Der Herrnhuter Weihnachtsstern In der vorweihnachtlichen Adventszeit sind sie hier in Süddeutschland an allen Ecken zu sehen: die Herrnhuter Sterne.

Things are not as they seem. And sometimes this leads to classification problems because the anticipated shape of things clashes with your own model of reality. :O)

In mathematics, surface models are a fascinating way to visualize and understand complex geometric shapes. Here we look at the surface models of sphere, torus and torus node.