The Emergence of Astroparticle Physics: From Cosmic-Ray Physics to a new Scientific Field
Astroparticle physics emerged during the late twentieth century as a new interdisciplinary field at the intersection of particle physics, astrophysics, and cosmology. This article examines the historical mechanisms through which it took shape as a distinct scientific field, focusing on the progressive interaction of previously separate experimental cultures, research traditions, and scientific communities. It argues that astroparticle physics emerged not through the simple convergence of established disciplines, but through the gradual reorganization of high-energy research around scientific problems that transcended traditional disciplinary boundaries. Three broad historical trajectories shaped this process: the transformation of postwar cosmic-ray physics; the emergence of a high-energy Universe through relativistic astrophysics and new astronomical windows; and the growing interaction between particle physics and cosmology. Their progressive interaction transformed naturally occurring particles into astrophysical messengers and the Universe itself into a laboratory for investigating fundamental physics beyond the reach of terrestrial accelerators. At the same time, new experimental practices, international collaborations, scientific forums, and institutional structures progressively gave organizational form to this emerging research landscape. More broadly, the emergence of astroparticle physics illustrates how new interdisciplinary fields develop through the co-evolution of scientific questions, experimental cultures, research communities, and institutions.