Do You Have the Keys to Rotate a 3D Cross Section?
This is a deep one for me, personally. So bear with me.
When I was a kid I came up with this idea: ghosts can actually exist. They just have to live in another dimension. That was enough to keep my childhood fear intact for a while. Later I realized the intuition behind it is very well known and I had not discovered anything. But at the time it felt like a discovery, and that feeling is what matters here. The thing was, in a sense, right there the whole time. It is very intuitive once you let yourself look at it.
The slice
Take a sphere and pass it through a flat plane. The plane only ever sees a slice of the sphere: a segment, a circle, that grows and then shrinks. If you are a being living in 2D, that circle is the sphere to you. You never see the whole thing at once. You see its cross section.
Do the same thing one dimension up. Pass a 4D sphere through our 3D space and what we would see is a bubble that appears from nothing, expands, contracts, and disappears. A sphere that grows and shrinks out of thin air. Up to here, everyone is more or less on the same page. This is the standard picture.
I built a little thing for this. Play around with the slicing to feel what I am talking about, from 1D all the way up to a tesseract.
But there is only one world
Here is the part I had to sit with. There cannot be two worlds. The world is not 3D and 4D at the same time. The number of dimensions does not change. We are just made of sensors, and there is only one universe.
So we must be experiencing a subset of what is actually there.
General relativity, and other theories too, imply a single world of higher dimension. The world has to be at least 4D. And arguably one of those dimensions is time. Because right now, if you want to say where you are, three spatial coordinates are not enough. You also need a fourth coordinate: when.
What if time is just space we can only read one way?
So here is the thought. Maybe time is just the way our body, think of it as a sensor, perceives another spatial dimension. Maybe everything is always the same. Maybe there is no time at all, and what we call time is only the mode through which our body experiences something that is higher dimensional. In that case time is not its own thing. Time is a property of space.
The beauty of math is that we can run the experiment without leaving the room. Imagine you are a being living in 2D. How would you ever experience 3D? You could do it like this: you live in a plane, but you anchor that plane on yourself. You become the pivot. Now you rotate the plane into a direction that does not exist for you, and each angle gives you a different cross section of the 3D universe. Rotate enough and you can, in principle, experience the entire 3D world through your moving slice.
The 3D slice of a 4D world
By the same logic, you can build a 3D cross section of a 4D universe. Theoretically we should be able to see the whole 4D world through that slice, just by rotating it.
Except, and this is the catch, as far as I can tell, we cannot rotate this 3D cross section. We do not have the keys to rotate it. We only get to experience it in one way, sliding along one direction. And that one direction we are allowed to move in is, potentially, time.
Which turns the whole thing into a single question.
Do you have the keys to rotate a 3D cross section?
I do not have the answer. But I think the question is the right one.
The hint that is already in the physics
And then there is something else, which I think is a hint. Time and space are correlated, and there is a hard limit on velocity: the speed of light. And the faster you travel relative to everything else, the less time actually passes for you between two points than for everyone who stayed behind. You never feel your own clock slowing down, it always ticks normally to you, but when you come back you have aged less than they have. To me that smells like it is about the keys, about turning them, or about something close to that. Either you turn the keys, or you do the opposite: you stop.
Picture it. You are living inside a 3D cross section that is constantly rotating, and that rotation is time. Now you start to move faster. The faster you go, the more the rotation slows. Push all the way to the speed of light and, for whatever reason, the cross section stops spinning entirely. At that point you no longer experience time at all. Which is exactly what happens if you are a photon.
Is time the gift to life?
And then there is one more question I want to leave here. If the universe is one, and we exist, then somehow we must also exist in a 4D way. Think about it: there is no way to build a true 2D being. You might say a line of atoms, but that is still wrong, because atoms are made of other things, so you can never have a line of something with zero thickness, which is what 2D would actually require. So no matter what you do, you must exist in 4D.
And here is the thought that follows. Maybe everything is static. A 4D world that just sits there, complete. And time is only the way you slide your 3D cross section through it.
So could it be that time is the gift to life? That without time there would be no life at all, simply because everything would be frozen and static? This is more of a random, existential question. I am not sure it is the right one. But I will leave it here.
Last meaningful edit: 1 June 2026.