Why supernovae still won't prove the universe isn't accelerating

Type Ia supernovae are distance markers for measuring cosmic acceleration, but their brightness depends on host-galaxy age in ways that can skew results. Wiseman et al. claimed this age bias is negligible, but the authors show their sample's wide redshift spread artificially hides the effect: galaxies hosting young and old supernovae get lumped together, flattening the age-brightness relation. After correcting for this, the cosmological correction remains robust—whether you assume fast or slow delays between star formation and explosions.