Daniel and Kelly’s Extraordinary Universe - What Is String Theory?

Episode Date: December 18, 2018

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Absolutely. We got big tasks. We want to understand the universe and make sense of it. But sometimes we come up with an idea, something that just looks beautiful, something which has an innate elegance to it. You mean like you'd see a theory walking down the road and you'd be like, oh man, that theory has it going on.

Yeah, there's some sexy curves in that theory. You mean like graphs, though, right? Like that kind of curve. That graph has a nice curve to it. Look at those peaks. And one of the most controversial theories of all time, one of the ones that gets people up in arms, is also one that's probably survived because it's so beautiful and elegant.

Is it the theory of attraction? No, it's a theory that was once described as a piece of 21st century physics that had fallen by accident into the 20th century. So it's a future babe. Future babe, exactly. Hi, I'm Jorge. I'm a cartoonist. And I'm Daniel. I'm a particle physicist. And we are the authors of the book, We Have No Idea.

Which talks about all the things we don't know about the universe and how we might hope to one day understand them. Yeah, so welcome to our podcast, Daniel and Jorge explain the universe. In which we take everything and anything in the universe and try to explain it to you. a way that makes sense and hopefully makes you laugh. Today on the program, we're going to talk about string theory. That's right, string theory. And this is a question that we've been getting from listeners. We ask people, please send in your requests for topics.

And maybe more than 50% of the request were can you explain string theory? What is string theory? Talk about string theory. More than 50%. Yeah. And it's fascinating. It's because string theory really is a part of the sort of cultural zeitguise. It's like an idea that people know exists, even if they don't understand it.

But it's a big part of that show, the Big Bang Theory, right? Like the people in that show, they supposedly study string theory. I don't know. I don't watch that show. Me neither, but that's what I've been told. Your cultural advice expert has told you that this is a culturally relevant thing. Well, yeah, it's something people have heard about. Well, have you heard about string theory before you started spending your time talking to physicists? No, yeah, I'd heard about it.

you know, it's one of these things that you hear a lot about. It's these, like, crazy theory about the universe, but it's really, and, you know, you hear certain things about it, like, oh, everything is made out of strings, but you don't really kind of know what it is, and what does it mean for things to be strings? You're a very visual person. What image do you get in your head if I tell you everything is made out of strings? Do you get like a universe, an idea of like a universe where everything is crocheted out of yarn, or how does it work in your head?

I would just ask, what are those strings made out of? Right, right. Of course, so you are a physicist at heart, right, because every question just leads to the next question. That's right. Yeah, beautiful. A physicist at heart, supermodel on the outside. No comment. But I thought it was an interesting question to tackle because it's something everybody's heard about, but very few people actually understand. I think that's why people wanted us to talk about it, to say, like, can you make this not just something we've heard this phrase, but something where we can know what it means and get some insight into why people are spending their time doing it. Right, yeah. So as usual, we went out into the street and asked, do you know what string theory is?

Yeah, so before you hear these answers, think for a moment. Could you define string theory? Do you know what it is and why it's persisted for so long? Here's what people who I asked had to say. No, I have no idea what that is. No, I do not. I've heard of it by only way of Big Bang Theory. Okay, awesome.

I don't know. I'm sorry. Turn to measure the connectedness of atoms and subatomic particles, I believe? Okay. I believe it's something that Sheldon worked on. Big Bang theory. Yes. Okay. Okay, so first of all, it's kind of interesting because normally you go out into your university campus to ask people, but this time you went somewhere different.

Yeah, that's right. UC Irvine was closed for a holiday, so instead I went to the mall here in Irvine, the Spectrum, and I asked a bunch of random strangers questions about science. And again, I was struck by how many people were willing to answer them. my questions. I thought people would say, who are you? Go away. Security, security. Right. Maybe they sense a certain beauty about you, Daniel. You're like,

who is this beautiful specimen of a person? No, who is apparently I just don't look very threatening, you know? I look like I could get knocked over with just a passing breeze or something. So everybody was willing to engage, which was awesome, and people had some pretty fun ideas

and everybody had heard of it. Nobody had said, huh, what? And your other speculation was correct. Some people had heard of string theory specifically because of the Big Bang Theory. So thank you, Big Bang Theory. You've mined all of this juice from nerd culture and you have actually communicated

something to the public. So congratulations. Nobody understands what string theory is, but they do understand that it is a theory. Well, I think that show doesn't even try to explain it, right? They almost use it for the opposite effect. Like, let's depict our character as this impenetrable, unrelatable genius that speaks

gobbly gook. So we'll just have him to talk about string theory. that nobody's going to understand that. So it's like they... So you're saying string theory represents the impenetrability of physics. I think it's more important to explain these things to people rather than just toss these words around and trying to intimidate people. Yeah, I think that's what I mean.

It's like they use it to intimidate people about physics. Yeah, when physics is nothing but warm and cuddly and just wants to explain the universe to you, man. There's nothing intimidating about physics, right? It's about revealing secrets and giving understanding and insight. And appreciating beauty. And that's the thing about string theory. It doesn't just potentially explain a lot of things.

It also offers some elegance, some gorgeousness, like a peek into what nature is doing underneath. Because, you know, you can have ugly theories and you can have elegant theories, you know? You might ask the difference. Like, what is the difference? Yeah. I can ask you the same question about art, right? Like, I look at it Kandinsky and I say, hey, that's beautiful. And somebody else says, whatever, I could do that in an afternoon, it's garbage.

It's subjective, right? You can't, it's like the whole question of what is beauty, something that's very difficult to nail down. Right. So you shouldn't judge a painting by the same metric used to judge a physics theory. And, you know, two physicists can disagree about what theory is pretty and what theory is ugly. So it's totally subjective. It's not an objective.

Can you have like a fetish? Like a, you know, I like this kind of theory. I like that kind of theory. Yeah. You know, I like theories with handcuffs in them instead of strings, right? My handcuff theory of the universe. Is that where you're going? Tall theories, or, yeah.

Okay, so let's break it down for people. What is string theory? Right, so string theory basically is the idea that the smallest elements of matter, the things that things are made out of, are not points, not particles, but instead they're lines, their strings. Strings of what?

Strings of basic universe stuff, right? So like the electron is not like a little ball. And we know it's like a quantum object, which is like a point with some kind of probability. But you're saying if you zoom in even more, maybe you would see a little squiggle there. Yeah. And there's sort of two ideas there. One is what is the most basic element? And the second is, is there a most basic element?

So this assumes that there is a most basic element, you know, that you look at something next. You pick up the nearest object you have. You know, maybe it's an apple. Maybe it's a platypus. Maybe it's a, you know, I don't know what. And think about what it's made out of. It's made of molecules, right? Tear those apart, you get atoms.

Tear those atoms apart. You get protons and neutrons, electrons. Tear those apart. You get quarks, right? And you could keep going. And eventually, you get to smaller and smarter particles, right? The question is, do you ever get to the smallest particle? Right.

That's one question. Is there a smallest thing? And we covered that in a whole podcast. But here we're just going to assume that there is, right? At some point, you get to end the most basic thing where you're not allowed to ask what it's made out of, because it's made out of the most basic universe. stuff. It's like the one circle on a Lego set. It's like you can't get any smaller than that. That's right. It's the unit, exactly. And that's, you might feel like that, well, that's

frustrating. Why can't I ask what it's made out of? You know, but it's also not frustrating because it would be the answer. I mean, if you actually got there and you said, look, everything in the universe is made out of this one basic thing, that's a deep insight, right? That's what we're going for. That's the day we wish for. We peel back a layer of reality and see, ah, everything is made, out of this thing because then you can ask why this thing. What does that mean? Oh, I see. So string theory is saying that everything, electrons, quarks, eventually if you break them down, you'll get to this one type of string. That's right. We think of things being made of particles. We think of them as tiny dots, right, in space. But string theory says they're not dots, they're lines. Okay.

And they're these loops and wiggles instead of being dots. And then everything is made out of these strings and you might ask well how can you get different kinds of particles for example out of one kind of string right and the idea there is that the strings can vibrate the strings can wiggle right the reverberations in the string just like you know a rubber band or a string is it like an actual vibration like it goes up and down or is it just like the different shapes you can make with a string oh i see no it's actual motion of the string yeah and so it's different different vibrational modes So they get excited and they can get into this state or that state. As the string vibrates in different ways, it makes different particles.

So some tiny particle, call in a set an electron, for example, is actually a string vibrating this way. And a quark is a string vibrating the other way. And a neutrino is a string vibrating a third way. So the same thing with different vibrations can appear as different particles. Oh, okay. So it's not like different strings in a guitar. That's not what we're talking about. we're talking about one string.

It's like a one string guitar and just the different ways in which it can vibrate, that gives rise to all the different stuff we see in the universe. Exactly. And like a guitar, you can pluck the string differently and you can get different notes, right? You can based on how fast it's vibrating

and where you put your finger in the end, you can get different notes out of the same string. And it's key here that it's one string, right? It's a single string because we're trying to explain everything in the universe in terms of one object. So we're trying to explain how you get all this complexity in terms of one thing. And that's the answer from string theory is that the string has different modes to it.

The string can do different things. Right. And you might think that's sort of weird. Like, I expect stuff, if it's all made of the same thing, to be the same thing. Right. Like, if everything is made of the same stuff, why is this red and that blue and this tastes delicious and this taste terrible, right? Right. And it comes from the way it's vibrating.

It's kind of like maybe light, you know? Light is just made out of one thing, photons, but depending on the frequency, then it's different colors. Yeah, exactly. And the way things move and vibrate can totally affect the way we perceive them. You know, think about, for example, water, right? Water is made out of water molecules, but so is ice, and so is steam. Right? They're made out of the same thing. But we feel them, we experience them very differently because of the way they're moving, right? Steam and liquid water have the water particles moving more than in ice, right?

And so it's the motion of those particles that generates them. macroscopic qualities that we use to define it. So the things we use to define the electron and the things we use to define a quark actually come just from the vibrations of these strings. Again according to this theory. Okay. So then my question

is still, what are these strings made? Is it just like made out of universe? I told you Jorge, you're not allowed to ask once we get down to the lowest level. No more questions. No, but do you know what I mean? Is it like a physical string or just like a mathematical string?

Do you know what I mean? Like is... Oh, okay. Now, ooh, prepare for a philosophical detour here. Like, what's actually vibrating? Like, universe stuff? Yeah. Yeah, well, so look, in the end, all physics theories are just models, right?

You can ask the question, is this really happening? Or is this just a mathematical model in my head I use to do calculations and predict the results of experiments? Okay. Boom. That is a big philosophical question, right? And there's no way to answer that. So we think of these things as models in our head.

reflect reality. Okay. You know, the top cork, does it exist or not, or is it just a calculation model in my head? We could, you know, smoke banana peels and talk about that for a long time without making any progress. So this model is just asking me to imagine that the most fundamental thing in the universe are these little strings that can vibrate in different ways. But then these strings can move around?

And they can't be cut into pieces, right? You can't get anything smaller than a string. It's the most basic unit. Oh, like there's something about the stuff of the universe that is just, you you can't vibrate or do things shorter than these little strings. Yeah, exactly. Or think about it from the other direction. You know, how do you make a universe?

Well, you start with a huge pile of tiny strings. And then the way those strings interact gives you all sorts of interesting structure. But that's what you start from. That's the universe's initial condition is like a huge pile of strings. And these strings can move around space? Yeah, they move and they interact with each other, right? And that's where all the interesting stuff happens. But are these related to like quantum fields?

How does that relate to quantum fields? Yeah, so everything would be built out of these strings, including all the particles and all the forces. And that's actually why string theory is so popular, because string theory we think can explain some of the mysteries of quantum fields and some of the mysteries of quantum fields and describe it in terms of a quantum field. So the short answer to your question is all the quantum fields arise from these string interactions. All these fields, all these particles just come from this one string guitar being plugged at different frequencies. That's right. Kind of. So while you're imagining a single string guitar of the universe, let's take a quick break.

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I didn't even know you've been a pastor for over 10 years. I think culture is any space that you live in that develops you. On a recent episode of Culture Raises Us podcast, I sat down with Warren Campbell, Grammy-winning producer, pastor, and music executive to talk about the beats, the business, and the legacy behind some of the biggest names in gospel, R&B, and hip-hop. This is like watching Michael Jackson talk about thoroughly before it happened. Was there a particular moment where you realize just how instrumental music culture was to shaping all of our global ecosystem.

I was eight years old, and the Motown 25 special came on. And all the great Motown artists, Marvin, Stevie Wonder, Temptations, Diana Raw. From Mary Mary to Jennifer Hudson, we get into the soul of the music and the purpose that drives it. Listen to Culture raises us on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. All right. So that's a crazy concept to ask people to digest. But let's assume that that's the theory. Who came up with this? And why do we think it's a good theory about the universe? Yeah, so string theories had a lot of people contribute to it. It's sort of an old theory that started out trying to explain something else and then was tossed aside when it didn't work. And then was later picked up again and reused as a theory of everything. And this sort of idea of string theory is to take a different approach to solving this question of what is the universe made out of. As an experimentalist, my approach is take something concrete, break it into pieces, get smaller and smaller and smaller.

You know, and as you discover new stuff, you're revealing secrets of the universe and just keep going until you get to the smallest bit. Sort of the top-down approach, right? This idea is different. This is sort of a bottom-up. They say, let's just start at the very bottom. Let's go to the most basic element and try to explain the universe from the start. If I hypothesize the universe is made of strings, can we put them together in a way that explains the universe and describes everything we see around us? But I guess how did someone even think of using strings?

How do you make a lot of things out of one thing? And a little string that vibrates different ways is one way to get a lot of things out of one simple thing. Is that kind of the origins of it? Yeah, exactly. You should imagine physicists are basically random, idea generators. Okay. And most of those just don't work. So at some point, somebody's like fed up with thinking about the universe in terms of particles. And they're like, well, what if they're not? You know, what if they're not dots? Let's just try it with lines. Does that work?

You know, and basically every idea that you can imagine, somebody has tried to make that work as a theory of everything. And usually given up after about two seconds because the theory of everything based out of little puppies or whatever doesn't work. It's very hard to make that put together. So like maybe they say, what if there's just one particle that makes of everything. How would you explain how this one particle can turn into other things? And so that's kind of difficult maybe. But a string, you can imagine it vibrating or moving in different ways to give rise to different particles, right? Yeah, exactly. And people were playing with it. And they're like, like I said, they try to use it to solve other problems. Specifically, they tried to

understand the strong nuclear force using strings. And it didn't work. And then later somebody else said, huh, I heard about this idea of strings. I wonder if I can use that to solve this other problem, which is why can we get gravity to play well with the other forces? If you want to understand the way the universe works, you have to try to explain everything in terms of one theory, right? To bring it all together into a single explanation. Because that's a big problem right now in physics, right? It's like marrying quantum physics with gravity. That's right. It's a marriage. We've been trying to arrange forever, but the two participants just do not want to play along. They don't like each other. They don't give into parental pressure. Yeah, so we have these sort of two

towering achievements of physics. On one hand, quantum mechanics, right, a revelation about 100 years old that tells us that the universe is very different from the way we thought it was, that there's uncertainty, that there's fuzziness, a limited amount of knowledge we can actually obtain about the universe, and it's most specifically that the universe is quantized, it's broken up into discrete little chunks, right? And on the other hand, we have gravity and general relativity, which is an incredibly successful theory that describes the motion of planets around stars and black holes and all sorts of crazy stuff and time dilation and the way space and time are connected all this incredible stuff but it assumes the universe is not quantum mechanical right it assumes that

energy can be subdivided into arbitrarily small bits and you could have an infinite number of locations and an infinite amount of information right and so the two theories are not consistent and most of the time they're talking about different stuff so they don't overlap But sometimes, like when you're talking about a black hole, then the two give you very different stories. Okay, so how is string theory able to marry gravity and quantum mechanics? Right, so that is exactly the right question. How does string theory allow us to bring together quantum mechanics and gravity? Well, to understand that, you really have to understand why we failed without string theory.

And the problem is that when you bring together quantum mechanics and gravity, you get lots of infinities, right? A theory doesn't work when it can't predict the results of extent. experiments. So if you ask a theory, what happens when I smash two particles together? It should give you a reasonable answer. If the answer is infinity or, you know, nothing will happen or something, then it doesn't make any sense. It has to give physical answers. And infinity is not a physical answer. The problem is when you try to bring gravity into quantum mechanics, you get lots of these infinities. And the infinities come because of the point particles, because you're trying to treat these objects as if they're just dots in space. And that leads to lots of craziness. You know, how do you have

in a tiny little dot in space that has infinite density, right? Now, we have lots of other theories that do play well with quantum mechanics, electromagnetism, for example, very happily married with quantum mechanics. And the reason that works is that we have tricks to hide those infinities. We can bundle up those infinities that pop up in the from the point particles in various other ways, mathematical tricks. Those tricks don't work for gravity, because gravity is very different from the other forces. The strength of the force grows with the energy of the object, right?

So in this case, when an object has more and more energy, it feels more and more gravity, right? Because gravity is proportional to the amount of energy in an object. So the typical tricks we use to hide those infinities under the rug that works for quantum electrodynamics doesn't work for gravity when we try to do quantum gravity. So how does string theory solve that problem? Simple. It just says there are no points. It says at a smallest scale, you don't have to worry about dealing with gravity tiny points

because there are none, because at its smallest scale, the universe is not made of points, but strings. And so it's a nice way to sort of circumvent that problem. And that's why string theory can bring together quantum mechanics and gravity so nicely. And that got people excited. And that's where the beauty was. People were like, wow, and it's beautiful. There's like these strings floating around.

You get these membranes, and it seemed really cool to people. So you said something interesting, which was that people thought that string theory was beautiful and elegant So can you try to explain like why people thought that? Like is it simple or is it just it's so open-ended or it just seems to be working or it doesn't fall into the ugliness of other theories? I think people just have fun working with it. You know, I think it's, I think it stimulates people's imagination. Physicists can have fun. And physicists can have fun, yeah.

And, you know, when you do string theory, you write down these diagrams. And instead of these diagrams being lines with squiggles, the diagrams are like loops and they have sheets. and to connect them, you know, membranes. And you get to think about these high dimensional surfaces and people have a lot of fun with them. And it's been so invigorating for physicists that it's actually led to a lot of good results just in mathematics. Like mathematicians have learned about things from the things that physicists have done

while exploring string theory. Wow. And so it's stimulated the whole field of mathematics. And mathematics is about the beauty and interconnectedness of numbers. They don't care if it actually describes anything in the real world, right? It's about these abstract ideas and how they come together. And one of the lead physicists who works on string theory, his name is Ed Witten. He won what's basically the Nobel Prize for Math, which is the Field Medal,

which is even harder to win than the Nobel Prize because they only give it every two years. And he's a physicist, and he won the top prize in mathematics for advances in string theory, which tells you that there's a huge amount of mathematical machinery that's been invented here. And these folks, they love it. It's a fascination for them. It's a deep pleasure in manipulating these equations and in thinking about it. Oh, usually it's the other way around. Like usually you guys have to come up with a theory and convince mathematicians that this is something fundamental.

Yeah. Here it seems to be coming from the other way. It's like here's something that even mathematicians think might be fundamental about the universe. Well, I don't know if mathematicians think it's fundamental about the universe. They just think it helps solve interesting problems. They're like, ooh, this is a cool tool. it can solve some problems in math, or it gives us a new way to think about mathematical problems.

And anytime you get a new tool, it's fascinating. And imagine, for example, you're an artist and somebody invents a new musical instrument. And you're like, ooh, cool, what can I use this for? I can invent a new kind of music. I can have a new kind of rhythm or a new kind of song. In the same way, you create a new physics theory, a new basic object you get to play with.

It's exciting. It gives you things to play with and ideas to try. So like physicists said, hey, look, I have a one-string guitar. And music is just were like, whoa. I can play the whole universe on that thing. But, you know, string theory has a lot of people who love it in adherence and a lot of people in departments who are working on it.

But there are also a lot of people who don't like string theory. It's got sort of a backlash as well. You know you've made it as a physics theory when you have haters, right? Oh, physics haters. Yeah, physics haters. All right, let's get into it. But first, let's take a quick break. Smokey the bear

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I'm Emily Tish Sussman, and on she pivots, I dive into the inspiring pivots of women who have taken big leaps in their lives and careers. I'm Gretchen Whitmer, Jody Sweeten. Monica Patton. Elaine Welter-a. I'm Jessica Voss. And that's when I was like, I got to go. I don't know how, but that kicked off the pivot of how to make the transition. Learn how to get comfortable pivoting because your life is going to be full of them.

Every episode gets real about the why behind these changes and gives you the inspiration and maybe the push to make your next pivot. Listen to these women and more on She Pivots now on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. I don't write songs. God write songs. I take dictation. I didn't even know you've been a pastor for over 10 years. I think culture is any space that you live in that, develops you. On a recent episode of Culture Raises Us podcast, I sat down with Warren Campbell, Grammy-winning producer, pastor, and music executive to talk about the beats, the business, and the legacy behind some of the biggest names in gospel, R&B, and hip-hop.

This is like watching Michael Jackson talk about Thurley before it happened. Was there a particular moment where you realize just how instrumental music culture was to shaping all of our global ecosystem? I was eight years old, and the Motown-25 special came on. And all the great Motown artists, Marvin, Stevie Wonder, Temptations, Diana Raw. From Mary Mary to Jennifer Hudson, we get into the soul of the music and the purpose that drives it. Listen to Culture raises us on the iHeart radio app, Apple Podcasts, or wherever you get your podcasts. All right, so strength theory has its haters, people who don't think it's all that or who think it might be wrong or maybe it's not.

all that beautiful. So what are some of the arguments against string theory? Yeah. So I would say there's really two categories of attacks people make against string theory. One is there are just too many of them. And the other is that we can't test it. Too many string theories. Too many string theories. Oh, it's not a singular concept. You know, string theory. It's actually string theories. I'm remember a lot of troll with the S is here. String theories. Pring theory. There are a lot of these things. There's lots of ways that you can put it together.

Lots of different ways you can shape the string. Lots of ways you can have them interact with each other. And we were saying earlier, you'd like a simple theory. You'd like to make your choices for how you built a theory, not be arbitrary, but be forced by the mathematical construction. You know, like, why is there a three here? It's the only way that it works. So if you have a theory where there are lots of ways it could work, then you have a question,

like, which way do we choose? And that's the problem with string theory. There's lots of ways to build one. They all have the same basic idea, right? Which is that the universe is made out of little strings and everything comes out of the way it vibrates. But you're saying there's a lot of options after that basic concept. Like how do these strings interact or what do they sound like?

Exactly. And the reason is that you can't make string theory work in four dimensions. Our universe that we experience has four dimensions. Three dimensions of motion, X, Y, Z, and then one dimension of time. So we live in four dimensions. But strings to get them to get them to have these math mathematical properties that we want to unify quantum mechanics and gravity, they have to operate in more dimensions for the math to work out. Is it like the dimension in which they're vibrating kind of thing? And then our four are just the ones where it's moving around it. In some theories, yes,

they vibrate in those other dimensions and that changes how we see them in these dimensions. But there's a lot of different kinds of string theory. And so that's not a general statement. And some of them are 11 dimensional theories and some of them are 26 dimensional theories right and so the idea is these strings are vibrating these other dimensions but we don't see those other dimensions like I don't I can't move in 26 dimensions how can you say that your theory which has 26 dimensions explains my four dimensional universe so to answer that to solve that problem they have to roll up those other dimensions and tuck them away and make them small make them like hidden kind of like too small to be experienced in our everyday lives yeah which

which is why you don't see them or experience them or see them in physics experiments. And there's lots of different ways to do that because 26 dimensions is a lot of freedom. And so you can organize that in lots of different ways. And you can make choices and you have to make choices. How do you take this 26 dimensional theory, boil it down to four dimensions? Turns out there's like 10 to the 500 different ways to organize that, which is a lot of different choices. Different flavors of string theory or different choices you can make. Yeah, different flavors.

You went to the ice cream shop for string theory. And they have 10 to the 500 different flavors. And if you want a sample of each one, you're not even going to order. You're going to be full before you leave. 10 to the 500, think about what that number is, right? For scale, there's like 10 to the 90 particles in the universe. Right. So is the problem in string theories that all of these string theories would work?

Is that kind of the problem? Yes. Yeah, and that gets into the second criticism, which is, you know, can we test string theory? We can only see the universe down to a certain scale so far. I mean, we use the large Hadron Collider, we smash particles together, we get down to distances of like 10 to the minus 20 meters, right? Really, really small distances. So all the string theories, the 10 to the 500 string theories,

they all can explain things that happen that we've seen so far. All of them, right? To distinguish between them, we'd need to look much deeper. Oh, I see. So mathematically, there's a whole bunch of possible ones, but experimentally, we can't test which one is right. Exactly. And that's the problem, because string,

if they exist, we think they're about 10 to the minus 35 meters in size, which is super duper tiny. And maybe you're thinking, I don't know, we can see down to 10 to the minus 20 meters, how much smaller is 10 to the minus 35? They're basically just zero, right? It's just tiny. It's much, much smaller. It's 10 to the 15 times smaller, right?

And to give you a sense of scale, like the solar system is about 10 to the 15 meters across. It's a big difference, you know, if you could see only solar system size, stuff or if you can see like one meter size stuff. So strings are really, really tiny, which is why we're not anywhere close to seeing them. Doesn't the theory have also ways in which it kind of builds up to our world? It does, but you can't distinguish between those theories. They all predict the same thing. And they're also competing theories.

You know, there's a theory of quantum loops, you know, not strings, but loops, right? That also explains quantum gravity. And we can't distinguish between the various string theories and this theory of quantum loops because we can't see small enough yet, right? And so it's a criticism of this whole bottom-up approach, right? Yeah, cool, you started at the bottom, but you haven't built up far enough for us to test your theory. Is this just mathematical masturbation,

or are you actually doing something useful, right? So sometimes people argue like, okay, string theory is nice, but it's not physics, it's math because it can't be tested. But then that's what they need to do. They need to build up their math to sort of our scale in our world. But you're saying that's really difficult. Absolutely. It's difficult because they've got a long ways to go. They have to go from 10 to the minus 35 meters up to 10 to the minus 20 meters. It's a tall mountain to climb. And they've been working on it for 20 years. And you know, like with any theory that had fanfare and excitement around it 20 years ago, they're going to be people who say, oh, you failed if you haven't succeeded yet, right? And so people are just sort of impatient? Are we ever going to get there? Is string theory ever going to provide something we can actually test? Or are these guys just going to be twiddling around on chalkboards for the next 200? years. I think the problem is maybe it seems kind of random that you would think that the universe is made out of little strings and that you would just come up with this concept out of the blue and say, hey, let's dedicate 20, 30 years of a lot of people's time to investigating this idea. You know, what...

Yeah, it was totally random. They just opened a dictionary, picked a random word and said, let's make a universe theory out of... Puppies. Ice cream. Cats. Puppies, yeah. No, as I said before, it's a bit random, but it works. You know, mathematically, it hangs together, and a lot of theories don't. You can't build a theory of the universe out of ice cream or out of puppies. Oh, triangles you couldn't make work. Oh, man, we never thought of triangles. I know, that's what I mean. Have you thought about all possible shapes?

Stick figures. I'll be right back. Hold on. I'm going to try to invent triangle theory right now. I'll get back to you. Stick figure theory. Why not? The XKCD theory of the universe.

How could we see string theory? string theory. Well, one thing is you could build a super duper collider the size of the solar system and see things that small, but that's the gazillion dollar solution. The other thing is you could try to be really clever and find some unique prediction of string theory that we could see in our experiments, something which would only be true if strings were happening at the lowest level, right? Because in physics, we don't always need to see things directly in order to prove that they exist or believe that they exist. You can kind of infer information or... Yeah. A lot of.

of our stuff is a lot of indirect information pointing in the same place, right? Like when you solve a murder, you don't need to see the murder on video to prove that somebody did it. You know, you have evidence from blood spatter and from DNA and from, you know, other circumstantial evidence builds a solid case. It was Mr. Green with the string in the dining room. Solved. That's right. We have solved the mystery today on the podcast.

There you go. All right. What do you think the future? holds for a string theory. Do you think it's promising or are people starting to lose faith? I think it's going to oscillate back and forth. I think people will lose faith for a while. It's going to vibrate. Exactly. It's going to wiggle and jiggle. It's going to lose, you know, it's popular right now. And for a while, everybody who's a planning grad school in physics wanted to do string theory because they heard about Brian Green's book and they heard about the Big Bank theory.

And it was popular. And then there's a bit of a backlash now. So fewer people are getting excited about string theory. Fewer physics departments are hiring string theorists. But it's a promising candidate and we don't have that many promising candidates for the theory of everything. So it'll stick around and people will come up with great ideas and then everybody get excited again. Like, oh my gosh, look, this guy came up with a cool way to make string theory do this new thing. So it'll go back and forth. I don't know if we'll ever be able to test it as a theory that we will require a real moment of insight to how to find some unique property of string theory that we can see. Well, I personally hope you guys figure it out and, you know,

stop stringing us along. You don't like that we're just in our offices, drawing things on the chalkboard going, that's pretty. That's pretty. I thought if anybody, a cartoonist, would appreciate enjoying the beauty of diagrams and doodles and stuff like that.

Because that's in the end what we're doing. We're trying to doodle the universe into understanding. Well, remember, I'm a musician, not a cartoonist. Oh, I forgot that, yes. Maybe you could sing something. for all our listeners. Go ahead. Yeah. Sing us your theory of the universe.

Let's hear it. I'm in the edge of my seat. You'll be running away from your seat if you hear me singing. All right, cool. That's a really great overview of the string theory, right? It's part of this quest to kind of find out what the universe is actually made of at the deepest level. Yeah, absolutely. And so thanks everybody for listening.

And I hope that we've explained you finally. What is string theory? Keep plucking away. If 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 at Facebook, Twitter, and Instagram at Daniel and Jorge, that's one word, or email us at Feedback at Danielandhorpe.com. I just think the process and the journey is so delicious.

That's where all the good stuff is. You just can't live and die by the end result. That's comedian Phoebe Robinson. And yeah, those are the kinds of gems you'll only hear on my podcast, The Bright Side. I'm your host, Simone Boyce. I'm talking to the brightest minds in entertainment, health, wellness, and pop culture. And every week, we're going places in our communities, our careers, and ourselves. So join me every Monday.

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