Flatness Without Tuning

The flatness problem in ΛCDM asks why the total energy density of the observable universe is so extraordinarily close to the critical density — with Ω_total = 1.000 ± 0.001 — when any slight departure from exactly unity at early times would have driven the universe rapidly into collapse or unbounded expansion. Without inflation, the initial density must have been tuned to within one part in 10⁵⁰ of critical at the Planck epoch, an extraordinary coincidence that demands explanation. Successive Collision Theory replaces this problem with a structural observation rooted in infinite eternal spacetime. Our observable universe is a 46.5 Gly radius patch within a genuinely infinite space. In an infinite universe with nonzero average mass-energy density, any sufficiently large region will statistically sample the mean density, which is by definition the critical density for that region's characteristic scale. This is not tuning — it is the law of large numbers applied to an infinite spatial volume. The global curvature of infinite spacetime is zero by definition; any finite patch sampled from it will measure near-zero curvature, with deviations shrinking as the inverse square root of the patch's volume relative to the correlation length of density fluctuations.

More precisely, the collision that produced our observable patch deposited energy uniformly across the entire overlap volume simultaneously — the superluminal collision front thermalized the full region instantaneously, ensuring that the energy density within our patch was set by the collision kinematics rather than by any pre-existing density fluctuation. The kinetic energy deposited per unit volume is determined by the collision geometry and the mass-energy content of the two parent pockets, which is drawn from the same infinite universe that sourced them. To the extent that both parent pockets were themselves typical regions of infinite spacetime, their kinetic energy density at collision naturally produces a post-collision density close to critical for the resulting patch size. Inflation is thus unnecessary — the observed flatness is a geometric consequence of sampling a large enough volume of infinite eternal spacetime through a collision whose energy input uniformly thermalized the full overlap volume.