Alvarez, Luis Walter (1911-1988)

US physicist. He led the research team that discovered the Ξ0 subatomic particle in 1959. He also made many other breakthroughs in fundamental physics, accelerators, and radar. He worked on the US atom bomb for two years, at Chicago and at Los Alamos, New Mexico, during World War II. He was awarded the Nobel Prize for Physics in 1968 for his work in elementary-particle physics, and discovery of resonance states, using the hydrogen bubble chamber and data analysis.

Extinction of the dinosaurs In 1980 Alvarez was responsible for the theory that dinosaurs disappeared because a meteorite crashed into Earth 65 million years ago, producing a dust cloud that blocked out the Sun for several years, causing dinosaurs and plants to die. The first half of the hypothesis is now widely accepted.

Early work Alvarez was born in San Francisco and studied at Chicago. In 1945 he became professor at the University of California, working at the Lawrence Livermore Radiation Laboratory there 1954-59. During World War II he moved to the Massachusetts Institute of Technology, where he developed the VIXEN radar for the airborne detection of submarines, phased-array radars, and ground-controlled approach radar that enabled aircraft to land in conditions of poor visibility. He also participated in creating the atomic bomb dropped on Hiroshima, Japan.

Observing particles Alvarez built the first practical linear accelerator and an accelerator for breeding plutonium, and invented the tandem electrostatic accelerator. He also devised, but never built, the microtron for accelerating electrons. In 1953 Alvarez met US nuclear physicist Donald Glaser, inventor of the bubble-chamber detector for subatomic particles. Alvarez decided to build a much larger chamber than Glaser had used, and to fill it with liquid hydrogen. He also developed automatic scanning and measuring equipment whose output could be stored on punched cards and then analysed using computers. Alvarez and co-workers used the bubble chamber to discover a large number of new short-lived particles. These experimental findings were crucial in the development of the ‘eightfold way’ model of elementary particles and, subsequently, the theory of quarks.