What are the popular theories in medieval Europe?

With the development of science and technology, in the 14 and 15 centuries, the popular legend of "the sky is round" in medieval Europe and the danger of sailing straight to rolling in the deep met with challenges, and more and more people began to believe in the theory of the earth circle. The technology of drawing maps in western Europe has been very advanced, and charts showing the location of coastlines and ports have appeared. The compass invented by China was widely used in Europe in the14th century after it was spread to the west by Arabs. The compass gave the ships "eyes" and gave them a basis to sail without getting lost.