To this post, I would like to add the words of The "Ben Ish Chai", Rabbi Yosef Chaim of Baghdad (1834–1909). The Ben Ish Chai writes (Benayau to Bava Basra 25b) that Chazal relied on the secular science of their generations, and therefore what they say is not neccessarily self-evident on matters of science (as opposed to matters of halacha). See there at great length. Of course some people just don't even beleive Chazal knew anything about halacha anyways (even if it was their area of expertise?).