[jamesgreenleaf]

The D&D cosmology is bonkers too. Every solar system exists inside its own separate "crystal sphere" which floats in the chaotic fiery substance called phlogiston that fills the universe. There's a hundred different dimensions and planes of existence. Gods exist in some crystal spheres, but not in others. There's an "astral plane" where time doesn't exist, but somehow creatures there can still move around, but they don't age.

It makes no sense, and it doesn't have to. It's all just for fun. D&D is a huge mishmash of all the ancient mythologies and folk tales, plus a bunch of modern ones invented just for the game.