How physics keeps mistaking a way of describing reality for a place inside it
When physicists talk about the universe at different scales—from quarks to galaxies—they often draw pictures where scale looks like an extra dimension. In holographic theories and modern quantum physics, this extra “depth” is drawn like a direction you could move along, almost as if reality has hidden layers stacked behind what we see. It’s an incredibly powerful picture. It’s also misleading.
The core claim of our new paper is simple but uncomfortable: depth is not a real spatial direction. Nothing actually moves “into” deeper layers of reality. What depth really tracks is not where things are, but how much information we are keeping in our description. Depth is a bookkeeping device, not a dimension of space. We obviously live in a three-dimensional world, and we really do move through depth. But making something permanent — turning an event into a fact — requires something different. You can move along a line forever, but you can’t protect a record there. The first place permanence becomes possible is on a surface, where you can draw a boundary and create an inside. That’s why facts, records, and information always end up living on surfaces. The paper shows that two dimensions are the minimum needed for facts to exist at all. What we think of as “depth” helps things move, but it isn’t where facts live — it’s how different views of the same facts get organized.
A useful way to see this is with a video game analogy. Imagine a role-playing game rendered on a computer. The game world itself is genuinely three-dimensional—characters move left–right, forward–back, up–down. Now change the rendering resolution from 4K to 1080p to 480p. The character hasn’t gone anywhere. No one traveled into a new direction. The same world is simply being described with fewer pixels. Information was discarded, not relocated. Renormalization “depth” in physics works the same way: it tells us how coarse or fine our description is, not where anything lives.
The confusion becomes especially tempting in virtual reality. In VR, resolution is often tied to distance—near objects are sharp, far ones are blurry. It can feel like resolution is depth. But that’s an illusion created by the rendering engine. Change the rendering strategy, and the illusion disappears. In modern physics, something similar happens: under special conditions, the organization of information across scale behaves as if it were an extra spatial dimension. That doesn’t make it one. It just means the representation is effective.
Why does this matter? Because treating depth as a real dimension quietly smuggles in assumptions that aren’t true—about locality, motion, reversibility, and independence. In real space, you can move back and forth, act locally, and keep track of what’s independent of what. Depth doesn’t allow that. Once information is coarse-grained away, it’s gone. You can’t travel back. That single fact breaks the logic of spatial dimensions.
The paper goes further than philosophy. It shows that if depth were a genuine dimension, certain symmetries would appear in experiments—symmetries that don’t actually exist. Instead, we predict specific asymmetries and correlations that can be tested in quantum simulators and tensor-network experiments. In other words, depth being an illusion isn’t just an interpretation—it has observable consequences.
The takeaway is this: physics has gotten very good at drawing pictures where everything becomes geometry. But not everything that looks like a dimension is one. Depth isn’t a hidden direction behind the universe. It’s the shadow cast by how we choose to describe it.
Or, in one sentence:
Renormalization depth is to spacetime what rendering resolution is to a video game: it can be drawn as an axis and behave geometrically in certain regimes, but nothing in the world actually moves along it.