Two models for the origin of the Solar System, the Nebula Theory and the Capture Theory, are discussed by protagonists, Simon and Steven respectively, in the presence of Solomon, who oversees the discussions. Modelled on Galileo’s Dialogue Concerning the Two Chief World Systems, this book provides new insight into different theories of cosmogony.The Nebula Theory, at present the standard model of planet formation, proposes that a star and planets are derived from a single spinning nebula. Woolfson here introduces an alternative, the Capture Theory, in which planets are produced from a protostar tidally disrupted by a condensed star which ‘captures’ most of the formed planets into orbits. These complex ideas are simplified and presented in an easily understandable, accessible way for all students of physics, astronomy, cosmology and those interested in the beginning of our world as we know it.