The 17th century is known for important advances in the study of motion (mechanics) by such great scientists as Galileo and Newton. They did not start from scratch, as is sometimes suggested. And they were not the first to use mathematics to describe motion. There was a tradition of the application of mathematical description to motion throughout Europe in the late middle ages. The group associated with this tradition is known as the Calculatores, the Oxford Calculators,or Mertonian school. The most famous of the Calculatores was Thomas Bradwardine, a Roman Catholic Archbishop.
The advances of the Calculatores are impressive. They separated motion into categories that are associated with modern treatments of motion such as uniform motion and uniformly accelerated motion. They also separated the study of motion into kinematics and dynamics; a division which survives today in engineering schools the world over. They also presented a law which is usually credited to Galileo; the "Mean Speed Theorem". This theorem states that "a body moving with constant velocity travels distance and time equal to an accelerated body whose velocity is half the final speed of the accelerated body" . The tradition originated with a English Roman Catholic archbishop, Thomas Bradwardine, and is associated with the University of Oxford. The tradition had many proponents and was taught in England and the Continent (e.g. Paris, Padua) for centuries after Thomas Bradwardine's death. In order to properly describe the different types of motion the writers associated with this tradition often used surprisingly sophisticated mathematics.
Why are these medieval scientists important? On the one hand, you have an important advance in the study of motion, usually credited to a scientist used to symbolize the opposition of science and church, but the advance was made by a Roman Catholic archbishop 250 years before Galileo was born. It is now accepted that Galileo knew of the work of the Calculatores. The idea that Galileo had debts to medieval natural philosophers was resisted by many noted historians of science including leading biographers of Galileo. This in spite of the fact it was known that the ideas and work associated with the Calculatores were widely discussed throughout Europe throughout the 14th, 15th and 16th centuries. The University of Padua, where Galileo taught from 1592 to 1610, was an important centre for the revival of Mertonian thought on the continent (through Paul of Venice). It would have been very difficult for Galileo to not have been exposed to their ideas since the Calculatores ideas pervaded some of the most important books on mechanics of his time (Oresme, DeSoto, Thomaz, etc). Knowledge of the Calculatores work does not take anything away from Galileo's genius. It simply means that like most other great scientists, he didn't start from scratch. There had been a calculatory tradition dealing with the science of mechanics for several hundred years before he first entered university in Pisa.
How these figures were ignored for so long does raise some issues regarding historian bias (see Sarton:A Case for Bias). That is because key proponents of the Mertonian school were amongst the most honored academics during the middle ages and were also very widely taught throughout Europe. Bradwardine had even been mentioned in Geoffrey Chaucer's Canterbury Tales. The historians of science from the early twentieth century were positivists. The possibility of critical scientific advances occuring in a period largely dominated by the church conflicted with the positivist view of the history of science.