Hey - I am working through one of the projects in the learning maya 7 Foundation books. I have just added a planet on the outside of this room. when I render the planet can be seen through the floor. The tutorial told me to reverse the normals on the faces of the room and also turn on backfaces, so does it have something to do with that? I tried messing around with them, but no luck. It also happens with the ceiling.

Any ideas?