The best depiction of Spacetime as not a rubber sheet: Jim Kelley

For speed of light to be invariant in all reference frames spacial curvature and time curvature must always play equal roles. In his 1911 paper, "On the Influence of Gravitation on the Propagation of Light," Einstein deduced that the speed of light is variable in a gravitational field, suggesting a refractive index proportional to gravitational potential. This implies that vacuum behaves like a dense medium, bending light toward regions of higher gravitational potential. Given that the mass density and gravitational potential of the early universe was as much as 5 or 6 orders of magnitudes greater than local mass density,...And as matter congealed into discreet pockets, the space between these discreet pockets expanded. But it expanded not so much by force, but rather as a relaxation of force. The decreased gravitational force effectively allows space to expand as a result of the expansion of mass. As the shape of the gravitational field lines changes so does the shape of spacetime. This effective change in shape may have had profound affects on our observations and on our interpretation of them in the evolution of the universe. Jim Kelley, Electronics Engineer, UCI Physics and Astronomy,