I am watching the wild Last Exile series again for the 3rd time. I have some theories going that the movie doesnt really talk about.
I am thinking that there are two planets. I am also thinking that they are somehow linked by this 'Grand Stream'. This would explain the 'hour glass' drawings of the Grand Stream, the wind joining the two worlds.
Another thing that supports this is all the refuge's getting into the huge rockets (perhaps 50+ stories high with Junkers Duraluminum skins). Why would they need colony ships to go to another continent. If the planet were too huge, the gravity would be so great they couldnt survive. Thus again I think they were going to the other world through the Grand Stream.
On one scene, the Silvanah had encountered some Disith heavy cruisers in the Grand Stream. After the battle, the Silvannah drops down out of the Grand Stream and enters Atmosphere. A wierd atmospheric 'thing' occurrs where the Silvannah, coming through a 'barrier' appears to be going through a bright electrical like shimmering hole in the sky, and they it seals up as the Silvannah clears it.
So I think the worlds are joined by this phenomenon.
All I can figure is Norkia is on one world, very Germanic type, colonized long ago, and the Disith, are on another world that is more severe weather wise. It seems one side needs water, and the other side has their needs as well.
You can see the 'hour glass icons' or art of the Grand Stream that appear to have two worlds that the GS surrounds.
So there. Thats my theory and I am sticking by it. Only makes sense to me.