So, if one starts from the Port of Palos, Spain, & goes West until one can go straight South to the Equator, & sails West across every ocean, & marches West across all the land (IOW, making an exact line on the Equator) until one can proceed directly North from the Equator back to the Port of Palos, Spain, that is called circumnavigation. It is not possible on a flat earth. Someone demonstrate that my penultimate sentence is wrong.