The true dimensions of the terrestrial globe were revealed mostly in the fifteenth and sixteenth centuries, principally through the technical development of truly ocean-going vessels and the magnetic compass, which enabled the exploration of the oceans. Even with these advantages, the real extent of the Great Southern Continent or terra australis incognita had to await the voyages of Cook in the eighteenth century. This flood of new geographic knowledge replaced the medieval view of the world (although Flat-Earth societies still persist). Such understanding was gained only very slowly. Adetailed knowledge of the topography of the ocean floors and our understanding of their composition and origin has been obtained only a little ahead of our radar pictures of the surface of Venus.

Our exploration of the solar system is at a similarly heroic stage. The distant points of light, barely resolvable in telescopes, have been revealed through the use of space vehicles, the latter-day equivalent of the Portuguese caravels, as separate worlds, with an astonishing amount of diversity.

The information has been rapidly and widely disseminated, electronic media having superseded the printing press of the Renaissance. Everyone is informed of the striking new discoveries. Although no Eldorados have emerged, the pictures reveal a plurality of worlds unimagined by the Elizabethans. Every satellite has turned out to differ in some significant feature from its neighbor: “… the sense of novelty would probably not have been greater if we had explored a different solar system” [1].