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The historians do not agree on when this device was invented, when it arrived in Europe it sparked "The Age of Exploration".
What is the compass?
(Invented in China. Some researchers say as early as 850, others say later, in 1050. Then passed on through trade routes, arriving in Europe in the early 1400s. This invention, along with other new technologies such as the astrolabe, chronometer, and triangular sail, came together to support improved map-making, which in turn allowed for greater exploration.)