If we start out from the South Pole and head north, at a certain point we will cross the equator: in our representation of the surface of our planet in two discs, we ‘leap’ from one disc to the next. Obviously, in reality, no such leap occurs, because the northern hemisphere seen by someone coming from the south ‘surrounds’ the southern hemisphere, just as the southern hemisphere ‘surrounds’ the northern hemisphere for anyone looking from the north.
