Luisa Bonolis

Stellar structure and compact objects before 1940 : towards relativistic astrophysics

Abstract Since the mid-1920s, different strands of research used stars as “physics laboratories” for investigating the nature of matter under extreme densities and pressures, impossible to realize on Earth. To trace this process this paper is following the evolution of the concept of a dense core in stars, which was important both for an understanding of stellar evolution and as a testing ground for the fast-evolving field of nuclear physics. In spite of the divide between physicists and astrophysicists, some key actors working in the cross-fertilized soil of overlapping but different scientific cultures formulated models and tentative theories that gradually evolved into more realistic and structured astrophysical objects. These investigations culminated in the first contact with general relativity in 1939, when J. Robert Oppenheimer and his students George Volkoff and Hartland Snyder systematically applied the theory to the dense core of a collapsing neutron star. This pioneering application of Einstein’s theory to an astrophysical compact object can be regarded as a milestone in the path eventually leading to the emergence of relativistic astrophysics in the early 1960s.

Bruno Pontecorvo: From slow neutrons to oscillating neutrinos

Bruno Pontecorvo’s work in neutrino physics is examined and due emphasis is given to the audacity of his ideas both theoretically and experimentally. The account ends with the first solar neutrinos detected by Raymond Davis in 1967 using the radiochemical method developed by Pontecorvo in 1945.

The Charm of Theoretical Physics (1958-1993)

Abstract Personal recollections on theoretical particle physics in the years when the Standard Theory was formed. In the background, the remarkable development of Italian theoretical physics in the second part of the last century, with great personalities like Bruno Touschek, Raoul Gatto, Nicola Cabibbo and their schools.

Walther Bothe and Bruno Rossi: The birth and development of coincidence methods in cosmic-ray physics

With the advent of the Geiger-Muller counter in the late 1920s, the nature of cosmic rays became accessible to exper- imentation. When used single as cosmic-ray detectors, these devices did not have significant advantages over ionization chambers. They became a powerful new tool for cosmic-ray experiments when used in coincidence arrangements. The coincidence technique, first used by Hans Geiger and Walther Bothe in 1924 to verify that Compton scattering produces a recoil electron simultaneously with a scattered c-ray, 1 achieved its full potential only in connection with the invention of electronic circuits at the beginning of the 1930s. Subsequently, in conjunction with the invention of new sophisticated detectors the coincidence method became one of the basic tools in experimental physics. In this paper we will discuss how the arrangement of arrays of counters, absorbers, and electronic recording circuits became standard in cosmic-ray studies, as well as in nuclear and particle physics.

The beginning of Edoardo Amaldi’s interest in gravitation experiments and in gravitational wave detection

Unedited documents and letters allowed to establish that Edoardo Amaldi’s first interests in experiments on gravitation date back to the late 1950s, about twelve years before the beginning of the research activity in gravitational wave (GW) detection in Rome (1970). Amaldi was connected to the main protagonists of the historical phenomenon that many historians call the Renaissance of General Relativity (GR), characterised by the new attitude of the scientific world towards Einstein’s theory of gravitation, which had its start in the middle of the 1950s and which grew along the 1960s, with the birth of relativistic astrophysics. Since the second half of the 1960s, Amaldi’s will of beginning an experimental activity for detecting gravitational radiation clearly emerges.

A life in statistical mechanics. Part 1: From Chedar in Taceva to Yeshiva University in New York

Abstract This is the first part of an oral history interview on the lifelong involvement of Joel Lebowitz in the development of statistical mechanics. Here the covered topics include the formative years, which overlapped the tragic period of Nazi power and World War II in Europe, the emigration to the United States in 1946 and the schooling there. It also includes the beginnings and early scientific works with Peter Bergmann, Oliver Penrose and many others. The second part will appear in a forthcoming issue of Eur. Phys. J. H.

International scientific cooperation during the 1930s. Bruno Rossi and the development of the status of cosmic rays into a branch of physics

Summary During the 1920s and 1930s, Italian physicists established strong relationships with scientists from other European countries and the United States. The career of Bruno Rossi, a leading personality in the study of cosmic rays and an Italian pioneer of this field of research, provides a prominent example of this kind of international cooperation. Physics underwent major changes during these turbulent years, and the traditional internationalism of physics assumed a more institutionalized character. Against this backdrop, Rossis early work was crucial in transforming the study of cosmic rays into a branch of modern physics. His friendly relationships with eminent scientists — notably Enrico Fermi, Walther Bothe, Werner Heisenberg, Hans Bethe, and Homi Bhabha — were instrumental both for the exchange of knowledge about experimental practices and theoretical discussions, and for attracting the attention of physicists such as Arthur Compton, Louis Leprince-Ringuet, Pierre Auger and Patrick Blackett to the problem of cosmic rays. Relying on material from different archives in Europe and the United States, this case study aims to provide a glimpse of the intersection between national and international dimensions during the 1930s, at a time when the study of cosmic rays was still very much in its infancy, strongly interlaced with nuclear physics, and full of uncertain, contradictory, and puzzling results. Nevertheless, as a source of high-energy particles it became a proving ground for testing the validity of the laws of quantum electrodynamics, and made a fundamental contribution to the origins of particle physics.