Luis W. Alvarez (b. 1911), American physicist. He joined Ernest Lawrence's Radiation Laboratory at Berkeley in 1937, & worked on radar & the atomic bomb during World War II. In the 1950s he played a major role in developing the bubble chamber & his team at Berkeley discovered numerous new particles with it. Alvarez won the physics Nobel prize for this work in 1968. In the 1970s & 1980s Alvarez became involved in other areas, including the dis- covery of an iridium layer in Cretaceous/Tertiary boundary clay & the theory that a comet crashed to Earth at the end of the Cretaceous era & caused the death of the dinosaurs. He is seen in his room at the Lawrence Berkeley Laboratory in 1984.