One thing holds consistent across the numerous worlds of science fiction and fantasy: everyone speaks the same language. Whether it's Lojban, English, Common, or the High Tongue of the Autumn Empire; there's one language that everyone knows, unless plot demands otherwise.
Do not gather and heap up and store for yourselves treasures on earth, where moth and rust and worm consume and destroy, and where thieves break through and steal. Matthew 6:19 KJV
A society in which people believe that the hundreds of stars that dot the sky are the dreams of the sleeping. When the sun goes down, and the people of the world rest, the dreams begin to seed the sky, disappearing in the morning as the populace awakes once more. It could be just a folk tale, or it could be real...