Daniel and Kelly’s Extraordinary Universe - Is physics discovered or invented?

Episode Date: October 23, 2025

Daniel and Kelly get concrete about whether physics is the map or the territory, the topic of Daniel's new book "Do Aliens Speak Physics?"See omnystudio.com/listener for privacy information.

This is an I-Heart podcast. Hey, I'm Kyle McLaughlin. You might know me as that guy from Twin Peaks, sex in the city, or just the internet stand. I have a new podcast called What Are We Even Doing? Where I embark on a noble quest to understand the brilliant chaos of youth culture. Each week, I invite someone fascinating to join me to talk about navigating this high-speed rollercoaster we call reality. Join me in my delightful guests.

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crisps by a planet-wide death ray as anything else. But this is seeing the alien arrival glass as half-empty. Instead, let's look at the glass as half-full, even if we aren't sure yet what it's full of. Maybe aliens have figured out the answers to puzzles that remain impenetrable to us, like what everything is made out of at the smallest level, or why time only flows forward, or how big the universe is. What if aliens know for a fact how our universe began and how it all might end? What if they know what it's like inside a black hole, or actually understand quantum mechanics like the back of their tentacle? Maybe to them the universe isn't a place of consistent mystery, but one that tidily follows some basic rules.

And what if they could just tell us how everything works so we don't have to blindly hack away for decades or centuries to gain this elusive knowledge? They might carry the product of millions or billions of years of alien scientific thought to catapult us unimaginably far in our quest to understand this wonderful, bizarre, violent, and beautiful cosmos. If our species met up, physicists hope that we'd be able to geek, out together sharing notes on this glorious galactic journey of discovery. But could that really happen? A lot of scientists, especially physicists, believe it could. They imagine that unraveling

the secrets of nature is a universal project that would be shared by the scientists of alien species across the galaxy, and that physics describes everything in the universe, not just life on Earth, and so should also form the foundation of alien science. Therefore, we should be able to use physics as a mental bridge between our species. But hold on a second. Are we accepting those arguments too quickly? Have we really given the question careful thought, or are we blinded by our fantasy of galactic scientific cooperation and the narrowness of our own experience? We have only our one example of science here on Earth, so it's hard to be sure how much of it might be colored by human nature and culture. Are human physics and math the only way to think about the universe?

Are they just the only way we can imagine it? Are the laws of physics something universal, something we have discovered, or are the human something we have invented? Welcome to Daniel and Kelly's extraordinary alien universe. Hello, I'm Kelly. I study parasites and space. but I don't think about aliens as much as Daniel does. Hi, I'm Daniel.

I'm a particle physicist, and I do want to figure out the secrets of the universe myself, but I'd rather just download them from alien brains, if possible. Yeah, that'd be nice. All right, so my question for you, Daniel, when you think about aliens, which is apparently all the time. Embarrassingly high fracture to my brain, yes. That's right.

That's right. For someone who's not like a conspiracy theorist or a cryptid fan, you think about them a lot. You're making some assumptions there. I've known you for a while. But when you imagine aliens, what do they look like in your head? Oh, boy. Wow.

You know, I think it's almost impossible to anticipate what aliens actually look like. Or at least I hope so. You know, there's two scenarios. One is aliens show up and they're basically Star Trek. You know, they're humans with fuzzy foreheads or, you know, just some little tweak on the kind of life we have here on. earth. The other scenario is they show up and there's so much weirder than we could ever possibly imagine. And that to me is the fascinating scenario. That's the non-starbucks scenario. It's like you don't want to travel the world and discover Starbucks on every corner. That's boring. You have Starbucks at

home. Says you. I mean, I like Starbucks too, but I prefer like local weird coffee. That's why I go traveling. And so if aliens show up and they're not really weird, I'm going to be disappointed. in the universe. Quick side note. When I travel, I do like to go to the McDonald's in other countries, but only because I like to see what other stuff they have on their menus, you know, because they usually don't have, like, the U.S. standard menu, and I like to see, like, oh, what's the, how did McDonald's homogenize with this culture to create something new?

But also, confession time, Zach and I were in Versailles for our honeymoon, and we had this lovely breakfast, and we went to go throw away our receipt in our. trash and I noticed a McDonald's arch. And I was like, wait a minute. And it was, it looked so nice. We didn't realize we had gotten breakfast at McDonald's on our honeymoon. And it was delicious. We had a great time. In your defense, McDonald's in France is really a different kind of thing. Yeah. It really is much more upscale. Absolutely. And that's like a cultural insight or something that I feel like you get by visiting the McDonald's. But anyway, I don't exclusively eat at McDonald's. Well, I went to a conference in Taipei.

once with an Israeli colleague, and he ate every single meal at Subway or McDonald's. And like, this is Taipei, people. I mean, the food there is incredible. I was a vegetarian at the time, and we had this 19-course banquet dinner, and they served me a separate, different vegetarian thing for each of the 19 courses, and each one blew my mind. Like, the food there is unbelievable. Plus, I also went to the night market and, like, ate all sorts of weird stuff that

probably had eyeballs in it. But to me, that was the joy of it, right? But he was like, yeah, no. I'm not touching any of that. Well, hold on. If you're a vegetarian but you eat eyeballs, is that like an eyeballitarian, like a pescatarian only eats fish?

Well, I was a vegetarian at the time, but I also wanted to explore. And I was at the night market and I couldn't speak the language, so I took some risks. And I'm not sure whether or not I ate eyeballs. I think probability Daniel ate eyeballs that evening 50%.

Yeah, good on you. It's good to try new stuff. But that's awesome. Yeah. Anyway, the joy of traveling is exploring the universe and having your mind blown. by how surprising it is, by breaking out of the box of your expectations. Absolutely.

And you always are so great at transitioning us home. And so here we are. Today we're talking about the joy of studying physics. And we're trying to nail down on the philosophical question. Is physics discovered or invented? Yeah, exactly. It's the physics that we have developed here on Earth. Are we figuring out basic rules of the universe?

Or are we just telling a human story, one that's approximate and a, effective and kind of only makes sense to us. And this is a philosophical question for sure, but I like to think about it in concrete terms and inject aliens into it by imagining the scenario that aliens arrive and we try to talk to them about this because that's when it matters, right? You might think, who cares if it's discovered or invented? It works, right? But number one, I'm curious about whether it's really deeply true. And also, I am concerned about this situation? What if aliens show up and they have these answers, but we can't make a scientific connection with them? That would be so frustrating. And that's why I wrote my new book,

Do aliens Speak Physics? Out November 4th from Norton and available at all fine bookstores. Please go check it out. Okay. So you said that it would be a real bummer if the aliens got here and we, like, you know, hadn't figured out the truth. Is that because you're worried about what they're going to think of us, in which case I have a speech that I tell my daughter about why? shouldn't worry about what other people think? Or is it because it would inhibit our ability to communicate in that case? My fantasy is that the aliens deliver to us answers to some of the puzzles. You know, like, I just want to know what is inside a black hole.

What is the real story of the universe? I would love to know the answer to these questions. And the idea that aliens have these answers out there is endlessly frustrating to me. If they could just show up and give them to us, you know, like somebody knows it. truth, please just share it with us. So my concern is that they show up and we're mismatched somehow so that we can't get those answers. Maybe we're not smart enough to understand it or maybe we're going down a different path or maybe they have a different way of explaining these things or maybe they're asking different questions. You know, they perceive the universe differently and

they're not interested in the questions we're asking. And so I'm worried about these scenarios where we're mismatched with the aliens and so we can't have that moment of scientific cross-emogenation. I mean, do you think it's possible that we're on the right track and they're not? Or if they get to us, then they must be on the right track because they're doing stuff we can't? That's a great question. I think if we're on different tracks, that probably says something about the nature of the universe. If you can be described in different ways, then maybe there is no one truth and you can't say who's on the right track or the wrong track. Well, when I'm interested in finding the truth, what I do is I reach out to the extraordinaries. And so

That's what we did. We reached out to our listeners, and we asked, are the laws of physics discovered or invented? I think the laws of physics are somewhere in between an invention and a discovery, maybe closer to the discovery, I will hop. And Einstein didn't invent space time doing its bendy, squishy, stretchy thing. He just caught it in the act, so definitely discovered. Our curiosity and need to understand the world around us has led us to discover the laws of physics. And we've had to invent tools to help us do that, both abstract and physical. So it's a little bit of both.

It seems it's some of both. There are realities in the universe that we can discover, and then we invent models to describe those realities. Surely the laws of physics are discovered, because they already exist. I think they are discovered. I think it's a little bit of both. I think they're invented as we're kind of putting the bits and pieces together, and then the more we can understand it,

the more we are discovering how things actually are. So the laws of physics are certainly discovered, while the maths used to describe them are human inventions. The laws of physics are, of course, discovered, but defined in our language as humans. If it is accurate, incorrect, it's discovered, otherwise it's invented because it's not correct. It doesn't seem to make sense to me to say that we invented gravity. I would say that the way things are is discovered, but the methodology by which we use to measure and categorize in our own terms is invented. But the laws of physics help us make order and meaning from what we discover, but they're not immutable.

So in that sense, they're invented and can change as new things are discovered. I would say while the fundamental mechanisms how physics work are discovered, the laws of physics are invented. They are useful and necessary for set mechanisms to make sense to a big monkey brains. I think the observations of the universe are constant, but how we describe them as laws depends on our particular moment in history and the mathematics available to us at the time. I think they were both. I think the laws of physics were first discovered, and then we invented the math to go with what we discovered. The laws of physics must be fundamental. And the way we do, oh, there goes the dog. And we discover it by doing inventions. That was the dog participating. I hope the dog was right. These are such great thoughtful answers, not surprised, of course, but impressed.

When I started researching a city on Mars, one of the things that I loved was that people would say, oh, obviously, X is the case. And then you'd go and talk to the next group, and they'd be like, obviously, why is the case? I think the most common version for me was, obviously we can't settle space right now. And then other people would be like, obviously, we're ready to do it right now. And I'd be like, oh, my goodness, how can everybody be so sure? But anyway, so we've got a nice mix of answers. I love those moments because then you get to dig into the assumptions that are leading you there and open people's mind.

So hold on a second. That's an assumption. That's not something you know. And maybe it feels natural to you. It feels intuitive. But do you have data? What are the reasons for holding those assumptions? Those are the moments when your mind expands, right?

When you're like, oh, wait, maybe eyeballs are a good snack after all. You know, I feel like at the top of my list of people that I want to correct me is you because when you're like, You know, when what you mean is, well, that sounds kind of wrong. Instead, it sounds like an amazing philosophical insight. I'm like, oh, that's such a cool way to think about it. And then afterwards, you're like, wait a minute, Daniel told me I'm wrong. You know, that's my process with students. And actually with podcast listeners, they often come to me with a question.

And the question doesn't really make sense. And it makes me realize they've absorbed some piece of information that's wrong. And that's led them down this path. And so I feel like the job of a teacher is not to say, you're wrong, here's the right. answer, but to unravel their thought process to the moment they took the wrong path and show them the right way to go. Yeah, and that's one of the reasons I like working with you so much, because I feel like you're an easy person to throw ideas out at because you're not going to be told, well, that was stupid. So anyway, all right. Our listeners are amazing. Let's jump into

what does this question even mean? What assumptions are in that question? I think a lot of people might hear this question, especially a lot of people in physics and say, well, of course, the laws of physics are something we're discovering because there's something real happening out there in the universe and we have this process of science for slowly deducing the truth and, you know, we use mathematics to express it and it just works so well. And so I think it's the natural point of view, the place people often start is that, okay, physics is something we're figuring out about the universe. And lots of physicists feel that I remember talking to string theorist Thomas Van Riet and he was like, yes, aliens will be doing string theory. I don't even doubt it.

his confidence was amazing. Yep, I loved that. And there's reasons for that. It's not an unreasonable point of view, but it's also not the only point of view. And, you know, this question is similar to another, maybe more widely discussed question in philosophy and in popular discussion, which is about mathematics, right? Is mathematics invented or discovered? And here, mathematics is the language of science? And so it's natural to ask, like, well, is mathematics like our mental shorthand for the way the universe works, or is it some part of the universe? Did the concept of seven exist before they're humans, you know, or is it something that we came up with to help explain the universe around us? You know, I think a way to sum up the question essentially is,

is physics the map or is it the territory? Are we describing something that's happening out there in the universe, or are we revealing the actual truth? So could you give me an example like, all right, so say you've got a theory and you make some observations and the observations matches what you would expect from the theory. Bing, bam, boom. You've got it, right? And so, like, why is that not sufficient? Yeah, well, that's a great question.

If you have a bunch of data and you have a theory that describes it, there's always another theory that also fits that data, right? Because you don't have infinite data. And you could have two theories that deviate between the two data points. Or, for example, I could just take our current theory and say, Here's another theory that also describes the universe. It's exactly the same, but it predicts that in a hundred years, electrons will lose their charge. I mean, that theory perfectly describes all of our experiments. It's sort of ridiculous. There's no reason to believe in. It obviously has this added twist to it that you don't need, and you can use Occam's Razor to reject it. But it's just an example of how there are always more theories that do describe the data. And so you can't be guaranteed just by having a theory that matches your data that it's the only theory, or even that it's the true theory. Yeah. I mean, could there be like some intermediate between your theory and the observation that wasn't incorporated in some way? Like, you think that X causes Y, but actually

there's a Z that's interacting there that wasn't in your theory at all, and that would change predictions in another environment or something? Exactly, because perhaps you only have data in a certain set of circumstances, right? And you haven't seen the wider picture. For example, for hundreds of years, we thought Newton was right about gravity. And his theory bore out every single test we did until we pushed the boundaries and we started looking at really high speed events and, you know, the orbit of Mercury and tiny little details. Only then was it revealed that Newton's theory wasn't as accurate as we thought. And in fact, the whole story that it was telling, masses and forces between them, that story is not the story of what's really happening in the

universe. Now we have another story, Einstein's story of curvature and space time, right? The two agree almost always in our experience, but they tell a very, very different story about what's really. happening behind the curtains. And that's philosophically sort of scary because it tells you that you could have a theory that describes almost everything you see in the universe, but it could be telling the wrong story about reality. And when the aliens show up and they're like, what? What are you guys talking about?

That's nonsense. Here's what's really going on. Okay, but so let's imagine a world where, and heaven forbid this is the case, where we never meet aliens. Like, I know, I'm so sorry. I'm so sorry. Would it still matter? Like, if we've got predictions and we can use those to make new technologies, does it matter if we actually are right or not?

Or if we've just figured out a way to understand the world that's helpful? Yeah, great question. I think it depends on what's important to you. If what's important to you is let's build cool technology and, you know, self-driving toothbrushes and whatever, then it doesn't really matter, right? But if your goal is to reveal something true about the universe, to understand, and I think in the end, that's what physics is about. out, fundamental physics is a desire to unravel the nature of the universe, not just to build cool gizmos, then it's fundamentally frustrating to think that we're not doing that, that we're just telling ourselves a story that works, that we're not actually hearing from the Oracle and

revealing the truth of the universe, that we're stuck in Plato's cave, essentially, just looking at shadows on the wall. Yeah, I think that would be fundamentally frustrating. Absolutely. Yeah, I'll give you that. But you ask a great question because aliens haven't arrived yet. And so you might ask like, well, what progress can we make anyway on this question before the aliens show up? Do we have to just sit here and wait for the aliens to arrive and say like yes or no or see how it works? And so that was sort of the struggle I faced trying to write this book. It's like, well, how do we make any progress before the aliens show up?

And it turns out you can, right? You can look at the structure of human science. And you can ask like, well, are there places where the choices we've made? made are arbitrary, or are there things that could only have happened this way? And in this area, I have to give a lot of credit to, like, biologists. Well, because biologists have already done this work. Congratulations, Kelly. You know, like, biologists have thought about, is life on Earth the only way it could be? We only have this one example of life on Earth, but they've tried their best to push beyond the box. For example, they see that all life on Earth has carbon as its backbone, but that doesn't mean you can

assume that all life in the universe is carbon-based. They imagine ways it could have gone differently. Maybe it's silicon in there, right? Or all life has water in it, but maybe it could have had ammonia. So there's been a lot of this like push beyond our one example thinking in biology. And I wanted to do the same thing for physics to examine the places in physics where, oh, maybe this could be different or no, this absolutely has to be this way. There's no other choice as a way to try to figure out before the aliens show up, what truths were revealing and what are just stories we're telling ourselves. All right, let's take a break.

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So Daniel was telling us about how biologists are leading the way in, like, probably everything, and physicists are trying to catch up. And so what kind of work are they doing to try to catch up, Daniel? Well, it's an impossible task to be as cool and as good-looking and as swath. and is socially well-adjusted as biologists. Athletic. But, you know, weak... Why are you laughing so hard? Oh, sorry, I thought you were joking.

I'm going to take that totally seriously. I'll have you know that we have a physics soccer game here every year, and the faculty usually win. Oh, nice. Way to go. Yeah. So following in the footsteps of the wise biologists, we can ask, like, well, where are the places where physics could be making assumptions.

What are the arguments that suggest physics has to be universal, and what are the arguments against that? And I think one of the most powerful arguments is that physics seems to apply everywhere, right? We have this universality of physics, which really goes back to Newton, Newton looking at the apple or thinking about gravity and imagining, oh, maybe gravity doesn't just apply here on Earth.

It applies also in the heavens, right? He takes the physics that we deduce these tiny little apes on this little rock and applies it to the cosmos. And that's such a huge leap, right? It's incredible to think that the laws of physics we're writing down on pieces of paper, never having left this planet, really, with a very small number of exceptions, very nearby, could apply to things happening across the universe.

And that might sound like hubris, right? But it's also totally backed by data. Like, we can look at distant galaxies in the telescope, and we can see they are following basically the same rules of physics. We can understand what's happening there back in time and far away. Yes, funny, hubris was exactly the word that was rolling around in my brain. Way to preempt Kelly's critique. And there's a really fantastic example of this, which is very recent.

Maybe people heard about this validation of Hawking's area theorem. Hawking was thinking about black holes and how they come together. And he applied the laws of thermodynamics. Thermodynamics, of course, having its origins in like 18th century dudes in essentially these steampunk outfits playing with gas and valves and engines, right? I'm in. Yeah. And they were thinking about heat and energy transfer.

And they figured out some cool stuff. And Hawking said, oh, let's apply this to black holes. And he came up with this theorem about how black holes merge. And because black holes have entropy, when black holes come together, he said, well, the merger of the two black holes have to result in a black hole that's bigger than the sum of the two initial areas because the area of the black hole is connected to its entropy. And we just saw this happen with this direct validation of Hawking's area theorem. So you have this direct line from like dudes with gas flasks to like black holes a billion light

years away. It really is incredible that the laws of physics we figure out here seem to apply everywhere. And so we have this, you know, Newton's leap to the cosmos. And then Carl Sagan and folks make another leap. Carl Sagan, when asked, do you think that aliens do physics and math the same way we do, he said, quote, yes, and the reason I think that's likely is that they live in the same universe as we. So they must deal with the same laws of physics and chemistry and astronomy as we. So this is Carl Sagan, who of course, you know, I hesitate to disagree with on anything because smart dude, fantastic science communicator, right? The best maybe. I want to, but I want to underline that he's making a second leap there, even bigger than Newton's leap to apply the laws of

physics across the heavens, he's saying that because the laws of physics that we have to do seem to work everywhere, they must be discovered the same way everywhere or thought of the same way everywhere. And that's really a step beyond, right? I want to separate those two for people, because I think a lot of people conflate those two arguments, that just because the laws of physics apply everywhere, our description of the laws of physics apply everywhere, doesn't mean it's the only way to describe them. So would there ever be a way that you could convince yourself, we have found the explanation, or is it just like a continuous process of testing your theories over and over and over and over again and being willing to get rid of them if they're wrong,

but never knowing 100% for sure if they're totally right until the aliens come? I don't think you can know 100% for sure if they're right, even after the aliens come. I mean, say the aliens show up and, you know, they do physics the same way we have and they follow the same path and they figured out the answers, and they're just like, you know, the simplest possible scenario. They're a thousand years ahead of us. That doesn't mean that it's the only way to do it, right? Even if five different groups of aliens show up and they're all doing quantum field theory,

that doesn't mean that it's the only way. Maybe we're all affected by having the same evolutionary history or the same conditions or something. There could always be another way to think about it that we don't know. And so even having the aliens show up, I don't think is conclusive. I think one way to approach this is to think about how close the map matches the territory, right? So this is the question of accuracy. And another argument people feel very strongly about is that our human physics must be true, must be real, because it works so darn well, right? It's not just like some fuzzy description of the territory, right? It's like, wow, bang on. And, you know,

we talked on this podcast a lot of times about the incredible power of the standard model of particle physics. But, you know, just to highlight it, like we can predict how particles interact, and sit down and do pages and pages and pages of calculations and predict some measurement experimentalists will try to do to like 10 decimal places. And then the experimentalists go out and they make these measurements and it's like, this is amazing science on both sides. Like the theoretical calculation takes so much work and careful thought.

The experiment to measure something so precisely is really difficult, requires very different skills. But the two numbers agree. And when you have a theory that predict something to 10 decimal places, boy, you're tempted to make that leap and to say, yeah, this isn't a description. This is a revelation, you know? This is like, we have found the source code of the universe. And I remember thinking that as like a junior in quantum mechanics at Rice, hearing about

these experiments and seeing them compared to the theory and feeling like, there's no way this is just a description. We have really pulled back a veil on nature. Yeah, and that's a very inspiring idea. I love that. But then you look and you're like, oh, wait a minute. but we don't know how to reconcile quantum mechanics and all this other, with all the other stuff. And so, like, you know, I, what do I want to say there?

You want to just generally go, have you guys really figured it out? Well, I think maybe you all have figured a lot of things out, and truth be told, I'm very impressed by what you all have figured out. But, you know, so you can look at all the things you have figured out, but there's still things that don't fit together the way that you would expect them to, which could mean that there's some. other theory out there that would explain all of that stuff that hasn't been found yet, which we were talking to Ethan Siegel about the other day, I think. Yeah, and that's the incredible puzzle of physics that quantum mechanics is super duper accurate in scenarios where you can ignore gravity like particle collisions or interactions, right, because gravity is so weak at the particle level.

And also general relativity, a classical theory that ignores quantum mechanics is super duper accurate in scenarios where you ignore quantum mechanics, so like black hole mergers and gravitational waves and through orbit of Mercury and, you know, ringdown of binary pulsars and frame dragging as measured in space with these super duper precise balls that spin in gyroscopes and satellites. It's amazing how accurate general relativity is also so you could make the same argument for general relativity. So like, wow, this has got to be reality, right? Because it's so correct that every test we've ever done of general relativity has been bang on completely accurate. And it leaves you with the impression, like, wow, this is also the truth.

But you make the point, like, you can't have two truths, especially if they disagree with each other. And these two don't agree. They don't agree not only on what's happening out there in the universe, like what's the story, you know, what's reality, what's really running the machinery. They also don't agree about what is going to happen. They make conflicting predictions about what's inside a black hole or how the universe began or how it's all going to end.

in frustratingly places we can't test, we can't do experiments to reconcile yet. But you're right. And that points to a problem with this argument, right? We have these very precise theories, but all of these theories are what we call effective. None of them, we think, are actually describing the real truth of the universe. We think that all of our theories are describing this process we call emergence. If you think that there's a real truth out there, that microscopically, universe has something happening and that our experience somehow bubbles out of that, right? Well, there's this incredible step there, this amazing feature of the universe, that we don't have to know how the universe works at the microscopic level as fundamental base layer of reality

in order to start doing science at the macroscopic level, because this magic happens, where when you zoom out from the microscopic to the macroscopic, the rules are different, somehow simple, right? Like the universe, imagine it's filled with these tiny buzzing strings or flings or whatever sproings, you know, is at the base layer of reality. And imagine you have no idea how that works, right? Still, somehow you can zoom out and you can describe how a baseball flies across your backyard with simple mathematics. Why is that possible, right? Why isn't it all just chaos from the bottom up, the way like we can't describe hurricanes using simple mathematics, because it's a bunch of raindrops and in doing all sorts of complicated things,

why doesn't the same thing hold for zooming out from the fundamental layer of reality? We don't know. Is it just too many moving pieces? Like you could maybe predict what, you know, two raindrops are going to do, but not a whole hurricane. And you can predict throwing a ball because that's, there's a limited number of things acting on that. But the more complicated it gets, the more we're like, ah! Yeah, exactly. Sometimes simplicity emerges, right?

And sometimes it doesn't. And when it doesn't, the reason is chaos. Like you have two raindrops, you can maybe describe it. You have 10 to the 20 raindrops. There's too many interactions, and the outcome is very sensitive to how those raindrops started, the direction they were going, and no simplicity emerges. It just gets more and more complicated as you add raindrops. But sometimes simplicity does emerge.

You have 10 to the 26 particles moving across your backyard. They pull together and they follow a simple parabola. Hurricanes don't follow simple parabolas. And so because we don't understand why it ever happens, right, and why it doesn't always happen, that tells us that we're not sure if it's a part of the universe, like, is the fact that we can attack the questions of the universe and make some progress at some levels without knowing what's going on underneath and we can make chicken soup without knowing quantum gravity? Is that because that's just how the universe is? Simplicity emerges and we'll figure that out why that is at some point. Or is it part of our minds?

Is it the way that we understand and filter the universe? Is it some selection we're making that we're like, we're going to choose this thing to focus on, ask questions, and do science? And we're going to choose that thing. Is it an interplay between our brains and the universe, or is it only part of the universe? And that's the kind of question we could answer if we had alien brains, right? Which worked differently. And maybe they saw different things emerging.

Or maybe they saw the same. We just don't know where the line is between the human and the universe. Alternative idea. We put a ton of money into trying to make bats, which echolocate, and bees which see in more colors. We try to make all of them have advanced intelligence and then see what they come up with, because now we'll have different ways of looking at the world, and we've discovered that biology needs more money. For physics sake. Oh, I see.

Right. Yes. Okay. In the end, it's all just a scheme. Yeah. Nice. For big biology. I'm schemy.

Okay, so is the idea here, then, that, like, if we could dig down and understand everything at exactly the base level, and then we could scale up and understand the hurricane, would that make us feel like we had discovered something, or would we still just be inventing because we just managed to describe what happened instead of necessarily knowing why? Yeah, great question. And that's the temptation. And, you know, I'm a particle physicist. That's my goal. It's like, I want to drill all the way down to the base layer of reality and find out what. What are the bits there? Because philosophically, that feels like that's a moment of possible revelation.

You force the universe to tell you, okay, I'm naked now. Here are all my basic components. Now you've seen the reality of how things work. Everything else, how things come together and make baseballs and marching bands and whatever. You know, that's more complex science. That's basically chemistry. But, you know, the fundamental physics is about the fundamental things in the universe. So, yeah, if we drilled all the way down to those, wouldn't we have those in common with aliens?

can we avoid all these questions of like, what's emergent and why? Well, the problem with that is we don't know if there is a fundamental layer. You know, I think about our theories as sort of like a tower. We have this tower of effective theories at different scales, like zoom all the way out. We have like theories about how galaxies work. Zoom a little bit in. You have theories about how planets form. Zoom a little bit more in. You have like classical physics of the everyday. Zoom even more. You have chemistry. Zoom even more. You have physics. Zoom even more. You have physics. Zoom even more, you have particle physics. You could keep zooming, and at every level we have a theory,

do we know that there is a foundational truth, like a base layer to reality? We haven't found it, right? We just got to get to the Plank Scale. Well, we definitely got to keep going. But the problem is, number one, we have no guarantee that there is a fundamental layer. And I hear this all the time.

Plank scale is the pixel of reality. And Elon Musk likes to say it. And it's sort of out there in the popular science world. that we somehow know that the plank scale is the layer, the finest grain we have of reality. And that's just fundamentally a misunderstanding. The plank scale is the point where we can no longer ignore gravity when we do our quantum mechanical calculations because things are so hot and so dense. And we can no longer ignore quantum mechanics when we do our gravity calculations,

because things are so small and the particles are now relevant. And so it's just the point beyond which we can no longer calculate. It's sort of like an intellectual horizon, right? We don't know anything about what's below the plank scale. I remember the plank scale is not even like a solid estimate of these things. It's just like, let's take a bunch of constants and mush them together until we get a distance. That's not like a reliable way to estimate things. It's what you do when you have no idea how to answer a question on a test.

You're like, I'm just going to guess the units and see what numbers I can mush together to get the right units. Maybe this is close. I hope it's within a factor of 100 or 1,000. So the plank scale is no guarantee that the universe has a fundamental layer. And if you talk to philosophers, they think it's just as likely to the universe is what they call gunky, right? That everything is made of something smaller. Nothing is made of itself. And immediately, you're like, what?

Come on. How could that possibly be? But actually, if you think about it, it's the more natural explanation. Everything we've ever seen has been made of something else. So why would we expect there to be something, which is just made of itself? It feels sort of like, you know, the cause that needs no cause. You know, it's a bizarre philosophical construct, and we assume it's natural, even though we've never seen it in the universe.

So this is the kind of stuff where you really got to ask yourself, hmm, why do I accept this explanation and not that other explanation when I have no evidence and not even really great arguments for it? Right, so you're saying that we might be just digging down and down and down and down at infinitum? Yeah. It could be that it goes on forever, right? That it's just smaller and smaller and smaller down infinitely, right? An infinite tower of effective theories, an infinite tower of emergent phenomena.

And so we can't shortcut this question by saying, we're just going to zoom down to the fundamentals and talk to the aliens about the sproings or the springs or the shmings or whatever is down there at the fundamental layer, because we don't know that there is a fundamental layer. Do you think they'll stop giving out Nobel Prizes eventually if it turns out there's just like infinite fundamental layers and they're like, you know, Kelly found the 20th one, Daniel found the 25th, array. Oh, in this scenario, you're a particle physicist who's discovered some fundamental layer of reality?

Love that. Welcome aboard. I'm a biologist, man. I can do anything. Thanks. After you win the Olympics, right? And I'm going to hang this Nobel next to my Olympic gold medal. Wow.

Wait, has there ever been anybody who won an Olympic medal and a Nobel Prize? Oh, Philip Noel Baker is the only person who has won both an Olympic medal and a Nobel Prize. Amazing. It was for a race in the 1920 Summer Olympics. I mean, things were easier then. That's an incredible achievement. Congrats, dude. I think he's passed away.

Yeah, so it could be that particle physics is just a big grift for, Infinite Nobel Prizes. Yes. That's the answer to your question. Oh, great. Okay. You've forced me to reveal that on air. Thank you.

Amazing. Amazing. Well, yeah. Good. My work here is done. All right. On the next episode. No.

So now imagine, right, we have this tower of effective theories that we use to describe science. We have chemistry. We have physics. We have particle physics. We have subatomic particle physics. And the question then is like, well, if there's no firmament in which to ground these, things and we don't know why these things seem to emerge to allow us to explain them, why they're not just like totally intractable, then do we know if aliens would or wouldn't find the same

tower of effective theories? Like, you know, the skeptic in you might say, well, look, you know, planets are obviously a thing. Aliens are going to think about planets, you know, orbiting stars. Like, let's not get ahead of ourselves and get too deep in the philosophy that we imagine that like aliens don't observe planets and come up with Kepler's laws, right? Right? I think that's like an intuitive argument people might make to feel like aliens are going to see the same stuff as we. But they're probably going to call it Zorblacks's laws or something, you know? Yeah, exactly. And that might be, right? And I don't want to say that that's impossible. But I do want to open your mind maybe a little bit to the possibility that they wouldn't see planets.

Think about why we think about planets. And does it actually make sense to think about planets? Because in reality, the solar system is a big spectrum of stuff. You know, you have the sun and then you've got a bunch of other little blobs. And those blobs go all the way from Jupiter down to dust specs. And humans, we like to categorize things. Right? We like to say this is A and this is B. And historically, we saw a few different kinds of things. And so we started making boxes. But also, we've seen over time that those boxes don't really make sense that our categories of stuff are sort of arbitrary dotted lines that we draw around things. And not just randomly, we draw those arbitrary dotted lines in a way to make ourselves more important. This whole concept of planets that we argued with Phil Metzger about it recently on the podcast, does it even make sense? to have this category. It's obvious to me because this category has become so baroque. They have to add so many qualifiers. It has to have cleared its path. It has to be gravitationally round. They're reverse engineering this category because we like it. We want there to be a special category of things that seem important and that are relevant to us. But if you're going to take

a hard, objective, scientific eye to the solar system, you might never come up with this special category of planets. You might just think about the whole spectrum of things. You might just think about the whole spectrum of things and not focus on Earth-like things at all. So would you argue that definitions are, I mean, they're certainly invented. Yeah. Is a definition ever discovering the nature of the universe? I guess it's always just our way of grappling with stuff. I think definitions are helpful, but categories are often very arbitrary and lead you down

the wrong path and make you think something is special or something is different. When in reality, there's a spectrum, you know? Think about gender. think about like, you know, the platypus, right, which is like, what? And in these categories, they're helpful for organizing your thoughts, but you got to remember that there are things we impose on the universe. They're not always things that emerge naturally from the universe. And that's the point I want to make is that even things that we feel like we are just observing have a lot of our cultural bias in them. I mean, think about the way we represent the solar system when we

draw it out, right? Like, it's not representative at all. We take the planets and we like magnify them by huge numbers to make them relevant, when in reality, they're pretty irrelevant. The solar system is basically the sun plus a few drops of gas, right? So it's obvious once you drill into it, that there's a lot of humanity in our choices of what to study and think about in the universe. And so it might be that aliens have made different choices, that they grew up in the atmosphere of a star, and they're like, planets, schmanitz, who cares? Or maybe they evolved in a subsurface ocean on a moon.

And so to them, like, who cares at all about planets? Maybe they think about things fundamentally differently. All right. Let's take a break. And when we get back, we will answer the simple question of whether or not there is a truth at all. Hey, I'm Cal Penn. And on my new podcast, Here we go again. And we'll take today's trends and headlines and ask, why does history keep repeating itself?

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Right. Yes, we're just going to wrap up a millennia-old philosophical conversation here on the pod today. So so far we've been talking, as part of the larger question of like, is physics discovered or invented? We've been asking, like, could you have several maps of the same territory? But it always in that sense assumes that there is a territory, that there is fundamentally something that's going on. And I heard the sentiment in the listener's responses, right? well maybe our description of the universe is human but there's something going on and so let's question that assumption like how do we know that there really is something going on out there in the universe one

truth whether or not we're discovering it or describing it or approximating it right how do we know that there really is something that's going on out there and when i first started digging into this i thought well of course there is right something is happening in the universe and there has to be a reason why stuff happens, right? But not surprisingly, philosophers have responses to that, and they've thought about ways that might not be true. Because remember that all of our descriptions of the universe, they are approximate, right? Because we can't do the really complicated calculations. Like we talked about earlier, we can describe a couple of raindrops. We can't describe the hurricane. Or we can't describe like a bunch of hurricanes smashing into

each other or really complicated situations is always going to be something that we cannot describe because all of our laws are approximate, right? They only apply in certain situations. Like, for example, take fluid dynamics, right? Fluid dynamics works really well. It helps you think about how water flows down pipes. But we know, number one, it's not a fundamental description of the universe, right? It's a description of an emergent phenomena.

But number two, it's only valid in certain situations. You freeze that water, you no longer going to apply fluid dynamics. You turn it into steam. You're no longer going to apply fluid dynamics. In that same way, everything we can do about the universe has boundaries where it's relevant, right? And you go beyond those boundaries, you can no longer use your fluid dynamics or your chemistry. Even fundamental physics, right, quantum mechanics and gravity are only relevant down to the plank scale. And beyond that, who knows where the laws of physics are?

So there's a school of philosophy that says, hmm, how do we know there are laws of physics beyond those boundaries? maybe instead of imagining that we have this patchwork of theories that eventually we could stitch together to describe the truth, maybe between those patches, there's nothing. So Nancy Cartwright wrote this book called How the Laws of Physics Lie. We're like, wow, bold title, right? And she imagines the universe where between these patches, where things get complicated, that maybe what happens happens by hap. That's her phrase, that there is no fundamental rule.

And, you know, every instinct in me, every fiber of my being says, no, that's crazy, right? The universe follows laws. But then I ask, well, how do I know that exactly? I only know that because it seems to work in simple situations where I can set up a simplified experiment and I can do a calculation to predict it. And that's really what experiments are. It's ways you've, like, tricked the universe into only doing. something simple enough that we can calculate it. That's the whole job of experimental physics is to

concoct these artificial scenarios where things are simple enough for us to predict. Most of the stuff that happens in the universe, from, you know, like tiny particles to hurricanes to even like the leaves swirling outside my office, we could never hope to calculate. So how do we know that it follows rules? If you're going to be a skeptic about it, you've got to say like, hmm, I guess we actually don't know, right? It could be that when things get complicated, there aren't laws that are being followed. And I don't believe that, but I don't have a scientific reason to not believe it. Yeah, my brain has trouble wrapping itself around how that could possibly be true, but that might be the limit of my imagination. Yeah, and I think even Nancy Cartwright probably doesn't like believe this

in her soul, but it's a very valuable exercise to think, well, is it possible for the universe to be different from what we expect at some deep fundamental way. Because historically, we've seen that happen, right? The universe turns out it violates lots of our intuition. You know, the way things operate near the speed of light or microscopically, the fact that cause and effect has a stochastic element to it. These things, we would have been rejected out of hand, right, initially. Like, that's crazy. There's no way the universe works that way. And yet it does. And so we do need to be prepared to have our minds blown. And that's the whole joy of this exercise, is to imagine, like, What if aliens show up and they tell us the universe is really fundamentally different from the way that we expect?

That's why we want the aliens to show up, to shock us, to reveal an amazing mind-blowing truth. And, yeah, it'd be kind of disappointed to discover that the laws of physics only apply in simplified situations. And beyond that, there is this darkness, right, where the universe doesn't follow laws. But we don't know that it's not true. I feel like if the aliens came and they were like, nah, you're. you guys are totally wrong. Like, I mean, it would be, wouldn't it be decades before you could convince yourself that they were right instead?

Would you, like, if the alien said, Daniel, you're wrong, would you just be like, all right, I'm throwing away everything we know? The alien said so, and I'm a super fan. Yeah, that's a really fun question. So in the book, I actually imagine a bunch of different alien contact scenarios, and one of them is that exact one. The aliens show up and they have a competing theory of physics. And in that hypothetical example, I imagine that some humans are like, oh, you know,

So our theory never made sense to me. I really like this alien idea. And they go over to the alien camp. And some aliens are like, oh, you know what? I really prefer the human way. And like people have different ways of thinking, the way that some people need to see something written out and other people need to hear it or some people need to play with or some people need to play with. Or some people need to play with. So maybe some people will find the alien description of the universe more intuitive and easier to play with.

And other people will feel the opposite. It would be fascinating how that breaks out. it would. I hope I'm alive to see it. Another objection people make to the idea that we could be getting physics all wrong or that physics could have a lot of humanity into it is the idea that you raised at the beginning of the episode. You know, what if we have a bunch of data and it describes the universe? Doesn't that tell us that our theory is right? And this is this question of uniqueness, right? Do we know that there has to be one explanation for the universe? And earlier we were giving the

examples of having a superseded theory. Like, well, maybe you have a theory and it works for now, but then later you get more data, so you got to toss out that theory for a new one. That's cool, and that's almost certainly what we're doing today, right? That in the future, we'll have a theory of quantum gravity that tells us a different story about what's happening in the universe than any of the stories we have now. So we'll toss out our whole explanation for what's really out there and come up with a new one. Cool. But what if we find the fundamental day of reality? We discover it and we explain it. And we have a thing. theory that works perfectly and incorporates dark energy and dark matter and the expansion and

everything and all of our questions are answered and it tells us this beautiful story about what's happening then aliens show up could they have a different theory that explains the same experiments could they have done the same experiments made the same observations but draw a different line through the same data points the answer is philosophically yeah maybe because you'll never have infinite data and even if you did you could always still draw two different curves right just imagine like plotting a bunch of points on a piece of paper, how many curves could you draw through those points? An infinite number, right?

Make the curve as complex as you like. You can draw an infinite number. And so we never really know if our explanation is the only one. And this is something philosophers are deeply debating. Like there's a bunch of philosophers who say, look, if you have another theory that explains the data equally well, it's got to be equivalent. You know, it's got to be like the same theory dressed in different. clothes. And they point to good examples like, we used to have a wave theory of quantum mechanics

and a matrix theory of quantum mechanics, each derived by a different German guy and those two guys disliked each other and called each other's theories crap. And then later, John von Neumann brought them together and said, look, guys, these are actually the same theory. I can draw connections between them and prove it. Or we used to have a bunch of different string theories until Ed Witten showed they're actually just extreme points of the same M theory, right? Or we have like Hamiltonian mechanics and Lagrangian mechanics, two different ways to think about complex physics that are fundamentally the same. So isn't it just like that? Maybe the aliens have a different description, but you know, you can make connections. We don't know, right? We don't know if every theory has to be

that way. And another group of philosophers say that there might be another explanation that it's possible to have another theory of physics that doesn't map over, that is conceptually different to our theory. But we don't know, right? We don't have that theory. We don't have a rest of for building this alternate theory. So it's just like a speculation. It's an argument we don't know how to defeat, which means it might be possible. Okay, so if we ended up discovering a theory of everything

and we felt like we had it all figured out, I was going to ask you if you would put up a giant billboard saying, never mind aliens, we got it all figured out. But what you're saying is you'd be interested to see if they had a different way to describe everything. But some philosophers would say, well, that doesn't really matter because it's, fundamentally going to be the same theory, even if it's wearing different clothes.

There's no scenario in which I'm putting up a billboard saying, aliens, never mind. No scenario. But yeah, if we have a theory of everything and they show up and they have a different theory of everything, then that's fascinating, right? Because even if it is fundamentally the same, you're still learning something mathematically or philosophically. And if it's fundamentally different, if you can't make a connection between the two, boom, that tells you something mind-blowing about the universe, that you could have two different maps of the same territory that both work, then like, is there really a territory? What does that say about our sense that there is an objective physical reality that's out there, that doing things following some laws

that we're figuring out? Like, maybe that's not the case. Maybe things are more complicated or weirder than we imagine. So I'm always in the camp of hoping for the weird, surprising outcome. Daniel, I really hope you get your aliens one day. I hope I do, and I hope that they don't nuke us from space before they tell us the answers to all of these questions. You are a weird one, Daniel. And this is just a taste of all the concepts we describe in the book. Do aliens speak physics, where we do a really deep dive into these questions? It also includes a bunch of really fun cartoons for my friend Andy Warner, who helped me write the book,

and little hypothetical case studies to examine concrete scenarios where aliens could show up and be weirdly different in ways you might not expect. So if you enjoy these questions and enjoyed this conversation, there's lots more in the book. Go check it out. Do aliens speak physics? You can get it at www.alienespeakphysics.com. And I think if aliens do come to visit the U.S., this book is going to be the first thing they grab. Travel across the cosmos for this book? Totally makes sense. Worth doing.

I hope they're not offended by our depictions. Daniel and Kelly's Extraordinary Universe is produced by IHeart Radio. We would love to hear from you. We really would. We want to know what questions you have about this extraordinary universe. We want to know your thoughts on recent shows, suggestions for future shows. If you contact us, we will get back to you. We really mean it.

We answer every message. Email us at Questions at Daniel and Kelly.org. Or you can find us on social media. We have accounts on X. Instagram, Blue Sky, and on all of those platforms, you can find us at D and K Universe. Don't be shy. Write to us. Hey, I'm Cal Penn.

And on my new podcast, here we go again. We'll take today's trends and headlines and ask, why does history keep repeating itself? Each week, I'm calling up my friends, like Bill Nye, Lily Singh, and Pete Buttigieg, to talk about everything from the space race to movie remakes to psychedelics. Put another way, are you high? Look, the world can seem pretty scary right now. But my goal here is for you to listen and feel a little better about the future. Listen and subscribe to here we go again with Cal Penn on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Hey, I'm Kyle McLaughlin.

You might know me as that guy from Twin Peaks, Sex and the City, or just the Internet stand. I have a new podcast called What Are We Even Doing, where I embark on a noble question. to understand the brilliant chaos of youth culture. Each week, I invite someone fascinating to join me to talk about navigating this high-speed rollercoaster we call reality. Join me and my delightful guests every Thursday. And let's get weird together in a good way. Listen to what are we even doing on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. The Big Take podcast from Bloomberg News keeps you on top of the biggest stories of the day.

My fellow Americans, this is Liberation Day. Stories that move markets. Chair Powell opened the door to this first interest rate cut. Impact politics, change businesses. This is a really stunning development for the AI world and how you think about your bottom line. Listen to the big take from Bloomberg News every weekday afternoon on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts.

Chicago. A white woman's murder, a black man behind bars, for a crime he didn't commit. 90 years of killing somebody I have never seen. The Crying Wolf Podcast is the story of a corrupt detective, two men bound by injustice, and the quest for redemption, no matter the price. Listen to the Crying Wolf Podcasts on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. This is an IHeart podcast.

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