@Owl Ki in one piece world magma > fire
And earth of one piece world has lots of moon
We do not know the size of the planet....what makes you think gravitational force is same as our planet
And earth of one piece world has lots of moon
We do not know the size of the planet....what makes you think gravitational force is same as our planet


For everything else, we just have to assume that everything is the same as our world unless otherwise explicitly stated.
If we go down the rabbit hole that you are implying then where does it end? Do One Piece characters inhale carbon dioxide and exhale oxygen?

Besides, Kaido and Gedatsu are of the same verse and are subject to the same gravitational conditions, so what would it matter anyway? Lol.