The observed flat rotation curves of disk galaxies remain one of the most compelling empirical challenges to the standard CDM cosmological model. We present observational evidence for a universal kinematic constant, c₀, that governs the relationship between the observed rotational velocity v₎₁ₒ and the Newtonian velocity expected from baryonic matter alone, v₁₀ₑ. Motivated by a phenomenological framework in which galactic dynamics are linked to an underlying causal optimality principle, we propose the relation v₎₁ₒ = v₁₀ₑ \, e^, where is a dimensionless field. From this, a characteristic speed c₀ = v₎₁ₒ / e^2 - 1 is constructed. If c₀ is truly fundamental, it must be independent of galaxy type and radius. Using the SPARC database, the largest homogeneous sample of high-quality rotation curves, we analyse 1572 independent measurements from 134 late-type galaxies. After applying a physically motivated quality cut (50 5 confidence. The dimensionless field saturates at _ = 0. 429 in massive galaxies, yielding a gravitational amplification factor e^2 = 2. 357. Plotting observed acceleration against baryonic acceleration, the data follow the relation g₎₁ₒ = 2. 357 \, g₁₀ₑ across four orders of magnitude, quantitatively explaining the apparent gravitational enhancement traditionally attributed to dark matter. These results establish c₀ = 104. 3 km s^-1 as a new empirical constant of galactic dynamics. The complete field-theoretic foundation---including the action principle and modified field equations from which this constant emerges---is developed in a companion paper (Paper~II). The present work provides the robust observational evidence motivating that theoretical framework.
Mahmoud F. Abdel-Sattar (Fri,) studied this question.