We consider how two physical realities can be represented over a common set of spacetime coordinates. As an example we will
utilize quantum electrodynamics since this is a familiar and well-understood theory. We will designate one world the 'red' one and
the other the 'green' one. We will try to show how they can interact in a physically plausible way. We will also examine whether
such an interacting theory is renormalizable. It will be shown that we can extend these ideas to the Standard Model. There are
implications for this theory if we consider General Relativity and these will be discussed briefly. If there are, in fact, such other
realities these could provide a plausible explanation for dark matter
