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The decline and fall of the Roman Empire in ∼410 A.D. marks the end of Classical Antiquity and the beginning of the Dark Ages in Western Europe (Christendom) while the Muslim scholars in Eastern Europe continued to make progress in astronomy and mathematics. For example, in Egypt, Alhazen (965 - 1040 A.D.) expanded the principle of least time to reflection and refraction. The Dark Ages involved a long scientific decline in Western Europe that languished for about 900 years. Science was dominated by religious dogma, all western scholars were monks, and the important scientific achievements of Greek antiquity were forgotten. The works of Aristotle were reintroduced to Western Europe by Arabs in the early 13$$^{th}$$ century leading to the concepts of forces in static systems which were developed during the fourteenth century. This included concepts of the work done by a force, and the virtual work involved in virtual displacements. Leonardo da Vinci (1452-1519) was a leader in mechanics at that time. He made seminal contributions to science, in addition to his well known contributions to architecture, engineering, sculpture, and art.
Johannes Kepler (1571-1630), a German mathematician, astronomer and astrologer, was a key figure in the 17$$^{th}$$ century Scientific Revolution. He is best known for recognizing the connection between the motions in the sky and physics. His laws of planetary motion were developed by later astronomers based on his written work "Astronomia nova", "Harmonices Mundi", and "Epitome of Copernican Astrononomy". Kepler was an assistant to Tycho Brahe (1546-1601) who for many years recorded accurate astronomical data that played a key role in the development of Kepler’s theory of planetary motion. Kepler’s work provided the foundation for Isaac Newton’s theory of universal gravitation. Unfortunately Kepler did not recognize the true nature of the gravitational force.