Ben Levi:
R’ Slifkin does not use R’ Dessler as a source for his reasoning why the halacha does not change. He uses R’ Dessler as a source that Chazal’s scientific statements can be incorrect. I thing I have brought enough sources to show that it is not kefira to say that Chazal based themselves on the science/scientists of their time (and therefore can be scientifically incorrect). So that means that you are claiming that the kefira aspect is that granted the science may be wrong, it is kefira to say that the halacha was based on the science. If I have accurately summed up your position, then please explain why this is would be kefira as well as explain why Chazal bothered to research the science. If I have not accurately summed up your position then feel free to correct me.