The Milan school of physics refers to the tradition of research in the field of physics in Milan, with particular reference to the first and second halves of the 20th century. During this period, the Institute of Complementary Physics of Milan was formed at the University of Milan, under the impulse of Orso Mario Corbino and Antonio Garbasso, and with the chair of theoretical physics by Aldo Pontremoli.
History Until the eighteenth century, the teaching of physics in Milan—and more broadly in Italy—developed significantly in the confessional institutes, which represented, to some extent, the secular thought on the one hand and the religious tradition on the other, before following in the twentieth century the events of the university. The first signs of studies, mainly based on astronomy, took place in 1764, when the Brera Astronomical Observatory was founded within the Jesuit College of Milan with the help of La Grange and subsequently of Ruggero Boscovich. It was then with Schiaparelli, a pupil of Quintino Sella and Luigi Menabrea, that the foundations were laid for modern astronomy that made Milan an astronomical center of world excellence.
First half of the 20th century (1900–1948)
In 1924, the first three absolute chairs of theoretical physics were assigned in Italy: Enrico Fermi, Aldo Pontremoli and Enrico Persico, who were appointed to the three chairs of some of the most prestigious Italian universities. This led Pontremoli himself to be assigned to the Lombard university, where he founded the so-called Institute of Complementary Physics. He directed the institute from 1924 to 1928, with the aim of founding a pole that would respond to the needs of science and technology, such as it suited the greatest Italian industrial center. Having had a part of the school building in via Sacchini available, he took care of the adaptation and the fixed installations so that the new Institute could carry out scientific and didactic activities effectively and without interference. With the means obtained by the university, he constituted the first nucleus of devices essential for the functioning of the new institution; through his relationships in the industrial field, he was able to complete these endowments with materials received as a gift. In this way the Institute in a short time was able to fully fulfill the task assigned to it. In November 1925, the institute was the organizer of the II Assembly of the International Federation of the Intellectual Union. Among the grants received by Pontremoli, the one received from Banca Popolare di Milano in 1926, which allowed the foundation of the radiology laboratory, specialized in ultraviolet radiation, and radioactive substances, should be noted. The foundation of the school, which later became part of the Physics Department of the University of Milan, was published in the physics magazine Il Nuovo Cimento, of the Italian Physics Society. Pontremoli's studies were particularly concerned with optics, radioactivity and hydrodynamics and were mainly published in the Rendiconti dei Lincei of the homonymous Academy and in the Reports of the Lombard Academy of Sciences and Letters. Some popular writings appeared in the magazine La Fiera Letteraria. In 1929, after the death of Aldo Pontremoli—who died in the tragedy of the airship Italia who disappeared in the ice of Antarctica in May of the previous year—Giovanni Polvani replaced him in the chair of Experimental Physics of the Institute which became part of the University of Milan. The Polvani Archive, containing historical volumes, is still kept in the Physics Library of the University of Milan. A classroom in the university department was then named after him. In Milan, Polvani, already before the Second World War, is committed with Bolla and also with Gentile to find new tools to develop research on cosmic rays. Starting from 1936, the physical institute suffered a constant decline due to the conflicts between its protagonists and the fascist regime, many of who left Italy to continue their research studies in the United States of America following the establishment of fascist racial laws.
Second half of the 20th century (1949–1998) After the war, the department returned to obtain particular successes thanks to the return of many influential personalities to Italy. In 1949, lectures were given by the Nobel laureate Enrico Fermi, which were then collected by the assistants of the universities of Rome and Milan, and published in 1950 by the Accademia Nazionale dei Lincei. In 1952, Giuseppe Occhialini, who returned to Italy, taught higher physics and founded the Laboratory of Cosmic Physics and Related Technologies of the CNR and the Astrophysics Section of the Physics Department of the University of Milan. Here he created a leading school in the research of cosmic rays with the use of nuclear emulsions exposed at high altitudes, an experience that culminated in 1954 with the G-Stack experiment. He also founded the Space Group, so called because it conducted high altitude observations—first with stratospheric balloons, then with rockets, and finally with artificial satellites. It is also through these activities that Italy and Milan quickly acquired positions of excellence in the field of high-energy astrophysics, and more particularly in x-ray and gamma-ray astronomy. To allow this type of activity, Beppo Occhialini also took action on the organizational level, founding various sections of various research institutes still present, and taking charge of both the theoretical and experimental direction of the department.
The Occhialini case
Occhialini was involved in two Nobel Prize-winning works: the discovery of the positron and the discovery of the pion. However, as he was an anti-fascist, during the publication of most of his studies he was an exile in England and could not publish in his name alone. Therefore, the articles he wrote were also signed by Patrick Maynard Stuart Blackett in 1932 for the work on the positron and by Cecil Frank Powell in 1947 for the work on the pion. Both of these works were awarded the Nobel Prize, but the awards went to Blackett and Powell. Blackett was honest enough to say that he had nothing to do with it and that Occhialini had done the work. Only many years later was it discovered from the documents of the Nobel Foundation that there had been an explicit veto on the name Occhialini. In fact, Occhialini, since he had not collaborated in the atomic enterprise during the war, could not be awarded the Nobel. Occhialini was then awarded the Wolf Prize for physics in 1979.
Occhialini himself, in the period between 1952 and 1955, supervised Riccardo Giacconi, who would then be awarded the Nobel Prize for physics in 2002 for his pioneering contributions to astrophysics, which led to the discovery of the first cosmic sources in X-rays, and Giovanni Bignami, then president of ASI, INAF, COSPAR and SKA. With the advent of particle accelerators, Occhialini explored new fields of research, including space physics, making a decisive contribution to the foundation of the Italian Space Agency (ASI) and the European Space Agency (ESA), as well as to the INAF-IASF section of Milan. From 1947 to 1961, Polvani was president of the Italian Physics Society, and through this role contributed to the reorganization of Italian research after the war. In 1953, he founded the International School of Physics of Varenna in the municipality of the same name and in the province of Lecco, subsequently named after Enrico Fermi. It was the site of periodic meetings between established scientists and young physicists. Fermi himself, in the summer of 1954, gave a lecture on the physics of π mesons. To date, the school has hosted speeches by over thirty-four Nobel laureates.
The cyclotron of Milan After World War II, Italian physicists felt the need to build accelerator machines for the research of particles. After long discussions, two machines were built: one in Frascati—the 1000 Mev synchrotron, intended for high energy physics—and one in Milan—the 45 Mev cyclotron, intended for low energy physics. While the construction of the Frascati machine was financed by the National Institute of Nuclear Physics, the Milan machine was built with local funding from companies and the Municipality of Milan.
The Lombard business world financed basic research activities even without seeing immediate technological progress. A favorable climate had been created for scientific research as a factor of progress; similarly, the industrial world showed interest in the construction of the first Italian technical-scientific museum, the Leonardo da Vinci Museum.
Between 1960 and 1965, the first Italian cyclotron was designed and built at the Institute of Physical Sciences of the University of Milan. It belonged to the category of fixed frequency cyclotrons, variable azimuth field (A.V.F.) and was of the Thomas strong focus type. A special shed and other buildings were built to house the machine and the research laboratories. The machine worked until the early 1980s and was subsequently dismantled when construction of the superconducting cyclotron was started in Segrate. The 1:5 scale model of the cyclotron is kept at the Museum of Science and Technology in Milan. At the time, it was specifically created to study the most suitable and economical shape of the magnets to guarantee the necessary field.