A nuclear physicist, in 1968 Luis W. Alvarez received the Nobel Prize in Physics for “his decisive contributions to elementary particle physics, in particular the discovery of a large number of resonant states, made possible through his development of the technique of using hydrogen bubble chambers and data analysis.”
Luis W. Alvarez wrote his autobiography in 1987, calling it Alvarez: Adventures of a Physicist. Being adventurous seems to have run in his family. His paternal grandfather, Luis F. Alvarez, was born in Asturias, Spain, and immigrated to California via Cuba in the 1870s. By the 1880s, Luis F. had made enough money in real estate in the Los Angeles area to enroll in medical school in San Francisco. Married and with a son (Walter), Luis F. graduated from medical school and became a physician for the Kingdom of Hawaii in Oahu, where Walter (Luis W.’s father) grew up. Luis W.’s maternal grandparents moved from Ireland to China, setting up a missionary school where Harriet Smyth (Luis W.’s mother) grew up. She completed high school in Berkeley, California, and graduated from the University of California in 1906. Walter enrolled in medical school in San Francisco after high school and interned at San Francisco General Hospital in 1906, at the time of the earthquake. Walter and Harriet met at the University of California in Berkeley (UC Berkeley) and were married in 1907, moving to a small mining town in Mexico, 25 miles south of the Arizona border, where Walter served as a physician. During their three years there, their first child Gladys was born. They moved back to San Francisco before their second child, Luis W., was born in 1911.
Luis W. Alvarez became fascinated with the physical sciences and engineering at a young age. When he was four years old, he was intrigued by the Machinery Hall exhibits at the 1915 San Francisco Pan-American Exhibition. Later, while his father worked in the physiology lab of the Hooper Foundation, Alvarez became interested in the electrical equipment in the room next door. By the time he was 10 years old, he was able to measure resistances and construct circuits. This ability helped him build his own radio at age 11 by following the description in a Literary Digest article. When he finished elementary school in 1924, his interest in mechanical things led him to the local polytechnic high school rather than a college preparatory school. His lessons in mechanical drawings helped him throughout his career in physics. In early 1926, Alvarez moved to Rochester, Minnesota, where his father had accepted a research position at the Mayo Clinic. Although the high school in Rochester had a more academic focus than the vocational school in San Francisco, Alvarez was ready to absorb more than the science classes had to offer. His father therefore took him to professional lectures (for example on electromagnetism) and hired a machinist at the Mayo Clinic to give Alvarez private lessons during the weekends. Alvarez ended up working in the clinic’s instrument shop during the summers of his junior and senior years in high school.
Alvarez graduated from Rochester high school in 1928. While for years he had assumed he would follow many of his family to the UC Berkeley, Alvarez instead followed his teachers’ advice to apply to the University of Chicago because of its strong science program. He first intended to major in organic chemistry but changed to physics in his junior year after taking an advanced class on light. In this class, Alvarez learned how to conduct experiments with optical spectrometry using a device to measure positions of spectral lines that characterize the light signature of chemical elements. While on vacation at his parent’s home in Rochester, he noticed that the light reflected off of a vinyl record was diffracted in such a way that he could use the record, a light bulb, and a yardstick to measure the wavelength of light in the living room. This experiment became the basis of his first scientific paper, which was published in the January 1932 issue of School Science and Mathematics.
In his final months of his undergraduate career in Chicago, Alvarez worked on a project to build a Geiger counter. Using the data in the original 1928 article (by Geiger and Muller) and his experience in Rochester in mechanical engineering, he constructed his Geiger counter out of metal and glass. Although crude, it worked. Alvarez continued on at the University of Chicago to get an advanced degree (he finished his graduate work at the University of Chicago when he earned his PhD in 1936). His graduate adviser was Arthur Compton, who had earned the Nobel Prize in Physics in 1927 for demonstrating the particle nature of electromagnetic radiation. Compton suggested that Alvarez adapt his Geiger counter to study cosmic rays, which were not well understood at the time. Manuel Vallarta, a professor at the Massachusetts Institute of Technology (MIT), had invited physicists to come to his native Mexico City to test the theory that cosmic rays are charged particles rather than gamma rays. Mexico City was a good location for this experiment due to its high altitude and proximity to the equator. Alvarez took his Geiger counter telescope to measure the deflection of cosmic rays due to the East-West effect. His results indicated that cosmic rays are positively charged. Alvarez published these results with his adviser in a letter to Physical Review.
In 1933, Alvarez set up his Geiger counter telescope as part of the General Motors exhibit at the Century of Progress Exposition in Chicago. At the Association for the Advancement of Sciences (AAAS) meetings being held there, Alvarez heard Ernest Lawrence, a professor at UC Berkeley, speak about the cyclotron, a device that accelerated nuclear particles. Alvarez’s sister Gladys worked for Lawrence and arranged for the two to meet, thus beginning a long friendship and scientific partnership. At this time, Alvarez also started taking flying lessons and became interested in aviation, which became a life-long passion.
Alvarez met Geraldine Smithwick through mutual friends at the University of Chicago. They were married in April 1936, after Alvarez passed the oral exams for his PhD. Their original plans to go to Europe were dropped due to the Spanish Civil War. Instead, they moved to California, where Lawrence offered Alvarez a position at the Radiation Laboratory in Berkeley. Starting in May, Alvarez’s work focused on the cyclotron as well as the linear accelerator. These devices, key tools in studying high-energy particle physics, often were built and repaired by the physicists themselves, so they worked as mechanics as well as nuclear physicists. Alvarez’s background in chemistry also was useful when identifying the chemical element and atomic weight of isotopes discovered in experiments using the cyclotron. Doing this work made Alvarez realize, however, that he did not have a firm background in nuclear physics, radio-frequency engineering, or electrical engineering. These he learned on-the-job as an experimental physicist at the Radiation Lab and would be of great importance in the future.
Experimental physicists like Alvarez often work in coordination with theoretical physicists, such as Robert Oppenheimer, who taught graduate students at UC Berkeley. Hans Bethe, a theoretical physicist who taught at Cornell University, built upon Enrico Fermi’s theory of beta decay by suggesting that a nucleus could decay by capturing an electron orbiting it. Such an electron would be captured from the level, or shell, that is closest to the nucleus, which is referred to as the K shell. Alvarez devised an experiment to test this theory using a Geiger counter filled with argon gas to catch the type of x-ray that would be emitted by a K-capture. His experiment demonstrated that K-shell electron capture does happen, and he published his results in 1938.
Sometimes an experiment does not support a theory but contradicts it. In 1932, a physicist at Columbia University discovered deuterium, an isotope of hydrogen. It was found that when an atom of deuterium is fused with another atom of deuterium, the result is either a helium nucleus with a mass of 3 or a hydrogen nucleus with a mass of 3 (known as tritium). In theory, the helium 3 atom was thought to be unstable or radioactive, while the tritium was thought to be stable. Using a cyclotron, Alvarez sought to determine the radioactive half-life of helium 3. HIs experiment, however, showed that helium 3 is stable. Later experiments showed that it is tritium that is radioactive, contrary to theory.
Towards the end of 1940, there were several major changes that happened in Alvarez’s life. In October he became a father, when his son Walter was born. About a month later, Alvarez moved from Berkeley to Cambridge, Massachusetts, to work at MIT as part of the U.S. war effort. He became part of a team focused on developing radar devices based on the transmission of electromagnetic pulses directed at and reflected off of an object (like aircraft) to produce pulses at a receiver. The time lag between directing a pulse at an object and having a corresponding pulse reflected back to the receiver can be used to determine the distance between the object and the receiver. The MIT team used a cavity magnetron, invented in England, as the source of the microwaves that were the basis for the research. Alvarez was appointed as coordinator for the project to produce the first pulsed microwave radar set.
In the midst of trying to get the project started, in April 1941 Alvarez had to return to Rochester to undergo gallbladder surgery at the Mayo Clinic. Due to complications, it took him several month to recover. Back at MIT, Alvarez was inspired by work done on a radar device developed to track and shoot down enemy aircraft to develop a device that would guide friendly aircraft to land in bad weather. Drawing on what he had been learning about flying and aviation since the 1930s, Alvarez led his team to create the Ground Controlled Approach (GCA), a new system that was the first to use a microwave phased-array antenna. Although the first trials of the GCA did not work as expected, with each trial what was seen as a mistake was corrected until finally the equipment worked as intended. After seeing the successful demonstration of the GCA, the Army and Navy ordered hundreds of units for the war effort. Later, GCA also was used for civilian and commercial aircraft. During the summer of 1943, Alvarez worked in London to collaborate with the British on further developments of the GCA.
Upon returning to the U.S. at the end of the summer 1943, Alvarez shifted the direction of his work yet again. While working on radar, he had also followed work being done in the field of radioactive isotopes of uranium and plutonium that could be used in nuclear bombs. This now became the focus of Alvarez’s work. He joined Robert Oppenheimer’s research lab to work on what was called the Manhattan Project. At first Alvarez worked with Fermi in the Argonne Lab in Chicago, testing materials that would be used in the reactors in Oak Ridge and Hanford, Washington state. General Leslie Graves, an Army engineer, was in charge of the Manhattan Project. He assigned Alvarez the task of devising a method to determine if Germany was operating nuclear reactors. The resulting method to monitor fission processes was effective after the war, but during the war it was used to determine that Germany was not developing a nuclear bomb (because scientists working in Germany never were able to initiate the chain reaction needed for a nuclear bomb).
Alvarez’s next assignment involved moving to the site in Los Alamos, New Mexico, where the Manhattan Project was focused on developing nuclear bombs. Despite being an important part of that team, when Alvarez prepared to move his family to the housing set aside for scientists at Los Alamos, some of those living there already resisted the idea that someone with a Spanish surname would live among them. By the time Alvarez brought his wife and son from Chicago one month later, the social situation had been smoothed out. That October, on his son Walter’s 4th birthday, Alvarez and his wife Gerry had a daughter, Jean.
At the Los Alamos lab in New Mexico, scientists working on the Manhattan Project were developing two methods to detonate nuclear devices: the gun method, to be used with the Little Boy (uranium) bomb, and the implosion method, to be used with the Fat Man (plutonium) bomb. Alvarez was assigned to the Fat Man team, under the supervision of George Kistrakowsky. Once the implosion detonation device for the Fat Man bomb was successfully finished, Oppenheimer asked Alvarez to devise a method to measure the energy released from the two bombs that were scheduled to be dropped on two cities in Japan. Alvarez developed a way to measure the strength of the blast wave and calculate the bomb’s energy using microphones and an oscilloscope.
After being commissioned as a lieutenant colonel in the U.S. Army, Alvarez tested the monitoring device in a B-29 airplane over the Trinity test site when the first atomic bomb was tested on July 16, 1945. He also joined the mission at the U.S. base at Tinian and monitored the explosion at Hiroshima on August 9. He did not fly on the flight that monitored the Nagasaki mission. Years later in his autobiography, Alvarez discussed the conflicting positions about whether dropping the bombs on Japan was morally defensible. Although most scientists he knew were reluctant to kill civilians at such a massive scale, Alvarez felt that it was preferable to a prolonged war that would have involved a military invasion of Japan. This conviction that powerful bombs could deter prolonged wars might have led Alvarez to join Lawrence in his support of having the U.S. develop a hydrogen bomb that would be more powerful than the plutonium bomb dropped on Nagasaki. After the Soviet Union detonated an atomic bomb for the first time in August 1949, Alvarez and Lawrence got support from influential people in Congress to start up a new projects for a Materials Testing Accelerator (MTA). A site was set up for the MTA at an old army base in Livermore, California, which became the Lawrence Livermore National Laboratory (LLNL).
After the war, as a civilian and professor, Alvarez was back at UC Berkeley with his family living close to campus. Alvarez and his colleague Ed McMillan renewed their research into particle physics, using microwave radar sets left over from the war effort. While McMillan focused on studying electrons, Alvarez set out to build a linear accelerator using radio frequencies to alternately push and pull protons through an electric field.
In the early 1950s, the area of high-energy particle physics was expanding as a field in which large accelerators create unstable particles by “materializing energy.” Many of Alvarez’s graduate students did work on the scattering of gamma rays by protons to observe whether pions materialize in nuclei. They also looked at “strange” particles like K mesons. Because these “strange” particles had much shorter lifetimes than other known particles, established methods using cloud chambers or nuclear film emulsions would not adequately track or capture their basic reactions for physicists to study. At a 1953 meeting of the American Physical Society, Alvarez talked with Don Glaser, who invented the bubble chamber, filled with ether in which particles left their tracks. Alvarez and his team at UC Berkeley replaced the ether with liquid hydrogen to study the single proton of a hydrogen atom. Over the next few years, they found that they could use their hydrogen (H) bubble chamber to study a variety of particles, atoms, and molecules, many with very short half-lives, in particular, three “strange resonances.” The H bubble chamber had glass windows through which researchers could take pictures of the tracks left by particles through the hydrogen gas that was alternately decompressed (reduced pressure led to a gas state) and compressed (high pressured led to a liquid state). The cycle of compression and decompression was synchronized with the action of the accelerator beam to allow a photo to be taken of the particle interactions. Alvarez and his team developed a computer system to measure and analyze the interactions and, in so doing, discovered families of new particles and resonance states. In recognition of this work, in October 1968 Alvarez was awarded the Nobel Prize in Physics, “for his decisive contributions to elementary particle physics, in particular the discovery of a large number of resonant states, made possible through his development of the technique of using hydrogen bubble chambers and data analysis.”
In April 1956, Alvarez was among a group of U.S. physicists who were invited by the Soviet Academy of Sciences to attend a conference on high-energy physics in Moscow. The diary that he kept during that trip was published in the journal Physics Today. This was followed by an international conference in particle physics held in Geneva, Switzerland. When he returned home, it was clear that his 21-year marriage with Geraldine was not working. The couple divorced when their son Walter was a senior in high school. In June 1957, at the annual dinner of the American Society of Mechanical Engineers (ASME), Alvarez met Janet Landis, daughter of the ASME President Jim Landis. Although she was 20 years younger than Alvarez, the two had similar interests and fell in love. They were married in December 1958. They had two children, Don (born in 1965) and Helen (born in 1967).
In August 1958, Ernest Lawrence died and a new director was named to head the Berkeley Radiation Lab. Eventually, Alvarez resigned as associate director and formed a new group that received independent funding from the National Air and Space Administration (NASA). In the following decades, Alvarez pursued a variety of projects covering a wide range of topics. During the Kennedy administration, he was appointed as a senior adviser to the Federal Aviation Administration (FAA). Later appointed to the PSAC Limited War Panel, Alvarez was chair of the PSAC military aircraft panel, and so was able to participate in test flights of several military aircraft. He also served on several NASA committees and obtained NASA funding for a bubble chamber program to study cosmic rays. In 1964, Alvarez developed a method to use cosmic ray muons to probe the Chephren pyramid in Egypt to see if there were any hidden chambers. In 1967, accompanied by his wife Janet and his son Walter, Alvarez showed that the technique could work but the Chephren pyramid had no hidden chambers. During a trip to Africa in 1963, Alvarez was frustrated by the need to prop up a zoom telephoto lens against something when trying to photograph animals, so he designed an optical lens attachment that led to stabilized optics.
One of Alvarez’s latest projects might be one of his best known. In 1980, Alvarez’s son Walter, a geologist, was studying residual magnetism of rocks in the Apennines of Italy. Walter showed his father Luis a rock that had white limestone on one side, red limestone on the other, and a layer of clay in between. The clay layer, found around the world, was laid down during what is known as the K/T boundary between the Cretaceous and Tertiary periods, a time when the dinosaurs became extinct. Alvarez thought it might be possible to determine how long it took for the clay layer to form by measuring traces of meteorite debris represented by iridium, which normally is deposited on earth at a known, regular rate. Neutron activation analysis conducted by a couple of Alvarez’s colleagues showed that 300 times as much iridium was concentrated in the clay layer than in the limestone layers, indicating that something out of the ordinary had happened. A lack of plutonium in the clay layer indicated that it was not the result of a supernova explosion. The next hypothesis they came up with was that an asteroid, possibly 10-kilometers wide, struck earth. As this coincided with the massive extinctions at the end of the dinosaur era, they looked at many possible explanations of how those extinctions occurred. Drawing a comparison with the dust produced when the volcano Krakatoa erupted in 1883, Alvarez suggested that asteroid dust could have stayed in the stratosphere in sufficient amounts to block sunlight for several years, reducing photosynthesis and the food supply for those large animals that disappeared from the fossil record. Computer modelling shows that temperatures could have fallen well below freezing for 6-9 months. Walter presented results of this research in paleontology meetings and published a paper in Science. In January 1980 he gave a talk on the impact hypothesis at the AAAS annual meeting. Many of the predictions made based on this theory were supported by later research. It was not until after Alvarez died that other scientists in 1990 found what they think is the crater caused by that asteroid impact off of the coast of Mexico. The impact theory of extinction had an effect on geopolitics and arms control as it was adapted into the “nuclear winter” theory that modern nuclear weapons could set off so much fire and smoke that the sun would be blocked again, recreating the type of situation that led to the extinction of the dinosaurs.
By the time Alvarez wrote his autobiography in 1987, he had accumulated a long list of honors in addition to the Nobel Prize, including the Collier Trophy in aviation, National Medal of Science, National Inventors Hall of Fame (with over 20 patents to his name), election to the National Academy of Sciences, and six honorary doctorates of science. Throughout his career, he was able to combine his passions for optics, aviation, cosmic rays, and particle physics. Like his friend and mentor Lawrence, Alvarez died of complications after surgery, for esophageal cancer, on September 1, 1988.
Sources:
Alvarez, Luis W. (1987) Alvarez: Adventures of a physicist. New York: Basic Books, Inc.
“Alvarez, Luis Walter (1911-1988) physicist, inventor” in Newton, David E, Latinos in Science, Math and Professions. New York: Facts on File (2007) Infobase Publishing
“Luis Walter Alvarez.” En.Wikipedia.org
“Luis Alvarez: Biographical”. http://www.nobelprize.org. Nobel Lectures, Physics 1963-1970. Amsterdam: Elsevier Publishing Co., 1972.
“Luis Alvarez: American Physicist”. http://www.britannica.com
“Luis Alvarez”. http://www.famousscientists.org
“Luis Alvarez”. Science Matters blog at umraish.wordpress.com
“10 Hispanic Scientists You Should Know.” at science.howstuffworks.com
Seidel, Robert W. “Alvarez, Luis Walter”. http://www.encyclopedia.com
Snodgrass, Mary Ellen. “Alvarez, Luis Walter: 1911-1988: Nuclear Physicist, Inventor, Educator” http://www.encyclopedia.com
“Alvarez, Luis (1911-1988)”. World of Earth Science.
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