Mechanical models of the paths of the stars have been popular ever since the controversy about Copernicanism. Looking at such models puts the viewer in the role of an external observer. After the founding of the Deutsches Museum, the director commissions the construction of not only a representative model of the Copernican system, but also a model of the Ptolemaic system it replaced, in which the planets and the fixed celestial sphere revolve around the static Earth.