Primary calculation using cosmic-ray composition and flux data (heavy nuclei, including lead, striking astrophysical and terrestrial targets) to derive a safety bound for heavy-ion collider experiments, addressing the kinematic objection that natural cosmic-ray collisions occur in a different (moving-target) frame than head-on collider collisions. relevance_note: primary source for the frame/kinematics caveat on the “nature already did this” argument, and an independent flux-to-bound computation distinct from the RHIC/LHC safety-committee reports themselves.