What's a Tesseract?

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Speaker 1: Hey, Jorge, if you could have just one of the Infinity Stones from the Avengers, which one would you pick? Oh? Man, there's five good choices, but I think the obvious one is the Time Stone. Oh yeah, why is that too? You'd have more time to nap or avoid missing deadlines then, and you could also go back in time and get the other stones. Very clever. It's like wishing for more wishes. Well, I would probably take the reality Stone. You're not happy with our current reality now. I'm feeling kind of tied down by all these physical laws. I want to break one or two of them. And that doesn't make me feel comfortable about giving billions of dollars to physicists. You don't want to watch the TV show called Physicists Gone Wild as long as nobody takes their shirts off. I am more handmade cartoonists and the creator of PhD comics. Hi, I'm Daniel. I'm a particle physicist, and I go wild for crazy particle physics discoveries. Oh nice, what does that mean? You let your hair grow out, you sleep out in nature or at the collider. Well, you know, I've only been in this field for twentysomething years, and in those two plus decades, we've basically only had one discovery, which was the Higgs boson. So that's really the only place I can refer to. And Yeah, we had a lot of parties. We drank a lot of nice champagne. We had a lot of French cheese. It was wow. Nobody picked their shirts off now that I can remember, well, Welcome to our podcast, Daniel and Jorge Explain the Universe, a production of I Heart Radio in which we celebrate all the crazy, wacky, wild stuff about the universe. The things that we don't understand going on in the hearts of black holes, to the things we think we might be grappling with on the quantum mechanical scale, Everything that you want to know about the universe, everything you didn't know that you wanted to know about the universe. We talk about all of it, and we explain all of it to you because it is a pretty fascinating universe. There's a lot going on out there and a lot for us to discover and also a lot for us to imagine happening. Absolutely, and it's fun to think about how the universe might work in different ways. Does it work the way we expect or is life here on Earth kind of unusual and weird, and if we could go to other places in the universe, we might see things working very differently and learned some deeper truth about the nature of the universe and reality. Yeah, unfortunately we have here in our human species, in our human society, we have awesome writers and artists who can imagine some of these things for us, and sometimes that spills over into reality. That's right. Sometimes art and literature and science actually connect and we can explore these fun concepts about the basic nature of space and time and how our universe works in lots of different fund ways, including superhero movies. Yeah, you know, I feel like something there are topics in these science fiction or fantasy or superhero movies that sort of feel like they could be real, but you're not sure. At least it looks pretty real in the movie. It does. And I know that Martin Scorsese is not a fan of superhero movies, but I like that they bring up a lot of these scientific elements. You know, I never saw Martin Scorsese movie bring up fundamental questions of the nature of space and time. There are some place concepts in fantasy and science fiction movies and superhero movies that you know, sound very techy and science and you sort of wonder if they are actually real things exactly in our goal on this podcast is not just to explain what scientists are thinking, but to dig deep into what you are thinking, to answer your questions about the nature of the universe, and explain to you things you might have heard about and wanted broken down. So to be on the podcast, we'll be asking the question what is a test iract now, Daniel, is it test irat or test rat or I think it's test i act? I said, you got you gotta say with some drama, some enthusiasm. Yeah. This is a concept that comes up in a couple of interesting places like the Avengers movies. It was one of the things that they were fighting about and trying to control, and also in the Wrinkle in Time Blox and wasn't it also in that movie Interstellar? Everything was an interstellar Man that was just like a garbage can of all the ideas that everybody had. Man, I was a pretty negative assessment there. Well, you know, time is love and you can move through the fifth dimension if you believe in love. Like, I don't even know what that was Obviously you're not paying attention, Daniel. Love is the fifth dimension? I love the fifth dimension? Is that what that means? And I think you to watch it again? And you know, I think I'm not smart enough to understand that movie. That's really the problem. That's Christopher Nolan movie for you. You need like a PhD or something. I need like seven peachd's like Brince Banner. M there you go back to the Avengers, all right, Yeah, the test arrect shows up in the Avengers movies. And so this actually came from one of our listeners. They posted a question to us. That's right. This is a concept that one of our listeners had heard all about and wanted broken down. So if you have a question you hear about in science that you'd like explained, please send it to us. We'd love to hear from you and love to help you understand these concepts. So here's the question from Zoe from Vietnam. Hi, Daniel, and hell, hey, I'm a big fan of your podcast. Um. I used to dislike physics in high school, but your podcast has now made me realize how funny and interesting physics can be. I've recently been introduced to the concept of a test arrect, and I was just wondering if you could make a podcast episode about how a test ract describes a four dimensional space, is the fourth dimension time and does the testrect relate to the concept of space time? Thank you? All right? Thank you? Zoe? When if she's seen the Avengers movies. They made it out there to Vietnam, didn't they They're everywhere. Yeah, it's an interesting question, and it's one that we were wondering. How many people out there had an idea about what this could be exactly. So we asked our other listeners questions from Zoe the listener, and so basically we're not even needed anymore. The listeners are asking questions and answering questions. Yeah, we're just here to provide the bad jokes and the Wikipedia reading no, and to make everybody realize that physics is awesome. That was my favorite moment in her question, that we have made physics fun for her awesome. So Daniel went out there and asked people and here's what they had to say. I think the test wractor is the four dimensional cube, right, have you seen that? Like my mind has the animation like the cube turning itself inside out. It's supposed to be like a visual aid to help you think about the fourth dimension. Never saw tessellation. Tessellate could be could be same route word. Yeah, I've heard of that before as being a fourth dimensional more model of a cube which acts in the three dimensions, And I've also seen an animation which shows how it behaves. But it's a little bit over my head how that works a fold in space, and apparently to make one you just have to think really hard about it. Testarunt is something super cube, like four dimensional cube, but I know it's something more than that. I don't know more. I don't know what test rings are in physics. When I remember the Avengers movie, they were like blue cubes that had like a lot of energy, So it might be something relating to energy. I remember hearing about it in the movies. A lot I don't remember, but I think it's something to do with like either time travel or bending space. All right, See, a lot of people had heard about it from the movies, Yeah, exactly, the Avengers. That's definitely made this idea, or at least this word popular, And according to them, it's a blue cube with a lot of energy. Yeah, a lot of power in it, somehow mysterious power. Why is mysterious stuff in the movie is always glowing blue? You know, it's like blue some special thing for our brains. It means like weird and unnatural. M Sometimes it's purple. Yeah, the Infinity Stones all had different colors. They're all mysterious and powerful. That's true. And you know, it turns out the Infinity Stones all used to have different colors like in the original comic books. And there's like a reboot, but they swapped all the colors. No kidding, Yeah, exactly. Maybe they used the Reality Stone, dude, with the colors. I come from an alternate universe where the Reality Stone was always purple. What It's all going towards the multiverse apparently. So that's alright, So break it down for us. What is a test react? Tests? React a super fun concept. It starts in geometry, where it's basically the fourth dimensional extrapolation of what a cube would be in three D. But it really does have deep connections to like the nature of space and space time, and then of course it does appear in science fiction. But at the root of it, it really is a geometrical object. Take a cube, which is a three D object, and try to imagine with the four D version of that would be that's a tests react M. You mean, like you know, length with depth would be three dimensions, And like what if you added a fourth one? Yeah, exactly. You start with a point to which is zero D. You make a line which is one D. Then you add the second dimension. You get a plane. You had a third dimension, you get a cube. A tessaract is what happens if you add a fourth dimension? M M. I see. And it has to be like a dimension in space, like could it be like a density? Could that be something or I don't know color. That's a cool idea, you know. Mathematically it doesn't have to be connected to anything physical in geometry. These are just you know, points in some arbitrary space. But by space they don't necessarily mean like physical space. It could be space, it could be time, it could be anything else really, and so mathematically it's just sort of like an abstract concept. It's like a relationship between points. It's the definition of like the number of ways you can move around in that space. I see. So, but mostly people think of it as sort of like something you can move around in, right, like you can't. It's hard to move around color or or density. You can map it dimension anything. Yeah, you could map it to color, you could map into density. Really, you take this abstract concept of a dimension and map into something physical basically anything you Like, The question is does that really mean anything? Like is there anything in our universe which really respects that as a dimension or refle lets that as a dimension. That's why, for example, and we'll dig into this later, why we think space and time might fit together into four dimensions because there are real physical things about our universe that reflect and respect that dimensionality. But you can make up your own dimensions doesn't necessarily mean anything. M So it has more to do with like a coordinate system, right, Like if you have a coordinate system like x, y and z, what happens if you add another one like double a or something? Yeah, or you go backwards you had W right, So like W X, y and z. And this is tricky to think about because we're used to thinking in three D, because they're you still living in three D. So you might be trying to imagine in your head, like, well, what is a four dimensional version of a cube? Look like it's not hard to imagine a point or a line, or a plane or even a cube. How do you like play the mental game of imagining a four D cube? What does it tests aract, look like other than like a blue glowing cube on the screen at the movie theater. I see, So it's a geometric shape basically, but it's a geometric shape in four dimensions, exactly in four dimensions, and we can play games trying to imagine what it might look like. Obviously, we can't like build something in four dimensional space because we think we live in three dimensional space, But that doesn't mean you can't like play some games to help yourself understand it. Like, you know, you can look at the drawing of a cube. Drawing is usually in two D. You write on pencil on paper that's on a plane, but you can draw the lines in a way that your brain looks at them and imagines a three D object in your three D mental space. You can do sort of similar stuff drawing things in three D or even in two D to give yourself the impression of what a four D object might look like in your mind. M M, I see, Like you draw a cube, and you you draw another cube, and you connect them together somehow. Yeah, exactly, you can extrapolate, like, how do you draw a three D cube on a two D piece of paper? When you take two squares and you connect all their edges, then it looks like a cube. Right, So if you want to play the same game, now draw two cubes piece of paper and can act all of their eight edges, And that's sort of maybe what it tests rack might look like if you were four D being with four D eyes and a four D brain. M right, But I guess that's just sort of like a a drawing or a or like a spatial way to depicnic But really, I mean if there was a fourth dimension, you wouldn't see it in our three dimensions, right, Yeah, that's a great question. I mean you would see it, but you would only see a slice of it. Right. The fourth dimension, if it was a real part of space and time, wouldn't be something hidden to us. It would just be that we couldn't see all of it. You know, imagine being a two D being in a three D space. You're still seeing that three D space, You're only seeing a two D slice of it though, So things would look pretty weird if we were in a four dimensional space and we were three D beings. All right, Well, maybe let's jump into this idea of a fourth dimension. What does that even mean, Daniel? It's hard to wrap your mind around because our brains are three D objects and we've been thinking about three dimensions for so long. And you know, if you think about X, Y and Z, those are like three glowing lines in your brain that are all ninety degrees from each other. It seems like they sort of fill the universe. The whole idea behind X, Y and Z is that that's all you need to know to know where anything is. Like with if you specify the X, the Y, and the z value, then you know where something is. There's isn't the need for another direction, But now try to add a fourth dimension, Like where does it fit? You can't stick another line coming out of that axis because it would be moving through three D space. So you have to like take this sort of mental leap and imagine a whole other direction. So imagine like a family of these X, Y, Z axes and the relationship between those is the fourth dimension. So you can move from like one access to another access to another access. That's motion in this now other direction, right, and I think that maybe the interesting thing, or the tricky thing to imagine is that moving in this other fourth dimension shouldn't affect how you look like in the original three dimensions. Right, Like I can move backwards, forwards, up and down into the sides in our regular three dimensions. But then if I moved in the fourth dimension, someone looking at me right here in the room wouldn't see me move. Right. Technically, that's right, they wouldn't see you move in three D. But it depends on your shape in the fourth dimension, right, And again it's hard to think about. So it's a little easier to step down in dimensions and think about like two versus three dimensions. Imagine we were living on a two D surface and somebody passed a stick through that two D surface. What would we see. We would just see like a slice of the stick. It would look like, you know, a flat circle, and even if it was moving in that extra dimension, we couldn't tell. I think that's the example you were giving. But what if it wasn't a stick. What if it was like a pyramid or a sphere, right, and we smooved that sphere through our two D slice, then we would see a flat circle that was growing, and then would grow and we get larger as the center of the sphere passed through a plane, and then it would shrink again as the back half of the sphere pass through a plane, and then it would disappear. So motion in the fourth dimension can be visible in your three dimensions, depending on your shape in that fourth dimension. M m m. Yeah. Like imagine, for example, that you were a three D person and I was a two D person, and I like try to put you in prison. I like build walls around you in my two D world. You would just laugh at me. You would just like step over them, right, because I'm just like drawing a box on the ground around you. It's no big deal for you to like escape my two D prison because you're a three D person. You can just like go up and over it. And from my point of view, it would be like you just disappear from my prison cell and appear on the other side of it. I wouldn't be able to understand how you had gone from inside to outside. In the same way, if a four D person is in a three D prison, in principle, they could move through that fourth dimension right and appear outside the prison. Cell Ummm. This is really hard because I feel like we're trying to describe four dimensions with one dimension, which is sound, which is a pretty impossible. But you say it sort of depends on your shape, I guess, But does that sort of depend on the idea that you are projecting onto a plane or a three dimensions? Like, isn't it possible that I still am projecting onto a plane, but I'm also moving in a fourth dimension without that changing that doesn't really depend on my shape. That's totally possible, it's just not necessary. There's lots of different configurations. It's possible for you to be moving in the fourth dimension and not have any apparent motion in the third dimension, just like you know, you could be moving in Z without changing anything in X and Y and that totally works. But it's also it is possible to move in the fourth dimension and to have that motion affect how you look in three dimensions. M all right. So it's tricky and we're not quite sure how it would work, right because we sort of don't know what our shape would be in the fourth dimension. Yeah, exactly, Like I could be a really long cylinder or I could be a sphere, right, yeah exactly. Or I could be you know, a really attractive you know perimeter, yeah, or you could be shaped like a peanut. Like we just we just don't know. We have no idea, you know, if a fourth dimension exists and what our extent in that fourth dimension would be. We also don't know the nature of that dimension. Like we're imagining that fourth dimension as if it's a flat dimension that goes on forever, just like X, Y and Z, but we don't actually even know if that's true, right, Yeah, And this actually answers another question we've got from a listener almost on the same topic. Yeah, exactly. People are thinking about four dimensions, and so we had Tom right in and ask his question. Here. It is Hi, Daniel and Johai. I'm tall, and I have a question about the fourth dimension. Can life forms exist in the fourth dimension? And if so, how would we interact with them? Good question, Tom, Yeah, I think we have answered it already, right, which is that would we be able to see them? Maybe? Maybe not? It so it depends on your shape in this fourth dimension, Like you could maybe have a really long shape in the fourth dimension, or you could not, right, yeah, exactly, So it depends on the nature of that fourth dimension and our shape in that fourth dimension, like what our extent is in that dimension, And we just don't know because we can't sense or detect the fourth dimension if it exists, so we just don't really know the answer to that question. But if the universe is four D and there's a life form out there that lives in that fourth dimension as well, you know, and looks at us the way we would look at people living on the surface of a piece of paper, then you know, it would have a much more complex and nuanced relationship with that dimension, and it could probably literally run circles around us. Yeah, and what they look like, thannas, it's the question, I think. And they have purple skin, they would be glowing blue of course. All right, well, let's get into why we think there might be more than three dimensions and also what those dimensions could be. But first let's take a quick break. All right, we're talking about four dimensions, and the tests are act which is not a blue cube in a superhero movie, but a geometric shape in four dimensions. Yeah, and I guess when we say it's a cuban four dimensions, because the cube is kind of like your most basic shape. Yeah, you could also imagine a four D sphere. I suppose, right, you can play the same game. You could say you have a dot in zero dimensions, you have a circle in two dimensions, you have a sphere in three dimensions. I'm not sure what a circle would be like in one dimension, but you can go zero to three, and then I suppose you could imagine a four dimensional sphere where the surface has the same distance from the central point, including the fourth dimensional distance. I think you can play similar games in four D for other objects. But yeah, a cube is sort of like the basic thing because you're moving perpendicular in all four directions, and so it's like the building block. Yeah, well step us through. Why do we think there might be more dimensions? Is it based on theory or a hunter just just like wild possibility. It's based on wild theories from physicists gone wild, of course, Yeah, exactly. You know, sometimes it's just the math works better if you assume more dimensions, Like we try to write down theories of physics that makes sense, and sometimes they just don't really work. And it turns out if you like assume that space has more dimensions, then all of a sudden, the math gets not simpler, it gets more complicated, but it fits together in a more natural way. Really, it makes the math easier, or it makes it make more sense. Like you're doing the math and something's not fitting quite right. But if you added a whole new dimension, you know, things would be smoother, exactly. And one of the places this comes up is in trying to understand the universe that a really really small scale, you know, down deep below atoms, below, nuclei, below protons, below, quarks, much much deeper down the very smallest scale. We don't know what the nature of the university is, but people have speculations, ideas business gone wild, think about how maybe it's made out of tiny little vibrating strings, and these strings vibrate in some funny dimensions, and so in order to make those calculations work, like to have those strings vibrate and have those vibrating strings turn into particles. At our scale, you need more ways for those strings to vibrate. You need for them to be able to wiggle in certain ways, and to make sheets when they wiggle, and to make complicated structures, and those structures make a lot more sense. It turns out if the universe has something like eleven dimensions rather than just three, because with only three dimensions, like, what's the problem, you can't get sort of the richness that you see in our universe. Yeah, you don't get the richness, you don't get the results you want. And also sometimes things just collapse, Like if you try to do calculations in string theory and go for more than eleven dimensions, like up to twenty four or thirty nine dimensions, that it always just sort of ends up collapsing back down to eleven dimensions. It's just like the most natural way to express some of these theories is in eleven dimensions, and that makes us wonder, like, wells that just mathematics or is that actually reflecting something fundamental about the universe? You know, often if physics were doing this, we're like noticing a pattern about the way things seem to work mathematically and wondering, who does that reflect something real in the universe. Is that like how we're discovering something about the structure of the universe or is this just the way we write things down because we're humans and that's where our brains work, And you know, it's a deep question. We just don't know the answer to right, is it maybe just physicists not wanting to do any more math? That's just add more dimensions? Why not more dimensions? This more math, man, it makes it more complicated. You know, eleven dimensional integral it's like, you know, eleven times harder than a three dimensional integraw. But yeah, sometimes the math just works. And it also makes for a cooler grand title grant application form. Yeah, but the money you get from that grant then gets thinner and thinner because it spreads out through all eleven dimensions, it gets diluted. Yeah, but you can build a grant in more dimensions than three. Yeah, maybe we can find funding agencies that work in these other dimensions as well. All right, Well, there's also this other idea that maybe more dimensions explains gravity in some way, right, like why gravity seems so weak? Or how can we kind of resolve this conflict between special relativity and quantum physics. There's other excuses for adding more dimensions. It's a really tempting idea for lots of reasons. And one is, you say, is to explain this mystery of gravity. You know, of all the fundamental forces, the strong force, the weak force, electromagnetism. Gravity is the weakest, and not by a little bit, but like ten to the thirty. So it's just like so much weaker than the other forces. And we physicists we like harmony. We like things to sort of fit together and be explainable as part of a package. When one thing really sticks out, we don't like that. We look for an explanation for why that might be. And as you say, the idea is that gravity might not actually be super weak. It might just seem like it's super weak because it's spreading out in these other dimensions. Remember that the power of gravity gets weaker as you get further away from something. Currently, we measured that to be like one over the distance squared, But if you actually had more dimensions than just three, then the distance would grow more rapidly because you'd be moving away in more dimensions. So if gravity actually moves through all these other dimensions as well, then the reason it feels weak is that it's spreading out through those dimensions, that your distance from the other object is actually greater than it seems like it is in just three dimensions. So maybe gravity is just as powerful as these other forces. It's just mostly getting wasted in the other eight or whatever dimensions, And so that would be super awesome because it would let us like discover other dimensions of the universe and also solve this really deep mystery about why gravity seems so different from the other forces, right, And the idea is that the other forces, like magnetism and the strong and the weak forces, they only act in the three dimensions that we know, right, or they're like more focused in our regular dimensions and they're they're not acting in the other dimensions like gravity is, yeah, exactly, and that's a question we don't know the answer to, like why would that be? And as often happens in physics, if you have found those dimensions and discover the gravity is the only one that moved through them, then you'd be left with another, maybe deeper question, which is like, well, what's different about gravity that it moves through these other dimensions but electromagnetism doesn't and the strong force doesn't. So you know, we're never going to run out of those questions, even if we make crazy discoveries about the nature of space. Right. So basically you would wait the same in other dimensions, but your cell phone and your magnets wouldn't work. That would be inconvenient. Yeah, exactly. But it also means that gravity might be much more powerful than we thought, and that if you managed to get really really close to something, if you can, for example, two particles super duper close together so their distance actually gets very very small, that you might see that very strong gravity. And that's why people think we might make many black holes at the Large Hadron Collider, because two protons getting pushed really really close together might trigger super strong gravity and create a black hole. That's the whole idea behind making many black holes. It might actually reveal the existence of other dimensions of space and time. Hey, let's give it a try. That sounds like a good idea. Let's make black holes here. Yeah, and let's do it million times a second. Yeah, what's the worst, Like, let's just go wild, all right? Well, there's also the idea that maybe the fourth dimension or the extra dimensions are not necessarily related to space, like a direction that we can move in or kind of like wiggle around in. There's also the idea that maybe this fourth dimension is timet exactly. The way we were talking about gravity a moment ago was as a force that gets weaker as it propagates through space, and that's sort of like the quantum mechanical views like trying to understand gravity is one of the other forces and maybe finding a quantum theory of it. But you're right, there's another way to look at gravity, and that's part of relativity. And relativity tells us that there's a deep connection between the three dimensions of space that we're familiar with and time. So it's like you were saying earlier, like do the dimensions all have to be space? Could they be like flavor or color or you know, sourness or whatever. But you're right, it's cool to think about other dimensions and have them be not necessarily just motion in space, but time. And the more we learn about space and special relativity, the more it feels like time should get promoted to like one of the dimensions. Promoter. Are you saying time is lesser than space, Daniel, you're saying it needs and promotion. I'm saying it's segregated. It's like put by itself. You know, quantum mechanics likes to say the time is really separate from space, that the two things are different, and you know, space can do all sorts of things that time can't do. Like, you know, you can go backwards and forwards in space and you can't do that in time. So it would be super awesome if we understood time is actually part of some four D object, which was three spatial dimensions and this one weird time to mention. I think that would be a promotion for time to get graduated up to a full dimension. Right, but you know what is space without time? Then? You know, do you think about it? It's brief. I can exist without space or you know, time doesn't need three dimensions of space. You know, I would could hang out with two dimensions of space. Yeah, that's true. So really, I mean, I think time is just cooler. It's more, it's more timeless. It's a classic. Yeah, you know, there's something good about everybody, but it's also just cool to understand them as part of the bigger picture. And I think there's something really beautiful. They're something really deep and insightful, and understanding time is part of this for D object. You know, it's not just like, hey, there's some similarities, let's write them down together. It's that the concept makes much more sense when you put them together. Then when you leave them apart. Special relativity really shows us that it shows us that space and time are really closely connected in the same way that the three spatial dimensions are really closely connected. You know, the universe makes much more sense if you look at it in three dimensions, and it turns out it makes even more sense if you packed it all together into a four dimensional concept. Right. This is the concept of space time, right, like you treated all is one concept or one thing or one like coordinate system that we live in. Yeah, exactly, you think about it is like one coordinate system, and some things just make more sense in that coordinate system. You know. Take for example, the length of an object in three dimensional space, right, doesn't really matter how you measure it, you know, or where your axes are, how you define your X, y and z. The length of a stick is the length of a stick, and you can turn that stick around and it still has the same length, right, And that would be true if you're only looking at like a two D slice of it. If you're only looking at a two D slice of that stick, it would seem like it changing length as you like rotated it around or whatever. But we know the stick has a certain length, and so we want our measurement system to reflect that. Well, the same thing is actually true in space time. If you add time to your universe as the fourth dimension, then you can have a new definition of distance, which is called a space time interval, which is a distance in space and in time. You like add another bit to the calculation. And we know in our universe that like distance between objects is actually weird. It depends on how where you are and how fast you're going, and that the distance in time between objects depends also on how fast you're going. This is like length contraction and time dilation. The universe seems really weird, like it doesn't follow a lot of rules. It turns out in four D it does follow those rules, and like the four D space time interval, it doesn't change no matter what reference frame you're in how you rotate your measuring stick. So there are these properties, these principles that are respected only in four dimensional space and not in three dimensional space. And that's what makes us think that the four D spaces like more natural, that it's the better way to think about the universe. M It's like you don't need a special kind of math or a whole different set of equations to deal with time. You can use the same equations if you treat it another dimension. Yeah, you can use the same equations, and a bunch of stuff now suddenly makes sense, and it is simple if you do the math altogether. You know, for example, our laws of physics don't change if you rotate them in four dimensional space. What that means is that they're the same for everybody in an inertial reference frame. It doesn't matter where you are and how fast you're going. You can always apply the same laws of physics, electromagnetism and the strong force. All that can be applied no matter who you are and how fast you're going. That's not true. If you ignore that fourth dimension, you're like missing part of the story. Mmmmm, I guess It's kind of like if I'm sitting here doing nothing, you know, taking it up. Maybe it doesn't look like I'm moving in the three special dimensions, but I'm actually sort of moving in the time dimension right, Yes, yes, exactly. And the distance between your like spacetime locations right can be measured in that four dimensional space. You have zero distance in x, y and z, but you have a non zero distance in time, right, So it only looks like I mean lazy and inactive, But really I'm like working out in the time dimension, right, I'm like going for a job. You're getting strong in time exactly. And somebody else flying by near the speed of light might have a different opinion about exactly when one event happened, but they would make the same measurement of your space time interval, your distance, and four dimensions between the beginning of your workout and the end of your workout. I see, I would look good no matter how fast you're going. Yes, your beauty is invariant. All right, Well, let's talk about how this relates to quantum physics and special relativity, and also let's talk about how it shows up in The Avengers. But first let's take another quick break. We're talking about the tests or act Daniel, and now in the Avengers the Tests I act shows up I think in the thor movies First or or No Captain America. Maybe. Yeah, So it's this cube, right, and I think it's actually in these movies it's a vessel. It's just like holds the space stone, one of these six infinity stones, and so like somebody at some point earlier on the Marvel Universe took the Infinity Stone and put it inside this cube which they call a test Aract to make it like sound awesome in science, right, I think it's called making it up as you go along in terms of the writing craft there. But yeah, it turns out that the talk connected and in particularly the tests I act and this one is the space Stone, right, like it's somehow control space and lets you like create warm holes and things like that. Yeah, the space Stone has a lot of power unless you do all sorts of crazy stuff. And so the space Stone itself is not the tests Irac, but the tests Ract is this thing which holds it and you know, test React we know now is a four dimensional cube, but in the Avengers movie they use a three D cube because I guess, you know, it's harder to write a four D cube or even the special effects that Marvel Studios can't do four D movies, and so it's really just a three D C but it's glowing blue, right, So maybe in the Marvel movies, color is the fourth dimension. Well, technically if you're watching in three D, you are watching a four D movie because it is playing out in time that's true, right, Yeah, exactly right. So if you saw the Avengers in three D, you probably did see a four D test a rack containing the Space Stone. So congrats to you. Right, and then I see your notes here that it's powered by dark energy, where they just like throwing all kinds of physics terms in there to try to impress people. Yeah, exactly. I don't know who the science consultant was for that movie, but you know, they give them a broad introduction to everything about the universe, and they just like cherry picked the words that sounded cool, and hey, dark energy does sound cool. So it's nice to know that if the Space Stone were real, it would be somehow powered by this mysterious force that's accelerating the expansion of the universe. I might have to marvel a fact check that. I think maybe it was another stone that was powered by dark energy, maybe the Red one. Maybe I'm not quite sure. Yeah, you you certainly might be right. I just remember watching this movie and going, oh, dark energy, that sounds fun. Now you were watching in black and white or something. Maybe I was watching it backwards in time accidentally, right, And it also shows up in other words, right, and the wrinkle in Time books, right, Yeah, The Wrinkle in Time is a really fun book which recently made into a pretty good movie. And in that book they can travel all around the universe and they call the fifth dimension a test I act. So like a tests iact is a four D cube in our universe, but in a Wrinkle in Time universe, the whole fifth dimension is a tests iract and you can like add that to other four dimensions as you travel through space without like having to go the long way around. So it's sort of like a portable wormhole you can use to get from one spot to the other. Wait, what the fifth dimension is actually a four dimensional cube? In that movie, they sort of brush over the tests Iract as a four D cube and they just call the tests Iract the fifth dimension. And so imagine if like space and time are four dimensions, and you wanted to get to somewhere else in the universe, and you wanted to do it without going through four D space, if you could somehow move in the fifth dimension, if the universe is like bent in the fifth dimension, so that you could like hop from one part of our four D sheet to another part of the four D sheet by moving in that fifth dimension. That's sort of like what wormholes do in our universe. So it's sort of like, you know, a little shortcut, m I see. It's kind of the idea that maybe, like here where we are now is and Jupiter, which is really far away or we think really far away, could be really close to each other in another dimension, right Like if I could somehow reach out in another dimension, maybe I could just reach out and touch Jupiter exactly. Imagine our universe again, just as a sheet and then like roll it up. Then all of a sudden, you're close to another layer of that sheet. And if you like went through our universe space, it would take you forever to get there. But you know, in this like other direction, the direction in which our universe is like a rolled up sheet or folded or whatever, then you could just hop from one part of the sheet to the other, moving in that other dimension. But you know, we don't know that that dimension exists, but in a ringle in time, it does exist. So it's sort of this like cool wormhole strategy. But for a reason that just really doesn't make any sense to me other than that it sounds cool and science e They call that fifth dimension the tests I Act, right, And it also shows up in the inter Sellar movies, right, like Matthew McConaughey goes into a black hole and he's somehow like navigating a tests I act where time is another dimension and he's able to like send messages to his daughter in the future. Right, Yeah, there is some weird stuff where Interstellar you go into the black hole and space and time are all twisted up. And it's certainly true that in a black hole, space and time are a very confusing, right, and like time and space sort of like switch relationships, and space is only forwards, you know. Outside of the black hole, time can only move forwards. Inside the black hole, you can only move sort of one direction in space, sort of forwards towards the singularity. As some people say that inside the black hole, space has become time, like so I think that's the origin of that. But in the movie, you know, he can then like move through time, but he moves through time as part of the story, so there still is time. There's like a time when he was earlier in time and a time when he was later in time. You know, honestly, it doesn't make any actual sense, but it's uh, you know, it makes for a poignant scene. You mean, Christopher Nolan movie doesn't make sense with regards to time. That's so weird. You know. I recently watched Tenant, which is really fun, but I had the impression the whole time that like, wow, I either I am not following because I'm not smart enough, or this makes no sense and I can't tell which it is. You couldn't tell, really tell, And I try to map it out and try to watch a scene by scene and be like, Okay, what's going on here? How does that make sense? Trying to build a map of like what's going on in that universe? But wow, it's very confusing, And eventually I just went on to read it, and of course somebody else had watched the movie like a hundred times and built a map. But even still, it's very confusing because it's hard to think about things moving backwards in time as the story moves forwards. Right, Yeah, I think the movie lost me at backwards oxygen. I was like, you need backwards oxygen to survive living backwards. I don't know how where are they going to get to so much oxygen backwards? Anyways? Yeah, so it shows up a lot in popular culture and movies and books, But extrat dimensions and the test arc are sort of real things that physicists are thinking about. Right, It might explain gravity, might explain how quantum mechanics and general relativity are connected. Right, it's a it's like a real thing. It's a real thing. It might be a real thing. Yeah, it's a real thing in science, and that it's a very valuable and useful way to think about the universe. And there's a larger lesson there, right, that we don't know the deep nature of the universe, and we keep making the same mistake as humans by imagining that the universe is the way we always thought it was. And so it's very healthy to try to like break out of the confines of our intuition and imagine different ways the universe might be. And this is a pretty deep one. So we'd like to be open minded about the nature of the universe and not just be stuck in three dimensions. And I think that's how we made this leap to thinking about the universe in four dimensions. This connection and special relativity between space and time really does show us that time is deeply connected to space in a way that's not just mathematical, real and physical, and that whole pully might help us bridge, as you say, between relativity and quantum mechanics. Is quantum mechanics is a very very different view of time. So whatever theory we come up with, whether it's string theory or something else, to bring these together and reveal the actual nature of the universe, it's got to definitely be something that figures out time and its relationship to space and all the other possible dimensions that might be out there, like they might be real. Yeah. I guess the history of science and physics and our exploration of it is that the universe is much more complex than we think it is. Right, There's more twit and what it seems like apparently, yeah, exactly. There might really be backwards oxygen and you might have to breathe it one day. Keep your mind open. Yeah, the universe might might be wilder than you think, exactly, And the universe is always builled with surprises, And so I look forward to learning about the deep nature of the universe and discovering other dimensions of space and or time. You know, we talked about other dimensions of space, but it's also possible there are the dimensions of time. What all right, let's get into that another time. Sounds good, But in the meantime we hope that answer the questions that our listeners had about the test are act and about living in four dimensions. You hope you enjoyed that. Thanks for joining us, see you next time. Thanks for listening, and remember that Daniel and Jorge explained. The Universe is a production of I Heart Radio. Or more podcast from my heart Radio visit the I heart Radio app, Apple Podcasts, or wherever you listen to your favorite shows.