Transcription
Up, down, left, right. When I say these words, you instinctively know what I mean. As a three-dimensional being, those directions align with the universe as you know it. Yet, mathematicians and physicists insist that there's another dimension. But we just can't perceive it.
The universe beyond three dimensions holds more secrets than you can ever imagine. And what's even more intriguing is how those secrets affect you every single day. Are you prepared to let go of your very limited view of reality? These are the secrets of the fourth dimension.
The distance in thinking between humans and every other living thing on Earth is inconceivable. As the apex species, we've set the benchmark of knowledge. But are we truly qualified to do so? If all we know is only a tiny fraction compared to what is truly knowable in the universe, of all the gaps of knowledge we have, there's one thing we can't seem to grasp despite our many attempts to try. The fourth dimension. We can try to explain it. We can theorize about it. We can even attempt to visualize it. But it's like a constant blind spot built into us by a function of who we are as a species.
Your intuition right now is telling you that you're sitting still. But are you? No, you're not. At least not according to physics. Right now, you're moving. Maybe not through space, but through time. You're aging. And the rate at which that's occurring is decided by mysterious forces. The forces you've never been taught to think about.
Take maps for example. If you go searching for the objective truth, you'll find that every map of the Earth is actually distorted by necessity. The reasoning is straightforward. You can't make a sphere flat without distorting it. So, while maps serve their purpose, they're not an accurate representation of the world. If we observe them accurately, every map of the Earth fundamentally misses its mark. We've navigated through the world using bad maps our entire lives and we've managed to get by because we understand both the two-dimensional world of maps and the three-dimensional world of our shared reality. But since we have no physical evidence or experience of the fourth dimension, how can we be sure that our three-dimensional maps are sufficiently accurate as navigational tools?
Let me paint that picture with an example. If we were two-dimensional creatures existing on a two-dimensional plane, traveling would be a lot simpler. Using a 2D map, the shortest distance between London and New York looks like a curved line towards the Arctic. But if that's applied in 3D, geometrically speaking, the real shortest distance between both locations would be through the Earth's crust. It's obviously impractical, yet it highlights the fundamental difference between dimensions. So, take it up a notch to 4D and you start to see how mindbending a fourthdimensional reality really is. Right now, we might currently be traveling millions of miles through 3D space to reach a star, but in 4D, some theories suggest that there might be a version of a straight line that could make that distance similar to just a few inches long. What if we're only taking the best route we can contemplate because three dimensions doesn't reveal the true thickness of the universe?
It's not fiction or a shower thought. Humans have been confidently wrong about the nature of reality before. Remember when people thought the universe revolved around the Earth? Or when we thought atoms were the smallest particles in the observable universe? The best thing about science is that new information always makes us better. Understanding the true motion of the planets helped spur a chain of ideas that led to the discovery of gravity. Meanwhile, learning that we could go even further than atoms into the subatomic has helped us with technology. The very transistors powering the device you're using to watch this video would not have existed if we accepted atoms as the actual smallest thing in the universe. So when we explore the fourth dimension, we aren't just running random mind experiments here. We may be grasping at knowledge that might one day totally change the world.
As fun as it is to explore 4D, though, there is a bit of a language problem that we will inevitably bump into. We don't have any words for four-dimensional directions because frankly, we've never really needed them. But we can at least try to visualize and explain it in ways that hopefully do it justice. And then there's the next problem, framing. The fourth dimension is a hot topic in two fundamentally important disciplines, uh, mathematics and physics. The mathematicians got here first and understood the fourth dimension as a purely geometrical concept. So to them, it has nothing to do with time. It's just shapes and space. But then Einstein comes in and shocks the world with his own claim, time. Einstein believed that time was the fourth dimension and this evolved into a physics-based view of 4D. So while we will inevitably explore the two versions of 4D, they are two acts of the same story. Uh, just remember that as we go along.
But before we actually start looking deep into the realities of the fourth dimension, we first have to ask, what even is a dimension? Well, let's strip it back to something almost painfully simple. So, bear with me here. A dimension is just a direction that you can move in. That's it. If you're standing on a straight line, you can only move forward or backward in well, one straight line. So, the world to you has one dimension. There's only one independent direction available to you. Now imagine you're standing on a flat sheet of paper instead. You can move forward and backwards, but you can also move left and right. That's two dimensions. Two independent directions. Add one more. Suddenly you have space. You can move forward, backward, left, right, up, down. Three independent directions. And that's the world that we live in. A dimension is simply a new way to move that isn't just a combination of the others.
So when mathematicians talk about a fourth dimension, they are saying something very specific. They're saying there is another direction, a direction that is completely separate from up, down, left, right, forward, backward. Not diagonally, not any angle, not very far away. We are talking a totally new bespoke direction. And if you're anything like me, this is where your intuition starts to fail because every direction you've ever experienced can be described using just three numbers: length, width, height. Your brain has never needed anything more than that. So trying to imagine a fourth spatial direction is like asking a 2D creature to imagine up. It just wouldn't look like anything to them. It would sound impossible, almost mystical. But from our perspective, it's just normal. And that's the weird idea.
If a two-dimensional being couldn't imagine up, could it even begin to understand a sphere passing through its world? It would only see a circle appear out of nowhere, grow, then shrink, then vanish. To it, that would look like magic. To us, it's just geometry. So when physicists and mathematicians talk about a fourth dimension, they aren't necessarily talking about something supernatural, they're talking about the possibility that there is another direction woven into reality and one we simply cannot turn towards. Our brains are built to imagine three independent directions and that's the limit. When we try to picture a fourth spatial direction, our mental image collapses. It neither turns into something three-dimensional or it becomes abstract and mathematical. We can understand the pattern logically. We just can't see it directly. It's not that the idea is impossible. It's that our imagination does have a ceiling. But hey, you know what? Who says we can't try anyway?
In 1884, a random Victorian school teacher wrote one of the strangest books ever published. It was about a world that was completely flat. Its citizens were triangles, squares, and circles, all living out their lives on an endless sheet of paper, completely unaware that anything more could exist. The book was called Flatland. The main character is a square. Yeah, his name is literally a square, and he's considered middle class in their world. In Flatland, women are simple lines and considered dangerous for their pointy ends. Triangles are a tier above them, followed by squares, like our protagonist, and then polygons. At the top are circles, and they are considered the absolute rulers of society. Such a society feels similar to ours in some ways, both in its flaws and its strange standards.
At one point in the story, a square's life takes a serious turn as a 3D sphere passes through Flatland. But he doesn't see it as a sphere. He simply sees a dot that becomes a circle. He watches it grow, shrink, and eventually vanish. It's a confusing feeling. A square watches what is essentially the mold of what he considers as a fellow person morphing and distorting between sizes with ease. As if this strange sequence is totally natural. Everything about a square's understanding of reality turns on its head. How could a dot, something even less than a line, the lowest of flatland society, transform into a circle, widen easily, and also vanish into the distance just as quickly as it arrived? Now you can see how this book brilliantly captures the scary reality of being a three-dimensional object that happens on a four-dimensional object.
What would it feel like to see a four-dimensional creature taking a stroll through reality? It would first appear as a strange three-dimensional shape that materializes out of nowhere. Then it morphs into things we recognize but can't quite put a finger on. And then almost in an instant, it would disappear with no explanation. The creepiest part of all of this is that a square never even got to see the 3D object, only its two-dimensional shadow. That's the exact same way we would experience a four-dimensional object. We would only be able to see its shadow. And yet, what we'd experience would completely break our minds and our understanding of reality. If only the crosssection of the fourth dimension is that profound, visualizing the real thing is not that different from insanity. A 4D creature would possess the ability to reach inside of a locked room without opening it. The same way we have the ability to touch the middle of a circle drawn on paper without crossing its circumference.
Edwin Abbott came up with Flatland thanks to the Victorian era fascination with mystics and spiritualists. Many of these individuals turned out to be con artists, but they did provide a fascinating case study for what higher dimension interactions could look like. A 4D being would certainly be able to pull a rabbit out of an empty hat. So, it's not like the deceptions were unfounded. During that period, many claimed that the dead were living in a higher dimension just out of reach. It's admittedly a a creepy thought that brings a new meaning to popular visions of loved ones who passed away. What if in their ascension to a new dimension, they gained the ability to cast 3D shadows that we see as ghosts and spirits? I don't know. Being on the wrong side of a dimension can feel invasive, but it's also helpful to know what it might feel like. To a 4D being, you're just as clueless as the average flatlander who creates rules around seemingly foolish ideas. However, you have something the Flatlanders don't, and that is a really good imagination.
Flatland quietly reveals something deeper about perspective. A square couldn't imagine a third dimension because his mind was built for two. Entire layers of reality existed around him, and he was simply never able to perceive them. And in a strange way, that reminds me something about our own world. Not in a dimensional sense, but in a biological one. There are billions of conscious creatures living lives right alongside us that we almost never think about. Many of whom are suffering unimaginable amounts of pain.
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Now, let's return to the fourth dimension. Our exceptional imagination as humans allows us to bend rules a little better than any other species could hope to. Therefore, imagining our way through 4D is not pure speculation, but rather a solid way to bypass our physical limitations. So, what I'm going to do now is help you build something in 4D. Here's how. First, we have a single point that extends into a line. It's basically what we established earlier for 1D. However, to upgrade it, we'll draw a few more lines to make it a square. And now we're in 2D. We extend the shape even further and we add a new perpendicular direction. After completing the lines, we now have a cube. Cubes are something we can draw as a representation of 3D even on a 2D surface. So, naturally, what would the 4D equivalent of the cube be? Thankfully, there is a real answer available and it's called a tesseract. Remember how we've used shadows as a step below representation of each dimension? I want you to hold on to that thought because what we'll do here is create a 3D shadow of this tesseract, a 4D object. See how strange it is to look at? It's almost like an optical illusion that pays off if you pay enough attention to it. The weird rotating shape isn't random or or trying to be imposing. It's just the strange logicbending rules of 4D at play in a 3D perspective. Some of you may have even seen this online and wondered what it was, but now you finally have your answer. Even if you're not necessarily equipped with what to do with this odd looping box thing, there's probably some sense of empowerment in being familiar with the shadow of a higher dimension.
Uh, well, forgive me for this, but I'm going to immediately take away that sense of empowerment. Because if a 4D creature had darker intentions towards you, there's absolutely nothing you could do about it. Uh, let's say by some miracle you came across a precious rare diamond. I I'm talking about Scrooge McDuck levels of wealth here. You could swim in it and you have to store it in a big cartoon vault. How would you keep it safe? Now, let's say you keep it in a sealed room built by science's greatest minds. They've developed the technology to keep even atoms away from penetrating without the right passcode. and you feel satisfied with your efforts. And then you step out of the facility. 2 minutes later, the alarm goes off. You assume it's an error in the system until you check the CCTV footage and your precious diamond is gone. Every sensor in the room failed to go off. So, how is that even possible? Well, to everyone presently inhabiting the Earth, it falls into two equally mystifying categories. Either it's an illusion or it's magic. To a 4D creature, it's just a random Tuesday. Its ability to take the diamond without the limitations of a 3D sealed box is the exact same geometric logic we use to open doors, lift objects, and interact with everything around us.
To really understand this, let's go back to Flatland. Imagine you're a 3D burglar, and your victim is a square, a 2D creature. This flat person stores their most valuable possessions inside a perfectly sealed square vault. The walls are all solid lines with zero visible cracks from their point of view. To them, it is absolutely secure. Now you, a 3D being, walks up to this vault. You don't have to break the walls or crack the safe or disable any alarms. You simply reach down from above, lift out the object, and just leave. From the 2D person's perspective, the object would simply vanish. No wall breached, no door opened, every boundary is still perfectly intact. And it's the same way with your three-dimensional vault. The four-dimensional creature would simply take the diamond and move in a direction that you can't access. From your perspective, the diamond would disappear. Sensors would show nothing, and the room would remain perfectly sealed.
A 4D being's understanding of us would probably be instinctive. And much like the geometry of stealing a sealed diamond, it can do even weirder things. Take our own bodies for example, it would possess the ability to see the interior surface of your body, like your organs, your brain, and your circulatory system. A 4D doctor would likely be incredibly efficient at removing cancerous tumors. There would be no need for incisions or special tools. the tumor would effectively vanish from your body and then appear in their hand. For a concept this rich, it's a tragedy knowing that we'll never get to see it in its full glory. Although 4D is impossible to see, the reason why we can't see it is also an equally interesting exploration.
Your brain doesn't show you reality in its most concrete sense. We only see a model of it. For example, if you went into a mosquito's mind and saw through its eyes, you'd be color blind. The world would be pixelated and you'd be extra sensitive to motion. As a trade-off for the terrible eyesight, you'd gain the ability to see heat signatures, giving you precise visuals for the juiciest veins. Now, think of any living thing with eyes or senses. And these variations feel endless. The reason mosquitoes see the way they do and we see the way we do comes down to evolution. The model of reality we evolved to perceive is what our genes prioritized for our survival. As humans, we can't feel magnetic fields the way some birds do. We can't see ultraviolet light. We can't hear a majority of the sound spectrum. Slowly you realize that we are missing out. And the fourth dimension might belong to one of the categories we never evolved to perceive. What if it's not an absence in reality, but an absence in us? In that case, the limits to our perception do feel like a huge hole in our evolution. But those limits can't stop us all. In fact, Einstein didn't need to see it. He found a way to detect its effects and prove that it shapes everything around us. And what he found is what comes next.
In 1908, a former mathematics teacher named Herman Mancowski stepped onto a stage in Cologne and changed the way that we describe the universe. Years earlier, he had taught a young student at the Zurich Polytenic. That student considered his lectures overly abstract, too mathematical, and too detached from reality. I'll spoil it right now. The student's name was, say it with me, Albert Einstein. By the time Manowski gave that 1908 lecture, Einstein had already published special relativity. He had shown that time slows down at high speeds and that space itself contracts, but he had done it all through physics with equations and algebra. He did not yet see the universe geometrically, but Manowski did. In that lecture, Manowski made a very bold declaration. Space and time, he said, are not separate things. They're woven together into a single fourdimensional fabric. What we experience as space and what we experience as time are just different aspects of the same structure. He called it spacetime.
When Einstein first heard this framing, he dismissed it. He referred to Manowsk's approach as a kind of superfluous learnedness. It sounded like mathematics for the sake of mathematics. But then something clicked. Einstein realized that Manowski had uncovered the deeper structure behind his own equations. Special relativity was not just a set of physical rules. It was a description of geometry, gravity, motion, time itself. They were not forces acting inside of space. They were features of space-time's shape. Even Einstein needed a moment to see it. And once he did, physics was never the same again.
To better understand it, I want you to answer me this question. Where's your phone? Go on, leave your answer in the comments down below. I'll start. Mine is currently laid down flat, sitting just over there on that table, almost away from my line of sight. Almost. When is my phone in this exact position? Right now, but what is now? 10:53 a.m. is how I would answer you. When asked this question, you likely answered by describing where it is in space, but then you left it at that. But when it is is an equally relevant detail that completes its location in spaceime. It's a little strange, but hang in there with me. I'll give you an even simpler way to understand it.
According to Einstein, you are always moving through something called spacetime. Even when you feel like you're completely still, you are still moving. The question isn't whether you are moving, but how that movement is divided. The strange rule is this. The faster you move through space, the slower you move through time. And the slower you move through space, the faster you move through time. You can picture it as a constant overall motion. Imagine that everyone is always traveling at the same total cosmic speed. But that speed can be split between space and time. If you're sitting still in your room, almost all of your motion is going into moving forward through time. Seconds pass normally and you age at the rate that you would expect. But when you start moving through space, even just a little, a tiny portion of that motion shifts away from time and into space. When that happens, time slows down slightly for you. At everyday speeds, this effect is so minuscule that you never really notice it. But it is real and it is in fact measurable. Astronauts orbiting the Earth age slightly slower than people on the ground because they are moving faster through space. The difference is tiny, but it has been scientifically confirmed. If you could travel close to the speed of light, the effect would become dramatic. From your perspective, time would feel normal. But to someone watching you from Earth, your clock would tick much more slowly. There's a lot more fancy science at play here, but the overall result stands, and that's pretty mind-blowing.
Remember when I said that to answer where your phone is, you should include when your phone is in that spot? Well, here's the full truth. If you didn't account for the time when it was there on a universal level, you'd be incorrect. Even if it's left untouched for 24 hours, your phone is actually moving through time the same as you and everyone around you. To take that idea even further, here's something that will genuinely mess with you. Clocks may be wrong. At least in a universal sense, my now and your now are fundamentally different depending on where we find ourselves and how fast we're moving through space. And I'm not just talking about time zones here. Even just a short distance away from someone moving at a different speed, we might experience the same events in totally new temporal ways.
Imagine a train moving at a high speed. Then suddenly, two lightning bolts strike both ends at exactly the same time. As a bystander waiting by the train tracks, you watch it happen and your jaw drops in awe. Meanwhile, let's switch perspectives. Now you're a passenger sitting in the middle of that same train. This time, what happened was that one bolt struck before the other. It was only a slight delay, but you unmistakably heard a loud boom towards the front followed by another at the back. Same two bolts, same moment, two different perspectives. Neither person is wrong. From where they stand, both of them got it right. The issue here is that the concept of at the same time is not a universal truth. Everything relies entirely on where you are and how fast you're moving. This is called the relativity of simultaneity and it dismantles an idea most of us have always accepted without question that there's one universal clock ticking the same for everyone around the world. 4D shows that the present is a relative concept. Same with regular concepts like directions. Past, present, and future all exist simultaneously like all directions in our three-dimensional space. With a difference in speed, time transforms and contorts itself. On that note, maybe you shouldn't accept time as a shared experience and instead embrace it as a personal one.
So far, we've only explained spaceime and 4D on a personal level. So, how does our own planet respond to these newly revealed truths? This is the part where everything you thought you knew about gravity gets dismantled. Newton taught us that gravity was a force. The invisible pull between objects that possesses mass, dragging them towards each other across empty space. For centuries, it was enough to know that gravity predicts the motion of planets and explains why things fall. Nobody really challenged his findings. But from Einstein's point of view, he saw something totally different. To him, there is no pull and there is no force. Rather, what we call gravity is the shape of spaceime itself. What that means is this. Stars, planets, and anything possessing significant mass aren't just reaching out and grabbing things. Instead, they are so big they warp the entire fabric of spaceime around them. This creates a curve so that everything nearby, including light, simply follows that curve. For us, that means the Earth isn't pulling the moon towards it. That's not an accurate way to describe what's happening. The Earth is actually bending the geometry of spaceime around it, and the moon follows accordingly. The mass of the moon isn't enough to overpower the Earth's space-time bending influence.
To put it in simpler terms, if I had a soccer ball and I placed it on a stretched piece of fabric like a bed sheet, the fabric would dip in the exact spot that I placed the ball. Now, if I were to bring a tennis ball onto this same fabric, the ball would roll up to the dip created by the soccer ball. After all, the soccer ball has a higher mass, so it dictates the bending. It's easy to see how one might think the tennis ball is attracted to the soccer ball. But no, the tennis ball, much like the moon, is only pulled by the change in geometry caused by something with a higher mass. This is what Einstein meant when he said that gravity and spacetime are inseparable. The fourth dimension goes beyond just tracking events in time. It can actually bend and it has a shape. This was confirmed by gravitational wave detection in the LIGO observations from 2015. So yes, scientists have evidence that all this is in fact real and we're only learning more. We've moved past pure theory and now we've realized that spaceime is physical enough to influence our universe significantly.
Taking everything we've discussed about curved spaceime and pushing it to its absolute limit, we find science fiction's favorite event, a black hole. Black holes happen when an object is so massively dense that it creates a curve in spaceime which essentially becomes a point of no return. The geometry governing spaceime doesn't dip like with the soccer ball in the bed sheet. Instead, it spirals inwards so severely that nothing nearby can ever follow a path that leads back out. That includes matter and even light. Since time is relative, like we explained earlier, the black hole also influences it significantly. Time near a black hole doesn't just slow down slightly like with our astronaut example. It actually slows down to almost a complete stop near a black hole. If you ever found yourself hovering near the edge of a black hole, you're better off exploring the cosmos than returning to Earth. Why? Because even if you were there for what felt like an hour, the Earth you left behind would be gone. And you'll find that centuries, if not millennia, have passed. The more space-time curves, the slower time moves within it. It's the same fabric we've come to know with planetary masses, only this time the rules are taken to an extreme conclusion.
Each time you open Google Maps, you're relying on information from a bunch of satellites orbiting the Earth at high speeds located far above the surface. GPS satellites move fast. According to the rules of special relativity, these satellites have clocks that are measurably slowed down compared to ours on Earth. But they are also sitting in weaker gravity than what we experience on the surface. That distinction makes a huge difference because according to general relativity, this also speeds up their clocks. So there are two opposing effects going on with GPS satellites. It sounds like a lot to deal with, especially since they are both significant enough to matter. How this issue is resolved comes down to the brilliance of engineers. They ensure that the gravitational effect actually wins here. Meaning that GPS clocks are programmed to run slightly faster overall. Every single day, engineers must correct for both of these factors by using Einstein's equations, not just as an interesting academic exercise, rather as a necessity. Without the corrections, the correlation between what your GPS says and where you are would be completely off by several miles. The fourth dimension isn't a theory waiting to be proven. It's already a part of our infrastructure in the modern world.
We've explored a concept that's already difficult on its own, but add two strong interpretations of it and we've got an even wilder mystery on our hands. one that creates a powerful premise. If a dimension is an independent axis of information, then 4D is a way to open our eyes beyond the boundaries of reality and into a higher dimension. Geometric 4D showed us that space has more structure than what our senses can comprehend. Meanwhile, the physics 4D showed us at that time isn't separate from that structure. Together, they are proof that the universe is richer than what we are evolutionarily equipped to perceive. Every time humanity learned something new about our world, we became better off because of it. The Earth wasn't really flat. The sun didn't orbit around us. Time wasn't fixed. All these ideas have had direct consequences that shaped our world today. The fourth dimension is that kind of expansion. We may never get to see it directly, but our ability to think in it, build with it, and navigate from it is no small thing. In the end, that's what makes us different from the flatlanders. We started this journey by asking an important question. Are we prepared to let go of reality if we ever manage to look beyond three dimensions? Having come this far with me, are you? If you are, may I interest you in even more dimensions? Watch this video to find out more.