The Creation of Worlds and Other Godly Pursuits

And God said, Let there be light: and there was light. (Genesis 1:3)

Whether a world is created to see if it can be done, or for your characters to explore there is more to creating worlds than saying let there be light. There are physics and chemistry elements, fauna, wildlife and the culture that results from all of the above. How do you show all of this? Why explore this world and not another world?