What did the universe do to make so many defects? What happens when they get trapped? And could they be hiding right in front of our noses? I discuss these questions and more in today’s Ask a Spaceman!

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EPISODE TRANSCRIPT (AUTO-GENERATED)

Every time you flip a light switch, or check the time, or feel the sodium ions wiggling in your brain, don't think about that one too much, you're assuming something fundamental. You're assuming that the universe is a finished product. It's a completed work. You think the Bing Bang happened, the forces of nature settled into their seats, and we've been cruising on a smooth, predictable ride ever since. It's just done. No, the universe isn't perfect. That's not what I'm getting at. In fact, its total lack of perfection is exactly why we're here. Long ago, like in the earliest moments of the Big Bang, things were a lot more even, more uniform, and just kind of okay. Then flaws appeared, and those flaws grew to become stars and galaxies, you and me, all the good stuff that makes this universe such a fun place to be in. We have a beautiful model of how that process unfolded. That model tells us that tiny random ripples in the quantum fields that soak all of space and time grew up during inflation to become not so tiny random ripples in the quantum fields that soak all of space and time.

It's an elegant theory. It works. It matches observations. And it's the standard picture. Okay, the universe is a little bit less than perfect, but those tiny little imperfections grew to become the largest things in the universe. But I'm not interested in the standard story. I'm interested in where that story breaks down. The thing is, that process of giving flaws to the universe didn't just stop with, well, the flaws. The universe wasn't content with just making a few galaxies and being done with it. Think about a lake freezing over in the dead of winter. If the water freezes perfectly and all at once, you get a clear sheet of black ice. But that almost never happens. Instead, you almost always get cracks. You get white lines where the crystals in the ice don't quite line up. You get defects. The phase transitions of the early universe, the same ones that laid down the conditions for the cosmos to be not quite so perfect, were full of defects. We're talking about a residue from creation itself.

Scars in the fabric of space-time. I've talked about some of these defects before. Cosmic strings, magnetic monopoles, domain walls, the usual suspects. But where are they? If these defects are real, they should be everywhere. And yet we look at the sky and... There's nothing. I mean, there's stars and galaxies, yes, but they're the imperfections. But where are the defects? Well, maybe they're not gone. Maybe they've just evolved into something else. Something so strange we wouldn't even recognize it, even if it was right in front of our noses the whole time. Maybe the defects of the early universe are here in the room with us right now. Let me go back in time a bit to when things were simpler, more orderly. In the earliest moments of the universe, there was just the universe. A hot but mostly bland soup of who knows what. Some sort of perfect symmetry of all the forces of nature melded into one unified whole. It was just one big happy physics family. There was no distinct gravity or light.

We don't know exactly how to describe this era, so we're just going to skip on past that for today. What comes next is what we care about. And what comes next is perhaps the single most consequential event in the entire history of the universe. This was inflation, which is exactly what is described on the label. A period where the universe underwent radical, huge, massive expansion in less time than it took to say this sentence out loud. A few trillion times over. Actually, more than a trillion. Because it all happened in like 10 to the minus 32 seconds. Anyway, inflation was powered slash triggered slash driven slash encouraged by the splitting of the forces. As the universe cooled, the unified forces split off from each other. That's what triggered inflation. No, we don't understand inflation either. So we're also going to skip the exact mechanisms of that for today. But by and large, we suspect that something like inflation happened based on a lot of circumstantial evidence. So we're going to go with that and just move on.

Now, here's where things get interesting, because it's the process of inflation that laid down the imperfections that would someday become stars and galaxies and groups and clusters and the whole entire cosmic web, including you and me. But that process of splitting the forces wasn't straightforward. The splitting the forces is when the universe had to make a choice. When the universe was perfect and whole and unified, there was only one way for it to be perfect and whole and unified. But when the forces split apart, they had a million different ways that they could have split apart. We live in one particular choice, with one particular arrangement of physics and forces and fields and constants and etc. etc. Like, here's an analogy. It's a rough one, but it's going to have to do. When a pencil is balanced on its tip, there's only one way for it to be balanced on its tip. You walk in a circle around it and, yeah, it looks the same, regardless of where you're looking at it from. Tip down, eraser up, balanced.

But when the pencil tips over, it has a choice. Not an actual choice. It's all random, but you get the idea. When it tips over, it points in one particular direction on the table. You walk around that table in a circle, and now the pencil looks different from different perspectives. In physics, we say that this is a broken symmetry. The pencil has symmetry when it's balanced, but then that symmetry breaks. The quantum fields that were unified had a symmetry to them in the early universe, but then as the universe cooled, that symmetry broke. And I don't want you to think that the fields actually point in an actual direction that is purely a metaphor. We're talking about very, very abstract mathematical concepts here. I'm doing my best, folks. But in these very abstract mathematical concepts, there is a choice or a randomization of what happens to these fields when they split apart. We live in one particular direction of the tipped pencil. We live in one particular arrangement of the broken forces.

The point is that... It's all random. Depending on which way the quantum winds blow, you can potentially get completely different rules of physics. It's true. Depending on how the quantum fields arrange themselves when everything's split, we might have had different forces of nature, or different constants, or different strengths, or different properties. This is all super theoretical physics, but... how we think it went down. And there's no reason at all that that process had to be perfect and uniform across the entire cosmos. Just like a pond freezing over, it doesn't freeze over in the exact same way all throughout the water. Some ice crystals choose one direction, other crystals choose other directions. Or to go back to our wonderful pencil analogy, if I had a table with a thousand pencils all balanced on their tips and I shook the table, I mean, sure, some would fall in the same direction if one pencil dominoes into another, but in general, it would be chaos. And this is where the universe gets its defects.

If the universe transitions in different ways across its volume, which at this stage is less than the size of a basketball, then eventually there will be places that get caught between two regions. It's like if pencils on one part of the table are falling in one direction and pencils in another part are falling in a different direction. And then those two places meet. And the pencils right on that line get stuck on each other with some pencils pushing them to the left and then other pencils pushing them to the right. So they stay up. And the defects... are the places where the universe gets stuck on itself. And what happens in those places where the universe gets stuck on itself? Well, the best way I can describe it is that they retain a memory of the before time. All around the defects, the universe reaches its new expression of reality, the forces, particles, fields, and all the other goodies that we're familiar with. But not in the defects. They're stuck. They didn't ever get the chance to settle down and pick a direction, pick a configuration.

So they become these tiny little hot pockets of the extremely early unified universe. While the rest of the cosmos broke, they stayed pure. And there are three standard kinds of defects. One-dimensional, two-dimensional, and three-dimensional. The one-dimensional ones are the points. We call these the monopoles. They're tiny little pinpricks in space. The two-dimensional ones are the cosmic strings, which are not the super strings of string theory. Sorry, lots of string-based action going on here in theoretical physics. Different thing. Same deal, though. Surrounding a string, you have normal as you have a universe, but within the string, you have a relic of the earliest moments of the Big Bang. And then you have the two-dimensional ones, the domain walls. These are the universe killers. With monopoles and cosmic strings, yeah, there are weird, nasty defects that the universe can't get rid of, like that one annoying friend that always shows up to every group event. But around them, the universe eventually smooths itself out and agrees on the same configuration.

Imagine just one of our pencils getting stuck. That'd be a monopole. All the other pencils shift around it to agree on a common direction, with just that one pencil remembering what it was like to live a balanced life. But the domain walls, they cut the universe in half. There's no way around a wall that stretches across the entire breadth of the universe. There's no way for the pencils, or quantum fields in this gloriously tortured analogy, to work themselves out and at least settle down. If domain walls existed, if these two-dimensional sheets, these defects left over from the Big Bang actually existed, the cosmos would simply exist in a permanent state of division with one kind of physics on one side and another kind of physics on the other. As you can imagine, that would be perfect. Really bad. House divided against itself cannot stand and all that jazz. The immense gravitational pressures and energies contained within that kind of defect would kind of sort of rip apart the vacuum of space-time.

We'd also kind of noticed it by now because it would stretch across the entire horizon. There would be a clear and obvious region where the stars and galaxies just stop. But there ain't none of that, which is a relief. So that takes care of the domain walls. But what about the rest? They don't just go away. They're stuck. That's the whole point. They're places where the universe can't agree on what to do. They're stuck just like those random Patreon ads. That's patreon.com slash pmsutter where you can contribute to this show. I greatly appreciate it. If you're old enough to remember... Phones used to live on the wall, and the handset was connected to the phone with a long, windy cord. And everyone wanted extremely long cords because, of course, you did, because you wanted to walk around your house doing stuff while still being on the phone. And the windy cords were designed to stretch to help accommodate that desire and then also return to a somewhat compact, neat configuration when you were done.

This never worked. The cords always tangled up on themselves and got themselves in knots. It's just a fact of the ancient world that doesn't exist anymore. But once a cord got a knot in it, the only way to untangle it was to start at the end, the handset, and work your way back, passing the handset through any knots that showed up. And if you're not old enough to remember when phones were like that, then I'm sure that you can still appreciate the analogy of the general difficulty of untying knots. These defects. These places where the universe gets stuck on itself are like knots. The universe can't just untie a knot. It can't just take a monopole or a cosmic string and just smooth it over and make it go away. We call these defects topological, which means of or relating to topology, which means it means shapes that are locked in. Let me give you some examples. Like a mug of coffee. Forget the coffee. The important part is the mug. The mug has a handle. Now imagine the mug was made of clay and you could squish and reshape the mug to your heart's content.

But you had to follow one and only one rule. Always had to be a hole. Think of all the wonderful shapes you could make. You could make a donut that has one hole. You could make a hula hoop. It's like a long skinny donut with also one hole. But you couldn't make a figure eight that has two holes. And you couldn't make a flat slab that has no holes at all. In the language of topology, all the possible shapes with one hole are in some sense the same. They have the same one-hole topology. And then there are the whole two-holers and no-holers, all sharing the same but distinct topologies. The same goes for knots. Once a knot appears in a rope, you have a different topology. It's a different thing. A rope with a knot in it is fundamentally different than a rope without a knot in it. A universe with a defect in it is different than a universe without. The only way to get rid of the knot in a line is to reach the end of the line. You have to go outside the system entirely. There's no way to get rid of the knot while staying inside the line.

No matter how much you squish and pull and reshape the rope, you can never get rid of the knot. That's what it means for a rope with a knot in it to be different than a normal rope. They have different topologies, which means you can't just squish and reshape to get from one to the other. Once you have a knot, you're stuck unless you cheat and get outside the system. But there is no outside to the universe. The quantum fields of the universe wrap themselves around the defects like the monopoles in the cosmic strings. They get trapped. They get knotted up. But the fields also exist throughout all of time and space. They're the fundamental building blocks of material reality. They have no end. They have no edge. There's no quantum handset that you can grab to pull the fields through to untwist them. The knots are there forever. I mean, kind of. It is possible to vanish a defect, but which now get the promoted title of topological defect because they are twists and knots in the vacuum fields of the universe, but it's not easy.

The thing is, the defects retain a memory of the very earliest universe. They exist in a kind of reality that the cosmos hasn't experienced in over 13 billion years. They're built different. And most importantly, they are concentrated points or threads of extremely high energy. The kinds of energies where the forces of nature are still united. The only way to untie the Gordian knot of a monopole or a cosmic string is to pull the full Alexander and slice the thing in half. You have to melt the knot by reaching insanely high energies, which, well, the universe ain't what it used to be. It's old. It's cold. It's low energy. You just can't do that kind of stuff anymore without pulling its back. You could blow up a supernova right next to one of these defects and it wouldn't even flinch. But the cosmos does have some tricks up its sleeve. When it comes to strings, they can sometimes get caught up on themselves. They are, after all, intensely vibrating, wiggling things. And once a string crosses itself, the loop pinches itself off.

Did I mention that vibrations can race up and down the spine of a cosmic string at nearly the speed of light? Yeah, pretty cool. But when a string becomes a loop, those vibrations amplify each other, reaching the energies needed to melt the defect away like a good massage hitting a knot in your back. And the loop evaporates in a giant shower of radiation and gravitational waves. Bye-bye defect. And monopoles, well, they have no extent whatsoever, so it's kind of hard for them to cross over on themselves. But despite that, they can still outweigh a bacterium, which is wild to even think about. But that's what we get for dealing with the extremely early universe and the relics and defects left behind. But the monopoles aren't alone. There are also the anti-monopoles, monopoles with opposite charge. And just like matter and antimatter, when monopoles and anti-monopoles meet, they go kablooey in a giant blast of radiation. Okay, so maybe these defects aren't so permanent after all. But when things go kablooey or twist up on themselves and going kablooey in the process, we should be able to see that, right? Astronomers are good at finding all the things that go bump in the night, so this should be the definitive evidence that we need that the universe does, or at least did, have defects.

And yeah, we have a problem. Mathematics, specifically the kind of topology that makes coffee mugs and donuts the same thing, insists that the early universe was a messy, knotted-up disaster. Our best theories of phase transition say that these defects had to be born. in the cooling fires shortly after the Big Bang. And just as we established, once you get a knot in the fabric of space-time, you're stuck with it. There is no cosmic eraser. There's no reset button. The knots are there forever. I mean, kind of. But when they go, they really go in an unignorable way. So we should be either seeing the defects themselves or the explosions left behind when some part of the universe reaches the energies necessary to make it go away. So where are they? I mean, look at the strings. We're talking about 1D cracks in the vacuum that are thinner than a proton but weigh more than a mountain range for every kilometer of length. They're massive. They have gravity. They're here. They have presence. If the universe is as glitchy as our theory suggests, the sky should be a chaotic spider web of these things.

We should be tripping over them. But when we look at the sky, it's suspiciously clean. Yes, we see the imperfections of the universe, but not the defects. It's like walking into a crime scene. There's DNA evidence, there's the motive, the weapon is just sitting on the table, but there's no body. There are other ways that we should be able to detect cosmic strings. They wiggle a lot. When that much energy moves that fast, it should create a chirp that ripples outward in the fabric of space-time. These are gravitational waves. We have detectors like LIGO and NanoGrav that can hear the collisions of black holes and neutron stars. But the background hum of vibrating cosmic strings? We've got nothing. Not a peep. There's more. There's always more. If a massive cosmic string passes between us and a distant galaxy, it warps spacetime so much that it splits the light around it. From our perspective on Earth, we should see two identical copies of the same galaxy side by side. A perfect double-take.

We've found plenty of lensing from regular old dark matter, but a perfectly straight, string-like lensing signature? Nada. Those are the cosmic strings. What about the monopoles? In 1982, a physicist named Blas Cabrera actually thought he caught one. It was on Valentine's Day, so we called the Valentine's Day monopole. His detector recorded a single perfect signal that matched the signature of a magnetic monopole passing through. But we never saw anything like it again. The missing monopole problem is actually even worse than that. If monopoles existed in the numbers that our theories predict, then their combined mass would be so immense that the universe should have stopped expanding and collapsed back into a big crunch before the first star even formed. The fact that you're sitting here listening to me talk about this, possibly dreaming of cheese in the process, is living proof that the standard story of the phase transitions of the early universe is missing something. So what happened to the cosmic strings and the monopoles? Well, this is where inflation comes in.

If the defects were created before or during inflation, then that radical expansion might have just swept the floor. Just made the universe so big that it diluted all these defects so that when we look around in our universe, we would only expect to see a monopole. And that's it. It's convenient to have inflation driving away all the defects produced in the early universe. Maybe a little too convenient. But even with inflation, we should see something. Maybe that one or two monopoles still left in our observable volume. Maybe a cosmic string still left over that's been stretched out, looped around itself. Come on, universe, throw us a bone here. Here's a radical idea. Maybe we aren't seeing the defects. Not because inflation drove them away, but because we're looking for the wrong thing. What if the defects didn't get swept away? What if they just changed? It might be possible for some defects to remain. We can take a string, one of these cosmic strings, wrap it around itself, but instead of having it vanish into a shower of radiation, what if it just stopped? You would have a universe filled with tiny, heavy, invisible knots that don't interact with light.

You did. What would you call it? Yeah, you'd call it the dark matter. It's time to talk about the Vortons. The what? Yeah, the Vortons. It's not an anime monster hunting show. It's not some AI startup company. It's a thing, I think. Listen, what I'm about to tell you is so hypothetical that I could make even a string theorist blush. We are deep in the annals of physics here, and I don't want you to trust any of what I'm about to say. But that's never stopped us before, has it? You see, cosmic string loops are supposed to be suicidal. They're these high-tension whips of space-time that vibrate and oscillate so fast that they scream out gravitational waves until they fade away into nothingness. Usually, that's the end of the story. The loop shrinks, it vanishes, and the universe is down one defect. But it doesn't have to be the end of the story. I mean, cosmic strings themselves are super theoretical. So we have some options. Imagine a cosmic string loop that isn't just vibrating. It's also spinning like a bicycle wheel.

Really, really, really fast. And if you ask why should they spin, well, why should they not spin, buddy? Who are you to say that they could never spin? And if they're spinning, they have angular momentum. That's kind of the definition. But as the loop emits energy, it gets smaller. But you just can't get rid of angular momentum, which means that as it gets smaller, it spins even faster. And at a certain point, that internal spin is so strong that it starts to push outwards. This makes a tension. The loop wants to shrink into itself from its own tension, but the spinning wants to stretch it back out. When those two forces find a perfect locked-in equilibrium, the shrinking stops. The loop doesn't evaporate. It doesn't vanish. It settles into a permanent, indestructible, subatomic ring of pure field energy. And this, my friends, is what we call a vorton. It's this little nugget of cosmic string stuff. A defect that stubbornly refuses to fade away into that long night. Oh, and it might be the dark matter.

We don't know what the dark matter is, but we know what it does. It has to be a particle or something like a particle. It has to be heavy. It has to be almost entirely invisible. And it has to have been around since the earliest moments of the Big Bang so that it can participate in all that cosmic web-building stuff that it's so good at. A vorton is not a particle, but it's small, like the size of a proton. And it doesn't glow or emit light. It's just a defect in spacetime, not a thing in the usual sense of the word thing. You could have a billion of them passing through you right now and you'd never notice, except that you would suddenly weigh more than a mountain, so I guess that counts as noticing. But here's the kicker. These things are dense. They're made of the trapped, high-energy vacuum of the early universe. And if the early universe was as messy as we think it was, then the Big Bang should have been a vorton-producing factory. Vortronforge? I don't know the right word. I just know it made a lot of vortons.

This is the story. Phase transitions created a lot of cosmic strings. Inflation stretched them out. Then they vibrated off each other and spawned an enormous number of loops which shrank until they got locked in place as vortons. That would explain why we don't see any cosmic strings anywhere. Those missing defects aren't actually missing. They've just evolved into a mist of dark matter that fills every galaxy. It means that dark matter might not be some extra ingredient that was added later. It might just be the residue left over from the Big Bang. The universe is far from perfect. That's part of why we exist. But do the imperfections stop with us, with the dust and the stars? Or do they extend down to a much deeper, more fundamental level? A level so deep that it's frozen into the very fabric of space-time? We don't know if Vortons exist, or if they're responsible for the dark matter, or even if they can exist. But that doesn't matter. The truth is, we owe our very existence to the fact that the universe is a bit of a mess.

If the Big Bang had been perfect, there would be no flaws to seed the growth of galaxies. There would be no knots in the field to provide a potential dark matter. Now I don't know about you, but I say it's our flaws that make us the most beautiful. Thanks to at Ian Bill Morris, Thunder Fluffy, at SMTR, and at literally there for the questions that led to today's episode. Thank you so much for listening. Please keep asking questions. That's askaspaceman at gmail.com or the website, just askaspaceman.com. Please drop a review on your favorite podcasting platform that helps to show visibility. And if you can, I would appreciate a contribution to Patreon. It's patreon.com slash pmsutter. I'd like to shout out the top contributors this month. They are Justin G, Chris L, Alberto M, Duncan M, Corey D, Michael P, Nyla, Sam R, Joshua, Scott M, Rob H, Scott M, Lewis M, John W, Alexis, Gilbert M, Rob W, Jessica M, Jules R, Jim L, David S, Scott R, Heather, Mike S, Pete H, Steve S, Lisa R, Kevin B, Eileen G, Stephen W, Deb A, Michael J, Philabelle, and Stephen B.

That's patreon.com slash pmsutter. And I will see you next time for more complete knowledge of time and space. Thank you.

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