DY: That’s more of a problem, then. How could Chazal be Chozer if their original Shittah came from a Mesorah from Sinai/Torah Sheba’al Peh? How could they have been wrong in the first place?
It seems clear from that Gemara that, at the very least on some level, Chazal trusted their contemporaries and/or did their own form of scientific research to discover physical realities, and not that they had a Mesorah from Sinai for them.
Oh, and HaLeiVi: I think the Artscroll Gemara in Mi She’achazo in Gittin says that Chazal had a Mesorah on the Refuos as well and the only reason they don’t work nowadays is either Nishtaneh HaTeva or that we don’t know the precise translation of all of the Aramaic words in them. I don’t remember if or who they quoted that from.