Luis Alvarez, at center, during the 1960 Rochester Conference.
AIP Emilio Segrè Visual Archives, Marshak Collection.
News notice: AIP is excited to announce a new funding opportunity through our Robert H. G. Helleman Memorial Grant and Fellowship Program. Grants of up to $150,000 per year will support multi-institutional collaborative research projects in the history of the physical sciences since 1850. For further details, please see the call for applications.
Publication notice: The Weekly Edition will not appear on November 28, 2025, due to the US Thanksgiving holiday.
Luis Alvarez can be counted among the 20th century’s most important experimental physicists, in large part due to his leadership in the 1950s implementing hydrogen bubble chamber detectors at the Berkeley Radiation Lab’s Bevatron accelerator. That work enabled a bonanza of discoveries in particle physics and resulted in Alvarez being the sole recipient of the 1968 Nobel Prize in Physics. It also forged a newly industrialized style of research that would become the standard way of doing high-energy particle physics in large-scale facilities that produce enormous volumes of data.
Collisions, a new biography of Alvarez by Alec Nevala-Lee, makes clear that this crowning achievement was in some ways aberrational for the physicist, who prized experimental agility and frowned on rote, factory-like approaches to science. Illuminating the outlook and strategies that Alvarez employed throughout his career, the book leverages and supplements earlier sources such as Alvarez’s 1987 autobiography , Peter Trower’s National Academy of Sciences memoir , and the two-session oral history that AIP conducted on February 14 and February 15 , 1967.
Alvarez’s ascent
Nevala-Lee traces Alvarez’s development as an experimenter from his undergraduate and graduate work at the University of Chicago. There, working under Arthur Compton, he honed his skills and patience on projects such as building an optical telescope and crafting Geiger counters, a new and finicky technology he used to study cosmic rays. He was also exposed to more sophisticated equipment, such as an automated machine that etched the highly precise lines in diffraction gratings.
Receiving his doctorate in 1936, Alvarez finagled a position at Ernest Lawrence’s Radiation Laboratory at the University of California, Berkeley, which was widely recognized as a center for cutting-edge experimental research. Beginning essentially as a paid hand, he initially spent most of his time attending to the lab’s hulking cyclotron particle accelerator while more established researchers used it as an engine for discovering and analyzing isotopes.
Although the pace of discovery at the cyclotron was rapid, the research could be repetitious, and Alvarez soon climbed the lab’s hierarchy by undertaking more creative experiments. Nevala-Lee emphasizes his cultivation of “good taste,” wedding an awareness of new questions raised by theory with an appreciation of the experimental possibilities held out by available equipment and materials. Some of his major achievements included conclusively detecting electron capture by the nucleus, ascertaining the radioactivity of tritium and non-radioactivity of helium-3, developing a method of isolating thermal neutrons , and, in a grueling experiment with Felix Bloch, determining the neutron’s magnetic moment .
In addition to designing important experiments, Alvarez hoped to avoid missing serendipitous discoveries by thinking too narrowly about his experimental goals. However, it did not prevent him and his student Philip Abelson from narrowly missing out on the world-changing discovery of nuclear fission.
As World War II approached, Alvarez joined the MIT Radiation Laboratory to work on radar, where the knowledge of electronics he honed at the cyclotron informed his development of new devices and applications. Among his contributions were Vixen, which decreased the strength of radar transmissions to fool U-boats into thinking pursuing aircraft were moving away, and Ground Control Approach, a radar-assisted technique for guiding aircraft into landings in low-visibility conditions. Alvarez’s technical creativity earned him leadership of a “Special Systems” division of the lab, where he could pursue projects at his own discretion.
In 1943, Alvarez moved over to the Manhattan Project, working initially in Chicago with Enrico Fermi before transferring to Los Alamos, where he joined the group developing an implosion mechanism for the atomic bomb. As the first bomb neared completion, he shifted to developing methods of studying the blast and witnessed the Trinity test from an airplane. He followed the bomb to Tinian in the Pacific Ocean and monitored the Hiroshima bombing from the B-29 bomber dubbed The Great Artiste.
The view from the summit
The Lawrence Radiation Laboratory’s 72-inch bubble chamber was relocated to a temporary site in July 1961.
Photo courtesy of Berkeley Lab. © The Regents of the University of California, Lawrence Berkeley National Laboratory.
After the war, Alvarez emerged with experience working in sprawling research organizations, and he was a recognized leader in the national physics community. Taking advantage of his position, he launched into two ambitious projects that put him on a years-long professional losing streak.
An ambitious linear accelerator project that Alvarez led at Berkeley fell technologically behind the synchrotron concept developed by his colleague and rival Edwin McMillan, and then a construction accident damaged his accelerator irretrievably. After the Soviet Union tested an atomic bomb in 1949, Lawrence and Alvarez pushed hard to involve Berkeley in the US hydrogen bomb program, ultimately leading Alvarez to take charge of building an enormous facility for producing nuclear materials at the lab’s new Livermore site. Called the Materials Testing Accelerator, it became a boondoggle.
At the same time, Alvarez became embroiled in the vicious political controversies surrounding the physics community in that era. His and Lawrence’s fierce advocacy for developing the hydrogen bomb pitted him against those who were opposed to, or less enthused by, the idea, including Robert Oppenheimer, who chaired the Atomic Energy Commission’s General Advisory Committee. That confrontation resulted in Alvarez testifying against Oppenheimer at the latter’s 1954 security clearance hearing, a headline-grabbing event that outraged many physicists. Meanwhile, at Berkeley, Alvarez firmly took the university’s side in a controversy over a loyalty oath it imposed on employees amid the Red Scare. Many physicists departed at that time, either forcibly or voluntarily, including every theorist on the faculty and Alvarez’s close colleague Pief Panofsky.
The turnaround for Alvarez came in 1953, when he learned of the bubble chamber from its inventor, Donald Glaser. He saw that, if filled with liquid hydrogen, it might be able to effectively resolve the blizzard of particle interactions that would be produced by the Bevatron, then under construction. For the remainder of the decade, he pushed relentlessly to increase the chamber’s size and to devise means of rapidly analyzing the endless rolls of photographic images it produced.
Whereas the cyclotron had admitted a degree of amateurism in its construction and operation, the bubble chamber demanded extreme discipline in its engineering, not least since the hydrogen it contained was highly explosive and cooled to near absolute zero. Physicists therefore yielded much of their control over the apparatus to engineers, while its operation and the initial analysis of the images it produced was handed to technicians.
For Alvarez, physicists’ lack of engagement with the workings of the bubble chamber was alienating, as was the prospect their work would be reduced to analyzing computer printouts. While working on the chamber, he also declined to pursue leadership of the lab following Lawrence’s death in 1958. Rather than build his stature further, he spent his final decades following his experimental muse.
The search for new problems
Luis Alvarez and his son Walter Alvarez at the K–T boundary.
Photo courtesy of Berkeley Lab.
Although Nevala-Lee does not dwell on Alvarez’s personality, he establishes that the physicist had a reputation for being tireless, publicity-seeking, domineering, and even cruel in his efforts to advance his agenda. After World War II, that agenda reached far beyond Berkeley as Alvarez parachuted into an extraordinary variety of subject areas, confident he could make decisive contributions.
Many of Alvarez’s contributions arose from his work as a consultant and adviser on problems of military or national interest, for instance with the RAND Corporation and the US Air Force, and as a member of the JASON advisory group and President’s Science Advisory Committee. He also independently dove into the fevered discourse surrounding President Kennedy’s assassination, conducting intensive analyses of the Zapruder film—and particularly the motion of Kennedy’s head, which many took as evidence of a second shooter, but which he insisted could be explained by physics.
Alvarez’s principal research projects similarly reflected his intellectual fecundity. In the 1960s, he undertook a series of high-altitude balloon experiments in an effort to study high-energy cosmic rays that in the end fell flat. He also launched a fruitless search for hypothesized magnetic monopoles in rock from Antarctica and the Moon. Another multiyear project involved using cosmic rays to try to detect hidden chambers in the pyramid of Khafre, though it eventually found the structure is solid.
His maverick tendencies notwithstanding, Alvarez consistently presented himself as an authority figure and often sought to defend established authorities, as he did in supporting the Warren Commission findings on the Kennedy assassination. He also cultivated a self-image as meticulous and principled, willing to admit failures and let go of tantalizing but ultimately disappointing findings. Sometimes he wielded such principles as weapons, as when he sought to publicly demolish his colleague Buford Price’s claim to have potentially detected a magnetic monopole.
Alvarez’s strategies were essential to an extraordinary late-career triumph, when he teamed with his geologist son Walter and other colleagues to argue that a meteor caused the mass extinction at the end of the Cretaceous period that wiped out the dinosaurs. Leaning on an abundance of iridium they serendipitously discovered in a geological layer called the K–T boundary, Alvarez condemned the scientific reasoning and attitude of geologists who were reluctant to accept the meteor theory. By the time of Alvarez’s death in 1988, the idea had garnered strong acceptance, and the case was further sealed soon after with the identification of the meteor’s likely impact site on the Yucatan Peninsula.
William Thomas
American Institute of Physics
wthomas@aip.org
You can sign up to receive the Weekly Edition and other AIP newsletters by email here.
More from AIP
