For starters, your only context behind the question is that you "heard jokes about the sky". You could as well ask if Tibia has a sun (or suns), moon(s), stars, other planets, UFO, Flying Spaghetti Monster etc. etc. Even if we receive an answer, it's difficult to find it valuable information. If you added more context on why answering this particular question (about the sky) brings value, that would help.
It was also poorly tagged and had a major grammar problem in the title but I already fixed that.