The Big Bang theory suggests that the known physical universe initiated itself into pre-existing space and from some position. This theory is based on late twentieth century scientific knowledge. It does not consider the interplay of this third dimension within the realms of multiple dimensions and planes.
Furthermore, the Big Bang Theory does not explain the relationship of time, or the creation of space. Accordingly, the existence of the third dimension can only ever be fully realized from a higher dimensional prospective.
Take for example the electron theory which considers that an electron "jumps" from one orbital to another. If in fact the electron disappears, or manifests itself into another universe or dimension and another electron, or itself, reappears with the "proper" orbital and energy level, then this alternate theory would not be acceptable without knowledge of other universes or dimensions.
The physical system as we know it, is expanding within itself, bringing forth new creativity and energy. The intelligent life forms that exist even within our own solar system cannot be met with an exterior reality viewpoint. They exist within another dimension and can only be reached by higher knowledge of inner dimensions.