Daniel and Kelly’s Extraordinary Universe - What's a Tesseract?

Episode Date: April 8, 2021

Daniel and Jorge talk about 4-dimensional cubes, life in the 4th dimension and the Infinity Stones! Learn more about your ad-choices at https://www.iheartpodcastnetwork.comSee omnystudio.com/listener for privacy information.

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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? So you'd have more time to nap or avoid missing deadlines. That and you could also go back in time and get the other stones. Oh, 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? No, I'm feeling kind of tied down by all these physical laws. I want to break one or two of them. 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 Jorge. I'm a cartoonist 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 20 something 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 ate a lot of French cheese, it was very bien. Wow.

Nobody took their shirts off. Not that I can remember. Well, welcome to our podcast, Daniel and Jorge, explain the universe, a production of I-Hard 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 wanted to know about the universe, everything you, 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 learn some deeper truth about the nature of the universe. and reality. Yeah. And fortunately 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 fun ways, including superhero movies. Yeah. You know, I feel like sometimes 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 sometimes concepts in fantasy and science fiction movies and superhero movies that, you know,

sound very techy and sciencey and you sort of wonder if they are actually real things. Exactly. And 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 today on the podcast we'll be asking the question. What is a Tesser? Now, Daniel, is it Tesseract or Tessorat or? I think it's Tesseract. Oh, I see.

You got to say with some drama. Yeah, exactly. Tesseract. Some enthusiasm. It's the Tesseract. 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 box. And wasn't it also in that movie, Interstellar?

Everything was in interstellar, man. And that was just like a garbage can of all the ideas that everybody had. Oh, man. That 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? I think you need to watch it again, Daniel. No, I think I'm not smart enough to understand that movie. That's really the problem. That's a Christopher Nolan movie for you. You need like a PhD or something. I need like seven PhDs like Bruce Banner.

Hmm, there you go. Back to the Avengers. All right, yeah, the Tesseract 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 Jorge. I'm a big fan of your podcast. I used to dislike physics in high school, but your podcast has now made me realize how fun and interesting physics can be. I've recently been introduced to the concept of a tesseract, and I was just wondering if you could make a podcast episode about how a tessaract describes a four-dimensional space. Is the fourth-th century? dimension time. And does the Tesseract relate to the concept of space time? Thank you.

All right. Thank you, Zoe. I wonder 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 tract is the four-dimensional cube, right? Have you seen that? Like my mind has that animation of like the cube turning itself inside out and it's supposed to be like a visual aid to help you think about the fourth dimension. Never saw that? Like tessellation? Tesolite. Could be same root word, yeah. I've heard of that before as being a fourth dimensional 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. Tesseract 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 Tesseract is in physics, but I remember in the Avengers movie, there 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 movies. I don't remember, but I think it had 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. Avengers has definitely made this idea, or at least this word popular. Mm-hmm. Yeah, 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. Sometimes it's purple, yeah.

The infinity stones all had different colors. They were 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 where they swapped all the colors. No kidding. Yeah, exactly.

Maybe they used the reality stone to flip the colors. I come from an alternate universe where the reality stone was always purple. Well, it's all going towards the multiverse, apparently. So maybe that's the risky. All right. So break it down for us. What is a Tesseract? Tesseract, a super fun concept.

It starts in geometry, where it's basically the fourth dimensional extrapolation of what a cube would be in 3D. 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 3D object. And try to imagine what the 4D version of that would be. That's a tesseract.

You mean like, you know, length, width and depth would be three dimensions. And like, what if you added a fourth one? Yeah, exactly. You start with a point, which is zero D. You make a line, which is 1D. Then you add the second dimension. You get a plane. You have a third dimension.

You get a cube. A tesseract is what happens if you add a fourth dimension. 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. But mostly people think of it as sort of like something you can move around it, right? Like you can't, it's hard to move around color or density. You can map a dimension to anything. Yeah, you could map it to color. You could map it to density. Really, you take this abstract concept of a dimension and map it to 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 reflects 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. 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 add W, right? So like WX, Y, and Z. And this is tricky to think about because we're used to thinking in 3D because we're used to living in 3D. So you might be trying to imagine in your head like, well, what does 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 4D cube? What does a Tesseract 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. 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. A drawing is usually in 2D. 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 3D object in your 3D object in your 3D. 3D mental space. You can do sort of similar stuff drawing things in 3D or even in 2D to give yourself the impression of what a 4D object might look like in your mind. I see.

Like you draw a cube and then you draw another cube and you connect them together somehow. Yeah, exactly. You can extrapolate. Like how do you draw a 3D cube on a 2D piece of paper? Well, 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 2D. cubes on your piece of paper and connect all of their eight edges. And that's sort of maybe what

a tesseract might look like if you were 4D being with 4D eyes and a 4D brain. Right. But I guess that's just sort of like a drawing or like a spatial way to depict it. 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 2D being in a 3D space.

You're still seeing that 3D space. You're only seeing a 2D slice of it, though. So things would look pretty weird if we were in a 4-dimensional space and we were 3D beings. All right. Well, maybe let's jump into this idea of a 4th dimension. What does that even mean, Daniel?

It's hard to wrap your mind around because our brains are 3D 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 90 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 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 3D 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 axis to another axis to another axis. 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 3D, 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 2D surface and somebody passed a stick through that 2D 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 moved that sphere through our 2D slice. Then we would see a flat circle that was growing and then we'd grow and we'd get larger as the center of the sphere passed through our plane and then it would shrink again as the back

half of the sphere passed through our 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. Yeah. Like imagine for example that you were a 3D person and I was a 2D person. person and I like try to put you in prison. I like built walls around you in my 2D 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 2D prison because

you're a 3D 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 4,000, you would be able to 4D person is in a 3D prison. In principle, they could move through that fourth dimension, right? And appear outside the prison cell. Hmm. 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 doesn't 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? Does it 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. That totally works. But it's also, it is possible to move in the fourth dimension. dimension and to have that motion affect how you look in three dimensions.

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 a 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, pyramid. Yeah, or you could be shaped like a peanut.

Like 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 got from a listener, almost on the same topic. Yeah, exactly. People are thinking about four dimensions. And so we had Tom write in and ask his question. Here it is. Hi, Daniel and Jorge. I'm Tom, 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 sort of answered it already, right? Which is that would we be able to see them? Maybe, maybe not. It sort of depends on your shape in this fourth dimension. Yeah.

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 4D 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 this. Yeah. And would they look like Thanos is the question, I think. And 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.

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or I get students who would be like, it's easier to punch someone in the face. When you think about emotion regulation, like, you're not going to choose an adaptive strategy, which is more effortful to use unless you think there's a good outcome as a result of it, if it's going to be beneficial to you. Because it's easy to say, like, go you, go blank yourself. right it's easy it's easy to just drink the extra beer it's easy to ignore to suppress seeing a colleague who's bothering you and just like walk the other way avoidance is easier ignoring is easier denial is easier drinking is easier yelling screaming is easy complex problem solving

meditating you know takes effort listen to the psychology podcast on the iHeart radio app apple podcasts or wherever you get your podcasts All right, we're talking about four dimensions and the Tesseract, which is not a blue cube in a superhero movie, but a geometric shape in four dimensions. Yeah. And I guess we say it's a cube in four dimensions because a cube is kind of like your most basic shape.

Yeah, you could also imagine a 4D 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, two, 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. Right. So I think you can play similar games in 4D for other objects. But yeah, a cube is sort of like the basic thing because you're moving perpendicular in all four directions. Right, right. 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 hunt or 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 make 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 similar. 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 at a really, really small scale, you know, down deep below atoms, below nuclei, below protons, below quarks, much, much deeper down at the very smallest scale. We don't know what the nature of the universe is, but people have speculations, ideas, physicists gone while, 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 11 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 11 dimensions, like up to 24 or 39 dimensions, then it always just sort of end. ends up collapsing back down to 11 dimensions. It's just like the most natural way to express some of these theories is in 11 dimensions. And that makes us wonder, like, well, is that just mathematics or is that actually reflecting

something fundamental about the universe? You know, often in physics we're doing this, we're like noticing a pattern about the way things seem to work mathematically and wondering, hmm, 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 this is where our brains work. And, you know, that'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? Like, let's just add more dimensions. Why not? More dimensions is more math, man. It makes it more complicated. You do an 11-dimensional integral. It's like, you know, 11 times harder than a three-dimensional interval.

Right. But, yeah, sometimes the math just works. Yeah. And it also makes for a cooler grant title, grant application form. Yeah, but the money. you get from that grant, then gets thinner and thinner because it spreads out through all 11 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.

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. Yeah, it's a really tempting idea for lots of reasons. And one, as you say, is to explain this mystery of gravity. You know, all the fundamental forces, the strong force, the weak force, electromagnetism, gravity is the weakest. And not by a little bit, but like 10 to the 30. 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. And 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 measure 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 objects is actually greater than it seems like it is in just three dimensions. So maybe gravity is just as powerful as these other forces is 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 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 found those dimensions and discover that 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 weigh 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 manage to get really, really close to something, if you get, for example, two particles super duper close together so their distance actually gets very, very small, then you might see that very strong gravity. And that's why people think we might make mini 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 mini 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 25 million times a second.

Yeah, what's the worst I can have? 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 time. 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. Promoted. Are you saying time is lesser than space, Daniel? You're saying it needs a promotion? I'm saying it's segregated. It's like put by itself. You know, quantum mechanics likes to say that 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 4D object, which was three spatial dimensions and this one weird time dimension. 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, Daniel? If you think about it, it's brief.

Time can exist without space. Or, you know, time doesn't need. three dimensions of space. You know, time would hang out with two dimensions of space. Yeah, that's true. So really, I mean, I think time is just cooler.

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 there, something really deep

and insightful in understanding time as part of this 4D 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 than 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 package it all together into a four-dimensional concept. Right. This is the concept of space time, right? Like you treat it all as one. concept or one thing or one like coordinate system that we live in? Yeah, exactly. You think about it as 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? It 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 wouldn't be true if you're only looking at like a two slice of it. If you're only looking at a 2D slice of that stick, it would seem like it was changing length as you like rotated it around or whatever. But we know the stick has a certain length. And so we want our like 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, universe that like distance between objects is actually weird. It depends on like how where you are and how fast you're going. And that the distance in time between objects depends also on like 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. Turns out in 4D it does follow those rules. And like the 4D 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 4D space is like more natural that it's the better way to think about the universe. 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 as another dimension. Yeah, you can use the same equations and a bunch of stuff now suddenly makes sense and 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. 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 spaces.

dimensions, but I'm actually sort of moving in the time dimension, right? Yes. Yes, exactly. And the distance between your like space time 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 jog. 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 in 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. December 29th, 1975, LaGuardia Airport. The holiday rush, parents hauling luggage, kids gripping their new Christmas toys. Then, at 6.33 p.m., everything changed. There's been a bombing at the TWA terminal.

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We're talking about the Tesser Act, Daniel. And now in the Avengers, the Tessoract shows up, I think, in the Thor movies first, 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 in the Marvel universe took the infinity stone and put it inside this cube, which they call a Tesseract, to make it like sound awesome and sciencey. 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 it's all connected. And in particular, the Tesseract, and this one is the Space Stone, right? Like it somehow controls space. It lets you like create warm holes and things like that.

Yeah, the space stone has a lot of power and lets you do all sorts of crazy stuff. And so the space stone itself is not the Tesseract, right? The Tesseract is this thing which holds it. And, you know, Tesseract we know now is a four-dimensional cube. But in the Avengers movie, they use a 3D cube because I guess, you know, it's harder to write a 4D cube or even the special effects that Marvel Studios can't do 4D movies. And so it's really just a 3D cube, but it's glowing blue. Right. So maybe in the Marvel movies, color is the fourth dimension. Well, technically, if you're watching in 3D, you are watching a 4D movie because it is playing out in time.

That's true. Right? Yeah, exactly. Right. So if you saw the Avengers in 3D, you probably did see a 4D. the Tesleract containing the space stone. So congrats to you. Right. And then I see in your notes here that it's powered by dark energy, where they're 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 gave them a broad introduction to everything about the universe and they just like cherry pick 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 four that's accelerating the expansion of the universe. I might have to marvel fact check that, Daniel. I think maybe it was another stone that was powered by dark energy. Maybe the red one, the reality one. Maybe?

I'm not quite sure. Yeah, you certainly might be right. I just remember watching this movie and going, ooh, dark energy, that sounds fun. Maybe you were watching it in black and white or something. Maybe I was watching it backwards in time accidentally. Yeah, there you go. And it also shows up in other works, right? In Rinkle and Time books, right?

Yeah, the Rinkle 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 Tesseract. So, like, a Tesseract is a 4D cube in our universe. But in a Rinkle in Time universe, the whole fifth dimension is a Tesseract. 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 Tesseract as a 4D cube. And they just call the Tessaract 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 4D 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 4D sheet to another part of the 4D 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 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 it's 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 wrinkle in time, it does exist. So it's sort of this cool wormhole strategy. But for a reason that just really doesn't make any sense to me, other than that it sounds cool and sciencey, they call that fifth dimension the tesseract. Right. And it also shows up in the interstellar movies, right?

Like Matthew McConaughey goes into a black hole and he's somehow like navigating a tesseract 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 in interstellia, 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 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 It's the singularity. And so 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 a, you know, it makes for a poignant scene. You mean a Christopher Nolan movie doesn't make sense with regards to time? That's so weird. You know, I recently watched Tenet, which is really fun, but I had the impression the whole time that, like,

wow, I either 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? And I tried to map it out. I try to watch it scene by scene be like, okay, what's going on here? How does that make sense? I tried 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 Reddit, and of course, somebody else had watched the movie like 120. 28 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. Where are they going to get so much oxygen? Backwards. Anyways. Yeah, so it shows up a lot in popular culture

and movies and books, but extra dimensions and the test track are sort of real things that physicists are thinking about, It might explain gravity. It might explain how quantum mechanics and general relativity are connected. It's like a real thing. It's a real thing. Or 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 confine. 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, but real and physical.

And that hopefully might help us bridge, as you say, between relativity and quantum mechanics because 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. 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 to it than 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 be wilder than you think. Exactly. And the universe is always filled 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 if there are other dimensions of time. What? All right, let's get to do that. Another time. Sounds good. But in the meantime, we hope that answered the questions

that our listeners had about the Tesseract and about living in four dimensions. We hope you enjoyed that. Thanks for joining us. See you next time. Thanks for listening. And remember that Daniel and Jorge Explain the Universe is a production of IHeart Radio.

For more podcasts from IHeart Radio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows. The holiday rush. Parents hauling luggage, kids gripping their new Christmas toys. Then, every day. Everything changed. There's been a bombing at the TWA terminal, just a chaotic, chaotic scene.

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