We met Luca Campagnoni, a PhD student at the University of Padua, last summer at the Fifth International Conference on the History of Quantum Physics, where he presented work drawing on newly discovered archival materials related to cosmic ray physicist Bruno Rossi. In December, Campagnoni received an AIP grant-in-aid to support continued work on Rossi at archives in the United States. We posed him several questions by email about how his work integrates historical research with the development and exploration of archival collections.

---

Will Thomas: To set the stage, can you tell us a little about who Bruno Rossi was and what his career looked like?

Luca Campagnoni: First things first, thank you for the opportunity to share my research! I will focus on Rossi’s life and career up to around 1943, which is the timespan I am currently considering. Bruno Benedetto Rossi was born in the Lido of Venice in 1905. He first studied engineering in Padua, then physics in Bologna, where he graduated in 1927. The following year, he became an assistant to Prof. Antonio Garbasso at the University of Florence. There, in 1929, Rossi became interested in cosmic rays, the nature of which was still unknown at the time. In just a couple of years, he mastered the techniques for studying such radiation and even invented the coincidence circuit, a game-changer for that strand of research.

In 1932, Rossi became a professor in Padua, and—among other remarkable results—a noteworthy expedition to Eritrea enabled him to identify the nature of cosmic rays as positively charged particles in 1933. During the same period, he designed the new Institute of Physics and started cutting-edge cosmic ray and nuclear physics programs. Tragically, in 1938, the infamous racial laws forced Rossi and his wife, Nora Lombroso, to flee. They first reached Niels Bohr in Copenhagen, then Patrick Blackett in Manchester, and, eventually, Arthur Compton in Chicago. After obtaining crucial results on the decay of the mesotron—later identified as the muon—Hans Bethe invited Rossi to Cornell and then brought him into the Manhattan Project. There, along with Hans Staub, Rossi coordinated the detector group.

From the end of World War II through his retirement, Rossi was a professor at MIT and created the famous MIT cosmic ray group, which achieved groundbreaking results on extensive air showers and the solar wind. Toward the end of his career, he collaborated with NASA and, helped by Riccardo Giacconi, observed the first extrasolar x-ray source. In 1993, after a long and full life, Bruno Benedetto Rossi died in Cambridge, Massachusetts.

Thomas: And so there’s been a significant archival discovery in Italy of materials related to Rossi?

Campagnoni: Exactly, and a very fortunate one! Upon clearing a portion of the family house in which Rossi was born and raised in Venice, today a semi-detached house, they found several boxes containing old papers and objects. The building administrator, Carlo Fano, and his wife, Laurie Pearlman, carefully preserved the material and contacted the Department of Physics and Astronomy “Galileo Galilei” in Padua. The group of History and Didactics of Physics of the Department, in particular Fanny Marcon and Sofia Talas, made a preliminary recognition of the material.

A little later, in 2023, I asked Prof. Giulio Peruzzi, of the same group, to supervise my master’s degree thesis project. This coincidence of events led me to be the first person working full-time on this new archival source, an opportunity I will always be grateful for. Although my project focused on Rossi’s Eritrean expedition, I began by photographing each item in the collection, resulting in around 3,000 pictures. Once carefully organised, both by topic and chronologically, the complete frame was thrilling. The main discovery was a vast correspondence with his mother, spanning the whole 1930s and part of the 1940s, which surprisingly contains specific descriptions of Rossi’s work. The strong bond he shared with his loved ones led him to write them long and detailed letters, a real gold mine of information.

Moreover, correspondence with major physicists of the time emerged. Among them, we highlight Walther Bothe and Erich Regener, since no other letters between them and Rossi had been found before. They are both nice examples of fruitful scientific collaboration seasoned with a long-lasting personal friendship. Then, the archive—for the moment named Bruno Rossi Venice Archive (VBRA)—provided us with another wonderful surprise: the portion of Rossi’s family correspondence concerning his escape from Italy to the USA. It sheds light on his and his wife’s long and tormented wandering, about which we only knew something from Rossi’s autobiography. Last, but not least, a small yet interesting collection of personal items was there, including a tiny address book in which he listed all his commitments for the year 1937.

Thomas: Can you tell us how the collection informed the article you’ve just published in Physics in Perspective with Giulio Peruzzi and Sofia Talas?

Campagnoni: The article is the culmination of a year and a half of research on the topic, which started with my master’s degree final project. Since I had the privilege to continue the work on the VBRA within a dedicated PhD project, Giulio, Sofia, and I decided to complete the analysis of Rossi’s expedition to Eritrea first. Most of the information came from Rossi’s letters to his mother, around 250 pages throughout the four months of the expedition. Letters with Italian scientific and political institutions, along with those from Rossi’s future expedition companions, Sergio De Benedetti and Ivo Ranzi, and documentation from CSUP, the historical archive of the University of Padua, completed the frame and provided us with information concerning every step of the project.

Rossi’s long and detailed letters to his mother were a real gift, as, without them, the official scientific publications and his autobiography would have remained the only historical sources on the expedition. Such letters can be seen as an actual diary for daily activities, both scientific and non-scientific. As Rossi had written to his mother a few years earlier, he wanted to let her live his life through his words, despite the distance. Thanks to this, we indirectly witness the way in which Rossi experimented, his personal thoughts and ideas, as well as a terrible yet faithful depiction of the fascist colonial environment.

Luckily enough, Rossi’s mother also carefully preserved every newspaper clipping related to her son’s academic career. We therefore have a collection of more than twenty articles concerning the expedition to Eritrea published in national and local newspapers. On one hand, it helps confirm how the regime used the expedition as a propaganda move to glorify Italian science. On the other hand, it shows how cosmic rays and science in general were very popular among the general public at the time.

The VBRA initially prompted the reconstruction of a scientific expedition, but, to our joy, we ended up with much more than that. Due primarily to the peculiar context in which the expedition took place, we eventually wrote about a fascinating interweaving of science, history, society, and politics.

Thomas: You’re now preparing to come to the US assisted by an AIP grant-in-aid to do some work across different collections with material relating to Rossi. What are you aiming to accomplish?

Campagnoni: Although the VBRA is an exceptional source of new information, it is only a small piece of the puzzle. After all, physical-historical research cannot only focus on or trust a single source. The CSUP has been a first step to widening my view, as well as several Italian archives that I plan to visit early this year. However, the largest collection on Rossi’s life and career is preserved at the MIT Distinctive Collections in Boston, Massachusetts, the Bruno Benedetto Rossi papers. Such material—which I have briefly explored only via video calls so far—spans Rossi’s entire life and, with respect to the period I am interested in, complements the Venetian documents exactly. However, a considerable portion of those papers has never been carefully studied.

Thanks to Prof. David Kaiser’s endorsement and to the great support of MIT’s archivists and staff, I will spend three months as a visiting student and work on the collection in Boston, starting in September 2026. During that period, which will be economically sustained by an AIP grant-in-aid, I also intend to consult related material preserved in other US institutions: the University of Chicago, Washington University in St. Louis, and—if Bethe’s papers are available again in time—Cornell University in Ithaca. The primary goal of my trip is to gather the scattered pieces of information related to Rossi’s Italian period and early American years, to help me create a more unified archival portrait of him. A thorough analysis of Rossi’s papers will indeed make it easier to navigate not only the material merely related to him, but also to the more general development of 1930s cosmic ray physics.

As a welcome side-effect, Rossi’s partially forgotten figure will be valorized. The University of Padua largely benefited from his hard work and far-sightedness, both as a researcher and a professor. Therefore, since 2027 will be the Institute’s 90th birthday, it is the perfect moment to revive his memory and make amends once more for his shameful expulsion, which left a gaping void in Italian science.

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.

---