I only learned the meaning of a manifold recently and in the most elementary terms but I thought that I might link it with this example. It seems that the universe is made out of 3D objects. So put all of them together (stars, blackholes, galaxies etc) and you have the whole universe. It also means that locally in the universe (or each individual object in the universe) such as the earth, it is just a 3D object. We ourselves are 3D objects as well. Every object in the universe can be fully described mathematically by mapping R^3->R which is the graph of any 3D object. So the space which the whole universe must 'live' in would be R^4 which is the 4th dimension. Is this a conventional view?