Spacetime Is a Synonym for Rest Mass and Momentum

Modern physics treats spacetime as the fundamental framework within which all physical events unfold. This paper proposes the opposite view: spacetime is not fundamental, but rather the macroscopic projection of two orthogonal components within the world quantum — the rest mass component (d) and the momentum component (v). Through a comparative analysis between the core equation of World Quantum Theory (c2 = v2 + d2) and the four-dimensional spacetime metric of relativity, this paper demonstrates that three-dimensional space is the directional decomposition of the momentum component, and one-dimensional time is the single-axis projection of the rest mass component. What physicists call spacetime is, in fact, a synonym for momentum and rest mass. This understanding reduces spacetime from a fundamental existence to a derived phenomenon, providing a new starting point for re-grounding physics. **Keywords**: World Quantum Theory; momentum component; rest mass component; spacetime metric; synonym