Abstract
The expansion of the universe is one of three pillars of the Big Bang theory and, therefore, an important aspect in cosmology. How the understanding hereof, including the complex concept of an expanding space, is developing, is not yet completely understood. On the basis of a hypothesis of a different study, which constructed a first structural setup of student understanding in this field, we developed it further to be able to reflect students’ processes of understanding the concept of an expanding universe. The assignment of open answers of N=126 German students from 11th- and 12th grade classes (16-20 years old) showed a good classification of these students into this construct with high interrater reliabilities.
