To what does the term iron curtain refer?

the captain of a steam ship naturally chooses the shortest route to his destination. since a sailing ship is usually pushed by winds and currents, its captain must find a route where the wind will probably blow in the right direction. tacking, i.e. using contrary wind to pull (sic) the sails, was always possible but wasted time because of the zigzagging required, and this would significantly delay long voyages. the early european explorers were not only looking for new lands. they also had to discover the pattern of winds and currents that would carry them where they wanted to go. during the age of sail winds and currents determined trade routes and therefore influenced european imperialism and modern political geography. for an outline to the main wind systems see global wind patterns.

pilotage or cabotage, in one sense, is the art of sailing along the coast using known landmarks. navigation, in one sense, is the art of sailing long distances out of sight of land.[1] although the polynesians were able to sail the pacific (with great difficulty) and people regularly sailed north and south across the mediterranean, before the time of columbus nearly all sailing was coastal pilotage

        it is some were in here? ///

i confess that there are several parts of this constitution which i do not at present approve, but i am not sure i shall never approve them: for having lived long, i have experienced many instances of being obliged by better information or fuller consideration, to change opinions even on important subjects, which i once thought right, but found to be otherwise. it is therefore that the older i grow, the more apt i am to doubt my own judgment, and to pay more respect to the judgment of others.