Luis W. Alvarez

American physicist

• Born: June 13, 1911
• Birthplace: San Francisco, California
• Died: September 1, 1988
• Place of death: Berkeley, California

A Nobel Prize-winning physicist with diverse interests, Alvarez discovered the radioactive isotope tritium and worked on the atomic bomb. He was aboard the plane that dropped the bomb on Hiroshima, Japan, during World War II. Like many atomic scientists, he believed nuclear weapons would discourage war. After his retirement, he and his son theorized that a meteor impact caused the extinction of the dinosaurs, a theory that has since become widely accepted.

Early Life

Luis Walter Alvarez (AHL-vah-rehz) was born in San Francisco to physician and medical researcher Walter Alvarez and Harriet Smyth Alvarez. Walter Alvarez was a respected researcher and internist who strongly encouraged young Luis’s interest in mechanics and electronics. Harriet Alvarez, trained as a school teacher, taught her son through the second grade, which allowed him to skip part of third grade and stay a year ahead in school.

The young Alvarez often accompanied his father to the lab where he conducted physiological research. Although Alvarez did not find the medical research very interesting, he was, however, fascinated by the electrical equipment. He learned to construct circuits by age ten.

In 1926, Walter Alvarez was offered a job at the Mayo Clinic, so the family moved to Rochester, Minnesota. The young Alvarez’s high school science courses were not special to him, but after he attended his first physics lecture, on the electromagnetic spectrum, his interest was caught. Alvarez left for college at the University of Chicago, where he spent his first two years as an unexceptional chemistry major. After taking the course Advanced Experimental Physics: Light as a junior, he switched to studying physics and finished the curriculum to graduate three months early in 1932 with a bachelor of science degree. His enthusiasm and aptitude impressed his professors. The same year he began graduate school, also at Chicago, and proceeded to earn his master’s degree in 1934 and his Ph.D. in 1936.

A few days after his exams, he married Geraldine “Gerry” Smithwick. The couple moved to California for Alvarez to begin working at Berkeley’s Radiation Laboratory under Ernest Lawrence, who won a Nobel Prize in physics in 1939 for inventing the cyclotron. Lawrence became a mentor and friend to Alvarez, whose impressive career was just beginning.

Life’s Work

Alvarez began work in Lawrence’s laboratory as a cyclotron operator in 1936. The cyclotron was used primarily for producing artificial radiation for the study of radioactive half-lives and newly discovered radioisotopes. Alvarez began reading everything he could obtain on nuclear physics. During his first year at Berkeley, he discovered the process of K-electron capture, whereby an atomic nucleus absorbs an electron from its innermost shell of its orbital electrons and becomes a different nuclide.

Although he received many job offers from other institutions in 1937, Alvarez stayed at the Radiation Laboratory, with the promise of becoming an instructor at Berkeley the following summer. In 1939, Alvarez and graduate student Bob Cornog found that helium 3 was stable and nonradioactive, while hydrogen 3 (tritium) was unstable and radioactive, contrary to the prevailing hypothesis. The discovery of tritium proved vital to the atomic bomb program. Shortly after tritium’s discovery, German scientists discovered nuclear fission.

In 1940, Alvarez left Berkeley for the Massachusetts Institute of Technology (MIT) in Cambridge, to work on the development of radar for World War II efforts. The same year, his son Walter was born. Alvarez developed several important radar technologies, including a narrow beam for directing airplane landing in poor weather, a method for locating and bombing targets on the ground that the pilot could not see, and an early-warning system for tracking aircraft movement in overcast skies.

Alvarez joined the staff of physicistEnrico Fermi at Argonne National Laboratories outside Chicago in 1943. At Argonne, Alvarez was able to again focus on research rather than administration. One of his first projects there was to develop a radiation detector for airplanes, which proved very important for gathering intelligence during and after the war. After six months at Argonne, Alvarez was assigned to the top-secret Manhattan Project in Los Alamos, New Mexico, where he worked on developing the atomic bomb.

The Alvarezes’ daughter, Jean, was born four years to the day after Walter, in 1944, during Alvarez’s first year at Los Alamos. His primary project there was to work on a detonator for the atomic bomb. He also developed a way of measuring the energy of the bomb from the air, and was present in a plane at the Trinity test on July 16, 1945. After Trinity, Alvarez was assigned to measure the energy of the atomic bomb that would be dropped on Hiroshima in 1945. Little Boy, as this bomb was known, had not been previously tested because of its high cost. Alvarez was on the Great Artiste with the measurement equipment. On his way back from Japan, he wrote a letter for his four-year-old son Walter to read when he was older, musing on the effects of the bomb. Like many atomic scientists, he believed that the bomb was terrible enough that it might lead to the end of war.

Alvarez’s postwar basic research focused on particle accelerators for studying high-energy physics, although he continued to be sporadically involved in military research and affairs, including testifying at the hearing to determine the matter of J. Robert Oppenheimer, whose government security clearance had been revoked because of his left-wing ties at the heart of the Cold War. Alvarez was elected to the National Academy of Sciences in 1946.

In 1950, Alvarez became interested in the so-called bubble chamber for particle detection, which was invented by Donald A. Glaser. Alvarez proceeded to improve on Glaser’s invention, and he was awarded the Nobel Prize in Physics in 1968 for his bubble chamber work. By this time, Alvarez had divorced, remarrying in 1958 to Janet Landis. They had two more children, Donald and Helen. Landis, who had an interest in physics and who worked at the Radiation Laboratory as well, shared a great deal of her husband’s professional life.

Alvarez’s oldest son Walter, a geologist, brought him a piece of Italian limestone that originated during the Cretaceous-Tertiary (K/T) boundary, the time when the dinosaurs became extinct. Alvarez, retired from Berkeley in 1978, set out to determine how long it took for the clay layer at the K/T boundary to form using radioactive iridium isotopes. While this attempt was unsuccessful, the two found that the iridium level in the clay was unusually high, and its composition was very different from the limestone above and below it, perhaps extraterrestrial in nature. The boundary clay has since been found all over the world.

Alvarez considered various possible explanations for both the iridium-rich clay layer and the mass extinction, finally agreeing with the suggestion of astronomer Chris McKee that a ten-kilometer meteor striking the earth sixty-five million years ago would throw up enough dust, creating a dark, cold global climate for several years (later revised to months). In the K/T extinction, all land animals weighing more than fifty pounds disappeared from the fossil record. While Luis and Walter Alvarez and their colleagues initially met with some resistance from geoscientists, their theory is now widely accepted.

In his autobiography Alvarez: Adventures of a Physicist, he wrote that he believed the work on nuclear energy at Los Alamos had ended the cycle of European wars and that he hoped to see the elimination of all weapons, both conventional and nuclear. Alvarez died of cancer in his Berkeley home on September 1, 1988, only a year after publishing his autobiography.

Significance

Alvarez was a brilliant physicist with unusually diverse research interests for a modern scientist. His contributions as a scientist and a teacher were extensive. The world has yet to achieve Alvarez’s dream of an end to warfare. Indeed, nuclear technology continues to play a key role in global politics.

Alvarez’s asteroid-extinction theory changed the field of geology. Most geologists now accept his theory for the K/T extinction, and research now focuses on the Permian mass extinction. The possibility of impact-extinction contributed to the theory of punctuated equilibrium proposed by paleontologists Niles Eldrege and Stephen Jay Gould. As a professor, Alvarez inspired several generations of physicists, many of whom have worked into the twenty-first century.

Bibliography

Alvarez, Luis W. Alvarez: Adventures of a Physicist. New York: Basic Books, 1987. Alvarez’s autobiography presents a strong picture of both his life and his personality, covering his childhood and academic influences as well as his professional career. Includes index.

Alvarez, Walter. T. Rex and the Crater of Doom. Princeton, N.J.: Princeton University Press, 1997. An informal, personal account by Walter Alvarez of how he and his father developed their impact-extinction theory. Includes notes and index.

Dardo, Mauro. Nobel Laureates and Twentieth-Century Physics. New York: Cambridge University Press, 2004. Chronicles major developments in physics since 1901, the year the first Nobel Prize in Physics was awarded. Discusses the work of the prizewinners.

Olesky, Walter. Hispanic-American Scientists. New York: Facts On File, 1998. Aimed at middle- and high-school students, this collection of profiles includes a short biography of Luis Alvarez. Includes further reading and index. Illustrated.

Powell, James Lawrence. Night Comes to the Cretaceous: Comets, Craters, Controversy, and the Last Days of the Dinosaurs. San Diego, Calif.: Harvest Books, 1998. An elegant treatment of the story of the development and testing of Walter and Luis Alvarez’s asteroid-impact theory, now widely accepted by paleontologists. Includes figures, references, and index.

Rhodes, Richard. The Making of the Atomic Bomb. New York: Simon & Schuster, 1995. A Pulitzer Prize-winning account of the men and women who pioneered atomic physics and ultimately developed the atomic bomb. Includes bibliography and index.

Trower, Peter, ed. Discovering Alvarez: Selected Works of Luis W. Alvarez with Commentary by His Students and Colleagues. Chicago: University of Chicago Press, 1987. A collection of Alvarez’s most influential articles, with commentary by the students and colleagues who worked closely with him. Includes publication and patent lists and photographs.