Rabbi Nachmanides explained the Big Bang in his writings some time before 1270.
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Do you have a reference? While the “Big Bang” singularity is not Biblical, infinity in the creation, the aftermath of the condensation of matter as the metronic size contracted is the Biblical equivalent.
It is included in Nachmanides’ commentary on the Torah, in which he says, “At the briefest instant following creation all the matter of the universe was concentrated in a very small place, no larger than a grain of mustard. The matter at this time was very thin, so intangible, that it did not have real substance. It did have, however, a potential to gain substance and form and to become tangible matter. From the initial concentration of this intangible substance in its minute location, the substance expanded, expanding the universe as it did so. As the expansion progressed, a change in the substance occurred. This initially thin noncorporeal substance took on the tangible aspects of matter as we know it. From this initial act of creation, from this etherieally thin pseudosubstance, everything that has existed, or will ever exist, was, is, and will be formed.”
Try entering ‘ramban big bang theory’ in a search engine. ‘Ramban’ is how Jews refer to a philosopher non-Jews usually call Nachmanides. A Jewish sage and philosopher known by a similar name, Maimonides, also described something akin to the big bang theory.