3.6 Summary

• The scientific approach arose in the Greek culture in the sixth century BCE. The Ionian natural philosophers then made attempts to find natural explanations for natural phenomena, without resorting to higher powers. Their science was based on practical experience and everyday observations.
• According to the Pythagoreans, the key to understanding the world was mathematics. Through this idea they have had a profound impact on the development of physics, though their philosophy based itself more on abstract ideas than on information provided by the senses.
• Aristotle's cosmology was inspired by Pythagorean thinking. In his universe the earth belonged to the region below the moon, which was riddled with imperfection and change. The region outside the moon was constant and perfect. For this reason, the planets must move at uniform speed in “perfect”, circular orbits. This influential idea was to become an obstacle to advances in astronomy throughout the Middle Ages.
• Copernicus laid the foundation of the scientific revolution during the renaissance by reviving the heliocentric theory of Aristarchus of Samos.
• Kepler united the Ionian and Pythagorean traditions: he developed a mathematical model of the universe, but it was based on exact observations of the real world. His breakthrough was embodied in three quantitative, mathematical laws for planetary motion. They were accurate but had little explanatory power.
• The scientific revolution was completed with the Newtonian synthesis, which unified Galileo's terrestrial mechanics with Kepler's celestial mechanics. Newton also invented the mathematical method that was crucial for the development of his theory. The synthesis resulted in a general theory of mechanics, applying to all objects in the universe. It explained the origin of Kepler's elliptic orbits and showed that no force is needed to pull the planets around the sun.
• The Newtonian synthesis is the foundation on which the coming developments in physics were built. Newton's breakthrough also served as a model for other sciences.
• Since the renaissance, humanity has ventured into a broad program of curiosity-driven research that has paid off in a more advanced understanding of the world we live in, as well as a wealth of convenient applications.