Since the Middle Ages, France has been a major contributor to scientific and technological achievement. Around the beginning of the 11th century, Pope Sylvester II, born Gerbert d'Aurillac, reintroduced the abacus and armillary sphere, and introduced Arabic numerals and clocks to Northern and Western Europe. The University of Paris, founded in the mid-12th century, is still one of the most important universities in the Western world. In the 17th century, mathematician René Descartes defined a method for the acquisition of scientific knowledge, while Blaise Pascal became famous for his work on probability and fluid mechanics. They were both key figures of the Scientific Revolution, which blossomed in Europe during this period. The Academy of Sciences was founded by Louis XIV to encourage and protect the spirit of French scientific research. It was at the forefront of scientific developments in Europe in the 17th and 18th centuries. It is one of the earliest academies of sciences.