Hubble Tension — Two Ages of the Universe

Two identical flat-ΛCDM universes, side by side, differing only in which Hubble constant measurement calibrates them: one uses the cosmic-microwave-background value from Planck, the other the local Cepheid–supernova distance-ladder value from the SH0ES collaboration. Both scale factors are computed from the exact closed-form solution of the Friedmann equation for a matter-plus-dark-energy universe, so the growing separation between the two galaxy lattices as you press Play is a real, physically-derived consequence — not an animation trick — of the genuine ~9% disagreement between the two H₀ measurements that cosmologists call the Hubble tension.