Daniel and Kelly’s Extraordinary Universe - The next revolution in theoretical physics

Episode Date: January 27, 2022

Daniel and Jorge explain Constructor Theory, a new way to approach building theories of everything. Learn more about your ad-choices at https://www.iheartpodcastnetwork.comSee omnystudio.com/listener for privacy information.

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Listen to Culture raises us on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Hey Daniel, did you guys figure out quantum gravity yet? Ooh, uh, not yet. How about dark matter? Nope, still working on it. Dark energy? Not that one either.

Quantum wave function collapse? We got nada. Oh man, we've been doing this podcast for years now, man. Talking about these mysteries and you've made no progress? What's going on? Maybe the problem is I've been spending a lot of time on the podcast. Or maybe you just need a new idea. Like another podcast?

Yeah, Daniel and Jorge actually saw, the mysteries of the universe instead of just talking about it. We could just put a microphone in your office, maybe. The sound of Daniel napping. to take to the streets for the next scientific revolution. What do you mean take to the streets? To protest or to celebrate? I don't know.

That's just how revolution starts, right? Everybody runs into the streets and raises a stick and yells and boom, the government just falls over. Isn't that what happens? Oh, I see. You want to promote a revolution. You need to put up like barricades and streets with equations, I guess? That's right.

Everybody grab a piece of chalk. We're going to do physics on the street literally. And then who are we claiming independence from or who are we overturning? Oh, big physics, man, of course. Oh. Is that like the big lobby for good physics or bad physics? I'm really confused about this revolutionary idea. It's a bunch of physicists in a back room.

Instead of smoking cigars, though, they're just napping around a bunch of chalkboards. Oh, and you want to overthrow them and put them to the guillotine. Theoretically speaking. Yes, intellectual guillotine, exactly. Intellectual guillotine. Oh, boy. heads will roll in your head But yeah, welcome to our podcast

Daniel and Jorge Explain the Universe, a production of iHeartRadio In which heads roll and minds are blown when we talk about the crazy ideas of the universe We know that our current theories of the universe must be wrong. They are definitely incomplete. They cannot describe nature correctly

and we join you in a search for those new ideas probing ever deeper into the very nature of space and time and the universe. what this reality is around us asking questions about the very basic nature of consciousness and measurement and information and just trying to figure it all out, man. Yeah, because it is a pretty crazy universe full of amazing things to discover and find out. And we're just puny little tiny beings on this floating rock and space trying to figure out how it all works. It's sort of like we are solving the biggest detective mystery in the universe because the whole universe is a big mystery for us to unravel. And over thousands of years, we've been slowly putting together a few ideas about how this bit works and how that bit works.

And sometimes those ideas even fit together to make a bigger, clearer idea. And we get these flashes of insight that tell us how the universe works. Yeah, because we don't just live in the universe. We also wonder about it. And we want to figure out how it works because sometimes that's very useful information, right? It depends on who has that information. It can be useful. It can be dangerous.

but it is absolutely enticing. To me, it's all about knowing the way the universe works, revealing that truth, peeling back those layers of reality to see its inner mechanisms. And we've done it pretty good over the years, the centuries now that science has been going on,

and we have some pretty good theories about how things work, and let us build amazing structures and machines and send things to space and back, but we are not quite there yet in terms of understanding the very small details of how the universe works, especially at the extremes.

Yeah, you might be forgiven for thinking that physics has it mostly figured out. You know, we've developed incredible technologies. We have revealed a lot about the way the universe works, but we've also revealed how little we know. There's so much of the universe that we haven't even begun to describe. The dark matter, the dark energy, and enormous open questions about the part of the universe that we can describe. We don't understand a lot of the fundamental forces.

We can't bring together gravity and quantum mechanics. There are all sorts of things where physics, has hit some sort of a roadblock. Yeah, so where would you put our estimate? Would you say that we understand about 3% of the universe now? Is that what you mean by mostly understand the universe? About 3%? Because we don't understand the full 5% of what we're made out of,

and there's like 95% of the universe we don't know anything about. Yeah, I would generously assess our understanding the universe at 0.0001%. And that's rounding up. What from zero? Rounding up from 2. Wow. So you think out of the 5% of the universe that is made out of, you know, atoms and quantum particles, you think we understand about 0.001% of it.

Yeah, I think we are very primitive in our understanding of the nature of reality. I think people will look back at our ideas in a thousand years and they will chuckle. You know, they will look down their nose at us because our ideas are so simple and so ridiculous. The way we look back at the Greeks or even further back, you know, at cavemen and cave women, their perspective on the universe. We are really just beginning our exploration, and so I think we haven't even really had time to develop the right ideas or the right way to generate those ideas. I mean, we've been asking questions about the universe for thousands of years, but we've only had a strategy for building knowledge, this empirical scientific method, for a few hundred years. And, you know, the mathematics to undergird it is much more recent. So we're really just getting started, you know, it's like we just put our shoes on.

And we haven't even really walked out the door to explore the universe yet. Man, those future scientists are so snobby. It should cut us a break, you know. There's a lot going on right now. You know, it's a lot of good stuff on Netflix. Not even just future scientists, future five-year-olds, right? There will be children's books about the universe in the year 3000 that you and I will not understand. We would read them and go, what?

That's crazy. That can't possibly be true. That's wild. So those five-year-olds give a seminar at like MIT and all of the, famous physicists would go and probably be clueless. Yes, it sort of sounds like we are not that far along in our knowledge of the universe sometimes, but, you know, there's always hope. And maybe there's always a sort of a revolution in theoretical physics and physical thinking,

maybe right around a corner. You never know, right? You never do know. And when we look back at the development of ideas, they seem sort of linear. You know, like Sally figured out this and then Alicia figured out that, and then Bob King along and put this cherry on top and tied it together and took credit for all of it and this kind of stuff, it seems sort of linear. But when you're in the middle of it, it feels much more like a huge cloud of confusion. There are people going in all sorts of

directions and nobody knows which one is going to be the foundation of future brilliance and which one is totally a dead end. And so it's really hard to tell in the moment what the path of future physics is. Yeah, it could be that the idea that changes everything or solves everything is out there right now in the mind of a physicist, but maybe nobody takes him or her seriously. Yeah, it certainly could be. And it also could be that there's been a new development of a kind of mathematics that was developed just because it's math and it's fun. And then in 10 years, some physicists will figure out how to use it to solve some deep problem in physics. We've seen that happen a bunch of times. You know, field theory and group theory, all these things were

developed not for physics, but then were later applied to physics and have become incredibly useful. So you never really know when sort of like the pieces of the puzzle are going to find each other and click together to really give us that glimpse of the next generation of ideas. So today on the podcast, we'll be asking the question, Are we witnessing a revolution in theoretical physics? You mean like it's happening right now? We could be witnessing it. We just don't know it.

Yeah, we could be living in the middle of it right now. Exactly. There are some crazy new ideas that have been developed in the last few years that suggest an entirely new way. to try to attack these questions of the fundamental nature of the universe. And we don't know if this is a dead end which will be added to the dustbin of dead ends

or if, you know, it will be seen later as a critical turning point in the history of physics. Yeah, it's interesting because, you know, if you look back at the history of science, it does seem like sometimes we think we figured everything out, but then the more we look into it, the more we realize that our theories don't work, you know, like Newtonian physics, we thought we had unlocked,

you know, the secrets of the universe. But then eventually, we found that it does. doesn't work all of the time. And then we came up with quantum theory and we thought we had solved the mysteries then. But then it turns out it doesn't quite work all of the time. Yeah, exactly. That's why the more we know, the more we realize we know less and less, which is why I was trying to really hard to be conservative in giving an estimate of our fraction of the universe that we have understood. Because frankly, it seems to just drop as time goes on. Well, I guess maybe when you gave such a low estimate, what you really mean is that maybe the

theories we have now are, you know, they work. for most of the time, for most of the cases that we sort of are in, you know, here on Earth, sending things to space, it works pretty well, but I think maybe what you're thinking about is that maybe it's like fundamentally wrong. Like there's something wrong with its very foundation. Yeah, it could just be the wrong way to attack the problem. And sometimes the wrong approach works for a while and then you get stuck. You know, for example, Aristotle and Plato and those folks, they made a lot of progress in understanding the nature of life and experience and consciousness and, you know, laid the foundations of philosophy, but it wasn't until Galileo and folks in the 1500s or so realized that it's important to actually go out and do experiments, to make measurements, to ask the universe questions. This branch of science we now call experimentation was a vital contribution to like building knowledge and adding to our machine to systematically build more knowledge. So sometimes we don't just make progress in the ideas, but in the ideas for how to make new ideas. And that can reveal something fundamentally new about the nature of the universe.

Yeah. I guess it's kind of a philosophical thing, you know, like if you have a theory that works 95% of the time, but it's fundamentally incorrect, is it still a good theory or not? You know, like our current theories allow us to send things to Mars and to manipulate atoms and things like that. And so I would say as an engineer, that's pretty good. You know, we're like 90% of the way there. We're not going into a black hole anytime soon or, you know, going faster than the speed of light anytime soon. And so I would say we've done pretty good. But maybe as a theoretical physicists, you might be thinking like, what if it's all fundamentally wrong? That means we're 0% right. Yeah. And it depends on the question you're asking. It depends on what your goal is.

If your goal is to send something to Mars, then you don't really need to understand quantum gravity and the deep fundamental nature of space time. But if those are your motivating questions, if the reason you get out of bed and the thing that pulls you through life is this desire to understand the universe at its most basic level, at its fundamental, foundational level, the essential ingredients that make it what it is, then you're not satisfied with like an approximate version that mostly works. Because the theory we have today, it does mostly work for the kinds of experiments we can do. We also know that it absolutely cannot be the real theory of the universe, the one that describes, you know, the very first few moments and the crazy situation of very high energy and high density.

It can't describe what happens when space and time distort very dramatically. It just fails. It breaks down. And so it can't be the real story of the universe. It can still be very, very useful. The way Newtonian physics is much more useful than Einsteinian physics to, like, calculate the trajectory of a baseball, right? It can still be very helpful and very effective.

It's just not the fundamental story. So that's what wakes you up in the morning, huh? Gets you out of bed. But then what makes you want to take a nap then? The same thing, because it's exhausting to think about. So we might be witnessing a revolution. theoretical physics. And in particular, we're going to talk about a special kind of theory or a special theory that is a pretty good candidate for maybe overtaking or overturning everything

we know about physics, right? That's right. And this is not necessarily a new idea about what the universe is as much as a new method to try to find new ideas. It's like adding experiments to your strategy for figuring out the universe. This is like, well, let's take a new approach to finding new ideas about the universe. Let's add to the scientific method. Let's give it a tweak. And maybe that will reveal new ideas we've overlooked before. It's like a meta theory. Yes. Like how to make theories theory. Interesting. But it's not controlled by Mark Zuckerberg. Thankfully. And it's real. You can actually maybe touch it. So we have this meta theory. This theory of theory is called constructor theory. That's the name of it.

Yeah, it's called the constructor theory. And it was developed by a couple of folks at Oxford. One of them is David Deutsch, and he's famous for doing like quantum information theory. He's an expert in quantum computing. And he's had sort of the inspiration for this idea a while ago. And then a grad student worked with him. Her name is Kiara Marletto. She really elaborated it and tried to make it concrete and try to turn it into something. And together, they've been developing this constructor theory for a few years now, and it's got

quite a few converts. And lots of our listeners have written in and said, what is this thing? Can you please explain it to us? Yeah, because it sounds interesting. It sort of sounds sort of like a toy for my childhood. Like a construction toy maybe. Like you get different pieces and you can build them together. Or like a transformer.

I think there's something called Constructicons. Well, you know, they do have transformations in constructor theory. So maybe you're on the right track. Maybe they'll develop, you know, tinker toys also. Yeah, maybe they watch the same shows. So yeah, this is a new theory of theories. And so as usual, we were wondering how many people out there had heard of this or had an idea of what it could be.

So Daniel went out there into. the internet to ask people, what is Constructor Theory? So thanks to everybody who was a willing participant in this fun game of answer a tough physics question without any preparation. If you'd like to participate, please don't be shy. If you've been listening

for a while and never dipped your toes in, now's the time. Write to us to questions at danielanhorpe.com. So think about it for a second. What would you guess is Constructor Theory? Here's what people had to say. I know that is linked with physics

but I don't know this time what is about I haven't heard of constructor theory before but I'm guessing it has to do with an idea of how either things on a very tiny

scale or a very large scale are put together Constructor theory is the theory of how there is planets and other types of stars have been created by ancient aliens.

Maybe an alternative to creationism as opposed to the Big Bang theory? The assumption is this has something to do with a theory that is based upon some form of building blocks, meaning that whatever that this constructed theory relates to, in whatever aspects of physics, this has something to do with building upon a base of knowledge. as opposed to something groundbreaking and out of left field. By the name, I would think it's something to do with creation, how the universe started, or how we have been created, or how just everything being created, really.

I've not heard of constructive theory, but it sounds like a theory on how the universe was made or constructed. My guess is it would be it's to do with building something, so it could be to do with putting atoms together or putting subatomic particles together to make something bigger. I've never heard of the constructor theory, but it does remind me of the Bible and God creating everything in seven days. So could the constructor theory have anything to do with that? I'd say something that has to do with engineering, maybe, like building things. but I have no idea 10 points to the person who said

something about physics because that's true in all situations right any answer can probably be answered by something about physics yeah that's true and especially when it's this podcast so yeah congratulations

99.9% of the time or something about bananas that would also work they'll take you that last percentage home but yeah somebody said something about engineering too which I technically also applies to all answers Yeah, that's true.

Because all engineering fundamentally is just physics. Yeah, and all physics is fundamentally useful only for engineering. And naps, engineering plus naps. That's right, yeah, making sure that you get enough rest. But yeah, some people thought it may be related to creation, right? Constructor, like maybe you're constructing the universe. It is a very general-sounding term, right? It's a little vague, so it doesn't give you a lot to really work with.

If you hadn't heard of it before, you probably weren't going to guess what it was just from the name. I guess it's interesting because you can read it as noun, like constructor theory. You know, like maybe there's a constructor like a person or an entity. And we're trying to figure out how it works. Yeah, or like who made the universe? Oh, I see. Yeah. Well, that explains why people were talking about God and creation.

Now it clicks for you. Now I get it. Yeah, yeah. Maybe there's a constructor, you know? Oh, I see theory of the constructor. This is just turned into conspiracy theory. Whoever the constructor is, I hope it took a good nap after he created the universe. he or she or it or they.

I think that's in the pile, Daniel. On the seventh day, the constructor took a nap. There you go. See, napping is crucial everywhere. That's right. It's a holy concept. Naps are sacred. Yeah. So maybe step us through as Daniel. What is constructor theory? Like, what's the overall idea of it?

The idea of constructor theory is to take a different approach to trying to develop theories of the universe. Now, our current approach is pretty good, but it has sort of a singular focus. It says try to figure out sort of, what's going on in the universe right now and then find the rules for how the universe is going to change the dynamics like the universe is like this it's two particles in this configuration what are the rules for how those particles should move and where will they be in the future and so you know Newtonian physics for example tells you if you hit a baseball how is it going to fly what is its path and even quantum mechanics tells you if you have a wave function and it hits a potential well

what's going to happen and so a lot of current physics is what we call like initial value problems. It says, here's the current situation in the universe. How is that going to change? And so that's like worked for us pretty well so far, but it does have its limitations. You mean like it's sort of embedded in the way and the reason we do science, right? Like we sort of invented science so we could predict the future. And so you're saying right now physics and science instead of geared or designed or sort of assumes that you want to predict what's going to happen in the future. Yeah, exactly. And not just that you're going to predict what happens the future, but that's all you want to think about is you take this configuration of particles

or the universe in its current state and you just want to know what are the rules that are going to tell it what's going to happen in the future. How is it going to evolve from now into the future? Right. And it's useful, right? Because if you want to predict what your spaceship is going to do when you throw it at the moon or whether your bridge is going to hold, that's kind of what science is good for, right? Yeah, it sounds like a great strategy, right? Because it's very effective. It helps you solve problems. If you have two particles and you shoot them together, then our current laws will tell you what's going to happen. And so that seems very natural. And like a lot of revolutions in physics, they come up against something which seems very intuitive and

seems like it must be all inclusive and like what could be missing out of that scenario. What possibly could you be overlooking using this approach? But those are also the times that you need to be skeptical when you realize, well, maybe we've made some assumption very back in the beginning of how we started things and we could have taken another path. We could have started somewhere else. And maybe we would have gotten to a different point. It's really hard to imagine sort of a different history of physics if Newton hadn't been around and somebody else had conceived physics in a different way. But that's essentially what we're trying to do here is go back to the very beginning and ask, is there another way to formulate physics other than this

basic approach of taking the universe and trying to write the rules of how it changes. Right. Because I think what you're saying is that where this way of approaching it has taken us, it has led us to a point where we have theories about the universe, but they fail at some point, right? Like they're not good all the way. And it could be that we do find theories. that follow this approach and eventually work. Maybe somebody will come up with a theory of quantum gravity that follows this sort of initial value problem approach and tells us how to treat the inside of black holes

and what happens when two particles interact gravitationally. Maybe somebody will figure that out so far we've been stuck. And so it's just a good idea to broaden your bets and to say, hey, let's send a few other people, you know, to the other side of the river or down another path and maybe they'll get there sooner. Right. It's a catapult. using some kind of launching mechanism.

So what are some of the ways in which our current theories have failed and how serious are they? Yeah, well, you know, one is just that we haven't solved some big problems, but the other is a little bit more subtle, but really fascinating. And it's that they sort of fail to treat some things that have become really important, you know, like especially information, some things that turned out to be really vital in understanding the universe, like how quantum information moves through the universe, how it goes into black holes and comes out of it.

These things are not really well described by our current theories because they're not exactly described. They are emergent phenomena. They're things that like arise from the lower level laws, but are not really treated exactly. They're more like statistical approximations. For example, if you describe the universe in terms of like balls that are banging against each other, then where are you describing information, right? The concept of information, which we now know to be so vital, it's just sort of like an abstract, fuzzy thing that comes out of that. It's not like written into the core laws of the universe.

Right. I think what you're saying is, you know, because this emerging phenomenon, like a great example of it is the weather. I think maybe what you're saying is that our current theories allow us to predict, you know, one drop of water, what happens to that drop of water, how far it's going to fall or where the wind is going to take it. But to predict like a storm or to predict, you know, how cold it's going to be all over the world, that's a much different problem. And your theories about the drop of water are not that useful in that case, in terms of describing the concept of weather. Yeah. And anytime you're talking about emergent phenomena, it's always going to be

approximate because you can't make exact calculations from drops of water up to hurricanes. And so it's always going to be rough. And so when we talk about information, for example, we don't really know in our current theories like what information is. You know, like I'm talking right now, which means I'm translating ideas, which are in my brain into sound waves, which get transformed into electrical signals in this microphone and get stored. somewhere and then eventually transmitted to these listeners and that information hasn't changed right but it's lived in lots of different physical systems it's been in shaking airwaves it's been in vibrating electrons it's been in neurons firing but it's described by all these different physical systems but none of our laws of physics really tell us what it is it seems to be sort of like independent from the physics itself right it's not captured by any of the laws that we're using currently interesting well i mean that's kind of a philosophical question right is information physical, a physical phenomenon, or is it like an abstract kind of like math, right? Like math is not necessarily a physical phenomenon, but it's still a phenomenon.

Right. Well, mathematics absolutely can be abstract, but information definitely has to be physical. It's about the arrangement of physical objects, right? You need a universe in order to contain any information. So it's definitely a physical thing, but it's not clear like where it is and sort of like a gap in our current description of the universe. And we have approximate ways to describe it. you know, like the Shannon Law of information captures the amount of information you could

store in a system. But again, it's sort of approximate. And that's, you know, a motivation for how you might design a different set of laws of physics. Instead of letting important concepts emerge sort of approximately from other laws, write them into the very core of the new theories. Well, my head is definitely rolling a little bit right now. And so let's get more into this idea of information and what this constructor theory is. But first, let's take a quick break. December 29th, 1975, LaGuardia Airport. The holiday rush, parents hauling luggage, kids gripping their new Christmas toys. Then, at 6.33 p.m., everything changed.

There's been a bombing at the TWA terminal. Apparently, the explosion actually. impelled metal, glass. The injured were being loaded into ambulances, just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged, and it was here to stay. Terrorism. Law and Order, Criminal Justice System is back. In Season 2, we're turning our focus to a threat that hides in plain sight.

That's harder to predict and even harder to stop. Listen to the new season of Law and Order. or criminal justice system on the iHeart radio app, Apple Podcasts, or wherever you get your podcasts. My boyfriend's professor is way too friendly, and now I'm seriously suspicious. Oh, wait a minute, Sam. Maybe her boyfriend's just looking for extra credit.

Well, Dakota, it's back to school week on the OK Storytime podcast, so we'll find out soon. This person writes, my boyfriend has been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now he's insisting we get to know each other, but I just want her gone. Now hold up, isn't that against school policy?

That sounds totally inappropriate. Well, according to this person, this is her boyfriend's former professor, and they're the same age. And it's even more likely that they're cheating. He insists there's nothing between them. I mean, do you believe him? Well, he's certainly trying to get this person to believe him because he now wants them both to meet. So, do we find out if this person's boyfriend really cheated with his professor or not? To hear the explosive finale, listen to the OK Storytime podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast.

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or wherever you get your podcasts. All right, we're talking about the potential next revolution in theoretical physics, the idea that might change not just science, but the way we do science. And right now, an interesting candidate for this is a theory called Constructor Theory. And, Daniel, you were telling me that it sort of arose because we have this gap in our current theories between what we think is physical and this idea of information, which sort of emerges from physical phenomena, but it's not in our theories currently connected to the kind of physical laws we have. Yeah. And, you know, I think it isn't it really interesting and deep

philosophical question, you know, about whether information is physical. And I think to me, the best argument that information has to be physical is that the laws that govern it are eventually the laws of physics. It's sort of like computation, you know, like the laws of computation, what you can and cannot calculate depend on the computer that you build and the rules that it follows, which in the And must be physical laws, which is different from like, you know, the laws about prime numbers, which are purely abstract. Doesn't really matter if you have a universe as long as you have numbers. But numbers sort of represent physical things, right?

Like two means two of something. Three means three of something. I guess I'm getting confused here. They can, but they don't necessarily have to. Like the numbers can just be pure numbers in and of themselves. But I think the point to underscore is that there are these properties of the universe, things like information that we recognize are really important. and might even like govern how things operate, right?

Like we've talked about how black holes are a mystery because they seem to eat information and then evaporate and we don't understand it. So it affects how things operate in the universe. And yet it's not like something we deeply understand. It's just something that sort of arises from the other laws that we've written. I see. It's like you realize information is important maybe to the universe

or theories that we've built so far are not good for handling that or don't know how to like define it or incorporate it into the physical laws. Exactly. If you write the universe as an initial value problem, it's just like, here's the configuration of stuff and here the rules for how that configuration can change. And there's no room for like really encoding information deeply into the universe. And I think that was probably the impetus for this new constructor theory that was actually broader than that. It's not just about information. It's about how to write new rules of physics that do let you encode things like information in them. All right. Well, step us through this. How is this new theory different?

Or what is it about? How does it do things differently? So it's called constructor theory. And at first glance, it sounds exactly the same as the current way we're doing things. Constructor theory is all about understanding how the universe transforms from one state to another. Like you have a current setup of the universe, you have all your particles arranged in one way. It's all about understanding what options are available for how those particles can transform in the future. And that sounds a lot like what we just talked about, which is like you have a bunch of stuff.

How does it change as you go into the future? There's a crucial difference, which is that constructor theory doesn't just want to talk about what happens. It wants to talk about what could have happened and what could not have happened. It's really focused on these loud transformations and disallowed transformations. Rather than just thinking about what happens, it wants to think about what the rules are for what could have happened. So there are all these like counterfactuals, they call them, these other possibilities for things that could have happened in the universe, but just didn't happen to occur this time that constructor theory examines

that our current theory doesn't? I see. But doesn't our current theory also sort of do that, especially with quantum dynamics? Like we have a state of the system and the laws of physics tell us where that state can go and what it cannot do

or what's more likely to happen or what's less likely to happen isn't that kind of what we have now? Or are you saying there's something more sort of allowable, not allowable about it? It's more the second. It's about what's allowed

and what's not allowed. You're right, the quantum theory is probabilistic in the end, once you've calculated the wave function, you can then predict what might happen and there are various options. But quantum theory is also fundamentally deterministic when it comes to calculating the wave function. If you have a certain wave function and you put it through some system, you know exactly what the wave function is going to look like on the other side. It's totally described by the Schrodinger equation. Now, when it comes to measuring it in the wave

function collapse, nobody has that figured out yet. But the actual wave function itself is deterministic. And our current theory say, well, you have one wave function. We'll tell you how to evolve it to the wave function in the future. This constructor theory would say, if you have this wave function, what's allowed? What's possible for this wave function to happen? And so it sort of examines other versions of the universe to consider what else might happen. I see at a fundamental level or like at a specific system, like if I have a baseball or I have a canister full of gas molecules, is it telling me what's allowed for those things?

Or is this more in a fundamental level? Like what can a system in general do or not do? Yeah, it's at a more fundamental level. And again, it's not rewriting the laws of physics. It's not saying this canister of gas is now allowed to do things that it couldn't do before. It's saying when you go to write the laws of physics, instead of just thinking about what's going to happen, think about what's allowed and what's not allowed. And that will let you write the laws of physics in a different way. Because, for example, information is not just about the current state of your set of switches, for example.

It's about how many different states could those switches hold, right? If you have like a bank of buttons in front of you, the amount of information. information stored in it depends on the number of possible different ways those buttons could be pressed or not. So thinking about what's allowed and what's not allowed lets you like encode information sort of more towards the core of your physical theory. I see. I think maybe what might be confusing is that maybe, you know, physicists and theoretical people sort of have a different idea of what information is kind of like information maybe for to a regular person is just like is the light on or off or is this object red or not red. You know, like,

That's information. That's sometimes useful to know. But I think to maybe a theoretical person, information is more abstract, right? It's about what can you know about something? Yeah. And it's about like how many different configurations can something hold. Like your hard drive, for example, it can store a bunch of pictures. Why can it store that many pictures?

Because inside of it, there are thousands and billions and trillions maybe of tiny little switches, which can either be on or off. And you can encode those pictures in those patterns of on and off switches. And so a hard drive with more switches can hold more information because it can have lots more different patterns. And so it can hold bigger pictures or more pictures. So we measure the information in a system by how many different states can it be in? Because that's a way to code some vital thing. Like if you have, for example, just a light switch.

A light switch can only be in two states on or off. So you can only possibly send two messages, right? You can't send a picture of your dog using a light switch or a picture of your cat. But if you have a billion light switches, then you can flip them in a way, which means the picture of your dog or means the picture of your cat. Right. I feel like it's almost like, you know, information for a regular person is like whether a ball is red, like that's information. But to a theoretical person, it's like how many colors can this ball be? Yeah, exactly.

So the more colors it can be, the more information that ball has or carries or, you know, manifests. Perfectly. I think that's a great way to describe it. Oh, good. I'm glad I wasn't napping. So if we then think about our laws of physics in terms of like, could this ball have been red or could it have been blue or could it have been green, then we're thinking about the possible states of the system. We're thinking about what could have happened and what couldn't have happened. Then we're directly addressing the information when we go to write those laws of physics.

Right. So it sounds like you're concerned about all of the different arrangements of a system. And so our current theories don't worry because they only sort of deal with one arrangement at a time. kind of. And so constructor theory says, first thing you do is not write down the laws of what happens. The first thing you do is you write down what can't happen and what can't happen. And you use that to constrain eventually the laws that you do write about what does happen. So it says start instead from basic principles about what's allowed and what's not allowed

and then go from there instead of starting from how things move and then figuring out what the laws of what's allowed and what's not allowed are and making them in exact. Start from exact laws of what's allowed and what's not allowed, and from there, write the rest of the dynamics. And by allowed and not allowed, do you mean, like, from an information point of view? Like, information can increase or decrease or things like that? That's one example, but it's really quite general. And, you know, there are examples in the past where this has worked really, really well. We know, for example, that special relativity is a great example.

We know that Einstein got the idea for special relativity from observing that the speed of light is constant. Once you start from that, you write down this basic principle. then the rest of special relativity sort of falls just from that. So if you start by saying, here the basic rules of what's allowed, everybody who measures the speed of light has to measure it at the same speed, no matter what their velocity is. From that, that constrains the possible laws of physics that you could develop, and it constrains it in a way that gives us special relativity,

the only rules that are consistent with that. So it's a great example of starting from principles and then finding laws of physics rather than starting from the other direction. Yeah, because I guess if you had started from, like, just looking at a photon, you might have built a different theory about the universe, right? And one in which light could go as fast as it wants, or anything can go as fast as it once. But you're saying, like, relativity is something that came from looking at what's allowed

and not allowed first. Like, we've observed that nothing can go faster than the speed of light, and therefore photons have to move this way with these laws. Yeah. And before we had relativity, we knew that light traveled just at that speed. It was measured, but it wasn't an exact statement. You know, something that sort of emerged. approximately from experiments and from our calculations and from electromagnetism,

you know, that light moved at this speed, but it wasn't an exact principle. It was approximate. So Einstein instead enshrined it as an exact statement, right? And he said, this has to be true absolutely and everything follows from that. And he did something similar when he developed general relativity, right? In general relativity, he said that acceleration is indistinguishable from gravitation. You can't tell the difference between accelerating and being. in a gravitational field.

And that principle led him to general relativity. So it's been done before in the past in this general sense of like find the basic principles and from that let the laws of physics flow instead of let's build up mechanics and then see what emerges from it. Well, it almost feels like you're trying to state what the laws are and then hope they work or see if they work rather than, you know, kind of discover what those laws are. Yeah, maybe it is a little bit backwards. You know, it's sort of like assume some basic principles about what's allowed in the universe and what's not allowed, see what the consequences of that are.

But then in the end, you still have to go out and check and say, well, does that actually describe reality or not? Right. You know, if Einstein's predictions hadn't worked, then he would have to toss it out no matter how beautiful it was. It seems like a bit of a scatter approach. You know, I could say, hey, maybe only pink elephants can go faster than the speed of light. And so we would have to design an experiment to prove me wrong. I'm looking forward to doing that experiment, actually. Actually, that sounds like that great way to spend an afternoon.

Let's spend a few months writing that application. Well, what are some other examples of this idea kind of working out? Another example is Stephen Hawking making progress on quantum gravity. You know, we have a theory of quantum mechanics that describes how particles move. And then we have general relativity that tells us how space bends and twists in the presence of mass. But nobody's been able to link those two together to understand how gravity affects tiny little particles, which seem to follow very different rules than the things that general relativity talks about, right? General relativity is happy to talk about baseballs and planets and things that follow smooth, continuous

curved paths. But quantum mechanics tells us particles don't do that. They're here, then they're there, and there is no path in between them. And sometimes they can be in multiple places simultaneously, right, or have the probability to be. And general relativity doesn't know how to handle that. And so Stephen Hawking said, well, let me think about what's allowed for black holes, and what's not allowed. And he said, well, we know that black holes have some information inside of them. Because when you put something inside a black hole, that information has to go somewhere. And therefore, black holes have entropy.

They have disorder because they're gathering information. They're gathering stuff as they grow. And therefore, they have to have some temperature. And this was his big breakthrough is to apply like statistical thermal physics to black holes. Because if black holes have some temperature, then they have to glow. Because everything in the universe that has a temperature also emits, radiation. And that led him to predict talking radiation, which he, of course, named after himself. And so that was sort of like a first step in the direction of trying to understand

quantum theory of gravity, like what happens to tiny particles right in the boundary of a black hole. Of course, not a full theory of quantum gravity. Lots of big questions remaining. But it's sort of like a good step forward, starting from making statements about what is allowed for black holes. It sort of sounds like maybe the idea it has to do with abstraction, maybe, like you're abstracting something from, you know, a bird's eye view really high up and you say, all right, what sort of the general shape of this or what should this behave as a whole, like a black hole? Like if I just treat a black hole as a black body or is a hot thing in space, then these are the things I should expect them. And then after that, you sort of go into

the nitty-degree to make sure that's true. And then that maybe reveals the small details of the laws of physics. Exactly. And it constrains you, right? It forces you to only consider certain kinds of laws of physics. And the thing that I like about it, that it does really enshrine important things fundamentally into the theory and makes them exact rather than approximate. Like think about conservation of energy. You know, if you didn't know that energy was conserved it, that wasn't like a core thing in your theory and you just made a bunch of measurements and developed a theory of chemistry and physics, then you might end up with like an approximate conservation of energy because you might notice like energy is almost always pretty close to exactly

conserved. But you wouldn't discover that it's like actually really conserved. That takes like a reformulation of your theory to say, well, you know what, we're going to put this in at the ground level because it seems like it really is exact. I see. You mean like the loss of thermodynamics. It's like, you know, we sort of observed that they were true that, you know, entropy always increases or energy is sort of always concerned. But let's just assume that's always true in all cases. Yes. And then built the theory of how molecules and things in a gas canister work after that. Yeah. And let's see where that leads us, right? Let's put these handcuffs on ourselves, assuming that the universe also obeys those restrictions

and see where that leads us. And it'll lead you to a theory which, if that describes the universe, should be closer to the true theory. Or it might lead you to a pink elephant collider or launching pink elephants into space. Exactly. And you might be handcuffed to that pink elephant,

and so it might be quite a ride. We'll put those physicists in the back room. We'll attach him to the pink elephants. All right. Then what are some maybe new developments in this theory about constructing from the ground, up. Well, one big obstacle in developing like a theory of quantum gravity, which in the end is one of the real big motivations for this. Like we haven't figured out quantum gravity. What's going on? We've been

working on this for a while. Maybe we need a new approach. One obstacle to making progress there has been that we don't really know which direction to take. Like there's two possibilities. One is maybe gravity is a force like everything else, you know, like electromagnetism and the weak force and the strong force. Maybe gravity really is a force. And it's quantum mechanical. And there's They're like little gravitons that go back and forth. Maybe we can use our whole quantum mechanical description of the other forces and we can apply it to gravity somehow. We haven't figured out how yet,

but maybe that's the path forward. But then it's a whole other group of people who are taking a completely different approach. They're saying, no, no, no, gravity is different. And the way to bring general relativity and space and time together with quantum mechanics is not to quantize gravity, but to quantize space itself. This idea that like maybe space is made out of tiny little pixels

And reality is like woven together this loop or this foam of these tiny little pixels. That would also make gravity quantized. But in a very, very different way, it wouldn't say gravity is a force. They would say it's the curvature of space, but that space itself is quantized. So nobody really knows, like, which direction to take. And there's this idea that if we could construct an experiment to sort of like not tell us how gravity works, but tell us which direction to go, that that could be a very useful thing to do to like at least get a clue as to which path to take.

I see. It's like we can marry the two theories together, so let's just invent a marriage and see if we can get the right theory from there. Yeah. And so people are wondering, like, is gravity a quantum force or is space itself quantized? And before we know which direction to take, let's say if maybe we can answer that question. And so constructive theory would say that's a very important step to take first, is to understand, is gravity a quantum theory or is space itself quantized? You should try to figure that out first, and then you should proceed to try to figure out quantum gravity. And you might think, well, yeah, it would be great to know that,

but how could you possibly figure that out? And people actually have come up with a pretty cool idea for how you might be able to figure out if gravity is a quantum force without actually understanding quantum gravity itself. Wow. All right, right. Let's get into some of the details of this arranged marriage and how it might let you copy information in new and interesting ways. But first, let's take another quick break.

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All right, we're talking about constructor theory, which is not a child to toy. It's like potentially a revolution in the way physicists think about the universe and how they build theories that describe the universe. And so we think it's a better approach because it might let us connect physics to concepts that are currently not connected together, like maybe information to physical laws or marrying quantum mechanics to gravity. And so, Daniel, we were talking about marrying quantum mechanics to gravity, which we currently don't have. They won't even talk to each other right now. So how can we make this a romance happen? Well, first, we have to figure out, you know, how this relationship is going to work, right?

Are we going to stick gravity into quantum mechanics or are we going to stick quantum mechanics into gravity? It's like, are we wrapping the peanut butter around the chocolate or the chocolate around the peanut butter? That's like step number one. That's what constructors theory would say. It's like, instead of like, fiddling around in a lab, trying to build a theory from scratch and from watching individual particles, let's decide from the beginning whether it's chocolate on peanut butter or peanut butter and chocolate. Yeah, let's have as many guiding principles as possible before we get started.

And let's code those guiding principles into the very, very basic layer of how we design this theory, so it's more likely to be right in the end. And, you know, that only works if the principles you're talking about are the ones that describe our universe. So you better make sure those are right. Well, it sounds a little anti-scientific in a way, right? Like it's almost like you're pre coming up with the answer in a way instead of basing it on observation. It's like another step in developing hypotheses, right?

It's like step zero is now write down a bunch of rules that your theories have to obey. And then step one is write down a theory of the universe. And then step two is go out and check and see if it actually works. But we have this like new step zero that constrains the kind of theories you can write down in step one. I see it. So it's like a meta hypothesis. It's like before we have a hypothesis, let's step back and have a meta hypothesis. where we sort of pick a direction of the way the universe is peanut butter or chocolate coated,

and then see if that works. If it doesn't, then we'll maybe try another direction. And the advantage is if it does work, then these, like, deep principles are encoded right into your laws of physics. They're exact rather than, like, coming out as emergent or approximate phenomena. But wouldn't the danger be that maybe you pick a direction, like chocolate covered inside of peanut butter? And it works most of the time, but then eventually down the road, it turns out that it's, you know, also an emergent. thing or something. Yeah. You could take a principle and claim that is perfect and exact. Then it could turn out to just be approximate. Absolutely. There's nothing in this new

constructor theory that prevents you from overthrowing people's previous ideas developed from constructor theory. Right. You can still do that. All right. But what I do think is really fun is that it's motivated people to try to ask this question of like the chocolate in the peanut butter, peanut butter in the chocolate before we get to quantum gravity. It's like first figure out which direction to take before you actually get the theory. I think that is pretty cool. That is something new because it actually inspired people to think up a really clever experiment that would answer that question. Not how does quantum gravity work, but is gravity quantum force or is space quantized? Oh, I see. Like maybe before because we didn't know whether it was peanut butter or chocolate,

the one that was outside, you know, people wouldn't commit to sort of exploring experiments or going down one path too much. But once you sort of say, okay, let's just say, okay, let's just say, assume it is chocolate covered with peanut butter. How would we build a whole science out of this? Yeah, it's really inspirational to know something about the answer. It really helps you drive in the right direction. But these experiments are really hard, right? Because what we're looking to do is to understand, do tiny little particles feel gravity? Or how do they feel gravity? What are the rules of gravity for tiny particles? And that's hard because tiny particles are tiny and gravity is really, really weak. And so like the gravitational forces between two

tiny particles are almost zero, which makes it really hard to do experiments of like measuring the gravitational forces between two electrons, for example. So you're saying that maybe just the idea of starting with, like, is gravity a quantum force has inspired a whole bunch of interesting experiments or interesting ideas about how that could work, whereas before people didn't really want to go down that rabbit hole. People thought for a while that that was not a question we could answer first. People thought, first, let's find a working theory of quantum gravity. then we can ask questions of that theory and say, like, well, does it tell us that gravity is a quantum force?

Or does it tell us that the universe is quantized? Now, instead they're saying, well, let's figure that out first. And, oh, actually, it might be possible to figure that out experimentally in the next few years. And then we can use that at the core of our theory and we can build from there. So what does this experiment look like? It's really fun. It's a crazy bonkers experiment. It involves these super tiny little microdiamonds that are really small. and inside of them, they have like a single nitrogen atom that can have different quantum states, like different spins, spin up or spin down.

And the idea is that these diamonds are so small that they're basically quantum mechanical. And the goal of the experiment is to put these diamonds in a quantum superposition. So like you have two diamonds and, you know, call one red and one blue. And maybe the red one is now in a quantum superposition where it like, it could be over here or it could be over there. And the blue one is also in a position of where it might be. Now, that's interesting because gravity, of course, depends on the distance between things. So the part of the red diamond that might be closer to the blue one should have a stronger gravitational force than the part of the red diamond that might be further away from it. So now you have this like red diamonds in these quantum superpositions and different parts of those wave functions and now affected differently by the gravity.

And so if gravity is a quantum force, it will talk to the different parts of those wave functions differently than if gravity is not a quantum force. like collapses that wave function before interacting with it. So you put these diamonds in like quantum superpositions and then you can see if gravity plays nicely with quantum states or not. You mean like almost like you're taking two atoms and putting them close to each other and see if there's a gravity between them kind of. Yes. Yeah, these diamonds like drift through the experiment.

They fall through the experiment and then they measure the distance between them to see how gravity has tugged on these two diamonds between each other. But before they did that, they put this quantum uncertainty into the local. location of the diamonds. So it's not exactly clear where the diamonds are. So then gravity has to make a choice. It's like, well, am I classical? Do I collapse the wave function and then make gravity happen? Or am I cool with quantum stuff? Because I'm a quantum force just like everybody else. And I can just like gravitationally attract the various bits of the wave function to each other. Interesting. I guess you're saying that if gravity changes the quantum wave function of the individual particles,

that means that it's a quantum force. Whereas if it only acts, of after you collapse the wave function, then it's not a quantum force. Exactly. And this experiment can tell the difference because it has these tiny little diamonds in quantum superpositions, and it can tell the difference between gravity collapsing those wave functions and then acting or gravity acting separately on the parts of the wave function, which would mean it's a quantum force. I see.

Because it sounds like a really cool experiment and that maybe we should have thought of a while ago, but you're saying that we only sort of thought about it or only conceived this experiment And because of this constructor approach of like, let's pick a direction and go with it and then think of experiments or theories that fit that general meta hypothesis. Yeah, it was Kiara Marletto herself who came up with this experiment as a sort of demonstration. She was thinking, if you want to figure out the basic principles first, you could actually try to attack those directly. And this is a good example of why like motivational principles or organizational strategies for theoretical physics are really important because you're right that somebody could have thought of this 10 years ago or 20 years ago. right? But the motivation for thinking up that this experiment was possible came from a new way of asking questions about the universe. So let's try to figure out some basic principles first that will

guide our theory going forward. I see. Like how would you design something directly to test those meta hypotheses? Yes. It's not something we would have come up with before because before we were sort of tinkling around with the atoms and the particles and trying to see what was going on. And it seems like nobody could sort of make heads or tails out of it. Yeah, exactly. So now people are setting up to do this experiment. And so we may know in the next few years, is gravity a quantum force or not? Which would be a huge piece of information. And, you know, if it is, that means like folks like Carlo Revelli who've been working on loop quantum gravity. Well, that was fun mathematically, but doesn't describe nature. And we can just sort of like cross out. Huge branches of theoretical

physics is inconsistent with our universe. And then we can dedicate our energies to the other direction. I see. All those people holding peanut butter cover chocolates would be left with a lot of calories on eating. That's right. And also delicious, right? Mathematically, a lot of fun. And we've learned a lot about math and maybe even about physics or the metaverse from that, but not necessarily our universe. Right. It could be true in another universe. Yeah, exactly. Maybe all those physicists will then decamp and go off to another universe. That's right. They'll get exiled to a different country as most revolutions go. There are always refugees, right?

These are intellectual refugees. Look at Argentina, maybe. We wish them safe voyage. All right, well, what are some of the criticisms of this constructor theory approach? One criticism is that, like, haven't we been doing this already? You know, the fact that we have previous examples, like Einstein using this to establish relativity and Hawking using similar ideas to establish his ideas about Black Hole tells us that, like, it kind of has been done in the past.

So really, what's new? I read a bunch of articles criticizing it, and that was essentially the strongest argument I read that, like, we've already basically done this. And the response from constructor theory folks is like, yeah, we've done it before, but this like formalizes it, it generalizes it, it identifies it as a good way to do things. It encourages us to do all of physics this way rather than just, you know, remarking on the couple of times that we did it and it worked. I see. Like right now it's sort of random the way we do it sometimes. Sometimes we start from the observation. Sometimes we start with some guiding theory, but it's sort of random. And sometimes it works, sometimes it doesn't.

I think you're saying this sort of camp or a physicist is saying, let's just call it what it is and let's know when we're doing it and not doing it. Yeah. Another criticism is that it's kind of fuzzy. I mean, it's even been tough for us to like figure out exactly what it means and how it would be different. And I think a lot of physicists sort of look at it and be like, huh, what are you talking about? We're just going to keep doing physics the way we're doing physics.

And so it hasn't like swept the world by storm. I mean, I'm here in a hallway with a bunch of theoretical physicists, and none of them would say that they're doing constructor theory or think about constructor theory at all. So it might just be that, you know, it takes another few years to really catch on, to really break through that it needs to have its like really killer app before people are convinced. Or could just be like, hey, that was kind of a cute idea. And then people move on to something else. We just really don't know at this point. Right, right. Then people move on to deconstructor theory.

Transformer theory into Scepticon theory. Yeah, there you go. And finally, the nap theory. All right, well, it sounds like another stay tuned. It sounds like a pretty exciting idea. Maybe a new way to look at science itself and the way we build theories about the universe, which could be maybe the right way. It sounds like a lot of progress has been made already thinking in this way.

Yeah, and it's always exciting to dig at the foundations of science to wonder, like, are the way we're doing things the only way, is it the best way? Have we all gone down one path? Are that even realizing there was another path back then, a thousand years ago? that we could have taken. So it's fun to sort of like lift up the layers of the rugs and look at what's underneath. And sometimes you find something really clever

in a new direction. Right. Sometimes it's caramel nugget all the way down and not peanut butter or chocolate. Sometimes it's turtles all the way down, right? Isn't that a candy? Chocolate turtles? Chocolate turtles.

All right. Well, another example of how science is an evolving thing. It's always changing and transforming and constructing itself. And maybe the people out there who are listening could be the ones who make it all. all work. That's right. Maybe some six-year-old or some eight-year-old or some 30-year-old out there is the one with the new idea about how the universe works, the one that takes us to the next level of understanding reality. Yeah. So hopefully they'll wake up from their nap and figure everything

out for you guys. We hope you enjoyed that. Thanks for joining us. See you next time. in 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. December 29th, 1975, LaGuardia Airport. The holiday rush. Parents hauling luggage, kids gripping their new Christmas toys.

Then everything changed. There's been a bombing at the TWA terminal. Just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged, terrorism. Listen to the new season of Law and Order Criminal Justice System on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. My boyfriend's professor is way too friendly. I'm seriously suspicious.

Wait a minute, Sam. Maybe her boyfriend's just looking for extra credit. Well, Dakota, luckily, it's back to school week on the OK Storytime podcast, so we'll find out soon. This person writes, my boyfriend's been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now he's insisting we get to know each other, but I just want her gone. Hold up. Isn't that against school policy?

That seems inappropriate. Maybe find out how it ends by listening to the OK Storytime podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. The U.S. Open is here and on my podcast, Good Game with Sarah Spain. I'm breaking down the players, the predictions, the pressure, and of course the honey deuses, the signature cocktail of the U.S. Open. The U.S. Open has gotten to be a very wonderfully experiential sporting event. To hear this and more, listen to Good Game with Sarah Spain, an Iheart women's sports production in partnership with deep blue sports and entertainment

on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Brought to you by Novartis, founding partner of IHeart. Women's Sports Network. This is an IHeart podcast.