I've been struggling to find a picture to illustrate, and I'm far too un-artistic to make one, but I always imagined as though we were all living on the surface of a sphere, and what we know is like a circle around us.
Our own circle looks perfectly round and complete. But if we look over to our neighbours circle, his one looks a bit, well, not quite round. And as for those people right over there, their circle is looking decidedly squooshed up. And by the time you half way around the globe, those people right at the 'edge' practically have straight lines instead of circles, and I can't even begin to imagine what might be on the other side of the sphere of which I am so obviously right at the centre.
This is the best image I can find, found here.