Non-Euclidean Geometry Explained - Hyperbolica Devlog #1 | 10:53: Yours truly does NOT guarantee the accuracy of this video, but it seems OK. An intro explication non-Euclidean geometry. Not appropriate for the classroom.
Spherical Geometry Is Stranger Than Hyperbolic - Hyperbolica Devlog #2 | 4:00: Yours truly does NOT guarantee the accuracy of this video, but it seems OK. The narrator is actually illustrating 3-spherical geometry which is the geometry of the surface of a hypersphere in a 4-dimensional Euclidean space Yours truly thinks that in the just as for the 2-spherical geometry case, the narrator only illustrates a "hemisphere" with a "ground". Otherwise, as the observer looks off in the distance they would see the back of their head if there were NO obstruction and things would generally look even weirder. In fact, a class of Friedmann equation (FE) models of the universe have 3-spherical geometry. These Friedmann equation (FE) models include the Einstein universe (1917) which is the first general relativistic cosmological model and was discovered by Albert Einstein (1879--1955) himself in 1917. Not appropriate for the classroom.
Rendering Hyperbolic Spaces - Hyperbolica Devlog #3 | 6:03: Yours truly does NOT guarantee the accuracy of this video, but it seems OK. On hyperbolic space. A bit deeper in the arcana. Not appropriate for the classroom.