Jean-Philippe Martinez

This article discusses the meaning of the notion of virtuality in modern physics. To this end, it develops considerations on the introduction and establishment in nuclear physics of two independent concepts at the turn of the 1920s and 1930s: that of the virtual state, used in the context of neutron scattering studies, and that of the virtual transition, useful for the theoretical understanding of strong nuclear forces, which forms the basis of what are now called virtual particles. Their comparative analysis highlights the theoretical nature of virtual entities and processes in modern physics. It also shows how the virtual has been associated with various purely physical attributes, leading to a form of polysemy of the term, from the beginning of the application of these concepts.

Vladimir Fock est un scientifique russo-soviétique connu pour diverses contributions à la physique moderne. Il en fut aussi un interprète, développant une position critique face à l’orthodoxie incarnée par Niels Bohr en mécanique quantique et Albert Einstein en relativité générale. Fock ayant adhéré au matérialisme dialectique, l’historiographie sur ses contributions aux débats d’interprétation met généralement l’accent sur sa défense d’une position réaliste, en faveur de l’objectivité du monde extérieur. Le présent article complète cette observation en s’appuyant sur un texte du physicien soviétique jusqu’alors peu connu : « La signification fondamentale des méthodes d’approximation en physique théorique ». En effet, il révèle une forme d’antiréductionnisme essentielle à la compréhension du discours de Fock sur l’interprétation des théories de la physique moderne.

Following Lenin’s critique of Mach in Materialism and Empiriocriticism, the name of the Austrian philosopher was often used in the Soviet Union to discredit philosophical positions, theories, or individuals, because of the assumed influence he had on them. This is what we define as the “Mach argument”, a matter of rhetoric that usually did not require any additional explanations and suited the political discourse required by the Soviet regime. This chapter aims to study its use by the Soviet physicist Vladimir Fock, to better understand the modalities of his scientific discourse. It highlights the complex situation he faced, as his need to defend modern theories of physics against unjustified ideological attacks in the Soviet Union was in some way at odds with his own belief that their interpretations needed revision. In response, Fock elaborated a strategy that required a form of politicization of his professional culture. Nevertheless, we argue that the scientist showed a great capacity for adaptation as it did not mean in any way an abandonment of his traditional scientific values and principles.