Two branches of physics have diverged to the point that they are now in direct conflict. The theory of Special Relativity, proposed by Einstein in 1905, was based on the hypothesis that motion is purely relative, that the relation between two bodies in uniform motion is a relation between them and not something belonging to one or the other; there is no body absolutely at rest to which the motion of each can be referred. At that time the universe was believed to consist only of our own galaxy, the Milky Way, but in the decades that followed astronomical observations revealed a large number of galaxies outside of our own stretching into the far reaches of space. Their red-shifts, indicating velocities of recession, showed an expanding universe in which there is a local rest frame defined by the isotropy of the galactic red-shifts and by the microwave background radiation. This is a clear conflict that needs to be resolved. It is found that the problem arises from an error in Einstein's original paper concerning the properties of time. He considers a clock A that is moved at constant velocity to a second clock B and concludes that its motion causes it to run slow so that on arrival A's clock indicates an earlier time than B's. But motion is purely relative so the relation between A and B must be symmetrical and neither can be earlier than the other. For this reason and others the effect know as time dilation is an incorrect deduction from the theory. This being so, a remote clock can be synchronized by the transportation of a standard clock and in this way a mesh of synchronized clocks can be set up to form a universal time scale. Combining this with the fundamental hypothesis that the speed of light is invariant, leads to a mathematical model based on the Voigt transformation rather than that of Lorentz. This modified theory of Cosmic Space-time contains a preferred inertial frame and a universal time. These features correspond to the those of the real universe as represented by the Big Bang theory. Originally all matter was compressed into a small volume and at time zero began a uniform expansion leading to a universe which is always homogeneous and isotropic. To an observer moving with local matter, known as the Hubble flow, the recession of the galaxies is the same in all directions. Any deviation from this isotropy is a measure of his motion through the cosmos. The Hubble flow defines the local rest frame and the uniform aging of all matter since the big bang defines a universal cosmic time. This modified space-time model is based on the Voigt transformation rather than that of Lorentz. They differ only by a constant factor and consequently nearly all their physical properties are the same, including the invariance of the laws of physics and the equivalence of mass and energy. So most of the experimental and observational evidence that supports relativity theory also supports cosmic space-time. A few experiments claim to measure time dilation but, as shown, this is not predicted by relativity theory.