes in after the big bang to somewhere around 1 to 2 dozen minutes after was like a massive traffic jam where things were hot enough to generate nuclear reactions, but not too hot that the protons and neutrons themselves just obliterated, and then eventually cooled off the traffic jam d's, and then you have a universe filled with the light elements.

With very basic calculations, you can predict the ratios of fundamental elements. Sometimes these are called the primordial elements, the the elements that fell out of big bang nucleosynthesis in the first few minutes. Like, how much helium is there relative to hydrogen? How much of this isotope of lithium is there versus hydrogen or that isotope of helium? How much deuterium versus hydrogen?

What fraction of the universe ought to be hydrogen, helium, lithium? Since then, in the 1,000,000,000 of years since then, there there's been enrichment and changes over time. We'll get to that. But that's your starting value. So now you can go out and observe on large scales how much hydrogen there is, how much helium there is, how much lithium there is, And you can compare notes with the theoretical predictions and see if you get it right and you get it right.

As an example of just how simple this is, consider helium. Initially, when the universe was super duper hot, protons and neutrons would be created and destroyed in equal numbers. They were just getting obliterated. They'd try to form and then they just get destroyed, because there's more than enough energy to go around. But as the universe cooled, protons and neutrons started to coalesce.

But protons are slightly less massive than neutrons, meaning that they are ever so slightly easier to create, and they ever so slightly stabilize sooner. So as the universe cools, there starts to be an imbalance with more and more protons congealing out of the primordial plasma. Eventually, the temperature drops enough, and there's no new protons or neutrons being formed. And by this point, and you could run the math, at this point there are about 6 protons for every neutron. Now the neutrons can't exist for very long on their own, unless neutrons are bound up in an atom, they actually decay with a half life of 880 seconds, which is very important when your universe is, like, 880 seconds old.

So throughout this process where we're done making protons and neutrons, and the neutrons and protons are now now starting to bind up to form heavier elements like helium and lithium, some of the neutrons are decaying away. They're going away before they can be used. And at this stage, when they're actually binding up, you're left with a ratio of about 7 protons for every neutron. And now you get to ask, what are those neutrons going to build with the protons? They're they're close enough and hot enough that they can bind together to form stable atoms.

What are they gonna make? They can build deuterium. They can build various isotopes of helium. They can build some isotopes of lithium. It turns out that helium 4, which is made of 2 protons and 2 neutrons, has the highest binding energy of all these light elements, which means that helium 4 is the easiest element to build, and the hardest to break apart.

So it's going to be the most abundant. So if you take- you've got uh- 7 protons running around for every neutron, You're gonna suck up every neutron and put it into helium 4 preferentially because that's the easiest one to make. You could run the numbers yourself. Seven protons to every neutron. To make helium 4, you need 2 neutrons and 2 protons, which means once you make these, you'll have 1 helium 4 atom with 12 protons left over.

But that 1 helium 4 atom takes up 25% of the mass, so you end up predicting that 25 percent of the mass of all normal matter is in the form of Helium-four. Just like that. 25 percent of all the mass of normal matter is Helium-four. The rest of it is hydrogen, which is just a bare proton. And then a tiny tiny tiny percentage of lithium.

And that's exactly what we observe. That's what we see in the universe. By mass, the universe is 75% hydrogen, 25% helium, and a small percentage other. That's it. Done.

A generic prediction. It's worth noting that there are no free parameters in these calculations. When we run these numbers, when we try to make this prediction, we have nuclear physics experiments. We have nuclear reactors and nuclear bombs. Like, we understand nuclear physics.

We know how protons and neutrons interact with each other. We know under what conditions they combine together to form helium and lithium and when they stop. We know this. We understand this. We can measure it in the laboratory.

There's one other important number that plays a role in the early universe, which is how much radiation there is relative to the amount of matter. We can actually measure that directly from the cosmic microwave background. It just tells us, and then that's it. You know the universe is hot and dense. It's expanding and cooling.

You know how nuclear matter interacts with each other, and that's it. And you know what? If nuclear matter reacted slightly differently or actually largely differently, if there was way more radiation in the early universe or way less radiation in the universe, it actually doesn't change the numbers. You still end up in a traffic jam and you still end up with the universe with 25% Helium by mass. That's one of the wildest things about big bang nucleosynthesis is how it just doesn't care about the details.

Once you understand the basics of nuclear physics, you're done. You have predicted the correct abundances of the light elements in the universe. It's wild. Why this isn't hailed as a triumph of modern physics is beyond me. It's it's just fascinating.

Like, I can sit here, and as soon as I understand the basics of nuclear physics and then the basics of big bang cosmology, this creation story, I am able to predict the abundance of the light elements in the universe. Oh, there's a small problem with lithium. It's called the lithium problem, handily enough. The observed abundances of 1 of the isotopes of lithium are lower than what we predict, so this is possibly alleviated by not finding enough primordial samples of lithium or maybe there are other nuclear chain reaction channels that, come into play in the early universe that we haven't thought of that we've and, you know, so there is it's not perfect. It's not perfect, but it's there.

No other creation story accurately predicts the ratios of hydrogen to helium in the universe, and the Big Bang story does. That's very interesting. That's very powerful, but our story isn't done. We're trying to build mountains, stars, chairs, slices of cheese. And so in the first few minutes of the big bang, let's check our list of elements.

We have a hydrogen, which again is just a single proton wandering around by itself, helium, a little bit of lithium. Last time I checked, which was just several minutes ago, there were slightly more elements than this. So if we're going to make cheese, we have our work cut out for us. In comes this second stage of creating elements, stellar nucleosynthesis, the second stage of our nucleosynthesis story. It takes 100 of 1000000 of years for the first stars to arrive on the scene in the universe, but once they do, they get to work.

They start making elements. They start making heavier elements because this is the magic of this story. You don't need to explain every single element in its lonesome. You just need to start with the lightest elements. Thank you, big bang nucleosynthesis.

We're good. And then you can just let nuclear fusion do the rest of the work to fill out the periodic table. In something like the sun, this process is dominated by a process called the proton proton chain, where you start with 2 pairs of protons. You mush them together to make 2 deuterons, which is a proton and neutron combo. Then you add another proton to each of these to make a pair of helium 3, and then you smash those together to make a helium plus 2 leftover protons.

It's a somewhat complicated process, but that's how our sun is generating energy right now. This process is incredibly slow and incredibly inefficient, but there's a lot of sun to go around and that's why our sun will shine for 10,000,000,000 years because this this is not the greatest process of generating energy. Larger stars fuse hydrogen into helium, but through a more complicated dance, you start with bare protons, and you involve carbon and nitrogen oxygen to mediate the reaction. It's called the CNO cycle, carbon nitrogen oxygen cycle. It's a very complicated dance.

And this is, actually creates a pickle for the 1st generations of stars in the universe because the first stars were very, very large, but there wasn't any carbonate or nitrogen or oxygen to help with these nuclear reactions, so we're not exactly sure the physics of how those first stars got started. Through all these stars through 1000000000 of years, you get more helium. Yay. In fact, there's about 4% more helium in a place like the solar system than there would be if there were no stars, so a little enhancement. But we're trying to build the rest of the periodic table, and so far all we've gotten is just more helium.

So once, once you run out of hydrogen to fuse into helium in the core of a sun or a star, then you can start fusing helium, and finally you get something more interesting. You get carbon and oxygen which are 2 of the most common elements in the universe. I mean the Earth the most common element in the Earth is oxygen. Carbon dioxide in the air, h two o in the water, silicates bound with oxygen, something we call dirt and ground. It is the most common element in the earth, and it's common because it's made in the cores of stars like the sun, and stars like the sun are very very common.

To get heavier elements, you need even bigger stars. Anything above, about 8 solar masses will start to do the trick. And inside of these stars, you get nuclear fusion going. You get, in no particular order, some nitrogen, some neon, some silicon, some sulfur, some magnesium, some nickel, some iron, some argon, and some chromium. Some of the elements produced in the cores of stars are more common than others.

Typically, even numbered nuclei are more favored because you can just add helium. It's very, very easy to add helium, and so you get, and each helium comes with 2 protons, so you you double up like that. And then also some of the elements produced inside of a star are highly radioactive or end up in highly radioactive versions of themselves, and so they just decay away very quickly, and so they don't get a chance to build up. So this look look at us doing cosmology and building a creation story. Not only are we explaining the origins of the elements, but we're explaining why some are more common than others.

Even though all these generations of stars only give us 4% more helium in the solar system now than there was in the same patch of the universe, you know, a few minutes after the big bang, that helium is still 185 times more abundant than oxygen, which is the next most common element in the solar system. But that's about where fusion processes within stars tap out. Other elements appear, don't get me wrong, but only usually briefly as some part of a chain reaction or they decay away. If you really want to fill out the periodic table and you do, at least if you want to get into some serious cheese making business at a fundamental level, you need those stars to die, and this is our last stage of creating the elements. This is the final chapter in this part of our creation story.

The story that started with the big bang and the formation of the light elements, the story that continued and continues till this day with the appearance of heavier elements inside the fusion cores of stars, and now the last part of nucleosynthesis comes from the death of stars. Stars die in all sorts of horrible, gory, and spectacular ways. Sometimes they just sputter out and release their atmospheres. Sometimes they go off in gigantic supernova explosions. Sometimes they leave behind a solid core that then goes boom later on.

Sometimes those leftover cores crash into each other. Sometimes stars leave behind white dwarfs or neutron stars. Material can spill onto a white dwarf and make it explode. Neutron stars can crash into each other. This is where we get planetary nebulae and nova, kilonova, supernova, hypernova.

All these kinds of deaths serve 2 very important functions. You know a good creation story involves death somewhere in the story. Right? 1, the deaths of stars can do things that normal stars can't. Namely, they can produce elements without having to worry about generating energy.

When you're in the core of a star, it is your job as an element to fuse and release energy. This can take you up to iron. Fusing anything above iron actually takes energy out, and so that's not gonna work out well for you. In fact, that is what will trigger the death of a massive star. And also inside of a star all you have is fusion and these chain reactions.

And it's regulated. The amount of energy available inside of a star is enormous, don't get me wrong, but it's limited. When a star explodes, there's essentially limitless energy and there's essentially limitless free neutrons just flying around because you have an explosion, a nuclear explosion, Atoms are slamming into each other, breaking apart. Neutrons are released, they go flying. They get embedded inside of other nuclei.

They make them radioactive. They make them eager to combine. You have smashing. You have splitting. You have so many complicated nuclear processes happening at once with essentially limitless energy to fuel it all, and you get all the elements.

Through these various processes, these stellar deaths, you get all the rest of the periodic table, except for some ones that we only have been able to make in in laboratory conditions. And the second nice thing about these stellar deaths is that they're explosions, literal explosions. They spread stuff around. You know, you you're fusing carbon and oxygen in the core of a star. Great.

That's not very useful for the wider universe. You need that star to die, to explode, so all that carbon and oxygen spews out, and it gets mixed up in the formation of a new system. It gets recycled. The only reason that oxygen is present in the air you're breathing right now is because some star somewhere had to blow up. And this is how we finally get our cheese and honestly are everything.

This is the story of modern cosmology. The story of nucleosynthesis, the formation of heavier elements from the fusion of lighter ones. Starting at the big bang, and continuing through the present day, through the evolution and death of stars where every atom, every proton in your body, in that piece of cheese, in every breath of air we can take can trace its origins back 1,000,000,000 of years in and out of the hearts of multiple generations of stars living and dying all the way back to the first few minutes of the big bang itself. I told you it was a good story. Thank you to Tim b on email at estudent on Twitter.

Keith k on email, Christian w on email, Calvin k on email, and Lazlo s for the questions that led to today's episode. And thank you to all my top Patreon contributors. Actually, thank you to all my Patreon contributors, especially my top ones, Justin g, Chris l, Barbara k, Duncan m, Corey d, Justin z, Nyla, Scott m, Rob h, Justin Lewis m, John w, Alexis, Gilbert m, Joshua, John s, Thomas d, Simon g, Aaron j, and Valerie h. That's patreon.com/pmsutter. I can't thank you enough, seriously, for all the wonderful questions, wonderful support.

Please keep sending me questions. I know I put a lot of pointers in this episode to future potential topics. Please ask. That's askaspaceman@gmail.com or check out the website, askaspaceman.com. And I will see you next time for more complete knowledge of time and space.

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