[cess11]

I imagine that elliptic geometry had some use before modern physics.

[saghm]

Yeah, even just trying chart a course on a ship across a reasonable distance will cause you to need to reevaluate some "obvious" things (like "what path is the shortest between these two ports" being a curve rather than a line).

[ecosystem]

The specific controversy was whether without the parallel/5th postulate, there existed a logical contradiction, i.e. proving the parallel postulate