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Newton’s Laws of Motion
Sir Isaac Newton’s work was the capstone of the Scientific Revolution, utilizing the advances made before him in mathematics, astronomy, and physics to derive a comprehensive understanding of the physical world. He was the first to conclusively affirm Galileo’s laws of motion on Earth and link them with Kepler's laws of planetary motion. Before Newton, no one had demonstrated conclusively that the movements of heavenly bodies were related to terrestrial physics. Galileo had suggested this, but was censored by the Church before he was able to do further work to prove his theories.
The first step in Newton's work was to solidify the laws of motion that Galileo had studied. The first law, of inertia, states that a body at rest tends to stay at rest, while a body in motion tends to stay in motion, unless either are compelled to change by an applied force. The second law states that the change in motion is proportional to the applied force, and takes place in the direction by which that force is applied. The final law states that, for every action, there is an equal and opposite reaction. Armed with these solidified theories of dynamics, Newton proved that the force that acted on planets and moons was the same force that caused a stone to fall to the ground: gravity.
Gravity and Calculus
The concept of universal gravitation—that every particle of matter attracts every other particle with a proportional force —is Newton's major contribution to science and the centerpiece of his work. The observed structure of the solar system was perfectly explained by assuming that the major organizing force among heavenly bodies was gravity. In order to apply the theory of universal gravitation to heavenly bodies with curved paths through space, Newton built upon the contributions of the mathematicians of the age and developed calculus. Using this tool, he discovered the concept of the center of mass. This theory was the final step in producing accurate calculations, and soon the mechanisms of organization in the universe became clear to him.
The Principia
In 1687, Newton set forth his findings in the most respected scientific work of all time, Philosphia Naturalis Principia Mathematica, better known as the Principia. This work established a model of the structure and functions of the universe based on universal gravitation which remains in use today, confirmed generation after generation by observation and calculation. The scientific community immediately recognized Newton's findings as revolutionary and proven with such clarity and logic as to be nearly indisputable by rational argument. Gradually, his mechanical analysis of the heavens became widely known, and was accepted as the basis for all future astronomy.
The Road to Newton
Newton's work represents the finale in a long chain of theory and discovery that evolved throughout the Scientific Revolution, from Copernicus to Galileo. Newton’s work was the culmination of this chain of science, inspired by the ideas of these men and the methods and tools developed by them and others of his predecessors. The Principia linked the last two remaining pieces of the puzzle—Galileo’s physics and Kepler's astronomy—and emerged with the “grand design” so many before him had sought. The design seemed not to have been established by any planning or simple geography, but rather by the interaction of the forces of nature, principally gravitation, on an enormous scale.
The Legitimization of Astronomy
At first, the full revolutionary extent of Newton's work was not recognized, even by Newton himself, but during the coming century, it became evident. The essence of Newton’s revolution was that he had conceived not only a plausible, but demonstrable model for the workings of the universe, solely relying on mechanics and completely separate of any spiritual influence. When this became clear, it was obvious that the Principia marked the most profound break from the grip of the Middle Ages. Until the time of Newton, astronomy had been considered at best a theoretical science, based little on direct evidence. However, Newton’s Principia changed the image of astronomy drastically. His theories were backed by solid mathematic tools, and his mechanical explanation of the universe contained no hint of mysticism or spirituality. With the advent of Newton, astronomy earned the right to be known as a science.
