Discussion on answer by AlexP: Is it possible to have a Newtonian universe but everything else behave the same way as this universe? What adjustments to physics is necessary?

Imported from a comment discussion on https://worldbuilding.stackexchange.com/questions/230991/is-it-possible-to-have-a-newtonian-universe-but-everything-else-behave-the-same/230994#230994