Alvarez won the 1968 Nobel Prize in Physics for "the discovery of a large number of resonance states, made possible through his development of the technique of using hydrogen bubble chamber and data analysis." Specifically, his research made it possible to record and study the short lived particles created in particle accelerators.
With geologist son Walter, Luis proposed the asteroid-impact theory to explain the iridium anomaly of the K-T extinction boundary. An impact by an extraterrestrial body is now widely accepted as causing the extinction that killed the dinosaurs.
Alvarez also proposed a jet-recoil theory to explain why Kennedy's head jerked the wrong way if Oswald was the shooter. Known somewhat disparagingly as the "Jet-wash theory", it suffers the evidentiary problem that motorcycle patrolman Bobby Harkis was thoroughly splattered by Kennedy's brain matter—ie, by the presumed jet— but Harkis was to Kennedy's left rear, implying the jet was in the opposite direction to that needed by the theory.