Add to ORKGThe expansion of our universe is fascinating. Additionally there are exciting mysteries about the early universe: How is causality achieved? How can we explain the era of cosmic inflation by gravity or by quantum gravity? How is the big bang singularity avoided?Here I present a teaching unit that I developed in the framework of a research club. Thereby observations are modeled systematically. When problems occur the model is improved progressively. So a sequence of observationally founded models is developed systematically by solving problems of previous models. In this framework also scientifically novel observationally founded models are presented. This illustrates how students can be involved in real research in a teaching unit at a rese...