From the Model to the Glance

Between the late 1960s and the early twenty-first century, the process by which astronomers identified gravitational lenses went from a time-consuming spectroscopic experiment to a two-second glance at a telescope image. This article analyzes discoveries of gravitational lenses over this period to explore the questions: How did astronomers learn to see new objects in the sky, and how did they train their eyes to effortlessly recognize these patterns in nature? Rather than separating procedural and intuitive approaches, I argue that the mathematical modeling and the spectroscopic identifications of the sixties and seventies were necessary scaffolding for the development of expert intuition in the eighties. By developing an intuition for what a lens looked like, astronomers increasingly relied on their own expert judgment rather than spectroscopy or calculations to initially identify lensing candidates. Through this history, I highlight intuition as a skill and explore the methods by which scientists train and retrain their intuition over the course of a career. The gamut of gravitational lens discoveries reveals that scientists used models to not only describe the world as it is but also to teach themselves what it could look like. To retrain their intuition and to learn how to see gravitational lenses, astronomers learned to see their models.