A Study of Simultaneity Based on the Speed-Limit Structure C = P₁ + S₁

In conventional physics, physical quantities belonging to the same domain have typically been treated individually through different theoretical approaches and equations. However, a close examination of experimental observations and calculated results indicates that these quantities do not vary independently; rather, once a single parameter is fixed, they tend to change in a correlated manner. This suggests that diverse physical quantities are being determined simultaneously on a more fundamental common structure. This study focuses on the fact that energy transport is always constrained by the speed of light as an upper limit, and takes as its starting point the speed-limit structure, in which the total speed is decomposed into an energy-attraction velocity and an energy-transport velocity . This structure is not based on forces or fields, but a systemic coordinate framework. Within this framework, represents a coordinate reflecting potential, density, or binding strength, while is interpreted as a coordinate associated with the actual transport of energy. The primary objective of this study is to verify that, when is specified in a given physical system, the associated physical quantities become simultaneously aligned on a single coordinate, and to directly compare and examine this structure against experimental observations in the stellar, atomic, and nuclear domains.