Causal Dynamical Triangulation: Spacetime Built from Simplices

Quantum gravity's central puzzle is that spacetime itself should be quantum — fluctuating, discrete at the smallest scales, yet smooth on average. This 2D simulator builds a real causal dynamical triangulation from the ground up with an actual Monte Carlo Markov chain: a stack of causally-ordered time slices, each a ring of spatial vertices, evolving under real local moves (vertex insertion/deletion and edge reconnection) accepted or rejected with a genuine Metropolis rule weighted by the combinatorial entropy of the triangulation itself. Start it from a deliberately jagged spacetime and watch — and measure — the volume-vs-time profile relax toward a smoother shape purely because smoother configurations vastly outnumber rough ones in the sum over triangulations, the same entropic mechanism that gives quantum gravity a well-defined classical limit.