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It happens to be close to one now, when observers exist.","posed_since":"","precise":"With $\\rho_m \\sim a^{-3}$ and a constant $\\rho_\\Lambda$, the ratio $r = \\rho_\\Lambda / \\rho_m = (\\Omega_\\Lambda / \\Omega_m) a^3$ is about 2.2 today and was about $2 \\times 10^{-3}$ at $a = 0.1$. Find a mechanism (tracker or coupled dark energy, or anthropic selection with an explicitly defined measure) that predicts $r$ of order one at the epoch when observers form without tuning its parameters, while staying consistent with the measured $w(z)$.","problem_ref":"26bce1511536ff3a9085d85a31f3bab9ad318986a8346f24001bdd374a5f669a","references":"","settled_by":"A model that predicts r of order one at the observed epoch and makes a further prediction for w(z) or for dark-sector couplings that is later confirmed.","status_note":"","title":"Why are the dark energy and matter densities comparable 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