We are slice observers
Spacetime is a four-dimensional geometric object with a hyperbolic structure, and we move along a single curve through it. From the inside, that curve looks like a life. From the outside, it would look like a thread laid through a richer geometry we never directly perceive. The next question is what kind of observer that makes us, and what follows from being that kind of observer.
A species calibrated to a slice
Human evolution did its work in a regime where relativistic effects round to nothing.
A walking human moves at about a meter per second. The Earth carries us around the Sun at 30 kilometers per second, roughly one ten-thousandth of the speed of light. The Sun carries the solar system around the galaxy at about 230 kilometers per second, less than one part in a thousand of c. Set those numbers against the scale at which the Lorentz transformation [the rule that mixes space and time when one observer moves relative to another] starts to bend ordinary intuitions, and they are not even on the chart. Across every speed that mattered for survival, the corrections to Newtonian mechanics are smaller than the noise in any sense organ we have.
Our nervous system was tuned to a flat-space approximation, because nothing in our evolutionary history rewarded paying for anything richer. We feel time as a single line that flows. We feel space as three independent directions. We feel simultaneity as a property of events out in the world. We feel motion as arrows that add the way arrows add on paper. Every one of those feelings is correct inside the slow corner where we were shaped. Every one of them is a lie about the geometry we are inside.
The geometry §02 described is real. Our perception of that geometry is a slice. The slice is good enough to walk to the bus stop on. It is not the object. Physics gives us the object; perception gives us a section through it.
Block universe as one consistent reading
The view sometimes called the block universe [the reading on which past, present, and future are all equally real, and four-dimensional spacetime is a fixed geometric object rather than a flowing process] is one consistent way of taking this seriously.
Two papers from the late 1960s sharpened the move. Cornelis Rietdijk argued in 1966 that careful application of special relativity entails determinism. His logic ran like this. Two observers in relative motion will disagree about which distant events count as “now.” Whose “now” is the real one? If neither observer is privileged, and both readings of “now” are equally valid descriptions of the same spacetime, then the events both observers are pointing at are equally real, including the ones one observer calls past and the other calls future (Rietdijk 1966). Hilary Putnam followed in 1967 with a tighter version: if simultaneity is observer-dependent, and if events simultaneous with a real event are themselves real, then the future, viewed from somewhere, is real now (Putnam 1967). The two arguments together are the canonical Rietdijk-Putnam case for the block.
Block universe is a live reading, not the consensus. Some philosophers prefer presentism [only the present is real; past and future are not], and some prefer the growing block view [past and present are real, the future is open]. The mathematics of relativity is the same under all of these. They are interpretive choices, and the empirical record does not pick between them.
What the block universe does, for this paper’s purposes, is name a coherent way of holding the four-dimensional geometry at face value. On this reading, the experience of time as a flowing process is a feature of the slice, not of the object. The flow is what it feels like to be a strand inside the geometry. The geometry itself does not flow.
I lean toward the block reading personally, but I am not endorsing it here. Even setting it aside, the slice-observer framing survives. Whether or not the future “really” exists in some metaphysical sense, perception is structurally limited in the way the framing describes.
What follows from being a slice observer
If we are observers calibrated to a slice through a richer geometry, three regularities should show up in what we perceive.
The first: things that look local from inside the slice can have non-local relationships in the object. Picture a sphere cut by a plane. The cut leaves a circle. Inside the circle, two points on the same arc look like neighbors; they are. Two points on opposite sides of the circle look distant; they are too, if you stay inside the circle and walk around the rim. From outside the slice, though, those opposite points are joined by a great-circle path that arcs through a region the circle does not contain. The slice records a long distance. The full object contains a shorter route. A slice through a connected geometric object will, in general, fail to mirror the connectivity of the object.
The second: certain features of the object will appear as artifacts in the slice. Simultaneity is the canonical case. From outside the slice, “now” is not a feature of spacetime; it is a feature of the slicing. Different observers cut the geometry into “before,” “now,” and “after” at different angles, and the disagreement between them is not a disagreement about facts in the world but about where the cut goes.
The third: a slice observer who looks carefully should expect to find that the world has more structure than the slice gives them direct access to. Connections between things that should be unconnected. Conserved quantities whose accounting requires reference to regions the slice does not contain. Wholes whose parts cannot be fully described as locally separate. That is exactly what physics has been finding for a century.
Three concrete examples of physics that does not stay in the slice
Three pieces of well-established physics already exhibit the structure the previous section described.
Quantum entanglement
Imagine preparing two particles together so their spins are perfectly anti-correlated, then sending one to a lab in Geneva and the other to a lab in Sydney. In Geneva, you measure the first particle’s spin along a chosen axis. The instant you do, the second particle’s spin along the same axis is fixed too. Run the experiment thousands of times and the statistics agree: every time Geneva sees “up,” Sydney sees “down,” and the other way around, no matter how far apart the labs are. The correlation is not a signal. Geneva cannot use it to send a message to Sydney; the result on each side, taken alone, looks random. But the joint statistics line up perfectly. Bell-test experiments since the 1980s have confirmed this at increasing distances, with increasing care, and recently across kilometers of free space.
The technical name is entanglement [the feature of quantum mechanics in which a multi-particle state cannot be decomposed into states of its constituent parts]. The pair has properties; the individuals, taken alone, do not. There is no separate “this particle’s spin” sitting somewhere waiting to be read; the spin only exists once you measure, and the measurement on either side determines what the other side will see.
From inside the slice, this looks like spooky action at a distance. From outside, the strangeness softens. The pair is one quantum-mechanical object. The slice draws a line between two parts of that object and labels them as separate, but the object does not respect the labeling. The non-locality is non-locality of the slice, not of the underlying state.
Gauge fields
Picture a long thin solenoid, a tightly wound coil of wire. Run a current through it. Inside the coil, a strong magnetic field appears. Outside the coil, the magnetic field is, in the idealized version, exactly zero. Now take an electron and route it on a path that goes around the solenoid but never enters it. Classical electromagnetism says the electron should be entirely unaffected; it never touched the field. Quantum mechanics says otherwise.
Yakir Aharonov and David Bohm pointed out in 1959 that the electron’s quantum-mechanical phase, the angle that determines how its wave interferes with itself when paths recombine, picks up a shift that depends on what is happening inside the region the electron never visited. Send the electron through a two-slit setup with the solenoid sitting between the slits, and the interference pattern on the far screen shifts as you turn the current up. The electron is sensing something it cannot, in a slice description, have touched. Tonomura’s group confirmed the effect cleanly in 1986 with electron holography, ruling out the loopholes earlier experiments had left open.
The mathematical apparatus that makes sense of this is the language of gauge fields [fields whose mathematical description has a built-in redundancy; physically meaningful quantities are the ones that stay invariant when you change the redundancy]. The fundamental forces of physics, electromagnetism and the weak and strong nuclear forces, are all of this kind. The redundancy is the structure the theory uses to encode how local quantities connect across regions of space. The phase the electron picked up was an integral around a loop, and integrals around loops can pick up contributions from what the loop encloses, even when the loop never crosses it. The particle, in a slice description, never went near the field. In a properly geometric description, it moved through a structure where the field’s effect is global.
Gauge fields make the same point as entanglement, in a different language. A faithful description of how the universe distributes its forces requires structure that does not stay where the slice puts it.
Conservation laws
Roll a ball on a frictionless table and let it bump into a second, stationary ball. Track them after the collision. The total momentum of the pair, before and after, comes out the same number. The total kinetic energy, in an elastic collision, comes out the same too. The total electric charge of any closed system never changes. These are not accidents of the bookkeeping. They hold across every experiment ever run.
The question is why. In 1918, Emmy Noether published a theorem that gave the answer with stunning generality (Noether 1918). Every continuous symmetry of the laws of physics corresponds, exactly, to a conserved quantity. Translate your experiment in time, do it tomorrow instead of today, and the laws give the same answer; that symmetry is conservation of energy. Translate it in space, do it across the room instead of here, and the laws still apply; that is conservation of momentum. Rotate it; that is conservation of angular momentum. Each conservation law is a symmetry of the geometry, viewed from inside the slice.
A slice observer who tracks only their immediate neighborhood will see energy come and go. To balance the books, they have to expand the accounting to a larger region, in time as well as space. Conservation is a constraint the geometry imposes on any slicing of itself, never visible at a single point. The slice has to respect the symmetry the geometry has, even when the slice cannot see the symmetry directly.
Three different fields, the same shape of finding. In each case, the slice observer meets a phenomenon that does not fit a strictly local description, and the resolution is to describe the structure as belonging to a larger object the slice is cut from. The same family of structural fact, non-local relationship inside a connected geometric object, applied to three different substances: quantum states, gauge field configurations, and conserved quantities.
The phenomenology of constrained observation
Across human cultures and recorded history, there are recurring intuitions that the world contains more than what perception delivers. Intuitions of hidden depth behind appearances. Intuitions that local actions have non-local consequences. Intuitions of connectedness between things that look separate. Intuitions of affected but non local observers with access to higher energy states or shapes. Different cultures dress these intuitions in different specific clothing, and the specific clothing has been the subject of much conflict over the centuries. The intuitions themselves are remarkably persistent across the dressing.
One reading is theological. I am not making that reading.
Another reading is structural. Constrained slice observers in a richer geometric object should be expected to produce intuitions of this shape, not because the metaphysical content the intuitions wrap around is necessarily true, but because the structural constraint is the same across observers. If you are a strand inside a four-dimensional connected geometry and you perceive only your local neighborhood, an intuition that “things are connected in ways I cannot directly see” is not mysterious. It is what the situation would feel like from inside.
This is phenomenology, not metaphysics. I am taking the cross-cultural intuitions as data about what it is like to be a constrained observer, not as data about hidden reality. The intuitions tell us something about the observer’s situation. They do not, on their own, tell us what is on the other side of the slice.
A prediction, before the next section tests it
If we are slice observers of a richer geometric object, we should not be surprised when modeling complex systems forces us into richer geometric structures than our perceptual default.
Physics has been making this trade for a century. The geometry of spacetime, the structure of quantum states, the bookkeeping of conservation laws: each required leaving flat-space three-dimensional intuition behind. We did not pick up richer geometry because we wanted it. We picked it up because the phenomena being modeled would not sit still in the simpler space.
The next section documents that the same pattern is now showing up in four other fields, all at once. Large language models. Quantum computation. Neural population activity. The substrate of consciousness. Each of those fields, on its own current best understanding, lives in a high-dimensional geometric structure that flat-space three-dimensional descriptions cannot capture. If the slice-observer framing is right, the convergence is what we should expect.