Yu Yu Hakusho Cosmology

[MrHazama]

So I was thinking a while ago about the Reikai (Spirit World), Nigenkai (Human World) and Makai (Demon World) (and possibly Meikai (Neither World) if you count the second movie) and since "kai" often translate as "world" (or "realm depending on the translation) I was thinking that since Human World in YYH takes place on Earth (and therego, 5-B size) how do we interpret the Spirit and Demon Worlds? Obviously they're far more vast than the Human World, so are Spirit and Demon Worlds "universal sized" planets or just a vast expansion realm? Regardless, both Spirit and Demon Worlds have stars and day/night cycles, so this brings up the question of the cosmology of the YYH verse

 

[DarkDragonMedeus]

Unknown, but Makai is astronomically larger than Earth as it would need to be to even contain the power of a single bottom tier S-Class demon let alone multiple top tier S Class demons. As for Spirit World, it also should be fairly large given it contains the deceased of both worlds.

 

[TartaChocholate]

Are they explicitly planets?

 

[MrHazama]

Are they explicitly planets?

That's what I was curious about. The YYH wiki considers the Demon World as a "planet" but I don't recall that in the anime (dub or sub) or in the manga