The treaty was basically just an agreement between Spain and Portugal, right?
Don't step on my side, and I don't step on yours.
The "Treaty of Tordesillas" - but mostly I came in to say it didn't divide the planet into two spheres, but two Hemispheres (i.e. they cut the world in two).
(Not that they did it perfectly, which is why Brazil intrudes into the Spanish sectory and the Philippines are in line with the Portuguese Spice Islands)
(Technically the Treaty of Tordesillas built upon the earlier papal bull "Aeterni regis", but that one didn't consider the earth roundness so it just had a single line drawn.) [Edit - this is not completely correct either, a later manga chapter reminded me that the Aeterni regis simply didn't consider the American continents at all, the Treaty of Tordesillas did that, and then yet another treaty came along to finalize the division on the far side of the globe.]