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Physics has no accepted explanation for that starting condition.","posed_since":"","precise":"Explain, within a stated measure on initial conditions (Liouville measure, or a measure from a quantum theory of gravity), why the coarse-grained entropy of the observable universe at early times was far below its maximum (today approximately $10^{104}\\,k_B$ against a black-hole bound of order $10^{123}\\,k_B$), or show that the low-entropy initial state must be postulated (the Past Hypothesis). An answer is a mechanism that makes it typical, or an argument that none can.","problem_ref":null,"references":"","settled_by":"A derivation from a specified theory of initial conditions that predicts the low early entropy and its form (nearly uniform matter, low tidal curvature) without assuming it.","status_note":"","title":"Why the early universe had low 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