Although it is clear that Columbus could sail easily across the Atlantic irrespective of the shape of the Earth (whether it were round like a ball, like a disc, or for that matter, even square), Magellan was able to circumnavigate the globe. The question is this. Although one can indeed leave Spain and return to it on a flat disc-shaped Earth, on a mono-polar map, the further South one goes the more messed up one's time frame becomes, and Magellan went pretty far South (all the way to the tip of South America, in fact; the Straits of Magellan are obviously named for him). A bi-polar map also presents problems in terms of time frame and distance. How can this be explained? I have to wrap this up, as I'm on a VERY unstable wi-fi connection (pulling off a neighbour). I'll get back on my phone. But any ideas?