Norse Cosmology

Having recently surveyed Norse cosmology (see here and also here) because of its importance to Poul Anderson's fantasies, I have concluded that this cosmology would have been a suitable setting for a series of novels by Anderson.

If, in the beginning, there was only a vacuum cold in the north and hot in the south, then where was the primeval cow born and where did the Tree grow from? The Tree, once grown, plays the role of the Absolute although it whithers and dies in Wagner's version. The Nine Worlds resemble the (former) nine planets and, in a different version of the story, we might imagine spacecraft flying between them.

Are dark elves and dwarfs the same or different? Is Hel part of Niflheim or separate? What happens in the new universe after the Ragnarok? There are more questions than answers.