Alvarez, Luis (1911-1988)

Alvarez, Luis (1911-1988)

American physicist

Luis Alvarez proposed a controversial theory involving the possibility of a massive collision of a meteorite with the earth 65 million years ago, an event that Alvarez believed may account for the disappearance of the dinosaurs. After a varied and illustrious career as a Nobel Prize-winning physicist, Alvarez shared his last major scientific achievement with his son Walter, who was then a professor of geology at The University of California at Berkeley. In 1980, the Alvarezes accidentally discovered a band of sedimentary rock in Italy that contained an unusually high level of the rare metal iridium. Dating techniques set the age of the layer at about 65 million years. The Alvarezes hypothesized that the iridium came from an asteroid that struck the earth, thereby sending huge volumes of smoke and dust (including the iridium) into the earth's atmosphere. They suggested that the cloud produced by the asteroid's impact covered the planet for an extended period of time, blocked out sunlight, and caused the widespread death of plant life on Earth's surface. The loss of plant life in turn, they theorized, brought about the extinction of dinosaurs, who fed on the plants. While the theory has found favor among many scientists and has been enhanced by additional findings, it is still the subject of scientific debate.

Luis Walter Alvarez was born in San Francisco, California. His father, Dr. Walter Clement Alvarez, was a medical researcher at the University of California at San Francisco and also maintained a private practice. Luis' mother was the former Harriet Skidmore Smythe. Alvarez's parents met while studying at the University of California at Berkeley.

Alvarez attended grammar school in San Francisco and enrolled in the city's Polytechnic High School, where he avidly studied science. When his father accepted a position at the prestigious Mayo Clinic, the family moved to Rochester, Minnesota. Alvarez reported in his autobiography Alvarez: Adventures of a Physicist, that his science classes at Rochester High School were "adequately taught [but] not very interesting." Dr. Alvarez noticed his son's growing interest in physics and hired one of the Mayo Clinic's machinists to give Luis private lessons on weekends. Alvarez enrolled at the University of Chicago in 1928 and planned to major in chemistry . He was especially interested in organic chemistry, but soon came to despise the mandatory chemistry laboratories. Alvarez "discovered" physics in his junior year and enrolled in a laboratory course, "Advanced Experimental Physics: Light" about which he later wrote in his autobiography: "It was love at first sight." He changed his major to physics and received his B.S. in 1932. Alvarez stayed at Chicago for his graduate work and his assigned advisor was Nobel Laureate Arthur Compton, whom Alvarez considered "the ideal graduate advisor for me" because he visited Alvarez's laboratory only once during his graduate career and "usually had no idea how I was spending my time."

Alvarez earned his bachelor's, master's, and doctoral degrees at the University of Chicago before joining the faculty at the University of California at Berkeley, where he remained until retiring in 1978. His doctoral dissertation concerned the diffraction of light, a topic considered relatively trivial, but his other graduate work proved to be more useful. In one series of experiments, for example, he and some colleagues discovered the "east-west effect" of cosmic rays, which explained that the number of cosmic rays reaching the earth's atmosphere differed depending on the direction from which they came. The east-west effect was evidence that cosmic rays consist of some kind of positively charged particles. A few days after passing his oral examinations for the Ph.D. degree, Alvarez married Geraldine Smithwick, a senior at the University of Chicago, with whom he later had two children. Less than a month after their wedding, the Alvarezes moved to Berkeley, California, where Luis became a research scientist with Nobel Prize-winning physicist Ernest Orlando Lawrence, and initiated an association with the University of California that was to continue for forty-two years.

Alvarez soon earned the title "prize wild idea man" from his colleagues because of his involvement in such a wide variety of research activities. Within his first year at Berkeley, he discovered the process of K-electron capture, in which some atomic nuclei decay by absorbing one of the electrons in its first orbital (part of the nuclear shell). Alvarez and a student, Jake Wiens, also developed a mercury vapor lamp consisting of the artificial isotope mercury–198. The U.S. Bureau of Standards adopted the wavelength of the light emitted by the lamp as an official standard of length. In his research with Nobel Prize-winning physicist Felix Bloch, Alvarez developed a method for producing a beam of slow moving neutrons, a method that was used to determine the magnetic moment of neutrons (the extent to which they affect a magnetic field ). Just after the outbreak of World War II in Europe , Alvarez discovered tritium, a radioactive isotope (a variant atom containing a different number of protons) of hydrogen.

World War II interrupted Alvarez's work at Berkeley. In 1940, he began research for the military at Massachusetts Institute of Technology's (MIT's) radiation laboratory on radar (radio detecting and ranging) systems. Over the next three years, he was involved in the development of three new types of radar systems. The first made use of a very narrow radar beam to allow a ground-based controller to direct the "blind" landing of an airplane. The second system, code-named "Eagle," was a method for locating and bombing objects on the ground when a pilot could not see them. The third invention became known as the microwave early-warning system, a mechanism for collecting images of aircraft movement in overcast skies.

In 1943, Alvarez left MIT to join the Manhattan Project research team working in Los Alamos, New Mexico. His primary accomplishment with the team was developing the detonating device used for the first plutonium bomb. Alvarez flew in the B–29 bomber that observed the first test of an atomic device at Alamogordo, south of Los Alamos. Three weeks later, Alvarez was aboard another B–29 following the bomber "Enola Gay" as it dropped the first atomic bomb on Hiroshima, Japan. Like most scientists associated with the Manhattan Project, Alvarez was stunned and horrified by the destructiveness of the weapon he had helped to create. Nonetheless, he never expressed any doubts or hesitation about the decision to use the bombs, since they brought a swift end to the war. Alvarez felt strongly that the United States should continue its nuclear weapons development after the war and develop a fusion (hydrogen) bomb as soon as possible.

After the war, Alvarez returned to Berkeley where he had been promoted to full professor. Determining that the future of nuclear physics lay in high-energy research, he focused his research on powerful particle accelerators—devices that accelerate electrons and protons to high velocity. His first project was to design and construct a linear accelerator for use with protons. Although his machine was similar in some ways to the electron accelerators that had been available for many years, the proton machine posed a number of new problems. By 1947, however, Alvarez had solved those problems and his forty-foot-long proton accelerator began operation.

Over the next decade, the science of particle physics (the study of atomic components) developed rapidly at Berkeley. An important factor in that progress was the construction of the 184-inch synchrocyclotron at the university's radiation laboratory. The synchrocyclotron was a modified circular particle accelerator capable of achieving much greater velocities than any other type of accelerator. The science of particle physics involves two fundamental problems: creation of particles to be studied in some type of accelerator and detection and identification of those particles. After 1950, Alvarez's interests shifted from the first to the second of these problems, particle detection, because of a chance meeting in 1953 with University of Michigan physicist Donald Glaser. Glaser had recently invented the bubble chamber, a device that detects particles as they pass through a container of superheated fluid. As the particles move through the liquid, they form ions that act as nuclei on which the superheated material can begin to boil, thereby forming a track of tiny bubbles that shows the path taken by the particles. In talking with Glaser, Alvarez realized that the bubble chamber could be refined and improved to track the dozens of new particles then being produced in Berkeley's giant synchrocyclotron. Among these particles were some with very short lifetimes known as resonance states.

Improving Glaser's original bubble chamber involved a number of changes. First, Alvarez decided that liquid hydrogen would be a more sensitive material to use than the diethyl ether employed by Glaser. In addition, he realized that sophisticated equipment would be needed to respond to and record the resonance states that often lasted no more than a billionth of a second. The equipment he developed included relay systems that transmitted messages at high speeds and computer programs that could sort out significant from insignificant events and then analyze the former. Finally, Alvarez aimed at constructing larger and larger bubble chambers to record a greater number of events. Over a period of about five years, Alvarez's chambers grew from a simple one-inch glass tube to his most ambitious instrument, a 72-in (183 cm) chamber that was first put into use in 1959. With these devices, Alvarez eventually discovered dozens of new elementary particles, including the unusual resonance states.

The significance of Alvarez's work with bubble chambers was recognized in 1968 when he was awarded the Nobel Prize for physics. At the awards ceremony in Stockholm, the Swedish Academy of Science's Sten von Friesen stated that, because of his work with the bubble chamber, "entirely new possibilities for research into high-energy physics present themselves….Practically all the discoveries that have beenmade in this important field [of particle physics] have been possible only through the use of methods developed by Professor Alvarez." Alvarez attended the Nobel ceremonies with his second wife, Janet Landis, whom he married in 1958. The couple had two children.

Advancing years failed to reduce Alvarez's curiosity on a wide range of topics. In 1965 he was in charge of a joint Egyptian-American expedition whose goal was to search for hidden chambers in the pyramid of King Kefren at Giza. The team aimed high-energy muons (subatomic particles produced by cosmic rays) at the pyramid to look for regions of low density, which would indicate possible chambers. However, none were found. Alvarez's hobbies included flying, golf, music, and inventing. He made his last flight in his Cessna 310 in 1984, almost exactly 50 years after he first learned to fly. In 1963, he assisted the Warren Commission in the investigation of President John F. Kennedy's assassination. Among his inventions were a system for color television and an electronic indoor golf-training device developed for President Eisenhower. In all, he held 22 patents for his inventions. Alvarez died of cancer in Berkeley, at the age of 77.