Luis Walter Alvarez

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Biographical Sketches

Luis Walter Alvarez


American Physicist and Engineer

Luis W. Alvarez was perhaps the best-known Hispanic scientist of the twentieth century, excelling in experimental physics and engineering. In the 1940s he worked on the Manhattan Project designing the detonating device for the first atomic bomb. In 1968 he won the Nobel Prize in physics for work that included the discovery of resonance particles—subatomic particles that have very short lifetimes and that occur primarily in high energy nuclear collisions, and the design of an experimental bubble chamber to measure these particles. In the late 1970s he theorized that the dinosaurs became extinct as a result of a meteor crashing into Earth 65 million years ago.

Alvarez was born June 13, 1911, in San Francisco. His father was a physician who enjoyed research, and his mother taught school. As a child Luis often traveled to work with his father, and he liked to play with the equipment in the lab. He showed no interest in the medical aspects of his father's medical practice, but by the time he was 10 years old he was capable of using all of the small tools in the lab and wiring electrical circuits. In 1925 the family relocated to the Mayo Clinic in Rochester, Minnesota, in order for the elder Alvarez to take a position there. During high school summers, Luis was employed in the instrument shop at the clinic.

Initially, he enrolled at the University of Chicago in chemistry, but he discovered that he had a natural aptitude for physics and optics. He took 12 physics courses in 5 quarters and spent all of his spare time in the physics library, beginning a long and productive acquaintanceship with research and libraries. He earned both his bachelor's (1932) and doctoral degrees (1936) at the University of Chicago. He joined the faculty of the University of California—Berkeley in 1936 and taught there until his retirement in 1978.

Alvarez's first scientific discovery was the phenomenon of orbital electron capture. He discovered that in certain elements, the nucleus could capture an electron that is in an inner orbit. In 1939 Alvarez was able to measure the magnetic moment of the neutron.

During the World War II years, Alvarez, worked at the Massachusetts Institute of Technology (MIT) and was responsible for the design of three important radar systems: the microwave early warning system, the Eagle high altitude bombing system, and a landing radar system for civilian and military planes. After he left MIT he worked on the first nuclear reactor with Enrico Fermi (1901-1954). He was recruited by the United States government with the outbreak of World War II to work on the top-secret Manhattan Project. While in Los Alamos he developed the detonating device for the atomic bomb. He was on board the aircraft that dropped the atomic bomb over Hiroshima, Japan. Alvarez was shocked and sickened by what he saw, but he continued to support the United States in weapons research.

After the war ended Alvarez continued his work in high energy theoretical physics. He was involved in the design and construction of the first proton linear accelerator completed in 1947. This led to the development of the liquid bubble chamber, in which subatomic particles and their reactions are detected and photographed. The new particles produced by these accelerators and measured by the bubble chamber gave scientists exciting new information on the behavior and lifespan of subatomic particles, particles so small that they can be identified only by the tracks they leave. Alvarez in the course of this work was able to detect, record, and analyze 70 subatomic particles. He received the Nobel Prize in 1968 for this body of work.

In the late 1970s Alvarez, in collaboration with his son Walter, a respected geologist, announced a theory of the extinction of dinosaurs. They suggested that a giant asteroid, perhaps six miles (10 km) in diameter, crashed into Earth and created inhospitable conditions for the dinosaurs. The theory was controversial and many scientists rejected it. However, fifteen years later the theory is widely accepted.