Here's another non-Euclidean geometry. This one is a finite geometry, meaning the space has only a finite number of points: here there are 7 points. It would be another talk to describe this, but I will use this geometry to connect difference sets to Riemann to 150 years, to Einstein, to Hamilton, to Arthur Conway, back to Octonions, and then to connect difference sets to the universe. Not modest, but it ties things together neatly.