Daniel Whiteson on Space Itself

thanks so much for having me on. Great to be back. Um. I'm Daniel Whitson. I'm a professor of particle physics at u c Irvine down here in southern California, and I'm also the co host of the podcast Daniel and Jorge Explain the Universe, a podcast with my good friend and collaborator Jorge cham in which we talk all about the craziness of the universe. We try to answer questions, We try to share the wonder and the mystery of the uni verse in a way that makes it accessible and

hopefully a little bit fun. Well, we really appreciate you joining us today, Daniel. So I wanted to invite you onto stuff to blow your mind today to talk about space. This is actually a subject I've I've wanted to tackle on the show for a while with uh, the unifying question of what is space? Why is there such a thing as the distance between the Earth and the Sun, or between an atomic nucleus and the electron that orbits it.

Because I think a lot of the time when we think about physical reality, we just immediately look past space to the things that occupy it. We we assume space as a kind of given, a de facto canvas on which physics can be realized. But I wanted to think about space itself. What is it? How does it exist? Do we know anything about where it comes from and

where it's going? So maybe the easiest way to start off today would be to to get as simple as we can so in simplest terms in a sentence, if you could do it, how would a physicist define space? While all of space in one sentence? That is a pretty tall order, you know, I have to say, to be honest, I'd have to say, we really have no idea what space is. I mean, I think it's wonderful

that you're asking this question. It's the kind of question that it takes like a sort of maturity of science and philosophy to even understand why the question is interesting and important. You know. It's like it's like we're have been fish scientists for a thousand years swimming through this fluid, and then only recently have realized that it's it's something fascinating, something to study, something that has property, something can do weird things. And so it's a it's a deep and

important question, you know. And and just to digress a tiny bit more like it makes me wonder how many other crazy basic questions we aren't even asking because we don't realize how rich the topic is, you know. So I feel sort of privilege that we're at this moment in science when we can ask this question what is

space and understand that it is an important question? Alright, So I totally dodged your question there, But I could try to give a one sentence answer if if you'd like, sure, we'll start simple and then and then we'll get more into the nuances here. All right, Well, a simple answer to what is space? Is that? Oh man? I mean I could try to maybe impossible, um, I'd say the simplest description I could give for what space is is

something which has various properties. We've discovered it can contain quantum fields, it can expand, and it has relationships to other parts of space. And so that's more a description of like what we've what we've observed about space. It's not really an inherent understanding of what it is because we don't have that understanding. Well, maybe this brings me to a question I wanted to ask later on. But if there is no good answer to this, it can

help ground us as we go forward. So I wanted to ask, is there such a thing as even a hypothetical physics without space? Does all physics assume space? And can we imagine, say a possible world that exists but does not contain space, or is that just inconceivable? Now? I think that all physics that we do assume space, Like all of our modern theories, the standard model and

quantum field theory, they all operate in some space. And there are different kinds of theories that we have, and some of those make different assumptions for what that space is. Like quantum field theory, you write down with the spaces in advance. You say I'm gonna assume space. You know is three dimensions and extents in all in all these directions, and then I'm going to talk about the fields that

are in that space. Other theories like general relativity. Space is a part of what you're sort of trying to get at. It's not like the backdrop. It's the thing you solve for. You say, if I have this configuration, then what does the space look like? But they all assume space. I mean space gives you a relationship between stuff, right, tells you this is here and this is not here. And in the end, all of our theories are trying to understand the world we live in, and everything we

live in has space. So it's pretty hard to grapple with a non spatial theories or non spatial physics. So yeah, I would say that we need space, okay, But so if we could come at it from the exact opposite angle you think, you you couldn't really have a physics without space. Could you have a universe full of space with no matter of energy in it? Could space exist without any contents? Could space exists without any contents in it? Yeah?

That is an awesome question, and it's fascinating because we have two theories of physics right now, quantum mechanics and general relativity, and they're both awesome achievements, staggering insights into the way the universe works, and they give different answers to this question. Right, So general activity um is Einstein's theory.

And he has a bunch of equations. Let's say, what the universe look like depending what you put in it, and he has and one of the and it's really hard to solve, like, there's very few ways you can actually solve these equations. One of the very few ways you actually can get an answer out is what they call the vacuum solution, like to say, assume there's nothing, then what does the universe look like? If there's nothing in it? All? Right? Einstein can solve that problem quantum

field theory. Though, quantum field theory says, hold on a second, um space is filled with all these quantum fields and particles and matter and all the stuff that you make me and you are just like excited states of these fields. So when you look at an electron, it's not a particle, it's not a wave. It's a little ripple in some field which is not in space. It's part of space. So if all these fields. You have the electron field, the electromagnetic field, all the fields associated with each of

the forces. As lots of them. We can talk about them later if you'd like. But some of them never relax completely. Some of them are always have some energy in them, for example, the Higgs field. The Higgs field is in every part of space, and it's always got some built intention to it, and that means that there's energy in every part of space. So quantum field theory says, no, you can't have space without some energy in it. There's some inherent energy to space, where the general relativity says,

I could totally imagine it. And we don't know which theory is the fundamental, true theory of the universe. If either one, we can't seem to make them play together very well. And so this question really goes to the

heart of the nature of reality itself. It's fascinating. It's the kind of thing that in five years physicists will know the answer to and look back at us and be like, oh, man, those people didn't understand anything about the nature of the universe they were living in, right, What a bunch of cave men and cave women like they were subjignary misses. So I love that idea about

quantum field theory. And if I understand this right, you're saying that under the assumptions of quantum field theory, you could have a big block of space, and even if you were able to clear everything out of it, clear out all the hydrogen particles, clear out all the dust, so there's no matter left in it, you'd still you still really wouldn't have an empty void. Is that correct?

That's right. Every unit of space comes with energy built in it comes from the factory with energy already in it, and um and and lots of those fields cannot cannot relax. The Higgs field is one example, but many of these fields cannot relax all the way down to zero. And so it's impossible, according to these quantum theories, to have space with no energy density in it at all. And that means and that's stuff, right, All stuff is is some kind of energy, like the matter that makes it

me and you. That's just a form of energy. So to say that this space has energy in it really means it's not empty. So what you're describing space as really goes against a lot of our intuitions, where you know, I think the standard understanding of empty space what's out there beyond Earth, you know, even if you could clear all the hydrogen and dust and everything out of it, is that it's just this empty relationship between two points.

But you mentioned, of course, the the idea that there, you know, quantum fields that can be excited and can give birth to particles and stuff. Well, I might be putting words in your mouth. There is that correct though. Yeah, okay, but earlier you mentioned also that it has other properties, So it sounds like you're saying space really is a thing. It's almost like a substance of a kind. Yes, space

is a goo. Right. We first imagine space sort of as a place to hold our ideas, right where like maybe when you think space and you think a deep space, you imagine some like glowing x y z axes that used to like the backdrop on which maybe your calculations take place or your spaceship flies through or whatever sort of. But they're like mental metrics we use to understand where things are. That sort of the initial idea of space.

But then it turns out the space can do things that are inconsistent with that, right, Like space can ripple we've seen gravitational waves. When black holes orbit each other and eventually collide or other things happen, they create these ripples in space itself. These ripples, they're space getting stretched and space getting contracted, right, squeezing and shrinking and then expanding again, and very very very small, which is why they were hard to discover. But yes, we've discovered that

space can do things. So it can ripple, it can expand, right, We've talked about the expansion of the universe, the universe expanding its first moments, and it's continuing to expand. In addition, space can bend. Maybe the most familiar example is understanding gravity as distortions in space by having mass nearby and and so space can do all these things that nothingness cannot do, that a backdrop cannot do. You can't just think of spaces like the theater of the universe. It's

a weird dynamical thing in itself. Yeah, I think in general our listeners are going to be more familiar with the idea that space can can bend in accordance with general relativity. There's a big object, you know, and that creates curvature, and in spacetime it's a little bit harder to picture exactly what's happening with the first thing you mentioned with the ripples through spacetime. So that's something that would be like, that's like how we detected gravitational waves, right,

is that correct? Um? So what what exactly is happening when a ripple goes through space? Like? How do how do you measure that? What? What is that in the moment? Right? Well, you know, a ripple through space is information propagating through the gravitational field. Something that's very important that came out of general relativity that we didn't have with Newton's gravity is the concept that information takes time to move gravitationally. Like if the Sun disappeared, would we feel the Sun's

gravity instantly disappear or would it take a moment? Turns out Newton says it would go away instantly. Einstein says, no, you wouldn't even notice for eight minutes because the gravity from the Sun would take The information about the Sun being gone would take eight minutes to get here gravitationally, And so that's propagation of information. And so gravitational wave is a special form of that. Say you're familiar with the concept of like putting a mass and that deforms space.

We'll imagine you put a mass in space, and then you take it away, and you put it in space, and you take it away, and you put in space and you take it away. What's going to happen, Well, you know it's not gonna be very pleasant for the occupants of your space. They're gonna get jerked around, right, It's back and forth and back and forth. And that's sort of a more dramatic version of what happens when

two black holes orbit each other. Is they're creating ripples in this gravitational field, and you feel those as stretching and squeezing of space itself. And we measured that here on Earth by having really long rods essentially and watching them shrink and expand shrink and expand. With those north there would be like lasers that you would use to measure that. Yeah, the practical way you measure a very small change in the length of a long rod is

that you don't actually of the physical rods. That was the first thing they tried, actually did that here, you see, I Jo Webber did that, and it's because he had no idea like maybe this is easy to spot right, let's just build a big block of metal and see if its shrinks and expands. I was gonna say, what was it made out of? Yeah, it's just a big cylinder of metal. Um. But nowadays they're miles long and their laser and they use lasers to measure the length

between two isolated mirrors. And I think that the biggest misconception people have about space being bent by mass is that they're used to this rubber sheet analogy where you have like a big rubber sheet and you put a bowling ball in it and it bends space. And the bowling ball is supposed to represent the sun and the rubber sheet is supposed to represent space. And that's helpful up to a point because it gets you to think about space being bent instead of flat. But it's also

I think confusing. And the way it's confusing is that it's bending in some sort of third dimension, right, and that analogy space the universe is two D and you put some object in it and it bends in some third dimension. But our space it's three D. First of all, when you put a mass in it, it doesn't bend in some fourth dimension. It's not like our space is embedded in some higher dimensional space and then it gets

bent in fourth dimension. It's an intrinsic bending, not an extrinsic It's not like there's somebody out there with a true set of rulers in four D space and they're noticing our space being bent. It's an intrinsic bending, which means it just changes the relationship between points in space. Right it says, Okay, now that space, that bit of space is closer and this bit of a space is

further away. Wow. So I've never thought of it that way. So, so you're saying that the gravitational influence of a large object like a star is in some literal sense shortening the distance between points of space as you get closer to it. Absolutely. You know, massless particles like photons travel not in straight lines. They travel along geodesics, which means the shortest path through curved space. Now out in the middle of nowhere, there's no mass anywhere that happens to

be a straight line. That's why it seems like photons travel straight. But photons can also be bent by the sun. How does that happen? Photons have no mass, right, Well, the the Sun is changing the shape of space, so that the shortest path from A to B is no longer what we would consider a straight line. It's a geodesic.

It's the shortest path. And so general relativity and mass changes the relationship between space between here and there, and um, that's what we maybe you hear people talk about like the spacetime metric that relates like how bits of space are connected. So this is sort of the biggest conceptual leap to make from the rubber sheet analogy to our actual three D space, which is that it's an intrinsic bending. It's a relationship between points in space, and that's what

a gravitational wave is doing. Also, it's a ripple in this metric as it passes through space, and it's saying, oh, these things are now closer together, now the further apart. Like you can change the distance, but weeen two things without those things moving relative to each other, right, because

you change the relative distances. Well, it almost makes me think in terms of how this is communicated to non experts, that would maybe be better to not use terms like bending of space and maybe more like compressing or squeezing of space. Yeah, but space can also be expanded, right, like what we're seeing in the universe right now is that space is expanding, which is crazy. It's like something out there is manufacturing new units of space all the time.

It's filling the universe with new space. Like that's that's the hardest thing for me to get my mind around. It's like where this new space is coming from, what it means to make new space? And are you making units of new space? There's space continuous and smooth and like, man, there's so many questions. Oh well, I want to talk about that. Maybe we should take a quick break and then when we come back we can explore the expansion

of space. Sounds good than all? Right, we're back. We're talking with Daniel Whitson about space, the nature of space. That's right. So before we went to the break, Daniel, you just introduced the idea of the expansion of space. As we've we've been talking about the properties of space as a as a thing and not just an emptiness. Uh. And so of course we know one of the things

that space is doing is that it's expanding. Uh. I think we all know now that the universe as a whole is expanding and maybe expanding at an accelerating rate. If I've got that writing, comment on that in a second. What exactly does it mean for space to expand? Because I think from an intuitive level, people might think, well, I don't notice space expanding, Like I don't notice it doesn't seem like the space in between the molecules in

my body is expanding. So so is space in general expanding or is it just say, the distance between galaxies is expanding. What form does that expansion take? Yeah, it's a great question. I love the intuition there. You know. The idea is like this thing is supposed to be happening everywhere in the universe. Kind of sort of reconcile that with my experience. Can I see that happening around me? And you know, like a few hundred years ago, that was a big conceptual leap to say like the rules

of the universe should also being applied here. Um. So it's a great question. And and the short answer is that space is expanding everywhere, Like every unit of space is the same. It's homogeneous as far as we understand. There's no difference to this chunk of space and a chunk of space out there in the deepest voids between galaxies. They're all the same from the point of view of the universe, and they're all expanding, which means they're all

creating new space. But that's not the only thing happening, right. You are made of a mesh of atoms that are held together with pretty strong bonds, and this expansion of space is dramatic, but per unit of space, it's pretty small. Like there's not a whole lot of space being made

between me and this microphone, for example. It adds up when you get to like cosmic scales between me and the galaxy, because there's a lot of space between us, but here on the small scale, it's not very powerful, so the bonds in my body are strong enough to hold me together. The same thing said for you know the reason why you're staying on Earth. You know, Earth is holding you down because if it's gravity, that's enough to overcome this expansion of space, and Earth is bound

gravitationally to the Sun for the same reason. The space between us and the Sun is expanding, but the gravity the Sun holds us there. It's like if you were sliding away from somebody on an ice sheet, but they had a rope around you, and so they were keeping you at a fixed distance. Okay, so there are forces within our bodies, holding our bodies together that are counteracting that expansive force. But I'm trying to imagine what exact

form does that take. So does that mean that the say, the bonds between the molecules and our body holding them together actually prevent the space from expanding there so it doesn't expand, or does the space somehow kind of roll out beyond us without affecting our you know, our bodies as it does. So you can't stop the expansion of space,

but you can't and keep your constant distance. If those bonds were deleted, then all the items would sort of drift further and further apart, but instead you have these bonds holding them together. And so it's more of that the answers the latter, that space sort of rolls out past you. So space is emanating from us at all times. Yeah, it's sort of like we're in a pool of space that's expanding larger and larger, and we're a smaller and

smaller dot inside of it. So as a result, you know, the universe is getting getting more and more dilute, like the matter energy density of the universe decreases with time because there's no more stuff being created, but there is more space being created all the time. And so that's really like the way to think about the whole expansion of the universe since the Big Bangs, that the universe

didn't start out small. It started out dense. It was like compressed and hot and nasty and wet, and then the Big Bang is just this rapid dilution of space into something much more sparse, and then that's just continued. The universe has just gotten more and more cold and dilute and spread out as new spaces being created and these little chunks of matter desperately clinging to each other

to avoid being totally isolated. And I think there's another part of your question which I think is fascinating, is

like at what scale does that take over? Like you hold yourself together, Yeah, the Earth holds onto you, the Sun holds onto the Earth, the galaxy holds onto the Sun and all the stars, and dark energy is probably not going to rip apart our galaxy, and even the neighboring galaxies like Andromeda is going to collide into us, and the direct gravity these two galaxies are going to smash them together, and the group of galaxies is mostly

gravitationally bound, and that's the biggest sort of gravitationally bound thing. Beyond that, things are not tightly connected enough by gravity to resist dark energy. And that's so it's these groups of galaxies that are getting pushed apart and getting further and further away because there's nothing really to resist the

dark energy push. Okay, So the reason then that you would normally see the expansion of the universe expressed in terms of like the separation of what galaxy clusters or what it would be that that's where gravity is no longer strong enough to hold back against it. And it's not just the amount of distance, you know, causes the uh causes all the expansion to add up there, That's right,

It's it's both things. I mean, the the amount of distance makes it more dramatic, and the distance makes gravity weaker. And so what you think which happens if you sort of project the universe forward billions or trillions of years, is that these gravitationally bound clusters continue to contract and hold themselves together, but they get more and more distant from everything else. So the future is is islands of stuff separated by even more vast distances of space. It's interesting.

So all of this talk about space as a substance and having all these properties that we can measure and not just as a you know, uh, the void or the distance between things is uh somehow on on one level, kind of makes a lot of these like sci fi plots where you manipulate space itself with technology seem more plausible. Robert, I think you had some questions about this, maybe right, yeah, yeah, this this got me thinking, you know about the expansion

explosive expansion. H Daniel, what do you make of the notion that faster than light travel could essentially be achieved by some manner of of work bubble manipulation moving the space containing the ship rather than the ship through space alone. Oh, I'm ready to invest in your work drive company for sure. UM. I read a lot of science fiction, and um, I

love these ideas. And there's a lot of bolognay and science fiction where they just like slap quantum mechanics on a plot hole because they don't really know how to think about it. But I give people a lot of flexibility when it comes to space because we really don't know what he can do. And there's a lot of opportunities there for new ideas. And the one that you mentioned I think is is a great um idea and

it's not just science fiction. I think it really could be that we could develop a warp drive that that gets us two distant stars. You know, there's one very hard and fast rule about the universe, which is you cannot move through space faster than the speed of light. But you've gotta be a bit of a lawyer about it, right, You're gonna be like, what on a second, you said move through space? Right? That's fine, so you can't travel through a light year of space in less than a year.

But what if you didn't want to move through space? Right? What if you squeeze space itself? Right? Or if you stretch space? And that's the basis of these warp drive ideas is to get around it by saying I don't want to go all the way to Alpha Centauri. I want to squeeze the distance between here and Alpha Centauri.

Or I want to create this warp bubble which continuously is like squeezing the space in front of me, so I can move really really fall What what what would have been otherwise really far in a short amount of time, and and that way you can get somewhere which would have taken light a long time to get there, but it only takes you a few moments because you've effectively shortened that distance. So I think that's totally plausible. Um,

I think it's far, far beyond our abilities. You know, it's sort of like this moment when physicists pass things off to engineers, you know, like we're interested in is it totally possible or totally impossible. Once we decide it's probably possible, then it's a practical question of like how do you focus that much energy in order to accomplish that? How do you actually build something which does this? And

that's a whole separate question. And you know, there are even other crazier ideas for how to get far through space which take advantage of this this new sort of modern conception of space, and that's like, don't even go through any space at all. General relativity tells us that you can be creative about assigning the distances between bits of space. Right, it doesn't have to be you lay out a grid and everything that's next to each other

has equal distances. Right, mass can change the relationship of points in space. And it's more than just like taking a she and stretching it and squeezing it to make gentle differences. You can have crazy rear arrangements. You can connect bits of space which are not adjacent to each other. And that's what we call a wormhole, is a connection between bits of space which you know, have no reason otherwise to be next to each other. But it's like,

I'm here in Orange County, you're in Atlanta. What if we just somehow said Orange County is next to Atlanta, and you know, we just rearrange the connections. That's what a wormhole does. And shockingly, crazily, mind bogglingly that's not

against the rules. Yeah, this makes me think of the examples we saw in the Hyperion novels where you had, uh, you know, essentially warp gates that were allowing a river in one world to flow into a river in the other world, which, you know, if it feels completely fantastic, but what what you're saying, if you lawyer up appropriately, it's not completely out of the realm of possibility. Yeah, it's not out of the realm of possibility at all.

And it's the kind of thing which might never be practical. They might be that we're never able to build something which allows you to have a house where your bathroom is in one planet, in your living room is another. I love that book, Um, But also might be totally possible, and it might be seem impossible, and then somebody has a breakthrough, like, oh, it turns out it's a lot easier than we thought. And it used to cost um the entire energy output of the human race for a

year just to transmit a particle through a wormhole. Now we can do it for or five cents, you know, and then the next year that's an app for it, right, and sort of the progression of technology, And you know, the way a wormhole would work is conceptually quite tricky. Still. You need to create a black hole, you need to open this wormhole up, you need to keep it open. It might require the creation of exotic matter and all

sorts of stuff, but it's tactically not impossible. And that's that's excite to me, um, mostly because I'd love to visit these other star systems and walk on another planet, or at least have humans walk on other planets and tell us about it, you know, um, it feels frustrated to be stuck in this tiny little island of our universe and not able to explore the neighborhood. And so if warp drives and wormholes could be built, then I'm all for it. So yeah, I'd love to invest in

your company. So to come back to another question about the properties of space, I was thinking about, um, So we think of space as a kind of undifferentiated, uncountable mass of potentially occupied territory, kind of the way you use the analogy of water earlier, the way we think about water. But of course in the modern world we know that water is not actually continuous and uncountable. It's a made up of h two molecules. In theory, you could separate them out and count them. Is there any

evidence that space works like that? Are their smallest indivisible units of space that could be counted? And does anybody have any ideas for how to look into this question? Yeah, that's a wonderful question. The short answer is that we think space should be pixelated, and we think that there should be a smallest meaningful unit of space. But the arguments are kind of fuzzy, and it goes something like this, you know, we look around in the universe and we

see that everything at the smallest scale is quantized. Like you can have one electron, you can have two electrons. You can't have one point six one electrons. Electrons in bound states have energy levels. You can be an energy level one or two. You can't be at one point to one. Right, the universe seems to be quantized everything, excitations of quantum fields. Everything comes down to numbers, integers,

not real numbers, but integers. And so we imagine that as we zoom in on space smaller and smaller and smaller, that we should similarly see the smallest bit of space. It would sort of be counter a lot of what we imagine to be foundational to quantum mechanics if it wasn't right, if you could always zoom into a smaller space. And so there's this idea that space could be made

out of these basic units, these pixels. And you can think of it either it's like space being pixels or space being sort of made out of this foam um. And you know, that's not a very strong argument, but it's it's consistent. You know, you find these general principles who say, hey, the universe seems to work this way, and so it should work this way in all categories. It should every part of it should follow these rules. Are there any ideas for types of experiments that could

test for this right now? Where is? That's just totally beyond our even guests of how to how to look for right now? Well, it's hard to know because we don't know how big these pixels should be. Right we let's think about scales for example, like we can look at really small things using particle colliders. For example, with a large hadron collider at certain we can zoom in and see things that are about ten to the minus

twenty meters. That's pretty small, um. But if we had to make a guess for how small these space pixels would be, we don't really have a lot of good reasons to guess. And what we do is we just sort of take all the numbers we have and we rearrange them until they give us something that have units of a meter. We're like, okay, take the speed of light. You know, that's meters per second multiplied by planks constant. Alright,

that has energy units. So keep throwing in fundamental constant to the universe until you get something that has units of meters, and you can do it, and you get a number, and that number is about ten to the minus thirty five meters, and it's called the plank length. And it sounds like a really deep insight. I mean, it's really nothing more clever than dimensional analysis. It's just saying,

how can I get a unit of meter? Doesn't mean that that's the fundamental scale of the universe, doesn't mean that space pixels are that size, but it's the only thing we can do. And often in science we start with like, let's start with the dumbest idea because that's all we can do, and then let's get more sophisticated. So if that's the case, and if space pixels are ten to the minus thirty five meters, that's really far from what we can see today, right, that's fifteen orders

of magnitude from what we can see. That's like, if you can see whole solar systems, then one over one, one over ten of the fifteen would be like seeing a meter stick. So it's like saying I can barely detect solar systems and other galaxies. Okay, well, can you see a meter stick on the surface of a planet? In another galaxy. No, I mean we're not even close. So we're trillions of scale factors away from being able

to see these things in particle collisions. Um. But there's a whole area of research that's built up the other directions. Let's start from the bottom instead of starting from the top and like breaking up protons and electrons into smaller bits all the way down to the plank scale, Let's start from the bottom. Imagine that it's true. Can we sort of build up and come up with the theory

of physics and then make a prediction? Right? And that's this this group of of theories called loop quantum gravity, and it's really fascinating stuff, and it's you know, they've instead of trying to bring general relativity together with quantum field theory by saying, oh, let's turn gravity into a quantum field theory, they go the other direction. They say, let's take space and make it into quantized units. Let's chop it up in the little bits and imagine that

the quantized. So then as space is expanding, you're like popping off new little bits of space, which is sort of conceptually hard to imagine. But your question really was like, have we figured that out, could we possibly see it? And so far that the whole field is sort of in its infancy. You know, it's decades old. They only realized if you know, fifty years ago, was even possible, and how to do basic calculations and how to just

get simple stuff right. Um, But the short answer is, and we could answer all these questions, we could resolve all these mysteries if we could see inside a black hole. You don't happen to have a black hole, dude, Uh, that's sort of impossable, right, Like you're not you're not getting information out of a black hole? Is that correct? That's exactly right. And that's the frustrating thing is that like gravity is very very weak, it's a very weak force.

It takes a lot for gravity to do anything very powerful. But inside a black hole you have in tremendous gravity, so much gravity that it could reveal things like you know, the creation of new bits of space or the distortion of space, or it could show us like what's, um,

what's the matter distribution like inside a black hole? Because general relativity says that there's a singularity, that there's all this mass concentrated in a single dot zero volume but if space is pixelated, if loop quantum gravity is right, then you can't have a tiny infinitesimal dot. You have need to have a basic unit of space. So if we could see what was going on inside a black hole, we could see what happens when gravity tries to compress

things down to these tiny units of space. But you're right, all the secret to the universe exists inside black holes, but they are unobservable. Will never get that information and out, which is so frustrating. It's like if you know, the oracle says, here are all the answers, and I'm gonna put them in a box, which if you try to open it destroys all the answers. It's like some cruel

Greek fable or something. You know. Also a really safe place to hide the secrets of the universe, right, that's right, and all your passwords. I keep all my passwords in a black hole. Just think. So the short answer is we're not anywhere close to discovering the basic pixels of space. But I think if you pulled physicists in them would

say that space is probably pixelated. So I'm sorry if I if you already alluded to this and I missed it, But um, so would you say looking for pixelated space the smallest units of space is something that could potentially be done by experimental methods available to us if we had, you know, the ultimate particle collider or energy levels you know you couldn't that are nowhere near what we have today? Or is it just like not within reach of any

reasonable experimental paradigm that we know about. That's a great question, um. And one of the amazing things about particle colliders is that there really is no limit to what they can do. It's really just a money question. Like the more money you give us, the bigger the particle collider we can build, the faster we can shoot those particles around. And speed is sort of inverse two distance, right, The faster your particles are going, the smaller the distance they can probe.

And so there's really no limit. If we built a Milky Way size particle collider, then yes, we could answer these questions, and uh, you know, we could find space pixels and we could you know, see quantum effects at this level. Um, but you know that would cost us. I don't even know if there's a number for the amount of money. If so, be bigger than this recent stimulus by a lot. So you're saying it would not be like, you know, something five to ten times bigger

than the large had round collider. It would need to be like galaxy sized or something. Yeah, it have to be like ten to the fifteen times larger than the larger run colider. And that would be like I don't even know what the acronym would be like, you can't just call it a large hage junk collider. You need like a very very very very very large hit junk lider V to the fifteen LHC or something. Nobody's even

asking for that money. But yeah, there's no limit to to sort of how small we can peer down if we have really powerful colliders and we know the technology right, like, um, we just add more little boosters to make the particles

go faster. Um. But you know, we also are working on other kinds of technologies to make these colliders more powerful without having to make them ridiculously big and expensive, because currently we're limited by sort of how fast we can make these particles move because it takes this these little units to give them a kick and then magnets to bend them. But if we can make those accelerators, the little units of accelerators, better and faster and more

compact than we could build like tabletop accelerators. There are people here you see Irvine, working on these plasma wakefield devices to try to get particles accelerated to really high energies and very short distances um and then it might be possible to you know, peel back a layer of reality and see what's going on underneath the without spending ten of the fifteen trillion dollars. So we've been looking

a lot at the very smallest properties of space. I say, we zoom out to the biggest possible, uh way of looking at space and talk about the shape of the universe we live in as a whole. Um. So, yeah, so you've I was reading an article that you and Jorge wrote about this. Uh could you talk a little bit about the shape of the universe. Yeah, the shape

of the universe is a wonderful question. It's it's sort of hard to imagine because I think people again think about the shape of the universe, they think about like a big blob, and then when like, what is the shape of that blob? Is it, you know, look like a pile of dog poop or like a bagel, or like a doughnut or whatever. But when we talk about the shape of the universe again, we're talking about something intrinsic, right, We're talking about how do the pieces of the universe

relate to each other? Because we don't imagine that the universe is like sitting in some larger space. We're not asking like, if you were outside the universe and looking at it, which shape would it have. We're really talking about how does the universe curve? You know, like when you put mass in a solar system, it bends space so that planets move in according to these geodesics, which happen to be orbits. So we're really talking about the

large scale like bending of the universe. And you know, as you put stuff in the universe, planets, stars, whatever, the universe bends in such a way so that it would tend to collapse, right, tend things We tend to sort of roll towards each other, moved towards each other, so that gets space one curvature. But what we've done is we've we've gone out, we've measured the curvature of space. We've we've asked like how much stuff is there in space?

And how do these things balance each other? Because it turns out there's a there's one way to bend the universe, and that's by having mass, and there are other ways to bend the universe the other direction. These things called dark energy, which are contributing to the expansion of space, actually has the opposite effect on this curvature. Some mass bends it one way, dark energy bends it the other way, and together the two things give you perfectly flat space.

So these two titanic forces which are balancing each other and giving you space which is completely flat, meaning that on average there is no curvature to the universe. That that you know that things should move in straight lines. So I've read the curvature of the universe described alternately as flat and as almost flat. Could you help me sort sort out the difference? There is one of those just wrong or or what's going on? Well, it's a measurement, right,

and we're measuring the curvature of the universe. And roughly how we do is we add up all these pieces and we ask, you know, what do they come out to? But they all have uncertainties, you know, we don't know precisely how much stuff there is in the universe. We don't know exactly how strong dark energy is. And we get better and better measurements every year, and those measurements are consistent with totally flat, right with adding up to

being exactly flat. But there's uncertainty there, and some measurements suggest a tiny deviation from flat, and some measurements are consistent with flat and other things, and so there's some wiggle room there. And and we're trying to measure in lots of different ways because we don't just trust one experiment or one experiment or and so we try to probe these things from different directions and sometimes they slightly disagree, so there can be some sort of momentary controversy there.

But you know, I think the larger question is like, why are we flat at all? You know, it seems sort of weird once you discover the space can be curved, to discover that our universe just sort of happens to be flat. So you say just sort of happens to be flat. That indicate that you think the flatness of the universe, in your expert opinion, is basically a coincidence, or do you think that that it's not a coincidence that it's a downstream effect of some thing we don't

understand or some other variable. It depends right like um, before we had this theory for how the universe began, it seemed really weird to have a flat universe. Seemed really strange for space to be so smooth and to not have curvature, because as you put stuff in the universe, it should sort of gather together, right, that's gravity, and it should make it more and more curt and so it's it's weird to start with the universe that's pretty flat and then end up with the universe it's pretty flat,

Like it doesn't seem stable. It seems like if you have any deviation from flatness, that deviation would build on itself and build on itself and build on itself, and eventually you'd be pretty far from flat. So then our universe is pretty old. It's fourteen billion years old. This has been going on for a long time. Why are

we still flat? And so for a long time that was that seemed like a coincidence, like either we were so closed to flat in the first few seconds that we've hardly deviated it all, Like we're like balanced on the knife's edge and we're still balanced fourteen billion years later,

which seems unlikely, or there's some reason for it. And the explanation that we've come up with recently is this idea of inflation, that the universe was stretched super quickly in the first few moments of the universe that made it essentially hyper hyper flat. It's like if you're standing on a tennis ball. You look around, and you can tell that the universe is a little bit curve, right, because the tennis ball is a lot of curvature to it.

But if the tennis ball suddenly gets inflated to the size of a planet where you look around, you can't tell that the Earth is not flat, right, it seems to be flat. And so that's what happened, we think in the first few moments of the universe. That explains how the universe got so flat in the beginning. So if if this is what it is like in a flat universe, I mean, is there any way to to even discuss like what it would be like within a round universe or a square universe or anything other than

a flat or almost flat universe. Yeah, Well, it has really fascinating applications for like the possible sizes of the universe. Right, if the universe is flat, then it can go on forever. Right, you can just keep going forever because it can be flat like an infinite sheet. Right, But in three dimensions, if the universe is curved, like if the universe is the surface of a sphere right in some higher dimensional space,

then it it might not be infinite. Right. It might be that you move and you keep curving and eventually you come back to where you were, and so it could be infinite, but not necessarily have any edges, right because like on the surface of the sphere or on the surface of the Earth, you walk for long enough, you come back to where you started. You don't like

run into the edge of the Earth. So the shape, this curvature of the universe has a lot of consequences for the potential size of the universe, And so if it was curved, it wouldn't necessarily be infinite. Um, if it's flat, that suggests it could be infinite, but it also might not be. Right, there's ways to connect the universe. It can be flat but also still be like weirdly connected like an asteroids game, so that you come off one side and you end up on the other side.

Because remember space can have these complicated, non trivial connections between parts of it. The whole edge of the universe could be basically a set of wormholes that bring you back to the other side. All Right, we're gonna take one more break, but we'll be right back. All right, we're back. So I've got a question about the Big Bang. Then, with respect to the the expansion of the universe, we often hear, of course, the Big Bang was that the universe was once in this hot, dense state, and then

there's this expansion. You you think, when you go through this period of inflation, that seems to be the consensus now and then we we keep expanding and cooling. But what form does that expansion take with respect to space? Does that mean that the universe or the contents of the universe expanded into pre existing space, or that space

itself expanded, space itself expanded. The way I think about it's not like a small blob of stuff that then blew up and moved through space, but instead an infinite universe created with infinite stuff in it. And then the Big Bang happened simultaneously everywhere, all at once, meaning that all that stuff just got diluted, like new space was being created everywhere. Space was expanding, and it's not like it was stretching stuff into what was previously empty space.

It was just creating new space everywhere between all the bits. So what used to be hot and dense and intense is now more dilute. And so I think one of the biggest misconceptions that the Big Bang started off like the whole universe the size of an atom, and then it's just a big explosion where stuff moves through space. But instead, I think it's much more natural to think about the universe be created um infinite amount of stuff created all at once, and then diluted and then expanded.

So that's like requires you to imagine an infinite creation of stuff and then an infinite big bang on top of it, which is sort of mind blowing and also sort of more natural. I really like that explanation because I feel like it places uh sit places that the the individual thinker within the model, instead of placing us trying to place us with outside of the model, which which excuse this UH, this attempt to understand like what space is, you know, and then you don't have to

ask questions like, well, where was the Big Bang? Was it over there and over there? And we're close to the center, and when we look around us, we see everything is moving away from us, and there's no directionality to it, like things over here moving away from us, things over there moving away from us. And that's true everywhere in the universe, which means that there is no center.

There's no place from which this explosion happened. It happened everywhere all at once, and that's what differentiates sort of things moving through space from the expansion of space itself. This makes me wonder if, kind of like the idea of bending in general relativity, if we're suffering from the

connotation ends of the word we happen to use. The idea of expanding usually indicates like the pushing of boundaries into areas that were previously out of bounds, Like if you expand a map, you know you're pushing the edges out, But that doesn't really make sense in this case. We're talking about the expansion of space, So it would almost make more sense to think about the Big Bang maybe as a um a population of or I don't know, a population of space expanding and infilling of space. Yeah.

I think of it like a take an infinite ruler, right and mark off two dots, and then somebody stretches it. Right. Well, it was infinite before, it's infinite now. But there's more of it, right, And so space is really this like it's it's it's more of a stretching, you know, than an expansion. It's not an explosion. It's more of like a Yeah, it's like a stretching. There has to be a social distancing metaphor, and all of us I keep,

I keep kind of grasping for it. Well, I'm certainly expanding inside my pants on a notice that they're all there. They're all denser these days, and then before this quarantine. But I think that's something that's hard to grapple with, is this creation of an infinite universe or an infinite amount of space. And people write us questions in our podcast all the time, and one of the most common

questions is what is the universe expanding into? Right? And I think that comes from this conception of the Big Bang as a small dot which is then exploding, right, or even if you imagine space as a chunk of stuff and you understand the space itself is expanding, you

wonder what is it expanding into? And I think that's this desperation to sort of place the universe in a context is to say, alright, we started off by drawing access lines and describing all the stuff happening in universe in this sort of construct we imagine called space, which was maybe philosophical or just a thought idea, and then it turns out it's real. Well, we'd like to place then that space in some sort of super space or

meta space. So sort of grapple with it. It's difficult even for me or for cosmologists, I think, to still, you know, grapple with this concept of space not being in anything else, not necessarily sitting in a superspace or a meta space on which you can define these axes. It just sort of is inherent. So I'm sure you've gotten this question before, but I think it always helps to to try as best we can to imagine it

on our own level. So imagine you have a space ship, you know, that can go faster than the light, as fast as you possibly wanted to go, there's no limit to it, and you just travel in the same direction forever but what do you imagine happens then, Well, I think you would really never get anywhere. I mean, you leave the galaxy, and then you leave the local group of galaxies, and then you're flying off towards another group of galaxies. But that group of galaxies is moving away

from us faster than the speed of light. Right now. It's not again physics lawyer talk, it's not moving through space fasten the speed of light. New space is being created between us and those galaxies faster than we could move to it, faster than even a photon could fly through it. So those galaxies, if you just sat here on Earth, those galaxies are disappearing from our view. Eventually, the photons being created by them will no longer get

to us. It's like if Lussin Bolt was running at you, but somebody was laying track in front of him faster than he was running. It doesn't matter how fast he is, right if they're laying track faster, he's never going to beat them. So, in that same way, those photons will never get to us, and we will never get to those galaxies, which means that the night sky is getting darker and darker. Right things are literally falling off the edge of the observable universe, and things are disappearing from

our view. You know, in fifty billion years or a hundred billion years, it may be that there are no galaxies visible in the sky. Imagine human civilization survives that long, or maybe we have some apocalypse when we rebuild and we start building human edge again, then there is no Edwin Hubble moment when you look out in the sky and discover distant galaxies and realize, oh, we're not alone in the universe is expanding. They would never know that.

There would be no way for them to learn that, and that to me is so tantalizing and frustrating to know that that knowledge could be hidden, because I project the other way. I'm like, all right, well, we're fourteen billion years into the universe. What has already disappeared from the night sky which we will never recover? What clues, what incredible context are we missing about the night sky that you know, astronomers thirteen billion years ago would laugh

at us for not understanding. We don't know, and we probably never will, and that drives me crazy. So this is our shot. We don't have time to re evolve from bacteria and do it again. That's right, that's right. If we haven't missed our shot already, we should scrape the bottom of the barrel and understand what's going on

out there in the universe. You know, we wrote a whole book about it's called We Have No Idea, And the point of that book is that we don't even really know what the denominator is on our ignorance, Like

what fraction of the universe do we have understood? You know, given the fact that we only in the last thirty years figured out that space is a thing and it's expanding and could do all these weird stuff, and the universe is growing and growing, that so many of our basic questions about the universe have different answers than we imagined, And we're discovering new basic questions like what is space? What is time? How many dimensions are there to space,

which we didn't even get into. Um. It tells me that there's a lot of stuff that we don't even know to ask yet. And I would just hope we figure out where the questions are before we run out of time to answer them. So I've got a question going in another direction. This might not make any sense, Feel free to decline it if it doesn't. But I was wondering, does it make sense to think that the fundamental properties of physics are actually properties of space, you know,

or of local space as we know it. I'm thinking about, for example, you know, I don't know relative strength of fundamental forces or the mass of the proton or something. Does the nature of space have anything to do with these constants or the laws of physics? And are they in some way contingent upon what kind of space we live in? Oh? My god. Absolutely, that's not a crazy idea. I mean, it is a crazy idea, but it's also real,

Like the universe is a crazy idea. So um, A lot of the things that we consider to be fundamental about the universe are actually just properties of space and the way that space around here at least seems to behave. For example, we know that particles. The reason particles have mass, tiny little particles like electrons have mass, it's not because

they have a little stuff to them. It's because they interact with this new field we discovered, the Higgs field, and it's in interacting with those fields that they get inertia. The reason a little electron when you push it it um takes some force to get it to move, is because it has some inertition. The inertia comes from the Higgs field. But where does the Higgs field come from? Well, the Higgs fields we talked about before is one of these quantum fields. It's part of space, and it's got

some tension built into it. Like when the universe cooled in the very first few moments, there's a lot of energy in the universe sort of cooled down, cooled down, But the Higgs field got stuck. It didn't go all the way down to zero, got like stuck on a little shelf, and it's very happy there for now. But if the Higgs field got kicked off that shelf and relaxed down to a lower level, then the electron would have less mass or zero mass, the proton, the corks

would have less mass or zero mass. All the fundamental particles could have different masses, and that includes the force carrying particles like the W and the z boson, which affect the strength of the forces. So like the reason the weak force is so weak is because the W N Z boson that carry it are so heavy. Because the Higgs field is stuck where it is, so everything is hanging on the Higgs field, being stuck on this shelf, and if it gets down to a different shelf or

falls off completely, space is totally different. I mean, it still follows laws of physics, but the laws of is if we've discovered a sort of emergent properties of all these assumptions, and if both changed, everything would be different and space would be almost unrecognizable. So yeah, crazy, but also true, and it's possible that that could happen. You know, we don't know what it takes to trigger the Higgs field to sort of collapse to what we call its

true vacuum. Some people worry that, for example, collisions of particles that high energies lack are being done by some people in Switzerland, you know, not now actually during this pandemic. But those kind of situations could create um vacuum bubbles of the Higgs field, and those vacuum bubbles would expand at the speed of light and pass through all space, and so we could end up collapsing the Higgs vacuum and changing the way space works, and you would still

have physics. You would just have very very different physics that we would you know, we wouldn't be around to explore it. But somebody would have a lot of fun figuring out what the rules of that space are. I think there's there's another fascinating as it's of space, which is sort of hard to grapple with. Which is so the relationship between space and stuff, Like we think about stuff as in space. It's like moving through space. Spaces like there for you to be in, like the way

a car is on a road. Right, But if you are serious about space having quantum fields in it, and all particles are just excitations of those quantum fields, then stuff is really just a property of space, right, Like if space is just like a big quantum field, then you know, you imagine your road is like a bigger rubber band, and a car on the road is like, okay, this part of the rubber band is bouncing, has it's excited, and then as the car moves down the road, it's

not like you move that car. Instead, that energy gets transported to a new part of space, which then has the bounces. So it's like every time you move from one piece of space to another, it's like star Trek teleporter. It's not actually the same particles, right, It's like the information is being transmitted, so you can excite that new bit of space in the same way. But is it at least still you you know, it's all ship of theses stuff. And so when I slide from over here

over here with the space isn't changing. It's just like different parts of space are getting excited and so, and that's the way. We are all sort of part of space. We're not in it, we are part of it. This almost seems like a sort of deeper reformulation of the ether idea, right, like that they used to think that there needed to be a uh, substance in space that electromagnetic radiation would propagate through, and then that was considered obsolete.

But maybe is space itself in a way that substance

that everything propagates through. Yeah, yeah, I mean that we're discovering all sorts of new forms of ether, like dark energy and a cosmological constant in the Higgs field, and like there are these things that that fill the universe with stuff with with something with some physical dynamical object and so, right, it used to be ridiculous to imagine that space was filled with something, and now it turns out space is everything, right cool, um, it is it

is very cool. Alright. So we talked about several other properties of space, but one that we're wondering about now is how many ways does it go? You know, so you gotta got up and down, left, right, back and forth. And we know that. Uh. Now, we generally think of time as another dimension of space. Space time that they're they're sort of combined there. But does it stop there or is it reasonable to think about additional directions that you could go in that are not even conceivable to

us in our you know, macroscopic movements. I think what physics has taught us over the last time of years is that every crazy idea is reasonable to think about for a few moments, and some of them will turn out to be true. And this is one of my favorite questions, is like how many dimensions are there to space? And I think you can start from just like, well, why would there be three? You know, like three is

a weird number. You know, it's uh, whenever you find something about the universe and has a number, and you've got to ask, like why that number? If you ask, like mathematicians, what like deep numbers do you expect to see in a description of the universe? You know, they'll say one or pie or e, but nobody says three, right unless they're Catholic and think that the trinity has really insight into the fundamental nature of reality. And hey,

you know, maybe they're right. But that's like clue number one. It's like, is there something three ish about the universe? Like that's kind of weird, but maybe it is. But it turns out that there's no reason to think that the universe couldn't have more dimensions. And you know what that would mean is like another way to move, Like you write your position in spaces, you know x y Z, right, you would just have another coordinate system. And the first

thought you might have is like, well where would it go? Right, Like where do you put it? You can't, like X y Z seems to describe everything. Where would it be? And you have to it's really hard to think it higher dimensions. So you have to do this trick where you think in two D and extrapolate the three D because your mind can handle both of them, and then try to use that three D that extrapolation to go from three to four. Right, So when you think about two D, you like on the surface of a piece

of paper, three D you're like a cube. So imagine moving that piece of paper through three dimensional space and thinking about what that would be like as you like interact with the three D objects. A sphere passing through a piece of paper would look like a dot that grows to a circle and then shrinks again to a dot and disappears. So in that same way, you can imagine four D objects in three D space. And so you use that sort of mental exercise to imagine like

what these other dimensions could be like. And but it turns out that that the current theories of physics don't imagine these other dimensions being like these first three that wouldn't be infinite dimensions that you could go like there's no limit to how far you can go and X or y or z. But these other dimensions, if they were infinite, we probably would have noticed them already. So

if they exist, they would be compactified. They would be like rolled up like instead of being infinite, there would be curved like we talked about before, and they might just be like a centimeter wide, and you know what that means. It's like, Okay, you have x, y, z, and then you have another number which varies between you know, zero and one centimeter, And it's actually quite a natural idea. If it's true, it would explain a lot of mysteries

of the universe. Like in the in the nineties, I remember when this happened, people came up with this idea that we might have um extra dimensions of space of time to explain why gravity is so weak. Like you know that we have these basic forces of the universe, the electromagnetic force, the weak force, the strong force. They're all pretty powerful compared to gravity. Gravity is like ten to the thirty times weaker in comparison. And that's weird.

Why can't we jump at all? And and that's weird right, Like if you hold a little magnet above the Earth, you have the entire gravitational force of the Earth, right is being outpowered by a tiny little fridge magnet. Right, it's pretty impressive. Um, so we wonder like why is gravity is so weak? And then we thought, well, maybe

gravity isn't actually so weak. It's just that most of gravity sort of leaking out into these other dimensions because the strength of gravity depends on how many dimensions there are. Like you know, as space grows, as you get further away from something the sort of same amount of gravitational

power spreads out through that dimensional space. So space was four or five or six dimensional, gravity would be weaker, right, And so they imagine that maybe space does have more dimensions and that gravity is actually really strong, and these dimensions are really really short and anywhere past like a centimeter distant, what you're feeling is gravity being weakened because it's spread out in these other dimensions. So that was

the idea. It's sort of cool insight. I love when you have like an idea that requires you to revolutionize the way you think about the universe and solves an existing puzzle. Um that was the idea, and it was especially tantalizing because they realized nobody had checked, like what is the gravitational force between two things that are just a centimeter apart? And they realized, oh my gosh, nobody's

actually done that experiment. We didn't even know. And the reason is that it's hard, like what's the gravitational force between two marbles? Almost nothing, So it takes like real experimental bravado to set up the test to test gravity really really short distances. And so they did that, and they've done a bunch of these cool experiments in the University of Washington testing really really isolated situations, and they found that gravity doesn't seem to get any stronger as

you bring things really really close together. And then we tried to discover these extra dimensions at the particle colliders, of course, because we use particle colliders for everything, you know, test the fundamental theories of the universe and new new new dimensions and you know, clean your laundry and all sorts of stuff. And the idea is that if gravity gets really strong when things get closed up, then maybe when proton get smashed together, you could create little mini

black holes. Because if gravity is really powerful as short distances, then even the really low mass stuff like protons might have enough energy to create black holes. And that's what you know, there's a whole hull baloo about whether or

not the particle collider was going to destroy the world. Um, and that's one reason why people thought maybe it could happen, is that we might create these black holes, which would prove that there are extra dimensions and explain why gravity is so weak, and then also you know, eat the Earth and end the human race. But it turns out that we haven't seen any of those black holes. And also we're pretty confident that that we're not going to

be creating a dangerous black holes. That's certain because there are other collisions that happen all the time, very high energy collisions from space that create the same configurations and haven't yet created a black hole to eat the Earth. So we thought that was safe. But we didn't see these black holes, which would have proven to us that there were extra dimensions, and so currently we don't know if there are other dimensions to space like we think

there might be. It still could be possible. They would just have to be smaller than about a millimeter, but we haven't seen them and we don't have any evidence that they exist. But there are some theories that like them, like Strength theory would love if there were eleven or twenty six dimensions, but at this point we sort of haven't seen them until we build that you know, trillion dollar galaxy sized particle collider. Well, it looks like we're

running out of time here, Daniel. You're you and Jore are still actively putting out episodes of the podcast. Can you give us just a brief idea of like what is out right now and what's coming out in the immediate future. Yeah, we're putting out episodes of Daniel and Jorge Explain the Universe twice a week. Recent topics include like could dark matter be made out of quarks? Or

what's the cosmological constant? Or We've been doing a really fun series on analyzing the science of science fiction universes where we interview famous science fiction authors and ask them nitpicky physics questions about their wormholes and their warp drives. So we're having a lot of fun and we answer a lot of listener emails. We had a whole episode recently where we just went through listener questions and answered all of their questions from seven year olds to seventy

seven year olds. Sorry, I just had a glance at the I was glanced into the episode list to see if I was particularly familiar with any of the authors. So that you've you've talked to thus far y'all doing? Uh, Kim Stanley Robinson by by chance? No, we have it yet, but we've talked to Bray Crouch. Should we talk to Hugh Award winning authors like Ann Lecky and Mary Robin and Cole and Becky Chambers um, it's been really fascinating to see, like, how do you build the science fiction universe?

At what point do you stop worrying about getting the science right and just think about the story. And then also, for me, since I'm such a science fiction buff, I just get a fanboy a little bit and talk to all these famous people. This might be too loaded of a question, but if you could interview a now deceased science fiction author and asked them some of these same questions,

which one would you choose? You know, until I learned that he was also a jerk, I would have loved to interview Isaac Asimov because he created not just you know, new technology fiction, but like his Foundation series where he creates like actually a new field of science in his prediction of the future. Um, I thought that was really fascinating. I would love to just understand the kind of development of that idea and how he built a story around it.

But then it turns out, like many greats from the past, he was also a jerk to lots of people he worked with. All right, well, well, thanks again for for coming on the show and chatting with us, And yeah, we encourage our listeners to check out those episodes and uh you know, and and hang with us. Thanks for calling in from your closet to talk with us. As we call in from our closets, don't expand out of reach before the next time we get to have you on. I hope I'll still fit in my pants by the

next time I talk to you, guys. Thanks very much for having me on. All right, thank you, Thanks Daniel. In the meantime, if you want to check out other episodes of Stuff to Boil your Mind, head over to stuff to Boil your Mind dot com. That'll shoot you over to the I Heart listing for this show. But ultimately you can find our podcast wherever you get your podcasts and wherever that happens to be. Just make sure you rate, review, and subscribe huge thanks as always to

our excellent audio producer Seth Nicholas Johnson. If you would like to get in touch with us with feedback on this episode or any other, to suggest a topic for the future, or just to say hi, you can email us at contact at stuff to Blow your Mind dot com. Stuff to Blow Your Mind is production of I Heart Radio. For more podcasts for my Heart Radio, this the iHeart Radio app Apple Podcasts or wherever you're listening to your favorite shows,