The science of the middle ages is called scholastic science. It was based largely on the science of Classical Greece although it was not static and there were various changes and additions over the centuries. Naturally, there were some important conflicts between Catholic doctrine and Greek science, but in the thirteenth century, a Dominican friar named Thomas Aquinas helped to meld Aristotle’s science into Catholic doctrine. By the fifteenth century, Aristotle’s physics was the physical science of Europe.
The method of science in those days was largely to debate over the classical works of Aristotle and other classical writers, and the works of those writers were taken largely as authorities. That is, one just assumed that what they said was true and went on from there. The Medieval scholars have taken lot of unfair abuse from moderns over this, but their approach was rational, given they believed that the ancients had a higher civilization than theirs, and they accepted the possibility of doing science from a priori principles.
Long before the Scientific Revolution scholastic science was undermined by European explorers in three ways: by showing that classical books were unreliable, by disproving scientific predictions, and by demonstrating that the Europeans of the late Middle Ages actually had a higher civilization than the Classical World.
One of the most widely read works of the Classical World was the Natural History of Pliny. This is a sort of encyclopedia of classical knowledge written in the first century AD. Along with a lot of useful facts about the world, this work contains a lot of myths about monsters and other things. Explorers found that these myths were not true, which not only brought Pliny into doubt, but many other classical sources which had similar stories.
There were two scientific theories in particular which explorers showed to be false, one was Aristotle’s and the other was a scholastic theory developed post-Aristotle. Aristotle believed that the equator would be too hot for humans to survive in; this was proven false by explorers who crossed the equator.
The second scientific theory takes a bit of background. It is described in the chapter on the Teraqueous Globe in The Discovery of Science, and in this blog post but I’ll summarize here: Aristotle taught that the sublunar world was made up of four elements, earth, air, fire and water, and that each of these elements had its own proper sphere with earth at the center of the universe, water above earth, air above water, and fire above air. That is, there were four concentric sphere which contained the “proper” place for each element. Gravity was explained as an attempt by each element to return to its proper place.
Later scholars added that there is ten times as much water as earth, ten times as much air as water, and ten times as much fire as air. Naturally, this made it difficult to explain how there is any dry land. There actually never was a good solution to this problem, but perhaps the most popular was to assume that the sphere of earth and the sphere of water did not have the same center, so that the known earth was just a bit of the sphere of earth sticking out of a much larger sphere of water. This would suggest that the measured diameter of the earth was just a fraction of the diameter of the whole earth/water conglomerate.
The discovery of dry continents on the other side of the earth made the theory that there is ten times as much water as earth collapse because although science is always willing to put up with a bit of tension between theory and observation, they do reach a limit beyond which they are not willing to go.
Finally, the explorers caused Europeans to re-evaluate their place in history. They were no longer the backward descendants of the classical civilization and the backward neighbors of the Muslim civilization; they were superior to both. They had explored more of the world; they had sea-faring abilities that dwarfed any other civilization in history; they had discovered entire continents that the ancients had had no clue about.
This encouraged them to take another look at their cathedrals which were grander than any building of Rome, and their water and wind power which were far, far more extensive than anything in the classical world, and their inventions like mechanical clocks and the printing press which were far more advanced than anything Rome had done, and they realized that they were no longer the backward civilization clinging to the coattails of better civilizations, they were at the top, and it was their turn to lead. This is where we find Europe when the presses started turning on a manuscript by an obscure mathematician named Nicolaus Copernicus.