parallel straight lines converge at this point only as an approximation. but actually, in the infinite universe that is assumed, if you hop into a taxi and follow the abstract extensions of the two parallel lines to wherever said "point at infinity" you've selected, arriving at that point, when you step out of the taxi and look, you'll again see space stretching out into infinity in all directions, and the parallel lines are still parallel at that point. if you must, you can again select another point in the far distance where the parallel lines would converge via the same mathematical approximation and deem that as your next "point at infinity." you can get back into the taxi and go all the way out there again and experience the same thing. that's if you don't first run out of cab fare