known_biases - The distribution of (habitable-)planet formation times across the observable universe (Lineweaver-type compilation from cosmic star-formation history + metallicity evolution), used by Tegmark-Bostrom as the selection-bias-free reference against which Earth’s own formation date (~9.1 Gyr after Big Bang) is compared. Model-dependent: assumptions about the planet-formation-rate model and the habitability window propagate directly into the ~1/Gyr bound derived from it.