Instrumental practices in seventeenth-century optics

In this dissertation I contextualise the development of the telescope in the early seventeenth century, and the development of the microscope at the time when high-power microscopy rose to prominence in the second half of the seventeenth century. My focus is on the interaction between optical theory and the production and usage practices of these instruments. Building on recent studies of practical knowledge, I evaluate the extent to which preserved historic telescopes and microscopes testify to such knowledge. I present interferometric studies of historic spectacles and some of the world’s oldest telescope lenses, preserved in various museum collections. In addition, I discuss the results of research by means of neutron tomography of Van Leeuwenhoek’s microscope lenses. Subsequently, I compare these archaeometric results with what contemporary written sources on optics reveal. The study of these written sources has long been characterised by a strong inclination towards theoretical developments as the main driving force behind the development of optical techniques. My archaeometric studies, by contrast, allow me to identify more securely what the share of practices and practical knowledge was in these developments. Combined with re-enactment studies, this methodology puts me in the position to clarify the interaction between theory and practice in the development of seventeenth-century optics. I argue that writing the history of optics using instrumental practices as a guiding principle leads to a more gradual narrative of seventeenth-century optical development. More specifically, such a history calls into question the traditional notion of a singular invention for the telescope and the microscope. Considered from a broader perspective, this dissertation argues that the telescope and the microscope were no stable historiographic categories in the seventeenth century. Instead, the meaning of these instruments was continuously being redefined through their embedding in evolving conceptual frameworks on the one hand, and their adaptation to changing user practices on the other.