In 1492, Columbus sailed the ocean blue.  We all know that and probably at least something about the Spanish Conquest of the Americas in the 16th century.  Spain's neighbor Portugal, however, has an equally stirring and incredible story.  At the same time as Spain, Portugal was forging their own far-flung empire around the Indian Ocean.  Guest host Mark Burns talks to the author of a new book on the Portuguese conquerors on today's Thinking Aloud.