Capítulo 22 From the Atom to the Cosmos, in three Stories on the Weight of Imagination in Science Andrés Rivadulla D. of Logic and Theoretical Philosophy, Universidad Complutense de Madrid Abstract. The aim of this article is to present three case studies that show the great repercussion that imagining daring hypotheses has for science. More often than not ideas introduced into science in form of explanatory hypotheses of surprising facts do so via ab- ductive reasoning, a form of scientific discovery that is also known as inference to the best explanation. In this article the hypotheses that concern us are those that led to the discovery of the neutron in nuclear physics, the discovery of the existence of double stars and later of white dwarfs, in astrophysics, and the discovery of dark matter, closely related to dark energy, in cosmology. 22.1 Introduction The path of scientific discovery runs along three main tracks, of which the first and oldest one, induction, has experienced the vicissitudes of time much more extensively than the other two. Abduction, although successfully applied since the beginning of science, has only gained recognition for a little over a century. While the third one, preduction, whose implementation in the methodology of