For decades, the scientific community and educational texts have asserted that the ozone layer, despite its extremely low concentration in the atmosphere, constitutes Earth's primary defense against harmful ultraviolet (UV) radiation. However, this assertion is rarely subjected to rigorous quantitative verification. This study performs a numerical evaluation of ozone's UV absorption capacity using fundamental physical data: atmospheric ozone concentration (0.000004% by volume), molecular density, absorption cross-section, and incident UV flux. The calculations reveal that ozone absorbs only approximately 2.4 × 10⁻⁹% of the incident UV energy — a fraction so small that it challenges the conventional narrative. This finding suggests that other atmospheric components, particularly molecular oxygen (O₂), which constitutes 21% of the atmosphere, must play the dominant role in UV protection. The study does not deny ozone's UV absorption capability but rather quantifies it, exposing a significant discrepancy between qualitative assertions and quantitative reality.