Drawing on knowledge and theory borrowed from the ancient Greeks, Romans, and Islamic scholars, the Scientific Revolution is generally described as the period from the end of the Renaissance in Europe to the end of the 1700's and early 1800's, and is closely tied to Enlightenment ideals and the new influence on reason, rational thinking, and knowledge. Although the change in thinking and growth of knowledge was generally not linear, for the purposes of study, one can identify three of the main "discoveries" that represented a major change in scholarly human thinking at this time. First, the revolutionary idea that the sun, not the earth was the center of the universe (heliocentrism), that science could best be studied through an experimental method derived from logic and reason, and that a material body did not move up or down of its own accord, but as related to the earth's gravitational pull. Nicholas Copernicus, Rene Descartes, and Isaac Newton were pioneers, and probably the best known scientists to work in those three areas, respectively. Interestingly, although all three men were immersed in the new scientific theories and focus on reason and logic, none of them ever abandoned their religious and spiritual beliefs.