Emergent spacetime

Emergent spacetime is the hypothesis that spacetime — the arena of physics — is not a fundamental structure but arises from more basic, non-geometric degrees of freedom. The leading evidence for this hypothesis comes from the holographic principle and the AdS/CFT correspondence, where a gravitational theory in a higher-dimensional bulk is exactly equivalent to a non-gravitational quantum field theory on a lower-dimensional boundary. In this duality, the bulk geometry is not postulated but derived from the entanglement structure of the boundary.

The emergent spacetime paradigm suggests that geometry, causality, and even dimensionality may be secondary properties of an underlying quantum information structure. Proposals such as the it from qubit program attempt to derive spacetime from tensor networks and quantum error-correcting codes. If correct, this would mean that the most fundamental description of reality is not a theory of fields in spacetime but a theory of information without spacetime — and that Einstein's geometry is merely the low-energy, coarse-grained approximation of a deeper quantum code.