: I think you are right and did split the "Geometry of the universe" in a "predating relativity" and a "including relativity" part, (not the nicest titles but I could not think of anything better at the moment) For the "including relativity" part I did pick bits of what you wrote above, please check and enlarge where needed,(some references would be nice) thanks for the discussion. It did teach me that Minkowski space has some euclidean dimensions, and that the anti-de Sitter space is (in my humble and not scientific opinion) the real thing