G. K. GILBERT, DISCIPLINE BOUNDARIES, AND THE IMPACT HYPOTHESIS

The impact hypothesis for the formation of craters found on the Earth, the Moon, and other planetary bodies has had a long and eventful history from the time it was first proposed in the seventeenth century to the present day, where it forms a pillar of the modern discipline of planetary science. This record has been summarized by several historians of science, particularly with the goal of determining reasons for the apparent delay in acceptance of the theory. Many factors have been suggested to have contributed to a continued skepticism of the impact hypothesis throughout the late nineteenth and twentieth centuries, ranging from an incomplete understanding of impact physics to the influence of specific scientific authority figures and their personalities. In this paper, I focus on an understudied aspect of the story: the interdisciplinary conflict between astronomers and geologists and the tensions generated by early cross-disciplinary studies of lunar and terrestrial craters. Each field possessed its own concept of “good science,” its own methods, professional hierarchies, and organizations. A successful application of geological principles to the craters of the Moon—an astronomical body—required not only interaction with the representatives of each discipline, but compromise as well. The mechanics of achieving such compromise were not straightforward, and neither were they always understood by those directly involved. Here I use the works of G. K. Gilbert (1843-1918) on lunar craters and Meteor Crater in Arizona to trace the attitudes of both communities regarding theories of crater formation and the emergence of researchers equipped to apply the methods of both disciplines.