Time Is The Universe: The Law of Conservation of Time and The Discovery of T0 as The Fifth Fundamental Field

For a century, physics has assumed space and time are different things stitched into spacetime. This assumption has blocked unification. This paper proposes a single, radical inversion: The Universe is not in space and time. The Universe IS Time. We postulate a fundamental Law: Time can neither be created nor destroyed. It can only transform as Time $\\leftrightarrow$ T0. T0 is Nothingness - the absolute ground state, the deepest layer of reality, deeper than vacuum. It is not empty. It is the source of all temporal flow. From T0, Time flows. That flow creates what we perceive as three dimensions of space. Therefore, we live in a 4-dimensional Time manifold, not 4D spacetime. Gravity is not a force carried by a graviton. Gravity is the refraction of Time. Like light bending in glass, time-flow bends near mass. We define the refractive index of time: $n(T) = c / v_T$. This one law eliminates the need for dark energy, explains why no graviton will ever be found, and makes four precise, testable predictions that can falsify it today.