Spacetime · Geometry · The Nature of Reality
The Fourth Dimension
What is time, geometrically? Work your way up from a single point and you'll find an answer that changes how you see everything.
Originally posted on Quora by Steve Gunnis · Presented with commentary by Robert J. Burtis
Working Down to Work Up
The trick to understanding the fourth dimension is to start somewhere familiar and systematically remove information. Each time you drop a dimension, you lose something. When you add it back — and then add one more — you gain something that was always there but invisible.
3D
Three dimensions — where we live. Imagine a shiny red ball in front of you. You see it as a three-dimensional object with depth, width, and height. You can walk around it. It has volume.
2D
Two dimensions — a slice. In a two-dimensional world, you can't see the whole ball. You see only a flat circle — a cross-section. As you move through the ball, the circle grows and then shrinks. The depth is gone. You're experiencing a 3D object as a sequence of 2D slices.
1D
One dimension — a line. Drop another dimension and you lose the width of the circle. Moving through it, you experience only a red point that grows into a line and then shrinks again. The 3D ball now appears as a changing 1D line.
4D
Four dimensions — time. Now add back up. We live in a 3D world — but it's actually a 4D world, and the fourth dimension is time. What information have we lost? Throw the ball across the room. The fourth dimension is required to fully visualize its movement. Without it, you have only a frozen snapshot. With it, the ball traces a tube through spacetime — a four-dimensional shape that contains its entire history.
The Implication That Changes Everything
We view the world in 2D snapshots — our retinas are flat surfaces. Our minds infer the third spatial dimension from cues like perspective and shadow. And our memory allows us to infer the fourth dimension — the passage of time. We are four-dimensional beings navigating a four-dimensional universe with only half the dimensions directly observable at any moment.
If you could observe all four dimensions simultaneously —
the way a 3D being can see an entire 2D surface at once —
you would see the entire trajectory of a moving object
as a single four-dimensional shape.
Past, present, and future would be visible at once.
Time would not flow. It would simply be.
This is not science fiction. This is what Einstein's spacetime geometry actually implies. A being with access to the full four-dimensional structure would not experience time as a river. They would see the entire Block Universe — every moment equally present, every event equally real, at different coordinates in a structure that does not prefer any particular "now."
What This Means for the Mystics
The mystics of virtually every tradition have spoken of states of consciousness in which time dissolves — in which past, present, and future become simultaneously available, in which the ordinary sense of being carried forward by a river of time yields to something more like a still ocean containing all moments.
From a River of Dreams perspective, this is not necessarily mystical language for something ineffable. It may be a description — in the vocabulary available to people without Einstein's mathematics — of what four-dimensional perception would actually feel like. If our consciousness is, in some states, capable of accessing the four-dimensional structure rather than the three-dimensional cross-section we normally inhabit, then the mystics' reports of "timeless" experience are not hallucinations. They are observations from a higher vantage point.
A Personal Reflection
The Seth Material, which I have returned to many times over the decades, describes what Jane Roberts called "simultaneous time" — the idea that all moments exist at once, that what we experience as the linear passage of time is a perceptual limitation rather than a feature of ultimate reality. I read this long before I understood the physics. When I finally encountered the Block Universe and Einstein's geometric treatment of time, something clicked. The physics and the mysticism were pointing at the same structure from different angles.
The fourth dimension is time. We can infer it through memory and anticipation. But we cannot perceive it directly — any more than a two-dimensional creature can directly perceive depth. The question the River of Dreams keeps returning to is this: what would it mean to perceive it directly? And is that what the contemplatives have been doing, in their various ways, all along?
— Robert J. Burtis · River of Dreams