The universe has been expanding since the Big Bang 13.8 billion years ago. Galaxies don't move through space — space itself expands. ΛCDM: 5% ordinary matter, 27% dark matter, 68% dark energy. Scale factor a(t) = A·sinh²/³(t/T_Λ), calibrated to a(13.8 Gyr)=1. CMB temperature T=2.725/a(t) K. Today's Hubble constant H₀ ≈ 68 km/s/Mpc. Verified against Planck 2018 cosmological parameters.
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