EXCERPT Dr. Roberto Trotta coordinates Oxford University’s Dark Sector Initiative, an enterprise dedicated to elucidating the nature of ‘dark matter’ and ‘dark energy’. The cross-disciplinary nature of this project—described as an intense collaborative work involving mathematics, theoretical physics, phenomenology and statistics—anticipates the problematic status of its objects. Trotta’s work as a theoretical cosmologist takes place at the intersection of cosmology (the attempt to construct a coherent model and narrative of the origin and evolution of the universe), astrophysics (the description in physical terms of the objects observed in the universe), and theoretical physics (positing models of the elementary constituents of matter and their interactions). Observations of astrophysical entities are interpreted in cosmology within the framework of theoretical physics, drawing upon powerful statistical techniques to derive probabilistic inferences on the fundamental phenomena under scrutiny, even in cases where the astrophysical objects themselves are poorly understood. Equally, some of the most advanced and speculative theoretical physics finds its best (and sometimes unique) testing ground in models of the early universe. Collapse interviewed Trotta at the Beecroft Institute for Particle Astrophysics and Cosmology (BIPAC) with a view to understanding how the process of determination of this field of research on the ‘outer edge’ of science, bounded equally by technological, probabilistic and logical constraints, brings to light the process of scientific thought, and problematises its very conceptual foundations, thus emphasising its continuities with traditionally ‘philosophical’ concerns…