Philosophy of Mathspeaking topic

Why did people spend centuries trying to 'prove' Euclid's fifth postulate (the parallel postulate), and how did abandoning it give birth to non-Euclidean geometries?

Euclid's parallel postulate

practice with this topic

Set the timer (5-30 min), take 20 seconds of prep if you like, start talking. Jot your thoughts onto the sticky-note board.