Take a (potentially very large) triangle and measure the sum of it's angles. 180 degree? It's euclidean space. More? Elliptic space. Less? Hyperbolic space.

## By the way, the type of geometry can be measured

Take a (potentially very large) triangle and measure the sum of it's angles.

180 degree? It's euclidean space. More? Elliptic space. Less? Hyperbolic space.