Zogg from Betelgeuse: Crash Course for Aliens

This is the first part of a three-part miniseries on the shape of the universe. Is the universe infinite? Does it have an edge? In this part, we will talk about the possibility of a flat, finite universe without edge.

This is the second part of a three-part miniseries on the shape of the universe. Could the universe be curved? What is curvature, anyway? What is the cosmological principle? And is the universe maybe some sort of hyperbanana?