The Fourth Dimension and Expansion

A flatland universe can be visualized as moving in a vertical dimension that is ``unobservable.'' The following hypothetical geometric model adds a fourth ``unseen'' dimension to spacetime that conforms to a specific geometric inter-dimensional relationship with our ``observable'' spacetime that is uniformly expanding and in motion. Physical properties such as ``intrinsic energy'' for a rest mass and inertia become kinematically described. A controversial alternative explanation for a cosmological red shift becomes possible while still preserving the accepted physics by which the wavelength of a photon increases while traveling through an expanding spacetime field.