When I teach about the antiquity of the universe, one point I always stress is how irrelevant it is to get bogged down on the details of carbon dating or other such things. Anti-rationalists seem to think that if you can show that one scientist believes the universe to be 13.4 billion years old, whereas another scientist believes it to be 16.7 billion years old, then you have shown that there is no consensus of evidence for the universe being more than 5771 years old. The folly of this line of reasoning should be self-evident.
A while back, I published my monograph The Sun's Path at Night, which discusses the Sages' view that the sun passes behind the sky at night - with the sky being believed to be a dome. It emerged that ALL of the Rishonim without exception, as well as many Acharonim, agreed that Chazal held this view. Only beginning with figures such as Maharal and Ramchal did people attempt to reinterpret Chazal - but there is no reason not to accept that the view of all the Rishonim and many Acharonim is correct.
I then moved on to a discussion about how this view of the sky (rakia) found in the Gemara is Chazal's view of the firmament as described in Tenach. And in a subsequent post, I pointed out that this means that the mesorah was reinterpreted in light on modern science. Hence, we can do the same with regard to the mesorah about the nature of creation.
Now this, of course, was anathema to my anti-rationalist opponents. So, the ones whose public mission is based around invalidating me, decided to challenge this chain of logic as follows: Throughout the Talmud and Midrash, we find a number of disputes amongst Chazal as to the precise nature of the firmament. Some held it to be very thin, while others believed it to be very thick. Some held it to be made of a form of congealed water, while others believed it to be composed of a mixture of fire and water. Some believed it to have two layers, while others believed it to have seven layers. Then, much later in the medieval period, it is possible that some Rishonim did not believe the spheres to be solid at all; indeed, there is much academic discussion about the nature of the Ptolemaic spheres.
My opponents conclude from all this that there was no mesorah about the nature of the firmament. Rather, different figures amongst Chazal had different ideas, based on some sort of combination of science and their understanding of Torah, but there was no mesorah about it.
Now, their position is already unacceptable according to many of the Gedolim who banned my books, who are of the view that is heretical to say that any statement in the Gemara or Midrash is a scientific statement made in error. But aside from this, they have entirely failed to make their case.
Their argument is like saying as follows: There was a huge dispute between Rambam and other Rishonim as to which parts of the Gemara are Sinaitic in origin. So there is no mesorah that there is an Oral Torah from Sinai! Or, even more appropriately: There are numerous different views amongst Chazal as to what exactly happened during the six days of Creation. So there is no mesorah regarding creation!
To be sure, there was much dispute about the nature of the firmament. But this has no bearing whatsoever on the unequivocal mesorah that there is a firmament - that is to say, a dome above the earth, made of some sort of substance (i.e. not air or space), on the surface of which the sun travels, and which obscures the sun when it passes behind it. This was the universal, uncontested, view of Chazal, based on Pesukim such as that in Iyov 37:18: "Can you spread out the heavens with Him, hard as a mirror of cast metal?" as well as various other usages in Tenach of the root רקע. The Torah had always been understood as describing the firmament as in the following illustration:
Now, much later, during the time of the Rishonim, Ptolemaic cosmology had already become widely accepted, and some of the Rishonim reinterpreted Tenach to suit it. It is possible that some of them did not believe the rakia to be a substantive firmament (the best general discussion that I have found on this topic is Edward Grant's paper "Celestial Orbs in the Latin Middle Ages"). But all this would mean is that the Rishonim were ignoring Chazal (as Rambam and Ibn Ezra did on several occasions) and reinterpreting Torah in light of science. None of the Rishonim claim that the Chachmei Yisrael did not believe the sun to be concealed behind the sky at night, or that Chazal's descriptions of the rakia in the Bavli, Yerushalmi and Midrash are not literal. Chazal's mesorah was clear and uncontested.