Daniel and Jorge Explain the UniverseLearn about cosmic strings with Daniel and Jorge.
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Hey, Daniel, I would question for you about how physics works?
All right? Shoot?
Yeah, what happens when it doesn't work? Like what happens when you're wrong? Hmm? That really depends depends on what how wrong you are.
No, it depends on whether you're an experimentalist or a theorist.
Oh it makes a difference.
Oh yeah. For an experimentalist, if you are wrong one time, it's like career death. It's like getting caught for murder. You know, once is enough to send you away forever.
You murdered science. If your results.
Are wrong, you murdered your credibility.
But not for theorists, like if a theorist is wrong, there's no consequence.
No, Almost every single paper written by a theorist is wrong, and in fact, if they are right even one time, they win the Nobel Prize.
Does sound like better? Odds? Daniel, why did you even become an experimentalist?
I ask myself that question every day.
I am Jorge, a cartoonists and the creator of PhD Comics.
Hi, I'm Daniel. I'm a particle of physicists. And though I've never been wrong in a scientific paper, I have zero Nobel prizes. No wait, that's not actually true. I do have a tiny slice of a Nobel Prize.
Well, you could be wrong about having a Nobel Prize, like you could.
I could write a paper about having a Nobel.
Prize and then be wrong, but then get a Nobel price for it. In literature maybe, But anyways, Welcome to our podcast, Daniel and Jorge Explain the Universe Even the Wrong Parts, a production of iHeartRadio.
In which we take a trip around the universe, giving you a tour of everything that's amazing, everything that's exciting, everything that's real, and everything that's theoretical. Not just what's out there in the universe, but what's inside the minds of scientists, what they are hoping to discover out there in our universe.
That's right. We take you on a trip across the cosmos, not just to see what's there, but what might be there, what physicists think might be the next big idea that could revolutionize how we understand the universe.
And we have a special group of people whose job it is just to come up with crazy ideas that might describe our universe.
You have a group of people just to be wrong. Is that kind of how it works?
They only have to be right occasionally, But yeah, basically just throw ideas out there.
It's like the brain the Brain Trust.
Yeah, it's like a brainstorming, you know, like maybe the universe works this way. Go check. Uh no, I guess not. Maybe the universe works that way. Go check. Oh no, I guess not. Keep coming up with the ideas, folks.
Yeah, because the universe is pretty crazy out there. You know, there are a lot of things that we didn't expect, and so as crazy and as an idea might seem right now, it could be right.
Yep. Absurdity is no obstacle to reality. I mean, you can't take a theory of physics and say that's too crazy. Because some of these crazy ideas turned out to be real, you know, quantum mechanics and relativity. There have been moments in history when we had to accept things that were very difficult to swallow, and that means we need to keep our minds wide open to future crazy ideas.
Yeah, you could be absurbed and be right at the same time.
That's the situation of the universe. That's your review of the Universe on its Amazon web page, Absurd but right, absurb but true five stars. Yeah, that's kind of like this podcast. It's been a cartoonist and a physicist and talk from physics for an error. And I wonder what that's like sometimes for a theorist, because I'm not a theorist. You know, you spend your life coming up with ideas maybe there's this particle, maybe the universe works that way, and predicting them and suggesting ways to check, but almost never correct right. Most theorists who write papers, most of their theories don't even get checked because we can't check all of them, and when they do, mostly they just get ruled out.
Yeah. I guess there are a lot of theorists out there, and they can't all be right, right, and they can't all be checked. So how does how do these ideas come through to get checked.
Yeah.
Well, if you're a theorist, you have some crazy new idea, you say, I think the universe works this way, and then you have to make a prediction. You have to say, well, if somebody did such and such experiment, they could verify my theory. Like Einstein had his theory relativity, and he predicted something what happen when light bent around the sun or when light bent around the moon during an eclipse. So we make a very specific prediction. Then the key is you have to find an experimentalist someone to do that experiment and check your prediction. If you can't convince anybody that your prediction's worth checking, it just doesn't get checked.
Is there like an app for physicists to match experimentalists with theories, you know, like a dating app physics or checker?
Yeah, I'm not sure. You know, it's sort of arbitrary. You know, experimentalists will read a paper and say, ooh, that's really cool, I want to check that. Or me as an experimentalist, I'll go to conferences and talk to theorists and hear about the new ideas and try to think about what it's most interesting to test because you can't test everything. You have to make your choices.
Yeah, I guess you swipe left or right depending on whether you think it could be right or what are you based on, Like are you tempted by like, Ooh, that would be a big fish to catch, or are you tempted by like is this an easy fish that I could verify?
Well, that's a great question. I'm a bit unusual in particle physics. Most people choose theories that they think sound sort of aesthetically beautiful, like supersymmetry and gravity and all these things. They have like a deep theoretical reason to motivate that theory, like why we think it exists. For me, I'm more interested in stuff that's going to be a surprise, Like I'd like to look for something that isn't predicted, So I try to do experiments that nobody's predicted, because then if you see something new and new particle, then you get to be the first person to describe it and it sort of comes out as a pleasant surprise for the community.
So it is like a dating app. You swipe left or right if it's like, oh it a full I like it, or huh, this floats my boat. I'm gonna swipe.
It all right, You're right, I give up. Physics is just like a dating app. It's basically the same thing.
Well a lot of it. Amazing and incredible discoveries have been made this way. For example, the Higgs boson was really just a theory out of the blue, and it was a theory for a long time until people decided to try to test it.
That's right, And people spend decades trying to test this theory, and finally we built a collider powerful enough that we could create the Higgs boson and prove that it existed. And so this theorist to fifty years earlier had predicted the existence of this particle was proved right and got his Nobel prize.
Yeah, that was a like a twenty billion dollars swipe there, You know, that was a big swipe.
That was a big swipe.
That was good, twenty billion dollars.
Yeah. But you know, he wasn't the only one to predict it. And there was a lot of controversy when we discovered the Higgs boson. Who was going to get the prize for it? Should it just be Higgs, Should it also be this guy Anglert who was around that wrote a lot of very similar papers but didn't get his name on the particle. And then there was a whole other group of people that wrote very similar papers, but we didn't get any part of the prize.
That's right. And so today we'll be talking about a prediction from a theorist that maybe should have gotten the Higgs Nobel Prize, but didn't. And he made a second prediction about the universe that we're going to be talking about today.
That's right. And this comes from a question from a listener. Somebody wrote it and said, hey, could you explain this to us? I just don't get it.
Yeah, so this is a question that Peter from Poland sent this via email it and so today on the program we'll be asking the question what is a cosmic string? I don't want to string people along, let's just get down to it, Daniel.
Yeah, well, I was thinking, you know, silly string versus string theory. You know, there's a lot of different combinations there, but.
There's a lot of strings in physics.
Yeah, it's a great question. Thank you Peter from Poland for writing in, and anybody out there, if there's something in physics you've heard about but haven't really understood any of the explanations. Send it to us. We're going to try to break it down.
And this is a tantalizing subject because we're not just talking about strings. We're talking about cosmic strings. So they sound like a very big deal, and they are kind of a big deal. They're not small strings like maybe some people might be imagining it.
That's right. This is not you know, star studied strings in your drawer or anything like that. These are things that could span the entire observable universe.
And so we were wondering how many people had heard of these two words put together cosmic and strings out there, and how many people maybe even had an idea about what it could be. So, as usual, Daniel went out there and as people on the street, if they've heard what a cosmic string is.
So before you hear these answers, think to yourself for a moment, do you know what a cosmic string is? What would you say if I asked you on the street.
Here's what people had to say. No, it sounds like a Marvel movie.
Is that similar to string theory? With the loops that lay upon that's like a fifth dimension? Potentially you know all this stuff.
I don't know any of this. I don't know any.
It's something I don't have no idea. Cosmic strings, something that, uh, quantum, I think that's what space string does.
I have no idea.
If you laugh, does it sound funny?
It just sounds like like science fiction.
I heard of cosmic bowling. You're not cosmic string?
Cosmic bowling?
What's that when they shut down the lights for Friday night bowling?
Strings that you know you unite like different potential space and time like you know, yeah, like space and time like a pass.
I guess in a way, planets stringing together, string together.
I have no idea something to do with I don't know energy, energy, and I have no idea.
So obviously cosmic, yes, but strings those two words together.
No, all right, not a lot of familiarity, although I do like the answer the person who said it sounds like a Marvel movie to me, which it totally does. You know, infinity, stones, cosmic strings, quantum realm. You guys are all watching the same movies.
You could put cosmic in front of anything. It would sound like a Marvel movie.
Cosmic quantum, cosmic bowling.
I like that answer. I was like, yeah, that does sound like a good idea. I'd like to go to cosmic.
Bowling, cosmic breakfast, cosmic all right. So, not a lot of people seem to know what it was, although it definitely sounded sciency and science fiction. A lot of people said, oh, it sounds like science fiction, or it sounds like something that might be related to string theory or physics or energy. It definitely has a sciency feel to it.
Yeah, and it might just in the way my hair looked that day, maybe I looked more like a crazy physicist, or maybe it just does sound like a sort of a physics thing. So people were definitely guessing that.
I'm trying to imagine how you can look more like a physicist, Daniel. It's kind of hard. It's kind of hard to imagine.
I don't know. I guess I could put on a lab coat. I mean, I don't usually wear a lab coat when I'm walking around.
She put on a Marvel costume and boom.
I need an MCU lab coat so I can do both things at once.
Oh, that would be that's a good idea. Actually print something fun on a lab coat.
M that sounds like merch. Get on that people.
Next product for the Daniel and Jorge explain the universe tour. But all right, so let's get into a Daniel, what what are they? What is a cosmic string? And I am totally with the people on the street. I'd never heard of this concept before this morning.
Well there's a good reason, because cosmic strings are a pretty crazy idea. They're pretty far out there, but they're really fun and conceptually sort of mind blowing, which is why I think the theory stuck around for a while.
People keept swiping it because it sounded fun.
Yeah, everybody wants this theory to be true. And so what is a cosmic string? A cosmic string is a line in space where the space itself is a little bit different from the way space is for us, for me and you, and most of the space in the universe. It's like a little bit of leftover from the Big Bang where it never quite cooled and relaxed the way the space for us has.
It's like a pocket, like a pocket or a bubble, or like a stretched out bubble. Is that kind of what mean?
No, it's a really long, thin line, like it's maybe a fectometer wide, So like super duper tiny, like the width of a proton, but then it can be super long, like it could be as long as the observable universe, like ninety billion light years.
It's kind of like a crack in space itself.
Yeah, and you have to think about what space is, and remember that space used to be really different. Right back when the universe was created. Everything was hot and dense, and the there's a lot of energy everywhere. And remember that space is not emptiness. Space has all this stuff in. It has these quantum fields. And when you put energy into space, what you're doing is you're making those fields wiggle. And so back in the very early universe, those fields were going crazy because there was so much energy everywhere. So everything was wiggling really fast, and everything had a lot of energy.
In our book, we talk about how space is kind of like a goo. It's like it's not emptiness. It's more like it's like something that you're swimming in almost, and it can wiggle and bend and push you in different directions. Right.
That's right. Gravity does really weird things to space. It can stretch it, it can bend it, it can ripple it. But for now, let's just think about like one unit of space, Like what's in that box of space? And in that box of space are quantum fields. Now, the universe started out really hot and dense and really energetic, and those fields had a lot of energy in them. But the space that we're familiar with that operates in the way that we expect, like has electrons in it and and atoms and stuff that only came about after the universe relaxed a little bit. We talked about on the Higgs Boson episode that there's one of these quantum fields, the Higgs one, that when it relaxed, when the universe cooled down, that this field didn't go all the way down to zero, so it got stuck on a shelf.
Right, Like the field that the universe is made out of are not necessarily static, like they can be kind of buzzing with energy.
That's right. Every time you have a particle, that's a ripple in the field, which means you've injected energy into it. Now, most of the fields can go down to zero, like you got no electrons in your box of space, that field is that zero. But the Higgs boson never gets down to zero. Got stuck on this shelf.
And so how does that explain these pockets or these cracks in space.
So what happens when the universe is expanding is is it's cooling. Right. All this energy is getting spread out into more and more space.
It's like you're stretching out the fields, right, Like you're stretching them out basically, and so they calm down.
Yeah, you have the same amount of energy in more space, and so it gets diluted. So everything's like cooling and relaxing and sort of like you know, you you toss your blanket over your bed and it sort of settles down and settles over your bed, right.
Like a cosmic nap. This is what I.
Like, a cosmic blanket. Yeah, and it settles down. But the Higgs field got stuck, right. But here's the thing. The Higgs field has lots of different ways to get stuck on that shelf. It's that shelf is not just like one little balcony. It's like a long round balcony. And the universe can get stuck in different spots on that shelf. And so as the universe is cooling, if this chunk of space over here got stuck on a different spot than that chunk of space then there's this sort of boundary between them, this place between them that doesn't quite work because it's sort of trapped between space that got that cooled in two different ways.
It's kind of like how you know water or air has different states, like solid liquid and gas. You know, as you cool something down, you can form these little pockets of liquid or gas or what's either one solid. Like when you stick water into the freezer and it cools down and forms ice. It doesn't form like this perfect solid of ice. It forms like it has bowls and cracks and wiggles, and it is that kind of what you're saying, is happened happened or is happening to space right now?
Exactly like that, if you cool water down, then you get a crystal. But it doesn't, as you say, turn into a crystal all at once. There's these sights that begin because they are the coldest little dots, and the crystals start to form there, and then they form out from those little spots where they have nucleated. And then what happens when two crystals meet. You have this boundary, right and we don't have a perfect crystal. You have a defect in the crystal that's why, like some diamonds are perfect and some diamonds are not, because there's a defect there in the crystal where one half of it is cooled in a different time than the other, so they're not all lined up perfectly. The same thing happened to space.
Maybe, like there are imperfections in space.
There are imperfections these there are defects or cracks in space where on one side the Higgs field, it's at the same level, right, it's just pointed in a different direction, because the Higgs field has sort of two we call them degrees of freedom, the level that it relaxed that and also where on that shelf it got stuck. So if this chunk of space is stuck on a different spot in the shelf than that chunk of space, it's sort of like your ice cooling at different ways. In different ways, the crystals are oriented in different directions, and so at the boundary you get this thing that doesn't quite make sense.
So I always thought the universe was pretty pretty good, But I guess it's not a triple a diamond quality space mane.
I mean, I love our universe. I would not trade it in for anything. I think it's perfect just the way it is, but it might have these cracks in it, right, and we don't know, we have never seen one of these things, but it might have these cracks in it. That's the idea. That's the concept of a cosmic.
Stre cosmic flaws.
In space itself. And so along that line, it's like the universe never got to cool because it doesn't know like should I cool in this way or should I cool in the other way. It's sort of like trapped between them, and so it still has that energy density from the initial universe when everything was really hot and dense. And so these cosmic strings, even though they're really really thin, they're like a femtometer wide. They're incredibly massive.
And they could be holding energy, like the cracks or the flaws in the universe could be storing some sort of energy or tension into them.
Absolutely incredible amounts of energy. Like two centimeters of a cosmic string weighs as much as Mount Everest. A kilometer of cosmic string weighs more than the Earth, And so we're talking about these things. They could be like ninety billion light years long. It's an enormous amount of energy.
Wow, you just totally cracked my mind here, Daniel cosmically cosmically dude. All right, so let's get into it and why physicists think these crazy cracks might exist, and whether or not they're real. But first, let's take a quick break.
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Okay, so you're saying that as the universe was cooling or assets cooling right now, you might have these areas, these lines, these huge lines in space that are sort of like cracks, like where space is kind of freezing into different crystals like structures or different modes. And so you have these kind of edges to the or wrinkles in space itself due to the Higgs field.
Precisely and we are in the crystal part, right, We're in the part of space that cooled, and these chunks of space that all cooled sort of together. That's like could be as wi as ninety five billion light years, like the observable universe. So it's not like you have a little pocket of space to size your hand, and the next pocket is different, the next pocket is different. If there are these pockets and they're vast, they're incredibly enormous, but then at their edges there can be these cracks.
And you're saying, these edges, these boundaries look like strings, and so why don't they look like walls or like you know, planes out in space. Why is it shaped like a long like it's super thin but really long string.
Yeah, that's a great question. That's because the Higgs boson, the field for the Higgs has a lot of different ways you can run, Like there's one level at which you can relax, one energy level, but on that energy level it can sort of point in a lot of different directions. And so the way to get a boundary is like if you had two different energy levels, and the boundary, like a would be like a plane between them. But because there's only one energy level. Everywhere in space has that energy level, but they just point in different directions, and so what you get is this defect that's like a string. And then as you go around the string, the Higgs field is pointing in different directions, and so it points in a different direction every point around the string. And then the only place where you can't get sort of like smoothness is along this one infinitesimally thin line where space doesn't know where to point because every point everything around it is pointing in a different direction. So it's like, ah, I can't relax. I don't know which way should I go.
It's kind of like me in this podcast, we're going in every direction. What happens if I touch one of these strings? Like what if I'm one of these things and I run into like you know, like a spiderweb or you know, I'm walking down the street and just run into one.
Well, I would recommend wearing oven mits first of all, because there's a lot of energy there.
Oh that's right. They trap energy. It's like a I guess it's more like a wrinkle in space, right, It's not so much like a crack, but it's more like, you know, like you're tucking in or you're bending a lot of space along a line of it.
Yeah, a wrinkle is a good way to do it. I think a cosmic wrinkle would have been a good way to sell this thing.
That could be the sequel to the Ursula Laguin novels A wrinkle in Space time.
Turns out there was physics behind that novel. Now, you would notice one almost immediately if you saw one, because there's so much mass that they bend the space around them the way everything does. Everything with mass bend space, and it would cause a huge gravitational lens, so it would really distort the way light moved around it.
Wow, like a black hole, be like a black string.
Yeah, it would be a lot like a black hole, except it would be really really thin and very very long.
Okay, there would be probably crazy stuff happening around it, right like a you know, it wouldn't just sort of sit there in space. There would be you know, some kind of you know, cosmic storm kind of swirling around it. Would there be.
In the MCU version of this movie, then, Yeah, the visual effects would be dramatic all around it. Is that what you're thinking?
Yeah, Yeah, what does the goblet that holds the cosmic strings look like.
No, it's actually fascinating because unlike a black hole, which has enormous gravitational pull and so has a huge amount of stuff around it, like a maelstrom that's like giving off light because of all the gravitational energy and the tidal forces, cosmic strings don't actually provide a strong gravitational pull, like they distort space, but they don't necessarily create gravity themselves. It's a really weird consequence. It depends on the shape of the string, if they're a loop or if they're straight. It's actually quite complicated.
Didn't you say that it has more mass than the Earth, yes, or like you know, it's distinctly massive, but it has mass but no gravity.
It has mass, it distors space, so it can become a gravitational lens, but it doesn't necessarily attract you because of the configuration of it. It depends precisely on the shape of it. Remember, general relativity tells us that gravity is much more complicated than just things that have mass pull on each other. It depends a lot on the shape of that stuff. That's why if you have the right configuration of stuff, you can even get repulsion like dark energy. And so these cosmic strings are a really weird little object. And it depends exactly on the configuration of it whether you get pulled into it or repelled, or whether it basically ignores you.
So when you say it's massive, it's really more like E equals empty square, Like it just has a lot of energy to it.
Yeah, it has a huge amount of energy, so a lot of energy density and a really small spot.
All right, Well, it sounds kind of dangerous and that maybe you don't want to run into one of these strings out there.
In space unless you want to win a Nobel prize.
Unless you want to die trying, I guess. But why do physics think they might exist? Is this something that you're pretty sure of or it's a crazy idea? Would what would make someone think of these strings as possibly being out there?
Well, it comes from this guy named Tom Kibble, and Kibble was one of the folks who was around when the whole idea of the Higgs boson was being invented. This question of like how do particles get masked? And do we need to invent a new quantum field that fills space that gives particles mass and you know, anytime theorists come up with some new idea, then they like to play with it. They say, ooh, okay, now we have a new toy, this Higgs field. What else does it mean? You know, how can we what consequences would it have? And so he was thinking about the early universe and how the Higgs field would be cooling as the universe expanded, and then he hit on this idea. He thought, wait a second, what if it doesn't cool evenly? Would you get these cracks? And I guess that was just really fun to think about. He also he didn't get included in the Nomail Prize because he sort of came in a ton I need a bit too late on those papers. So maybe he was going for a backup Nobel Prize strategy.
I wonder if his name help, you know, maybe the committee was like, we can't give a Nobel Prize to someone named Kibble.
You know, there's a whole group of people, there's like three folks out there who are writing papers right at the same time as Higgs and Englert, and they just got totally snubbed by the Nobel Prize committee. Wow.
Just about when they submitted the paper, or when when they came up with the idea.
There's a lot of controversy because it's you know, some journals that the date on the paper reflects when you submitted it, and in other journals it reflects when it was finally accepted after review. And so there's a lot of controversy about who came up with the idea first. And you can only give the prize to three people. And the three people who everybody mostly agrees came up with the idea first Higgs, Englert, and Brout. They were they won the prize except for Brown, who had died already, so it was just splitting the Higgs and England. And then in the second tier there were like three people and so they were like, well, either give it to two or we give it to five. We can't give it to five, so I guess we'll just snub that whole second tier.
Wow, is there a runner up Noble Prize.
Literary. Yeah, it's sort of like fake gold. You know, it's just like hollow and plastic. It's not nearly as cool.
Okay, So that's the theory. The theory is that as the universe is cooling, you got these kind of flaws and how the Higgs field was cooling down, and so you form these crazy strings. But they're not related to string theory, right. That might be confusing because they're both strings, but they're totally different scales.
That's right, they're not related to string theory at all. String theory deals with like the fundamental nature of the universe on the smallest scale, like ten to the minus thirty five meters, is everything actually made out of these tiny vibrating strings. The thing they have in common is the sort of analogy we use in our minds where we put them that, like, you know, this thing is really long and thin, so let's call it a string. So fundament mental strings that are really tiny we think might be these one dimensional objects. So they're really long and thin, not that long actually, but they're much longer than they are thin. And cosmic strings are you know, light years long and a femtometer thin. So the only thing they really have in common is that name. But there were other reasons to think that cosmic strings might have existed.
All right, So then, so what was the motivation for these Like I know they were playing around with the theory of the Higgs field, but what makes this a particularly fun theory, like you said, or interesting theory to look for.
Well, you're right, it's a fun idea and it's fun to play with. But there's a lot of things that get theorists excited and fun to play with.
You mean, they're fun strings, that's what they do.
They just go in their office and play with strings. No, the thing that made this idea sort of stick in people's minds was that they thought it might solve a problem that we had, which is that we didn't understand like why we had galaxies. We didn't understand why the universe had structure at all. We talked about this on the podcast before, Like the universe started out totally smooth. How do you get any clumping? How do you get things started so that gravity can take over and give you stars and planets and rabbits and hamsters?
Right, Like, where did that initial texture of the universe come from, or the initial clumping of stuff?
Exactly?
We could have been in the universe where everything was just spread out and bland and boring and gray, right.
That's right. And somebody was thinking about cosmic strings early on, and they calculated, like, well, how many cosmic strings would there have been. And then they calculated, like, well, how many galaxies are there? And those two numbers were pretty similar. So then they thought, wait a second, maybe cosmic strings cause galaxies. Maybe the reason we have structure is because of cosmic strings. Maybe these cracks in space, these imperfections, are the reason that stuff started to clump together and form structure and planets and hamsters and ice cream and bananas. So maybe cosmic strings explain the universe.
It would have tied everything up pretty neatly with a strength exactly.
It would have been quite the cosmic solution. That's why people got excited about it, because you have this new toy which is connected to this fun new theoretical idea of a Higgs boson, and maybe it solves the problem you have.
All right, well, it sounds really tantalizing, and I'm definitely seeing the fun of it, and I definitely feel like I'm being strung along here to some interesting conclusion. So let's get into whether or not they are real and how we might actually see these cosmic strings out in space. But first, let's take another quick break.
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Leo OKAYDNA. So are cosmic strings real? And how will we know?
We?
Are we going to see them out in space? Are we going to be looking out into space one day and see, like, wait a minute, what is that little crack? We check our glasses and our telescopes, but it's not a crack in the lens, it's an actual crack in space in the universe itself.
That would be pretty awesome. I mean, what a thing to discover, What a moment that would be to see a crack in space itself. Unfortunately, no human has had that experience yet. As far as we know, there are no cosmic strings out there.
Like how you said, no humans.
I don't want to rag on alien science, you know. I'm hoping those guys have made some advances well past what we have done, so that when they come visit, they share with us all those secrets.
No human that we know of.
No human that we know of, and no human would make this discovery, and I think keep it to themselves because it would be of really cosmic significance. And remember we also we can't say they don't exist. We can just say we haven't seen them, so we don't know that they exist.
Okay, so we haven't seen one yet, but it's a theoretical prediction that it sounds fun and that might explain some of the structure in the universe. So are people looking for these cosmic cracks or are we just hoping that one day we maybe see them? Like these are an active search for these cracks.
I'm just waiting for alien unicorns to come pulling one and drop it on the Earth.
That's what they use. That's what they used to steer the cosmic unicorns. They use cosmic strings.
No, that'll be the opening scene in the Marvel movie about cosmic strings. But people were thinking that maybe this affected the shape of the universe, and they had all these predictions, like if these cracks in space were the things that caused sort of the large scale structure, the reason we have galaxies, then they had predictions for how the universe should have sort of been rippling in its first moments. And remember that we have seen the early universe. We can look back in time and see what the universe looked like when it was very young. Called this the cosmic microwave background radiations leftover glow from the Big Bang.
But didn't these strings form way after the Big Bang when everything was cooling down? Or was it that it did they start wrinkling right after the Big Bang?
Right after the Big Bang? Yeah, it's when as space was expanding, that's when sort of things were cooling and the ice crystals of space were forming, and so the cosmic microwave background happened like hundreds of thousands of years later, and now we've seen that. So these cosmic strings, the idea was invented before we had precise measurement of this cosmic microwave background light, and it made very specific predictions for what that light should look like. And then we saw that light from the early universe and it didn't look right. It doesn't look the way you would expect it to. If cosmic strings were real.
Really, you would see this in the cosmic microwave background, like we aren't these I mean, aren't these cracks you're saying they're one fetometer thin? How would you even see them in the cosmic background.
If they're there and they did affect the sort of structure of the universe, you would start to see that structure beginning to form in the very early universe. I mean they've had three hundred thousand years or so to start of get things starting to wiggle, and we do see structure in the early universe. I mean, the early universe is very smooth because it was early on and things were just getting started. But we look at that light and we see like hotspots and cold spots. We can analyze those rates of hot spots and cold spots, and say, what theory would give us sort of that level of fluctuation, that level of structure at that time, and cosmic strings just predict sort of a different distribution of hot spots and cold spots than we see.
Really, even if the if there aren't as many strings as you thought there might be, do you know what I mean? Like, maybe there's just just far and few in between for you to see them.
No, the pattern is just wrong. It's not like about the number, it's about the distribution, how far apart they are, and sort of how they affect the shape of space. Instead, it's totally consistent with just quantum fluctuations in the early universe then getting blown up by inflation. So there were sort of two competing theories like this random fluctuation plus inflation or cosmic strings. And now the data really look a lot like random fluctuations plus inflation and not like cosmic strings.
I guess that's good, right, because if it turned out that the universe as a baby had a lot of wrinkles in it, that would be kind of strange and disturbing. Who wants to see a wrinkly, old looking baby?
Man?
If the universe is listening to this podcast, you're in trouble.
I'm already in trouble, Dane.
But you know, if cosmic strings do exist, they don't have to have formed the structure. This is like, if they caused the structure, here's what that structure should look like. But they could still exist. It could be that they're still out there. They're just not responsible for the structure of the universe as we know it.
Oh, I see. We know that they maybe didn't have a hand in structuring the universe, but they could still be out there. They're just sort of like under the radar more than you thought they would be.
That's right. And so we have other ways to look for cosmic strings that people are actively doing right now.
What are some of the ways that we can search for these cosmic strings.
Well, cosmic strings have a lot of energy density, and so they do this gravitational lensing thing. They bend space, and so if you have a really bright source of light behind a cosmic string and you're standing in front of it, then you'd see like sort of a doubling of an image because the light would get bent around the string, Like if I had a flashlight and there's a cosmic string between us, and I turned on my flashlight, you'd see two.
Bulbs, right, But wouldn't Aren't these strings really thin? You know, I'm trying to think about how much distorting a little string and meg And it'd be kind of tiny, right would It'd be really hard to see, like a small imperfection in such a huge canvas.
It'd be really thin, but it'd be really really massive.
Right.
Say we took Mount Everest and squeezed it down to a tiny string, right, then it could have a significant impact.
All right, and we would maybe see not as a lens, but like a kind of like a lens in the form of a string, kind of like we would see doubles all along the string itself precisely.
And so what we've done is we looked out in a space and we look for this kind of effect, and we see gravitational lensing all the time in space. Usually it's black holes or blobs of dark matter, this kind of stuff. But as you say, a cosmic string would look a little different. And people have seen like pairs of galaxies in the sky near each other that looked really really similar and they thought, ooh, wait, maybe that's a cosmic string. But then they look closer and they discover it. Nope, it's just two similar galaxies. It's not a reflection.
It was just Bob's hair that fill in the lens of our telescope.
Yeah. And so these days there's another way to look for cosmic strings that people think is the most promising.
What's that?
And that also has to do with their gravitational effects, because these cosmic strings, we don't think they're just floating there. We think that there have so much energy. They're like whipping and ripping and crackling.
No way.
What Yeah, like you know lightning bolts coming from fingertips in a Marvel movie.
Right, yeah, Oh, they're active, these strings. These boundaries can move, yeah, because I guess the field is shifting around it, and so that boundaries is like fluid.
Yep. And also the strings can get twisted and if they cross over each other, they can break, and then you get ends, and those ends can like whip around like crazy. It's it's pretty nuts.
Can they form loops and knots?
They can form loops absolutely, yep.
Can you make a cosmic knot?
I cannot make a cosmic knot, but the universe might be capable. If you get one of these crazy strings in a strange shape, then its movement can get generate a lot of gravitational waves. And we now have gravitational wave detectors like Ligo that saw when two black holes eight each other, or when two neutron stars collided, they create these ripples in space itself, and we can see that. Now.
Wow, it's like a picturing like a snake trashing in a puddle of water, Like it's moving and it's generating ripples that we might be able to see precisely.
But we don't know how fast they move, and so they could be like zipping around really fast, generating enormous signals of gravitational waves that we could detect, or it could be like a cosmic time scale thing where they're like decades long signals. These ripples you have to like take data for one hundred years before you see the up and the down, So we don't quite know what to look for.
They could be not whipping around, but maybe just whiping around.
Precisely precisely, and so people are using gravitational wave detectors. Here on Earth. You have these long hauls filled with vacuum and lasers to measure space really precisely to see if these little ripples. And then people are also trying to use the entire galaxy as a gravitational wave detector.
Yeah, why not?
Well, I mean, I got other things to use the galaxy war but if it's.
There, if it's there, might as well use it to find cosmic blacks whole strings. Why not?
Yeah?
And I love this idea because it just sort of takes what's already out there and tries to use it to do science. Like you could never build a galaxy size physics experiment, but hey, just take the galaxy and turn it into an experiment. I love this idea.
Oh and so what's the idea here that the string might, as it's moving around, kind of affect the things around it.
The idea is just to build a bigger detector, Like the larger your gravitational wave detector is the smaller a wiggle you can see easier to see in a larger detector because it's it's just more. You have more sensitivity too, because it's over more space. And so the idea is to build one the size of the galaxy. You know, you can't build your own detector. But there are things out there that you can use as a detector. And the thing that we can use are these stars called pulsars. These are stars that are emitting light in a regular pattern, like when they were first discovered. You see these these regular beeps from space. And so if the space between us and some of these pulsars gets wrinkled in a little bit, or ripples happen, then it changes the pulsing of these pulsars. And so the idea is to use all of these to sort of measure the smoothness of space.
Oh, I see, but that's only if these strings are moving fast enough for us to sort of notice them or notice the difference.
Yeah, if they take one hundred years to send a signal, then our grad students are going to be really old before they get their PhDs.
You don't sound that surprise, Daniel, like it's a big deal. You're like, I might take a five years or one hundred years.
I can't say, Hey, it's research. I can't predict, right. That's what I always tell my students. You never know. You're the first person to ever do this.
So you told them that you could be wrong.
I tell them We've never published a paper knowingly wrong yet, so don't be the first.
So many caveats in that statement, Daniels, So many caveats.
I had that vetted by my legal department.
Oh all right, So I guess that answers a question. What is a cosmic string? It's like an imperfection in this in the fabric of the universe itself. It's like a wrinkle caused by the stretching of it and the weird cooling of the Higgs field. I can't believe I just said that in one sentence.
Yeah, and you know, these quantum fields are not just an idea, They're real. They're out there. And as the universe cooled from the like hot, nasty quantum fields to cold, crystallized quantum fields that we have today, then how that cooling happened could have affected the where the universe is formed.
And it's cool to think that what we might do with this knowledge, right, Like, if we know that space can wrinkle and crack like this, who knows what we could do with space? Possibly? Can we fold space? Can we make space origami?
The one thing we can never do is get the Nobel Prize for Tom Kimble.
Oh, did he pass away?
He passed away, so he missed the Nobel Prize for the Higgs boson, And if he was right about cosmic strings, he missed that one. Also right.
But you can still get in on the party by maybe being the person who discovers it.
Right, that's right, and maybe Tom Kimble will get another kind mention in the Nobel Prize acceptance speech, which is almost like a runner up prize.
Right. Well, I guess the idea is that maybe someone listening to this out there might be the person who discovers it. Might be you, might be me, might be someone listening to this who discovers these wrinkles in reality.
That's right, or something even crazy. The next time you hear a theorist talk about some totally bonker's notion by the way the universe or space might work, then remember there are crazier ideas out there that are actually real.
That's right. They could still be crazy, but they might also be right. You never know. That's the wrinkle on your reason.
Thank you very much, Peter for that question. I love email questions from listeners, so please, if there's something you'd like to hear us discuss, send it to us. To questions at Daniel and Jorge dot com.
You hope you enjoyed that. Thanks for listening. See you next time.
Before you still have a question after listening to all these explanations, please drop us a line. We'd love to hear from you. You can find us on Facebook, Twitter, and Instagram at Daniel and Jorge That's one word, or email us at Feedback at Danielanjorge dot com. Thanks for listening and remember that Daniel and Jorge Explain the Universe is a production of iHeartRadio. For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows. When you pop a piece of cheese into your mouth, you're probably not thinking about the environmental impact. But the people in the dairy industry are. That's why they're working hard every day to find new ways to reduce waste, conserve natural resources, and drive down greenhouse gas emissions. House US dairy tackling greenhouse gases. Many farms use anaerobic digestors to turn the methane from manure into renewable energy that can power farms, towns, and electric cars. Visit you as dairy dot COM's last Sustainability to learn more.
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Go safely.
California from the California Office of Traffic Safety and Caltrans.
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