I've been debating a creationist youtuber for quite a while, and I pointed out that many celestial objects are so far away, if the universe is <10000 yearsold, their light would never have reached us, he countered by saying that we judge distance by brightness which is too arbitrary, when I brought up cepheids, he said that the nearest one(polaris) behaves erratically and thus cepheids do not make good standard candles. So, does anyone have any specific information on the correlation between a cepheid's variability period and luminosity, or information about polaris' behavior?