>>/749131/
Well unitary distance (every centimetre being the same distance) is almost universally accepted, and if you accept that then you get a equilateral square, which means a unit grid, and the relationship of right angles, and thus Pythagorean math, and elucidian math. They are all inherently related. 

I often think people reject the world being a sphere simply because they don't accept or understand how math applies to spheres.