On the “direct detection” of gravitational waves

Abstract

In this paper, I provide an account of direct (vs. indirect) detection in gravitational-wave astrophysics. In doing so, I highlight the epistemic considerations that lurk behind existing debates over the application of the term “direct”. According to my analysis, there is an epistemically significant distinction between direct and indirect detections in this context. Roughly, our justification for trusting a direct detection depends mainly on the reliability of instruments that are under our control, rather than on the reliability of our models of separate target systems. In contrast, indirect detections rely on confidence in such models. Overall, this paper solves a puzzle about what counts as a “direct” detection of gravitational waves in a way that is true to scientific usage, and (more importantly) both philosophically precise and epistemically perspicuous. Having done so, this paper provides a foundation for a broader project of analyzing the epistemic situation of (gravitational-wave) astrophysics.