Ignored Common Sense: Why Has No One Measured Quantum Density Changes in Expanding Space?

This paper challenges a fundamental oversight in modern cosmology: the lack of systematic measurement of quantum density per unit space amid universal expansion. Using the framework of Trend Cosmology, it proposes that changes in quantum density—whether decreasing, increasing, or stable—could profoundly reshape our understanding of cosmic structure, trend factor sources, and entropy. It critiques the inertia of current models that assume background density constancy and urges the development of a long-term observational plan based on fixed structural units. This work offers a new pathway for empirical verification of trend-based cosmological principles.