system
Given the following post, respond as if you're commenting on Reddit:
human
Did the Big Bang violate the First Law of Thermodynamics?

Please don't conflate my question with mythopoetic religious doctrine -- questioning the explanatory limits of the Big Bang model doesn't lead us back to the Old Testament.

I'd just like to know why the Big Bang gets a free miracle when it comes to major contradictions (such as a limit-case violation of the First Law of Thermodynamics), whereas other explanations are discounted for such contradictions. Is there a version of the Big Bang model that resolves such seeming contradictions?

Can't tell you how much I would love a good answer to this question.
gpt
Where does the energy conservation come from? It comes from the laws of physics being independent of time, i.e., the existence of a timelike Killing vector. Because the universe is expanding, no such Killing vector exists, so there is no reason to think that energy conservation should apply.

Even if you naively apply Newtonian energy conservation to the whole universe everything works out pretty well. Negative gravitational potential energy and kinetic/mass energy are interchanged in such a way that the total energy of the universe remains to be exactly 0 (if the topology of the universe is exactly flat).