This paper offers a rigorous physical analysis of entropy, challenging common misconceptions that equate it with disorder or statistical abstraction. It argues that entropy is best understood as the irreversible dispersal of usable energy, governed by geometric principles and radiative loss. Once energy radiates outward—especially at light speed—it becomes practically unrecoverable, rendering entropy reversal infeasible.The author demonstrates how the inverse-square law and radiative propagation establish a unidirectional flow of energy, anchoring the arrow of time in physical reality rather than probabilistic analogy. The paper distinguishes between theoretical reversibility and practical impossibility, showing that even hypothetical reconstructions (e.g., reassembling coal from ash) would require disproportionate energy input, thereby increasing net entropy.This work reframes entropy as the universe’s guarantee of temporal directionality, with implications for cosmology, thermodynamics, and philosophical interpretations of time.