We all like to build worlds for our games. It's fun, it's rewarding, it gives a great feeling when finishing it... But there's a thing that always crops to my mind when I read other people's worlds. The heavy place that realism takes in the games and it can go quite extreme sometimes.
"If the sun doesn't move and lights a certain country all the time, what's the temperature there?"
This, at least to my eyes, is wrong question. Why? Because it doesn't help to make the game or the story better, and because it talks about the last question that should be asked about a world that the GM is building: "How this X is real?" Realism should be the last thing to think about. After the world is complete and the sun shines there, then it's time to think about realism. 'Till then, it's an easy way to both distract the writer from the world building job, and also to destroy the initiative of build such a world.
So please, whenever you come to someone who builds a world and asks for remarks on it, leave the realism for the end. It's not that important...