Aruch Hashulchan (EH 13), Quote: “I will tell you a great principle: Chazal, besides their holiness and wisdom in the Torah, were also greater scholars in the natural sciences those savants (“mischakmim”) who would argue against their pure words. And someone who disagrees with them testifies about himself that he does not believe in Torah she bal peh, even though he would be embarrassed to admit it outright.”
The Gemora in Sanhedrin (100a) tells that R. Yochanan derived from a posuk that when Moshiach comes, the gates of Jerusalem will be made of jewels 30 amos long and 30 amos high. Some student said that such big jewels do not exist – “we do not even find jewels as big as doves eggs,” he said. Then, one day the student saw angels (!) cutting such big stones, and he asked them what they are for. The angels answered: “They are for the gates of Jerusalem”. When next he saw R. Yochana, he praised his qualifications for expounding the Torah, based on his “scientific observation” that confirmed the Rebbi’s interpretation. R. Yochanan responded, “Bum! You only believe because of what you see? You dishonor the words of the Sages!”, and the student died.
The Ran (Drashos #13) points out that the statement of R. Yochana had no halachic relevance at all – it was merely an Agadic interpretation, and the disagreement was regarding a scientific fact, yet the student was punished for not believing in its truth. Therefore, he concludes: “Just as we are commanded to follow their opinions regarding laws of the Torah, so too are we commanded to follow all of what they say from tradition in Hashkafa (“Deos”), and medrash on Pesukim. And someone who veers from their words, even in something that has no relevance to any Mitzvah, is an apikores and has no share in the next world.